Bio-inspired zinc oxide nanoparticles from onion peels

Onion peel waste poses significant environmental pollution challenges. However, nanotechnology offers a sustainable solution by transforming this waste into nano-fertilizers with targeted delivery, specificity, and controlled release. This study synthesized zinc oxide nanoparticles (ZnONP) using onion peel extract and characterized them through advanced techniques, including field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), and particle size distribution (PSD). FE-SEM analysis revealed spherical particles ranging from 95.35 to 124.5 nm, while PSD showed a size distribution between 50 to 400 nm with a zeta potential of -17.9 mV. FTIR analysis identified organic molecule capping from onion peel extract, indicated by bands within 1000 - 1800 cm⁻¹. The synthesized ZnONP were tested as a nano-fertilizer on soybean plants. At a concentration of 500 mg kg-1, ZnONP significantly improved soybean seed germination by 75 % compared to control seeds. Additionally, they promoted root and shoot growth and increased chlorophyll content in soybean leaves. Chlorophyll a, chlorophyll b, and total chlorophyll levels improved by 55.7 %, 61.1 % and 57.5 % respectively, as a relative value compared to the control condition. These findings demonstrate that ZnONP derived from onion peel waste can serve as an effective nano-based nutrient source, offering an environmentally friendly approach to improving agricultural productivity.