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

Abstract

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 Gd1.71Eu0.1Li0.15Zn0.04O3 was found to be 1.82 times that of Gd1.75Eu0.1Li0.15O3 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 Gd1.71Eu0.1Li0.15Zn0.04O3 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.