title: One- and two-photon singlet oxygen generation with new fluorene-based photosensitizers.
abstract: The spectral properties of new fluorene-based photosensitizers for efficient singlet oxygen production are investigated at room temperature and 77 K. Two-photon absorption (2PA) cross-sections of the fluorene derivatives are measured by the open aperture Z-scan method. The quantum yields of singlet oxygen generation under one- and two-photon excitation (phi(delta) and 2PAphi(delta), respectively), are determined by the direct measurement of singlet oxygen luminescence at approximately 1270 nm. The values of phi(delta) are independent of excitation wavelength, ranging from 0.6-0.9. The singlet oxygen quantum yields under two-photon excitation are 2PAphi(delta) approximately 1/2 phi(delta), indicating that the two processes exhibit the same mechanism of singlet oxygen production, independent of the mechanism of photon absorption.
authors.affiliation: Department of Chemistry and CREOL, College of Optics and Photonics, University of Central Florida, P.O. Box 162366, Orlando, FL 32816-2366, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Andrasik
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Belfield
authors.forename: Mykhailo V
authors.initials: MV
authors.lastname: Bondar
authors.forename: Florencio E
authors.initials: FE
authors.lastname: Hernandez
authors.forename: Alma R
authors.initials: AR
authors.lastname: Morales
authors.forename: Olga V
authors.initials: OV
authors.lastname: Przhonska
authors.forename: Sheng
authors.initials: S
authors.lastname: Yao
mesh_terms: D005449:Fluorenes / Q000737:chemistry*; D015394:Molecular Structure; D017785:Photons; D017319:Photosensitizing Agents / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*
chemical_list: D005449:Fluorenes; D017319:Photosensitizing Agents; D026082:Singlet Oxygen; C041509:fluorene