Kinetics of partly diffusion-controlled reactions

Spectrofluorimetric methods allowing an estimation of the “microviscosity” (or the microfluidity) of synthetic and natural membranes may be used if the emisive phenomenon is dependent upon the cohesion of its local environment. Of the different methods that may be proposed, the study of the reactions between electronically excited molecules A^*, which emit fluorescence, and B quenchers embedded in membranes, the rate constant of which is partly controlled by diffusion, are expected to inform about the values of diffusion coefficients of quenchers and therefore the “microviscosity” of the environment. Information may be improved when the product of the reaction between A^* and B is itself emissive (excimers, exciplexes). We propose here that a kinetic model may apply this type of reaction when a process of static quenching occurs. The use of this kinetic model in studies carried out in this area should lead to a more accurate determination of the diffusion coefficients of A^* and B and therefore of the “microviscosity.”