What is meant by quenching in chemistry?

Quenching refers to any process which decreases the fluorescence intensity of a given substance. A variety of processes can result in quenching, such as excited state reactions, energy transfer, complex-formation and collisional quenching. … Molecular oxygen, iodide ions and acrylamide are common chemical quenchers.

What do you mean by quenching of fluorescence?

Abstract. Fluorescence quenching refers to any process that decreases the fluorescence intensity of a sample. A variety of molecular interactions can result in quenching. These include excited-state reactions, molecular rearrangements, energy transfer, ground-state complex formation, and colli-sional quenching.

What are the two types of quenching?

There are two different ways of quenching: static and dynamic quenching.

What does self-quenching mean?

Self-quenching (also called cross-relaxation) occurs between two identical molecules (ions) when a first molecule (or ion) initially in an excited state exchanges energy with the second molecule (ion) that is initially in the ground state, resulting in both molecules (ions) simultaneously changing to excited states …

What is the example of quenching?

An example of to quench is to have a cold drink when thirsty. An example of to quench is to put out a fire.

What are the types of quenching?

There are ten quenching methods in the heat treatment process, which are:

  • single-medium (water, oil, air) quenching;
  • interrupted quenching;
  • martempering;
  • martempering below MS point;
  • isothermal quenching of bainite;
  • compound quenching;
  • precooled isothermal quenching;
  • delayed cooling quenching;

Is fluorescence quenching reversible?

Main. Reversible quenching of single-walled carbon nanotube (SWNT) fluorescence by means of oxidative charge-transfer reactions with small redox-active organic dye molecules has been demonstrated recently6. In these studies, the redox-active molecules functionalized the nanotubes in a non-covalent manner.

What is the function of quenching?

In materials science, quenching is the rapid cooling of a workpiece in water, oil or air to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, such as phase transformations, from occurring.

How can you tell the difference between static and dynamic quenching?

The static quenching mechanism is the formation of an intramolecular dimer between reporter and quencher, to create a non-fluorescent ground-state complex with a unique absorption spectrum. In contrast, the FRET quenching mechanism is dynamic and does not affect the probe’s absorption spectrum.

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What is the difference between quenching and annealing?

After annealing, the grains are refined. the structure is adjusted, and the tissue defects are eliminated. Quenching causes the supercooled austenite to undergo martensite or bainite transformation. A martensite or bainite structure is obtained.

What is quenching and tempering process?

Quenching and tempering are processes that strengthen materials like steel and other iron-based alloys. These processes strengthen the alloys through heating the material while simultaneously cooling in water, oil, forced air, or gases such as nitrogen.

What is in quenching oil?

They are composed of base mineral or petroleum oils, and often contain polar lubricants like fats, vegetable oils, and esters, as well as extreme pressure additives such as chlorine, sulfur, and phosphorus. Straight oils provide the best lubrication and the poorest cooling characteristics among quenching fluids.

Why does quenching occur?

Dynamic quenching is caused by interaction between two light-sensitive molecules; a donor and acceptor. The donor fluorophore transfers energy to the acceptor, which may then emit light itself or completely absorb the energy. In dynamic quenching, electron excitation takes place before the quenching process.

Why is fluorescence quenching important?

Fluorescence quenching is an important technique for measuring binding affinity between ligands and proteins. Fluorescence quenching is the decrease in the quantum yield of fluorescence from a fluorophore, induced by a variety of molecular interactions with quencher molecule(s).

What causes self-quenching fluorescence?

The self-quenching has been attributed to the clustering of the fluorophores that occurs during the labelling process and results in an aggregation of the fluorophores bound to the biomacromolecule31 , 32.

How do you calculate quenching efficiency?

Quenching efficiency was determined by dividing the fluorescence intensity of the hybrid by the fluorescence intensity of the fluorophore-labeled oligodeoxyribonucleotide, multiplying the result by 100 and then subtracting the result from 100.

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What is electron transfer quenching?

Quenching refers to any process which decreases the fluorescence intensity of a given substance. It refers to reduction of fluorescence intensity by another molecule, one that causes some of the excited fluorophore to return to their ground states without emitting photons.

Which is used as common quenching agent?

Despite reports of decomposition of DBPs caused by some quenching agents, particularly sulphite and thiosulphate, a survey of the literature shows that they are still the most commonly used quenching agents in analysis of DBPs.

What is the quenching process?

Quenching is the soaking of a metal at a high temperature, above the recrystallization phase, followed by a rapid cooling process to obtain certain desirable material properties. … Quenching also increases toughness of both alloys and plastics. Quenching may also be known as quenched or quench hardening.

What is quenching of time?

Quench time is a measure of how long a steel casting spends at high temperature during quenching. While castings cool, the quench water warms; therefore, there is a one-to-one relationship between the two.

What is the difference between oil quenching and water quenching?

Water quenching is a rapid cooling, where water as a qenching medium extracts heat much faster. While oil as a medium will extract heat much slower, hence rate of cooling will be slower than water. Each of these have advantages and disadvantages.

How is quenching constant calculated?

Plot the ln of intensity versus time and from the slope determine (kf + knr). Once (kf + knr) is determined, the value of the quenching rate constant can be determined from the Stern-Volmer plot.

Is quenching the same as photobleaching?

The two phenomena are distinct in that quenching is often reversible whereas photobleaching is not. … Most quenching processes act to reduce the excited state lifetime and the quantum yield of the affected fluorophore.

Is photobleaching Reversible?

The frequently used eCFP, eGFP, eYFP, and Citrine are all susceptible to reversible photobleaching. This light-induced and pH-dependent phenomenon leads to the generation of a nonfluorescent species which recovers spontaneously or through illumination.

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Why is quenching in oil better than water?

Oil is preferable to the traditional quenching medium of water because it reduces the risks of distortions or cracking by cooling metals more evenly and more quickly.

Why do blacksmiths quench in oil?

Items cooled in fast oils cool more quickly. … Hot oils are kept at much higher temperatures and are used to ensure that a part’s core temperature and surface temperature do not vary too greatly during a quench. This controls distortion and reduces the risk of cracking.

Why does tempering increase hardness?

In general, elements like manganese, nickel, silicon, and aluminum will remain dissolved in the ferrite during tempering while the carbon precipitates. When quenched, these solutes will usually produce an increase in hardness over plain carbon-steel of the same carbon content.

How do you quench a reaction?

cooling the reaction mixture or adding an antisolvent to induce precipitation, and collecting or removing the solids by filtration, decantation, or centrifugation. removal of solvents by evaporation. separating the reaction mixture into organic and aqueous layers by liquid-liquid extraction.

What is quenching of lime?

The vast majority of lime produced from limestone is “quenched,” alternatively called “slaking.” To quench or slake lime is a process whereby just enough water vapour or mist is introduced so that the quicklime combines chemically with the water to convert to a safer, less caustic form known commercially as hydrated …