Stern-Volmer expression plotting

This expression is known as the Stern-Volmer equation and Ksv as Stern-Volmer constant. Ksv is the ratio of bimolecular quenching constant to unimolecular decay constant and has the dimension of litre/mole. It implies a competition between the two decay pathways and has the ch".acter of an equilibrium constant. The Stern-Volmer expression is linear in quencher concentration and Ksv is obtained as the slope of the plot of 4>f°If vs [Q], if the assumed mechanism of quenching is operative. Here, t is the actual lifetime of the fluorescer molecule in absence of bimolecular quenching and is expressed as... 

We note that the expressions above have been derived for a homogeneous system, where only one triplet lifetime is involved even here a Stern-Volmer type plot based on data from gated spectrometers is not expected to follow "conventional" Stern-Volmer behaviour. 

This is known as the Stern-Volmer expression. A plot of () versus [Q gives a straight line with an intercept equal to 1.0 and a slope equal... 

Triplet sensitization (Section 2.2.2) can be used to determine 3A v for the quenching of a triplet reactant. A complete reaction scheme for sensitization of a reactant A yielding product B from the triplet state would lead to a rather complex Stern Volmer expression, if all steps are treated explicitly. However, if ISC of the sensitizer is very fast and efficient (< >T= 1) and if the concentration of A is chosen to be much higher than that of the quencher added, then we may assume that triplet energy transfer from the sensitizer to A is fast and efficient at all quencher concentrations, so that a plot of versus cq will... 

Inhomogeneous systems can give Stem-Volmer plots that curve downward with increasing [Q], as shown by the dashed curve in Fig. 5.7B. In this situation, a modified Stern-Volmer expression is useful [40]. Consider a protein in which a fraction da of the tryptophan residues is accessible to quenchers in the solvent and a fraction di is inaccessible. In the absence of external quenchers, the overall fluorescence yield will be... 

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. 

A Stern-Volmer type expression is obtained. At constant [B], a plot of 4>r/Ar vi [Q] will be linear and the slope is equal to Kq. 

Following a similar approach to that of pyrene exclmer formation, activation energies for pyrene- 4. exciplex formation can be obtained from expression of Eqn. 9 in an Arrhenius form and differentiation by 1/T. ki+k2 are obtained from data taken in eyelohexane (32), and A3 and E3 from the lifetime taken at f CA1 - 0. E3 can also be obtained from the slope of the phase dependent dynamic Stern-Volmer plots. As seen in Table 1 the data from each method are in good agreement. The small differences in activation parameters measured in the cholesteric and isotropic phases probably reflect changes in viscosity that accompany phase transitions. 

Figure IX-D-6. Stern-Volmer plot of l/ I>co versus pressure of added nitrogen gas. Experiments were all performed using 248 lun excitation of acetone. Measurements of OchjCO reported by Rajakumar et al. (2008) were converted to CO data using the mass balance expression, co = 1 - cH3CO- The data for <1>ch3 determined by Khamaganov et al. (2007) were converted to equivalent values of co using the expression, 4>co =

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