Research projects

We use Raman spectroscopy as an advanced characterisation tool for nanotechnologies in chemistry, biochemistry, materials science, and physics. A large part of our research is aimed at understanding and improving this technique and other related spectroscopy tools, in particular surface-enhanced Raman spectroscopy (SERS). Theoretical work in electromagnetic theory, electromagnetic modeling and plasmonics is carried out in parallel to support the experimental SERS work.

Raman green laser

Current research activities

Fundamental studies

SERS is a technique which enhances the Raman scattering effect by observing molecules after their adsorption onto metallic (silver and gold) nanostructures. The enhancement can large enough to allow single molecules to be detected. This technique was discovered more than 30 years ago and has been studied extensively, but the mechanisms responsible for the effect are still debated. We design and carry out SERS experiments to probe these mechanisms and seek to answer key outstanding questions, such as: what are the origins of SERS resonances, what is the SERS cross section of a single molecule, can SERS result in optical pumping of vibrations?

Plasmonics

Prof Etchegoin with the krypton laser

SERS relies on the excitation of sub-wavelength metallic surface structures, in particular gold and silver colloids. The resulting plasmon resonances vary according to the optical properties of the substrate and have many potential applications in sub-wavelength optics. We use SERS to examine these ‘plasmon structures’ to develop theory as well as studying the plasmon resonances themselves.

SERS applications

Such is the power of SERS, that a single molecule at a femtomolar concentration can be detected by the technique. Dye molecules can be selectively attached to a protein or a tumour cell at these extremely low levels and in principle be tracked in a biological system. The numbers of molecules present, the orientation of single molecules and the features of a chemical environment can also be determined using SERS.

Electromagnetic theory and modeling

We use and develop advanced numerical tools for the modeling on plasmonic nanostructures. These include semi-analytical methods such as Mie theory for spheres and its extensions to shells and multiple spheres, T-matrix methods for non-spherical particles, and surface-integral equation and finite element methods for more complex geometries. Fundamental questions of electromagnetic theory are also investigated, for example the validity of the Rayleigh Hypothesis.

Publications

Check out the full publication list.

Available research projects

Research projects on the following topics are available on a regular basis:

  • Surface enhanced Raman scattering (SERS) of single molecules
  • Plasmonics (theory and experimental)
  • Electromagnetic theory and modeling

For more information, please contact:

Research collaborations

Our group has strong links with:

  • the ITODYS laboratory in University Paris Diderot (France)
  • Imperial College in London (UK)
  • the centro atomico Bariloche (Argentina)
  • the Nanophotonics and Metrology (NAM) lab in EPFL (Switzerland)