Abstract
Transparent polycrystalline TiO2 thin films have been deposited on unheated glass substrates using RF reactive magnetron sputtering. Depositions were carried out at different glancing angles and with different total gas mixture pressures. The variation of these parameters affected the crystal phase composition and the surface morphology. Depending on the glancing angle and the pressure, rutile, mixed anatase/ rutile and pure anatase were deposited at low substrate temperature. Both hydrophilic and hydrophobic TiO2 were obtained, exhibiting fast photoconversion to superhydrophilic upon UV irradiation. The effect of the materials physicochemical properties on the wettability and rate of the UV induced superhydrophilicity is evaluated.
Highlights
Wetting properties of solid surfaces are of great importance both from a theoretical point of view and for industrial applications
The prevailing mechanism of the UV-induced hydrophilicity of TiO2 suggests that the photogenerated electron-holes migrate to the TiO2 surface and induce surface oxygen vacancies which act as energetically favored sites for the dissociative adsorption of water [9,10] The intrinsic wettability in dark, and the rate of the photoinduced superhydrophilic conversion (PSH) determine the extent of the applicability of the TiO2 surfaces
After long term storage in dark environment, the TiO2 films deposited at low glancing angle or pressure turned to hydrophobic, while those deposited at high glancing angle or pressure showed permanent hydrophilicity
Summary
Wetting properties of solid surfaces are of great importance both from a theoretical point of view and for industrial applications. The prevailing mechanism of the UV-induced hydrophilicity of TiO2 suggests that the photogenerated electron-holes migrate to the TiO2 surface and induce surface oxygen vacancies which act as energetically favored sites for the dissociative adsorption of water [9,10] The intrinsic wettability in dark, and the rate of the photoinduced superhydrophilic conversion (PSH) determine the extent of the applicability of the TiO2 surfaces. Rough nano/mesoporous surfaces exhibit enhanced hydrophilicity or hydrophobicity and provide large surface area required for the acceleration of the PSH. For this reason, the wetting properties of nanostructured TiO2 surfaces have been thoroughly investigated [11,12]. Iwnotrhki,s wweorpkr,ewseentprtheseenfatbtrhiceaftaiobnricoaftiToinOo2fthTinO2fitlhmins fbilymGsLbAyDGRLAF DmaRgFnemtraognnestpruotntesrpinugtteorninugnohneautendhegalatesds sgulabssstrsautebss.trTahtees.effTehcet eofffetchteogflathnecinglganacnignlge angdlteheanwdortkhiengwporreksisnugrepornestshuerTeiOo2nfitlhmesTstirOu2ctfuilrme sansdtrpuhcatuserecoamndpopsihtaiosne, cthoemspuorfsaitcieomn,otrhpehosluorgfaiccael mchoarrpahctoelroisgticas,l thcheaorpatcitcearlipstriocps,ertthiees,oapntdictahle wpreotptienrgticehsa, ranctderitshteicswheatvtienbgeecnheavracluteartiesdti.cSsuhbasevqeuebnetelny, ethvealruealatteido.n Sbuetbwseqenuethnetlyp,hathseecoremlaptoiosnitiobnetawnedernoutghhenpeshsawseithcothmepwoesittiaobnilitaynodf trhoeuTgihOn2efisslmwsiitnhdtahrek wanedttathbeiliptyhootfotihneduTciOed fsiulmpesrihnydarorkphainlidcitthyeaprehointoviensdtiugcaetedds.uperhydrophilicity are investigated
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