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Complex Chiral Colloids and Surfaces via High-Index Off-Cut Silicon

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posted on 2014-05-14, 00:00 authored by Kevin M. McPeak, Christian D. van Engers, Mark Blome, Jong Hyuk Park, Sven Burger, Miguel A. Gosálvez, Ava Faridi, Yasmina R. Ries, Ayaskanta Sahu, David J. Norris
Silicon wafers are commonly etched in potassium hydroxide solutions to form highly symmetric surface structures. These arise when slow-etching {111} atomic planes are exposed on standard low-index surfaces. However, the ability of nonstandard high-index wafers to provide more complex structures by tilting the {111} planes has not been fully appreciated. We demonstrate the power of this approach by creating chiral surface structures and nanoparticles of a specific handedness from gold. When the nanoparticles are dispersed in liquids, gold colloids exhibiting record molar circular dichroism (>5 × 109 M–1 cm–1) at red wavelengths are obtained. The nanoparticles also present chiral pockets for binding.

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