Eco-friendly approach for ZnO nanoparticles synthesis and evaluation of its possible antimicrobial, larvicidal and photocatalytic applications

The synthesis of nanoparticles (NPs) from plants is a viable eco-friendly approach with applications in different sectors. Thus, we aim to synthesize and characterize zinc oxide NPs (ZnO NPs) from Ficus racemosa L. leaf extract and to evaluate their larvicidal potential against Aedes albopictus larvae, their efficacy against human clinical pathogenic bacteria (Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli). Furthermore, we evaluated its use in photocatalytic rhodamine B (RhB) dye degradation and its possible acute toxicity to a non-target organism (Artemia salina). The biosynthesized ZnO NPs were characterized using UV–Vis, XRD, SEM-EDX, TEM, and FT-IR. UV–vis absorption spectrum indicates that the green synthesized ZnO NPs absorb at the wavelength centered at 365 nm, corresponding to the band gap of 3.2 eV. We reported that A. albopictus mosquito larvae were highly susceptible to ZnO NPs, especially when exposed to 250 μg ZnO NPs/mL. The reduction of acetylcholinesterase (AChE) activity and the carboxylesterases phosphatases evaluated was concentration-dependent, constituting a possible mechanism of larvicidal action of NPs. Biosynthesized ZnO NPs also significantly inhibited the growth of the bacterial species evaluated, suggesting good bactericidal activity. Furthermore, the ZnO NPs efficiently degraded RhB dye in an aqueous solution under UV light irradiation, proving promising in dye remediation in wastewater. Finally, ZnO NPs suspension exhibited lower acute toxicity of A. salina after 48 h of exposure. Therefore, our study pioneeringly demonstrates that biosynthesis of ZnO NPs from F. racemosa leaf extract can be a great approach to developing versatile and environmental products.