Charge-transfer mechanism

A positive inter-pulse bias voltage between 0.4 and 0.8 V versus Ag AgCl can increase the charge injection capacity of iridium oxide up to as high as three 

Another reason for higher charge injection capacity with a positive interpulse offset voltage is presumably a higher double layer capacitance for more positive electrode potentials. At higher potentials the higher electric field absorbs the oppositely loaded ions towards the electrode surface and therefore the double layer thickness reduces. 

Asymmetric charge balanced waveforms in which the anodic pulse is delivered at a lower current but a longer pulse length compared to the cathodic one were found to allow higher values of anodic bias voltages, thus maximizing the iridium oxide charge injection capacity [28], 

Iridium oxide electrodes can be classified into four types based on the manufacturing method  

For manufacturing AIROF, an iridium electrode is inserted into an acidic or buffer electrolyte and electrically activated. Investigations have shown that AIROF electrodes are very good in biocompatibility, good in lifetime but bad in reproducibility. 

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Reaction 6 might conceivably proceed through either an ion-atom interchange mechanism (Reaction 7) or a charge transfer mechanism (Reaction 8),... 

A sample of 14N15NO was used to investigate whether Reaction 14 proceeds through a dissociative charge transfer mechanism involving an... 

The benzene ring per se does not impart any particular pharmacological response to a drug. It is widely held that its planarity, its ability to bind to tissue receptors by Van der Waals and charge transfer mechanisms, and, particularly, its ability to serve as a conductor of electrons within a substance serve as modulators, enhancing or diminishing the intensity of response to a molecule that is otherwise inherently bioactive. 

This result eliminates an a-cleavage pathway to form ketene since deuterium in this case should have appeared a to the carbonyl group of the ester. This result is, however, compatible with the charge-transfer mechanism. 

Figure 6 indicates a change in the charge transfer mechanism at a pH between 9 and 9.5, corresponding to the pH of zero charge of aluminum oxide.33,34 Experimental results on the slopes enabled speculation on the values of transfer coefficients and reaction orders. From that, Valand and Heusler concluded that the most probable mechanism of oxygen ion transfer [reaction (21)] is... 

A number of fluorescent dyes with internal charge transfer mechanism allow the molecule to twist (rotate) between the electron donor and electron acceptor moieties of the fluorescent dipole. In most cases, the twisted conformation is energetically preferred in the excited Si state, whereas the molecule prefers a planar or near-planar conformation in the ground state. For this reason, photoexcitation induces a twisting motion, whereas relaxation to the ground state returns the molecule to the planar conformation. Moreover, the Si — So energy gap is generally smaller in the twisted conformation, and relaxation from the twisted state causes either a... 

Brinkley et al. demonstrated89 a simple to use, easy to interpret, low cost, and environmentally friendly colorimetric detector of the chemical warfare agent - mustard gas (HD, l,l-thiobis(2-chloroethane)). An optically transparent xerogel encapsulating Cu(II) acetate was fabricated to detect HD analogues and can serve as the optical sensor based on metal-ligand charge-transfer mechanism. 

In the middle range of styrene concentrations, a compromise is attained where there is sufficient styrene to scavenge all excess methanol radicals not involved in activation of the trunk polymer, yet an excess of monomer remains for grafting by the charge-transfer mechanism proposed by Dilli and Garnett (12) originally for copolymerisation to cellulose (4) and subsequently extended to wool (3), polyolefin (2,5) and PVC (13) systems. The data in Table V are consistent with this interpretation. 

Brown (1959) has presented a charge transfer model of the transition state for electrophilic reactions which differs appreciably from that proposed by Fukui and his collaborators and leads to the definition of a new reactivity index termed the Z value . The model is based on a more conventional formulation of the charge transfer mechanism, which avoids the complete transfer of electrons associated with v = 0,1,2 in Fukui s model. There is no dependence on the formation of a pseudo tt orbital in the transition state, nor is hyperconjugation invoked. A wave function for a charge transfer complex is written as a linear combination of a wave function < o describing the unperturbed ground state of the molecule under attack, and a function which differs from (Pq in the replacement... 

The visible and near-infrared LID results for NO/Pt were discussed in terms of hot electrons combined with a charge transfer mechanism. For the 193 nm LID result considered here, the photon energy is above the substrate work function, thereby providing a direct source of electrons to bathe the adsorbed NO species. Comparison of translational energy and vibrational state distributions for NO/Pt(lll), NO/Pt(foil), and N0/Ni(100)-0 suggests that the mechanisms driving the desorption processes in these systems might be related. However, the details of the specific interaction potentials must be substantially different to account for the disparate spin-orbit and rotational population distributions. 

Another important mechanism, which is responsible for the formation of the colored products in the reaction between nitroaromatic compounds and some basic reagents such as aromatic amines, is the well-known charge transfer mechanism [16-19]. The aromatic amine acts as a 7l donor whereas the nitroaromatic compound serves as a 7l acceptor. 

Some polycyclic hydrocarbons, which are well-known 7l donors, also give colored products by a charge transfer mechanism [22]. 

Salvador [100] introduced a non-equilibrium thermodynamic approach taking entropy into account, which is not present in the conventional Gerischer model, formulating a dependence between the charge transfer mechanism at a semiconductor-electrolyte interface under illumination and the physical properties thermodynamically defining the irreversible photoelectrochemical system properties. The force of the resulting photoelectrochemical reactions are described in terms of photocurrent intensity, photoelectochemical activity, and interfacial charge transfer... 

In the context of this chapter, we focus on the undoped or lightly doped 7i-conjugated systems that are commonly referred to as organic semiconductors. Conducting polymers, such as PEDOT PSS, plexcore, polyaniline, polypyrrole, and others are not addressed here as their charge transfer mechanisms are rather different and would warrant an article in its own right. 

A number of studies on the fluorescence decay of tyrosine, tyrosine derivatives, and small tyrosyl peptides have been carried out. 36-38 Whereas the tyrosine zwitterion and tyrosine derivatives with an ionized a-carboxy group exhibited monoexponential fluorescence decay (x = 3.26-3.76 ns), double- or triple-exponential decay was observed in most other cases. As in the case of the tryptophan model compounds, the complex decay kinetics were again interpreted in terms of rotamer populations resulting from rotation around the C —Cp bond. There is evidence to indicate that the shorter fluorescence lifetimes may arise from rotamers in which the phenol ring is in close contact with a hydrated carbonyl group 36 37 and that a charge-transfer mechanism may be implicated in this quenching process. 39 ... 

In this respect, etching is considered as an electrochemical process, taking place under the OCP conditions. The charge-transfer mechanism is the same as the electrochemical corrosion, and the reaction rate is derived from... 

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