Charge transfer by ions

Although most modern research on contact charging, as described in the previous section, generally assumes that the underlying process is essentially 

This complexity explains why definitive, quantitative verification of ionic contact charging has proved to be so elusive. Nevertheless, a body of convincing evidence for the role of ions in the charging process now exists for special categories of polymers with ionic features in their compositions. 

The clearest instances of contact charging by ion transfer are exhibited by ionomers, e.g. poly(styrene-co-N-methyl-4-vinyl-pyridinium toluenesulphonate), 

When a polymer simply contains ionic salts that are not bound covalently to the polymer chains themselves, e.g. tetraalkylammonium toluenesulphonate, the situation is more complicated, because ions of both sign are mobile and are available for transfer. The magnitude of the net charge transferred will then depend on the relative transfer aptitude of the two ions in the salt. Both of the ions tend to transfer in excessive amounts, which contaminates the second surface and produces a relatively low net surface charge density. 

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Faraday s law relates the charge transferred by ions in the electrolyte and electrons in the external circuit, to the moles of chemical species reacted (Newman and Thomas-Alvea, Electrochemical Systems, 3d ed., Wiley Interscience, 2004) ... 

It is pointed out above that metal deposition is different from outer-sphere charge-transfer reactions in that charge is carried across the metal/solution interface by the ions, not by electrons. Although this has been acknowledged by several noted electrochemists, a theory of charge transfer by ions, comparable in detail and depth to the theories of electron transfer, has yet to be developed. So far,... 

Later, McGlynn et al. (101) reported an extensive study of the gas-phase reaction of octaethylporphyrin with 12 metal monocations, which were produced by laser ablation of Al, V, Cr, Fe, Ni, Nb, Mo, Hf, W, Re, Pt, and Au targets. Three different processes were suggested charge transfer, metal-ion incorporation, and dimerization. ... 

Therefore, we have developed a pump/pump-probe experiment to obtain more informations on the structures of these geminate ion pairs. It allows the investigation of the excited states dynamics of the transient species at different time delays after photo-triggering the charge transfer, by monitoring the ground state recovery (GSR) of those transient species (Fig. lb). In the present study, we have used perylene (Pe) as fluorescer (electron donor) and either trans-l,2-dicyanoethylene (DCE) or 1,4-dicyanobenzene (DCB) as quencher (electron acceptor) in acetonitrile (ACN). 

The activation energy for monomer transfer by ion pairs could also be reduced relative to that by free ions because of a counterion stabilising effect on both leaving and developing charges in the transition state for monomer transfer (82,160)... 

The ion QH was obtained by charge transfer with ions having recombination energies in... 

The fraction of charge transported by ion i, relative to the total transported charge, is called the transference number t, of ion i. It is expressed as... 

Charge transfer band absorption occurs whenever inter- or intramolecular complexes between donor and acceptor are formed. In these complexes, anions may be, among the most effective donors. When an ion pair shows such an absorption band, the electronic transition is named ion-pair charge-transfer (IPCT). Ion pairs of coordination compounds are often concerned by IPCT and... 

Ionization by Charge Transfer. Many ion-molecule reactions between small species (< 50 amu) occur in flames (24), As mentioned above, the only primary ion in fuel-lean flames (non-sooting) is CHO", formed by chemi-ionization (13, 24, 25). 

From Table 7 we see that there is no significant difference in covalency parameters for Mn2+ — F and Mn + — O -. This agrees with the neutron diffraction data for Ni2+ (Section 4.1). Although /<, is much less than for Ni2+, the total ligand-to-metal charge transfer by a and n bonding from Eq. (2.23) is very similar for the two ions ( 0.2e). 

Charge-Transfer and Ion-Molecule Reactions. Both positive and negative ion-molecule reactions have recently been studied by a variety of experimental methods, and consistent values for many rate constants... 

Along with electrophoresis, the electric field applied to free disperse system causes the flow of electric current, related to both the motion of ions in dispersion medium and charge transfer by particles moving with velocity o . The specific electric conductance of the free disperse system, v, is equal to phenomenological coefficient a22 and includes the specific electric conductance of the dispersion medium,, and the additional conductance caused by moving charged particles. A more detailed consideration shows that for free disperse system... 

Powder particles may be charged by the contact electrification mechanism, when they acquire their charge on contact with the electrodes, or by the ion absorption mechanism, when air is ionized under the gas discharge effect followed by charge transfer from ions to powder particles. 

The rate of ion formation in flames has been studied by many techniques and shown to be a complex phenomenon which must take account of thermal and chemiionization, of charge transfer and ion recombination. The ionization may be dominated by an added substance of low ionization potential, or it may be the natural ionization of a hydrocarbon flame. This natural ionization is of widespread importance, and it has been suggested that even in so-called pure hydrogen flames, the background ionization is due to traces of hydrocarbon. Other experiments with ultra-pure gases have yielded strange, though unconfirmed, results. 

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