Fluorescence spectroscopy or fluorometry is a type of electromagnetic spectroscopy used for analyzing fluorescent spectra. It involves using a beam of light, usually ultraviolet light, that excites the electrons in molecules of certain compounds and causes them to emit light of a lower energy, typically, but not necessarily, visible light. A complementary technique is absorption spectroscopy. Electromagnetic spectroscopy a. ... A fluorescence spectrum is an electromagnetic spectrum that describes fluorescent radiation. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... Absorption spectroscopy is an analytical tool used by chemists. ...

Theory

Molecules have various states referred to as energy levels. Fluorescence spectroscopy is primarily concerned with electronic states and vibrational states. Generally, the species being examined will have a ground electronic state (a low energy state) of interest, and an excited electronic state of higher energy. Each of these electronic states has various vibrational states. An energy level is a quantified stable energy, which a physical system can have; the term is most commonly used in reference to the electron configuration of electrons, in atoms or molecules. ...

Photons of light are small "packets" of energy, each with an energy proportional to its frequency; photons of high frequency light have higher energy than those of low frequency light. These can be absorbed by molecules, with the molecule gaining the energy of the photon, or emitted by molecules, with the photon carrying some of the energy of the molecule away.

In fluorescence spectroscopy, the species is first excited, by absorbing a photon of light, from its ground electronic state to one of the various vibrational states in the excited electronic state. Collisions with other molecules cause the excited molecule to lose vibrational energy until it reaches the lowest vibrational state of the excited electronic state. The photon can be perceived as a wave or a particle, depending on how it is measured In physics, the photon (from Greek φοτος, meaning light) is a quantum of the electromagnetic field, for instance light. ...

The molecule then drops down to one of the various vibrational levels of the ground electronic state again, emitting a photon in the process. As molecules may drop down into any of the vibrational levels of this ground state, the photons will have different energies, and thus frequencies. Therefore, by analysing the different frequencies of light emitted in fluorescent spectroscopy, the structure of these different vibrational levels can be determined.

Fluorometer

A fluorometer measures fluorescence. Fluorescence induced by exposure to ultraviolet light in vials containing various sized cadmium selenide (CdSe) quantum dots. ...

Types

• Filter fluorometers use filters to isolate the incident light and fluorescent light.
• Spectrofluorometers use diffraction grating monochromators to isolate the incident light and fluorescent light. In these devices, the spectrum can consist of the intensity of emitted light as a function of the wavelength of either the incident light (excitation spectrum) or the emitted light, or both.

A filter fluorometer is a type of fluorometer that may be employed in fluorescence spectroscopy. ... The incident ray is the ray of light that strikes the surface before reflection, transmission, or absorption. ... A compact fluorescent lamp A fluorescent lamp is a type of electric lamp that excites argon and mercury vapor to create luminescence. ... The spectrofluorometer is an instrument which takes advantage of fluorescent properties of some compounds in order to provide information regarding their concentration and chemical environment in a sample. ... A huge diffraction grating. ... A monochromator is an optical device that transmits a mechanically selectable narrow band of wavelengths of light chosen from a wider range of wavelengths available at the input. ... The noun spectrum (plural: spectra) has a variety of meanings. ...

Analysis of data

There is a relationship between concentration and fluorescence intensity. Concentration is a very common concept used in chemistry and related fields. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized cadmium selenide (CdSe) quantum dots. ... In physics, intensity is a measure of the time-averaged energy flux. ...

Applications

It used in, among others, biochemical, medical, and chemical research fields, for analysing organic compounds. There has been report of its use in differentiating malign skin tumours from benign. Organic has several meanings and related topics. ...

See also

• Confocal microscopy
• Fluorescence Correlation Spectroscopy
• X-ray fluorescence spectroscopy.
• Beer's law