Briefly, water extract of C. longa tubers (0.1 g) was added to distilled deionized water (20 mL) with vigorous stirring for 4 hours. Forty milliliters of AgNO3 (1 × 10−3 M) was then added and mixed at room temperature (25°C) for 24 hours. Ag-NPs were gradually obtained during the incubation period. Throughout the reduction process, the solution was kept at a room temperature in the dark to avoid any photochemical reactions. The solution component was purged with nitrogen gas prior to use. Subsequently, reduction proceeded in the presence of nitrogen to eliminate oxygen. The obtained colloidal suspensions of Ag/C. longa were then centrifuged at 15,000 rpm for 20 minutes and washed four times to remove silver ion residue. The precipitate nanoparticles were then dried overnight at 30°C under vacuum to obtain the Ag/C. longa.