Skip to main content

EELS

Scientific highlights

Tailored nanoscale plasmon-enhanced vibrational electron spectroscopy

Toc.png

Atomic vibrations and phonons are an excellent source of information on nanomaterials that we can access through a variety of methods including Raman Scattering, infrared spectroscopy, and electron energy-loss spectroscopy (EELS). In the presence of a plasmon local field, vibrations are strongly modified, and in particular, their dipolar strengths are highly enhanced, thus rendering Raman scattering and infrared spectroscopy extremely sensitive techniques. Here, we experimentally demonstrate that the interacion between a relativistic electron and vibrational modes in nanostructures is fundamentally modified in the presence of plasmons. We finely tune the energy of surface plasmons in metallic nanowires in the vicinity of hexagonal boron nitride, making it possible to monitor and disentangle both strong phonon-plasmon coupling and plasmon-driven phonon enhancement at the nanometer scale. Due to the near-field character of the electron beam-phonon interaction, optically-inactive phonon modes are also observed. Read more »

Plasmonic quantum size effects in silver nanoparticles are dominated by interfaces and local environments

Campos.jpg

The physical properties of metals change when their dimensions are reduced to the nano-scale and new phenomena such as the localized surface plasmon resonance (LSPR) appear. This collective electronic excitation can be tuned over a large spectral range by adapting the material, size and shape. The existing literature is as rich as it is controversial—for example, size-dependent spectral shifts of the LSPR in small metal nanoparticles, induced by quantum effects, are reported to the red, to the blue or entirely absent. Here we report how complementary experiments on size-selected small silver nanoparticles embedded in silica can yield inconsistent results on the same system: whereas optical absorption shows no size effect in the range between only a few atoms and ~10 nm, a clear spectral shift is observed in single-particle electron spectroscopy. Our quantitative interpretation, based on a mixed classical/quantum model, resolves the apparent contradictions, not only within our experimental data but also in the literature. Our comprehensive model describes how the local environment is the crucial parameter controlling the manifestation or absence of quantum size effects. Read more »

Publications

de Seauve, V., et al. Spectroscopies and electron microscopies unravel the origin of the first colour photographs. Angewandte Chemie International Edition (2020).doi:10.1002/anie.202001241
Saito, H., et al. Emergence of point defect states in a plasmonic crystal. Physical Review B 100, (2019).
Yankovich, A.B., et al. Visualizing spatial variations of plasmon-exciton polaritons at the nanoscale using electron microscopy. Nano Letters (2019).doi:10.1021/acs.nanolett.9b03534
Campos, A., et al. Plasmonic quantum size effects in silver nanoparticles are dominated by interfaces and local environments. Nature Physics (2018).doi:10.1038/s41567-018-0345-z Download: CNP.pdf (1.79 MB)
Lourenço-Martins, H., Das, P., Tizei, L.H.G., Weil, R. & Kociak, M. Self-hybridization within non-Hermitian localized plasmonic systems. Nature Physics 89, (2018). Download: LM2018.pdf (3.41 MB)
Syndicate content