Study of deprotonation processes of polyaniline by differential multiwavelength Raman spectroscopy in an electrochemical system

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A layer of polyaniline has been deposited at a gold electrode and studied by differential multiwavelength Raman spectroelectrochemistry. A set of laser line excitation wavelengths was used, including blue (442 nm), green (532 nm), red (633 nm) and far red (785 nm). From the results obtained, the difference spectra between deprotonated (pH 9.0) and protonated (pH 1.0) forms of oxidized and reduced polyaniline were derived and analysed. The characteristic features for different forms of polyaniline were identified, and their dependence on the excitation wavelength was shown. In addition to the usual Raman spectroscopy, the differential spectroscopy enables one to analyse the increase or decrease of intensity for selected Raman bands upon a reversible deprotonation of this polymer.