Emeraldine Salt Research Articles

Formation and Electrochemical Characterisation of Enzyme-Assisted Formation of Polypyrrole and Polyaniline Nanocomposites with Embedded Glucose Oxidase and Gold Nanoparticles

Enzyme-assisted synthesis of electrochemically active nanocomposite structures based on π-π conjugated polymers polyaniline (PANI) and polypyrrole (Ppy) is reported. The synthesis of both conducting polymers was induced by hydrogen peroxide, which is generated during catalytic action of glucose oxidase (GOx), and this polymerisation was performed in the presence of (i) gold nanoparticles of 6 nm diameter (AuNPs(6nm)) or (ii) tetrachloroauric acid (HAuCl4). Formed nanocomposites were evaluated electrochemically and spectrophotometrically. Field emission scanning electron microscopy results illustrated that nanocomposites are poly-dispersed particles tend to agglomerate during centrifugation. Hydrodynamic diameter evaluated by dynamic light scattering technique for PANI/AuNPs(6nm)&GOx- or PANI/AuNPs(AuCl4 −)&GOx-based nanocomposites after 108 h lasting polymerization was 1.90 or 1.70 times larger than that determined for Ppy/AuNPs(6nm)&GOx or Ppy/AuNPs(AuCl4 −)&GOx, respectively. Oxidation peaks in cyclic voltammograms determined for electrodes modified by PANI/AuNPs(6nm)&GOx-, PANI/AuNPs(AuCl4 −)&GOx- and PANI/GOx-based nanocomposites were observed at +0.332, +0.349, and +0.542 V. For Ppy/AuNPs(6nm)&GOx-, Ppy/AuNPs(AuCl4 −)&GOx- and Ppy/GOx-based nanocomposites oxidation peaks were observed at +0.425, +0.545 and +0.508 V, respectively. Oxidation peaks of PANI nanocomposites without and with AuNPs or AuCl4 - appeared due to the conversion of PANI leucoemeraldine form to emeraldine salt, while for Ppy – are attributed to the transition of cation-polaron into the cation-bipolaron-based state of Ppy.

Development of water-based polyaniline sensor for hydrazine detection

In this study, water-soluble polyaniline-methylcellulose complex (PAni-MC) was applied as an environmental friendly chemical sensor for hydrazine detection. PAni was rendered water-soluble through chemical modification with MC. Fourier transform infrared (FTIR) and Ultraviolet-visible (UV–vis) spectroscopies confirmed the chemical structures of PAni-MC to be the conducting emeraldine salt form with electrical conductivity values of 0.068 S cm−1 for pristine PAni and 0.132 S cm−1 for PAni-MC respectively. In the hydrazine detection procedure, PAni-MC solution was added into samples containing various concentrations of hydrazine (10−100 ppm) and the sensor responses were recorded using a conductivity meter. Several parameters have been studied, including (i) different volume ratio of PAni to hydrazine, (ii) different mass ratio of aniline (Ani) monomer to MC, and (iii) detection at low concentration range of hydrazine (1−10 ppm). From the results obtained, PAni-MC (volume ratio 2:5 of PAni-MC: hydrazine) with the mass ratio 0.2:1 of Ani: MC has achieved the best sensitivity of 0.0143 ppm−1, hence it was selected to further study its sensor performance. Calibration has shown a good sensitivity of 0.0132 ppm-1 and a good linear correlation (R2 = 0.9953), the limit of detection (LOD) of 0.55 ppm, and the limit of quantitation (LOQ) of 1.82 ppm respectively. The sensor performance was supported by UV–vis and FTIR analyses. Significant decrease in the UV–vis absorbance was observed at bipolaron (∼821 nm) and polaron (∼450 nm) bands, meanwhile the intensity of quinoid/benzenoid (IQ/IB) ratio in the FTIR spectra has shown a decrease from 1.03 to 0.97. In real sample analysis, PAni-MC eventually indicated the best recovery range of 96–136 % and a good relative standard deviation (RSD) of 2.69–5.84 %.

Chemically copolymerized poly(2-chloroaniline-co-2-ethylaniline) as an anodic material in Li-ion batteries

Poly(2-chloroaniline-co-2-ethylaniline)(poly(OCA-co-OEA)) was synthesized by in situ chemical oxidative method using ammonium per sulfate as an initiator and HCl as dopant. The copolymer was characterized by FTIR, UV-Visible, NMR spectroscopic techniques and XRD. FESEM and EDAX were taken to study the surface morphology and elemental composition. Thermal stability of the copolymer was confirmed by thermogravimetric analysis. The conduction was examined in terms of the dielectric constant and the electrical conductivity of 8.083 × 10–6 S cm−1 measured shows semi conducting nature of the emeraldine salt form of the copolymer. FESEM images show spongy and porous surface. The oxidation/reduction potentials and electrochemical reaction of Li/copolymer cells were tested by cyclic voltammetric technique. The discharge capacity of 63.4 mAh/g and charge capacity 62.8 mAh/g at 7–8 cycles show good reversibility. The practical specific charge capacity was 58.2% of the theoretical specific charge capacity which is 107.76 mAh/g. Hence it can efficiently be used as an anodic electrode material in lithium ion secondary batteries.

Impact of Acidity Profile on Nascent Polyaniline in the Modified Rapid Mixing Process-Material Electrical Conductivity and Morphological Study.

Polyaniline (PANI) was synthesized chemically with the modified rapid mixing protocol in the presence of sulfuric acid of various concentrations. A two-step synthetic procedure was utilized maintaining low-temperature conditions. Application of the modified rapid mixing protocol allowed obtaining a material with local ordering. A higher concentration of acid allowed obtaining a higher yield of the reaction. Structural characterization performed with Fourier-transform infrared (FTIR) analysis showed the vibration bands characteristic of the formation of the emeraldine salt in both products. Ultraviolet–visible light (UV–Vis) spectroscopy was used for the polaronic band and the p–p* band determination. The absorption result served to estimate the average oxidation level of PANI by comparison of the ratio of the absorbance of the polaronic band to that of the π–π* transition. The absorbance ratio index was higher for PANI synthesized in a more acidic solution, which showed a higher doping level for this polymer. For final powder products, particle size distributions were also estimated, proving that PANI (5.0 M) is characterized by a larger number of small particles; however, these particles can more easily agglomerate and form larger structures. The X-ray diffraction (XRD) patterns revealed an equilibrium between the amorphous and semicrystalline phase in the doped PANI. A higher electrical conductivity value was measured for polymer synthesized in a higher acid concentration. The time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis showed that the molecular composition of the polymers was the same; hence, the difference in properties was a result of local ordering.

Polyaniline emeraldine salt as selective electrochemical sensor for HBr over HCl: a systematic density functional theory study through oligomer approach.

Density functional theory (DFT) calculations are performed to rationalize the experimentally observed sensitivity and selectivity of polyaniline emeraldine for hydrogen bromide over hydrogen chloride. The interaction behaviour is studied at UB3LYP method of density functional theory through oligomer approach. The properties for polymers are obtained extrapolation through second-degree polynomial fit. Optimized of geometries, interaction energies, Mulliken and natural bond orbital charges are analysed to study the sensing behaviour. In the preferred orientation modes, emeraldine salt acts as a hydrogen donor, whereas HBr and HCl are hydrogen acceptors (nucleophile). Basis set superposition error corrected interaction energies are calculated for accurate determination of interaction strength between sensor and analyte. The basis set superposition error is significant for HBr complex compared to HCl. The decrease in energy gap between highest occupied and lowest unoccupied molecular of conducting polymer (sensor) on complex formation with both analytes has been studied. The results of computational study show that polyaniline emeraldine salt shows more selectivity towards HBr as compared to HCl and this outcome is in agreement with reported results based on experimental observations. Graphical abstract.

Polyaniline as a charge storage material in an aqueous aluminum-based electrolyte: Can aluminum ions play the role of protons?

The high redox activity of polyaniline emeraldine salt (PANI-ES) was revealed in the aqueous solution of Al-salt, which makes this polymer attractive as an electrode material for aqueous aluminum electrochemical storage devices. Its redox behavior in Al(NO3)3, Al(NO3)3+HCl, AlCl3 and HCl was investigated by Cyclic Voltammetry and Chronopotentiometry. While the proton exchange determines PANI's redox behavior in strong acidic solutions, anion doping/dedoping is a more dominant process in less acidic Al-salt solutions. The formation/dissolution of solid-state nitrate complexes is proposed to happen during PANI's redox switching in Al(NO3)3, which causes disappearance and reappearance of grain boundaries, as revealed by AFM. Combined experimental and DFT approaches identify Al-salt as a secondary dopant of protonated PANI-ES (by Lewis acid-base complexation), which causes polaron→bipolaron conversion. The change in the redox mechanism of PANI-ES, caused by the substitution of HCl with Al(NO3)3, did not attenuate its charge storage ability. Moreover, PANI-ES delivers a higher capacitance in Al(NO3)3, amounting to 269 F g−1 at 10 A g−1. Furthermore, the use of Al(NO3)3 results in attenuated electrochemical PANI overoxidation, when compared to HCl, thus providing better capacitance retention upon potentiodynamic cycling. The results open novel perspective of using PANI-based materials for more suitable energy storage devices.

Synthesis, characterisation and electrochemical application of hybrid nanocomposites of polyaniline with novel clay mineral

Clay mineral obtained from Tuticorin in Tamilnadu, India (Indian Clay- IC) was purified and used to synthesise polyaniline-Indian clay nanocomposites (Pani-IC NCP) by polymerising aniline with the clay by chemical oxidation method using potassium perdisulphate as oxidant and by varying the aniline to clay ratio. The formation of composite in nanoscale was confirmed by XRD and TEM analysis. The in situ intercalative polymerization of monomer within the clays was ascertained by FTIR, UV–visible, XRD, SEM and TEM studies. The analyses of UV visible and FTIR spectroscopy demonstrated that aniline has been polymerized to Pani in its conducting emeraldine form. The conformation adopted by Pani Chains in the clay interlayer depended on the molar ratio of aniline to clay. SEM analysis showed the variation in morphology from granular agglomerate to layered flaky structure as the clay concentration was increased. Thermal stability of the nanocomposites was studied using TGA/DTA and DSC studies and it was found that they showed better thermal stability than their pristine polymers indicating the enhanced barrier property of the nanoclay. XRD showed that the clay host used accommodates higher amount of emeraldine salt than MMT. The Cyclic voltammetry studies of the synthesized nanocomposites showed the one with 0.5 g clay showed better electrochemical response. It exhibited good adherent behaviour on electrode surface at pH 1.0 with two oxidation peaks at 463 and 672 mV and two reduction peaks at 360 and 126 mV. By varying the atmosphere it was found that the nanocomposite modified electrode exhibited oxygen reducing capacity than their Bentonite counterpart. Chronoamperometric and Chronocoulometric studies were also carried out at inert as well as oxidising atmosphere which confirmed the above fact. EIS studies of the modified electrodes showed double layer capacitance value of 5.95 × 10−8 Fcm−2 with the bode phase angle of 70°.

Remarkable enhancement in sensor ability of polyaniline upon composite formation with ZnO for industrial effluents

Polyaniline emeraldine salt and Polyaniline Zinc Oxide composite are comprehensively studied to compare their sensing ability towards ammonia, acetone, methanol and ethanol. Sensing ability is evaluated through thermodynamic, geometric and electronic parameters. A number of orientations are evaluated in search for the lowest energy structure. The comparison of thermodynamic, geometric and electronic parameters of simple and composite sensors confirmed that composite sensor shows better sensing ability than simple PANI. Composite formation between polyaniline and zinc oxide is a thermodynamically feasible process with interaction energy of −42.8 kcal/mol. Both sensor shows highest interaction energy for ethanol among four analytes. Composite sensor shows almost twice the interaction with ethanol, methanol and acetone while 1.5 times the interaction energy for ammonia. The results of run simulations and subsequent calculations showed that in composite sensors, zinc oxide not only enhances the binding power of conducting polymer with analytes but also interacts directly with analytes. Strong hydrogen bonding as well as weak dispersion forces of attraction are responsible for the stability of composite and all complexes, as revealed by non-covalent interaction (NCI) studies. Acetone shows a different behaviour in composite sensor complex than other analytes.

Comparative study on sensing abilities of polyaniline and graphene polyaniline composite sensors toward methylamine and ammonia

Graphene composite of polyaniline (PANI) emeraldine salt is systematically studied to explain its experimentally observed enhanced sensitivity for methylamine and ammonia as compared with simple PANI emeraldine salt conducting polymer sensor. The interaction behavior is studied with M062X method of density functional theory. Optimization of geometries, calculation of interaction energies, and natural bond orbital charge analyses are performed to study and explain the sensing behavior. Charge analysis is performed to know the magnitude and direction of electronic charge flow during sensing phenomenon. Frontier orbitals interaction theory is used to compare the strength of interaction of analytes with simple and composite sensors. The selectivity of both sensors toward analytes is also verified using the same theory. Absorption behavior of simple and composite sensors against incident electromagnetic radiations is also studied before and after sensing. Non‐covalent interaction analysis is performed to identify and distinguish different types of attractive and repulsive forces present within addition products. It is concluded that graphene composited PANI sensor shows greater sensitivity toward considered analytes as compared with PANI emeraldine salt sensor and this outcome is in agreement with reported results based on experimental observations. The better efficiency of composite sensor is due to direct interaction of analytes with graphene in addition to their interaction with PANI conducting polymer.

Graphene-polyaniline composite as superior electrochemical sensor for detection of cyano explosives

Polyaniline emeraldine salt (PANI-ES) and its composite with graphene are evaluated for sensing ability towards chemical warfare agents cyanogen chloride and hydrogen cyanide. The anticipative research work is designed to compare the performance of pure PANI sensor with graphene polyaniline composite sensor for selectivity between HCN and ClCN analytes. The response mechanism is studied through geometric parameters, interaction energies, non-covalent interactions (NCI), natural bond orbital (NBO), frontier molecular orbital analysis and UV–Visible analyses. Charge analysis revealed that in all complexes, polyaniline behaves as electronic charge acceptor while analytes are the electron donors. HOMO-LUMO interaction theory is used to determine changes in conductivity after complexation. Non-covalent interaction (NCI) properties revealed the existence of van der Waals interactions between analytes and polyaniline-composite sensor. The results of thermodynamic, geometric and electronic studies conclude that both 2PANI and G54/2PANI composite sensors are more selective towards HCN than ClCN where composite sensor shows better sensitivity than simple one.

Polyaniline coated gold-aryl nanoparticles: Electrochemical synthesis and efficiency in methylene blue dye removal

Synthesis of gold-carbon σ-bond nanoparticles was achieved by the electrochemical reduction of aryldiazonium tetrachloroaurate(III) salt [HOOC-4-C6H4N≡N]AuCl4 in the presence of polyaniline (PANI) emeraldine salt. The in situ electrochemical synthesis of PANI coated Au−COOH NPs was efficient in KNO3 supporting electrolyte at different potential values using two electrodes cell. The deposition potential was determined from the cyclic voltammetry study of aryldiazonium gold(III) salt. The nanocomposites were characterized with thermal gravimetric analysis (TGA), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The multi-branched nanoparticles display the strongest diffraction peak in the direction of (111) which implies the deposition occurred preferentially along this highly energetic facet. The results concluded the thermal stability of the gold nanocomposites and the gold percentage in the range 5−23 wt.%. Selected area electron diffraction pattern (SAED) analysis displayed typical rings of face centered cubic structure of crystalline gold(0) nanoparticles. Raman analysis supported the completeness of the reduction of the aryldiazonium cation and gold(III) supported by the absence of the diazonium and [AuCl4]− vibrations and the presence of the gold-carbon peak. Emeraldine coated gold-carbon nanoparticles soaked to nanosand showed high removal percentage for methylene blue. The adsorption kinetics follows a pseudo-second order. It may indicate that the prepared materials could be used to remove synthetic dyes in textile wastewater treatment.

Polyaniline Nanovesicles for Photoacoustic Imaging-Guided Photothermal-Chemo Synergistic Therapy in the Second Near-Infrared Window.

Photoacoustic imaging-guided photothermal therapy in the second near-infrared (NIR-II) window shows promise for clinical deep-penetrating tumor phototheranostics. However, ideal photothermal agents in the NIR-II window are still rare. Here, the emeraldine salt of polyaniline (PANI-ES), especially synthesized by a one-pot enzymatic reaction on sodium bis(2-ethylhexyl) sulfosuccinate (AOT) vesicle surface (PANI-ES@AOT, λmax ≈ 1000nm), exhibits excellent dispersion in physiological environment and remarkable photothermal ability at pH 6.5 (photothermal conversion efficiency of 43.9%). As a consequence of the enhanced permeability and retention effect of tumors and the doping-induced photothermal effect of PANI-ES@AOT, this pH-sensitive NIR-II photothermal agent allows tumor acidity phototheranostics with minimized pseudosignal readout and subdued normal tissue damage. Moreover, the enhanced fluidity of vesicle membrane triggered by heating is beneficial for drug release and allows precise synergistic therapy for an improved therapeutic effect. This study highlights the potential of template-oriented (or interface-confined) enzymatic polymerization reactions for the construction of conjugated polymers with desired biomedical applications.

Effects of Doping on Zeta Potential and pH of Polyaniline Colloidal Suspension

Polyaniline (PANI) has successfully been prepared by chemical oxidation polymerization of aniline monomer. The prepared polymer was confirmed by XRD. The conducting form of PANI known as emeraldine salt (ES) through different concentrations of formic acid; 0.4 mmol/ L, 2mmol/ L, 6 mmol/ L, 8 mmol/ L, 10 mmol/ L, and 12 mmol/L is prepared from its insulating emeraldine base (EB) by levels of doping. The objective is to establish a correlation between the levels of doping, the zeta potential of the suspension. Positive zeta potential values (24.75, 27, 33.25, 36.75, 40.50, and 42) mV were obtained for the various PANI suspension. This showed the acquisition of positive charges by the PANI after doping. The observation was made that zeta potential values increases as formic acid concentration increased. This was correlated using UV/VIS spectra and electrophoretic coating with the polyaniline suspensions.

Polyaniline Functionalized Impedimetric Paper Sensor for Urine pH Measurement

A miniaturized paper-based disposable pH sensor has been developed for the measurement of urine pH. The proposed sensor requires $2~\mu \text{l}$ of analyte solution for rapid detection of the analyte pH with a response time of 3.07 sec and 36.04 sec for acidic and basic pH, respectively. The sensor is fabricated via in situ deposition of polyaniline over the paper substrate by chemical oxidative synthesis. The sensitivity of the sensor is 1.6 $\text{k}\Omega $ /pH for acidic pH and 6.2 $\text{K}\Omega $ /pH for basic pH, at a frequency of 1kHz. The sensor has been characterized using scanning electron microscopy, Raman spectroscopy, and UV-vis spectroscopy to validate the formation of emeraldine salt and emeraldine base state of polyaniline. The varying optical band gap values of the in-situ deposited paper sensor in the acidic and basic region also validates the presence of polaron in acidic pH and formation of emeraldine base in basic pH. DC conductivity measurement reveals that the conductivity of the polyaniline coated paper substrate decreases at a higher pH value. For an in-depth understanding, a novel electrical equivalent model is proposed, and the electrical parameters extracted from the Bode impedance and phase plot. The fabricated sensor exhibits an average accuracy of 95.53% when tested with urine sample of healthy subjects and patients suffering from urinary tract infection (UTI).

Nano-flowered manganese doped ferrite@PANI composite as energy storage electrode material for supercapacitors

Herein, we report a 3D nanoflower MnFe2O4@PANI composite as electrode material in supercapacitor. Manganese doped ferrites were synthesized by hydrothermal method followed by in-situ chemical oxidative polymerization of aniline to form a nanoflower composite. The nanoscale MnFe2O4 were infused with polyaniline (PANI) that offer superior synergistic effects by favouring access to charge/ion transit route, which is further improved by providing a broad surface area that is electrochemically active. It is entrenched that MnFe2O4@PANI involves charge transfer pseudocapacitance at both the ionic sites of Mn and Fe and oxidized emeraldine salt of PANI, balanced by the inclusion/exclusion of proton within/outside the lattice. On the one hand, the fluffy nature of PANI provided channels for charge transport, and manganese ferrites helped in storing the electrons through changes in the valence state of the active sites. We obtained a high specific capacitance of 623 F/g at a current density of 1 A/g. A prototype of the developed supercapacitor showed excellent device performance with a high energy density of 179 Wh/kg and maximum power density of 982 W/kg with ~95% retention of specific capacitance after 10,000 cycles.

Water-dispersible polyaniline/graphene oxide counter electrodes for dye-sensitized solar cells: Influence of synthesis route on the device performance

The fabrication of efficient and platinum-free counter electrodes (CE) is a highlighted topic for the development of advanced dye-sensitized solar cells (DSSCs). Here, we developed water-dispersible polyaniline/graphene oxide (PANI-GO)-based CEs, which can be straightforwardly prepared by deposition of the nanocomposite dispersion onto FTO substrate. The water-dispersibility properties of PANI-GO allow the formation of smooth films without organic solvents making it a promising material for high-scalable, reduced cost and ‘greener’ fabrication of energy conversion-storage devices. Aqueous dispersions of PANI-GO nanocomposites were prepared by two different routes: physical mixture of PANI and GO, and in situ polymerization of aniline in GO aqueous dispersion. DSSC assembled with emeraldine salt polyaniline (PANI-ES)-based CE generated current density (Jsc) of 12.37 mA/cm2 and power conversion efficiency (PCE) of 5.09%, which was comparable to the device prepared with Pt-based CE (PCE of 5.15%). The addition of GO is found to increase the Jsc to 12.91 mA/cm2 and the fill factor to 67% in CE containing 0.45 wt% of GO (in respect to aniline during synthesis) where the PCE is boosted to 6.12%, which is about 20% higher than Pt-based CE. The investigation of both morphological features and spectroscopic properties showed that PANI-GO nanocomposites prepared by in situ route have dissimilar protonation and oxidation states when compared with those prepared by physical mixture route. These results give insights into the role of GO in tuning PANI chemical and physical properties. Also offers a simpler and more efficient methodology for the synthesis of new CEs for DSSCs.

Polysulfonate-doped polyanilines—oxidation of ascorbic acid and dopamine in neutral solution

The redox behavior of polyaniline (PANI) doped with polysulfonic acids is studied in slightly acidic and neutral solutions (from pH 4 to pH 7). The dopants used are polystyrene sulfonic acid (PSSA), poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA), and poly-(4,4′-(2,2′-disulfonic acid)-diphenylene-tere-phthalamide) (t-PASA). Thin PANI layers are used in order to identify clearly the redox peak structure. Based on deconvolution of the reductive currents, the pH dependence of the constituent peaks is studied and pathways of the reductive transitions are suggested. With increasing pH, a loss of electroactivity is observed for all three dopants but to a different extent: the largest for PAMPSA- and the smallest PSSA-doped PANIs. In the same time, a stabilization of the conductive emeraldine salt state is observed at pH 7 for all PANIs with the largest extent of stabilization in the PANI/PAMPSA case. The electrocatalytic properties of the polysulfonic acid-doped PANIs are comparatively studied for ascorbic acid (AA) and dopamine (DA) oxidation at pH 7. It is found that all three types of PANI are good electrocatalysts for both reactions with advantage of the PAMPSA-doped layers showing higher absolute oxidative currents for both reactions. The results concerning DA oxidation demonstrate the possibility to involve polysulfonic acid-doped PANIs in electrocatalytic reactions in neutral solutions occurring at high positive potentials beyond the peak potential of the PANI oxidative transition.

The Use of Silane-Aniline as Coupling Agent between Titanium (IV) Oxide Core and Polyaniline Emeraldine Salt Shell

Stable electronic configuration between the interface of an n-type oxide semiconductor core and a p-type polymer shell is necessary in order to guarantee a consistent functioning core-shell structure. This research aims to use silane-aniline to link between an n-type Titanium (IV) oxide (TiO2) core and p-type polyaniline emeraldine salt (PANI-ES) shell. Core-shell structure was created by functionalizing TiO2 powders with silane aniline molecules using simple soaking technique and then polymerizing the attached aniline molecules using an oxidative technique. Infrared spectroscopy reveals the presence of Si-O bonds signifying the presence of linkage between the inorganic core and polymeric shell. Polymerization of the attached aniline molecules may have led to coupling of aromatic rings to form long polymeric structures which caused widening and shifting of aromatic rings’ IR peak to lower wavenumber. In conclusion, silane-aniline was successfully utilized to connect the n-type TiO2 core and p-type PANI-ES shell.

Effect of temperature on the electrical conductivity of polyaniline/cashew gum blends

The electrical properties of polymeric films/blends comprising polyaniline (PANI) and cashew gum (CG) blends were studied by impedance spectroscopy in the temperature range from 300 K to 353 K. Protonation promoted by sulfuric acid was responsible for changing the oxidation state from undoped emeraldine base (EB) to doped emeraldine salt (ES). The low-frequency conductivity of the films varied more than 6 orders of magnitude by doping. In (PANI- EB)/CG blends, the presence of cashew gum acts a dispersing agent, lowering the electrical conductivity contrasting to (PANI-ES)/CG blends, where the electrical conductivity increases with CG concentration up to 20% (w/w). Moreover, undoped films presented a thermally-activated electrical conductivity, whereas doped films presented a decrease in the conductivity by increasing temperature. An equivalent circuit model is proposed to analyze the data by considering the system being composed of highly conductive regions separated by insulating/semiconducting ones.

Facile preparation of polyaniline covalently grafted to isocyanate functionalized reduced graphene oxide nanocomposite for high performance flexible supercapacitors

Graphene oxide nanosheets (GO) is simultaneously reduced and functionalized by isophorone diisocyanate (IPDI), followed by grafting polyaniline (PANI) in mild condition to produce a novel PANI-IPDI-rGO composite useful for supercapacitors application. The structural and morphological analysis indicates only a few nanometers thickness of emeraldine salt form of PANI layer is anchored to the surface of rGO sheets. On account of high pseudo-capacitance of PANI, high conductivity of graphene scaffolds and the synergistic effect between the components, the PANI-IPDI-rGO electrode shows dramatically optimized gravimetric specific capacitance of 1415 F/g without compromising rate capability, which is much higher than that of PANI/rGO non-functionalized composites. In addition, the assembled all-solid-state supercapacitor device based on PANI-IPDI-rGO positive electrode exhibits high electrochemical performance, such as a remarkable gravimetric specific capacitance of 485 F/g (9.1 F/cm3), superior energy storage capacitance with maximum energy density of 113.8 Wh/kg (2.07 mW h/cm3), and excellent capacitance retention of 95 % after 2000 consecutive charge-discharge cycles. Preliminary results reveal that the effective synthesis strategy paves an alternative avenue for nanostructure hybrid electrode materials in wearable and portable energy storage systems.