*2.2. AgNPs Synthesis*

The AgNPs stabilized with citrate (Cit) and L-Cysteine (L-cys) were prepared and characterized in analogy to literature reports [60,61]. 1.47 g of sodium citrate were dissolved in 50 mL of distilled water (0.01 M), 0.006 g of L-cys in 25 mL of distilled water (0.002 M) and 0.21 g of AgNO3 in 25 mL of distilled water (0.05 M). Then, 25 mL of L-cys solution, 10 mL of Cit solution and 2.5 mL of AgNO3 solution were added sequentially in a 100 mL flask, provided with a magnetic stir. The mixture was degassed with Argon for 10 min, then 4 mL of NaBH4 solution (0.016 g in 4 mL distilled water) were added. The mixture was allowed to react at room temperature for 2 h and at the end the brown solution was recollected and purified by centrifugation (13,000 rpm, 10 min, 2 times with deionized water). AgNPs main characterizations: UV-Vis (λmax [nm], H2O) = 400 nm; < 2R H > ([nm], H2O) = 8 ± 1; TEM Ø = 5 ± 2 nm.
