Jerome Wenger NanoBioPhotonics

On January 05-06th, the entire Fresnel Institute will be evaluated regarding its activities during the 2007-2010 period. The final slide of my presentation for this evaluation will summarize the main achievements (see the links to read more):

2007: live cell membrane investigations with nanoapertures

2008: complete fluorescence characterization in nanoapertures & microsphere-enhanced fluorescence

2009: 100x speed increase in FCS measurements & crucial role of the gold adhesion layer in plasmonics

2010: smallest single molecule fluorescence endoscope & quantum dots to probe nanoantennas

As I will go through several evaluation processes in 2011 (for fundings, CNRS progress...), I hope this type of slide may also help.

A certain fraction of the visits paid to my blog every month come here through searching for surface-enhanced fluorescence. So I guess writing up a few words about this effect isn't totally useless...

Surface-enhanced fluorescence deals with the improvement (enhancement) of the detection sensitivity for fluorescent molecules. Increasing the emission rate of fluorescent molecules and/or shaping their emission properties (lifetime, spectrum, polarization,...) is generally performed close to metal surfaces that are textured on the nanometer scale. The idea behind the use of metals is to take advantage of surface plasmon resonances, that couple light to collective oscillations of electrons in the metal, and give rise to huge electromagnetic intensity enhancements close to metal surfaces.

Up to a certain extend, it is the equivalent for fluorescence that surface-enhanced Raman spectroscopy (SERS) is for Raman scattering. The main difference is that Raman scattering is insensitive to quenching losses to the metal, whereas fluorescence in the very close vicinity to metal surfaces (< 5nm) is dominated by non-radiative energy transfer to the metal, which imposes a trade-off between gain and losses.

I highly recommend reading the following references (I don't get any money for advertising):

- Principles of Nano-Optics, by L. Novotny and B. Hecht

- Principles of Fluorescence Spectroscopy, by J. R. Lakowicz

- Radiative decay engineering 5: metal-enhanced fluorescence and plasmon emission, J. R. Lakowicz, Analytical Biochemistry 337 (2005) 171–194

- Surface enhanced fluorescence, E. Fort and S. Gresillon, J. Phys. D: Appl. Phys. 41 (2008) 013001.

- You may also have a look at my own work, mostly on nanoaperture-enhanced detection of fluorescent molecules in solution (see the selected papers, a citation is always appreciated )

My colleague Renaud Bachelot will give a seminar on plasmonic nanosources of light during the next annual meeting of the French Observatory of Micro and Nano Technologies OMNT.

If you have the opportunity to attend to this series of seminars, don't miss it. The general quality is very high, and I'm sure Renaud will do an excellent job. Inscriptions go here.

Currenly open is a position for undergraduate internship training project working on nanophotonics for advanced fluorescence sensing and single molecule detection. More details are given here.

Relevant candidates have a physics, biophysics or engineering background, with a strong motivation and willingness to join a multidisciplinary international team.

The position can be continued as PhD project, conditionnal to the succesful application for a PhD grant.

According to national rules, undergraduate trainees will be supported by a monthly grant of 398,13 € (only valid or training periods longer than two months).

My team has recently published a study on second harmonic generation on single gold nanoapertures. This was released in the December 1st issue of Optics Letters. You can find a free reprint here.

Metal nanostructures are interesting emitters for second harmonic generation (SHG) radiation, which occurs essentially from the non-centrosymmetry breaking at the metal-medium interface for objects of the order of 50nm-100nm size.
At MOSAIC we demonstrate the ability of single-subwavelength-size nanoapertures fabricated in a gold metal thin film to enhance second-harmonic generation (SHG) as compared to a bare metal film. Nonlinear microscopy imaging with polarization resolution is used to quantify the SHG enhancement in circular and triangular nanoaperture shapes.

This study has two main results:
* The SHG enhancement on circular nanoapertures is demonstrated to originate from both phase retardation effects and field enhancements at the aperture edge.
* Triangular nanoapertures exhibit superior SHG enhancement compared with circular ones, as expected from their noncentrosymmetric shape.