Photoluminescence and structural characteristics of CdS nanoclusters synthesized by hydrothermal microemulsion

Spherical and uniform CdS nanoclusters were synthesized by hydrothermal microemulsion. The reaction of Cd2+ ions with S2− ions generated from the decomposition of thioacetamide proceeded in water microdroplets. The mean diameter of the CdS nanoclusters can be varied from 20 to 80 nm by increasing the reaction temperature from 30 to 120 °C. XRD results indicate that the resulting CdS nanoclusters have a reduced and distorted hexagonal lattice compared to bulk materials. Two intense luminescence bands, i.e., green and red, were observed to coexist in the CdS nanoclusters. Their peak positions and relative intensities were found to be sensitive to the size and structure of nanoclusters. These emissions are attributed to surface defects (green emission) and the Cd–Cl composite vacancies (red emission).