Enhanced photocatalytic and antibacterial performance of ZnO and ZnS synthesized using natural fuel: Influence of green synthesis, particle size, and morphology

Abstract

This study reveals the eco-friendly synthesis of zinc oxide (ZnO) and zinc sulfide (ZnS) nanoparticles using aqueous neem flower (Azadirachta indica) extract as a green reducing and stabilizing agent. The nanoparticles have been characterized by XRD, FTIR, UV-visible spectroscopy, FESEM, EDX, and DLS techniques. Structural and morphological characterization confirmed the efficacious development of hexagonal ZnO and cubic ZnS phases, with crystallite sizes of 40.42 nm and 16.24 nm, respectively. FTIR analysis revealed the existence of phytochemical capping groups, indicating the role of neem extract in nanoparticle stabilization. DLS analysis further supported these results, which showed a broader size distribution for ZnO (85.69 nm) and a narrower, polydisperse distribution for ZnS (24.93 nm). The photocatalytic performance has been examined under sunlight for degradation of Acrylic Orange and Alizarin Red S dyes. ZnO exhibited superior photocatalytic performance, degrading 95.72% of Acrylic Orange and 92.37% of Alizarin Red S, with higher rate constants than ZnS, and maintaining over 88% stability after five reuse cycles. Additionally, both nanoparticles demonstrated effective antibacterial activity, with ZnO showing larger inhibition zones against S. aureus and E. coli, likely due to its higher reactive oxygen species generation and more favourable morphology.