Mechanistic studies on the nucleation of zinc sulphide nanoparticles by means of XAFS spectroscopy

Mechanistic studies on the nucleation of zinc sulphide nanoparticles from thioacetic acid were performed by means of X-ray absorption fine structure spectroscopy. Solutions of thioacetic acid and zinc salt (acetate or oxide) dissolved in a solvent (acetic acid or acetone) were investigated and compared with the corresponding zinc precursor and crystalline zinc sulphide to study the evolution of the structural environment around the zinc atoms in the solution. The investigations reveal that the coordination of sulphur atoms take place immediately when the mixture is prepared and zinc-sulphur species gradually evolve during the course of the reaction. However, the complete formation of zinc sulphide could not be evidenced even after a considerable period of time. This is likely due to the presence of unreacted zinc-oxygen species. The obtained results indicate that, once dissolved, zinc oxide reacts comparatively faster with thioacetic acid than with zinc acetate and that the choice of the reaction medium plays a crucial role in determining the kinetics and mechanism of zinc sulphide nucleation.