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41.
L-Ascorbate anion electro-oxidation on a silver electrode in hydroxide solution in the absence and presence of sodium polysulfide of concentrations from 1 × 10-5 to 4.5 × 10-4 mol/L was studied using cyclic voltammetry and electrochemical impedance spectroscopy.Both hydroxide and polysulfide ions inhibited L-ascorbate ion oxidation,with the poisoning effect of polysulfide ion being more pronounced in the potential range of-0.3 to-0.2 V/SCE.The time constants for L-ascorbate ion oxidation in the absence and presence of polysulfide were,10-3 to 1 × 10-2 s and 1 × 10-4 to 1 × 10-2 s,respectively depending on the potential used for the impedance analysis.Based on the cyclic voltammetry findings,a mechanism for L-ascorbate oxidation in the presence of polysulfide ions was proposed.Impedance calculations based on the kinetic analysis can account for the occurrence of a negative impedance in a potential region around-0.2 V/SCE in the Nyquist polts. 相似文献
42.
Laleh Safari Denys Iablonskyi Filippo Fratini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(2):1-8
We present secondary phase identification studies on Cr doped ZnO nanoparticles prepared by the sol-gel method. X-ray diffraction analysis confirms the formation of chromium oxides and there is found to be an increase of lattice parameter with thermal annealing. Scanning electron microscopic studies show the increase in the crystalline nature and particle size. Optical absorption measurements of the as prepared sample exhibit a strong band at 356 nm due to the free exciton absorption of the ZnO nanoparticles. An absorption band at 277 nm is due to the 3T1 → 3T2 transition in Cr4+ ions which appears only for the annealed samples. Photoluminescence studies show that deep level emission is completely suppressed after Cr2O3 formation/thermal annealing. Raman and FTIR spectra reveal formation of the Cr2O3 phase. Thermal annealing leads to the increase of crystalline nature which gives an enhancement to the Raman modes. 相似文献
43.
H Ebrahimzadeh AA Asgharinezhad L Adlnasab N Shekari 《Journal of separation science》2012,35(16):2040-2047
Ion-pair based hollow fiber liquid phase microextraction (IP-HFLPME) coupled with high performance liquid chromatography-ultraviolet detection was applied for the preconcentration and determination of methimazole in biological samples and animal feed. Optimization of the conditions for the high extraction efficiency was studied simultaneously using the experimental design. For the first step, the Plackett-Burman design was applied to screen the significant factors on the extraction efficiency. Central composite design (CCD) was then used for the optimization of important factors and the response surface equations were obtained. The optimum experimental conditions were donor phase pH, 12.2; extraction temperature, 45°C; extraction time, 50 min; sodium perchlorate concentration, 1.5 M; cetyltrimethylammonium bromide concentration, 0.65 mM, and without salt addition in donor phase. The limit of detection and the dynamic linear range were in the range of 0.1-0.7 μg L(-1) and 0.5-1000 μg L(-1) , respectively. Preconcentration factors were obtained in the range of 93-155 in different matrices. Finally, the performance of the proposed method was tested for the determination of trace amounts of methimazole in plasma, urine, bovine milk, and animal feed samples, and satisfactory results were obtained (RSDs < 7.1%). 相似文献
44.
This article describes an efficient, simple, and clean method for the synthesis of α,α′-bis(arylidene, furylidene and cinnamylidene)cycloalkanones under solvent-free conditions. The cross-aldol condensation of cycloalkanones with aldehydes in the presence of silica-supported phosphorus pentoxide (P2O5/SiO2) or silicaphosphinoxide (silphox, [POCl3-n(SiO2)n]) as heterogeneous reagents produces the title compounds in good to excellent yields. 相似文献
45.
A convenient method for the synthesis of 3‐substituted quinazolin‐4(3H)‐ones using the convergent reactions of formic acid, a primary amine, and isatoic anhydride under solvent‐free conditions and with brief microwave irradiation is described. 相似文献
46.
AbstractPervaporative ethanol dehydration was studied using some chitosan-boehmite nanocomposite membranes. Nanocomposite membranes were prepared by incorporation of 1 and 2?Wt. % loading of the boehmite nanoparticles synthesized by the low temperature sol-gel process. The prepared samples were characterized by FTIR, FESEM and XRD analysis. The results showed the filler particles uniform distribution within the chitosan matrix. Pervaporation performance of the prepared pristine and the nanocomposite membranes were evaluated for ethanol dehydration. The 2?Wt. % loaded boehmite nanocomposite membrane exhibited highest ethanol dehydration performance for 20?Wt. % water content feed at 50?°C as 0.513?kg/m2 h and 676 as permeation flux and separation factor revealed ~50% and 2 times increments, respectively. 相似文献
47.
Fatemeh Hedayati Nasrin Moshiri‐Gomchi Mahmood Assaran‐Ghomi Sara Sabahi Naeimeh Bahri‐Laleh Shahram Mehdipour‐Ataei Javad Mokhtari‐Aliabad Seyed Amin Mirmohammadi 《先进技术聚合物》2020,31(3):566-573
In order to lower brittleness of biobased polylactic acid (PLA), its blending with polycarbonate and nanosilica is aimed. In this line, to increase compatibility of the ingredients, dicumyl peroxide (DCP) and Cobalt (II) acetylacetonate (Co) were used as grafting and transesterification catalysts, respectively. The X‐ray diffraction (XRD) spectra demonstrated high compatibility of the ingredients by broadening of the PLA characteristic peaks and, also, good dispersion of nanosilica particles, especially in PLA/PC/Silica/Co sample. The EDX maps confirmed good nanosilica dispersion, too. The silica nanoparticle size was ranged from 20 to 100 nm in transmission electron microscopy (TEM) pictures. All nanocomposites showed improved thermal stability in thermogravimetric analysis (TGA). Differential scanning calorimetry (DSC) results demonstrated lower Tg, Tm, and crystallinity values for the fabricated nanocomposites. Notably, the dynamic mechanical thermal analysis (DMTA) curves confirmed the Tg, Tm, and Tcc trend obtained in DSC; moreover, much higher surface under tan δ peak for PLA/PC/Silica/Co sample was obtained, which implies its higher toughness. The precise tensile study of the samples confirmed significantly higher elongation at break of the nanocomposites, more considerably in PLA/PC/Silica/Co sample, with nearly negligible defect on tensile strength and modulus. In a concise, the obtained results confirmed the higher efficiency of Co catalyst, which leads to the sample with improved characteristics compared with DCP. 相似文献
48.
Laleh MoghaddamJames P. Blinco John M. ColwellPeter J. Halley Steven E. Bottle Peter M. FredericksGraeme A. George 《Polymer Degradation and Stability》2011,96(4):455-461
Degradation of polypropylene (PP) during melt processing was studied using a novel profluorescence technique. The profluorescent nitroxide probe, 1,1,3,3-tetramethyldibenzo[e,g]isoindolin-2-yloxyl (TMDBIO) was added to PP during melt processing to act as a sensor for carbon-centred radicals. Trapping of carbon-centred radicals, formed during degradation of PP, led to an increase in fluorescence emission from TMDBIO adducts. Through analysis of viscosity changes during processing cumulative chain scission degradation was estimated. At processing temperatures of 210 °C or below, fluorescence emission from TMDBIO adducts could be correlated with cumulative chain scissions when the number of chain scissions was small. At higher temperatures, a correlation was not observed most probably due to radical-trap instability rather than decomposition of the TMDBIO. Thus, TMDBIO may be used as a profluorescent sensor for degradation of PP during melt processing when the processing temperature is 210 °C or below. 相似文献
49.
Synthesis and characterization of Ni(II) complexes bearing of 2‐(1H–benzimidazol‐2‐yl)‐phenol derivatives as highly active catalysts for ethylene oligomerization
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Marzieh Haghverdi Azadeh Tadjarodi Naeimeh Bahri‐Laleh Mehdi Nekoomanesh‐Haghighi 《应用有机金属化学》2018,32(2)
Novel Ni(II) complexes of 2‐(1H–benzimidazol‐2‐yl)‐phenol derivatives (HLx: x = 1–5; C1–C5 ) have been synthesized and characterized. In the mononuclear complexes, the ligands were coordinated as bidentate, via one imine nitrogen and the phenolate oxygen atoms. The structures of the compounds were confirmed on the basis of FT‐IR, UV–Vis, 1H‐, 13C–NMR, inductively coupled plasma and elemental analyses (C, H and N). The purity of these compounds was ascertained by melting point (m.p.) and thin‐layer chromatography. The geometry optimization and vibrational frequency calculations of the compounds were performed using Gaussian 09 program with B3LYP/TZVP level of theory. All Ni(II) complexes were activated with diethylaluminum chloride (Et2AlCl), so that C2 showed the highest activity [6600 kg mol?1 (Ni) h?1], where the ligand contains a chlorine substituent. Oligomers obtained from the complexes consist mainly of dimer and trimer, and also exhibit high selectivity for linear 1‐butene and 1‐hexene. Both the steric and electronic effects of coordinative ligands affect the catalytic activity and the properties of the catalytic products. 相似文献
50.
Mojtaba Bagherzadeh Reza Latifi Laleh Tahsini Vahid Amani Arkady Ellern L. Keith Woo 《Polyhedron》2009
The synthesis of a Mo(VI) Schiff base complex, cis-[MoO2{(4,6-bis(tert-butyl)-2-{(benzyl)iminomethyl}phenolate)2}], cis-[MoO2(L)2] where L = 4,6-bis(tert-butyl)-2-{(benzyl)iminomethyl}phenol, derived from benzylamine and 3,5-di-tert-butylsalycilaldehyde is reported. Full characterization of this complex was accomplished with elemental analyses, spectroscopic studies (NMR, IR and electronic) and X-ray structure analysis. This complex was tested as a catalyst for the homogeneous oxidation of olefins. The Mo(VI) complex is catalytically active for the epoxidation of aliphatic substrates at 80 °C, yielding the epoxide as the sole product in yields up to 100% and turnover numbers up to 5000. Under the optimized conditions styrene was oxidized in an 81% conversion to produce styrene oxide, benzaldehyde, and acetophenone. 相似文献