ABSTRACT
In this work, we report the synthesis of a family of donor-acceptor (D-A) π-conjugated aggregation-induced red emission materials (TPABT, DTPABT, TPEBT and DTPEBT) with the same core 2,2-(2,2-diphenylethene-1,1-diyl)dithiophene (DPDT) and different amounts and different strengths of electron-donating terminal moieties. Interestingly, TPABT and TPEBT, which have asymmetric structures, give obviously higher solid fluorescence quantum efficiencies in comparison with those of the corresponding symmetric structures, DTPABT and DTPEBT, respectively. In particular, the thin film of TPEBT exhibited the highest fluorescence quantum efficiency of ca. 38% with the highest αAIE. Moreover, TPEBT and DTPEBT with TPE groups showed two-photon absorption cross-sections of (δ) 1.75 × 103 GM and 1.94 × 103 GM at 780 nm, respectively, which are obviously higher than the other two red fluorescent materials with triphenylamine groups. Then, the one-photon and two-photon fluorescence imaging of MCF-7 breast cancer cells and Hela cells, and cytotoxicity experiments, were carried out with these red fluorescent materials. Intense intracellular red fluorescence was observed for all the molecules using one-photon excitation and for TPABT using two-photon excitation in the cell cytoplasm. Finally, TPEBT is biocompatible and functions well in mouse brain blood vascular visualization. It is indicated that these materials can be used as a specific stain fluorescent probe for live cell imaging.
ABSTRACT
In this work, two rigid, multiple tetraphenylethene (TPE)-substituted, π-conjugated, snowflake-shaped luminophores BT and BPT were facilely synthesized by using a 6-fold Suzuki coupling reaction. These molecules are constructed based on the nonplanar structure of propeller-shaped hexaphenylbenzene (HPB) or benzene as core groups and TPE as end groups. As a result, they reserve the intrinsic aggregation-induced emission (AIE) property of the TPE moiety. Meanwhile, both fluorescence quantum yield and piezochromic behavior in the solid state can be tuned or switched by inserting the phenyl bridges through changing the twisting conformation. The more extended structure BPT showed a much stronger AIE effect and higher ΦF,f in the solid state in comparison with that of BT. Furthermore, an excellent optical waveguide application of these molecules was achieved. However, the revisable piezofluorochromic behavior has only appeared when BT was ground using a pestle and treated with solvent.
ABSTRACT
Diacetone acrylamide (DAAM) is an important monomer which can be copolymerized with other monomers, so the copolymers with different properties can be obtained. In the present paper, the ultraviolet spectra of diacetone acrylamide solutions in four different solvents (water, acetonitrile, methanol, cyclohexane) were studied, and it was found that there were two strong absorption peaks around 200 nm and 226 nm, respectively. The absorption peak around 200 nm was sensitive to the polarity of the solvent. The absorption shifted to the lower wavelength as the polarity of the solvent was increased, especially in water and acetonitrile. And the adsorption shifted to longer wavelength with the increase in the concentration. However, the other absorption peak at 226 nm remained basically stable when the concentration or the polarity of the solvent was changed. Obviously the absorption at 226 nm is reasonably considered as a characteristic peak of DAAM in the ultraviolet quantitative analysis. And the other absorption peak at 200 nm which is sensitive to the solvent and concentration can be taken to study the interactions between DAAM and solvent molecules. Also, the strength of the adsorption was affected by the polarity of the solvent.
