Low temperature deposition of photocatalytic TiO2 coatings by ink-jet printing

TiO2 coatings can be used to create transparent, photocatalytically active, self-cleaning surfaces and therefore have a very high industrial relevance. Functionality in this kind of TiO2 layers is only obtained after crystallization of the material at temperatures above 400 °C. This means that chemical deposition approaches do not allow deposition on heat-sensitive substrates such as polymers. Therefore, it is important to investigate innovative deposition processes that can significantly reduce the minimal temperature required for crystallization and full processing. In this work, we studied the synthesis of crystalline titania nanoparticles by microwave-assisted solvothermal methods. The use of microwaves allows to optimize the production and energy efficiency of the synthetic process. Once stable suspensions of anatase nanoparticles are obtained, these are optimized for use in ink-jet printing devices. The fact that the crystalline building blocks for the layer are now already present in the precursor inks, allows efficient deposition of transparent titania coatings at reduced temperatures. Weathering/durability tests and extensive characterization of the photocatalytic activity and hydrophilic behaviour of these layers was performed to analyze the performance and processing limits for this kind of titania coatings