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Chiral amine-squaramide is a kind of effective hydrogen bond donor bifunctional catalyst to promote many asymmetric transformations. In this paper, novel chiral tertiary amine-squaramide derived from the natural product of the stevioside was developed and applied into the asymmetric Michael addition of acetylacetone to nitroolefins. This asymmetric reaction performed well, and a series of enantiomerically enriched compounds were obtained in high yields (up to 96%) with excellent enantioselectivities (up to 99% ee).

A novel indolium-based fluorescent probe (probe 1) for the recognition and detection of hypochlorite (OCl−) has been explored via a double oxidation reaction mechanism. Probe 1 exhibited excellent selectivity and sensitivity for OCl− over other analytes, and with a detection limit of 0.11 μM. Meanwhile, probe 1 showed fast response toward OCl− in less than 3 min with obvious changes in color, which could be observed by naked eye. Moreover, fluorescence imaging experiments by using Eca109 cells were performed utilizing the new probe, demonstrating its practical applications in living cells.

The high voltage circuit breaker plays an important role in the circuit. In order to extend the service life of the circuit breaker, it is necessary to have materials with excellent ablation resistance. At present, The PTFE with boron nitride (BN) is widely used to produce the nozzle of high voltage circuit breaker. With the increase of BN filler particle size, the arc ablation performance of the composite increases gradually. In order to obtain the nozzle material with excellent ablation performances, nanoscale and microscale h-BN were divided into five groups with different mass ratio, then added into PTFE to prepare five kinds of composite materials with constant BN mass fraction. To study the influence of mass ratio on the thermal conductivity and arc ablation characteristics of PTFE/BN composites, arc ablation, thermal conductivity and spectral reflectance are tested. After adding microscale and nanoscale hybrid BN, the ablation amount of the composite decreased firstly and then increased, reaching the minimum in the third group. This work indicates there is a certain proportion with the excellent performance in arc ablation characteristics. This paper offers a feasible method for the preparation of PTFE/BN high-voltage circuit breaker.

As an important part of power equipment, high voltage circuit breakers play an important role in circuit breaking and isolating. However, during the breaking process of high voltage circuit breakers, arcs and recovery voltages are generated between the moving and stationary contacts, which may cause serious ablation and breakdown of the nozzles in the circuit breaker, shortening the life of the circuit breakers. Therefore, nozzles with superior performance are urgently needed. PTFE filled with different proportions of micron-BN and nano-BN was prepared in this paper to study the effect of hybrid fillers on the AC breakdown performance of PTFE. Scanning electron microscope (SEM) is used to characterize the dispersion state of micron-BN sheets and nano-BN sheets in PTFE matrix. The Thermally stimulated depolarization currents (TSDC) experiment is used to test and calculate the trap parameters of the sample. The AC breakdown experiment is used to test the breakdown strength of the specimen. The relationship between the breakdown performance and the change of trap parameters is discussed. And these factors are considered to be closely related.

During the breaking process of high voltage circuit breaker (HVCB), the arcs generated between the contacts may cause severe ablation of the nozzle, shortening the life of HVCB. Therefore, it is necessary to study the nozzle material with better ablation resistance. Polytetrafluoroethylene (PTFE)/boron nitride (BN) composite materials are commonly used in the industry to prepare nozzles. The particle size of BN can affect the ablation resistance of PTFE/BN composites, but the law is still unclear. In this paper, several kinds of PTFE composite samples doped with different nanoscale and micron-scale BN were prepared to study the effect of BN size on ablation resistance. The experimental results show that micron-scale BN fillers are more effective for improving the ablation resistance. With the increase of micron-scale BN particle size, the arc ablation resistance becomes better first and then worsens. The results are discussed and explained from the perspective of thermal transport and spectral reflectance characteristics.

A representative ferroelectric tetragonal potassium niobate (TKN) and antiferroelectric orthorhombic sodium niobate (ONN) crystalline powder samples were polarized by using an external electric field. The changes in lattice distortion and crystal symmetry of these samples polarized were revealed. The photocatalytic activities of the samples before and after the polarization were evaluated by photocatalytic decomposition of water and photocatalytic reduction of Ag+. The results imply that the polarization of such kind of perovskite-type niobate samples using the external electric field is one of effective ways to improve the photocatalytic performance, whether ferroelectric TKN or antiferroelectric ONN. The exploration of mechanism suggests that the polarization can change the ferroelectricity of niobate powder crystals. Furthermore, the photocatalytic activity on different exposed facets of these niobate crystals was also evaluated by detecting Ag content on the surfaces of sample via photocatalytic reduction of Ag+. It is found that {001} facet is the highest active facet of TKN, and {101} facet of ONN crystals has the highest photocatalytic activity among the exposed facets. The photocatalytic activity on each exposed facet can be increased to a certain extent by polarization, and the influence of polarization on photocatalytic activity is greater than that of surface energy. Keywords: Polarization, Photocatalytic activity, KNbO3, NaNbO3, Exposed facets

A novel ratiometric fluorescence probe (M1) for hypochlorite (ClO−) based on a mechanism of Fluorescent Resonance Energy Transfer (FRET) has been constructed. Probe M1 can be regarded as a difunctional probe for ClO− and Hg2+. Probe M1 exhibited good specificity and sensitivity towards ClO− over other related analytes as along with low detection limit (13.6 nM). Furthermore, it has been successfully used in living Eca109 cells for fluorescence imaging hypochlorite.

1D [Formula: see text]-MoO3 nanobelts were prepared using ammonium heptamolybdate tetrahydrate [(NH[Formula: see text]Mo7O[Formula: see text]H2O] as raw material by one-step hydrothermal method without template or guide agent at 180∘C. The layered [Formula: see text]-MoO3 nanobelt electrode has favorable electrochemical performance, and displays a fairly high specific capacitance, which can be up to 445[Formula: see text]F/g at a current density of 0.5[Formula: see text]A/g.

In this work, six isosteviolamino acid conjugates were designed and synthesized through simple condensation on a large scale without protecting group (Scheme). These amphiphilic organocatalysts mediated asymmetric three-component Mannich reactions of cyclohexanone and anilines with aromatic aldehydes in the presence of H2O. Meanwhile, the isosteviolproline conjugate 3b has been established as a highly efficient catalyst (Table 1), and afforded syn-Mannich products with excellent diastereoselectivities (syn/anti up to 98 : 2) and enantioselectivities (up to >99% ee; Table 3). The transition state of the reaction in the presence of H2O is proposed (Fig. 2).

Isosteviol-amino acid conjugates were synthesized and used as chiral catalysts for the asymmetric three-component Mannich reaction with hydroxyacetone as donor molecule. Good yields (up to 98%) and excellent stereoselectivities (up to 97:3 dr and 99% ee) were achieved in a short reaction time. In addition, syn- or anti-configurations of α-hydroxy-β-amino carbonyl compounds were obtained as main products with different chiral catalysts.

Among the conjugates tested, IPC is found to show good activity and stereoselectivity for the reaction of anilines, aromatic aldehydes and cyclohexanone.

New polymer-supported palladium complexes with C,N-ligands are easily synthesized and applied efficiently for the Heck reaction of iodobenzene and butylacrylate with high turnover frequencies up to 12 600.