Helically Twisted Chiral Arrays of Gold Nanoparticles Coated with a Cholesterol Mesogen

• Published in: Journal of the American Chemical Society Vol. 137; no. 40; pp. 12736 - 12739
• Main Authors: Cseh, Liliana, Mang, Xiaobin, Zeng, Xiangbing, Liu, Feng, Mehl, Georg H, Ungar, Goran, Siligardi, Giuliano
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.10.2015
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.5b05059

Gold nanoparticles have been prepared and surface-functionalized with a 1:1 molar mixture of a hexylthiol ligand and a chiral mesogenic ligand consisting of a cholesterylbenzoate attached via an undecylthiol spacer. Grazing incidence X-ray diffraction showed that upon annealing a columnar liquid crystal (LC) structure develops with the nanoparticles forming strings on a regular oblique 2d lattice. Synchrotron radiation circular dichroism is substantially enhanced upon the isotropic–LC transition. In the proposed structural model, layers of Au columns rotate by a small angle relative to their neighbors, with the columns winding around a helical axis. The work demonstrates that it is possible to obtain chiral LC superstructures from nanoparticles coated with chiral mesogen without the addition of a separate LC or chiral dopants. The results provide direction in the development of plasmonic metamaterials interacting selectively with circularly polarized light.