Eco-friendly synthesis of silver nanoparticles using the fungus Alternaria sp. OP242500: Optimization through box-Behnken design

Abstract

Fungi efficiently biosynthesize nanoparticles by utilizing their enzymatic and metabolic functions to reduce metal ions and improve colloidal stability. This study presents a sustainable method for producing silver nanoparticles through a cell-free extract from the fungus Alternaria sp. OP242500, emphasizing its value for green nanotechnology applications. Key synthesis parameters, including silver acetate concentration, pH, temperature, and incubation time, were optimized using the Box-Behnken design. Under optimal conditions (5.5 mM silver acetate, pH 7.8, 33.5 °C, and 96 h), the synthesized nanoparticles achieved an optical density of 2.11 at 430 nm, closely matching the predicted value of 2.15 with an accuracy of 98.14 %. Structural and stability analyses conducted through UV–visible spectroscopy, scanning electron microscopy, X-ray diffraction, zeta potential analysis, and Fourier-transform infrared spectroscopy confirmed the formation of uniformly spherical, well-crystallized silver nanoparticles with a face-centered cubic structure. The biosynthesized nanoparticles exhibited sizes ranging from 10.9 to 68.5 nm and displayed excellent colloidal stability, as evidenced by a zeta potential value of −20.8 mV. These findings demonstrate the efficiency of the fungal extract-based synthesis method and underscore its promising applications in medicine, nanotechnology, and environmental science.