Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Tsuyohiko Fujigaya Last modified date:2019.06.29

Professor / Molecular Information Chemistry / Department of Applied Chemistry / Faculty of Engineering

1. Zehui Yang, Tsuyohiko Fujigaya, Naotoshi Nakashima, NaOH-Aided Platinum Nanoparticle Size Regulation on Polybenzimidazole-Wrapped Carbon Nanotubes for Use as Non-Humidified Polymer Electrolyte Fuel Cell Catalyst, ChemCatChem, 10.1002/cctc.201501089, 8, 1, 268-275, 2016.01, We describe a method to control the size of platinum nanoparticles (Pt-NPs) on poly[2,2′-(2,6-pyridine)-5,5′-bibenzimidazole] (PyPBI)-wrapped pristine multi-walled carbon nanotubes (MWNTs) without changing the loading amount by adding various concentrations of sodium hydroxide (NaOH) to the ethylene glycol aqueous solutions. The Pt-NP sizes decreased from 3.8±0.4 to 1.7±0.1 nm with increasing NaOH concentrations. The mass activity of the oxygen reduction reaction was 224 mA mgPt
-1 for the electrocatalyst with 3 nm Pt-NPs, in which the power density reached 350 mW cm-2, which was 1.4 times higher than that of the electrocatalyst synthesized without NaOH (250 mW cm-2) at 120 °C and without any extra humidification. The electrocatalyst synthesized from a small amount of additional NaOH (0.5 mm) in the starting solution shows an enhanced performance and similar Pt stability. More importantly, the Pt-NP size showed no effect on the Pt stability owing to the use of the PyPBI..
2. Tsuyohiko Fujigaya, Yusuke Saegusa, Shogo Momota, Nobuhide Uda, Naotoshi Nakashima, Interfacial engineering of epoxy/carbon nanotubes using reactive glue for effective reinforcement of the composite, Polymer Journal, 10.1038/pj.2015.98, 48, 2, 183-188, 2016.02, We describe a novel strategy for reinforcing an epoxy resin using carbon nanotubes (CNTs), in which polybenzimidazole (PBI) was used as the glue to enable effective adhesion between the epoxy matrix and the CNT surface. Because PBI strongly interacts with the surfaces of the CNTs and reacts with epoxy matrices to form covalent bonds, the PBI-wrapped CNTs are a promising novel epoxy-CNT hybrid. The PBI-wrapped CNTs (CNT/PBI) exhibited an effective reinforcement of the epoxy resin hybrid, resulting in a higher tensile strength and Young's modulus (that is, +28.1% and +8.8%, respectively) compared with those of the hybrid using oxidized CNTs in place of PBI-wrapped CNTs (+18.6% and -4.8% reinforcement for tensile strength and Young's modulus, respectively). Scanning electron microscopy measurements of the fracture surfaces of the CNT/PBI-epoxy hybrid revealed that only very short CNTs were observed for the CNT/PBI-epoxy hybrid due to effective load transfer resulting from the formation of covalent bonds between the PBI on the CNTs and the epoxy resin, which is in contrast to that observed for oxidized CNT-epoxy, which exhibited long CNTs in the fracture surfaces owing to slippage at the interfaces..
3. Mohamed Mahmoud Nasef, Tsuyohiko Fujigaya, Ebrahim Abouzari-Lotf, Naotoshi Nakashima, Zehui Yang, Enhancement of performance of pyridine modified polybenzimidazole fuel cell membranes using zirconium oxide nanoclusters and optimized phosphoric acid doping level, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2016.03.022, 41, 16, 6842-6854, 2016.05, Nanocomposite proton conducting membranes incorporating zirconium oxide (ZrO2) nanoclusters into solution cast 2,6-pyridine polybenzimidazole (2,6-Py-PBI) films and doped with phosphoric acid (PA) were prepared. The content of ZrO2 nanoclusters in the membrane matrix was varied from 0 to 10 wt%. The parameters of the acid doping reaction were optimized by the response surface method (RSM). The membrane properties were evaluated by Fourier transform infrared (FTIR), scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), universal mechanical tester and DC impedance. The incorporation of 5 wt% ZrO2 nanoclusters increased the acid doping level and remarkably enhanced the proton conductivity of the membrane. A maximum proton conductivity of 60.0 mS/cm was recorded compared to 21.5 and 12.0 mS/cm for pristine and 10 wt% ZrO2 containing membranes at 150 °C and dry condition, respectively. The membrane with 5 wt% ZrO2 also showed the highest performance in a single cell at 120 °C under dry conditions. The results suggest that the composite membrane containing 5 wt% ZrO2 nanoclusters has a potential for application in high temperature proton exchange membrane fuel cell application..
4. Hua Li, Akiko Inada, Tsuyohiko Fujigaya, Hironori Nakajima, Kazunari Sasaki, Kohei Ito, Effects of operating conditions on performance of high-temperature polymer electrolyte water electrolyzer, Journal of Power Sources, 10.1016/j.jpowsour.2016.03.108, 318, 192-199, 2016.06, Effects of operating conditions of a high-temperature polymer electrolyte water electrolyzer (HT-PEWE) on the electrolysis voltage are evaluated, and the optimal conditions for a high performance are revealed. A HT-PEWE unit cell with a 4-cm2 electrode consisting of Nafion117-based catalyst-coated membrane with IrO2 and Pt/C as the oxygen and hydrogen evolution catalysts is fabricated, and its electrolysis voltage and high-frequency resistance are assessed. The cell temperature and pressure are controlled at 80-130 °C and 0.1-0.5 MPa, respectively. It is observed that increasing the temperature at a constant pressure of 0.1 MPa does not increase the ohmic overvoltage of the cell; however, it does increase the concentration overvoltage. It is also found that the increase in the overvoltage resulting from the rise in the temperature can be suppressed by elevating the pressure. When operating the cell at a temperature of 100 °C, pressure greater than 0.1 MPa suppresses the overvoltage, and so does pressures greater than 0.3 MPa at 130 °C. This behavior suggests that keeping the water in a liquid water phase by increasing the pressure is critical for operating PEWEs at high temperatures..
5. Syouhei Nishihama, Seitaro Takayama, Kazuharu Yoshizuka, Tsuyohiko Fujigaya, Naotoshi Nakashima, Photo-swing extraction system for the separation of lanthanide using a pyrene group-containing thermosensitive polymer combined with carbon nanotubes, Separation Science and Technology (Philadelphia), 10.1080/01496395.2016.1147468, 51, 15-16, 2492-2500, 2016.11, A novel photo-swing extraction system for lanthanide separation was developed using a copolymer of acid phosphoxy ethyl methacrylate (Phosmer-M), N-isopropylacrylamide (NIPAM), and (1-pyrene)methyl methacrylate (Phosmer-M/NIPAM/PyMMA). Single-walled carbon nanotubes (CNTs) were successfully dispersed in the Phosmer-M/NIPAM/PyMMA as a result of the π-π interactions of the pyrene groups. The phase transition of the copolymer was successfully induced via photo-irradiation as a result of heat generation by the CNTs. The extraction of Eu(III) was increased by the photo-irradiation because of changes in volume and hydrophobicity of the copolymer. Separation of the lanthanides was improved by the photo-irradiation, especially for the combination of Eu(III)/Sc(III)..
6. Hua Li, Tsuyohiko Fujigaya, Hironori Nakajima, Akiko Inada, Kohei Ito, Optimum structural properties for an anode current collector used in a polymer electrolyte membrane water electrolyzer operated at the boiling point of water, Journal of Power Sources, 10.1016/j.jpowsour.2016.09.086, 332, 16-23, 2016.11, This study attempts to optimize the properties of the anode current collector of a polymer electrolyte membrane water electrolyzer at high temperatures, particularly at the boiling point of water. Different titanium meshes (4 commercial ones and 4 modified ones) with various properties are experimentally examined by operating a cell with each mesh under different conditions. The average pore diameter, thickness, and contact angle of the anode current collector are controlled in the ranges of 10–35 μm, 0.2–0.3 mm, and 0–120°, respectively. These results showed that increasing the temperature from the conventional temperature of 80 °C to the boiling point could reduce both the open circuit voltage and the overvoltages to a large extent without notable dehydration of the membrane. These results also showed that decreasing the contact angle and the thickness suppresses the electrolysis overvoltage largely by decreasing the concentration overvoltage. The effect of the average pore diameter was not evident until the temperature reached the boiling point. Using operating conditions of 100 °C and 2 A/cm2, the electrolysis voltage is minimized to 1.69 V with a hydrophilic titanium mesh with an average pore diameter of 21 μm and a thickness of 0.2 mm..
7. Zehui Yang, Akiyo Nagashima, Tsuyohiko Fujigaya, Naotoshi Nakashima, Electrocatalyst composed of platinum nanoparticles deposited on doubly polymer-coated carbon nanotubes shows a high CO-tolerance in methanol oxidation reaction, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2016.08.198, 41, 42, 19182-19190, 2016.11, High CO-tolerance and durability of anodic fuel cell electrocatalysts is one of the important factors for commercialization of direct methanol fuel cells (DMFCs). In this study, we describe the preparation of an electrocatalyst composed of poly[2,2′-(2,6-pyridine)-5,5′-bibenzimidazole] (PyPBI) and poly(vinylphosphonic acid) (PVPA) coated multi-walled carbon nanotubes (MWNTs) on which ∼3 nm Pt nanoparticles (Pt[sbnd]NPs) are deposited. The fabricated electrocatalyst shows 1.5-times higher CO tolerance compared to the commercial CB/Pt, which would be due to the wrapping of the CNTs with PVPA by the aid of PyPBI. Meanwhile, the electrocatalyst almost maintains its initial electrochemical surface area (ECSA) and mass activity of the methanol oxidation reaction (MOR) after 10,000 potential cycling in the range of 1–1.5 V vs. RHE. In contrast, the commercial CB/Pt shows almost a 50% loss in its ECSA and mass activity. These results indicate that the durability of the newly fabricated electrocatalyst is quite high and the obtained high CO-tolerance and durability are important for the design of an electrocatalyst for DMFC applications..
8. Keita Ozono, Masashi Fukuzawa, Fumiyuki Toshimitsu, Tomohiro Shiraki, Tsuyohiko Fujigaya, Naotoshi Nakashima, Chiral Selective Chemical Reaction of Flavin-Derivative-Wrapped Semiconducting Single-Walled Carbon Nanotubes Based on a Specific Recognition, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.20180206, 91, 11, 1646-1651, 2018.01, A specific chiral selective chemical reaction on flavinwrapped single-walled carbon nanotubes (SWNTs) is recognized based on a unique assembled structure formation of the flavin when using a chlorinated solvent such as chloroform; namely, the self-assembled flavin onto the SWNT surface protected (8,6)SWNTs from the chlorine radical reaction..
9. Yukiko Nagai, Yusuke Tsutsumi, Naotoshi Nakashima, Tsuyohiko Fujigaya, Synthesis of Single-Walled Carbon Nanotubes Coated with Thiol-Reactive Gel via Emulsion Polymerization, Journal of the American Chemical Society, 10.1021/jacs.8b03873, 140, 27, 8544-8550, 2018.07, Single-walled carbon nanotubes (SWNTs) have unique near-infrared absorption and photoemission properties that are attractive for in vivo biological applications such as photothermal cancer treatment and bioimaging. Therefore, a smart functionalization strategy for SWNTs to create biocompatible surfaces and introduce various ligands to target active cancer cells without losing the unique optical properties of the SWNTs is strongly desired. This paper reports the design and synthesis of a SWNT/gel hybrid containing maleimide groups, which react with various thiol compounds through Michael addition reactions. In this hybrid, the method called carbon nanotube micelle polymerization was used to noncovalently modify the surface of SWNTs with a cross-linked polymer gel layer. This method can form an extremely stable gel layer on SWNTs; such stability is essential for in vivo biological applications. The monomer used to form the gel layer contained a maleimide group, which was protected with furan in endo-form. The resulting hybrid was treated in water to induce deprotection via a retro-Diels-Alder reaction and then functionalized with thiol compounds through Michael addition. The functionalization of the hybrid was explored using a thiol-containing fluorescent dye as a model thiol, and the formation of the SWNT-dye conjugate was confirmed by energy transfer from the dye to SWNTs. Our strategy offers a promising SWNT-based platform for biological functionalization for cancer targeting, imaging, and treatment..
10. Kulbir K. Ghuman, Tsuyohiko Fujigaya, Electronic Structure of a Polybenzimidazole-Wrapped Single-Wall Carbon Nanotube, Journal of Physical Chemistry C, 10.1021/acs.jpcc.8b00247, 122, 28, 15979-15985, 2018.07, Polymer wrapping on a carbon nanotube (CNT) surface by polybenzimidazoles (PBIs) allows us to immobilize platinum nanoparticles on pristine CNTs and to use it as the electrocatalyst of polymer electrolyte membrane fuel cells (PEMFCs), thereby improving the durability of PEMFCs. In this work, for the first time, we present the fundamental insights into the electronic structure and the interaction present in the single-wall CNT (SWCNT) and PBI composite through comprehensive theoretical study supported by experiments. Our analyses predict that PBI possesses stable helical wrapping around SWCNT because of the strong noncovalent π-π interaction between them, in which PBI participates more than SWCNTs. It is also found that the functionalization of SWCNTs by PBI is independent of the SWCNT chiralities and that the functionalization does not affect the intrinsic properties of SWCNTs, making the SWCNT/PBI-based membrane electrode assembly a good candidate for high-performance PEMFCs..
11. Hisashi Onitsuka, Tsuyohiko Fujigaya, Naotoshi Nakashima, Tomohiro Shiraki, Control of the Near Infrared Photoluminescence of Locally Functionalized Single-Walled Carbon Nanotubes via Doping by Azacrown-Ether Modification, Chemistry - A European Journal, 10.1002/chem.201800904, 24, 37, 9393-9398, 2018.07, Doped semiconducting single-walled carbon nanotubes (SWNTs) through local chemical functionalization (lf-SWNTs) show fascinating photoluminescence (PL) that appears with a longer wavelength and enhanced quantum yield compared to the original PL of non-modified SWNTs. In this study, we introduce an azacrown ether moiety at the doped sites of lf-SWNTs (CR-lf-SWNTs), and observe selective PL wavelength shifts depending on different interaction modes of silver ion inclusion and protonation of the amino group in the ring. Interestingly, their different values of the wavelength shifts show a clear correlation with calculated electron density of the nitrogen atom in the azacrown moiety in case of the inclusion form and the protonated form. This newly-observed responsiveness based on molecular interactions is expected to create doped sites that can versatilely control the PL functions based on molecular systems..
12. Ki Hong Park, Seung Hoon Lee, Fumiyuki Toshimitsu, Jihoon Lee, Sung Heum Park, Tsuyohiko Fujigaya, Jae Won Jang, Gate-enhanced exciton-phonon coupling in photocurrent of (6,5) single-walled carbon nanotube based visible sensing field effect transistor, Carbon, 10.1016/j.carbon.2018.07.002, 139, 709-715, 2018.11, A visible sensing field effect transistor (FET) with a channel length of 100 nm for individual (6,5) single-walled carbon nanotubes (SWCNTs) is fabricated via a selective sorting method using 9,9-dioctyfluorenyl-2,7-diyl–bipyridine (PFO–BPy) polymer. The FET of the (6,5) SWCNTs shows p-type behavior with hundreds of on-off ratios and on-state conductivity of 50 ± 4.0 (Ω m)
. In addition, the photocurrent of the FET of the (6,5) SWCNTs in the visible range increases (maximum 200 times at 620 nm) with higher gate voltage. E
transition and PFO-BPy transition are observed in the FET of the (6,5) SWCNTs without application of a gate voltage. Interestingly, exciton-phonon coupled E
transition due to gate-doping (p-type), which has been reported in photoluminescence and absorption studies, is expected to occur in the photocurrent of the FET at negatively higher gate voltage (≤−4 V). In addition, the exciton-phonon coupled E
transition is prominently observable when carrier concentration by gate doping becomes approximately two-hundred sixty times (260 ± 43) larger than carrier concentration without application of a gate voltage. This demonstration would be useful for the development of SWCNT-based visible sensors with gate control in the SWCNT devices..
13. Tomohiro Shiraki, Tamehito Shiga, Tomonari Shiraishi, Hisashi Onitsuka, Naotoshi Nakashima, Tsuyohiko Fujigaya, Multistep Wavelength Switching of Near-Infrared Photoluminescence Driven by Chemical Reactions at Local Doped Sites of Single-Walled Carbon Nanotubes, Chemistry - A European Journal, 10.1002/chem.201805342, 24, 72, 19162-19165, 2018.12, Local chemical functionalization is used for defect doping of single-walled carbon nanotubes (SWNTs), to develop near-infrared photoluminescence (NIR PL) properties. We report the multistep wavelength shifting of the NIR PL of SWNTs through chemical reactions at local doped sites tethered to an arylaldehyde group. The PL wavelength of the doped SWNTs is modulated based on imine chemistry. This involves the imine formation of aldehyde groups with added arylamines, imine dissociation reaction, exchange reaction of bound arylamines in the imine, and the Kabachnik–Fields reaction of imine groups using diisopropyl phosphite. Using doped sites as a localized chemical reaction platform can exploit the versatile molecularly driven functionality of carbon nanotubes and related nanomaterials..
14. Mohamed R. Berber, Tsuyohiko Fujigaya, Naotoshi Nakashima, A potential polymer formulation of a durable carbon-black catalyst with a significant fuel cell performance over a wide operating temperature range, Materials Today Energy, 10.1016/j.mtener.2018.08.016, 10, 161-168, 2018.12, Polymer electrolyte membrane fuel cells (PEMFCs) that quickly operate at relatively low temperatures, while generating a high-power output is of particular interest, especially for portable devices, since no external power source is required to reach the highest power at higher operating temperatures. Here, we describe the temperature-dependence and the performance of a membrane electrode assembly (MEA) of a newly fabricated fuel cell catalyst of carbon black (CB) which was functionalized for the first time by two conductive polymers; i.e., polybenzimidazole and Nafion. The fabricated MEA quickly operated at room temperature, providing a power density of 130 mW/cm2 (172 mW/mgPt) and 174 mW/cm2 (230 mW/mgPt) under 50% RH and 100% RH conditions, respectively. It also showed a remarkable durability (900-h long-term durability testing and 100,000 potential-stress cyclings) with a maximum power density of 250 mW/cm2 (330 mW/mgPt) at 60 °C. The electrochemical impedance spectroscopy (EIS) analysis showed an enhanced ionic conductivity of the assembled MEA at low temperatures due to the fabrication design which provided more useful conductive pathways for the smooth proton transport on the polymer's backbone. The results of this research satisfies the market demands, and offer reasonably priced materials with a remarkable performance and durability. In addition, it will stimulate industrial researchers to be involved in similar activities..
15. Wenxin Huang, Eriko Tokunaga, Yuki Nakashima, Tsuyohiko Fujigaya, Thermoelectric properties of sorted semiconducting single-walled carbon nanotube sheets, Science and Technology of Advanced Materials, 10.1080/14686996.2019.1567107, 20, 1, 97-104, 2019.01, Single-walled carbon nanotubes (SWNTs), especially their semiconducting type, are promising thermoelectric (TE) materials due to their high Seebeck coefficient. In this study, the in-plane Seebeck coefficient (S), electrical conductivity (σ), and thermal conductivity (κ) of sorted semiconducting SWNT (s-SWNT) free-standing sheets with different s-SWNT purities are measured to determine the figure of merit ZT. We find that the ZT value of the sheets increases with increasing s-SWNT purity, mainly due to an increase in Seebeck coefficient while the thermal conductivity remaining constant, which experimentally proved the superiority of the high purity s-SWNT as TE materials for the first time. In addition, from the comparison between sorted and unsorted SWNT sheets, it is recognized that the difference of ZT between unsorted SWNT and high-purity s-SWNT sheet is not remarkable, which suggests the control of carrier density is necessary to further clarify the superiority of SWNT sorting for TE applications..
16. W. Huang, F. Toshimitsu, K. Ozono, M. Matsumoto, A. Borah, Y. Motoishi, K. H. Park, J. W. Jang, Tsuyohiko Fujigaya, Thermoelectric properties of dispersant-free semiconducting single-walled carbon nanotubes sorted by a flavin extraction method, Chemical Communications, 10.1039/c8cc10264c, 55, 18, 2636-2639, 2019.01, Semiconducting single-walled carbon nanotubes (s-SWNTs) were extracted from SWNT mixtures using a flavin derivative (FC12). We evaluated the thermoelectric properties of the s-SWNT sheets. Electrical conductivity, power factor and figure of merit values of the sheets were increased by two orders of magnitude after removing FC12 simply by dipping in dichloromethane..
17. Tomohiro Shiraki, Yoshiaki Niidome, Fumiyuki Toshimitsu, Tomonari Shiraishi, Tamehito Shiga, Boda Yu, Tsuyohiko Fujigaya, Solvatochromism of near infrared photoluminescence from doped sites of locally functionalized single-walled carbon nanotubes, Chemical Communications, 10.1039/c9cc00829b, 55, 25, 3662-3665, 2019.01, The doped sites of locally functionalized single-walled carbon nanotubes emit red-shifted and bright near-infrared photoluminescence compared to non-doped nanotubes. Here, we observe unique photoluminescent solvatochromism. Organic solvent environments induce photoluminescent energy shifts that linearly correlate with a solvent polarity function. A high responsiveness at the doped sites is found..
18. Tsuyohiko Fujigaya, Development of thermoelectric conversion materials using carbon nanotube sheets, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.20180272, 400-408, 2019.01, Recently, thermoelectric (TE) conversion has attracted strong interests toward converting waste heat to electrical potential for applications such as portable and wearable electronic devices. Among a number of different candidates including inorganic and polymeric materials, single-walled carbon nanotubes (SWCNT) are particularly attractive due to their non-toxicity, material abundance, solution processability, remarkable electrical conductivity and so on. Here, progress in TE research based on SWCNT sheets is reviewed mainly for air stabilization of n-type SWCNT sheets and the TE properties of semiconducting SWCNT sheets..
19. Samindi Madhubha Jayawickrama, Ziyi Han, Shusaku Kido, Naotoshi Nakashima, Tsuyohiko Fujigaya, Enhanced platinum utilization efficiency of polymer-coated carbon black as an electrocatalyst in polymer electrolyte membrane fuel cells, Electrochimica Acta, 10.1016/j.electacta.2019.05.007, 312, 349-357, 2019.07, The utilization efficiency of platinum (Pt)in polymer electrolyte membrane fuel cells (PEMFCs)needs to be increased to lower the cost of PEMFCs to facilitate their widespread commercialization. Here we developed a novel method to improve the Pt utilization efficiency by coating of polybenzimidazole (PBI)on the surface of the carbon support material; Vulcan. Electrochemical experiments revealed that Pt nanoparticle-loaded PBI-coated Vulcan (denoted as Vulcan/PBI/Pt)electrode possessed a much larger electrochemically active surface area (ECSA)compared with that of Pt nanoparticles directly deposited on Vulcan (Vulcan/Pt). The power density of the cell with Vulcan/PBI/Pt was 1.16 kW g
, which was ca. 20% higher than that of the control cell using Vulcan/Pt (0.97 kW g
). We considered that the higher Pt utilization efficiency of Vulcan/PBI/Pt than Vulcan/Pt resulted in such an enhanced ECSA and power density of the PBI-coated system. Two possible reasons were considered for the improvement; namely 1)the polymer layer prevented the loading of Pt nanoparticles into inaccessible micropores of Vulcan and 2)the polymer layer improved the coating homogeneity of Nafion ionomer, and thus improved the proton accessibility for Pt nanoparticles..
20. Edyta Turek, Tomohiro Shiraki, Tomonari Shiraishi, Tamehito Shiga, Tsuyohiko Fujigaya, Dawid Janas, Single-step isolation of carbon nanotubes with narrow-band light emission characteristics, Scientific reports, 10.1038/s41598-018-37675-4, 9, 1, 2019.12, Lack of necessary degree of control over carbon nanotube (CNT) structure has remained a major impediment factor for making significant advances using this material since it was discovered. Recently, a wide range of promising sorting methods emerged as an antidote to this problem, all of which unfortunately have a multistep nature. Here we report that desired type of CNTs can be targeted and isolated in a single step using modified aqueous two-phase extraction. We achieve this by introducing hydration modulating agents, which are able to tune the arrangement of surfactants on their surface, and hence make selected CNTs highly hydrophobic or hydrophilic. This allows for separation of minor chiral species from the CNT mixture with up to 99.7 ± 0.02% selectivity without the need to carry out any unnecessary iterations. Interestingly, our strategy is also able to enrich the optical emission from CNTs under selected conditions..
21. Sumit Verma, Yuki Hamasaki, Chaerin Kim, Wenxin Huang, Shawn Lu, Huei Ru Molly Jhong, Andrew A. Gewirth, Tsuyohiko Fujigaya, Naotoshi Nakashima, Paul J.A. Kenis, Insights into the Low Overpotential Electroreduction of CO2 to CO on a Supported Gold Catalyst in an Alkaline Flow Electrolyzer, ACS Energy Letters, 10.1021/acsenergylett.7b01096, 3, 1, 193-198, 2018.01, Cost competitive electroreduction of CO<sub>2</sub> to CO requires electrochemical systems that exhibit partial current density (j<sub>CO</sub>) exceeding 150 mA cm<sup>-2</sup> at cell overpotentials (|η<sub>cell</sub>|) less than 1 V. However, achieving such benchmarks remains difficult. Here, we report the electroreduction of CO<sub>2</sub> on a supported gold catalyst in an alkaline flow electrolyzer with performance levels close to the economic viability criteria. Onset of CO production occurred at cell and cathode overpotentials of just -0.25 and -0.02 V, respectively. High j<sub>CO</sub> (∼99, 158 mA cm<sup>-2</sup>) was obtained at low |η<sub>cell</sub>| (∼0.70, 0.94 V) and high CO energetic efficiency (∼63.8, 49.4%). The performance was stable for at least 8 h. Additionally, the onset cathode potentials, kinetic isotope effect, and Tafel slopes indicate the low overpotential production of CO in alkaline media to be the result of a pH-independent rate-determining step (i.e., electron transfer) in contrast to a pH-dependent overall process..
22. Koichiro Mori, Minoru Kawaguchi, Tsuyohiko Fujigaya, Jun Ohno, Tetsuro Ikebe, Polymer-coated carbon nanotubes as a molecular heater platform for hyperthermic therapy, Journal of Hard Tissue Biology, 10.2485/jhtb.27.139, 27, 2, 139-146, 2018.01, Carbon nanotubes have been explored as heat-delivery vehicles for thermal ablation of tumors. To use single-walled carbon nanotubes (SWNT) as a “molecular heater” for hyperthermic therapy in cancer treatment, stable dispersibility and smart-targeting potential are necessary. The current study reports the dispersibility and exothermic properties with near-infrared (NIR) exposure for SWNT coated with a copolymer of N-isopropylacrylamide and polyethyleneglycol methacrylate (SWNT/PNIPAM-PEG-hybrid). The SWNT/PNIPAM-PEG hybrid showed stable dispersibility in PBS solution and exothermic potential with NIR exposure. Raman spectroscopy results revealed a hybrid derived Raman peak in mouse liver and spleen lysates for 7 days post-injection that disappeared by 14 days in all tissues (liver, spleen, heart, lung and kidney). These results suggested that the hybrid did not accumulate in mouse organ tissues in the long-term. The SWNT/PNIPAM-PEG hybrid decreased the cell viability (of mouse macrophages) with heat generation by NIR exposure. The results of this study demonstrate that the SWNT/PNIPAM-PEG hybrid is a useful platform for a “molecular heater” applicable to hyperthermic cancer therapy..
23. Tomoya Shimono, Masaya Matsuki, Teppei Yamada, Masa-Aki Morikawa, Nobuhiro Yasuda, Tsuyohiko Fujigaya, Nobuo Kimizuka, Selective ionic conduction in choline iodide/triiodide solid electrolyte and its application to thermocells, Chemistry Letters, 10.1246/cl.171069, 47, 3, 261-264, 2018.01, A thermocell consisting of choline iodide/triiodide solid electrolyte is developed. Seebeck coefficient of the cell is10.87 mV K11 at ambient temperature, which sign is opposite to that of the aqueous I1/I3 1 cell. The ionic conductivity of I3 1doped choline iodide is higher than that of pure choline iodide by two to four orders of magnitude, reflecting high conductivity of I3 1 in the solid electrolyte. The selective ionic conduction observed in the solid electrolytes provides a novel design principle for the thermoelectric conversion materials..
24. Huei Ru “Molly” Jhong, Claire E. Tornow, Chaerin Kim, Sumit Verma, Justin L. Oberst, Paul S. Anderson, Andrew A. Gewirth, Tsuyohiko Fujigaya, Naotoshi Nakashima, Paul J.A. Kenis, Gold Nanoparticles on Polymer-Wrapped Carbon Nanotubes
An Efficient and Selective Catalyst for the Electroreduction of CO2, ChemPhysChem, 10.1002/cphc.201700815, 18, 22, 3274-3279, 2017.11, 優れた電気伝導性を持つカーボンナノチューブ上に金ナノ粒子を担持することに成功し、二酸化炭素電気化学還元触媒として用いたところ、高い選択性と低い過電圧を示すことが明らかとなった。.
25. Inas H. Hafez, Mohamed R. Berber, Tsuyohiko Fujigaya, Naotoshi Nakashima, High Electronic Conductivity and Air Stability of Ultrasmall Copper-Metal Nanoparticles Supported on Pyridine-Based Polybenzimidazole Carbon Nanotube Composite, ChemCatChem, 10.1002/cctc.201700921, 9, 22, 4282-4286, 2017.11, The development of synthetic methods of copper nanoparticles (Cu-NPs) on conductive supports is very challenging and receives much attention. Here, we describe a novel technique to grow stable and uniform metallic Cu-NPs homogeneously on the surface of pristine multiwalled carbon nanotube (MWNTs) catalyst support physically functionalized with a pyridine-based polybenzimidazole (PyPBI) polymer that acts as a ligand to capture the Cu-NPs. Cu-metal nanoparticles with a particle size of 5.0±0.5 nm were obtained on the surface of MWNTs with homogenous and uniform distribution. The newly prepared Cu-NPs show a remarkably enhanced air stability and electrical conductivity, compared to the current state of the art Cu-NPs, over 20 days and 500 potential cycles, respectively, with a limited degradation rate of Cu-metallic state. The PyPBI polymer plays an essential role in the stability of Cu-NPs on the surface of MWNTs through coordination with PyPBI, suppressing the Cu-degradation process, which usually decreases the Cu application efficiency. Accordingly, the prospects of applications of the present Cu-NPs composite are excellent..
26. Mohamed Mahmoud Nasef, Tsuyohiko Fujigaya, Ebrahim Abouzari-Lotf, Naotoshi Nakashima, Electrospinning of poly(vinylpyrrodine) template for formation of ZrO2 nanoclusters for enhancing properties of composite proton conducting membranes, International Journal of Polymeric Materials and Polymeric Biomaterials, 10.1080/00914037.2016.1201829, 66, 6, 289-298, 2017.04, Nanosized ZrO2 clusters were prepared by electrospinning a poly(vinylpyrrodine) (PVP)/ZrO2 mixture for calcination to remove PVP template and sizing. The morphological, chemical, structural, and thermal resistance changes during preparation stages were investigated using scanning electron microscope, energy-dispersive X-ray spectroscopy, transmission electron microscope, X-ray diffraction, and thermogravimetric analysis. The obtained ZrO2 clusters were used for preparation of nanocomposite membranes by dispersion in 2,6-pyridine polybenzimidazole (2,6-Py-PBI) matrix at 5 wt% content followed by phosphoric acid (PA) doping. The ZrO2 nanoclusters were found to be uniformly distributed in 2,6-Py-PBI/PA matrix leading to a remarkable increase in the PA doping level and proton conductivity of the obtained composite membrane..
27. Jun Yang, Tsuyohiko Fujigaya, Naotoshi Nakashima, Decorating unoxidized-carbon nanotubes with homogeneous Ni-Co spinel nanocrystals show superior performance for oxygen evolution/reduction reactions, Scientific Reports, 10.1038/srep45384, 7, 2017.03, We present a new concept for homogeneous spinel nanocrystal-coating on high crystalline pristine-carbon nanotubes (CNTs) for efficient and durable oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Oxidized CNTs have widely been used to functionalize with metal or metal oxides since the defect sites act as anchoring for metal oxide binding. However, such defects on the tubes cause the decrease in electrical conductivity and stability, leading to lower catalyst performance. In the present study, at first, pristine multi-walled carbon nanotubes (MWNTs) were wrapped by pyridine-based polybenzimidazole (PyPBI) to which uniform Ni x Co 3-x O 4 nanocrystals were homogeneously deposited by the solvothermal method without damaging the MWNTs, in which PyPBI acted as efficient anchoring sites for the deposition of spinel oxide nanocrystals with ∼5 nm size. The obtained catalyst (MWNT-PyPBI-Ni x Co 3-x O 4) outperformed most state-of-the-art non-precious metal-based bifunctional catalysts; namely, for OER, the potential at 10 mA cm -2 and Tafel slope in 1 M KOH solution were 1.54 V vs. RHE and 42 mV dec -1, respectively. For ORR, the onset and half-wave potentials are 0.918 V and 0.811 V vs. RHE, respectively. Moreover, the MWNT-PyPBI-Ni x Co 3-x O 4 demonstrates an excellent durability for both ORR and OER..
28. Yuki Nakashima, Naotoshi Nakashima, Tsuyohiko Fujigaya, Development of air-stable n-type single-walled carbon nanotubes by doping with 2-(2-methoxyphenyl)-1,3-dimethyl-2,3-dihydro-1H-benzo[d]imidazole and their thermoelectric properties, Synthetic Metals, 10.1016/j.synthmet.2016.11.042, 225, 76-80, 2017.03, 近年ウェアラブルデバイスの電源として有望視されている熱電変換材料のうち、フレキシブル性に優れ、高い電気伝導率を持つカーボンナノチューブに注目が集まっている。しかし、カーボンナノチューブのような有機系材料においては大気安定なn型材料を作るのが困難であった。我々はベンズイミダゾール誘導体がカーボンナノチューブを大気安定n型化するドープ剤であることを世界に先駆けて発見した。.
29. Tsuyohiko Fujigaya, Yilei Shi, Jun Yang, Hua Li, Kohei Ito, Naotoshi Nakashima, A highly efficient and durable carbon nanotube-based anode electrocatalyst for water electrolyzers, Journal of Materials Chemistry A, 10.1039/c7ta01318c, 5, 21, 10584-10590, 2017.01, Iridium (Ir) nanoparticles with a uniform diameter of 1.1 ± 0.2 nm were homogeneously deposited on multi-walled carbon nanotubes (MWNTs) wrapped by polybenzimidazole (PBI), in which PBI enables efficient anchoring of the Ir nanoparticles. The Ir nanoparticles were electrochemically oxidized to afford Ir oxide (IrO) and evaluated as an oxygen evolution reaction catalyst by half-cell measurements. The composite was also used as an anode electrocatalyst for proton exchange membrane water electrolyzers (PEMWEs). It was revealed that the IrO2 on the PBI-wrapped MWNTs exhibited a very high electrocatalytic mass activity and durability even compared to the other state-of-the-art Ir-based catalysts, while the IrO2 deposited on conventional carbon black showed only a poor durability..
30. Tsuyohiko Fujigaya, Chiori Saito, Ziyi Han, Naotoshi Nakashima, Ionomer grafting to polymer-wrapped carbon nanotubes for polymer electrolyte membrane fuel cell electrocatalyst, Chemistry Letters, 10.1246/cl.170744, 46, 11, 1660-1663, 2017.01, Polybenzimidazole-wrapped carbon nanotubes (CNTs) is grafted by quaternized 1,4-diazabicyclo[2,2,2]octane (DABCO) and used as a new electrocatalyst for the anion-exchange membrane fuel cells after loading of platinum nanoparticles. Single-cell measurements reveal that the power density of the cell is 58.8mWcm-2, higher than that of non-grafted analogue. We found the grafting approach to be a promising strategy to avoid leaching of the water-soluble quaternized ionomer..
31. J. Yang, F. Toshimitsu, Z. Yang, Tsuyohiko Fujigaya, N. Nakashima, Pristine carbon nanotube/iron phthalocyanine hybrids with a well-defined nanostructure show excellent efficiency and durability for the oxygen reduction reaction, Journal of Materials Chemistry A, 10.1039/C6TA07882F, 5, 3, 1184-1191, 2017.01, Development of non-platinum electrocatalysts with high performance, durability, and scalability for fuel cells and batteries is a strong social demand for a next-generation eco-friendly energy society. Here, we present a pristine multi-walled carbon nanotube/iron phthalocyanine (MWNT/FePc) hybrid catalyst with a well-defined nanostructure for the oxygen reduction reaction (ORR) in alkaline media that meets this demand. By carefully tuning the microstructure of the FePc stack layer deposited on the highly crystallized graphitic surface of a MWNT support, an ultra-high ORR activity as well as excellent durability are obtained. Moreover, a power density of 185 mW cm−2 at 0.8 V was obtained for a zinc-air battery using this optimized MWNT/FePc cathode at room temperature. Density functional theory-based calculations of such a well-defined nanostructure of MWNT/FePc have suggested that deposition on the bent graphitic surface of MWNTs significantly changes the geometric and electronic structures of FePc that originated from π-π interactions, leading to such enhanced electrocatalytic activity and durability..
32. Tsuyohiko Fujigaya, Toward the development of highly durable polymer electrolyte fuel cell using carbon nanotube, Sen'i Gakkaishi, 73, 5, 213-214, 2017.
33. H. Wenxin, N. Nakashima, Tsuyohiko Fujigaya, Solvent-free Fabrication of Carbon Nanotube/Resin Composite for Printable Thermoelectric Device, CHEMISTRY LETTERS, 10.1246/cl.160399, 45, 8, 875-877, 2016.08.
34. Tsuyohiko Fujigaya, Shinsuke Hirata, M. R. Berber, Improved Durability of Electrocatalyst Based on Coating of Carbon Black with Polybenzimidazole and their Application in Polymer Electrolyte Fuel Cells, ACS APPLIED MATERIALS & INTERFACES, 10.1021/acsami.6b01316, 8, 23, 14494-14502, 2016.06.
35. Li Hua, Akiko Inada, Tsuyohiko Fujigaya, Hironori NAKAJIMA, Kazunari SASAKI, Kohei Ito, Effects of operating conditions on performance of high-temperature polymer electrolyte water electrolyzer, Journal of Power Sources, doi:10.1016/j.jpowsour.2016.03.108, 318, 192-199, 2016.04.
36. Yusuke Tsutsumi, Tsuyohiko Fujigaya, Naotoshi Nakashima, Requirement for the Formation of Crosslinked Polymers on Single-walled Carbon Nanotubes Using Vinyl Monomers, CHEMISTRY LETTERS, 10.1246/cl.151086, 45, 3, 274-276, 2016.03.
37. Tsuyohiko Fujigaya, Yusuke Saegusa, Shogo Momota, Nobuhide Uda, Naotoshi Nakashima, Interfacial Engineering of Epoxy/Carbon Nanotube by using Reactive Glue for Effective Reinforcement of the Composite, Polymer Journal, 48, 183-188, 2016.02.
38. Tsuyohiko Fujigaya, ChaeRin Kim, Yuki Hamasaki, Naotoshi Nakashima, Growth and Deposition of Au Nanoclusters on Polymer-wrapped Graphene and Their Oxygen Reduction Activity, SCIENTIFIC REPORTS, 10.1038/srep21314, 6, 2016.02.
39. Tsuyohiko Fujigaya, C.R Kim, Yiki Hamasaki, Naotoshi Nakashima, Growth and Deposition of Au Nanoclusters on Polymer-wrapped Graphene and Their Oxygen Reduction Activity, SCIENTIFIC REPORTS, 10.1038/srep21314, 6, 2016.02.
40. Yusuke Segusa, Tsuyohiko Fujigaya, Naotoshi Nakashima, Interfacial Engineering of Epoxy/Carbon Nanotube by using Reactive Glue for Effective Reinforcement of the Composite, Polymer Journal, 2016.02.
41. Naoki Imazu, Tsuyohiko Fujigaya, Naotoshi Nakashima, Fabrication of flexible transparent conductive films from long double-walled carbon nanotubes, Sci. Technol. Adv. Mater. , 10.1088/1468-6996/15/2/025005, 15, 025005, 2016.01.
42. Zehui Yang, Tsuyohiko Fujigaya, Naotoshi Nakashima, Homogeneous coating of ionomer on electrocatalyst assisted by polybenzimidazole as an adhesive layer and its effect on fuel cell performance, JOURNAL OF POWER SOURCES, 10.1016/j.jpowsour.2015.09.069, 300, 175-181, 2015.12.
43. Yusuke Tsutsumi, Tsuyohiko Fujigaya, Naotoshi Nakashima, Requirement for the Formation of Cross-linked Polymer on Single-walled Carbon Nanotubes Using Vinyl Monomers, Chem. Lett., 45, 3, 274-276, 2015.12.
44. Tsuyohiko Fujigaya, Hirata Shinsuke, Naotoshi Nakashima, A highly durable fuel cell electrocatalyst based on polybenzimidazole-coated stacked graphene, JOURNAL OF MATERIALS CHEMISTRY A, 10.1039/c3ta14469k, 2, 11, 3888-3893, 2015.11.
45. BERBER MOHAMED, Tsuyohiko Fujigaya, Naotoshi Nakashima, A highly durable fuel cell electrocatalyst based on double-polymer-coated carbon nanotubes, Scientific Reports, 5, 167111, 2015.10.
46. Yusuke Tsutsumi, Tsuyohiko Fujigaya, Naotoshi Nakashima, Size reduction of 3D-polymer-coated single-walled carbon nanotubes by ultracentrifugation, NANOSCALE, 10.1039/c5nr05066a, 7, 46, 19534-19539, 2015.10.
47. BERBER MOHAMED, Tsuyohiko Fujigaya, Naotoshi Nakashima, A highly durable fuel cell electrocatalyst based on double-polymer-coated carbon nanotubes, Scientific Reports, 5, 167111, 2015.10.
48. Zehui Yang, ChaeRin Kim, Shinsuke Hirata, Tsuyohiko Fujigaya, Naotoshi Nakashima, Facile Enhancement in CO-Tolerance of a Polymer-Coated Pt Electrocatalyst Supported on Carbon Black: Comparison between Vulcan and Ketjenblack, ACS APPLIED MATERIALS & INTERFACES, 10.1021/acsami.5b03371, 7, 29, 15885-15891, 2015.07.
49. Zehui Yang, ChaeRin Kim, Shinsuke Hirata, Tsuyohiko Fujigaya, Naotoshi Nakashima, Facile Enhancement in CO-Tolerance of a Polymer-Coated Pt Electrocatalyst Supported on Carbon Black: Comparison between Vulcan and Ketjenblack, ACS APPLIED MATERIALS & INTERFACES, 10.1021/acsami.5b03371, 7, 29, 15885-15891, 2015.07.
50. Zehui Yang, Tsuyohiko Fujigaya, Naotoshi Nakashima, A phosphoric acid-doped electrocatalyst supported on poly(para-pyridine benzimidazole)- wrapped carbon nanotubes shows a high durability and performance, J. Mater. Chem. A, 5, 12236, 2015.01.
51. ChaeRin Kim, Tsuyohiko Fujigaya, Naotoshi Nakashima, One-pot Synthesis of Gold-Platinum Core-Shell Nanoparticles on Polybenzimidazole-decorated Carbon Nanotubes, CHEMISTRY LETTERS, 10.1246/cl.140663, 43, 11, 1737-1739, 2014.11.
52. Akiyo Nagashima, Tsuyohiko Fujigaya, Naotoshi Nakashima, Effect of Nanostructure of the Electrocatalyst Based on Carbon Nanotube for the Activation Overpotential for PEFC, JOURNAL OF MATERIALS CHEMISTRY C, 10.1149/06403.0151ecst, 64, 3, 151-157, 2014.10.
53. Tsuyohiko Fujigaya, BERBER MOHAMED, Naotoshi Nakashima, Design of Highly Durable Electrocatalyst for High-Temperature Polymer Electrolyte Fuel Cell, POLYMER ELECTROLYTE FUEL CELLS 14, 10.1149/06403.0159ecst, 64, 3, 159-169, 2014.10.
54. Takao Sada, Tsuyohiko Fujigaya, Naotoshi Nakashima, Layer-by-layer Assembly of Trivalent Metal Cation and Anionic Polymer in Nanoporous Anodic Aluminum Oxide with 35 nm Pore, CHEMISTRY LETTERS, 10.1246/cl.140489, 43, 9, 1478-1480, 2014.09.
55. Yoo JongTae, ChaeRin Kim, Tsuyohiko Fujigaya, Naotoshi Nakashima, Graphene oxide and laponite composite films with high oxygen-barrier properties, NANOSCALE, 10.1039/c4nr03429e, 6, 18, 10824-10830, 2014.09.
56. Naotoshi Nakashima, Tsuyohiko Fujigaya, Junichi Morita, Grooves of Bundled Single-Walled Carbon Nanotubes Dramatically Enhance the Reactivity of Oxygen Reduction Reaction, ChemCatChem, 10.1002/cctc.201402565, 6, 11, 3169-3173, 2014.09.
57. Hafez Inas H, BERBER MOHAMED, Tsuyohiko Fujigaya, Naotoshi Nakashima, Enhancement of Platinum Mass Activity on the Surface of Polymer-wrapped Carbon Nanotube-Based Fuel Cell Electrocatalysts, SCIENTIFIC REPORTS, 10.1038/srep06295, 4, 2014.09.
58. BERBER MOHAMED, Tsuyohiko Fujigaya, Naotoshi Nakashima, Durability Analysis of Polymer-coated Pristine Carbon Nanotube-based Fuel Cell Electrocatalyst at Non-humidified Conditions, Journal of Materials Chemistry A , 2, 44, 19053-19059, 2014.09.
59. Takao Sada, Tsuyohiko Fujigaya, Naotoshi Nakashima, Manipulation of cell membrane using carbon nanotube scaffold as a photoresponsive stimuli generator, SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS, 10.1088/1468-6996/15/4/045002, 15, 4, 2014.08.
60. JongTae Yoo, ChaeRin Kim, Tsuyohiko Fujigaya, Naotoshi Nakashima, Homogeneous decoration of zeolitic imidazolate framework-8 (ZIF-8) with core-shell structures on carbon nanotubes, RSC ADVANCES, 10.1039/c4ra06792d, 4, 91, 49614-49619, 2014.07.
61. Takao Sada, Tsuyohiko Fujigaya, Naotoshi Nakashima, Design and fabrication of Ni nanowires having periodically hollow nanostructures, NANOSCALE, 10.1039/c4nr02625j, 6, 19, 11484-11488, 2014.05.
62. BERBER MOHAMED, 藤ヶ谷 剛彦, 中嶋 直敏, High-Temperature Polymer Electrolyte Fuel Cell Using Poly(vinylphosphonic acid) as an Electrolyte Shows a Remarkable Durability, CHEMCATCHEM, 10.1002/cctc.201300884, 6, 2, 567-571, 2014.02.
63. 藤ヶ谷 剛彦, 金 菜リン, 松本 和也, Palladium-Based Anion- Exchange Membrane Fuel Cell Using KOH- Doped Polybenzimidazole as the Electrolyte, CHEMPLUSCHEM, 10.1002/cplu.201300377, 79, 3, 400-405, 2014.03.
64. Takahiro Fukumaru, Fumiyuki Toshimitsu, Tsuyohiko Fujigaya, Naotoshi Nakashima, Effects of the chemical structure of polyfluorene on selective extraction of semiconducting singlewalled carbon nanotubes, Nanoscale, 10.1039/c4nr00809j, 6, 5879 -5886, 2014.03.
65. 堤 優介, 藤ヶ谷 剛彦, 中嶋 直敏, Polymer synthesis inside a nanospace of a surfactant-micelle on carbon nanotubes: creation of highly-stable individual nanotubes/ultrathin cross-linked polymer hybrids, RSC ADVANCES, 10.1039/c3ra46841k, 4, 12, 6318-6323, 2013.12.
66. Takahiro Fukumaru, Tsuyohiko Fujigaya, Naotoshi Nakashima, Fabrication of Poly(p-phenylene benzobisoxazole) Film Using a Soluble Poly(o-alkoxyphenyl amide) as the Precursor, Macromolecules, 4, 6318-6323, 2013.11.
67. 藤ヶ谷 剛彦, 中嶋 直敏, 福丸貴弘, Fabrication of Poly(p-phenylene benzobisoxazole) Film Using a Soluble Poly(o-alkoxyphenyl amide) as the Precursor, Macromolecules, 10.1021/ma4024526, 47, 2088-2095, 2013.05.