Study of de-aggregation of mechanochemically synthesized ZnSe nanoparticles by re-milling in the presence of ZnCl2 solution

Conventional mechanochemical synthesis of zinc selenide, ZnSe nanoparticles was performed in a planetary ball mill by highenergy milling of zinc (Zn) and selenium (Se) powders. Mechanochemically synthesized ZnSe was subsequently re-milled in circulation mill in ZnCl2 solution in order to study de-aggregation, physical-chemical and optical properties of ZnSe nanoparticles. The mechanochemically synthesized and re-milled samples were characterized by X-ray diffraction analysis (XRD) that confirmed the presence of cubic and hexagonal ZnSe phases. Size of crystallites calculated from XRD patterns has decreased from 50 to 19 nm for cubic ZnSe phase and from 145 to 2.5 nm for hexagonal ZnSe phase after re-milling for 110 min in ZnCl2 solution. Size, phase composition, morphology, and crystallinity of ZnSe nanoparticles were studied by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). UV-Vis optical spectroscopy has provided an evidence of blue shift of the re-milled nanocrystalline ZnSe particles from the direct band gap of 2.67 eV characteristic of bulk ZnSe crystals. Colloidal stability of ZnSe nanoparticles dispersions was studied by ζ–potential measurements.