Latest ArticlesBi draws increasing attention as anode materials for lithium-ion batteries and sodium-ion batteries due to its unique layered crystal structure, which is in favor of achieving fast ionic diffusion kinetics during cycling. However, the dramatic volume expansion upon lithiation/sodiation and an insufficient theoretical capacity of Bi greatly hinder its practical application. Herein, we report the Fe2O3 nanoparticle-pinning Bi-encapsulated carbon fiber composites through the electrospinning technique. The introduction of Fe2O3 nanoparticles can prevent the growth and aggregation of Bi nanoparticles during synthetic and cycling processes, respectively. Fe2O3 with high specific capacity also contributes to the specific capacity of the composites. Consequently, the as-prepared Bi-Fe2O3/carbon fiber composite exhibits outstanding long-term stability, which delivers reversible capacities 504 and 175 mAh/g after 1000 cycles at 1 A/g for lithium-ion and sodium-ion batteries, respectively.
In this study, Mn catalysts have been designed based on manganese oxide octahedral molecular sieve (OMS-2) supports to optimize the catalytic activity in the degradation of organic pollutants. Herein, two different synthetic strategies: Pre-incorporation vs. wet-impregnation have been employed to synthesize [PW]-OMS-2 and [PW]/OMS-2. For [PW]-OMS-2, energy dispersive X-ray spectroscopy (EDX) confirmed that dispersed granular phosphotungstic acid attached and located at the surface of OMS-2, meanwhile some W atoms have been doped into frameworks of OMS-2. However, for [PW]/OMS-2, the W atoms cannot enter the OMS-2 frameworks. A correlation has been established between the different synthetic strategies and catalytic activities. The [PW]-OMS-2 is the most highly effective and stable over than [PW]/OMS-2 and OMS-2 itself for the organic pollutants removal. This may be caused not only by the synergetic effect of [PW] and OMS-2, but also by doping W into frameworks of OMS-2. Therefore, this work provides a new environmentally-friendly and heterogeneous PMS activator and it may be put into practice to degrade organic pollutants.
MnOx-CeO2 catalysts are developed by hydrolysis driving redox method using acetate precursor (3Mn1Ce-Ac) and nitrate precursor (3Mn1Ce-N) for the selective catalytic reduction (SCR) of NOx by NH3. A counterpart sample (Cop-3Mn1Ce) was prepared by the NH3·H2O co-precipitation method for comparison purpose. Combining the results of physicochemical properties characterization and performance test, we find that the 3Mn1Ce-Ac catalyst with some nanorod structures is highly active for the deNOx process. The SCR activity of the 3Mn1Ce-Ac catalyst is more admirable than the 3Mn1Ce-N and the Cop-3Mn1Ce catalysts due to plentiful Lewis acid sites, excellent low-temperature reducibility, and superior surface area resulted from O2 generation during the preparation procedure. The 3Mn1Ce-Ac still exhibits the greatest performance for the deNOx process when gaseous acetone is in the SCR feed gas. The NOx conversion and N2 selectivity over the 3Mn1Ce-Ac are both improved by gaseous acetone above 150 ℃ due to the inhibition of SCR undesired side reactions (NSCR & C-O reactions) and "slow-SCR" process.
An N-heterocyclic carbene (NHC)-catalysed retro-aldol/aldol cascade reaction of spirooxindole-based β-hydroxyaldehyde has been developed. The ring opening-closure process enables the diastereodivergent synthesis of spirocyclopentaneoxindole products with four consecutive stereocenters by simply changing the reaction solvents (THF or DCE). The Michael/aldol/retro-aldol/aldol sequential protocol allows the diastereodivergent synthesis of spirocyclopentaneoxindoles from 3-substituted oxindole and α, β-unsaturated aldehyde under the relay catalysis of a chiral secondary amine and an NHC catalyst. Moreover, four stereoisomers of the product can be selectively provided by using different combinations of a chiral secondary amine and a solvent.
A visible light and base promoted O-H insertion/cyclization of para-quinone methides with aryl diazoacetates is developed. This one-pot two step reaction offers a mild and efficient approach for the synthesis of biologically important 2, 3-dihydrobenzofuran derivatives in good yields and moderate diastereoselectivities.
Ynamides are electron-rich alkynes with unique reactivities and act as flexible building blocks in organic synthesis. Therefore, the investigation for transformation of ynamides with exceptional selectivity and efficiency is attractive and interesting. Herein, we report an oxoarylation of ynamides with N-aryl hydroxamic acids. In the presence of catalytic Cu(OTf)2, both the terminal and internal ynamides could undergo an addition/[3,3] sigmatropic rearrangement cascade with N-aryl hydroxamic acids to achieve oxoarylation, along with providing selective entry to (ortho-amino)arylacetamides and oxindoles. Moreover, deuterium-labelling reaction and gram-scale reaction were conducted to probe the mechanism and showcase the scalability.
In this paper, the host-guest interaction of cucurbit[7]uril (Q[7]) and chromone (CMO) has been developed as a fluorescent probe for the highly selective detection of Zn2+ and Cd2+ in water based on a chelation-enhanced fluorescence (CHEF) mechanism. There was a good linear relationship between the fluorescence intensity of the CMO@Q[7] probe and the concentration of Zn2+ or Cd2+ in the range of 0–3.0 × 10–5 mol/L and the detection limit for Zn2+ and Cd2+ was found to be 2.03 × 10–6 mol/L and 1.89 × 10–6 mol/L, respectively. The X-ray crystal structure indicated that different coordination fashions were triggered by Zn2+ and Cd2+ in the CMO@Q[7] complexes, respectively. However, both metal ions coordinated with the carbonyl oxygen of CMO, which was encapsulated in the cavity of Q[7], thus leading to the enhancement of recognition fluorescence emission of CMO.
The photoisomerization properties of azo derivatives have been widely used in the fields of materials and biology. One serious restriction to the development of functional azo-based materials is the necessity to trigger switching by UV light, which damage the corresponding surfaces and penetrate only partially through the matter. Therefore, developing the visible and near-infrared light activated azo switches can solve this problem. This review provides a summary of molecular design strategies for driving the isomerization of azo derivatives with visible light and near-infrared light: (1) smart design directly excited by visible light, (2) the addition of upconversion nanoparticles, (3) the employment of two-photon absorption, (4) indirect excitation in combination with metal sensitizer.
The fascinating luminescence properties of gold nanoclusters (AuNCs) have drawn considerable research interests, and been widely harnessed for a wide range of applications. However, a fundamental understanding towards ligand density's role in the luminescence properties of these ultrasmall AuNCs remains unclear yet. In this communication, through systematic investigation of surface chemistries of glutathione-protected AuNCs (GSH-AuNCs) with different density of GSH as well as other thiolates, it is discovered that the density of surface ligands can significantly regulate the luminescence properties of AuNCs. Fluorescence lifetime spectroscopy and X-ray photoelectron spectroscopy showed that AuNCs with a higher density of electron-rich ligands facilitate their luminescence generation. Moreover, differences in the surface coverage of AuNCs can also affect their interactions with foreign species, as illustrated by significantly different fluorescence quenching capability of GSH-AuNCs with different ligand density towards Hg2+. This study provides new insight into the intriguing luminescence properties of metal NCs, which is hoped to stimulate further research on the design of metal NCs with strong luminescence and sensitive/specific responses for promising optoelectronic, sensing and imaging applications.
A novel approach for the synthesis of 4-aminoquinazolines has been developed via rhodium(III)-catalyzed [4 + 2] annulation of N-arylbenzamidines with 1, 4, 2-dioxazol-5-ones. This reaction features excellent regioselectivity, broad substrate scope and high step economy, which would provide the reference for the construction of the fused 4-aminoquinazolines with biologically and pharmacologically active compounds.
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