Fluorescence Definition and 13 Discussions

Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. The most striking example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, while the emitted light is in the visible region, which gives the fluorescent substance a distinct color that can be seen only when exposed to UV light. Fluorescent materials cease to glow nearly immediately when the radiation source stops, unlike phosphorescent materials, which continue to emit light for some time after.
Fluorescence has many practical applications, including mineralogy, gemology, medicine, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, biological detectors, cosmic-ray detection, vacuum fluorescent displays, and cathode-ray tubes. Its most common everyday application is in energy-saving fluorescent lamps and LED lamps, where fluorescent coatings are used to convert short-wavelength UV light or blue light into longer-wavelength yellow light, thereby mimicking the warm light of energy-inefficient incandescent lamps.
Fluorescence also occurs frequently in nature in some minerals and in many biological forms across all kingdoms of life. This is sometimes referred to as biofluorescence to indicate that the fluorophore derives from a living organism (as opposed to artifically adding a dye or stain). However, in many cases the substance may be fluorescent even if the organism is dead, thus fluorescence is still the preferred term.

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  1. RooneyChemistry

    Fluorescent Sample with Cuvette but not with Plate -- Why?

    I am doing an assay where the formed compound is fluorescent when I use a cuvette in a fluorometer, but not when I put the same sample into the well of a 96 well plate. Why is this? The fluorometer reads from the top and the plates I am using are 96 well plates, black, flat-bottomed well...
  2. dykuma

    A A mathematical description of the physics behind Aurora?

    Maybe a bit of an odd question (not really sure where it would belong on this site to be honest), but I was wondering if anyone can explain, or at least knows of a source that explains in a quantitative way, the physics behind aurora? Now I've seen websites like this that discuss conceptually...
  3. littledog

    Nucleic dye in bacteria

    I found that it's difficult to stain dormant bacteria or bacteria in lag phase with Nucleic acid dye like SYTO9/SYBR Green Ⅰ, does anyone know why? DNA 3D structure too complex? DNA binding protein too much? Low material transport efficiency in bacteria? Or anyother factors? Is there any...
  4. L

    Intensity characterization of laser pulses

    754/5000 I am using the fluroescence spectroscopy technique to obtain the fluorescence spectrum of exposed neuroblasts to uv radiation (355 nm) from a Nd:YAG source and I need to characterize the radiation pulses of the laser. Specifically, I use a spectrometer (Avantes brand) with integration...
  5. S

    Why Fluorescence is detected @right angle to the excitation?

    Hi everybody, I would like to know what would be the best angle (or best geometry) to put the detector relative to the light source in order to observe the emission radiation from the fluorescent materials? As I know the most common geometry used for fluorescence is right angle observation...
  6. H

    Looking for the right fluorescent compound

    Hi I'm searching for one or more fluorescent compounds with the following characteristics: 1. High quantum efficiency > 0.85 2. 200-400nm excitation range. 3. Approximately 440nm, 625nm or 678nm emmission range 4. Decent stability (At least 30 days) Does anyone know of a either specific...
  7. patrickbotros

    Explain Different Types of Light Microscopy

    Okay so first I would like someone to add detail to my descriptions of different types of light microscopy. Here's what I know: Brightfield (unstained): standard view of partially opaque, live cells. Brightfield (stained): standard view of colored, dead cells. Phase Contrast: Not sure how it...
  8. G

    Fluorescent lamp: who emits UV?

    Hi everyone, searching on the web about how the fluorescent lamps work, I cannot understand if the UV is emitted by the noble gas or the mercury. For what I understand, both of them ionize, and the UV light is emitted after the collision of the electrons with the atoms, but I would like to...
  9. B0b-A

    Can pure water fluoresce ?

    Can pure* water be made to fluoresce if illuminated by some particular frequency of Ultra-Violet light ? [* No chemicals added ]
  10. G

    Dichroic mirrors that reflect two wavelengths

    In fluorescence microscopy, dichroic mirrors reflect light under a critical wavelength (used to excite the sample) and transmit light over a critical wavelength (emission light from the sample). Are there mirrors that reflect two different wavelengths of light and transmit the rest? Essentially...
  11. S

    488nm LED's?

    Why can't I find any LED's at 488nm? I am trying to find a cheaper light source than the traditional argon ion laser for a possible fluorescence activated cell sorter. See link below for schematic. Does anybody know a good retail site for lights in this spectrum I can't find good results with...
  12. N

    Is CFL an inductive load?

    As far as I know, Compact Fluorescent Lamp (CFL) is an inductive load. I understand that inductive load doesn't allow an immediate change in current. When the circuit was initially open (through open switch) then became close, the inductive load was energized. So opening again the circuit after...
  13. B

    Bi-directional transport of light

    In several fiber-optic-based probes in medical imaging fields, the light travels towards an object through an optical fiber (or even free space), interacts with the object and then travels back through the same fiber (or the same path in free space) and is captured by a camera or photodetector...