Steady state and time-resolved studies of pyrene in solution and in single microcrystals

Single microcrystals of pyrene have been studied by steady state and time resolved fluorescence microscopy. The fluorescence spectra of microcrystals exhibit vibrational structure unlike the broad spectrum observed in pyrene excimer. A risetime is observed in the decay curves of the concentrated solutions, indicating the excimer formation. In contrast, the fluorescence decay profiles of the single microcrystals are nonexponential in nature and the decay times vary with their size and the wavelength of emission. This behaviour has been explained mainly by considering the pyrene dimer stabilized in the ground state.