Quenching refers to the reduction of fluorescence intensity due to interactions with another molecule or environmental conditions.
Types:
1. Static Quenching:
Quencher and fluorophore form a non-fluorescent complex; fluorescence decreases without changing the fluorescence lifetime.
2. Dynamic Quenching:
Quencher collides with the excited fluorophore, causing non-radiative de-excitation.
3. Concentration Quenching:
At high fluorophore concentrations, reabsorption of emitted photons reduces overall emission.
4. Photoinduced Electron Transfer (PET):
An electron is transferred from the excited fluorophore to a nearby quencher.
5. Forster Resonance Energy Transfer (FRET):
Energy transfer from an excited donor chromophore to a nearby acceptor without fluorescence emission.
6. Intersystem Crossing:
Fluorophore transitions from a singlet excited state to a triplet state, reducing fluorescence.