NaGdF₄:Dy³⁺ nanocrystals: new insights into optical properties and energy transfer processes

NaGdF₄:Dy³⁺ nanocrystals (NCs) have been synthesized using a precipitation technique. The structural characteristics and morphology of the materials were analyzed using X-ray diffraction patterns and scanning electron microscopy images, respectively. The photoluminescence excitation spectra, emission spectra and decay curves of all samples were recorded at room temperature. The color feature of Dy³⁺ luminescence was estimated using CIE chromaticity coordinates and the correlated color temperature. The radiative properties of the Dy³⁺:⁴F_9/2 level in the material were analyzed within the framework of JO theory. In NaGdF₄:Dy³⁺ NCs, the energy transfer from Gd³⁺ to Dy³⁺ causes an enhancement in the luminescence of the Dy³⁺ ions. The rate of the processes taking part in the depopulation of Gd³⁺ ions was estimated. The energy transfer between Dy³⁺ ions leads to the luminescence quenching of NaGdF₄:Dy³⁺. In this process, the dipole-dipole interaction, which is found by using the Inokuti-Hirayama model, is the dominant mechanism. The characteristic parameters of the energy transfer processes between Dy³⁺ ions have also been calculated in detail.