TiO2 based photocatalytic coatings: From nanostructure to functional properties

The present study shows the results of direct ceramization of textile substrates with commercial derived TiO2 nanosols. A deep investigation on relationship between TiO2 based nanosols and nanocoatings properties and their performances in term of hydrophilicity and photocatalytic efficiency was performed. Five nanosols, differing for starting pH and relative agglomerates size were analyzed. The hydrophilic behavior and the catalytic performance of TiO2 coatings supported on different substrates (fabric, glass and ceramic) were assessed and related to physicochemical characterization results. The described correlations between TiO2 nanoscale properties (nanostructure or surface chemistry), macroscale properties (hydrophilicity), as well as functional properties (photocatalytic activity), represents a first attempt to provide sound criteria for the control of material performance by design experiments. The pH dependent aggregation state, is correlated to an increase of surface acidity as the shift of i.e.p. towards acid pH reveals. Such increase of acidity justifies an increase of hydrophilicity, consequent to stronger interaction with water molecules, that occurs when a higher amount of Ti−O− sites are available. As well, the photocatalytic performances and the hydrophilic behavior, resulted in a good agreement: the higher the hydrophilicity, the better the self-cleaning activity, so providing useful indications for the scale-up exploitation of such application.