Visible light-induced super-hydrophilic anatase porous thin film with easy-to-clean and antifogging properties

Atmospheric dust on the surface of modern building glass requires frequent cleaning to keep high diaphaneity and esthetics. Visible light-induced super-hydrophilic anatase porous thin films with easy-to-clean and antifogging properties were controllably synthesized through the neutralization of ammonia and nitric acid-driven phase separation by sol–gel spin coating method. Surface microstructure, root-mean-squared roughness, crystalline structure, surface chemical composition, transmittance, hydrophilic, antifogging, and easy-to-clean properties of the films were characterized by super depth of field microscopy, atomic-force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet–visible–near-infrared spectrophotometer and automatic contact angle measuring device, respectively. With NH₃·H₂O concentration increasing from 0.7 to 1.1 vol.%, the average pore size of anatase porous thin films increases from 1.05 to 2.36 μm and the water contact angles decrease from 5.2° to 1.7° under 100-lux visible light irradiation (400–800 nm). Besides, the larger NH₃·H₂O concentration, the larger root-mean-squared roughness roughness, ranging from 5.67 to 88.00 nm. Moreover, X-ray photoelectron spectroscopy results demonstrate that there are Ti–O bonds and Si–O bonds on the samples surface, indicating that porous area bottom is Si–O bonds by soda-lime glass. These films exhibit excellent visible light-induced super-hydrophilic, antifogging and easy-to-clean properties, which make them suitable to be used in modern buildings and automotive glass.