Photocatalytic degradation of methylene blue using undoped and Ag-doped TiO2 thin films deposited by a sol–gel process: Effect of the ageing time of the starting solution and the film thickness

Undoped and Ag-doped TiO2 thin films were deposited on glass substrates by the sol–gel method. A novel propose to prepare the solution is the use of titanium monohydrate oxyacetyl acetonate as the starting reagent. The effect of the ageing time of the starting solution as well as the number of coatings on the photocatalytic degradation of methylene blue (MB) was studied. The variation of the absorption spectra shows the degradation of MB dissolved in water, as a result of the reaction produced on the surface of the films, and promoted by ultraviolet irradiation during 5 h. The results show an optimum photocatalytic activity, in the order of 35%, presented in the 5-immersion Ag-doped TiO2 thin films, deposited from 7- and 14-day aged solutions. On the other hand, the Ag-doped TiO2 films deposited at different coatings show small changes in the photocatalytic activity. Morphological studies show the presence of silver particles on the film surface, due to the different number of coatings, affecting the photocatalytic performance.