Partial doping

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

In Figure 4.10 a typical uv-vis-nir spectrum of a partially doped conjugated polymer is presented. The coexistence of the n—n transition band and two doping induced bands can be observed. 

The IR and NMR H spectra of poly(3-alkyl thiophene) samples were similar to those already published [157,158] except for some peaks due to partial doping in the case of FeCl3 synthesised samples. 

H. Kajii, K. Takahashi, J.-S. Kim, and Y. Ohmori, Study of the transient electroluminescence process using organic light-emitting diode with a partial doping layer, Jpn. J. Appl. Phys., 45(4B), 3721-3724 (2006). 

One-dimensional metals of d -complexes with a quadric-planar surrounding are good electrical conductors (For a very recent review on polymers with transition metal chains see J.K. Bera, K.R. Dunbar, Angew. Chem. 2002, 114, 4633). Partial doping of tetracyanoplatinate (Kroogmann salt) with columnar stacks results in metallic-like conductivity [7]. A linear chain polymer containing Rh-Rh bonds has been obtained by galvanostatic reduction of... 

At present, it can be concluded firom the data reported in literature that (i) chemical and electrochemical polymerization of EDOT in the presence of CNTs results in covalent functionalization of the mbe wall and (ii) the mixing of CNTs with PEDOT-type polymers involves a partial doping process. 

FIGURE 8.1 Electronic structures of (a) neutral PPy, (b) polaron in partially doped PPy and (c) bipolaron in fully doped PPy. 

Beginning in 1999, Kiebooms and Wudl reported the production of isothianaphthene analogs as shown in Scheme 12.29 [168]. After the removal of lower My, fractions by Soxhlet extraction with methanol and THF, polymer 124a was isolated as a purple solid that was found to be only soluble in 1,1,2,2-tetrachloroethane. It was found that the initially isolated material was partially doped, but could be dedoped by conventional hydrazine treatment. From the absorption onset of solvent cast films, the Eg was determined to be 1.2-1.5 eV [168,169]. Characterization of the IRAV modes correlated with the generation of charge within the doped polymer revealed sharp bands of quite low intensity, indicative of strongly localized charge carriers [98,169]. 

Highly conductive when oxidized (even partially) Doped state is especially stable Commercially available in many forms, including aqueous suspensions... 

Conjugated polymers in neutral state are normally semiconducting materials. However, a partial doping of conducting polymers improves electric conductivity. The conductivity of a doped conducting polymer is of the order of 10 S/cm depending on polymer structures and doping levels. 

As shown in the previous section, the oligothiophenes form the CT (or partially doped) crystals of high quality. Therefore one has a unique opportunity to study both the crystal and molecular structures of the doped form relative to the neutral form. These investigations provide important and precise information about the structural change of the crystals and molecules caused by the charge injection. 

The thermopower data for various types of doped PANl are shown in Figs. 2.51a and 2.51b [172,193]. The room temperature value is approximately 10 /itV/K with small variations ( 2 p.V/K) depending on the details of the process for casting the film. The magnitude and positive sign of 5(7) are similar to those obtained from a number of partially doped p-type conducting polymers [89-92]. The positive sign of the thermopower is consistent with the calculated band structure of the metallic emeraldine salt, a three-quarter-filled tt band with one hole per... 

Pervaporation was next carried out to test the selectivity of polyaniline membranes toward acetic acid-water mixtures. Different feed ratios of acetic acid and water were pervaporated through both undoped and doped polyaniline, as shown in Fig. 33.18, where the feed water content is plotted versus the permeant water content. For comparison the vapor-liquid equilibrium curve for acetic acid-water [78] is plotted just above the line of no separation. From Fig. 33.18 it is clear that undoped polyaniline has a small preference for permeating water over acetic acid at essentially any composition. However, this small preference at an average water permeability of about 0.5 g mm/(m--h) is too low to have any utility. More interesting is fully HCl-doped polyaniline, which permeates water over acetic acid in a much more selective fashion. In fact, even with a mixture of 859f acetic acid-15% water, at least 93 wt % of the permeant was water. It should be pointed out that when undoped membranes are used in the presence of acids, they will partially dope the polyaniline, the extent depending on the pH of the acid used. However, when a... 

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