New Two-Photon-Absorbing Probe with Efficient Superfluorescent Properties

Abstract

The synthesis, linear photophysical and photochemical parameters, two-photon absorption (2PA), and superfluorescence properties of 2,2′-(5,5′-(9,9-didecyl-9H-fluorene-2,7-diyl)bis(ethyne-2,1-diyl)bis(thiophene-5,2-diyl))dibenzo[d]thiazole (1) were investigated, suggesting its potential as an efficient fluorescent probe for bioimaging applications. The steady-state absorption, fluorescence, and excitation anisotropy spectra of 1 were measured in several organic solvents and aqueous media. Probe 1 exhibited high fluorescence quantum yield (∼ 0.7-0.8) and photochemical stability (photobleaching quantum yield ∼ (3 - 7)·10-6). The 2PA spectra were determined over a broad spectral range (640-920 nm) using a standard two-photon induced fluorescence method under femtosecond excitation. A well-defined two-photon allowed absorption band at 680-720 nm with corresponding 2PA cross sections δ2PA ≈ 800-900 GM was observed. The use of probe 1 in bioimaging was shown via one- and two-photon fluorescence imaging of HCT-116 cells. An amplification of the stimulated emission of 1 was demonstrated in organic solvents and thin polystyrene films, which potentially can be used for the development of new fluorescent labels with increased spectral brightness.

Femtosecond Spectroscopy of Superfluorescent Fluorenyl Benzothiadiazoles with Large Two-Photon and Excited-State Absorption

“…The development of new organic molecules with efficient two-photon absorption (2PA) and specific linear photophysical and nonlinear optical properties remains a subject of great interest for a wide range of emerging applications, including two-photon fluorescence bioimaging, − optical power limiting, − microfabrication and optical data storage, − and singlet oxygen-based photodynamic therapy. − The nature of molecular electronic structure and fast inter- and intramolecular dynamic processes plays an important role in the formation of particular linear and nonlinear optical properties, such as transient excited-state absorption (ESA), − stimulated emission depletion (STED), − and superfluorescence and lasing abilities, − which are of great fundamental interest and need to be clearly determined. Fast dynamic processes of photochemical reactions, − formation of triplet–triplet ESA and triplet–triplet annihilation, , intramolecular hydrogen transfer, − relaxation rates and deactivation pathways of excited states in solvents of different polarities, ,− charge-transfer kinetics in metal–organic complexes and light-harvesting biological systems, , and solvation dynamics , have been investigated for a number of organic compounds using a well-defined transient absorption pump–probe method. , …”

Systematic Molecular Engineering of a Series of Aniline-Based Squaraine Dyes and Their Structure-Related Properties

“…The excitation anisotropy spectra of the dyes in viscous polytetrahydrofuran (pTHF) are presented in Figure 3C. We can see that the values of anisotropy were nearly constant in the main long-wavelength absorption band 48 and reached their maximum value r ≈ r 0 ≈ 0.37 for the modified dyes, and the value of SD-0 is around 0.31, reflecting a nearly parallel orientation of the absorption and the emission transition dipoles of new dyes in this spectral range. At higher energy, the anisotropy decreased and dips were observed near 470 nm for SD-0, SD-1, SD-2a, and SD-2b and 400 nm for SD-3, respectively, which suggests an additional electronic state with a transition dipole noncollinear with the main absorption band.…”

Far‐Red‐Emitting TEG‐Substituted Squaraine Dye: Synthesis, Optical Properties, and Selective Detection of Cyanide in Aqueous Solution

“…The values of excitation anisotropy are nearly constant in the main absorption band. This reflects the electronic transition S 0 – S 1 with similar dipole orientations, corresponding to the main absorption band . From the functional anisotropy value r 0 = (3cos 2 α – 1)/5, the angle α between absorption S 0 – S 1 and emission S 1 – S 0 transition dipole moments can be calculated.…”