Abstract: Recent advances in nanophotonics open the way for promising applications towards efficient single molecule fluorescence analysis. In this review, we discuss how photonic methods bring innovative solutions for two essential questions: how to detect a single molecule in a highly concentrated solution, and how to enhance the faint optical signal emitted per molecule? The focus is set primarily on the widely used technique of fluorescence correlation spectroscopy (FCS), yet the discussion can be extended to other single molecule detection methods.
The Fresnel Institute at the University of Marseilles (http://www.fresnel.fr), a leading laboratory in the field of Optics, Electromagnetism and Image Processing invites applications for an Associate Professor level position in the field of Biophotonics.
Outstanding candidates with demonstrated excellence in basic research in linear and nonlinear optical microscopy will have high priority. Expertise in nanoparticles fabrication and/or bio-labelling, optical field enhancement with nanostructure for bio-detection will be appreciated. Responsibilities will include conducting basic laboratory research in the Mosaic group http://www.fresnel.fr/mosaic) together with teaching (in French) at undergraduate and graduate levels at the University of Marseilles (Université de Provence) .
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Intensity is not enough. Many techniques in optical microscopy take advantage of analysis methods based on single molecule detection events. These measurements provide access to a wide variety of data such as local concentration, structure or mobility of molecules. However, single molecule detection is a challenging task, which requires complex microscope apparatus and is very difficult to take out of the lab.
A mobile endoscope to observe single molecules.
On collaboration with Bordeaux I University (France), my team has recently demonstrated the possibility to detect single fluorescent molecules with an optical fiber. The original system contains a glass microbead at the end of the optical fiber which works as a tiny lens to focus light. The fiber-microbead ensemble is also used to collect the low amount of light emitted by the individual molecules. That way, the bulky microscope is replaced by a remote fiber sensor connected to a miniaturized USB-connected device. This patented technique opens biomedicine and environment monitoring to single molecule analysis.
ReferenceH. Aouani, F. Deiss, J. Wenger, P. Ferrand, N. Sojic, H. Rigneault, "Optical-fiber-microsphere for remote fluorescence correlation spectroscopy", Optics Express 17, 18912-18919 (2009)
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“Imaging chromophores with undetectable fluorescence by stimulated emission microscopy”, Wei Min, Sijia Lu, Shasha Chong, Rahul Roy, Gary R. Holto, X. Sunney Xie, Nature 461, 1105-1109 (2009)
Fluorescence, that is, spontaneous emission, is generally more sensitive than absorption measurement, and is widely used in optical imaging. However, many chromophores, such as haemoglobin and cytochromes, absorb but have undetectable fluorescence because the spontaneous emission is dominated by their fast non-radiative decay. Yet the detection of their absorption is difficult under a microscope. Here we use stimulated emission, which competes effectively with the nonradiative decay, to make the chromophores detectable...
« Optical Antennas », Palash Bharadwaj, Bradley Deutsch, and Lukas Novotny, Advances in Optics and Photonics 1, 438–483 (2009) doi:10.1364/AOP.1.000438
Optical antennas are an emerging concept in physical optics. Similar to radiowave and microwave antennas, their purpose is to convert the energy of free propagating radiation to localized energy, and vice versa...
« Photonic Nanojets », Alexander Heifetz, Soon-Cheol Kong, Alan V. Sahakian, Allen Taflove, and Vadim Backman, Journal of Computational and Theoretical Nanoscience 6, 1979–1992 (2009).This paper reviews the substantial body of literature emerging since 2004 concerning photonic nanojets. The photonic nanojet is a narrow, high-intensity, non-evanescent light beam that can propagate over a distance longer than the wavelength λ after emerging from the shadow-side surface of an illuminated lossless dielectric microcylinder or microsphere of diameter larger than λ...