Electrochemical sensors based on conducting polymer—polypyrrole

Polyaniline nanostructures and the role of aniline oligomers in their formation

New modern technologies require new materials. During the past decade, the movement towards nanodimensions in many areas of technology aroused a huge interest in nanostructurized materials. The present article reviews recent works dealing with electrochemistry-related aspects of nanostructurized conducting polymers. Electrochemical synthesis and some properties of nanostructurized conducting polymers, and nanocomposites derived from conducting polymers and metals, carbon, and inorganic and organic materials are considered. Some potential areas for electrochemistry-related applications of nanocomposites are highlighted, including batteries, supercapacitors, energy conversion systems, corrosion protection, and sensors.

https://iopscience.iop.org/article/10.1088/0957-4484/16/10/R01/pdf

Conducting polymer-based nanostructurized materials: electrochemical aspects.

In this work, single-crystalline gold nanoplates were produced by treating an aqueous solution of chloroauric acid with the extract of the unicellular green alga Chlorella vulgaris at room temperature. The results suggest proteins as the primary biomolecules involved in providing the dual function of Au(III) reduction and the size- and shape-controlled synthesis of the nanogold crystals. A protein with a molecular weight of approximately 28 kDa was isolated and purified by reversed-phase HPLC; this protein tested positive for the reduction of chloroauric acid in aqueous solution. The isolated protein (named gold shape-directing protein, or GSP for convenience) was then used to produce gold nanoplates with distinctive triangular and hexagonal shapes in high yields (approximately 90 %). The kinetics of the reduction reaction could be manipulated through changes in the GSP concentration to produce plates with lateral sizes ranging from nanometers to micrometers. The growth of gold nanoplates in the GSP solution with time was monitored by microscopic and spectroscopic techniques, thereby allowing the detection of several key intermediates in the growth process.

Identification of active biomolecules in the high-yield synthesis of single-crystalline gold nanoplates in algal solutions.

This review discusses recent advances in the nonlinear optics of environmental interfaces. We discuss the quantitative aspects of the label-free approaches presented here and demonstrate that nonlinear optics has now assumed the role of a Swiss Army knife that can be used to dissect, with molecular detail, the fundamental and practical aspects of environmental interfaces and heterogeneous geochemical environments. In this work, nonlinear optical methods are applied to complex organic molecules, such as veterinary antibiotics, and to small inorganic anions and cations, such as nitrate and chromate, or cadmium, zinc, and manganese. The environmental implications of the thermodynamic, kinetic, spectroscopic, structural, and electrochemical data are discussed.

Second Harmonic Generation, Sum Frequency Generation, and χ(3): Dissecting Environmental Interfaces with a Nonlinear Optical Swiss Army Knife

Composite colloids of gold and polypyrrole were prepared using two different methods: 1, using pyrrole colloid, created by the oxidation of pyrrole by ferric chloride, to subsequently reduce chlorauric acid and, 2, oxidizing pyrrole monomer with chlorauric acid in a sodium dodecylbenzene sulfonate solution. In each case, the polypyrrole colloid consisted of irregularly shaped particles approximately 500 nm in diameter. The gold produced in each case was in the form of irregular spheres, approximately 407 nm in diameter in method 1 and 13 nm in method 2. X-ray photoelectron spectroscopy was used to determine the oxidation state of the species present. Transmission electron microscopy and light scattering data were used to determine the particle sizes of both gold and polypyrrole colloids. Energy dispersed spectrum X-ray analysis and electron diffraction were used to confirm the presence of metallic gold in the composite colloids. The second-order rate constant for the reaction of chlorauric acid with pyrrole in dilute solution was found to he 13 M -1 s -1 . Aqueous solutions of palladium, platinum, rhodium, cobalt, tin, silver, zinc, nickel, titanium, cadmium, mercury, arsenic, and selenium were also examined for their potential to act as oxidants to produce composite polypyrrole colloids. Palladium, platinum, and rhodium salts were suitable oxidants, producing polypyrrole in less than 12 h.

https://iopscience.iop.org/article/10.1149/1.1405802/pdf

Reaction of Pyrrole and Chlorauric Acid A New Route to Composite Colloids

Model reversed-phase chromatographic interfacial systems were examined using sum-frequency generation (SFG) spectroscopy to study the effect of solvent on the structure and conformation of the stationary phase. Monolayers formed from mixed C18 and C1 alkysilanes (both polymeric octadecyltrichlorosilane-methyl trichlorosilane mixed monolayers and monomeric octadecyldimethylchlorosilane-trimethylchlorosilane mixed monolayers) on fused silica were examined in contact with air, deuterated acetonitrile (CD3CN), D2O, and mixtures of CD3CN and D2O. When mixed composition (C18 and C1) monolayers were examined, significant disorder was observed in the alkyl chains for all solvents examined at intermediate alkyl chain densities for the polymeric materials, and at all chain densities for the monomeric materials. Maximum order for intermediate polymeric chain densities was found to occur in contact with 40−50 vol % D2O solutions. These results indicate that solvent microheterogeneity has a large effect on alkyl chain...

In Situ Examination of the Structure of Model Reversed-Phase Chromatographic Interfaces by Sum-Frequency Generation Spectroscopy

The adsorption of methanol−D2O and acetonitrile−D2O solutions at model chromatographic interfaces (octadecylsiloxane and quartz) was studied using sum-frequency spectroscopy. Methanol did not adsorb at either interface in detectable quantities, while acetonitrile adsorbs at the octadecylsiloxane− and quartz−solution interfaces in a concentration-dependent manner and is well ordered at the interface. Adsorption of acetonitrile was decreased by the addition of KCl at 10 and 100 mM. Acetonitrile adsorption was also observed during simulated gradient elution, demonstrating that adsorption of acetonitrile occurs on a time scale relevant to actual chromatographic separations. Examination of the OH stretch spectra of acetonitrile−H2O and methanol−H2O solutions at the interface revealed concentration-dependent changes in the acetonitrile−H2O spectra that are consistent with hydrogen bonding between interfacial water and acetonitrile, indicating that interfacial water is involved in mediating acetonitrile adsorpti...

Sum-frequency observation of solvent structure at model chromatographic interfaces: acetonitrile-water and methanol-water systems.

Chemically diverse modified electrodes : A new approach to the design and implementation of sensor arrays

Competitive adsorption of 2,4,7,9-tetramethyl-5-decyn-4,7-diol (TMDD) with octanesulfonic acid Na+ salt, decanesulfonic acid Na+ salt, dodecanesulfonic acid Na+ salt, and protonated and deprotonated octanoic acid was observed using sum frequency generation (SFG) spectroscopy. SFG spectroscopy allows the direct observation of the relative surface density of TMDD. Various models of competitive adsorption for mixed surfactant systems were compared. Models taking into account kinetic, steric, and electrostatic factors were compared to the experimental data. For systems not undergoing a two-dimensional phase transition, a model incorporating steric and kinetic factors provided the best agreement with experimental observations.

Matthew C. Henry

Papers

Reaction of Pyrrole and Chlorauric Acid A New Route to Composite Colloids

In Situ Examination of the Structure of Model Reversed-Phase Chromatographic Interfaces by Sum-Frequency Generation Spectroscopy

Sum-frequency observation of solvent structure at model chromatographic interfaces: acetonitrile-water and methanol-water systems.

Chemically diverse modified electrodes : A new approach to the design and implementation of sensor arrays

Competitive Adsorption of 2,4,7,9-Tetramethyl-5-decyn-4,7-diol and Linear Alkane Surfactants at the Air/Water Interface