Fluorescence

Fluorescence . Emission of light from a substance that has absorbed light or other electromagnetic radiation . It is a form of luminescence . In most cases, the light emitted has a shorter wavelength , and therefore less energy , than the absorbed radiation.

However, when the radiation is intense, it is possible for an electron to absorb two photons , which can result in the emission of radiation with a shorter wavelength than that absorbed. The emitted radiation can also be of the same wavelength as that absorbed, which is called resonant fluorescence .

Summary

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  • 1 History
  • 2 Applications
    • 1 Lighting
    • 2 Analytical chemistry
    • 3 Biochemistry and Medicine
  • 3 Sources

History

Fluorescent fish from the deep that uses light to attract prey

Nicolás Monardes described the phenomenon in an infusion of Eysenhardtia polystachya (tree known as Palo Dulce in Mexico ) in 1565 . The chemical compound responsible for this fluorescence is matlanin , which is the product of the oxidation of the flavonoids found in the wood of this tree. In 1819 , Edward D. Clarke and in 1822 , René Just Haüy , described fluorescence in fluorite , Sir David Brewster described it in chlorophyll in 1833, and Sir John Herschelthey did it in quinine in 1845 .

George Gabriel Stokes , in 1852 , wrote an article describing the ability of fluorite and uranium crystal to transform light above the visible spectrum into blue light. He named this phenomenon fluorescence , deriving it from the mineral fluorite ( calcium di fluoride ), which in some cases contains traces of divalent europium , which acts as a fluorescent activator to emit blue light. In another experiment, he used a prism to isolate ultraviolet radiation from sunlight and observed blue light emitted by a solution of ethanol and quinine. exposed to it.

Applications

There are many natural and synthetic compounds that exhibit fluorescence, and have a large number of applications. Some deep-sea fish use fluorescence naturally, such as the Chlorophthalmidae

illumination

Fluorescent Lamp Diagram

The most common example of the use of fluorescence is the fluorescent lamp , or cold light. Inside the glass tube there is a partial vacuum and a small amount of mercury . An electric shock causes mercury atoms to emit ultraviolet light. The inside of the tube is lined with a fluorescent compound, which absorbs ultraviolet light and emits visible light.

Fluorescent lights are more efficient than incandescent lights , in which much of the energy is released in the form of heat. However, due to the spectrum of light emitted by conventional fluorescent lamps, some colors may appear different when viewed in sunlight .

Fluorescent lights were first shown to the public in 1939 in New York . Since then, many improvements have been made, such as better fluorescent compounds, longer life, more efficiency and more comfortable shapes, such as the well-known energy saving bulbs, compact lamps, circular lamps, tubes, etc.

White light-emitting diodes (LEDs) began to be used in the mid-1990s. Blue light emitted by the semiconductor falls on a fluorescent material that emits red light, which combined with blue generates white light.

Analytic chemistry

Many analytical processes require the use of a fluorometer , usually with simple excitation frequency and simple detection frequency. These kits are capable of detecting concentrations of fluorescent molecules of up to 1 part per billion.

Biochemistry and Medicine

Cells seen by a microscope with three channels pointing out specific cellular components.

Fluorescence in these branches of science is generally used as a non-destructive mode of biological molecules using fluorescent emission at a specific frequency without the need for excitation light, since many cellular components are naturally fluorescent (a phenomenon known as intrinsic fluorescence or autofluorescence ). . In fact, a protein or other component can be marked with a special fluorescent ink, which has many biological applications.

 

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