Publisher：Catalysis Science and Technology  

Boron nitride has received much attention as an emerging heterogeneous catalyst. Porous boron nitride catalysts were synthesized using boric acid (B) and urea (U) at different molar ratios via a pyrolysis method and applied for cycloaddition of CO2 to epoxides as metal-free catalysts. The synthesized boron nitride samples had a turbostratic structure, and their porous properties, such as surface area, pore size distribution, and pore volume, largely depended on the molar ratio of B : U precursors. The sample synthesized at a molar ratio of B : U = 1 : 5 with the highest pore volumes among the samples prepared from boric acid and urea exhibited the highest activity for cycloaddition of CO2 to epoxides, epichlorohydrin and styrene oxide in the presence of tetrabutylammonium bromide (TBAB). There was a good correlation between the corresponding carbonate yield and the pore properties of the catalyst. The addition of melamine (M) during the synthesis greatly developed the porous structure, exceeding 1000 m2 g−1 surface area. The sample synthesized at a molar ratio of B : M : U = 1 : 1 : 5 having a large surface area of 1380 m2 g−1 with a high pore volume of 1.8 mL g−1 afforded a remarkable yield of 96% for the reaction of epichlorohydrin. The catalyst could be reused at least three times without a significant loss of activity. A cooperative reaction mechanism was proposed in which the hydroxyl groups of porous boron nitride catalysts as weak Brønsted acid sites polarize the oxygen atom of the epoxide, and the bromide ions of TBAB as Lewis base sites activate the carbon atom of the epoxide by the nucleophilic attack.

DOI： 10.1039/d4cy01080a

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Publisher：Journal of Materials Chemistry A  

Photocatalysis offers a sustainable solution for essential reactions such as CO2 conversion and water splitting, but constraints in catalyst properties like bandgap and active site availability often limit its efficiency. High-entropy oxides (HEOs), which incorporate five or more different cations, present significant potential for this application due to their elemental diversity. This study explores active HEO development for photocatalytic applications by integrating cations with d0 and d10 electronic configurations. A single-phase HEO with a monoclinic structure was successfully synthesized, comprising elements with d0 (titanium, zirconium, niobium and tantalum) and d10 (zinc) electronic configurations. Comprehensive analyses of its microstructure, chemical composition, optical properties and photocatalytic activity were conducted. The resulting TiZrNbTaZnO10 exhibited superior UV and visible light absorption, a low bandgap of 2.5 eV, minimal radiative electron-hole recombination and high stability under photocatalytic conditions. Remarkably, TiZrNbTaZnO10 outperformed the TiZrHfNbTaO11 photocatalyst which contains solely d0 electronic configuration. This enhanced performance is attributed to the mixed electronic configurations fostering heterogeneous chemical environments, which facilitate efficient charge carrier separation and transfer.

DOI： 10.1039/d4ta04689g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

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Formic acid is considered a promising hydrogen carrier. Biomass‐derived formic acid can be obtained by oxidative decomposition of sugars. This study explored the production of formic acid from cellobiose, a disaccharide consisting of d‐glucose linked by β‐glycosidic bonds using heterogeneous catalysts under mild reaction conditions. The use of alkaline earth metal oxide solid base catalysts like CaO and MgO in the presence of hydrogen peroxide could afford formic acid from cellobiose at 343 K. While CaO gave 14 % yield of formic acid, the oxide itself was converted to a harmful metal peroxide, CaO₂ after the reaction. In contrast, MgO could produce formic acid without the formation of the metal peroxide. The difficulty in selectively synthesizing formic acid from cellobiose using these solid base catalysts was due to the poor conversion of cellobiose to glucose. Using a combination of solid acid and base catalysts, a high formic acid yield of 33 % was obtained under mild reaction conditions due to the quantitative hydrolysis of cellobiose to glucose by a solid acid followed by the selective decomposition of glucose to formic acid by a solid base.

DOI： 10.1002/open.202400079

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Language：English   Publisher：Wiley-VCH GmbH  

Formic acid is considered a promising hydrogen carrier. Biomass-derived formic acid can be obtained by oxidative decomposition of sugars. This study explored the production of formic acid from cellobiose, a disaccharide consisting of d-glucose linked by β-glycosidic bonds using heterogeneous catalysts under mild reaction conditions. The use of alkaline earth metal oxide solid base catalysts like CaO and MgO in the presence of hydrogen peroxide could afford formic acid from cellobiose at 343 K. While CaO gave 14 % yield of formic acid, the oxide itself was converted to a harmful metal peroxide, CaO2 after the reaction. In contrast, MgO could produce formic acid without the formation of the metal peroxide. The difficulty in selectively synthesizing formic acid from cellobiose using these solid base catalysts was due to the poor conversion of cellobiose to glucose. Using a combination of solid acid and base catalysts, a high formic acid yield of 33 % was obtained under mild reaction conditions due to the quantitative hydrolysis of cellobiose to glucose by a solid acid followed by the selective decomposition of glucose to formic acid by a solid base.

CiNii Research

Language：English   Publisher：Chemistry - An Asian Journal  

Novel D-A1-A2-π-A organic sensitizers (FZ-sensitizer), utilizing spiro [fluorene-9,9′-phenanthren]-10′-one and benzo [c][1,2,5]thiadiazole moiety as two auxiliary acceptors, are synthesized and applied in dye-sensitized solar cells (DSSCs) and hydrogen production. By incorporating a bulky spiro [fluorene-9,9′-phenanthrene]-10′-one (A1) and benzo[c][1,2,5]thiadiazole (A2) between the donor (D) and π-bridge moiety, structural modifications inhibit molecular aggregation, while the carbonyl group enhances the capture of Li+ ions, thereby delaying charge recombination. Furthermore, the extended π-conjugation broadens the light absorption range and enhances the power conversion efficiency (PCE) of FZ-2 under AM1.5 conditions, achieving up to 5.72%. Co-sensitization with N719 and FZ-2 shows PCE of 9.60% under one sun. Under TL84 indoor light conditions, the efficiency is 29.69% at 2500 lux. The superior co-sensitization performance of N719 and FZ-2 can be attributed to FZ-2′s high absorptivity at short wavelengths, compensating for N719′s shortcomings in this range. FZ-sensitizers also exhibit high efficiency in photocatalytic hydrogen production. The hydrogen production activities of FZ-2 are 9190 μmol/g (1 hour) and 76582 μmol/g (12 hours) respectively, while those of FZ-1 are 7430 μmol/g (1 hour) and 64004 μmol/g (12 hours), indicating that FZ-2 can inject charges into TiO2 more efficiently and utilize them for water splitting. Stability testing of photocatalytic water splitting after 12 hours shows a turnover number (TON) of 4249 for FZ-1 and 5378 for FZ-2.

DOI： 10.1002/asia.202400697

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Publisher：ACS Applied Energy Materials  

Metal-supported protonic ceramic fuel cells were prepared, and the effects of a double columnar layer at the cathode side of BaZr0.44Ce0.36Y0.2O3 (BZCY) on power density and open-circuit voltage (OCV) were studied. The double columnar structure of Pr0.2Ce0.8O2 (PrDC) and BZCY was prepared with pulsed laser deposition. It was found that the insertion of the double columnar layer was highly effective for increasing the power density and OCV. The optimum composition of the double columnar was BZCY:PrDC = 7:3, with a thickness of 200 nm. The power density of PCFCs with the BZCY-PrDC double columnar reached 413 mW/cm2, and the OCV was approximately 1.05 V at 873 K, which is six times higher than that of a cell without a functional layer. The high power density of the cell was attributed to the decreased overpotential of the cathode. Therefore, the BZCY-PrDC double columnar layer is effective in expanding the reaction site by increasing the proton concentration at the cathodic interface.

DOI： 10.1021/acsaem.4c01529

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Publisher：Applied Physics A: Materials Science and Processing  

Bis(2,2′-bipyridine)bis(isothiocyanato)ruthenium complexes are organo-metallic dyes having broad absorption properties in the visible region that are widely used in dye-sensitized opto-electronic devices. Here, we report the photocurrent measurement and stability studies of three Ru-complexes, cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II) (N3), its hydrophobic analogues cis-bis(isothiocyanato)(2,2’-bipyridyl-4,4’-dicarboxylato)(4,4’-di-nonyl-2’-bipyridyl)ruthenium(II) (Z-907) and hydrophilic analogues (di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II), (N719). Z907 shows higher stability and photoelectric conversion efficiency after 2 h analysis than its hydrophilic counter-molecules, N3 and N719. The Z907-TiO2 system exhibited a 1.09 mA/cm2 photocurrent density after 2 h of analysis, with 78% of its performance retained even after an extended 48 h of analysis. The activity of N719-TiO2 and N3-TiO2 sharply decreased after 2 h of analysis, and significant desorption of the dye present on titanium oxide was also observed. This study suggests that hydrophobicity at the electrode-dye interface is a major factor supporting the stability of the dye-sensitized photoanode.

DOI： 10.1007/s00339-024-07730-1

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Publisher：Journal of Materials Chemistry A  

Aqueous dual-ion batteries have good safety, environmental compatibility, and low cost due to the use of an aqueous electrolyte. However, water electrolysis occurs during charging at high potential, resulting in a poor cyclic stability of aqueous dual-ion batteries. Hence, novel anode materials are urgently needed to be developed for aqueous dual-ion batteries with low water electrolysis. A niobium-based binary-phase composite material is reported with a capacity of 135 mA h g−1 at a current density of 0.2 mA cm−2 and with excellent reversibility in the potential range of −1.3-0 V vs. Ag/AgCl. The activation energy of Li+ intercalation was obviously decreased because of the formation of an interface, which enhanced the Li+ intercalation reaction between FeNbO4 and MoNb12O33. In addition, the lower amount of Fe2+ in the lattice of MoNb12O33 caused localized compressive strain, which promoted fast Li+ diffusion in MoNb12O33. A full dual-ion battery of 3.0 V was constructed using the binary-phase niobium-based composite for the anode, and demonstrated a high cycle stability and an average coulombic efficiency of 91% over 300 cycles. Furthermore, considering both the electrolyte and electrode materials, the theoretical energy density of this dual-ion battery was estimated to be 250 W h kg−1, which is close to that of the current Li-ion rechargeable battery.

DOI： 10.1039/d4ta01293c

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Publisher：Advanced Engineering Materials  

Astronomical impacts by small solar system bodies (meteoroids, asteroids, comets, and transitional objects) are considered a mechanism for delivering amino acids and their polymerization to proteins in early Earth conditions. High-pressure torsion (HPT) is a new methodology to simulate such impacts and clarify the behavior of biomolecules. Herein, two amino acids, crystalline L-serine and L-glutamic acid that are detected in meteorites, are processed by HPT and examined by ex situ X-ray diffraction, Raman spectroscopy, nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and in situ mechanical shear testing. No polymerization, chemical reactions, or phase transformations are detected after HPT, indicating that the stability and presence of these two amino acids in meteorites are quite reasonable. However, some microstructural and mechanical changes like crystal size reduction to the nanometer level, crystal defect formation, lattice expansion by vacancy formation, and shear strength enhancement to the steady state are found which are similar to the behaviors reported in metals and ceramics after HPT processing.

DOI： 10.1002/adem.202302267

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Publisher：ACS Sustainable Chemistry and Engineering  

[FeFe]-hydrogenase (HydA) is an active biocatalytic enzyme for solar-to-hydrogen (H2) conversion. However, stability is a main challenge that limits practical applications. This work aims to encourage the efficiency of HydA by encapsulating it in the zeolitic imidazolate framework-8 (ZIF-8) as a synthetic protective shield. The construction of HydA@ZIF-8 nanoparticles, with an average diameter of 700-1000 nm, at ambient conditions can preserve HydA activity within a spatially confined microenvironment, as characterized by scanning electron microscopy and X-ray diffraction analysis. Based on MV•+-dependent H2 production activity and kinetic analysis, both the stability and efficiency of HydA@ZIF-8 surpass those of free HydA and whole-cell biocatalysts over a wider range of pH and temperature. The achievement of robust HydA@ZIF-8 construction represents a significant step forward in the development of biocatalysts for various future applications.

DOI： 10.1021/acssuschemeng.3c08560

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

<p>A dense NiO-Fe₂O₃ (NiFe) pellet has been developed as a potential anode-support for thin-film solid oxide fuel cells (SOFCs). However, preparation of dense NiFe is very challenging. Hole-formed NiFe pellets or porous NiFe pellets are frequently formed, which cannot be used as a support (substrate) for thin-film SOFCs. Therefore, this hole-formed NiFe support is simply wasted. In this report, we attempt to re-qualify this NiFe support to be a valuable substrate, which can be used for fabricating thin-film SOFCs. By deposition of smaller NiFe particles to cover the hole-formed NiFe support, the surface of this NiFe pellet is modified. Large holes on the surface disappear. The newly formed NiFe support can be used for fabricating a single cell with La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ as thin-film electrolyte operated at intermediate temperature. Maximum power density generated from this cell is 0.45, 0.86 and 1.28 W cm⁻² at 873, 923 and 973 K, respectively.</p>

DOI： 10.5796/electrochemistry.23-00164

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

NH3 is an important chemical fertilizer and expecting as H2 carrier. Several methods have been investigated for eco-friendly NH3 production under mild conditions instead of Haber-Bosch process using 400 °C, 20 MPa. Here, cyanobacterial Anabaena variabilis was utilized as a nitrogenase-producing biocatalyst that converts N2/H2O to NH3 under ambient conditions. Biocatalytic reactions revealed that MV•+ can penetrate cell membrane and transfer electrons generated in inorganic photocatalyst. We first reported photobiocatalytic NH3 production of cyanobacteria and TiO2. Comparing with natural system, NH3 formation rate of the hybrid system increased 81.3 times with an initial rate of 2031.7 nmol·h−1 and turnover number of 216.8.

DOI： 10.1016/j.apcatb.2023.123431

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Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society  

Effects of channel size in NiO-YSZ porous substrate were studied on power density in solid oxide fuel cell mode and electrolysis current in steam electrolysis mode. It was found that the cell deposited on anode substrate with larger pore diameter shows a superior performance. The LSGM cell prepared on Ni-YSZ tube with average channel diameter of ca. 2.5 μm shows the maximum power density of 0.36 W cm⁻² in SOFC mode and 0.42 A cm⁻² at 1.6 V in SOEC mode at 873 K. Spike potential noise which may be caused by insufficient gas diffusion in NiO-YSZ porous substrate was observed under constant current electrolysis condition in case of NiO-YSZ tube with narrow channel and the spike noise is suppressed by increasing channel size. NiO-YSZ tube with large channel size is also effective for increasing long term stability in electrolysis mode.

DOI： 10.1149/1945-7111/ad2815

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Other Link： https://iopscience.iop.org/article/10.1149/1945-7111/ad2815/pdf

Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

In this study, a hybrid photocatalyst with titanium oxide using reduced graphene nanoribbons (rGNR) was fabricated.

DOI： 10.1039/d3tc03622g

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Photocatalytic hydrogen peroxide (H2O2) by oxygen and phosphorus co-doped graphitic carbon nitride (C3N4) with cobalt phosphate (CoP) cocatalyst is investigated. The photocatalyst powder of CoP-C3N4 1:n, n = 0–4, n is the weight ratio of cyanuric acid added) was synthesized by melamine cyanurate template method. Characterization of the catalyst was performed by X-ray diffraction analysis, and scanning electron microscopy, X-ray photoemission spectra, and fluorescence decay spectra. Oxygen doping was performed by the melamine and cyanuric acid template method, followed by phosphorus doping of the C3N4 backbone by the introduction of CoP. Co-doping of O and P atom facilitated charge transfer on the C3N4 backbone, while CoP facilitated charge separation at the C3N4 interface. The CoP-C3N4 (1:4) photocatalyst increased H2O2 production rate by 293 % compared to that of the cyanuric acid-free photocatalyst and also achieved the photocatalytic oxygen evolution from water. These results indicate that O,P co-doped CoP-C3N4 can perform sacrificial agent-free hydrogen peroxide under visible light irradiation.

DOI： 10.1016/j.cattod.2023.114400

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Publisher：2024 31st International Workshop on Active-Matrix Flatpanel Displays and Devices, AM-FPD 2024  

The structural modifications prevent molecular aggregation by adding a bulky spiro[fluorene-9,9'-phenanthrene ]-10' auxiliary acceptor (A1) and benzo[c][1,2,5]thiadiazole (A2) between the donor and π-bridge moiety. Additionally, the carbonyl group improves the capture of Li+ ions, delaying charge recombination. Moreover, sensitizer FZ-2's light absorption range is expanded and its energy conversion efficiency is improved under AM1.5 circumstances, reaching up to 5.72%, thanks to the enlarged π-conjugation. Co-sensitization testing under one sun revealed an effectiveness of 9.60% using N719 and FZ-2. Due to FZ-2's strong absorption efficiency at short wavelengths, which offsets N719's inadequacies in this range, the co-sensitization performance of FZ-2 and N719 is superior. Additionally, FZ-sensitizers demonstrate excellent photocatalytic hydrogen production efficiency. The hydrogen production activities of FZ-1 are 7430 μmol/g (1 hour) and 64004 μmol/g (12 hours), FZ-2 hydrogen production activities are 9190 μmol/g (1 hour) and 76582 μmol/g (12 hours). This suggests that FZ-2 is more effective at injecting charges into TiO2 and using them for water splitting. After 12 hours of photocatalytic water splitting stability tests, FZ-1 and FZ-2 exhibited TON of 4249 and 5378, respectively.

DOI： 10.23919/AM-FPD61635.2024.10615532

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Mullite-phase bismuth gallate (Bi2Ga4O9) was successfully synthesized with partial substitution of bismuth with alkaline-earth cation, Mg2+, Ca2+, Sr2+, and Ba2+. The effect of this substitution on the electrical conductivity was investigated. In this study, substitution with Ca2+ of Bi site was further studied for increasing the ionic conductivity as well as the phase stability in reducing atmospheres. Substitution with Ca2+ was found to be the most effective and with 12.5 mol% of Ca2+ as the optimized doping amount. Conductivity and stability in reducing atmospheres was increased down to pO2 ≤ 10−19 atm while keeping the conductivity of σ = 2.6 × 10−2 S·cm−1 at 973 K largely independent of oxygen partial pressure. Oxygen permeation analysis estimates 76% of theoretical oxygen permeation rate at 973 K suggesting main charge carrier is oxide ion. Partial electronic conductivity was measured with the ion blocking method. Oxide ion conductivity is dominated over wide pO2 range excepting for hole conduction at high pO2. Density functional theory (DFT) analysis on oxide ion diffusion route suggests oxygen hoping through lattice vacancy is main pathway for oxide ion conductivity in this doped Bi2Ga4O9. Despite the low oxide ion conductivity in Mullite-phase oxide, it was found that Ca doped Bi2Ga4O9 shows good oxide ion conductivity over wide pO2 range.

DOI： 10.1016/j.ssi.2023.116343

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Optimizing hydrogen production in ascorbic acid solutions: enhancing BODIPY dye-sensitized processes through alkyl-chain-enhanced second coordination sphere effects.

DOI： 10.1039/d3ta03682k

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

The correlation between lattice strain induced by metal dispersion into grain and the cathodic overpotential is studied for increasing oxygen‐dissociation activity and improving power density of solid oxide fuel cells (SOFC) at decreased temperature. Pt or Au dispersion in Pr_1.90Ni_0.71Cu_0.21Ga_0.05O_4+d (PNCG) is prepared and the 3D tensile strain is successfully induced after sintering by a mismatch in thermal expansion coefficient. Due to higher hardness and melting temperature, Pt dispersion into bulk of PNCG introduces larger tensile strain than that by Au at the same amount. In particular, at 1 mol% Pt dispersion, large tensile strain of 0.67% is induced. Overpotential of 1 mol% Pt‐PNCG cathode is 8 times smaller (35 mV) than that of PNCG (270 mV) at 800 °C and 300 mA cm⁻², and it is found that the cathodic overpotential of PNCG is decreased with tensile strain on both Pt and Au dispersion. This cathodic activity enhancement appears to be related with the increased diffusivity of oxide ion in PNCG. In this study, cathodic overpotential is more significantly influenced by the induced tensile strain comparing with the intrinsic catalytic activity of the dispersed metal.

DOI： 10.1002/aesr.202300084

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

For increasing the performance of PCFC (Protonic Ceramic Fuel Cells), it is important to prepare high-quality thin films of electrolyte materials. In this study, the preparation condition of the thin film of BaZr0.8Yb0.2O2.9 (BZYb) by pulsed laser deposition (PLD) method was optimized and the electrical conductivities of the obtained films were measured. The thin film was prepared by PLD using two kinds of BZYb targets, which were prepared by solids state reaction and Pechini method. Both thin-film samples have the single phase of the cubic perovskitetype structure, however, morphology as well as the orientation of the BZYb film was significantly different. The thin film using the target material by Pechini method is a high crystalline orientation and partially oriented [211] direction. The electrical conductivities of the obtained thin films at reduction atmosphere are dominated by proton conductivity, which is almost the same as that of the bulk sample despite [211] orientation.

DOI： 10.1016/j.ssi.2023.116240

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Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

In the CO2 electrocatalytic reduction reaction (CO2RR) technology, high CO2 conversion rate is highly required for efficient CO2 utilization from the CO2 resource. In this study, we propose the strategy of combining UiO-66 metal organic framework (MOF) structure with Bi electrocatalyst for highly active CO2RR with selective formic acid production. The synthesized Bi/UiO-66 catalyst shows superior CO2 reduction property, 4.6 times higher current density at −0.7 V vs. reversible hydrogen electrode (RHE) than bare Bi without UiO-66 despite of low electrochemical surface area. Also, NH2 functionalized UiO-66 shows almost no effect on CO2RR as compared to without NH2 probably due to disassembled linkers during CO2RR. Various characterizations such as Fourier transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) indicate carbonate species captured form of CO2 at Zr-MOF site should contribute the high CO2 conversion rate. Our findings demonstrate the feasibility of Zr-MOF as a Supporting material to achieve efficient CO2 reduction.

DOI： 10.1016/j.apcatb.2023.122400

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Language：English   Publisher：Wiley  

The amount of support salt in electrolytes determines the capacity of a dual-ion battery (DIB), and highly concentrated electrolytes are required for developing the high energy density DIB. In this study, hybrid aqueous tetraglyme (G4) electrolyte is investigated to develop high energy density aqueous DIB that is composed of carbon and Mo_6S_8 for cathode and anode, respectively. Impedance measurement reveals that introduced G4 increases the activation energy of the anode; however, decreases the activation energy for anion intercalation into the carbon cathode. This decreases the activation energy resulted from the G4 molecule strongly solvated to Li^+ resulting in weakening anion trapped in “contact ion pair” in concentrated aqueous electrolyte. So, hybrid G4-aqueous electrolyte is useful for better electrochemical intercalation of anion. In addition, this hybrid electrolyte is highly stable by formation of stable solid electrode–electrolyte interphase on Mo_6S_8 anode and discharge capacity of 37 mAh g^<−1>, and 72% retained capacity after 500 cycles with a high average coulombic efficiency of 93% is achieved.

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The amount of support salt in electrolytes determines the capacity of a dual-ion battery (DIB), and highly concentrated electrolytes are required for developing the high energy density DIB. In this study, hybrid aqueous tetraglyme (G4) electrolyte is investigated to develop high energy density aqueous DIB that is composed of carbon and Mo6S8 for cathode and anode, respectively. Impedance measurement reveals that introduced G4 increases the activation energy of the anode; however, decreases the activation energy for anion intercalation into the carbon cathode. This decreases the activation energy resulted from the G4 molecule strongly solvated to Li+ resulting in weakening anion trapped in "contact ion pair" in concentrated aqueous electrolyte. So, hybrid G4-aqueous electrolyte is useful for better electrochemical intercalation of anion. In addition, this hybrid electrolyte is highly stable by formation of stable solid electrode-electrolyte interphase on Mo6S8 anode and discharge capacity of 37 mAh g(-1), and 72% retained capacity after 500 cycles with a high average coulombic efficiency of 93% is achieved.

DOI： 10.1002/smtd.202300249

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A rechargeable Zn-air battery is expected as a large capacity battery alternative to the Li ion battery; however, short cycle life is the current issue. In this study, it was found that the addition of 3,3-diaminodipropylamine was effective for preventing the formation of a Zn dendrite in the anode resulting in a long cycle life with more than 300 cycles and a discharge capacity larger than 700 mAh/g (>85% Zn used for discharge) when Ni0.8Fe0.2Co2O4 and 8 M KOH-H2O were used for the air electrode and electrolyte, respectively. The increased cycle stability could be assigned to the change in the solvated structure of Zn2+ in the electrolyte by the strong interaction between 3,3-diaminodipropylamine and solvated water, which is suggested by Raman and Fourier transform infrared spectroscopic analyses. Ab initio molecular dynamics simulations suggest that the amine is strongly interacted with OH of solvated water molecules and changes the coordination number of Zn2+, and as result, the size of the solvated Zn2+ cluster was increased, resulting in enhanced Zn2+ mobility in the electrolyte for the uniform deposition of Zn on the anode during charge by increased mobility.

DOI： 10.1021/acs.jpcc.2c08682

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

Photobiocatalytic system has been developing as a promising approach for H2 production. Herein, the rational characteristics of biocatalysts and the role of individual components affecting the efficiency of the system were investigated. Photocatalytic studies showed that tris (2-amino-2-hydroxymethyl-1,3-propanediol) was an ideal electron donor for viologen reduction by TiO2. Biocatalytic reaction revealed that cell permeability, the redox potential of electron mediators and the cell envelope were crucial to the activity of whole-cell biocatalysts. In photobiocatalytic system, recombinant Escherichia coli with a turnover frequency of 39.43 +/- 3.77 s-1 based on [FeFe]-hydrogenase activity was a more rational biocatalyst than Anabaena variabilis. A comprehensive study found that the presence of TiO2, light and biocatalysts strongly enhanced H2 production, whereas Tris and MV2+ had less influence. A maximum rate was found at 16.73 +/- 1.03 mu mol/min with a solar-to-H2 conversion of 1.58 +/- 0.10 %. Understanding the role of each component will guide the development of high-efficient photobiocatalysis.

DOI： 10.1016/j.apcata.2022.119019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Squaraine dyes are organic dyes having strong and narrow absorption properties in the near-infrared region that are widely used in photovoltaic and biomedical applications. In this work, squaraine dye (SA1) was synthesized as a dye sensitizer for a dye-sensitized photocatalytic system, which was composed of SA1 and Pt-loaded TiO2 powder photocatalyst (SA1/Pt-TiO2). The SA1/Pt-TiO2 system exhibited a good hydrogen production performance within 150 h and an apparent quantum yield of 1.4% under 800 nm monochromatic light irradiation. However, during the photocatalytic reaction, the photocatalytic activity of SA1/Pt-TiO2 decreased due to photodecomposition. Ultraviolet-visible absorption spectroscopy, H-1 nuclear magnetic resonance spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry measurements were performed to investigate the mechanism of the decomposition of the squaraine moiety of SA1, the decomposition process, and the structure of the decomposed material. The results show that even without the Pt-loaded TiO2 powder photocatalyst, SA1 undergoes photodissociation, which cleaves the bond between the indoline moiety and the square acid.

DOI： 10.1007/s00339-022-06281-7

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DOI： 10.1111/ncn3.12681

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Water-acetonitrile (AN) hybrid electrolyte with high concentration of bis(trifluoromethanesulfonyl) imide (LiTFSI) and Lithium bis(fluorosulfonyl) imide (LiFSI) (LiTFSI-LiFSI=3:1, molar ratio) supporting salts are studied for the high potential and large capacity rechargeable dual-ion battery. Water-acetonitrile hybrid electrolyte (WA) shows a wide electrochemical stability window of 3.1 V in 20 m aqueous electrolyte and 3.6 V in 20 m 9LiFSI-1LiTFSI in water: AN=1:3 molar ratio electrolyte. In particular, high oxidation potential, which can be assigned to the strong solvated ionic cluster formed between AN, water and LiTFSI-LiFSI supporting salts. The dual-ion battery is assembled using the graphitic carbon (KS6) and the activated carbon (AC) as cathode and anode, respectively, and 20 m LiTFSI-LiFSI in hybrid AN-water as electrolyte. It is found that the reasonably large capacity, coulombic efficiency and cycle stability were achieved. The KS6/AC cell shows 86 mAh g(-1) at the initial cycle and 50 mAh g(-1) at 100th cycle in a voltage range of 0-3.25 V, and the average coulombic efficiency of 85% is sustained over 200 cycles. The solvated structure of water to Li+ is strengthened by addition of AN from ATR-IR and NMR spectrums analysis and this change in the solvated structure is the main reason for the increased performance of the aqueous dual-ion battery.

DOI： 10.1149/1945-7111/acaad1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The solvated structure of a highly concentrated hybrid tetraglyme (G4)-water electrolyte was studied for an increasing cycle stability and performance of a KS6 used dual-ion battery. Hybrid solvent of G4 and water with a weight ratio of 2 to 8 was able to dissolve 9LiFSI-1LiTFSI supporting salts up to 37 mol kg(-1) (37 mol kg(-1) G2W8). In spite of such high concentration of supporting salts, reasonable charge and discharge performance of dual-ion battery (discharge capacity of approximate to 40 mAh g(-1) and coulombic efficiency of 90 %) were exhibited over 300 cycles. This was attributed to the decreased hydrogen evolution reaction (HER) potential to -1.05 V vs. Ag/AgCl by addition of G4. From Fourier-transform infrared, nuclear magnetic resonance, and Raman spectroscopies, G4 molecules were more strongly coordinated to Li+ to form ion pairs of [Li(G4)(x)(H2O)(y)](+) complex in hybrid G4-water electrolyte. Co-intercalation of bis(trifluoromethanesulfonyl)imide (TFSI-) and bis(fluorosulfonyl)imide (FSI-) into graphitic carbon KS6 cathode was confirmed in hybrid aqueous electrolyte.

DOI： 10.1002/cssc.202201805

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

CO(2 )photoreduction on photocatalysts is a nature-friendly solution to decrease the CO2 amount, but the method still has low efficiency because of difficult separation and easy recombination of charge carriers in available catalysts. In this study, a high-entropy oxynitride was introduced as an active photocatalyst for photoreduction. The material had a chemical composition of TiZrNbHfTaO6N3 and was produced by a high-pressure torsion method followed by oxidation and nitriding. It showed higher photocatalytic CO2 to CO conversion compared to corresponding high-entropy oxide, benchmark photocatalyst P25 TiO2, and almost all catalysts introduced in the literature. The high activity of this oxynitride, which also showed good chemical stability, was attributed to the large absorbance of light and easy separation of electrons and holes, the low recombination of charge carriers, and the high CO(2 )adsorption on the surface. These findings introduce high-entropy oxynitrides as promising photocatalysts for CO(2 )photoreduction.

DOI： 10.1016/j.cej.2022.137800

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Strained metal oxides are known to exhibit improved activity for redox and photocatalytic reactions. Here, we intentionally introduced tensile strain into rutile-type TiO2 by utilizing the difference in thermal expansion coefficients between TiO2 and Au and applied it as a solid acid catalyst. It was demonstrated that its acid catalytic activity in the acetalization of furfural was enhanced by increasing the degree of the strain introduced.

DOI： 10.1039/d2cy00736c

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Petroleum Institute  

<p>The particle size effect of platinum nanoparticles on the conversion of methane (CH₄) into hydrogen cyanide (HCN) using nitric oxide (NO) as an oxidant over the Pt supported (γ + θ)-alumina was investigated. The Pt catalysts with various average particle size in the range of 1.6 to 4.1 nm were obtained by controlling the loading amount and calcination temperature. Amount of the Pt surface sites was determined by CO titration using a pulse method and the catalytic activity was evaluated under same contact time. In case of the catalysts having small particle size (1.6-3.2 nm) of Pt, NO conversion was lower than the large one. The catalysts having large particle size (4.1-4.2 nm) exhibited high selectivity of HCN reaching 53.5 % at 1.3 % C-based yield at 400 °C over 10 wt% Pt/Al₂O₃. One of the reasons for higher activity with the larger Pt particles is suppression of the sequential reaction of HCN to carbon dioxide and ammonia which likely proceeded at the interface between metal and support. Pt L₃-edge X-ray adsorption fine structure (XAFS) spectra showed that the small particle catalysts were covered with Pt–CN species after the reaction test. In contrast, Pt–CO was observed as main adsorbed species on the large particle catalysts, suggesting that HCN desorption process was facile for the larger Pt particle case.</p>

DOI： 10.1627/jpi.65.184

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DOI： 10.1016/j.cej.2022.136209

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Novel donor-acceptor dyads containing [2.2]- and [3.3]paracyclophane (PCP) as the bridging moiety were synthesized and used to effectively fabricate dye-sensitized hydrogen production systems. All the prepared compounds had a phenothiazine and a cyanoacrylic acid/pyridinyl acrylonitrile moiety acting as an electron donor and acceptor, respectively. Although cyclic voltammetry measurements showed similar electron-donating properties among all the synthesized dyads, the lowest absorption energy of the [2.2]PCP moiety was lower than that of the [3.3]PCP one; this was due to its shorter distance between benzene rings, which could effectively drive the charge transfer between the donor and acceptor chromophores. Under visible light (>395 nm), a dyad-loaded photocatalyst in a 0.5 M aqueous glycerol solution generated detectable hydrogen gases. The optimal turnover number and photocurrent order exhibited the same trend as the hydrogen production rate since the suggested number of excited photons played a critical role in hydrogen production.

DOI： 10.1002/chem.202200790

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The modification effect of acene dyes such as 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-PEN) and difuranoan-thracene derivatives on the photocatalytic water splitting activity of Pt-loaded KTa(Zr)O-3 was studied. The surface modification of KTa(Zr)O-3 powder with acene dyes was conducted with an evaporation-to-dryness method using pyridine as a solvent. TIPSPEN is the most effective dye for increasing the hydrogen formation rate on the KTa(Zr)O-3 catalyst, which became larger by 14 times. The fluorescence spectrum of the TIPS-PEN-modified catalyst revealed that the excitation energy of KTa(Zr)O(3 )was transferred to the Pt cocatalyst through the TIPS-PEN moiety. The wavelength dependence of the photocatalytic activity was investigated, and the water splitting activity was improved by irradiating with both ultraviolet and visible light comparing with the case of irradiating with only ultraviolet light. Furthermore, the water splitting reaction did not occur under visible light irradiation, which suggests that a Z-scheme-type water splitting reaction, that is, a two-step photoexcitation mechanism similar to that occuring in plant photosynthesis, proceeded on PtOx/TIPS-PEN/KTa(Zr)O-3.

DOI： 10.1021/acs.jpcc.2c02532

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Publisher：Electrochemical Science Advances  

The addition of 3,3,3-trifluoropropyl acetate (TFPA) to electrolyte in a Li-ion rechargeable battery (LIB) provides a means for increasing the discharge performance at low temperatures as a result of the formation of a superior solid electrolyte interphase (SEI) on the graphite anode. For instance, the addition of 2 wt% TFPA to the electrolyte significantly increased the cycle stability and the discharge capacities at low temperatures (-10°C) even at current rates of 3 C. The SEI films formed on the graphite anodes were characterized by electrochemical and spectroscopic techniques and by computational analysis. Although the formation of LiF on the anode has been recognized, present research revealed that the decomposition of TFPA on the anode surface resulted in the formation of an SEI layer consisting predominantly of organic fluorides. This layer suppressed the decomposition of the electrolyte resulting in a decreased anode impedance and an increase in cycle stability and discharge capacity at low temperatures.

DOI： 10.1002/elsa.202100062

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

Porous boron nitride was synthesized using boric acid with urea and/or hexamethylenetetramine (HMTA) via pyrolysis method. X-ray diffraction and Fourier transform infrared measurements indicated that the synthesized boron nitride has a turbostratic structure with both amino and hydroxyl group on the surface. The synthesis using a mixture of two nitrogen-containing precursors was found to not only significantly increase the porosity, but also improve the surface functionality. X-ray photoelectron spectroscopy and B K-edge and O K-edge X-ray absorption fine structure measurements revealed that the proportion of amino and hydroxyl groups on the surface increased with increasing concentration of HMTA during synthesis. Solid-state 11B nuclear magnetic resonance spectroscopy indicated that all samples contained trigonal B-N, trigonal B-O and tetrahedral B-O sites, and that samples prepared with high concentrations of HMTA had less tetrahedral B-O sites, suppressing the formation of BOx species as byproducts. Solid base catalytic activity was evaluated through Knoevenagel condensation, and the catalytic performance was significantly improved by synthesizing boron nitride catalyst using a mixture of the two nitrogen-containing precursors. The enhancement of the activity was influenced by the development of the pore structure as well as the emergence of functional groups on the surface.

DOI： 10.1016/j.apcata.2022.118635

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DOI： 10.1016/j.apcatb.2021.120896

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Charge-discharge performance at -30 degrees C was studied by using low-viscosity ester solvents (propyl acetate (PA), propyl propionate (PP), and ethyl propionate (EP)) as electrolyte for improving the low-temperature performance of lithium-ion rechargeable batteries. Among the studied ester, PA based electrolyte shows the most superior cycle stability, and it was found that EC-PA based electrolyte increased the discharge capacity of the cell at -30 degrees C by 6% compared to the EC-DEC based electrolyte. Although the cell capacity at low temperature was increased, favorable solid electrolyte interface (SEI) may not be formed and the cycle stability was decreased in the cell using PA component as the electrolyte. By using an electrolyte additive for SEI formation in combination with PA based electrolyte, the low temperature discharge capacity and cycle stability were much increased which is strongly demanded for electric vehicle application.

DOI： 10.1246/bcsj.20210185

Language：English   Publishing type：Research paper (scientific journal)  

Heptacene (1) has been produced via a monoketone precursor, 2, which was prepared from 1,2,4,5-tetrabromobenzene in nine steps in a total yield of 10 %. Compound 2 was converted to 1 quantitatively by heating at 202 degrees C. Heptacene exhibited high thermal stability in the solid state without any observable change over two months. To investigate the potential value of 1 as a material for p-type organic field-effect transistors (OFETs), top-contact OFET devices were fabricated by vacuum deposition of 1 onto a hexamethyldisilazane (HMDS)/SiO2/Si substrate. The best hole mobility performance was 2.2 cm(2) V-1 s(-1). This is the first report of stable heptacene being used in an effective device and examined for its charge carrier properties.

DOI： 10.1002/chem.202100936

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Metal oxynitrides are promising photocatalysts due to their narrow bandgap, but their lower stability compared to metal oxides is a drawback. The introduction of high-entropy alloys with entropy-stabilization features has shown high potential for various functional applications in recent years. By considering these two types of materials, we developed a high-entropy oxynitride for photocatalytic water splitting. The material, with a general composition of TiZrHfNbTaO6N3 and a d(0) electronic configuration, showed a narrow bandgap of 1.6 eV, which is much lower than the bandgaps of relevant binary and high-entropy oxides. The material exhibited photocurrent generation and photocatalytic hydrogen production with high chemical stability, suggesting the high potential of high-entropy oxynitrides as advanced low-bandgap and stable photocatalysts.

DOI： 10.1039/d1ta03861c

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A high-concentration aqueous electrolyte with a wide electrochemical stability window represents a novel development direction for traditional aqueous batteries. Herein, a novel high-concentration water-in-bisalt electrolyte using LiFSI (lithium bis(fluorosulfonyl)imide) and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) as supporting salts was first applied as an electrolyte of a dual-ion battery, and the solvated structure changes were studied in detail. Electronic interactions were detected between the two supporting salts. Furthermore, when 37 mol/kg LiFSI-LiTFSI/H2O was applied to a 3 V dual-ion battery, by using graphitic carbon (KS6) and activated carbon (AC) as cathode and anode materials, the full cell delivered a high specific capacity of 72 mAh/g. In addition, excellent cycling stability for (>)100 cycles was achieved with negligible capacity fading.

DOI： 10.1016/j.ensm.2021.03.029

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The aggregation states and physical properties of polymers in thin films deviate from those found in the bulk. Although an effect of the thickness on the carrier mobility for thin films of poly(3-hexylthiophene) (P3HT) has been widely studied, there is a lack of discussion in terms of crystallographic distortion. Here, we demonstrate how the out-of-plane hole mobility in P3HT, which is a typical semiconducting polymer, changes with decreasing film thickness. Time-of-flight measurements with an analysis using the Gaussian disorder model revealed that the zero-field out-of-plane hole mobility decreased with decreasing thickness because of an increase in the energetical and spatial distribution of hopping sites. Grazing incidence wide-angle x-ray diffraction measurements revealed that such distributions of charge carriers were induced by the crystallographic distortion of P3HT in the thin films.

DOI： 10.1063/5.0041881

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To develope an alternative efficient hole-transporting materials (HTMs) to 2,2',7,7',-tertrakis(N,N-p-dimethox-yphenylamino)-9,9'-spirobifuorene (spiro-OMeTAD) for high performance perovskite solar cells (PSCs), we demonstrate a series of donor-pi-donor HTMs (WS-1, WS-2, and WS-4 HTMs) with [2.2]paracyclophane ([2.2] PCP) as the core structure and triphenylamine as four arms at pseudo-para and pseudo-ortho orientations. Compared with the well-known HTM of spiro-OMeTAD, WS-HTMs has a simpler synthetic route and short synthesis steps (3-4 steps). Due to the improved hole mobility and good charge transfer efficiency of pseudo-para- [2.2]PCP HTMs (WS-1 and WS-2), the out-of-plane carrier transport is enhanced and the PSC base on WS-1/WS-2 HTMs achieve higher J(sc) and ff values than the device based on pseudo-ortho-[2.2]PCP HTM (WS-4). A SnO2 electron transport layer (ETL) with WS-1 HTM shows the best power conversion efficiency of 19.13% in a PSC, which is higher than that of spiro-OMeTAD (17.71%) under the same conditions. The WS-HTMs also provided better stability and moisture resistance in PSCs, which prolongs the lifetime in the ambient environment than in case of spiro-OMeTAD.

DOI： 10.1016/j.jpowsour.2021.229543

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Co-intercalation of Hexafluorophosphate(PF6-) and Bis(trifluoromethane sulfonyl)imide (TFSI-) anions as a result of the use of a mixed salt of LiPF6 and LiTFSI is studied for the increased performance of a dual-carbon battery (DCB). Unlike the fluorineor the imide-based anions (e.g., PF6- and TFSI-), the cluster formation between co intercalated PF6- and TFSI- in the positive electrode of a DCB results in achieving high discharge capacities with significantly increased cycle properties. A reversible discharge capacity of 85 mAh/g-cathode over 350 cycles with no significant degradation is presented. The Coulombic efficiency of almost 100% is reached after the initial 10 cycles and suitable rate property is also observed. F NMR analysis on graphitic carbon intercalated with PF6- and TFSI- suggests the interaction between two anions and ratio of intercalated PF6 and TFSIwas changed by applied voltage, resulting in the increased stability of the intercalated structure which is also supported by the first principles calculations.

DOI： 10.1016/j.jpowsour.2020.229084

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SrTiO3 is a well-known highly active photocatalyst with high energy conversion efficiency. In this study, we investigated the formation of oxygen vacancy by using the chemo-mechanical effect that was introduced by the dispersion of metal particles into grain and photocatalytic activity to water splitting. Au dispersion on SrTiO3 followed by sintering treatment was studied for introduction of chemo-mechanical strain because of a different thermal expansion coefficient; the introduced chemo-mechanical strain generated oxygen vacancy in SrTiO3. Thus, induced chemo-mechanical strain shows change in electronic band structure resulting in increasing lowest unoccupied molecular orbital (LUMO) level with increasing Au content. Since photoluminescence was significantly decreased by sintering after Au dispersion, the introduced strain effects may work for increasing a charge separation efficiency and adsorption site in water splitting. Therefore, the photocatalytic activity was much increased by sintering treatment after Au dispersion on SrTiO3.

DOI： 10.1016/j.apcatb.2020.119292

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Porous boron nitride was synthesized by pyrolysis from boric acid and urea mixed in varying molar ratios. The boron nitride prepared had high surface areas ranging from 376 to 647 m(2) g(-1)with both microporous and mesoporous structures. The sample prepared with a urea-to-boric acid molar ratio of 5 exhibited the highest pore volume with the highest surface area of mesopores. Boron-K edge X-ray absorption fine structure spectroscopy revealed that the surface structure consisted of BN(3)sites along with BN2O, BNO2, and BO(3)sites. Fourier transform infrared (FTIR) spectroscopy indicated the formation of amino and hydroxyl groups on the surface. Analysis using color indicator reagents and deuterated chloroform-adsorbed FTIR results indicated that the porous boron nitride had very weak base sites of strength +7.2>H->=+6.3. Porous boron nitride exhibited a high activity for the nitroaldol reaction with a high selectivity for nitroalkene (>97 %). A good correlation was observed between the catalytic activity of the boron nitride catalysts and their porous structures.

DOI： 10.1002/cctc.202001435

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An inorganic-biological hybrid system that integrates features of both stable and efficient semiconductors and selective and efficient enzymes is attractive for facilitating the conversion of solar energy to hydrogen. In this study, we aimed to develop a new photocatalytic hydrogen-production system based onEscherichia coliwhole-cell genetically engineered as a biocatalysis for highly active hydrogen formation. The photocatalysis part was obtained by bacterial precipitation of cadmium sulfide (CdS), which is a visible-light-responsive semiconductor. The recombinantE. colicells were sequentially subjected to CdS precipitation and heterologous [FeFe]-hydrogenase synthesis to yield a CdS@E. colihybrid capable of light energy conversion and hydrogen formation in a single cell. The CdS@E. colihybrid achieved photocatalytic hydrogen production with a sacrificial electron donor, thus demonstrating the feasibility of our system and expanding the current knowledge of photosensitization using a whole-cell biocatalyst with a bacterially precipitated semiconductor.

DOI： 10.1002/cbic.202000383

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Porous boron nitride (BN) was synthesized using a pyrolysis method in conjunction with varying NH3 flow rates, followed by washing as a post-treatment. The performance of this material as a solid base catalyst was assessed. It was found that the post-treatment rather than the synthesis conditions significantly improved the activity of the BN during the nitroaldol reaction. The BN catalyst obtained after washing gave a ten times higher product yield. Both an increase in the surface areas of the material and the emergence of micropores after washing were observed. B-11 solid-state nuclear magnetic resonance spectroscopy demonstrated that boron oxide species were present in the BN after synthesis but were removed by the washing process. B K-edge X-ray absorption fine structure analyses indicated the formation of oxygen-substituted trigonal boron sites on the BN surface. Fourier transform infrared spectroscopy showed that amino groups on the samples functioned as moderately strong basic sites.

DOI： 10.1016/j.apcata.2020.117843

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DOI： https://doi.org/10.1016/j.scriptamat.2020.06.052

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Bismuth oxide (Bi2O3), a yellow semiconductor ceramic, is considered as an advanced photoactive energy material, but its activity still needs further improvement for practical applications. In this study, black Bi2O3 with nanocrystalline structure and large fraction of oxygen vacancies is synthesized by mechanical straining via the high-pressure torsion (HPT) method. The black oxide exhibits enhanced light absorbance under both UV and visible lights. It shows a bipolar photocurrent behavior with up to six times higher photocurrent density compared with the unprocessed yellow Bi2O3. This study shows the high potential of severely-strained black Bi2O3 for photovoltaic, photoconductivity and photocatalytic applications. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2020.06.052

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Artificial photosynthesis from CO₂ reduction to methane is severely hampered by the kinetically challenging eight-electron transfer process. Accumulated electrons has been demonstrated can decrease this kinetic barrier. However, charge accumulation were mainly reported in several homogenous systems because of its difficulties in heterogenous systems. Here we identify that highly accumulated electrons exist in Au loaded ultrathin MoS₂ under light irradiation, resulting in a superior performance of CO₂ reduction to methane. The selectivity for methane is up to 80 % with an average production rate of about 19.38 μmolg⁻¹ h⁻¹ in pure water. Further detailed studies reveal that plasmon-excited hot electrons transfer from Au to charged excitons in ultrathin MoS₂ promotes electron accumulation and multi-electron CO₂ reduction kinetics for methane generation. This is further supported by the CO₂ reduction performance of Ag-MoS₂. Along with the vanished accumulated electrons, CO is the main product with a selectivity of 98 %.

DOI： 10.1016/j.apcatb.2020.118931

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Artificial photosynthesis from CO2 reduction to methane is severely hampered by the kinetically challenging eight-electron transfer process. Accumulated electrons has been demonstrated can decrease this kinetic barrier. However, charge accumulation were mainly reported in several homogenous systems because of its difficulties in heterogenous systems. Here we identify that highly accumulated electrons exist in Au loaded ultrathin MoS2 under light irradiation, resulting in a superior performance of CO2 reduction to methane. The selectivity for methane is up to 80 % with an average production rate of about 19.38 mu molg(-1) h(-1) in pure water. Further detailed studies reveal that plasmon-excited hot electrons transfer from Au to charged excitons in ultrathin MoS2 promotes electron accumulation and multi-electron CO2 reduction kinetics for methane generation. This is further supported by the CO2 reduction performance of Ag-MoS2. Along with the vanished accumulated electrons, CO is the main product with a selectivity of 98 %.

DOI： 10.1016/j.apcatb.2020.118931

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Direct decomposition of NO on Ba3Y4O9 doped with Cu and Sc was studied and it was found that co-doping of Sc and Cu into Ba3Y4O9 was effective for increasing both lattice stability and NO decomposition activity. In particular, Ba3Y3Sc0.6Cu0.4O9 (10 % Cu and 15 % Sc doping) catalyst showed N-2 and O-2 yield of 90 % and 99 %, respectively, in NO decomposition reaction at 700 degrees C. Comparing with the pristine and single-metal doped system, the optimized catalyst showed superior long-term stability and increased activity under O-2, and water vapor co-existence conditions because of the increased stability of crystal structure, improved lattice oxygen mobility and weakened oxygen adsorption on the surface. TPD and in-situ FT-IR results suggested that the co-doping effect was assigned to the easier removal of surface NO2- or NO3- species which blocks the active site to NO decomposition.

DOI： 10.1016/j.apcata.2020.117743

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Photocatalytic water splitting on Pt/KTa(Zr)O-3 modified with poly(3-hexylthiophene-2,5-diyl) (P3HT) as a photoconductive organic polymer is investigated. The photocatalyst powder of Pt/P3HT/KTa(Zr)O-3 was synthesized by evaporation to dryness method. The H-2/O-2 production ratio of the unmodified catalyst was 2.90, whereas the H-2/O-2 production ratio become close to 2 (1.66-2.26) with loading P3HT (0.1 wt% to 0.8 wt%). The optimum amount of P3HT added was 0.4 wt% and the H-2/O-2 production ratio was 2.00, which increased the hydrogen production rate by 476 % compared to the unmodified photocatalyst. As a result of the fluorescence lifetime measurement, when the dye and platinum were supported on KTa(Zr)O-3, charge separation into the dye and platinum was confirmed in both UV and visible light irradiation. Irradiation with visible light in addition to UV light increased the water splitting activity, while water decomposition was not performed only with visible light, suggests Z-scheme type water splitting reaction.

DOI： 10.1016/j.apcata.2020.117737

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Magnesium oxide (MgO), which is an insulator ceramic with high significance in geology and earth sciences, is not generally considered as a photocatalyst due to its wide bandgap as ~7.8 eV. Experimental studies show that nanocrystalline MgO can have optical bandgaps down to 5.25–5.95 eV and density functional theory calculations suggest that the introduction of oxygen vacancies can reduce the optical bandgap below 5 eV. In this study, oxygen monovacancies and divacancies (F, F⁺ and F₂ ⁺ centers) are experimentally introduced in nanocrystalline MgO by severe plastic deformation via the high-pressure torsion (HPT) method. The overall optical bandgap is successfully reduced to 3.9 eV after HPT processing. The HPT-processed samples exhibit photocatalytic dye degradation, while the degradation rate improves with increasing the imposed strain. These results not only confirm that the simultaneous introduction of oxygen vacancies and nanocrystals is quite effective to tune the optical properties of nanocrystalline MgO as a nature-friendly photocatalyst, but also introduce a pressure-strain-based mechanism for the formation of vacancy defects in MgO-based minerals.

DOI： 10.1016/j.mtla.2020.100670

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Titanium oxide (TiO2), with the anatase and rutile structures, has been widely studied for photovoltaic and solar cell applications, but its main drawback is large bandgap, which limits its activity to the UV light region. In this study, a high-pressure TiO2-II (columbite) phase, which has already been suggested to have low bandgap with downward-shifted Fermi level, is stabilized by the high-pressure torsion (HPT) method and its photovoltaic activity is examined. The TiO2-II formation by HPT processing leads to photocurrent generation under visible light, while the visible-light photocurrent is enhanced further after the recovery of oxygen vacancies by thermal annealing.

DOI： 10.1021/acs.jpcc.0c03923

Language：English   Publishing type：Research paper (scientific journal)  

The need for sustainable, renewable and low-cost approaches is a driving force behind the development of solar-to-H(2)conversion technologies. This study aims to develop a new strategy using a visible-light photocatalyst coupled to a biocatalyst for H(2)production. Photocatalytic methyl viologen (MV2+) reduction activity was investigated to discover active oxynitrides. In comparative studies with LaTiO2N, BaTaO2N and Ta3N5, it was revealed that the suitable surface area, band gap and band edge potentials are some physical factors that are responsible for the photocatalytic behaviors of GaN:ZnO in MV(2+)reduction. The activity is enhanced at higher concentrations and the alkaline pH of triethanolamine (TEOA). The expression of an active [FeFe]-hydrogenase fromEscherichia coli(Hyd(+)E. coli) as a recombinant biocatalyst was confirmed by its MV center dot+-dependent H(2)production activity. In the photobiocatalytic system of GaN:ZnO and Hyd(+)E. coli, the rate of H(2)production reached the maximum level in the presence of MV(2+)as an electron mediator at neutral pH as a biocompatible condition. The present work reveals a novel hybrid system for H(2)production using visible-light active GaN:ZnO coupled to Hyd(+)E. coli, which shows the feasibility of being developed for photobiocatalytic H(2)evolution under solar light.

DOI： 10.1039/d0cy00128g

Language：English   Publishing type：Research paper (scientific journal)  

Magnesium oxide (MgO), which is an insulator ceramic with high significance in geology and earth sciences, is not generally considered as a photocatalyst due to its wide bandgap as similar to 7.8 eV. Experimental studies show that nanocrystalline MgO can have optical bandgaps down to 5.25-5.95 eV and density functional theory calculations suggest that the introduction of oxygen vacancies can reduce the optical bandgap below 5 eV. In this study, oxygen monovacancies and divacancies (F, F+ and F-2(+) centers) are experimentally introduced in nanocrystalline MgO by severe plastic deformation via the high-pressure torsion (HPT) method. The overall optical bandgap is successfully reduced to 3.9 eV after HPT processing. The HPT-processed samples exhibit photocatalytic dye degradation, while the degradation rate improves with increasing the imposed strain. These results not only confirm that the simultaneous introduction of oxygen vacancies and nanocrystals is quite effective to tune the optical properties of nanocrystalline MgO as a nature-friendly photocatalyst, but also introduce a pressure-strain-based mechanism for the formation of vacancy defects in MgO-based minerals.

DOI： 10.1016/j.mtla.2020.100670

Language：English   Publishing type：Research paper (scientific journal)  

Dye-sensitized photocatalytic hydrogen production using a boron-dipyrromethene (BODIPY) organic material having a pyridyl group at the anchor site was investigated. Phenyl, carbazole, and phenothiazine derivatives were introduced into BODIPY dyes, and their photocatalytic activities were examined. Identification was performed by nuclear magnetic resonance (NMR), infrared (IR), mass (MS) spectra, and absorption spectra, and catalyst evaluation was performed by using visible-light irradiation and photocatalytic hydrogen production and photocurrent. These dyes have strong absorption at 600–700 nm, suggesting that they are promising as photosensitizers. When the photocatalytic activity was examined, stable catalytic performance was demonstrated, and the activity of the Pt-TiO₂ photocatalyst carrying a dye having a carbazole group was 249 μmol/g_cat·h. Photocurrent measurements suggest that dye-sensitized photocatalytic activity is occurring. This result suggests that BODIPY organic materials with pyridyl groups as anchor sites are useful as novel dye-sensitized photocatalysts.

DOI： 10.3390/catal10050535

Language：English   Publishing type：Research paper (scientific journal)  

Dye-sensitized photocatalytic hydrogen production using a boron-dipyrromethene (BODIPY) organic material having a pyridyl group at the anchor site was investigated. Phenyl, carbazole, and phenothiazine derivatives were introduced into BODIPY dyes, and their photocatalytic activities were examined. Identification was performed by nuclear magnetic resonance (NMR), infrared (IR), mass (MS) spectra, and absorption spectra, and catalyst evaluation was performed by using visible-light irradiation and photocatalytic hydrogen production and photocurrent. These dyes have strong absorption at 600-700 nm, suggesting that they are promising as photosensitizers. When the photocatalytic activity was examined, stable catalytic performance was demonstrated, and the activity of the Pt-TiO(2)photocatalyst carrying a dye having a carbazole group was 249 mu mol/g(cat)center dot h. Photocurrent measurements suggest that dye-sensitized photocatalytic activity is occurring. This result suggests that BODIPY organic materials with pyridyl groups as anchor sites are useful as novel dye-sensitized photocatalysts.

DOI： 10.3390/catal10050535

Language：English   Publishing type：Research paper (scientific journal)  

Stable photoelectrochemical (PEC) operation is a critical issue for the commercialization of PEC water-splitting systems. Unfortunately, most semiconductor photocathodes generating hydrogen in these systems are unstable in aqueous solutions. This is a huge limitation for the development of durable PEC water-splitting systems. Lanthanum iron oxide (LaFeO3) is a promising p-type semiconductor to overcome this drawback because of its stability in an aqueous solution and its proper energy level for reducing water. In this study, we fabricated a crystalline LaFeO3 thin film by radio frequency magnetron sputtering deposition and a post-annealing process in air for use as a PEC photocathode. Based on the morphological, compositional, optical and electronic characterizations, we found that it was ideal for a visible light-responsive PEC photocathode and tandem PEC water-splitting system with a small band gap absorber behind it. Furthermore, it showed stable PEC performance in a strong alkaline solution during PEC operation without any protection layers. Therefore, the crystalline sputtered LaFeO3 thin film suggested in this study would be feasible to apply as a PEC photocathode for durable, simple and low-cost PEC water splitting.

DOI： 10.1039/d0nr01762k

Language：English   Publishing type：Research paper (scientific journal)  

The direct decomposition of nitrogen oxides (NO_X) is an ideal way to remove NO_X pollution created by chemical industries and automobiles. Ba₃Y₄O₉ is a promising candidate for the NO_X direct decomposition reaction, however, its catalytic activity is not high enough and the stability is insufficient. Here, NO decomposition activity on several metal ion doped Ba₃Y₄O₉ catalysts is reported and it is found that Cu is the most effective for increasing the activity. With 10% Cu doping, the catalytic activity and the stability were improved simultaneously. Temperature programmed desorption (TPD) results indicate that doping with Cu increased the amount of surface oxygen vacancies and mobility of the lattice oxygen resulting in an increase of NO adsorption and the promotion of the decomposition of NO_X intermediate species. In situ FT-IR spectra prove that Cu doping weakened the association of NO₃^- species, thus promoting the decomposition of NO₃^- species at low temperatures, which resulted in high catalytic activity for NO_X decomposition. These results indicate that introducing Cu into the Ba₃Y₄O₉ system is an effective way to achieve high activity and a stable catalyst for the direct decomposition of NO_X.

DOI： 10.1039/d0cy00194e

Language：English   Publishing type：Research paper (scientific journal)  

The direct decomposition of nitrogen oxides (NOX) is an ideal way to remove NOX pollution created by chemical industries and automobiles. Ba3Y4O9 is a promising candidate for the NOX direct decomposition reaction, however, its catalytic activity is not high enough and the stability is insufficient. Here, NO decomposition activity on several metal ion doped Ba3Y4O9 catalysts is reported and it is found that Cu is the most effective for increasing the activity. With 10% Cu doping, the catalytic activity and the stability were improved simultaneously. Temperature programmed desorption (TPD) results indicate that doping with Cu increased the amount of surface oxygen vacancies and mobility of the lattice oxygen resulting in an increase of NO adsorption and the promotion of the decomposition of NOX intermediate species. In situ FT-IR spectra prove that Cu doping weakened the association of NO3- species, thus promoting the decomposition of NO3- species at low temperatures, which resulted in high catalytic activity for NOX decomposition. These results indicate that introducing Cu into the Ba3Y4O9 system is an effective way to achieve high activity and a stable catalyst for the direct decomposition of NOX.

DOI： 10.1039/d0cy00194e

Language：English   Publishing type：Research paper (scientific journal)  

Oxynitrides are considered as new potential candidates for photocatalysis due to their lower bandgap compared with traditional oxide photocatalysts. However, the formation of native nitrogen monovacancies during the synthesis of oxynitrides reduces their photocatalytic activity due to the vacancy-induced electron/hole recombination. This study shows that a transition from the native nitrogen monovacancies to the nitrogen-based vacancy complexes in a GaN–ZnO oxynitride not only diminishes the recombination but also enhances the photocatalytic hydrogen production. Here, the vacancy complexes are introduced by mechanical straining via the high-pressure torsion (HPT) method and it is shown that the vacancy complexes reduce the bandgap and increase the over-potential for hydrogen production on the conduction band. The current results introduce a simple but effective approach to turn the nitrogen vacancies to favorable defects for photocatalysis.

DOI： 10.1016/j.actamat.2019.12.007

Language：English   Publishing type：Research paper (scientific journal)  

Photocatalysis on semiconductors using solar energy sources provides a clean technology to produce hydrogen from water splitting. Although zirconia (ZrO2) is a semiconductor oxide, it is not generally considered as a photocatalyst owing to its poor light absorbance and wide bandgap (over 5 eV). In this study, black ZrO2 with a large concentration of lattice defects such as oxygen vacancies, dislocations and nanograin boundaries is stabilized by high-pressure torsion (HPT) straining. The black ZrO2, which experiences monoclinic-tetragonal phase transformations during the HPT process, shows large light absorption, a small bandgap, reduced conduction band energy and high photocatalytic activity for hydrogen evolution due the presence of oxygen vacancies. These results confirm that the introduction of strain-induced oxygen vacancies is a potential method to produce low-bandgap photocatalysts.

DOI： 10.1039/c9ta11839j

Language：English   Publishing type：Research paper (scientific journal)  

Tantalate perovskites are potential candidates for photocatalytic hydrogen production without cocatalyst addition; however, these oxides have large bandgaps, which result in their low photocatalytic activity. In this study, to enhance the photocatalytic activity, CsTaO3 as a potential photocatalyst and LiTaO3 as a well-known photocatalyst are subjected to severe plastic strain using the high-pressure torsion (HPT) method. Both superstrained tantalates exhibit optical bandgap narrowing and similar to 2.5 times enhancement of photocatalytic hydrogen production. Such bandgap narrowing is mainly due to the formation of oxygen vacancies, although nanocrystal formation and partial amorphization also occur by straining. These findings not only introduce CsTaO3 as a photocatalyst but also confirm the significance of strain-induced vacancies on the photocatalytic activity of perovskites.

DOI： 10.1021/acsaem.9b02197

Language：English   Publishing type：Research paper (scientific journal)  

Oxynitrides are considered as new potential candidates for photocatalysis due to their lower bandgap compared with traditional oxide photocatalysts. However, the formation of native nitrogen monovacancies during the synthesis of oxynitrides reduces their photocatalytic activity due to the vacancy-induced electron/hole recombination. This study shows that a transition from the native nitrogen monovacancies to the nitrogen-based vacancy complexes in a GaN-ZnO oxynitride not only diminishes the recombination but also enhances the photocatalytic hydrogen production. Here, the vacancy complexes are introduced by mechanical straining via the high-pressure torsion (HPT) method and it is shown that the vacancy complexes reduce the bandgap and increase the over-potential for hydrogen production on the conduction band. The current results introduce a simple but effective approach to turn the nitrogen vacancies to favorable defects for photocatalysis. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actamat.2019.12.007

Language：English   Publishing type：Research paper (scientific journal)  

Photocatalysis on semiconductors using solar energy sources provides a clean technology to produce hydrogen from water splitting. Although zirconia (ZrO₂) is a semiconductor oxide, it is not generally considered as a photocatalyst owing to its poor light absorbance and wide bandgap (over 5 eV). In this study, black ZrO₂ with a large concentration of lattice defects such as oxygen vacancies, dislocations and nanograin boundaries is stabilized by high-pressure torsion (HPT) straining. The black ZrO₂, which experiences monoclinic-tetragonal phase transformations during the HPT process, shows large light absorption, a small bandgap, reduced conduction band energy and high photocatalytic activity for hydrogen evolution due the presence of oxygen vacancies. These results confirm that the introduction of strain-induced oxygen vacancies is a potential method to produce low-bandgap photocatalysts.

DOI： 10.1039/c9ta11839j

Language：English   Publishing type：Research paper (scientific journal)  

Tantalate perovskites are potential candidates for photocatalytic hydrogen production without cocatalyst addition; however, these oxides have large bandgaps, which result in their low photocatalytic activity. In this study, to enhance the photocatalytic activity, CsTaO₃ as a potential photocatalyst and LiTaO₃ as a well-known photocatalyst are subjected to severe plastic strain using the high-pressure torsion (HPT) method. Both superstrained tantalates exhibit optical bandgap narrowing and ∼2.5 times enhancement of photocatalytic hydrogen production. Such bandgap narrowing is mainly due to the formation of oxygen vacancies, although nanocrystal formation and partial amorphization also occur by straining. These findings not only introduce CsTaO₃ as a photocatalyst but also confirm the significance of strain-induced vacancies on the photocatalytic activity of perovskites.

DOI： 10.1021/acsaem.9b02197

Language：English   Publishing type：Research paper (scientific journal)  

Photocatalytic water splitting is the most ideal system to harvest solar energy for the production of useful chemicals. There have been many attempts to increase the photocatalytic activity of the TiO₂ photocatalyst, such as loading co-catalysts and dopants, and the introduction of oxygen vacancies. Strain effects have also attracted much interest to increase the charge mobility in bulk oxide. Here, we report on the effectiveness of tensile strain in stabilizing the anatase phase of TiO₂ at high temperature and increasing the photocatalytic activity by an increase in the charge separation with a unique mixed phase structure. The rate of H₂ formation over TiO₂ was decreased upon spark plasma sintering (SPS) treatment because of a decrease in the surface area; however, SPS treatment with Au dispersion significantly increased the H₂ formation rate to higher than that over commercially available P-25 TiO₂ (no SPS treatment) loaded with Au. The O₂ formation rate was also increased by strain effects in TiO₂. Furthermore, strain effects were effective for visible light sensitivity on TiO₂

DOI： 10.1039/c9ta11048h

Language：English   Publishing type：Research paper (scientific journal)  

Photocatalytic water splitting is the most ideal system to harvest solar energy for the production of useful chemicals. There have been many attempts to increase the photocatalytic activity of the TiO2 photocatalyst, such as loading co-catalysts and dopants, and the introduction of oxygen vacancies. Strain effects have also attracted much interest to increase the charge mobility in bulk oxide. Here, we report on the effectiveness of tensile strain in stabilizing the anatase phase of TiO2 at high temperature and increasing the photocatalytic activity by an increase in the charge separation with a unique mixed phase structure. The rate of H-2 formation over TiO2 was decreased upon spark plasma sintering (SPS) treatment because of a decrease in the surface area; however, SPS treatment with Au dispersion significantly increased the H-2 formation rate to higher than that over commercially available P-25 TiO2 (no SPS treatment) loaded with Au. The O-2 formation rate was also increased by strain effects in TiO2. Furthermore, strain effects were effective for visible light sensitivity on TiO2.

DOI： 10.1039/c9ta11048h

Language：English   Publishing type：Research paper (scientific journal)  

Alumina is an insulator oxide with a large abundance in the earth's crust, but it shows no photocatalytic activity due to its large bandgap (9 eV). Based on first-principles calculations, the Al₂O₃ bandgap can be reduced below 3 eV, if large oxygen vacancies are generated. Here, Al₂O₃ with large oxygen vacancy concentrations and ~2.5 eV optical bandgap is produced by severe plastic deformation via the high-pressure torsion (HPT) method. The material exhibits photocatalytic dye degradation with a reasonable rate compared with TiO₂ photocatalysis. This finding introduces a simple but effective approach to produce new nature-friendly photocatalysts even from insulator oxides.

DOI： 10.1016/j.scriptamat.2019.08.011

Language：English   Publishing type：Research paper (scientific journal)  

Spark plasma sintering (SPS) treatment was studied for Pt dispersed SrTiO3 as photocatalytic water splitting catalyst. The oxygen vacancy was introduced by SPS treatment and it was found that H-2 formation rate was increased by SPS treatment since large amount of oxygen vacancy was introduced. H-2 formation rate became the highest (6.15 mmol h(-1) g(-1)) at 2.5 wt% Pt dispersed on SrTiO3 and this H-2 formation rate was almost double of Pt loaded SrTiO3 and O-2 formation rate was also much increased (5.66 mmol h(-1) g(-1)). ESR measurement suggests that amount of Ti3+ was intense after SPS treatment with 2.5 wt% Pt. Therefore, it seems that the oxygen vacancy introduced by SPS treatment effectively worked for charge separation and photocatalytic activity of SrTiO3 to water splitting was increased.

DOI： 10.1002/cctc.201901549

Language：English   Publishing type：Research paper (scientific journal)  

Alumina is an insulator oxide with a large abundance in the earth's crust, but it shows no photocatalytic activity due to its large bandgap (9 eV). Based on first-principles calculations, the Al2O3 bandgap can be reduced below 3 eV, if large oxygen vacancies are generated. Here, Al2O3 with large oxygen vacancy concentrations and similar to 2.5 eV optical bandgap is produced by severe plastic deformation via the high-pressure torsion (HPT) method. The material exhibits photocatalytic dye degradation with a reasonable rate compared with TiO2 photocatalysis. This finding introduces a simple but effective approach to produce new nature-friendly photocatalysts even from insulator oxides. (C) 2019 Acta Materialia Inc Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2019.08.011

Language：English   Publishing type：Research paper (scientific journal)  

Spark plasma sintering (SPS) treatment was studied for Pt dispersed SrTiO₃ as photocatalytic water splitting catalyst. The oxygen vacancy was introduced by SPS treatment and it was found that H₂ formation rate was increased by SPS treatment since large amount of oxygen vacancy was introduced. H₂ formation rate became the highest (6.15 mmol h⁻¹ g⁻¹) at 2.5 wt% Pt dispersed on SrTiO₃ and this H₂ formation rate was almost double of Pt loaded SrTiO₃ and O₂ formation rate was also much increased (5.66 mmol h⁻¹ g⁻¹). ESR measurement suggests that amount of Ti³⁺ was intense after SPS treatment with 2.5 wt% Pt. Therefore, it seems that the oxygen vacancy introduced by SPS treatment effectively worked for charge separation and photocatalytic activity of SrTiO₃ to water splitting was increased.

DOI： 10.1002/cctc.201901549

Language：English   Publishing type：Research paper (scientific journal)  

The synthesis, structure, physical properties, and electrocatalytic hydrogen production of tetrathiatetracene ligand based [FeFe]-hydrogenase mimic molecules were investigated. By adjusting the amount of iron, mono- and bis-[FeFe] coordinated complexes 1 and 2 were synthesized. The structures of 1 and 2 were analysed by NMR, IR, and absorption spectroscopies, and cyclic voltammetry and DFT computational analysis. In the DFT electron density maps, the HOMOs and LUMOs were located at tetrathiatetracene units, indicating that these complexes retain mainly acene characteristics. When weak acid Et3NHBF4 was added to CH2Cl2 solutions of 1 or 2, the reduction potential of iron complexes was shifted to more positive values proportional to the concentration of acid. As the acid concentration increased, the current of the reduction wave also increased, indicating the occurrence of a catalytic proton reduction reaction. The bulk electrolysis reaction showed 65.8 TON for 1 and 52.8 TON for 2.

DOI： 10.1039/c9nj02790d

Language：English   Publishing type：Research paper (scientific journal)  

Solar water splitting to produce hydrogen is a promising solution for global energy issues. One of the main bottlenecks in this technology is the spontaneous fast backward reaction (2H₂ + O₂ → H₂O, ΔG < 0), limiting the solar energy conversion efficiency. How to suppress backward reaction is vitally important but rarely reported. Here we found that single-electron-trapped oxygen vacancy (Vo·) can suppress spontaneous backward reaction in pure water splitting. Taking WO₃·0.33H₂O catalyst as an example, ultrathin WO₃·0.33H₂O {100} facets with large amount of surface Vo· realized a continuous H₂ evolution from pure water splitting with a productivity of 9.9 μmol/g·h without the assistance of any sacrifice agent and noble metal cocatalyst. Quantum chemical calculations revealed that the backward-reaction suppression ability of Vo· is attributed to the high concentration of localized electrons around Vo·, stimulating unidirectional simultaneous water dissociation into H and OH under light irradiation.

DOI： 10.1021/acs.jpclett.9b01032

Language：English   Publishing type：Research paper (scientific journal)  

Solar water splitting to produce hydrogen is a promising solution for global energy issues. One of the main bottlenecks in this technology is the spontaneous fast backward reaction (2H(2) + O-2 -> H2O, Delta G < 0), limiting the solar energy conversion efficiency. How to suppress backward reaction is vitally important but rarely reported. Here we found that single-electron-trapped oxygen vacancy (Vo center dot) can suppress spontaneous backward reaction in pure water splitting. Taking WO3 center dot 0.33H(2)O catalyst as an example, ultrathin WO3 center dot 0.33H(2)O {100} facets with large amount of surface Vo center dot realized a continuous H-2 evolution from pure water splitting with a productivity of 9.9 mu mol/g.h without the assistance of any sacrifice agent and noble metal cocatalyst. Quantum chemical calculations revealed that the backward-reaction suppression ability of Vo center dot is attributed to the high concentration of localized electrons around Vo center dot, stimulating unidirectional simultaneous water dissociation into H and OH under light irradiation.

DOI： 10.1021/acs.jpclett.9b01032

Language：English   Publishing type：Research paper (scientific journal)  

Photocatalytic water splitting or CO
₂
reduction is one of the most promising strategies for solar energy conversion into hydrogen-containing fuels. However, these two processes typically compete with each other, which significantly decreases the solar energy conversion efficiency. Herein, we report for the first time this competition can be overcome by modulation of reactive sites and electron transfer pathway of heterogeneous photocatalysts. As a prototype, BiO composite reduced graphene oxide quantum dots (RGO-BiO QDs) were synthesized, which can provide large amounts of photogenerated electrons as well as individual reactive sites for H
⁺
and CO
₂
reduction. The productivity of H
₂
, CH
₄
, and CO by the RGO-BiO QDs catalyst were 102.5, 21.75, and 4.5 μmol/(g·h), respectively, in pure water without the assistance of any cocatalyst or sacrificial agent. The apparent quantum efficiency at 300 nm reached to 4.2%, which is more than 10 times higher than that of RGO-TiO
₂
QDs (0.28%) under the same conditions. In situ DRIFT, ESR, and photoelectrochemical studies confirmed that the unique circled electron transfer pathway (E
_vb
(BiO) → E
_cb
(BiO) → E
_f
(RGO) → E
_Vo•
(BiO)) and the large amount of separated different reactive sites are responsible for the highly efficient simultaneous H
₂
evolution and CO
₂
reduction performance.

DOI： 10.1021/acsaem.8b02153

Language：English   Publishing type：Research paper (scientific journal)  

Photocatalytic water splitting or CO2 reduction is one of the most promising strategies for solar energy conversion into hydrogen-containing fuels. However, these two processes typically compete with each other, which significantly decreases the solar energy conversion efficiency. Herein, we report for the first time this competition can be overcome by modulation of reactive sites and electron transfer pathway of heterogeneous photocatalysts. As a prototype, BiO composite reduced graphene oxide quantum dots (RGO-BiO QDs) were synthesized, which can provide large amounts of photogenerated electrons as well as individual reactive sites for H+ and CO2 reduction. The productivity of H-2, CH4, and CO by the RGO-BiO QDs catalyst were 102.5, 21.75, and 4.5 mu mol/(g.h), respectively, in pure water without the assistance of any cocatalyst or sacrificial agent. The apparent quantum efficiency at 300 nm reached to 4.2%, which is more than 10 times higher than that of RGO-TiO2 QDs (0.28%) under the same conditions. In situ DRIFT, ESR, and photoelectrochemical studies confirmed that the unique circled electron transfer pathway (E-vb(BiO) -> E-ch (BiO) -> E-f(RGO) -> E-vo center dot(BiO)) and the large amount of separated different reactive sites are responsible for the highly efficient simultaneous H-2 evolution and CO2 reduction performance.

DOI： 10.1021/acsaem.8b02153

Language：English   Publishing type：Research paper (scientific journal)  

Novel perfluoroalkyl gelators without hydrogen bonds-bis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl) iso-phthalate (1m), bis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl) terephthalate (1p), and tris-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl) benzene-1,3,5-tricarboxylate (2)-were synthesized. Their molecular structures were investigated by density functional theory calculations at the B3LYP/cc-pVDZ level. The gelation abilities of 1m, 1p, and 2 were examined and compared to their normal octyl homologues 1m', 1p', and 2'. None of the gelators could be gelated in common organic solvents, but gelated well in fluorinated solvents.

DOI： 10.1246/bcsj.20180261

Language：English   Publishing type：Research paper (scientific journal)  

The synthesis, structure, physical properties, and electrocatalytic hydrogen production of tetrathiatetracene ligand based[FeFe]-hydrogenase mimic molecules were investigated. By adjusting the amount of iron, mono- A nd bis-[FeFe] coordinated complexes 1 and 2 were synthesized. The structures of 1 and 2 were analysed by NMR, IR, and absorption spectroscopies, and cyclic voltammetry and DFT computational analysis. In the DFT electron density maps, the HOMOs and LUMOs were located at tetrathiatetracene units, indicating that these complexes retain mainly acene characteristics. When weak acid Et₃NHBF₄ was added to CH₂Cl₂ solutions of 1 or 2, the reduction potential of iron complexes was shifted to more positive values proportional to the concentration of acid. As the acid concentration increased, the current of the reduction wave also increased, indicating the occurrence of a catalytic proton reduction reaction. The bulk electrolysis reaction showed 65.8 TON for 1 and 52.8 TON for 2.

DOI： 10.1039/c9nj02790d

Language：English   Publishing type：Research paper (scientific journal)  

Novel perfluoroalkyl gelators without hydrogen bondsbis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl) iso-phthalate (1m), bis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadeca-fluorooctyl) terephthalate (1p), and tris-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl) benzene-1,3,5-tricarboxylate (2)were synthesized. Their molecular structures were investigated by density functional theory calculations at the B3LYP/cc-pVDZ level. The gelation abilities of 1m, 1p, and 2 were examined and compared to their normal octyl homologues 1m¤, 1p¤, and 2¤. None of the gelators could be gelated in common organic solvents, but gelated well in fluorinated solvents.

DOI： 10.1246/bcsj.20180261

Language：English   Publishing type：Research paper (scientific journal)  

The unique frictional behavior of polyethylenimine/molybdenum disulphide (PEI/MoS₂)_n thin films on steel substrates, deposited via the layer-by-layer (LbL) technique, is explored. The effects of gaseous atmosphere (i.e. air vs. dry nitrogen), and heat treatment of the coatings are investigated. The coefficients of friction (COFs) are reduced by factors of ca. 2 and 11 in air and N₂ respectively, compared to an uncoated steel substrate. Ultra-low friction (COF < 0.02) is achieved in dry N₂. After heat treatment of the coating at 500 °C, the COF in air and nitrogen does not change significantly, but the coating demonstrates much higher durability. Detailed characterization of the coating and wear debris are performed to understand the origin of these tribological properties.

DOI： 10.1016/j.triboint.2018.06.003

Language：English   Publishing type：Research paper (scientific journal)  

The monomer, dimer, and trimer of 5,15-diphenyl-10,20-di(pyridin-4-yl)porphyrin are used to investigate the multianchoring effect on TiO2 for visible light-driven photocatalytic hydrogen production in a water medium. Further, the porphyrin trimer is prepared and analyzed by nuclear magnetic resonance (NMR) spectroscopy, absorption spectroscopy, electrochemical voltammetry, fast atom bombardment (FAB) mass spectroscopy, and density functional theory (DFT) computation. The results of this study indicate that the peak intensities of the absorption spectra increase as the number of porphyrin units increases, while changes couxld be barely observed in the highest occupied molecular orbital (HOMO)lowest unoccupied molecular orbital (LUMO) gaps. The porphyrin dimer in a 1 wt % Pt-loaded TiO2 powder photocatalyst system exhibited optimal hydrogen production performance in a stable state over a period of 80 h and at a superior rate of 1023 mu mol center dot g(-1) center dot h(-1). Further, the stability of the photocatalytic system was systematically investigated using films containing dyes on 1 wt % Pt-loaded TiO2/FTO. For a film containing the dimer, almost no change was observed in the hydrogen-bond coordination mode of the dimer and the photocurrent during the photocatalytic reaction. However, the photocurrents of the monomer and trimer were altered during visible light irradiation without altering the coordination mode, indicating that the arrangements and orientations of the porphyrins on TiO2 surfaces were altered. These results indicate that the presence of multiple anchoring groups enhance the stability of the photocatalytic system and the rate of hydrogen production.

DOI： 10.1021/acsaem.8b01113

Language：English   Publishing type：Research paper (scientific journal)  

The unique frictional behavior of polyethylenimine/molybdenum disulphide (PEI/MoS2)(n) thin films on steel substrates, deposited via the layer-by-layer (LbL) technique, is explored. The effects of gaseous atmosphere (i.e. air vs. dry nitrogen), and heat treatment of the coatings are investigated. The coefficients of friction (COFs) are reduced by factors of ca. 2 and 11 in air and N-2 respectively, compared to an uncoated steel substrate. Ultra-low friction (COF < 0.02) is achieved in dry N-2. After heat treatment of the coating at 500 degrees C, the COF in air and nitrogen does not change significantly, but the coating demonstrates much higher durability. Detailed characterization of the coating and wear debris are performed to understand the origin of these tribological properties.

DOI： 10.1016/j.triboint.2018.06.003

Language：English   Publishing type：Research paper (scientific journal)  

The monomer, dimer, and trimer of 5,15-diphenyl-10,20-di(pyridin-4-yl)porphyrin are used to investigate the multianchoring effect on TiO
₂
for visible light-driven photocatalytic hydrogen production in a water medium. Further, the porphyrin trimer is prepared and analyzed by nuclear magnetic resonance (NMR) spectroscopy, absorption spectroscopy, electrochemical voltammetry, fast atom bombardment (FAB) mass spectroscopy, and density functional theory (DFT) computation. The results of this study indicate that the peak intensities of the absorption spectra increase as the number of porphyrin units increases, while changes could be barely observed in the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps. The porphyrin dimer in a 1 wt % Pt-loaded TiO
₂
powder photocatalyst system exhibited optimal hydrogen production performance in a stable state over a period of 80 h and at a superior rate of 1023 μmol·g
^-1
·h
^-1
. Further, the stability of the photocatalytic system was systematically investigated using films containing dyes on 1 wt % Pt-loaded TiO
₂
/FTO. For a film containing the dimer, almost no change was observed in the hydrogen-bond coordination mode of the dimer and the photocurrent during the photocatalytic reaction. However, the photocurrents of the monomer and trimer were altered during visible light irradiation without altering the coordination mode, indicating that the arrangements and orientations of the porphyrins on TiO
₂
surfaces were altered. These results indicate that the presence of multiple anchoring groups enhance the stability of the photocatalytic system and the rate of hydrogen production.

DOI： 10.1021/acsaem.8b01113

Language：English   Publishing type：Research paper (scientific journal)  

Donor-donor-acceptor triads (1, 2), based on [3.3]paracyclophane ([3.3]PCP) as a bridge, with electron-donating properties (D) using 1,4-dithiafulvene (DTF; TTF half unit) as a donor and dicyanomethylene (DCM; TCNE half unit) or an ethoxycarbonyl-cyanomethylene (ECM) as an acceptor were designed and synthesized. The pulse radiolysis study of 1a in 1,2-dichloroethane allowed the clear assignment of the absorption bands of the DTF radical cation (1a(center dot+)), whereas the absorption bands due to the DCM radical anion could not be observed by -ray radiolysis in 2-methyltetrahydrofuran rigid glass at 77K. Electrochemical oxidation of 1a first generates the DTF radical cation (1a(center dot+)), the absorption bands of which are in agreement with those observed by a pulse radiolysis study, followed by dication (1a(2+)). The ESR spectrum of 1a(center dot+) showed a symmetrical signal with fine structure and an ESR simulation predicted that the spin of 1a(center dot+) is delocalized over S and C atoms of the DTF moiety and the central C atom of the trimethylene bridge bearing the DTF moiety. Pulse radiolysis, ESR, and electrochemical studies indicate that the DTF radical cation of 1a(center dot+) is more stable than that of 6(center dot+), and the latter shows a strong tendency to dimerize. This result indicates that the [3.3]PCP moiety as a bridge can stabilize the DTF radical cation more than the 1,3-diphenylpropane moiety because of kinetic stability due to its rigid structure and the weak electronic interaction of DTF and DCM moieties through [3.3]PCP.

DOI： 10.1002/chem.201801774

Language：English   Publishing type：Research paper (scientific journal)  

The hydrogen evolution reaction using semiconductor photocatalysts has been significantly improved by cocatalyst loading. However, there are still many speculations regarding the actual role of the cocatalyst. Now a photocatalytic hydrogen evolution reaction pathway is reported on a cocatalyst site using TiO
₂
nanosheets doped with Rh at Ti sites as one-atom cocatalysts. A hydride species adsorbed on the one-atom Rh dopant cocatalyst site was confirmed experimentally as the intermediate state for hydrogen evolution, which was consistent with the results of density functional theory (DFT) calculations. In this system, the role of the cocatalyst in photocatalytic hydrogen evolution is related to the withdrawal of photo-excited electrons and stabilization of the hydride intermediate species; the presence of oxygen vacancies induced by Rh facilitate the withdrawal of electrons and stabilization of the hydride.

DOI： 10.1002/anie.201803214

Language：English   Publishing type：Research paper (scientific journal)  

The hydrogen evolution reaction using semiconductor photocatalysts has been significantly improved by cocatalyst loading. However, there are still many speculations regarding the actual role of the cocatalyst. Now a photocatalytic hydrogen evolution reaction pathway is reported on a cocatalyst site using TiO2 nanosheets doped with Rh at Ti sites as one-atom cocatalysts. A hydride species adsorbed on the one-atom Rh dopant cocatalyst site was confirmed experimentally as the intermediate state for hydrogen evolution, which was consistent with the results of density functional theory (DFT) calculations. In this system, the role of the cocatalyst in photocatalytic hydrogen evolution is related to the withdrawal of photo-excited electrons and stabilization of the hydride intermediate species; the presence of oxygen vacancies induced by Rh facilitate the withdrawal of electrons and stabilization of the hydride.

DOI： 10.1002/anie.201803214

Language：English   Publishing type：Research paper (scientific journal)  

Fully conjugated macrocycles 1a−1c composed of m-diethynylene-phenylene-bridged two dibenzofuran, dibenzothiophene and carbazole units were synthesized via Sonogashira cross coupling reactions under high-diluted condition. These conjugated macrocycles were fully characterized by ¹H NMR, ¹³C NMR, FT-IR, Mass spectroscopies and elemental analysis. Photophysical and redox properties of 1a−1c were investigated by means of UV–vis/fluorescence spectroscopies and cyclic voltammetry, respectively, and those features were compared with those of the corresponding linear phenylethynyldibenzoheterols 11a−11c. Furthermore, their structural and electronic insights were studied by theoretical calculations at the B3LYP/cc-pVDZ//B3LYP/6-31G(d) level of theory.

DOI： 10.1016/j.tet.2018.03.072

Language：English   Publishing type：Research paper (scientific journal)  

Artificial photosynthesis from CO2 reduction is severely hampered by the kinetically challenging multi-electron reaction process. Oxygen vacancies (Vo) with abundant localized electrons have great potential to overcome this limitation. However, surface Vo usually have low concentrations and are easily oxidized, causing them to lose their activities. For practical application of CO2 photoreduction, fabricating and enhancing the stability of Vo on semiconductors is indispensable. Here we report the first synthesis of ultrathin WO3 center dot 0.33H(2)O nanotubes with a large amount of exposed surface Vo sites, which can realize excellent and stable CO2 photoreduction to CH3COOH in pure water under solar light. The selectivity for acetum generation is up to 85%, with an average productivity of about 9.4 mu mol g(-1) h(-1). More importantly, Vo in the catalyst are sustainable, and their concentration was not decreased even after 60 h of reaction. Quantum chemical calculations and in situ DRIFT studies revealed that the main reaction pathway might be CO2 -> (COOH)-C-center dot -> (COOH)(2) -> CH3COOH.

DOI： 10.1021/jacs.8b03316

Language：English   Publishing type：Research paper (scientific journal)  

Fully conjugated macrocycles la-lc composed of m-diethynylene-phenylene-bridged two dibenzofuran, dibenzothiophene and carbazole units were synthesized via Sonogashira cross coupling reactions under high-diluted condition. These conjugated macrocycles were fully characterized by H-1 NMR, C-13 NMR, FTIR, Mass spectroscopies and elemental analysis. Photophysical and redox properties of la-lc were investigated by means of UV-vis/fluorescence spectroscopies and cyclic voltammetry, respectively, and those features were compared with those of the corresponding linear phenylethynyldibenzoheterols 11a-11c. Furthermore, their structural and electronic insights were studied by theoretical calculations at the B3LYP/cc-pVDZ//B3LYP/6-31G(d) level of theory. (C) 2018 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2018.03.072

Language：English   Publishing type：Research paper (scientific journal)  

Artificial photosynthesis from CO₂ reduction is severely hampered by the kinetically challenging multi-electron reaction process. Oxygen vacancies (Vo) with abundant localized electrons have great potential to overcome this limitation. However, surface Vo usually have low concentrations and are easily oxidized, causing them to lose their activities. For practical application of CO₂ photoreduction, fabricating and enhancing the stability of Vo on semiconductors is indispensable. Here we report the first synthesis of ultrathin WO₃·0.33H₂O nanotubes with a large amount of exposed surface Vo sites, which can realize excellent and stable CO₂ photoreduction to CH₃COOH in pure water under solar light. The selectivity for acetum generation is up to 85%, with an average productivity of about 9.4 μmol g^-1 h^-1. More importantly, Vo in the catalyst are sustainable, and their concentration was not decreased even after 60 h of reaction. Quantum chemical calculations and in situ DRIFT studies revealed that the main reaction pathway might be CO₂ → ^•COOH → (COOH)₂ → CH₃COOH.

DOI： 10.1021/jacs.8b03316

Language：English   Publishing type：Research paper (scientific journal)  

Donor-donor'-acceptor triads (1, 2), based on [3.3]paracyclophane ([3.3]PCP) as a bridge, with electron-donating properties (D') using 1,4-dithiafulvene (DTF; TTF half unit) as a donor and dicyanomethylene (DCM; TCNE half unit) or an ethoxycarbonyl-cyanomethylene (ECM) as an acceptor were designed and synthesized. The pulse radiolysis study of 1a in 1,2-dichloroethane allowed the clear assignment of the absorption bands of the DTF radical cation (1a^.+), whereas the absorption bands due to the DCM radical anion could not be observed by γ-ray radiolysis in 2-methyltetrahydrofuran rigid glass at 77K. Electrochemical oxidation of 1a first generates the DTF radical cation (1a^.+), the absorption bands of which are in agreement with those observed by a pulse radiolysis study, followed by dication (1a²⁺). The ESR spectrum of 1a^.+ showed a symmetrical signal with fine structure and an ESR simulation predicted that the spin of 1a^.+ is delocalized over S and C atoms of the DTF moiety and the central C atom of the trimethylene bridge bearing the DTF moiety. Pulse radiolysis, ESR, and electrochemical studies indicate that the DTF radical cation of 1a^.+ is more stable than that of 6^.+, and the latter shows a strong tendency to dimerize. This result indicates that the [3.3]PCP moiety as a bridge can stabilize the DTF radical cation more than the 1,3-diphenylpropane moiety because of kinetic stability due to its rigid structure and the weak electronic interaction of DTF and DCM moieties through [3.3]PCP.

DOI： 10.1002/chem.201801774

Language：English   Publishing type：Research paper (scientific journal)  

A halide-substituted higher acene, 2-bromohexacene, and its precursor with a carbonyl bridge moiety were synthesized. The precursor was synthesized through 7 steps in a total yield of 2.5%. The structure of precursor and thermally converted 2-bromohexacene were characterized by solid state NMR, IR, and absorption spectra, as well as by DFT computation analysis. It exhibited high stability in the solid state over 3 months, therefore can be utilized in the fabrication of opto-electronic devices. The organic thin-film transistors (OFETs) were fabricated by using 2-bromohexacene and parent hexacene through vaccum deposition method. The best film mobility of 2-bromohexacene was observed at 0.83 cm² V^-1 s^-1 with an on/off ratio of 5.0 × 10⁴ and a threshold of -52 V, while the best film mobility of hexacene was observed at 0.076 cm² V^-1 s^-1 with an on/off ratio of 2.4 × 10² and a threshold of -21 V. AFM measurement of 2-bromohexacene showed smooth film formation. The averaged mobility of 2-bromohexacene is 8 fold higher than the non-substituted hexacene.

DOI： 10.1039/c7ra13632c

Language：English  

This study focuses on [FeFe]-hydrogenase and its metallorganic mimics in terms of electronic and photophysical properties, which can be applied to the electrochemical and/or photochemical production of molecular hydrogen. Natural [FeFeJ-hydrogenase, synthetic mimics of its active site and recent progresses in hybrid-type hydrogen production, for example, inorganic-combination photoelectrochemical and photochemical hydrogen production, are reviewed. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jphotochemrev.2017.09.001

Language：English  

Renewable hydrogen production is a sustainable method for the development of next-generation energy technologies. Utilising solar energy and photocatalysts to split water is an ideal method to produce hydrogen. In this review, the fundamental principles and recent progress of hydrogen production by artificial photosynthesis are reviewed, focusing on hydrogen production from photocatalytic water splitting using organic-inorganic composite-based photocatalysts.

DOI： 10.1080/14686996.2017.1375376

Language：English   Publishing type：Research paper (scientific journal)  

Effects of nitridation condition on gallium-zinc oxynitride solid solution (GaN:ZnO) was investigated to optimize the composition of GaN:ZnO for dye-modified photocatalysts. Gallium nitride (GaN) formed from Ga₂O₃ at 973 K, and GaN:ZnO was obtained over 1073 K under NH₃ gas flow. Nitrogen content in GaN:ZnO increased with increasing nitridation temperature and time, while zinc content decreased because of evaporation. Although UV–vis absorption spectra of GaN:ZnO powders were not significantly changed in different compositions, the water splitting activities of the dye-modified GaN:ZnO photocatalysts depended on the composition of GaN:ZnO. The highest formation rates of H₂ and O₂ were achieved by the GaN:ZnO containing 15% of zinc and 73% of nitrogen. Finally, the nitridation condition was optimized at 1123 K 15 h under NH₃ gas flow (200 ml/min) for preparation of the dye-modified GaN:ZnO powder as water splitting photocatalyst.

DOI： 10.1016/j.surfcoat.2016.10.054

Language：English   Publishing type：Research paper (scientific journal)  

Effects of nitridation condition on gallium-zinc oxynitride solid solution (GaN:ZnO) was investigated to optimize the composition of GaN:ZnO for dye-modified photocatalysts. Gallium nitride (GaN) formed from Ga2O3 at 973 K, and GaN:ZnO was obtained over 1073 K under NH3 gas flow. Nitrogen content in GaN:ZnO increased with increasing nitridation temperature and time, while zinc content decreased because of evaporation. Although UV vis absorption spectra of GaN:ZnO powders were not significantly changed in different compositions, the water splitting activities of the dye-modified GaN:ZnO photocatalysts depended on the composition of GaN:ZnO. The highest formation rates of H-2 and O-2 were achieved by the GaN:ZnO containing 15% of zinc and 73% of nitrogen. Finally, the nitridation condition was optimized at 1123 K 15 h under NH3 gas flow (200 ml/min) for preparation of the dye-modified GaN:ZnO powder as water splitting photocatalyst. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2016.10.054

Language：English   Publishing type：Research paper (scientific journal)  

To obtain a clean hydrogen production system, we have developed an inorganic-bio hybrid photocatalyst system based on the combination of anatase TiO2, methylviologen (MV) as an electron mediator, and a whole-cell biocatalyst consisting of [FeFe]-hydrogenase and maturase gene-harboring recombinant Escherichia coli; however, the apparent quantum yield at 300 nm (AQY(300)) for hydrogen production was low (0.3%). The system consists of a two-step reaction: (1) photocatalytic MV reduction by Ti02, and (2) hydrogen production with reduced MV using a biocatalyst. The enhancement of step 1 under biocatalyst-friendly conditions was investigated in an attempt to further improve the reaction efficiency. Among the condition tested, the use of 100mM Tris-HCl (pH 7), 150mM NaCl, and 5% (v/v) glycerol with P-25 TiO2 especially enhanced the step 1 reaction by a 300-fold increase in the MV reduction rate compared with previously tested reaction condition (100 mM Tris-HCl( pH 7), 150 mM NaCl, 5% (v/v) glycerol, and 100 mM ascorbate with anatase Ti02). Under the enhanced step 1 reaction, AQY(300) and AQY350 for photocatalytic MV reduction reached 60.8% and 52.2%, respectively. The enhanced step 1 reaction thus significantly improved the overall photocatalytic hydrogen productivity of the hybrid system and AQY(300) and AQY(350) reached 26.4% and 31.2%, respectively. The inorganic-whole-cell biohybrid system can therefore provide noble metal-free, efficient, and clean hydrogen production. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcatb.2017.04.015

Language：English   Publishing type：Research paper (scientific journal)  

A series of six new ethynylene-bridged conjugate carbazole trimers (1–6) were synthesized through sequential Pd-catalyzed Sonogashira cross-coupling reactions. The structural properties of these trimers were examined by using DFT calculations. Compound 6, in which the two terminal carbazole moieties were substituted at the 1-position, exhibited the longest-wavelength UV/Vis absorption maximum in CH₂Cl₂, whereas compound 1, in which the two terminal carbazole moieties were substituted at the 3-position, exhibited the shortest-wavelength absorption maximum. These trends were rationalized by using TDDFT calculations. Electrochemical measurements and DFT calculations revealed that trimers 1–6 had smaller HOMO–LUMO gaps compared with that for the corresponding monomer (14), which was caused by a lowering of the LUMO levels, rather than by a raising of the HOMO levels. Trimers 2–6 exhibited excellent emission properties with high fluorescence quantum yields, which were derived from their rigid structures.

DOI： 10.1002/ajoc.201700088

Language：English   Publishing type：Research paper (scientific journal)  

A series of six new ethynylene-bridged conjugate carbazole trimers (1-6) were synthesized through sequential Pd-catalyzed Sonogashira cross-coupling reactions. The structural properties of these trimers were examined by using DFT calculations. Compound 6, in which the two terminal carbazole moieties were substituted at the 1-position, exhibited the longest-wavelength UV/Vis absorption maximum in CH2Cl2, whereas compound 1, in which the two terminal carbazole moieties were substituted at the 3-position, exhibited the shortest-wavelength absorption maximum. These trends were rationalized by using TDDFT calculations. Electrochemical measurements and DFT calculations revealed that trimers 1-6 had smaller HOMO-LUMO gaps compared with that for the corresponding monomer (14), which was caused by a lowering of the LUMO levels, rather than by a raising of the HOMO levels. Trimers 2-6 exhibited excellent emission properties with high fluorescence quantum yields, which were derived from their rigid structures.

DOI： 10.1002/ajoc.201700088

Language：English   Publishing type：Research paper (scientific journal)  

CaFe2O4 (CFO) can be used as a photocathode to evolve H-2 from water in a photoelectrochemical cell. However, CFO degrades during operation and an external voltage is necessary for PEC H-2 evolution because the onset potential is less than the potential required for water oxidation considering the overpotential at the counter electrode. In order to develop a reliable CFO electrode with a greater onset potential, improvement of chemical stability and suppression of surface recombination is necessary. In this study, a chemically stable electrode structure with a greater onset potential was achieved by coating the [00l]-oriented CFO with a thin layer of titanium dioxide (TiO2). A CFO vertical bar TiO2 electrode was designed using a device simulator. The simulation results predict that coating CFO with TiO2 produces a positive or negative shift in the onset potential under visible and ultraviolet light irradiation, respectively. The experimental onset potentials matched the simulation prediction. The observed onset potential for TiO2-coated CFO was around (1.6 V vs. RHE) under visible light (470 nm) and 0.9 V under ultraviolet light (300 nm), compared to 1.2-1.3 V vs. RHE for a bare CFO electrode. The onset potential (1.6 V) under visible light irradiation is the most positive onset potential among the oxide photocathodes ever reported for PEC water splitting. Using the TiO2-coated CFO as the photocathode and RuO2-loaded Pt as the anode, stable photocurrent was observed under 470 nm excitation without an external voltage and evolution of H-2 from the system was confirmed.

DOI： 10.1039/c7se00084g

Language：English   Publishing type：Research paper (scientific journal)  

To obtain a clean hydrogen production system, we have developed an inorganic-bio hybrid photocatalyst system based on the combination of anatase TiO₂, methylviologen (MV) as an electron mediator, and a whole-cell biocatalyst consisting of [FeFe]-hydrogenase and maturase gene-harboring recombinant Escherichia coli; however, the apparent quantum yield at 300 nm (AQY₃₀₀) for hydrogen production was low (0.3%). The system consists of a two-step reaction: (1) photocatalytic MV reduction by TiO₂, and (2) hydrogen production with reduced MV using a biocatalyst. The enhancement of step 1 under biocatalyst-friendly conditions was investigated in an attempt to further improve the reaction efficiency. Among the condition tested, the use of 100 mM Tris-HCl (pH 7), 150 mM NaCl, and 5% (v/v) glycerol with P-25 TiO₂ especially enhanced the step 1 reaction by a 300-fold increase in the MV reduction rate compared with previously tested reaction condition (100 mM Tris-HCl (pH 7), 150 mM NaCl, 5% (v/v) glycerol, and 100 mM ascorbate with anatase TiO₂). Under the enhanced step 1 reaction, AQY₃₀₀ and AQY₃₅₀ for photocatalytic MV reduction reached 60.8% and 52.2%, respectively. The enhanced step 1 reaction thus significantly improved the overall photocatalytic hydrogen productivity of the hybrid system and AQY₃₀₀ and AQY₃₅₀ reached 26.4% and 31.2%, respectively. The inorganic-whole-cell biohybrid system can therefore provide noble metal-free, efficient, and clean hydrogen production.

DOI： 10.1016/j.apcatb.2017.04.015

Language：English   Publishing type：Research paper (scientific journal)  

Four novel organic dyes (H-1, H-2, H-3, H-4) containing phenyl-thiophenyl-thiophenyl as a bridge unit were synthesized and effectively used for the fabrication of dye-sensitized solar cells (DSSCs). In both compounds, a triarylamine moiety and cyanoacrylic acid function as an electron donor and an electron acceptor, respectively. H-1 and H-3 exhibited high interaction between lithium ions and [3.3]para-cyclophane, resulting in low charge recombination and high open-circuit voltage (V-oc). When deoxycholic acid was used as a coadsorbent, the optimal device performance was observed in H-3, involving a short-circuit current of 16.96 mA cm(-2), a V-oc of 705 mV, and a fill factor of 0.64, which correspond to an overall conversion efficiency of 7.55%. Photophysical properties were analyzed using a time-dependent density functional theory model and the B3LYP functional. Furthermore, the electronic characteristics of the DSSCs were determined using electrochemical impedance spectroscopy and controlled intensity modulated photospectroscopy. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dyepig.2016.09.043

Language：English   Publishing type：Research paper (scientific journal)  

New pi-conjugated 1,2-bis(2-aryl-1H-indol-3-yl)ethynes 1a-j having various substituents on the two aryl groups were efficiently synthesized via unusual 5-exo-digonal double isocyanide-acetylene cyclization reactions of 1,4-bis(2-isocyanophenyl)buta-1,3-diyne 3 and aryl Grignard reagents (R-MgBr, R = C6H5 (1a), 4-H3CC6H4 (1b), 2-H3CC6H4 (1c), 3-MeOC6H4 (1d), 3-(CH3)(2)NC6H4 (1e), 4-F3CC6H4 (1f) 4-FC6H4 (1g), 3-FC6H4 (1h), 4-PhOC6H4,(1i), and 2-Naph (1j)) in 19-85% yields. The UV-vis spectra were rationalized in detail using time-dependent DFT and single point calculations. The fluorescence emission peaks for 1a-j were observed at around 450 nm. Especially for If and 1j, those spectra displayed broad emission bands and relatively large Stokes shifts (3977-4503 cm(-1)), indicating the contribution of an intramolecular charge transfer. The absolute quantum yields (0.50-0.62) of 1a-j were higher than those of parent 8 (0.19) and 2-phenyl-1H-indole (0.11). The electrochemical features for 1a-j were investigated by cyclic voltammetry. The frontier molecular orbital levels for 1a-j were estimated based on the combination of oxidation potentials, UV-vis, and DFT calculated data. The structural property of 1,2-bis(2-phenyl-1H-indol-3-yl)ethyne 1a was characterized by several spectroscopic.methods and finally determined by X-ray analysis of a single crystal of la recrystallized from ethyl acetate. The structural features of 1a-j were also supported by DFT calculations.

DOI： 10.1021/acs.joc.6b02668

Language：English  

Photocatalytic water splitting is a potential next generation hydrogen production process which can directly convert light energy to chemical energy without greenhouse gas emission. The effects of dye-modification on the water splitting activity of inorganic semiconductor photocatalysts were investigated to utilize visible light energy for solar energy conversion. The photocatalytic activities of metal oxides, sulfides, oxysulfides, and oxynitrides were improved by dye-modification, because the charge recombination of photogenerated electrons and holes in inorganic semiconductors was effectively suppressed. The charge transfer mechanism of the dye-modified photo catalyst is a two-step excitation process, which is similar to that of photosynthesis. This study revealed that dye modification is a very effective method to enhance the photoabsorption of visible light and improve the water splitting activity of inorganic semiconductor photocatalysts.

DOI： 10.1627/jpi.60.10

Language：English   Publishing type：Research paper (scientific journal)  

Four novel organic dyes (H-1, H-2, H-3, H-4) containing phenyl-thiophenyl-thiophenyl as a bridge unit were synthesized and effectively used for the fabrication of dye-sensitized solar cells (DSSCs). In both compounds, a triarylamine moiety and cyanoacrylic acid function as an electron donor and an electron acceptor, respectively. H-1 and H-3 exhibited high interaction between lithium ions and [3.3]paracyclophane, resulting in low charge recombination and high open-circuit voltage (V_oc). When deoxycholic acid was used as a coadsorbent, the optimal device performance was observed in H-3, involving a short-circuit current of 16.96 mA cm⁻², a V_oc of 705 mV, and a fill factor of 0.64, which correspond to an overall conversion efficiency of 7.55%. Photophysical properties were analyzed using a time-dependent density functional theory model and the B3LYP functional. Furthermore, the electronic characteristics of the DSSCs were determined using electrochemical impedance spectroscopy and controlled intensity-modulated photospectroscopy.

DOI： 10.1016/j.dyepig.2016.09.043

Language：English   Publishing type：Research paper (scientific journal)  

New π-conjugated 1,2-bis(2-aryl-1H-indol-3-yl)ethynes 1a-j having various substituents on the two aryl groups were efficiently synthesized via unusual 5-exo-digonal double isocyanide-acetylene cyclization reactions of 1,4-bis(2-isocyanophenyl)buta-1,3-diyne 3 and aryl Grignard reagents (R-MgBr, R = C₆H₅ (1a), 4-H₃CC₆H₄ (1b), 2-H₃CC₆H₄ (1c), 3-MeOC₆H₄ (1d), 3-(CH₃)₂NC₆H₄ (1e), 4-F₃CC₆H₄ (1f), 4-FC₆H₄ (1g), 3-FC₆H₄ (1h), 4-PhOC₆H₄ (1i), and 2-Naph (1j)) in 19-85% yields. The UV-vis spectra were rationalized in detail using time-dependent DFT and single point calculations. The fluorescence emission peaks for 1a-j were observed at around 450 nm. Especially for 1f and 1j, those spectra displayed broad emission bands and relatively large Stokes shifts (3977-4503 cm^-1), indicating the contribution of an intramolecular charge transfer. The absolute quantum yields (0.50-0.62) of 1a-j were higher than those of parent 8 (0.19) and 2-phenyl-1H-indole (0.11). The electrochemical features for 1a-j were investigated by cyclic voltammetry. The frontier molecular orbital levels for 1a-j were estimated based on the combination of oxidation potentials, UV-vis, and DFT calculated data. The structural property of 1,2-bis(2-phenyl-1H-indol-3-yl)ethyne 1a was characterized by several spectroscopic methods and finally determined by X-ray analysis of a single crystal of 1a recrystallized from ethyl acetate. The structural features of 1a-j were also supported by DFT calculations.

DOI： 10.1021/acs.joc.6b02668

Language：English   Publishing type：Research paper (scientific journal)  

CaFe
₂
O
₄
(CFO) can be used as a photocathode to evolve H
₂
from water in a photoelectrochemical cell. However, CFO degrades during operation and an external voltage is necessary for PEC H
₂
evolution because the onset potential is less than the potential required for water oxidation considering the overpotential at the counter electrode. In order to develop a reliable CFO electrode with a greater onset potential, improvement of chemical stability and suppression of surface recombination is necessary. In this study, a chemically stable electrode structure with a greater onset potential was achieved by coating the [00l]-oriented CFO with a thin layer of titanium dioxide (TiO
₂
). A CFOvTiO
₂
electrode was designed using a device simulator. The simulation results predict that coating CFO with TiO
₂
produces a positive or negative shift in the onset potential under visible and ultraviolet light irradiation, respectively. The experimental onset potentials matched the simulation prediction. The observed onset potential for TiO
₂
-coated CFO was around (1.6 V vs. RHE) under visible light (470 nm) and 0.9 V under ultraviolet light (300 nm), compared to 1.2-1.3 V vs. RHE for a bare CFO electrode. The onset potential (1.6 V) under visible light irradiation is the most positive onset potential among the oxide photocathodes ever reported for PEC water splitting. Using the TiO
₂
-coated CFO as the photocathode and RuO
₂
-loaded Pt as the anode, stable photocurrent was observed under 470 nm excitation without an external voltage and evolution of H
₂
from the system was confirmed.

DOI： 10.1039/c7se00084g

Language：English   Publishing type：Research paper (scientific journal)  

A series of allcylated indigos were synthesized. Alkylated indigos were characterized by NMR, mass spectrometry, absorption spectra, cyclic voltammetry, and density functional theory (DFT) calculations. Propyl and butyl group substituted indigo was most soluble in chloroform and 1,2-dicrolobenzene, and these solubility were 65-89 times increased as compared to the parent indigo. DFT calculations suggested that the presence of the alkyl chains at the 5.5'-position increases the energy of the highest occupied molecular orbital, while reducing the energy of the lowest unoccupied molecular orbital. This theoretical finding was in good agreement with the experimental results. Crystal structures obtained by X-ray diffraction showed one-dimensional pi pi stacking. Alkylated molecules were converted to leuco structure, and these structures were then converted to the corresponding indigos in the film state. After deposition of the films on TiO2/FTO substrate, oxidative photocurrents were observed. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2016.05.069

Language：English   Publishing type：Research paper (scientific journal)  

All possible pseudogeminal-, pseudoortho-, pseudometa-, and pseudopara-dibromo[3.3] paracyclophanes were synthesized by the (p-tolylsulfonyl) methyl isocyanide (TosMIC) coupling method, and characterized by the aromatic proton signals of the H-1 NMR spectra and finally by the X-ray crystal structure analyses of the pseudogeminal, pseudoortho, and pseudopara isomers.

DOI： 10.1055/s-0035-1560421

Language：English   Publishing type：Research paper (scientific journal)  

Photocatalytic water splitting is one of the ideal methods for solving the global energy crisis and its associated environmental problems. In this study, the effect of altering the molecular structure of porphyrins was investigated to improve the water splitting activity of Zr-doped KTaO₃ (KTa(Zr)O₃) modified with porphyrin dyes. UV-vis spectra indicated that porphyrins with long alkoxy chains tended to form well-developed H-aggregates on the KTa(Zr)O₃ surface. The photocatalytic activity of Pt-loaded KTa(Zr)O₃ was improved by using porphyrins with longer alkoxy chains because of the improvement in the charge migration between porphyrin dye molecules. While the charge transfer between the inorganic semiconductor and porphyrin dye interface is important, it was found that the formation of H-aggregation was more effective in improving the water splitting activity of the porphyrin-modified photocatalysts.

DOI： 10.3390/catal6030042

Language：English   Publishing type：Research paper (scientific journal)  

Photocatalytic water splitting is one of the ideal methods for solving the global energy crisis and its associated environmental problems. In this study, the effect of altering the molecular structure of porphyrins was investigated to improve the water splitting activity of Zr-doped KTaO3 (KTa(Zr)O-3) modified with porphyrin dyes. UV-vis spectra indicated that porphyrins with long alkoxy chains tended to form well-developed H-aggregates on the KTa(Zr)O-3 surface. The photocatalytic activity of Pt-loaded KTa(Zr)O-3 was improved by using porphyrins with longer alkoxy chains because of the improvement in the charge migration between porphyrin dye molecules. While the charge transfer between the inorganic semiconductor and porphyrin dye interface is important, it was found that the formation of H-aggregation was more effective in improving the water splitting activity of the porphyrin-modified photocatalysts.

DOI： 10.3390/catal6030042

Language：English   Publishing type：Research paper (scientific journal)  

All possible pseudogeminal-, pseudoortho-, pseudometa-, and pseudopara-dibromo[3.3]paracyclophanes were synthesized by the (p-tolylsulfonyl)methyl isocyanide (TosMIC) coupling method, and characterized by the aromatic proton signals of the ¹H NMR spectra and finally by the X-ray crystal structure analyses of the pseudogeminal, pseudo-?ortho, and pseudopara isomers.

DOI： 10.1055/s-0035-1560421

Language：English   Publishing type：Research paper (scientific journal)  

A series of alkylated indigos were synthesized. Alkylated indigos were characterized by NMR, mass spectrometry, absorption spectra, cyclic voltammetry, and density functional theory (DFT) calculations. Propyl and butyl group substituted indigo was most soluble in chloroform and 1,2-dicrolobenzene, and these solubility were 65–89 times increased as compared to the parent indigo. DFT calculations suggested that the presence of the alkyl chains at the 5.5′-position increases the energy of the highest occupied molecular orbital, while reducing the energy of the lowest unoccupied molecular orbital. This theoretical finding was in good agreement with the experimental results. Crystal structures obtained by X-ray diffraction showed one-dimensional pi–pi stacking. Alkylated molecules were converted to leuco structure, and these structures were then converted to the corresponding indigos in the film state. After deposition of the films on TiO₂/FTO substrate, oxidative photocurrents were observed.

DOI： 10.1016/j.tet.2016.05.069

Language：English   Publishing type：Research paper (scientific journal)  

The effects of LiPF₆ concentration in ethylene carbonate (EC)-dimethyl carbonate (DMC) on PF₆^- intercalation into graphitic carbon were studied for a high-energy-density dual-carbon battery. The capacity as well as potential for PF₆^- intercalation decreased with increasing LiPF₆ concentration when EC-DMC was used as an electrolyte. Low-viscosity carbonate was found to be suitable as a high-concentration LiPF₆ electrolyte, and DMC is thus a promising electrolyte for high-concentration LiPF₆. The PF₆^- intercalation capacity as well as the intercalation potential in 3.7 M LiPF₆/DMC (100 mAh g^-1) were almost the same as those in 1 M LiPF₆/EC-DMC (89 mAh g^-1). Considering the anode capacity, 3.1 M LiPF₆ is suitable for the full cell. Using 3.1 M LiPF₆ in DMC, the energy density of the dual-carbon battery could be significantly increased.

DOI： 10.1149/2.0381607jes

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New pyromellitic diimide-based tetrabromo[2+2]macrocycle ([2+2]MC) 2, tribromo- and hexabromo[3+3]MCs 3a and 3b, as well as triiodo[3+3]MC 3c were synthesized as structural units of covalently bound nanotubes, and their absorption spectra and redox properties, as well as inclusion phenomena of the [2+2]MC 2 were reported. Tetrabromo[2+2]MC 2 forms a 1:1 inclusion complex with toluene, whose structure was revealed by X-ray structural analysis.

DOI： 10.1016/j.tetlet.2015.10.070

Language：English   Publishing type：Research paper (scientific journal)  

New pyromellitic diimide-based tetrabromo[2+2]macrocycle ([2+2]MC) 2, tribromo- and hexabromo[3+3]MCs 3a and 3b, as well as triiodo[3+3]MC 3c were synthesized as structural units of covalently bound nanotubes, and their absorption spectra and redox properties, as well as inclusion phenomena of the [2+2]MC 2 were reported. Tetrabromo[2+2]MC 2 forms a 1:1 inclusion complex with toluene, whose structure was revealed by X-ray structural analysis. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2015.10.070

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A series of syn/anti mixtures of anthradifuran (ADF) and substituent compounds were systematically synthesized, and the effect of substitution at the 5,11-positions on the neutral and radical states of ADF was investigated. All compounds were measured and analyzed by absorption and fluorescence spectroscopy, cyclic voltammetry, electrochemical absorption spectroscopy, and DFT calculations. The absorption spectra of 5,11-substituent compounds in their neutral state were red-shifted. In addition, the substituted compounds exhibited increased thermal stability with respect to the parent 1a because of elongation of the conjugation and an increased steric hindrance effect due to the bulky ethynyl substituent groups. The cyclic voltammograms of all of the compounds exhibited irreversible reduction potentials and irreversible oxidation potentials, except in the case of (trimethylsilyl)silylethynyl-substituted ADF. When the materials were subjected to oxidation/reduction potentials, the radical cation and anion species were generated. The absorption spectra of the radical-cation species of the compounds exhibited similar characteristics and similar absorption ranges (550-1400 nm), whereas the spectra of the radical anion species were blue-shifted (550-850 nm) compared than that of the parent 1a^•- (550-1100 nm). The DFT computation results suggested that the radical states of lowest energy transitions occurred primarily from to _SOMO or from _SOMO to.

DOI： 10.1021/acs.joc.5b01525

Language：English   Publishing type：Research paper (scientific journal)  

A series of syn/anti mixtures of anthradifuran (ADF) and substituent compounds were systematically synthesized, and the effect of substitution at the 5,11-positions on the neutral and radical states of ADF was investigated. All compounds were measured and analyzed by absorption and fluorescence spectroscopy, cyclic voltammetry, electrochemical absorption spectroscopy, and DFT calculations. The absorption spectra of 5,11-substituent compounds in their neutral state were red-shifted. In addition, the substituted compounds exhibited increased thermal stability with respect to the parent la because of elongation of the pi-conjugation and an increased steric hindrance effect due to the bulky ethynyl substituent groups. The cyclic voltammograms of all of the compounds exhibited irreversible reduction potentials and irreversible oxidation potentials, except in the case of (trimethylsilyl)-silylethynyl-substituted ADF. When the materials were subjected to oxidation/reduction potentials, the radical cation and anion species were generated. The absorption spectra of the radical-cation species of the compounds exhibited similar characteristics and similar absorption ranges (550-1400 nm), whereas the spectra of the radical anion species were blue-shifted (550-850 nm) compared than that of the parent 1a(center dot-) (550-1100 nm). The DFT computation results suggested that the radical states of lowest energy transitions occurred primarily from pi to pi(somo) or from pi(somo) to pi*.

DOI： 10.1021/acs.joc.5b01525

Language：English   Publishing type：Research paper (scientific journal)  

Novel ferrocene-oligothiophenylene-cyanoacrylic acid in the form of donor-spacer-acceptor dyads was synthesized. The compound with a single unit of thiophenylene showed the lowest energy transition in neutral state. For radical cations, the lowest energy transition appears red-shifted along with the increased number of thiophenylene units. These results suggested that the electronic structure of radical cations is significantly different from that of neutral molecules.

DOI： 10.1016/j.tetlet.2015.02.012

Language：English   Publishing type：Research paper (scientific journal)  

Three 2-halo-subsituted pentacene derivatives were prepared from stable and soluble carbonyl adduct precursors of high purity in high yields. These precursors were synthesized from the corresponding anthraquinones in overall yields about 30%. The crystals of 2-substituted pentacenes were grown by using a method of physical vapor transport. Organic field effect transistors made with these crystals displayed p-type charge carrier characteristics with the highest hole mobility of 5.0 cm(2) V-1 s(-1). (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2015.01.056

Language：English   Publishing type：Research paper (scientific journal)  

Novel ferrocene-oligothiophenylene-cyanoacrylic acid in the form of donor-spacer-acceptor dyads was synthesized. The compound with a single unit of thiophenylene showed the lowest energy transition in neutral state. For radical cations, the lowest energy transition appears red-shifted along with the increased number of thiophenylene units. These results suggested that the electronic structure of radical cations is significantly different from that of neutral molecules. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2015.02.012

Language：English   Publishing type：Research paper (scientific journal)  

Three 2-halo-subsituted pentacene derivatives were prepared from stable and soluble carbonyl adduct precursors of high purity in high yields. These precursors were synthesized from the corresponding anthraquinones in overall yields about 30%. The crystals of 2-substituted pentacenes were grown by using a method of physical vapor transport. Organic field effect transistors made with these crystals displayed p-type charge carrier characteristics with the highest hole mobility of 5.0 cm² V^-1 s^-1.

DOI： 10.1016/j.tet.2015.01.056

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The [4+2] cycloaddition of hexacene and C₆₀ yielded 1:1 and 1:2 adducts. The highest yield of 1:1 adduct was 90% by heating hexacene and C₆₀ in toluene. The formation of 2 was achieved by reacting 1 with an excess amount of C₆₀ in the presence of silica gel 60 with a yield up to 69%. The function of silica gel was rationalized by the effect of concentration enhancement inside the pore of silica gel. The reaction was examined systematically by changing the parameters of solvent, temperature, reaction time, and the pore size of silica gel. Both purified compounds 1 and 2 can be used for the fabrication of bulk heterojunction solar cells.

DOI： 10.1016/j.tetlet.2015.01.093

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The [4+2] cycloaddition of hexacene and C-60 yielded 1:1 and 1:2 adducts. The highest yield of 1:1 adduct was 90% by heating hexacene and C-60 in toluene. The formation of 2 was achieved by reacting 1 with an excess amount of C-60 in the presence of silica gel 60 with a yield up to 69%. The function of silica gel was rationalized by the effect of concentration enhancement inside the pore of silica gel. The reaction was examined systematically by changing the parameters of solvent, temperature, reaction time, and the pore size of silica gel. Both purified compounds 1 and 2 can be used for the fabrication of bulk heterojunction solar cells. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2015.01.093

Language：English   Publishing type：Research paper (scientific journal)  

Alkoxyphenyl-substituted carbazole-based metal-free organic dyes were synthesized and effectively used for dye-sensitized, visible-light-driven, photocatalytic hydrogen production. Photocatalytic hydrogen production was investigated using a TiO₂/dye/Pt structure with triethanolamine as the sacrificial reagent. The dye-loaded TiO₂ photocatalyst exhibited a high yield of hydrogen production when the length of the alkoxy chain was long enough to sufficiently improve the hydrophobicity at the interface between the dye-loaded TiO₂ and the water medium. In the alkoxyphenyl-substituted carbazole dyes, the dye with the longest alkoxy chain (C22) exhibited the best hydrogen production performance, but it had a yield only slightly better than that of the dye with the second longest chain length (C16). The dye C22 displayed a turnover number (TON) of 3094 after 24 h of visible light irradiation (>420 nm). However, the compound with no hydrophobic substituent (C1), exhibited the lowest hydrogen production performance with a TON of 1497. Thus, a 207% increase in the hydrogen production yield was observed when hydrophobic substituents were present. Analysis of time-resolved absorption spectra, impedance spectra and incident photon conversion efficiency spectra revealed that the alkoxy chain has a hydrophobic effect at the interface between the dye-loaded TiO₂ and the water. Specifically, the hydrophobicity of the dye improved the charge-recombination lifetime for electron injection from the dye into the TiO₂ surface in the water for hydrogen production.

DOI： 10.1039/c5ta04991a

Language：English   Publishing type：Research paper (scientific journal)  

We performed X-ray structural analyses of the five- and six-layered [3.3]metacyclophanes (MCPs) 1 and 2 and the six-layered [3.3]MCP tetraone 3. In the solid state, the MCP moieties of 1, 2, and 3 adopt different conformations from those of the free MCPs in solution. In the five-layered [3.3]MCP 1, all the [3.3]MCP moieties adopt anti (chair/boat) conformations. In the six-layered [3.3]MCP 2, two three-layered [3.3]MCPs are connected by a [3.3]MCP in the anti conformation with completely parallel benzene rings. In the six-layered [3.3]MCP tetraone 3, the outer [3.3]MCP moieties and diones adopt general syn and anti geometries, respectively. However, the inner [3.3]MCP moiety adopts an anti geometry. Based on density functional theory (DFT) calculations, the most stable conformers of 1, 2, and 3 are syn (chair/chair) in the [3.3]MCP moieties and anti (twist boat/twist boat) in the dione moieties.

DOI： 10.1016/j.tetlet.2014.10.151

Language：English   Publishing type：Research paper (scientific journal)  

Three types of the donor(D)-donor'(D')-acceptor(A) triads 1-6 with different D-A combinations, carbazole (Cz, D)-[n.n]PCP(D')-1,8-naphthalimide (NI, A) (1-3), 10H-phenothiazine (PTZ, D)-[n.n]PCP(D')-NI(A) (4, 5), and 10-methyl-10H-phenothiazine (Me-PTZ, D)-[2.2]PCP-2,1,3-benzothiadiazole (BTD, A) 6, were synthesized for the elucidation of their photophysical properties. The absorption spectra and electrochemical properties indicated that the chromophores (D, D', and A) do not interact with each other in the ground state. Cz-(CH2)(3)-[2.2]PCP-(CH2)(3)-NI 1 and Cz-(CH2)(3)-[3.3]PCP-(CH2)(3)-NI 2 show an exciplex emission between the PCP and NI moieties in cyclohexane and the intensity of the band is much higher in 2 than in 1, whereas Cz-(CH2)(2)-[2.2]PCP-(CH2)(2)-NI 3 does not show any exciplex emission in cyclohexane. These results indicated that the combination of [3.3]PCP and a trimethylene chain is preferable for the exciplex formation. PTZ-(CH2)(3)-[2.2]PCP-(CH2)(3)-NI 4 shows a broad band at 519 nm in cyclohexane, which is associated with the formation of the exterplex band among the NI, [2.2]PCP, and PTZ moieties, while PTZ-(CH2)(3)-[3.3]PCP-(CH2)(3)-NI 5 does not show the band. Me-PTZ-(CH2)(2)-[2.2]PCP-(CH2)(2)-BTD 6 shows a broad fluorescence band due to both the BTD and PTZ moieties in cyclohexane. In CH3CN, the fluorescence spectra of 1-6 suggest the presence of a photoinduced charge separation process. The study of the photoinduced charge separation process will be soon reported elsewhere.

DOI： 10.1021/jo5020273

Language：English   Publishing type：Research paper (scientific journal)  

We performed X-ray structural analyses of the five- and six-layered [3.3]metacyclophanes (MCPs) 1 and 2 and the six-layered [3.3]MCP tetraone 3. In the solid state, the MCP moieties of 1, 2, and 3 adopt different conformations from those of the free MCPs in solution. In the five-layered [3.3]MCP 1, all the [3.3]MCP moieties adopt anti (chair/boat) conformations. In the six-layered [3.3]MCP 2, two three-layered [3.3]MCPs are connected by a [3.3]MCP in the anti conformation with completely parallel benzene rings. In the six-layered [3.3]MCP tetraone 3, the outer [3.3]MCP moieties and diones adopt general syn and anti geometries, respectively. However, the inner [3.3]MCP moiety adopts an anti geometry. Based on density functional theory (DFT) calculations, the most stable conformers of 1, 2, and 3 are syn (chair/chair) in the [3.3]MCP moieties and anti (twist boat/twist boat) in the dione moieties. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2014.10.151

Language：English   Publishing type：Research paper (scientific journal)  

Three types of the donor(D)-donor′(D′)-acceptor(A) triads 1-6 with different D-A combinations, carbazole (Cz, D)-[n.n]PCP(D′)-1,8-naphthalimide (NI, A) (1-3), 10H-phenothiazine (PTZ, D)-[n.n]PCP(D′)-NI(A) (4, 5), and 10-methyl-10H-phenothiazine (Me-PTZ, D)-[2.2]PCP-2,1,3-benzothiadiazole (BTD, A) 6, were synthesized for the elucidation of their photophysical properties. The absorption spectra and electrochemical properties indicated that the chromophores (D, D′, and A) do not interact with each other in the ground state. Cz-(CH₂)₃-[2.2]PCP-(CH₂)₃-NI 1 and Cz-(CH₂)₃-[3.3]PCP-(CH₂)₃-NI 2 show an exciplex emission between the PCP and NI moieties in cyclohexane and the intensity of the band is much higher in 2 than in 1, whereas Cz-(CH₂)₂-[2.2]PCP-(CH₂)₂-NI 3 does not show any exciplex emission in cyclohexane. These results indicated that the combination of [3.3]PCP and a trimethylene chain is preferable for the exciplex formation. PTZ-(CH₂)₃-[2.2]PCP-(CH₂)₃-NI 4 shows a broad band at 519 nm in cyclohexane, which is associated with the formation of the exterplex band among the NI, [2.2]PCP, and PTZ moieties, while PTZ-(CH₂)₃-[3.3]PCP-(CH₂)₃-NI 5 does not show the band. Me-PTZ-(CH₂)₂-[2.2]PCP-(CH₂)₂-BTD 6 shows a broad fluorescence band due to both the BTD and PTZ moieties in cyclohexane. In CH₃CN, the fluorescence spectra of 1-6 suggest the presence of a photoinduced charge separation process. The study of the photoinduced charge separation process will be soon reported elsewhere.

DOI： 10.1021/jo5020273

Language：English   Publishing type：Research paper (scientific journal)  

The title compound, C40H46N2 {systematic name: 12,30-diazaheptacyclo[21.13.1.1(5,19).1(6,18).1(10,14).1(24,36).1(28,32)]dotetraconta- 1(37),5(40),6(41),10(42),11,13,18,23,28,30,32(39),36(38)-dodecaene}, has syn-anti-syn geometry wherein the two outer [3.3]metacyclophane (MCP) moieties have a syn geometry, and contain the facing benzene and pyridine rings at dihedral angles of 26.26 (10) and 26.46 (10)degrees, respectively. The rings of the central [3.3]MCP unit are not parallel, but orientated at a slight angle of 2.66 (9)degrees. Three bridging methylene groups are disordered over two sets of sites in a 0.60:0.40 ratio. In the crystal, the molecules are linked by C-H center dot center dot center dot N interactions and intermolecular C-H center dot center dot center dot pi short contacts, generating a three-dimensional network.

DOI： 10.1107/S1600536814023691

Language：English   Publishing type：Research paper (scientific journal)  

Photoswitching of conductance through both stable isomers of salicylidene methylamine was investigated using nonequilibrium Greens function method combined with density functional theory. This study demonstrates how the optically induced intramolecular proton transfer between the hydroxyl group and the amino group of salicylidene methylamine can lead to molecular size photodiode with on/off current ratio of 1 order of magnitude. It was further elucidated that the optical switching alone is not sufficient to realize the molecular switch. Of primary importance was found to be the anchoring between the molecule and the metal electrodes. When the anchoring groups were connected to the benzene ring in para-orientation, minimal on/off current ratio was estimated. When the anchoring groups were connected to the benzene ring in meta-orientation, 1 order of magnitude on/off current ratio was calculated. Molecular orbital analysis was successfully employed to elucidate the difference in the photoswitching properties of the meta- and para-anchored isomers of salicylidene methylamine. This study demonstrates the potential application of aromatic Schiff bases as photodiodes in the field of molecular electronics.

DOI： 10.1021/jp5081884

Language：English   Publishing type：Research paper (scientific journal)  

Water splitting activity of a GaN:ZnO photocatalyst was improved by meso-hexakis(pentafluorophenyl) [26]hexaphyrin (3). The hexaphyrin (3) assisted the water splitting reaction over the GaN:ZnO photocatalyst by using visible light energy around 600 nm. This journal is

DOI： 10.1039/c4cc05127k

Language：English   Publishing type：Research paper (scientific journal)  

Synthesis of bona fide N-confused phlorin derivatives through simple chemical reduction of N-confused porphyrin precursors using sodium borohydride, p-toluenesulfonyl hydrazide, etc. is described. Spectroscopic, X-ray diffraction analyses and DFT-assisted calculations of these species support the nonaromatic phlorin electronic structure.

DOI： 10.1142/S1088424614500692

Language：English   Publishing type：Research paper (scientific journal)  

Novel organic dyes that consist of either a benzo[1,2-b:4,5-b']dithiophene or a benzo[1,2-b:4,5-b']difuran core exhibited remarkable solar-to-energy conversion efficiency in dye-sensitized solar cells. The planar geometry of bridge moiety and its bulky substituents helped the dyes to form a high quality monolayer on the surface of titanium oxide. A typical device displayed photon-to-current conversion efficiency 60% in the region of 380-575 nm, a short-circuit photocurrent density 13.45 mA cm(-2), an open-circuit photovoltage 0.72 V, and a fill factor 0.63, corresponding to an overall conversion efficiency 6.12%. In a test of using deoxycholic acid as a co-absorbent, an improvement of quantum efficiencies 8.37% was observed for certain compounds. However, for others the quantum efficiency decreased in 6.60-7.91%. The latter result indicated that the quality of some films cannot be further improved by the addition of deoxycholic acid. The photophysical properties were analyzed with the aid of TDDFT. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.dyepig.2014.04.043

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In the title compound, C21H14N2O2S, a donor-acceptor type of benzo[b]phenothiazine (bpz) derivative, the thiazine ring adopts a boat conformation and the bond-angle sum at the N atom is 360.0 degrees. The dihedral angle between the benzene ring and the naphthelene ring system fused to the thiazine ring is 32.76 (5)degrees. In the crystal, carboxylic-acid inversion dimers linked by pairs of O-H center dot center dot center dot O hydrogen bonds generate R-2(2)(8) loops. Aromatic pi-pi stacking [ shortest centroid-centroid separaton = 3.5242 (13) angstrom] consolidates the structure and very weak C-H center dot center dot center dot O and C-H center dot center dot center dot N interactions also occur.

DOI： 10.1107/S1600536814018388

Language：English   Publishing type：Research paper (scientific journal)  

Metal-free organic dyes containing benzo[b]phenothiazine were synthesized and effectively used for dye-sensitized visible-light-driven photocatalytic hydrogen production. The materials exhibited high stability and hydrogen production when numerous π-conjugated bridges were inserted as spacers between the donor and the anchor moiety. Photocatalytic hydrogen production was investigated in a TiO₂/dye/Pt structure using triethanolamine as the sacrificial reagent. Compound dye 3, which had the longest spacer between the donor and the acceptor, exhibited the best hydrogen production performance of the series examined in this study. It displayed a turnover number (TON) of 4460, a turnover frequency of 278 after 16 h, and a photo-quantum efficiency of 1.65% at 420 nm. Furthermore, it showed the longest electron injection lifetime because its coordination structure was considered to be vertically standing on the TiO₂ surface by theoretical calculations. On the other hand, dye 1 showed the lowest hydrogen production performance with a TON of 483 and very short electron injection lifetime. This observation is confirmed by the computation results, which showed the lying geometry of 1 with monodentate coordination of the dye with respect to the TiO₂ surface. This spacer effectproperty relationship study may provide a good strategy for the development of metal-free organic dyes for dye-sensitized photocatalytic water splitting.

DOI： 10.1039/c4ta02720e

Language：English   Publishing type：Research paper (scientific journal)  

Metal-free organic dyes containing benzo[b]phenothiazine were synthesized and effectively used for dye-sensitized visible-light-driven photocatalytic hydrogen production. The materials exhibited high stability and hydrogen production when numerous pi-conjugated bridges were inserted as spacers between the donor and the anchor moiety. Photocatalytic hydrogen production was investigated in a TiO2/dye/Pt structure using triethanolamine as the sacrificial reagent. Compound dye 3, which had the longest spacer between the donor and the acceptor, exhibited the best hydrogen production performance of the series examined in this study. It displayed a turnover number (TON) of 4460, a turnover frequency of 278 after 16 h, and a photo-quantum efficiency of 1.65% at 420 nm. Furthermore, it showed the longest electron injection lifetime because its coordination structure was considered to be vertically standing on the TiO2 surface by theoretical calculations. On the other hand, dye 1 showed the lowest hydrogen production performance with a TON of 483 and very short electron injection lifetime. This observation is confirmed by the computation results, which showed the lying geometry of 1 with monodentate coordination of the dye with respect to the TiO2 surface. This spacer effectproperty relationship study may provide a good strategy for the development of metal-free organic dyes for dye-sensitized photocatalytic water splitting.

DOI： 10.1039/c4ta02720e

Language：English   Publishing type：Research paper (scientific journal)  

Synthesis of bona fideN-confused phlorin derivatives through simple chemical reduction of N-confused porphyrin precursors using sodium borohydride, p-toluenesulfonyl hydrazide, etc. is described. Spectroscopic, X-ray diffraction analyses and DFT-assisted calculations of these species support the nonaromatic phlorin electronic structure.

DOI： 10.1142/S1088424614500692

Language：English   Publishing type：Research paper (scientific journal)  

The effect of switching the phenylene and thiophenylene units in the triarylene bridge of organic donor-bridge-acceptor dyads on the performance of dye-sensitized solar cells is investigated. A thiophenylene group displays several distinctive advantages over those of a phenylene group. The electron-donating nature of thiophenlene elevates the electron energy level of the dyads and narrows down the energy gap of the electronic transition, therefore elongates the absorption wavelength. The presence of thiophenylene unit along the bridge also increases the planarity of the molecular geometry, therefore enhances the degree of pi-delocalization; however, it also speeds up the rate of charge recombination. The multiple effects of thiophene group along the bridge are examined systematically on two types of dye derivatives, i.e., the T-series and theM-series dyes. Among all the dyes, the ones containing a phenylene-thiophenylene-thiophenylene bridge (T-PSS) showed the highest performance. A typical device made with T-PSS displayed the maximal monochromatic incident photon-to-current conversion efficiency of 65% in the wavelength region between 350 nm and 515 nm, a short-circuit photocurrent density 15.88mA cm(-2), an open-circuit photovoltage 0.64 V, and a fill factor 0.60, that corresponds to an overall conversion efficiency of 6.13%. The packing order of T-PSS can be further improved by adding deoxycholic acid to an overall conversion efficiency of 6.71%. (C) 2014 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.tsf.2014.03.010

Language：English   Publishing type：Research paper (scientific journal)  

The title complex C42H48 center dot 2C6N4{systematic name: heptacyclo[21.13.1.1(5,19).1(6,18).1(10,14).1(24,36).1(28,32)] dotetraconta-1(37), 5(40),6(41), 10(42), 11,13,18,23,28,30,32( 39), 36( 38)-dodecaeneethenetetracarbonitrile (1/2)}, consisting of four-layered [3.3]metacyclophane (MCP) with two tetracyanoethylene (TCNE) molecules, was grown from a mixture of MCP and TCNE in chloroform solution. The four-layered [3.3] MCP has an Sshaped structure in which three [3.3] MCP moieties take syn(chair-boat), anti-(chair-boat) and syn-(chair-boat) conformations. The two outer [3.3] MCP moieties with syn geometry contain benzene rings with a tilt of 32.95 (7)degrees. The central [ 3.3] MCP moiety has an anti geometry, in which the two benzene rings are oriented parallel to each other at a transannular distance of 2.31 angstrom. The TCNE molecules are stacked on either side of the outer [3.3] MCP units at a distance of 3.19 angstrom on one side and 3.24 angstrom on the other, and showed 0.80: 0.20 and 0.44:0.56 disorder, respectively.

DOI： 10.1107/S1600536814009362

Language：English   Publishing type：Research paper (scientific journal)  

The effect of switching the phenylene and thiophenylene units in the triarylene bridge of organic donor-bridge-acceptor dyads on the performance of dye-sensitized solar cells is investigated. A thiophenylene group displays several distinctive advantages over those of a phenylene group. The electron-donating nature of thiophenlene elevates the electron energy level of the dyads and narrows down the energy gap of the electronic transition, therefore elongates the absorption wavelength. The presence of thiophenylene unit along the bridge also increases the planarity of the molecular geometry, therefore enhances the degree of π-delocalization; however, it also speeds up the rate of charge recombination. The multiple effects of thiophene group along the bridge are examined systematically on two types of dye derivatives, i.e., the T-series and the M-series dyes. Among all the dyes, the ones containing a phenylene-thiophenylene-thiophenylene bridge (T-PSS) showed the highest performance. A typical device made with T-PSS displayed the maximal monochromatic incident photon-to-current conversion efficiency of 65% in the wavelength region between 350 nm and 515 nm, a short-circuit photocurrent density 15.88 mA cm^{- 2}, an open-circuit photovoltage 0.64 V, and a fill factor 0.60, that corresponds to an overall conversion efficiency of 6.13%. The packing order of T-PSS can be further improved by adding deoxycholic acid to an overall conversion efficiency of 6.71%.

DOI： 10.1016/j.tsf.2014.03.010

Language：English   Publishing type：Research paper (scientific journal)  

The synthesis, physical properties, and structure of triisopropylsilylethynyltetracenodifuran (2) and pentacenodifuran (3) derivatives were reported. There showed high stability in solution in the dark, yet decomposed under light. Single crystal of pentacenodifuran was analyzed by X-ray diffraction analysis, and showed one dimensional packing array along the c-axis. The molecules were stacked with a 3.30 Å interlayer distance. The crystals exhibited a high thermal stability under an ambient condition.

DOI： 10.1016/j.tetlet.2014.01.036

Language：English   Publishing type：Research paper (scientific journal)  

The synthesis, physical properties, and structure of triisopropylsilylethynyltetracenodifuran (2) and pentacenodifuran (3) derivatives were reported. There showed high stability in solution in the dark, yet decomposed under light. Single crystal of pentacenodifuran was analyzed by X-ray diffraction analysis, and showed one dimensional packing array along the c-axis. The molecules were stacked with a 3.30 angstrom interlayer distance. The crystals exhibited a high thermal stability under an ambient condition. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2014.01.036

Language：English   Publishing type：Research paper (scientific journal)  

Organic dyes that consist of an anthracene moiety between a triphenylamine donor group and a cyanoacrylic acid acceptor group displayed remarkable solar-to-energy conversion efficiency in dye-sensitized solar cells. The planar geometry of anthracene and its bulky substituents helped the dyes to form a high quality monolayer on the surface of TiO₂. A typical device made with the dye AN-Bu displayed a maximal photon-to-current conversion efficiency (IPCE) 65% in the region of 350-510 nm, a short-circuit photocurrent density (J_sc) 12.78 mA cm^-2, an open-circuit photovoltage (V _oc) 0.73 V, and a fill factor (FF) 0.67, corresponding to an overall conversion efficiency 6.23%. In an experiment of using deoxycholic acid (DCA) as a co-absorbent, the values of V_oc stayed in a similar range, yet the values of J_sc were reduced in ca. 11% due to a decrease of loading amounts. This result indicated that the quality of the dye films cannot be further improved by the adding of DCA. The photophysical properties were analyzed with the aid of a time-dependent density functional theory (TDDFT) model with the B3LYP functional.

DOI： 10.1016/j.tet.2013.11.072

Language：English   Publishing type：Research paper (scientific journal)  

Organic dyes that consist of an anthracene moiety between a triphenylamine donor group and a cyanoacrylic acid acceptor group displayed remarkable solar-to-energy conversion efficiency in dyesensitized solar cells. The planar geometry of anthracene and its bulky substituents helped the dyes to form a high quality monolayer on the surface of TiO2. A typical device made with the dye AN-Bu displayed a maximal photon-to-current conversion efficiency (IPCE) 65% in the region of 350-510 nm, a short-circuit photocurrent density (J(sc)) 12.78 mA cm(-2), an open-circuit photovoltage (V-oc) 0.73 V, and a fill factor (FF) 0.67, corresponding to an overall conversion efficiency 6.23%. In an experiment of using deoxycholic acid (DCA) as a co-absorbent, the values of Vo, stayed in a similar range, yet the values offs were reduced in ca. 11% due to a decrease of loading amounts. This result indicated that the quality of the dye films cannot be further improved by the adding of DCA. The photophysical properties were analyzed with the aid of a time-dependent density functional theory (TDDFT) model with the B3LYP functional. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2013.11.072

Language：English   Publishing type：Research paper (scientific journal)  

Photoswitching of conductance through both stable isomers of salicylidene methylamine was investigated using nonequilibrium Green's function method combined with density functional theory. This study demonstrates how the optically induced intramolecular proton transfer between the hydroxyl group and the amino group of salicylidene methylamine can lead to molecular size photodiode with on/off current ratio of 1 order of magnitude. It was further elucidated that the optical switching alone is not sufficient to realize the molecular switch. Of primary importance was found to be the anchoring between the molecule and the metal electrodes. When the anchoring groups were connected to the benzene ring in para-orientation, minimal on/off current ratio was estimated. When the anchoring groups were connected to the benzene ring in meta-orientation, 1 order of magnitude on/o ff current ratio was calculated. Molecular orbital analysis was successfully employed to elucidate the difference in the photoswitching properties of the meta- and para-anchored isomers of salicylidene methylamine. This study demonstrates the potential application of aromatic Schiff bases as photodiodes in the field of molecular electronics. (Figure Presented).

DOI： 10.1021/jp5081884

Language：English   Publishing type：Research paper (scientific journal)  

The title complex C₄₂H₄₈·2C₆N ₄ {systematic name: heptacyclo[21.13.1.1^5,19.1 ^6,18.1^10,14.1^24,36.1^28,32] dotetraconta-1(37),5(40),6(41),10(42),11,13,18,23,28,30,32(39),36(38) -dodecaene-ethenetetracarbonitrile (1/2)}, consisting of four-layered [3.3]metacyclophane (MCP) with two tetracyanoethylene (TCNE) molecules, was grown from a mixture of MCP and TCNE in chloroform solution. The four-layered [3.3]MCP has an S-shaped structure in which three [3.3]MCP moieties take syn-(chair-boat), anti-(chair-boat) and syn-(chair-boat) conformations. The two outer [3.3]MCP moieties with syn geometry contain benzene rings with a tilt of 32.95(7)°. The central [3.3]MCP moiety has an anti geometry, in which the two benzene rings are oriented parallel to each other at a transannular distance of 2.31Å. The TCNE molecules are stacked on either side of the outer [3.3]MCP units at a distance of 3.19Å on one side and 3.24Å on the other, and showed 0.80:0.20 and 0.44:0.56 disorder, respectively.

DOI： 10.1107/S1600536814009362

Language：English   Publishing type：Research paper (scientific journal)  

In the title compound, C₂₁H₁₄N₂O₂S, a donor-acceptor type of benzo[b]phenothiazine (bpz) derivative, the thiazine ring adopts a boat conformation and the bond-angle sum at the N atom is 360.0°. The dihedral angle between the benzene ring and the naphthelene ring system fused to the thiazine ring is 32.76(5)°. In the crystal, carboxylic-acid inversion dimers linked by pairs of O-H⋯O hydrogen bonds generate R 2 ²(8) loops. Aromatic π-π stacking [shortest centroid-centroid separaton = 3.5242(13)Å] consolidates the structure and very weak C-H⋯O and C-H⋯N interactions also occur.

DOI： 10.1107/S1600536814018388

Language：English   Publishing type：Research paper (scientific journal)  

The title compound, C₄₀H₄₆N₂ {systematic name: 12,30-diazaheptacyclo[21.13.1.1^5,19.1^6,18.1^10,14.1^24,36.1^28,32]dotetraconta-1(37),5(40),6(41),10(42),11,13,18,23,28,30,32(39),36(38)-dodecaene}, has syn-anti-syn geometry wherein the two outer [3.3]metacyclophane (MCP) moieties have a syn geometry, and contain the facing benzene and pyridine rings at dihedral angles of 26.26 (10) and 26.46 (10)°, respectively. The rings of the central [3.3]MCP unit are not parallel, but orientated at a slight angle of 2.66 (9)°. Three bridging methylene groups are disordered over two sets of sites in a 0.60:0.40 ratio. In the crystal, the molecules are linked by C - H⋯N interactions and intermolecular C - H⋯π short contacts, generating a three-dimensional network.

DOI： 10.1107/S1600536814023691

Language：English   Publishing type：Research paper (scientific journal)  

Novel organic dyes that consist of either a benzo[1,2-b:4,5-b′] dithiophene or a benzo[1,2-b:4,5-b′]difuran core exhibited remarkable solar-to-energy conversion efficiency in dye-sensitized solar cells. The planar geometry of bridge moiety and its bulky substituents helped the dyes to form a high quality monolayer on the surface of titanium oxide. A typical device displayed photon-to-current conversion efficiency 60% in the region of 380-575 nm, a short-circuit photocurrent density 13.45 mA cm
^-2
, an open-circuit photovoltage 0.72 V, and a fill factor 0.63, corresponding to an overall conversion efficiency 6.12%. In a test of using deoxycholic acid as a co-absorbent, an improvement of quantum efficiencies 8.37% was observed for certain compounds. However, for others the quantum efficiency decreased in 6.60-7.91%. The latter result indicated that the quality of some films cannot be further improved by the addition of deoxycholic acid. The photophysical properties were analyzed with the aid of TDDFT.

DOI： 10.1016/j.dyepig.2014.04.043

Language：English  

Acenes are a class of aromatic hydrocarbons composed of linearly fused benzene rings. Noteworthy features of these molecules include their extended flat structure and the narrow gap between the HOMO and LUMO energy levels. However, the preparation of larger acenes, those that are larger than pentacene, has been challenging. These molecules are relatively unstable and have low solubility In typical solvents. Recently researchers have developed a new synthesis route for higher acenes using stable and soluble "precursors," which generate these structures on demand by either heating or irradiation of light. Using this method, nonsubstituted hexacene, heptacene, octacene, and nonacene were successfully prepared.In this Account, we summarize the preparation of nonsubstituted acenes from corresponding precursors, describe their physical properties, and discuss potential applications including potential usage in organic semiconductor devices. We first introduced the concept of using a precursor in the work with pentacene. Overall, we divide this methodology into two categories: masking pentacene itself with a dienophile to form a cycloadduct and the construction of higher acenes through conventional synthetic procedures. For the first category, a diverse array of dienophiles could be chosen, depending on the processing needs, especially for use in field-effect transistors (FETs). For the second category, researchers synthesized the pentacene precursor molecules using a multistep procedure. Upon proper activation, these molecules expel small fragments to generate pentacene readily. This strategy enabled the production of pentacene andunprepared higher acenes ranging from hexacene to nonacene. This new method provides a way to unravel the fascinating chemistry of higher acenes.

DOI： 10.1021/ar400002y

Language：English   Publishing type：Research paper (scientific journal)  

A soluble precursor of hexacene is prepared from a cycloaddition of hexacene and diethyl ketomalonate in high yield. It can be used to make hexacene thin-films through spin-coating for the fabrication of organic field effect transistors.

DOI： 10.1039/c3cc00278k

Language：English   Publishing type：Research paper (scientific journal)  

1,2,3,4-Tetrafluoropentacene is prepared from a soluble precursor containing a carbonyl bridge across the central benzene ring. It underwent dimerization readily in solution, yet displayed a high stability in the solid state. While fabricated into OFET devices, it exhibited an ambipolar charge transport characteristic. Its spectral and electronic properties are described.

DOI： 10.1016/j.tetlet.2012.11.126

Language：English   Publishing type：Research paper (scientific journal)  

1,2,3,4-Tetrafluoropentacene is prepared from a soluble precursor containing a carbonyl bridge across the central benzene ring. It underwent dimerization readily in solution, yet displayed a high stability in the solid state. While fabricated into OFET devices, it exhibited an ambipolar charge transport characteristic. Its spectral and electronic properties are described. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2012.11.126

Language：English   Publishing type：Research paper (scientific journal)  

Layering up: The synthesis, physical properties, crystal structures, and optoelectronic properties of trialkylsilylethynylanthradifuran derivatives have been reported. Their high solubility enabled them to be processed through a solution phase for the fabrication of organic field-effect transistors (OFETs) and photovoltaic devices.

DOI： 10.1002/asia.201200834

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/asia.201200834

Language：English   Publishing type：Research paper (scientific journal)  

A series of organic dyes containing oligo-phenothiazine were synthesized and used effectively on the fabrication of dye-sensitized solar cells (DSSCs). In these compounds the phenothiazine moiety functions both as an electron donor and as a π-bridge. These materials exhibit considerably high values of open-circuit voltage (V
_oc
) ranging from 0.78-0.83 V under an AM1.5 solar condition (100 mW cm
^-2
). Two kinds of substituents, i.e., hexyl and hexyloxyphenyl groups, were added onto the N(10) of phenothiazine for comparison. The best device displayed a short-circuit current (J
_sc
) of 14.3 mA cm
^-2
, an open-circuit voltage (V
_oc
) of 0.83 V, a fill factor (FF) of 0.65, corresponding to an overall conversion efficiency of 7.78%. Their photophysical properties were analyzed with the aid of a time-dependent density functional theory (TDDFT) model with the B3LYP functional. The electronic nature of the devices was further elucidated by using electrochemical impedance spectroscopy.

DOI： 10.1039/c2jm35556f

Language：English   Publishing type：Research paper (scientific journal)  

A series of organic dyes containing oligo-phenothiazine were synthesized and used effectively on the fabrication of dye-sensitized solar cells (DSSCs). In these compounds the phenothiazine moiety functions both as an electron donor and as a pi-bridge. These materials exhibit considerably high values of open-circuit voltage (V-oc) ranging from 0.78-0.83 V under an AM1.5 solar condition (100 mW cm(-2)). Two kinds of substituents, i.e., hexyl and hexyloxyphenyl groups, were added onto the N(10) of phenothiazine for comparison. The best device displayed a short-circuit current (J(sc)) of 14.3 mA cm(-2), an open-circuit voltage (V-oc) of 0.83 V, a fill factor (FF) of 0.65, corresponding to an overall conversion efficiency of 7.78%. Their photophysical properties were analyzed with the aid of a time-dependent density functional theory (TDDFT) model with the B3LYP functional. The electronic nature of the devices was further elucidated by using electrochemical impedance spectroscopy.

DOI： 10.1039/c2jm35556f

Language：English   Publishing type：Research paper (scientific journal)  

Tetracene of high purity was produced in a quantitative yield from a new precursor, which consists of a carbonyl bridge across the benzene ring. The precursor can be synthesized readily through four steps in an overall yield of 30%. Its structure, along with three other synthetic intermediates, was resolved by X-ray crystal diffraction analyses. High performance organic thin film transistors (OTFTs) were fabricated by using tetracene generated directly from this precursor without further purification being necessary. Two kinds of OFET devices were investigated, i.e., single crystal type and thin film type, while both were processed through solutions. The device made with a single crystal of tetracene displayed a charge carrier mobility of 0.56 cm ² V ^-1 s ^-1 with an on/off ratio of 1.0 × 10 ⁵. Devices made with thin films showed a charge mobility of 6.42 × 10 ^-2 cm ² V ^-1 s ^-1 with an on/off ratio of 2.6 × 10 ⁴. These performances are comparable with those fabricated by using a vapor deposition method.

DOI： 10.1039/c2jm31134h

Language：English   Publishing type：Research paper (scientific journal)  

Acenes can be thought of as one-dimensional strips of graphene and they have the potential to be used in the next generation of electronic devices. However, because acenes larger than pentacene have been found to be unstable, it was generally accepted that they would not be particularly useful materials under normal conditions. Here, we show that, by using a physical vapour-transport method, platelet-shaped crystals of hexacene can be prepared from a monoketone precursor. These crystals are stable in the dark for a long period of time under ambient conditions. In the crystal, the molecules are arranged in herringbone arrays, quite similar to that observed for pentacene. A field-effect transistor made using a single crystal of hexacene displayed a hole mobility significantly higher than that of pentacene. This result suggests that it might be instructive to further explore the potential of other higher acenes.

DOI： 10.1038/NCHEM.1381

Language：English   Publishing type：Research paper (scientific journal)  

Acenes can be thought of as one-dimensional strips of graphene and they have the potential to be used in the next generation of electronic devices. However, because acenes larger than pentacene have been found to be unstable, it was generally accepted that they would not be particularly useful materials under normal conditions. Here, we show that, by using a physical vapour-transport method, platelet-shaped crystals of hexacene can be prepared from a monoketone precursor. These crystals are stable in the dark for a long period of time under ambient conditions. In the crystal, the molecules are arranged in herringbone arrays, quite similar to that observed for pentacene. A field-effect transistor made using a single crystal of hexacene displayed a hole mobility significantly higher than that of pentacene. This result suggests that it might be instructive to further explore the potential of other higher acenes.

DOI： 10.1038/nchem.1381

Language：English   Publishing type：Research paper (scientific journal)  

High performance thin-film transistors were fabricated using a new precursor of pentacene through a multiple spin-heat procedure. High quality pentacene thin films can be prepared by this method and hence a FET device can be made in a top-contact configuration. The device exhibited a remarkable field-effect mobility of 0.38 cm ² V ^-1 s ^-1 with an on/off ratio of 10 ⁶.

DOI： 10.1039/c2cc31754k

Language：English   Publishing type：Research paper (scientific journal)  

2-Chlorotetracene and 2-bromotetracene were generated in high purity from their monoketone precursors either by heating or upon irradiation of light. Crystals of two compounds were prepared by physical vapor transport method. Organic field effect transistors made with the single crystals of these two compounds were fabricated effectively. Their p-type transistor characteristics are described.

DOI： 10.1016/j.tetlet.2012.02.060

Language：English   Publishing type：Research paper (scientific journal)  

2-Chlorotetracene and 2-bromotetracene were generated in high purity from their monoketone precursors either by heating or upon irradiation of light. Crystals of two compounds were prepared by physical vapor transport method. Organic field effect transistors made with the single crystals of these two compounds were fabricated effectively. Their p-type transistor characteristics are described. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2012.02.060

Language：English   Publishing type：Research paper (scientific journal)  

A series of organic dyes were prepared that displayed remarkable solar-to-energy conversion efficiencies in dye-sensitized solar cells (DSSCs). These dyes are composed of a 4-tert-butylphenylamine donor group (D), a cyanoacrylic-acid acceptor group (A), and a phenylene-thiophene-phenylene (PSP) spacer group, forming a D-π-A system. A dye containing a bulky tert-butylphenylene-substituted carbazole (CB) donor group showed the highest performance, with an overall conversion efficiency of 6.70 %. The performance of the device was correlated to the structural features of the donor groups; that is, the presence of a tert-butyl group can not only enhance the electron-donating ability of the donor, but can also suppress intermolecular aggregation. A typical device made with the CB-PSP dye afforded a maximum photon-to-current conversion efficiency (IPCE) of 80 % in the region 400-480 nm, a short-circuit photocurrent density J _sc=14.63 mA cm ^-2, an open-circuit photovoltage V _oc=0.685 V, and a fill factor FF=0.67. When chenodeoxycholic acid (CDCA) was used as a co-absorbent, the open-circuit voltage of CB-PSP was elevated significantly, yet the overall performance decreased by 16-18 %. This result indicated that the presence of 4-tert-butylphenyl substituents can effectively inhibit self-aggregation, even without CDCA.

DOI： 10.1002/asia.201100777

Language：English   Publishing type：Research paper (scientific journal)  

A series of organic dyes were prepared that displayed remarkable solar-to-energy conversion efficiencies in dye-sensitized solar cells (DSSCs). These dyes are composed of a 4-tert-butylphenylamine donor group (D), a cyanoacrylic-acid acceptor group (A), and a phenylene-thiophene-phenylene (PSP) spacer group, forming a D-p-A system. A dye containing a bulky tert-butylphenylene-substituted carbazole (CB) donor group showed the highest performance, with an overall conversion efficiency of 6.70?%. The performance of the device was correlated to the structural features of the donor groups; that is, the presence of a tert-butyl group can not only enhance the electron-donating ability of the donor, but can also suppress intermolecular aggregation. A typical device made with the CB-PSP dye afforded a maximum photon-to-current conversion efficiency (IPCE) of 80?% in the region 400480 nm, a short-circuit photocurrent density Jsc=14.63 mA?cm-2, an open-circuit photovoltage Voc=0.685 V, and a fill factor FF=0.67. When chenodeoxycholic acid (CDCA) was used as a co-absorbent, the open-circuit voltage of CB-PSP was elevated significantly, yet the overall performance decreased by 1618?%. This result indicated that the presence of 4-tert-butylphenyl substituents can effectively inhibit self-aggregation, even without CDCA.

DOI： 10.1002/asia.201100777

Language：English   Publishing type：Research paper (scientific journal)  

A series of organic dyes containing a phenothiazine central unit were synthesized and were used effectively in the fabrication of dye-sensitized solar cells (DSSCs). A cyanoacrylate moiety was added at the C(3) position of the phenothiazine as an electron acceptor, and a triarylamine moiety was attached at the C(7) position as an electron donor. The DSSCs made with these dyes displayed remarkable quantum efficiency, ranging from 4.2-6.2% under an AM 1.5 solar condition (100 mW cm
^-2
). A variety of substituents, i.e., methyl, hexyl and triphenylamino groups, were added at the N(10) of phenothiazine in order to optimize the incident photon-to-current conversion efficiency. Along the main chromophore a thiophenylene group was inserted at different positions to examine its influence on the properties of devices. The best performance was found in compound NSPt-C6, in which a hexyl group was attached at the N(10) of phenothiazine and a thiophenylene at the C(7) position. It displayed a short-circuit current (J
_sc
) of 14.42 mA cm
^-2
, an open-circuit voltage (V
_oc
) of 0.69 V, and a fill factor (ff) of 0.63, corresponding to an overall conversion efficiency of 6.22%. Their photophysical properties were analyzed with the aid of a time-dependent density functional theory (TDDFT) model with the B3LYP functional. Their photovoltaic behavior was further elucidated by the electrochemical impedance spectroscopy.

DOI： 10.1039/c2jm13961h

Language：English   Publishing type：Research paper (scientific journal)  

Organic dyes consisting of a [2.2]paracyclophane unit along the main chromophore are examined for their application in sensitized solar cells. These materials exhibit considerably high values of open-circuit voltage (V _oc) ranging 0.69-0.72 V, and an overall efficiency up to 3.8%.

DOI： 10.1039/c1cc16248a

Language：English   Publishing type：Research paper (scientific journal)  

We have synthesized p-conjugated acceptor-type molecules 3a-d containing a cyanomethylene unit as the electron acceptor site and a 4,5-diazafluorene ligand for metal complexation. In the crystal, the planar 3a molecules stack along the b axis in the head-to-tail fashion. Compound 3a shows distinctive electrochromism and its three differently colored redox states (dianion (3 ^2-), anion radical (3^.-), neutral (3)) exhibit remarkable stability.

DOI： 10.1016/j.tetlet.2011.08.164

Language：English   Publishing type：Research paper (scientific journal)  

We have synthesized pi-conjugated acceptor-type molecules 3a-d containing a cyanomethylene unit as the electron acceptor site and a 4,5-diazafluorene ligand for metal complexation. In the crystal, the planar 3a molecules stack along the b axis in the head-to-tail fashion. Compound 3a shows distinctive electrochromism ;and its three differently colored redox states (dianion (3(2-)), anion radical (3(center dot-)), neutral (3)) exhibit remarkable stability. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2011.08.164

Language：English   Publishing type：Research paper (scientific journal)  

In the solid state, the cyclophane (CP) moieties of the charge-transfer (CT) complexes of four- and five-layered [3.3]metacyclophanes (MCPs) 1 and 2 with tetracyanoethylene (TCNE) take different conformations from those in the solid state of the free MCPs. In the four-layered [3.3]MCP 1-TCNE complex, the CP moiety takes an s-shaped syn-anti-syn geometry, whereas the inner three benzene rings take the all-syn geometry and the two outer [3.3]MCP moieties have deformed anti-conformations in the five-layered [3.3]MCP 2-TCNE complex. In the crystal-packing diagrams of each complex, intermolecular CH/π-type interactions are observed between adjacent molecules.

DOI： 10.1016/j.tetlet.2011.07.060

Language：English   Publishing type：Research paper (scientific journal)  

In the solid state, the cyclophane (CP) moieties of the charge-transfer (CT) complexes of four- and five-layered [3.3]metacyclophanes (MCPs) 1 and 2 with tetracyanoethylene (TCNE) take different conformations from those in the solid state of the free MCPs. In the four-layered [3.3]MCP 1-TCNE complex, the CP moiety takes an s-shaped syn-anti-syn geometry, whereas the inner three benzene rings take the all-syn geometry and the two outer [3.3]MCP moieties have deformed anti-conformations in the five-layered [3.3]MCP 2-TCNE complex. In the crystal-packing diagrams of each complex, intermolecular CH/pi-type interactions are observed between adjacent molecules. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2011.07.060

Language：English   Publishing type：Research paper (scientific journal)  

The synthesis, thermal and photophysical properties, and solution-processed organic field effect transistors fabricated from a soluble tetraceno[2,3-b] thiophene precursor 1. Compound 1 was synthesised in 9.8% through 6 steps. The TGA profiles showed that a 9.1% weight loss occurred at ca. 130 °C, corresponding to an expulsion of a carbonyl group. The photogeneration of tetraceno[2,3-b]thiophene from 1 in the solution state could be fitted into a first-order rate law with a rate constant (k) of 2.05 × 10^-2 s^-1 in a yield of 55.6% (±0.9%) under a 1.25 mW cm ^-2 UV lamp. The platelet micro crystals of 1, formed either by heat or by light, were confirmed by XRD to be identical to a simulated one from reported X-ray crystallographic data. The field effect mobility across a single crystal was measured to be 4.75 × 10^-1 cm² V ^-1 s^-1 with on/off ratio 10⁵. The high purity of single crystals formed both by heat and by light are supported by an EPR analysis. This is the first report of a solution-processed single-crystal OFET of linear acenes without bulky substituent groups. In another experiment, the devices made directly from an amorphous thin film of 1, prepared by spin-coating, exhibited a charge mobility 3.0 × 10^-4 cm ² V^-1 s^-1 with on/off ratio 10³.

DOI： 10.1039/c1jm11834j

Language：English   Publishing type：Research paper (scientific journal)  

In the solid state, multilayered [3.3]paracyclophanes (PCPs) 2-6 and tetracyanoethylene (TCNE) form charge-transfer (CT) complexes with a 1:1 stoichiometry. All the benzene rings overlapped each other. All the [3.3]PCP units and dione units assume chair conformations and the transannular distances are shorter than those of the corresponding free multilayered [3.3]PCP except for the dione unit in the four-layered dione 6. In the crystal-packing diagrams, the PCP and TCNE are located in alternating donor-acceptor stacking in columns, and effective short contacts are observed in the neighboring molecules.

DOI： 10.1016/j.tetlet.2011.04.087

Language：English   Publishing type：Research paper (scientific journal)  

In the solid state, multilayered [3.3]paracyclophanes (PCPs) 2-6 and tetracyanoethylene (TCNE) form charge-transfer (CT) complexes with a 1:1 stoichiometry. All the benzene rings overlapped each other. All the [3.3]PCP units and dione units assume chair conformations and the transannular distances are shorter than those of the corresponding free multilayered [3.3]PCP except for the dione unit in the four-layered dione 6. In the crystal-packing diagrams, the PCP and TCNE are located in alternating donor-acceptor stacking in columns, and effective short contacts are observed in the neighboring molecules. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2011.04.087

Language：English   Publishing type：Research paper (scientific journal)  

In the present study, delocalization of a positive charge in π-stacked multi-benzene rings in multilayered para-and meta-cyclophanes, in which benzene rings are connected by propyl chains to form a chromophore array with the face-to-face structure, was investigated by means of transient absorption spectroscopy during the pulse radiolysis using dichloroethane as a solvent. The local excitation and charge resonance (CR) bands were successfully observed. It was revealed that the CR band shifted to the longer wavelength side with the number of the benzene rings. The stabilization energy estimated from the peak position of the CR band showed the efficient charge delocalization over the cyclophanes. Furthermore, the CR bands showed the slight spectral change attributable to the change in distribution of the conformers. The substantially long lifetime of the CR band can be explained on the basis of the smaller charge distribution on the outer layers of the multilayered cyclophanes.

DOI： 10.1021/jp110916m

Language：English   Publishing type：Research paper (scientific journal)  

In the present study, delocalization of a positive charge in pi-stacked multi-benzene rings in multilayered para- and meta-cyclophanes, in which benzene rings are connected by propyl chains to form a chromophore array with the face-to-face structure, was investigated by means of transient absorption spectroscopy during the pulse radiolysis using dichloroethane as a solvent. The local excitation and charge resonance (CR) bands were successfully observed. It was revealed that the CR band shifted to the longer wavelength side with the number of the benzene rings. The stabilization energy estimated from the peak position of the CR band showed the efficient charge delocalization over the cyclophanes. Furthermore, the CR bands showed the slight spectral change attributable to the change in distribution of the conformers. The substantially long lifetime of the CR band can be explained on the basis of the smaller charge distribution on the outer layers of the multilayered cyclophanes.

DOI： 10.1021/jp110916m

Language：English   Publishing type：Research paper (scientific journal)  

The cyclophanes comprised of two 2,1,3-benzothiadiazole (BTD) rings, anti-and syn-[2.2](4,7)benzothiadiazolophanes (anti-1 and syn-1), were prepared for the first time. The differences of the physical properties in the overlapping mode of the π-systems are clearly observed, and syn-1 shows much more significant transannular π-electronic interactions than anti-1 especially in the redox properties and the stability of the radical anion species.

DOI： 10.1246/bcsj.20100085

Language：English   Publishing type：Research paper (scientific journal)  

The cyclophanes comprised of two 2,1,3-benzothiadiazole (BTD) rings, anti- and syn-[2.2](4,7)benzothiadiazolophanes (anti-1 and syn-1), were prepared for the first time. The differences of the physical properties in the overlapping mode of the pi-systems are clearly observed, and syn-1 shows much more significant transannular pi-electronic interactions than anti-1 especially in the redox properties and the stability of the radical anion species.

DOI： 10.1246/bcsj.20100085

Language：English   Publishing type：Research paper (scientific journal)  

Figure presented. The synthesis, structural, redox, and photophysical properties of the two- and three-layered donor-acceptor (D-A) type [3.3]paracyclophanes ([3.3]PCPs) are described. The synthesis of the two- and three-layered [3.3]PCPs 1 and 2 containing 2,1,3-benzothiadiazole (BTD) as an acceptor was achieved by the (p-ethylbenzenesulfonyl)methyl isocyanide coupling method. The cyclic voltammograms of 1 and 2 along with those of respective dione precursors 5 and 7 clearly indicate that the presence of the -CH ₂COCH₂- bridge interferes with the electronic interactions between the BTD and the benzene rings, suggesting the importance of the through-bond interaction in the ground state. In sharp contrast, the UV/vis spectra of 1 and 5 as well as those of 2 and 7 exhibit similar bands regardless of the presence of the -CH₂COCH₂- or -CH ₂CH₂CH₂- bridges, indicating that the charge-transfer (CT) interaction is mainly responsible for the through-space interaction. The two-layered PCPs, 5 and 1, show broad structureless fluorescence bands at the same position of 468 nm, while those of the three-layered PCPs, 7 and 2, appear at 501 and 496 nm, respectively, with lower quantum yields compared to those of the two-layered PCPs probably due to the stronger intramolecular CT interaction of the three-layered PCPs in the ground state.

DOI： 10.1021/jo100688m

Language：English   Publishing type：Research paper (scientific journal)  

The synthesis, structural, redox, and photophysical properties of the two- and three-layered donor acceptor (D-A) type [3.3]paracyclophanes ([3.3]PCPs) are described. The synthesis of the two- and three-layered [3.3]PCPs 1 and 2 containing 2,1,3-benzothiadiazole (BTD) as an acceptor was achieved by the (p-ethylbenzenesulfonypmethyl isocyanide coupling method. The cyclic voltammo-grams of 1 and 2 along with those of respective dione precursors 5 and 7 clearly indicate that the presence of the -CH2COCH2- bridge interferes with the electronic interactions between the BTD and the benzene rings, suggesting the importance of the through-bond interaction in the ground state. In sharp contrast, the UV/vis spectra of 1 and 5 as well as those of 2 and 7 exhibit similar bands regardless of the presence of the -CH2COCH2- or -CH2CH2CH2- bridges, indicating that the charge-transfer (CT) interaction is mainly responsible for the through-space interaction. The two-layered PCPs, 5 and 1, show broad structureless fluorescence bands at the same position of 468 nm, while those of the three-layered PCPs, 7 and 2, appear at 501 and 496 nm, respectively, with lower quantum yields compared to those of the two-layered PCPs probably due to the stronger intramolecular CT interaction of the three-layered PCPs in the ground state.

DOI： 10.1021/jo100688m

Language：English   Publishing type：Research paper (scientific journal)  

A variable temperature ¹H NMR study of the [3.3](3,5)pyridinophane indicated that the syn(chair/chair) is more stable than syn(chair/boat) by 0.2 kcal/mol in solution, whereas the trimethylene bridges show disorder even at -150 °C in the solid state. A transition state search by ab initio MO calculations suggested two competitive conformational changes for syn(chair/chair)-syn(chair/boat) conversion via a bridge wobble or a ring inversion in the [3.3](3,5)pyridinophane.

DOI： 10.1016/j.tetlet.2009.01.051

Language：English   Publishing type：Research paper (scientific journal)  

A variable temperature H-1 NMR Study of the [3.3](3,5)pyridinophane indicated that the syn(chair/chair) is more stable than syn(chair/boat) by 0.2 kcal/mol in solution, whereas the trimethylene bridges show disorder even at -150 degrees C in the solid state. A transition state search by ab initio MO calculations suggested two competitive conformational changes for syn(chair/chair)-syn(chair/boat) conversion via a bridge wobble or a ring inversion in the [3.3](3,5)pyridinophane. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tetlet.2009.01.051

Language：English   Publishing type：Research paper (scientific journal)  

Two- to four-layered [3.3](3,5)pyridinophanes (PyPs) have been synthesized by the (4-tolylsulfonyl)methyl isocyanide (TosMIC) method. The coupling reaction between 3,5-bis[2-iso-cyano-2-(4-tolylsulfonyl)ethyl]pyridine (TosMIC adduct) and bis(chloromethyl) or tetrakis(bromomethyl) compounds in the presence of sodium hydride in N,N-dimethylformamide or sodium hydroxide and tetrabutylammonium iodide under high-dilution conditions gave the two-layered dione or three- and four-layered tetraones. Wolff-Kishner reduction of the ketones afforded the desired two- to four-layered [3.3](3,5)PyPs. The structure of the dione units take an anti geometry whereas the cyclophane units take a syn geometry in solution.

DOI： 10.1055/s-0028-1083633

Language：English   Publishing type：Research paper (scientific journal)  

Two- to four-layered [3.3](3,5)pyridinophanes (PyPs) have been synthesized by the (4-tolylsulfonyl)methyl isocyanide (TosMIC) method. The coupling reaction between 3,5-bis[2-iso-cyano-2-(4-tol ylsulfonyl)ethyl]pyridine (TosMIC adduct) and bis(chloromethyl) or tetrakis(bromomethyl) compounds in the preseence of sodium hydride in N,N-dimethylformamide or sodium hydroxide and tetrabutylammonium iodide under high-dilution conditions gave the two-layered dione or three- and four-layered tetraones. Wolff-Kishner reduction of the ketones afforded the desired two- to four-layered [3.3](3.5)PyPs. The structure of the dione units take an anti geometry whereas the cyclophane units take a syn geometry in solution.

DOI： 10.1055/s-0028-1083633

Language：English   Publishing type：Research paper (scientific journal)  

(Figure Presented) A racemic mixture of three-layered [3.3]paracyclophane ([3.3]PCP), 1, has been resolved into two enantiomers, and their absolute configuration was determined from a comparison of experimental chiroptical properties and density functional theory (DFT) calculations. A simple model comprising two p-xylenes and 1,2,4,5-tetramethylbenzene (durene) was used to explain the origin of the chiroptical properties of the three-layered cyclophane system.

DOI： 10.1021/jo801441h

Language：English   Publishing type：Research paper (scientific journal)  

A racemic mixture of three-layered [3.3]paracyclophane ([3.3]PCP), 1, has been resolved into two enantiomers, and their absolute configuration was determined from a comparison of experimental chiroptical properties and density functional theory (DFT) calculations. A simple model comprising two p-xylenes and 1,2,4,5-tetramethylbenzene (durene) was used to explain the origin of the chiroptical properties of the three-layered cyclophane system.

DOI： 10.1021/jo801441h

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/jo8013484

Language：English  

DOI： 10.1021/jo8013484

Language：English   Publishing type：Research paper (scientific journal)  

(Figure Presented) The synthesis of three- and four-layered [3.3]paracyclophanes ([3.3]PCPs) 3-5 has been accomplished by utilizing the (p-ethylbenzenesulfonyl)methyl isocyanide (EbsMIC) method. The structures of the three- to four-layered [3.3]PCPs 3-5 and their diones 8, 10, and 11 have been elucidated based on the ¹H NMR spectra and finally by X-ray structural analysis. In the three-layered [3.3]PCP-dione 8, the trimethylene bridges of the [3.3]PCP unit assume a chair conformation similar to that of 2, while the [3.3]PCP-2,11-dione unit assumes a boat conformation different from that of [3.3]PCP-dione 1 with a chair conformation. On the other hand, the two [3.3]PCP units in three-layered [3.3]PCP 3 both assume a boat conformation. In the four-layered [3.3]PCP-dione 10, the two outer [3.3]PCP units assume a boat conformation while the inner dione unit has a chair conformation. The trimethylene bridges in the four-layered [3.3]PCP 4 are highly disordered even at -150°C. All the outer benzene rings are distorted into a boat form while the inner ones are distorted into a twist form. In the electronic spectra, bathochromic shift and hyperchromic effect are observed, but the magnitude decreases with an increase in the number of layers and the spectra become structureless. In the charge-transfer (CT) bands of the three- to four-layered [3.3]PCPs 3-5 with tetracyanoethylene (TCNE), two absorption maxima (λ_max) are observed. The effect of an increase in the layers becomes significant, and the changes in the longest wavelength λ_max values from two to three and three to four are ca. 60 and 50 nm, respectively. By comparison of the stereoisomeric four-layered [3.3]PCPs 4 (meso) and 5 (racemic), the helical arrangement of the trimethylene bridges of 5 shows a more efficient transannular π-electronic interaction. In the three- to four-layered [3.3]PCP-diones, a magnitude of the CT interaction almost comparable to that of [3.3]PCP 2 was observed, and this indicates that the -CH₂COCH₂- bridges inhibit the CT interaction and that this tendency is supported by the calculated HOMO energy levels and observed oxidation potentials. Three- and four-layered [3.3]PCPs 3-5 show reversible redox processes, and 4 and 5 show an electron-donating ability almost comparable to that of [3₆]CP. Very good correlation between the λλ_max of the CT bands with TCNE and the oxidation potentials is observed.

DOI： 10.1021/jo8003309

Language：English   Publishing type：Research paper (scientific journal)  

The synthesis of three- and four-layered [3.3]paracyclophanes ([3.3]PCPs) 3-5 has been accomplished by utilizing the (p-ethylbenzenesulfonyl)methyl isocyanide (EbsMIC) method. The structures of the three- to four-layered [3.3]PCPs 3-5 and their diones 8, 10, and 11 have been elucidated based on the H-1 NMR spectra and finally by X-ray structural analysis. In the three-layered [3.3]PCP-dione 8, the trimethylene bridges of the [3.3]PCP unit assume a chair conformation similar to that of 2, while the [3.3]PCP-2,11-dione unit assumes a boat conformation different from that of [3.3]PCP-dione 1 with a chair conformation. On the other hand, the two [3.3]PCP units in three-layered [3.3]PCP 3 both assume a boat conformation. In the four-layered [3.3]PCP-dione 10, the two outer [3.3]PCP units assume a boat conformation while the inner dione unit has a chair conformation. The trimethylene bridges in the four-layered [3.3]PCP 4 are highly disordered even at -150 degrees C. All the outer benzene rings are distorted into a boat form while the inner ones are distorted into a twist form. In the electronic spectra, bathochromic shift and hyperchromic effect are observed, but the magnitude decreases with an increase in the number of layers and the spectra become structureless. In the charge-transfer (CT) bands of the three- to four-layered [3.3]PCPs 3-5 with tetracyanoethylene (TCNE), two absorption maxima (lambda(max)) are observed. The effect of an increase in the layers becomes significant, and the changes in the longest wavelength lambda(max) values from two to three and three to four are ca. 60 and 50 nm, respectively. By comparison of the stereoisomeric four-layered [3.3]PCPs 4 (meso) and 5 (racemic), the helical arrangement of the trimethylene bridges of 5 shows a more efficient transannular pi-electronic interaction. In the, three- to four-layered [3.3]PCP-diones, a magnitude of the CT interaction almost comparable to that of [3.3]PCP 2 was observed, and this indicates that the -CH2COCH2- bridges inhibit the CT interaction and that this tendency is supported by the calculated HOMO energy levels and observed oxidation potentials. Three- and four-layered [3.3]PCPs 3-5 show reversible redox processes, and 4 and 5 show an electron-donating ability almost comparable to that of [3(6)]CP. Very good correlation between the lambda(max) of the CT bands with TCNE and the oxidation potentials is observed.

DOI： 10.1021/jo8003309

Language：English   Publishing type：Research paper (scientific journal)  

(Figure Presented) The synthesis of a series of three- to six-layered [3.3]metacyclophanes ([3.3]MCPs) 3-6 has been successfully accomplished by the (p-tolylsulfonyl)methyl isocyanide (TosMIC) method as a critical coupling reaction. Their important synthetic intermediates are the two- and three-layered bis(bromomethyl) compounds 11, 17, 21, and tetrakis(bromomethyl) compounds 25 and 28. The structures of the three- to six-layered [3.3]MCPs (3-6) as well as three- to six-layered [3.3]MCP-di- (22-24) and tetraones (26, 27, and 29) as the synthetic intermediates have been elucidated based on the ¹H NMR data and X-ray structural analysis. These multilayered cyclophanes are constructed with two different geometries, syn[3.3]MCP and anti-[3.3]MCP-2,11- dione. In principle, their geometries are maintained in the multilayered [3.3]MCPs, but deformation of the dihedral angle of the two benzene rings of the syn-[3.3]MCP moiety is generally observed. In the four-layered MCP 4, the central [3.3]MCP moiety takes an anti geometry. These data indicate the structural flexibility of the [3.3]MCP moiety. In the electronic spectra, rather simple and structureless absorption curves are observed, and the most significant spectral change is observed for the two to three layers and becomes less effective even if it is more layered. In the charge-transfer (CT) bands of the multilayered [3.3]MCPs with tetracyanoethylene (TCNE), the λ_maxmax gradually shifts to the longer wavelength region, but the extent of the shift is much smaller as the number of layers increases. In the multilayered [3.3]MCP-di- and tetraones, the anti-[3.3]MCP-dione moiety works as an insulator. Therefore, the CT interaction of the four- and five-layered [3.3]MCPs with one anti-[3.3]MCP-dione moiety (23 and 24) shows the almost comparable magnitude of the interaction with the two- and three-layered [3.3]MCPs (2 and 3), respectively. The tetraones of the three and four-layered MCPs (29 and 26) do not show CT interactions except for the six-layered MCP 27.

DOI： 10.1021/jo062220m

Language：English   Publishing type：Research paper (scientific journal)  

The synthesis of a series of three- to six-layered [3.3]metacyclophanes ([3.3]MCPs) 3-6 has been successfully accomplished by the (p-tolylsulfonyl)methyl isocyanide (TosMIC) method as a critical coupling reaction. Their important synthetic intermediates are the two- and three-layered bis(bromomethyl) compounds 11, 17, 21, and tetrakis(bromomethyl) compounds 25 and 28. The structures of the three- to six-layered [3.3]MCPs (3-6) as well as three- to six-layered [3.3]MCP-di- (22-24) and tetraones (26, 27, and 29) as the synthetic intermediates have been elucidated based on the H-1 NMR data and X-ray structural analysis. These multilayered cyclophanes are constructed with two different geometries, syn-[3.3]MCP and anti-[3.3]MCP-2,11-dione. In principle, their geometries are maintained in the multilayered [3.3]MCPs, but deformation of the dihedral angle of the two benzene rings of the syn-[3.3]MCP moiety is generally observed. In the four-layered MCP 4, the central [3.3]MCP moiety takes an anti geometry. These data indicate the structural flexibility of the [3.3]MCP moiety. In the electronic spectra, rather simple and structureless absorption curves are observed, and the most significant spectral change is observed for the two to three layers and becomes less effective even if it is more layered. In the charge-transfer (CT) bands of the multilayered [3.3]MCPs with tetracyanoethylene (TCNE), the lambda(max) gradually shifts to the longer wavelength region, but the extent of the shift is much smaller as the number of layers increases. In the multilayered [3.3]MCP-di- and tetraones, the anti-[3.3]MCP-dione moiety works as an insulator. Therefore, the CT interaction of the four- and five-layered [3.3]MCPs with one anti-[3.3]MCP-dione moiety (23 and 24) shows the almost comparable magnitude of the interaction with the two- and three-layered [3.3]MCPs (2 and 3), respectively. The tetraones of the three and four-layered MCPs (29 and 26) do not show CT interactions except for the six-layered MCP 27.

DOI： 10.1021/jo062220m

Language：English   Publishing type：Research paper (scientific journal)  

Event date： 2023.6

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Type：Peer review 

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