Photoactive and antibacterial TiO2 thin films on stainless steel

This paper describes an innovative method to achieve highly photoactive and antibacterial titania thin films on stainless steel by a novel combination of flame-assisted CVD (FACVD) – to deposit silica, and thermal APCVD – to deposit titania. We compare the chemical and structural characteristics, and photocatalytic activities of thin films of titania deposited onto stainless steel using APCVD from two different precursors. We show that the silica layer acts as a barrier to prevent the deleterious effect on photoactivity of iron and chromium from the substrate, and in particular, we show that the interaction of the precursor chemistry with the steel surface influences the structure of the films. The films were analysed using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and secondary neutral mass spectrometry (SNMS). Photocatalytic activity of the coatings was determined by the destruction of stearic acid layers, monitored using FT-IR spectroscopy. Studies show selected films to be effective as antibacterial coatings against Escherichia coli, with antibacterial performance comparable to reported values of TiO2 on other substrates. The shape-forming capabilities and mechanical robustness of steel make it an ideal substrate for the exploration of new applications of photocatalysis. Applications of this technology include water purification, air cleaning, self-sterilizing and self-cleaning surfaces such as those used in hospitals or food preparation.