**2.4. Photocatalytic deposition**

In this method, the TiO2 powder is dispersed into ethanol and water, followed by stirring or sonicating for about 15 min to form titania sol. The AgNO3 solution is added to the sol. The mixture is irradiated with UV lamp for a certain period of time along with constant stirring. After a certain time, the solid was separated by filtration and dried at around 300–400°C [31, 33, 67, 69–71, 73, 79, 81]. In this method, when TiO2 photocatalyst is exposed to UV light, electrons are revealed along with the formation of OH radicals. The electrons will interact with Ag+ coming from AgNO3 resulting in the reduction reaction of the Ag+ to form Ag0 metallic particles. The small particle of Ag0 can be inserted into the crystal lattices of TiO2 [67] and/or deposited onto TiO2 surface to form a small cluster.
