Emeraldine Salt Research Articles

A Self-Healing, All-Organic, Conducting, Composite Peptide Hydrogel as Pressure Sensor and Electrogenic Cell Soft Substrate.

Conducting polymer hydrogels (CPHs) emerge as excellent functional materials, as they harness the advantages of conducting polymers with the mechanical properties and continuous 3D nanostructures of hydrogels. This bicomponent organization results in soft, all-organic, conducting micro-/nanostructures with multifarious material applications. However, the application of CPHs as functional materials for biomedical applications is currently limited due to the necessity to combine the features of biocompatibility, self-healing, and fine-tuning of the mechanical properties. To overcome this issue, we choose to combine a protected dipeptide as the supramolecular gelator, owing to its intrinsic biocompatibility and excellent gelation ability, with the conductive polymer polyaniline (PAni), which was polymerized in situ. Thus, a two-component, all-organic, conducting hydrogel was formed. Spectroscopic evidence reveals the formation of the emeraldine salt form of PAni by intrinsic doping. The composite hydrogel is mechanically rigid with a very high storage modulus ( G') value of ∼2 MPa, and the rigidity was tuned by changing the peptide concentration. The hydrogel exhibits ohmic conductivity, pressure sensitivity, and, importantly, self-healing features. By virtue of its self-healing property, the polymeric nonmetallic hydrogel can reinstate its intrinsic conductivity when two of its macroscopically separated blocks are rejoined. High cell viability of cardiomyocytes grown on the composite hydrogel demonstrates its noncytotoxicity. These combined attributes of the hydrogel allowed its utilization for dynamic range pressure sensing and as a conductive interface for electrogenic cardiac cells. The composite hydrogel supports cardiomyocyte organization into a spontaneously contracting system. The composite hydrogel thus has considerable potential for various applications.

Infrared Spectra: Useful Technique to Identify the Conductivity Level of Emeraldine form of Polyaniline and Indication of Conductivity Measurement either Two or Four Probe Technique

A new insight was watched the connection between’s the conductivity and Fourier Transform Infrared (FT-IR) spectra of the emeraldine type of polyaniline (PANI) structures. The conductivity of polyaniline emeraldine salt (PANI-ES) can be varied from 101 to 10-12 S cm-1. FT-IR spectrum is a tool to determine the conductivity level and also conductivity measuring methods of PANI system, i.e., either two probe or four probe techniques. This information is very useful for the researcher and industrialists working on emeraldine form of PANI systems to identify the conductivity level and method of measurements from FT-IR spectra. This data was seen from the infrared spectra of different PANI salts obtained by the oxidation of aniline in water/solvent medium by ammonium persulfate (APS) without utilizing any acids. PANI-ES samples having reasonably good conductivity (> 0.3 S cm-1) showed mostly nanowires or nanorods morphology, whereas, lower conductivity (< 0.3 S cm-1) samples showed mostlyagglomerated spheres or particles morphology. In these investigations, however, no report was made of the use of infrared technic to determine the conductivity of PANI system.

Formation Mechanism and Characterization of PANI Nanoparticles by Hybrid Chemical and Gamma Irradiation Technique

Here we present additional data regarding specific doping process in nanoparticle samples of PANI. In such technique, the ionizing γ-irradiation and (dodecylbenzenesulfonic acid), DBSA were being used as dopants and as accelerators to the oxidizing agent to polymerize aniline monomer into conductive PANI Emeraldine Salt (ES), in which PANI was produced from its monomer by this noble methodology by a single-step process. In such synthesis technique, the interactions promote a more extended conformation of PANI chains, which leads to the improvement in solubility, the thermal stability and conductivity. Hence the dielectric and optical properties of PANI nanoparticles could be improved tremendously by incorporation of a long-chain organic acid (DBSA) as the dopant ion under the influence of γ-irradiation. It was also expected that the single step, direct double doping procedure (γ-ray and DBSA) could be used for synthesizing these nanomaterials with different long-chain dopant ions instead of the standard route of synthesizing, to avoid tedious steps involved like de-doping, re-doping etc.

Structural and electrical properties of HCl–polyaniline–Ag composites synthesized by polymerization using Ag-coated (NH4)2S2O8 powder

Ag nanoparticles were sputter-deposited on ammonium persulfate ((NH4)2S2O8) powder to obtain (NH4)2S2O8−Ag powder, which was used to synthesize the HCl-doped polyaniline−Ag (HCl−PANI−Ag) composite via a polymerization procedure. The Ag nanoparticles were dispersed in the HCl−PANI matrix, and their sizes mainly ranged from 3 to 6 nm. The Ag nanoparticles did not affect the structure of emeraldine salt in the composite, and they increased the ordered crystalline regions in the HCl−PANI matrix. The HCl−PANI−Ag composite had a conductivity of (6.8 ± 0.1) S/cm, which is about four times larger than that of the HCl−PANI. The charge transport mechanism in the composite is explained by the three-dimensional Mott variable-range hopping (3D-Mott-VRH).

Preparation and characterization of nanofibers of polyvinyl alcohol/polyaniline-montmorillonite clay

This work describes the preparation of polyvinyl alcohol/polyaniline-montmorillonite clay (PVA/PANI-OMMT) nanofibers through electrospinning. Initially, for improving the compatibility of the clay towards the organic polymer, the montmorillonite (MMT) was submitted to an organophilization process using hexadecyltrimethylammonium bromide (CH3(CH2)15N(Br)(CH3)3). The PANI-OMMT composite, which was obtained after the in situ polymerization of aniline in presence of the organophilic clay (ratio of ≈1:3 in weight), was then placed in a matrix of PVA (weight ratio of 1:7 of composite:PVA) for the production of the PVA/PANI-OMMT composite fibers through electrospinning. We used several characterization techniques (X-ray diffraction (XRD); infrared absorption spectroscopy (FTIR), ultraviolet visible absorption spectroscopy (UV–Vis), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS)) to analyze the different samples produced. The clay organophilization was confirmed after observing the (001) plane displacement from 5,6° to 4,7° and absorption bands in 2924 cm−1, 2853 cm−1 and 1479 cm−1, as analyzed by XRD and FTIR, respectively. The presence of polyaniline in its emeraldine salt was identified by the presence of the characteristic UV–Vis absorption bands in 360 nm, 430 nm and 822 nm, while the formation of the PANI/OMMT nanocomposite was confirmed by observing the characteristic FTIR bands of each individual component. From the SEM images, we could establish that the resulting nanocomposite mats were composed by uniform fibers with an average diameter of 240 nm and presented good surface quality. We have found that EIS is an efficient technique for the evaluation of changes in the electric properties of the nanofibers after their exposure to vapors of methanol. We suggest that this organic-inorganic composite may find useful applications in the preparation of several devices based on polymers, such as heavy metal filtration membranes and gas sensors.

DBSA to improve the compatibility, solubility, and infusibility of cellulose nanowhiskers modified by polyaniline in reinforcing a natural rubber-based nanocomposite

In this study, the authors evaluate the potential of the reinforcement of cellulose nanowhiskers coated with polyaniline-DBSA (CNW-PANiDB) in a natural rubber latex nanocomposite. For this purpose, cellulose nanowhiskers (CNWs) were obtained by acid hydrolysis and coated with polyaniline by in situ polymerization in an acidic medium using dodecylbenzenesulfonic acid (DBSA). The nanocomposites based on natural rubber (NR) reinforced with CNW-PANiDB were obtained by a casting/evaporation method. Sample characterization was performed by DC electrical conductivity, thermogravimetric analysis, strain–stress test, UV–Vis–NIR and field emission scanning electron microscope. The UV–Vis–NIR spectrum of the NR/CNW-PANiDB nanocomposite revealed three characteristic absorption peaks around 350, 425, and 830 nm, assigned to PANiDB in emeraldine salt form. The mechanical properties of the nanocomposite, such as Young’s modulus and tensile strength, were improved by increasing the amount of CNW-PANiDB. The electrical conductivity of the nanocomposite increased by seven orders of magnitude by adding 10 mass% of CNW-PANiDB. This result indicates that CNWs coated with polyaniline-DBSA are an excellent material for use as mechanical reinforcement and to improve electrical conductivity. Thus, NR/CNW-PANiDB nanocomposite films have potential to be used as anticorrosive, electrostatic discharge, electromagnetic interference shielding materials, transducers, and electroactive materials.

H2S Sensing Material Based on Cotton Fabrics Modified with Polyaniline

In this work, intelligent materials were developed from the cotton fabric modified with polyaniline (PAni). PAni was used in different oxidation states (Emeraldine Salt, Emeraldine, Leucoemeraldine and Pernigraniline Base). The obtained materials were tested as colorimetric hydrogen sulfide gas sensors. The intelligent fabrics were analyzed by Infrared Spectrometry (FTIR), X‐ray powder diffraction (XRD), Thermogravimetric Analysis (TGA), Energy Dispersive X‐Ray Spectroscopy (EDS), Optical Microscopy and Electrical Resistivity Analysis. Smart fabrics were exposed to hydrogen sulfide gas, and colorimetric analyses were performed before and after exposure to identify fabrics capacity of detection. The obtained results allowed inferring that the best material was the one modified with Emeraldine base. This low‐cost material can be easily obtained, constituting a valuable hydrogen sulfide gas detection tool.

Novel preparation of self-assembled HCl-doped polyaniline nanotubes using compressed CO2-assisted polymerization

Recently, extraordinary attention has been given to the preparation of strong acid-doped polyaniline in distinct morphologies, such as nanofibers, nanotubes, and nanoflowers, while seeking proper and cheap energy polymeric materials. This work introduces the CO2-supported polymerization process as an advanced and novel polymerization technique to prepare rectangular cross-sectional self-assembled HCl-doped polyaniline nanotubes (HCl-PANNT) without the need to use any surfactants for the first time. Based on the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results, a rectangular cross-sectional HCl-PANNT with an average outer diameter and wall thickness of 110 and 35 nm, respectively, was prepared. Furthermore, X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) were employed to reveal the crystallinity and the chemical structure of the prepared polyaniline, respectively. Accordingly, the produced PANNT has a partial crystalline structure and emeraldine salt form. Moreover, the produced HCl-PANNT showed a high electrical conductivity of 1.5 S/cm.

Analysis of Superfine-Resolution Printing of Polyaniline and Silver Microstructures for Electronic Applications

Additive manufacturing (printing) of micrometer-scale patterns of metal and semiconductor particles is receiving significant attention due to its potential as an inexpensive alternative to the top-down fabrication of silicon microelectronic devices. However, printing of such devices needs an in-depth understanding of physico-chemical interactions between the liquid ink droplets and the substrate used for printing the devices. The paucity of detailed experimental studies in this area warrants a systematic investigation into the challenges involved in printing stable and reliable electronic devices. In this paper, we have analyzed the interactions between the liquid dispersions of polyaniline emeraldine salt (PANI-ES) and silver nanoparticles (Ag NPs) over various substrates such as silicon, glass, indium tin oxide, polyethylene terephthalate, and polyvinyl alcohol surfaces. The analysis has been carried out in terms of concentration of the dispersion, particle size, solvophilic or solvophobic nature of the substrate, evaporation rate of solvents, ambient humidity, and postprocessing. Furthermore, the resistors of various lengths and widths are printed on glass surface via a superfine resolution molecular printing system (MPS) that uses a piezoelectric response from a cantilever to deposit picoliters of Ag NP ink at precise locations. Substantially, low ratios of printed dot feature size to suspended particle size (1 for PANI-ES and 10 for Ag NP) have been obtained, indicating that the MPS can provide a much finer print resolution for flexible and printed electronic circuit components as compared to traditional inkjet, screen, or gravure printing.

Electric impulse spring-assisted contact separation mode triboelectric nanogenerator fabricated from polyaniline emeraldine salt and woven carbon fibers

In this article, we used modified woven carbon fiber mat (wCF-COOH), as one of the contact-electrification Triboelectric Nanogenerator (TENG) friction layer to generate high open circuit voltage (Voc) and short circuit current (Isc). We designed the contact-separation mode TENG which is functional using spring structure. The oxidation of wCF into wCF-COOH by Piranha solution followed by coupling of aniline through electrostatic interactions and in-situ oxidative polymerization to get woven carbon fiber-polyaniline emeraldine salt (wCF.PANI.ES) composite is a novel approach. The wCF-PANI.ES composite displays the surface resistivity of 0.324 Ω m and serves as a friction layer to generate charges by harvesting energy through vertical contact-separation mode TENG against PVDF membrane. The dynamic interactions of novel wCF-PANI.ES and PVDF membrane produced high Voc of 95 V, and Isc of 180 μA, respectively. In particular, wCF-PANI.ES-TENG has shown an enhancement of 498% of Voc with respect to wCF-COOH-TENG due to availability of PANI layer. In addition, it was observed that the proposed wCF-PANI.ES-TENG has shown the output power of 12.4 mW at 5 Hz, and the rectified current upto 180 μA. The novel wCF-PANI.ES is the potential candidate for fulfilling the need of optimized energy harvesting device as an alternate material option for contact-separation mode TENGs.

Catalyst Support Effect on the Activity and Durability of Magnetic Nanoparticles: toward Design of Advanced Electrocatalyst for Full Water Splitting.

Earth-abundant element-based inorganic–organic hybrid materials are attractive alternatives for electrocatalyzing energy conversion reactions. Such material structures do not only increase the surface area and stability of metal nanoparticles (NPs) but also modify the electrocatalytic performance. Here, we introduce, for the first time, multiwall carbon nanotubes (MWNTs) functionalized with nitrogen-rich emeraldine salt (ES) (denoted as ES-MWNT) as a promising catalyst support to boost the electrocatalytic activity of magnetic maghemite (γ-Fe2O3) NPs. The latter component has been synthesized by a simple and upscalable one-step pulsed laser ablation method on Ni core forming the core–shell Ni@γ-Fe2O3 NPs. The catalyst (Ni@γ-Fe2O3/ES-MWNT) is formed via self-assembly as strong interaction between ES-MWNT and Ni@γ-Fe2O3 results in NPs’ encapsulation in a thin C–N shell. We further show that Ni does not directly function as an active site in the electrocatalyst but it has a crucial role in synthesizing the maghemite shell. The strong interaction between the NPs and the support improves notably the NPs’ catalytic activity toward oxygen evolution reaction (OER) in terms of both onset potential and current density, ranking it among the most active catalysts reported so far. Furthermore, this material shows a superior durability to most of the current excellent OER electrocatalysts as the activity, and the structure, remains almost intact after 5000 OER stability cycles. On further characterization, the same trend has been observed for hydrogen evolution reaction, the other half-reaction of water splitting.

Detail Photophysical Studies of Sulfonated Polyaniline in Aqueous Medium.

Sulfonated polyaniline (SPANI) has emerged as a promising polymer in the past few decades due to its solubility in water and relatively moderate conductivity. However, to date, literature data on the optical characterization of SPANI are very limited and preliminary in nature. In the present work, SPANI is synthesized by direct sulfonation of emeraldine salt form of polyaniline with chlorosulfonic acid in an inert solvent. Detail photophysical properties of SPANI are investigated in aqueous medium by using steady state (concentration, temperature, pH, and excitation wavelength dependence) and time-resolved spectroscopic techniques. The steady state fluorescence emission measurements are carried out carefully to avoid inner filter effect (especially secondary inner filter effect or reabsorption effect) as well as scattering. Two ground state conformations of SPANI are suggested to exist in aqueous medium. Excitation wavelength dependence of the fluorescence emission spectra is attributed to red-edge effect. All these observations are nicely corroborated by the fluorescence lifetime data of SPANI obtained from time-resolved measurements. All these new findings are extremely important in view of the potential applications of SPANI in polymer optoelectronics.

Polyaniline Emeraldine Salt Molecules Coated on Polyethylene Board Using SILAR Technique

In this study, conducting polyaniline (PANI) Emeraldine salt molecules were coated on polyethylene (PE) board using successive ionic layer adsorption and reaction (SILAR) technique. The number of dipping cycles were varied and the surface conductivity of the samples were measured using four-point probe technique. Fourier Transform Infrared (FTIR) spectroscopy was also done to verify the identities of the coated samples. Results show that PANI Emeraldine salt was successfully coated on PE board as indicated by the peaks of FTIR spectra. Surface conductivity of the PANI Emeraldine salt coated PE board increases with increased number of dipping cycles due to increases interconnectivity of PANI molecules. The conductivity decreases after reaching an optimum point at 80 dipping cycles due to either hindrance of movement of charges or the breaking away of chunks of PANI molecules. These results opens up several applications such as memory devices and erasable circuit boards.

Enzymatic Synthesis of Highly Electroactive Oligoanilines from a p-Aminodiphenylamine/Aniline Mixture with Anionic Vesicles as Templates.

Oligoanilines with characteristic properties of the electrically conductive emeraldine salt form of polyaniline (PANI-ES) are promising molecules for various applications. A mixture of such oligoanilines can be obtained, for example, enzymatically under mild conditions from the linear aniline dimer p-aminodiphenylamine (PADPA) with hydrogen peroxide (H2O2) and low amounts of horseradish peroxidase (HRP) in an aqueous pH = 4.3 suspension of anionic vesicles formed from AOT, the sodium salt of bis(2-ethylhexyl)sulfosuccinate. However, the simultaneous formation of undesired side products containing phenazine-type units or oxygen atoms is unsatisfactory. We have found that this situation can be improved considerably by using a mixture of PADPA and aniline instead of PADPA only but otherwise nearly identical conditions. The PANI-ES-like oligoaniline products that are obtained from the PADPA and aniline mixture were not only found to have much lower contents of phenazine-type units and not contain oxygen atoms but also were shown to be more electroactive in cyclic voltammetry measurements than the PANI-ES-like products obtained from PADPA only. The AOT vesicle suspension remained stable without product precipitation during and after the entire reaction so that it could be analyzed by in situ UV/visible/near-infrared, in situ electron paramagnetic resonance, and in situ Raman spectroscopy measurements. These measurements were complemented with ex situ high-performance liquid chromatography analyses of the deprotonated and reduced products formed from mixtures of PADPA and either fully or partially deuterated aniline. On the basis of the results obtained, a reaction mechanism is proposed for explaining this improved HRP-triggered, vesicle-assisted synthesis of electroactive PANI-ES-like products. The oligomeric products obtained can be further used, without additional special workup, for example, to coat electrodes for their possible application in biosensor devices.

Synthesis and characterization of nanocomposites consisting of polyaniline, chitosan and tin dioxide

Polymeric nanocomposites composed of polyaniline (PANI)/tin dioxide (SnO2), and PANI/chitosan(CS)/SnO2 were synthesized chemically by in situ polymerization method. The aniline polymerization was carried out using DBSA as protonating agent, and APS as oxidizing agent. The tin dioxide nanoparticles dissolved in hydrochloric acid (HCl) was added during the synthesis process. Nanocomposites were examined by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TGA), Fourier transform infrared spectroscopy (FTIR), photoelectrons excited by X-rays (XPS), and Mössbauer (EM). The results of XRD pattern indicate that nanocomposites are crystalline due to the presence of SnO2 nanoparticles with reflection planes corresponding to the tetragonal rutile structure. XPS and FTIR results reveal that the protonation degree of PANI/CS/SnO2 sample is higher than that of the PANI/SnO2 and pure emeraldine salt PANI samples. These results suggest that the conductivity would be much larger in the PANI/CS/SnO2 sample. TGA results reveals samples with SnO2 shows more thermal stalibility due to Sn4+ interaction with amide and imide groups of PANI. SEM images of both nanocomposites showed an irregular morphology with agglomerate of particles, attributed to the presence of SnO2 nanoparticles which were not dispersed homogeneously during the synthesis process.

Conducting Properties of Polyaniline Emeraldine Salt on Paper in the Low-Frequency Region

Polyaniline emeraldine salt (PAni-ES) was successfully deposited on paper through layer-by-layer technique. In this method, a paper was alternately dipped in aniline monomer and an oxidizing agent for different dipping cycles. This process produced green PAni-ES on paper. The morphology of the samples showed polymeric networks with pores, fiber-like structures and aggregates. There is a transition from frequency-independent to frequency-dependent conductivities of the samples. The conductivity increased with increasing number of dipping cycles. The frequency-dependent conductivities follow the power-law behavior reflecting conducting network and hopping mechanisms. Lastly, the conductivities with frequency followed a scaling behavior reflecting a common physical mechanism in PAni-ES on paper.

Synthesis of polyaniline/MWCNTs by interfacial polymerization for superior hybrid supercapacitance performance

Polyaniline/Multiwalled carbon nanotubes (PANI/MWCNTs) nanocomposite was prepared via liquid-liquid interfacial polymerization method. The morphology studies of the nanocomposite using SEM and TEM techniques confirmed the presence of PANI as aggregates along with MWCNTs and X-ray diffraction studies indicated the presence of graphitic planes of MWCNTs along with PANI in semi-crystalline emeraldine salt form. The PANI/MWCNTs nanocomposite electrode exhibited specific capacitance (Cs) of 1551 F/g at a scan rate of 2 mV/s in aqueous 1 M H2SO4 in a potential window of 0–1.2 V. The material exhibited good cycle life with 95% capacitance retention in a life cycle test conducted at 5 A/g for 1000 cycles. Further, an asymmetric supercapacitor device (ASD) was fabricated using PANI/MWCNTs as positive and activated carbon as negative electrodes in aqueous 1 M H2SO4. The ASD exhibited a Cs of 142 F/g at a scan rate of 5 mV/s in a wide potential range of 0–1.6 V. The device offered high energy and power densities of 29 Wh/Kg and 7.3 kW/Kg respectively and also demonstrated an excellent cyclic stability by retaining 97% of its initial capacitance after 5000 cycles at high current density of 20 A/g.

Laccase 촉매 작용에 의한 아닐린 중합에 Soft Template이 미치는 영향

A comparison of laccase-catalyzed polymerization of aniline in the presence of two different “soft” templates - micelle forming surfactant sodium dodecylbenzenesulfonate (SDBS) and sulfonated natural polyelectrolyte calcium lignosulfonate (LGS) - was investigated to check the influences of different templates on the kinetics of the polymerization and on the characteristics of the complexes obtained. Under respective optimal conditions, pH 4.5 for SDBS and pH 3.5 for LGS, the reaction with LGS was much slower than that in SDBS emulsion. The conditions for laccase-catalyzed synthesis of emeraldine salt of polyaniline (PANI-ES) in both cases were optimized using UV-vis spectroscopy. It was found that PANI-ES obtained with LGS template had a higher degree of oxidation with a higher amount of benzene rings than PANI-ES obtained in SDBS emulsion. Since the protonation of PANI occurred on its imine sites, the doping effect of LGS-doped PANI-ES, confirmed by XPS, was thus better than that of SDBS-doped one.

Hybrid biodegradable scaffolds of piezoelectric polyhydroxybutyrate and conductive polyaniline: Piezocharge constants and electric potential study

Hybrid biodegradable piezoelectric electrospun fibrous scaffolds based on polyhydroxybutyrate (PHB) and polyaniline (PANI, emeraldine salt) were fabricated. Fourier transform infrared spectroscopy and X-ray diffraction confirmed the presence of PANi in the structure of hybrid PHB-based scaffolds. The piezoelectric coefficient d33 and surface electric potential under cyclic mechanical stress at the frequency of 4 Hz were increased in 4.2 times and 3.5 times, respectively, in the case of hybrid PHB scaffolds with the addition of 2% PANi compared with pure PHB ones.

Preparation of high surface area and high conductivity polyaniline nanoparticles using chemical oxidation polymerization technique

In this work, polyaniline nanoparticles were synthesized using a chemical oxidation polymerization technique. The ammonium peroxydisulfate (APS)/aniline ratio, APS dropping time, and polymerization temperature were optimized to increase the surface area and conductivity of the polyaniline.The Fourier-transform infrared (FTIR) spectrum confirmed the formation of emeraldine salt polyaniline. X-ray diffraction (XRD) patterns indicated that amorphous and crystalline phases of the polyaniline were formed with crystallinity less than 40%. Scanning electron microscope (SEM) micrographs showed that the finest nanoparticles with uniform size distribution were obtained at the polymerization temperature of 0°C. A surface area analyzer (SAA) showed that the highest Brunauer-Emmett-Teller surface area (SBET) of 42.14 m2/gwas obtained from an APS/aniline ratio of 0.75 with a dropping time of 0 s at a polymerization temperature of 0°C. A four-point probe measurement conducted at 75–300K indicated relatively high conductivity of the semiconductor characteristic of the polyaniline.