Polyaniline Nanostructures Research Articles

Proton Acid Doped Superior Capacitive Performances of Pseudocapacitance Electrodes for Energy Storage

AbstractIn this work, three‐dimensional (3D) nanostructures of polyaniline nano‐sheets, nano‐particles, nano‐nets and nano‐flowers were synthesized with valine, sulfuric acid, sodium acetate and L‐phenylalanine as doping acids, respectively. Conductive polyaniline with 3D nanostructure was proven as an excellent energy storage material because of its superior electrical properties and unique structure. The porous structure not only greatly improved the charge transfer efficiency and reduced the resistance, but also improved the cycle stability and energy storage of the electrode material. Polyaniline nano‐flowers doped with L‐phenylalanine (PANI‐NF) showed a maximum specific capacitance of 580 F g−1(I=0.5 A g−1), a maximum energy density of 53.9 Wh kg−1, and excellent cycle stability at high current density.

Preparation and Electrochemical Properties of Polyaniline Nanostructures Using Vertically Aligned Mesochannels as Confinement

AbstractOne‐dimensional conducting polymer nanowire arrays have shown promising potential in applications of electrochemical supercapacitors, sensors, and more. Herein, vertically aligned mesoporous silica films (VMSF) with hexagonally packed mesochannels were generated on indium‐tin oxide (ITO) electrodes by an electrochemically‐assisted self‐assembly (EASA) method. The prepared VMSF/ITO electrode was then exploited as a hard template for electrochemical growth of well‐aligned polyaniline (PANI) nanofilaments within silica mesochannels, eventually forming a PANI/VMSF/ITO composite electrode. The electrochemical conditions of the PANI growth through the mesochannnels were investigated in detail, and the electrochemical capacitance was also tested. It is shown that the resulting nanofilaments separated through silica walls exhibit significantly improved electrochemical performance, including better electrochemical reversibility and high specific capacitance (3.00 mF/cm2 at 20 μA/cm2), which is increased by about 152 % in comparison to PANI directly on an ITO (PANI/ITO) substrate. Such an improved electrochemical performance is mainly contributed to by enhanced charge transfer efficiency and improved electrochemical reaction kinetics resulting from the well‐aligned PANI nanostructure.

Amino Acid-Doped Polyaniline Nanotubes as Efficient Adsorbent for Wastewater Treatment

A natural amino acid-doped polyaniline nanostructure was prepared by a simple in situ chemical polymerization method in an aqueous medium. The structure and morphology of composite material were characterized by FESEM, TEM, FT-IR, and XRD. The results showed that the product possesses a large aspect ratio and a hollow tubular morphology. As-synthesized products were further applied to remove dyes and heavy metal ions from the aqueous solution, which exhibited good removal capacity toward Congo red (955.6 mg·g−1) and Cr(VI) (60.0 mg·g−1). The adsorption data for the former were found to be well described by the pseudo-first-order kinetic and Langmuir adsorption isotherm model. Thermodynamic studies show that the adsorption of Congo red by GluP is a spontaneous and endothermic process. Moreover, cyclic experiment results show that the polyaniline composites exhibited good recyclability. Therefore, these amino acid-doped polyaniline nanotubes can be expected to be an ideal candidate for the removal of organic dye and heavy metal ions from wastewater.

Research Progress on Polyaniline-Ionic liquids for Long Cycle-Stable Supercapacitors with High Capacitance

Ionic liquids have been used either as polymerization medium or as electrolytes for polyaniline (PANI) electrodes to produce long cycle-stable supercapacitors with high capacitance. As a polymerization medium, ionic liquids play the role of a soft template agent and induce the formation of nanostructured PANI morphology. Nanorod, nanowire, or spherical PANI morphology has been obtained in ionic liquids instead of agglomerated particles resulted in the conventional media. The well-defined one-dimensional PANI morphology ensures a short charge transfer distance in the PANI materials and low contact resistance between PANI and electrolyte interfaces. The efficiency of ionic liquids as a soft template agent is related to their structure as well as to their proportion in the reaction medium. As electrolytes, “neat” ionic liquids provide low but stable specific capacitance of PANI over more than hundreds of cycles. Binary mixtures of ionic liquids and solvents (e.g. acetonitrile, water) have increased both the specific capacitance and the capacitance retention of PANI compared with the performances resulting in the conventional aqueous acid electrolytes. Using ionic liquids to carry out both the synthesis and the electrochemical characterization of PANI is an effective approach to improve PANI cycle life. The key parameter is to choose the convenient ionic liquids. This review covers the most significant studies conducted on PANI/ionic liquids for supercapacitor applications.

A robust approach for designing N‐doped reduced graphene oxide/polyaniline nanocomposite‐based electrodes for efficient flexible supercapacitors

Abstract2D multilayered reduced graphene oxide (rGO) has received enormous research interest as a potential electrode material for flexible supercapacitor (FSC), owing to its excellent electrochemical and mechanical properties. However, rGO suffers from the restacking of graphene (GN) layers, lower electrical conductivity resulting from the residual oxygen functional groups and the relatively poor real‐time electrochemical performance. One of the finest ways overcoming the drawbacks of rGO by doping heteroatom into GN network and surface modification to enhance its electrochemical properties. In this work, a simple and robust approach for designing an efficient and high‐performance flexible electrode with nitrogen‐doped reduced graphene oxide (N‐rGO) framework coupled with surface modification through in situ chemical polymerization with aniline to form a long‐range interconnected polyaniline (PANI) nanostructure is presented. In a two‐electrode system, PANI/N‐rGO flexible electrode has delivered a higher specific capacitance of 322 F g−1 at a current density of 1 A g−1. Further, the composite exhibited notable cyclic stability over 1000 charge–discharge cycles. Surface‐modified in‐situ grown PANI nanostructures on N‐rGO nanosheets prevent the volume changes that occur in PANI during the charge–discharge process, and offer a higher charge transportation rate throughout the surface area. As a result of enhanced electrochemical properties, PANI/N‐rGO composites provide a feasible route for designing FSCs.

Self-assembled polyaniline nanostructures in situ deposited on silica optical fibers for ammonia gas sensing

Optical fibers coated with polyaniline (PANI) nanostructures were used to sense ammonia gas (NH3) concentration. The PANI nanostructures were synthesized using the oxidative polymerization process in a solution containing poly(methyl vinyl ether-alt-maleic acid) (PMVEA). The PANI nanostructures were in situ deposited on silica optical fibers by immersing the fibers in the solution during the polymerization process for specific durations. The morphology and the thickness of the PANI nanostructure coatings were characterized using Scanning Electron Microscopy (SEM). Raman and Fourier Transform Infra-red (FTIR) spectra confirmed that the PANI nanostructures were in the emeraldine salt (ES) state. The sensors were exposed to various concentrations of NH3 gas at room temperature. The sensor with a coating thickness of 639 nm shows the highest response with a cumulative absorbance response of 2.2 towards 1% NH3 in synthetic air. The response and recovery times are 2.82 min and 11.52 min, respectively.

Interlinked polyaniline nanostructure for enhanced electrochromic performance

An optimized, facile and low-cost approach has been applied to fabricate a prototype electrochromic device. For this purpose, an ionic liquid (IL) i.e. 1-(4-Vinylbenzyl)-3-methylimidazolium chloride [VBMIM]Cl has been doped into conducting polymer (polyaniline (PANI)) by electrochemical polymerization on FTO substrate. The structural, morphological and optical characterizations of the electrochromic (EC) electrodes have been studied by using FT-IR, NMR, XRD, FESEM, and UV–vis spectroscopic techniques. The EC electrodes showed multiple reversible colour changes from dark to light green appearance via electrochemical measurement. The EC electrodes with an optimum concentration of the IL show efficient bleaching (tb) and colouring time (tc) as compared to the other electrodes. The EC-2 electrode was selected to fabricate a portable ECD. The cyclic stability of the EC-2 electrode was durable-maintaining almost its original electroactivity after the performance of multiple cycles. The portable ECDs are expected to be a good candidate for smart displays and intelligent windows applications.

Regulation of nanostructured polyaniline synthesis and its properties through organic solvent in interfacial polymerization

Tuning of the polyaniline (PANI) morphologies and properties during interfacial polymerization at various organic/aqueous interfaces (o-xylene/aq., Chlorobenzene/aq., Toluene/aq., Benzene/aq., CHCl3/aq., CCl4/aq., DCM/aq.) by chemical oxidation has been presented. The effect of various organic solvents on the grown PANIs properties has been investigated by SEM, XRD, FT-IR, UV–Vis, elemental, TGA, MALDI-TOf and AC impedance spectroscopic analyzes. Distinctly visible morphologies with changed spectroscopic properties of PANI have been obtained in various systems. Obtained PANIs properties have been correlated with the organic solvent’s octanol-water partition coefficient (log P), density, etc. and a very clear understanding has been established towards this correlation. PANI electrical properties, band structure, crystallinity, thermal properties have a clear sequence with the property of organic solvent or nature of interface. Diffusion controlled interaction of constituents for polymerization, nucleation and growth of PANI at the interface is dependent on the log P values and other properties of the organic solvent in the various organic/aq. systems.

Exploring C, H and O isotope-specific adsorption of CO2 and H2O vapour in nanostructured polyaniline

Exploring C, H and O isotope-specific adsorption of CO2 and H2O vapour in nanostructured polyaniline

Enhancement of Cr(VI) reduction by polyaniline nanorod-modified cathode in flow-through electrode system

Cr(VI) reduction to Cr(III) has been demonstrated to be an effective method for Cr(VI) detoxification. Herein, we fabricated polyaniline (PANI) nanorod forests-modified Carbon fiber felt (CFF) as CFF-PANI cathode in a Flow-through electrode system (FES) with the counter CFF anode for enhancing Cr(VI) reduction. The CFF-PANI was synthetized via in-situ polymerization under different aniline concentration to investigate the effect of PANI nano-structures on Cr(VI) reduction. It was revealed that BET and electrochemical surface area of PANI nanorods significantly affected the Cr(VI) reduction, and CFF-PANI cathode with the largest BET and electrochemical surface area exhibited ∼ 45% higher Cr(VI) removal and ∼ 35% lower specific energy consumption than the CFF cathode. A decrease-then-stable Cr(VI) removal was observed within 120 min operation time, which was attributed to the electro-adsorption of Cr(VI) species on CFF anode. In-situ sampling experiments revealed that the electrochemical oxidation on CFF anode inhibited the Cr(VI) electro-adsorption, and at applied voltage above 0.7 V, the Cr(VI) reduction on cathode was the main mechanism for Cr(VI) removal. The operation of FES at 0.8 V had the lowest specific energy consumption (48.5 Wh/mol) and maintained ∼ 95% energy efficiency for Cr(VI) reduction with minor competitive reduction of H2O or O2 species. The results suggested that CFF-PANI can be a promising cathode for Cr(VI) reduction from aqueous solutions.

Bioinspired Dynamically Switchable PANI/PS‐b‐P2VP Thin Films for Multicolored Electrochromic Displays with Long‐Term Durability

AbstractElectrochromism has attracted wide attention as futuristic adaptive camouflage technologies due to its reversible and sustainable optical modulation with low energy consumption. However, limited color control of the electrochromic materials has hampered its applications. Inspired by the remarkable dynamic camouflage capabilities of cephalopods, polyaniline (PANI) and polystyrene‐block‐poly (2‐vinyl pyridine) (PS‐b‐P2VP) thin films are integrated to simulate chromatophores and iridophores in the skin of cephalopods, respectively. Herein, it is demonstrated that the adaptive lamellar PANI/PS‐b‐P2VP thin film exhibits a wide range of color control, switchable vivid coloration, and excellent durability. It serves as an ideal multicolored electrochromic platform due to the combined effect of electrochromism from PANI and structural coloration from PS‐b‐P2VP. Unambiguous evidence shows that optical properties of the PANI/PS‐b‐P2VP thin film are related to the thickness of each layer and nanostructure of PANI, pronounced color changes mainly depend on electronic states of PANI and transition of hydrated SO42− ions between PANI and P2VP. The coloration mechanism is discussed using quantitative analysis via RGB color specification and optical transmittance and reflectance simulations. The new insights will advance the design of reflection‐contributed superior multicolored electrochromic materials, and have great potential in the fields of displays and camouflage.

Fabrication of paper based carbon/graphene/ZnO aerogel composite decorated by polyaniline nanostructure: Investigation of electrochemical properties

The cellulose derived carbon/graphene/ZnO aerogel composite was prepared as an electrode in order to investigate the electrochemical properties. Carbon aerogel was synthesized using paper as an available cellulose source, and the composite was obtained through a new and simple preparation method including the immersion of monolithic carbon aerogel in graphene oxide/Zn2+ suspension and subsequent chemical reduction and freeze drying. The morphology, functional groups and crystalline structure of the samples were studied with Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction Spectroscopy (XRD), respectively. Electrochemical performance of the prepared binder free electrodes was examined using Cyclic Voltammetry (CV), Galvanostatic Charge-Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS). The data revealed that flexible carbon/graphene/ZnO composite resulted in a low density (0.035 g cm−3) electrode with the capacitance of 900 mF cm−2 at a high current density of 10 mA cm−2, lower IR drop and high cyclic stability (capacitance retention of 96%) after 1000 cycles, at 10 mA cm−2. These features were due to the presence of 3D porous conductive network, highly reduced graphene oxide, and the formation of ZnO nanoparticles on graphene sheets. Moreover, polyaniline (PANI) was introduced to carbon/graphene/ZnO composite electrode using electro-oxidation method at different reaction time and aniline concentration in order to achieve remarkably improved capacitance of 2500 mF cm−2 (at 10 mA cm−2) and low charge transfer resistance. Also, after the supercapacitor device assembly, the capacitance was retained. Based on the results, the synthesized composite is a promising material for new generation of lightweight freestanding electrodes with the high electrochemical performance.

Reduced Graphene Oxide and Polyaniline Nanofibers Nanocomposite for the Development of an Amperometric Glucose Biosensor.

The control of glucose concentration is a crucial factor in clinical diagnosis and the food industry. Electrochemical biosensors based on reduced graphene oxide (rGO) and conducting polymers have a high potential for practical application. A novel thermal reduction protocol of graphene oxide (GO) in the presence of malonic acid was applied for the synthesis of rGO. The rGO was characterized by scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and Raman spectroscopy. rGO in combination with polyaniline (PANI), Nafion, and glucose oxidase (GOx) was used to develop an amperometric glucose biosensor. A graphite rod (GR) electrode premodified with a dispersion of PANI nanostructures and rGO, Nafion, and GOx was proposed as the working electrode of the biosensor. The optimal ratio of PANI and rGO in the dispersion used as a matrix for GOx immobilization was equal to 1:10. The developed glucose biosensor was characterized by a wide linear range (from 0.5 to 50 mM), low limit of detection (0.089 mM), good selectivity, reproducibility, and stability. Therefore, the developed biosensor is suitable for glucose determination in human serum. The PANI nanostructure and rGO dispersion is a promising material for the construction of electrochemical glucose biosensors.

Enhanced energy density of polyaniline nanostructured polymer nanocomposites at low electric field

This work exhibits anionic sodium dodecyl sulfate (SDS), nonionic triblock copolymer F127, and polyaniline (PANI) nanostructures. The nanorod shaped PANI-SDS-F127 1:1 demonstrates noteworthy features—scalable and extended electrical characteristics, dielectric response, and significance in high-density energy storage devices. High-frequency measurements (1 MHz–1 GHz) preserve dielectric relaxation, which is attributed to excellent charge polarization. Uniformly distributed PANI nanorods align with the induced electric field and develop high current density (J ∼ 5.270 × 105 mA m–2), electric displacement (Dmax ∼ 7.408 × 105 C m–2), and lower impedance (Zs ∼ 3.28 Ω), which result in an improved charge polarization leading to increased capacitance (Cs ∼ 6.21 μF). These properties yield notable energy density (Ue ∼ 1.08 J cm–3) and signify a polymer matrix viable to high-density energy storage capacitor devices that would be actively favorable in developing efficient electronic and electrical devices.

Evanescent Wave Optical Fiber Sensors Using Enzymatic Hydrolysis on Nanostructured Polyaniline for Detection of β-Lactam Antibiotics in Food and Environment.

β-Lactam antibiotics such as penicillins and cephalosporins are extensively used for human infection therapy. Consistent unintended exposure to these antibiotics via food and water is known to promote antibiotic-resistant bacterial pathogenesis with high morbidity and mortality in humans. An optical enzymatic biosensor for rapid and point-of-use detection of these antibiotics in food and water has been developed and tested. Enzymatic hydrolysis of β-lactams, on the electroactive polyaniline nanofibers, altered the polymeric backbone of the nanofibers, from emeraldine base form to emeraldine salt, which was measured as an increase in evanescent wave absorbance at 435 nm. The sensors were calibrated by spiking antibiotic-free milk with ceftazidime (as a model β-lactam analyte) in a linear range of 0.36-3600 nM (R2 = 0.98). The calibration was further validated for packaged milk, local cow milk, and buffalo milk. A similar calibration was devised for chicken meat samples in a linear range of 9-1800 nM (R2 = 0.982) and tap water in a linear range of 0.18-180 nM (R2 = 0.99). Interestingly, it was possible to use the same calibration for the determination of other β-lactam antibiotics (ampicillin, amoxicillin, and cefotaxime), which reflects the usefulness of the sensor for wide-scale deployment. The sensor performance was validated with a wastewater sample, from a wastewater treatment plant (WWTP), qualitatively analyzed by high-resolution liquid chromatography coupled with mass spectroscopy for detection of β-lactams. The sensor scheme developed and tested is of grassroot relevance as a quick solution for measurement of β-lactam residues in food and environment.

One–step template–free fabrication and capacitive properties of flower–like polyaniline in strong acidic solution

Three-dimensional hierarchical nanostructured polyaniline (PANI) was constructed through a simple and efficient template-free frozen polymerization of aniline in strong acid condition for fabricating high performance electrode for supercapacitor. The morphology and structure of flower-like PANI was investigated, and its charge storage ability was evaluated. The PANI electrode exhibited the specific capacitance of 428.5 F g−1 at a current density of 1 A g−1, the capacitive retention remains 78.8% from 1 to 10 A g−1, and cycling retention of 62 % after 1000 cycles, exhibiting its great potential application as the supercapacitor electrode materials.

Nano-Structured Polyaniline as a Potential Adsorbent for Methylene Blue Dye Removal from Effluent

The textile sector is one of the major culprits of water pollution, and demands immediate attention. The coloured textile effluent, loaded with toxic dyes, when mixed with waterbodies, may harm aquatic life, plants, animals, and humans. Although polyaniline in its different forms was utilised for the adsorption of different dyes, the pure nano-fibrous form of polyaniline, i.e., PANI nanofibers, have reportedly not been used for the removal of dyes from wastewater. The present study aimed to employ nano-structured polyaniline, in the form of polyaniline nanofibers (base; PNB—polyaniline nanofiber base) for the elimination of methylene blue (cationic dye; MB) dye from its solution. The polyaniline nanofiber base (PNB) was synthesised by an interfacial polymerisation technique using ammonium persulphate as the oxidant and toluene as the organic solvent, and was characterised by FTIR, SEM, BET, HRTEM and XRD techniques. The HRTEM and SEM results showed that the average size of the synthesised polyaniline nanofiber base (PNB) was about 60 nm. BET revealed the enhanced surface area of polyaniline nanofiber base (PNB), i.e., 48 m2g−1 in comparison to that of conventionally synthesised polyaniline, which is only 14 m2g−1. The electric conductivity of the polyaniline nanofiber base (PNB) was reportedly lesser (2.3 × 10−2 S/cm) than the salt form of the polyaniline, measured by four probe technique. The batch-wise adsorption of MB was conducted onto the polyaniline nanofiber base (PNB), and the influence of the preliminary dye concentration, duration of contact and polyaniline nanofiber base (PNB) dose, etc., were studied. The equilibrium values of these parameters are reported as 6 mg/L, 60 min and 2 g/L, respectively. The results revealed the 91% sorption of dye onto the polyaniline nanofiber base (PNB). The experimental data were best-fitted to Pseudo-second order (R2 = 0.99) and followed Freundlich isotherm model (R2 = 0.97). On desorption, about 86% of the absorbed dye was recovered and the regenerated adsorbent could be used efficiently for three more cycles.

Nanoengineered Conductive Polyaniline Enabled Sensor for Sensitive Humidity Detection

We report results of the studies relating to the fabrication of a paper-based humidity sensing element comprising a nanostructured polyaniline (PANI) coating on a filter paper substrate. The electrical conductivity of the PANI integrated conductive paper increases from $1.9\times 10^{-6}$ Scm−1 to $1.1\times 10^{-1}$ Scm−1 on modification of the polymerization protocol. This increase in conductivity is ascribed to the change in morphology of the PANI coating from nanogranular ( $\text{N}_{\text{g}}$ ) to partially nanofibrous (pNf). We investigate the effect of observed morphologies of PANI-paper composites on their resistive-type humidity sensing performances. The partially nanofibrous (pNf) PANI-paper exhibits a bimodal humidity response due to polymer-swelling effect at higher humidity (≥ 55% RH). However, the nanogranular ( $\text{N}_{\text{g}}$ ) PANI-paper yields a unimodal, linear humidity response within the humidity range, 16–96.2% RH, with a sensitivity of 9.79 $\text{k}\Omega $ /% RH ( ${R}^{2}~\approx 0.996$ ). Hence, the $\text{N}_{\text{g}}$ PANI-paper is a promising alternative to the conventional humidity sensors fabricated on ITO glass/bare glass/PET substrates.

A novel Ag/PANI/ZnTiO3 ternary nanocomposite as a highly efficient visible-light-driven photocatalyst

Fabrication and designing of effective visible light responsive photocatalysts are exhaustively needed for tackling the critical environmental issues. The present research aims to design highly effective visible-light oriented ternary photocatalyst based on ZnTiO3 nanostructures which possess excellent photocatalytic performance simply by doping it with polyaniline (PANI) and Ag nanoparticles for the environmental remediation purpose. Ag and PANI doped ZnTiO3 ternary framework were synthesized via a modified sol-gel method followed by an ultra-sonication approach. XRD analysis displayed the rhombohedral phase of ZnTiO3, whereas the XPS and FTIR spectra confirmed the successful formation of a ternary combination between Ag, PANI and ZnTiO3 nanostructures. TEM investigation showed that Ag nanoparticles (10–20 nm) were successfully attached with ZnTiO3 nanoparticles (~70 nm) and sheet-like PANI particles (>300 nm), confirming the ternary photocatalyst formation. The UV–vis spectroscopy revealed lowering of bandgap energies upon Ag and PANI incorporation. The newly prepared Ag/PANI/ZnTiO3 nanocomposites were successfully utilized for the photocatalytic destruction of methylene blue (MB) and insecticide (imidacloprid) molecules under visible light. The 1%Ag/10%PANI/ZnTiO3 ternary photocatalyst exhibited extraordinary performance with 95.6% removal of target MB molecule, yielding the highest degradation rate, which is 1.85 times higher than that of undoped ZnTiO3. Furthermore, the 1%Ag/10%PANI/ZnTiO3 ternary framework was found to be highly destructive for the removal of insecticide imidacloprid under visible-light illumination.

Role of polarity of surfactants on the morphology of electrochemically synthesized polyaniline nanostructures: Towards faster and efficient electrochromic response

In the light of fabricating an efficient electrochromic device with fast response, various nanostructures of polyaniline (PANI) have been synthesized using facile surfactant assisted electrochemical polymerization. Effect of polarity of surfactant head on the shape and size of PANI structure is investigated by taking neutral, anionic and cationic surfactants. In the process, different shape transitions were observed like from nanospheres to nanorods to nanosheets, from nanospheres to ellipsoidal nanoparticles and from nanorings to nanorods to nanosheets. Effect of different surfactants on electrochemical and electrochromic behavior was analyzed. The anionic surfactant, SDS (sodiumdodecylsulphate) in particular due to its doping ability, was found more capable for enhancing electrochromic property. Long entangled nanorods of PANI (25 nm diameter), were found to exhibit best electrochromic behavior with superior contrast of 51% and fastest response of 0.5 s/0.3 s. Being of opposite polarity SDS was found to enhance the electrochemical stability upto 5000 cycles.