Pristine Polyaniline Research Articles

Performance Evaluation of Low-Cost Flexible Gas Sensor Array With Nanocomposite Polyaniline Films

The aim of this paper is to present the design of a sensor array based on a single substrate with various composite polymer films as active layers for gas detection. A low power, four element flexible sensor platform with heater and temperature sensor was designed. The advantages of resistive sensors are easy fabrication, simple operation, and low production cost. Composite polymer films exhibit good sensitivity to low gas concentrations at room temperatures. The principle of the designed sensor array is a change of electrical resistance in dependence of gas concentration. Polyaniline (PANI), PANI/carbon nanotubes, PANI/SnO2, and PANI/TiO2 composites were used as active layers. Gas sensing properties of active layers for NH3, CO2, NO2, O2, acetone, toluene, and relative humidity were studied. PANI composites, unlike pristine PANI, exhibit good reversibility and lower temperature dependence.

Electrodeposition of Ni(OH)2 reinforced polyaniline coating for corrosion protection of 304 stainless steel

In the present paper, polyaniline (PANI) coating was electropolymerized in the presence of phosphoric acid with subsequent deposition of Ni(OH)2 particles. The Ni(OH)2 reinforced PANI coating significantly enhances the corrosion resistance of 304 stainless steel (304SS) in comparison with the pristine PANI coating. The galvanostatically deposited Ni(OH)2 particles fill the pores of the pristine PANI coating and improves the coatings hydrophobicity which decreases the diffusion of aggressive media. Importantly, the Rp values of Ni(OH)2 reinforced PANI coating is much higher than that of pristine PANI coating and the Ni(OH)2 reinforced PANI coating presents a long-term anti-corrosive ability (360 h) in 3.5 wt% NaCl solution. The prolonged corrosion protection of Ni(OH)2 reinforced PANI coating is attributed to the improved physical barrier as well as the facile formation of passive oxide film that sustain the anodic protection of the coating.

Carboxymethyl cellulose: an efficient material in enhancing alternating current conductivity of HCl doped polyaniline

In the present research, to enhance the alternating current conductivity of polyaniline (PANI), carboxymethyl cellulose (CMC), a biopolymer, is used to prepare optimized polyaniline-carboxymethyl cellulose (PANI-CMC) composite. The composite was synthesized by in situ polymerization and then characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Improvement in π-electron delocalization in the composite due to CMC was confirmed from FTIR studies. Decrease in d-spacing and inter-chain separation of PANI chains and increase in the degree of crystallinity of the composite, all determined from XRD studies suggested increase in conductivity of the composite. SEM image of the composite has shown crumpled PANI on CMC forming a kind of network facilitating easier transport of charge carriers. Alternating current (AC) response characteristics of PANI-CMC composite were investigated in the frequency range 100 Hz–1 MHz and comparatively analyzed with those of pristine PANI. Increase in AC conductivity of PANI-CMC composite by one order magnitude as compared to that of PANI, mainly due to the presence of CMC in it, was confirmed experimentally. Decrease in density of states at Fermi level of PANI-CMC composite as compared to that of PANI calculated as per correlated barrier hopping model confirmed and supported experimentally observed increase in AC conductivity of the composite. So, CMC as a component of PANI based composites can effectively replace metals/metal oxides in increasing AC conductivity of such composites and has the potential for applications in electronic circuit elements and sensors.

Mesoporous silica wrapped with graphene oxide-conducting PANI nanowires as a novel hybrid electrode for supercapacitor

A high charge-carrier transport is an important aim in the synthesis of nanostructures for an effective supercapacitor. This article describes a methodology to prepare mesoporous silica nanoparticles (MSNs) wrapped with graphene oxide (GO) together with conducting polyaniline (PANI) wires. The morphology and chemical structure of the prepared samples have been tested by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and X-ray diffraction (XRD), whereas the stability and electrostatic interaction of the structures have been verified by thermogravimetric analysis (TGA) and Fourier-transform infrared (FT-IR) spectroscopy, respectively. The supercapacitive behaviour of these nanocomposites has been analysed by cyclic voltammetry (CV), charge–discharge tests, and electrochemical impedance spectroscopy (EIS). Compared with pristine MSNs and PANI, the 20%-GO@MSNs/PANI nanocomposite had the highest specific capacitance, reaching 412 F g−1. The nanocomposite structure maximizes the synergy between mesoporous metal oxide, conducting PANI, and GO, yielding a significantly enhanced specific capacitance, rapid charge–discharge rates, and good cycling stability of the resulting device. The wrapping with GO prevents the structural breakdown and acts as a highly conductive pathway by bridging the individual particles, whereas the MSNs nanoparticles greatly enlarge the specific surface area to facilitate ion transport and charge transfer throughout the cycling performance of supercapacitor. The approach adopted in this article can be applied for preparing similar novel functional materials in future for electrochemical applications.

Fabrication of hierarchical carbon layer encapsulated polyaniline core-shell structure nanotubes and application in supercapacitors

A novel polyaniline (PANI) nanotube structure was prepared according to a facile in-situ polymerization process using MnO2 nanotubes as the reactive template. The obtained PANI nanotubes possess an excellent specific capacitance of 455.7 F/g at 0.5 A/g, exhibit good rate capability of 63.2% even up to 30 A/g, however PANI nanotubes reveal low cycle stability due to the swelling and shrinking during intercalating/deintercalating process. Thus, carbon layer was introduced via a facile hydrothermal method to fabricate core-shell structure of carbon layer encapsulated PANI (PANI-C) nanotubes, which is supposed to alleviate the swelling and shrinking of PANI and improve the cycle stability. The PANI-C nanotubes prepared with 2 h hydrothermal reaction exhibit well-controlled core-shell structure, possess an excellent specific capacitance of 410.5 F/g at 1 A/g and reveal optimal cycle stability as well, (63% of its original value up to 2000 cycles), which shows significant improvement with the pristine PANI nanotubes (maintaining 39% of its original value). Furthermore, symmetric supercapacitors (SCs) were assembled based on PANI-C 2 h, the symmetric SCs exhibit high energy density of 42.32 Wh/kg and power density of 16.44 kW/kg, which also deliver good cycle stability. Additionally, the tandem SCs can light up a red LED. Above all, the carbon layer encapsulated core-shell structure materials offer a feasible strategy to fabricate high cycle stability material for promising applications in high performance supercapacitors.

Synthesis and characterization of polyaniline-grafted CNT as electrode materials for supercapacitors

Polyaniline (PANI) was grafted with carbon-nanotubes (CNT) via azobenzene (Azo) to increase the pseudo-capacitance of PANI. CNT was functionalized with azobenzene and used in the in-situ polymerization of aniline using emulsion polymerization. X-ray diffraction result supports the formation of composite materials. Morphology of grafted composites showed a higher uniform growth in PANI/ CNT-Azo composite than PANI/CNT composite. Electrochemical performance was evaluated by symmetric super-capacitor cells using cyclic voltammetry and chargedischarge studies. PANI/CNT-Azo showed a higher specific capacitance value than pristine PANI. The results show grafting of PANI onto CNT via Azo helps to achieve higher capacitance and thermal stability than non-grafted PANI/CNT composite materials. Open image in new window

The use of conducting polymer to stabilize the nanostructured photocatalyst for water remediation

The graphene (G) doping in both titanium oxide (TiO2) and zinc oxide (ZnO) in our earlier studies, has brought about a reduction in photocorrosion, and an increase in the photocatalytic efficiency for remediation of organics under visible light (λ>400nm). The graphene doped photocatalysts have proven to be hard to coat on a surface, due to the strong hydrophobic nature of graphene. So, attempts have been made to use polyaniline (PANI), a conducting polymer, as a binder material by insitu polymerization of aniline over G-TiO2 nanoparticles (G-TiO2 NP) and G-ZnO nanowires (G-ZnO NW). The undoped PANI:G-TiO2 NP and PANI:G-ZnO NW, synthesized are dissolved in a solution of N-methyl-2-pyrrolidone (NMP) was coated over various surfaces and dried at 100°C & characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis spectroscopy (UV-vis) and Fourier transform infrared spectroscopy (FTIR) techniques. Pristine PANI was also synthesized for comparative studies. The photocatalytic, as well as photoelectrochemical catalytic performance of PANI:G-TiO2 NP and PANI:G-ZnO NW, were investigated. The standard methyl orange (pollutant) in water was used for both PANI:G-TiO2 NP and PANI:G-ZnO NW electrodes on conducting substrates. The ease in coating of PANI:G-TiO2 NP and PANI:G-ZnO NW on various substrates, on top of the visible light remediation allows for the use of these materials and process to be used for applications of remediation of organics from water.

Fabrication of Organic Transistors Using Nanomaterials for Sensing Applications

In this work, an organic field-effect transistor (OFET) was fabricated and characterized based on the bottom contact of a polyaniline (PANI) or PANI/TiO2 nanocomposite as an active layer and SiO2 as an insulating layer to be used for ammonia gas sensing applications. The OFET sensors exhibited a change in the drain current when exposed to NH3. Titanium dioxide (TiO2) nanoparticles with different weight percentages (0–50 wt.%) were added to dope PANI and enhance charge carrier transport, although the response of both the PANI OFET sensor and PANI/TiO2 OFET sensor has reached saturation value at almost the same period. The response of PANI/TiO2 transistor is (2.5), which is much higher than that of PANI (0.17). The results showed that the sensor response of the OFET device fabricated with PANI/TiO2 is 15 times greater than that with an OFET device fabricated using pristine PANI.

Synthesis, characterization, thermal properties, conductivity and sensor application study of polyaniline/cerium-doped titanium dioxide nanocomposites

This work focuses on the in situ chemical oxidative polymerization of aniline with different contents of cerium-doped titanium dioxide (Ce–TiO2) nanoparticles for the synthesis of polyaniline (PANI)/metal-doped TiO2 nanocomposites. The interaction of nanoparticles with PANI segments was characterized by FT-IR, UV, XRD, SEM, DSC, TGA and conductivity studies. The sensitivity of ammonia gas through the fabricated nanocomposite was also evaluated with respect to different contents of nanoparticles. The shift in FT-IR peak and UV absorption bands of nanocomposite with respect to pure PANI was clearly observed from the spectroscopic studies. Results from XRD studies showed the uniform arrangement of nanoparticles within the polymer matrix. SEM analysis showed the uniform structure of nanocomposites with spherically shaped dispersion of metal oxide nanoparticles. DSC studies revealed the increased glass transition and melting temperature of nanocomposites with an increase in the concentration of nanoparticles indicating the strong intermolecular interaction between nanoparticles and the polymer chain. TGA showed a higher thermal stability of nanocomposites than that of pure PANI, and thermal stability increases with the increase in the concentration of nanoparticles. Electrical properties such as AC conductivity, dielectric constant and dielectric loss tangent of nanocomposites were greater than pure PANI, and the magnitude of these properties increased with the loading of nanoparticles. Like AC conductivity, the DC conductivity of nanocomposite increased with the loading of nanoparticles. The maximum electrical conductivity was noted for 7 wt% composite. The ammonia sensing properties of composite were higher than the pristine PANI.

Study of polyaniline and functionalized ZnO composite film linked through a binding agent for efficient and stable electrochromic applications

A highly stable electrochromic film based on a composite of polyaniline with surface functionalized zinc oxide nanoparticles has been prepared by electrochemical polymerization. Core shell type structure was obtained by preferential polymerization of aniline around ZnO linking through (3-Aminopropyl)trimethoxysilane (3-APTS), as confirmed by High resolution transmission electron microscopy (HRTEM) investigations. Electrochemical and electrochromic properties were investigated using cyclic volatammetry, chronoamperommetry, electrochemical impedance spectroscopy (EIS) and UV–vis spectroscopy. The composite exhibited enhanced stability of 104 cycles with high coloration efficiency of 89cm2C−1 and found to have superior (65%) optical contrast. As compared to pristine polyaniline, the response time reduces from 1.3s to 0.4s for coloration and from 1.7s to 0.8s for bleaching. A mechanism for its improved stability has been proposed. The pani-fZnO hybrid seems to be a potential candidate for anodically coloring electrochromic material.

In-Situ Reduction of Au, Pd, and Pt Metal Precursors in Polyaniline: Electrochemistry of Variable Metal Content Polymer/Metal Composites in Alkaline Solution

The controlled electrochemical uptake and reduction of metal precursors, AuCl4−, PdCl42−, and PtCl42− in polyaniline (PANI) is used in the synthesis of variable metal content composites. The potential and current associated with the initial electrochemical deposition of each metal precursor into pristine PANI is unique when compared to subsequent reduction in the composite materials. Deposition into the polymer and at existing deposits is resolved in the voltammetry for the reduction of Au and Pd in PANI. In contrast, distinct processes for Pt reduction into the polymer and at existing metal deposits are not resolved. After the initial reduction of the Pt precursor, the peak current continues to shift to more positive potential and diminishes as a function of increasing metal content. The PANI/metal composites are characterized using FTIR spectroscopy, thermal gravimetric analysis, and conductivity measurements to evaluate the interactions between the metal and polymer, the total metal content, and the electronic properties of the composites. The Au, Pd, and Pt metals deposited in PANI are evaluated using surface specific electrochemical reactions including the formation/reduction of metal oxide and the catalytic oxidation of n-propanol in alkaline solutions (pH ≈ 14). Furthermore, the electrochemical studies demonstrate that the oxidation/reduction of the polymer directly influences the polarization and reactivity of the metal surface in the organic matrix. The results confirm that PANI/metal composite materials containing Au, Pt, and Pd remain conductive in alkaline environments thereby expanding their use outside traditional acid solutions.

Facile synthesis of polyaniline nanofibers/porous carbon microspheres composite for high performance supercapacitors

Abstract Conductive polyaniline (PANI)/porous carbon microspheres (PCMs) composite (PANI/PCMs) was synthesized by simple solution polymerization method with PCMs as carbon support. The morphology and structure were analyzed by scanning electron microscope and X-ray diffraction. Electrochemical performances were analyzed by Cyclic Voltammetry and constant-current Charge and Discharge. The results show that the carbon support (PCMs) plays a vital role in regulating the morphology and structure of PANI. In PANI/PCMs composite, small and uniform PANI nanofibers were grown on the surface of PCMs, but only micronfibers were formed for the pristine PANI. The PANI/PCMs composite shows excellent capacitance performances in 1 M H 2 SO 4 aqueous electrolyte. At a current density of 1 A/g, the PANI/PCMs composite represents a maximum specific capacitance of 242.5 F/g, which is much higher than those of pristine PANI (135.2 F/g) and PCMs (37.2 F/g).

Optical, structural, and morphological properties of PANI/CdSe(TPs) nanocomposite thin films

Polyaniline (PANI) thin films and cadmium selenide tetrapods (CdSe TPs) have been prepared by low-cost chemical bath deposition and solvothermal route, respectively. Hybrid PANI/CdSe(TPs) nanocomposite layers were obtained by dipping the PANI layers into the solution of CdSe(TPs) for various duration. The optical, structural, morphological and compositional properties of pristine PANI and nanocomposite layers are studied. The dipping time of PANI layer into CdSe(TPs) solution significantly affect onto the above properties. The absorption and PL intensities for PANI/CdSe(TPs) layers in visible to NIR region increases upon increasing the dipping time. CdSe TPs revealed hexagonal crystal structure by X-ray diffraction analysis. The inter-planer distance was measured about 0.352 nm corresponds to (002) plane of hexagonal CdSe with HRTEM. Growth of void free, granular, and densely packed PANI/CdSe(TPs) layers was confirmed from SEM images. Stoichiometric atomic percentage contents of Cd and Se were obtained by EDAX analyses in PANI/CdSe(TPs) thin film. FTIR results indicate the interaction between CdSe and the acid protonated N–H groups of PANI. The LO1 peak of CdSe and increased relative intensity of C–N+ band of PANI observed in the Raman spectra demonstrates the formation of PANI/CdSe nanocomposites. Thermogravimetric result reveals enhanced thermal stability of PANI/CdSe(TPs) nanocomposite compared to pristine PANI.

Polyaniline film-based wireless photo reactor for hydrogen generation through exciton mediated proton reduction

The unique light absorption property of semiconductors has been exploited to build photovoltaic (PV), photo electrochemical solar cells (PESC) and photocatalytic (PC) reactors that not only convert sunlight into electrical energy but also drive useful chemical reactions. Hydrogen, the clean fuel of 21st century has been targeted for several decades. However, the above systems possess complex architecture with two or more semiconductor-solution interfaces that are often plagued with material instability and show poor photon conversion efficiency. Here we demonstrate a simple pristine polyaniline (PANI) film based photo H2 generating system. The ‘wireless’ system with only one PANI/solution interface, utilizes internal redox chemistry in the conjugated polymer for ‘photo exciton’ formation and charge separation. The electrons migrate to the PANI/aq. H2SO4 interface and reduce H+ to produce H2. The polymer film is light weight, flexible, and solution-processable. The reported system is simple and scalable for high volume production of hydrogen.

Multi-walled carbon nanotubes modified by polyaniline for the removal of alizarin yellow R from aqueous solutions

Multi-walled carbon nanotubes (MWCNTs) encapsulated by polyaniline (PANI) were synthesized by in situ polymerization. Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and thermal gravimetric analysis (TGA) were used to characterize the synthesized composites (O-MWCNTs/PANI), and the surface area was calculated by the Brunauer–Emmett–Teller (BET) method. The removal capacity of alizarin yellow R (AYR) with O-MWCNTs/PANI was further investigated. Experiments were conducted to optimize the adsorption conditions, including contact time, pH, initial concentration of AYR and temperature. The results showed that the maximum adsorption capacity for AYR was 884.80 mg/g. The adsorption kinetics and the adsorption isotherm could be better described by the pseudo-second-order model and the Langmuir isotherm, respectively. Energy changes revealed that the adsorption process was exothermic and spontaneous in nature. Additionally, the O-MWCNTs/PANI showed higher adsorption capacity than pristine MWCNTs or PANI. Therefore, O-MWCNTs/PANI would be applied as an efficient adsorbent for the removal of dye from water.

Alternating current conduction studies of hybrid nanocomposite at room temperature

Polyaniline (PANI) and polyaniline-yttrium oxide (PANI-Y2O3) hybrid nanocomposite were synthesised separately by simple chemical polymerisation method and then they were structurally characterised by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The alternate current (AC) conduction parameters of PANI and the nanocomposite were comparatively studied in the frequency range 100 Hz-1 MHz at room temperature. The AC conduction results were interpreted as power law of frequency and the frequency exponent s was found to lie in the range 0 < s < 1. Decrease in ac conductivity of the nanocomposite as compared to pristine PANI because of decreased delocalisation of electronic states in the band gap of the nanocomposite due to the presence of Y2O3 in it was observed.

Alternating current conduction studies of hybrid nanocomposite at room temperature

Polyaniline (PANI) and polyaniline-yttrium oxide (PANI-Y2O3) hybrid nanocomposite were synthesised separately by simple chemical polymerisation method and then they were structurally characterised by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The alternate current (AC) conduction parameters of PANI and the nanocomposite were comparatively studied in the frequency range 100 Hz-1 MHz at room temperature. The AC conduction results were interpreted as power law of frequency and the frequency exponent s was found to lie in the range 0 < s < 1. Decrease in ac conductivity of the nanocomposite as compared to pristine PANI because of decreased delocalisation of electronic states in the band gap of the nanocomposite due to the presence of Y2O3 in it was observed.

A Novel Polyaniline-Coated Bagasse Fiber Composite with Core-Shell Heterostructure Provides Effective Electromagnetic Shielding Performance.

A facile route was proposed to synthesize polyaniline (PANI) uniformly deposited on bagasse fiber (BF) via a one-step in situ polymerization of aniline in the dispersed system of BF. Correlations between the structural, electrical, and electromagnetic properties were extensively investigated. Scanning electron microscopy images confirm that the PANI was coated dominantly on the BF surface, indicating that the as-prepared BF/PANI composite adopted the natural and inexpensive BF as its core and the PANI as the shell. Fourier transform infrared spectra suggest significant interactions between the BF and PANI shell, and a high degree of doping in the PANI shell was achieved. X-ray diffraction results reveal that the crystallization of the PANI shell was improved. The dielectric behaviors are analyzed with respect to dielectric constant, loss tangent, and Cole-Cole plots. The BF/PANI composite exhibits superior electrical conductivity (2.01 ± 0.29 S·cm-1), which is higher than that of the pristine PANI with 1.35 ± 0.15 S·cm-1. The complex permittivity, electromagnetic interference (EMI), shielding effectiveness (SE) values, and attenuation constants of the BF/PANI composite were larger than those of the pristine PANI. The EMI shielding mechanisms of the composite were experimentally and theoretically analyzed. The absorption-dominated total EMI SE of 28.8 dB at a thickness of 0.4 mm indicates the usefulness of the composite for electromagnetic shielding. Moreover, detailed comparison of electrical and EMI shielding properties with respect to the BF/PANI, dedoped BF/PANI composite, and the pristine PANI indicate that the enhancement of electromagnetic properties for the BF/PANI composite was due to the improved conductivity and the core-shell architecture. Thus, the composite has potential commercial applications for high-performance electromagnetic shielding materials and also could be used as a conductive filler to endow polymers with electromagnetic shielding ability.

Voltage and capacity control of polyaniline based organic cathodes: An ab initio study

Abstract Polyaniline (PANI) is a promising organic cathode material for electrochemical batteries. Its specific capacity is limited by irreversible formation of pernigraniline base, and its energy density is limited by the voltage which could be improved. We present an ab initio study of PANI and PANI functionalized with functional groups which lead to increased voltage and stabilization of the pernigraniline salt. Specifically, the oxidation potential achieved by functionalization with CN on the nitrogen is computed to be 1.3 V higher than that of pristine PANI oligomer, leading to a higher voltage, and the formation of the pernigraniline base is predicted to be simultaneously suppressed, leading to a higher reversible capacity. Therefore, functionalized PANI could be a promising candidate organic cathode for Li-ion batteries.

Adhesion, Proliferation and Migration of NIH/3T3 Cells on Modified Polyaniline Surfaces.

Polyaniline shows great potential and promises wide application in the biomedical field thanks to its intrinsic conductivity and material properties, which closely resemble natural tissues. Surface properties are crucial, as these predetermine any interaction with biological fluids, proteins and cells. An advantage of polyaniline is the simple modification of its surface, e.g., by using various dopant acids. An investigation was made into the adhesion, proliferation and migration of mouse embryonic fibroblasts on pristine polyaniline films and films doped with sulfamic and phosphotungstic acids. In addition, polyaniline films supplemented with poly (2-acrylamido-2-methyl-1-propanesulfonic) acid at various ratios were tested. Results showed that the NIH/3T3 cell line was able to adhere, proliferate and migrate on the pristine polyaniline films as well as those films doped with sulfamic and phosphotungstic acids; thus, utilization of said forms in biomedicine appears promising. Nevertheless, incorporating poly (2-acrylamido-2-methyl-1-propanesulfonic) acid altered the surface properties of the polyaniline films and significantly affected cell behavior. In order to reveal the crucial factor influencing the surface/cell interaction, cell behavior is discussed in the context of the surface energy of individual samples. It was clearly demonstrated that the lesser the difference between the surface energy of the sample and cell, the more cyto-compatible the surface is.