Unravelling the atomically resolved 3D shape of {111}, {010}, and {001} faceted small anatase nanoparticles

Anatase nanoparticles with exposed {111}, {010}, and {001} facets exhibit excellent photocatalytic properties. While decreasing particle size, surface area increases, hence photocatalytic property enhances. Therefore, knowing the 3D shape of small-sized nanoparticles is important for optimizing their photocatalytic property and synthesis parameters. Although scanning electron microscope is generally used for morphological analysis of nanoparticles, determining the 3D shape of the nanoparticles sized below 20 nm using scanning electron microscope leads to ambiguity. There is no experimental report yet on the 3D shape of the {111}, {010}, and {001} faceted anatase nanoparticles sized below 20 nm. To address this issue, the atomically resolved 3D shape of small nanoparticles (size <20 nm) was reconstructed using inline 3D holography. The feasibility of this method on the system mentioned previously was first investigated using simulation and later implemented on experimental data. The final tomograms revealed that the 3D shape of the examined {111} faced nanoparticle is nanocuboid, {010} and {001} are truncated tetragonal bipyramids. In this work, the applicability of the line-3D-holography method on a non-cubic tetragonal system with a complex arrangement of light and heavy atoms was validated.