Preparation of cadmium sulfide nanoparticles in self-reproducing reversed micelles

Octyl octanoate (O-OL) underwent hydrolysis in sodium octanoate (NaOA) reversed micelles in 85: 15 = isooctane: octanol (OL) (v/v), containing w = [H2O]/[NaOA] = 40. The products of the hydrolysis, octanoic acid (OA) and octanol (OL), lead to the formation of additional (albeit smaller) reversed micelles; hence the process is considered to be self-reproducing. Self-reproduction was found to be catalyzed by lithium hydroxide, solubilized in the water pools, as well as by hydrogen sulfide, added to the solution of the reversed micelles. Addition of hydrogen sulfide to cadmium perchlorate containing self-reproducing reversed micelles resulted in the formation of cadmium sulfide (CdS) nanoparticles. Diameters of the CdS containing nanoparticles could be altered from 5.4 to 1.8 nm by changing the [Cd2+]/[H2S] ratios from 0.25 to 10. The CdS nanoparticles formed were capped by mercaptopropionic acid, isolated as solids, and could be repeatedly redispersed in water without changing their sizes. Additional CdS nanoparticles were generated in the supernatants removed from the precipitated capped CdS nanoparticles. (C) 2002 Elsevier Science (USA).