Decrease in particle size and enhancement of upconversion emission through Y³⁺ions doping in hexagonal NaLuF₄:Yb³⁺/Er³⁺nanocrystals

Abstract

The upconversion (UC) enhancement with size decrease has been realized through Y 3+ ions doping in β-NaLuF 4 :Yb 3+ /Er 3+ nanocrystals (NCs) by a solvothermal process. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and UC luminescence spectra were used to characterize the resulting samples.With an increase of the Y 3+ doping concentration, the NCs size is continuously decreased with no phase transition. Meanwhile, the UC intensity is firstly increased and then it decreases when the Y 3+ ions concentration is over 30 mol%. The NCs IJβ-NaLu 0.48 Y 0.3 Yb 0.2 Er 0.02 F 4 ) with the optimum Y 3+ ions doping concentration (30 mol%) for UC emission have a diameter of about 80 nm. Compared with β-NaLu 0.78 Yb 0.2 Er 0.02 F 4 and β-NaY 0.78 Yb 0.2 Er 0.02 F 4 prepared under the same conditions, the green UC emission is enhanced by a factor of 1.8 and 16, respectively, for β-NaLu 0.48 Y 0.3 Yb 0.2 Er 0.02 F 4 . The variation of the UC intensity with the increasing Y 3+ ions concentration is attributed to the changing of the symmetry of the local crystal field induced by Y 3+ ions doping, which has been proved by the structural probe Eu 3+ ions. For β-NaLu 0.78 Yb 0.2 Er 0.02 F 4 and β-NaLu 0.48 Y 0.3 Yb 0.2 Er 0.02 F 4 , a three-photon green UC process and a three-photon red UC process occur simultaneously at high pump power density, which can be described as 4 G 11/2 (Er 3+ ) + 4 I 15/2 (Er 3+ ) → 2 H 11/2 / 4 S 3/2 (Er 3+ ) + 4 I 13/2 (Er 3+ ) and 4 G 11/2 (Er 3+ ) + 2 F 7/2 (Yb 3+ ) → 4 F 9/2 (Er 3+ ) + 2 F 5/2 (Yb 3+ ), respectively.CrystEngComm, 2015, 17, 3103-3109 | 3103This journal is

Concentration-Dominated Temperature-Dependence of Upconversion Luminescence in Gd6WO12 Nanophosphor Co-Doped with Er3+ and Yb3+

“…For the purpose of investigating UC mechanism, the UC luminescence spectra were measured for all the samples under 980 nm excitation when the laser was working at various currents ranging from 0.4 A to 0. and red ( 4 F 9/2 → 4 I 15/2 ) UC emissions were observed, 19 and their intensities monotonously increase with increasing the laser working current. Moreover, it is also found that the green UC emissions are dominant for the sample with 1 mol% Er 3+ , but the red UC emission is much more intense than the green one for the sample with 25 mol% Er 3+ .…”

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