聚多巴胺功能化硅胶沉积单分散Pd纳米粒子的简易原位合成及用作醇需氧氧化反应的多相可循环使用的纳米催化剂（英文）

本文报道了一种不使用任何稳定剂或还原剂,原位合成硅胶/聚多巴胺复合物(SiO_2/PDA)负载的Pd纳米颗粒(Pd NPs)的简易方法.该方法先将PDA涂覆的SiO_2颗粒浸在Pd镀液中,然后利用PDA中含N基团的还原能力将Pd物种原位还原为纳米簇合物.并采用高分辨透射电镜、前场扫描电镜、能量散射谱、X射线衍射、X射线光电子能谱、诱导耦合等离子体和红外光谱等手段对所得纳米复合物的结构、形貌和物化性质进行了表征.被PDA基团锚合的Pd NPs具有显著的小颗粒(30–40 nm)特性.作为一个可循环使用的纳米催化剂,SiO_2/PDA/Pd NPs在醇的需氧氧化反应中表现出高活性.另外,催化剂经回收和多次重复使用时未出现明显的失活.     

A novel carbon/chitosan paste electrode for electrochemical detection of normetanephrine in the urine

Normetanephrine is a marker for pheochromocytoma, a rare catecholamine-secreting and neuroendocrine tumor, that arises from sympathetic and parasympathetic paraganglia. In this work, a novel carbon/chitosan electrode paste was used for sensitive voltammetric determination of normetanephrine and dopamine in the presence of ascorbic acid and uric acid. The modified electrode has shown an increase in the effective area of up to 68%, well-separated oxidation peaks, and an excellent electrocatalytic activity. The electrochemical response characteristics were investigated by cyclic and differential pulse voltammetry. Interestingly, high sensitivity and selectivity in the linear range of normetanephrine, dopamine, ascorbic acid, and uric acid concentrations were observed. The present method was applied in the urine sample and satisfactory results were obtained showing that this electrode is very suitable in pharmaceutical and clinical preparations.     

KAl(SO4)2 · 12H2O (alum) a reusable catalyst for the synthesis of some 4-substituted coumarins via Pechmann reaction under solvent-free conditions

A simple, efficient, and practical procedure for the Pechmann condensation using KAl(SO₄)₂ · 12H₂O (alum) as a non-toxic, reusable, inexpensive, and easily available catalyst is described under solvent-free condition at 65°C. These improved reaction conditions allow the preparation of a wide variety of some new substituted coumarins in high yields (86–96%) and purity under mild reaction conditions. Compared to the classical Pechmann condensation, this new method consistently has the advantage of high yields. Correspondence: Ali A. Mohammadi, Department of Chemistry, Shahid Beheshti University, P.O. Box 19839-4716, Tehran, Iran.     

Sensitive determination of ethosuximide in human fluids by electromembrane extraction coupled with high performance liquid chromatography ultraviolet spectroscopy

Ethosuximide (ETX) is a common antiepileptic drug in the first line of absence epilepsy. In this study, for the first time, an economical and efficient electro-membrane (EME) method for determination of ETX in a complex biological matrix using HPLC-UV has been developed. Factors affecting conventional EME were evaluated. 1-Octanol was immobilized in a polypropylene membrane and a voltage of 35 V was applied between two platinum electrodes for 15 min. The pH of acceptor and donor phases for ionization of ETX was adjusted to 13 and 11, respectively. Under optimal microextraction conditions, the enrichment factor was 21.02 and the linear range of ETX was 0.25 to 8.00 μg/mL with an acceptable R² ≥ 0.9986. Inter-day and intra-day precision and accuracy of the suggested method were calculated with RSD < 9.5% and relative error <7.0%, respectively. The mean relative recovery of ETX in the human saliva and plasma samples was 81.68% and 74.47, respectively; while limit of detection and quantification concentrations were 0.08 and 0.25 μg/mL, respectively. Furthermore, to evaluate the application of the method, plasma and saliva samples of volunteers administering a single dose of ETX were analyzed successfully by EME-HPLC-UV method.     

Electrochemical Sensing Platform Based on Graphene Oxide-chitosan for Simultaneous Determination of some Antihypertensive Drugs

The development of selective and simple methods for the determination of different analytes is of great interest. This is the first time to show the applicability of graphene oxide-chitosan (GO-CS) nanocomposite for designing an electrochemical nanosensor for determination of Amlodipine, Valsartan, and Hydrochlorothiazide, simultaneously. Differential pulse voltammetrics current of AML, HCT, and VAL increased linearly in the ranges of 0.1–110, 0.1–110, and 1–230 μM with LOD of 5.5×10⁻², 3.5×10⁻² and 8.6×10⁻² μM, respectively. Finally, GO-CS/GCE was used for the detection of these drugs in commercial tablets and compared with the reference method (HPLC).     

A novel method for fast determination of vitamin B6 by fast continuous cyclic voltammetry

In this work a novel method for the determination of Vitamin B6 in flow-injection systems has been developed. The fast Fourier transform continuous cyclic voltammetry (FFTCV) at gold microelectrode in flowing solution system was used for determination of Vitamin B6. This method is rapid, simple and highly sensitive procedures allowing the determination of Vitamin B6 in pharmaceutical analysis. The effects of various parameters on the sensitivity of the method were investigated. The best performance was obtained with the pH value of 2, scan rate value of 30 V/s, accumulation potential of 200 mV and accumulation time of 0.3 s. The proposed method has some advantages over other reported methods such as, no need for the removal of oxygen from the test solution, a sub-nanomolar detection limit, and finally the method is fast enough for the determination of any such compound, in a wide variety of chromatographic methods. To obtain a sensitive determination, the integration range of currents was set for all the potential scan ranges, including oxidation and reduction of the Au surface electrode, while performing the measurements. The potential waveform, consisting of the potential steps for cleaning, accumulation and potential ramp of analyte, was applied on an Au disk microelectrode (12.5 μm in radius) in a continuous way. The detection limit of the method for Vitamin B6 was 2.8 pg/ml. The relative standard deviation of the method at 2.1% was 8 runs. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 2, pp. 173–181. The text was submitted by the authors in English.     

Cr(VI) ion removal from artificial waste water using supported liquid membrane

In this study, a novel flat-type synergic-supported liquid membrane was evaluated with a mixture of N-methyl-N,N,N-trioctylammonium chloride (Aliquat 336) and tributyl phosphate (TBP) as the carrier and kerosene as the diluent to remove Cr(VI) from synthetic waste water. The main parameters involved in the process were identified and optimised. The parameters were divided into two groups, those that were independent and those having an interaction. The parameters of the carrier/kerosene volumetric proportion and stirring rate were optimised individually due to their nature. The optimal values of these parameters were 0.5 and 500 min^?1, respectively, for a constant carrier/kerosene ratio and stirring rate in the designed experiments using the response surface method (RSM). The four parameters of TBP/Aliquat 336, chromium concentration in the feed phase, feed and product pH were optimised using RSM; it was observed that the TBP/Aliquat 336 ratio, feed pH, pH of the stripping phase and interaction of this parameter with feed concentration have the most important effects on the removal of Cr(VI). The optimal levels of these parameters were 0.61, 71.75 mg L^?1, 3.5 and 12.66 for the ratio of TBP/Aliquat 336, feed chromium concentration, pH of the feed and pH of the product, respectively. An experimental removal rate of 94.63 % at the optimized levels was obtained.     

Charge separation by tetrahexahedron-SrTiO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> heterojunction as an efficient photocatalyst

Charge separation plays a key role in the conversion of solar energy into chemical energy for use in the redox reaction and as well as in the photocatalytic activity. In this study, SrTiO₃ particles with different morphologies including irregular, tetrahexahedron, and cube were synthesized by an in situ solvothermal method. The photocatalytic activity of the synthesized nanoparticles was investigated in the photocatalytic decomposition of methylene blue under UV light irradiation. Tetrahexahedron SrTiO₃ particles exhibited high decomposition activity (70 %), which is about two times higher than those of the irregular and cubic SrTiO₃ particles. The high decomposition activity of tetrahexahedron SrTiO₃ particles could be attributed to the improvement of charge separation achieved on different crystal facets. To reach a good charge separation, tetrahexahedron SrTiO₃/TiO₂ coupled nanoparticles were fabricated by impregnation method. Results showed that coupling tetrahexahedron SrTiO₃ with TiO₂ could produce efficient charge separation between tetrahexahedron SrTiO₃ and TiO₂ due to their matched band edges. In order to achieve better charge separation, the tetrahexahedron SrTiO₃/90 %TiO₂ sample was calcined at different temperatures in the 450–750 °C range. Tetrahexahedron SrTiO₃/90 %TiO₂ coupled nanoparticles calcined at 650 °C show high photocatalytic activity compared with other samples. The prepared samples were characterized by using various techniques such as X-ray diffraction, scanning electron microscopy, photoluminescence emission spectra, and UV–Vis diffuse reflectance spectroscopy.