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Posted: January 28, 2007

Nano urchins made of gold

(Nanowerk News) Researchers from Francesco Stellacci's research group at MIT report on an aqueous room temperature synthesis method for the production of gold nanoparticles that have a number (>4) of branches ultimately resembling the shape of sea urchins ("High-Yield Synthesis of Multi-Branched Urchin-Like Gold Nanoparticles").
TEM image of the synthesized gold 'nano-urchins' (Image: American Chemical Society)
Multi-branched, odd-shaped metallic nanoparticles have been synthesized before and they are of a lot of interest to researchers because of their unique optical and electronic properties.
The nanoparticles of ∼40nm synthesized by the MIT researchers are stable and water soluble, and they can be stored for days in the dried state and redissolved many times. After drying, the particles dissolve in a stable and reproducible aggregate form.
Finite difference time-domain calculations performed on a nanoparticle with four branches suggest that nano-urchins have large local electromagnetic field enhancements (approx. 3000-fold) near the tips of their horns. The plasmon resonance peak of these particles is narrow and has a narrow full width at halfmaximum that is almost invariant with particle size and shape distribution, suggesting that the dipole of the plasmon is mostly concentrated at the tips of the multi-pods. These particles may find applications in surface enhanced Raman scattering and in catalysis.
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