Photoactivity of nano-structured calcium silicate–titanium dioxide composite materials

Abstract

Titanium dioxide TiO2 in the anatase form and nanosize crystals is well known for its photoactivity. The electron–hole pairs produced in the TiO2 as a result of irradiation by UV light (sunlight) have a sufficiently high redox potential to produce hydroxyl radicals in the presence of H2O that can oxidise organic compounds to CO2. Thus TiO2 sees applications in water and air purification and in self-cleaning systems. For practical purposes in many applications, it is necessary to bind the TiO2 nanocrystals onto a substrate while at the same time ensuring maximum exposure of the TiO2 surface to the UV light (sunlight) and the medium containing the organic material to be oxidised. Here we report the development and characterisation of a novel nano-structured calcium silicate–TiO2 composite material comprising a proprietary nano-structured calcium silicate host material which has an open framework structure and a large surface area to which anatase TiO2 has been attached during synthesis. The composite material has been characterised and tested in the photocatalytic degradation of phenolphthalein. The highest photocatalytic activity was observed when the calcium silicate–TiO2 composite material contained discrete TiO2 particles of about 30–100 nm in size on the surface of the silicate host.