Investigations on certain metal oxide based semiconductor nanomaterials for photocatalytic activities

Abstract

Photocatalysis is an acceleration of a photoreaction using semiconductor catalyst by the activation of a light energy. It can be referred to the combination of both photochemistry and catalysis. As compared to metal, semiconductors are the best photocatalysts due to their distinctive bandgap structure which makes the photoexcitation. They also act as sensitizers due to their filled valence band and empty conduction band in the light induced redox reaction. Indeed, most of the semiconductor nanomaterials have some intriguing properties such as less toxic, cost efficient, reusable, stable, insoluble and easy to fabrication. Among them, the semiconductor metal oxides (ZnO, MoO3 and Nb2O5), metal sulfide (MoS2) and their heterostructure (ZnO-MoS2) are greatly attracted in the field of heterogeneous photocatalyst for the toxic dye removal applications due to their unique band gap energy and tunable physico-chemical properties. Thus, our focuses on the synthesis of different semiconductor nanomaterials by simple and ecofriendly method for waste water treatment applications. The preparation of zinc oxide (ZnO) nanoparticles (NPs) by green synthesis route using carica papaya leaf extract for photocatalytic application has been demonstrated. In this work, the phase pure ZnO NPs were synthesized via facile green synthesis method, where zinc acetate dihydrate was used as precursor and papaya leaf extract as reducing agent. The structure and phase formation of the synthesized material was confirmed by X-Ray diffraction and FT-IR analysis. The bandgap energy for the prepared ZnO NPs was calculated from the DRS spectra and it is found to be 3.32 eV. The surface morphology and phase purity of ZnO NPs was characterized by FE-SEM and EDX analysis, respectively. Electron microscopic analysis indicates that ZnO NPs are spherical in shape with particle size of ~50 nm. Importantly, the as synthesized ZnO NPs were used as efficient photocatalyst for Methylene Blue (MB) dye degradation. It is persistent to note that the prepared ZnO NPs almost completely degraded the MB dye under UV light condition after 180 min illumination tim newline