5 research outputs found

    Direct Detection of DNA below ppb Level Based on Thionin-Functionalized Layered MoS<sub>2</sub> Electrochemical Sensors

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    A layered MoS<sub>2</sub>–thionin composite was prepared by sonicating their mixture in an ionic liquid and gradient centrifugation. Because DNA is rarely present in single-stranded form, either naturally or after PCR amplification, the composite was used for fabrication of a double-stranded DNA (dsDNA) electrochemical biosensor due to stable electrochemical response, intercalation, and electrostatic interaction of thionin with DNA. The linear range over dsDNA concentration from 0.09 ng mL<sup>–1</sup> to 1.9 ng mL<sup>–1</sup> is obtained, and moreover, it is suitable for the detection of single-stranded DNA (ssDNA). The biosensor has been applied to the detection of circulating DNA from healthy human serum, and satisfactory results have been obtained. The constructed DNA electrochemical biosensor shows potential application in the fields of bioanalysis and clinic diagnosis. Furthermore, this work proposes a new method to construct electrochemical biosensors based on MoS<sub>2</sub> sheets

    Electrodeposited Mo<sub>3</sub>S<sub>13</sub> Films from (NH<sub>4</sub>)<sub>2</sub>Mo<sub>3</sub>S<sub>13</sub>·2H<sub>2</sub>O for Electrocatalysis of Hydrogen Evolution Reaction

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    Molybdenum sulfides are considered to be one kind of the promising candidates as cheap and efficient electrocatalysts for hydrogen evolution reaction (HER). But this is still a gap on electrocatalytic performance toward Pt. To further enhance electrocatalytic activity of molybdenum sulfides, in this work, we prepared Mo<sub>3</sub>S<sub>13</sub> films with high ratio of sulfur to molybdenum by electrodeposition. The Mo<sub>3</sub>S<sub>13</sub> films exhibit highly efficient electrocatalytic activity for HER and achieve a current density of 10 mA/cm<sup>2</sup> at an overpotential of 200 mV with an onset potential of 130 mV vs RHE and a Tafel slope of 37 mV/dec, which is superior to other reported MoS<sub>2</sub> films. The highly electrocatalytic activity is attributed to high percentage of bridging S<sub>2</sub><sup>2–</sup> and apical S<sup>2–</sup> as well as good conductivity. This study provides an avenue for designing new molybdenum sulfides electrocatalysts

    Biosensor Based on Ultrasmall MoS<sub>2</sub> Nanoparticles for Electrochemical Detection of H<sub>2</sub>O<sub>2</sub> Released by Cells at the Nanomolar Level

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    Monodispersed surfactant-free MoS<sub>2</sub> nanoparticles with sizes of less than 2 nm were prepared from bulk MoS<sub>2</sub> by simple ultrasonication and gradient centrifugation. The ultrasmall MoS<sub>2</sub> nanoparticles expose a large fraction of edge sites, along with their high surface area, which lead to attractive electrocatalytic activity for reduction of H<sub>2</sub>O<sub>2</sub>. An extremely sensitive H<sub>2</sub>O<sub>2</sub> biosensor based on MoS<sub>2</sub> nanoparticles with a real determination limit as low as 2.5 nM and wide linear range of 5 orders of magnitude was constructed. On the basis of this biosensor, the trace amount of H<sub>2</sub>O<sub>2</sub> released from Raw 264.7 cells was successfully recorded, and an efficient glucose biosensor was also fabricated. Since H<sub>2</sub>O<sub>2</sub> is a byproduct of many oxidative biological reactions, this work serves as a pathway for the application of MoS<sub>2</sub> in the fields of electrochemical sensing and bioanalysis

    Facile Synthesis of Mesoporous and Thin-Walled Ni–Co Sulfide Nanotubes as Efficient Electrocatalysts for Oxygen Evolution Reaction

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    Development of high-performance and inexpensive electrocatalysts for oxygen evolution reaction (OER) is of important significance for sustainable energy conversion technologies. In this work, mesoporous Co and Ni–Co sulfide nanotubes with ultrathin nanowalls are designed and fabricated by a facile and template-free solvothermal method. The obtained CoS<sub>1.097</sub> nanotubes can be used as an OER electrocatalyst, and the incorporation of Ni into the CoS<sub>1.097</sub> lattice could further enhance the catalytic activity of the catalysts. The best-performing Ni<sub>0.13</sub>­Co<sub>0.87</sub>S<sub>1.097</sub> nanotubes exhibit high performance for OER with a small overpotential of 316 mV to achieve a current density of 10 mA cm<sup>–2</sup> and excellent stability, which outperform those of commercial IrO<sub>2</sub> and most of the studied Co-based OER catalysts. Our work demonstrates a new strategy to design highly efficient non-previous-metal OER electrocatalysts with unique structures and can be extended to other transition-metal-based systems

    Tuning Sn-Catalysis for Electrochemical Reduction of CO<sub>2</sub> to CO via the Core/Shell Cu/SnO<sub>2</sub> Structure

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    Tin (Sn) is known to be a good catalyst for electrochemical reduction of CO<sub>2</sub> to formate in 0.5 M KHCO<sub>3</sub>. But when a thin layer of SnO<sub>2</sub> is coated over Cu nanoparticles, the reduction becomes Sn-thickness dependent: the thicker (1.8 nm) shell shows Sn-like activity to generate formate whereas the thinner (0.8 nm) shell is selective to the formation of CO with the conversion Faradaic efficiency (FE) reaching 93% at −0.7 V (vs reversible hydrogen electrode (RHE)). Theoretical calculations suggest that the 0.8 nm SnO<sub>2</sub> shell likely alloys with trace of Cu, causing the SnO<sub>2</sub> lattice to be uniaxially compressed and favors the production of CO over formate. The report demonstrates a new strategy to tune NP catalyst selectivity for the electrochemical reduction of CO<sub>2</sub> via the tunable core/shell structure
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