Co-Doping Effects of Zn²⁺ on Upconversion Luminescence of Gd₂O₃:Er Nanophosphors

Abstract

Zn 2+ and Er 3+ ions co-doped Gd 2 O 3 nanophosphors were synthesized via a citric acid complexing method. The crystalline characterization shows that the Zn 2+ doping induced a shrinking effect of the host cell by changing the lattice constant. Both Stokes photoluminescence and upconversion emission were significantly enhanced by the Zn 2+ doping. The reason for emission enhancement was mainly ascribed to the lowered crystal symmetry of lattice by introducing oxygen vacancy.

Upconverting/magnetic: Gd2O3:(Er3+,Yb3+,Zn2+) nanoparticles for biological applications: effect of Zn2+ doping

“…al. 24 in Gd 2 O 3 :Er 3+ and Pandey et al 25 in Y 2 O 3 :Ho 3+ -Yb 3+ . The former author ascribed the reason for emission enhancement predominantly as a result of the lowered lattice crystal symmetry that resulted by introducing oxygen vacancy.…”

“…from the 2 F 5/2 to 2 F 7/2 level, corresponding to a wavelength of 1030 nm. In Gd 2 O 3 NPs doped Er 3+ and Zn 2+ synthesized via a citric acid complexing method, Xu et al 24 showed an increase in green luminescence with Zn 2+ . In our case, the NPs in this work, exhibits an increase in red luminescence at a 5% Zn 2+ concentration at both power densities.…”

“…The electronegativity values for Er 3+ , Yb 3+ , Gd 3+ ions are 1.24, 1.1, 1.2, respectively. 24,48 The function of charge and compensation of the oxygen vacancies can be distinguished, due to the difference in electronegativity, between zinc ions Zn 2+ and the rare earth ions in the Gd 2 O 3 host matrix. In our study, the Kröger-Vink notation was applied for the determination of oxygen vacancies arising in doped phosphors: 24 Gd 2 O 3 !…”

“…This leads to suppression of the luminescence and shortening of its lifetime. 24 In order to understand the UC process we examined intensity dependences of the upconverted uorescence as a function of the excitation power at 980 nm (see Fig. 7).…”