Extract-dependent size control of silver nanoparticles using tropical artisan tea extracts under identical green synthesis conditions

Green synthesis of silver nanoparticles (AgNPs) offers a sustainable alternative to conventional chemical methods; however, controlled size regulation through plant-mediated routes remains challenging, particularly without modifying reaction conditions or introducing chemical additives. In this study, a comparative, extract-driven strategy is presented for the synthesis of AgNPs using three tropical artisan tea extracts: butterfly pea (Clitoria ternatea), jasmine tea (Jasminum sambac), and roselle (Hibiscus sabdariffa). All syntheses were performed under strictly identical and mild conditions (2 mM Ag precursor, 5 % v/v crude extract, pH 10, room temperature), with the plant extracts functioning exclusively as both reducing and stabilizing agents. UV–Vis spectroscopy confirmed AgNP formation through characteristic surface plasmon resonance bands, while particle size analysis and transmission electron microscopy revealed spherical nanoparticles with average sizes of 5.9 nm, 10.5 nm, and 16.1 nm, respectively. The observed size variation is attributed to extract-dependent phytochemical composition, which governs Ag⁺ reduction kinetics and nanoparticle growth. This work demonstrates, for the first time, the feasibility of producing 3-discrete AgNP size grades through plant extract selection alone, providing mechanistic insight and a practical, sustainable pathway for tailoring AgNP properties without additional chemical reductants or stabilizers.