Effect of pH and Antioxidant Activity of Plant Extracts on Green Synthesis of Silver Nanoparticles

This study presents an eco-friendly synthesis of silver nanoparticles (AgNPs) using leaf extracts of gooseberry, honeysuckle, strawberry and sea buckthorn, characterized by increasing antioxidant activity (AOA). Successful nanoparticle formation occurs in near-neutral and alkaline media, while the nucleation process is inhibited in acidic media. The nanoparticles were characterized using a combination of spectroscopic (TEM, EDX, UV–vis, SAED, XRD, FTIR, ICP-OES) and electrochemical (CV, LV, EIS) methods. A comprehensive analysis of the nanoparticles revealed the following dependencies: a decrease in silver nanoparticle size with increasing AOA and synthesis medium pH; an increase in efficiency of silver nanoparticle synthesis as the plant extract AOA rose from 1.8 ± 0.3 mmol-eq L−1 to 15.7 ± 1.2 mmol-eq L−1; enhanced electron-transport properties and catalytic activity of silver sols formed in an alkaline medium with high AOA; and an increase in oxidation current of Brilliant Blue FCF, carbofuran, and tryptophan, alongside a reduction in electrode process overvoltage, when using silver sols formed in media with higher AOA and pH. Targeted adjustment of the reaction medium pH and AOA enables to use the controlled synthesis of AgNPs with specific optical, dispersion, and electrochemical properties for various applications, including highly sensitive electrochemical sensors.