1997 Fiscal Year Final Research Report Summary
Ultrafast photoresponses of organized molecular assemblies
| Project/Area Number |
08044137
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Field |
工業物理化学
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| Research Institution | Shizuoka University |
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Principal Investigator |
NAGAMURA Toshihiko Shizuoka University, Research Institute of Electronics, Professor, 電子工学研究所, 教授 (90117200)
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| Co-Investigator(Kenkyū-buntansha) |
FURLONG Donald N. CSIRO Australia, Molecular Science, Manager, 室長
MULVANEY Paul University of Melbourne, School of Chemistry, Lecturer, 化学科, 講師
GRIESER Franz University of Melbourne, School of Chemistry, Reader, 化学科, 助教授
KAWAI Hideki Shizuoka University, Research Institute of Electronics, JSPS Fellow, 特別研究員
SAKAGUCHI Hiroshi Shizuoka University, Research Institute of Electronics, Research Associate, 電子工学研究所, 助手 (30211931)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Organized molecular assemblies / Ultrafast photoresponses / Femtosecond laser / CdS nano-particles / Transient bleaching / Exciton formation / Photoinduced electron transfer / Ion-pair charge-transfer complex |
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| Research Abstract |
The development of ultrafast photoresponsive materials and devices is essential for the near future implementation of all-optical information processing technology. One of the more promising approaches with respect to the above is the subject of the present project. It deals primarily with the construction and examination of ultrafast photoresponses of several organized molecular assemblies.
1) Size-quantized CdS nano-particles were prepared in Nafion films, self-assembled films of amphiphiles, and other systems by reacting H_2S gas with Cd^<2+> ions dispersed, by ion-exchange. The size and the surface state of the CdS nano-particles were controlled by various treatments.
2) Transient bleaching, by exciton formation, was studied with a fs pump-probe method excited at 400 nm. All samples except the LB films showed a very fast bleaching response on a time scale of less than 1 ps. The bleached spectra and their recovery rate depended markedly on the particle size and size distribution, the surface states, or the microenvironments. In Nafion films, the bleached spectra for "large" nano-particles (5 nm) were broad and the peaks red-shifted during the recovery process. For "small" nano-particles (3.4 nm), the peak of the bleached spectrum was at shorter wave-lengths and showed no spectral shift during the recovery process.
3) Transient absorptions in the visible and the near infrared (NIR) regions appeared in less than 1 ps upon excitation of p-substituted styrylpyridinium tetraphenylborates. The decay in the visible region was composed of a fast and a slow component, whereas it was single exponential in the NIR region. The lifetime of the fast component in the visible region corresponded with that of the NIR absorption. The reverse electron transfer reaction from dimer radical cations to oxidized tetraphenylborate was found to be faster than that from monomer radicals.
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