*2.1. Materials*

Four-hundred copper mesh substrates were used as obtained. Deionized water was self-prepared. Other reagents including AgNO3, HCl, Oil Red O (Sudan) etc. from Sinopharm Chemical Reagents Group were of analytical grade and were used without any further purification. Diesel and gasoline were purchased from Sinopec, and sunflower oil was purchased from the supermarket.
