Supramolecular assembly facilitating adsorbate-induced chiral electronic states in a metal surface

Bovet, N., McMillan, N., Gadegaard, N. and Kadodwala, M. (2007) Supramolecular assembly facilitating adsorbate-induced chiral electronic states in a metal surface. Journal of the American Chemical Society, 111(33), pp. 10005-10011. (doi: 10.1021/jp074056s)

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Through the application of optically active second-harmonic generation measurements (OA-SHG) we have demonstrated that the adsorption of amino acids cysteine (HSCH<sub>2</sub>CHNH<sub>2</sub>COOH) and penicillamine (HSC(CH<sub>3</sub>)2CHNH<sub>2</sub>COOH) from solution can induce chiral electronic states in an initially achiral polycrystalline Au film. The chiral induction is strongly dependent upon the pH of the deposition solution; adsorption of penicillamine and cysteine under acidic conditions (pH = 3) induces the same level of optical activity, whereas at pH = 11, the optical activity induced by cysteine is reduced by ca. 50% and penicillamine does not induce optical activity at all. The pH dependence indicates that the presence of interadsorbate hydrogen bonds, and consequently the supramolecular assembly of the adsorbates, facilitates the induction of chiral electronic states in the Au surface. This observation demonstrates that the symmetry properties of the extended structure of the self-assembled layer, and not the local adsorption geometry of the isolated adsorbed moiety, play the lead role in the induction of chiral metallic electronic states. The dependence of the chiral induction on COOH groups is identical to that observed in studies of optical activity in chiral thiol-protected nanoparticles, suggesting a common mechanism for the chiral perturbation in extended films and nanoparticles.

Item Type:Articles
Glasgow Author(s) Enlighten ID:McMillan, Miss Nicola and Kadodwala, Professor Malcolm and Gadegaard, Professor Nikolaj
Authors: Bovet, N., McMillan, N., Gadegaard, N., and Kadodwala, M.
College/School:College of Science and Engineering > School of Chemistry
College of Science and Engineering > School of Engineering > Biomedical Engineering
Journal Name:Journal of the American Chemical Society
Publisher:American Chemical Society
ISSN (Online):1520-5126
Published Online:28 July 2007

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
397491Adventurous research in chemistry: from proteins to surfaces (pushing the limits of powder diffraction; towards protein crystallography on a laboratory powder diffractometer)C GilmoreEngineering & Physical Sciences Research Council (EPSRC)EP/C532236/1Chemistry