Complex chiral colloids and surfaces via high-index off-cut silicon.

McPeak, Kevin M; van Engers, Christian D; Blome, Mark; Park, Jong Hyuk; Burger, Sven; Gosálvez, Miguel A; Faridi, Ava; Ries, Yasmina R et al. · Nano Lett · 2014

basic_science · Level V

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Abstract

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 × 10(9) M(-1) cm(-1)) at red wavelengths are obtained. The nanoparticles also present chiral pockets for binding.