The Growth and Optical Properties of CdS Nanorods via Solvent-Thermal Route

CdS nanocrystals were synthesized by a solvent-thermal method in ethylenediamine at different temperature and time. The samples were investigated by XRD, TEM, Uv-vis absorption and PL spectroscopy. The solvent-thermal temperature at 200 °C is an optimal reaction temperature for preparing CdS nanorods with high crystallinity. The PL spectra exhibited two typical emissions: near band edge emission (centered at ~520nm) and defect emission (a broad peak in the range of 550-750nm). The defect emission decreased gradually and disappeared finally with the reaction time increasing from 1 to 12h, but the near band edge emission increased. This revealed that the quality of the CdS samples improved by degrees as the reaction time increased. The growth of single-crystalline CdS nanorods followed three steps; (a) CdS nuclei formed by reacting Cadmium chloride dihydrate and thiourea in ethylenediamine at 200 °C, (b) CdS nuclei grew into thin nanowhiskers after 1h reaction, (c) the growth of CdS nanorods based on nanowhiskers via a Ostwald ripening process.