(640a) Covalent Surface Modification of Carbon Coated Nanomagnets Allow Stable Dispersions in Aqueous Solutions and Specific Post-Modification

For many applications of magnetic nanoparticles
such as for medical diagnostics, biotechnology, biomedical applications and
magnetic biosensors, stable dispersions of magnetic nanoparticles in aqueous
solutions are crucial¹.
Ferromagnetic pure metallic nanoparticles possess a very high saturation
magnetization but also show a considerable tendency to agglomerate. Thus, it is
highly desirable to create a material which combines the high saturation
magnetization but still forms stable dispersions in aqueous solutions.

Here, we describe how specific covalent surface
coating can lead to the formation of a metal cobalt nanoparticle based
ferromagnetic fluid with unprecedented dispersion stability and chemical
functionality ². More detailed, graphene-like
carbon protected metallic nanomagnets, prepared by
flame spray synthesis³, which
are covalently functionalized on the particle surface via diazonium chemistry
are shown. A block-copolymer is grown directly from the particle surface by
SI-ATRP. This block-copolymer consists of a negatively charged polymer block
that is responsible for the colloidal stability of the particles and a second
polymer block, which allows post-modification of the particles. The length of
both polymer blocks is crucial for the colloidal stability of the particles and
is studied in this work. Post-modification
of this material by introduction of azide-functionality
followed by the well-known “click”-reaction, allows the attachment of various
desired target molecules.  These nanoparticles form stable dispersions in
various aqueous solutions, including biological relevant buffer systems.

1              A. H. Lu, E. L.
Salabas and F. Schuth, Angew. Chem.-Int.
Edit., 2007, 46, 1222.

2              C.
J. Hofer, V. Zlateski, P. R. Stoessel, D. Paunescu, E. M. Schneider, R. N.
Grass, M. Zeltner and W. J. Stark, Chem. Commun., 2015, 51, 1826.

3              R. N. Grass, E.
K. Athanassiou and W. J. Stark, Angew.
Chem.-Int. Edit., 2007, 46,
4909.