An in situ redox process in microfluidic reactors was developed to synthesize hybrid nanoparticles with amorphous metallic cores and uniform metal oxide shells embedded with nanocrystallites at large scale. For example, the fabricated Fe(B)@iron oxides nanoparticles (NPs) exhibit permanent ferromagnetic properties at room temperature due to the strong magnetic coupling between different parts and the nanocrystalline pinning effect, providing an alternative design of nanostructures to break out the superparamagnetic limit in ultratiny particles. The NPs with amorphous metallic cores and uniform metal oxide shells can be well maintained over 4–5 months. The dictated novel microfluidic process provides a large-scale synthetic strategy for metal@metal oxide core–shell NPs with uniform shells and long-term stability and can be extended to a variety of material systems.

No abstract

Abstract:Co@Au core shell nanoparticles (NPs) of different shell thicknesses were fabricated by a combination of the displacement process and the reduction-deposition process in a microfluidic reactor. The effect of the shell thickness on the fine structures (local atom arrangement) of core materials was investigated by X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS). The results indicate that the shell thickness affects the fine structure of the core materials by causing atomic re-arrangement between the hexagonal close pack (hcp) and the face centered cubic (fcc) structure, and forming Co-Au bonds in the core-shell interface.

were developed by conjugating multimode nanohybrids with active ingredients of natural herbs using Au@CoFeB nanoparticles as one model of multimode nanohybrids and the ginsenoside Rg3 as one model of active ingredients of natural herbs. Au@CoFeB nanoparticles were first synthesized using a temperatureprogrammed microfluidics process. Then, the surface of Au@ CoFeB nanoparticles was modified via an amino-silane coupling agent of (3-aminopropyl) trimethoxysilane (APTMS) and then activated by the bifunctional amine-active cross-linker. They were thereafter conjugated to ginsenosides preactivated by APTMS by cross-linking the surface-activated nanohybrids, forming Au@ CoFeB-Rg3 nanomedicines. Their multimode imaging functions were evaluated with the characterization of their magnetic and optical properties and the response to X-ray radiation. They can be optically detected via dark-field microscopy and can be imaged through X-ray computed tomography. They can also be used as magnetic resonance imaging contrast agents with excellent T2-weighted spin−echo imaging effects. Au@CoFeB-Rg3 nanomedicines exhibited distinct cytotoxicity and inhibitory effects on the proliferation of human hepatocellular carcinoma cells (HepG2/C3) and human chronic myeloid leukemia cells (K562) but were less toxic to 3T3 cells than other cells at concentrations more than 200 μg/ mL. However, Au@CoFeB nanoparticles showed markedly lower cytotoxicity and inhibitory effects on the proliferation of these cell lines, particularly at concentrations <100 μg/mL, than Au@CoFeB-Rg3 nanomedicines. Clearly, there is a distinct synergistic effect between nanohybrids and Rg3. Additionally, Au@CoFeB nanohybrids showed almost no toxicity to Jurkat-CT cells at low concentrations (47 μg/mL), indicating that they may be used as multimode nanoprobes at a suitable concentration. These findings provide an efficient alternative for the synthesis of multifunctional antitumor nanomedicines based on multimode nanohybrids and active ingredients of natural resources.

We have developed a core alloying and shell gradient doping strategy for the controlled surface modification of Fe or CoFe nanoparticles for enhanced magnetic resonance imaging.