What is Quenching ?

Quenching relates to a process that reduces the fluorescence intensity of a supplied substance. A variety of methods can succeed in quenching, such as excited state reactions, energy transfer, complex-formation and collisional quenching. As an outcome, quenching is often profoundly dependent on pressure and temperature. Some examples of common chemical quenchers are Molecular oxygen, iodide ions and acrylamide.

Quenching is divided into two categories such as dynamic quenching and static quenching.

Dynamic quenching

In dynamic or collisional quenching, interaction of an excited state fluorophore with the quencher results in radiationless deactivation of the fluorophore to the ground state. The efficiency of dynamic quenching is hence sensitively dependent on the concentration of the quenching species.

Static quenching

The static quenching occurs when the molecules form a complex in the ground state, i.e. before excitation occurs.

Difference between static quenching and dynamic quenching

Topic	Static quenching	Dynamic quenching
Occurrence	Occurs in ground state.	Occurs in excited state of the molecule
Effect of temperature	If the temperature increase (chemical stability will change), the rate of static quenching will decrease.	If the temperature increase, the dynamic quenching rate will increase.
Measurement	It can be measure by using a spectrophotometer.	It only measured by using Spectrofluorimeter.
Lifetime	there is no change in excited state lifetime	There is change in excited sate life time
Fluorophore absorption spectrum	Fluorophore absorption spectrum distorted	Fluorophore absorption spectrum unchanged