Shaping Up

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Science  20 Sep 2002:
Vol. 297, Issue 5589, pp. 1959
DOI: 10.1126/science.297.5589.1959d

The control of nanoparticle size and shape is often difficult, and the tailored growth of only a few materials has been achieved so far. Lee et al. now show that the growth of lead sulfide (PbS) can not only be controlled, but a number of unusual and transient nanocrystal shapes can be obtained. When dodecylamine was used as the capping ligand, only cube-shaped nanocrystals were obtained. Switching to dodecanethiol, which forms a much stronger bond with the Pb, produced cubic nanocrystals but only at low concentrations of the ligand. At high concentrations, nearly spherical nanocrystals were observed, as the growth on the {111} faces was selectively restricted. Lower growth temperatures and high precursor flux rates led to kinetic control of the growth, with enhanced growth along the {100} faces, to create nanocrystals with T, L, star, and cross shapes. By programming the right conditions for each of the variables, the authors believe it should be possible to consistently obtain desired nanocrystal products, including species that were previously only transient, such as the star shapes. — MSL

J. Am. Chem. Soc. 10.1021/ja025805j (2002).

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