Energy transfer and dipole–dipole interaction in Er3+/Eu3+/Yb3+:Gd2(MoO4)3 upconverting nanophosphors

Abstract

Er³⁺–Eu³⁺–Yb³⁺:Gd₂(MoO₄)₃ nanophosphors synthesized by a chemical co-precipitation method have been analyzed by using XRD, FESEM, photoluminescence (PL) and decay curve analysis. Intense green upconversion (UC) emissions have been observed upon ∼980 nm NIR excitation. The codoping of Yb³⁺ ions in Er³⁺/Er³⁺–Eu³⁺ doped/codoped Gd₂(MoO₄)₃ nanophosphors enhances the UC green and red emission intensity by ∼8/9 and ∼88/3 times. The downconversion (DC) spectra of the developed nanophosphors recorded upon ∼396 nm UV excitation exhibit intense emission in the red region. The spectral properties have been explained by the nephelauxetic ratio and Judd–Ofelt parameters. The dipole–dipole interaction is found to be responsible for concentration quenching between the Eu³⁺ ions. The colour tunability with pump power density variation has been visualised in the chromaticity diagram.