Controlled morphology and EDTA-induced pure green upconversion luminescence of Er3+/Ho3+-Yb3+ co-doped NaCe(MoO4)2 phosphor

Abstract

Uniform and well-crystallized NaCe(MoO₄)₂: Er³⁺/Ho³⁺, Yb³⁺ up-conversion (UC) phosphors have been successfully synthesized by a facile hydrothermal route at 180 °C for 12 h at pH = 9. The crystalline phase, size and morphology were systematically characterized using powder X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM). The experimental results showed that the ethylene diamine tetraacetic acid (EDTA) was a key parameter which not only determined their spacial arrangement, but also affected the size distributions of the final products. Moreover, we found that EDTA could tune the band edge absorption of the molybdate system by changing the lattice parameters, so as to realize their bicolour tunable luminescence of Er³⁺/Ho³⁺-Yb³⁺ co-doped NaCe(MoO₄)₂ for the first time. Studies of the behavior as a function of dopant concentration were all described. The different UC mechanisms of the samples with and without EDTA were systematically depicted as well. It was found that an innovative route to increase the green UC emission and simultaneously suppress red UC emission in Er³⁺/Ho³⁺-Yb³⁺ co-doped NaCe(MoO₄)₂ prepared with the assistance of 0.1 g EDTA, which enhanced the efficiency of the single green color.