4640480878

44 M. SIKORSKI

ABSTRACT

The aim of this paper is to review the most widely used techniąue for studies of fast bimolecular reactions — Time Correlated Single Photon Count-ing Techniąue (TCSPCT). The TCSPCT has become one of the most powerful tools to investigate the fluorescence time behaviour. The most prominent point of this method is the use of time-resolved fluorescence ąuenching as a method for studying diffusion-controlled reactions. The experimentally measured fluorescence decay D(t) is the convolution of the instrument responsc function £(t) and the fluorescence decay function /(f). The problem to solve is simply to determine the function I(t) when both D(t) and £(t) are known. In practice, however, the problem is highly complicated due to severe experimental distor-tions and correlations between adjusted parameters. In this paper we have attempted to evaluate the possibilities and limitations of TCSPCT under various conditions in determining the fluorescence ąuenching kinetics. To in-vestigate fluorescence ąuenching using SCK theory it is esscntial to determine the values of R, D and k, because these parameters describe the ratę coeflicient of the reaction between the excited donor and the ąuenchcr — k (/). D re-presents the sum of the diffusion coefficients and R the sum of the rad i i of the donor in the electronic excited State and of the ąuenchcr respcctively, and k represents the specific ratę constant. However, from the point of view of the fluorescence decay measurement, it is necessary to determine the values ofr°, S, G₀ and z_r, where G₀ is a scaling factor. In this paper particular emphasis is placed on the method enabling the determination of the numerieal values of £(i) or the elimination of it from the procedurę of data fitting according to SCK theory. Table 1 summarises details of experiment when the TCSPCT was employed to study kinetics of fast bimolecular reactions by observation of fluorescence ąuenching.