Acid doping Raman spectroscopy

As mentioned in the previous sections, the electrolyte materials are doped with H3PO4 in order to assure high proton conductivity. Acid uptake is a result of the interactions of the polar basic pyridine group with phosphoric acid. The pyridine ring can react and be protonated by H3PO4 [7, 36, 37] as illustrated in Fig. 5.13a. These specific interactions were surveyed and demcaistrated by means of FT-Raman spectroscopy. Spectra of Copolymer I, pristine and after gradual doping with phosphoric acid are depicted... 

IR and Raman spectroscopy are common tools to study organic compounds like. The methods are rapid, non-destructive and with no need for sample preparation [78]. There is a considerable number of experimental studies using IR spectroscopy to characterise PBI-type polymers doped with phosphoric acid [7-9, 60, 61, 74, 79, 80]. The number of Raman studies is still limited, despite the fact that the intensity of vibration modes from polymer skeleton are enhanced compared to N-H and O-H vibration modes, i.e. there are less interferences due to the presence of water. 

Thirdly, the collision-induced Raman resonances can expand the application of Raman spectroscopy to situations where the conventional Raman susceptibility vanishes. Andrews et al., for example, have demonstrated that sharp vibrational transitions in an initially unpopulated excited electronic state of a molecule can be observed as extra four-wave mixing resonances, even though they cannot be observed in absorption because of rapid dephasing of the electronic transition. In these experiments pentacene molecules were doped in a benzoic acid crystal, and phonon scattering rather than collisions provided the dephasing mechanism. CARS of equally-populated ground state rotational levels in molecules would also become possible by observing collision-induced resonances. 

Camphorsulfonic acid doped polyaniline/ PE blends, prepared by mixing hot solutions of polyaniline in m-cresol and PE in decalin, have been studied using resonance Raman spectroscopy [46]. The results obtained showed that polyaniline treated with m-cresol maintained an extended conformation in the blends. The homogeneous regions of the blend samples exhibited bands at 1160 and 1173 cm which were attributed to polyaniline chains, indicating that polyaniline maintained its characteristics and conformations in the insulating PE matrix. Moreover, the lack of significant differences in the Raman spectra of the blends, compared to the spectra... 

In contrast to the minimal activity in infrared reflection studies the technique of inelastic electron tunneling spectroscopy (IETS) recently has contributed a large amount of information on monolayer adsorption of organic molecules on smooth metal oxide surfaces,Q),aluminum oxide layers on evaporated aluminum. These results indicate that a variety of organic molecules with acidic hydrogens, such as carboxylic acids and phenols chemisorb on aluminum Oxide overlayers by proton dissociation - 1 — and that monolayer coverage can be attained quite repro-ducibly by solution doping techniques. - The IETS technique is sensitive to both infrared and Raman modes. — However, almost no examples exist in which Raman il and or infrared spectra have been taken for an adsorbate/substrate system for which IETS spectra have been observed. 

The mechanism and kinetics of electrochemical reactions at electrodes covered with PT studied using the voltammetric behavior of PT films depend on the nature and concentration of mobile charge carriers within the polymer and therefore on the potential range [193,194]. The dependence of the processes during the electrochemical reduction and oxidation on the medium in contact with the PT film can be revealed by in situ Raman spectra [195]. The doped and neutral states of PMT and poly(3-thienylacetic acid) and the anion and cation dopants can be clearly identified by an improved specular reflectance IR spectroscopy. This method allows the use of the same electrode as that used in... 

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