Steady-state and time-resolved fluorescence investigations of pyrene excimerformation in supercritical CO2

Steady-state and time-resolved fluorescence studies of pyrene emission in supercritical CO2 wereundertaken. Ground-state, excimer-like pyrene dimers were not formed in supercritical CO2, indicating that CO2 association around the pyrene is too weak to oppose the repulsion of the ground-state pyrene molecules. However, pyrene excimers are formed in the excited state and is absolutely diffusion controlled. Moreover, the amount of excimer decreases with increasing CO2 density.