Photoluminescence characteristics and energy transfer between Bi³⁺ and Eu³⁺ in Gd₂O₃: Eu³⁺, Bi³⁺ nanophosphors

Abstract

Bi³⁺ and Eu³⁺ codoped cubic Gd₂O₃ nanocrystals were prepared by the Pechini sol-gel method. Their photoluminescent properties were investigated under ultraviolet light excitation. The introduction of Bi³⁺ ions broadened the excitation band of Eu³⁺ emission, of which a new strong band occurred ranging from 320 to 380 nm due to the 6s²→6s6p transition of Bi³⁺ ions, implying a very efficient energy transfer from Bi³⁺ ions to Eu³⁺ ions. Upon 325 and 355 nm light excitation, the luminescent intensity of Eu³⁺ ions was remarkably improved by the incorporation of Bi³⁺ ions. But a significant quenching of Eu³⁺ emission was observed under 266 nm light excitation when Bi³⁺ was codoped. The possible energy transfer processes between Bi³⁺ and Eu³⁺ were discussed. The decay curves of Eu³⁺ emission under the excitation of 266 nm pulsed laser were measured and gave further evidence for our discussion.