Sol-gel-synthesized titania-vanadia nanocrystal films for triple-functional window coatings

In this study we employed mixtures of titanium and vanadium sols, with various ratios of titanium to vanadium, in a polyvinylpyrrolidone solution to generate precursor titania-vanadia composites. Titania-vanadia nanocrystals (TVNCs) were then obtained after calcination at 700 degrees C for 3 h. Acanthosphere-, actinia-, and gear wheel-like structures appeared on the surfaces of the TVNCs when the ratio of titanium to vanadium sols was 2, 1, and 0.5, respectively. The acanthosphere-like structures decreased the surface contact area sufficiently to result in superhydrophobicity. Falling water droplets rebounded completely from the film, thereby potentially preventing fouling of such materials. The super hydrophobicity of the film remained stable after 180 min of UV irradiation, suggesting excellent self-cleaning ability. The acanthosphere-like structures enhanced the visible transmittance and near-infrared switching efficiency, similar to the behavior of an antireflection coating. In addition, the ability to photocatalytically degrade organic component under irradiation with UV and visible light was enhanced because of the TVNCs. Such triple-functional (self-cleaning, photocatalytic, thermochromic) nanomaterials might have applications in energy-saving smart windows. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.