Effects of proton irradiation on structures and photo-catalytic property of nano-TiO2/CNTs films

Thin nano-TiO2 films were prepared using aqueous SILAR (successive ionic layer adsorption and reaction) technique on the carbon nanotubes (CNTs) films using titanium trichloride and water as precursors. TiO2-deposited carbon nanotubes (TiO2/CNTs) films were irradiated with 120 keV proton beam, and then analyzed using Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and photocatalytic degradation tests. The results indicate that irradiation could transfer the amorphous deposited TiO2 films to a crystalline state, while the CNTs substrate would also be damaged, namely CNT tube diameter shrinkage and the Raman peak ratio of ID/IG decreases with increasing proton fluences. It was also found that the TiO2 modification could result in more damage to the CNTs substrate as the proton fluence is lower. This is largely due to the fact that the process of activation before deposition could cause damage to the CNTs to some degree. It is interested to be noted that proton irradiation would induce the nano-TiO2/CNTs films to show the remarkable photocatalytic degradation behaviors using methylene blue as the test additive. Moreover, the case with thinner TiO2 on CNTs appears relatively better photocatalytic degradation behaviors. The reasons for the change of photocatalytic behaviors may be due to both crystallization of TiO2 layers and carrier trapping effect of CNTs.