This energy transfer is more efficient and works over a greater distance than the energy transfer phenomena used in different biosensing methods. Thanks to this resonant cavity effect, the green light trapped in the microsphere then excites these red dyes very efficiently, only when they are present in the first few tens of nanometers above the surface. In collaboration with a team of chemists from the Laboratory of Bioimaging and Pathologies (LBP, University of Strasbourg/CNRS), they then placed nanoparticles loaded with red-emitting dyes close to the surface of the microsphere. For certain wavelengths, the light travels around the circumference of the sphere returning to the starting point with the same phase, forming a resonant cavity in which the light can travel from tens of thousands up to millions of revolutions before escaping. The fluorescence of the nanocrystals then excites so-called whispering gallery modes, in which the light is trapped by total internal reflection inside the microsphere. They have loaded micrometric polymer spheres with fluorescent semiconductor nanocrystals emitting in the green. Researchers from the Laboratory of Physics and Study of Materials (LPEM, ESPCI/Sorbonne University/CNRS) have highlighted a new phenomenon that could allow sensitive and simple to implement bio-detection. New challenges related to public health and the advent of personalized medicine require the development of more sensitive, easy-to-use bio-detection methods that can efficiently detect proteins or other biomolecules in a specific way.
When red dyes (dyeNP) in solution come and bind near the surface of the microsphere, for example because of the recognition of a specific biomolecule, they can then be excited by this green light, and re-emit in the red. Their green fluorescence emission is coupled with so-called whispering gallery modes, in which the light circulates and remains trapped under the surface of the microsphere. Schematic diagram : The incident blue light excites fluorescent nanocrystals ("quantum dots", QDs) placed under the surface of a polymer sphere a few micrometers in diameter. Polarisation des vallées de Dirac du bismuth par le champ magnétique Les nanoplaquettes : des nanocristaux colloïdaux bidimensionnels. Strongly correlated and low dimensionality electronic systems Nanophysics, Nanostructures and Nanomaterials Acta Applicandae Mathematicae Springer Journals Synthesis and Imaging of Inorganic Nanoprobes Finally, a 2-spinor treatment of optical geometry and geometric optics in curved spacetime is examined, leading to a description of the photon field as a section of the vertical bundle of the bundle of Riemann spheres associated with S. Then various developments are considered, concerning some features of the electromagnetic gauge and a partly new covariant description of electroweak geometry and fields. Here, first a revised version of the above mentioned geometric tools and field theory is presented, in which the geometric data consist only of a complex vector bundle S → M with two-dimensional fibres (all the needed structures are functorially derived from S any considered object which is not a functorial construction is assumed to be a dynamical field). Two-Spinors, Field Theories and Geometric Optics in Curved Spacetime Two-Spinors, Field Theories and Geometric Optics in Curved SpacetimeĪ partly new approach to 2-spinor geometry, recently developed, turns out to yield a naturally integrated formulation of Einstein–Cartan and Maxwell–Dirac fields, and to be suitable for describing several topics in field theories which are relevant to covariant quantization on curved spacetime.