Bactericidal Performance of Flame-Sprayed Nanostructured Titania-Copper Composite Coatings

A large concern surrounding stainless steel surfaces is the ability of bacteria to grow and attach to them quite easily. One possible solution to destroy these pathogens is to coat surfaces with a biocidal agent. The photocatalytic effect of titanium dioxide (TiO₂) is known to have a bactericidal effect. Coatings of TiO₂ were prepared on 1010 low carbon steel substrates using an oxy-acetylene flame spray torch. TiO₂ coatings containing 5 wt.% copper (Cu) were fabricated to increase the bactericidal effect of the coating. After deposition, the coatings were polished to an average roughness of 1 μm. Solutions of Pseudomonas aeruginosa (PAK) bacteria were placed onto the coating surface for periods of up to 3 h, and the amount of surviving bacteria were counted. Some samples were irradiated with white light and other samples were held in a dark chamber. In coatings of copper-free flame-sprayed TiO₂, the high flame temperatures facilitated the conversion of the anatase phase to the rutile phase, which limited the photocatalytic destruction of the bacterial cells. However, TiO₂-copper composite coatings showed a large bactericidal effect, killing approximately 75% of PAK bacterial cells after 3 h. Under the same conditions, the TiO₂-copper composite coatings had the same bactericidal capabilities as pure copper surfaces, with the composite coatings showing improved bactericidal performance when exposed to light. It was proposed that increased concentrations of reactive oxide species produced due to TiO₂ photocatalysis improved the performance of the irradiated TiO₂-copper composite coatings.