Stern-Volmer constants, quenching

Table 2 lists the apparent Stern-Volmer quenching constants (Ksv) for APh-x, estimated from the initial slopes of the Stern-Volmer plots, along with the... 

In some cases it is possible to obtain a measure of the association constant for intercalation directly from fluorescence quenching data. This method is applicable when the dynamic quenching of the hydrocarbon fluorescence by DNA is small and when the intercalated hydrocarbon has a negligible fluorescence quantum yield compared to that of the free hydrocarbon. If these conditions are met, the association constant for intercalation, Kq, is equal to the Stern-Volmer quenching constant Kgy (76) and is given by Equation 1. 

Table II. Intercalation Association Constants and Stern-Volmer Quenching Constants for Benzo[a]pyrene Metabolites and Metabolite Model Compounds3 with Calf Thymus DNA...

Stern-Volmer Quenching Constants. d Measured in 15% methanol. Taken from refs. 15 and 18. e Measured in 2.5% DMSO. Taken from ref. 9. 

As in the former cases, k2 was calculated from the integrated extinction coefficients,149 k3 + kt was derived from fluorescence quantum yields,149 while k3 and k4 were separately estimated from the maximum quantum yields of photooxygenations at high oxygen concentrations.150 Flash spectroscopy techniques were used in order to determine k5 and k7, while kB was obtained from the Stern-Volmer quenching constant of oxygen.149 The ratio ke/kg was determined from the variation of AOz with the concentration of the anthracene.71 When photodimerization occurred, k13l(kia + k13) was calculated from the maximum yield of... 

Equation (3) is the well-known Stern-Volmer equation and kgv = kq r° is the Stern-Volmer quenching constant. In practice, the ratio of lifetime without to that with quencher is plotted against [B] and kq is obtained by dividing the slope by r°. Analogous Stem-Volmer equations can be obtained for the emission intensity and the reaction quantum yield... 

Figure 3.13. The Stern-Volmer quenching constant Ko obtained in Ref. 53 versus the free energy of ionization AG . The open circles are the data borrowed from another work [106], The free-energy dependence shown by the solid line represents the theoretical expectation of Rehm and Weller deduced from their original approach to the simplest reaction mechanism of quenching [53], (From Ref. 107.)...

Fig. 11.11 Upper graph Schematic energy-level diagram showing energy transfer between F3 (left) and the iridium complexes studied by Thompson and coworkers (right). Lower graph Stern-Volmer plot for quenching of the five phosphors by F3. (Legend FP, PPY, B"f PQ, BTP). The table shows the triplet energies of the phosphors and their Stern-Volmer quenching constants [52],...

Aliphatic amines have been found to quench the fluorescence of acridine efficiently and a linear relationship has been demonstrated between the logarithms of the Stern-Volmer quenching constants and the ionization potentials of the amines. The photoreduction of the acridine occurs in 20% MejCOH-MeCN via an exciplex formed between the ground state of the amine and the acridine (ti, n ) state and in 20% McaCOH-CgHg via the (n,n ) state of the acridine. A quantitative study has been reported of the photoreactivity of 2-nitrophenazine with tertiary amines. Excitation to the state leads via a non-emitting... 

There are a number of studies on pyrene labelled or doped polymer materials. Dendritic size and electrostatic forces in poly(amido) dendrimers with pyrene residues have been determined through the use of a variety of quenchers. As the dendritic size increases so the Stern-Volmer quenching constant decreases, owing to blocking of the pyrene chromophore by the growing dendritic network. The photophysical properties of poly(acrylic acids) tagged with pyrene has been measured in micellar media at various pHs." The ratio of monomer to excimer gave valuable information on the micropolarity sensed by the pyrene label, as well as the influence of external stimuli. The surfactant... 

The light-induced Fmax level of room-temperature chlorophyll fluorescence was recorded with a Perkin-Elmer LS-5 spectrometer using 620 nm excitation and analyzed using conventional and modified Stern-Volmer techniques as previously employed [7-10]. The Stern-Volmer relation, Jq/I = 1 + Ksv [Q]> describes the ratio of the chlorophyll fluorescence intensity in the absence of quencher (Iq) to the level in the presence of added quinone (I) as a function of the quinone concentration ([Q]). The y-intercept of 1 is indicative of complete accessibility of the added quinone to the site of action, while the Stern-Volmer quenching constant (Ksv) measures the effectiveness of the quinone as a fluorescence quencher once it has been transported to its site of action. A modified Stern-Volmer relation, I MI = 1/fa l/ fa-K sv [Q]), describes the fluorescence quenching (AI) when the added inhibitor has limited accessibility to the binding site. The fa parameter is the fraction of chlorophyll fluorescence that may be quenched by the added inhibitor. 

Stern-Volmer quenching constant (iTsv) Constant for a given quenching process it is the product of the bimolecular rate constant for the reaction of quencher and the luminescent species and the luminescence lifetime in the absence of quencher... 

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