| Project/Area Number |
61550617
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
有機工業化学
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| Research Institution | Osaka University, Faculty of Engineering |
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Principal Investigator |
YANAGIDA Shozo Osaka University, Faculty of Engineering., 工学部, 教授 (10029126)
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| Project Period (FY) |
1986 – 1987
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| Project Status |
Completed (Fiscal Year 1987)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1987: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1986: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | semiconductor photocatalysis / zinc sulfide / quantum size effect / photoredox reaction / photoreduction / electron transfer reaction / photon-induced electron transfer / 光電荷分離 / 二電子還元 / サイズ量子化効果 / 水酸化還元 |
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| Research Abstract |
The ZnS supension(ZnS-O) prepared under cooling from aqueous ZnSO_<> and Na_<>S solutions was established to be an efficient photocatalyst for two-electron reductions of aldehydes and ketones in aqueous medium. Based on the following results of photocatalytic activities and spectroscopic properties, it has been concluded that ZnS-O suspension should consist of loosely held aggregates of very small ZnS crystallites(quantized ZnS) and that the crystallites should be so free form surface states attributable to sulfur vacancies and impurities that photoformed electrons are sequentially and efficiently transfered to adsorbed substrates(aldehydes and ketones) without trapping at surface states.
1. ZnSo-O and the refluxed ZnS-O(ZnS-100) have band gap emission at 340nm and self-activated(SA) emission at 420 or 450nm. The most efficient Zn-S-O has the longest lifetie(23ns) of the band gap emission.
2. The ZnS-O has the sharpest and the most blue-shifted onset of the reflectance and excitation spectra, indicating the least presence of surface states.
3. Under >290nm irradiation in the presence of S^2 and SO_3^<2-> as sacrificial electron donors, the ZnS-O catalyzes photoreductions of some aliphatic and cyclic ketones to alcohols and concomitant photo-oxidation of S^<2-> and SO_3^<2-> to S_2O_3^<2->. 4. The coexistance of S^<2-> and SO_3^<2-> inhibits the SA emission of ZnS-O, indicating the least formation of surface states attributable to the sulfur vacancy and interstitial impurty like S_2^<2->. The contribution of quantum size effect was elucidate from the observation of the blue-shifted absorption spectrum(-290nm) and the photoreduction of 2-butene-1-ol which have the reduction potential more negative than the conduction band potential of ZnS.
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