用聚(L-蛋氨酸)/纳米金修饰玻碳电极同时灵敏检测多巴胺和尿酸(英文)

A novel electrochemical sensor was fabricated by electrodeposition of gold nanoparticles on a poly(L-methionine)(PMT)-modified glassy carbon electrode(GCE) to form a nano-Au/PMT composite-modified GCE(nano-Au/PMT/GCE).Scanning electron microscopy and electrochemical techniques were used to characterize the composite electrode.The modified electrode exhibited considerable electrocatalytic activity towards the oxidation of dopamine(DA) and uric acid(UA) in phosphate buffer solution(pH = 7.00).Differential pulse voltammetry revealed that the electrocatalytic oxidation currents of DA and UA were linearly related to concentration over the range of 5.0 ×10–8 to 10–6 mol/L for DA and 7.0 × 10–8 to 10–6 mol/L for UA.The detection limits were 3.7 × 10–8mol/L for DA and 4.5 × 10–8 mol/L for UA at a signal-to-noise ratio of 3.According to our experimental results,nano-Au/PMT/GCE can be used as a sensitive and selective sensor for simultaneous determination of DA and UA.     

Diazabicyclo[2.2.2]octane stabilized on Fe3O4 as catalysts for synthesis of coumarin under solvent-free conditions

Fe₃O₄-diazabicyclo[2.2.2]octane (Fe₃O₄-DABCO) magnetic nanoparticles (MNPs) catalyst was readily prepared from inexpensive starting materials in aqueous media which catalyzed the synthesis of coumarin. FTIR spectroscopy, X-ray diffraction, transmission electron micrographs were employed to characterize the properties of the synthesized Fe₃O₄-DABCO MNPs. High catalytic activity and ease of recovery from the reaction mixture using external magnet, and several reuse times without significant losses in performance are additional eco-friendly attributes of this catalytic system.     

Synthesis,characterization and crystal structure determination of mononuclear and dinuclear copper(II) carboxylates: [Cu(Hdpa)2(en)] and [{Cu2(μ-na)4(CH3OH)2}·2CH3OH]

Two new copper complexes [Cu(Hdpa)₂(en)] (1) and [{Cu₂(μ-na)₄(CH₃OH)₂}·2CH₃OH] (2) (where en is ethylene diamine, Hdpa is 2′-carboxy-[1,10-biphenyl]-2-carboxylate anion and na is 1-naphtalenecarboxylate) have been synthesized and their crystal structures were determined by X-ray crystallography. Complex 1 was prepared from the reaction of Cu(NO₃)₂·3H₂O with ethylene diamine and 2,2′-biphenyldicarboxylic acid in a mixture of water and methanol and complex 2 was prepared from the reaction of CuSO₄·5H₂O with 1-naphtalenecarboxylic acid in methanol. The two complexes were characterized by IR, UV–vis, luminescence and elemental analysis. Moreover, complex 2 was characterized by EPR spectroscopy and thermogravimetric analysis. Complex 1 is a monomer and complex 2 is a dimer with a paddle-wheel structure; both structures are without precedent in the literature.     

Infinitely many solutions for Steklov problems associated to non-homogeneous differential operators through Orlicz-Sobolev spaces

Employing variational methods and critical point theory, in an appropriate Orlicz-Sobolev setting, we establish the existence of infinitely many solutions for Steklov problems associated to non-homogeneous differential operators. We also provide some particular cases and a concrete example in order to illustrate the main results.     

Kinetics and Mechanism of the Oxidation of 4-Oxo-4-arylbutanoic Acids by N-bromophthalimide in Aqueous Acetic Acid Medium

The kinetics of oxidation of a series of substituted 4-oxobutanoic acids (Y–C₆H₄COCH₂CH₂COOH: Y = H, OCH₃, CH₃, C₆H₅, Cl, Br or NO₂) by N-bromophthalimide have been studied in aqueous acetic acid medium at 30 °C. The total reaction is second-order, first-order each in oxidant and substrate. The oxidation rate increases linearly with [H⁺], establishing the hypobromous acidium ion, H₂O⁺Br, as the reactive species. A variation in ionic strength has no effect on the reaction rate. The order of reactivity among the studied 4-oxoacids is: 4-methoxy > 4-methyl > 4-phenyl > 4-H > 4-Cl > 4-Br > 3-NO₂. The effect of changes on the electronic nature of the substrate reveals that there is a development of positive charge in the transition state. The activation parameters have been computed from Arrhenius and Eyring plots. Based on the kinetic results, a suitable mechanism has been proposed.     

Theoretical Study of the Solvent Effect on the Methyltrioxorhenium/Hydrogen Peroxide System

The effect of solvent on the stability and reactivity of methyltrioxorhenium (MTO) for activation of hydrogen peroxide (H₂O₂) was investigated theoretically. The possible geometries for all Re complexes present in this system, MTO, monoperoxo complexes [A: MeReO₂(η ²–O₂) and A·H ₂ O: MeReO₂(η ²–O₂)(H₂O)], and bisperxo complexes [B: MeReO(η ²–O₂)₂ and B·H ₂ O: MeReO(η ²–O₂)₂(H₂O)] were calculated. Based on the theoretical calculations, species A lacks coordinated water while species B·H ₂ O definitely has water coordinated to the Re. The changes of thermodynamic parameters (ΔH and ΔG) for six reactions in the MTO/H₂O₂, system including formation of mono- and bisperoxo complexes, were determined.     

A novel Lu fluorescent nano-chemosensor using new functionalized mesoporous structures

A new Lu³⁺ sensitive fluorescent chemosensor is designed using 8-hydroxyquinoline functionalized mesoporous silica with highly ordered structure (LUS-SPS-Q). The characterization of LUS-SPS-Q showed that the organized structure has been preserved after the post grafting procedure. The synthesized material showed a selective interaction with Lu³⁺ ion, most probably due to the presence of the fluorophore moiety at its surface. The emission intensity of the Lu³⁺-bound mesoporous material increases with an increase in concentrations of Lu³⁺ ion. Addition of other mono-, di-, trivalent ions resulted in insignificant change in the fluorescent intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Lu³⁺ ion. The linear response range of Lu³⁺ chemo-sensor was from 1.6 × 10⁻⁷ to 1.0 × 10⁻⁵ mol L⁻¹. The Limit of detection obtained was 8.2 × 10⁻⁸ mol L⁻¹ and the pH range which the proposed chemo-sensor can be applied was 3.3–8.3.     

Regioselective Synthesis of Indolizines,Pyrrolo[2,1-a]isoquinolines,and Quinolines

Convenient and regioselective synthesis of indolizine and pyrrolo[2,1-a]isoquinoline/quinoline derivatives by one-pot multicomponent reaction of N-substituted pyridinium and isoquinolinum/quinolinium salts with alkyl propiolates in the presence triphenylphosphine is described.