Photochemical Properties of Size-quantized Semiconductor Microcrystals and Their Applications

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Photochemical properties and potential applications of size-quantized semiconductor microcrystals were investigated in the present research. Major achievements are as follows;1.Fluorescence properties of quantized CdS prepared in poly(ethylene oxide). Quantized-CdS microcrystals prepared in poly(ethylene oxide) (PEO) film exhibited a strong orange fluorescence. The fluorescence intensity of CdS incorporated in PEO film was increased by the introduction of Ni^<2+> ions into the film by electrolysis.2.Preparation and optical nonlinearity of quantized InAs and GaAs microcrystals. Quantized InAs and GaAs microcrystals were synthesized by organometallic methods. The particle size of these microcrystals ranged from 1 to 8 nm, and great size-quantization effects were confirmed. It was also demonstrated that quantized InAs and GaAs microcrystals exhibited a large optical nonlinearity when these colloids were irradiated with the second harmonics of Nd:YAG laser beams.3.Photoinduced electron tra … More nsfer on size-separated CdS microcrystals. The rate of reduction of methylviologen on CdS microcrystals prepared by fractionation with the use of gel electrophoresis increased with decreasing the particle size. The observed results were successfully analyzed in terms of shifts in the conduction bandedge due to the size-quantization.4.Surface structures of PbS microcrystals modified with 4-hydroxythiophenol and their influences on photoinduced charge transfer. Quantized and monodispersed PbS microcrystals capped with 4-hydroxythiophenol(ArSH) were prepared using two different concentration ratios of [Pb^<2+>]/[S^<2->] = 1.2 and 3.0 with fixed concentration ratio of [ArSH]/[Pb^<2+>] = 4.0. The surface structures of ArSH-capped PbS microcrystals were analyzed in atomic scale by examining the fitness of the chemical analyses data of the PbS particles to the evaluated compositions for two kinds of surface structure models (fully and partially occupied surface sites with the capped ArSH). The proposed surface structures were rationalized by experimentally found differences both in agglomeration tendencies of the particles and in the effect of the addition of Pb^<2+> ions on the rate of photoinduced reduction of methylviologen on the particles. Less