This project aims to visualize the dynamic processes through which functional properties emerge in fast photoresponsive materials--such as photocatalytic materials and ultrafast optical switching materials--by utilizing quantum beams.
For example, in artificial photosynthesis systems based on photocatalytic reactions, unlike solar cells that extract energy (ΔE) via a simple single-electron transfer, multiple separated electrons are utilized for chemical transformations without recombination. Therefore, to design highly efficient systems, it is essential to visualize electronic states and structures and to trace the pathways of photogenerated carriers during the picosecond to nanosecond timescale where catalytic reactions occur.
In addition, for photoinduced phase transitions--where the region initially exposed to light triggers a domino-like transformation of crystal structures or magnetic properties across the material--it is critical to visualize the evolution of long-range ordered structures (lattice, charge, spin), which serve as the origin of physical properties, immediately after photoexcitation. This is key to designing materials capable of ultrafast and versatile control of their physical properties.
In this project, regarding photocatalytic reactions, we aim to develop high-performance photocatalytic materials by visualizing photoexcited states (electronic and structural) using picosecond soft/hard X-ray absorption fine structure (XAFS) measurements with synchrotron radiation. Furthermore, we will provide design guidelines for catalytic activity and reaction selectivity by visualizing the differences in adsorbed atomic structures on various crystal facets using slow positron beams.
As for photoinduced phase transitions, we will conduct detailed characterizations of the equilibrium states of the target nonequilibrium strongly correlated materials using neutron techniques. We will also attempt to elucidate the mechanism of function emergence by visualizing lattice, charge, and spin structures of the photoinduced phases using picosecond soft/hard X-ray diffraction with synchrotron radiation, and by visualizing surface structures of the photoinduced phases with slow positrons to understand their contribution to photoresponsive functionalities.
NOZAWA Shunsuke, FUKAYA Ryo, KANAZAWA Tomoki, HARUKI Rie,
MAEDA Kazuhiko (Tokyo Institute of Technology)
ADACHI Junichi, NAKAO Hironori (KEK)
TABATA Chihiro, ABE Ryu (Kyoto University)
YAMASAKI Yuichi (NIMS)
FUJIOKA Jun (Tsukuba University)
KIMURA Hiroyuki (Tohoku University)
KUDO Akihiko (Tokyo University of Science)
Measurement Techniques: Pump-probe measurements using quantum beams and lasers
Time-resolved X-ray measurements (TR-XAFS, TR-XRD)
Time-resolved slow positron measurements (TR-HEPD)
Inelastic neutron scattering
