Photocatalytic Degradation of Rhodamine B Dye Using Histidine-Stabilized CdS Quantum Dots

CdS quantum dots were prepared using the amino acid histidine as a stabilizing agent. Using a concentration of 4 x 10(-4) M for the precursor Cd2+ and S2- ions and taking the concentration of histidine as 20 mM, the average size of the CdS nanoclusters was determined to be 4.2 nm. The absorption onset of these particles was 452 nm which is considerably blue shifted compared to those of the bulk CdS. Such particles are known as quantum dots. The photocatalytic efficiency of the CdS quantum dots was evaluated by studying the degradation of rhodamine B dye. About 21 % of the dye was degraded in 30 min of irradiation using light of wavelength longer than 400 nm. The degradation of the dye was found to follow first order reaction kinetics. The addition of adenine was found to enhance the photocatalytic activity of the CdS quantum dots.