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Stern–Volmer kinetic relationships

This term applies broadly to variations of quantum yields of photophysical processes (e.g. fluorescence or phosphorescence ) or photochemical reactions (usually reaction quantum yield) with the concentration of a given reagent which may be a substrate or a quencher. In the simplest case, a plot of Φ 0 Φ (or M 0 M for emission) vs. concentration of quencher, [Q], is linear obeying the equation:
Φ 0 Φ or M 0 M = 1 + K sv Q
In equation (1) K sv is referred to as the Stern–Volmer constant. Equation (1) applies when a quencher inhibits either a photochemical reaction or a photophysical process by a single reaction. Φ 0 and M 0 are the quantum yield and emission intensity radiant exitance, respectively, in the absence of the quencher Q, while Φ and M are the same quantities in the presence of the different concentrations of Q. In the case of dynamic quenching the constant K sv is the product of the true quenching constant k q and the excited state lifetime, τ 0, in the absence of quencher. k q is the bimolecular reaction rate constant for the elementary reaction of the excited state with the particular quencher Q. Equation (1) can therefore be replaced by the expression (2):
Φ 0 Φ or M 0 M = 1 + k q τ 0 Q
When an excited state undergoes a bimolecular reaction with rate constant k r to form a product, a double-reciprocal relationship is observed according to the equation:
1 Φ p = ( 1 + 1 k r τ 0 [S] ) 1 A · B
where Φ p is the quantum efficiency of product formation, A the efficiency of forming the reactive excited state, B the fraction of reactions of the excited state with substrate S which leads to product, and [S] is the concentration of reactive ground-state substrate. The intercept/slope ratio gives k r τ 0. If [S] = [Q], and if a photophysical process is monitored, plots of equations (2) and (3) should provide independent determinations of the product-forming rate constant k r. When the lifetime of an excited state is observed as a function of the concentration of S or Q, a linear relationship should be observed according to the equation:
τ 0 τ = 1 + k q τ 0 [Q]
where τ 0 is the lifetime of the excited state in the absence of the quencher Q.
See also: self-quenching
Source:
PAC, 1996, 68, 2223 (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2277
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IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook.
Last update: 2014-02-24; version: 2.3.3.
DOI of this term: doi:10.1351/goldbook.S06004.
Original PDF version: http://www.iupac.org/goldbook/S06004.pdf. The PDF version is out of date and is provided for reference purposes only. For some entries, the PDF version may be unavailable.
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