Phase transformation of nanocrystalline CdS synthesized by solvothermal reaction

Abstract

CdS was synthesized by solvothermal reaction of CdCl2.2.5H 2O and (NH2)2CS in ammonia solution at 200°C for 10 h. XRD, TEM and SAED show that the products are nanocrystalline CdS. The phase is 100 % hexagonal (hep) in pure water, gradually transformed into cubic with the increase of NH3 concentration, and 100 % cubic in 25 % NH3 solution. By using FTIR, no solvents were detected in the products. Raman analysis revealed the presence of ILO (longitudinal optical) and 2LO phonon peaks at 297.0 and 597.1 cm-1 for CdS (hep), and 295.9 and 596.9 cm-1 for CdS (cubic), respectively. Strong peaks of the photoluminescent (PL) spectra were detected at 450 nm for hep, and 519 nm for cubic.