Synthesis, Characterization and manipulation of Magnetic Nanoparticles

Guangjun Cheng, Angela R. Hight Walker
Physics Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg , MD, USA

Magnetic nanoparticles have shown great potential for applications not only in catalysis and magnetic recording, but also in medical sensors and biomedicine. Their biological applications include contrast enhancement agents for magnetic resonance imaging (MRI) and site-specific drug delivery agents for cancer therapies. Here we report on the synthesis of Fe, Co and Ni nanoparticles with controllable sizes and shapes via thermo-decomposition. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) have been used to characterize the magnetic nanoparticles. Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) were used to probe the structures of Co nanoparticles.

Here we also show the magnetic-field-induced (MFI) assemblies of Co nanoparticles. Under the influence of a magnetic field, Co nanoparticles can assemble into linear chains along the direction of the applied field in a colloidal solution. After the removal of the magnetic field, the MFI chains fold into a three-dimensional (3D) super-coiled structure.  Optical Microscope and TEM have been used to characterize these morphologies. A superconducting quantum interference device (SQUID) magnetometer is used to measure the magnetic properties of MFI assemblies of Co nanoparticles.

In order to fully realize the biological applications of these magnetic nanoparticles, one needs to develop the methods for improving their bio-compatibility. Here we present the synthesis of Co/Au and Co/Ag bimetallic nanoparticles. These bimetallic nanoparticles are expected to maintain their magnetic properties of Co, while Au or Ag can improve their biocompatibility. Co/Au and Co/Ag Nanoparticles are prepared by growing Au or Ag on the pre-synthesized Co nanoparticles. The magneto-Raman spectroscopy developed in our laboratory and SQUID magnetometer would be utilized to characterize the properties of these nanoparticles.

 

Guangjun Cheng

Mentor: Angela R. Hight Walker

phone: (301) 975-5209

fax: (301) 975-6991

Optical Technology Division (844), Physics Laboratory (PL)

Building 216, Room B226

100 Bureau Drive, Stop 8443

Gaithersburg, MD 20899-8443

email: guangjun.cheng@nist.gov

Sigma Xi member: No

Category: Physics