Transparent superhydrophilic metal oxide coating with mechanical and chemical robustness for photocatalytic self-cleaning applications

Abstract

A photoactive TiO2-KH550 (3-aminopropyltriethoxysilane) - PEG (Polyethelyneglycol) coating film with excellent superhydrophilicity is deposited on a glass substrate by means of the dip coating method for self-cleaning applications. The effects of the number of coating layers, molecular weight of PEG (200–8000), surface roughness, and film thickness on the hydrophilicity of the film coated on the glass substrate are analyzed. In addition, the mechanical durability, and thermal and chemical stability of the coated film are studied. The tribological properties (friction coefficient and wear track) of the film coated on the glass substrate are investigated. The photo-catalyzed self-cleaning properties of the film are also evaluated. In addition, the effect of withdrawal speed on the optical properties (transmittance) of the film are investigated by obtaining and analyzing its UV spectra. The results indicated that the hydrophilicity of the TiO2 coating film decreased as its surface roughness and thickness increased. The TiO2-KH550-PEG coating fabricated using PEG with a low molecular weight of 400 exhibited a smooth and uniform morphology. The composite TiO2 coating film prepared herein exhibited excellent mechanical durability in a sandpaper abrasion test and retained its superhydrophilicity under harsh chemical conditions (strong acidic and basic media). The coated glass substrate presented superior wear resistance compared to that of the uncoated glass substrate. Moreover, the transparent TiO2 composite film coating exhibited excellent photocatalytic self-cleaning properties. Therefore, it is expected that the TiO2 composite film coated on glass has good potential for use in applications such as window glasses, architectural buildings, and photovoltaic modules.