Photocatalytic TiO2 Thin Films on Fluorinated Ethylene Propylene Copolymer (FEP) Substrates

There currently are several issues affecting the prolonged usage of polymeric contact lenses and these include pathogenic infection, scumming by formation of biofilms, and consequent alteration of the reflection and dispersion of light received by the retina. A novel idea to address the aforementioned problems is the application of incoherent TiO2 films to hard and gas-permeable contact lenses. A common material used for contact lenses is fluorinated ethylene propylene copolymer (FEP). Using a novel hybrid sol-gel technique, nanocrystalline TiO2 sols were deposited on glass and FEP substrates, followed by annealing at temperatures in the range of 100 degrees-200 degrees C for 8 h. The microstructures of the films were examined by optical microscopy (OM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). The chemical compositions were assessed by X-ray photoelectron spectrometry (XPS) and transmission electron microscopy (TEM) equipped with EDS. The mineralogies of the films were examined using laser Raman microspectroscopy (Raman). The film thicknesses were determined by transmission electron microscopy (TEM) using samples prepared by dual-beam focussed ion bean milling (FIB). The optical transmissions of the films were estimated by UV-Vis spectrophotometry (UV-Vis). The photocatalytic activities were compared by methylene blue degradation under UV irradiation (MB). The antimicrobial activity was evaluated by preliminary testing using gram-positive bacteria. The results demonstrate that this method can be used to deposit relatively flat photocatalytic anatase of transmission >60% on glass and FEP substrates at temperatures <= 200 degrees C. Even at these low temperatures, contamination from the substrates occurred. Although the photocatalytic performances were affected by crystallinity and contamination, the photocatalytic activities correlated with the locations of the absorption edges. The antimicrobial testing was inconclusive owing to factors including low distribution densities of TiO2, presence of residual organic phases, differential adhesion, and/or the effects of immersion in saline solution.