Upconversion luminescent property and EPR study of NaGdF_4:Yb~(3+)/Tm~(3+) synthesized by the hydrothermal method

摘要

Water soluble upconversion (UC) luminescence hexagonal-phase NaGdF_4: Yb~(3+)/Tm~(3+) nanoparticles have been successfully synthesized by the hydrothermal method. XRD, SEM, UC photoluminescence spectra and electron paramagnetic resonance (EPR) spectrum were used to characterize the nanoparticles. The intensity of UC emission region could be controlled through different sodium source and the fluorine source, ~6P_J→~8S_(7/2) emission of Gd~(3+) is also observed at 310 nm. A broad spectrum with a dominant resonance at g of about 2 was observed by the EPR spectrum of the NaGdF_4:Yb~(3+)/Tm~(3+) nanoparticles. The transparent NaGdF_4:Yb~(3+)/Tm~(3+) solution presented naked eye-visible violet-blue light under the 980 nm LD excitation. The current work paves the way for their potential application in infrared tomography and magnetic resonance imaging (MRI).