Abstract
This work investigated the suppression of photocatalytic activity of titanium dioxide (TiO2) pigment powders by extremely thin aluminum oxide (Al2O3) films deposited via an atomic-layer-deposition-type process using trimethylaluminum (TMA) and H2O as precursors. The deposition was performed on multiple grams of TiO2 powder at room temperature and atmospheric pressure in a fluidized bed reactor, resulting in the growth of uniform and conformal Al2O3 films with thickness control at sub-nanometer level. The as-deposited Al2O3 films exhibited excellent photocatalytic suppression ability. Accordingly, an Al2O3 layer with a thickness of 1 nm could efficiently suppress the photocatalytic activities of rutile, anatase, and P25 TiO2 nanoparticles without affecting their bulk optical properties. In addition, the influence of high-temperature annealing on the properties of the Al2O3 layers was investigated, revealing the possibility of achieving porous Al2O3 layers. Our approach demonstrated a fast, efficient, and simple route to coating Al2O3 films on TiO2 pigment powders at the multigram scale, and showed great potential for large-scale production development.
Highlights
The brilliant white color and high photostability of nanoparticulate titanium dioxide (TiO2 ) make it an excellent white pigment in the paint, plastic, and paper industries [1]
The deposition was carried out in a home-built fluidized bed reactor operating at atmospheric pressure and room temperature, as described elsewhere [34]
We have demonstrated the deposition and investigated the photocatalytic suppression ability of ultrathin Al2 O3 films on different types of TiO2 powders: anatase, rutile and P25
Summary
The brilliant white color and high photostability of nanoparticulate titanium dioxide (TiO2 ) make it an excellent white pigment in the paint, plastic, and paper industries [1]. This work reports on the suppression of photocatalytic activity of various types of TiO2 powders (i.e., anatase, rutile, and P25 TiO2 ) by Al2 O3 films deposited via an ALD-like process using TMA and H2 O as precursors, which was carried out at room temperature and atmospheric pressure in a home-built fluidized bed reactor. This gas-phase deposition process enabled the control of coating thickness at the sub-nanometer level, allowing us to investigate the dependence of photocatalytic suppression ability of Al2 O3 on the film thickness. The influence of high-temperature annealing on the properties of the Al2 O3 layers was investigated, revealing the possibility to achieve porous Al2 O3 layers, which could be useful for other applications
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