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Abstract: In this work, a comparative study on the electrocatalytic activities of ordered mesoporous carbons (OMCs) and graphene (GR) is presented. Using voltammetry and amperometry as detection methods, four DNA bases, double-stranded DNA (dsDNA), six important electroactive compounds and various biomolecules were employed to investigate their electrochemical responses on OMC and GR modified glassy carbon electrodes (OMC/GCE and GR/GCE). The results show that OMC/GCE enhances the electron transfer kinetics of these compounds compared to GR/GCE. The discrepancy in electrochemical activities can be attributed to the different microstructures of OMC and GR, which were examined by transmission electron microscopy, X-ray photoelectron spectra, X-ray diffraction, Raman spectra and nitrogen adsorption–desorption. [Copyright &y& Elsevier]

Abstract: This work demonstrates a novel and facile route for preparing graphene-based composites comprising of metal oxide nanoparticles and graphene. A graphene nanosheet–bismuth oxide composite as electrode materials of supercapacitors was firstly synthesized by thermally treating the graphene–bismuth composite, which was obtained through simultaneous solvothermal reduction of the colloidal dispersions of negatively charged graphene oxide sheets in N,N-dimethyl formamide (DMF) solution of bismuth cations at 180°C. The morphology, composition, and microstructure of the composites together with pure graphite oxide, and graphene were characterized using powder X-ray diffraction (XRD), FT-IR, field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetry and differential thermogravimetry (TG–DTG). The electrochemical behaviors were measured by cyclic voltammogram (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The specific capacitance of 255Fg−1 (based on composite) is obtained at a specific current of 1Ag−1 as compared with 71Fg−1 for pure graphene. The loaded-bismuth oxide achieves a specific capacitance as high as 757Fg−1 even at 10Ag−1. In addition, the graphene nanosheet–bismuth oxide composite electrode exhibits the excellent rate capability and well reversibility. [Copyright &y& Elsevier]

Abstract The development of high-performance noble metal-free electrochemical catalyst for effective water splitting is a key factor to achieve low-cost and sustainable renewable energy production. Herein, for the first time, highly dispersed cobalt nanoparticles decorated uniform nitrogen doped graphene (CoNPs-N-GR) was design synthesized. In the preparation procedure, graphene oxide (GO) was employed as supporting material, polydopamine as nitrogen source, location reagent as well as connecting agent for uploading cobalt metal ion, and then cobalt metal-organic frameworks (ZIF-67) in situ grew on GO. During the calcining process, GO reduction, nitrogen doping and cobalt nanoparticles forming were finished in one step. Scanning electron microscopy (SEM) images, transmission electron microscopy (TEM), energy-dispersive X-ray (EDS), X-ray photoelectron spectrometer (XPS) and X-ray diffraction (XRD) were applied to characterize the as-prepared CoNPs-N-GR. Moreover, owing to the presence of dopamine, high dispersed cobalt nanoparticles were obtained, leading to high electrocatalytic activity of CoNPs-N-GR for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. HER reaches 10 mA cm−2 at the over-potential of 0.453 V with a Tafel slope of 67 mV dec−1. OER reaches 10 mA cm−2 at the over-potential of 1.63 V with a Tafel slope of 65 mV dec−1. And the as-prepared CoNPs-N-GR shows excellent durability in the long-term stability for HER and OER. Graphical abstract Image 1 Highlights • Highly dispersed CoNPs decorated uniform nitrogen doped graphene was prepared. • Polydopamine as nitrogen source, location reagent as well as connecting agent. • In situ grow of cobalt metal-organic frameworks (ZIF-67) as cobalt precursor. • High electrocatalytic performance for both HER and OER in alkaline media. [ABSTRACT FROM AUTHOR]

Abstract: A rapid, environmental friendly, and sensitive biosensor for detection of zearalenone (ZEN) was developed at glassy carbon electrode (GCE) using nanoporous bimetallic alloy as label of secondary antibody (Ab2). The biosensor was prepared by immobilizing nitrogen-doped graphene sheets (N-GS) captured primary antibody (Ab1) on GCE. The analytes were then bound to Ab1 for further capture of antibodies, labeled by the nanoporous bimetallic alloy, nanoporous PtCo alloy (NP-PtCo). NP-PtCo with three-dimensional bicontinuous spongy structures and various hollow channels was prepared by corrosion of PtCoAl alloy, and exhibited remarkably improved electrocatalytic activity toward H2O2. Within ZEN concentration range (0.005–25ngmL−1), the biosensor exhibited a highly sensitive response to ZEN with a detection limit of 2.1pgmL−1. Several factors that would affect the performance of the biosensor were studied, such as erosion time of NP-PtCo, concentration of NP-PtCo, pH of buffer solution, and concentration of N-GS. After H2O2 was injected into the buffer solution, the amperometric response of the biosensor can be used to detect ZEN by chronoamperometry. The developed biosensor shows good selectivity and sensitivity to ZEN and is promising in feed safety analysis. [Copyright &y& Elsevier]