Photosensitized Generation of Singlet Oxygen
- 1 January 2006
- journal article
- review article
- Published by Wiley in Photochemistry and Photobiology
- Vol. 82 (5), 1161-77
- https://doi.org/10.1562/2006-03-03-ir-833
Abstract
This work gives an overview of what is currently known about the mechanisms of the photosensitized production of singlet oxygen. Quenching of pi pi* excited triplet states by O2 proceeds via internal conversion of excited encounter complexes and exciplexes of sensitizer and O2. Both deactivation channels lead with different efficiencies to singlet oxygen generation. The balance between the deactivation channels depends on the triplet-state energy and oxidation potential of the sensitizer, and on the solvent polarity. A model has been developed that reproduces rate constants and efficiencies of the competing processes quantitatively. Sensitization by excited singlet states is much more complex and hence only qualitative rules could be elaborated, despite serious efforts of many groups. However, the most important deactivation paths of fluorescence quenching by O2 are again directed by excess energies and charge-transfer interactions similar to triplet-state quenching by O2. Finally, two recent developments in photosensitization of singlet oxygen are reviewed: Two-photon sensitizers with particular application potential for photodynamic therapy and fluorescence imaging of biological samples and singlet oxygen sensitization by nanocrystalline porous silicon, a material with very different photophysics compared to molecular sensitizers.Keywords
This publication has 95 references indexed in Scilit:
- Physical Mechanisms of Generation and Deactivation of Singlet OxygenChemical Reviews, 2003
- Radiationless Deactivation of the Second Excited Singlet State 1Σg+ of O2 in SolutionThe Journal of Physical Chemistry A, 1998
- Direct Spectroscopic Evidence of Photosensitized O2 765 nm (1Σ+g → 3Σ-g) and O2 Dimol 634 and 703 nm ((1Δg)2 → (3Σ-g)2) Vibronic Emission in SolutionJournal of the American Chemical Society, 1996
- Collision-Induced Radiative Transitions b1.SIGMA.g+ .fwdarw. a1.DELTA.g, b1.SIGMA.g+ .fwdarw. X3.SIGMA.g-, and a1.DELTA.g .fwdarw. X3.SIGMA.g- of O2The Journal of Physical Chemistry, 1995
- Time-Resolved Measurement of O2(1.SIGMA.+g) in Solution. Phosphorescence from an Upper Excited StateThe Journal of Physical Chemistry, 1994
- Efficiencies of O2(1Σ+g) and O2(1Δg) formation in the primary steps of triplet state photosensitization in solutionChemical Physics Letters, 1993
- Relative fraction of excited-state oxygen formed as b1.SIGMA.g+ in solution-phase photosensitized reactionsThe Journal of Physical Chemistry, 1993
- Sensitization of O21Σg+ → 1Δg emission in solution, and observation of O21Δg → 3Σg− chemiluminescence upon decomposition of 1,4-dimethylnaphthalene endoperoxideChemical Physics Letters, 1985
- Spectroscopic Detection of the Photosensitized Formation of 1Σ Oxygen in the Gas PhaseThe Journal of Chemical Physics, 1971
- Formation of O2(1Σg+) by 1-fluoronaphthalene sensitizationChemical Physics Letters, 1971