Synthesis of ultra-small ZnS nanoparticles by solid-solid reaction in the confined space of AOT reversed micelles

Ultra-small ZnS nanoparticles have been synthesized by a novel solid-solid reaction between Na2S and ZnSO4 nanoparticles in the confined space of AOT reversed micelles. The reaction was performed by mixing two dry AOT/n-heptane solutions, containing Na2S and ZnSO4 nanoparticles, respectively. This synthetic route has been revealed to have specific advantages giving anhydrous systems with high nanoparticle concentration. From these systems, by simple evaporation of the organic solvent, interesting AOT/ZnS composites can be prepared. Size, polydispersity, and photophysical properties of AOT reversed micelles containing ZnS nanoparticles dispersed in n-heptane have been investigated as function of salt and AOT concentrations by SAXS and UV spectroscopy. The UV spectra of all samples, including AOT/ZnS composites, showed a red shift of the first excitonic transition band with time but, as assured by SAXS experiments performed on liquid samples, this phenomenon was not associated with any change in mean size and/or polydispersity of ZnS containing AOT reversed micelles.