Effect of alcohol and alcohol/water mixtures on crystalline structure of CdS nanoparticles

A simple approach is discussed to synthesise CdS nanoparticles using various pure alcohols and their mixtures with water as a reaction medium. The study highlights that the solvent plays an effective role not only in controlling the particle size but also the structure. The size and phase of CdS nanoparticles were controlled by thermal reaction between cadmium precursor and thiourea in alcohol and their mixtures with water. Use of pure alcohols for the synthesis produces cubic structure as revealed from X-ray diffraction (XRD), while mixture of water with alcohol gives rise to hexagonal phase. XRD showed the presence of CdS nanoparticles with size 10-13 nm in an alcohol-water mixture whereas use of alcohols alone showed size in the range 1-3 nm. The composition and structural features were also studied by Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. Thiourea, in the presence of pure alcohol seems to be responsible for reduction in particle size as compared to that in the presence of alcohol/water mixture. The possible mechanism for the structural phase transition is discussed on the basis of change in surface energy and solvent-solvent interaction.