Fluorescence, Chinese words.Also called "fluorescent", it refers to a kind of photoluminescentluminescence Phenomenon.When a substance at normal temperature passes throughincident light(Usuallyultraviolet raysorX-ray）Irradiation, entering after absorbing light energyexcited stateAnd immediately de excitation and emit the output light longer than the wavelength of the incident light (usually the wavelength isvisible lightBand);Once many fluorescent materials stop incident light, the luminescence phenomenon will disappear immediately.The outgoing light with this property is called fluorescence.In addition, some substances can emit light for a long time after the incident light is removed. This phenomenon is called afterglow.In daily life, people generally refer to all kinds of weak lights as fluorescence in a broad sense, without carefully investigating and distinguishing their luminous principles.Also refers to low temperature (not color temperature)Cold light。
Chinese name
fluorescence
Foreign name
fluorescence
Alias
Fluorescence
Pinyin
yíng guāng
Interpretation
A cold luminescence phenomenon of photoluminescence
Light hits someAtomic time, the energy of lightNucleusSome of the surrounding electrons have jumped from the original orbit to the higher energy orbit, that is, fromground stateTransition to the first excitationSinglet stateOr the second excited singlet state.The first excited singlet state or the second excited singlet state is unstable, so the ground state will be recovered. When the electron recovers from the first excited singlet state to the ground state, the energy will be released in the form of light, so fluorescence will be generated.
Fluorescence is the absorption of light or other substanceselectromagnetic radiationThe light emitted after.In most cases, the emission wavelength is longer than the absorption wavelength, and the energy is lower.But whenAbsorption strengthWhen the wavelength is larger, two-photon absorption may occur, which may lead to the situation that the radiation wavelength is shorter than the absorption wavelength.When the radiation wavelength is equal to the absorption wavelength, it isResonance fluorescence。A common example is material absorptionultraviolet, emitting visible band fluorescenceFluorescent lampThis is the principle of coatingPhosphorAbsorb the ultraviolet light emitted by mercury vapor in the lamp tube, and then emitted by phosphorvisible lightTo make it visible to the human eye.
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Cadmium selenide quantum dots emit fluorescence under ultraviolet irradiation
(4) Fluorescencequantum yield Q: Quantum yield indicates that the material will absorbLight energy conversionThe ability of fluorescence is the emission of fluorescent substancesPhoton numberRatio to the number of photons absorbed.
(5) Stokes displacement: Stokes displacement is the maximum fluorescence emission wavelength andMaximum absorptionDifference in wavelength.
（6）fluorescence lifetime: When a bundlePhotoexcitationWhen a fluorescent substance is used, its molecule will jump from the ground state to a certain state after absorbing energyexcited stateAnd then emit fluorescence in the form of radiation to return to the ground state. When the excitation stops, the time required for the fluorescence intensity of the molecule to reduce to 1/e of the maximum excitation intensity is the fluorescence lifetime.[1]
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lighting
Fluorescent lamp
commonFluorescent lampThis is an example.The inside of the lamp tube istake a percentageVacuum and inject a small amount ofMercury。The discharge of the lamp electrode causes mercury to emitUltraviolet bandLight.These ultraviolet lights are invisible and harmful to human body.So the inner wall of the lamp tube is covered with a layer of material called phosphor, which can absorb those ultraviolet light and emitvisible light。
Capable of emitting white lightlight-emitting diode(LED) is based on a similar principle.The light emitted by the semiconductor is blue. These blue lights can excite phosphors (fluorescents) attached to the reflector electrode to make them emit orange fluorescence. When the two colors of light are mixed, they will approximately present white light.
Highlighter YesFluorescent agent, it encounteredultraviolet rays（sunlight、Fluorescent lamp、Mercury lampMore) will produce fluorescent penFluorescence effect, emitting white light, so that the color looks dazzling fluorescent.The fluorescence of the fluorescent pen and our watcheslight stickThe fluorescence principle of is different, and the fluorescent rod is internally generatedradioactivityReaction, the generated rays excite the phosphors around them to emit light, so they can emit light at night without any ultraviolet rays.The fluorescent pen will fluoresce only when it has ultraviolet lightHandwritingnearMosquito trap lamp、Currency DetectorYou can see it very clearly.
Biochemical and medical
Fluorescence is widely used in biochemistry and medicine.People canchemical reactionGlue fluorescent chemical groups toBiomacromoleculeAnd then observeTracerThese biomolecules can be detected sensitively by the fluorescence emitted by the group.
Used forDNAChain for automatic sequencingEnd termination method: In the original method, the primer end of DNA needs to be fluorescent labeled to determine the position of DNA ribbon on the sequencing gel plate.In the improved method, four kinds of chain terminatorsDideoxynucleotide(ddTBP) were respectively fluorescent labeledDNA moleculeSeparated from each other, four labeled dideoxynucleotides emitted fluorescence of different wavelengths after ultraviolet irradiation.DNA sequence can be distinguished by analyzing fluorescence spectrum.DNA detection:Ethidium bromideIs a kind ofFluorescent dyeWhen it freely changes its configuration in solution, it can only emit very weak fluorescence;When it is embedded in nucleic acidDouble chainOfBase pairAfter binding with DNA molecules, it can emit strong fluorescence.So ingel electrophoresisIn general, ethidium bromide is added to stain DNA.DNA microarray（biochip）: Need toGenome probeCarry out fluorescent labeling, and finally determine the target sequence through the fluorescent signal.Immunity in immunologyFluorescence method: YesantibodyFluorescent labeling, which can be determined according to the distribution and morphology of fluorescenceantigenThe location and nature of.Flow cytometry(also called fluorescence activationCell sortingDevice,FACS）: Fluorescent label the sample cells, and thenlaserBeam excitation makes it produce specific fluorescence, and then useoptical system Detect and transmit the signal to the computer for analysis, so as to obtain the corresponding characteristics of cells.Fluorescence technologyIt is also used to detect and analyze DNA andproteinOfmolecular structure, especially the more complexBiomacromolecule。Jellyfish luminous protein was originally derived frommarine organismjellyfish(Aequorea victoria).When it is connected with CaIon coexistenceIt can emit green fluorescence.This property has been applied to real-time observation of cellsCa ionThe flow of.The discovery of jellyfish luminous protein has promoted people to further study marine jellyfish and foundgreen fluorescent protein(Green Fluorescent Protein, GFP)Polypeptide chainContains specialChromophoreStructure, no need to addCofactorOr any special treatment, it can emit stable green fluorescence under ultraviolet radiation, asBiomoleculeorGene probeIt has great advantages, so green fluorescent protein and related proteins have becomebiochemistryandCell BiologyAn important tool for research.Fluorescent microscopic imaging technology:Total internal reflection fluorescence microscopeMany biological molecules have intrinsic fluorescence and can emit fluorescence without adding other chemical groups.Sometimes this intrinsic fluorescence will change with the change of environment, so we can use thisenvironmental change Sensitive fluorescence to detect the distribution and properties of molecules.for examplebilirubinAndserum albuminWhen it binds to a special site, it can emit strong fluorescence.It's like being bloodred blood cellWhen there is a lack of iron or lead in theZinc protoporphyrinNot normalhemoglobin（hemoglobin）；Zinc protoporphyrin has strong fluorescence, which can be used to help detect the etiology.
Gems, minerals
Gems, minerals, fibers and other materials that can be used as criminal evidence canX-rayIt emits fluorescence of different properties under the irradiation of.
Ruby, jadeiteDiamondsIt can emit red fluorescence under short wavelength ultraviolet light,emerald、Xanthine（Topaz）Pearl can also emit fluorescence under ultraviolet light.Diamonds can also be emitted under X-rayphosphorescence。
Conceptual differentiation
The luminescence caused by the excitation of light (usually ultraviolet or X-ray) is calledPhotoluminescence, such as fluorescence and phosphorescence;The luminescence caused by chemical reaction is calledCold light, the fluorescent rod used in the concert is chemically reacted and luminous after mixing two kinds of chemical liquids;fromCathode rayThe light emission caused by (high-energy electron beam) is calledCathodoluminescence, TVKinescopeOfFluorescent screenLuminescence is cathodoluminescence;Biologicalluminescence The phenomenon isBioluminescence, such asglowwormThe light emitted is "fluorescent"ancient ChineseThe Chinese character "Ying" is interchangeable with the Chinese character "Ying". In some Chinese regions, the word "Ying" is related to insects.Fluorescence is popular in TaiwanFluorescence；More in mainland Chinafluorescence, and "fluorescence" usually refers to the light emitted by fireflies.
instrument
There must be an instrument for measuring fluorescence.The instrument usually used to detect the fluorescence content of substances is calledFluorescence spectrophotometer。
Petroleum and most of its products, exceptLight oilAnd paraffin wax, whether on its own or soluble inOrganic solventIn, inUltraviolet radiationIt can emit light under, called fluorescence.
The luminescence of oil depends on itsChemical structure。PetroleumPolycyclic aromatic hydrocarbonAnd non hydrocarbon, andSaturated hydrocarbonIt does not glow at all.The fluorescence of light oil isLight blue, the oil with more colloid is green and yellow, containingAsphalteneMore oil orasphaltThe substance is brown fluorescence.Therefore, the luminous color changes with the properties of petroleum or asphalt, and is not affected by the solvent properties.The degree of luminescence is related to the concentration of petroleum or asphalt.
Because the luminescence of petroleum is very sensitive, as long as the solvent contains 1/100000 petroleum or asphalt, it can emit light.Therefore, in theOil and gas explorationIn work, commonly usedfluorescence analysisTo identify whether there is oil in the rock sample, and roughly determine its composition and content.This method is simple, fast, economical and practical.This is how Daqing Oilfield was discovered.
