Synthesis and study of optical properties of a Gd³⁺-doped NaYF₄ phosphor for phototherapy lamp application

In recent trends, radiation falls under the narrowband ultraviolet-B region (305-315 nm) widely used in phototherapy lamp applications in the treatment of skin diseases. In this paper, we report a Gd³⁺-doped NaYF₄ luminescent material synthesized for the first time using the low-temperature co-precipitation method. It crystallized into a face-centred cubic structure, as confirmed by X-ray diffraction characterization techniques and Rietveld refinement. The photoluminescence property of the as-prepared sample shows a highly intense, sharp emission band obtained at 311 nm, which belongs to the narrowband ultraviolet-B region and corresponds to the transition of the ⁶P_7/2→⁸S_7/2 level of the Gd³⁺ ions under 272 nm excitation (⁸S_7/2 to ⁶I_J). The transitions of the Gd³⁺ ions are detected entirely with different concentrations of Gd³⁺ ions. Scanning electron microscopy analysis indicated that the average particle was 288 nm. The critical distance for energy transfer was calculated to be equal to 11.5017 Å. Dipole-dipole interaction is responsible for energy transfer, as analyzed by Dexter theory. These excellent optical characteristics, together with their highly efficient and low-cost synthesis approach, indicate that synthesized NaYF₄:Gd³⁺ phosphors have excessive potential for phototherapeutic lamp applications.