Didi Chen

A malonitrile-functionalized metal-organic framework for hydrogen sulfide detection and selective amino acid molecular recognition

A novel porous polymeric fluorescence probe, MN-ZIF-90, has been designed and synthesized for quantitative hydrogen sulfide (H2S) fluorescent detection and highly selective amino acid recognition. This distinct crystalline structure, derived from rational design and malonitrile functionalization, can trigger significant enhancement of its fluorescent intensity when exposed to H2S or cysteine molecules. Indeed this new metal-organic framework (MOF) structure shows high selectivity of biothiols over other amino acids and exhibits favorable stability. Moreover, in vitro viability assays on HeLa cells show low cytotoxicity of MN-ZIF-90 and its imaging contrast efficiency is further demonstrated by fluorescence microscopy studies. This facile yet powerful strategy also offers great potential of using open-framework materials (i.e. MOFs) as the novel platform for sensing and other biological applications.

A diethylaminophenol functionalized Schiff base: crystallization-induced emission-enhancement, switchable fluorescence and application for security printing and data storage

In this study, we report the synthesis and photoluminescence (PL) behaviour of a new luminogen, SBOH, a diethylaminophenol functionalized Schiff base. SBOH possesses electron donor (D) and acceptor (A) units, showing twisted intramolecular charge transfer (TICT) properties. Interestingly, SBOH is weakly emissive in the amorphous phase but becomes highly emissive upon crystallization as confirmed by spectroscopic methods and fluorescence microscopy; in other words, SBOH is crystallization-induced emission-enhancement (CIEE)-active. Similar to the typical CIEE luminogens, the emission of SBOH is also sensitive to molecular packing modes. The weak emission of amorphous SBOH can be switched on via a deprotonation process caused by strong alkali. Meanwhile, exposure to acetic acid vapour rapidly switches the emission to the “off” state through re-protonation. The protonation and deprotonation processes display good reversibility. This deprotonation process is further confirmed by 1H NMR analysis and UV-vis spectroscopy. By taking advantage of the stimuli responsive fluorescence, a convenient and efficient technology for security printing and data storage is designed.

A fluorescent probe with an aggregation-enhanced emission feature for real-time monitoring of low carbon dioxide levels

Novel fluorescent probes based on the 1,2,5-triphenylpyrrole core containing a different number of tertiary amine moieties, 2-(dimethylamino)ethyl 4-(2,5-diphenyl-1H-pyrrol-1-yl)benzoate (TPP-DMAE), bis(2-(dimethylamino)ethyl) 4,4′-(1-phenyl-1H-pyrrole-2,5-diyl)dibenzoate (TPP-BDMAE) and tris(2-(dimethylamino)ethyl) 4,4′,4′′-(1H-pyrrole-1,2,5-triyl)tribenzoate (TPP-TDMAE), with an aggregation-enhanced emission (AEE) feature, were prepared for the quantitative detection of low levels of carbon dioxide in the gas mixture with the fraction of carbon dioxide ranging from 0.4% to 5%. Compared with the other two compounds, TPP-TDMAE showed the most selective, fastest and most iterative response to carbon dioxide. A significant fluorescence decrease with a turn-off ratio over 20-fold was triggered by the disaggregation process through the reaction with carbon dioxide. Response time results indicated that the emission intensity of TPP-TDMAE can be quickly decreased to the minimum level in less than 12 s upon bubbling of carbon dioxide. It is desirable to develop a novel method for the selective, real-time and quantitative detection of CO2 for biological and medical applications.

The synthesis of chiral triphenylpyrrole derivatives and their aggregation-induced emission enhancement, aggregation-induced circular dichroism and helical self-assembly

A pair of enantiomers ((R)-TPPBAm and (S)-TPPBAm) and their raceme (rac-TPPBAm) were designed and prepared by conjugating (R)-, (S)- or racemic 1-phenylethylamine to an aggregation-induced emission enhancement (AIEE) active triphenylpyrrole fluorophore. The three target compounds were thoroughly characterized and their optical properties were systematically investigated. The fluorescence analyses indicate that they all retain the AIEE activities originating from the triphenylpyrrole moiety, irrespective of the attaching groups. More importantly, both the enantiomers containing (R)- or (S)-1-phenylethylamine attachment exhibit aggregation-induced circular dichroism (AICD) features with mirror-image signals. Besides, they also exhibit circularly polarized luminescence (CPL) with an emission dissymmetry factor (gem) from 1.5 × 10−4 to 3 × 10−3 for (R)-TPPBAm and −1.3 × 10−4 to −4 × 10−3 for (S)-TPPBAm in aggregate states. As expected, consistent with the variations of their CD signals, (R)-TPPBAm and (S)-TPPBAm could self-assemble into helical nanofibers with the opposite screw direction during the aggregation process in the THF–water mixed solution, while the racemic compound rac-TPPBAm exhibits no CD and CPL signals, and self-assembles to form nanoparticles blocks. These results demonstrate that the morphologies and optical activities can be controlled simultaneously without losing the solid-state emission performance of the material by attaching a chiral group to an AIEE fluorophore, which could shed light on the design of optical active fluorophores for sensitive and time-efficient enantiomer determination.

The application of CO 2 -sensitive AIEgen in studying the synergistic effect of stromal cells and tumor cells in a heterocellular system

Reciprocal signaling between stromal and tumor cells was believed to contribute to tumor cell proliferation and apoptosis in heterocellular systems. Herein we used the CO2-sensitive AIEgen as bioprobe to study the synergistic effect of stromal cells and tumor cells in a heterocellular system. The experimental results demonstrated that metabolic rates of living tumor cells in the co-culture system were still faster than that of stromal cell through the detection of CO2 generation rate in living cell. All rates were, however, slower than that in homocellular system. It indicated that tumor cells would induce neighboring stromal cells to establish a common protection mechanism against foreign material invasion, which enhanced the cell activity and drug resistance. In addition, tumor cells in solid carcinoma exhibited delayed growth but less apoptosis in co-culture systems. Taken these results together, a bidirectional signaling pathway theory was proposed between tumor and stromal cells in co-culture system and could play a different and important role in anticancer drug molecules designs.