Stem-Volmer quenching

Our simplest continuous microheterogeneous model assumes that the luminophore exists in a distribution of spectroscopically different environmental sites. For a tractable, yet plausible, model each site is assumed to be quenched by normal Stem-Volmer quenching kinetics. For luminescence decays each individual component is assumed to give a single exponential decay with the following impulse response ... 

The spectra observed with four concentrations of pyrene are shown in Figures 18 and 19. The spectra of normal fluorescence are similar to those previously reported by Forster and Kasper. The relative intensity of the dimer band increases as the concentration of pyrene increases and the simultaneous reduction in fluorescence efficiency, n, of the monomer follows the Stem-Volmer quenching law with a mean quenching constant of 2.0 X 10s liter mole-1 (Table VII). 

The constant K is known as the Stem-Volmer quenching constant /cQ is the rate constant for the quenching reaction, and t0 the lifetime in the absence of quencher. Fluorescence quenching of tryptophan in proteins by acrylamide or 02 has been used to determine whether tryptophan side chains are accessible to solvent or are "buried" in the protein.141 142 The long-lived phosphorescence of tryptophan can be studied in a similar... 

Figure 3. Stem-Volmer quenching curves for 2-naphthol and 5-cyano-2-naphthol.

Figure 35 Stem-Volmer quenching of the uranyl donor by europium acceptor when bound to 3 mM ZrCEP. The high value of Ksv eliminates the possibility of diffusional contribution to the fluorescence quenching of the donor in the galleries of a-ZrCEP. (From Ref. 71. Copyright 1999 Elsevier Publications.)...

In this equation, F0 and F are the fluorescence intensities in the absence and presence of the quencher, t0 and x are the lifetimes of the fluorophore in the absence and presence of the quencher, kq is the biomolecular quenching constant, and [Q] is the concentration of the quencher (in this case, molecular oxygen). The Stem-Volmer quenching constant is Kn, and is calculated as the product of kq and r0. The Smoluchowski equation describes the biomolecular quenching constant, kq, and is given by... 

An important aspect of the photophysics of the Pt(diimine)(dithiolate) photochemistry that has received increasing attention is the ability of the excited-state complexes to undergo self-quenching. Initial work by Connick and Gray (111) showed that the lifetime of the complex Pt(bpy)(bdt) (bdt = benzene-1,2-dithiolate, 31) decreased with increasing solution concentration. The bimolecular self-quenching rate constant, calculated from a Stem-Volmer quenching analysis, was found to be 9.5 x 109 A/-1 s-1 in acetonitrile and 4 x 109 M 1 s 1 in chloroform. However, no evidence of excimer formation... 

As Table I Indicates, Stem-Volmer quenching constants obtained in SDS by measuring either excited state lifetimes or luminescence Intensities were within experimental error, moreover the observed quenching constants are strongly dependent on surfactant concentration. The decay of the... 

The bimolecular reaction of the respective constituents (non-hydrogen bonded) as determined by Stem-Volmer quenching kinetics. 

In the situation described as Stem-Volmer quenching, the fluorescence quantum yield is reduced to in the presence of Q, a quenching molecule of concentration [Q],... 

The rate constants for hydrogen atom transfer can be measured by Stem-Volmer quenching and have been studied for a wide range of substrates, such as alcohols, hydrocarbons, and tin hydrides 134). The rate constants fall in the range 10 -10 s and qualitatively... 

Hall, R.D. and Chignell, C.F. (1987) Steady-state near-infrared detection of singlet molecular oxygen a Stem-Volmer quenching experiment with sodium azide, Photochem. Photobiol., 45, 459 464. 

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