Photocatalytic Thin Films Their Characterisation and Antimicrobial Properties

3 | P a g e Abstract This thesis is concerned with the synthesis and characterisation of TiO2 based photocatalyst thin films and the assessment of their antimicrobial properties. When exposed to light of wavelength less than 380 nm TiO2 films can demonstrate self-cleaning and self-disinfecting properties. This is due to photocatalytic processes occurring on the film surface resulting in film superhydrophilicity and reactive oxygen species (ROS) production. These ROS and radicals readily oxidise organic pollutants and microbes adherent to the material surface. Consequently, TiO2 thin films are of great research interest as self-cleaning, antimicrobial coatings. TiO2 and doped TiO2 materials were prepared by a simple sol-gel route from titanium n-butoxide as the principle precursor material. Film deposition was carried out using a dip-coating technique, with substrates withdrawn from the precursor sol at a fixed speed. Deposited films were calcined to produce crystalline thin films, with excellent adherence to the substrate (glass slides). Films were characterised using a number of analytical techniques including UV-visible spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and EXAFS/XANES. Photocatalysis and film hydrophilicity were investigated using established methods. Stearic acid photodegradation, monitored by FT-IR was used to assess film photocatalysis, by monitoring the peak areas of the C-H stretching region. Relative film hydrophilicities were determined by measuring the contact angle of a sessile droplet of water. Antimicrobial properties of the films were assessed with typical examples of Grampositive and Gram-negative organisms. Staphylococcus aureus (NCTC 6571) and Escherichia coli (NCTC 10418) were selected. Films demonstrated microbicidal activity against both organisms under 365nm UV illumination, and under illumination by a typical hospital lamp (28W 2-D fluorescent). Microbial adhesion to various substrates was also examined, using a dip-blot method. Films produced in this study demonstrate excellent potential as durable surface coatings with significant antimicrobial activity against microbes of clinical importance.