TP fluorophores

Figure 3.40. Molecular engineering of D-7I-D fluorophores for TP excited fluorescence. (Adapted from Ref. [470].)...

Quenching may also occur by a static process, which does not involve diffusion, due to a reversible formation of a nonfluorescent fluorophore-quencher complex in the ground state. In this case, part of fluorophore is incorporated into the complex and does not contribute to the fluorescence at aU, and another part of the fluorophore exhibits the unaffected fluorescence with the natural fluorescence lifetime, Tp o. The intensity of the fluorescence in the presence of the quencher is weaker, but the lifetime is unaffected. The Stern-Volmer plot is again linear and reads ... 

Static quenching does not assmne diffusion of components. It is a result of the reversible formation of a nonfluorescent fluorophore-quencher complex in the ground state. A fraction of the fluorophore is boxmd in a complex and makes no contribution to the emission, but the remaining fraction is not affected and exhibits fluorescence with the natural lifetime, Tp o- The emission intensity is weaker and obeys the Stem-Volmer plot... 

Therefore the fluorescence lifetime, Tp, is a measure of the fluorescence quantum yield. Op. This indicates that the rate constant for the radiative decay processes kg, is constant for a particular fluorophore as it is an intrinsic electronic property of the molecule. Consequently the fluorescence lifetime is influenced by changes in the nonradiative decay pathways. For example, a subsequent increase in nonradiative decay rates will reduce the fluorescence lifetime. As such, fluorescence lifetimes are extremely sensitive to the molecular environment surrounding the fluorophore. Therefore, this makes fluorescence lifetime measurement of individual fluorophores present in complex aquatic samples difficult to interpret. 

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