Facile growth of monocrystalline gold–iron nanocrystals by polymer nanoemulsion

Abstract

Monodisperse, monocrystalline AuFe opticalmagnetic multifunctional nanocrystals were prepared by the nanoemulsion method using a copolymer surfactant. The structure and properties of the monocrystalline nanocrystals were analyzed by X-ray diffraction, transmission electron microscopy (TEM, including high-resolution TEM), selected-area electron diffraction, UV-vis spectroscopy, and vibration sampling magnetometry. The characterization shows the outstanding monodispersity and high monocrystallinity of the nanocrystals, which possess both well-defined optical and magnetic properties revealing broadband absorption with the surface plasmon resonance, peaking at~600 nm, and clear soft ferromagnetic behavior at room temperature. Such long-term stable, monocrystalline AuFe nanocrystals have novel optical and magnetic properties, which may offer exciting opportunities in fundamental studies and tremendous applications.

Facile synthesis of multifunctional La1−xSrxMnO3@Au core–shell nanoparticles for biomedical applications

“…5e. 52 The distinct red-shiing and broadening of the SPR of the La 1Àx Sr x MnO 3 @Au core-shell nanoparticles relative to that of the Au nanoparticles is consistent with a previous report. 37 It is valuable to point out that the SPR band of metal nanoparticles strongly depends on the size, shape, composition, and dielectric property of the nanoparticles and the local environment.…”

“…Compared to the La 1Àx Sr x MnO 3 nanoparticles, the decrease of T C and T B of the La 1Àx Sr x MnO 3 @Au core-shell nanoparticles may be due to the particle size and the Au shell effect. 16,52 In our samples, no magnetic relaxation is observed below T B , so the spin glass behavior does not exist and the system can be considered both the single domain and superparamagnetic in nature. Consequently, we have for the rst time synthesized a free-standing La 1Àx Sr x MnO 3 nanoparticle system with a sharp, tight phase transition from ferromagnetic to superparamagnetic states.…”

Superparamagnetic Nanoparticles as High Efficiency Magnetic Resonance Imaging T2 Contrast Agent

“…14 −16,31,40 The corresponding peaks of iron and gold, reported in Figure 1e and Figure 1f, are analyzed and are in good agreement with reported values. [14][15][16]31,40 The lattice parameters of bulk Au/Fe alloys have been characterized in a wide range of compositions, for example, 3.3% Fe (4.0690 Å) and 20% Fe (3.995 Å). 41 Application of Vegard's law in this range allows for an estimation of the iron composition from the lattice parameter, which results in 10.3% Fe for MPSA:OT Au/ Fe NPs and 12.3% Fe for MUS:OT Au/Fe NPs.…”

“…A number of different methods have been previously reported for the preparation of bimetallic Au/Fe alloy nanoparticles, 13−15,20−26 core−shell or dumbbell nanoparticles, 27,28 with protocols including thermal decomposition, 15,23 pulsed laser deposition, 29,30 microemulsion techniques, 16,31 thermal vaporization, 32,33 laser-assisted synthesis in solution, 13,20 and aqueous reduction by borohydride derivates. 14 Chemical reduction of metal ions by sodium borohydrides has previously been used to prepare nanocrystalline magnetic materials, nanoalloys, and amorphous metals.…”

“…Many recent studies report on the synthesis and MRI potential of Au-coated iron oxide nanoparticles and Au/Fe bimetallic and alloy nanoparticles. − Both solutions lead to superparamagnetic nanoparticles with contrast agent capability that in addition present an exposed, inert, noble metal surface. The presence of Au provides two main advantages: (i) a well-known and versatile platform for surface functionalization, the gold–thiol chemistry, and (ii) gold adds plasmonic features to the superparamagnetic NPs that can be exploited for multimodal imaging, such as contrast for CT (computed tomography) and SERS (surface enhanced Raman spectroscopy) imaging in vivo, and photothermal therapy …”