The combination of semiconducting oxides and polyaniline in the nanoscale range may result in hybrid materials having enhanced properties, such as electrochromism and charge capacity. This paper reports the spectroscopic, morphological and electrochromic characterization of hybrid films made up of hexaniobate one-dimensional (1D) nanoscrolls and polyaniline prepared by the layer-by-layer assembly technique (LbL). Secondary electron imaging and backscattered electron imaging techniques performed using a scanning electron microscope showed that polyaniline is adsorbed on the hexaniobate nanoscrolls, which confirms the combination of the components in the nanoscale domain. UV-VIS-NIR electronic spectra of the LbL hybrid films showed the absorption tail in the NIR region, assigned to delocalized polarons of the polyaniline. Resonance Raman spectra in the 1000-1700 cm À1 range indicated that hybrid films present a higher relative intensity of polaron bands at 1337 and 1508 cm À1 than pristine polyaniline in the emeraldine salt form. These results suggest that hexaniobate nanoscrolls induce a secondary doping of polyaniline. The cyclic voltammetry (CV) data for the hybrid film showed a specific capacity of 870 C cm À3 . According to CV results, the synergistic effect on charge storage properties of the hybrid material is attributed to the enhanced electroactivity of the hexaniobate component in the LbL film. Spectroelectrochemical experiments showed that the electrochromic efficiencies at 420 nm are ca. À41 and 24 cm 2 C À1 as the potential changes from 0.8 to À0.9 V and from À0.9 to À1.8 V, respectively, whereas at 800 nm the efficiencies are ca. À55 and 8 cm 2 C À1 for the same potential ranges. The electrochromic efficiencies and multi-colour character of the LbL film of hexaniobate nanoscrolls and polyaniline indicate that this novel hybrid material is an interesting modified electrode for electrochromic devices.

Summary: Polyaniline nanofibers (from 93 to 220 nm) doped with β‐naphtalenesulfonic acid (PANI‐NSA) have been characterized. Nonhomogeneity in the thickness of fibers, as can be seen with scanning electron microscopy, is the reason for their instability under the HCl doping process. Resonance Raman spectral profiles of PANI‐NSA fibers suggest a lower protonation state than the emeraldine salt forms. Observation of Raman bands, which are a result of cross‐linking, confirms that one of the properties of the polymeric structure formed in micellar polymerization is the type of connection between chains. magnified image

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This paper reports the spectroscopic study on the structural differences of thermally induced cross-linking segments in polyaniline in its emeraldine salt (PANI-ES) and base (PANI-EB) forms. Casting films of PANI-ES (ES-film) and PANI-EB (EB-film) were prepared and heated at 150 °C under atmospheric air for 30 min. Raman spectra excited at 632.8 nm of heated ES-film presented the characteristic bands of phenazine-like structures at 1638, 1392, and 575 cm(-1), whereas EB-film showed lower relative intensities for these bands. The lower content of phenazine-like segments in heated EB-film is related to residual polaronic segments from preparation procedures, as revealed by Raman. This statement was confirmed by a sequence of thermal and doping experiments in both films. Quantum-chemical calculations by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) showed that the phenazine-like structure presents the intense Raman band at 1350 cm(-1) due to heterocycle breathing mode, and the non-phenazine-like structure (substituted hydrophenazine-type) presents higher energy for HOMO-LUMO transition, indicating the lack of conjugation in the heterocycle compared with the phenazine-like structure. According to experimental and theoretical data reported here, it is proposed that only thermally treated PANI-ES presents phenazine-like rings, whereas PANI-EB presents heterocyclic non-aromatic structures.

There is urgent need to improve the clinical outcome of peripheral nerve injury. Many efforts are directed towards the fabrication of bioengineered conduits, which could deliver stem cells to the site of injury to promote and guide peripheral nerve regeneration. The aim of this study is to assess whether graphene and related nanomaterials can be useful in the fabrication of such conduits. A comparison is made between graphene oxide (GO) and reduced GO substrates. Our results show that the graphene substrates are highly biocompatible, and the reduced GO substrates are more effective in increasing the gene expression of the biomolecules involved in the regeneration process compared to the other substrates studied.