Au Nanorods@NaGdF4/Yb3+,Er3+ Multifunctional Hybrid Nanocomposites with Upconversion Luminescence, Magnetism, and Photothermal Property

Multifunctional nanomaterials possessing upconversion luminescence, magnetic, and photothermal properties show promising applications in biology and medicine. In this study, a new kind of luminescent-magnetic-thermal core-shell hybrid nanocomposite was fabricated combining rare earth Yb3+ and Er3+ ions doped NaGdF4 nanocrystals as shell layer materials and gold nanorods (AuNRs) as cores. The structure, morphology, composition, and properties of the multifunctional hybrid nanocomposites were characterized by X-ray powder diffraction, transmission electron microscopy, energy dispersive spectroscopy, upconversion photoluminescence spectra, vibrating sample magnetometer, sensitive thermometer, and cytotoxicity assessment, respectively. The multifunctional hybrid nanocomposites have rodlike morphology and core-shell structure. The uniform NaGdF4/Yb3+,Er3+ shell with a thickness of around 4.5 nm was coated on the surface of AuNRs with a length of 40 nm and a diameter of 12 nm. The AuNRs@NaGdF4/Yb3+,Er3+ multifunctional nanocomposites provide an excellent upconversion emission under excitation at 980 nm and a superparamagnetic behavior with magnetic susceptibility of 8.0 X 10(-5) emu.g(-1).Oe(-1) at 300 K and saturation magnetization value of 102 emu-g(-1) at 2 K. More significantly, when AuNRs@NaGdF4/Yb3+,Er3+ aqueous suspensions of 100 mu g.mL(-1) were irradiated by a 980 nm NIR laser for 10 min, the temperature was significantly elevated to 48 degrees C. At the same time, the temperature of photothermal transduction can be easily controlled by adjusting the concentration of nanocomposites. Preliminary investigation of incubating with HeLa cells displays that the multifunctional nanocomposites exhibit a good biocompatibility. Moreover, the nanocomposites may be effectively utilized for bioimaging and photothermal therapy in living cells.