A method to obtain photocatalytically active thin films of anatase nanocrystals on polymer substrates was explored. Anatase nanocrystals were synthesized by a fast hydrolysis synthesis in an apolar solvent and characterized with regard to their crystallinity, size, and dispersibility and the stability of the resulting suspensions. The stable titania nanocrystal suspensions were further processed for their use in polar solvents using ligand exchange. Oleic acid was exchanged for 3-aminopropyltriethoxysilane (APTES), resulting in aqueous suspensions of charge-stabilized nanocrystals. These were adapted for use as coating suspensions for surface-treated PMMA substrates in order to obtain thin films containing anatase nanocrystals covalently coupled to the surface of the PMMA substrates. Thereby, the ligand exchange was beneficial for increasing the compatibility and durability of the inorganic/organic composite, by the formation of a covalent amide bond between the silane ligands on the nanocrystals and the carboxylic acid groups on the polymer substrate. The surface morphology, transparency, and photocatalytic activity toward the degradation of organic pollutants of the coatings, obtained through dip-coating, were evaluated.
Keywords: TiO2; ligand exchange; nanoparticles; photocatalysis; polymer substrates; surface functionalization.