Time-resolved fluorescence measurements are reported of a triphenylmethane dye (malachite green), adsorbed at and aqueous/quartz interface, studied by evanescent wave excitation. The importance of internal conversion as the dominant deactivation pathway from the first excited singlet state of malachite green is observed to be greatly reduced for molecules at a solid/liquid interface compared to those in low viscosity solvents. Surface coverage dependent decay kinetics are observed, and at the lowest surface coverages studied, the excited singlet state lifetime of the dye is more than two orders of magnitude greater than the value observed for the dye in aqueous solution. Fluorescence decay kinetics are found to be non mono-exponential under all conditions, and the limitations of simple sum-of-exponentials fitting are discussed in light of other models currently available. It is possible to distinguish at least two populations of malachite green adsorbed at the surface.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Condensed Matter Physics
- Atomic and Molecular Physics, and Optics
- Surfaces and Interfaces