Processing, characterization and photocatalytic properties of Cu doped TiO₂ thin films on glass substrate by sol-gel technique

The present paper describes processing, properties and photocatalytic application of Cu doped TiO₂ thin films on glass substrate. Cu doped TiO₂ coatings were successfully prepared on glass slide substrates using sol-gel method. The obtained solutions exhibit acidic characteristics. The phase structure, thermal, microstructure and surface properties of the coatings were characterized by using XRD, DTA/TG, SEM and AFM. Their adhesion properties and spectroscopic analysis were investigated by a scratch tester and UV-vis spectroscopy. Four different solutions were prepared by changing Cu/Ti ratios. Glass substrates were coated by solutions of Ti-alkoxide, Cu-chloride, glacial acetic acid and isopropanol. The obtained gel films were dried at 300 °C for 10 min and subsequently heat-treated at 500 °C for 5 min in air. The oxide thin films were annealed at 600 °C for 60 min in air. TiO₂, CuO, Cu₄Ti, Ti₃O₅ and Cu₃TiO₄ phases were found in the coating. The organic matters were burned at temperatures between 200 and 350 °C and TiO₂ crystallization was formed at 450 °C. The weight loss of the powder during process up to 600 °C is approximately 70%. The microstructural observations demonstrated that CuO content was led an improved surface morphology while thickness of the film and surface defects were increased in accordance with number of dipping. According to AFM results, it was found that as the Cu/Ti content increases the surface roughness of the films increases. In addition structural, thermal and microstructural results, it was found that the films of 0.73 ratio have better adhesion strength to the glass substrate among other coatings. The oxide films were found to be active for photocatalytic decomposition of metylene blue.