Needle from a Haystack

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Science  07 Feb 2014:
Vol. 343, Issue 6171, pp. 581
DOI: 10.1126/science.343.6171.581-b

A current challenge in nanoscale science is the selective assembly of large quantities of particles into ordered arrays. Abécassis et al. consider the case of colloidal semiconducting nanoplatelets, which can be considered a two-dimensional analog of anisotropic nanorods. Solutions of a single population of particles coated with oleic acid were dispersed in hexane, and exposure to a few drops of ethanol, acting as an antisolvent, led to the formation of superparticles up to 20 µm in length. These initially showed a sausage-chain structure where sections 10 to 20 units wide were joined together with defect areas much narrower in size, but these defects disappeared on aging. The authors further examined the superparticles by depositing them on a substrate, causing the plane of the platelets to lie perpendicular to the surface. In testing the optical properties, they found that the superparticles emit strongly polarized light in a direction perpendicular to the long axis.

Nano Lett. 10.1021/nl4039746 (2014).

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