title: Physico-chemical processes and kinetics of sunlight-induced hydrophobic ↔ superhydrophilic switching of transparent N-doped TiO₂ thin films.
abstract: Sunlight-responsive anatase N-doped TiO2 thin films undergoing reversible and switchable hydrophobic to superhydrophilic transition were synthesized by ultrasonic spray pyrolysis in a single step. Film thickness, roughness, surface morphology, crystal structure, composition, band gap, and wetting properties were studied using surface profilometry, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and water contact angle measurements, respectively. Surface X-ray photoelectron spectroscopy before and after sunlight irradiation revealed the major physicochemical process responsible for the hydrophobic → hydrophilic transition as surface hydroxylation and that responsible for hydrophilic → superhydrophilic transition as destruction of surface adsorbed organic species. The kinetic rates of the hydrophobic → superhydrophilic transition under sunlight and superhydrophilic → hydrophobic transition when kept under dark are found to be 0.215 min(-1) and 2.03 × 10(-4) min(-1), respectively.
authors.affiliation: Surface and Nanoscience Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu, India.
authors.forename: Madhusmita
authors.initials: M
authors.lastname: Sahoo
authors.forename: Tom
authors.initials: T
authors.lastname: Mathews
authors.forename: Rajini P
authors.initials: RP
authors.lastname: Antony
authors.forename: D Nandagopala
authors.initials: DN
authors.lastname: Krishna
authors.forename: S
authors.initials: S
authors.lastname: Dash
authors.forename: A K
authors.initials: AK
authors.lastname: Tyagi