The keys to avoid undesired structural defects in nanotubular TiO2 films prepared by electrochemical anodization

The effect of the viscosity of solvent mixtures based in ethylene glycol on the formation of undesired structural defects (nanograss) during the electrochemical synthesis of nanotubular TiO2 structures is analyzed. High quality nanotubular TiO2 films can be achieved by diminishing the viscosity of ethylene glycol-based media by increasing the water content as well as using ethanol as additive. High surface tension of water also promotes the film fracture and accumulation of agglomerates on the film surface. A previously unexplored one-step strategy consisting in the addition of ethanol to ethylene glycol/water mixtures as an alternative anodization medium is proposed. The evidence obtained indicate that this medium allows obtaining nanotubular TiO2 films with superior structural stability against capillary forces during the film drying, avoiding the use of time consuming post-treatments such as the commonly employed supercritical CO2 dehydrating, improving the properties of the obtained nanomaterials.