Electron hopping/mobility

In the present case, the electron hopping chemistry in the polymeric porphyrins is an especially rich topic because we can manipulate the axial coordination of the porphyrin, to learn how electron self exchange rates respond to axial coordination, and because we can compare the self exchange rates of the different redox couples of a given metallotetraphenylporphyrin polymer. To measure these chemical effects, and avoid potentially competing kinetic phenomena associated with mobilities of the electroneutrality-required counterions in the polymers, we chose a steady state measurement technique based on the sandwich electrode microstructure (19). 

The benefit of a hybrid phase for the intercalation-deintercalation of mobile species such as Li+ cations is well illustrated by the study of conductive polymers such as polyaniline or polypyrrole intercalated into a V2O5 framework as potential electrode materials in lithium batteries [34]. For PANI/V2O5, an oxidative post-treatment performed under an oxygen atmosphere allowed the authors to compare the conductivity attributed to the polymer, as in absence of reduced cations, there was no electronic hopping between ions, and the conductive state was due only to the... 

First, high-mobility anions occur both in liquids whose molecules have negative and positive EAg. The gas-phase electron affinity has no effect on the rate and the activation barrier of electron hopping in neat liquid solvents. 

Above room temperature, the mobile 3 d electrons are well described by a random mixture of Fel" and FeB ions with the mobile electrons diffusing from iron to iron, some being thermally excited to FeA ions, but the motional enthalpy on the B sites is AH < kT. As the temperature is lowered through Tc, the Seebeck coefficient shows the influence of a change in mobile-electron spin degeneracy, and at room temperature the Seebeck coefficient is enhanced by correlated multielectron jumps that provide a mobile electron access to all its nearest neighbors. The electron-hopping time xi, = coi = 10" s... 

Here, the potentiometric selectivity coefficient is given with respect to the hydroxyl ion. Single-crystal lanthanum fluoride is a wide bandgap semiconductor in which the electrical conductivity is due only to the hopping mobility of fluoride ions through the defects in the crystal. It does not respond to the La3+ ion because of the slow ion exchange of that ion. Hydroxyl ion is the only other ion that has appreciable mobility, and is the only known interference. For this reason, the measurements with a fluoride electrode are always done below pH 7, which circumvents this interference. As shown later, the consideration of ionic and/or electronic conductivity of the membrane plays a critical role also in the design of the internal contact in nonsymmetric potentiometric sensors. 

Mobility Scales with Average Inter site Hopping Distance, Gill identified an exponential dependence of electron drift mobility on average TNF intersite hopping distance and noted an associated decrease in hole drift mobility (35). Gilfs subsidiary observation that TNF addition also decreased hole mobility precisely because complexed carbazole is removed as a hole transport site provided evidence for the key role of the discrete carbazole groups in hole transport. 

In contrast with the short-lived MLCT-excited states [Ru(bpy)3] [74], the electrogenerated [Ru(bpy)3]"+ can be conveniently studied by temperature-dependent ESR [42, 50a, b. Analysis of the broad unresolved lines of this and related species reveals electron hopping between the three equivalent ligand sites with activation energies of approximately 10 kJ mol . Similar slow vs. fast exchange phenomena were reported for the extended atom [75] species 17 which contains an encapsulated Na+ ion and mobile spins in the bpy-containing periphery. 

The uniquely high mobility displayed by SWNT (146, 147) makes them attractive for applications in nanodevices, such as thin-film transistors (TFT), which could be produced by solution-processed random networks of SWNT. An optimum TFT would be composed entirely of semiconducting nanotubes, since their performance is limited by the presence of metallic tubes. It has been proposed that even below the percolation threshold of metallic tubes, electron hopping or tunneling may occur between neighboring metallic tubes (148). This electron channeling reduces the on/off ratio and therefore, the overall performance of the transistor. Removal of metallic nanotubes from the network has been achieved by electron breakdown (149, 150). 

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