Dr. Kazuhito Hashimoto, who has strong belief in the important role of chemists in the solution of global environmental and energy problems, has conducted many world-leading studies not only on the fundamental chemistry including physical chemistry of photofunctional metal oxides and metal complexes, but also on their industrial applications. In addition, his recent research interest extends to understanding metabolic processes in microorganisms from the viewpoint of a physical chemist, based on which he proposed a completely novel system for light energy conversion. His academic achievements greatly contributed to vast research field related not only to photochemistry, but also to environmental chemistry and materials science. His important achievements are introduced as follows.

1. Study on UV light-induced hydrophilicity of titanium oxide and its expansion to visible-light responsive materials
Dr. Hashimoto focused on the photocatalytic activity of titanium oxide (TiO₂) under the irradiation of weak light, and discovered a novel phenomenon in which the surface of TiO₂ showed superhydrophilicity by the irradiation of UV light. Subsequently, he clarified that the UV light irradiation causes structural change of TiO₂ surface into a metastable state with high surface energy and proved that this is the cause of the conversion to superhydrophilicity. This discovery opened up a new academic research field of gphotoinduced hydrophilicity switchingh, and moreover, it led to the birth of new material industry that produces TiO₂-coated building materials with self-cleaning and cooling functions by utilizing solar light and rain water.
Subsequently, he found that amorphous nanoclusters of Cu(II) and Fe(III) dispersed on TiO₂ surface have high catalytic activity for multielectron oxygen reduction reaction. He showed that these surface-modified TiO₂ exhibit a unique photoinduced electron transfer from the valence band of TiO₂ to the amorphous metal oxide clusters under visible light irradiation. This phenomenon can be regarded as gphotoinduced electron transfer across the solid-solid interfaceh that is characteristic of nanointerfaces. Based on this finding, he successfully developed the surface-modified TiO₂ photocatalysts that showed high oxidation activity under the irradiation of visible light; these materials contrasts sharply to the conventional visible light sensitive photocatalysts that sacrifice their oxidation ability for the visible light absorption. At the same time, these new materials are very effective to inactivate the infectivity of viruses and pathogenic bacteria. Therefore, the application of these visible light sensitive photocatalysts to the functional materials is now highly anticipated and the applicability for practical use is acclaimed from the industrial society.

2. Design and invention of photomagnetic materials based on metal cyanide complexes
It was a long-cherished dream for the researchers studying on magnetism to synthesize a material that shows a photoinduced switching behavior between on and off states of spontaneous magnetization. Dr. Hashimoto focused on Prussian blue analogues that have characteristic structural properties such as firm structure independent on the kinds and the valences of the metal ions and high degree of coordination freedom around the metal ions. He made a good use of molecular field theory that considers the exchange interactions between the nearest neighboring metals and succeeded in the development of novel photomagnetic materials in which ferromagnetism can be induced by light irradiation. Namely, by taking an iron-cobalt six coordinated cyanide complex as the base material and precisely controlling the ratios between iron and cobalt ions to change the ligand field strength, he succeeded for the first time in the world in designing and synthesizing the materials that show bistability of paramagnetic and ferromagnetic states and photoinduced reversible conversion between these two states. This discovery led to the developments of series of novel materials with photoinduced ferromagnetic properties such as iron-manganese six coordinated cyanide complexes, cobalt-iron six coordinated cyanide complexes, nickel-tungustate eight coordinated cyanide complexes, and copper-molybdenum eight coordinated cyanide complexes. This approach of using molecular field theory also enabled him to design and synthesize the material that shows magnetic pole inversion by light irradiation. His studies on the photomagnetism of metal complexes pioneered a new research field in the complex chemistry and are rated highly by both domestic and overseas researchers.

3. Extracellular electron transfer of microbes and light energy conversion system
Dr. Hashimoto extended his study and knowledge on the interactions between light and materials to those between light and living organism. He focused his interest on current producing microbes that have highly concentrated cytochrome c in their periplasmic membrane and conducted in vivo analysis on the redox processes by using various physicochemical and spectroscopic techniques, especially cutting-edge laser technologies such as laser trapping method and time resolved spectroscopy. His works took the initiative in exploring a new research field in which the dynamics of the extracellular electron transfer processes are directly observed and analyzed in the living microbe systems.
Based on this fundamental study, he also discovered that in the presence of nanocolloids of semiconducting iron oxide or metallic iron sulfide, the current producing microbes have a unique ability to construct long-range extracellular electron transport networks. This ability relies on the interactive electron transfer between the microbes and the nanocolloids and as the result, the metabolic current from the microbes shows striking increase. Subsequently, he succeeded in the construction of a microbiological electrochemical system to convert the solar energy to electric energy by using symbiotic relationship between the current producing and photosynthetic microbes. All these works of him guide us to the new direction of the future studies that pursue environmentally friendly energy conversion systems.

Dr. Kazuhito Hashimoto has made valuable contributions with his extraordinary creativity toward the development of interdisciplinary science, namely by the discovery of photoinduced hydrophilicity of TiO₂ driven by weak UV light irradiation, the development of visible-light sensitive photocatalysts for environmental cleanup, synthesis of novel photomagnetic materials, and the construction of energy conversion systems based on the electron transfer processes between microorganisms and inorganic nanoparticles. His achievements are rated very highly by both domestic and overseas researchers. Accordingly, it was approved that his achievements merit the Chemical Society of Japan (CSJ) Award.