Kinetic-dependent crystal growth of size-tunable CdS nanoparticles

The general study of crystal growth of spherical-like nanoparticles involve s monitoring the kinetics during the progress of the reaction. In the case of cadmium sulfide (CdS), cadmium acetate and sodium sulfide are employed a s starting reagents that are dissolved in different solvents (ethylene glyc ol, glyme, diglyme, and trioctylphosphine) to study the solvent effect on m onomers, nucleation rates, and the quality of the seeds. Trialkylphosphine oxide (alkyl = ethyl or octyl) is chosen as a surfactant to passivate the s urface of CdS nanoparticles. We propose a kinetic approach model to illustr ate the unreported time-evolved crystal growth mechanism observed in this c ase. An experimental value for the diameter of critical volume (V-c), a nan osized volume with a relative minimum surface-volume tension and considered a temporal stable stage (r = 5.7 nm in this case), is derived from transmi ssion electron microscopy images. The size of the nanoparticles made by thi s synthesis route is tunable by variation of the reaction time and control of the reaction temperature; in addition, the resulting sizes are suitable for spectroscopic testing of electron quantum confinement. The X-ray powder diffraction data are consistent with a pure hexagonal CdS lattice and show no evidence for a mixed phase involving cubic symmetry.