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Interaction of the lacunary [alpha-XW9O33](9-) (X = As(III), Sb(III)) with Cu(2+) and Zn(2+) ions in neutral, aqueous medium leads to the formation of dimeric polyoxoanions, [(alpha-XW9O33)2M3(H2O)3](12-) (M = Cu(2+), Zn(2+); X = As(III), Sb(III)), in high yield. The selenium and tellurium analogues of the copper-containing heteropolyanions are also reported: [(alpha-XW9O33)2Cu3(H2O)3](10-) (X = Se(IV), Te(IV)). The polyanions consist of two [alpha-XW9O33] units joined by three equivalent Cu(2+) (X = As, Sb, Se, Te) or Zn(2+) (X = As, Sb) ions. All copper and zinc ions have one terminal water molecule resulting in square-pyramidal coordination geometry. Therefore, the title anions have idealized D3h symmetry. The space between the three transition metal ions is occupied by three sodium ions (M = Cu(2+), Zn(2+); X = As(III), Sb(III)) or potassium ions (M = Cu(2+); X = Se(IV), Te(IV)) leading to a central belt of six metal atoms alternating in position. Reaction of [alpha-AsW9O33](9-) with Zn(2+), Co(2+), and Mn(2+) ions in acidic medium (pH = 4-5) results in the same structural type but with a lower degree of transition-metal substitution, [(alpha-AsW9O33)2WO(H2O)M2(H2O)2](10-) (M = Zn(2+), Co(2+), Mn(2+)). All nine compounds are characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis. The solution properties of [(alpha-XW9O33)2Zn3(H2O)3](12-) (X = As(III), Sb(III)) were also studied by 183W-NMR spectroscopy. 相似文献
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F. Kadi Allah S. Yapi Abé C.M. Núñez L. Cattin A. Bougrine F.R. Díaz 《Applied Surface Science》2007,253(23):9241-9247
Al or Sn doped ZnO films were deposited by spray pyrolysis using aqueous solutions. The films were deposited on either indium tin oxide coated or bare glass substrates. ZnCl2, AlCl3 and SnCl2 were used as precursors. The effect of ZnCl2 molar concentration (0.1-0.3 M) and doping percentage (2-4% AlCl3 or SnCl2) have been investigated. The main goal of this work being to grow porous ZnO thin films, small temperature substrates (200-300 °C) have been used during the spray pyrolysis deposition. It is shown that, if the X-ray diffraction patterns correspond to ZnO, the films deposited onto bare glass substrate are only partly crystallized while those deposited onto ITO coated glass substrate exhibit better crystallization. The homogeneity of the films decreases when the molar concentration of the precursor increases, while the grain size and the porosity decrease when the Al doping increases. The optical study shows that band tails are present in the absorption spectrum of the films deposited onto bare glass substrate, which is typical of disordered materials. Even after annealing 4 h at 400 °C, the longitudinal resistivity of the films is quite high. This result is attributed to the grain boundary effect and the porosity of the films. Effectively, the presence of an important reflection in the IR region in samples annealed testifies of a high free-carriers density in the ZnO crystallites. Finally it is shown that when deposited in the same electrochemical conditions, the transmission of a polymer film onto the rough sprayed ZnO is smaller than that onto smooth sputtered ZnO. 相似文献
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Kadi A Hefnawy M Julkhuf S Abounassif M Mostafa G Kassem MG Attia S Al-Ghamdi A 《The Analyst》2011,136(13):2858-2865
For the first time, a capillary electrophoretic (CE) method with sample stacking induced by a reverse migrating pseudostationary phase (SRMP) technique has been developed and validated for sensitive determination of phenobarbital (PB) and its p-hydroxyphenobarbital (PHPB) metabolite in rat urine samples. Separation and determination were optimized on a fused-silica capillary with a total length of 50 cm (effective length 40 cm) and 75 μm ID. The microemulsion background electrolyte consisted of 0.8% (v/v) ethyl acetate, 6.6% (v/v) butan-2-ol, 1.0% (v/v) acetonitrile, 2.0% (w/v) sodium n-dodecyl sulfate (SDS), and 89.6% (v/v) of 7.5 mM ammonium formate at pH 8. When this preconcentration technique was used, the sample stacking and the separation processes took place successively with changing the voltage with an intermediate polarity switching step. For practical application, a solid-phase extraction (SPE), C(18) sorbent with n-hexane/ethyl acetate (1?:?1%, v/v) as the elution solvent was used for sample purification and concentration. The SPE method gave good extraction yields for all the analytes, with absolute recovery values of 96.9% and 99.1% for PB and PHPB, respectively. The regression equations for PB and PHPB showed excellent linearity over a concentration range of 55-1386 ng mL(-1) for PB and PHPB (r = 0.998). The developed microemulsion electrokinetic capillary chromatography (MEEKC) method for separation of the studied compounds with SRMP as the electrophoretic preconcentration technique allowed detection limits in urine samples at 16.8 ng mL(-1) for PB and PHPB which are 15-fold lower than the reported CE method in the literature. The precision results, expressed by the intra-day and inter-day relative standard deviation (RSD) values range from 3.6 to 7.1% (repeatability) and from 3.2 to 7.2% (intermediate precision) for PB and PHPB, respectively, which were in line with Food and Drug Administration (FDA) criteria. 相似文献
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Aboul-Fadl T Abdel-Aziz HA Kadi A Bari A Ahmad P Al-Samani T Ng SW 《Molecules (Basel, Switzerland)》2011,16(5):3544-3551
A facile and efficient method for synthesis of fenamic acid hydrazides from their acids in one-step reaction under microwave irradiation and solvent-free conditions was developed. Compared with the two-step conventional heating method, the process was simple, the reaction time was very short and the yields were almost quantitative. 相似文献
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M. S. El-Shahawi M. W. Kadi S. H. El-Khouly A. Abd El-Mohty S. M. Saad N. E. A. Eweda 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):1873-1880
A low cost and selective method has been developed for the separation of trace concentrations of 90Y3+ from its parent 89Sr2+. The proposed procedure is based upon complete retention of 90Y3+ onto zirconium-vanadate (Zr-V) gel ion exchanger packed column from aqueous solutions containing HCl (1.0 × 10?5mol dm?3). Under these conditions, 89Sr2+ species were not retained onto Zr-V sorbent. The retained 90Y3+ species were then recovered with HCl. The performance of Zr-V sorbent packed column was determined via the height equivalent to the theoretical plates (HETP) and the number of plates (N). Validation of the developed method was checked by calculating the radionuclidic purity in terms of purification factor (P f = A/A0) and radiochemical purity of the eluted 90Y from the column. Zr-V sorbent packed column offers unique advantages of retention and quantitative separation of 90Y from retention over conventional solid sorbents in rapid and effective separation of trace concentration of 90Y3+ from 89Sr2+ in their aqueous equilibrium media. 相似文献
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M. S. El-Shahawi M. W. Kadi S. H. El-Khouly A. Abd El-Mohty S. M. Saad N. E. A. Eweda 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):15-22
A new zirconium vanadate (Zr–V) ion-exchanger was synthesized and characterized for fast and selective separation procedure of 90Y from 89Sr. The method was based on 90Y(III) sorption from aqueous HCl solution containing 89Sr(II) onto Zr–V gel exchanger. The kinetics of Y(III) sorption from HCl solution by Zr–V exchanger was subjected to Weber–Morris, Lagergren, Bhattacharya and Venkobachar, and Bt models. Initially, the uptake of Y(III) onto the exchanger was fast followed by kinetically first-order sorption with an overall rate constant, K Lager = (3.55 ± 0.03) × 10?4 min?1. Film and intraparticle transport are the two steps that might influence Y(III) sorption. The negative values of ΔG of 90Y retention dictate that, the process is a spontaneous. The negative values of ΔH and ΔS reflect the exothermic nature of 90Y(IIsorption and the random uptake of 90Y(III) onto Zr–V sorbent. Zr–V exchanger offers unique advantages of 90Y(III) retention over conventional solid sorbents in rapid and effective separation of traces of 90Y(III) from Sr. The exchanger was successfully packed in column for an effective separation of 90Y. 相似文献
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The bisucaberin biosynthetic gene cluster has been identified in Vibrio salmonicida and a domain from within the BibC multienzyme encoded by the cluster has been shown to catalyse ATP-dependent dimerisation and macrocyclisation of N-hydroxy-N-succinylcadaverine to form bisucaberin. 相似文献