Tsuyohiko Fujigaya

Carbon nanotubes (CNTs) have been recognized as a promising material in a wide range of applications from biotechnology to energy-related devices. However, the poor solubility in aqueous and organic solvents hindered the applications of CNTs. As studies have progressed, the methodology for CNT dispersion was established. In this methodology, the key issue is to covalently or non-covalently functionalize the surfaces of the CNTs with a dispersant. Among the various types of dispersions, polymer w

Iron(II) complexes of triazole derivatives having two C12 and C16 long alkyl chains, (C12trz)FeII and (C16trz)FeII, serve as novel spin-crossover materials, which display a spin-state transition in response to a phase transition. In contrast, a triazole complex with two C8 alkyl chains ((C8trz)FeII) exhibits only a poor response. EXAFS and XRD analyses of (C16trz)FeII indicate an interdigitating self-assembled structure of polynuclear iron(II) species. According to DSC, VT-IR, and VT-XRD profile

Iron(II) triazolate coordination polymers with lipophilic sulfonate counterions with alkyl chains of different lengths have been synthesized. In hydrocarbon solvents, these polymers formed a physical gel and showed a thermoreversible spin transition upon the sol-gel phase transition. The formation of a hydrogen-bonding network between the triazolate moieties and sulfonate ions, bridged by water molecules, was found to play an important role in the spin-crossover event. The spin-transition temper

Multiple approaches will be needed to reduce the atmospheric CO₂ levels, which have been linked to the undesirable effects of global climate change. The electroreduction of CO₂ driven by renewable energy is one approach to reduce CO₂ emissions while producing chemical building blocks, but current electrocatalysts exhibit low activity and selectivity. Here, we report the structural and electrochemical characterization of a promising catalyst for the electroreducti

The development of n-type single-walled carbon nanotubes (SWCNTs) stable under an air atmosphere is a key issue to prepare an efficient and stable thermoelectric conversion device using SWCNTs. Doping of SWCNT sheets with 2-(2-methoxyphenyl)-1,3-dimethyl-2,3-dihydro-1H-benzo[d]imidazole (o-MeO–DMBI) offers air-stable n-type SWCNT sheets. However, a clear mechanism of the stabilization in air has not been clarified yet. In this study, air stability is found to largely depend on the doping concent

Poly(benzyl ether) dendrons having a focal triazole unit (Gntrz: trz = triazole; n = generation number = 0−2) were found to react with (MeSO3)2Fe to form dendritic coordination polymers ([Fe(Gntrz)3](MeSO3)2·2H2O) that undergo the thermal spin transition. When the generation number of the dendritic unit was larger (n = 0 → 1 → 2), the average degree of polymerization (Dp = 20 → 10 → 3) and spin-crossover temperature (Tc = 335 → 315 → 300 K) of the resulting polymer were lower. However, the abrup

We describe the fabrication of a well-defined carbon nanotube (CNT)-based composite, in which the CNTs are individually wrapped by a polymer in a homogeneous fashion and platinum nanoparticles (Pt) are immobilized on the polymer-wrapped CNTs. Polybenzimidazoles (PBIs) are used as the wrapping polymer since a strong adsorption of PBIs onto the CNT surfaces enables the exfoliation of CNT bundles and nanometre-thick PBI wrapping layer serves as a glue for the efficient immobilization of Pt. We demo

UV-curable monomers provide an ideal mixture for the fabrication of composite materials containing single-walled carbon nanotubes (SWNTs) in terms of dispersion stability and excellent processablity. Precise patterns of SWNT composites on a sub-micrometer scale have been manufactured by nanoimprint lithography using a polydimethylsiloxane stamp.

The continuous advance of the device performance in microelectronics requires the development of the lower dielectric constant (low-k) materials. We target the development of a next generation low-k material based on poly(p-phenylene benzobisoxazole) (PPBO) films due to their low k value, remarkable mechanical toughness, excellent thermal stability, extremely low coefficient of thermal expansion and chemical inertness. In order to overcome the poor processability caused by the insolubility in or

A polymer electrolyte fuel cell (PEFC) that shows high durability at elevated temperature and under non-humidified conditions is strongly demanded for the next generation PEFCs. Here we show the importance of using pristine carbon nanotubes (CNTs) as catalyst supports for fuel cell (FC) durability. For that purpose, two different membrane electrode assemblies (MEAs) using pristine CNTs and commercial carbon black (CB) as carbon supports were coated by polybenzimidazole on which platinum (Pt) nan

We describe here the finding that, with the aid of poly(benzimidazole) (PBI), soluble graphene was obtained in solution by the exfoliation of graphite without introducing oxidative sites on graphene, and the homogeneous loading of Pt-nanoparticles onto the PBI-covered non-oxidized graphene was successful. The prepared electrocatalyst showed very high electrochemical durability; namely, the electrochemical surface area of the catalyst was not much different even after 2000-cyclic voltammogram (CV

Abstract The development of a high‐performance, durable, and less expensive membrane electrode assembly (MEA) composed of a polymer electrolyte membrane and electrocatalysts is important for developing fuel cells. Herein, we described the design and fabrication of an electrocatalyst with carbon black, polybenzimidazole doped with poly(vinylphosphonic acid) (PVPA), and platinum nanoparticles as an electron‐conducting support material, an electrolyte, and a metal catalyst, respectively. Most impor

The development of a non-Pt electrocatalyst with a high performance for the oxygen reduction reaction (ORR) is one of the central issues in polymer electrolyte fuel cells science. Au-nanoparticles (Au-NPs) with a diameter of <2 nm are one of the promising substitutes of Pt-NPs; however, it is still a challenge to synthesize such a small-sized Au-NPs with a narrow diameter distribution on a carbon support without using capping agents. We here describe a facile method to deposit uniform Au-NPs (di