Preparation and characterisation of Na2S and ZnSO4 nanoparticles in water/sodium bis(2-ethylhexyl)sulphosuccinate/n-heptane microemulsions

The preparation procedure for nanoparticles of the water-soluble salts Na2S and ZnSO4, two commonly used reagents to synthesise ZnS nanoparticles, by evaporation of volatile components of salt-containing water-in-oil microemu lsions is described. In suitable conditions, the evaporation leads to the f ormation of dry salt-surfactant composites and to the formation of Na2S or ZnSO4 nanoparticles. It was found that the salt-surfactant composites can b e totally redissolved in a dry apolar organic solvent allowing the formatio n of virtually water-free solutions containing a considerable amount of the water-soluble salts. The presence of nanoparticles in these solutions and in the composites has been proved by small-angle X-ray scattering and trans mission electron microscopy, respectively. By mixing these solutions, the s olid-solid reaction between Na2S and ZnSO4 nanoparticles leading to the for mation of very small-sized ZnS nanoparticles has been ascertained by UV spe ctrophotometry.