Eu3+ Doped Y3+ Dipicolinate Crystals: Differences in the Luminescence Spectra and Concentration Quenching of Eu3+ Luminescence

Abstract

Materials doped with lanthanide(III) ions are used in solar cells, LEDs, bioimaging etc. However, we still need to understand effect of concentrantion on the luminescent properties. Here, the Na(Gua)₂[Ln(DPA)₃]∙6H₂O crystal system was explored. Luminescent Eu³⁺ ion was doped into non-luminescent Na(Gua)₂[Y(DPA)₃]∙6H₂O crystals. The crystal structures were determined using single-crystal X-ray diffraction and the doping percentage was determined through ICP-based elemental analysis. The luminescent properties were indeed found to change as a function of the doping percentage. In the emission spectra, the position of the lines in the ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₄ bands was observed to change as a function of Eu³⁺ concentration. The spectra of the pure Eu³⁺ sample had the largest splitting, while the identical spectra for 30%, 20%, and 10% doping with Eu³⁺ had the smallest splitting. No change was observed in the luminescence lifetime for the samples with 10-30% Eu³⁺ doping. Above 30% doping a decrease in luminescence lifetime was observed with increased doping. Above 30% doping, the distance between the Eu³⁺ ions becomes so small that concentration dependent quenching was observed, which allowed for the rate constant of concentration dependent quenching to be determined. We conclude that the concentration dependent quenching is orders of magnitude less efficient than quenching by e.g. water.