OPTICAL-PROPERTIES OF QUANTIZED SEMICONDUCTOR PARTICLES

CdS nanoclusters ranging in diameters between 1 and 4 nm were prepared in aqueous solution using aliphatic mercaptoalcohols as ligands. The photon energies of the 1s1s absorption and the respective oscillator s trengths are in accordance with size quantization theory Nonlinear opt ical properties are discussed in terms of the influence of trapped cha rge carriers on the excitonic transition. Onion-shell-like composite p articles from CdS and HgS were prepared by successive substitution and reprecipitation processes. Particles with a core radius of 2 nm, a sh ell of up to 1 nm HgS followed by a final shell of up to 1.5 nm CdS we re obtained. Electrons and holes were localized in the HgS shell, givi ng rise to excitonic fluorescence. Dense, yet randomly packed, nanopar ticulate ZnO films were found to show reversible optical changes upon cathodic polarization. Some cluster species crystallize in the form of macroscopic three-dimensional superlattices, which were investigated by single-crystal X-ray analysis. The neutral Cd17S4(RS)(26) clusters are covalently linked in the superlattice, the structure of which exhi bits self-similarity to the interior structure of the clusters.