Chemistry

A Bit of Charge Is Plenty

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Science  07 Dec 2012:
Vol. 338, Issue 6112, pp. 1264-1265
DOI: 10.1126/science.338.6112.1264-d

For nanoparticles to find use in an array of applications, new techniques are needed to deposit and order the individual particles into large structures. Electrophoretic deposition, in which charged particles in a solution are exposed to a uniform electric field, has been used to close-pack spherical particles or deposit them into trenches or order a layer of nanocrystal rods. Singh et al. show that control over net particle charge and dipole can lead to the formation of well-ordered, tightly packed multilayers of vertically aligned rods. The best ordering was obtained for CdS rods, where a low net charge (or zeta potential) on the as-synthesized rods facilitated the slow deposition necessary for good ordering. Increasing the zeta potential by ligand exchange led to much poorer ordering. In contrast to CdS, CdSe rods showed a tapered rice shape less amenable to close-packing. However, it was still possible to pack the rods in a vertical orientation at high density, an arrangement needed for application of this material as a solar cell photoabsorber.

J. Phys. Chem. B 10.1021/jp305184n (2012).

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