**2.3. Precipitation**

In the precipitation method, titanium tetra-isopropoxide and silver nitrate were used as a source of titanium and silver, respectively. Ag-doped TiO2 nanocrystalline powder was prepared by controlled addition of TTIP to absolute ethanol with constant stirring to get a clear solution. A sufficient amount of surfactant solutions (1% CTAB +1% SDS) was added to the solution with constant stirring. The aqueous solution of silver nitrate was added to the solution. A solution of aqueous ammonia was added dropwise to the last solution under stirring with the special arrangement at room temperature until the solution pH reaches 8. After complete precipitation, the solid was washed with Millipore deionized water and acetone several times to remove excess of surfactant. The precipitate was kept under microwave irradiation for 20 min. The dried powder was ground and calcined at 300°C for 3 h in a temperature-controlled muffle furnace [68]. Following calcination, the TiO2 -AgNP was obtained.
