Dr. You Qiang, a assistant professor at Physics Department at University of
Idaho, gave audiences of Physics Department of UTA a
colloquium. The talk is titled "Core-shell
nanoclusters: synthesis, magnetism and biomedical application". The abstract of the seminar is as follows:
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.
