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

• Published in: Nano letters 2014-05, Vol.14 (5), p.2934-2940
• Main Authors: McPeak, Kevin M, van Engers, Christian D, Blome, Mark, Park, Jong Hyuk, Burger, Sven, Gosálvez, Miguel A, Faridi, Ava, Ries, Yasmina R, Sahu, Ayaskanta, Norris, David J
• Format: Article
• Language: English
• Subjects: Circularity; Colloids; Cross-disciplinary physics: materials science; rheology; Dichroism; Etching; Exact sciences and technology; Gold; Materials science; Nanocrystalline materials; Nanoparticles; Nanoscale materials and structures: fabrication and characterization; Physics; Planes; Surface structure
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl501032j

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.