FORMATION STEPS OF CDS CLUSTERS IN AQUEOUS-SOLUTION CONTAINING 2-MERCAPTOETHANOL

Growing steps of CdS clusters in aqueous solution containing HOCH2 CH2 SH (2-mercaptoethanol, RSH) was investigated by means of stopped how o ptical spectroscopy and proton NMR spectroscopy. When the amount of RS (-) was 4 times larger than Cd2+ ions at alkaline pH, the growing clus ter showed the change in the absorption peak via 242, 260, 280, 308, a nd 315 nm. Initial three peaks were assigned to [Cd-1(SR)(4)](2-), [S1 Cd4(SR)(12)](6-), and [S1Cd8(SR)(16)](2-), respectively. Among them, t he cluster at 280 nm was very stable, comparable with the reported thi ophenolate cluster [S1Cd8(SPh)(16)](2-). The relationship between the size and the absorption maximum for ultrasmall CdS particles reported was continuous to that obtained for the clusters in the present study.