FORMATION OF POLYNUCLEAR CADMIUM-THIOLATE COMPLEXES AND CDS CLUSTERS IN AQUEOUS-SOLUTION STUDIED BY MEANS OF STOPPED-FLOW AND NMR SPECTROSCOPIES

Formation processes of CdS ultrasmall particles from cadmium complexes of 2-mercaptoethanol (RSH) were investigated by means of stopped-flow and NMR spectroscopies. Two different initial processes depending on the amount of RS(-) ions have been found. The presence of S-4-Cd-10(SR )(12) clusters in solution was observed by NMR spectroscopy. Formation of [S4Cd17(SR)(24)](2+) clusters having a 290-nm absorption peak was suggested. The correlation between the absorption peak and the diamete r for polynuclear Cd2+-SR(-) complexes is expressed with the finite-de pth quantum well model for ultrasmall particles. Electronic interactio n between the capping agent and particle framework was suggested on th e basis of the differences observed in the absorption wavelengths of t he CdS-RSH clusters and the corresponding CdS-thiophenol clusters.