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