•The synthesized new AIE templates exhibit obvious mechanochromic behavior.•D-π-A 2, 6-dimethyl-4-pyrone-cored derivatives present AIEE and solvatochromism.•Mechanochromic behavior was mainly depended on substituents' position and length.Three series of D-π-A 2,6-dimethyl-4-pyrone-cored derivatives were designed and synthesized. Evaluation by spectroscopic methods indicated that all the compounds exhibited aggregation-induced emission enhancement (AIEE) effect and solvatochromism. The experimental results revealed that the restriction of intramolecular rotation is the key element for showcasing the AIEE phenomenon. Moreover, all of the compounds presented red-shifted mechanochromic behavior, the extent of the red-shift was mainly dependent on the position and length of alkoxyl group. The PXRD and DSC profiles demonstrated a transformation from crystalline to amorphous state upon grinding. The D-A strategy introduced in this work could facilitate the development and application of ingenious mechanochromic materials.

•MNG nanocatalysts were easily obtained via one-pot hydrothermal synthesis process.•The catalytic activity of MNG hybrids is remarkably enhanced by Fe3O4 NPs loading.•N doping mode was changed by the in situ synthesis of Fe3O4 NPs.•The in situ synthesis of Fe3O4 NPs did not alter the C/N mass ratio of MNG hybrids.•The reduction of 4-nitrophenol over MNG no longer followed the pseudo-zero-order kinetics.Magnetic 3D nitrogen doped graphene gels (MNG) were easily obtained via one-pot hydrothermal synthesis process. It was found that N doping process, reduction of graphene oxide and Fe3O4 nanoparticles (NPs) generation in situ proceeded simultaneously, accompanied by the three-dimensional self-assembly. The MNG hybrids were confirmed to be interconnected poriferous frameworks of graphene sheets with uniform dispersion of Fe3O4 NPs embedded or encapsulated in N-doped graphene layers. The catalytic performance of MNG nanocatalysts was evaluated by the reduction of 4-nitrophenol to 4-aminophenol. It was worth noting that the catalytic activity of MNG hybrids was remarkably enhanced by Fe3O4 NPs loading due to the change of N doping mode induced by the in situ synthesis of these magnetic NPs, which did not alter the C/N mass ratio in fact. Meanwhile, the reaction no longer simply followed the pseudo-zero-order kinetics in late stage, this might be attributed to the enhancement of catalytic activity. Furthermore, MNG nanocatalysts were easily recycled by virtue of their superparamagnetism and exhibited excellent stability.Download high-res image (120KB)Download full-size image

A heptamethine cyanine-based near-infrared (NIR) fluorescent probe Cy-1 for hydrosulfide detection was developed, with the response mechanism based on nucleophilic substitution of acryloyl moiety by HS−. Upon addition of NaHS, Cy-1 displayed a rapid fluorescence quenching (excited at 700 nm) and a quick fluorescence enhancement (excited at 544 nm) as well as obvious changes in absorption spectra and color. The response was fast within tens of seconds and could be observed by naked eyes. By contrasting Cy-1 with the reported probe CyAC, the superiority of Cy-1 in selectivity over Cys was demonstrated. Besides, it also exhibited excellent selectivity and sensitivity to HS− over various anions (0.33-μM detection limit). Additionally, this probe was successfully applied in fetal bovine serum samples and imaging of hydrosulfide in living cells.

A series of Pd/γ-Al2O3 catalysts modified by potassium salts were prepared and evaluated in the reductive cyclization of 2-nitro-2′-hydroxy-5′-methylazobenzene without additional base. These solid base-hydrogenation bifunctional catalysts were characterized and the results demonstrated that potassium salts could have an important impact on the properties and catalytic performance of Pd/γ-Al2O3.

A mitochondria-targeting probe, by conjugating a quaternary ammonium cation with glucosamine modified pH-activated cyanine, was designed and synthesized. This probe has excellent selectivity and sensitivity toward pH, stability, cellular membrane permeability and low cytotoxicity. Owing to the acidic feature of tumors and the more negative mitochondrial membrane potential of tumor cells than that of normal cells, this probe can selectively accumulate in tumor cells and light up its fluorescence. It has been successfully applied for in vivo tumor imaging with a high signal-to-noise ratio. Moreover, this multifunctional switchable sensor was also employed for the fluorescent imaging of the fluctuation of intracellular pH in HeLa cells.

A glucosamine modified near-infrared cyanine fluorescent probe has been synthesized and developed as an efficient and visual sensor for the trace level determination of glutamic acid (Glu) and aspartic acid (Asp) with no interference by other amino acids. A prominent fluorescence enhancement at 805 nm and a remarkable color change from pale red to colorless were observed in the presence of Glu and Asp respectively. This probe may also serve as a highly sensitive acidic pH probe with a pKa value of 5.82. Furthermore, the chemosensor has been successfully applied for the imaging of Glu and Asp in living cells, and the cytotoxicity assay exhibited that it is of low toxicity under the experimental conditions.

A series of chiral pyrrolidine quaternary derivatives were designed and synthesized. It was found that these derivatives are highly efficient organocatalysts for the asymmetric Michael addition reactions of aldehydes and ketones to nitroolefins with high yields (up to 96%), high enantioselectivities (up to 99% ee), and high diastereoselectivities (up to 97:3 dr). Furthermore, catalyst 7a could be recycled without remarkable loss of catalytic activity and stereoselectivity.

A series of fluorescein esters of straight chain fatty acid were synthesized and applied to the fluorometric assay of lipase. The rate of change in the fluorescence of the solution, due to the production of fluorescein, was measured and correlated with enzyme activity. The hydrolytic properties of fluorescein esters were investigated. In addition, the relationship between their hydrolytic properties and the chain length of fluorescein esters was discussed in this paper. In contrast to fluorescein dibutyrate, fluorescein dilaurate was found to be a better substrate for the assay of lipase with the higher rate of hydrolysis and better Km value. As little as 0.0001 mg/ml of lipase can be detected with a relative accuracy of about 1.5%.

•Heterogeneous catalyst was achieved via simple N-acylation reaction.•This heterogeneous catalyst presented satisfied results.•The catalytic mechanism was investigated through XPS.•Continuous reaction was realized in a fixed-bed reactor with this catalyst.Wang resin was modified by (1R,2R)-(+)-1,2-DPEN by means of a triazine ring. The catalyst was characterized by thermogravimetric (TG) analysis, elemental analysis, and Fourier transform infrared spectroscopy (FT-IR). Subsequently, this catalyst was employed for the asymmetric Michael addition of acetone to β-nitrostyrene. Under optimized conditions, 76.6% of β-nitrostyrene conversion and 82.8% enantioselectivity of Michael adduct were obtained. On the basis of the characterization of the catalyst by X-ray photoelectron spectroscopy (XPS), the mechanism of catalysis was proposed. In addition, the generality of the catalyst was evaluated with Michael additions of acetone to β-nitroolefins. Finally, the continuous reaction was realized in a fixed-bed reactor.Mechanism of Michael addition of acetone to β-nitrostyrene over the catalyst with acetic acid.Download full-size image

A mitochondria-targeting probe, by conjugating a quaternary ammonium cation with glucosamine modified pH-activated cyanine, was designed and synthesized. This probe has excellent selectivity and sensitivity toward pH, stability, cellular membrane permeability and low cytotoxicity. Owing to the acidic feature of tumors and the more negative mitochondrial membrane potential of tumor cells than that of normal cells, this probe can selectively accumulate in tumor cells and light up its fluorescence. It has been successfully applied for in vivo tumor imaging with a high signal-to-noise ratio. Moreover, this multifunctional switchable sensor was also employed for the fluorescent imaging of the fluctuation of intracellular pH in HeLa cells.