Intercalators effect

McEvoy, A.J., Etman, M. and Memming, R. 1985. Interface charging and intercalation effects on d-band transition metal diselenide photoelectrodes. J. Electroanal. Chem., 190.225-241. 

Besides, the authors discovered an intercalation effect during activation. Intercalation involves the insertion of calcium ions into aluminium hydroxide lattice which possesses a layered structure. Intercalation takes place between hydroxide layers over the planes with Miller index 002. A maximum increase of the distance is observed in Al(OH)3+CaO mixture (from 0.4850 to 0.4875 nm) while in Al(OH)3+ Ca(OH)2 mixture, it changes not so significantly (to 0.4867 nm). 

Many layer-lattice compounds can intercalate additional metal atoms of the same element as comprised in the original structure (e.g. niobium in niobium diselenide), but molybdenum disulphide will not do so. The behaviour may be determined by the availability of electrons suitably oriented to form bonds with the additional metal atoms, although it seems unlikely that this single factor applies to all intercalation effects. 

The pore model is unable to describe this late reactivity maximum around X=0.7 as it foresees a possible maximum reactivity to occur only between 0 X < 0.393. In the literature, the late occurrence has been explained by intercalation of alkali metal species into the carbon stmeture, leading to a gradual release of active centres with conversion. We note, however, that intercalation effects have seldom been reported for charcoals (in contrast to graphite). In our opinion the cause for the "anomalous" reactivity behaviour stems from a combination of structural and catalytic phenomena emerging from the reaction mechanism involved. The most important mechanism proposed nowadays is the oxygen transfer mechanism in which the oxygen is extracted from the reactant gas (CO2) by the catalyst, which then supplies it in an active form to the carbon. 

Another property of transition metal dichalcogenides is an intercalation effect. Most of the atoms in the periodic table and organic molecules which are Lewis bases can be intercalated in the van der Waals gap sites, forming intercalation compounds(intercalates). One of the most striking features is a transport phenomenon. Alkali metal intercalates of IV] - and VIb-MX2, for example, NaxMoS2 or LixZrSe2 become metallic and show a superconductivity at low temperatures(10,11). A charge transfer occurs between the alkali atom and the mother crystal. 

Very T, Ambrosek D, Otsuka M, Gourlauen C, Assfeld X, Monari A, Daniel C (2014) Photophysical properties of luthenium (II) polypyridyl DNA intercalators effects of the molecular surroundings investigated by theory. Chem Eur J 40 12901-12909... 

Solid Superacids. Most large-scale petrochemical and chemical industrial processes ate preferably done, whenever possible, over soHd catalysts. SoHd acid systems have been developed with considerably higher acidity than those of acidic oxides. Graphite-intercalated AlCl is an effective sohd Friedel-Crafts catalyst but loses catalytic activity because of partial hydrolysis and leaching of the Lewis acid halide from the graphite. Aluminum chloride can also be complexed to sulfonate polystyrene resins but again the stabiUty of the catalyst is limited. 

Antineoplastic Drugs. Cyclophosphamide (193) produces antineoplastic effects (see Chemotherapeutics, anticancer) via biochemical conversion to a highly reactive phosphoramide mustard (194) it is chiral owing to the tetrahedral phosphoms atom. The therapeutic index of the (3)-(-)-cyclophosphamide [50-18-0] (193) is twice that of the (+)-enantiomer due to increased antitumor activity the enantiomers are equally toxic (139). The effectiveness of the DNA intercalator dmgs adriamycin [57-22-7] (195) and daunomycin [20830-81-3] (196) is affected by changes in stereochemistry within the aglycon portions of these compounds. Inversion of the carbohydrate C-1 stereocenter provides compounds without activity. The carbohydrate C-4 epimer of adriamycin, epimbicin [56420-45-2] is as potent as its parent molecule, but is significandy less toxic (139). 

The mechanism of interaction with DNA is suggested. Ethidium bromide (EB) displacement assay was performed. We determine the binding constant of Tb-E to DNA to be in the order of Ig K = 6.47 0.4. The bathochromic and hypsochromic effects in the absorption spectra of investigated complex were observed and the interaction is assumed to be mainly of the mono-intercalating type. 

After briefly introducing the main electronic features of CNTs (Sec. 2) and some general aspects of electronic conduction and transmission (Sec.. 1), we will show how complex electrical measurements to perform on such tiny entities are (Sec. 4). Then we will present the main experimental results obtained on the electrical resistivity of MWCNT and SWCNT and the very recent data relative to the thermopower of SWCNT bundles (Sec. 5). We will also discuss the effect of intercalation on the electrical resistivity of SWCNT bundles (Sec. 6). Finally, we will present some potential applications (Sec. 7). 

In Fig. 7 we present the effect of Br2 intercalation on the temperature dependence of the electrical resistivity of pristine SWCNT bundles before and after heat treatment in vacuum at 450 K for several hours [35]. In Fig. 8 the effect of fiotassium intercalation is presented for different treatments. 

For SWCNT bundles [35], ID intercalation would occur between the CNTs columns as it is the case for jxilyacetylene. Intercalation either by acceptors (Fig. 6) or donors (Fig. 7) increases the electrical conductivity as expected, however the effect is less pronounced than in bulk graphite [34]. 

Fig. 7. The effect of Brj intercalation on the temperature dependence of the resistivity of a bulk SWCNT sample. Curve a, pristine material curve b, saturation-doped with Br2 curve c, after heating in the cryostat vacuum to 4. 0 K for several hours [3. ].

In conclusion, wc have shown the interesting information which one can get from electrical resistivity measurements on SWCNT and MWCNT and the exciting applications which can be derived. MWCNTs behave as an ultimate carbon fibre revealing specific 2D quantum transport features at low temperatures weak localisation and universal conductance fluctuations. SWCNTs behave as pure quantum wires which, if limited in length, reduce to quantum dots. Thus, each type of CNT has its own features which are strongly dependent on the dimensionality of the electronic gas. We have also briefly discussed the very recent experimental results obtained on the thermopower of SWCNT bundles and the effect of intercalation on the electrical resistivity of these systems. 

Xenon difluoride may be used as the pure reagent or as a graphi te intercalate for the effective fluonnation of polynuclear aromatics [86 87] (equations 49 and 50)... 

Xenon difluoride [55], xenon difluoride complexed with dialkyl sulfides [59], and xenon difluoride intercalated with graphite [90] are all effective reagents for the fluonnalion of acids, enolates, or enols (Table 2)... 

FIGURE 12.16 The structures of ethidiutn bromide, acridine orange, and actinomycin D, three intercalating agents, and their effects on DNA structure. 

Pandya et al. have used extended X-ray ascription fine structure (EXAFS) to study both cathodically deposited -Ni(OH)2 and chemically prepared / -Ni(OH)2 [44], Measurements were done at both 77 and 297 K. The results for / -Ni(OH)2 are in agreement with the neutron diffraction data [22]. In the case of -Ni(OH)2 they found a contraction in the first Ni-Ni bond distance in the basal plane. The value was 3.13A for / -Ni(OH)2 and 3.08A for a-Ni(OH)2. The fact that a similar significant contraction of 0.05A was seen at both 77 and 297K when using two reference compounds (NiO and / -Ni(OH)2) led them to conclude that the contraction was a real effect and not an artifact due to structural disorder. They speculate that the contraction may be due to hydrogen bonding of OH groups in the brucite planes with intercalated water molecules. These ex-situ results on a - Ni(OH)2 were compared with in-situ results in I mol L"1 KOH. In the ex-situ experiments the a - Ni(OH)2 was prepared electrochemi-cally, washed with water and dried in vac-... 

Numerous research activities have focused on the improvement of the protective films and the suppression of solvent cointercalation. Beside ethylene carbonate, significant improvements have been achieved with other film-forming electrolyte components such as C02 [156, 169-177], N20 [170, 177], S02 [155, 169, 177-179], S/ [170, 177, 180, 181], ethyl propyl carbonate [182], ethyl methyl carbonate [183, 184], and other asymmetric alkyl methyl carbonates [185], vinylpropylene carbonate [186], ethylene sulfite [187], S,S-dialkyl dithiocarbonates [188], vinylene carbonate [189], and chloroethylene carbonate [190-194] (which evolves C02 during reduction [195]). In many cases the suppression of solvent co-intercalation is due to the fact that the electrolyte components form effective SEI films already at potential which are positive relative to the potentials of solvent co-intercalation. An excess of DMC or DEC in the electrolyte inhibits PC co-intercalation into graphite, too [183]. 

Graphitic anodes which have been "prefilmed" in an electrolyte "A" containing effective film-forming components before they are used in a different electrolyte "B" with less effective film-forming properties show lower irreversible charge losses and/or a decreased tendency to solvent co-intercalation [155, 201, 202], However, sufficient insolubility of the pre-formed films in the electrolyte "B" is required to ascertain long-term operation of the anode. 

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