基于纳米结构的电化学传感器同时测定溶液中异丙肾上腺素、尿酸和叶酸的浓度(英文)

A carbon paste electrode modified with 2‐((7‐(2,5-dihydrobenzylideneamino)heptylimino)methyl) benzene‐1,4‐diol(DHB) and carbon nanotubes were used to simultaneously determine the concen-trations of isoproterenol(IP), uric acid(UA), and folic acid(FA) in solution. First, cyclic voltammetry was used to investigate the redox properties of the modified electrode at various scan rates. Next, the mediated oxidation of IP at the modified electrode is described. At the optimum pH of 7.0, the oxidation of IP occurs at a potential about 90 mV less than that of an unmodified carbon paste elec-trode. Based on the results of differential pulse voltammetry(DPV), the oxidation of IP showed a dynamic range between 10 and 6000 μmol/L, and a detection limit of 1.24 μmol/L. Finally, DPV was used to simultaneously determine the concentrations of IP, UA, and FA in solution at the modified electrode.     

Thermal performance of poly(ethylene disulfide)/expanded graphite nanocomposites

In this study, the influences of expanded graphite oxide (EG) nanosheets presence with and without surfactant on structural and thermal performance of poly(ethylene disulfide) (PEDS)-based nanocomposites are investigated. Sodium dodecylbenzenesulfonate (SDBS) is used as a surfactant for the preparation of modified-EG nanosheets. The structural, morphological, and thermal properties of prepared nanocomposites are studied using X-ray diffraction (XRD), scanning electron microscopy, and differential scanning calorimetry techniques, respectively. XRD patterns of nanocomposites reveal that a high degree of expanded graphite nanosheets dispersion is achieved with and without surface modification using in situ polymerization method. Moreover, the presence of immobilized polysulfide chains near the interface region of nanosheets is suggested as a possible reason for the observed increase in the number of semi-crystalline organic fractions in the structure of PEDS via EG nanosheets incorporation. In addition, the morphology of SDBS-modified-EG loaded nanocomposite shows a smoother fracture surface than unmodified-nanosheets reinforced nanocomposite. Therefore, more interactions between nanosheets and polysulfide chains are expected in the structure of unmodified-EG reinforced nanocomposite. Moreover, thermal resistance and degradation kinetics of prepared nanocomposites are studied using thermogravimetric analysis results and degradation activation energy calculations, respectively. The required activation energy for the degradation process of SDBS-EG loaded nanocomposite is about 140 kJ mol^?1 lower than the required degradation activation energy of unmodified-nanosheets reinforced nanocomposite.     

A Simple Approach to Assess the Performance of Non-ideal Aluminum/Ammonium Perchlorate Composite Explosives as Compared to the Best Available Methods

Composite explosives containing aluminum/ammonium perchlorate (Al/AP) are widely used for blasting cut of old warship, blasting droll and decoupled charge of blast underwater. The available complex computer codes and empirical methods cannot usually provide a reliable estimation of detonation velocities of explosives containing Al/AP. This work introduces a reliable method for the desk calculation of detonation velocity. The percent of the reacted Al with detonation products and decomposition of AP, as well as composition of the detonation products, are specified according to the distribution of oxygen atoms between Al, C(s), CO(g) and H₂(g). The values of the mean absolute percentage error (MAPE) of the new model are lower than one of the best available methods for CHNO explosives (260 experimental data) and CHNOFCl explosives (50 measured data). For composite explosives, CHNOFClAl and CHNOFClAlAP, the MAPE value of the new model is 3.50, corresponding to 55 experimental data, which is much smaller than the MAPE values of the BKW computer code (8.37) and the comparative empirical model (14.20).     

An Efficient Method for Chemoselective Reduction of Nitro Compounds Using Bimetallic Fe‐Ni NPs/H3PW12O40.×H2O System

The selective reduction of nitro compounds by treatment with bimetallic Fe‐Ni nanoparticles (NPs) and tungestophosphoric acid hydrate (H₃PW₁₂O₄₀.×H₂O) in H₂O is reported. The method has been applied to a broad range of nitro compounds with different sensitive functionalities, including halides, carbonyl, hydroxyl, aldehyde, methyl, acetyl, nitrile, and ester substituents with excellent yields. The reaction yielded single product in all cases with very high yield. The simple experimental procedure and easy purification make the protocol advantageous.     

Efficient and Eco‐friendly Syntheses of 1,5‐Benzothiazepines and 1,5‐Benzodiazepines Catalyzed by [Hmim][NO3] under Mild Conditions

This article presents a synthetic method and reaction mechanism of the 1,5‐benzothiazepines and 1,5‐benzodiazepines derivatives. In this research, 36 thiazepines and diazepines (mostly new) with a new method have been prepared and their structures have been characterized by spectroscopic methods. Crystal structures of a new thiazepine and diazepine (seven‐membered rings) have also been determined and compared with thiazine (six‐membered ring). In this method, N‐methylimidazolium nitrate [Hmim][NO₃] has been used as a catalyst that acts as an environmental friendly system.     

Magnetite-doped eggshell membrane as a magnetic sorbent for extraction of aluminum(III) ions prior to their fluorometric determination

We have explored the feasibility of using a magnetite-doped eggshell membrane as a magnetic solid phase extraction sorbent for the separation of aluminum ion from aqueous solutions. The sorbent was characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. A fast, simple and non-expensive method was then developed for the determination of trace quantities of Al(III) in water and food samples by combining magnetic solid phase extraction with fluorometric quantitation via its highly fluorescent complex with 8-hydroxyquinoline. The effects of pH value, amount of sorbent, sample volume, elution conditions and interfering ions on extraction were optimized. Under optimum conditions, the calibration graph extends from 0.5 to 65.0 μg L^?1, the limit of detection is 0.2 μg L^?1, and the enrichment factor is 84. The method was validated by the successful analysis of a standard reference material (NIST SRM 1549; nonfat milk powder) and applied to the determination of Al(III) in several waters, black tea, tomato paste and cocoa powder samples. Figure

Synthesis and application of magnetite-doped eggshell membrane for the separation of aluminum(III) ions from aqueous solutions is shown. After extraction for 5 min, the sorbent was gathered under an external magnetic field and the clear supernatant was directly decanted. The enriched analyte was then eluted from the sorbent prior to determination.     

Nanofiltration membranes based on blend of polysulfone-g-poly(tert-butylacrylate) copolymer and polysulfone

Nanofiltration membranes based on blend of polysulfone-g-poly(tert-butylacrylate) copolymer and polysulfone were prepared by phase inversion technique. ATRP grafting of tert-butylacrylate from chloromethylated polysulfone was used for the grafted polymer synthesis. The copolymer was characterized with FTIR, NMR, DSC and TGA. The prepared membranes were characterized in terms of pure water flux, water contact angle, cut off molecular weight, salt rejection and scanning electron microscopy.     

Solid‐phase microextraction of phthalate esters by a new coating based on a thermally stable polypyrrole/graphene oxide composite

A novel polypyrole/graphene oxide coating was made by the electrochemical polymerization of pyrrole in the presence of sodium dodecyl sulfate and graphene oxide on a platinum wire. The prepared fiber has shown a good thermal stability up to 300°C. The fiber was applied to the direct solid‐phase microextraction and gas chromatographic analysis of four phthalate esters. The effect of four parameters on gas chromatography peak area including extraction temperature, extraction time, injection temperature, and ionic strength were investigated. Under the optimized conditions, the detection limits were between 0.042 and 0.26 μg/L. The intraday and interday relative standard deviations obtained at 55 μg/L, using a single fiber, were 8.2–16% and 17.3–25.6%, respectively. The method was successfully applied to the analysis of phthalate esters in two real samples of boiling water in cheap disposable clear plastic drinking cups showing recoveries from 83 to 120%.     

Fe(HSO4)3·SiO2 as an efficient,heterogeneous and recyclable catalyst for the synthesis of bis-(β-enaminones) and bis-(β-enamino esters)

Fe(HSO₄)₃·SiO₂ is used to catalyze the condensation of β-diketones and β-keto esters with aromatic and aliphatic diamines in solvent-free conditions at room temperature. This afforded the corresponding bis-(β-enaminones) and bis-(β-enamino esters) in very good to excellent yields. Short reaction times, easy work-up procedure, and reusability of the catalyst are the merits of this study.     

Molecular dynamics simulation of the diffusion of nanoconfined fluids

A new molecular dynamics simulation technique for simulating fluids in confinement [H. Eslami, F. Mozaffari, J. Moghadasi, F. Müller-Plathe, J. Chem. Phys. 129 (2008) 194702] is employed to simulate the diffusion coefficient of nanoconfined Lennard-Jones fluid. The diffusing fluid is liquid Ar and the confining surfaces are solid Ar fcc (100) surfaces, which are kept frozen during the simulation. In this simulation just the fluid in confinement is simulated at a constant temperature and a constant parallel component of pressure, which is assumed to be equal to the bulk pressure. It is shown that the calculated parallel (to the surfaces) component of the diffusion coefficients depends on the distance between the surfaces (pore size) and shows oscillatory behavior with respect to the intersurface separations. Our results show that on formation of well-organized layers between the surfaces, the parallel diffusion coefficients decrease considerably with respect to the bulk fluid. The effect of pressure on the parallel diffusion coefficients has also been studied. Better organized layers, and hence, lower diffusion coefficients are observed with increasing the pressure.