**2.3 Synthesis of NSs**

30 ml of 1 mM AgNO3/HAuCl4 aqueous solution was produced, and 6 ml of extracts were mixed to the 30 ml of solution at 24°C. The solution was first colorless, then progressively turned ashy, indicating the formation of Ag NPs. In the instance of Au NPs, the yellow solution turned ruby red, it showed that the forming of Au NPs. It is conducted three times to ensure that it is repeatable.
