Direct generation of titanium dioxide nanoparticles dispersion under supercritical conditions for photocatalytic active thermoplastic surfaces for microbiological inactivation

Thermoplastic poly(propylene) (PP) and acrylonitrile-butadiene-styrene (ABS) surfaces were coated with silica based films via the sol-gel process, containing titanium dioxide (TiO2) as photocatalyst. TiO2 was previously synthesized via sol-gel and treated under supercritical conditions in water dispersions. The characterization of the TiO2 dispersions was performed via disc centrifuge to determine the particle size and via Raman spectroscopy and X-Ray Diffraction (XRD) to characterize the crystallinity of TiO2. The synthesized TiO2 dispersions and commercially available TiO2 particles were incorporated in silica based films which were synthesized under acidic or basic conditions, leading to dense or porous films respectively. The morphology of the films was characterized via Scanning Electron Microscopy (SEM). The incorporation of synthesized TiO2 in the coating led to photocatalytically more active thermoplastic surfaces than films formulated with commercially available TiO2 as determined via dye discoloration test. A microbiological test performed with Sarcina lutea confirmed this result and showed an inactivation factor of 6 (99.9999%) after 24 h UV irradiation, for synthesized TiO2 incorporated in acidic formulated silica layer on ABS surfaces.