Synthesis of fluorescent and magnetic bi-functional NaLuF4-based upconversion nanocrystals

Fluorescent and magnetic bi-functional NaLuF4-based upconversion nanocrystals have been developed by a facile thermal decomposition method. The influences of Mn2+ and Gd3+ doping on the upconversion luminescent and magnetic properties of the nanocrystals were investigated. The results show that Mn2+ doping can promote the transition of green to red and increase the red emission significantly. When the Mn2+ and Gd3+ are co-doped in the nanocrystals, it has a synergistic effect which can further improve the transition and red emission. Moreover, the nanocrystals co-doped with Mn2+ and Gd3+ exhibit excellent superparamagnetic properties. These results suggest that the developed nanocrystals, which have strong pure red upconversion emission and superparamagnetic properties, can serve as a potential upconversion luminescence and magnetic resonance probe for dual-modality bioimaging. This work presents a facile and effective method for modulating the transition of short-wavelength emission to red emission of upconversion nanocrystals, leading the naocrystals exhibiting excellent upconversion luminescence and magnetic properties.