Chemistry

Dendrimer-Coated Nanoparticles

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Science  16 May 2003:
Vol. 300, Issue 5622, pp. 1057
DOI: 10.1126/science.300.5622.1057b

Most polymers are synthesized by adding units to one end of a growing chain, but other architectures can be created by adding several monomer units at sites around a growing core. Dendrimers are the most ordered type of these polymers, in which each round of synthesis (or “generation”) geometrically increases the number of units added. A relatively open structure after one or two generations is converted to an almost spherical structure after about five generations. Gopidas et al. adapted a synthesis route for gold nanoparticles that assembles dendrimer “wedges” (which grow out in a limited number of directions) into a spherical structure. Polyaryl ether wedges that are linked initially via disulfide bonds react with a stabilized solution of HAuCl4 and sodium borohydride. A gold core about 2 to 3 nm in diameter forms. For low-generation number wedges (less than three), this spherical core gives the final structure more dendrimer-like properties. The fifth-generation wedges, however, still retain some openness that allows access to the gold core from solution.—PDS

J. Am. Chem. Soc. 10.1021/ja029544m (2003).

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