*2.1. Preparation of Nanocrystalline TiO2 and Ag-TiO2*

Ethanol 99.9%, Titanium(IV) butoxide, silver nitrate and acetic acid were of analytical grade and procured from Sigma Aldrich (Bangalore, India). About 1.5 wt% of Ag+ ion doped nanocrystalline anatase TiO2 was prepared by homogeneous hydrolysis of titanium butoxide-ethanolic solution using acetic acid-water as acid catalyst. The stoichiometric amount of AgNO3 was dissolved in aqueous acetic acid and then added drop wise into the titania sol with stirring for 30 min at room temperature, and allowed to stand for two days at room temperature. Undoped TiO2 gel was prepared by the same procedure without the addition of AgNO3. All the gels were isochronally annealed initially at 100 °C for 2 h then at 500 °C for 4 h.
