Rechercher
Fluorescence, a light born from light
When a substance absorbs light in certain regions of the visible spectrum, i.e. at certain wavelengths, it appears coloured. If an object illuminated with white light appears red for example, it is because it absorbs all the radiations except those in the red region, which are reflected. These are colours by absorption, often referred to as chemical colours because they depend on the chemical nature of the substance.
Following the absorption of light, some substances can emit light : this is the phenomenon of fluorescence. The colour of the light emitted is directly related to the fluorescence spectrum (fluorescence intensity changes according to the wavelength). This spectrum is usually found at greater wavelengths than those at which the substance absorbs. The colour of the light emitted by fluorescence is superimposed on the colour by absorption, described above. A fluorescent object therefore appears in a particularly bright colour, commonly referred to as "fluo" colour.
The chemists and physico-chemists from the ENS Cachan have long been studying the interactions of light with molecules and supermolecules, and particularly the resulting fluorescence emission. They develop new fluorescent molecules and supermolecules, particularly with a view to producing sensors.
The fluorescence phenomenon frequently occurs in everyday life. The fluorescent compounds used for common objects are mostly organic dyes such as fluorescein, rhodamines, coumarins, etc., while inorganic compounds are used in fluorescent tubes and lamps, and for security marking.
Laboratoire de photophysique et photochimie supramoléculaires et macromoléculaires, CNRS-ENS Cachan
Facebook
Twitter