Fluorescence quenching of polycyclic aromatic hydrocarbons by cetylpyridinium bromide: Discrimination between alternant and nonalternant hydrocarbons

Molecules of polycyclic hydrocarbons (PAHs) that contain between two and five rings undergo quenching processes in the presence of cetylpyridinium bromide (CPB), which can act as quencher and as surfactant. The CPB concentration and the nature of the PAHs notably influence the inhibition mechanisms of fluorescence, Dynamic quenching is predominant for all hydrocarbons in solutions in which CPB is found in the form of monomers. When the quencher forms premicellar aggregates, fluoranthene, benzo[a]pyrene, and benz[a]anthracene undergo dynamic quenching, while for the remaining PAHs the dynamic and static processes coexist. In micellar CPB solutions the static quenching mechanism is predominant, The correlations existing between the quenching constant in the premicellar zone and topological and geometrical descriptors of the PAHs show the different behavior of alternant and nonalternant hydrocarbons.