Resonance Raman, ESR, and UV−vis−NIR techniques were used to characterize the secondary doping process in polyaniline (PANI). Experimental results obtained with the first two techniques showed the transformation of diamagnetic quinoid segments into radical semiquinone units while UV−vis−NIR experiments showed the increase of free carriers concentration due to extended conformation. Thermal effects on primarily and secondarily doped polyaniline were also studied by TGA, Raman, ESR, and UV−vis−NIR techniques. The appearance of new Raman bands with temperature was assigned to the formation of “phenazine-like” structures provoked by cross-linking. ESR and UV−vis−NIR experiments showed the absence of formation of addition radicalar structures due to thermal treatment in contrast to that observed after treatment with m-cresol.

Nanoscale composites of polyaniline (PANI) and vanadium oxide (V 2 O 5 ) were assembled via the electrostatic layer-by-layer (LBL) technique, with a thickness per bilayer of 2.5 nm. Interactions between PANI and V 2 O 5 are maximized in comparison to the usual xerogel films due to the nanostructured nature of the LBL films, in which V 2 O 5 causes PANI to be oxidized. This has been demonstrated in Raman spectroscopy measurements and is consistent with electrochemical data. These strong interactions make the LBL film to display a color that is different from the colors of the individual materials. Furthermore, they promote a cooperative effect that enhances the charge storage capability of the films, with a total charge of 2.25 mC cm -2 for the PANI/ V 2 O 5 LBL films, in comparison with 1.86 mC cm -2 for the sum of the isolated contributions from PANI and V 2 O 5 .

Nanoparticles of a Prussian blue (PB) analogue, copper hexacyanoferrate, were synthesized by using ultrasonic radiation and characterized by spectroscopic and electrochemical techniques. The nanoparticles (ca. 10 nm diameter) were immobilized onto transparent indium tin oxide electrodes by electrostatic layer-by-layer deposition. These modified electrodes showed interesting electrochromic properties, changing the coloration during the redox process from brown to orange when oxidized. The nanostructured electrode presented high stability, in contrast to that observed for PB nanoparticles; this fact must be related to the maintenance of the electrostatic assembly because the oxidized compound, CuII/FeIII(CN)6, still possesses a negative excess of charge due to the high number of cyanide groups that link the nanoparticles with the polycation, assuring the integrity of the whole electrostatic assembled film.

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