Novel Carbon–Carbon Bond Formation between N‐Methyl‐3‐phenyl‐3‐hydroxypropylamine and Cresols Catalyzed by p‐Toluenesulphonic Acid

The p‐toluenesulphonic acid–catalyzed reaction between appropriate cresols and N‐methyl‐3‐phenyl‐3‐hydroxypropylamine in refluxing toluene resulted in the formation of o‐substituted phenol derivatives by an aromatic nucleophilic substitution reaction.     

Magnetic Properties of Ni‐Co‐B Coated Carbon Nanofibers

Continuous and uniform Ni‐Co‐B coatings were successfully deposited onto carbon nanofibers via electroless plating. SEM images of the prepared Ni‐Co‐B coated carbon nanofibers were presented. The magnetic properties of the coated carbon nanofibers were investigated. The CoSO₄/(CoSO₄+NiSO₄) ratio in the electroless bath has obvious influence on the coercivity and residual magnetic flux density of the Ni‐Co‐B coated carbon nanofibers.     

Microstructure and Magnetic Properties of Carbon‐Coated Nanoparticles

Abstract

In the present work, microstructure and superparamagnetic properties of two types of carbon‐coated magnetic Ni and Fe nanoparticles [Ni(C) and Fe(C)] are reviewed. High‐resolution transmission electron microscopy (HRTEM), electron diffraction (SAED), and x‐ray diffraction (XRD) analyses have been used to reveal the distinct structural morphologies of Ni and Fe nanoparticles. Moreover, novel carbon‐coated Ni nanoparticle assemblies offer us great opportunities for studying the mechanism of superparamagnetism in particle assemblies. Magnetization measurements [M(T) and M(H) curves] for assemblies of Ni nanoparticles indicate that modified superparamagnetic properties at T > T _B, have been found in the assemblies of Ni(C) particles. The blocking temperature, T _B, is determined to be near 115K under a certain applied field. Above T _B, the magnetization M(H, T) can be described by the classical Langevin function L using the relation, M/M _s (T = 0) = coth (μH/kT) ? kT/μH. It is suggested that these assemblies of carbon‐coated Ni nanoparticles have typical single‐domain, field‐dependent superparamagnetic relaxation properties. Finally, Mössbauer spectra and hyperfine magnetic fields at room temperature for the assemblies of Fe(C) nanoparticles confirm their distinct nanophases that were detected by structural analysis. Modified superparamagnetic relaxation is observed in the assemblies of Fe(C) nanoparticles, which is attributed to the nanocrystalline nature of the carbon‐coated nanoparticles.     

Organocatalytic Synthesis of Higher‐Carbon Sugars: Efficient Protocol for the Synthesis of Natural Sedoheptulose and d‐Glycero‐l‐galacto‐oct‐2‐ulose

Herein we report a short and efficient protocol for the synthesis of naturally occurring higher‐carbon sugars—sedoheptulose (d‐altro‐hept‐2‐ulose) and d‐glycero‐l‐galacto‐oct‐2‐ulose—from readily available sugar aldehydes and dihydroxyacetone (DHA). The key step includes a diastereoselective organocatalytic syn‐selective aldol reaction of DHA with d‐erythrose and d‐xylose, respectively. The methodology presented can be expanded to the synthesis of various higher sugars by means of syn‐selective carbon–carbon‐bond‐forming aldol reactions promoted by primary‐based organocatalysts. For example, this methodology provided useful access to d‐glycero‐d‐galacto‐oct‐2‐ulose and 1‐deoxy‐d‐glycero‐d‐galacto‐oct‐2‐ulose from d‐arabinose in high yield (85 and 74 %, respectively) and high stereoselectivity (99:1).     

Electrochemical Analysis of Mercury Using a Kryptofix Carbon‐Paste Electrode

Abstract

Successful applications of different analytical procedures to determine quantitatively mercury in aqueous media can be found in recent literature. Fundamentally it has made use of Cold Vapour Atomic Absorption Spectrometry (CV‐AAS), X‐Ray Fluorescence or UV Spectrophotometry, Inductively Coupled Plasma Atomic Emission Spectrometry (ICP‐AES), or Inductively Coupled Plasma Mass Spectrometry (ICP‐MS), which are the techniques commonly used for trace measurement of heavy metal in the laboratory. In this paper a new and alternative methodology to determine quantitatively mercury in aqueous media is reported. A kryptofix carbon‐paste electrode has been used to determine voltammetrically mercury. The detection limit for mercury was evaluated to be 0.12 µg/l.     

Nafion‐Modified Glassy Carbon Electrode for Trace Determination of Indium

Abstract

A new method for determination of trace indium is proposed by the adsorption stripping voltammetry (ASV) using a Nafion‐modified glassy carbon electrode (NMGCE). This chemically modified electrode (CME) shows a better stability. A sensitive oxidation peak was observed, and the anodic peak potential is ca. ?0.548 V (vs. SCE). The influences of various experimental parameters on the current peak were completely studied. Under the optimized condition, the method has been applied to the determination of indium in water samples. There is a good linear relationship between the peak current (i_p) and indium(III) concentration in the range of 1.0×10^?9–1.0×10^?7 mol/l, and the limit of detection is 7.5×10^?10 mol/l.     

Sensitive Determination of Clomipramine at Poly‐ABSA/Pt Nano‐Clusters Modified Glassy Carbon Electrode

Abstract

Clomipramine, an important tricylic antidepressant drug with low redox activity, was effectively electrocatalyzed on poly‐aminobenzene sulfonic acid/Pt nano‐clusters modified glassy carbon electrode (i.e., poly‐ABSA/Pt/GCE) and generated a sensitive anodic peak at about 0.80 V in pH 8.1 PBS. ABSA was electropolymerized on the surface of GCE modified with Pt nano‐clusters. Pt nanoparticles provide a 3 D and conductive structure for the polymer immobilization. The resulting sensor exhibited a considerable enhancement in voltammetric response characteristics: extending the linear range and lowering the detection limit. The anodic peak current of clomipramine was linear with its concentration over two concentration intervals, viz., 1.0×10^?7～4.0×10^?6 M and 4.0×10^?6～4.0×10^?5 M, with the detection limit of 1.0×10^?9 M (S/N=3). This method was successfully applied to the determination of clomipramine in drug tablets and proved to be reliable compared with UV.     

Electrical Property of Tin Oxide Doped with Multi‐Walled Carbon Nanotubes

Tin oxide doped with multi‐walled carbon nanotubes (MWNTs) was prepared via a wet‐chemical process and characterized with x‐ray diffraction (XRD) and transmission electron microscope (TEM). Meanwhile, the conductivity of composites obtained was measured using Source Meter. The results show that carbon nanotubes have great effect on the electrical property of SnO₂ nanoparticles. Compared with undoped SnO₂ nanoparticles, the resistivity of SnO₂ nanoparticles doped with 0.3‰ wt MWNTs decreased by a factor of 37. This may be ascribed to the presence of π energy levers of MWNTs and their high aspect ratio. Moreover, the effect of annealing temperature on the electrical property of SnO₂ nanoparticles doped with MWNTs also was discussed.     

Synthesis and Characterization of Multi‐Walled Carbon Nanotube/Polythiophene Composites

Multi‐walled carbon nanotube (MWCNT)/polythiophene (PTh) composites have been prepared by in situ chemical oxidative polymerization. PTh is synthesized onto the sidewalls of the MWCNTs, which play a role as hard templates for PTh to produce one‐dimensional nanostructures. The morphology and structures of the MWCNT/PTh composites are characterized by High‐resolution transmission electron microscopy, x‐ray diffraction, and Fourier transform infrared spectrometry. Their electrical property and thermal stability are determined using vector network analyzer and thermal gravimetric analyzer. Moreover, the mechanism of MWCNT/PTh nanowire formation is described. The studies show that the composites are nanowires with core‐shell structure, in which the outer shells and inner cores are formed by PTh and MWCNTs, respectively. The addition of MWCNTs does not change the backbone structure of PTh and affect the amorphous condition of PTh very slightly, however, it improves the electrical conductivity and thermal stability of PTh.     

Unambiguous Assignment of the Stereochemistry at the Anomeric Carbon in Methyl‐α‐D‐C‐Aryl‐glucopyranoside Derivative: A Representative of Products from our New Strategy for 2‐Deoxy‐C‐aryl‐glucopyranosides

The X‐ray study firmly establishes the stereochemistry at the anomeric carbon in methyl‐α‐D‐C‐aryl‐glucopyranoside derivative.     

Electrocatalytic Activity of Bamboo‐Structured Carbon Nanotubes Paste Electrode Toward Hydrogen Peroxide

Abstract

In this report, we describe the finding that bamboo‐structured carbon nanotubes (CNT) showed superior electrocatalytic activity toward hydrogen peroxide. The slope of the calibration curve for hydrogen peroxide obtained with the bamboo‐structured CNT paste electrode was more than 20 times as large as the slopes obtained with hollow‐structured CNT paste and glassy carbon electrodes at an operating potential of ?0.1 V, with no interfering reactions. Incorporation of glucose oxidase within the bamboo‐structured CNT paste electrode allows the selective detection of glucose in the presence of common interferents without using any permselective membranes. This excellent ability of the bamboo‐structured CNT paste electrode toward hydrogen peroxide is applicable to the development of other enzymatic biosensors.     

Voltammetric Determination of Hydroquinone using β‐Cyclodextrin/Poly(N‐Acetylaniline)/Carbon Nanotube Composite Modified Glassy Carbon Electrode

Abstract

An electrochemical sensor for hydroquinone (HQ) using β‐cyclodextrin/poly(N‐acetylaniline)/carbon nanotube composite (β‐CD/PAA/MWNTs) modified glassy carbon electrode has been successfully developed. Based on the synergistic effect of MWNTs and conducting PAA polymer and the accumulation effect of β‐CD, the analytical response of the β‐CD/PAA/MWNTs film to the electrochemical behavior of HQ was better than that of a β‐CD/PAA film, a PAA/MWNTs film, a PAA film, or a bare glassy carbon (GC) electrode. Under the conditions chosen, the anodic currents increased linearly with HQ concentration from 1×10^?6 to 5×10^?3 mol l^?1 and the detection limit was 8×10^?7 mol l^?1. This electrochemical sensor showed excellent reproducibility, stability and recovery for the determination of HQ.     

Dibromomethane as One‐Carbon Source in Organic Synthesis: Formal Total Synthesis of (±)‐Nephrosteranic Acid

A diastereoselective formal total synthesis of (±)‐nephrosteranic acid (10) is described. The key step is to introduce the α‐methylene group by the ozonolysis of monosubstituted alkenes followed by reaction with a preheated mixture of CH₂Br₂–Et₂NH. The α‐methyl group of compound 10 was formed from the reduction of the corresponding α‐methylene precursor.     

Electrochemical Oxidation at a Glassy Carbon Electrode of the Anti‐Arrhythmia Drug Disopyramide

Abstract

A voltammetric study of the oxidation of disopyramide has been carried out using a glassy carbon electrode. The electrochemical oxidation of disopyramide was investigated by cyclic, differential pulse, and square wave voltammetry. The oxidation of disopyramide is an irreversible, diffusion‐controlled process. The diffusion coefficient of disopyramide was calculated in pH 7.0 phosphate buffer to be D _disopyramide=3.8×10^?6 cm² s^?1. The oxidation of disopyramide is also pH dependent and for electrolytes with pH between 4 and 7 occurs with the transfer of one electron and one proton. In alkaline electrolytes, two consecutive charge transfer reactions are observed: both oxidation reactions involve the transfer of two electrons but only the first also involves the transfer of two protons. Two procedures for the analytical determination of disopyramide in pH 7.0 phosphate buffer were developed and compared and a detection limit LOD=1.27 µM was obtained.     

Adsorption of Carbon Dioxide on Activated Carbon

The adsorption of CO2 on a raw activated carbon A and three modified activated carbon samples B, C, and D at temperatures ranging from 303 to 333 K and the thermodynamics of adsorption have been investigated using a vacuum adsorption apparatus in order to obtain more information about the effect of CO2 on removal of organic sulfur-containing compounds in industrial gases. The active ingredients impregnated in the carbon samples show significant influence on the adsorption for CO2 and its volumes adsorbed on modified carbon samples B, C, and D are all larger than that on the raw carbon sample A. On the other hand, the physical parameters such as surface area, pore volume, and micropore volume of carbon samples show no influence on the adsorbed amount of CO2. The Dubinin-Radushkevich (D-R) equation was the best model for fitting the adsorption data on carbon samples A and B, while the Preundlich equation was the best fit for the adsorption on carbon samples C and D. The isosteric heats of adsorption on carbon samples A, B, C, and D derived from the adsorption isotherms using the Clapeyron equation decreased slightly increasing surface loading. The heat of adsorption lay between 10.5 and 28.4 kJ/mol, with the carbon sample D having the highest value at all surface coverages that were studied. The observed entropy change associated with the adsorption for the carbon samples A, B, and C (above the surface coverage of 7 ml/g) was lower than the theoretical value for mobile adsorption. However, it was higher than the theoretical value for mobile adsorption but lower than the theoretical value for localized adsorption for carbon sample D.     

Carbon–Carbon Bond Formation by Radical Cyclization: Regioselective Synthesis of Spiro Heterocyclic Compounds by n Bu3SnH‐Mediated Reaction

Several spiro heterocyclic compounds have been regioselectively synthesized in excellent yield by ⁿ Bu₃SnH‐AIBN‐mediated radical cyclization of 4‐(2′‐bromoaryloxymethyl)‐1‐methylquinolin‐2(1H)‐ones in refluxing benzene under nitrogen for 4 h.     

Two‐Step Novel Synthesis of 2‐Amino‐6‐(1,3‐dioxo‐2,3‐dihydro‐1H‐inden‐2‐yl)‐4,7‐diphenyloxepine‐3‐carbonitrile and 5‐(1,3‐Dioxo‐2,3‐dihydro‐1H‐inden‐2‐yl)‐2‐imino‐6‐phenyl‐2H‐pyran‐3‐carbonitrile

Starting from indan‐1,3‐dione, a novel two‐step synthesis of the oxepine derivatives 5a,b and the pyran derivatives 7 and 8 under very simple reaction conditions is described.     

Chemical Surface Treatment for Highly Improved Dispersibility of Multi‐Walled Carbon Nanotubes in Water

In order to increase the dispersibility of multi‐walled carbon nanotubes (MWNTs) in water without any additives, various acid treatments were used. Generally, acid treatment used to remove or purify carbon nanotubes. MWNTs treated with a mixture of nitric and sulfuric acids showed high dispersion stability by means of UV‐visible spectrophotometry and higher crystallinity than other samples. In addition, it was clearly shown that acid treatment efficiently removed the impurities of MWNTs, which was proven by thermogravimetric analysis. In particular, one of functional groups, cyano (C‐N) bonding characterized by Fourier transform‐infrared after acid treatment were formed the surface of MWNTs.     

Controlled Nanofiber Composed of Multi‐Wall Carbon Nanotube/Poly(Ethylene Oxide)

We have successfully fabricated poly(ethylene oxide) (PEO) nanofibers containing embedded multi‐wall carbon nanotubes (MWCNTs). An initial dispersion of the MWCNTs in distilled water was achieved using sodium dodecyl sulfate. Subsequently, the dispersion was decanted into a PEO solution, which enabled separation of the MWCNTs and their individual incorporation into the PEO nanofibers on subsequent electrospinning. Initially, the carbon nanotube (CNT) rods were randomly oriented, but owing to the sink‐like flow in the electrospinning wedge, they became gradually oriented along the streaming direction, in order that oriented CNTs were obtained on entering the electrospun jet. Individual MWCNTs became embedded in the nanofibers, and were mostly aligned along the fiber axis. Evidence of load transfer to the nanotubes in the composite nanofiber was observed from the field‐emission scanning electron microscopy, transmission electron microscopy and conductivity data.