Preparation,morphology, size quantization effect and photocatalytic properties of CdS Q-nanocrystals

CdS nanoclusters were synthesized by using n- octylthiol as a ligand and n- hexadecyl- trimethyl-ammonium bromide (or n-tetrabutylammonium bromide) as an organic cation. Size- selective precipitation techniques have enabled the preparation of different CdS Q-nanoparticles with narrow size distribution and mean diameters ranging from 2 to 5 nm. UV-Vis spectroscopy, transmission electron microscopy (TEM) and small-angle X-ray scattering were used to determine the mean cluster size. Their size quantization effect has been observed in UV-Vis spectra, fluo-rescence spectra and small-angle X-ray diffraction, but it became too weak to be observed for large particles (2r > 10 nm). Moreover, their photo-catalysis has been studied by ESR technique and the results revealed that the photo-catalytic reaction occurred in the solution system and some free radicals such as CH2-OH in methanol, or CH3-CH-OH in ethanol were generated if some CdS Q-particles were added to methanol (or ethanol) and initiated by UV light at the same time, which may be very crucial in organic synthesis.