Role of TiO2 morphological characteristics in EVOH-TiO2 nanocomposite films: self-degradation and self-cleaning properties

The role of TiO2 morphological characteristics in the ultimate performance of advanced, light-triggered EVOH-TiO2 nanocomposite films is analyzed using four different inorganic anatase-TiO2 materials obtained from the same initial solid precursor. Morphological variations in the inorganic component lead to differences in the inorganic-organic interface, described here through a detailed structural investigation using wide angle X-ray diffraction (WAXS), Raman and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopies together with microscopy tools. Two significant properties of these composite films induced by light absorption were studied: a) the self-degradation of the films under sunlight and b) their self-cleaning or disinfection properties against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria upon UV excitation. The analysis of results provides evidence that, within the series of samples studied, the optimization of these two light-induced properties is related to specific morphological aspects of the oxide component. The different charge carrier species involved in the two processes allow rationalizing the self-degradation as a main function of primary particle size of the oxide component while the self-cleaning properties seem to be related to a more complex root on oxide morphological features, likely associated with particle-particle networking details.