55 research outputs found
Solid-state reference electrodes based on carbon nanotubes and polyacrylate membranes
A novel potentiometric solid-state reference electrode containing single-walled carbon nanotubes as the transducer layer between a polyacrylate membrane and the conductor is reported here. Single-walled carbon nanotubes act as an efficient transducer of the constant potentiometric signal originating from the reference membrane containing the Ag/AgCl/Clâ ions system, and they are needed to obtain a stable reference potentiometric signal. Furthermore, we have taken advantage of the light insensitivity of single-walled carbon nanotubes to improve the analytical performance characteristics of previously reported solid-state reference electrodes. Four different polyacrylate polymers have been selected in order to identify the most efficient reservoir for the Ag/AgCl system. Finally, two different arrangements have been assessed: (1) a solid-state reference electrode using photo-polymerised n-butyl acrylate polymer and (2) a thermo-polymerised methyl methacrylate:n-butyl acrylate (1:10) polymer. The sensitivity to various salts, pH and light, as well as time of response and stability, has been tested: the best results were obtained using single-walled carbon nanotubes and photo-polymerised n-butyl acrylate polymer. Water transport plays an important role in the potentiometric performance of acrylate membranes, so a new screening test method has been developed to qualitatively assess the difference in water percolation between the polyacrylic membranes studied. The results presented here open the way for the true miniaturisation of potentiometric systems using the excellent properties of single-walled carbon nanotubes
Single-Molecule Electrochemical Transistor Utilizing a Nickel-Pyridyl Spinterface
Using a scanning tunnelling microscope
break-junction technique,
we produce 4,4âČ-bipyridine (44BP) single-molecule junctions
with Ni and Au contacts. Electrochemical control is used to prevent
Ni oxidation and to modulate the conductance of the devices via nonredox
gatingîžthe first time this has been shown using non-Au contacts.
Remarkably the conductance and gain of the resulting Ni-44BP-Ni electrochemical
transistors is significantly higher than analogous Au-based devices.
Ab-initio calculations reveal that this behavior arises because charge
transport is mediated by spin-polarized Ni <i>d</i>-electrons,
which hybridize strongly with molecular orbitals to form a âspinterfaceâ.
Our results highlight the important role of the contact material for
single-molecule devices and show that it can be varied to provide
control of charge and spin transport
Metal-supported cathodically activated graphite via self-reduction as electrocatalysts for efficient hydrogen evolution reaction
International audienc
Variations of Diffusion Coefficients of Redox Active Molecules in Room Temperature Ionic Liquids upon Electron Transfer
International audienc
Reactivity of platinum metal with organic radical anions from metal to pt negative oxidation states
J. Amer. Chem. Soc., 2007, 129, 6654-666
Facile Electrochemical Characterization of Core/Shell Nanoparticles. Ag Core/Ag 2 O Shell Structures
ABSTRACT We report in this paper a facile approach for the formation and electrochemical characterization of silverâsilver oxide coreâshell nanoparticles (NPs). Thus, thermal treatment at temperatures between 200 and 360°C of Ag NP, in the gas phase or in an organic solvent, has been used to achieve the formation Ag@Ag 2 O NP. The evidence of formation of such a coreâshell structure was obtained by cyclic voltammetry using a Nafion modified electrode (where Nafion containing carbon particles is used as the matrix to encapsulate the coreâshell NP). Initial positive scans measure free Ag. Initial negative scans measure Ag 2 O, with the following positive scan, compared to the initial one, providing a measure of "trapped" or core Ag. The results presented demonstrate the utility of this approach in characterizing coreâshell structures, like Ag@Ag 2 O, which could be extended to other coreâshell forms, such as bimetallic coreâshell NP
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