Fluorescence quenching of CdS nanocrystallites in AOT water-in-oil microemulsions

The luminescence of CdS nanoparticles suspended in ''dry'' AOT reversed micelles is quite intense but is quenched by water and even more effectively by thiol-containing compounds. Stern-Volmer plots provide information about the quenching efficiencies of various compounds. Of particular interest is 4-hydroxythiophenol which interacts strongly with the surfactant headgroups and thereby partitions to the nanoparticle surface. The quenching efficiency of 4-hydroxythiophenol is more than an order of magnitude greater than that of thiophenol. At the very low concentrations of 4-hydroxythiophenol required to bring about quenching, a remarkable recovery of fluorescence is observed upon continued irradiation. The fluorescence recovery is attributed to photochemical oxidation which consumes the hydroxythiophenol presumably giving a disulfide product. (C) 1997 Elsevier Science B.V.