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The use of humidity sensors in environmental monitoring application such as the creation of safe, comfortable, and cost-effective environment has been the subject of interest right from the beginning. The current study is focused on the organic–inorganic composite material as humidity sensor. Polyaniline (PANI) and its composites with copper oxide (PANI-CuO) doped with sulfuric acid (H2SO4) are prepared by the in-situ polymerization method. Structural features are investigated by different techniques including Ultraviolet/Visible (UV/Vis), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA), and Scanning Electronic Microscopy (SEM). The structural characterizations confirm the emeraldine salt (ES) form of the PANI doped with H2SO4. The conductivity measurements are recorded by using a four-probe conductivity meter, which indicates higher conductivity of the composites as compared to neat PANI. The cyclic voltammetry of the synthesized PANI and its composites with CuO is performed to study the redox properties. The humidity sensing properties in terms of measurement of capacitance are studied by using an LCR meter, which show the linear increase in the capacitance of the prepared composites. The sensor shows fast response and recovery with high stability.

We present an efficient, highly selective and binder free non-enzymatic glucose sensor based on polyaniline@copper-nickel (PANI@CuNi) nanocomposite. PANI@CuNi nanocomposites with different loading ratio of nanoparticles (1: 025, 1: 0.33, 1: 05 and 1: 1) were prepared by mixing solution of PANI, synthesized through inverse emulsion polymerization method, and CuNi nanoparticles, synthesized through polyol process. The as prepared PANI@CuNi nanocomposites were coated on glassy carbon substrate without binder for non-enzymatic glucose sensing. A considerable increase in the active surface area of the electrode occurred after coating of this material. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry demonstrated that PANI@CuNi nanocomposite with 1: 0.5 ratio could be a good choice to be used as electrode material for non-enzymatic glucose sensing. The PANI@CuNi modified electrode exhibited high sensitivity (1030 μA mM−1 cm−2), good lower detection limit (0.2 μM) and a linear range of 5.6 mM (R2 = 0.992) with additional advantage of excellent selectivity, high stability and effective detection in real blood samples.

For the first time, chloroform and 2-butanol were used as solvent systems for the preparation of ZrO2–PANI and CeO2–PANI composites. Solubility of the synthesized composites was studied in chloroform, N-methyl-2-pyrrolidinone (NMP), and in mixture of toluene + 2-propanol (2:1). XRD and cyclic voltammetry data showed that the ZrO2–PANI and CeO2–PANI composites possess both crystalline and amorphous domains indicating some sort of conductivity. TGA results showed that ZrO2–PANI composite have a better thermal stability than pure PANI; however, CeO2–PANI composite has lower thermal stability than pure PANI. The conjugated unsaturated structure of PANI is responsible for the enhanced photocatalytic properties of ZrO2–PANI and CeO2–PANI. Photocatalytic results showed that, at photolysis time of 60 min, rhodamine B (RhB) dye was degraded up to 34 and 35% by ZrO2–PANI and CeO2–PANI, respectively. The degradation products of RhB were quantified by LC–MS and GC–MS, and accordingly, a detailed pathway was proposed.

The behaviour of gold electrode modified with polyaniline/graphene oxide composites (PGO) was studied for electrochemical and charge storage properties in aqueous acidic media. The surface of gold electrode was modified with aqueous slurry of PGO by using Carboxymethyl cellulose (CMC) as binder. The intercalation of polyaniline in the GO layers, synthesized by in situ polymerization was confirmed by scanning electron microscopy (SEM). The electrochemical behaviour and charge storing properties were investigated using cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS). A high specific capacitance of 1721 F g−1 was obtained for PGO with 69.8% retention of capacitance even after 1000 voltammetric cycles in the potential range of 0–0.9 V at 20 mV s−1. EIS indicated low charge transfer resistance (Rct) and solution resistance (Rs) values of 0.51 Ω and 0.07 Ω, respectively. This good performance of PGO coated electrode is attributed to the use of CMC binder which generate a high electrode/ electrolyte contact area and short path lengths for electronic transport and electrolyte ion.

We report the utilization of polyaniline (PANI), co-doped with DBSA and sulfuric acid (PANI/DBSA/H2SO4), as a novel and promising electrode material for aqueous supercapacitors. The co-doped PANI/DBSA/H2SO4 salts were characterized by in situ conductance measurements, in situ UV–vis spectroelectrochemistry, cyclic voltammetry (CV) and UV–vis NIR spectroscopy. Elemental analysis of the synthesized PANI salt revealed its remarkable (50%) doping level while intrinsic viscosity indicated its highest molecular weight. Furthermore, PANI salt with best set of properties was tested for application in supercapacitors. For this purpose a systematic study was carried out in selected acidic electrolytes (HClO4, H2SO4, and H3PO4) by employing CV, Galvanostatic Charge-Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS). Different parameters such as applied potential limits, current density as well as type and concentration of electrolytes were optimized. The kinetics of the electrochemical degradation as well as specific capacitance of the PANI film was determined in the above mentioned electrolytes, which helped in choosing the appropriate conditions and electrolyte for the maximum exploitation of this material for supercapacitor. All the results suggest 0.5 M HClO4, along with other optimized parameters, as the most appropriate electrolyte solution. The PANI film showed electroactivity even after 6000 cycles applied through cyclic voltammetry. A capacitance retention of 57% after 1000 charge discharge cycles was observed in this electrolyte. Similarly, the film exhibited a specific capacitance value of 516 F g−1 with a relatively high energy density and power density of 34 W h kg−1 and 11.51 K W kg−1, respectively. As compared with the literature, the prepared polymer can be used as an electrode material for supercapacitors.

The eco-friendly and cost-efficient synthesis of polyaniline (PANI) is one of the perplexing tasks in the research horizons of conducting polymers while keeping the desired properties unaffected. The present work reports an eco-friendly and comparably cost-efficient pathway for the synthesis of corrosion-resistant, thermally stable, and highly soluble PANI salt using coconut oil as a novel dispersion medium. The PANI salt was optimized by varying the reaction parameters, such as concentration of monomer, oxidant, surfactant, and solvent. The UV/Visible spectra indicated absorption peaks in the range of 344–353, 424–433, and 740–779 nm. The FTIR analysis of PANI salt reveals the stretching of the benzenoid and quinoid rings at 1460 and 1559 nm respectively. X-ray diffraction shows peaks on 2Ө at 19° and 25° which are the characteristic peaks of PANI. PANI salt was found to be soluble in several organic solvents such as 2-propanol, n-Methylpyrolidinone (NMP), and highly soluble in chloroform and Dimethyl sulfoxide (DMSO) up to 7.6 and 6.9% respectively. SEM images and TGA analysis of PANI confirmed the porous morphology like cauliflower and quite thermally stable up to 538 °C respectively. The layer of synthesized PANI shows remarkable corrosion inhibiting behavior on the surface of mild steel which reduces the rate of corrosion up to 82%. Hence, boost up the global economy.

Ion diffusion rate and contact surface area of conducting polymers increased by composite formation with nanometric-size materials make them promising materials in the fabrication of energy storage devices. In this work, electronically conducting polyaniline and manganese oxide (PANI/MnO2) nanofibrous composites were electrochemically co-deposited on stainless steel from binder-free electrolyte solution. Structural characterization and morphological characterization of the materials were performed with Fourier-transformed infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). SEM images show fibrous micro/nano-architecture of the composites with cluster networking structure having 200–500 nm length and 100–200 nm diameter. Electrochemical and energy storage properties of the as-synthesized materials were investigated with cyclic voltammetry (CV), galvanostatic charge discharge curves(GCDC), and potentiostatic electrochemical impedance spectroscopy (PEIS) without any binders. Electrochemical measurements as well as galvanostatic charge discharge curves at 1 mA constant current have shown maximum specific capacitance of 149 F/g for the composite prepared with 0.15 M MnSO4 in the co-deposition bath. The composites retain 67% specific capacitance even after 400 cycles, indicating the stability of synthesized composite. PEIS confirms the pseudocapacitive nature of the synthesized composites.

This paper reports on the synthesis and characterization of poly(2-methylaniline), PmA, a derivative of a very fascinating electronically conducting polymer polyaniline. PmA was synthesized in its salt form by one pot emulsion polymerization route using DBSA and sulfuric acid as co-dopants. Fourier transform infrared spectroscopy and Ultraviolet visible spectroscopic analysis confirmed formation of conducting emeraldine salt form of PmA. These PmA salts showed good redox reversibility and high purity. Thermogravimetric analysis revealed very good thermal stability up to 520 °C which is the highest reported thermal stability for PmA so far. Potentiodynamic polarization measurements clearly revealed that the PmA acts as corrosion protective coating on stainless steel with the protection efficiency of 55.59%.

Oligomeric synthesis of phenyl-end-capped oligoaniline (4PANI LB) has been carried out through a weak oxidizing agent, CuCl 2 , using chemical oxidative polymerization protocol. The sample was characterized by mass spectrometry, UV–vis, IR, and CHN elemental analysis. The experimental results are counterchecked with the aid of Quantum mechanical calculations such as density functional theory (DFT). DFT at B3LYP/6–31 G (d) level of theory was used for the geometric and electronic properties simulations which also confirm the existence of 4PANI LB. Excellent correlation is observed between the experiment and theory, particularly in the UV–vis spectra which conclude the formation of tetramer (fully reduced form) 4PANI LB (C 24 H 20.06 N 4.07 ). Electronic properties such as Ionization Potential (I.P), Electron Affinities (E.A), the coefficient of highest occupied molecular orbital (HOMO), the coefficient of lowest unoccupied molecular orbital (LUMO) of 4PANI LB were evaluated at the above-mentioned level of theory.

In this work nickel modified polymer composites have been synthesized electrochemically for methanol electrooxidation on platinum and graphite electrodes. Ni (II) ions were incorporated on polyaniline and poly (o-aminophenol)(PANI/POAP) bilayer structure from 0.1 M Nickel sulphate hexahydrate solution at open circuit potential (OCP).TheNi (II) deposited composites were characterized with Fourier Transform Infrared (FTIR) spectroscopy, Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). Cyclic voltammetry characterization exhibits stable redox pair of Ni+3/Ni+2 for both electrodes. Fourier transform infrared spectroscopy was used for functional group analysis. Ni (II) peaks were observed in the region of 400–700 cm−1 along with peaks at 1102 cm−1 and 1400–1600 cm−1 for polyaniline and phenoxazine units. The Ni-polymer composite on platinum and graphite electrode followed different phenomenon for methanol electroxidation in alkaline media. The cyclic voltammetry results showed significantly large methanol oxidation on platinum substrate with charge storage capacity of 196 μ F/cm2 for 1.5 M methanol in alkaline media as compared to 8.306 μF/cm2 of graphite. The diffusion controlled linear response for increase rate of methanol concentration has been obtained for Ni (II)/PANI/POAP-Pt. The electrochemical impedance spectroscopy (EIS)results indicated increase in charge storage capacity from 10−4F/cm2 to 10−3 F/cm2 with increasing potentials at lower frequency region.The phase shift was observed from 60–40 degrees for increased potentials at low frequency range in EIS analysis. The increased conductive behavior from 10−5 to 10−2 s/cm2 has been obtained fornickel modified polymer composite at higher frequency region in EIS analysis.

The properties of conducting polymers (CPs) such as polyaniline (PANI) and its derivatives can be modified, improved and even enhanced by making composites with materials which can change the extent and level of doping in the CPs. This paper reports on the synthesis of PANI in the presence of various concentration of polyvinyl alcohol by inverse emulsion polymerization. The as synthesized PANI and PANI/PVA were characterized with UV/VIS, FTIR, XRD, TGA, SEM, conductivity and electrochemical measurements. The results demonstrated the formation of polyaniline doped with polyvinyl alcohol showing high thermal stability and improved room temperature conductivity. The synthesized composites were found to be soluble in common organic solvents such as N-methylpyrolidinone (NMP), Chloroform, 2:1 mixture of toluene and 2-proanol, 1:1 mixture of chloroform and toluene and 2:1 mixture of toluene and methanol. Cyclic voltammetric studies showed good redox properties of synthesized PANI and PANI/PVA.

Microbial electrosynthesis (MES) is a promising technology to convert CO2 into value-added chemicals. Enhancing the interactions between biofilms and electrodes is the key of bioelectrochemical systems (BES). In this work, we studied the conversion of CO2 by MES in reactors equipped with novel gas diffusion electrodes (GDEs) modified with a polyaniline (PANI) polymer binary doped with H2SO4 and ammonium lauryl sulfate. The enhanced conductive and hydrophilic properties of the polymer increased the biocompatibility of the PANI-modified GDEs compared to the non-modified carbon GDEs. This increased biocompatibility resulted in faster start-up and higher bioproduction of volatile fatty acids (VFAs) such as acetate and butyrate. Up to 4400 ppm acetate was produced in PANI-modified reactors after 24 days of operation, compared to 408 ppm in reactors equipped with non-modified GDEs. A maximum acetate concentration of 7500 ppm (production rate of 554.8 ± 267.5 ppm day−1) was reached in reactors equipped with PANI-GDEs. After 60 days, apart from acetate, 245 ppm butyrate was produced in reactors equipped with the electrodes modified with PANI, while less than 60 ppm was produced with non-modified GDEs. SEM analysis revealed the development of biofilms on both modified and non-modified electrodes, but the images also suggest differences in compositions.

Electroconductive polymeric patches are being developed in the hope to interface with the electroresponsive tissues. For these constructs, conjugated polymers are considered as conductive components for their electroactive nature. Conversely, the clinical applications of these conductive polymeric patches are limited due to their short operational time&mdash, a decrease in their electroactivity occurs with the passage of time. This paper reports on the polymerization of aniline on prefabricated chitosan films on microscopic glass slides in the presence of sodium phytate. The strong chelation among sodium phytate, aniline and chitosan led to the formation of electoconductive polymeric patch. We assume that immobilization of sodium phytate in the polymeric patch helps to prevent electric deterioration, extend its electronic stability and reduce sheet resistance. The patch oxidized after three weeks (21 days) of incubation in phosphate buffer (pH 7.4 as physiological medium). This feasible fabrication technique set the foundation to design electronically stable, conjugated polymer-based patches, by providing a robust system of conduction that could be used with electroactive tissues such as cardiac muscles at the interface.

Polyaniline/Poly(o-aminophenol) (PANI/POAP) bilayered films were deposited by electro polymerization on platinum (Pt) and graphite (Gra) electrodes for methanol oxidation in direct methanol fuel cells. The chemical composition of bilayered structure was characterized by Fourier transform infrared (FTIR) spectroscopy. Results demonstrated the presence of FTIR peaks associated to PANI and POAP constituents confirming the bonding of PANI and POAP in the bilayered composite structure. The electrochemical properties of PANI/POAP electrodes were examined in pure and sulfuric acid mixed methanol solutions using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). PANI/POAP-Gra electrode showed less reactivity towards methanol oxidation, as well as poor stability upon repeated cycling. On the other hand, PANI/POAP-Pt electrode exhibited superior performance with high methanol oxidation current (Ia), capacitance (C), and specific capacitance (Cs). In addition, PANI-POAP-Pt electrode was found better than PANI-POAP-Gra electrode in terms of operation stability based on continuous cycling in methanol up to 100 cycles. The dielectric properties and AC conductivity (σac) of the PANI/POAP-Pt electrode with respect to the applied potential have been discussed.

Quantum mechanical calculations are performed to establish the structure of an oligomer of aniline and pyrrole [Poly(Ani-co-Py)], through comparison of experimental and theoretically calculated properties, including conductivity. The copolymer was synthesized through chemical oxidative polymerization and then confirmed from the experimental IR, UV–vis, mass spectra, elemental, XRD, TGA, and SEM analysis. Quantum mechanical calculations are performed at Density Functional Theory (DFT) and Time dependent DFT (TD-DFT) methods for the electronic and spectroscopic properties of the oligomer. A very nice correlation is found between the theory and experiment which consequences the structure of Poly(Ani-co-Py). Poly(Ani-co-Py) is not explored like other conducting polymers; however, by tuning this molecular structure, the electro-active nature of this material can be enhanced adequately.

We report a sophisticated emulsion polymerization route for the synthesis of polyaniline (PANI) salts. In this process, the chemical oxidative polymerization of aniline was carried out in the presence of two dopants i.e., dodecylbenzenesulfonic acid (DBSA) and sulfuric acid (H2SO4). The synthesized PANI salts were highly soluble in a large number and variety of common organic solvents (so far highest number of solvents including the less hazardous ethanol) and showed very good conductance. Presumably the presence of DBSA and sulfuric acid moieties, respectively, contributed toward the improvement in solubility and conductance. After optimization of the reaction parameters, the obtained polymers were systematically characterized with cyclic voltammetry, in situ conductance, in situ UV–vis spectroelectrochemical and intrinsic viscosity measurements. X-ray diffraction, TGA and SEM were used for further analysis. The materials showed very good electrochemical and electrochromic reversibility and high thermal stability (up to 500 °C). Moreover, potentiodynamic measurements revealed that coatings of this polymer can provide extra ordinary resistance to the steel surfaces particularly against the harsh corrosive environment of the oceans.

Sensitivity and selectivity of polypyrrole (PPy) toward NH3, CO2, and CO have been studied at density functional theory (DFT). PPy oligomers are used both in the doped (PPy+) and neutral (PPy) form...

Density functional theory (DFT) and time dependent DFT (TD-DFT) calculations have been carried out at the oligomers of poly( o -chloroaniline- co-o- toluidine)(POTOC), poly( o -chloroaniline)(POC) and poly( o- toluidine) (POT). This work discusses conductivity, structural parameters, spectral properties, electronic properties like IPs, EAs, HOMOs, LUMOs and band gaps of POTOC, POT and POC by the application of density functional theory to their oligomers up to eight repeating units. The simulated vibrational frequencies at B3LYP/6-31G (d) along with their assignments are correlated with experimental frequencies. The UV–vis spectra are simulated with TD-DFT 6-31G (+d p) level of theory. For polymeric studies, the electronic properties of oligomers were extrapolated through second degree polynomial fit equation. The calculated band gap of POTOC is 3.836 eV while those of POC and POT are 3.456 eV and 3.641 eV, respectively. The larger band gap, low delocalization of HOMO–LUMO orbital over entire frame work, lower extent of conjugation and hypsoochromic shift in UV–vis spectra of POTOC as compared to POT and POC showed that donor-acceptor concept is not playing any role in POTOC and its conductivity after doping might not be increased as compared to the respective homo-polymers.

A comprehensive study of thermally treated polyaniline in its emeraldine salt form is presented here. It offers an understanding of the thermal stability of the polymer. Emeraldine salt was prepared by a novel emulsion polymerization pathway using dodecylbenzene sulfonic acid and sulfuric acid together as dopants. The effect of temperature and heating rate on the degradation of this emeraldine salt was studied via thermogravimetric analysis. The thermally analyzed sample was collected at various temperatures, that is, 250, 490, 500, and 1000°C. The gradual changes in the structure of the emeraldine salt were followed through cyclic voltammetry, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy. Results demonstrate that emeraldine salt shows high thermal stability up to 500°C. This is much higher working temperature for the use of emeraldine salt in higher temperature applications. Further heat treatment seems to induce deprotonation in emeraldine salt. Cyclic voltammetry and ultraviolet-visible spectroscopy revealed that complete deprotonation takes place at 1000°C where it loses its electrical conductivity. It is interesting to note that after the elimination of the dopants, the basic backbone of emeraldine salt was not destroyed. The results reveal that the dopants employed have a stability effect on the skeleton of emeraldine salt.

Polyaniline and its composites with Cu II chloride were synthesized by inverse emulsion polymerization. The synthesized composites were characterized with UV/vis, FT-IR, XRD and SEM. The results show the presence of polyaniline in the emeraldine base form doped with copper II chloride. The thermal properties of the composites were studied by carrying out TGA. The electrical transport properties were calculated from the conductivity measurement. The composites were found to be soluble in common organic solvents such as chloroform, NMP, DMSO, 1:2 mixture of 2-propanol and toluene and 1:2 mixture of 2-propanol and chloroform. Cyclic voltammetry was carried out to find out the redox properties of synthesized composites.

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations at the UB3LYP/6-31G(d) level have been performed to investigate the tunable nature, i.e., doping and dedoping processes, of polypyrrole (PPy). The calculated theoretical data show strong correlation with the recent experimental reports, which validates our computational protocol. The calculated properties are extrapolated to the polymer (PPy) through a second-order polynomial fit. Changes in band gap, conductivity, and resistance of nPy and nPy-X (where n = 1–9 and X = +, NH3, and Cl) were studied and correlated with the calculated vibrational spectra (IR) and electronic properties. Upon doping, bridging bond distance and internal bond angles decrease (decrease in resistance over polymer backbone), whereas dedoping results in increases in these geometric parameters. In the vibrational spectrum, doping is characterized by an increase in the band peaks in the fingerprint region and/or red shifting of the spectral bands. Dedoping (9...

Platinum-free counter electrodes are crucial for developing cost effective solar energy harvesting technology. We describe here the fabrication of efficient platinum free FTO counter electrodes for dye sensitized solar cells based on pristine polyaniline, polyaniline doped with sulfuric acid, ammonuim lauryl sulfate, as well as binary doped with sulfuric acid and ammonium lauryl sulphate. The characteristics of these counter electrodes were analyzed using cyclic voltammetry, photocurrent density–voltage and electrochemical impedance spectroscopy measurements. At optimized fabrication conditions, the counter electrode shows significantly high photoelectric conversion efficiency of 4.54% compared to 4.03% for reference platinum counter electrode. Charge transfer resistance at the interface between electrolyte and counter-electrode is also decreased for the optimized polyaniline based counter electrode. Furthermore, the device presented characteristics of multiple start/stop ability and fast activity. The simple preparation procedure, low cost and improved photoelectric properties permit fabricated counter electrode to be a reliable alternative for dye sensitized solar cells.

Density functional theory studies (DFT) have been carried out to evaluate the ability of polyaniline emeraldine salt (PANI ES) from 2 to 8 phenyl rings as sensor for NH3, CO2, and CO. The sensitivity and selectivity of nPANI ES among NH3, CO2, and CO are studied at UB3LYP/6-31G(d) level of theory. Interaction of nPANI ES with CO is studied from both O (CO(1)) and C (CO(2)) sides of CO. Interaction energy, NBO, and Mulliken charge analysis were used to evaluate the sensing ability of PANI ES for different analytes. Interaction energies are calculated and corrected for BSSE. Large forces of attraction in nPANI ES-NH3 complexes are observed compared to nPANI ES–CO2, nPANI ES-CO(1), and nPANI ES-CO(2) complexes. The inertness of +C≡O– in nPANI ES-CO(1) and nPANI ES-CO(2) complexes are also discussed. Frontier molecular orbitals and energies indicate that NH3 changes the orbital energy of nPANI ES to a greater extent compared to CO2, CO(1), and CO(2). Peaks in UV–vis and UV–vis–near-IR spectra of nPANI ES are ...

Density Functional Theory (DFT) and TD-DFT calculation have been performed to investigate the response mechanism of polypyrrole towards ammonia as sensor. Geometric and electronic properties of oligopyroles up to nine repeating units are evaluated theoretically, and the calculated properties are extrapolated for the polymer (polypyrole) through 2nd order polynomial fit. Hydrogen bonds between ammonia and oligopyrole are about 10–11 kcal mol −1 (7–8.5 kcal mol −1 BSSE corrected) in strength. Interaction of ammonia with the oligopyrrole causes certain geometric features to change (for example ∠C 1 C 2 N 3 C 5 ) which results in decrease in resistance for the movement of electron over the oligomer backbone. The reduction in the resistance is also measured by perturbation in electronic properties including ionization potential (I.P), electron affinity (E.A.), HOMO, LUMO, band gap and λ max . E.A. and band gap (HOMO to LUMO) also support the sensing ability of nPy oligomers towards ammonia. Band gaps decrease while LUMO energies for oligopyroles increase upon interaction with NH 3 . Ammonia donates electron to the LUMO (electron acceptor) of nPy oligomers and increases its electronic clouds density therefore E.A. of nPy decreases. Moreover the extended conjugation in the oligopyrole backbone upon complexation with ammonia, combined with other electronic and geometric properties illustrate the potential of undoped oligopyrole as sensor for ammonia.

This paper evaluates comparatively the behavior of 2-methylaniline (2-MA) and 3-methylaniline (3-MA) in a UV–vis spectroelectrochemical study of their homo- as well as copolymerization with 1,2-diaminobenzene (1,2-DAB). The homopolymers poly(2-methylaniline) (P2-MA) and poly(3-methylaniline) (P3-MA) show similar spectroelectrochemical properties. However, differences were observed in the properties between the copolymers of 2-MA and 3-MA with 1,2-DAB that could be due to the variation in the monomer units and orientation along the copolymer chains. The formation of head-to-tail coupled p-aminodiphenylamine (PPD) type of mixed dimers/oligomers, presumably resulting from the dimerization of 1,2-DAB and 2-MA or 3-MA cation radicals, is proposed. An absorption peak around λ = 497 nm in the UV–vis spectra is assigned to these intermediates. A mechanism is proposed for the growth of the copolymers. Characteristic UV–vis features of the copolymers have been identified and their dependencies on the electrode potential are discussed. Clear variations in spectroelectrochemical properties of the materials from mixed solutions can be observed just by varying the concentration of 1,2-DAB and by replacing 3-MA with 2-MA in the feed. One of the possible reason for the difference in the properties of the copolymers of 2-MA and 3-MA might be the effect of the electron-donating methyl group in meta-position resulting in an increased electron density in the second meta-position contributing to meta-coupling of radical cations.

Surface tensions of aqueous solutions of sodium salts of chloride, bromide and nitrate; potassium salts of chloride, bromide and nitrate; lithium chloride and potassium iodide has been determined experimentally at different concentrations and temperatures ranging from 0.10 to 2.00 mol kg−1 and 10–30 °C, respectively. Concentration and temperature dependence of the surface tension of the selected salts has been studied for further estimation of surface excess concentration, enthalpy and entropy of surface formation. The results show that the surface excess concentration decreases linearly with concentration but remains almost constant with the variations of temperature. Similarly the enthalpy of surface formation was observed to decrease with concentration but remained almost constant with the change in temperature. The entropy of surface formation was found to decrease with concentration in most cases.

This paper presents synthesis and characterization of soluble polyaniline-dodecylbenzenesulfonic acid (PANI-DBSA) via inverse polymerization. A mixture of chloroform and 2-butanol was used as dispersion medium for the first time. This polymerization pathway leads to the formation of PANI-DBSA salts which are completely soluble in a number of common organic solvents (such as DMSO, DMF, chloroform and in a mixture of toluene) and 2-propanol (so far highest number of solvents for solubility of PANI). The influence of synthesis parameters such as concentration of aniline, benzoyl peroxide and dodecylbenzenesulfonic acid (DBSA) on the yield and other properties of the resulting PANI-DBSA salts was studied. Further characterization of the synthesized materials was done with the help of viscosity measurements, UV–Vis spectroscopy, cyclic voltammetry, XRD and SEM. TGA was used to analyze the thermal properties of synthesized polymer. The synthesized salts were found to be highly stable.

An attempt has been made to evaluate comparatively the behavior of 2-methylaniline (2MA) and 3-methylaniline (3MA) during electrochemical homo- and copolymerization. As comonomer in the copolymerization bath with 2MA and 3MA 1,2-diaminobenzene (1,2-DAB), an aromatic diamine, was selected. Cyclic voltammetry was used both for the electrochemical synthesis and characterization of the homopolymers and copolymers on a gold electrode. In the copolymerization bath mixed solutions of the monomers having different concentrations of 1,2-DAB and a constant concentration of 2MA or 3MA were used. The voltammograms exhibit different behavior for different concentration ratios of the monomer in the feed. The homopolymers poly(2-methylaniline) (P2MA) and poly(3-methylaniline) (P3MA) show similar electrochemical properties. However, differences were observed in the properties between the copolymers of 2MA and 3MA with 1,2-DAB that could be due to the variation in the monomer units and orientation along the copolymer chains. The copolymerization of 1,2-DAB seems to be more facilitated when instead of 3MA, 2MA is present as comonomers. The effect of scan rate and pH on the electrochemical activity was studied. The copolymers are surface confined, electroactive and show good electrochemical activity even at pH = 8.0 and pH = 9.0 in case of poly(1,2-DAB-co-3MA) and poly(1,2-DAB-co-2MA), respectively. In situ conductivity measurements further support the differences in the structure of the copolymers of 1,2-DAB with 2MA and 3MA.

A comparative discussion of the electrochemical and spectroelectrochemical properties of poly(o-phenylenediamine) POPD, an aromatic diamine, is presented. In situ conductance measurements show that POPD shows some conductance around the redox peak potentials, i.e. = −0.02 < ESCE < 0.00 V. In situ UV–vis and Raman spectroelectrochemical results suggest that radical cations of polyaniline (PANI)-like segments in POPD backbone might be responsible for imparting conductance to this otherwise nonconducting polymer (as commonly supposed in the literature). The presence of radical cations was confirmed by in situ Raman spectra showing a band at 1390 cm−1 characteristic of a C–N+-stretching vibration having an intermediate single/double bond character and being coupled to quinoid rings/polaronic form of PANI segments in the polymer. Results also reveal that POPD shows a close correlation between its electrochemical and spectroelectrochemical properties in the range of −0.02 < ESCE < 0.00 V, and provide support for the suggested presence of doped PANI-like segments in said potential range.

Conducting homo- and copolymers of o -phenylenediamine (OPD) and o -toluidine (OT) were studied with in situ Raman spectroelectrochemical measurements using red laser illumination (647.1 nm) within a broad electrochemical potential window ranging from E SCE = −0.2 to 0.6 V. Experimental results show that the spectroelectrochemical characteristics of the polymers synthesized from mixed OT and OPD solution, particularly at lower OPD feed concentration, are considerably different from those of the corresponding homopolymers, suggesting formation of a copolymer during the electrolysis of mixed solutions of OPD and OT. Specific Raman features of the homo-/copolymers have been identified. The effects of polymerization conditions with respect to OPD feed concentration on the Raman intensity of various bands of the polymers are discussed. The influence of applied electrode potential on the Raman intensity of various bands is demonstrated.

A comparative discussion of the electrochemical and spectroelectrochemical properties of poly(o-toluidine) POT, a methyl substituted derivative of polyaniline, PANI, is presented. POT exists in various oxidation states and shows an insulator to conductor transition when doped by electrooxidation. The transformation of the polymer film from its non-conducting leucoemeraldine to its conducting emeraldine state and further on to its again non-conducting pernigraniline form was observed with different techniques including cyclic voltammetry, in situ conductivity measurements and in situ UV–vis and Raman spectroelectrochemical methods. Results reveal that POT shows a good correlation between its electrochemical and spectroelectrochemical properties in its different oxidation states.

Surface tension of aqueous electrolyte solutions has been determined experimentally. Concentration and temperature dependence of the surface tension of three different salts has been studied. These include the chloride, bromide and iodide salts of potassium. The study was conducted at five different concentrations, i.e. 0.1, 0.5, 1.0, 1.5 and 2.0 mol dm −3 , and five different temperatures ranging from 10 to 30 °C with 5 °C interval. The surface tension data were fitted into linear regression for estimation of surface excess concentration using Gibbs adsorption equation. The thermodynamic quantities of surface formation such as enthalpy and entropy were estimated from the slopes (d γ /d T ) C of surface tension versus temperature plots at constant concentration. Concentration and temperature dependence of surface excess concentration and thermodynamic parameters of surface formation have been discussed.

Results of in situ UV–vis spectroelectrochemical studies of the electropolymerization of o-phenylenediamine (OPD), m-toluidine (MT) and the copolymerization of OPD with MT are reported. Electropolymerization was performed in aqueous acidic medium at a constant potential of ESCE = 1.0 V at an indium doped tin oxide (ITO) coated glass electrode. The course of homopolymerization was followed for MT and OPD solutions with various monomer concentrations. The spectral characteristics of the mixed solutions were studied at a constant concentration of MT and various concentrations of OPD in the comonomer feed. An absorption band at λ = 497 nm was assigned to the head-to-tail mixed dimer/oligomer resulting from the cross reaction between OPD and MT cation radicals. UV–vis spectra recorded during copolymerization show dependence of the growth of the band at λ = 497 nm on OPD concentration in the feed. At lower OPD feed concentration it appears as the major band in the corresponding spectra. The UV–vis spectra recorded for the copolymer films suggest the incorporation of both monomer units in the copolymer. The FT-IR spectra of the copolymers show the presence of phenazine type structures in the copolymer backbone.

Electroactive copolymers of m-toluidine (MT) and o-phenylenediamine (OPD) were prepared electrochemically in aqueous sulfuric acid by potential cycling and characterized with cyclic voltametry, in situ conductivity measurements and FT-IR spectroscopy. The voltammograms of the copolymers exhibit different behavior for different concentrations of OPD in the comonomer feed. At optimum conditions the resulting poly(OPD-co-MT) shows an extended useful potential range of the redox activity as compared to the corresponding homopolymers. The effect of scan rate and pH on the electrochemical activity was studied. The copolymer was electrochemically active even at pH 8.0. The stability of the copolymer film was also tested. The copolymer has a potential region of maximum conductivity different from that of PMT and POPD. The conductivity of the copolymer is between the conductivity of the homopolymers. The vibrational bands at 3122/3450 and 2922/875 cm−1 in the FT-IR spectra of the copolymer indicate the presence of both OPD and MT units, respectively, in the copolymer backbone.

Electroactive copolymers of o-toluidine (OT) and o-phenylenediamine (OPD) were electrosynthesized in aqueous sulfuric acid. Cyclic voltammetry was used both for the electrochemical synthesis and characterization of the copolymers deposited on a gold electrode. The voltammograms exhibited different behavior for different concentrations of OPD in the feed. At optimum conditions the rate of copolymerization was found to be between the rates of homopolymerizations. The resulting poly(OPD-co-OT) shows an extended useful potential range of the redox activity as compared to the corresponding homopolymers. The effect of scan rate and pH on the electrochemical activity was studied. The copolymer was electrochemically active even at pH 9.0. In situ conductivity measurements further support the formation of a copolymer because the copolymers have a potential region of maximum conductivity completely different from that of POT. However, conductivities of the copolymers were lower by 2–2.7 orders of magnitude than of POT.

Polypyrrole (PPy) and poly(pyrrole-2,6-dimethyl-β-cyclodextrin) [P(Py-β-DMCD)] films prepared by potential cycling in aqueous acidic solutions on indium tin oxide (ITO)-coated glass and gold electrodes were studied by in situ UV–vis and Raman spectroscopy. Characteristic UV–vis and Raman bands were identified and their dependencies on the electrode potential have been discussed. Spectroelectrochemical results reveal differences both in the position of the spectral bands and their potential dependence for PPy and P(Py-β-DMCD) films indicating interactions between polymer chains and CDs during electropolymerization process. The films were also characterized by cyclic voltammetry and FT-IR spectroscopy.

Phytochemical investigations on the chloroform and ethyl acetate soluble fractions of the roots of Ranunculus repens led to the isolation of methyl 3,4,5-trihydroxybenzoate 1, R(+)- 4-methoxydalbergione 2 and R(+)-dalbergiophenol 3. The structures of these compounds were established through spectral studies including 1D and 2D NMR experiments and by comparison with literature data. These compounds showed potent inhibitory activity against urease.

Polyaniline (PANI) is one of the most promising candidates for possible technological applications. PANI has potential applications in batteries, anion exchanger, tissue engineering, inhibition of steel corrosion, fuel cell, sensors and so on. However, its insolubility in common organic solvents limits its range of applications. In the present study an attempt has been made to synthesize soluble polyaniline salt via inverse polymerization pathway using benzoyl peroxide as oxidant and dodecylbenzenesulfonic acid (DBSA) as dopant as well as a surfactant. A mixture of chloroform and 2-butanol was used as dispersion medium for the first time. The influence of synthesis parameters such as concentration of aniline, benzoyl peroxide and DBSA on the yield and other properties of the resulting PANI salt was studied. The synthesized PANI salt was found to be completely soluble in DMSO, DMF, chloroform and in a mixture of toluene and 2-propanol. The synthesized polymer salt was also characterized with cyclic voltam-metry, SEM, XRD, UV-Vis spectroscopy and viscosity measurements. TGA was used to analyze the thermal properties of synthesized polymer. The extent of doping of the PANI salt was determined from UV-Vis spectra and TGA analysis. The activation energy for the degradation of the polymer was calculated with the help of TGA.

Results of in situ UV-visible (UV/vis) spectroelectrochemical studies of the electro-oxidation of o-phenylenediamine (OPD), o-toluidine (OT), and their mixtures, as well as the redox activity of the obtained polymer films, performed in an aqueous acidic solution at an indium-doped tin oxide-coated glass electrode, are reported. UV-vis spectra recorded at different time intervals during the electrolysis of mixed solutions, containing a constant concentration of OT and various OPD concentrations in the feed, are different from those obtained with single monomer solutions. A band at λ = 497 nm was assigned to the head-to-tail mixed dimer/oligomer resulting from the cross reaction between OPD and OT cation radicals. At lower OPD feed concentration this band appears as the major band. The dependence of the spectral characteristics of the copolymer films on the OPD feed concentration was deduced. The UV-vis spectra of the copolymers reveal that the copolymer backbone probably consists of a mixture of copolymer chains with different monomer contents and has a significant number of block segments. Fourier transform infrared spectral analysis of the copolymers suggests the presence of both OPD and OT units and thus the formation of a copolymer during the electrolysis of mixed solutions of OPD and OT.