Bright white upconversion emission from Yb3+, Er3+, and Tm3+-codoped Gd2O3nanotubes

Abstract

Yb³⁺, Er³⁺, and Tm³⁺-codoped Gd₂O₃ nanotubes were synthesized via a simple wet-chemical route at low temperature and ambient pressure followed by a subsequent heat treatment at 800 °C. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), upconversion (UC) emission spectra, and kinetic decay were used to characterize the samples. Bright white UC luminescence in the nanotubes was observed under diode laser excitation of 980 nm. The white light consists of the blue (¹G₄ → ³H₆ of Tm³⁺), green (²H_11/2/⁴S_3/2 → ⁴I_15/2 of Er³⁺), and red (⁴F_9/2 → ⁴I_15/2 of Er³⁺) UC emissions. As the excitation power density changed in the range of 20–200 W cm⁻², the calculated CIE color coordinates shift only slightly and fall well within the white region. This material may be a potential candidate for applications of color displays, lighting and photonics.