Barbara Palys

Template synthesis of polyaniline and poly(2-methoxyaniline) nanotubes: comparison of the formation mechanisms

The process of polyaniline (PANI), poly(2-methoxyaniline) (POMA) nanotubes formation was investigated. Polyaniline and poly(2-methoxyaniline) nanotubes were prepared by chemical in situ deposition within the pores of polycarbonate membranes. It was found that the formation of polyaniline and poly(2-methoxyaniline) proceeds by two substantially different mechanisms. In the case of PANI, the polymer is first formed in the polymerization solution (the solution containing the monomer and oxidant, where the polycarbonate substrate is placed), and then it precipitates on/into the membrane. In the case of POMA, the oxidized 2-methoxyaniline molecules are first adsorbed on polycarbonate surface, and then, as a consequence of their accumulation, they recombine to form the polymer.

SERS of 1,8-diaminonaphthalene on gold, silver and copper electrodes polymerisation and complexes formed with the electrode material

Abstract Oxidation of 1,8-diaminonaphthalene (1,8DAN) on gold, silver and copper electrodes has been studied by SERS spectra. SERS results have been compared with Raman spectra of poly-1,8DAN thin film deposited on the platinum support. Oxidation of 1,8DAN on gold and silver electrodes leads to polymerisation. The pretreatment of the silver electrode influences the polymerisation: exposing the silver electrode to day light during the ORC procedure encourages growth of the polymer layer. In the case of a copper electrode the Cu 2+ -(1,8DAN) n complex is formed.

Effective Charge Transport in Poly(3,4-ethylenedioxythiophene) Based Hybrid Films Containing Polyoxometallate Redox Centers

Electrodeposition and electrochemical charging of hybrid organic/inorganic films composed of the poly(3,4-ethylenedioxythiophene), PEDOT, conducting polymer matrix, and Keggin type polyoxometallate, phosphododecamolybdate(PMo 1 2 O 3 - 4 0 ) or phosphododecatungstate (PW 1 2 O 3 - 4 0 ), redox centers, are described under conditions of aqueous solutions. The systems are electropolymerized through potential cycling as thin and moderately thick (μm level) films on electrode surfaces. They are capable of fast charge propagation during redox reactions in strong acid medium (0.5 mol dm - 3 H 2 SO 4 ). The high overall physicochemical stability of PEDOT is explored to produce a robust, conductive, matrix for such polynuclear mixed-valence inorganic nanostructures as PMo 1 2 O 3 - 4 0 and PW 1 2 O 3 - 4 0 . The composite (hybrid) materials are stabilized due to the existence of electrostatic attraction between anionic phosphomolybdate or phosphotungstate units and positively charged conducting polymer (oxidized). Charge transport is facilitated by the fact that the reversible and fast redox reactions of polyoxometallate appear in the potential range where PEDOT is conductive. The effective diffusion coefficients are on the level 4 X 10 - 8 cm 2 s - 1 . The whole concept may lead to the fabrication of composite (hybrid) films that are capable of effective accumulation and propagation of charge in redox capacitors.

Effect of anions on the electrosynthesis, electroactivity and molecular structure of poly(o-methoxyaniline)

Abstract The effect of different anions (Cl − , ClO 4 − ) on the electrooxidation of o -methoxyaniline ( o -MA), on the electroactivity of poly( o -methoxyaniline) (POMA) and on the molecular structure of the polymer has been studied. It has been found that the rate of o -MA oxidation is much higher in HCl than in HClO 4 solution. It was also found that the nucleation and growth mechanisms of POMA films depend on anions being diffusion-controlled progressive nucleation with three-dimensional growth in HCl solution and two-dimensional growth in HClO 4 . It was shown that the electroactivity of POMA depends on the composition of the polymerization bath and that the ability of POMA degradation increases in HCl solution.

Sensitivity of poly 1,8-diaminonaphthalene to heavy metal ions — electrochemical and vibrational spectra studies

Abstract The sensitivity of poly(1,8-diaminonaphthalene) [poly(1,8-DAN)] to heavy metal ions (Ag + , Hg 2+ , Cu 2+ ) was studied by means of electrochemical (open circuit potential (oep), cyclic voltammetry) and spectroscopic methods (IR, Raman spectra). Changes of the open circuit potential of the polymer electrode indicate that (Ag + and Hg 2+ ions are able to oxidise poly(1,8-DAN), while Cu 2+ ions do not influence the oep of the polymer. Cyclic voltammograms of poly(1,8-DAN) give direct evidence that Ag + ions are reduced at the polymer surface whereas Hg 2+ or Hg 2 2+ ions are bonded by the polymer matrix, IR and Raman spectra indicate that Cu 2+ and Hg 2+ or Hg 2 2+ ions are complexed by the amino groups of the polymer.

Electrosynthesis and spectroelectrochemical characterization of poly(3,4-dimethoxy-thiophene), poly(3,4-dipropyloxythiophene) and poly(3,4-dioctyloxythiophene) films

Abstract Poly(3,4-dialkoxythiophene) films with different length of alkyl chain (1,3 and 8 carbon atoms) were obtained on Pt and ITO electrodes from the monomer solutions in acetonitrile by cyclic voltammetry (CV). The properties of the resulting films were studied by electrochemical methods, UV–Vis, FTIR and NMR spectra. The CVs were correlated with differential cyclic voltabsorptograms (DCVA) recorded at the absorption maxima to explain the shape of the voltammograms of the polymers studied, dependent on the alkyl-chain length in alkoxy group. The presence of the zones of different crystallinity in the polymer film was postulated. Significant influence of the type of the solvent on asymmetry of the cyclic voltammograms for the polymer doping–undoping has been discussed in terms of the solvent interaction with radical cation (polaron) delocalized on the alkoxy side groups. The polaron delocalization was proved by 1H-NMR spectra. Appearance of infrared activated vibrations (IRAVs) in the range 1500–600 cm−1 and a characteristic electronic band at 3300 cm−1 at the polarization potential +0.25 V versus Ag/Ag+ and their gradual changes upon further polymer oxidation were interpreted in terms of evolution of different charge carriers in lightly and heavily doped polymer.

Preparation and characterization of composites that contain small carbon nano-onions and conducting polyaniline

Small multilayer fullerenes, also known as carbon nano-onions (CNOs; 5-6 nm in diameter, 6-8 shells), show higher reactivity than other larger carbon nanostructures. Here we report the first example of an in situ polymerization of aniline on phenyleneamine-terminated CNO surfaces. The green, protonated, conducting emeraldine polyaniline (PANI) was directly synthesized on the surface of the CNO. The functionalized and soluble CNO/PANI composites were characterized by TEM, SEM, DSC, Raman, and infrared spectroscopy. The electrochemical properties of the conducting CNO/PANI films were also investigated. In comparison with pristine CNOs, functionalized carbon nanostructures show dramatically improved solubility in protic solvents, thus enabling their easy processing for coatings, nanocomposites, and biomedical applications.

Poly-o-aminophenol as a laccase mediator and influence of the enzyme on the polymer electrodeposition

Applicability of poly-o-aminophenol (POAP) as a redox mediator for fungal laccase is investigated. Laccase has been entrapped by means of electrochemical polymerization. The obtained layers have been characterized by cyclic voltammetry, as well as by spectroscopic methods. The enzyme activity has been verified by the standard test using syringaldazine. Laccase immobilized in the POAP matrix catalyses oxygen reduction without any additional mediators. POAP is able to mediate the electron transfer between the enzyme active site and the electrode surface similarly to poly-o-phenylenediamine which has been studied previously, but its redox potential is shifted significantly towards positive values. The role of laccase in electrodeposition of POAP has been studied. It has been found that the presence of the enzyme influences the structure of electrodeposited films. Furthermore, laccase facilitates the electrodeposition. The monomer-o-aminophenol (OAP) belongs to typical laccase substrates. The polymer can be precipitated from the solution containing the monomer and laccase. The morphology of POAP formed by laccase differs from typical polymer samples synthesized chemically or electrochemically. It contains round microstructures composed of nano-needles. Laccase is therefore a promising polymerization initiator for synthesis of nanostructured conducting polymers.

Spectroscopic and Electrochemical Studies of Bilayer Lipid Membranes Tethered to the Surface of Gold

This work presents the results of the structural characterization and blocking properties of thiolipid mono- and bilayers containing dipalmitoylphosphatidylethanolamine and cholesteryl moieties tethered to a gold electrode via suitable side-chain alkanethiol molecules. Various electrochemical and spectroscopic techniques were used to evaluate the organization, thickness, and stability of both the monolayers and bilayers on the surface of polycrystalline gold electrodes. Infrared absorbance-reflectance spectroscopy, surface-enhanced Raman spectroscopy, and Langmuir-Blodgett techniques were used to assess the molecular structure, intermolecular orientation, and fluidity of self-assembled thiolipid films on gold surface. Electrochemical measurements were used to examine the molecular integrity within the monolayers and bilayers. We demonstrate that the investigated bilayer lipid membranes attached to gold form well-blocking, well-oriented, fluid-like films that can be used in future investigations as a good model of cell membranes addressing numerous applications. ranging from the understanding of functioning of membrane integral proteins to the development of biomembrane-based sensing techniques.

The Electrochemical Properties of Nanocomposite Films Obtained by Chemical In Situ Polymerization of Aniline and Carbon Nanostructures

Interactions between the π bonds in the aromatic rings of polyaniline (PANI) with carbon nanostructures (CNs) facilitate charge transfer between the two components. Different types of phenyleneamine-terminated CNs, including carbon nano-onions (CNOs) and single-walled and multi-walled carbon nanotubes (SWNTs and MWNTs, respectively), were prepared as templates, and the CN/PANI nanocomposites were easily prepared with uniform core-shell structures. By varying the ratio of the aniline monomers relative to the CNs in the in situ chemical polymerization process, the thickness of the PANI layers was effectively controlled. The morphological and electrical properties of the nanocomposite were determined and compared. The thickness and structure of the PANI films on the CNs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and infrared spectroscopy. TEM and SEM revealed that the composite films consisted of nanoporous networks of CNs coated with polymeric aniline. The electrochemical properties of the composites were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. These studies showed that the CN/PANI composite films had lower resistance than pure polymeric films of PANI, and the presence of CNs much improved the mechanical stability. The specific electrochemical capacitance of the CNO/PANI composite films was significantly larger than for pure PANI.