Two-photon STED Spectral Determination for a New V-Shaped Organic Fluorescent Probe with Efficient Two-Photon Absorption

摘要

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 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 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 pumpprobe technique, resulting in relatively high two-photon stimulated emission depletion cross sections (~1200 GM). A potential application of >1 in bioimaging was demonstrated via one- and two-photon fluorescence microscopy images of HCT 116 cells incubated with micelle-encapsulated dye.