Synthesis and Characterization of CdS Nanocrystals in a Novel Phosphate Glass

Zinc-borophosphate glasses doped with various concentrations (<= 5 wt. %) of cadmium sulfide (CdS) were synthesized. Nanocrystals of CdS were developed in the glass matrices at different concentrations, with emphasis on the quantum confinement effect. The effects of CdS content on the optical and various other properties were investigated. The optical characterization of the glasses was carried out using UV-Visible spectrophotometry. There was a red shift in the optical cut-off with increasing CdS content in the glass. The band gap of the CdS nanocrystals doped in the glass matrix ranged from 3.5 eV to 4.2 eV. The structural characterization, which was carried out using X-ray diffraction, shows the CdS to have hexagonal crystal structure. The average size and shape of the nanocrystals doped in the glass matrix were determined using transmission electron microscopy (TEM). The particle sizes of the doped CdS crystals were in the range of 3 nm to 6 nm for 2 wt. % CdS, and 15 nm to 20 nm for 5 wt. % CdS.