Singlet Oxygen Generation Using New Fluorene-based Photosensitizers Under One- And Two-photon Excitation
Singlet oxygen, Luminescence, Two-photon absorption, Photochemistry, Photosensitization, Photodynamic therapy
Molecular oxygen in its lowest electronically excited state plays an important roll in the field of chemistry. This excited state is often referred to as singlet oxygen and can be generated in a photosensitized process under one- or two-photon excitation of a photosensitizer. It is particularly useful in the field of photodynamic cancer therapy (PDT) where singlet oxygen formation can be used to destroy cancerous tumors. The use of two-photon activated photosensitizers possesses great potential in the field of PDT since near-IR light is used to activate the sensitizer, resulting in deeper penetration of light into biological tissue, less photobleaching of the sensitizer, and greatly improved resolution of excitation. The synthesis and photophysical characterization of new fluorene-based photosensitizers for efficient singlet oxygen production were investigated. The spectral properties for singlet oxygen production were measured at room temperature and 77 K. Two-photon absorption (2PA) cross-sections of the fluorene derivatives were measured by the open aperture Z-scan method. The quantum yields of singlet oxygen generation under one- and two-photon excitation (Φ∆ and 2PAΦ∆, respectively) were determined by the direct measurement of singlet oxygen luminescence at ≈ 1270 nm. The values of Φ∆ were independent of excitation wavelength, ranging from 0.6 - 0.9. The singlet oxygen quantum yields under two-photon excitation were 2PAΦ∆ ≈ ½Φ∆, indicating that the two processes exhibited the same mechanism of singlet oxygen production, independent of the mechanism of photon absorption.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Andrasik, Stephen James, "Singlet Oxygen Generation Using New Fluorene-based Photosensitizers Under One- And Two-photon Excitation" (2007). Electronic Theses and Dissertations. 3065.