Download Synthesis and Magnetic Characterization of

Core-shell nanoclusters: synthesis, magnetism and biomedical application
You Qiang, Physics Department, University of Idaho, Moscow, ID 83844-0903
Biocompatible magnetic nanoparticles have been found promising in several
biomedical applications for tagging, imaging, sensing and separation in recent years.
Most magnetic particles or beads currently used in biomedical applications are based on
ferromagnetic iron oxides with low specific magnetic moments of about 30 emu/g and
polydispersive. In my talk, I will report a new approach based on magnetic metal
nanoparticles passivated by an oxide coating. Specifically we prepared passivated or
coated monodispersed magnetic nanoclusters in sizes between 1-100 nm. We attached
proteins, including antibodies, to these magnetic nanoparticles. The magnetic properties
of nanoparticles have be investigated by superconducting quantum interference device
(SQUID) magnetometry and related tools such as HRTEM, AFM and XPS.
The cluster beam deposition apparatus developed recently in our laboratory is mainly
composed of three parts: a cluster source, an e-beam evaporation chamber and a
deposition chamber. The mean size of clusters, from 1 nm to 100 nm, is easily varied by
adjusting the aggregation distance, the sputter power, the pressure in the aggregation
tube, and the ratio of He to Ar gas flow rate. A major advantage of this type of system is
that the clusters have much smaller size dispersion than grains obtained in any typical
pro. A typical size distribution is less than 10%. Applying a pulsed-field mass selector to
nanoclusters reduces it to about 3%.
We have synthesized monodispersive core-shell nanostructured iron clusters. The
specific magnetic moment of core-shell nanoclusters is size dependent, and increases
rapidly from about 80 emu/g at the cluster size of around 3 nm to over 200 emu/g at the
size larger than 80 nm. This moment is almost 10 times higher than commercial products.
The use of high magnetic moment and monodispersive nanoparticles can dramatically
enhance the contrast for MRI, reduce the concentration of magnetic particle needs for cell
separation, or make drug delivery possible with much lower magnetic field gradients.