Controlled synthesis, photoluminescence, and the quantum cutting mechanism of Eu(3+) doped NaYbF4 nanotubes.

Quantum cutting down-conversion has been the subject of intense research activity due to its wide application in optoelectronic devices. However, the energy transfer mechanism behind this down-conversion process is not fully understood. In this work, monodispersed Eu(3+) doped NaYbF4 nanotubes were synthesized by a hydrothermal route. Simultaneous phase transition from cubic to hexagonal and size modification are controlled by changing the Eu(3+) doping concentration. Excited by 393 nm ultraviolet monochromatic light, Eu(3+) doped NaYbF4 nanotubes show quantum cutting down-conversion involving visible and broadband near-infrared emissions through an energy migration process (5)D2 (Eu(3+)) → (2)F5/2 (Yb(3+)) + (2)F5/2 (Yb(3+)). Based on the emission spectra of Eu(3+) ions, an improved method is proposed to calculate Judd-Ofelt intensity parameters and radiative transition probability. A comprehensive seven-level rate-equation model is developed to study the energy transfer mechanism. This work offers a method to calculate Judd-Ofelt parameters of opaque powder phosphors and to evaluate the population dynamics of excited states.