Restructuring and Remodeling of NaREF₄ Nanocrystals by Electron Irradiation

NaREF₄ nanocrystals are found to be highly manipulable by electron beam irradiation. With 200 kV electron beam irradiation, both 14.6 nm spherical NaGdF₄:Yb,Er nanoparticles and 44.7 nm × 34.1 nm ellipsoidal NaYF₄:Yb,Er nanorods form hollow structures and eventually convert to the corresponding REF₃ upon prolonged irradiation. Furthermore, the NaYF₄ nanorods fractured with irradiation with a 100 kV electron source are found to be subsequently self‐healed when irradiated with a 200 kV source. The detailed experimental results, in combination with theoretical analysis, suggest that knock‐on effects, specific lattice energy, and the inherently low surface energy of NaREF₄ collectively contribute to the formation of the hollow structures. These mechanisms allow controlled engineering and manipulation of RE nanomaterials on the nanometer scale.