Crystal Structures, Anisotropic Growth, and Optical Properties: Controlled Synthesis of Lanthanide Orthophosphate One-Dimensional Nanomaterials

The fundamental understanding of the relationship between crystal structure and the dynamic processes of anisotropic growth on the nanoscale, and exploration of the key factors governing the evolution of physical properties in functional nanomaterials, have become two of the most urgent and challenging issues in the fabrication and exploitation of functional nanomaterials with designed properties and the development of nanoscale devices. Herein, we show how structural and kinetic factors govern the tendency for anisotropic growth of such materials under hydrothermal conditions, and how the crystal structure and morphology influence the optical properties of Ln3+‐doped nanocrystals. The synthesis of phase‐pure and single‐crystalline monoclinic, hexagonal, and tetragonal one‐dimensional LnPO4 nanostructures of different aspect ratios by means of kinetically controlled hydrothermal growth processes is demonstrated. It is shown that the tendency for anisotropic growth under hydrothermal conditions can be enhanced simply by modifying the chemical potentials of species in the reaction solution through the use of carefully selected chelating ligands. A systematic study of the photoluminescence of various Eu3+‐doped lanthanide phosphates has revealed that the optical properties of these nanophosphors are strongly dependent on their crystal structures and morphologies. By modifying the chemical potentials of the species in the reaction solution, the tendency for anisotropic growth of nanocrystals can be magnified, even for seemingly isotropic crystal structures (see picture). The key factors governing the evolution of the optical properties of Eu3+‐doped lanthanide phosphates have also been systematically investigated and the findings are discussed.