β-NaGdF4 nanotubes: one-pot synthesis and luminescence properties

Abstract

Hexagonal-phase NaGdF₄ nanotubes were successfully fabricated through a template- and catalyst-free method in a hydrothermal environment. The intrinsic and external factors contributing to the formation of tubular nanocrystals were discussed, namely the anisotropic crystal structure of the hexagonal-phase NaGdF₄ and the insufficient supply of reagents. Furthermore, the addition of ethylene glycol and hydrazine had a significant effect on the morphological variation. The desirable multicolor outputs were achieved by co-doping Ce³⁺ and Ln³⁺ (Ln = Eu, Tb, and Dy) ions in the NaGdF₄ crystal, in which the Gd³⁺ ions acted as an intermediate medium transforming the excitation energy to the activator ions. Finally, the upconversion luminescence and magnetic performance of the sodium rare earth fluoride were demonstrated.