AgNO 3 (99%) was purchased from Sigma-Aldrich, St. Louis, MO, USA; ascorbic acid (99%) and melamine (98.0%) were purchased from Across Organic; sodium hydroxide, potassium hydroxide, and sodium citrate dihydrate were purchased from Fisher Scientific, Suwanee, GA, USA; Triton X-100 was purchased from VWR analytics, Radnor, PA, USA; 100% cotton fabrics were purchased from Walmart, Woodstock, GA, USA. All chemicals and solvents were used without further purification. All glassware was cleaned with aqua regia (3:1 v/v HCl (37%)/HNO 3 (65%) solutions) and then rinsed thoroughly with DI H 2 O before use. Caution: aqua regia solutions are dangerous and highly corrosive. This should be used with extreme care. Fresh aqua regia solutions should not be stored in closed containers. The DI water in all experiments was Milli-Q water (18 MΩ cm, Millipore, Burlington, MA, USA).