A General Approach to Spindle-Assembled Lanthanide Borate Nanocrystals and Their Photoluminescence upon Eu3+/Tb3+ Doping

Uniform-assembled lanthanide borate nanocrystals have been synthesized via a facile self-assembly process under hydrothermal conditions. All of the prepared lanthanide borate assemblies exhibit a spindle-like profile despite the fact that they belong to different crystal systems and have different formulas for composition. Each assembly is composed of small nanocrystals that are tightly attached along with their lateral surfaces. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy have been used to characterize the structure and morphology of these samples. The mechanism responsible for the growth and assembly of these lanthanide borate assemblies is also demonstrated. After Eu3+ and/or Tb3+ ions are doped inside these assemblies, strong and multicolor emissions can be realized. Notably, tunable emission and a warm-white color can be achieved in the Eu3+/Tb3+ codoped samples.