Cool Clustering

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Science  14 Mar 2008:
Vol. 319, Issue 5869, pp. 1459
DOI: 10.1126/science.319.5869.1459b

The decomposition of a precursor within a polymeric medium can yield metal nanoclusters with narrow size distribution and uniform morphology. Gazit et al. explored the impact of this approach, performing the synthesis below the glass transition temperature (Tg) of the polymer, thereby precluding large-scale motions of the polymer segments. For iron nanoparticles within a polystyrene (PS) matrix, a large reduction in temperature shifted size and morphology from 70-nm spherical particles to 50-by-3-nm needles, whereas intermediate temperatures produced 8-nm spheres. Formation rates scaled exponentially with temperature above and below Tg. In the case of a poly(methyl methacrylate) (PMMA) matrix, similar size and morphology changes occurred, but the rate of cluster growth below Tg proved insensitive to temperature. The authors attribute the discrepancy to the relatively strong coordinative bonding between cluster and polymer present in the PMMA matrix but absent from PS. Taken together, the results support tuning of polymer segment mobility as an additional control variable in the synthesis of metal clusters. MSL

Macromolecules 41, 10.1021/ma071816o (2008).

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