Biosynthesized Mn2O3 nanoparticles from Syzygium alternifolium leaf extract: Structural characterization, Crystal violet dye degradation, and Antibacterial activity

Abstract

The green synthesis, characterisation, photocatalytic, and antibacterial assessment of Mn2O3 nanoparticles made with Syzygium alternifolium leaf extract are presented in this study. The synthesized α- Mn2O3 NPs were characterized by UV-Vis, XRD, FTIR, SEM-EDX, and TGA analyses, confirming phase-pure cubic crystallinity, nanoscale morphology, thermal stability, and elemental purity. SEM images revealed agglomerated spherical nanostructures, while EDX confirmed manganese and oxygen as the predominant elements. The biosynthesized α-Mn2O3 NPs exhibited excellent visible-light-driven photocatalytic activity toward crystal violet dye degradation, achieving nearly 99% efficiency under optimized conditions, particularly at alkaline pH. Photocatalytic performance was significantly influenced by pH, catalyst dosage, dye concentration, and irradiation time, with reactive oxygen species (•OH and O2•⁻ radicals) playing a key role in dye mineralization. The nanoparticles also demonstrated notable stability and reusability over five cycles. Additionally, the Mn2O3 NPs showed significant concentration-dependent antibacterial activity against S.aureus and E.coli, attributed to oxidative stress and membrane disruption.