Intrinsically redox states

XPS provides a truly unique tool in the quantitative differentiation of the various intrinsic redox states of PAN. Earlier XPS studies on electrochemically synthesized PAN and its substituted derivatives [76,77] revealed an increase in the Nls core-level spectral linewidth (full width at half maximum or FWHM) for the neutral EM base when compared with that of protonated PAN. The increase in Nls linewidth for the EM base was attributed to the presence of different neutral nitrogen species. A number of subsequent studies on the chemically [78,79] and electrochemically [70-80] synthesized PAN has demonstrated that the proportion of quinonoid imine (=zN-), benzenoid amine (—NH—) and positively charged nitrogen atoms, corresponding to a particular oxidation state and protonation level of PAN, can be quantitatively differentiated in the properly curve-fitted Nls corelevel spectrum. They correspond respectively to peak components with BEs at about 398.2 eV, 399.4 eV and... 

Table 3.2. Changes in intrinsic redox states of EM base Alms after one cycle of acid-base treatment. (Reprinted with permission from ref 85, Elsevier Sci. S.A.)...

The presence of various intrinsic redox states in PPY and various chloride species in the PPY/chloride complex suggest that any reaction stoichiometry based on the total chlorine balance of the complex can be quite misleading. For instance, based on the observed [C1]/[N] rations of the polymer complexes prepared from FeClj at least two reaction schemes have been proposed ... 

Thus, proton modifications of nitrogen atoms in PPY can give rise to a number of intrinsic redox states analogous to those observed in PAN. The behaviour of the corresponding intrinsic oxidation states in both polymers towards protonation/de-protonation, oxida-tion/reduction, or CT interactions with electron acceptors has been critically compared by the XPS technique [105,106]. In addition to the protonation/de-protonation behaviour shown above, sulphonation of DP-PPY readily gives rise to a self-doped or seld-protonated... 

The rate of metal reduction is dependent on the intrinsic redox states of the polymer, the effective surface area, and the pH of the solution. The XPS NIs core-level spectra of protonated and de-protonated PAN and PPY after metal reduction reveal that the intrinsic stnjcture of each polymer at the polymer/metal interface remains intact, even at [metal]/[N] ratios substantially above I [81,112]. Figures 3.33 (a)-(c) show, respectively, the NIs, Au4f and C12p core-level spectra of a DP-PPY film recovered after 48 h from a dilute chloroauric solution. The corresponding core-level spectra after the film has been treated with 0.5M... 

Polyaniline (PANI) is one of the most frequently investigated conducting polymers because of its ease of synthesis, its relative environmental stabUity and its abUity to exist in a range of intrinsic redox states. PANI exists in various oxidation states, ranging Irom a reduced leucoemeraldine form to the fully oxidized pemigraniline form. 

Kang, E.T., K.G. Neoh, and K.L. Tan. 1998. Polyaniline A polymer with many interesting intrinsic redox states. ProgPolym Sci 23 (2) 277-324. 

In the present work, we used polyaniline (PANI)/polyacrylonitrile (PAN) blend to form a nonwoven mat. The PANI exists in a large number of intrinsic redox states. The half oxidized emeraldine base is the most stable and widely investigated state in the PANI family that can be dissolved in N-methyl-2 pyrohdon (NMP). The polyaniline emeraldine base (PANIEB)/polyacrilonitrile blend solution in NMP was prepared and then it was electrospun with different blending ratio. The fibers diameter, fibers morphology, and electrical conductivity of the mats were analyzed and discussed. 

Relatively much less attention has been devoted to PES of polytoluidines compared to PANI. The POT base and salt systems were found to be structurally similar to the PANI base and salt by Jozefowicz et al. [54]. In POT, the methyl group substituent on the phenyl ring leads to an increase in electron localization. This leads to an increase in the interchain spacing as well as disorder in POT. Therefore, XPS is an excellent tool to study and compare the intrinsic redox states as well as the protonation behaviour of POT with that of PANI. 

Raman spectroscopy has been employed in the analysis of intrinsic redox states of PANI. Ohira et al. [100] have reported the Raman spectra of PANI films prepared on a Pt electrode. The spectra of NH4OH-treated PANI and electrochemically reduced PANI were almost independent of the excitation wavelength between 457.9 and 514.5 nm, while the spectra of as-... 

Chemically contrasting fluids, particular fluids of contrasting redox state appear intrinsic to productive mineral systems. 

A similar relationship between the intrinsic fluorescence and the redox state of the copper atoms in lacquer tree laccase was reported (43). 

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