Europium doped In(Zn)P/ZnS colloidal quantum dots

Abstract

Chemically synthesised In(Zn)P alloy nanocrystals are doped with Eu³⁺ ions using europium oleate as a molecular precursor and are subsequently covered with a ZnS shell. The presence of zinc in the synthesis of the InP core nanocrystals leads to the formation of an In(Zn)P alloy structure, making it possible to obtain stable fluorescence emission at 485 nm. We demonstrate by means of steady state and time resolved photoluminescence measurements that resonant energy transfer takes place from the In(Zn)P/ZnS host to the Eu³⁺ dopant ions. It results in the characteristic phosphorescence lines of Eu³⁺ originating from the transitions between the lowest-lying excited state ⁵D₀ to the ⁷F_J (J = 1, 2, 3, 4) ground states. The maximum phosphorescence efficiency is obtained for an initially applied Eu³⁺ : In³⁺ molar ratio of 0.3 : 1, resulting in a final doping level of approximately 4%.