Preparation of glass substrate containing CdS quantum dots for photocatalytic degradation of some industrial dyes

Photocatalytic degradation of pollutants based on semiconductor quantum dots (QDs), which utilize the solar energy can be used for wastewater purification methods. But, application of free QDs was associated with some difficulties, such as oxidation and agglomeration of QDs and difficulties in separation. As a solution for these problems, we have studied the production and application of glass substrate containing CdS quantum dots for photocatalytic degradation of some industrial dyes (alizarin, acid violet, mordant red and thymol blue).The glass substrates containing CdS QDs were prepared by a dip coating method. Glass sheets (2cm×4cm) were carefully cleaned by sonication in acetone, for 5 minutes. These supports were then immersed in a HF (10%) solution for 2h and then washed with double distilled water. Now, the surface of glass sheet was prepare for dip coating process. The prepared sheet immersed in a solution containing 3 g CdCl2 in 10 ml water for 2 min (solution A); then rinsed with double distilled water followed by immersing in a solution containing 2 g Na2S in 10 ml water for 2 min (solution B); then rinsed again with double distilled water and this cycle was repeated for 10 cycles. Finally, the obtained sheet was heated at 80 °C for 2h, followed by annealing at 300 °C for 30 min.To examine the photocatalytic activity of prepared substrates, a glass substrates containing CdS QDs was immersed in 10 mL aqueous solution of malachite green (100 ppm). Afterwards, the suspension was irradiated by ultraviolet (UV) lamp for the photocatalytic experiment under moderate stirring. At specified time intervals, the concentration of dye in the supernatant was determined by UV–vis absorption spectroscopy at the λmax. The same procedure was done for sunlight irradiation [1]. 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.