Suppressing the Photocatalytic Activity of TiO(2) Nanoparticles by Extremely Thin Al(2)O(3) Films Grown by Gas-Phase Deposition at Ambient Conditions

This work investigated the suppression of photocatalytic activity of titanium dioxide (TiO(2)) pigment powders by extremely thin aluminum oxide (Al(2)O(3)) films deposited via an atomic-layer-deposition-type process using trimethylaluminum (TMA) and H(2)O as precursors. The deposition was performed on multiple grams of TiO(2) powder at room temperature and atmospheric pressure in a fluidized bed reactor, resulting in the growth of uniform and conformal Al(2)O(3) films with thickness control at sub-nanometer level. The as-deposited Al(2)O(3) films exhibited excellent photocatalytic suppression ability. Accordingly, an Al(2)O(3) layer with a thickness of 1 nm could efficiently suppress the photocatalytic activities of rutile, anatase, and P25 TiO(2) nanoparticles without affecting their bulk optical properties. In addition, the influence of high-temperature annealing on the properties of the Al(2)O(3) layers was investigated, revealing the possibility of achieving porous Al(2)O(3) layers. Our approach demonstrated a fast, efficient, and simple route to coating Al(2)O(3) films on TiO(2) pigment powders at the multigram scale, and showed great potential for large-scale production development.