Tuning the properties of optical metamaterials in real time is one of the grand challenges of photonics. Being able to do so will enable a class of adaptive photonic materials for use in applications such as surface enhanced Raman spectroscopy and reflectors/absorbers. One strategy to achieving this goal is based on the electrovariable self-assembly and disassembly of two-dimensional nanoparticle arrays at a metal | liquid interface. As expected, the structure results in plasmonic coupling between NPs in the array but perhaps as importantly between the array and the metal surface. In such a system, the density of the nanoparticle array can be reversibly controlled by the variation of electrode potential. Theory suggests that due to a collective plasmon-coupling effect less than 1 V variation of electrode potential can give rise to a dramatic simultaneous change in optical reflectivity from ∼93% to ∼1% and the amplification of the SERS signal by up to 5 orders of magnitude. This is experimentally demonstrated using a platform based on the voltage-controlled assembly of 40 nm Au-nanoparticle arrays at a TiN/Ag electrode in contact with an aqueous electrolyte. We show that all the physics underpinning the behavior of this platform works precisely as suggested by the proposed theory, setting the electrochemical nanoplasmonics as a promising direction in photonics research.
Bibliographical noteFunding Information:
The work was supported by an Engineering and Physical Sciences Research Council grant, “Electrotunable Molecular Alarm”, EP/L02098X/1. J.B.E. also acknowledges receipt of European Research Council consolidator grant (NanoPD). Y.M. has been supported in part by a China Scholarship Council-Imperial Scholarship (201506320194). L.V. and D.S. acknowledge the support of Marie Skłodowska-Curie fellowships, N-SHEAD and S-OMMs, respectively. D.J.K. and S.-H.O. acknowledge support from Seagate Technology through the Centre for Micromagnetics and Information Technologies (MINT) at the University of Minnesota.
Copyright © 2019 American Chemical Society.
- surface enhanced Raman spectroscopy
PubMed: MeSH publication types
- Journal Article