Photocatalytic activity, hydrophilic and optical properties of nanocrystalline titania thin films prepared by sol-gel di
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Photocatalytic activity, hydrophilic and optical properties of nanocrystalline titania thin films prepared by sol-gel dip coating M.C. Ferrara1, L. Pilloni2, A. Mevoli1, S. Mazzarelli1, L. Tapfer1 ENEA, Brindisi Materials Technology Technical Unit (UTTMATB), Brindisi Research Centre, Strada Statale 7 Appia, 72100 Brindisi, Italy 2 ENEA, Materials Technology Technical Unit ( UTTMAT-CHI), Casaccia Research Centre, Via Anguillarese 301, 00060 S. M. di Galeria, Rome, Italy
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ABSTRACT Nanocrystalline anatase titania thin films were prepared by using two different precursor solutions, a highly acid solution (Sol-1) and a polymer-like solution (Sol-2), via the dip-coating technique on different substrates (-Si wafer, fused silica and soda lime glass). The influence of the two sol-gel titania precursor solutions and of the substrate type on the film morphology, coating porosity, surface roughness, crystalline phases and grain size of the titania films were investigated. Our experimental results clearly indicate that the sol - composition and substrate type remarkably influence the microstructural/morphological properties of the titanium dioxide. They consequently modify the optical response and hydrophilic performances of the samples. The photocatalytic oxidations of the methylene blue in water of the samples grown on the glass substrate were monitored to investigate the influence of the sol-gel precursor solution on the photocatalytic activity of the titania coatings, and the results were put in relation with the hydrophilic and optical properties of the films. The outcome demonstrates that the optical properties and the hydrophilic and photocatalytic performances of nanocrystalline titania can be opportunely tailored tuning the size dimension of the crystalline domain according to the specific coating applications. INTRODUCTION Nanocrystalline TiO2 anatase coatings are attracting much interest for their various industrial application such as photocatalytic degradation of air and water pollutants [1, 2] and for self-cleaning or antifogging materials [3, 4]. We have recently reported on the synthesis of nanocrystalline titania thin films by using two different sol-gel routes, i.e. different acid catalyzed sol-gel titania precursor solutions, via the dip-coating technique on (100)-Si wafer, fused silica and soda lime glass substrates [5]. In particular, the influence of two sol-gel titania precursor solutions, a TiO2 nanoparticles bath, Sol-1, and a polymer titania sol, Sol-2, on the morphological, microstructural, optical and hydrophilic properties of TiO2 films were investigated in detail. The results demonstrated that the sol composition and the substrate type have an influence on the structural, morphological and hydrophilic properties of the coating properties. We found that the coatings grown by using the polymeric sol are made of grains constituted of crystalline aggregated forms whereas the ones generated from the nanoparticulate bath were single crystals. The experimental results have also shown that the films pre
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