We contribute to the world through the advanced researches on Photosynthesis and Artificial Photosynthesis




The extreme objective of our defined terminology “Physics of Biological Materials” is to explain the biological events (especially photosynthesis in plants, alga, and bacteria) with the words of the condensed matter physics. Nature had evolved photosystems in photosynthetic organisms that are gentle to the environment of the earth and can most effectively utilize the solar energy after 3.9 billion years of trial and errors. For example, light-harvesting antenna pigment-protein complexes from purple photosynthetic bacteria have a beautiful Chrismas-wreath like ring structure with 9-fold symmetry (8-fold symmetry depending on the species fo bacteria). It is highly required to clarify the light-harvesting and energy-transferring mechanisms of such structures in order to open a new door for next generation technology (bio-nanotechnology).

We are mainly focusing our attention to the studies of carotenoid pigments that are playing essential roles in the primary process of photosynthesis. X-ray crystal structure analysis has been applied to determine the electron distribution and molecular structure of the artificial photosynthetic pigment protein complexes in which the structures of carotenoids are systematically modified. Simultaaneously the excitation energy transfer mechanisms and inter-molecular interactions have been determined using various spectroscopic methods. Through these research works, artificial pigment-protein complexes that do not exit in nature have been created and the detailed functional mechanisms are clarified. Our research objective is to interpret the blueprint of life activity using the words of “condensed matter physics”. Our final goal is to build the new basic ideas that can break through the old or current ideas in the solar energy conversion processes, to establish the solid foundation of ultrafast and highly efficient excitation energy-transfer, and to create completely new condensed matter physics.

In order to gain deeper insight into these fascinating supra-molecular complex systems, we are also investigating the relationship between molecular structures and optical responses fo relatively simpler systems (e.g. organic thin-solid films or bulk crystals). As an example, the generation mechanisms of terahertz radiation from organic nonlinear crystals are being studied. Human beings are utilizing light (electromagnetic radiation) with various frequencies for telecommunication, spectroscopic analyses and medical applications. However, far-infrared light in the terahertz frequency regime is a light with unprecedented frequency domain and it is still not put to practical use because of low efficiency of generation and detection. Exploiting this frequency regime of light directly connects to create new scinece and technology as well as the field of condensed matter physics. We are fabricating organic thin-solid films or bulk crystals in which the structures of the component molecules are systematically modified based on our unique strategies. The generation mechanisms of coherent pulsed terahertz radiation from these organic nonlinear materials have been investigated. We are aiming to create basic ideas and technologies to generate high power terahertz radiation using organic optical functioning materials.

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