Well dispersed CdS quantum dots (QDs) were in-situ prepared using poly(amidoamine) (PAMAM) dendrimers and poly(N-vinyl-2-pyrrolidone) (PVP) as templates respectively, and effects of both polymer templates on the preparation and photocatalytic properties of CdS QDs were studied through methyl orange degradation. The results show that the size distribution of PAMAM dendrimers-stabilized CdS QDs (CdS QDs/PAMAM) is much narrower than that of PVP stabilized CdS QDs (CdS QDs/PVP), and the exciton absorption peak and PL intensity of the former are much stronger. At the similar size, the photocatalytic efficiency of CdS QDs/PAMAM is much higher than that of CdS QDs/PVP. Differences in molecular structure between PAMAM and PVP are the major influence factors to the above contrast. PAMAM dendrimers are excellent templates for preparing CdS QDs with controlled size and narrow size-distribution. And most of the catalytic active sites in the surface of CdS QDs are not passivated by PAMAM dendrimer branches, which act as porous channels for methyl orange. However, many catalytic active sites in the surface of CdS QDs/PVP are passivated by the long twining PVP chains, which decrease the photocatalytic efficiency of CdS QDs/PVP. Besides, the narrower size-distribution of CdS QDs/PAMAM contributes to their high photocatalytic efficiency to some degree. In addition, the photocatalytic efficiency of CdS QDs increases when the size becomes smaller because of the larger specific surface area, stronger quantum confinement effect, and higher photo-production electron and hole energy of smaller QDs.

Key words: CdS quantum dots, PAMAM dendrimer, poly(N-vinyl-2-pyrrolidone), photocatalyst, methyl orange