Latest ArticlesA novel BF3-promoted [3 + 2] annulation of azonaphthalenes and ynamides is described. This protocol provides a modular and efficient entry to functionalized amino benzo[e]indole derivatives smoothly.
Two isostructural Ni(Ⅱ)/Co(Ⅱ)-based metal-organic frameworks (MOFs), namely {[M3(L)2(bpb)3(H2O)4]·2DMF·2H2O}n [M = Ni (HL-5, HL is short for Hui-Ling Liu); M = Co (HL-6); H3L = 2', 6'-dimethyl-[1, 1'-biphenyl]-3, 4', 5-tricarboxylic acid; bpb = 1, 4-bis(pyrid-4-yl)benzene], have been hydrothermally syn-thesized and structurally characterized. Both HL-5 and HL-6, which have the same three-interpenetrated 3D pillared-layer framework with sqc306 type topology, present good selective methyl orange (MO) adsorption over rhodamine B (RhB). Moreover, the catalytic CO2 cycloaddition properties with epoxides of the two MOFs have also been studied at ambient pressure and temperature.
Experiments indicate that a catalytic amount of CuI plays an important role in the siloxane-mediated Pd-catalyzed cross-coupling reactions with the direct use of organolithium reagents. Addition of organolithium to the siloxane transfer agent generates an organosilicon intermediate. DFT calculations indicate that CuI initially accelerates the Si-Pd(Ⅱ) transmetalation of the organosilicon intermediate by the formation of CuI2-. Subsequently, CuI2- works as a shuttle between the Si-Cu(I) and Cu(I)-Pd(Ⅱ) transmetalation processes.
The 2D nanomaterials have achieved the superlubrication property whatever in solid or liquid lubrication in recent years. However, whether or not the nanosheets can stably disperse in oils and smoothly enter into the asperity of friction pairs is crucial for exerting the function of antifriction. The structure of 2D QDs is desirable for addressing these issues due to its smaller 3D size. In this study, we developed a facile preparation process for WS2 QDs with uniform 2 nm size from nanosheets via hydrothermal-assisted grinding approach. The structure of the as-obtained WS2 QDs was determined by a series of characterizations. The results showed that the as-obtained WS2 QDs exhibited the typical spectrum features of nanosized quantum dot. The results of the tribological performance in grease verified that the average friction coefficient (ACOFs) and wear volume (AWVs) were decreased by 7.89% and 63.90% relative to grease, respectively, exhibiting a preferable friction reducing and wear resistance.
Colorimetric sensing strategies as a powerful point-of-care testing (POCT) tool have attracted significant interest in various chem/biosensing applications. Taking the excellent bare-eye-detectable signaling feature, nanozymes-based colorimetric sensors enable more potential applications and have been a new forefront in the colorimetric POCT analysis toward different target analytes. However, the low catalytic activity of nanozymes in most cases limits their practical application. Recent efforts demonstrate that the aggregation-induced nanozymes provide a general means to modulate nanozymes activity and enhance colorimetric sensing performances of some nanozymes-based colorimetric sensors. But there are few reports are explored to discuss and review such aggregation-induced nanozymes and their colorimetric sensing applications. To highlight the advances and progress in aggregation-induced nanozymes based colorimetric assays, we herein summary the fundamentals, classify and applications of this newly-developing field, focusing on the aggregation-induced activity enhancement of nanozymes (AIAE-nanozymes) with a significant "signal-on" feature and aggregation-induced activity inhibition of nanozymes (AIAI-nanozymes) with a dramatical "signal-off" characteristics. Finally, we also propose the current challenges and the future prospects on both AIAE-nanozymes and AIAI-nanozymes.
The necessity to explore high-efficiency and high-value utilization strategy for biomass-waste is desirable. Herein, the strategy for direct conversion biomass-waste (rice husks) to Si/C composite structure anode was built. The Si/C composite materials were successfully obtained via the typical thermal reduction with magnesium, and the Si nanoparticle was uniformly embedded in carbon frame, as revealed by Raman, X-ray diffraction (XRD) and transmission electron microscope (TEM) measurement. The carbon structure among rice husks was effectively used as a protective layer to accommodate the volume variation of Si anode during the repeated lithiation/delithiation process. Benefitting from the structure design, the batteries show a superior electrochemical stability with the capacity retention rate above 90% after 150 cycles at the charge/discharge rate of 0.5 C (1 C = 600 mAh/g), and hold a high charge capacity of 420.7 mAh/g at the rate of 3 C. Therefore, our finding not only provides a promising design strategy for directly conversion biomass-waste to electrochemical storage materials but broadens the high-efficiency utilization method for other biomass by-products.
3-CF3S substituted thioflavones and benzothiophenes were achieved via the reactions of AgSCF3 with methylthiolated alkynones and alkynylthioanisoles, respectively, promoted by persulfate. This protocol possesses good functional group tolerance and high yields. Mechanistic studies suggested that a classic two-step radical process was involved, which includes addition of CF3S radical to triple bond and cyclization with SMe moiety.
We studied the cascade nucleophilic addition reactions of 1,2,3-triazines with activated acetonitriles or ketones, which were used to construct highly substituted pyridines that are not easily accessed by conventional methods. The strategy addressed some structural diversity issues currently facing medicinal chemistry, and the resulting pyridines could be used as convenient precursors for the synthesis of related pharmaceuticals. In particular, our method was applied to the syntheses of the marketed drug etoricoxib and several biologically important molecules in a few steps.
Graphene nanosheets are widely used in anti-corrosion polymeric coating as filler, owing to the excellent electrochemical inertness and barrier property. However, as the arrangement of graphene nanosheets is difficult to form a perfect layered structure, polymeric coating with graphene nanosheets usually needs micron-scale thickness to ensure the enhancement of corrosion protection. In this work, layer-by-layer stacked graphene nanocoatings were fabricated on stainless steel by self-assembly based on Marangoni effect. The anti-corrosion property of graphene coatings were studied through Tafel polarization curves, electrochemical impedance spectroscopy and accelerated corrosion test with extra applied voltage. The self corrosion current density of optimized three-layered graphene coated sample was one quarter of that of bare stainless steel. And the self corrosion potential of optimized sample is increased to -0.045 V. According to the results, graphene nanocoatings composed of layered nanosheets exhibits good anti-corrosion property. Besides, the self-assembly method provide a promising approach to make layered-structure coating for other researches about 2D material nanosheets.
An efficient synthesis of 3-(diarylallylidene)oxindoles from 3-(1H-indol-3-yl)-1, 1-diarylpropan-1-ol under metal-free conditions is described. NBS serves as a critical medium leading to a facile oxygen-migration in the transformation. The protocol has advantages of high efficiency, simple opreation, mild reaction conditions, good atom-economy, wide substrate scope and good yields of products. A detailed mechanism is proposed after careful investigation.
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