Dual-mode blue emission, enhanced up-conversion luminescence and paramagnetic properties of ytterbium and thulium-doped BaGdF multifunctional nanophosphors.

A series of BaGdF:Yb, Tm nanophosphors (NPs) with dual-mode (down-conversion (DC) and upconversion (UC)) luminescence were successfully prepared by hydrothermal method at 180°C. The NPs have sphere-like morphology and cubic structure. Under the excitation of ultraviolet 355nm and near-infrared 980nm, Yb and Tm ions co-doped BaGdF phosphors exhibit bright blue dual-mode emission. The mechanism of UC emissions was determined three-photon absorption. The energy transfer processes from Yb to Tm were discussed in detail. The up-conversion luminescence of BaGdF:Yb/Tm nanophosphors were enhanced by introducing the sensitizer Yb ions and modifying the cetyltrimethylammonium bromide (CTAB) surfactant, respectively. Moreover, the as-prepared samples exhibit paramagnetic properties at room temperature. This type of multifunctional nanophosphors have promising applications in anti-counterfeiting, drug delivery, solid state lasers, biolabels, MRI, light emitting diodes (LEDs).