A novel strategy for the synthesis of polyaniline nanostructures with controlled morphology

Polyaniline-Derived Nitrogen-Containing Carbon Nanostructures with Different Morphologies as Anode Modifier in Microbial Fuel Cells

Anode modification with carbon nanomaterials is an important strategy for the improvement of microbial fuel cell (MFC) performance. The presence of nitrogen in the carbon network, introduced as active nitrogen functional groups, is considered beneficial for anode modification. In this aim, nitrogen-containing carbon nanostructures (NCNs) with different morphologies were obtained via carbonization of polyaniline and were further investigated as anode modifiers in MFCs. The present study investigates the influence of NCN morphology on the changes in the anodic microbial community and MFC performance. Results show that the nanofibrillar morphology of NCNs is beneficial for the improvement of MFC performance, with a maximum power density of 40.4 mW/m², 1.25 times higher than the anode modified with carbonized polyaniline with granular morphology and 2.15 times higher than MFC using the carbon cloth-anode. The nanofibrillar morphology, due to the well-defined individual nanofibers separated by microgaps and micropores and a better organization of the carbon network, leads to a larger specific surface area and higher conductivity, which can allow more efficient substrate transport and better bacterial colonization with greater relative abundances of Geobacter and Thermoanaerobacter, justifying the improvement of MFC performance.

PANI–WO3·2H2O Nanocomposite: Phase Interaction and Evaluation of Electronic Properties by Combined Experimental Techniques and Ab-Initio Calculation

The development of conjugated polymer-based nanocomposites by adding metallic particles into the polymerization medium allows the proposition of novel materials presenting improved electrical and optical properties. Polyaniline Emeraldine-salt form (ES–PANI) has been extensively studied due to its controllable electrical conductivity and oxidation states. On the other hand, tungsten oxide (WO₃) and its di-hydrated phases, such as WO₃·2H₂O, have been reported as important materials in photocatalysis and sensors. Herein, the WO₃·2H₂O phase was directly obtained during the in-situ polymerization of aniline hydrochloride from metallic tungsten (W), allowing the formation of hybrid nanocomposites based on its full oxidation into WO₃·2H₂O. The developed ES–PANI–WO₃·2H₂O nanocomposites were successfully characterized using experimental techniques combined with Density Functional Theory (DFT). The formation of WO₃·2H₂O was clearly verified after two hours of synthesis (PW₂ nanocomposite), allowing the confirmation of purely physical interaction between matrix and reinforcement. As a result, increased electrical conductivity was verified in the PW₂ nanocomposite: the DFT calculations revealed a charge transfer from the p-orbitals of the polymeric phase to the d-orbitals of the oxide phase, resulting in higher conductivity when compared to the pure ES–PANI.

Some Important Issues of the Commercial Production of 1-D Nano-PANI

One-dimensional polyaniline nano-materials (1-D nano-PANI) have great promise applications in supercapacitors, sensors and actuators, electrochromic devices, anticorrosive coatings, and other nanometer devices. Consequently, commercial production of 1-D nano-PANI at large-scale needs to be quickly developed to ensure widespread usage of this material. Until now, approaches—including hard template methods, soft template methods, interfacial polymerization, rapid mixing polymerization, dilute polymerization, and electrochemical polymerization—have been reported to be used to preparation of this material. Herein, some important issues dealing with commercial production of 1-D nano-PANI are proposed based on the complexity of the synthetic process, its characters, and the aspects of waste production and treatment in particular. In addition, potential solutions to these important issues are also proposed.

Transformation of para arsanilic acid by manganese oxide: Adsorption, oxidation, and influencing factors

Aromatic organoarsenic compounds tend to transform into more mobile toxic inorganic arsenic via several processes, and can inadvertently spread toxic inorganic arsenic through the environment to water sources. To gain insight into the transformation mechanisms, we herein investigated how the process of para arsanilic acid (p-ASA) transformation works in detail on the surface of adsorbents by comparing it with phenylarsonic acid (PA) and aniline, which have similar chemical structures. In contrast to the values of 0.23 mmol g^-1 and 0.68 mmol g^-1 for PA and aniline, the maximum adsorption capacity was determined to be 0.40 mmol g^-1 for p-ASA at pH 4.0. The results of FTIR and XPS spectra supported the presence of a protonated amine, resulting in a suitable condition for the oxidation of p-ASA. Based on the combined results of UV-spectra and UPLC-Q-TOF-MS, we confirmed that the adsorbed p-ASA was first oxidized through the transfer of one electron from p-ASA on MnO₂ surface to form a radical intermediate, which through further hydrolysis and coupling led to formation of benzoquinone and azophenylarsonic acid, which was identified as a major intermediate. After that, p-ASA radical intermediate was cleaved to form arsenite (III), and then further oxidized into arsenate (V) with the release of manganese (Mn) into solution, indicating a heterogeneous oxidation process.

Preparation and Electrochemical Properties of Polyaniline Composite Electrodes Prepared by In-Situ Polymerization in Hydrous Ruthenium Oxide Dispersed Aqueous Solution

Polyaniline (PANI)/ruthenium oxide (RuO2) composites were prepared by a chemical oxidation polymerization with various amount of hydrous RuO2. In the PANI/RuO2 composites, RuO2 particles were surrounded by PANI. The morphology and structure of the PANI/RuO2 composites were examined by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Analysis by TEM revealed that the aggregations of the composites were increased with the amounts of hydrous RuO2. Electrochemical performances of prepared composites were characterized by cyclic voltammetry (CV). The composites prepared with 20 wt% of hydrous RuO2 per aniline monomer showed the highest specific capacitance of 710 F/g at 5 mV/s among the prepared composites. However, the specific capacitance of the composites with excess amounts of hydrous RuO2 is lower than the highest one. The large aggregation of RuO2 particles prevents the participation in electrochemical reaction due to the long pathway from the electrolyte and a decrease of effective surface area.

Investigation of templated and supported polyaniline adsorbent materials

Diverse poly(aniline) (PANI) were synthesized in water, acid catalyzed solution with various acids (CH₃COOH, HCl, or H₂SO₄) and/or a chitosan support to afford nanoparticle PANI (in water), bulk-PANI (in aqueous acids), and a chitosan-PANI composite.

Structural-controlled synthesis of polyaniline nanoarchitectures using hydrothermal method

Three new polyaniline (PANI) micro/nanostructures featuring square nanosheets, microspheres and microdisks are successfully synthesized via hydrothermal method. Uniform sizes and thickness of highly crystalline PANI square structural nanosheets can be tuned by the oxidation polymerization in the presence of cetyltrimethylammonium bromide (CTAB) as a template. Mechanistic studies indicate that concentrations of aniline and CTAB, reaction temperature and time have great influence on the morphology of PANI polymers. Particularly, CTAB is essential to determine the morphology of synthetic PANI. In aqueous solution at extremely high temperature and pressure, CTAB provides various self-assembly of micelles, such as spherical micelle, planar bilayer, and lamellar phase, in which corresponding micro/nanostructures are formed. This hydrothermal fabrication gives an excellent example for the preparation of well-defined two-dimensional PANI micro/nanomaterials and potentially for other synthetic polymers.

Exfoliated clay/polyaniline nanocomposites through tandem diazonium cation exchange reactions and in situ oxidative polymerization of aniline

Exfoliated, conductive clay/polyaniline nanocomposites were prepared by polymerization of aniline in the presence of diazonium cation exchanged bentonite.

Synthesis and characterization of "hairy urchin"-like polyaniline by using β-cyclodextrin as a template

A novel synthesis of "hairy urchin"-shaped polyaniline (PAni) and its surface coverage with nanospikes was achieved from a simple microemulsion polymerization technique in the presence of β-cyclodextrin (β-CD). The rodlike micelle phase was characterized, and the key factors affecting the formation of PAni nanostructures were systematically examined. Ferric chloride (FeCl(3)) has played a role as a structural directing agent to fabricate the polymer as hairy urchin-like structure/nanorods via a cooperative interaction between FeCl(3) and DoTAC in an aqueous medium. Host-guest inclusion complex of β-cyclodextrin with aniline was used as a monomer. It has been revealed that the formation of the supramolecular complexes of polyaniline with β-CD due to host-guest interaction is indispensable for the fabrication of these unique PAni nanostructures, and a suitable β-CD to aniline molar ratio is essential to their exclusive formation. Different varieties of PAni nanostructures such as hairy urchin, branched particles consisting of rodlike branches, and regular rodlike particles were obtained in the presence of FeCl(3). Also, in the absence of FeCl(3), a predominant product of regular spherical particles and wirelike aggregation exhibiting faceted surfaces were obtained. The structures of polyaniline hairy urchin-like nanorods were analyzed using transmission electron microscopy (TEM). The synthesized polymer was characterized by Fourier-transform infrared spectroscopy and X-ray diffraction technique. Additionally, the relationship between the morphology and the conductivity of the PAni nanostructures was investigated as well.