LUMINESCENCE QUENCHING MECHANISM FOR MICROHETEROGENEOUS SYSTEMS

Determining quenching mechanisms for luminescent species adsorbed or bound to a variety of heterogeneous systems (e.g., silicas, organic, inorganic, and biopolymers) is quite difficult in the absence of detailed information on system heterogeneity. A method for assessing the relative contributions of static and dynamic quenching in heterogeneous systems is presented. While the method does not provide direct information on the details of system heterogeneity, it requires no a priori information on the nature of the heterogeneity. This approach is based on a comparison of intensity quenching data with lifetime quenching data using a preexponential weighted lifetime, tau-M. Tau-M is calculated by fitting the observed decay curves to a sum of a relatively small number (2-4) of exponentials. For time-correlated single-photon counting the parameters obtained from a statistically acceptable fit can be used to accurately estimate tau-M, even though the computed model may bear no resemblance to the true decay kinetics. Simulations confirm that the method works for a wide range of heterogeneous systems. The technique is applied to oxygen quenching of a luminescent metal complex on a silica surface.