title: Two-photon STED spectral determination for a new V-shaped organic fluorescent probe with efficient two-photon absorption.
abstract: Two-photon stimulated emission depletion (STED) cross sections were determined over a broad spectral range for a novel two-photon absorbing organic molecule, representing the first such report. The synthesis, comprehensive linear photophysical, two-photon absorption (2PA), and stimulated emission properties of a new fluorene-based compound, (E)-2-{3-[2-(7-(diphenylamino)-9,9-diethyl-9H-fluoren-2-yl)vinyl]-5-methyl-4-oxocyclohexa-2,5-dienylidene} malononitrile (1), are presented. Linear spectral parameters, including excitation anisotropy and fluorescence lifetimes, were obtained over a broad range of organic solvents at room temperature. The degenerate two-photon absorption (2PA) spectrum of 1 was determined with a combination of the direct open-aperture Z-scan and relative two-photon-induced fluorescence methods using 1 kHz femtosecond excitation. The maximum value of the 2PA cross section ~1700 GM was observed in the main, long wavelength, one-photon absorption band. One- and two-photon stimulated emission spectra of 1 were obtained over a broad spectral range using a femtosecond pump-probe technique, resulting in relatively high two-photon stimulated emission depletion cross sections (~1200 GM). A potential application of 1 in bioimaging was demonstrated through one- and two-photon fluorescence microscopy images of HCT 116 cells incubated with micelle-encapsulated dye.
authors.affiliation: Department of Chemistry, University of Central Florida, P.O. Box 162366, Orlando, FL 32816-2366, USA. belfield@ucf.edu
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Belfield
authors.forename: Mykhailo V
authors.initials: MV
authors.lastname: Bondar
authors.forename: Alma R
authors.initials: AR
authors.lastname: Morales
authors.forename: Lazaro A
authors.initials: LA
authors.lastname: Padilha
authors.forename: Olga V
authors.initials: OV
authors.lastname: Przhonska
authors.forename: Xuhua
authors.initials: X
authors.lastname: Wang
mesh_terms: D000042:Absorption; D004579:Electron Transport; D005449:Fluorenes / Q000138:chemical synthesis / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D045325:HCT116 Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D057054:Molecular Imaging; D015394:Molecular Structure; D017785:Photons; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D014753:Vinyl Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: C570803:(E)-2-(3-(2-(7-(diphenylamino)-9,9-diethyl-9H-fluoren-2-yl)vinyl)-5-methyl-4-oxocyclohexa-2,5-dienylidene) malononitrile; D005449:Fluorenes; D005456:Fluorescent Dyes; D012997:Solvents; D014753:Vinyl Compounds