Observing single molecules complexing with cucurbit[7]uril through nanogap surface-enhanced Raman spectroscopy

Sigle, Daniel Oliver, Kasera, Setu, Herrmann, Lars Oliver, Palma, Aniello, de Nijs, Bart, Benz, Felix, Mahajan, Sumeet, Baumberg, Jeremy J. and Scherman, Oren A. (2016) Observing single molecules complexing with cucurbit[7]uril through nanogap surface-enhanced Raman spectroscopy. The Journal of Physical Chemistry Letters, 7 (4), 704-710. (doi:10.1021/acs.jpclett.5b02535).

Abstract

In recent years, single molecule sensitivity achievable by surface-enhanced Raman spectroscopy (SERS) has been widely reported. We use this to investigate supramolecular host-guest chemistry with the macrocyclic host cucurbit[7]uril, on a few-to-single molecule level. A nanogap geometry, comprising individual gold nanoparticles on a planar gold surface spaced by a single layer of molecules, gives intense SERS. Plasmonic coupling between the particle and the surface leads to strongly enhanced optical fields in the gap between them, with single molecule sensitivity established using a modification of the well-known bi-analyte method. Changes in the Raman modes of the host molecule are observed when single guests included inside its cavity internally stretch it. Anisotropic intermolecular interactions with the guest are found which show additional distinct features in the Raman modes of the host molecule.

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Contributors

Author: Sumeet Mahajan

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