Controlled synthesis, photoluminescence, and the quantum cutting mechanism of Eu3+ doped NaYbF4 nanotubes

Abstract

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 Eu³⁺ doped NaYbF₄ nanotubes were synthesized by a hydrothermal route. Simultaneous phase transition from cubic to hexagonal and size modification are controlled by changing the Eu³⁺ doping concentration. Excited by 393 nm ultraviolet monochromatic light, Eu³⁺ doped NaYbF₄ nanotubes show quantum cutting down-conversion involving visible and broadband near-infrared emissions through an energy migration process ⁵D₂ (Eu³⁺) → ²F_5/2 (Yb³⁺) + ²F_5/2 (Yb³⁺). Based on the emission spectra of Eu³⁺ 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.