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Cobalt nanoparticles

Attractive synthesis

Combining solid-supported synthesis with magnetic separation is an attractive proposition for carbon-coated cobalt nanoparticles

Credit: © 2007 Wiley

Often the most difficult and tedious aspect of chemical synthesis involves the separation and purification of the target compound from a mixture of side-products and unreacted starting materials. One solution to this problem makes use of solid supports, whereby molecules are built up step-by-step on polymer beads that can be easily separated from reaction mixtures, either by filtration or with a magnet if they are magnetic.

Because magnetic microbeads are quite expensive and can be loaded with only limited quantities of molecules, Wendelin Stark and co-workers1 from the ETH in Zurich have developed carbon-coated magnetic cobalt nanoparticles that have the potential to be used as solid platforms for chemical synthesis. The nanoparticles are prepared using a flame-aerosol method that is based on a widely used industrial process. In previous work, Stark and co-workers have made pure cobalt nanoparticles with this technique, but by introducing a carbon source (acetylene) they can make particles with shells comprising roughly 2–4 layers of graphitic carbon.

The carbon coating of the nanoparticles can be covalently functionalized with chloro- and nitro- functional groups, the latter of which can undergo further reaction to form amines, which are traditionally used to link molecules to solid supports. The nanoparticles can be made in large quantities and they exhibit good magnetic properties, are stable in air up to almost 200 °C and can be loaded more heavily than magnetic microbeads on a per gram basis.


  1. Grass, R. N. Athanassiou, E. K. & Stark, W. J. Covalently functionalized cobalt nanoparticles as a platform for magnetic separations in organic synthesis. Angew. Chem. Int. Edn 10.1002/anie.200700613 (2007).

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Cantrill, S. Attractive synthesis. Nature Nanotech (2007).

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