Use of Mercury Film Glassy Carbon Electrode Modified with Multiwalled Carbon Nanotubes in Electrochemical Analysis of DNA

Mercury film plated on a glassy carbon electrode modified with multiwalled carbon nanotubes (MF/MWNTs/GCE) was used for the analysis of single (ss) and double stranded (ds) DNA, as well as for Jurkat genomic DNAs methylated to different degrees. The results indicated that the DNA molecules adsorbed quite strongly on the MF/MWNTs/GCE surface allowing ex situ adsorption and produce well developed peaks (due to cytosine and adenine) by using adsorptive stripping (Ads, ex situ) square wave voltammetry (SWV). Also, SWV of Jurkat DNA mixtures methylated to different degrees revealed a linear decrease of the peak height with increasing methylation indicating an increase of structural rigidity.     

Highly selective synthesis of single-walled carbon nanotubes from methane in a coupled Downer-turbulent fluidized-bed reactor

For the synthesis of single-walled carbon nanotubes (SWCNTs) from CH₄ over a Fe/MgO catalyst, we proposed a coupled Downer-turbulent fluidized-bed (TFB) reactor to enhance the selectivity and yield (or production rate) of SWCNTs. By controlling a very short catalyst residence time (1–3 s) in the Downer, only part of Fe oxides can be reduced to form Fe nano particles (NPs) available for the growth of SWCNTs. The percentage of unreduced Fe oxides increased and the yield of SWCNTs decreased accordingly with the increase of catalyst feeding rate in Downer. SWCNTs were preferentially grown on the catalyst surface and inhibited the sintering of the Fe crystallites which would be formed thereafter in the downstream TFB, evidenced by TEM, Raman and TGA. The coupled Downer-turbulent fluidized-bed reactor technology allowed higher selectivity and higher production rate of SWCNTs as compared to TFB alone.     

Preparation of Bromoiodopropenoic Acids by Stereospecific Nucleophilic Substitution at Vinylic Carbon

The bromoiodopropenoic acids (E)‐2‐bromo‐3‐iodopropenoic acid 5 and (Z)‐2‐bromo‐3‐iodopropenoic acid 6 were prepared by stereospecific nucleophilic substitution of the corresponding vinylic bromides. The structure of the (Z)‐isomer was confirmed by X‐ray crystallography.     

Micron Particles of AlN/Al: Efficient,Novel, and Reusable Heterogeneous Catalyst for the Synthesis of Bis(indolyl)methanes

The present work introduces for the first time the catalytic utility of micron particulate aluminium nitride (AlN/Al) as a novel and reusable heterogeneous catalyst for the synthesis of bis(indolyl)methanes involving the electrophilic substitution of indoles on aldehydes. The catalyst is recyclable and works without any significant change in its catalytic activity.     

Mild and Convenient Synthesis of Organic Carbamates from Amines and Carbon Dioxide using Tetraethylammonium Superoxide

A safe and simple method of preparing organic carbamates has been achieved from amines and carbon dioxide using tetraethylammonium superoxide generated in situ.     

Polyethylene Glycol–Enhanced Chemoselective Synthesis of Organic Carbamates from Amines,CO2, and Alkyl Halides

An efficient and environmentally benign method for the synthesis of organic carbamates was developed. Amines, CO₂, and alkyl halides underwent a three-component reaction with the aid of K₂CO₃ and polyethylene glycol (PEG, MW = 400), affording the organic carbamates under ambient conditions. PEG could presumably act as a solvent and phase-transfer catalyst (PTC). Notably, the presence of PEG could also depress the alkylation of both the amine and the carbamate, thus resulting in enhanced selectivity toward the target carbamate.

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Microstructural evolution during oxidative ablation in air for polyacrylonitrile based carbon fibers with different graphite degrees

Polyacrylonitrile‐based carbon fibers with different graphite degrees were oxidative ablated at 500 and 600 °C in air. By Thermal gravimetric (TG), Raman spectroscopy, X‐ray diffraction, and SEM, the mass loss, microstructure, and surface morphology of carbon fibers were investigated. The mass loss of carbon fiber increases linearly with increasing oxidative ablated time under 500 and 600 °C. The carbon fiber with higher graphite degree shows higher oxidative resistance, and the surface roughness increases gradually because of chemical ablation during the whole oxidation. A gloss morphology appears on the surface primarily because of physical denudation for carbon fibers with lower graphite degree and then burn off according to carbon and oxygen reaction. The crystallite size (La) decreases significantly, while interlayer spacing(d₀₀₂) remains nearly unchanged. SEM observation suggests the two kinds of ablation mechanisms for carbon fibers with different graphite degrees indicating that CC band in sp³ hybridization prefers to be attacked by oxygen molecule more than that in sp² hybridization during oxidation ablation in air. Copyright © 2012 John Wiley & Sons, Ltd.     

Orientational and electro-optical properties of liquid crystal aligned with a directly spinnable carbon nanotube web

We investigated the orientational and electro-optical properties of a nematic liquid crystal (LC) aligned with a directly spinnable carbon nanotube (CNT) web functioning both as an electrode and as an alignment layer. The LC molecules were uniformly oriented along the drawing direction of the CNT web and the spatially averaged birefringence was comparable to a rubbed polyimide sample. The CNT web sample also showed smaller residual DC and hysteresis compared to the polyimide sample.     

Influence of surface properties on the interfacial adhesion in carbon fiber/epoxy composites

A polyacrylonitrile‐based carbon fiber was electrochemically oxidized in an aqueous ammonium bicarbonate solution with current density of up to 2.76 A/m² at room temperature. X‐ray photoelectron spectroscopy revealed that the oxygen content increased with increasing current density before approaching saturation. The increase can be divided into two regions, the rapid increase region (0–1.78 A/m²) and a plateau region (1.78–2.76 A/m²). The surface chemistry analysis showed that the interlaminar shear strength (ILSS) value of the carbon fiber/epoxy composite could be improved by 24.7%. The carbon structure was examined using Raman spectroscopy in terms of order/disorder in the graphite structure and the results indicated that the relative percentage of graphite carbon in the form of sp² hybridization increased above a current density of 1.39 A/m². The increasing non‐polar graphite carbon on the carbon fiber surface decreased the surface energy. As a result, both the surface free energy () and its polar component () decreased when current density increased above 1.78 A/m². The ILSS value had no direct relationship with the nature and surface density of the oxygen‐containing functional groups nor with the carbon structure. It is the surface free energy (), especially the polar component (), which played a critical role in affecting the interfacial adhesion of carbon fiber/epoxy composites. The ILSS value changed with increasing current density and could be divided into three distinct regions, as chemical interaction region (I), anchor force region (II) and matrix damage region (III). Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and thermal properties of a new styryl-functionalized pentafulvene glassy carbon precursor

The first preparation of a styryl-functionalized aryl pentafulvene 4 was carried out. In the crystal structure of 4, the packing of fulvene molecules results in the shortest intermolecular contacts between aligned vinyl groups. Thermal reactivity studies of 4 (DSC and TGA, under N₂) revealed a small difference between the melting point (120 °C) and the T_onset for cross-linking (125 °C), and provided strong evidence for the production of a network material (net4) due to reactivity of the attached styryl group. Pyrolysis of net4 under N₂ gave a glassy carbon product in low yield as revealed by powder X-ray and TGA analyses (carbon yield (TGA) of 38% (900 °C)).