Low Temperature Fabrication of Photoactive Anatase TiO2 Coating and Phosphor from Water–Alcohol Dispersible Nanopowder

Abstract

Low temperature fabrication of durable photoactive anatase TiO2 coatings (on glass and plastic substrates) has been accomplished using the synthesized water and water-EtOH dispersible organic-free TiO2 nanopowder. This nanopowder has been synthesized by refluxing the mixture of Ti(OiPr)4, EtOH, and H2O in the presence of excess NO3– ion as a stabilizer at 80 °C for 24 h. The nanopowder has a small crystallite size (∼5 nm) and a high specific surface area of about 268 m2 g–1. It is highly dispersible in water (up to 20 wt %), and the water–EtOH mixture (10 wt %) and the resulting dispersions are very stable. The water–EtOH (1:3 w/w) dispersion of the TiO2 nanopowder (4–5 wt %) has been used to prepare transparent coatings on glass and flexible plastic (polypropylene and polycarbonate) substrates with a surface hardness of ∼2–3 and 1–2 H, respectively, and good adhesion (5B; high quality). The reasons behind good adhesion and hardness of these coatings have been discussed. Such coatings on plastic and glass substrates have been used as reusable photocatalysts for degradation of toxic dye (methylene blue) to show the self-cleaning property under UV (365 nm) and visible light (Xenon source; 1 sun) sources. Further, by using this TiO2 powder, a fluorescent ZnS:Mn/TiO2 phosphor can be easily prepared at a much lower temperature.