Radioluminescence studies of colloidal oleate-capped β-Na(Gd,Lu)F4:Ln3+ nanoparticles (Ln = Ce, Eu, Tb)

Abstract

We report on the synthesis, characterization, and radioluminescence quantification of several new varieties of nanoparticles with the general composition β-NaLnF₄, incorporating known luminescent activator/sensitizer pairs. Using Monte Carlo modeling to complement luminescence measurements, we have calculated the radioluminescence yields and intrinsic conversion efficiencies of colloidally-dispersed nanoparticles by comparison to an organic liquid scintillator. While five of the compositions had low to modest radioluminescence yields relative to bulk materials, colloidal β-Na(Lu_0.65Gd_0.2Tb_0.15)F₄ displayed a strong output of 39 460 photons per MeV absorbed, comparable to some of the best non-hygroscopic bulk crystal scintillators and X-ray phosphors such as Gd₂O₂S:Tb. Measurements of β-Na(Lu_0.65Gd_0.2Tb_0.15)F₄ powder samples revealed persistent luminescence as well as stable charge trapping, warranting further investigation.