Production and testing of novel photocatalytic TiO2 surface-exposed nanoparticle (TiO2-SEN) thin plastic films

Thin, flexible, surface-active, polystyrene-based, optically transparent films, embedded with a coating of commercially sourced titanium dioxide nanoparticles (Evonik P25), are made by coupling protonated TiO2 particles with an anionic phase transfer agent (tetraphenylborate), to create an ion-paired species that is drawn to a water/dichloromethane (DCM) interface to form a monolayer. The latter is subsequently embedded in a thin polystyrene (PS) film, typically 2.5 μm thick, by allowing the DCM to evaporate. The resulting clear TiO2 Surface-Exposed Nanoparticle (TiO2-SEN) thin plastic films are characterised using scanning electron microscopy (SEM) and found to have 25.3 ± 5.4 nm TiO2 nanoparticles exposed to the air on one side and PS on the other. The photocatalytic activity of these films is demonstrated using a number of different tests including: the photo-oxidation of 4-chlorophenol (4-CP) and methylene blue (MB) and the photoreduction of resazurin (Rz) and MB. In most of these tests the photoactivity of the film is more than double compared to that of a commercial photocatalytic film, Activ™.