ZnS quantum dots impregnated-mesoporous TiO2 nanospheres for enhanced visible light induced photocatalytic application

ZnS quantum dots were impregnated on the surface of TiO2 mesospheres by a soft template-assisted solvothermal approach. XRD and elemental analysis confirmed the presence of ZnS in the TiO2 nanostructures. Morphological analysis showed that the ZnS quantum dots were firmly immobilized on the TiO2 mesospheres, which improved electron and hole pair separation at the TiO2/ZnS interface. The photocatalytic activity of the mesoporous nanostructures was assessed by photodegradation of methylene blue (MB) as a model pollutant under visible light irradiation. Impregnation with ZnS quantum dots enhanced reaction activity remarkably compared with mesoporous TiO2. The maximum degradation efficiency was observed for 0.025 M of ZnS impregnated on TiO2. The MB-related absorption peak completely disappeared after 32 min of irradiation. Photo-charge scavenger analysis indicated that hydroxyl radicals played a pivotal role in the photodegradation mechanism. The mesoporous photocatalyst was stable and can be used repeatedly under visible irradiation.