From the fluorescent lamp-induced bactericidal performance of sputtered Ag/TiO2 films to re-explore the photocatalytic mechanism

摘要

Ag/TiO2 composite films with the different Ag contents of 1, 3, and 5 vol.% were deposited at 25, 200, and 400 degrees C on glass substrates by radio frequency sputtering with a single cermet target formed by hot pressing the Ag nanoparticle-decorated TiO2 nanopowder at 900 degrees C in argon atmosphere for 30 min, followed by annealing in air and the reduction under vacuum heating or by NaBH4. All the TiO2 films were analyzed by X-ray diffraction technique to have an amorphous structure. High deposition and annealing temperatures all led to Ag aggregation in AgiTiO(2). Photodegradation of acid black 1 dye was used as the screen test to evaluate the photocatalytic ability of Ag/TiO2 films, before the antibacterial test was preceded. The antibacterial ability on Escherichia coli was also evaluated. The 25 degrees C-deposited 3% Ag/TiO2 films of 80 nm in thickness had the best performance in optical transmittance above 70% and killing the E. coli. The mechanism for the fluorescent lamp-induced bactericide of the 3% Ag/TiO2 film is proposed. The amorphous 3% Ag/TiO2 film had larger band gap of 3.67 eV than the annealed ones and is expected not to be excited by the fluorescent lamp, but to prolong the lifetime of the thermally induced, not photo induced, charge carriers in the Ag/TiO2 by its electric field of the illumination light and the attraction by Ag nanoparticles <8 nm in size. The Ag+ release mechanism for bactericide is not the major one here after comparing with the tests in the dark. (C) 2015 Elsevier B.V. All rights reserved.