Three-dimensional atomic-scale characterization of titanium oxyhydroxide nanoparticles by data-driven lattice...

Metal oxyhydroxides are essential nanomaterials for recent technologies because of their diverse applications, such as catalysis, adsorbents, and precursors of metal oxides. These applications rely on the controlled crystal structures of metal oxyhydroxides formed via hydrolyzed metal monomers' condensation. However, characterizing the atomic-scale structures of the metal oxyhydroxides has still been challenging due to their diverse structural types, nanometer-scale sizes, and beam sensitivity. Here, we developed a data-driven analysis approach for atom-resolved transmission electron microscopy images of titanium oxyhydroxide (metatitanic acid) nanoparticles. Lattice spacings and angles were measured for each of the 1300 nanoparticles with random crystal orientations, providing three-dimensional structural information. Our findings reveal their anatase-like structure with alternating layers of titanium dioxide (TiO₂) and titanium hydroxide (Ti(OH)₄) planes. The revealed structure is key to understanding their role as a precursor for metastable anatase TiO₂. Our approach unveils the three-dimensional structure of metal oxyhydroxides with high statistical reliability and low electron dose, paving the way for property understanding and application design.