Effect Of Aniline Concentration Research Articles

Facile approach to produce water-dispersible conducting polyaniline powder

In this work, electrically conducting polyaniline (PAni) was obtained as a highly water-dispersible powder. The chemical aniline oxidative polymerization was conducted in the presence of poly(styrenesulfonic acid) (PSS) using ammonium peroxydisulfate (APS) as oxidative agent. The effects of aniline concentration and Ani:APS molar ratio on the redispersion capability of PAni.PSS powders were investigated. The purified PAni.PSS powders were redispersed in water and evaluated by UV–vis spectroscopy, field-emission scanning electron microscopy (FE-SEM) and dynamic light scattering (DLS). The electrical conductivity was measured on the dried material by the four-point probe method. As-prepared dispersions were also evaluated for comparative analyses. Conducting PAni.PSS as a powder with remarkable dispersibility and stability in water was obtained using Ani:APS 4:1 and aniline concentration of 0.256 mol.L−1. This material presented electrical conductivity of 10-3 S. cm−1 and granular morphology. Nanoparticles were obtained after sonication in water for only 4 min, with reproducible results. This colloidal dispersion remained stable for at least two months. Further analyses of zeta potential and stability in alkaline medium revealed negatively charged particles without flocculation signs in alkaline pHs for 240 h. At lower aniline concentration (0.032 mol.L−1) particles with 10 nm were obtained, however, not adequate for typical filtration. At Ani:APS 1:1 molar ratio yielded larger particles with heterogeneous distribution and partial precipitation.

Effect of Aniline Concentration on the Morphology and Electrochemical Properties of DBSA-Doped Polyaniline for Flexible Supercapacitor Electrode Materials

Polyaniline as a supercapacitor electrode material has attracted great research interest due to its advantages, especially including high pseudocapacitance. Dodecylbenzenesulfonic acid-doped polyaniline materials are prepared at different aniline concentrations and characterized by various measurements. The effect of the aniline concentration on the morphology, chemical structure, crystallinity, and electrochemical properties is thoroughly investigated. Based on the morphology alteration with the increase of aniline concentration, the formation mechanism of dodecylbenzenesulfonic acid-doped polyaniline microstructure is proposed. Dodecylbenzenesulfonic acid-doped polyaniline with an aniline concentration of 0.5 mol/L exhibits the superior electrochemical properties with a specific capacitance of 146 F/g, low charge transport resistance of 1.27 Ω, and steep slope in the low frequency region. In combination with its solubility, dodecylbenzenesulfonic acid-doped polyaniline is an excellent candidate for the electrode materials of a flexible supercapacitor.

Surface modification of poly (L-lactic acid) films to improve electrical conductivity by surface entrapment/in situ polymerization methods

Electrical properties play an important role in the interaction of cells and biomaterials. The aim of this study was to increase surface electrical conductivity of poly (L-lactic acid) (PLLA) films by polyaniline (PANI) using surface entrapment (SE) and surface entrapment in situ polymerization (SEIP) methods. The entrapment modification technique was performed by the reversible gelation of the PLLA surface region following exposure to a solvent and non-solvent mixture, while PANI chains were diffused into the swollen PLLA surface. In SEIP method, PANI was entrapped through in situ chemical oxidative polymerization of aniline on PLLA films. The effects of PANI concentration, the ratios of solvents and immersion time on the electrical conductivity were studied by SE method. The effects of aniline concentration, doping effect, temperature and time of polymerization were evaluated by SEIP method too. The results obtained by attenuated total reflection Fourier transformer infrared spectroscopy, scanning electron microscopy and energy dispersive x-ray mapping analysis confirmed the presence of PANI on the surface of PLLA films. UV-visible analysis was employed to investigate the doping effect on the reduction of energy and conductivity of the films. Experimental results also indicated that the electrical conductivity, uniformity and density of the SEIP modified films were significant in comparison to those of the modified films by SE method.

Effect of monomer concentration on the performance of Polyaniline based redox capacitors

Supercapacitors are promising alternatives for answering the thirst for ever increasing demand for power. They bridge the gap between the batteries and the conventional capacitors. Redox capacitors in the family of supercapacitors consist of conducting polymers or transition metal oxide electrodes. In this study, symmetric redox capacitors have been fabricated utilizing Polyaniline electrodes and a Polyvinylidenefluoride based gel polymer electrolyte. The effect of aniline concentration on the performance of redox capacitors was investigated. Aniline concentration was varied from 0.20 M to 0.50 M. Capacitors were characterized using Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and Galvanostatic Charge-Discharge tests. Redox capacitor with 0.40 M aniline concentration showed the highest performance. From EIS measurements it was shown that the lowest relaxation time was 0.22 s. This implies that 0.40 M aniline system has the fastest ion movement behavior. Cyclic Voltammetry (CV) test of this capacitor resulted 81% of specific capacity retention between the 1 st and the 200 th cycle. Galvanostatic Charge-Discharge (GCD) for 1000 cycles showed an average discharging capacity of 323 F g -1 , power density of 760 W kg -1 and energy density of 6.5 Wh kg -1 . The results of this study confirm that aniline concentration has a significant effect on the performance of PANI films when they are served as electrodes in redox capacitors.

Fabrication of novel solid-state supercapacitor using a Nafion polymer membrane with graphene oxide/multiwalled carbon nanotube/polyaniline

In the current work, the effect of aniline concentration on the polymerization process and supercapacitive behavior of graphene oxide/multiwalled carbon nanotubes/polyaniline (GMP) nanocomposites were studied. Based on the obtained results, GMP nanocomposite with 0.5 M aniline (GMP5) was selected as the optimum concentration in terms of high current density and high specific capacitance. Nafion-based ionic polymer-free metal composite (IPFMC) supercapacitor was fabricated for the GMP5 nanocomposite. Solid-state symmetric supercapacitor was made after spraying of GMP5 in. on both sides of Nafion membrane. The electrochemical properties were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (CD), and electrochemical impedance spectroscopy (EIS) techniques in 0.5 M Na2SO4.The specific capacitance of 383.25 F g−1 (326 mF cm−2) and 527.5 F g−1 (42 mF cm−2) was obtained for the GMP5 in solid-state supercapacitor and three-electrode cell at a scan rate of 10 mV s−1, respectively. The maximum energy and power densities of 53.64 and 1777.4 W kg−1 were obtained for the IPFMC-based supercapacitor.

Reversible immobilization of glucose oxidase on polyaniline grafted polyacrylonitrile conductive composite membrane

Polyacrylonitrile membrane surfaces were modified with chemical polymerization of conductive polyaniline. The effect of aniline concentration on the grafting efficiency was investigated. As the amount of grafted PANI increased on the PAN membrane, the electrical resistance of composite membrane decreased. Composite (PAN/PANI)-1–5 membrane were used for reversible immobilization of GOD. The immobilization efficiency and the activity of the immobilized GOD were increased with increasing PANI contents of the composite membrane. The maximum amount of immobilized enzyme into composite PAN/PANI-5 membrane containing 2.1% PANI was about 251 μg/cm 2. Immobilized GOD exhibited 66% of its original activity even after two months of storage at 4 °C while the free enzyme lost its initial activity after three weeks.

Surface modification of polyacrylonitrile film by anchoring conductive polyaniline and determination of uricase adsorption capacity and activity

Polyacrylonitrile (PAN) films were modified with chemical polymerization of conductive polyaniline (PANI) in the presence of potassium dichromate as an oxidizing agent. The effect of aniline concentration on the grafting efficiency and on the electrical surface resistance of PAN and (PAN/PANI)-1–3 composite film was investigated. The surface resistances of the conductive composite films were found to be between 6.32 and 0.97 kΩ/cm. As the amount of grafted PANI increased on the PAN films, the electrical resistance of composite film decreased. The PAN/PANI composite films were also characterized using SEM and FTIR. The changes in the surface properties of the films were characterized by contact angle measurements. As expected, the PAN, PAN/PANI and PAN/PANI-uricase immobilized films, exhibited different contact angle values and surface free energy due to different interactive functional groups of the films. The conductive films were well characterized and used for immobilization of uricase. The amount of adsorbed enzyme increases with the increase of surface concentration of grafted fibrous polyaniline polymer. The maximum amount of immobilized enzyme onto composite film containing 2.4% PANI was about 216 μg/cm 2 (i.e., PAN/PANI-3). The immobilized uricase was reused 24 times in batch wise assay in a day. Finally, the immobilized uricase enzyme system was successfully fabricated and applied to determine the uric acid level in human serum samples.

The Effect of Aniline Concentration in the Ligand Exchange Reaction with Citrate-Stabilized Gold Nanoparticles

Sodium citrate reduction of hydrogen tetrachloroaurate is one of the most efficient routes in the synthesis of gold nanoparticles (AuNPs). However, a major limitation of this method is that it results only in citrate-stabilized AuNPs, and exchange reactions of the citrate for another stabilizer must be undertaken in cases where other surface functionalities are desired. These exchange reactions can be studied using a variety of techniques. Two techniques we have used for analysis are ultraviolet-visible spectroscopy, which takes advantage of the plasmon resonance (PR) of AuNPs, and liquid chromatography (LC) to examine residual exchanger in the supernatant at equilibrium. The exchange of the citrate on the surface of AuNPs with aniline was studied where different concentrations of aniline are added. While the equilibrium PR band spectra were similar for high and low concentrations of added aniline, the spectra as a function of time differed markedly. Surprisingly, increasing the concentration of added aniline slowed the evolution of a second red-shifted band. Transmission electron microscopy (TEM) imaging showed that addition of neither high nor low concentrations of aniline caused a significant difference in particle size, and the appearance of the large second band was most likely due to the presence of an oligomeric aniline species surrounding the particles. As aniline is known to undergo polymerization under a variety of conditions, it is postulated that aniline polymerization is a competitive event to the ligand exchange process, and increasing the aniline concentration increases the likelihood of polymerization kinetically competing with association of the aniline species interacting with the AuNP surface. This was further supported by LC data, which demonstrated that the aniline exchanged at approximately 4% of the initial amount of citrate present in the synthetic mixture.

Polyaniline grafted polyacylonitrile conductive composite fibers for reversible immobilization of enzymes: Stability and catalytic properties of invertase

Polyacylonitrile fibers (PAN) surfaces were modified with chemical polymerization of conductive polyaniline (PANI) in the presence of potassium dichromate as an oxidizing agent. The effect of aniline concentration on the grafting efficiency and on the electrical surface resistance of PAN/PANI composite fibers was investigated. The surface resistance of the conductive composite fibers in this work was found to be between 8.0 and 0.5 kΩ/cm. As the amount of grafted PANI increased on the PAN fibers the electrical resistance of composite fibers decreased. The PAN/PANI composite fibers were characterized by SEM and FTIR studies. Composite PAN/PANI fibers were used for reversible immobilization of invertase. The immobilization efficiency and the activity of the immobilized invertase (from 1.0 mg/mL invertase solution at pH 5.5) were increased with increasing PANI contents of the composite fibers. The maximum amount of immobilized enzyme onto composite fibers containing 2.0% PANI was about 76.6 mg/g. The optimum pH for the free enzyme was observed at 5.0. On the other hand, immobilized invertase yielded a broad optimum pH profile between pH 5.0 and 7.0. Immobilized invertase exhibited 83% of its original activity even after two months storage at 4 °C while the free enzyme showed only 7% of its initial activity.

Polyaniline Nanofiber Synthesis by Co-Use of Ammonium Peroxydisulfate and Sodium Hypochlorite

The polymerization to polyaniline nanofibers was carried out in an aqueous system using aniline, 1 M HCl. and ammonium peroxydisulfate (APS) with additional use of sodium hypochlorite solution as a co-oxidant. The addition of sodium hypochlorite solution was made either before or after the addition of APS. This new method always produces polyaniline nanofibers with long length. Additional advantages of this new method are discussed. The effect of aniline concentration, hypochlorite concentration, different acid use, reaction temperature, and both aniline and hypochlorite purity on morphology and electrical property of the nanofibers synthesized by this new method was investigated.

The characteristic of electrochemical oxidation of aniline on SnO2/Ti electrode

The characteristic of electrochemical oxidation of aniline on SnO2/Ti electrode is studied. The results indicate that SnO2/Ti electrode dopedF plays a wonderful role in the oxidation of aniline comparing with Pt electrode. The kinetics factors that influence the oxidation rate of aniline on the SnO2/Ti electrode are determined by the dissolving of the film on the electrode. The dissolving of the film consisted of intermediate products on the electrode is the slow step. The effects of aniline concentration, pH in aniline solution and the current density (i) on the rate of aniline oxidation, the complexity of intermediate products and the basic category of the intermediate products consisted of the film are introduced.

Electrochemical Oxidation for the Degradation of Aniline on the SnO<sub>2</sub>/Ti Anode

The characteristic of electrochemical degradation of aniline on SnO2/Ti anode have been studied. The results indicate that SnO2/Ti anode doped with F plays an obvious role of electrocatalysis on the degradation of aniline different from that on Pt anode. The kinetics factors that influent the oxidation rates of aniline on SnO2/Ti anode are determined by the dissolving of intermediate products on anodes. The dissolving of the organic film with intermediate products on the anode is the rate determining step. The effects of aniline concentration, pH of aniline solution and the current density on the rate of aniline degradation has been studied. Under the best condition, the most efficient rate of elimination of aniline(99.1%) and current efficiency (99.8%) could be achieved. The complexity of the intermediate products, the basic category of the intermediate products consiste of the black film have been analyzed.

The effect of monomer and acid concentrations on electrochemical polyaniline formation in acetonitrile

The electro-oxidation behavior of aniline on a Pt surface in acetonitrile + tetrabutylammonium perchlorate (TBAP) solution was investigated using cyclic voltammetry. The effects of aniline concentration and the added acid were elucidated. The polyaniline films were characterized by their cyclic voltammograms in blank solution and dry conductivities were measured using the four-probe technique. As expected from the mechanism of the electro-oxidation of aniline, improvements in the quality and quantity of the polyaniline films were obtained by adding anhydrous acid to the medium. Furthermore, it was found that the concurrent generation of acid through in-situ oxidation of dissolved molecular hydrogen was the most efficient way of improving the polymer yield and properties.

Comparative studies of sheep liver and lung microsomal aniline 4-hydroxylase

1. The specific activity of the aniline 4-hydroxylase which catalyses hydroxylation of aniline to p-aminophenol was found to be 0.65 (N = 10) and 0.15 (N = 13) nmol p-aminophenol formed/mg protein, min. in sheep liver and lung microsomes, respectively. 2. The effects of aniline concentration. pH. cofactors. amount of enzyme and incubation period, on enzyme activity were studied, and the optimum conditions for maximum activity of liver and lung microsomes were determined. 3. Liver and lung microsomal aniline 4-hydroxylase activity was found to be completely dependent on the presence of cofactor NADPH. 4. The Lineweaver-Burk and Eadie-Hofstee plots of the liver enzyme were found to be curvilinear, suggesting that the enzyme did not follow the Michaelis-Menten kinetics. From these graphs, two different K m values were calculated for the liver enzyme as 3.21 and 0.072 mM aniline. K m of the lung enzyme was calculated to be 1.43 mM aniline from its Lineweaver-Burk graph. 5. The effects of magnesium, nickel and cadmium ions on the liver and lung aniline 4-hydroxylase activity were examined. Magnesium ion was found to have stimulatory effect, whereas nickel and cadmium ions inhibited the activity of the both liver and lung enzyme.