Nanosecond Laser-Assisted Fabrication of Photocatalytically Active TiO2 Nanocoatings: Implication in Organic Dyes Degradation

The development of systems capable of efficiently eliminating organic dyes from wastewater is crucial for the environment. In this context, TiO2-based photocatalytic systems are of particular interest. However, the development of eco-friendly and single-step methods for the fabrication of such systems remains a challenge to their practical use. Here, we demonstrate a fabrication approach for a catalytic system composed of TiO2 nanocoating created on the surface of a bulk titanium plate by exposure to a nanosecond laser. The exposure conditions affect the relief and phase composition of the nanocoating, as revealed by a combination of scanning electron microscopy (SEM), contact profilometry, Raman, High-resolution Xray photoelectron spectroscopy (HR XPS), and grazing incidence X-ray diffraction (GIXRD) methods. Using the GIXRD method, we establish that nanocoatings consist of a mixture of anatase and rutile grains with sizes of 22.7-24.4 and 29.8-32.2 nm, respectively. HR XPS analysis demonstrates that changes in the number of pulses per spot modify the anatase surface content from 40.6 to 70.4%. The samples with a higher anatase content exhibit up to 6.3 times higher catalytic activity, which is confirmed by methylene blue degradation when exposed to UV light and can be related to the synergistic effect of the anatase-rutile heterojunction. The reusability of the samples is supported by repeated degradation experiments. The photocatalytic activity of the obtained TiO2 nanocoatings is improved by Au nanoparticles deposited on their surface by magnetron sputtering. The proposed approach lays the foundation for the application of nanosecond laser-assisted technologies in the eco-friendly fabrication of catalytic systems.