F0/F versus Concentration of Quencher is a straight line, but I am unable to calculate the binding constant and number of binding sites.
Moreover, what will be the unit of the binding constant? Is it necessary to take the molar concentration of quencher?
The IUPAC definition of Stern-Folmer equation http://goldbook.iupac.org/S06004.html
What does "binding constant" mean?
Read our paper:
Ind. Eng. Chem. Res., 2012, 51 (37), pp 11850–11859
DOI: 10.1021/ie202950h
The Stern-Volmer equation has units of reciprocal concentration (e.g. M-1) and is a measure of potency of the quencher. Since fluorescence quenching can be caused by collisional quenching or static quenching, it is not possible to be sure that there is a binding interaction involved. However, if you knew that there was a binding interaction, you could use nonlinear least squares regression to the Langmuir binding isotherm equation to obtain the Kd:
% quenching = %Qmax[Q]/(Kd + [Q]), where [Q] is the quencher concentration and %Qmax is the maximal % quenching.
Stern-Volmer equation have been used to study the quenching mechanism whether is it static or dynamic quenching. We do not able to find the bind constant or bind sites using Stern-Volmer equation. if you want to calculate the binding constant and bind sites you have to employ the Double-logarthemic equation.
If you want to know more about Stern-Volmer equation, just refer the book
J. R. Lakowicz. Principles of fluorescence spectroscopy, third ed. Springer Science+Business Media, New York, 2006.
I agree with the statements above, just because F0/F vs. [Q] gives a strait line does not mean that you have a ground state adduct being formed (i.e. you have no way of knowing if your quencher is acting by the static or the dynamic mechanism). If you are looking for a static quenching (binding) than you can prove that this is occurring by measuring the excited state lifetimes and plotting T0/T vs. [Q]. If you have a true static quenching then there should be no change in the excited state lifetime as you add the quencher. This is an easy way to demonstrate static quenching.
Moreover, if you have purely dynamic quenching the T0/T plot should give you the same slope as your F0/F plot.
Good luck.
But you should specify the M-Ln complex( like Ru (III) bpy3 / Rh complex ) as well as quencher ( like Fe ( H2O)6 or Iodide ion , I - ) complying Stern - Volmer kinetics .The standard fluremetric data is to be analysed for correlation coefficiant ( r ) lies
in between or less than 1. This data analysis signifies a linear with relevant value of r proves the co-ordination number of metal M like Ru , Rh complexes are hexa-co-ordinated ( n=6) .
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