Organic mediated solvothermal synthesis, enhanced luminescence dynamics, photometric and Judd-Ofelt analyses of Zn²⁺ modified Gd₂O₃: Eu³⁺, Li⁺ nanophosphors for deep UV LEDs and security inks

Highly luminescent red emitting Zn²⁺ modified Gd₂O₃:Eu³⁺, Li ⁺ nanophosphors with superior colour purity were prepared by the organic mediated solvothermal combustion of metal-citrates in diethylene glycol. Structure, morphology, spectroscopic and luminescence dynamics of the nanophosphors were found to be sensitive to Zn²⁺ concentration. Simultaneous incorporation by Zn²⁺ and Li⁺ ions in Gd₂O₃:Eu³⁺ resulted in better emission features and improved photophysical radiative properties. Enhanced photoemission has resulted from the cooperative and combined roles caused by Li⁺ and Zn²⁺ ions, improvement of crystallinity, modifications of the crystal field and reduced symmetry around Eu³⁺ ions in Gd₂O₃. Photoemission intensity of the optimal zinc compensated phosphor with composition Gd_1.71Eu_0.1Li_0.15Zn_0.04O₃ was found to be 1.82 times that of Gd_1.75Eu_0.1Li_0.15O₃ and it exhibited a lifetime of 1.467 ms with the highest colour purity of 97.06 %. Luminescence decay profiles of all the synthesized phosphors were found to follow single exponential behaviour. Judd-Ofelt analysis revealed that the emission intensity parameters were found to be optimum for Gd_1.71Eu_0.1Li_0.15Zn_0.04O₃ phosphor, indicating the highest asymmetry of local environment around Eu³⁺ ions in this material. Better radiative and Judd-Ofelt intensity parameters obtained indicate that this highly luminescent red emitting phosphor can act as a promising material for high resolution phosphor coated displays, deep UV excited phosphor converted LEDs and for developing defence security inks.