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

Abstract

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.