Nanocrystals of II–VI Semiconductor Materials

Abstract

CdS nanoclusters ranging in diameter between 1 and 4 nm were prepared in aqueous solution using aliphatic mercaptoalcohols as ligands. The photon energies of the Is Is absorption and the respective oscillator strengths are in accordance with size quantization theory. Some clusters crystallize as macroscopic 3-D 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 exhibits self similarity to the interior structure of the clusters.

Onion-shell-like composite particles from CdS and HgS were prepared by successive substitution and re-precipitation processes. Particles with a core radius of 2 nm, a shell of up to 1 nm HgS followed by a final shell of up to 1.5 nm CdS were obtained. Electrons and holes were localized in the HgS shell giving rise to excitonic fluorescence.