In a collaboration between the Fresnel Institute and ICFO-the Institute for Photonic Sciences, we report in Nature Nanotechnology a novel “antenna-in-box” platform for single molecule fluorescence detection with unprecedented resolutions and sensitivity. The innovative approach combines a plasmonic gap antenna for ultra-high fluorescence enhancement with a metal nanoaperture for optimized background-free operation. It allows for 1100-fold fluorescence brightness enhancement together with detection volumes down to 58 zeptoliters (1 zL = 1e-21L), realizing a gain of four orders of magnitude as compared to classical microscopes. The antenna-in-box offers a highly efficient platform for nanoscale biochemical assays with single molecule sensitivity at physiological conditions.
Submissions and registrations for the 3rd Summer School On Plasmonics are now open. This summer school will bring together international specialists in Plasmonics on one of the most beautiful islands of the Mediterranean. Check out the exciting program and the list of invited speakers at http://www.fresnel.fr/ssop3/
11 courses and 2 tutorials will be presented by international specialists on the following topics:
-Light scattering by metallic particles
-Limits of diffraction
-Dielectric permittivity of metals
-Nonlocal and quantum effects
-Quantum Plasmonics and Magnetic Metafluids
-3D optical metamaterials and transformation optics
-Optical spectroscopy of metal nanoparticles
Deep's abstract on Plasmonic nanoantennas for enhanced single molecule analysis at micromolar conentrations has just been promoted for invited talk presentation at the 6th International Conference on Surface Plasmon Photonics SPP6.
As a teaser, our main claims are:
- fluorescence enhancement up to 1100-fold AND fluorescence brightness per molecule up to 400kHz (detected)
- detection volume measured down to 58 zeptoliters, four orders of magnitude below the diffraction limit
- true single molecule detection above 20 µM concentration actually measured
- our dedicated design is fully compatible with detection of single fluorescent molecules in solution and fluorescence correlation spectroscopy
Optical fiber probes are generating a large interest to develop portable fluorescence spectrometers. However, the sensitivity of conventional fibers is severely limited by the high luminescence background generated in the glass and the low collection efficiency of fibers.
We solve this issue in a recent Optics Express publication by using a hollow core photonic crystal fiber probe combined with a polystyrene microsphere. Thanks to the hollow-core photonic crystal fiber, the background noise is reduced by two orders of magnitude. Thanks to the microsphere, the excitation beam is further focused and the fluorescence collection efficiency is improved. As compared to the previous state-of-the-art, we report a 200x improvement of the signal-to-noise ratio for single molecules detection events, together with a 1000x gain on the minimum detectable concentration.
Our approach takes advantage of a polystyrene microsphere directly set at the fiber end-face to focus the fiber mode down to a spot of 540 nm FHWM. These results and their application for fluorescence imaging and direct laser writing have been reported in Applied Optics.
We believe that this device offers new opportunities for remote or in vivo optical characterization together with a miniaturization of bulky microscope setups. Applications include inspection of semiconductor wafers, photolithography, laser surgery, and fluorescence sensing.