*3.5. Wetting Behaviour of Thin Films*

All TiO2 thin film samples produced exhibited UV induced hydrophilicity in varying degrees, as seen by the reduction in contact angle of deionised water on the TiO2 surface after 30 min UV irradiation shown in Table 2. Some samples that were produced with surfactant exhibited superhydrophilicity whereby the contact angle dropped to below 5° after UV irradiation, such as sample D2 and E2, which both had contact angles after 30 min UV irradiation which were around 3°. As these samples were produced with the lighter weight surfactant, Tween® 20, the effects on particle growth were that slightly larger and more spherical particles were grown in comparison to samples B and C, as the surfactant was not as bulky when surrounding titania particles during growth, therefore were not as obstructing. This can be seen in the SEM images and is also reflected in the particle sizes as shown in Table 2.
