SURFACE-STRUCTURES OF PBS MICROCRYSTALS MODIFIED WITH 4-HYDROXYTHIOPHENOL AND THEIR INFLUENCES ON PHOTOINDUCED CHARGE-TRANSFER

Quantized PbS microcrystals capped with 4-hydroxythiophenol (ArSH) were prepared using two different concentration ratios of [Pb2+]/[S2-] = 1.2 and 3.0 with fixed concentration ratio of [ArSH]/[Pb2+] = 4.0. The size distributions of the prepared PbS particles were determined. Two different surface structure models of fully occupied and partially occupied surface sites of PbS microcrystals with the capped ArSH are assumed, and chemical compositions of these particles are evaluated by taking the experimentally determined particle size distributions into account. By examining the fitness of the chemical analyses data of the PbS particles to the evaluated compositions, it is proposed that the PbS particles prepared [Pb2+]/[S2-] = 3.0 had the capped ArSH in all the surface sites, while PbS particles prepared with [Pb2+]/[S2-] = 1.2 had some surface sites free from the modifier. The proposed surface structures of the two kinds of PbS microcrystals were rationalized by experimentally found differences both in agglomeration tendencies of the particles and in the effect of the addition of Pb2+ ions on the rate of photoinduced reduction of methyl viologen on the particles.