Intercalation mechanism

Formally, an electrode is defined as an interface between an ionically conductive electrolyte (A or B ) and an electronic conductor [15]. At the junction a chemical potential /t, of the species (A or B) is imposed for the electrochemical reaction)  

In this ideal scheme, the electrode is a surface without any capacity. The electrical capacity would be observed only if the surface electrode is expanded in volume, by interposing a material possessing the three properties of the junction (1) an electronic conductivity (e ), (2) an ionic conductivity (A or B ) and (3) a chemical potential (//a or imposed. As a consequence, the electrode material must have a host lattice stmcture, H) and participates to the electrochemical reaction via an intercalation mechanism (Fig. 3.1) 

The intercalate acts as a source and a sink of either A or B. In practice, there are very few examples of an anionic intercalation mechanism (graphite salts BxC), and we mainly restrict ourselves to the intercalation of monopositive species. Among them, Li plays a dominant role, as a large majority of studies deal with compounds of this light element. Synchronous or consecutive intercalation of different guest species may basically occur by the exchange reactions  

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This approach finds experimental support in FTIR measurements of the oxidation of PANI in organic solvents which indicate an anion intercalation mechanism for the second oxidation step. However, the IR findings may also be interpreted as support for the formation of a protonated imine structure... 

Vanadium pentoxide has been investigated for 30 years ° ° it has a layered structure with weak vanadium—oxygen bonds between the layers and is now known to react by an intercalation mechanism 40,85 + V2O5 = LLV2O5. 

In addition to the intercalation mechanism described, the anthracycline ring of doxorubicin can undergo a one-electron reduction to form free radicals and participate in further electron transfer. These highly active substances can then react with tissue macromolecules. This type of interaction suggests an alternative mechanism of cytotoxicity for the anthracyclines. In particular, the cardiac toxicity of anthracyclines may result from the generation of free radicals of oxygen. 

The results of the Hg2 reaction experiments using particle-size-mediated synthesized metal sulfides are shown in Table 5. The powder XRD pattern of the resulting solids reveals amorphous material formation. Previous studies using Cu,S revealed the removal of Hg by a process other than dissolved sulfide precipitation [10], Other researchers have shown that MoS2 removes Fig2 from aqueous solutions via an intercalation mechanism [11]. 

Lepoittevin, B., Devalckenaere, M., Pantoustier, N., Alexandre, M., Kubies, D., Calberg, C., Jerome, R., and Dubois P. Poly (l-caprolactone)/clay nanocomposites prepared by melt intercalation Mechanical, thermal and rheological properties, Polymer (2002), 43,4017-4023. 

Although electrochemical characterizations have recently been performed on single intercalation particles, in most cases composite powdery electrodes containing a mixture of intercalation particles, electrically conductive additives (e.g., carbon black) and PVDF binder have also been used. In order to obtain consistent results and to reach comprehensible intercalation mechanisms in these electrodes, basic electroanalytical characterizations such as slow-scan rate -> cyclic voltammetry (SSCV), -> potentiostatic intermittent titration (PITT) (or -> galvanostatic intermittent titration, GITT), and -> electrochemical impedance spectroscopy (EIS) should be applied in parallel or in a single study. 

A chronopotentiometric method for determination of amino derivatives of PAH is based on the high affinity of DNA for such compounds. In a cell consisting of a DNA-modified CPE, a reference SSCE and a Pt wire auxiliary electrode, an aqueous solution of the PAA is submitted to an accumulation period, during which the analytes are transferred to the working electrode by an intercalation mechanism, after which the solution is changed... 

In addition to the intercalation mechanism, other types of binding occur between DNA and alkaloids. Following administration to rats various isotopically labeled pyrrolizidines have been found to contribute covalently bound label to DNA of liver, lung, and kidney perhaps because... 

There is less information in the literature about binding of alkaloids to ribonucleic acid than there is for deoxyribonucleic acid but such binding does occur. However, since ribonucleic acid is single-stranded, the intercalation mechanism does not apply. Binding of the purine alkaloids caffeine and theophylline follows the reverse order from their binding to DNA — theopylline binds with 10,000 times the affinity of caffeine [345], Elliptinium acetate, best-known for its intercalation into DNA, is easily oxidized to an A-ring quinone amine that binds to the 2 -oxygen atom of ribose units in RNA. The first product then cyclizes to a spiro derivative [346]. 

It has been shown, in vitro, that proflavine (30 /xM) inhibits bacterial DNA polymerase by 85% and RNA polymerase by 30% (Hurwitz etaL, 1962). Some typical data for the RNA system are shown in Fig. 10.4. The inset graph (of the reciprocal of the velocity plotted against the reciprocal of the DNA-primer concentration) points to the site of action of proflavine as being mainly on this primer, thus inhibiting DNA and RNA synthesis in the living bacterium. The intercalating mechanism by which aminoacridines combine with DNA helices and impede strand separation is outlined in the next Section (10.3.2). 

In this article, recent developments in the formation and properties of epoxy layered silicate nanocomposites are reviewed. The effect of processing conditions on cure chemistry and morphology is examined, and their relationship to a broad range of material properties elucidated. An understanding of the intercalation mechanism and subsequent influences on nanocomposite formation is emphasized. Recent work involving the structure and properties of ternary, thermosetting nanocomposite systems which incorporate resin, layered silicates and an additional phase (fibre, thermoplastic or rubber) are also discussed, and future research directions in this highly active area are canvassed. 

A possible explanation of these phenomena involves the presence in heavily lithiated nickel oxide samples of two different phases or, more simply, of two different intercalation mechanisms for lithium ions. Assuming that pristine nickel oxide films are defective p-type materials due to the presence of trivalent nickel [26], it may be supposed that the electrons initially injected to balance the insertion of the first lithium ions (Qinteract with Ni " in the host matrix. However, and as described for proton intercalation in... 

Conventional active materials in positive electrodes of lithium-ion batteries are metal oxides that accommodate lithium via the intercalation mechanism. Intercalation involves the insertion of lithium into unoccupied sites in the crystal lattice, thus resulting in a small change in the imit cell volume and reversibility on the order of hundreds or thousands of cycles. The most common intercalation materials for positive electrodes are LiCo02, which has a two-dimensional layered structure, and LiMn204, which has a three-dimensional spinel structure. Nanoparticulate or nanocrystalline versions of these materials have been examined with the hope of achieving enhanced capacity, rate capability, or cycling performance. 

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