Jerome Wenger NanoBioPhotonics

Förster resonance energy transfer (FRET) is widely used as a molecular ruler to monitor biomolecular conformations and interactions dynamics. However, an intrinsic limitation in FRET is that the signal decreases very rapidly with the dye to dye distance, and FRET is generally not detectable anymore beyond 10 nm.

In a recent paper published in ACS Nano, we use nanoapertures milled in an aluminum film (called zero-mode waveguides ZMW) to overcome the spatial range limit in FRET. Our optimized structures creates favorable conditions to enhance the FRET efficiency by 3-fold at a large donor-acceptor distance of 13.6 nm, well beyond the classical Förster radius.

Significance:

- We demonstrate that ZMWs can extend the spatial range of FRET to distances where dipole-dipole interactions would otherwise be too weak to produce detectable FRET signals.

- ZMWs can be combined with molecular constructs featuring multiple acceptor dyes to further improve the FRET efficiency and extend the spatial range.

- General guidelines are discussed for performing quantitative FRET measurements inside ZMWs and nanoapertures and apply our approach for biophysics and biochemistry applications.

Also freely available on ArXiv 1907.03734

Optical absorption in plasmonic structures lead to a local temperature increase. It was long assumed that in the case of nanoapertures, the extended metal layer was acting as an efficient heat sink to mitigate the warming. However, the reality is that temperature increases higher than 10°C can be readily achieved in gold apertures illuminated by a tightly focused infrared beam of mW power. We find this in a recent article published in ACS Photonics, as we develop three independent fluorescence readouts to measure locally the temperature in single and double nanoholes.

Significance:

- We provide a clear quantification of the temperature increase in nanoaperture-based optical tweezers

- We establish several methods to locally measure the temperature by recording fluorescence properties (intensity, diffusion time and lifetime). These approaches can be easily implemented and applied to other nanophotonic systems.

- The easy control of the temperature inside nanoapertures opens their use for thermoplasmonics in confined sub-femtoliter volumes for nucleation, polymerization or crystal growth applications.

Also freely available on ArXiv 1906.01947.

As a teaser to Jerome's talk at the Institut Fresnel PhD days next Thursday, here is a video of the scientific communication expert and gourou Jean-Luc Doumont. The slides can be found on the Principiae website here, along with many other stimulating resources. Jean-Luc Doumont's book "Trees, maps and theorems" should be a must-have for every scientist.

On May 25th, we will present several demonstration experiments about manipulating light with optics. This year, we have a special celebration with the bicentenary of Augustin Fresnel's theory of diffraction, and we will be redoing the historical Fresnel Arago experiment.

Venue and schedule are detailed here.

Our coworker Kaizad Rustomji recently got awarded the thesis prize of the Doctoral School "Physics and Sciences of the Matter" for his PhD work. Congratulations Kaizad for this well-deserved prize!

You can read more about Kaizad's work here.