Novel low-temperature photocatalytic titania films produced by plasma-assisted reactive dc magnetron sputtering

Robust, active, anatase titania films, 250 nm thick, are deposited onto glass at low temperatures, i.e., <100 °C, using plasma-assisted, reactive dc magnetron sputtering (PAR-DC-MS). The films are transparent and colourless and truly photocatalytic, exhibiting turnover numbers >2.0 for the photocatalytic mineralization of stearic acid. These films are typically 6.9 times more active than a sample of commercial self-cleaning glass, comprising a 15 nm layer of titania deposited by CVD, mainly because they are much thicker and, therefore, absorb more of the incident UV light. The most active of the films tested comprised particles of P25, but lacked any significant physical robustness. Similar results, but much more quickly obtained, were generated using a photocatalyst-sensitive ink, based on the redox dye, resazurin, Rz. All titania films tested, including those produced by magnetron sputtering exhibited photo-induced superhydrophilicity. The possible future application of PAR-DC-MS for producing very active photocatalytic films on substrates not renowned for their high temperature stabilities, such as plastics, is noted.