Cubic-to-hexagonal phase transition and optical properties of chemically synthesized ZnS nanocrystals

Cubic phase of ZnS nanocrystals, having particle size of 1.1-1.5 nm, is synthesized by the chemical co-precipitation method with different pH (4-12) of the reaction mixture. The nanostructures are characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-Visible spectrophotometry. As-synthesized ZnS samples are annealed for 2 h at different temperatures (T-c), determined from the differential scanning calorimetry (DSC) study. The phase-transformation (similar to 25%) from cubic to hexagonal phase of ZnS has been observed at very low temperatures at similar to 250 degrees C. Enhanced photoluminescence (PL) emissions are observed in the annealed samples as well as in the samples synthesized with higher pH values. (C) 2012 Elsevier B.V. Open access under CC BY-NC-ND license.