Photocatalysis based on semiconductor quantum dots, which utilize the solar energy can be used for
elimination of pollutants from aqueous media and applied for water purification. In this paper, high
stable CdS quantum dots (QDs) with good optical properties were successfully synthesized in a facile
in-situ method, using Na2S2O3 as precursor and thioglycolic acid (TGA) as a catalyst, as well as capping
agent in aqueous media. The synthesis process was optimized with a 27—3
IV fractional factorial design
method. Then, we studied the degradation of some industrial dyes including: alizarin, acid violet, mor-
dant red and thymol blue as a tool to check the photocatalytic activity of synthesized CdS QDs. Results
specified that the synthesized CdS QDs are capable for degradation of organic dyes under visible light
irradiation with good recycling stability during photocatalytic experiments. Structural and spectroscopic
properties of the synthesized CdS QDs were studied by TEM, XRD and absorption and fluorescence spec-
troscopy techniques. The synthesized TGA-capped CdS QDs have sizes in the range of 2.65–2.93 nm with
cubic crystalline structures.