Polyaniline/polyacrylamide conducting composite hydrogel with a porous structure

A polyaniline/polyacrylamide composite hydrogel is synthesized, characterized and measured. Fourier transform infrared spectroscopy reveals that partial polyaniline chains have grafted on the nitrogen atoms of polyacrylamide. X-ray diffraction shows that typical polyaniline crystallization is formed in polyaniline/polyacrylamide composite, which is advantageous to increase the electrical conductivity of the composite hydrogel. UV–Vis spectra indicates the formation of high conductive emeraldine polyaniline salt in polyaniline/polyacrylamide composite. Scanning electron microscopy shows a typical porous structure in the composite hydrogel. The polyaniline/polyacrylamide hydrogel has a good conductivity of 0.6 S/cm and good release stability in acidic and neutral conditions.     

Preparation and characterization of polyaniline/chitosan blend film

Films consisting of a blend of a chitosan hydrogel and a conductive polymer, polyaniline (PANI), were prepared and characterized for their electrical and mechanical properties. Polyaniline in emeraldine base (EB) form was dispersed in chitosan solution and blend films were obtained by solution casting. The PANI particles in the blend films were then doped with HCl where we observed reductions in the film tensile strength and Young's modulus by about 30%, but the films electrical conductivity increased by 6 orders of magnitude. The highest electrical conductivity of the blend films was of the order 10⁻⁴ S/cm. The electrical and mechanical properties of the films varied with polyaniline content, acid dopant type, acid dopant concentration, and doping time.     

Biomimetic synthesis of water-soluble conducting copolymers/homopolymers of pyrrole and 3,4-ethylenedioxythiophene

A novel biomimetic route for the synthesis of electrically conducting homopolymers/copolymers of pyrrole and 3,4-ethylenedioxythiophene (EDOT) in the presence of a polyelectrolyte, such as polystyrene sulfonate (SPS), is presented. A poly(ethylene glycol)-modified hematin (PEG-hematin) was used to catalyze the homopolymerization of pyrrole and EDOT as well as copolymerization of EDOT and pyrrole in the presence of SPS to yield homopolymers of polypyrrole/SPS and PEDOT/SPS as well as a polypyrrole-co-poly(3,4-ethylenedioxythiophene)/SPS complex. Spectroscopic characterization [UV-visible, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS)], thermal analysis, (TGA), and electrical conductivity studies for these complexes indicated the presence of a stable and electrically conductive form of these polymers. Furthermore, the presence of SPS that serves as a charge-compensating dopant in this complex provides a unique combination of properties such as processability and water solubility.     

Heterogeneous preparation of cellulose–polyaniline conductive composites with cellulose activated by acids and its electrical properties

A series of conductive composites cellulose–polyaniline (PANI) were heterogeneously synthesized by chemical oxidative polymerization of aniline with native cellulose activated by various acids. The chemical structure and morphology of the composites were examined by FT-IR analysis and TEM. TGA was used to study their thermal properties. The composites prepared using the di-basic acids exhibited more favorable conductivity than the composites prepared using the monobasic acids. The content of PANI increased with increasing of activation time, and while the conductivity decreased because of the aggregation of PANI particles at the activation time range from 50 to 120 min. Both the PANI content and the electrical conductivity increased with an increase of the amount of aniline, and reached the maximum values at the 0.5 g aniline, respectively. The acids were able to successfully activate cellulose and lead to the improvement of the accessibility and reactivity of the O–H groups. The composites were highly stable compared to pure cellulose due to the safeguard from PANI slices. This work provided a facile method for the synthesis of cellulose–polyaniline conductive composites with excellent conductivity.     

Labeless AC impedimetric antibody-based sensors with pgml(-1) sensitivities for point-of-care biomedical applications

This paper describes the development and characterisation of labeless immunosensors for (a) the cardiac drug digoxin and (b) bovine serum albumin (BSA). Commercial screen-printed carbon electrodes were used as the basis for the sensors. Two methods were used to immobilise antibodies at the electrode surface. Aniline was electropolymerised onto these electrodes to form a thin planar film of conductive polyaniline; the polyaniline film was then utilised as a substrate to immobilise biotinylated anti-digoxin using a classical avidin-biotin affinity approach. As an alternative approach, poly(1,2-diaminobenzene) was electrodeposited onto the carbon electrodes and this modified surface was then sonochemically ablated to form an array of micropores. A second electropolymerisation step was then used to co-deposit conductive polyaniline along with antibodies for BSA within these pores to produce a microarray of polyaniline protrusions with diameters of several mum, containing entrapped anti-BSA. The resulting antibody grafted electrodes were interrogated using an AC impedance protocol before and following exposure to digoxin or BSA solutions, along with control samples containing a non-specific IgG antibody. The impedance characteristics of both types of electrode were changed by increasing concentrations of antigen up to a saturation level. Calibration curves were obtained by subtraction of the non-specific response from the specific response, thereby eliminating the effects of non-specific adsorption of antigen. Both the use of microelectrode arrays and affinity binding protocols showed large enhancements in sensitivity over planar electrodes containing entrapped antibodies and gave similar sensitivities to our other published work using affinity-based planar electrodes. Detection limits were in the order of 0.1ngml(-1) for digoxin and 1.5ngml(-1) for BSA.     

A Polyaniline‐Coated Sulfur/Carbon Composite with an Enhanced High‐Rate Capability as a Cathode Material for Lithium/Sulfur Batteries

Polyaniline‐coated sulfur/conductive‐carbon‐black (PANI@S/C) composites with different contents of sulfur are prepared via two facile processes including ball‐milling and thermal treatment of the conductive carbon black and sublimed sulfur, followed by an in situ chemical oxidative polymerization of the aniline monomer in the presence of the S/C composite and ammonium persulfate. The microstructure and electrochemical performance of the as‐prepared composites are investigated systematically. It is demonstrated that the polyaniline, with a thickness of ≈5–10 nm, is coated uniformly onto the surface of the S/C composite forming a core/shell structure. The PANI@S/C composite with 43.7 wt% sulfur presents the optimum electrochemical performance, including a large reversible capacity, a good coulombic efficiency, and a high active‐sulfur utilization. The formation of the unique core/shell structure in the PANI@S/C composites is responsible for the improvement of the electrochemical performance. In particular, the high‐rate charge/discharge capability of the PANI@S/C composites is excellent due to a synergistic effect on the high electrical conductivity from both the conductive carbon black in the matrix and the PANI on the surface. Even at an ultrahigh rate (10C), a maximum discharge capacity of 635.5 mA h per g of sulfur is still retained for the PANI@S/C composite after activation, and the discharge capacity retention is over 60% after 200 cycles.     

Green synthesis of conductive polyaniline by Trametes versicolor laccase using a DNA template

The green synthesis of highly conductive polyaniline by using two biological macromolecules, i.e laccase as biocatalyst, and DNA as template/dopant, was achieved in this work. Trametes versicolor laccase B (TvB) was found effective in oxidizing both aniline and its less toxic/mutagenic dimer N‐phenyl‐p‐phenylenediamine (DANI) to conductive polyaniline. Reaction conditions for synthesis of conductive polyanilines were set‐up, and structural and electrochemical properties of the two polymers were extensively investigated. When the less toxic aniline dimer was used as substrate, the polymerization reaction was faster and gave less‐branched polymer. DNA was proven to work as hard template for both enzymatically synthesized polymers, conferring them a semi‐ordered morphology. Moreover, DNA also acts as dopant leading to polymers with extraordinary conductive properties (～6 S/cm). It can be envisaged that polymer properties are magnified by the concomitant action of DNA as template and dopant. Herein, the developed combination of laccase and DNA represents a breakthrough in the green synthesis of conductive materials.     

Electrical conductivity in a mixed-species biofilm

Geobacter sulfurreducens can form electrically conductive biofilms, but the potential for conductivity through mixed-species biofilms has not been examined. A current-producing biofilm grown from a wastewater sludge inoculum was highly conductive with low charge transfer resistance even though microorganisms other than Geobacteraceae accounted for nearly half the microbial community.     

Effects of glucosinolates and flavonoids on colonization of the roots of Brassica napus by Azorhizobium caulinodans ORS571

Plants of Brassica napus were assessed quantitatively for their susceptibility to lateral root crack colonization by Azorhizobium caulinodans ORS571(pXLGD4) (a rhizobial strain carrying the lacZ reporter gene) and for the concentration of glucosinolates in their roots by high-pressure liquid chromatography (HPLC). High- and low-glucosinolate-seed (HGS and LGS) varieties exhibited a relatively low and high percentage of colonized lateral roots, respectively. HPLC showed that roots of HGS plants contained a higher concentration of glucosinolates than roots of LGS plants. One LGS variety showing fewer colonized lateral roots than other LGS varieties contained a higher concentration of glucosinolates than other LGS plants. Inoculated HGS plants treated with the flavonoid naringenin showed significantly more colonization than untreated HGS plants. This increase was not mediated by a naringenin-induced lowering of the glucosinolate content of HGS plant roots, nor did naringenin induce bacterial resistance to glucosinolates or increase the growth of bacteria. The erucic acid content of seed did not appear to influence colonization by azorhizobia. Frequently, leaf assays are used to study glucosinolates and plant defense; this study provides data on glucosinolates and bacterial colonization in roots and describes a bacterial reporter gene assay tailored easily to the study of ecologically important phytochemicals that influence bacterial colonization. These data also form a basis for future assessments of the benefits to oilseed rape plants of interaction with plant growth-promoting bacteria, especially diazotrophic bacteria potentially able to extend the benefits of nitrogen fixation to nonlegumes.     

Effects of Glucosinolates and Flavonoids on Colonization of the Roots of Brassica napus by Azorhizobium caulinodans ORS571

Plants of Brassica napus were assessed quantitatively for their susceptibility to lateral root crack colonization by Azorhizobium caulinodans ORS571(pXLGD4) (a rhizobial strain carrying the lacZ reporter gene) and for the concentration of glucosinolates in their roots by high-pressure liquid chromatography (HPLC). High- and low-glucosinolate-seed (HGS and LGS) varieties exhibited a relatively low and high percentage of colonized lateral roots, respectively. HPLC showed that roots of HGS plants contained a higher concentration of glucosinolates than roots of LGS plants. One LGS variety showing fewer colonized lateral roots than other LGS varieties contained a higher concentration of glucosinolates than other LGS plants. Inoculated HGS plants treated with the flavonoid naringenin showed significantly more colonization than untreated HGS plants. This increase was not mediated by a naringenin-induced lowering of the glucosinolate content of HGS plant roots, nor did naringenin induce bacterial resistance to glucosinolates or increase the growth of bacteria. The erucic acid content of seed did not appear to influence colonization by azorhizobia. Frequently, leaf assays are used to study glucosinolates and plant defense; this study provides data on glucosinolates and bacterial colonization in roots and describes a bacterial reporter gene assay tailored easily to the study of ecologically important phytochemicals that influence bacterial colonization. These data also form a basis for future assessments of the benefits to oilseed rape plants of interaction with plant growth-promoting bacteria, especially diazotrophic bacteria potentially able to extend the benefits of nitrogen fixation to nonlegumes.     

Synthesis of electroconductive polyaniline using immobilized laccase

A new method for synthesis of the conductive complex between polyaniline (PANI) and poly(2-acrylamido-2-methyl-1-propanosulfonic acid) (PAMPS) was proposed; in this method, the immobilized laccase from the basidiomycete Trametes hirsuta is used as a biocatalyst for aniline oxidative polymerization. The conditions for laccase immobilization on CM cellulose by bifunctional Woodward’s reagent were optimized. The catalytic properties of immobilized and native laccases were compared. The immobilized laccase appeared an efficient catalyst for the oxidative radical polymerization of aniline on polysulfonic acid matrix at 4°C. It was demonstrated that the immobilized enzyme could be repeatedly used for enzymatic synthesis of this polymer. Several spectral characteristics of the PANI/PAMPS complexes synthesized at various pH values were studied. The conductance of PANI specimens produced using immobilized laccase as a catalyst was 13 mS/cm.     

Comparison of thermal insulation performance of fibrous materials for the advanced space suit

The current multi-layer insulation used in the extravehicular mobility unit (EMU) will not be effective in the atmosphere of Mars due to the presence of interstitial gases. Alternative thermal insulation means have been subjected to preliminary evaluation by NASA to attempt to identify a material that will meet the target conductivity of 0.005 W/m-K. This study analyzes numerically the thermal conductivity performance for three of these candidate insulating fiber materials in terms of various denier (size), interstitial void fractions, interstitial void media, and orientations to the applied temperature gradient to evaluate their applicability for the new Mars suit insulation. The results demonstrate that the best conductive insulation is achieved for a high-void-fraction configuration with a grooved fiber cross section, aerogel void medium, and the fibers oriented normal to the heat flux vector. However, this configuration still exceeds the target thermal conductivity by a factor of 1.5.     

Langer-Giedion syndrome and deletion in the long arm of chromosome 8

Del(8) (q24.11-q24.13) were detected in 3 patients with typical Langer-Giedion syndrome (LGS) and studied by high-resolution methods. Analysis of the literature strongly suggests the chromosomal ethiology of the LGS, because in all patients examined in detail a deletion of the segment 8(q24.11-q24.13) was revealed, which is critical for the LGS. Interrelationships between the LGS and two monogenic conditions-tricho-rhino-phalangeal syndrome type I and multiple exostoses are discussed. The possible role of c-myc oncogene in exostoses' (including those in LGS) origin is anticipated.     

Reversible immobilization of uricase on conductive polyaniline brushes grafted on polyacrylonitrile film

Polyacrylonitrile film (PAN) surfaces were modified with chemical polymerization of conductive polyaniline (PANI) in the presence of potassium dichromate as an oxidizing agent. The conductive films were used for immobilization of uricase. The surface resistance of the conductive film in this work was found to be 0.97 kΩ/cm. The maximum amount of immobilized enzyme on conductive film containing 2.4% PANI was about 216 μg/cm². The optimum pH for free and immobilized enzymes was observed at 7.0 and 7.5, respectively. The K _m values for free and immobilized uricase were found to be 94 and 138 μM, respectively. V _max values were calculated as 1.87 and 1.63 U/mg protein for the free and immobilized enzymes, respectively. Immobilized uricase exhibited ~68% of its original activity even after 2 months of storage at 4 °C while the free enzyme lost its initial activity within 4 weeks.     

Development of a label-free impedance biosensor for detection of antibody-antigen interactions based on a novel conductive linker

We developed a label-free impedance biosensor based on an innovative conductive linker for detecting antibody-antigen interactions. As the often used conventional long chain thiol is a poor conductor, it is not a suitable material for use in a faradaic biosensor. In this study, we adopted a thiophene-based conductive bio-linker to form a self-assembled monolayer and to immobilize the bio-molecules. We used cyclic voltammetry and impedance spectroscopy to verify the enhanced conductivity properties. Results showed that the electron transfer resistance of this new conductive linker was 3 orders of a magnitude lower than for a case using a conventional long chain thiol linker. With the decreased impedance (i.e. increased faradaic current), we can obtain a higher signal/noise ratio such that the detection limit is improved. Using fluorescence microscopy, we verified that our new conductive linker has a protein immobilization capability similar to a conventional long chain thiol linker. Also, using S100 proteins, we verified the protein interaction detection capability of our system. Our obtained results showed a linear dynamic range from 10 ng/ml to 10 μg/ml and a detection limit of 10 ng/ml. With our new conductive linker, an electrochemical impedance biosensor shows great potential to be used for point-of-care applications.     

Photoelectropolymerization of aniline in a dye-sensitized solar cell.

A dye-sensitized solar cell was constructed using a porphyrin photosensitizer and, in place of the usual iodide redox system, a solution in aniline solvent containing lithium perchlorate electrolyte, camphorsulfonic acid, and poly(ethylene oxide) copolymer. Irradiation generated polyaniline within the cell, initially following a proposed photoelectropolymerization mechanism, and eventually operating as a solar cell with polyaniline as the hole transport medium. Overall energy conversion efficiency was 0.8% at moderate light intensities (14.6 mW cm(-2)) but lower at higher light intensities due to conductivity limitations.     

Synthesis of conducting polyelectrolyte complexes of polyaniline and poly(2-acrylamido-3-methyl-1-propanesulfonic acid) catalyzed by pH-stable palm tree peroxidase

Comparison of the stability of five plant peroxidases (horseradish, royal palm tree leaf, soybean, and cationic and anionic peanut peroxidases) was carried out under acidic conditions favorable for synthesis of polyelectrolyte complexes of polyaniline (PANI). It demonstrates that palm tree peroxidase has the highest stability. Using this peroxidase as a catalyst, the enzymatic synthesis of polyelectrolyte complexes of PANI and poly(2-acrylamido-3-methyl-1-propanesulfonic acid) (PAMPS) was developed. The template polymerization of aniline was carried out in aqueous buffer at pH 2.8. Varying the concentrations of aniline, PAMPS, and hydrogen peroxide as reagents, favorable conditions for production of PANI were determined. UV-vis-NIR absorption and EPR demonstrated that PAMPS and PANI formed the electroactive complex similar to PANI doped traditionally using low molecular weight sulfonic acids. The effect of pH on conformational variability of the complex was evaluated by UV-vis spectroscopy. Atomic force microscopy showed that a size of the particles of the PANI-PAMPS complexes varied between 10 and 25 nm, depending on a concentration of PAMPS in the complex. The dc conductivity of the complexes depends also on the content of PAMPS, the higher conductivity being for the complexes containing the lower content of the polymeric template.     

Efficiency of enzymatic and non-enzymatic catalysts in the synthesis of insoluble polyphenol and conductive polyaniline in water

The present work analyzes the potential use of white-rot fungi (WRF) and hematin for phenol and aniline polymerization, as a low-cost alternative to horseradish peroxidase (HRPC). The objective is to evaluate the capability of these catalysts to produce tailor-made aniline as well as to eliminate phenols by precipitation from aqueous solution. 4-Aminoantypirine (4AAP) was used to test phenoxide formation by crude protein preparations of white-rot fungi at selected conditions. The crude extracts of Pleurotus sajor-caju (PSC) were selected because of the promising values obtained for the phenoxide formation rate. HRPC/H₂O₂ and P. sajor-caju derived enzymes/H₂O₂ (PSC/H₂O₂) systems produced soluble polyaniline in the presence of polystyrene sulphonated (PES), with high aniline conversions at 45 °C. For the case of insoluble polyphenol production, the PSC-derived enzymes, in absence of hydrogen peroxide, produced insoluble polyphenol with similar efficiencies as those found with HRPC or hematin in a one step phenol treatment (near 40% phenol conversion). For the aniline process, at least 75% aniline conversion was obtained when using PSC enzymes at room temperature. After long reaction times, the lignin-modifying enzymes derived from PSC only produced a conductive form of polyaniline (PANI) at lower temperatures than those required when employing HRPC. Fungal enzymes look promising for eliminating aniline/phenol from wastewaters since the obtained results demonstrated that they are able to polymerizate and precipitate them from aqueous solutions.     

Reliability, repeatability and accuracy of the falling head method for hydraulic conductivity measurements under laboratory conditions

The aim of this study was to verify under lab conditions the reliability, repeatability and accuracy of the falling head method (FHM) for hydraulic conductivity measurements. The FHM is a reliable procedure that has slight variations (less than 10%) in repeated measurements and turns out to be a reliable technique to record the hydraulic conductivities typically described for clogged and unclogged subsurface-flow constructed wetlands (from 4 to ca. 360 m/day). The accuracy of the method is acceptable considering difficulties in the measurement of hydraulic conductivity in highly conductive media. Accordingly, results show measurement deviations of 20% when compared with a laboratory constant head method for highly conductive media (higher than 250 m/day), and 80% for media with low hydraulic conductivity (lower than 50 m/day). The main conclusion of the present paper is that of the FHM is a reliable and repeatable technique for hydraulic conductivity measurements and it is accurate enough for on-site clogging assessment in full-scale constructed wetlands.