title: Unfolding the contents of sub-nm plasmonic gaps using normalising plasmon resonance spectroscopy.
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.
authors: NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thompson Ave, Cambridge, CB3 0HE, UK. jjb12@cam.ac.uk.
authors: Bart
authors: B
authors: de Nijs
authors: Richard W
authors: RW
authors: Bowman
authors: Lars O
authors: LO
authors: Herrmann
authors: Felix
authors: F
authors: Benz
authors: Steve J
authors: SJ
authors: Barrow
authors: Jan
authors: J
authors: Mertens
authors: Daniel O
authors: DO
authors: Sigle
authors: Rohit
authors: R
authors: Chikkaraddy
authors: Anna
authors: A
authors: Eiden
authors: Andrea
authors: A
authors: Ferrari
authors: Oren A
authors: OA
authors: Scherman
authors: Jeremy J
authors: JJ
authors: Baumberg