Mid-infrared-perturbed molecular vibrational signatures in plasmonic nanocavities

Rohit Chikkaraddy; Angelos Xomalis; Lukas A. Jakob; Jeremy J. Baumberg

doi:10.1038/s41377-022-00709-8

Mid-infrared-perturbed molecular vibrational signatures in plasmonic nanocavities

Rohit Chikkaraddy^*, Angelos Xomalis, Lukas A. Jakob, Jeremy J. Baumberg

^*Corresponding author for this work

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

3 Citations (Scopus)

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Abstract

Recent developments in surface-enhanced Raman scattering (SERS) enable observation of single-bond vibrations in real time at room temperature. By contrast, mid-infrared (MIR) vibrational spectroscopy is limited to inefficient slow detection. Here we develop a new method for MIR sensing using SERS. This method utilizes nanoparticle-on-foil (NPoF) nanocavities supporting both visible and MIR plasmonic hotspots in the same nanogap formed by a monolayer of molecules. Molecular SERS signals from individual NPoF nanocavities are modulated in the presence of MIR photons. The strength of this modulation depends on the MIR wavelength, and is maximized at the 6–12 μm absorption bands of SiO₂ or polystyrene placed under the foil. Using a single-photon lock-in detection scheme we time-resolve the rise and decay of the signal in a few 100 ns. Our observations reveal that the phonon resonances of SiO₂ can trap intense MIR surface plasmons within the Reststrahlen band, tuning the visible-wavelength localized plasmons by reversibly perturbing the localized few-nm-thick water shell trapped in the nanostructure crevices. This suggests new ways to couple nanoscale bond vibrations for optomechanics, with potential to push detection limits down to single-photon and single-molecule regimes.

Original language	English
Article number	19
Journal	Light: Science and Applications
Volume	11
Issue number	1
DOIs	https://doi.org/10.1038/s41377-022-00709-8
Publication status	Published - 19 Jan 2022

Bibliographical note

Funding Information:
The authors acknowledge support from European Research Council (ERC) under Horizon 2020 research and innovation programme PICOFORCE (Grant Agreement No. 861950), THOR (Grant Agreement No. 829067) and POSEIDON (Grant Agreement No. 861950). We acknowledge funding from the EPSRC (Cambridge NanoDTC EP/L015978/1, EP/L027151/1, EP/S022953/1, EP/ P029426/1, and EP/R020965/1). R.C. acknowledges support from Trinity College, University of Cambridge.

Publisher Copyright:
© 2022, The Author(s).

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Atomic and Molecular Physics, and Optics

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chikkaraddyr2022midinfraredperturbedFinal published version, 2.14 MBLicence: Creative Commons: Attribution (CC BY)

Cite this

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title = "Mid-infrared-perturbed molecular vibrational signatures in plasmonic nanocavities",

abstract = "Recent developments in surface-enhanced Raman scattering (SERS) enable observation of single-bond vibrations in real time at room temperature. By contrast, mid-infrared (MIR) vibrational spectroscopy is limited to inefficient slow detection. Here we develop a new method for MIR sensing using SERS. This method utilizes nanoparticle-on-foil (NPoF) nanocavities supporting both visible and MIR plasmonic hotspots in the same nanogap formed by a monolayer of molecules. Molecular SERS signals from individual NPoF nanocavities are modulated in the presence of MIR photons. The strength of this modulation depends on the MIR wavelength, and is maximized at the 6–12 μm absorption bands of SiO2 or polystyrene placed under the foil. Using a single-photon lock-in detection scheme we time-resolve the rise and decay of the signal in a few 100 ns. Our observations reveal that the phonon resonances of SiO2 can trap intense MIR surface plasmons within the Reststrahlen band, tuning the visible-wavelength localized plasmons by reversibly perturbing the localized few-nm-thick water shell trapped in the nanostructure crevices. This suggests new ways to couple nanoscale bond vibrations for optomechanics, with potential to push detection limits down to single-photon and single-molecule regimes.",

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note = "Funding Information: The authors acknowledge support from European Research Council (ERC) under Horizon 2020 research and innovation programme PICOFORCE (Grant Agreement No. 861950), THOR (Grant Agreement No. 829067) and POSEIDON (Grant Agreement No. 861950). We acknowledge funding from the EPSRC (Cambridge NanoDTC EP/L015978/1, EP/L027151/1, EP/S022953/1, EP/ P029426/1, and EP/R020965/1). R.C. acknowledges support from Trinity College, University of Cambridge. Publisher Copyright: {\textcopyright} 2022, The Author(s).",

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Mid-infrared-perturbed molecular vibrational signatures in plasmonic nanocavities

Abstract

Bibliographical note

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