Dual-model upconversion luminescence from NaGdF4:Nd/Yb/Tm@NaGdF4:Eu/Tb core-shell nanoparticles

Dual-model upconversion luminescence in NaGdF4:Nd/Yb/Tm@NaGdF4:Eu/Tb core-shell nanoparticles under 980 and 808 nm laser excitation has been demonstrated. Effects of the doping concentrations of Eu3+ and Tb3+ ions on the upconversion emissions were investigated, and two possible processes were proposed as mechanisms responsible for the dual-model upconversion luminescence. These upconverting nanoparticles are promising for biological applications.