Guixiang Du

Facile one-step synthesis of Co(OH)2 microsphere/graphene composites for an efficient supercapacitor electrode material

A simple one-step hydrothermal method is developed for the synthesis of Co(OH)2/graphene (Co(OH)2/GN) composites, during which graphite oxide was reduced and Co(OH)2 particles were in situ formed on the GN sheets. The morphologies, structures and the electrochemical properties of the composites were investigated. The results show that flower-like Co(OH)2 microspheres, self-assembled by the acicular particles, are enveloped by the wrinkled GN sheets to form the Co(OH)2/GN composites. The composite electrode exhibits the highest specific capacitance (Cspec) of 433 F g−1 at a discharge current density of 0.1 A g−1 in 6 M KOH, which is much higher than that of pure Co(OH)2 (217 F g−1) and GN (187 F g−1), and shows excellent rate capability (the capacitance retains 90.3% at 10 A g−1) and a long cycle life along with 99% Cspec retained after continuous 1000 cycle tests at a current density of 1 A g−1. The enhanced electrochemical performance is attributed to the synergistic effects of the good redox activity of the Co(OH)2 particles combined with the high electronic conductivity of the GN sheets, which predicts the composite to be a highly promising candidate as an electrode material in energy conversion/storage systems.

Facile synthesis of multifunctional multi-walled carbon nanotube for pathogen Vibrio alginolyticus detection in fishery and environmental samples

Interest in carbon nanotubes for detecting the presence of pathogens arises because of developments in chemical vapor deposition synthesis and progresses in biomolecular modification. Here we reported the facile synthesis of multi-walled carbon nanotubes (MWCNTs), which functioned as immuno-, magnetic, fluorescent sensors in detecting Vibrio alginolyticus (Va). The structures and properties of functionalized MWCNTs were characterized by ultraviolet (UV), Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), magnetic property measurement system (MPMS) and fluorescent spectra (FL). It was found that the functionalized MWCNTs showed: (1) low nonspecific adsorption for antibody-antigen, (2) strong interaction with antibody, and (3) high immune-magnetic activity for pathogenic cells. Further investigations revealed a strong positive linear relationship (R=0.9912) between the fluorescence intensity and the concentration of Va in the range of 9.0 × 10(2) to 1.5 × 10(6) cfum L(-1). Moreover, the relative standard deviation for 11 replicate detections of 1.0 × 10(4) cfum L(-1) Va was 2.4%, and no cross-reaction with the other four strains was found, indicating a good specificity for Va detection. These results demonstrated the remarkable advantages of the multifunctional MWCNTs, which offer great potential for the rapid, sensitive and quantitative detection of Va in fishery and environmental samples.

Facile fabrication of hierarchical porous carbon for a high-performance electrochemical capacitor

The template method is often used to synthesize porous materials. However, removing the template during post-processing is difficult and harsh reagents are frequently used, which is unfavorable for the carbon structure. In this paper, a facile and green synthesis route is developed for the synthesis of a 3D honeycomb-like hierarchical porous carbon based on rapid thermal decomposition of the mixture of a low-cost carbon precursor (typically starch) and Na2CO3 followed by KOH activation, in which Na2CO3 particles are employed as the water-soluble renewable macroporous template. Benefiting from the high specific surface area (1171 m2 g−1) and the interconnected micro-, meso-, and macropores, the porous carbon exhibits superior capacitive performance, including high specific capacitance, good rate capability and excellent cycling stability. Moreover, the porous carbon-based symmetric supercapacitor delivers a maximum energy density of 33 W h kg−1 at 100 W kg−1 and presents excellent long-term cycling stability. Considering the easy-availability of the raw materials and the facile synthesis process, this environmentally friendly and cost-effective method can be expected to be widely applied, and we estimate that the obtained porous carbon could find additional applications in other fields.

Fabrication of MPEG-b-PMAA capped YVO4:Eu nanoparticles with biocompatibility for cell imaging.

A novel nanoparticle with multilayer core-shell architecture for cell imaging is designed and synthesized by coating a fluorescent YVO4:Eu core with a diblock copolymer, MPEG-b-PMAA. The synthesis of YVO4:Eu core, which further makes MPEG-b-PMAA-YVO4:Eu NPs adapt for cell imaging, is guided by the model determined upon the evaluation of pH and CEu%. The PMAA block attached tightly on the YVO4:Eu core forms the inner shell and the MPEG block forms the biocompatible outermost shell. Factors including reaction time, reaction temperature, CEu% and pH are optimized for the preparation of the YVO4:Eu NPs. A precise defined model is established according to analyzing the coefficients of pH and CEu% during the synthesis. The MPEG-b-PMAA-YVO4:Eu NPs, with an average diameter of 24 nm, have a tetragonal structure and demonstrate luminescence in the red region, which lies in a biological window (optical imaging). Significant enhancement in luminescence intensity by MPEG-b-PMAA-YVO4:Eu NPs formation is observed. The capping copolymer MPEG-b-PMAA improves the dispersibility of hydrophobic YVO4:Eu NPs in water, making the NPs stable under different conditions. In addition, the biocompatibility MPEG layer reduces the cytotoxicity of the nanoparticles effectively. 95% cell viability can be achieved at the NPs concentration of 800 mgL(-1) after 24h of culture. Cellular uptake of the MPEG-b-PMAA-YVO4:Eu NPs is evaluated by cell imaging assay, indicating that the NPs can be taken up rapidly and largely by cancerous or non-cancerous cells through an endocytosis mechanism.

N-(Naphthalen-1-yl­methyl­idene)-4H-1,2,4-triazol-4-amine

In the title molecule, C13H10N4, the dihedral angle between the triazole ring and the naphthalene ring system is is 56.1 (2)°. In the crystal, molecules are connected by weak C—H⋯N hydrogen bonds into chains along [100]. A short intramolecular C—H⋯N contact is also observed.

Experimental and first-principles study of a metal–organic framework with sulfur embedding cathode for enhanced performance lithium–sulfur battery

Lithium–sulfur (Li–S) batteries, which are well-known and much studied rechargeable batteries, are very promising because of their low cost, environmental friendliness, very high specific capacity and superior energy density. However, applications of Li–S batteries have been obstructed by their fast capacity fading and low coulombic efficiency due to soluble polysulfide migration during charge/discharge cycling. Herein, we present a strategy utilizing cobalt metal–organic framework (CoMOF) with rough porous surface and defective structure as a host material for sulfur accommodation, which implements a CoMOF and S composite (CoMOF–S) as a cathode. Capacity retention of CoMOF–S cathode surpasses that of pure sulfur by 87.18% after 100 cycles at 0.1C, while achieving coulombic efficiency above 98% at a high rate of 2.0C. We reveal structural features by combining X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations, which confirm the covalent bond connection between CoMOF and S. We attribute the excellent cycling performance to covalent bond immobilization of sulfur.

Li2S–Embedded copper metal–organic framework cathode with superior electrochemical performance for Li–S batteries

Li–S rechargeable batteries are desirable for electric transportation because of their low cost, environmental friendliness, and superior energy density. However, the Li–S system has yet to conquer the market owing to its drawbacks such as soluble polysulfide formation. To tackle this issue, we report herein a strategy based on the use of a micro-porous copper metal–organic framework named CuMOF as a host material for sulfur immobilization via chemical bonds between sulfur and the MOF structure. CuMOF has been obtained by simple chemical synthesis using copper salt and benzene-1,3,5-tricarboxylic acid as the ligand. Then, by the melt-diffusion method, sulfur-impregnated CuMOFS material is finally fabricated. As a cathode material for Li–S batteries, the CuMOFS cathode delivers a capacity of 1051.3 mA h g−1 after 300 cycles at a charge/discharge current density of 200 mA g−1. It is worth noting that the main cathode structure can retain more than 19.3 wt% sulfur due to the CuMOF host, which dramatically decreases capacity fading and improves coulombic efficiency during prolonged charge/discharge cycling. The XPS peaks of CuMOFS are assigned according to the information obtained from density functional theory (DFT) calculations. Linear scaling DFT structure relaxation for a model with >1000 atoms is carried out to exemplify the interactions between CuMOF framework and embedded Li2S. The excellent electrochemical performance can be due to firm confinement of sulfur/polysulfides because of strong chemical interactions between carbon and sulfur species in the CuMOF host.

1,4-Bis(4H-1,2,4-triazol-4-yl)benzene dihydrate

The asymmetric unit of the title compound, C10H8N6·2H2O, comprises half the organic species, the molecule being completed by inversion symmetry, and one water molecule. The dihedral angle between the 1,2,4-triazole ring and the central benzene ring is 32.2 (2)°. The water molecules form O—H⋯N hydrogen bonds with N-atom acceptors of the triazole rings. C—H⋯N hydrogen bonds are also observed, giving a three-dimensional framework.