Effect of Crystalline Phase and Facet Nature on the Adsorption of Phosphate Species onto TiO2 Nanoparticles

The current use of TiO2 nanoparticles raises questions about their impact on our health. Cells interact with these nanoparticles via the phospholipid membrane and, in particular, the phosphate head. This highlights the significance of understanding the interaction between phosphates and nanoparticles possessing distinct crystalline structures, specifically anatase and rutile. It is crucial to determine whether this adsorption varies based on the exposed facet(s). Consequently, various nanoparticles of anatase and rutile TiO2, characterized by well-defined morphologies, were synthesized. In the case of the anatase samples, bipyramids, needles, and cubes were obtained. For the rutile samples, all exhibited a needle-like shape, featuring {110} facets along the long direction of the needles and facets {111} on the upper and lower parts. Phosphate adsorption experiments carried out at pH 2 revealed that the maximum adsorption was relatively consistent across all samples, averaging around 1.5 phosphate<middle dot>nm-2 in all cases. Experiments using infrared spectroscopy on dried TiO2 powders showed that phosphates were chemisorbed on the surfaces and that the mode of adsorption depended on the crystalline phase and the nature of the facet: the anatase phase favors bidentate adsorption more than the rutile crystalline phase.