Structural Characterization and Tunable Crystal Size of Phytogenic Silver Nanoparticles From Mentha piperita Waste via RSM Optimization

ABSTRACT

The synthesis of silver nanoparticles (AgNPs) using green methods is an environmentally friendly alternative to traditional methods, and these nanoparticles can be used in various applications such as food coatings, water treatment, and catalysis. In the present study, the aqueous extract of Mentha piperita L. waste leaves served as both a reducing and stabilizing agent, and the reaction time, temperature, and pH were optimized using response surface methodology (RSM) to control the crystal size. The crystal size varied from 10 to 43 nm in 17 experimental runs. The quadratic model showed an excellent fit ( F = 74.26, p < 0.0001; adjusted R ² = 0.9763). The minimum crystal size of 9.88 nm was predicted at 31.16°C, pH 5.92 and 15.96 min, and 10 nm AgNPs were obtained by experimental validation. The x‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x‐ray spectroscopy (EDX) results showed that the structure of the silver was face‐centered cubic, the morphology was mostly spherical, and the purity of the elements was high. This RSM‐guided green synthesis allows the production of AgNPs in a precise and reproducible manner from waste biomass, which is a sustainable alternative to the trial and error synthesis for industrial applications.