Molecular oxygen is known to be an efficient quencher of the fluorescence of aromatic hydrocarbons (Berlman, 1965; Ware, 1962). The studies so far published show quenching by oxygen to be a diffusion-controlled process in which virtually every collision with the excited fluorophore is effective in quenching.
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What does quenching mean in chemistry?
Chemical quenching means that a reactant is introduced to favor an endothermic reaction with an associated reduction of temperature. Also, the lowered temperature of the introduced reactant strengthens the effect.
What is the principle of quenching?
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.
What does quenching mean in biology?
The process of stopping a chemical or enzymatic reaction.
How does oxygen quench phosphorescence?
Oxygen quenches phosphorescence by energy transfer from the phosphor when oxygen molecules collide with molecules of the phosphor in the excited triplet state.
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;
What do you mean by quenching in physics?
quenching (countable and uncountable, plural quenchings) (physics) The extinction of any of several physical properties. (metallurgy) The rapid cooling of a hot metal object, by placing it in a liquid, in order to harden it.
What is quenching with example?
Quench is defined as to satisfy or to extinguish. 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 factors affect quenching?
Collision Quenching :-
It is due to the several factor like presence of halide, heavy metal, increase temp.,and decreased in viscosity, where number of collision are increased.
How is quenching measured?
Assuming that quenching is diffusion-controlled (kq = kdiff) calculate the quenching rate constants kq using equation 9 (ηH2O≈ 10−3 kg m−1s−1).
Why quenching is done?
quenching, rapid cooling, as by immersion in oil or water, of a metal object from the high temperature at which it has been shaped. This usually is undertaken to maintain mechanical properties associated with a crystalline structure or phase distribution that would be lost upon slow cooling.
What is the difference between quenching and annealing?
After quenching, metal tends to become brittle, and that can increase the risk of breakage. Annealing balances the properties of metal alloys to maximize strength and durability for a variety of applications. Annealing removes residual stresses in the metal, improves machinability and makes the metal more formable.
What is the function of a quencher?
A dark quencher (also known as a dark sucker) is a substance that absorbs excitation energy from a fluorophore and dissipates the energy as heat; while a typical (fluorescent) quencher re-emits much of this energy as light. Dark quenchers are used in molecular biology in conjunction with fluorophores.
What do you mean by quenching of fluorescence?
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 is difference between fluorescence and phosphorescence?
In fluorescence, the emission is basically immediate and therefore generally only visible, if the light source is continuously on (such as UV lights); while phosphorescent material can store the absorbed light energy for some time and release light later, resulting in an afterglow that persists after the light has been
What is fluorescence and phosphorescence?
Phosphorescence is light energy produced by a particular type of chemical reactionwhere the excess chemical energy of the reactants is given off as light energy. Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence.
What are the three stages of quenching?
The three stages of quenching are: Vapor stage (stage A or vapor blanket stage). Boiling stage (stage B or nucleate boiling stage). Convection stage (stage C).
Can you quench in air?
Air quenching is the process of cooling metal using air or inert gas. This rapid cooling process occurs after metal has been heated, to attain the desired properties. The air or gas is forced over the metal to cool down the material.
What is the best quenching medium?
Oil is the most popular quenchant because it is relatively severe but with a diminished risk of cracking and warping. In addition, a wide range of parts quenches well in oils because the chemical makeup and temperature of a quenching oil can be adjusted to suit desired end results.
What is quench temperature?
1,500 to 1,650 °F
Process. The process of quenching is a progression, beginning with heating the sample. Most materials are heated to between 815 and 900 °C (1,500 to 1,650 °F), with careful attention paid to keeping temperatures throughout the workpiece uniform.
What is the synonym of quench?
douse. (also dowse), extinguish, put out, snuff (out)