Unfolding the contents of sub-nm plasmonic gaps using normalising plasmon resonance spectroscopy

Bart de Nijs, Richard W. Bowman, Lars O. Herrmann, Felix Benz, Steve J. Barrow, Jan Mertens, Daniel O. Sigle, Rohit Chikkaraddy, Anna Eiden, Andrea Ferrari, Oren A. Scherman, Jeremy J. Baumberg

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

Plasmonic coupling of gold nanoparticles to a gold surface creates intense plasmonic hot spots with large electromagnetic field-enhancements within the cavity formed by the two metallic surfaces. The localised field in such structures is extremely sensitive to morphological fluctuations and subtle changes in the dielectric properties of the cavity contents. Here, we present an optical method that pins down the properties of the gap contents with high sensitivity, termed normalising plasmon resonance (NPR) spectroscopy. We use this on a variety of ultrathin molecular spacers such as filled and empty cucurbiturils, and graphene. Clear differences in the spectral positions and intensities of plasmonic modes observed in the scattering spectrum resolve thickness differences of 0.1 nm, and refractive index changes from molecular filling.
Original languageEnglish
Pages (from-to)185-193
Number of pages9
JournalFaraday Discussions
Volume178
Early online date14 Nov 2014
DOIs
Publication statusPublished - 1 Jun 2015

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