Phyto-mediated synthesis of ZnO/TiO₂/bentonite nanocomposites: structural characterization and enhanced antibacterial and antioxidant activities

Abstract

The rise of antibiotic-resistant pathogens and the physiological damage from oxidative stress necessitate novel therapeutic agents. This study reports the green synthesis of a multifunctional ZnO/TiO₂/Bentonite (ZTB) nanocomposite (NCs) using an aqueous leaf extract of Hagenia abyssinica as both a reducing agent. The physicochemical properties of the ZTB NCs were systematically investigated. Characterization confirmed the successful formation of a ternary nanocomposite, where ZnO/TiO₂ heterojunctions are supported on a bentonite matrix. The resulting ZTB NC exhibited the smallest crystallite size (24.7 nm) and the narrowest optical bandgap (3.18 eV). In bioactivity assays, the ZTB NCs demonstrated markedly superior performance, exhibiting broad-spectrum antibacterial efficacy with inhibition zones reaching up to 23.9 mm. This strong antibacterial activity was further confirmed by very low minimum inhibitory (MIC) and bactericidal (MBC) concentrations, reaching 0.813 μg/mL and 1.625 μg/mL, respectively, against Gram-positive strains. Furthermore, ZTB exhibited excellent antioxidant capacity, achieving a radical scavenging activity of 94.5 % and a low half-maximal inhibitory concentration (IC₅₀) of 52.57 μg/mL. These findings highlight the synergistic advantages of the ternary ZTB structure and establish it as a highly promising and eco-friendly candidate for advanced biomedical applications.