Investigation of superhydrophilic mechanism of titania nano layer thin film—Silica and indium oxide dopant effect

Abstract

In this paper, TiO 2-SiO 2-In 2 O 3 nano layer thin films were deposited on glass substrate using sol-gel dip coating method. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements were used to evaluate chemical structure, surface composition, hydroxyl group contents and superhydrophilicity of titania films. FTIR result indicated that Si-O-Si, Si-O-Ti and Ti-O-Ti bands formed in TiO 2-SiO 2-In 2 O 3 sample. According to XPS, the hydroxyl content for TiO 2 , TiO 2-SiO 2 and TiO 2-SiO 2-In 2 O 3 films was calculated as 11•6, 17•1 and 20•7%, respectively. The water contact angle measurements indicated that silica and indium oxide dopant improved the superhydrophilicity of titania nano film surface especially in a dark place. The enhanced superhydrophilicity can be related to the generation of surface acidity on the titania nano film surfaces. In the present state, superhydrophilicity is induced by the simultaneous presence of both Lewis and Bronsted sites.

Laser oxidative pyrolysis synthesis and annealing of TiO2 nanoparticles embedded in carbon–silica shells/matrix

“…The intense peak centered at 1095 cm −1 with his shoulder at 1227 cm −1 , found only for silica-containing powders was also reported at 1065 and 1200 cm −1 in [1] and attributed to Si O Si vibrations. The small peak visible in the same powders spectra centered around 940 cm −1 was considered an indication of the chemical connection between titania and silica, being reported and ascribed to Ti O Si vibrations [2,4,38]. Also, at 955 cm −1 the presence of Si OH stretching vibrations corresponding band was also reported in [1], whereas the same Si OH attributed peak was found at 921 cm −1 from SiO x films prepared by plasma CVD [40].…”

“…There are also many peaks that are common to all samples. The large peak at 3390-3420 cm −1 and the small peak at 1632 cm −1 can be also found in [4,38,39]. They were attributed to the stretching modes of O H bonds from the surface adsorbed water and to the bending vibrations of physisorbed and/or chemosorbed water, respectively.…”

“…[2][3][4][5], all the resulted raw crystalline nanoparticles (including those from the TLOP 01 reference sample without silica) are surrounded by a more or less thick disordered shell/coating. In order to explain their formation, one must take into account the composition of the reaction mixture and the particularities of the laser pyrolysis technique.…”

“…Moreover, silica-titania material was found to able to photodecompose the water (accelerated by RuS 2 doping) with H 2 and O 2 generation under UV light [3]. The same sol-gel approach was used to obtain materials with various other light-related applications: superhydrophilic [4] or antireflective self-cleaning films [5], solar [6] and transparent UV-shielding poly(methyl methacrylate) (PMMA)-based composites [7]. The gas-phase methods starting from various Ti and Si containing vaporized/sprayed precursors allow the synthesis of TiO 2 /SiO 2 films and powders in a continuous mode and much faster than in the sol-gel methods.…”

Evaluation of interfacial water on super-hydrophilic surface by THz-TDS

“…In contrast, the dielectric property after the UV -irradiation was not described by the model for the uniform water layer. Commonly, it can be recognized that the surface is converted to super-hydrophilicity by photoexcited carriers migrated to the surface, where water molecules are dissociatively adsorbed on the oxygen vacancy sites generated by the photo excited holes [4]. However, the dielectric behavior after the UV -irradiation suggests not only Is) is that the hydrogen-bonding strength between water molecules in the interfacial layer was larger than in free water.…”