Latest ArticlesElectrical double-layer capacitors are widely concerned for their high power density, long cycling life and high cycling efficiency. However, their wide application is limited by their low energy density. In this study, we propose a simple yet environmental friendly method to synthesize cobalt and nitrogen atoms co-doped porous carbon (CoAT-NC) material. Cobalt atoms connected with primarily pyridinic nitrogen atoms can be uniformly dispersed in the amorphous carbon matrix, which is benefit for improving electrical conductivity and density of states of the carbon material. Therefore, an enhanced performance is expected when CoAT-NC is served as electrode in a supercapacitor device. CoAT-NC displays a good gravimetric capacitance of 160 F/g at 0.5 A/g combing with outstanding capacitance retention of 90% at an extremely high current density of 100 A/g in acid electrolyte. Furthermore, a good energy density of 30 Wh/kg can be obtained in the organic electrolyte.
In this study, large-scale Te-doped polycrystalline SnSe nanopowders were synthesized by a facile hydrothermal approach and the effect of Te doping on the thermoelectric properties of SnSe was fully investigated. It is found that the carrier concentration increases due to the reduction of band gap by alloying with Te, which contributes to significant enhancement of electrical conductivity especially at room temperature. Combined with the moderated Seebeck coefficient, a high power factor of 4.59 μW cm−1 K−2 is obtained at 773 K. Furthermore, the lattice thermal conductivity is greatly reduced upon Te substitution owing to the atomic point defect scattering. Benefiting from the synergistically optimized both electrical- and thermal-transport properties by Te-doping, thermoelectric performance of polycrystalline SnSe is enhanced in the whole temperature range with a maximum ZT of ~0.79 at a relatively low temperature (773 K) for SnSe0.85Te0.15. This study provides a low-cost and simple low-temperature method to mass production of SnSe with high thermoelectric performance for practical applications
Acid-controlled, chemodivergent and redox-neutral annulations for the synthesis of isocoumarins and isoquinolinones have been realized via Rh(III)-catalyzed C—H activation. Diazo compounds act as a carbene precursor, and coupling occurs in one-pot process, where adipic acid and trimethylacetic acid promote chemodivergent cyclizations.
Atkamine is a complex marine pyrroloiminoquinone alkaloid that comprises a heptacyclic scaffold bearing five different heterocycles and four contiguous stereocenters, and therefore it is a highly challenging target for synthetic chemists. We herein reported a modular synthetic strategy toward this alkaloid, featuring a formal [5 + 2] annulation and an asymmetric Michael addition. The efficient synthesis of the long-chain aliphatic aldehyde and chiral amino acetal fragments have been achieved. A simplified tetracyclic intermediate bearing the core structure of atkamine has been successfully constructed through the formal [5 + 2] annulation.
Two new hydrostable two-dimensional (2D) uranyl coordination complexes [(UO2)5(μ3-O)2(nbca)2]·7H2O (1) and [(UO2)3(nbca)2(H2O)3]·2H2O (2) (H3nbca = 5-nitro-1,2,3-benzenetricarboxylic acid) were hydrothermal synthesized. Single-crystal structural refinements reveal that both of the two complexes were formed by the packing of 2D uranyl coordination sheets via the hydrogen bonds. The nbca ligand coordinating to the uranyl polyhedron centers constructed the 2D sheets. There are UO8 hexagonal bipyramids and UO7 pentagonal bipyramids in 1 while only UO7 pentagonal bipyramids in 2. Photocatalytic degradation of rhodamine B (RhB) in aqueous solution was studied. Complex 2 possesses better performance than 1 with 96.2 % of the RhB was degraded in only 60 min. Mechanism studies reveal that the dissolved oxygens are essential to the RhB degradation. The photocurrent density of 2 is more stable than that of 1, which indicating the stronger ability to separate photoexcited electrons and hole pairs of 2.
Flexible Na-ion storage cathodes are still very few due to the challenge in achieving both reliable mechanical flexibility and excellent electrochemical performances. Herein, a new type of flexible Na3(VOPO4)2F cathode with nanocubes tightly assembled on carbon cloth is fabricated by a facile solvothermal method for the first time. The cathode is able to exhibit superior rate capability and stable cycling performance up to 1000 cycles, due to the surface-assembling of crystalline nanocubes on carbon fibers. In addition, it shows good mechanical flexibility, nearly no capacity decay is observed after continuous bending of 500 times. With this novel cathode and a directly-grown Na2Ti2O5 anode, a fully binder-free Na-ion battery is assembled. It can deliver a high working voltage and increased gravimetric energy/power densities (maximum values: 220.2 Wh/kg; 5674.7 W/kg), and can power a LED indicator at bending angles from 0° to 180°.
Smart strategies that can decrease the side effect and enhance the therapeutic efficacy of chemotherapy are in urgent need to meet the special demands of cancer therapy. Herein, two water-soluble macrocyclic hosts, i. e., a carboxylated leaning tower[6]arene (CLT6) and a carboxylated [2]biphenyl-extended pillar[6]arene (CBpP6), are used to load chemotherapy drug oxaliplatin (OxPt) by forming inclusion complexes (OxPt⊂CLT6 and OxPt⊂CBpP6) through host-guest interactions. Interestingly, OxPt can be released from the macrocyclic cavities of these drug delivery systems (DDSs) via the competitive binding effect of spermine (SPM) because of the stronger binding abilities of CLT6/CBpP6 toward SPM as compared with OxPt, leading to enhanced cytotoxicity on SPM-overexpressed cancer cells, such as breast cancer MCF-7 cells. Moreover, compared to free OxPt, due to the low concentration of SPM in normal cells, OxPt⊂CLT6 and OxPt⊂CBpP6 demonstrated a decreased cytotoxicity on liver L02 cells, which is beneficial for reducing the side effect of anticancer drug during chemotherapy. Such a strategy might be extended to other antitumor drugs and water-soluble macrocycles with suitable cavity sizes to achieve controllable drug delivery and enhanced anticancer ability in supramolecular chemotherapy.
The detection of bacterial pathogen such as Staphylococcus aureus (S. aureus) is essential for the regulation of food hygiene and disease diagnosis. Herein, we developed a simple one-step fluorescence resonance energy transfer (FRET)-based sensor for specific and sensitive detection of S. aureus in food and serum samples, in which aptamer-modified quantum dots (aptamer-QDs) was employed as the energy donor and antibiotic of teicoplanin functionalized-gold nanoparticles (Teico-AuNPs) was chosen as the energy acceptor. Within 1 h, the FRET-based sensor showed a linear range of from 10 cfu/mL to 5×108 cfu/mL, with the low limit of detection (LOD, 2 cfu/mL) for S. aureus in buffer. When further applied to assay S. aureus in real samples, the FRET-based sensor showed good recoveries ranging from 84.5% to 110.0%, with relative standard derivations (RSDs) of 0.01%–0.44% and a LOD of 100 cfu/mL in milk, orange juice and human serum.
Imitating the signal transduction and transmembrane transport controlled by biological channels in the cell membrane, artificial nanochannels with a similar capability of sensing and transport are constructed as bionic nanochannels. To accomplish selective sensing and transport of biological analyte (as "guest"), the bionic nanochannels are modified with the artificial receptor (as "host"). Based on selective recognition between host and guest, bionic nanochannels translate the stimulus of the guest to electrochemical signal as sensors, and further regulate the transmission of guest as transporters. However, throughout all kinds of guests, the selective sensing and transport of ions and chiral molecules is a challenging problem. And throughout all hosts of ions and chiral molecules, the macrocyclic hosts with multisite of recognition show better selectivity, such as crown ethers, cyclodextrins, calixarenes, and pillararenes. In this article, we highlight recent advances in the macrocyclic host-based nanochannels for the selective sensing and transport of ionic and chiral guests, summarize the similarities and differences of different kinds of macrocyclic host-based nanochannels, and expect the research direction and application prospect.
Multiple hydrogen bonds containing nucleophilic phosphines derived from dipeptide dual-reagents catalyzed asymmetric Michael addition reactions between indene esters and activated olefins in high yields and good to excellent enantioselectivities under mild reaction conditions. The success of current highly selective reactions should provide inspiration for expansion to other reactions and would open up new paradigms for the synthesis of indanone derivatives bearing chiral quaternary carbon centers.
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