Polyaniline Nanostructures Research Articles

Recent progress in the preparation of polyaniline nanostructures and their applications in anticorrosive coatings

Research on composites/blends containing polyaniline (PANI) has attracted numerous scientists and engineers due to their excellent adhesion and anticorrosive properties. Nano-structured PANI composites and matrix resins play a key role in physical and anticorrosive performance. This paper reviews the synthesis, growth mechanisms and corrosion application with different resin coatings of PANI-based nano-composites. It also highlights the failures of corrosion protection and methods and suggestions to improve it.

Shape-controlled porous nanocarbons for high performance supercapacitors

Porous activated nanocarbons with well-controlled dimensionality and morphology (i.e. 0D activated carbon nanoparticles, 1D activated carbon nanotubes, and 2D activated carbon nanosheets) were derived successfully from different template-induced polyaniline nanostructures by facile carbonization and activation processes. The obtained nanocarbons show large specific surface areas (1332–2005 m2 g−1), good conductivities, and highly porous nanoscale architectures. The supercapacitors fabricated using the shape-controlled nanocarbons exhibit high specific capacitance, excellent rate capability, and superior long-term cycling stability in both aqueous and ionic liquid electrolytes. More importantly, a very high energy density of 50.5 W h kg−1 with a power density of 17.4 kW kg−1 can be obtained from the activated carbon nanotube based supercapacitors in an ionic liquid electrolyte (with a charge time of ∼10 s), making the shape-controlled nanocarbons promising candidates for high-performance energy storage devices.

Efficient dye-sensitized solar cell from spiny polyaniline nanofiber counter electrode

We demonstrate here the growth of spiny polyaniline (PANi) nanofibers on Pt layer through a stepwise control of current density and employment as CE in DSSC. The superiority of this new nanostructure is evaluated by electrochemical characterizations. The resulting PANi nanostructures give an enhanced electrocatalytic activity toward iodides. Careful examination of data and characterizations indicates that the promising properties are impressive to fulfill the task of CEs. A promising power conversion efficiency of 7.66% is obtained in Pt/spiny PANi nanofiber CE in comparison with 5.89% from Pt-only CE and 6.30% from traditional PANi nanofiber CE. This strategy provides new opportunities for fabricating highly efficient DSSCs.

Electrocatalytic Activity of Carbonized Nanostructured Polyanilines for Oxidation Reactions: Sensing of Nitrite Ions and Ascorbic Acid

A comparative study of the electrocatalytic activity of nitrogen-containing carbon nanomaterials, prepared by the carbonization of nanostructured polyaniline (PANI) salts, for the electrooxidation reactions is presented. Nanostructured PANI salts were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in an aqueous solution in the presence of 5-sulfosalicylic acid (PANI-SSA), 3,5-dinitrosalicylic acid (PANI-DNSA) as well as without added acid (PANI), and subsequently carbonized to c-PANI-SSA, c-PANI-DNSA and c-PANI, respectively. Glassy carbon tip was modified with nanostructured c-PANIs and used for the investigation of sensing of nitrite and ascorbic acid in aqueous solutions as model analytes by linear sweep voltammetry. All three types of the investigated c-PANIs gave excellent response to the nitrite ions and ascorbic acid electrooxidation. The lowest peak potential for nitrite ion oxidation exhibited c-PANI (+0.87V vs. SCE), and for ascorbic acid oxidation both c-PANI and c-PANI-SSA (ca.+0.13V vs. SCE). Electrochemical data were correlated with structural and textural data obtained by Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental and nitrogen sorption analysis.

Inter-relationship between nanostructures of conducting polyaniline and the photocatalytic methylene blue dye degradation efficiencies of its hybrid composites with anatase TiO2

Present work is an investigation of the inter-relationship between nanostructures of conducting polyaniline (PANI) and photocatalytic efficiencies of its composites with anatase TiO2. Two composites with/without ultra-sonication (PANI-TiO2-S and PANI-TiO2) of the polymerization mixture and pristine PANI were prepared by in situ chemical oxidation method. IR and XRD characterizations revealed the core (TiO2) – shell (PANI) arrangement of the hybrid composites. PANI-TiO2-S had nanorods structures grown with TiO2 template and some irregularly shaped secondary grains; but PANI-TiO2 had only spherical submicron size particles. In visible light photodecomposition of methylene blue, PANI, TiO2, PANI-TiO2-S and PANI-TiO2 had the efficiencies of 58%, 71%, 77% and 65% respectively. The greatest efficiency of PANI-TiO2-S originated from the nanostructures of PANI and the combined effect of PANI and TiO2 components in hybrid. Besides this, the characteristics of composites remained invariable during photocatalytic run, which facilitated retain of efficiency during second/third run.

Thermal and dielectric investigations on the blends of κ-carrageenan and nano-structured polyaniline

There are some biosensors and biochips for the recognition and quantization for particular biological molecules. They are made of conductive polymers and natural biomolecules such as protein, DNA and polysaccharides. The conductive polymers work as electric wires for signal transmission, while the natural biomolecules are receptors. Such electric devices are of complex and heterogeneous structures, in either single chain or condensed chains or dispersive phase separations. In order to investigate the complex structures of the polymer blends in the devices and the relation between the structure and the electrical properties, we have prepared several kinds of nano-structured polyaniline (PANI) with defined aggregate morphologies, i.e., nano-granules or nano-fibers with different aspect ratios. The blends of κ-carrageenan and PANIs have been prepared through sol–gel process. The multi-level structures of PANIs have been characterized with X-ray diffraction (XRD) and scanning electron microscope (SEM). The thermal analysis and dielectric relaxation spectroscopy help to evaluate and to understand the chain relaxation and the interfacial structures of the blends.

Structural and electrical characterization of polyanilines synthesized from chemical oxidative polymerization via doping/de-doping/re-doping processes

Structural characterization of various emeraldine salt (ES) and emeraldine base (EB) polyaniline (PANI) powders synthesized from chemical oxidative polymerization and then via de-doping and re-doping processes is first presented. Partial crystallinity with well-separated x-ray diffraction peaks is observed in the as-prepared ES PANI powder and an amorphous characteristic is identified in the de-doped EB PANI powder. From scanning electron microscopy, both the nanostructures of the as-prepared ES and de-doped EB PANI precipitated powders possess similar morphology. This finding reveals that the de-doping process to remove the counter-ions intercalated between the as-prepared ES PANI chains makes the de-doped EB PANI pieces become soft but does not change the nanostructures significantly. Then, the electrical conductivity perpendicular to the surface of the pressed PANI disc pellets is studied. The re-doped ES PANI pellets possess less electrical conductivity than their as-prepared counterparts, which suggests that during the re-doping process the counter-ions (Cl− or ) are re-adsorbed predominantly on the surface region of the PANI nanostructures. Besides, the re-doping of larger counter-ions (with respect to Cl−) intercalated between the PANI chains increases the d-spacing of (1 0 0) planes and hence reduces the corresponding π–π inter-chain interaction. Finally, from the temperature dependence of the electrical conductivity together with the structural information, the charge carrier hopping mechanisms perpendicular to the surface of the pressed pellets corresponding to various PANI samples are compared and discussed.

Sono-assisted synthesis of nanostructured polyaniline for adsorption of aqueous Cr(VI): Effect of protonic acids

Polyaniline (PANI) nanoparticles and 1D nanostructures were prepared by a facile sono-assisted chemical oxidation method in protonic acids like HCl, surfulamic acid (SA), citric acid (CA), taurine (TA) and neutral deionized (DI) water for removal of aqueous Cr(VI). Results showed that all the prepared PANI nanostructures showed efficient adsorption for Cr(VI), however, their adsorption efficiencies varied depending on the protonic acids and the consequent molecular structures of PANIs. Among them, the PANI-HCl prepared in strong HCl acid showed the highest adsorption capacity, followed in descending order by PANI-SA, PANI-CA, PANI-TA and PANI-DI. The adsorption capacity was correlated well with oxidation state and protonation extent of PANIs. Solution pH had an obvious effect on Cr(VI) adsorption, especially for PANI-TA and PANI-DI. A mechanism of electrostatic adsorption followed by reduction of Cr(VI) to Cr(III) was proposed by analyzing FTIR, zeta potential and XPS spectra of PANIs before and after Cr(VI) adsorption.

Synthesis of nanostructured polyaniline via chemical oxidative polymerization: Investigation of morphology and conductivity of the prepared polymers

In this study, nanostructure polyaniline was prepared from aniline monomer via chemical oxidative polymerization in the presence of ammonium persulfate as an oxidizing agent. Interfacial, emulsion, rapid mixing and ultrasonic techniques are used for polymer synthesis. In the interfacial method, chloroform, n-hexane, hexanole and toluene were used as organic solvents and sulfuric acid, methane sulfonic acid and acetic acid were employed as electrolyte solutions. In the emulsion polymerization, dodecyl benzene sulfonic acid and aqueous solution of hydrochloric acid were used as emulsion agent and electrolyte solution respectively. In rapid mixing reaction and ultrasonic method, hydrochloric acid and salicylic acid were used as dopants. The structure, conductivity, morphology and particle size distribution of prepared polymers were investigated after purification and drying by FTIR spectroscopy, scanning electron microscopy and electrical conductivity measurements.

Relaxation Dynamics and Morphology-Dependent Charge Transport in Benzene-Tetracarboxylic-Acid-Doped Polyaniline Nanostructures

The relaxation dynamics and charge-transport mechanisms of different benzene tetracarboxylic acid (BTCA)-doped polyaniline (PANI) nanostructures had been probed by the electric ac response of the samples from 42 Hz up to 5 MHz within the temperature range 133–303 K. The experimental results reveal that the overall frequency-dependent transport properties of these nanostructures significantly depend on the difference in morphologies obtained from the BTCA doping at different concentrations. The above study also illustrates the common origin of the charge-transport mechanism, and the relaxation of these PANI nanostructures and the hopping models is most suitable to describe the electrical response in the measured temperature and frequency range. The observed morphology-dependent variation of the ac and dc conductivity has been correlated with the simultaneous and consistent deviation of the degree of localization of the polaron lattice sites and the hopping lengths, evaluated from the qualitative analysis o...

Thermoelectric performance of electrodeposited nanostructured polyaniline doped with sulfo‐salicylic acid

ABSTRACTConducting polymers, in present days, are considered to be potential thermoelectric (TE) materials. Among them polyaniline (PANI) is a promising candidate. Nanostructured polyaniline doped with organic dopant is electrodeposited and structurally characterized. Its transport properties are investigated for thermoelectric applications. The analysis of transmission electron microscopy image reveals that the sample is rod like nanostructure. This study shows that the type (inorganic/organic) of dopants plays an important role to influence the dimension of nanostructure and the electrical transport properties of PANI. In this study, organic dopant sulfosalicylic acid is proposed for enhancement of figure of merit through an increase in thermoelectric power and decrease in thermal conductivity. Compared to our earlier work the figure of merit evaluated is two orders higher than that of the inorganic dopant bismuth nitrate doped PANI. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39920.

Polyaniline Nanostructures Doped with Fluorescent TPA-BTD-BN

In this paper, a novel fluorescent material with high conductivity as 0.45 S·cm-1 and strong fluorescence has been successfully synthesized basing on polyaniline (PANI) nanostructures doped with a new prepared fluorescein TPABTDBN. The PANI nanostructures were prepared via a simplified template-free method (STFM) with FeCl3 as oxidant and dopant. The resulting sample was characterized by SEM, IR and fluorescence spectroscopy. The fluorescence intensity of synthesized composite improves with the increasing content of TPABTDBN. The electrical properties of pressed composite pellets were measured from room temperature about 291K down to 132K, the conductance follow the exponential temperature dependence of three-dimensional variable-range hopping (VRH) model.

Polyaniline nanostructures expedient as working electrode materials in supercapacitors

Granular type polyaniline (PANi), PANi nanofibers (NFs), and PANi nanotubes (NTs) expedient as working electrode materials for supercapacitors are synthesized. The synthesis procedure used in this work facilitates not only the synthesis of solid powders of the PANi nanostructures, but also thin films constituted by the same PANi nanostructures in the same experiment. PANi NFs are found to exhibit faster electrode kinetics and better capacitance when compared to PANi NTs and granular PANi. Specific capacitance and energy storage per unit mass of PANi NFs are 239.47 Fg−1 (at 0.5 Ag−1) and 43.2 Wh kg−1, respectively. Electrical conductivity of PANi NFs is also better when compared to the other two nanostructures. Properties of the three PANi nanostructures are explicated in correlation with crystallinity, intrinsic oxidation state, doping degree, BET surface area, and ordered mesoporosity pertaining to the nanostructures.

Hexavalent chromium synthesized polyaniline nanostructures: Magnetoresistance and electrochemical energy storage behaviors

In this work, the oxidant Cr(VI) dose was observed to have influenced the polyaniline (PANI) nanostructures as well as the crystallization structure. The temperature dependent resistivity study revealed a quasi 3-dimensional variable range hopping (VRH) electrical conduction mechanism. The permittivity was found to be affected by the PANI nanostructures. The observed positive MR at room temperature in the synthesized PANI samples was analyzed by the wave-function shrinkage model. The electrochemical energy storage was investigated using the cyclic voltammetry (CV) and galvanostatic charge–discharge measurements. The highest gravimetric capacitance of 298.5 F g−1 was obtained in the prepared PANI sample using 3 mmol K2Cr2O7 derived from the CV at a scan rate of 5 mV s−1 and the maximum value of gravimetric capacitance of 330.2 F g−1 was achieved in the galvanostatic charge–discharge measurements at a current density of 0.5 A g−1. After applying an external magnetic field, the capacitance decreased due to the observed positive magnetoresistance phenomenon. The cyclic stability studies revealed that the synthesized PANI samples exhibited good durability and retained around 80% of the capacitance even after 1000 charge–discharge galvanostatic cycles.

Formation of nanostructured polyaniline by dopant-free oxidation of aniline in a water/isopropanol mixture

AbstractNanostructured polyaniline (PANI) was synthesised by the oxidation of aniline in a water/ isopropanol (propan-2-ol, IPA) (50 vol. %) mixture, without added acid, using ammonium peroxydisulfate (APS) as an oxidant. Influence of the IPA co-solvent and the reaction time on the molecular structure, morphology and properties of synthesised PANI samples was studied by FTIR, Raman, and UV-VIS spectroscopies, scanning and transmission electron microscopies (SEM and TEM), and conductivity measurements. The course of the reaction was followed by monitoring changes in the temperature and acidity of the reaction medium. The results were compared with those obtained for PANI prepared in water without IPA under the same reaction conditions. The importance of the solvation effects, dielectric constant of the solvent, and the enthalpy of mixing of IPA with water on the course of the polymerisation reaction and on the properties of polymeric products in the water/IPA medium in comparison with those in water was pointed out.

Electrochemically polymerized vine-like nanostructured polyaniline on activated carbon nanofibers for supercapacitor

Vine-like polyaniline (PANI) nanostructures were prepared using electrochemical polymerization on activated carbon nanofibers (ACNF) in order to use as a supercapacitor. Electrospun polyacrylonitrile (PAN)-based nanofibers were firstly carbonized and physically activated to increase the specific surface area. The PANI formed a vine-like shape and well-contacted with the surface of ACNF. The remarkably improved electrochemical performances of PANI-deposited ACNF electrode were investigated using cyclic voltammetry (CV) and galvanostatic charge/discharge test, and electrochemical impedance analysis. The current area of the PANI-ACNF electrode is higher than that of ACNF electrode in CV curves and the specific capacitance of the PANI-ACNF was 832Fg−1 which is much higher than 353Fg−1 of ACNF at a current density of 1Ag−1 in galvanostatic charge/discharge analysis. During galvanostatic charge/discharge test of 1000 cycles at 1Ag−1, the PANI-ACNF sample keeps its specific capacitance up to the value of 765Fg−1 (92% retention). Also, the PANI nanostructure on the ACNF substrate achieved a rapid doping/dedoping process between the surface of electrode and electrolyte ions in comparison with ACNF electrode.

Superior capacitive and electrocatalytic properties of carbonized nanostructured polyaniline upon a low-temperature hydrothermal treatment

Carbonized nanostructured polyaniline (C.PANI) was hydrothermally treated in 1moldm−3 KOH at 200°C. The treatment caused significant reduction of micropore volume but negligible changes in mesoporous domain, as evidenced by nitrogen adsorption measurements, as well as significant increase of surface N/C and O/C ratios, as evidenced by XPS method. In comparison to the C.PANI precursor, the new material, denoted as C.PANI.HAT200, delivered twice as high gravimetric capacitances, amounting to 363, 220 and 432Fg−1, in 6moldm−3 KOH, 2moldm−3 KNO3 and 1moldm−3 H2SO4, respectively, when measured potentiodynamically at a scan rate of 5mVs−1. Moreover, its exceptionally high electrocatalytic activity towards the oxygen reduction reaction (ORR), almost one order of magnitude higher than that of C.PANI was evidenced in alkaline media, approaching closely a four-electron pathway. The onset potential for ORR matched the one of platinum-based electrocatalyst. Significant improvements of both capacitive and electrocatalytic properties of C.PANI.HAT200 were discussed in correlation to the modification of surface functional groups. These findings affirm the low temperature hydrothermal post-synthetic modification of N-doped nanocarbons as a route of production of advanced multifunctional carbon materials with exceptional characteristics.

Highly Oriented Self-Assembly of Conducting Polymer Chains: Extended-Chain Crystallization during Long-Range Polymerization

We investigated a self-assembly of conjugated polymer chains resulting in crystalline one-dimensional (1D) nanostructures with a high length-to-diameter aspect ratio. Conjugate polymer 1D nanostructures were obtained via a biphase interfacial polymerization method in which aniline monomers were oxidized by metal ions dissolved in aqueous solution. High-resolution transmission electron microscopy (TEM) analyses revealed polymer chains with remarkable π-electron interchain interactions intensive enough to form long crystalline nanowires and nanobelts, which have been difficult to obtain in conjugate polymer nanostructures. The remarkably uniform nanostructures along the long axis indicate the cooperative effects of chain-end oxidative polymerization and close-packing condensation (π-electron coupling) between linear chains and the prevention of random cross-linking and coiling of polymer chains. Electrical conductance along the polymer-chain direction of nanowires forming a long ribbon was estimated to be 46 kΩ via a four-probe measurement, suggesting that stable and partially oxidized polyaniline nanostructures can be produced in the presense of Au ions as effective electron acceptors. The resulting products may find potential uses in nanoelectronics and optoelectronic devices where highly uniform and oriented conducting channels are desired.

Morphology-Dependent Enhancement of the Pseudocapacitance of Template-Guided Tunable Polyaniline Nanostructures

Polyaniline is one of the most investigated conducting polymers as supercapacitor material for energy storage applications. The preparation of nanostructured polyaniline with well-controlled morphology is crucial to obtaining good supercapacitor performance. We present here a facile chemical process to produce polyaniline nanostructures with three different morphologies (i.e., nanofibers, nanospheres, and nanotubes) by utilizing the corresponding tunable morphology of MnO2 reactive templates. A growth mechanism is proposed to explain the evolution of polyaniline morphology based on the reactive templates. The morphology-induced improvement in the electrochemical performance of polyaniline pseudocapacitors is as large as 51% due to the much enhanced surface area and the porous nature of the template-guided polyaniline nanostructures. In addition, and for the first time, a redox-active electrolyte is applied to the polyaniline pseudocapacitors to achieve significant enhancement of pseudocapacitance. Compared to the conventional electrolyte, the enhancement of pseudocapacitance in the redox-active electrolyte is 49%–78%, depending on the specific polyaniline morphology, reaching the highest reported capacitance of 896 F/g for polyaniline full cells so far.

Synthesis and characterization of polyaniline and polyaniline – Carbon nanotubes nanostructures for electrochemical supercapacitors

Nanostructures of polyaniline (PANI) and PANI with embedded carbon nanotubes (CNT) were synthesized through a chemical method of self-organization. An oxidative polymerization process was performed in the monomer acid solution with the presence of a surfactant and the addition of multi-walled CNT. The CNT were added with and without pretreatment, CNTf and CNTnf, respectively. Furthermore, ammonium persulfate and sodium dodecyl sulfate were incorporated to the reaction solution as dispersant and oxidizing agents, respectively. Different nanostructures such as nanoparticles or nanotubes were obtained depending on the CNT added, and characterized by scanning electron microscopy, transmission electron microscopy, UV–vis spectroscopy, infrared spectroscopy and electrochemical techniques. Spectroscopy results showed variations in the observed bands of the synthetized nanostructures attributed to changes in the molecular structures, to the state of doped PANI reached during polymerization and to the stabilization of these links by hydrogen bridge interactions. PANI and PANI–CNT composites were evaluated by electrochemical techniques to test their behavior in relation to supercapacitors properties. PANI–CNTf nanocomposites displayed improved capacitive properties in H2SO4 solutions, namely 1744 F g−1at 2 A g−1. Also, the specific capacitance was strongly influenced by the developed morphologies. These characteristics point to their feasible application as supercapacitors materials.