Fluorescence quenching of vaporous polycyclic aromatic hydrocarbons by oxygen
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The fluorescence quenching by oxygen of vapors of nine polycyclic aromatic hydrocarbons with strongly different oxidation potentials 0.44 eV < E ox < 1.61 eV (anthracene, 9-methylanthracene, 2-aminoanthracene, 9,10-dibromanthracene, pyrene, chrysene, phenanthrene, fluoranthene, and carbazole) is studied. From the dependences of the fluorescence decay rates and intensities on the oxygen pressure P O2, the quenching rate constants k S O2 for the excited singlet states S 1 and the fraction f S O2 of the S 1 states quenched by oxygen are estimated. At P O2 = 5 Torr, the k S O2 constants vary from 1.2 × 107 to 3.0 × 105 s−1 Torr−1, while the fraction of the quenched excited singlet states changes from 0.1 (fluoranthene) to 0.7 (chrysene) and 0.8 (pyrene). The dependences of k S O2 on the photophysical and electron-donor characteristics of the fluorescing compounds are analyzed. It is shown that, in the gas phase of anthracene and its derivatives, the magnitudes of k S O2 are limited by the rate constants of gas-kinetic collisions k gk and do not depend on the electron-donor characteristics of fluorophores, while the fraction of quenched states f S O2 changes with the oxidation potential. For compounds with k S O2 < k gk, both the rate constants k S O2 and the fraction of quenched states f S O2 depend on the E ox of sensitizers, which demonstrates an important role played by the charge-transfer interactions in quenching of the S 1 states. The dependence of the rate constants k S O2 on the free energy of electron transfer ΔG et is considered.
PACS numbers33.50.Hv 34.70.+e
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- 1.N. J. Turro, Modern Molecular Photochemistry (Univ. Science Books, Mill Valley, 1991).Google Scholar
- 2.C. Schweizer and R. Schmidt, Chem. Rev. 103, 1685 (2003).Google Scholar
- 9.U. S. Tasic and E. R. Davidson, J. Phys. Chem. 107, 3552 (2003).Google Scholar
- 16.B. F. Minaev, Zh. Prikl. Spektrosk. 42(5), 766 (1985).Google Scholar
- 17.J. B. Birks, Photophysics of Aromatic Molecules (Wiley, New York, 1963).Google Scholar
- 18.G. A. Zalesskaya, D. L. Yakovlev, E. G. Sambor, and D. V. Prikhodchenko, Opt. Spektrosk. 90(6), 596 (2001) [Opt. Spectrosc. 90 (6), 526 (2001)].Google Scholar