CHEMISTRY: Small-Scale Synergy

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Science  24 Mar 2006:
Vol. 311, Issue 5768, pp. 1675d
DOI: 10.1126/science.311.5768.1675d

In metallic and semiconductor nanoparticles, the material properties can be tuned simply by changing the particle size. Shi et al. have explored the additional dimension of varying nanoparticle composition to incorporate multiple kinds of materials—specifically magnetic-metallic, magnetic-semiconducting, and semiconducting-metallic hybrids, as well as ternary combinations.

The synthetic strategy involved spontaneous epitaxial nucleation and growth of the second and third components onto seed particles in high-temperature organic solutions. For the magnetic-metallic particles (Fe3O4 grown on gold), solvent choice influenced the particle morphology, with good electron donors leading to core-shell geometries and poor electron donors yielding peanut-shaped fused particles. For Au-PbS particles, which combine a metal and a semiconductor, the choice of solvent did not influence the particle morphology, but the concentration of gold seed particles was critical. Finally, heating strategy and seed particle dimensions were the key variables for setting the ternary particle morphologies. The optical and magnetic properties of the particles were influenced by the hybrid interface. For example, the Au plasmon resonances were red-shifted in the hybrid particles; at the same time, the magnetization saturation field of the Fe3O4-Au particles was an order of magnitude greater than that of pure magnetite. — MSL

Nano Lett. 6, 10.1021/nl0600833 (2006).

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