Abstract
Abstract Metallic nanostructures with nanometer gaps support hybrid plasmonic modes with an extremely small mode volume and strong local field intensity, which constitutes an attractive plasmonic platform for exploring novel light-matter interaction phenomena at the nanoscale. Particularly, the plasmonic nanocavity formed by a metal nanoparticle closely separated from a thin metal film has received intensive attention in the nanophotonics community, largely attributed to its ease of fabrication, tunable optical properties over a wide spectral range, and the ultrastrong confinement of light at the small gap region scaled down to sub-nanometer. In this article, we review the recent exciting progress in exploring the plasmonic properties of such metal particle-on-film nanocavities (MPoFNs), as well as their fascinating applications in the area of plasmon-enhanced imaging and spectroscopies. We focus our discussion on the experimental fabrication and optical characterization of MPoFNs and the theoretical interpretation of their hybridized plasmon modes, with particular interest on the nanocavity-enhanced photoluminescence and Raman spectroscopies, as well as photocatalysis and molecular nanochemistry.
Highlights
Metallic nanostructures have played an important role nowadays in materials science and photonic research because they support localized surface plasmons (LSPs) that can strongly confine light into the deep subwavelength volume
We focus our discussion on the experimental fabrication and optical characterization of metal particle-on-film nanocavities (MPoFNs) and the theoretical interpretation of their hybridized plasmon modes, with particular interest on the nanocavity-enhanced photoluminescence and Raman spectroscopies, as well as photocatalysis and molecular nanochemistry
We comprehensively reviewed many aspects of MPoFNs, including the fabrication techniques of constructing such nanostructures with atomically smooth surface and controllable gap distance ranging from a few angstroms to tens of nanometers, the typical optical setups and configurations to characterize their plasmon responses, discussions with great details on their rich plasmon modes and promising applications in surface-enhanced Raman scattering (SERS) spectroscopy, spontaneous emission, as well as the vast potential in photocatalysis and nanochemistry
Summary
Metallic nanostructures have played an important role nowadays in materials science and photonic research because they support localized surface plasmons (LSPs) that can strongly confine light into the deep subwavelength volume. Self-assembling approach has been employed to form complex nanostructures This method allows for fabrication of plasmonic gap size with sub-nanometer scale, but accurate control over the gap size is difficult. The stacked fabrication procedure largely facilitates the integrating of various active materials into the gaps between the nanoparticles and the metal film, rendering the MPoFN a versatile plasmonic platform that has triggered a series of breakthrough in photonic research and applications, including plasmonic nanolasers at deep subwavelength scale [24], realization of huge spontaneous emission enhancement [25, 26], and more recently, single molecule-light strong coupling at room temperature [27] and single molecule optomechanics in “pico-cavities” [28]. We conclude the review by a prospective of this kind of compact nanocavities in future nanophotonic researches and applications
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