Eco friendly fabrication of Psidium guajava mediated hematite ZnO/chitosan biopolymeric nanocomposite for enhanced visible light driven photocatalytic and antimicrobial efficacy

Waterborne pathogens are intrinsically hazardous and accumulate within living organisms, leading to health risks such as dysentery, cholera, and pneumonia. Hybrid materials combining metal oxides and polymers provide synergistic adsorption properties, facilitate the degradation process, and exhibit strong antimicrobial activity against pathogenic microorganisms. To enhance the functions of polymer-based photocatalysis, we synthesized a psidium guajava leaf extract-mediated single-phase Fe 2 O 3 (Hematite)-ZnO/Chitosan (HZC) biopolymeric nanocomposite, demonstrating improved photocatalytic activity and potent antibacterial efficacy. XRD confirmed the formation of crystalline heterojunction Fe 2 O 3 -ZnO within the chitosan matrix with an average crystallite size of 28.5 nm. FTIR showed a wide spectrum of abundant amine groups in chitosan resulting in a spherical morphology that facilitated effective HZC conjugation as revealed through SEM analysis. The optical bandgap observed with UV-Vis spectroscopy was 2.0 eV, while chitosan transformed the Fe 2 O 3 -ZnO nanoparticles from passive candidates into highly active functional materials. The increase in adsorption and surface contact resulted in considerably high dye degradation efficiencies of methylene blue (MB) and Rhodamine B for 180 min. A gradual increase in the concentration of the HZC nanocomposites demonstrated progressively stronger inhibitory effects using zone of inhibition assays against the waterborne bacterial pathogens including Klebsiella pneumoniae (15.00 ± 2.65 mm), Shigella dysenteriae (19.67 ± 0.58 mm), Streptococcus pneumoniae (15.33 ± 4.04 mm), and Bacillus subtilis (15.3 ± 3.51 mm), at a concentration of 60 µg/mL. The dual nature of HZC biopolymeric NCs underscores the multifunctional material with promising applications in both photocatalytic and antibacterial applications supported by effective charge separation, surface reactivity, and metal ion release.