Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
BENJAMIN LE OUAY Last modified date:2021.06.16

Assistant Professor / Department of Chemistry / Faculty of Sciences

1. David S. Wragg, Peter J. Byrne, Gaetan Giriat, Benjamin Le Ouay, Robert Gyepes, Andrew Harrison, A. Gavin Whittaker, Russell E. Morris, In Situ Comparison of Ionothermal Kinetics Under Microwave And Conventional Heating, JOURNAL OF PHYSICAL CHEMISTRY C, 10.1021/jp907785t, 113, 48, 20553-20558, 2009.12, We have used in situ energy dispersive synchrotron X-ray diffraction to study the crystallization of aluminum phosphate frameworks under ionothermal conditions with conventional and microwave heating. The reaction is shown to follow slightly different routes depending on the type of heating used and a kinetic analysis shows that the rate constant is 10 times higher under microwave heating (1.4 compared to 0.14 min(-1)). The conventionally heated reaction is shown to proceed by a transformation of SIZ-3 to SIZ-4 via an intermediate, while the microwave-heated reaction forms SIZ-4 directly. The kinetic analysis is used to rationalize the differences in reaction rate and the findings are supported by SEM images of the crystal morphologies which result from the two heating methods..
2. David S. Wragg, Benjamin Le Ouay, Andrew M. Beale, Matthew G. O'Brien, Alexandra M. Z. Slawin, John E. Warren, Timothy J. Prior, Russell E. Morris, Ionothermal synthesis and crystal structures of metal phosphate chains, JOURNAL OF SOLID STATE CHEMISTRY, 10.1016/j.jssc.2010.05.002, 183, 7, 1625-1631, 2010.07, We have prepared isostructural aluminium and gallium phosphate chains by ionothermal reactions in 1-ethyl-3-methylimidazolium bromide and 1-ethylpyridinium bromide under a variety of conditions. The chains can be prepared as pure phases or along with three dimensional framework phases. The chains are favoured at shorter heating times and the crystallinity can be improved by addition of transition metal acetates and amines which are not included in the final structure. The chain can be prepared with or without the presence of hydrofluoric acid. (C) 2010 Elsevier Inc. All rights reserved..
3. Thomas Devic, Patricia Horcajada, Christian Serre, Fabrice Salles, Guillaume Maurin, Beatrice Moulin, Daniela Heurtaux, Guillaume Clet, Alexandre Vimont, Jean-Marc Greneche, Benjamin Le Ouay, Florian Moreau, Emmanuel Magnier, Yaroslav Filinchuk, Jerome Marrot, Jean-Claude Lavalley, Marco Daturi, Gerard Ferey, Functionalization in Flexible Porous Solids: Effects on the Pore Opening and the Host-Guest Interactions, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 10.1021/ja9092715, 132, 3, 1127-1136, 2010.01, The synthesis on the gram scale and characterization of a series of flexible functionalized iron terephthalate MIL-53(Fe) type solids are reported. Chemical groups of various polarities, hydrophilicities, and acidities (-Cl, -Br, -CF3, -CH3, -NH2, -OH, -CO2H) were introduced through the aromatic linker, to systematically modify the pore surface. X-ray powder diffraction (XRPD), molecular simulations, thermogravimetric analyses, and in situ IR and Fe-57 Mossbauer spectrometries indicate some similarities with the pristine MIL-53(Fe) solid, with the adoption of the narrow pore form for all solids in both the hydrated and dry forms. Combined XRPD and computational structure determinations allow concluding that the geometry of the pore opening is predominantly correlated with the intraframework interactions rather than the steric hindrance of the substituent. Only (MIL-53(Fe)-(CF3)(2)) exhibits a nitrogen accessible porosity (S-BET approximate to 100 m(2) g(-1)). The adsorption of some liquids leads to pore openings showing some very specific behaviors depending on the guest-MIL-53(Fe) framework interactions, which can be related to the energy difference between the narrow and large pore forms evaluated by molecular simulation..
4. Benjamin Le Ouay, Stephanie Lau-Truong, Emmanuel Flahaut, Roberta Brayner, Jean Aubard, Thibaud Coradin, Christel Laberty-Robert, DWCNT-Doped Silica Gel Exhibiting Both Ionic and Electronic Conductivities, JOURNAL OF PHYSICAL CHEMISTRY C, 10.1021/jp2115669, 116, 20, 11306-11314, 2012.05, Silica gels doped with double-walled carbon nanotubes (DWCNTs) were prepared using an aqueous sol gel route in mild conditions (neutral pH, room temperature). The wet gels exhibited both ionic and electronic conduction. Electrochemical impedance spectroscopy was used to study these two different conduction pathways that prevail at different characteristic time scales. The ionic conduction in the silica network was found to be independent of the DWCNT-doping rate. The electronic conduction through the DWCNT network was found to occur above a critical concentration (0.175 wt %) corresponding to nanotube percolation threshold. The highest content in DWCNTs (0.8 wt %) exhibited a conductivity of 0.05 S/m. Furthermore, the DWCNTs network was found to evolve even after the macroscopic solidification of the gel, suggesting a reorganization of the DWCNTs at the molecular level. This phenomenon could be attributed to the polarization effect of the electrode and was confirmed by Raman spectroscopy studies. Such materials can be useful for the design of sensors incorporating electroactive chemical or biological species..
5. Benjamin Le Ouay, Thibaud Coradin, Christel Laberty-Robert, Mass Transport Properties of Silicified Graphite Felt Electrodes, JOURNAL OF PHYSICAL CHEMISTRY C, 10.1021/jp403990m, 117, 31, 15918-15923, 2013.08, Mass transport properties of electrodes prepared from graphite felt, as such and after silicification, have been studied using cyclic voltammetry. Within the graphite felt, the mass transport of a probe changes with decreasing scan rate, from a radial diffusion around fibers to a regime that is analogous to "thin-layer" systems. Furthermore, unlike classical "thin-layer" systems, the volume comprised in the felt is macroscopic (resulting in high current densities), while the time required to consume all diffusive species remains in the 1 min range. Silicification of graphite felt does not impact on the mass transport of the negatively charged molecular probe Fe(CN)(6)(3-) but significantly slows mass transport of positively charged Ru(NH3)(6)(3+). In the latter case, a parallel decrease of peak current intensity reflects limited mobility of the probe due to its strong interaction with the surface of the pore walls. These data provide important information for the optimization of the working conditions of these electrodes for the design of biosensors and biofuel cells..
6. Benjamin Le Ouay, Francesco Stellacci, Antibacterial activity of silver nanoparticles: A surface science insight, NANO TODAY, 10.1016/j.nantod.2015.04.002, 10, 3, 339-354, 2015.06, Silver nanoparticles constitute a very promising approach for the development of new antimicrobial systems. Nanoparticulate objects can bring significant improvements in the antibacterial activity of this element, through specific effect such as an adsorption at bacterial surfaces. However, the mechanism of action is essentially driven by the oxidative dissolution of the nanoparticles, as indicated by recent direct observations. The rote of Ag+ release in the action mechanism was also indirectly observed in numerous studies, and explains the sensitivity of the antimicrobial activity to the presence of some chemical species, notably halides and sulfides which form insoluble salts with Ag+. As such, surface properties of Ag nanoparticles have a crucial impact on their potency, as they influence both physical (aggregation, affinity for bacterial membrane, etc.) and chemical (dissolution, passivation, etc.) phenomena. Here, we review the main parameters that will affect the surface state of Ag NPs and their influence on antimicrobial efficacy. We also provide an analysis of several works on Ag NPs activity, observed through the scope of an oxidative Ag+ release. (C) 2015 Elsevier Ltd. All rights reserved..
7. Benjamin Le Ouay, Mickael Boudot, Takashi Kitao, Takeshi Yanagida, Susumu Kitagawa, Takashi Uemura, Nanostructuration of PEDOT in Porous Coordination Polymers for Tunable Porosity and Conductivity, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 10.1021/jacs.6b05552, 138, 32, 10088-10091, 2016.08, A series of conductive porous composites were obtained by the polymerization of 3,4-ethylenedioxythiophene (EDOT) in the cavities of MIL-101(Ci). By controlling the amount of EDOT loaded into the host framework, it was possible to modulate the conductivity as well as the porosity of the composite. This approach yields materials with a reasonable electronic conductivity (1.1 X 10(-3) while maintaining high porosity (S-BET = 803 m(2)/g). This serves as a promising strategy for obtaining highly nanotextuted conductive polymers with very high accessibility for small gas molecules, which are beneficial to the fabrication of a chemiresistive sensor for the detection of NO2..
8. Benjamin Le Ouay, Stefan Guldin, Zhi Luo, Sergio Allegri, Francesco Stellacci, Freestanding Ultrathin Nanoparticle Membranes Assembled at Transient Liquid-Liquid Interfaces, ADVANCED MATERIALS INTERFACES, 10.1002/admi.201600191, 3, 15, 2016.08, A synthetic route is presented for the realization of ultrathin freestanding nanoparticle membranes that are built of gold nanoparticles protected with trimethoxysilane-bearing ligands. The mechanism relies on interfacial assembly in an oil-water mixture. Upon shaking, nanoparticles are transported to the liquid-liquid interface of the oil droplets and form a network through the formation of Si-O-Si bridges. Reticulation of the nanoparticles during the dynamic process of droplet coalescence allows the formation of ultrathin membranes of only a few nanoparticle layers in thickness and square centimeters in dimension. The membranes can be manipulated, such as locally perforated, without causing their collapse. Furthermore they can be transferred onto solid or holey substrates. The synthetic route is compatible with a coassembly of dopants. As an example, membranes were doped with single walled carbon nanotubes, which resulted in a sizable increase of their electric conductivity..
9. Takashi Kitao, Michael W. A. MacLean, Benjamin Le Ouay, Yotaro Sasaki, Masahiko Tsujimoto, Susumu Kitagawa, Takashi Uemura, Preparation of polythiophene microrods with ordered chain alignment using nanoporous coordination template, POLYMER CHEMISTRY, 10.1039/c7py00309a, 8, 34, 3077-+, 2017.09, The properties of polymeric materials can be amplified by macromolecular alignment. The highly ordered chain alignment of unsubstituted polythiophene, an unprocessable polymer, has been achieved using a porous coordination polymer (PCP) as a template. Due to the extended conjugation system, the obtained anisotropic polymer particles exhibit higher conductivity than that of polythiophene prepared by solution polymerization..
10. Benjamin Le Ouay, Susumu Kitagawa, Takashi Uemura, Opening of an Accessible Microporosity in an Otherwise Nonporous Metal-Organic Framework by Polymeric Guests, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 10.1021/jacs.7b02402, 139, 23, 7886-7892, 2017.06, The development Of highly porous metal organic frameworks (MOFs) is greatly sought after, due to their wide range of applications. As an alternative to the,development of new structures, we propose to obtain new stable configurations for flexible MOFs by insertion of polymeric guests. The guests prevent the otherwise spontaneous closing of the host frameworks and result in stable opened forms. Introduced at a fraction of the maximal capacity, polymer chains cause an opening of the occupied nanochannels, and because of the MOF reticular stiffness, this opening is propagated to the neighboring nanochannels that become accessible,for adsorption. Composites were obtained by in situ,polymerization of vinyl monomers in the: nanochannels of an otherwise nonporous MOP, resulting in homogeneously loaded materials with a significant increase of porosity (S-BET m(2)/g);:in addition, by limiting the accessible configurations for the framework and forbidding the forbidding of a reactive intermediate, the polymeric guest prevented the thermal degradation of the host MOP even at very low loading (as low as. 3 wt %) and increased it's stability domain by more than 200 degrees C..
11. Yizhan Wang, Offer Zeiri, Manoj Raula, Benjamin Le Ouay, Francesco Stellacci, Ira A. Weinstock, Host-guest chemistry with water-soluble gold nanoparticle supraspheres, NATURE NANOTECHNOLOGY, 10.1038/NNANO.2016.233, 12, 2, 170-176, 2017.02, The uptake of molecular guests, a hallmark of the supramolecular chemistry of cages and containers, has yet to be documented for soluble assemblies of metal nanoparticles. Here we demonstrate that gold nanoparticle-based supraspheres serve as a host for the hydrophobic uptake, transport and subsequent release of over two million organic guests, exceeding by five orders of magnitude the capacities of individual supramolecular cages or containers and rivalling those of zeolites and metal-organic frameworks on a mass-per-volume basis. The supraspheres are prepared in water by adding hexanethiol to polyoxometalate-protected 4 nm gold nanoparticles. Each 200 nm assembly contains hydrophobic cavities between the estimated 27,400 gold building blocks that are connected to one another by nanometre-sized pores. This gives a percolated network that effectively absorbs large numbers of molecules from water, including 600,000, 2,100,000 and 2,600,000 molecules (35, 190 and 234 g l(-1)) of para-dichorobenzene, bisphenol A and trinitrotoluene, respectively..
12. Sanjog S. Nagarkar, Satoshi Horike, Tomoya Itakura, Benjamin Le Ouay, Aude Demessence, Masahiko Tsujimoto, Susumu Kitagawa, Enhanced and Optically Switchable Proton Conductivity in a Melting Coordination Polymer Crystal, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 10.1002/anie.201700962, 56, 18, 4976-4981, 2017.04, The melting behavior of a coordination polymer (CP) crystal was utilized to achieve enhanced and optically switchable proton conductivity in the solid state. The strong acid molecules (triflic acid) were doped in one-dimensional (1D) CP, [Zn(HPO4)(H2PO4)(2)](ImH(2))(2) (ImH(2) = monoprotonated imidazole) in the melt state, and overall enhancement in the proton conductivity was obtained. The enhanced proton conductivity is assigned to increased number of mobile protons and defects created by acid doping. Optical control over proton conductivity in the CP is achieved by doping of the photo acid molecule pyranine into the melted CP. The pyranine reversibly generates the mobile acidic protons and local defects in the glassy state of CP resulting in the bulk switchable conductivity mediated by light irradiation. Utilization of CP crystal in liquid state enables to be a novel route to incorporate functional molecules and defects, and it provides a tool to control the bulk properties of the CP material..
13. Elif Ertem, Beatrice Gutt, Flavia Zuber, Sergio Allegri, Benjamin Le Ouay, Selma Mefti, Kitty Formentin, Francesco Stellacci, Qun Ren, Core-Shell Silver Nanoparticles in Endodontic Disinfection Solutions Enable Long-Term Antimicrobial Effect on Oral Biofilms, ACS APPLIED MATERIALS & INTERFACES, 10.1021/acsami.7b13929, 9, 40, 34762-34772, 2017.10, To achieve effective long-term disinfection of the root canals, we synthesized core-shell silver nanoparticles (AgNPs@SiO2) and used them to develop two irrigation solutions containing sodium phytate (SP) and ethylene glycol-bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid (EGTA), respectively. Ex vivo studies with instrumented root canals revealed that the developed irrigation solutions can effectively remove the smear layer from the dentinal surfaces. Further in vitro experiments with single- and multispecies biofilms demonstrated for the first time that AgNPs@SiO2-based irrigation solutions possess excellent antimicrobial activities for at least 7 days, whereas the bare AgNPs lose the activity almost immediately and do not show any antibacterial activity after 2 days. The long-term antimicrobial activity exhibited by AgNPs@SiO2 solutions can be attributed to the sustainable availability of soluble silver, even after 7 days. Both solutions showed lower cytotoxicity toward human gingival fibroblasts compared to the conventionally used solution (3% NaOCl and 17% EDTA). Irrigation solutions containing AgNP@SiO2 may therefore be highly promising for applications needing a long-term antimicrobial effect..
14. Benjamin Le Ouay, Chikara Watanabe, Shuto Mochizuki, Masayoshi Takayanagi, Masataka Nagaoka, Takashi Kitao, Takashi Uemura, Selective sorting of polymers with different terminal groups using metal-organic frameworks, NATURE COMMUNICATIONS, 10.1038/s41467-018-06099-z, 9, 2018.09, Separation of high-molecular-weight polymers differing just by one monomeric unit remains a challenging task. Here, we describe a protocol using metal-organic frameworks (MOFs) for the efficient separation and purification of mixtures of polymers that differ only by their terminal groups. In this process, polymer chains are inserted by threading one of their extremities through a series of MOF nanowindows. Selected termini can be adjusted by tuning the MOF structure, and the insertion methodology. Accordingly, MOFs with permanently opened pores allow for the complete separation of poly(ethylene glycol) (PEG) based on steric hindrance of the terminal groups. Excellent separation is achieved, even for high molecular weights (20 kDa). Furthermore, the dynamic character of a flexible MOF is used to separate PEG mixtures with very similar terminal moieties, such as OH, OMe, and OEt, as the slight difference of polarity in these groups significantly changes the pore opening kinetics..
15. Benjamin Le Ouay, Takashi Uemura, Polymer in MOF Nanospace: from Controlled Chain Assembly to New Functional Materials, ISRAEL JOURNAL OF CHEMISTRY, 10.1002/ijch.201800074, 58, 9-10, 995-1009, 2018.10, Preparation of composites by inclusion of polymers inside metal-organic frameworks (MOFs) is a very powerful strategy to prepare innovative functional materials. MOF's nanosized pores disrupt polymer chains natural coiling and constrain them in an extended conformation, bringing new properties. At the single nanochannel scale, polymerization reactions are significantly modified due to confinement, and control over the primary structure (sequence, tacticity or branching) can be achieved. Because of confinement and chain extension, physical and chemical properties can also be significantly improved compared to the bulk state. Inclusion is also useful to control organization at a higher scale, for instance for precise polymer positioning or by acting as scaffold for an accessible microporous polymer network. Furthermore, the MOF ordering can be maintained in pure polymer systems even after removal of the host..
16. Benjamin Le Ouay, Hikaru Takaya, Takashi Uemura, Controlling the Packing of Metal-Organic Layers by Inclusion of Polymer Guests, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 10.1021/jacs.9b07563, 141, 37, 14549-14553, 2019.09, The preparation of metal-organic structures with a controlled degree of disorder is currently one of the most promising fields of materials science. Here, we describe the effect of guest polymer chains on the transformation of a metal-organic framework (MOF). Heating a pillared MOF at a controlled temperature resulted in the exclusive removal of the pillar ligands, while the connectivity of the metal-organic square-grid layers was maintained. In the absence of a polymer, 2D-layers rearranged to form a new crystalline phase. In contrast, the presence of a polymer in the MOF inhibited totally the recrystallization, leading to a turbostratic phase with layers threaded and maintained apart by the polymer chains. This work demonstrates a new synthetic approach toward the preparation of anisotropic metal-organic materials with controlled disorder. It also reveals how guests can dramatically modify the conversion of host MOFs, even though no chemical reaction occurs between them..
17. Benjamin Le Ouay, Takashi Uemura, Terminus-dependent insertion of molten poly(ethylene glycol) into a flexible metal-organic framework, EUROPEAN POLYMER JOURNAL, 10.1016/j.eurpolymj.2020.109855, 134, 2020.07, Insertion of polymers into microporous metal-organic frameworks (MOFs) appeared recently as a powerful strategy to accomplish very difficult separations. However, the dynamics of their insertion remains to be fully unravelled. In this article, we describe the spontaneous insertion of poly(ethylene glycol) (PEG) into a flexible MOF. Thanks to the structural changes upon PEG insertion, in situ powder X-ray diffraction (PXRD) analysis could be performed. For PEGs with identical main chains, the insertion speed was strongly dependent on the nature of the terminus. Furthermore, a concentration dependence for terminal groups was observed, providing insight into the pore-opening mechanism, and suggesting a mildly cooperative terminus-first insertion. This establishes polymers as very valuable tools to study MOF dynamics, as their extended size allows domains with clearly different properties within the same macromolecule..
18. Nagi Mizutani, Nobuhiko Hosono, Benjamin Le Ouay, Takashi Kitao, Ryoichirou Matsuura, Takuya Kubo, Takashi Uemura, Recognition of Polymer Terminus by Metal-Organic Frameworks Enabling Chromatographic Separation of Polymers, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 10.1021/jacs.9b13568, 142, 8, 3701-3705, 2020.02, Unlike commonly used molecular recognition techniques, recognition of polymer structures requires an additional aspect of extremely high recognition ability, by which marginal structural differences can be identified in a large polymer chain. Herein we show that metal-organic frameworks (MOFs) can recognize polymer terminal structures, thus enabling the first reported chromatographic separation of polymers. End-functionalized polyethylene glycols (PEGs) are selectively inserted into the MOF channel, the insertion kinetics being dependent on the projection size of the PEG terminus. This size-selective insertion mechanism facilitates precise discrimination of end-functionalized PEGs using liquid chromatography (LC). An MOF-packed column thus provides an efficient and easily accessible method for the separation of such end-functionalized polymers using conventional LC systems..