Stokes and upconverted luminescence in Er3+/Yb3+-doped Y3Ga5O12 nano-garnets

Abstract

The green, red, near-infrared and near-infrared-to-visible upconverted luminescence properties of Er³⁺/Yb³⁺ codoped Y₃Ga₅O₁₂ nanocrystalline powders have been studied using laser spectroscopy. A diffuse reflectance and luminescence spectra confirm that Er³⁺ and Yb³⁺ ions occupy the Y³⁺ sites of the single-phase cubic nano-garnet. Very bright green and red luminescence of the Er³⁺ ions are detected by the naked eyes, even for a laser power as low as 15 mW, when the Yb³⁺ ions are excited at 970 nm. The red upconverted emission is more intense than that under direct excitation of the Er³⁺ ions. The power dependence and the dynamics of the near-infrared-to-green and near-infrared-to-red upconverted emissions show the existence of different two-photon energy transfer upconversion processes. The results here presented indicate that Er³⁺/Yb³⁺ codoped Y₃Ga₅O₁₂ can be a good candidate as an optical nanoheater and nanothermometer in biomedicine applications in the first biological window.