Determination of Crystallographic Orientation and Exposed Facets of Titanium Oxide Nanocrystals.

Qu, Jiangshan; Wang, Yueshuai; Mu, Xulin; Hu, Jingcong; Zeng, Bin; Lu, Yue; Sui, Manling; Li, Rengui et al. · Adv Mater · 2022

basic_science · Level V

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Abstract

Titanium dioxide (TiO<sub>2</sub> ) nanocrystals have attracted great attention in heterogeneous photocatalysis and photoelectricity fields for decades. However, contradicting conclusions on the crystallographic orientation and exposed facets of TiO<sub>2</sub> nanocrystals frequently appear in the literature. Herein, using anatase TiO<sub>2</sub> nanocrystals with highly exposed {001} facets as a model, the misleading conclusions that exist on anatase nanocrystals are clarified. Although TiO<sub>2</sub> -001 nanocrystals are recognized to be dominated by {001} facets, in fact, anatase nanocrystals with both dominant {001} and {111} facets always co-exist due to the similarities in the lattice fringes and intersection angles between the two types of facets (0.38 nm and 90° in the [001] direction, 0.35 nm and 82° in the [111] direction). A paradigm for determining the crystallographic orientation and exposed facets based on transmission electron microscopy (TEM) analysis, which provides a universal methodology to nanomaterials for determining the orientation and exposed facets, is also given.