QUENCHING OF FLUORESCENCE OF AROMATIC HYDROCARBONS BY PROTONS IN CAFFEINE- SOLUBILIZED AQUEOUS SOLUTION. INTRACOMPLEX ENERGY TRANSFER

The fluorescence of pyrene and five other aromatic hydrocarbons solubilized with caffeine in aqueous solution was quenched by 0.001–1mol dm−3 sulfuric acid; this quenching did not occur in the absence of caffeine. Exceptionally a non-alternative hydrocarbon, fluoranthene, showed an increase of the fluorescence intensity by the acid. The observed quenching rate was explained by the rate of energy transfer from the aromatic molecules to protonated caffeine in the complex.