Journal Article Femtosecond time-resolved X-ray absorption spectroscopy of anatase TiO2 nanoparticles using XFEL

Obara, Yuki  ,  Ito, Hironori  ,  Ito, Terumasa  ,  Kurahashi, Naoya  ,  Thürmer, Stephan  ,  Tanaka, Hiroki  ,  Katayama, Tetsuo  ,  Togashi, Tadashi  ,  Owada, Shigeki  ,  Yamamoto, Yo-ichi  ,  Karashima, Shutaro  ,  Nishitani, Junichi  ,  Yabashi, Makina  ,  Suzuki, Toshinori  ,  Misawa, Kazuhiko

4 ( 4 ) 2017-07 , American Institute of Physics
光触媒ナノ粒子における光照射後10兆分の1秒での電子の動きをX線自由電子レーザーで観測. 京都大学プレスリリース. 2017-07-06.
The charge-carrier dynamics of anatase TiO2 nanoparticles in an aqueous solution were studied by femtosecond time-resolved X-ray absorption spectroscopy using an X-ray free electron laser in combination with a synchronized ultraviolet femtosecond laser (268 nm). Using an arrival time monitor for the X-ray pulses, we obtained a temporal resolution of 170 fs. The transient X-ray absorption spectra revealed an ultrafast Ti K-edge shift and a subsequent growth of a pre-edge structure. The edge shift occurred in ca. 100 fs and is ascribed to reduction of Ti by localization of generated conduction band electrons into shallow traps of self-trapped polarons or deep traps at penta-coordinate Ti sites. Growth of the pre-edge feature and reduction of the above-edge peak intensity occur with similar time constants of 300–400 fs, which we assign to the structural distortion dynamics near the surface.

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