Biosynthesis of ZnO nanoparticles using Averrhoa bilimbi fruit extract: evaluation of photocatalytic and antibacterial activities

Contaminated wastewater poses serious environmental and biological risks, necessitating effective treatment methods. Among various techniques, photocatalysis offers a cost-effective solution with minimal secondary pollutants. This study employed Averrhoa bilimbi fruit extract as a green fuel for synthesizing zinc oxide nanoparticles (ZnO NPs) using the sol-gel combustion method. X-ray diffraction confirmed the hexagonal wurtzite phase, while Field Emission Scanning Electron Microscopy (FESEM) images revealed randomly dispersed quasi-spherical ZnO NPs averaging 50 nm in size. Fourier Transform Infrared (FTIR) spectroscopy analysis was utilized to identify the functional groups present in the biosynthesized NPs. The photocatalytic activity was assessed via degradation of 5 ppm methylene blue dye, achieving 99.87% efficiency with 40 mg of ZnO NPs under UV light (8 W, λ = 254 nm) for 2 h at pH 10. Antibacterial properties were evaluated using the minimum inhibitory concentration (MIC) method against Klebsiella pneumoniae and Staphylococcus aureus, showing significant inhibition of Klebsiella pneumoniae.