Nanotechnology Now - News Story: "Superlattices are key to advanced nanocrystal applications"

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September 11th, 2007

Superlattices are key to advanced nanocrystal applications

Abstract:
Zinc Oxide (ZnO) has long been used in its powdered form as pigments in paints, coatings for papers, in the commercial manufacture of rubber goods as well as UVA and UVB blocker and mild antimicrobial in cosmetics. ZnO is also one of the most important semiconductor compounds and numerous reports have been documented in the literature about the preparation and characterization of ZnO nanocrystals. While polycrystalline forms of ZnO have been used for technical uses such as piezoelectric transducers, light emitting diodes, and transparent conducting films, the progress in developing single crystal bulk ZnO have brought its promise as a wide band gap semiconductor to the fore. Superstructures formed from ZnO nanocrystal quantum dots may find applications in various areas such as optics, electronics and magnetism. For these 2D and 3D superstructures to be useful they need to be well-ordered. Usually, nanocrystals without any surface modification are less stable and they usually undergo aggregation or crystal growth, and consequently it is rather hard for bare nanocrystals to self-assemble into 2D, and especially into 3D, ordered structures. So far, most well-ordered assemblies of nanocrystals have been prepared through a surface modification approach. Efforts have been made to prepare superstructures composed of ZnO nanocrystals but it is rather challenging to obtain well-ordered 3D ZnO superlattices. Researchers in China have now found that ZnO nanocrystals capped with ionic liquids spontaneously assemble into a three-dimensional lattice. Apparently, simply drying a solution of the modified ZnO nanocrystals is all that is needed for the superlattice to form. The presence of the ionic liquid prevents the nanocrystals from aggregating.

Source:
nanowerk.com

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