A TiO2 nanotubes film with excellent antireflective and near-perfect self-cleaning performances

Abstract

SiO2/TiO2 composite films have been frequently used to realize the functions of self-cleaning and antireflection. Increasing the TiO2 volume ratio in SiO2/TiO2 composite film is beneficial to enhance the self-cleaning effect, while high TiO2 content leads to a strong Rayleigh scattering and depresses the antireflective performance, resulting in a bottleneck problem for the dual-functional application. Here, we have achieved a high-quality TiO2 nanotubes film with excellent antireflective and near-perfect self-cleaning performances. Ultrasound assisted pickling method has been developed to effectively prepare the well-dispersed protonated titanate nanotubes colloid. After spin-coating and annealing treatment, glass substrate coated with double-side TiO2 nanotubes film has a peak transmittance of 99.2 % and average transmittance of 97.4 % at 400−800 nm. Ultra-high porosity of TiO2 nanotubes film (80 %) and ultra-fine size of TiO2 nanotubes (8.6 nm in outer diameter) lead to excellent antireflective performance. With high UV absorptivity (80 % at 254 nm) and formal quantum efficiency of stearic acid (10.9 × 10−3), TiO2 nanotubes film shows near-perfect self-cleaning performance. A persistent anti-fogging ability is also presented. This study demonstrates the feasibility to fabricate pure TiO2 antireflective coating for glass substrate, extends application field of the classic TiO2 nanotubes, and sheds lights on the practical applications of high-powered TiO2 nanotube-based multi-functional films.