Magnetic and upconverted luminescent properties of multifunctional lanthanide doped cubic KGdF4 nanocrystals

摘要

Lanthanide (Ln~(3+)) doped KGdF4 (Ln = Yb~(3+), Er~(3+), Ho~(3+), Tm~(3+)) nanocrystals with a mean diameter of approximately 12 nm were synthesized by a hydrothermal method using oleic acid as a stabilizing agent at 180 °C. The nanocrystals crystallize in the cubic phase as α-NaGdF4. When excited by a 980 nm laser, these Ln~(3+) doped nanocrystals exhibit multicolor up-conversion (UC) emissions in red, yellow, blue and white. The calculated color coordinates demonstrate that white UC emission (CIE-X = 0.352, CIE-Y = 0.347) can be obtained by varying the dopant concentrations in the Yb~(3+)/Ho~(3+)/Tm~(3+) triply-doped nanocrystals to yield different RGB emission intensities. The measured field dependence of magnetization (M-H curves) of the KGdF4 nanocrystals shows their paramagnetic characteristics that can be ascribed to the non-interacting localized nature of the magnetic moment of Gd~(3+) ions. Moreover, low temperature thermal treatment can enhance UC properties, magnetization and magnetic mass susceptibility of Ln~(3+) doped KGdF4 nanocrystals. The multifunctional Ln~(3+) doped KGdF4 nanocrystals have potential applications in color displays, bioseparation, and optical-magnetic dual modal nanoprobes in biomedical imaging.