An expression relating fluorescence quenching to the concentration of the quenching substance, c, and the fluorescence lifetime, τ. It is: Fo/F = 1 + kc τ, where Fo is the fluorescence intensity when the concentration of quenching substance is zero, F is the fluorescence intensity in the presence of the quenching substance, and k is the second order rate constant for the interaction of quenching substance and fluorophore.
