Enhanced solar Photocatalysis: Zinc oxide modified Yb2Zn-TiO6 doped g-C3N4 heterostructures for bromothymol blue mineralization and bacterial inhibition

Abstract

A new composite material, ZnO/Yb₂Zn-TiO₆@g-C₃N₄ has been synthesized by simple hydrothermal process. This composite has been characterized using various material characterization techniques and was found to have a heterojunction amongst Yb₂Zn-TiO₆ and g-C₃N₄, leading to higher light absorption and poorer charge carrier recombination rates. Furthermore, the evaluation of the charge carrier density revealed that the incorporation of small sized ZnO (40 nm) into Yb₂Zn-TiO₆@g-C₃N₄ led to heightened disintegration of the photoinduced charge carriers. This observation implies that the presence of said metal oxide enhances the photocatalytic performance by greatly promoting the effective separation of charge carriers for various applications. When tested with bromothymol blue, the 20 wt% ZnO/Yb₂Zn-TiO₆@g-C₃N₄ composite showed a photodegradation rate several times greater (98 %) than individual ZnO, C₃N₄ and Yb₂Zn-TiO₆, respectively. The degradation efficiency of the ZnO/Yb₂Zn-TiO₆@g-C₃N₄ nanostructure in the absence of light was 24 %. The increased photoactivity of the composite material is due to the efficient separation of charge carriers and also due to the high redox capabilities resulting from the heterojunction. The composite also demonstrated stable photocatalytic performance over five cyclic runs and was effective in treating real printed ink wastewater. Furthermore, ZnO/Yb₂Zn-TiO₆@g-C₃N₄ was found to have excellent antibacterial properties in opposition to Escherichia coli, (Inhibition = 16(±0.2) mm) as well as Bacillus subtilis (Inhibition = 22(±0.3) mm). The MIC of the said nanomaterials against Escherichia coli as well as Bacillus subtilis were 50 µg/mL and 30 µg/mL respectively. The detailed explanation of the photodegradation mechanism was also provided. The use of this composite material can help to reduce the harmful effects of contaminants and microbes in aquatic environments and promote environmental sustainability.