Stern-Volmer

Another useful technique for measuring the rates of certain reactions involves measuring the quantum yield as a function of quencher concentration. A plot of the inverse of the quantum yield versus quencher concentration is then made Stern-Volmer plot). Because the quantum yield indicates the fraction of excited molecules that go on to product, it is a function of the rates of the processes that result in other fates for the excited molecule. These processes are described by the rate constants (quenching) and k (other nonproductive decay to ground state). [Pg.747]

A plot of FJF vs. Cq is called a Stern-Volmer plot. From the slope, the quantity qTq is evaluated. This is a relative rate. [Pg.181]

Figure 10 illustrates Stern-Volmer plots for the fluorescence quenching of APh-x by MV2+ and SPV in aqueous solution [74]. With MV2+, the quenching is so effective that it occurs at very low quencher concentrations (in the range of 10 6 M), whereas with SPV, it proceeds to about the same extent at two-orders of magnitude higher quencher concentration (in the range of 10 4 M). [Pg.70]

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... [Pg.70]

Figure 11 shows Stern-Volmer plots for fluorescence quenching of the amphiphilic cationic copolymer QPh-x [74]. The quenching of QPh-x with MV2+ is expected to be much less effective than that of APh-x. The quenching data for the QPh-x system are presented in Table 3. For comparison, the data for a related... [Pg.72]

Fig. 15. Stern-Volmer plots for (O) po-ly(A/St/Phen) (29) and ( ) APh-2 (8 with x = 2) with MV2+ in aqueous solution excitation wavelength, 297 nm [119]...

Fedorenko S. G., Burshtein A. I. Deviations from linear Stern-Volmer law in hopping quenching theory, J. Chem. Phys. 97, 8223-32 (1992). [Pg.282]

The quenching effects of these esters and the phenolic products were also measured using standard Stern-Volmer quenching procedures. [Pg.148]

Fig. 1. a) UV-Vis absorption and fluorescence emission spectra of riboflavin (RF, 20 pM) and Gum Arabic aqueous solutions at pH 7 (phosphate buffer 100 mM). b) Transient absorption spectra of RF (35 pM) in N2-saturated MeOH-Water (1 1) solution. The insets show the transient decay at 720 nm for the RF species and the Stern-Volmer plot for the quenching of 3RF by GA, eqn 11. [Pg.13]

Figure5.9 Spectral changes upon addition ofCH3OH to aCH2Cl2 solution of [(8-QNS)2Au(AuPPh3)2]BF4 (7.72 x 10 M) with excitation at 320 nm. Inset Changes in lifetime according to Stern-Volmer equation. Reproduced with permission from [35]. Copyright (2003) American Chemical Society.

This method is applicable when the fluorescence of a ligand is quenched in presence of DNA or RNA and provides base-dependent specificity [135]. In fluorescence quenching experiments the titration data is plotted according to the Stern-Volmer equation ... [Pg.170]

This result and the fact that a Stern-Volmer quenching plot for (75) and (77) had somewhat different slopes (no statistical analysis given) led the author to propose that the (75) and (76) were n -> n triplet products and (77), (78), and (79) were triplet products. [Pg.171]

The Stern-Volmer plot is represented by the following equation ... [Pg.228]

It should be noted that this expression is a general one that can be used for any photochemical reaction that can be quenched. It is commonly called the Stern-Volmer equation. This equation predicts that if the proposed mechanism is correct, the data, when plotted as 4>a0/4>a vs. [Q], should be linear with an intercept equal to unity and a slope equal to kqr. Linear plots were indeed observed out to large d>°/d> values. Assuming a value of 5 x 10 M 1 sec-1 for the quenching rate constant,(7) the data presented in Table 4.1 were obtained. [Pg.375]

Laser flash photolysis techniques offer the possibility of examining in detail the transient processes responsible for the photostabilizing effect discussed above. The triplet lifetimes are frequently too short, even for this technique however, they can still be estimated using as a probe the quenching by 1-methyl-naphthalene, which leads to the formation of its easily detectable triplet. The optical absorbance due to the 1-methylnaphthalene triplet (Aft) produced as a result of energy transfer is related to the Stern-Volmer slope by equation 5, where N stands for... [Pg.22]

Figure 3. Stern-Volmer plots for quenching of yellowing following photolysis of PVCa solutions in methylene chloride by (a) piperylene and (b) naphthalene. Yellowing is measured as the increase in absorption at 390 nm.

Pqq - 1 atm) with various concentrations of cosolvents added led to significant quenching of by donor solvents and gave linear Stern-Volmer type plots (e.g., f°/ f versus [THF]) with slopes (KSy) of 34 1, 26 1 and 16 1 M 1 for THF, diglyme and cyclohexene, respectively. In contrast, photolysis in 2,5-dimethyltetrahydrofuran led to quantum yields comparable to those observed in hydrocarbon solutions, an observation which reinforces the view that the ability to coordinate may be important to the quenching process. [Pg.128]

If Fq is the yield in the absence of quenchers, F the yield in the presence of quenchers ( concentration Q ), and XQ is the fluorescence lifetime when [Q] = 0, the relative yield as a function of [Q] is given by the Stern-Volmer equation ... [Pg.122]

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. [Pg.220]

Measurements of the hydrocarbon fluorescence lifetimes provide important information which is useful in interpreting the Stern-Volmer plots. In cases where Equation 1 is valid, the hydrocarbon fluorescence decay profiles must be the same with and without DNA. In some cases, BP for example, this is not the case. For BP the observed decay profile changes significantly when DNA is added (72). [Pg.222]

Figure 4. Stern-Volmer plots and quenching constants derived from the fluorescence quenching of DMA (T), 1,2,3,4-tetra-hydro-BA ( ), 5,6-dihydro-BA (A), 8,9,10,11-tetrahydro-BA ( ) and anthracene ( ) by DNA in 15% methanol at 23° C. Emission and excitation wavelengths and details concerning the experimental conditions are given in refs. 12 and 14. The open symbols, o and V, show I /I for 1,2,3,4-tetrahydro-BA and DMA respectively in denatured DNA([P04"] 4.4 x 10 4 M).

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