bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dioxomolybdenum(VI) Epoxidation Catalyst Supported on Mesoporous Silica Containing Phosphane Oxide Groups
Authors: Castro Alichandra , Alonso João C. , Neves Patrícia , Valente Anabela A. , Ferreira Paula 
Published: December 2009

AbstractA new mesoporous hybrid material (denoted LP‐TEPPPO‐Mo) has been prepared by tethering [MoO2Cl2] onto mesoporous silica previously functionalised with phosphane oxide spacer ligands. The LP‐TEPPPO‐Mo material was tested in the liquid‐phase epoxidation of olefins [cis‐cyclooctene, (R)‐(+)‐limonene, trans‐2‐octene and 1‐octene] with tBuOOH, at 55 °C, and without a co‐solvent, giving at least 90 % selectivity to the corresponding epoxide at 36–77 % conversion: in the case of limonene, regioselectivity favours the epoxidation of the endocyclic double bond, giving mainly 1,2‐epoxy‐p‐menth‐8‐ene. The catalytic system based on a liquid–liquid biphasic system containing the homogeneous complex [MoCl2(O)2{OP(CH2CH3)(Ph)2}2] dissolved in the ionic liquid 1‐butyl‐4‐methylpyridinium tetrafluoroborate leads to lower epoxide selectivity (91 % at 64 % conversion) in the reaction of cyclooctene in comparison to that observed for LP‐TEPPPO‐Mo (100 % at 87 % conversion). The reused solid–liquid and liquid–liquid biphasic catalytic systems show partial loss of catalytic activity.
Subvalent Organometallic Compounds of the Alkaline Earth Metals in Low Oxidation States
Authors: Krieck Sven , Yu Lian , Reiher Markus , Westerhausen Matthias 
Published: December 2009

AbstractAlkaline earth metals (Ae) are regarded as redox‐inactive, and their chemistry is dominated by the oxidation state +2. Nevertheless, in recent years several compound classes with alkaline earth metals in low oxidation states were investigated. Various concepts proved to be valid for the stabilization of such compounds and are discussed in this review. In the solid state, subvalency can be achieved by offering a matrix that takes over the excess electrons as, for example, in subnitrides. This fact leads to normal‐valent alkaline earth metals with electrons free to move between alkaline‐earth‐metal‐containing cages with or without a metal matrix. Another concept focuses on the synthesis of [Ae2]2+ cations with adequate substituents. The homodinuclear Ae–Ae bonds exhibit binding energies that should allow the synthesis of molecules such as R–Ae–Ae–R. The synthesis of magnesium derivatives succeeded by use of extremely bulky bidentate ligands with a delocalized anionic charge. The heavier alkaline earth metal derivatives are investigated by quantum chemical methods. Another possibility takes advantage of the fact that the first and second ionization potentials of the alkaline earth metals are clearly separated. Therefore, an arene with an extended π‐system having an energy level between the two ionization potentials should be able to overtake only one electron, which leads to Ae+ cations. Sophisticated procedures allowed the synthesis of a calcium(I) derivative, [(thf)3Ca(μ‐η6,η6‐C6H3‐1,3,5‐Ph3)Ca(thf)3], and such structures are investigated by quantum chemical methods also for the other alkaline earth metals.
Enantioselective Michael Addition of Aromatic Ketones to Nitroolefins Catalyzed by Bifunctional Thioureas and Mechanistic Insight
Authors: Li Bai‐Lin , Wang Yi‐Feng , Luo Shu‐Ping , Zhong Ai‐Guo , Li Zhao‐Bo , Du Xiao‐Hua , Xu Dan‐Qian 
Published: December 2009

AbstractA highly enantioselective Michael reaction of aromatic ketones with nitroolefins was accomplished in the presence of a chiral bifunctional primary amine–thiourea catalyst and 4‐nitrobenzoic acid as the co‐catalyst; the corresponding adducts were obtained in excellent enantioselectivities (up to 99 % ee) and yields (up to 98 %). The catalytic mechanism of the Michael reaction was confirmed through the ESI‐MS detection of proposed reaction intermediates and the 1H NMR detection of hydrogen bonding between thiourea and the nitroolefins. DFT calculations showed that chiral moieties of the thiourea impacted the yields and enantioselectivities of the adducts remarkably, which corresponds to the observed experimental results.
Reactivity‐Controlled Regioselectivity: A Regiospecific Synthesis of 1,2‐Disubstituted Benzimidazoles
Authors: Deng Xiaohu , Mani Neelakandha S. 
Published: December 2009

AbstractWe demonstrate exceptional levels of regioselectivity in the tandem amination reactions between 1,2‐differentiated dihaloarenes and N‐substituted amidines. The regiochemical outcome of this CuI‐catalyzed reaction is achieved through a combination of N1/N2 chemoselectivity on the amidine and reactivity‐controlled X1/X2 chemoselectivity on the 1,2‐dihaloarene. This reaction proves to be fairly general for the regiospecific synthesis of 1,2‐substituted benzimidazoles.
Reusable, Polystyrene‐Resin‐Supported, Palladium‐Catalyzed, Atom‐Efficient Cross‐Coupling Reaction of Aryl Halides with Triarylbismuths
Authors: Zhou Wen‐Jun , Wang Ke‐Hu , Wang Jin‐Xian , Huang Dan‐Feng 
Published: December 2009

AbstractA rapid, atom‐efficient, cross‐coupling reaction of triarylbismuths with aryl bromides or aryl iodides was reported, and the reaction involves the use of a catalytic amount of polystyrene‐supported palladium in the presence of KF as base in DMSO at 105 °C in an open atmosphere. All three aryl groups of the triarylbismuths participated in the reaction and produced polyfunctional biaryls in excellent yields. The polymeric catalyst can be easily separated from the reaction mixture and reused more than 10 times without showing any obvious decrease in activity.
Sensitive Voltammetric Determination of Methyl Parathion Using a Carbon Paste Electrode Modified with Mesoporous Zirconia
Authors: Tan Xiaohong , Li Buhai , Zhan Guoqing , Li Chunya 
Published: December 2009

AbstractA mesoporous zirconia modified carbon paste electrode was developed for electrochemical investigations of methyl parathion (MP, Phen‐NO2). The significant increase of the peak currents and the improvement of the redox peak potential indicate that mesoporous zirconia facilitates the electronic transfer of MP. The oxidation peak current was proportional to the MP concentration in the range from 1.0×10−8 to 1.0×10−5 mol L−1 with a detection limit of 4.6×10−9 mol L−1 (S/N=3) after accumulation under open‐circuit for 210 s. The proposed method was successfully applied to the determination of MP in apple samples.
Electrode Modified with Cobalt Cyclohexylbutyrate for the Determination of Low Molecular Weight Thiol Group Bearing Compounds Using Catalytic Stripping Voltammetry
Authors: Jakubec Petr , Halouzka Vladimir , Skopalova Jana , Hrbac Jan 
Published: December 2009

AbstractGlassy carbon electrode, modified with cobalt(II) cyclohexylbutyrate monohydrate immobilized in polystyrene matrix is usable for determination of thiol group bearing compounds both in oxidized and reduced forms using catalytic stripping voltammetry. The measurements are carried out in acetate buffer (pH 4.3) containing Tween 40. After the accumulation step at −850 mV vs. Ag/AgCl a peak at −170 mV is observed on linear sweep voltammogram, the height of which is proportional to the concentration of added thiol. Addition of carbon nanotubes into polystyrene film enhances the sensitivity of the modified electrode. The detection limit is 1×10−6 mol dm−3 for all studied thiols. The electrode can be regenerated by exposing it to the potential between 300–600 mV.
Solid‐State Electrochemical Method for Determining Core and Shell Size in Pd@PdO Nanoparticles
Authors: Doménech‐Carbó Antonio , Coronado Eugenio , Díaz Pilar , Ribera Antonio 
Published: December 2009

AbstractElectrochemical characterization of palladium nanoparticles surrounded by a palladium oxide shell (Pd@PdO) is described from a combination of voltammetry plus electrochemical quartz crystal microbalance experiments at nanoparticle deposits on graphite electrodes in contact with aqueous H2SO4 and NaOH solutions. A method for determining the metal core size and oxide shell thickness of the Pd@PdO nanoparticles, based on a combination of conventional voltammetry of nanoparticles in DMSO solution and voltammetry of nanoparticle deposits in contact with 0.10 M aqueous NaOH solution, is described.
Rapid Method for Quantitative Determination of Proteolytic Activity with Cyclic Voltammetry
Authors: Baş Deniz , Hakkı Boyacı İsmail 
Published: December 2009

AbstractAn alternative electrochemical method for the determination of proteolytic activity based on cyclic voltammetry of the electroactive probe ferricyanide (Fe(CN)63−) on the gelatin film coated ITO electrodes was proposed. The gelatin film behaves as a kinetic barrier for Fe(CN)63− and the proteolytic digestion of the gelatin film results an increase in the penetration of the Fe(CN)63−. Thus, by the change of peak potential in cyclic voltammogram of Fe(CN)63−, activity of the enzyme was determined.
Mediated Electron Transfer Across Supported Bilayer Lipid Membrane with TCNQ‐Based Organometallic Compounds
Authors: Qu Meili , Lv Qiying , Yang Bing , Zhang Weide , Zhang Jiaqi , Zhan Shuzhong , Ye Jianshan 
Published: December 2009

AbstractSupported bilayer lipid membrane (s‐BLM) containing one‐dimensional compound 1, TCNQ‐based (TCNQ=7,7,8,8‐tetracyanoquinodimethane) organometallic compound {(Cu2(μ‐Cl)(μ‐dppm)2)(μ2‐TCNQ)}∞, was prepared and characterized on the self‐assembled monolayer (SAM) of 1‐octadecylmercaptan (C18H37SH) deposited onto Au electrode. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results showed that the compound 1, dotted inside s‐BLM, can act as mediator for electron transfer across the membrane. Two redox peaks and the charge‐transfer resistance of 400 kΩ were observed for compound 1 inside s‐BLM. The mechanism of the electron transfer across s‐BLM by TCNQ is by electron hopping while TCNQ‐based organometallic compound is by conducting. Further conclusion drawn from this finding is that the TCNQ‐based organometallic compound embedded inside s‐BLM exhibits excellent electron transfer ability than that of free TCNQ. This opens a new path for the development of s‐BLM sensor and/or biosensor by incorporation with TCNQ‐based organometallic compounds.
Simple Fabrication of Amperometric Nitric Oxide Microsensors Based on Electropolymerized Membrane Films
Authors: Ho Shim Jun , Do Hyunkyung , Lee Youngmi 
Published: December 2009

AbstractDemand for highly sensitive, selective, and practically reliable sensors which could be easily fabricated is increasing for various applications in biological and biomedical systems. Thus, here we present a novel and simple amperometric NO microsensor based on electropolymerized polymeric films. The sensor consists of a platinized Pt disk anode (25‐μm diameter) which surface is modified with electropolymerized polymer films and a Ag/AgCl wire cathode coiled around the anode. Three different electropolymerized films prepared from m‐phenylenediamine (m‐PD), 2,3‐diaminonaphthalene (2,3‐DAN), and 5‐amino‐1‐naphthol (5A1N) are compared in terms of their permselectivity for NO over major biological interferents such as anionic nitrite, ascorbic acid, uric acid; neutral acetaminophen; and cationic dopamine. Poly‐5A1N film layer among the three different polymers shows the best anti‐interference characteristics for all the electroactive interferents examined. Indeed, single polymer film of electropolymerized 5A1N without any additional modification as a NO selective membrane is confirmed to be sufficient to reject anionic, neutral, as well as cationic interferents while allowing relatively high permeation of NO through it. Other analytical performance of the NO microsensor fabricated with poly‐5A1N is evaluated: reliable linear dynamic range (a few tens nM to μM); sensitivity of 122.0±2.5 pA/μM; detection limit of <5.8 nM (S/N=3); response time, t90%<5 s, which are excellent when considering the small sensor size. Another sensor design which has both an anode (poly‐5A1N modified platinized Pt) and a cathode (Ag/AgCl disk) embedded in a single sensor body is also presented.
Electrochemical Oxidation of Sanguinarine and of Its Oxidation Products at a Glassy Carbon Electrode – Relevance to Intracellular Effects
Authors: Diculescu Victor Constantin , Enache Teodor Adrian , Oliveira Paulo Jorge , Oliveira‐Brett Ana Maria 
Published: December 2009

AbstractThe electrochemical behavior of sanguinarine, a quaternary benzophenanthridine glycoside alkaloid with antimicrobial, anti‐inflammatory, antioxidant and/or immune‐stimulatory activities, was studied at a glassy carbon electrode using cyclic, differential pulse, and square wave voltammetry. The oxidation of sanguinarine is a quasireversible, diffusion‐controlled process and occurred in a cascade mechanism with the formation of several oxidation products which adsorbed at the electrode surface. The oxidation of sanguinarine is pH dependent and involves the transfer of the same number of electrons and protons. The adsorbed sanguinarine oxidation products are reversibly oxidized at the glassy carbon electrode surface and their oxidation for a wide range of pHs was also studied by differential pulse and square wave voltammetry. A mechanism for the oxidation of sanguinarine at glassy carbon electrode is proposed.
Analysis of the Effect of Potential Cycles on the Reflective Infrared Signals of Nitro Groups in Nanofilms: Application of the Fractional Moments Statistics
Authors: Nigmatulin Raoul R. , Alekhin Alexander P. , Baleanu Dumitru , Dinç Erdal , Üstündağ Zafer , Ekşi Haslet , Solak Ali Osman 
Published: December 2009

AbstractThe effect of the potential cycles on the reflective IR signals of nitro‐groups in nanofilms was studied for the statistical characterization of nitrobenzene (NB) and nitroazobenzene (NAB)‐modified glassy carbon (GC) surfaces. Both NB and NAB nanofilms were obtained by the electrochemical reduction of the diazonium tetrafluoroborate salts in acetonitrile using cyclic voltammetry (CV). The modified surfaces were denoted as GC‐(NB)n and GC‐(NAB)n, respectively, where n indicates the number of CV cycles performed during modification. Reflective IR signals of the normalized NB and NAB nanofilms and GC were used for the quantitative evaluation of the effect of the potential cycles on the reflective IR signals of nitro‐groups in nanofilms. The detection and quantitative ‘reading’ of the influence of number of CV cycles were realized in the frame of a new error controllable approach that was applied for analysis of all available set of data. This approach includes in itself the following basic steps: (a) the procedure of the division (normalization) on the GC spectra, (b) the comparison of the smoothed spectra for their statistical proximity in the frame of the statistics of the fractional moments, (c) extraction of possible calibration parameters for possible calibration of the normalized spectra with respect to the number of CV cycles. These three basic steps are becoming effective for detection of the influence of some external factors. In our case it is important to detect the influence of the factor n characterizing CV cycles.
A Simple Contactless Conductivity Detector Employing a Medium Wave Radio Integrated Circuit for the Signal Treatment
Authors: Opekar František , Štulík Karel , Fenclová Kateřina 
Published: December 2009

AbstractA new procedure has been tested for the treatment of the alternating signal coming from a contactless conductivity detection cell. The cell consists of a polyethylene (2 mm o.d., 1.5 mm i.d.) or polytetrafluoroethylene (1.6 mm o.d., 0.8 mm i.d.) tubing, with 5 mm wide tubular electrodes placed over the tubing and separated by a 5 mm gap. An unmodulated or an amplitude‐modulated AC voltage is applied to the cell and the AC current passing through the cell is treated by a TDA 1072A integrated circuit, obtaining a signal depending on the conductivity of the quiescent or flowing solution inside the cell. Under optimized conditions, the solution conductance can be measured within a range from ca. 10 to 700 μS cm−1, corresponding to ca. 9×10−5 to 5×10−3 M KCl. The detector was used to measure the conductivities of various drinking waters and the values obtained were in a good agreement with those provided by a commercial contact conductometer. It has been found that the use of unmodulated input voltage is advantageous both experimentally, and from the point of view of the quality of the analytical characteristics. The integrated circuit tested is not, however, sufficiently sensitive for application to capillary detection cells with diameters of a few tens of μm, employed in microseparation procedures.
Electrochemical Assay to Quantify the Hydroxyl Radical Scavenging Activity of Medicinal Plant Extracts
Authors: Hilgemann Maurício , Scholz Fritz , Kahlert Heike , de Carvalho Leandro Machado , da Rosa Marcelo Barcellos , Lindequist Ulrike , Wurster Martina , do Nascimento Paulo C. , Bohrer Denise 
Published: December 2009

AbstractA new electrochemical assay has been developed which is based on quantifying the attack of OH. radicals on a self‐assembled thiol monolayer on electrodes in the presence and absence of antioxidants. The OH. radicals were produced in Fenton solutions. The radical scavengers diminish the concentration of the OH. radicals in the Fenton solution, and the extent of thiol layer destruction is monitored with the help of a redox probe in solution, the signal of which is only generated at SAM‐free electrode surface. The results of the electrochemical assay were compared with those of the standard DPPH. assay. In case of each plant extract, an excellent linear correlation was observed between the radical scavenging activity and the concentration of plant extracts; however, the scavenging properties of different plants strongly differ in the electrochemical and the DPPH. assay. Since the proposed new method probes the reactivity of radical scavengers towards OH., one of the most important reactive oxygen radicals in tissues, it is supposed to provide much more relevant information than the DPPH. or other assays.
Potential Response of Monolayer‐Modified Indium Tin Oxide Electrodes to Indole Compounds
Authors: Nakanishi Takuya , Ueno Tsubasa , Matsunaga Mariko , Khan Md. Zaved Hossain , Osaka Tetsuya 
Published: December 2009

AbstractPotential response of indium tin oxide (ITO) electrode modified by treatment with disuccinimidyl suberate (DSS) was investigated to various target molecules. Distinctively, the DSS‐modified ITO electrode exhibited a potential shift to the molecules possessing an indole group such as tryptophan, tryptamine and indole propionic acid, while little response to benzoic acid, phenylalanine, proline, proline amide, and arginine was observed. In addition, the combination of this specificity to indoles and enantioselective affinity of human serum albumin (HSA), which was additionally immobilized on the DSS‐modified ITO electrode, brought about enantioselective potential response to tryptophan.
Modified Electrodes with Switchable Selectivity for Cationic and Anionic Redox Species
Authors: Tam Tsz Kin , Pita Marcos , Motornov Mikhail , Tokarev Ihor , Minko Sergiy , Katz Evgeny 
Published: December 2009

AbstractThe modified electrode functionalized with a mixed‐polymer brush composed of poly(2‐vinylpyridine) and polyacrylic acid tethered to the surface demonstrated switchable interfacial properties discriminating negatively and positively charged redox species. The switchable electrochemical process was characterized by differential pulse voltammetry and Faradaic impedance spectroscopy. The electrochemical system was discussed as a model of an electrochemical multiplexer with two chemical redox inputs, the pH input operating as the selecting signal and one electronic output signal readable by the impedance spectroscopy in the form of the interfacial resistance. The modified electrode represents a novel component for integration with biocatalytic and biocomputing systems aiming at biochemically and electronically controlled actuators.
A Sensitive Electrochemical Immunosensor for α‐Fetoprotein Detection with Colloidal Gold‐Based Dentritical Enzyme Complex Amplification
Authors: Liu Xueping , Wu Huiwang , Zheng Yue , Wu Zaisheng , Jiang Jianhui , Shen Guoli , Yu Ruqin 
Published: December 2009

AbstractA sensitive and specific electrochemical immunosensor was developed with α‐fetoprotein (AFP) as the model analyte by using gold nanoparticle label for enzymatic catalytic amplification. A self‐assembled monolayer membrane of mercaptopropionic acid (MPA) was firstly formed on the electrode surface through gold‐sulfur interaction. Monoclonal mouse anti‐human AFP was covalently immobilized to serve as the capture antibody. In the presence of the target human AFP, gold nanoparticles coated with polyclonal rabbit anti‐human AFP were bound to the electrode via the formation of a sandwiched complex. With the introduction of goat anti‐rabbit IgG conjugated with alkaline phosphatase, the dentritical enzyme complex was formed through selective interaction of the secondary antibodies with the colloidal gold‐based primary antibody at the electrode, thus affording the possibility of signal amplification for AFP detection. Current response arising from the oxidation of enzymatic product was significantly amplified by the dentritical enzyme complex. The current signal was proportional to the concentration of AFP from 1.0 ng mL−1 to 500 ng mL−1 with a detection limit of 0.8 ng mL−1. This system could be extended to detect other target molecules with the corresponding antibody pairs.
Group dynamics effectiveness of water user associations under different irrigation systems in an eastern Indian state
Authors: Ghosh Souvik , Kumar Ashwani , Nanda Prabhakar , Anand P.S.B. 
Published: December 2009

AbstractMost of the irrigation systems in India, whether large or small, are reported to have problems relating to the management of irrigation system at grass‐root level. Therefore, a solution that has been tried in various places is irrigation management transfer to water user groups. However, group dynamics plays a pivotal role in the functioning of groups in an efficient manner. The present study was conducted to study the group dynamics effectiveness of water users' associations (WUAs) under different irrigation systems in the state of Orissa, India. A group dynamics effectiveness index (GDEI) was formulated to measure group effectiveness of selected WUAs, which included 10 parameters. The study was carried out following an interview survey of 159 farmers representing eight WUAs under different irrigation systems. All 10 parameters of the GDEI were highly regarded by the farmers of lift irrigation WUAs, except social support. Most of the parameters of group effectiveness were found to be high in the case of minor irrigation WUAs. Farmers of major irrigation WUAs have perceived many of the parameters (participation, decision‐making procedure, group atmosphere, empathy, interpersonal trust and social support) to be weak. Differential group effectiveness may be attributed to the temporal and spatial variation in the irrigation command areas under the group's jurisdiction. Copyright © 2009 John Wiley & Sons, Ltd.