Li+ ion induced three-dimensional aggregation growth of single-crystal perovskite octahedrons

Abstract

Li⁺ ions were introduced into a hydrothermal system as surfactants to tailor the growth of perovskite tetragonal PbTiO₃ (PT) nanocrystals, giving rise to single-crystal octahedrons with {111} facets exposed. Systematic investigations reveal that single-crystal PT octahedrons were formed via a three-dimensional (3D) aggregation growth process. In the initial stage, the intermediate phase primary nanoparticles, with a size of 2–5 nm, aggregated to form an octahedral shaped particle agglomeration with a size of 20–50 nm; then, the particle crystallized via an oriented attachment (OA) mechanism, resulting in the observed single-crystal PT octahedrons. During this process, the interplay of Li⁺ ions and the electrostatic force of the primary nanoparticles are essential for octahedral aggregation and subsequent crystallization. Moreover, the concentration of Li⁺ ions has been demonstrated to significantly modify the growth of PT, leading to nanostructures with various shapes from hexahedral particles to cubic conglomerates to cuboids. These nanostructures demonstrate shape-dependent visible light photocatalytic activity.