Facile synthesis of ultra-long Cu microdendrites for the electrochemical detection of glucose

Ultra-long Cu microdendrites (MDs) were prepared by one-step electrodeposition on a glassy carbon electrode. The results demonstrated that the reduction potential, pH, and temperature of the electrolysis solution, as well as the amount of Cu²⁺ and citrate ions, play important roles in the formation of the Cu MDs. Notably, the X-ray diffraction experiments confirmed that the aggregations of the Cu nanocrystals preferred to grow along (111) direction. In addition, the resulting Cu MDs-modified electrode showed good electrochemical performance as a non-enzyme glucose sensor in alkaline media.     

Studies on the Cationic Copolymerization of α-Pinene and Styrene with Complex SbCl3/AlCl3 Catalyst Systems. I. Effects of the Polymerization Conditions on the Copolymerization Products

Abstract

The copolymerization products of α-pinene and styrene were prepared with the compound catalyst system SbCl₃/AlCl₃ by changing the Sb/Al ratio, feeding monomer ratio, solvent, and polymerization temperature. The compositions of the copolymerization products were quantitatively characterized by the method of the combination of micro-ozonization and thin-layer chromatography in terms of the contents of the homopolymers and the copolymers containing high or low mole fractions of α-pinene, the yields of pure copolymer, and the monomer unit ratios (F ₁) of copolymers. The results show that it was easier to obtain the higher yield (up to 80%) of the pure copolymer with the complex catalyst system than with AlCl₃ alone. The F ₁ values could be controlled between 30 and 56% under the following polymerization conditions: Sb/Al  1/2, α-pinene/styrene  70%, and the conversion of styrene  90%.     

Monodisperse mesocrystals of YF3 and Ce3+/Ln3+ (Ln=Tb, Eu) co-activated YF3: shape control synthesis, luminescent properties, and biocompatibility

A family of monodisperse YF(3), YF(3):Ce(3+) and YF(3):Ce(3+)/Ln(3+) (Ln=Tb, Eu) mesocrystals with a morphology of a hollow spindle can be synthesized by a solvothermal process using yttrium nitrate and NH(4) F as precursors. The effects of reaction time, fluorine source, solvents, and reaction temperature on the synthesis of these mesocrystals have been studied in detail. The results demonstrate that the formation of a hollow spindle-like YF(3) can be ascribed to a nonclassical crystallization process by means of a particle-based reaction route in ethanol. It has been shown that the fluorine sources selected have a remarkable effect on the morphologies and crystalline phases of the final products. Moreover, the luminescent properties of Ln(3+)-doped and Ce(3+)/Ln(3+) -co-doped spindle-like YF(3) mesocrystals were also investigated. It turns out that Ce(3+) is an efficient sensitizer for Ln(3+) in the spindle-like YF(3) mesocrystals. Remarkable fluorescence enhancement was observed in Ce(3+)/Ln(3+) -co-doped YF(3) mesocrystals. The mechanism of the energy transfer and electronic transition between Ce(3+) and Ln(3+) in the host material of YF(3) mesocrystals was also explored. The cytotoxicity study revealed that these YF(3) -based nanocrystals are biocompatible for applications, such as cellular imaging.     

Microwave-assisted synthesis of highly luminescent CdSeTe@ZnS-SiO2 quantum dots and their application in the detection of Cu(II)

Highly luminescent and low toxic glutathione-capped CdSeTe@ZnS-SiO(2) quantum dots were successfully synthesized via a promising microwave strategy, and then applied in the detection of Cu(2+).     

Total synthesis of (-)-fusarisetin A and reassignment of the absolute configuration of its natural counterpart

The first total synthesis of (-)-fusarisetin A, the enantiomer of naturally occurring acinar morphogenesis inhibitor (+)-fusarisetin A, was accomplished in 13 steps, leading to the reassignment of the absolute configuration of the natural product. The synthesis featured a Lewis acid-promoted intramolecular Diels-Alder reaction, a Pd-catalyzed O→C allylic rearrangement, a chemoselective Wacker oxidation, and a Dieckmann condensation/hemiketalization cascade.     

Chip-based nanoflow high performance liquid chromatography coupled to mass spectrometry for profiling of soybean flavonoids

In this work a chip-based nano HPLC coupled MS (HPLC-chip/MS) method with a simple sample preparation procedure was developed for the flavonoid profiling of soybean. The analytical properties of the method including the linearity (R(2) , 0.992-0.995), reproducibility (RSD, 1.50-7.66%), intraday precision (RSD, 1.41-5.14%) and interday precision (RSD, 2.76-16.90%) were satisfactory. Compared with the conventional HPLC/MS method, a fast extraction and analysis procedure was applied and more flavonoids were detected in a single run. Additionally, 13 flavonoids in soybean seed were identified for the first time. The method was then applied to the profiling of six varieties of soybean sowed at the same place. A clear discrimination was observed among different cultivars, three isoflavones, accounting for nearly 80% of total flavonoid contents, were found increased in the spring soybeans compared with the summer cultivars.     

Stereoselective tribromomethylation of N-(tert-butanesulfinyl)imines with bromoform: practical synthesis of α-tribromomethyl amines

The unprecedented nucleophilic tribromomethylation of N-(tert-butanesulfinyl)imines with bromoform has been shown to be a highly stereoselective and practical method for the synthesis of enantiomerically pure α-tribromomethyl amines. THF has proven to be the best solvent in this addition reaction. By changing the reaction solvent from THF to DMF, 2,2-dibromoaziridines can also be synthesized directly from bromoform and N-(tert-butanesulfinyl)imines under similar reaction conditions.     

Four-component assembly of chiral N-B heterocycles with a natural product-like framework

The dative N-B bond was used to simply assemble heterocycles with a skeleton akin to the 5-oxofuro[2,3-b]furan motif. Twenty-five new N-B heterocycles were prepared via a highly efficient one-pot four-component reaction in yields and diastereoselectivities up to 95% and >97%, respectively. Several reaction intermediates were discovered using electrospray ionization mass spectroscopy which set the basis for the mechanism elucidation using DFT calculations.     

Giant metal-organic frameworks with bulky scaffolds: from microporous to mesoporous functional materials

New concepts on the design and synthesis of crystalline metal-organic frameworks (MOFs) have made them a subject of considerable interest in the growing field of materials science. By creating larger cavity sizes by a nearly infinite combination of metal nodes and organic linkers, many innovative characteristics of microporous MOFs have been revealed. The primary goal of this perspective article is to highlight the frontiers in the development of giant MOFs that are deliberately constructed from metallated or metal-free bulky scaffolds. Incorporating these types of distinct bulky ligands into giant MOFs may lead to MOFs with a large cavity size, intriguing properties and new framework topology. Emerging applications of these materials in catalysis, adsorption, and sensors are also discussed.     

Fully converged integral cross sections of collision induced dissociation, four-center, and single exchange reactions, and accuracy of the centrifugal sudden approximation in H2 + D2 reaction

The initial state selected time-dependent wave packet method was employed to calculate the integral cross sections for the H(2) + D(2) reaction with and without the centrifugal sudden (CS) approximation by including all important K (the projection of the total angular momentum on the body-fixed axis) blocks. With a full-dimensional model, the first fully converged coupled-channel (CC) cross sections for different competitive processes from the ground rotational state were obtained: collision induced dissociation (CID), four-center (4C) reaction and single exchange (SE) reaction. The effect of the total angular momentum J on the reaction dynamics of H(2) + D(2) and the accuracy of the CS approximation have also been studied. It was found that the CID and SE processes occur in a wide range of J values while the 4C process can only take place in a narrow window of J values. For this reason, the CC cross section for the 4C channel is merely comparable to the SE channel. A comparison of the integral cross sections from CC and CS calculations showed that the CS approximation works well for the CID process but not for the 4C and SE processes, and the discrepancy between the CC and CS cross sections grows larger as the translational energy and/or the vibrational energy increase(s).