Title: Upconversion luminescence of Er³⁺ doped Y₂O₃ and Gd₂O₃ nanophosphors

Authors: Tran Kim Anh; Dang Van Thai; Vu Thi Thai Ha; Wieslaw Strek; Le Quoc Minh

Addresses: Institute of Theoretical and Applied Research, Duy Tan University, Hanoi 100000, Vietnam; Faculty of Natural Sciences, Duy Tan University, Da Nang 550000, Vietnam ' Institute of Theoretical and Applied Research, Duy Tan University, Hanoi 100000, Vietnam; Faculty of Environmental and Chemical Engineering, Duy Tan University, Da Nang 550000, Vietnam ' Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, 100000, Vietnam ' Institute of Low Temperature and Structure Research, Polish Academy of Science, 2 Okolna, Wroclaw, Poland ' Institute of Theoretical and Applied Research, Duy Tan University, Hanoi 100000, Vietnam; Faculty of Natural Sciences, Duy Tan University, Da Nang 550000, Vietnam

Abstract: The luminescence process and mechanism of Er³⁺ doped Y₂O₃ and Gd₂O₃ nanophosphors are investigated with focus on their upconversion luminescence properties. Here the strong up-conversion (UC) emissions of both Y₂O₃:Er³⁺ nanoparticles prepared by combustion with EDTA and Gd₂O₃:Er³⁺ nanospheres synthesised by multistep chemical reaction using urea have been measured at room or low temperatures. The downward-conversion luminescence spectra in visible and near infrared region have been assigned from the transitions in the energy level system of Er³⁺ion. For Y₂O₃:Er³⁺nanoparticles, the upconversion luminescent intensity depends on excitation power at 980 nm have properly indicated the two photon process which are the calculated slope values of main transitions in Er³⁺ions: ²H_11/2-⁴I_15/2, ⁴S_3/2-⁴I_15/2and ⁴F_9/2-⁴I_15/2 are 2.07, 1.72, 1.87 (0.5% Er) and 2.32, 1.82 and 2.07 (Er 1.0%) respectively. The integral intensity of the red band is smaller than that of the green band in the upconversion emission of nanoparticles Y₂O₃ doped with Er³⁺ with 0.50, 1.00 and 1.50%. However it was the integral intensity of red emission bands that dominated in Gd₂O₃: 1% Er³⁺. The lifetimes of the band in green colour peaked at 562 nm upon excitation at 380 nm in Y₂O₃:Er³⁺ with 0.50, 1.00 and 1.50%, and have shown the two sequent time decay processes, the shorter and the longer, both in millisecond scale, 0.14 ms (0.5%); 0.28 ms (1.00%) and 0.13 ms (1.50%) and 4.49 ms (0.5%); 6.89 ms (1.00%) and 5.16 ms (1.50%), respectively. For the nanoparticles Gd₂O₃: 1% Er the intensity decrease of the upconversion emission peaked at 562 nm with only a single process with a decay time of 1.24 ms. Both nanophosphors Y₂O₃ and Gd₂O₃ doped with Er³⁺ are promising materials to develop multifunctional units for medical applications.

Keywords: Y₂O₃:Er³⁺; Gd₂O₃:Er³⁺; upconversion luminescence; nanophosphores; nanoparticles; nanospheres.

DOI: 10.1504/IJNT.2020.111334

International Journal of Nanotechnology, 2020 Vol.17 No.7/8/9/10, pp.689 - 707

Published online: 20 Nov 2020 *

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