RF-plasma pretreatment of surfaces leading to TiO2 coatings with improved optical absorption and OH-radical production
Evidence is presented for the RF pretreatment of polyester enhances the TiO2 coating generation of oxidative species/radicals under a low level actinic light irradiation. After 30 min RF-plasma pretreatment of the polyester samples, the fastest bacterial inactivation was observed concomitant with a) the largest ratio of surface oxidized to the reduced functionalities as determined by XPS, b) a strong sample optical absorption as seen by DRS and c) the highest concentration surface OHradicals monitoring the fluorescence of the hydroxy-terephthalic acid. Evidence for the photocatalyst self-cleaning was found by XPS due to the lack of accumulation of bacterial residues on the polyester-TiO2. A further proof of self-cleaning was the ability by the polyester-TiO2 samples to inactivate again bacterial charge at the end of an inactivation cycle. By XPS evidence is presented for the Ti4+/Ti3+ related redox catalysis and the details of the the C and O-functionalities. Surface techniques such as: XRF; DRS; TEM; contact angle (CA); XRD and XPS, were applied to relate the microstructure of the TiO2 coatings with the destruction of E. coli taken as a probe.