1 Concordia University Centre for NanoScience Research, 7141 Rue Sherbrooke Ouest, Montreal, QC H4B 1R6, Canada. john.capobianco@concordia.ca.
2 LumiLab, Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, 9000 Ghent, Belgium.
3 Medical Physics Unit, McGill University, Cedars Cancer Centre, 1001 Décarie Blvd, Montreal, QC H4A 3J1, Canada.

Trivalent praseodymium exhibits a wide range of luminescent phenomena when doped into a variety of different materials. Herein, radioluminescent NaLuF4:20%Pr3+ nanoparticles are studied. Four different samples of this composition were prepared ranging from 400-70 nm in size. Kinetic studies of radioluminescence as a function of X-ray irradiation time revealed a decrease in the emissions originating from the 1S0 level, due to the formation or optical activation of defects during excitation, and a simultaneous increase in the visible emissions resulting from the lower optical levels. Thermoluminescence measurements elucidated that a local de-trapping mechanism was responsible for the increase in steady state emission and persistent luminescence originating from the lower optical levels. The results and mechanism described through this study serve to provide a novel nanoparticle composition with versatile luminescent properties and provides experimental evidence in favor of a local trapping model.