Resonant laser processing of nanoparticulate Au/TiO2 films on glass supports: Photothermal modification of a photocatalytic nanomaterial

Resonant laser processing at lambda = 532 nm is used to modify thin Au/TiO2 nanoparticle films on soda lime glass plates. A microfocused continuous-wave laser is employed for local patterning at distinct laser powers. In conjunction with microscopic techniques this approach allows for reproducible high-throughput screening of laser-induced material modifications. Optical microscopy and microspectroscopy reveal laser darkening, i.e. a significantly increased optical absorbance. Scanning electron microscopy and X-ray photoelectron spectroscopy show laser-induced film growth and roughening along with the integration of SiO2 from the glass supports. Raman spectroscopy displays a phase transition from anatase to rutile. Au evaporation and/or integration only takes place at high laser powers. All these modifications provide promising perspectives in view of photocatalytic applications. Data from complementary laser experiments with unblended pure TiO2 coatings at lambda = 532 nm and lambda = 355 nm point to a photothermal process, in which the optical energy is selectively deposited in the Au nano particles and transformed into heat. As a result, thermally activated modifications take place. General prospects of laser processing in targeted modification of nanomaterials for photocatalysis are emphasized. (C) 2016 Elsevier B.V. All rights reserved.