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In chemistry, quenching refers to any process which decreases the fluorescent intensity of a given substance. A variety of processes can result in quenching, such as excited state reactions, energy transfer, complex-formation and collisions. As a consequence, quenching is often heavily dependent on pressure and temperature.
The Dexter energy transfer rate, , is indicated by the formula: = ′ [] where is the separation of the donor from the acceptor, is the sum of the Van der Waals radii of the donor and the acceptor, and ′ is the normalized spectral overlap integral, where normalized means that both emission intensity and extinction coefficient have been adjusted to unit area.
Photobleaching is an important parameter to account for in real-time single-molecule fluorescence imaging in biophysics. At light intensities used in single-molecule fluorescence imaging (0.1-1 kW/cm 2 in typical experimental setups), even most robust fluorophores continue to emit for up to 10 seconds before photobleaching in a single step. For ...
The Stern–Volmer relationship, named after Otto Stern and Max Volmer, [1] allows the kinetics of a photophysical intermolecular deactivation process to be explored. Processes such as fluorescence and phosphorescence are examples of intramolecular deactivation ( quenching ) processes.
Relaxation from an excited state can also occur through collisional quenching, a process where a molecule (the quencher) collides with the fluorescent molecule during its excited state lifetime. Molecular oxygen (O 2 ) is an extremely efficient quencher of fluorescence because of its unusual triplet ground state.
Photoinduced electron transfer (PET) is an excited state electron transfer process by which an excited electron is transferred from donor to acceptor. [ 1 ] [ 2 ] Due to PET a charge separation is generated, i.e. , redox reaction takes place in excited state (this phenomenon is not observed in Dexter electron transfer ).
Most time the radical neutralize each other very quickly and nonradiatively. This is a Dexter electron transfer process that quenches the fluorescence and creates the rotation of the YOYO-1 molecule. As such, the rotation is a product of the quenching, not the cause of the quenching proposed in the intramolecular charge transfer mechanism.
is the Stern–Volmer quenching constant, which depends on the chloride concentration, []. in a linear manner. Thus, quinoline-based indicators are one-wavelength dyes - the signal results from monitoring the fluorescence at a single wavelength.