In situ solid-state fabrication of Z-Scheme BiVO4/g-C3N4 heterojunction photocatalyst with highly efficient-light visible activity and their antibacterial properties against bacterial pathogens

Abstract

Here, BiVO4/g-C3N4 composite photocatalyst with various weight percent of BiVO4 were synthesized by in-situ solid-state fabrication via calcination process. Photocatalyst was characterized by various analytical techniques (XRD, SEM, TEM, UV–vis-DRS, and TGA). The SEM and TEM results showed that composites materials BiVO4 dispersed uniformly on the surface of g-C3N4 sheets, revealing that g-C3N4 sheets was probably a promising support for in-situ growth of nano-size materials. The achieved intimate interfacial contact between BiVO4 and g-C3N4 promoted the charge transfer and inhibited recombination rate of photogenerated electron-hole pairs, which significantly improved the photocatalytic activity. Remarkably, catalytic efficiency of BiVO4/g-C3N4 composites has been demonstrated, via photodegradation of organic pollutants such as rhodamine-B (RhB) and ciprofloxacin (CIP). The 5 wt.% BiVO4/g-C3N4 showed excellent photocatalyst activity and potentially degraded RbB (98 %) and CIP (95 %) in 75 min of irradiation time in the presence of visible light. Moreover, radical trap experiment indicated that the –•O2 and •OH acted as main reactive species for photocatalytic degradation. In addition, BiVO4/g-C3N4 nanocomposite showed strong antibacterial potential against bacterial pathogens; E. coli ATCC-15224, Staphylococcus aureus MTCC-3160 and Pseudomonas aeruginosa PAO1. Studies revealed that depended on time and BiVO4/g-C3N4 concentration, bacterial growth, and viability (CFU count) was consistently declined. The increasing doses of BiVO4/g-C3N4 significantly (p ≤ 0.05) inhibited the virulence factors like pyoverdin, pyocyanin, elastase, exoprotease, rhamnolipid, and swimming motility of P. aeruginosa PAO1 by 76.9, 49.0, 71.1, 53.3, 89.5, and 60 %, respectively. Furthermore, biofilms formed by E. coli, S. aureus and P. aeruginosa PAO1 were maximally inhibited at 10 µgmL−1 BiVO4/g-C3N4 to a maximum of 67, 56 and 56 %, respectively. Also, exopolysaccharide (EPS) releasing ability of isolates were suppressed by BiVO4/g-C3N4. The fluorescently labelled probe DCFH-DA staining of bacterial isolates showed nanocomposite-dependent increase in ROS production and superoxide radicals. The photodegradation of RhB and (CIP) recommends that synthesized BiVO4/g-C3N4 nanocomposite have strong photocatalytic properties. Summarily, newly synthesized BiVO4/g-C3N4 photocatalyst can be employed as an alternative to remediate the environmental pollution as well as a therapeutic agent for topical administration in controlling the pathogenic infections.