Michael S. Freund

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

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.

Self-doped conducting polymers

1. Introduction. 1.1 Conducting Polymers. 1.2 What Are Self-doped Conducting Polymers? 1.3 Types of Self-doped Polymers. 1.4 Doping Mechanism in Self-doped Polymers. 1.5 Effect of Substituents on Properties of Polymer. 1.6 Applications of Self-doped Polymers. References. 2. Self-doped Derivatives of Polyaniline. 2.0 Introduction. 2.1 Chemical Synthesis of Sulfonic Acid Derivatives. 2.2 Electrochemical Synthesis of Sulfonic Acid Derivatives. 2.3 Enzymatic Synthesis of Sulfonic Acid Derivatives. 2.4 Properties of Sulfonic Acid Derivatives. 2.5 Synthesis and Characterization of Carboxyl Acid Derivatives. 2.6 Synthesis and Characterization of Phosphonic Acid Derivatives. 2.7 Self-doped Polyaniline Nanostructures. References. 3. Boronic acid Substituted Self-doped Polyaniline. 3.1 Introduction. 3.2 Synthesis. 3.3 Properties of Self-doped PABA. 3.4 Self-Cross-Linked Self-doped Polyaniline. 3.5 Applications. References. 4. Self-doped Polythiophenes. 4.1 Sulfonic Acid Derivatives. 4.2 Carboxylate Derivatives. 4.3 Phosphanate Derivatives. References. 5. Miscellaneous Self-doped Polymers. 5.1 Self-doped Sulfonated Polypyrrole. 5.2 Carboxyl Acid Derivative. 5.3 Self-doped Poly(3,6-carbaz-9-yl)propanesulfonate. 5.4 Self-doped Poly(p-phenylenes). 5.5Self-doped Polyphenylenevinylene. 5.6 Self-doped Poly(indole-5-carboxylic acid). 5.7 Self-doped Ionically Conducting Polymers. References.

Mechanism of the carbon catalyzed reduction of nitrobenzene by hydrazine

The reduction of nitroaromatics to anilines by hydrazine is catalyzed by carbons. The carbon serves as an adsorbent and electrical conductor to enable the reaction to occur. Hydrazine is a two-electron reducing agent as shown by trapping the diimide intermediate with norbornene. The nitrobenzene reduction is a four-electron process proceeding first to phenylhydroxylamine which was observed in low concentrations in the reacting system by NMR. Phenylhydroxylamine is reduced to aniline in a second step. The two-electron intermediate, nitrosobenzene, gave different products than nitrobenzene under the reaction conditions and could not be trapped, supporting the expected four-electron pathway. By serving as an adsorbent and collecting hydrazine on their surfaces, carbons make it possible to execute a four-electron reduction using a two-electron reducing agent. This role of carbon was confirmed by successfully operating an emf cell using graphite or carbon paste electrodes immersed in solutions of hydrazine and nitrobenzene. The initial rates of reduction of substituted nitrobenzenes showed only a tiny substituent effect and proceed at nearly the same rate as the carbon-catalyzed decomposition of hydrazine leading to the conclusion that hydrazine reaction at the carbon surface is the rate determining step.

Large Enhancement and Tunable Band Gap in Silicene by Small Organic Molecule Adsorption

Adsorption of eight organic molecules (acetone, acetonitrile, ammonia, benzene, methane, methanol, ethanol, and toluene) onto silicene has been investigated using van der Waals density functional theory calculations (DFT-D). The calculated values of the adsorption energies vary from −0.11 to −0.95 eV. Quantitatively, these values are higher than the corresponding adsorption energies of the molecules adsorbed on graphene. In addition, electronic structure calculations have been performed. The obtained values of the band gap range from 0.006 to 0.35 eV for acetonitrile to acetone, respectively. Furthermore, the effective mass of the electron is estimated and found to be comparatively small, which is expected to result in high electron mobility. In addition, we study the effect of Li atoms doped in pristine and acetone adsorbed silicene. In particular, we focus on the variation of the adsorption energy with respect to the number of Li atoms in the systems. Our results suggest new approaches for the use of si...

Anion-excluding polypyrrole films.

A new method for modifying polypyrrole films is described. It involves complete oxidation of the film. The film produced is electronically non-conductive but ionically conductive, and has ion-selective properties based on the exclusion of anionic species. The effective pH within the film can be controlled by the choice of supporting electrolyte used during the oxidative treatment, without loss of selectivity. Cyclic voltammetry is used to demonstrate the effect of film pH on the rate of dopamine oxidation in a neutral supporting electrolyte.

Saccharide imprinting of poly(aniline boronic acid) in the presence of fluoride

A new approach for the electrosynthesis of saccharide-imprinted poly(aniline boronic acid) is described. The method involves the formation of a saccharide-aminophenylboronic acid complex in the presence of fluoride to allow the electropolymerization of a self-doped, molecularly imprinted polyaniline. The formation of the anionic monomer complex enables electrochemical polymerization at near neutral pH (5-7) ensuring the incorporation of saccharide in the resulting, self-doped polymer. In this work, films were imprinted with D-fructose where saccharide-aminophenylboronic acid complexation occurred in the presence of one equivalent of fluoride. The selectivity toward D-fructose relative to D-glucose showed an increase of over 25% as a result of imprinting. In addition to the enhanced selectivity, to the best of our knowledge this is the first example of the electropolymerization of a self-doped polyaniline homopolymer under neutral pH conditions.

Exploitation of spatiotemporal information and geometric optimization of signal/noise performance using arrays of carbon black-polymer composite vapor detectors

We have investigated various aspects of the geometric and spatiotemporal response properties of an array of sorption-based vapor detectors. The detectors of specific interest are composites of insulating organic polymers filled with electrical conductors, wherein the detector film provides a reversible dc electrical resistance change upon the sorption of an analyte vapor. An analytical expression derived for the signal/noise performance as a function of detector volume implies that there is an optimum detector film volume which will produce the highest signal/noise ratio for a given carbon black-polymer composite when exposed to a fixed volume of sampled analyte. This prediction has been verified experimentally by exploring the response behavior of detectors having a variety of different geometric form factors. We also demonstrate that useful information can be obtained from the spatiotemporal response profile of an analyte moving at a controlled flow velocity across an array of chemically identical, but spatially nonequivalent, detectors. Finally, we demonstrate the use of these design principles, incorporated with an analysis of the changes in detector signals in response to variations in analyte flow rate, to obtain useful information on the composition of analytes and analyte mixtures.

Current developments in silicene and germanene

Exploration of the unusual properties of the two-dimensional materials silicene and germanene is a very active research field in recent years. This article therefore reviews the latest developments, focusing both on the fundamental materials properties and on possible applications.

Electrolytic actuators: alternative, high-performance, material-based devices.

The emerging field of materials-based actuation continues to be the focus of considerable research because of its inherent scalability and its promise to drive micromechanical devices that cannot be realized with conventional mechanical actuator strategies. The electrolytic phase transformation actuator offers a new broad-spectrum solution to the problem of direct conversion of electrical to mechanical energy. Strains of 136,000% and unoptimized work cycle efficiencies near 50% are demonstrated in a prototype device. Conceivably capable of generating stress beyond 200 MPa, this new approach promises performance orders of magnitude beyond other novel actuation strategies.

Use of Bipolar Membranes for Maintaining Steady‐State pH Gradients in Membrane‐Supported, Solar‐Driven Water Splitting

A bipolar membrane can maintain a steady-state pH difference between the sites of oxidation and reduction in membrane-supported, solar-driven water-splitting systems without changing the overall thermodynamics required to split water. A commercially available bipolar membrane that can serve this purpose has been identified, its performance has been evaluated quantitatively, and is demonstrated to meet the requirements for this application. For effective utilization in integrated solar-driven water-splitting systems, such bipolar membranes must, however, be modified to simultaneously optimize their physical properties such as optical transparency, electronic conductivity and kinetics of water dissociation.