Results 1 - 10 of 5481
Results 1 - 10 of 5481. Search took: 0.025 seconds
|Sort by: date | relevance|
[en] The electrochemical decoration of Au and Pd nanoparticles by Pd and Au atoms respectively is discussed in a statistical mechanical framework. It is found that depending on precursor nanoparticle size and shape, controlled decoration may be achieved in undersaturation or oversaturation conditions. Multilayer deposition is also considered, with the finding that this phenomenon is also size dependent.
[en] Supramolecular (multi-component) systems can perform complex functions which result from the cooperation of actions performed by suitably selected molecular components. Looking at supramolecular systems, from the viewpoint of the functions, shows that the concept of macroscopic device can be extended to molecular level. Nature exploits very complex molecular-level devices to substain life, and, in the last twenty years, the development of supramolecular chemistry has allowed the construction of simple molecular-level devices, that are of interest not only for basic research, but also for the growth of nanoscience and nanotechnology. Molecular-level devices operate via electronic and/or nuclear rearrangements, and like macroscopic devices, they need energy to operate and signals to communicate with the operator. Electrochemistry can provide the answer to this dual requirement, since electrons/holes, besides supplying the energy needed to make a devices work, can also be useful to 'read' the state of the system and thus to control and monitor the operation of the device. In this article, some examples of molecular-level devices investigated in our laboratory will be reviewed
[en] Highlights: ► We modify the doping front migration process. ► The migration velocity is controlled by a separate electrode. ► The process may be used in “best use before” labels. - Abstract: We demonstrate a new method of modifying the doping front migration process in multilayer structures, enabling the control of migration velocity. The presence of two interfaces in contact with the migration layer strongly affects the migration mechanism. Electrochemical switching of an electrode at one interface may be used to control the chemical doping front migration at the second interface. The process may be used to produce ultralow-cost devices acting as electronic “best use before” labels on food and drink or “use-by” labels on drugs. Control of the migration velocity may be used as a method for weighting storage conditions (i.e. opening of a package during the measurement period increases the migration velocity).
[en] A new definition for the electrochemical cell constant in conductivity measurements is presented in this paper. Electrochemical Impedance Spectroscopy and DC pulses measurements have been carried out in non-Faradaic conditions in order to evaluate the effects of the cell geometry. The results obtained demonstrate that conductivity measurements are affected not only by the electrodes surface and separation but also by the cross section of the electrochemical cell. In order to obtain a linear behavior of the resistance versus the distance between electrodes, the cross section of the cell should be equal to the electrodes surface. Differences between the cell cross section and the electrodes surface produce a heterogeneous distribution of the electric field that causes the non-linear behavior for low values of the electrodes separation. This study shows that the reproducibility in electronic tongue and humid electronic nose measurements can be improved by designing an electrochemical cell structure that warrants a homogeneous distribution of the electrical field, which results in a reduction of the detection threshold in these types of system
[en] The induced-charge electrophoretic (ICEP) motion of ideally polarizable particles is numerically studied in this paper. A complete three-dimensional multi-physics model is set up to simulate the transient ICEP motion of ideally polarizable, spherical particles in an unbounded liquid. The study shows the nonlinear induced zeta potential on the particle's surface causing a varying slipping (electroosmotic flow) velocity along the particle's surface, and hence producing microvortexes in the liquid. ICEP particle-particle interactions are also studied. The simulations show that a low pressure zone between the two polarizable conducting particles will be induced if the external electric field is applied parallel along the imaginary line connecting the two particles, resulting in an attracting effect between the two particles. Oppositely, a high pressure zone is induced between the two particles if the applied field is perpendicular to the imaginary line connecting the two particles, giving a repelling effect. The ICEP attracting or repelling effects depend on the particles' separation distance, the electric field strength and the particle size.
[en] It has been proven that including elementary potential-dependent transfer coefficient (α) into mathematical model of E, EC, ECE, ECEC, ECE-ECE and ECEC-ECEC mechanisms leads to creation of set of cyclic voltammetry curves with the intersection point called isoalpha point. The isoalpha points have been detected by the use of the models of particular mechanisms with and without ∂α/∂E parameter included or through different alpha values introduction. The point of intersection unknown in electrode kinetics so far, seems to exemplify an electrochemical analog of isosbestic point in absorption spectroscopy or isopotential point in electrochemistry. Moreover, an example of the experimental data that demonstrates the presence of the isoalpha point has been provided. The presented phenomenon can be of importance for solid state and modified electrodes
[en] A major advantage of NST lies in the unimportance of the probability distribution of observations. In this paper, the sign test, the rank-sum test, the Kruskal-Wallis test, the Friedman test, and the runs test illustrate the potential of certain rapid NST for the evaluation of electrochemical process performance.
[en] Electrochemistry provides unique features for the preparation of low-dimensional structures, but in situ spectroscopy with atomic/molecular resolution at such structures is at present not well established yet. This paper shows that in situ scanning probe spectroscopy at solid/liquid interfaces can be utilized to study electronic properties at nanoscale, if appropriate conditions are applied. Tunneling spectroscopy provides information about tunneling barrier heights and electronic states in the tunneling gap, as shown on Au(1 1 1) substrates, contact spectroscopy allows for transport measurements at single nanostructures, as shown at Au/n-Si(1 1 1) nanodiodes. The influence of the electrolytic environment on spectroscopic investigations is not a principal limitation, but offers additional degrees of freedom, which allow, for example, spectroscopic studies of potential dependent surface phenomena at solid/liquid interfaces
[en] Microelectrode steady-state voltammetry is used to monitor on-line the progress of preparative electrolyses. This allows to follow educt and product concentrations as a function of the advance of the electrolysis, end-point detection, calculation of the number of electrons transferred per molecule, and determination of diffusion coefficient ratios for redox couples. The technique is demonstrated by numerical simulation, experiments with mixtures of redox partners, electrolyses in macrocells, and miniaturized electrolyses in vials or the wells of microtiter plates