Evanescent wave-induced fluorescence study of Rhodamine 101 at dielectric interfaces

Abstract

Time-integrated and time-resolved evanescent wave-induced fluorescence spectroscopies (EWIFS) have been used to probe the photophysical properties of Rhodamine 101 at two solution/solid interfaces. Interaction of Rhodamine 101 with a fused silica surface leads to a reduction in the molecular fluorescence quantum efficiency in both cases. The fluorescence kinetics of interfacial species are shown to be complex (non-exponential), a function of bulk solution concentration, and a function of distance normal to the interface. The application of the maximum entropy method to the analysis of EWIF decays is presented. Recovered lifetime distributions expose inherent complexity and heterogeneity that is hidden to conventional analysis techniques.