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Published online 18 October 2007 | Nature | doi:10.1038/news.2007.178
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Gold nanoparticles revealed
Crystal study unveils chemistry of tiny gold tracers.
Nanoparticles are set to lose their air of mystery: the structure of a widely used class of gold nanoparticle has been unambiguously determined, and the structures of other nanoparticles could soon follow. The structure reveals that the molecules grown on the surface of the gold nanoparticles don’t behave quite as they were thought to.
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I agree with the implication that a homogenous size and structure of nanoparticles would render investigations of target effect as well as environmental and toxicological effects much easier to accomplish. However, a success in creating a perfect crystal could not support a conclusion that the mother liquor had been be as homogenous in particle variability as the final specimen used for the X-ray characerization. More likely than not the final specimen had been obtained not before finding and fine tuning conditions for repeated recystallization. Obviously, an investigation of size and shape among nanoparticles generated by chemical and/or physical processes used for commercial applications would require completely different methods beyond the scope of this study. Furthermore, nanoparticles of different chemical composition may exhibit a completely different variability in size and shape as compared to those with a gold core. The study appears to me as no mean feat, and thus a promising step --- on a long way to really understand nanoparticles and their effects.
Horst Plettenberg is correct that the mother liquor from which Au102 was crystallized was not homogenous. However, the Au102 crystals used in this study did not require recrystallization, but rather formed directly from a mother liquor made with the crude synthetic material. So far, Au102 appears to be a minor product in this synthesis, but it is reliably formed and easily crystallized.