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排序方式: 共有326条查询结果,搜索用时 31 毫秒
61.
Sihem Khaddar-Zine Abdelhamid Ghorbel Claude Naccache 《Journal of Sol-Gel Science and Technology》2000,19(1-3):637-641
Alumina or silica supported chromium oxide catalysts prepared by sol-gel technique have been investigated by X-ray diffraction, BET analysis, combined diffuse reflectance spectroscopy, EPR and reduction-extraction by ethane 1,2 diol. The results reveal the presence of Cr3+, Cr5+ and Cr6+ ions. Chromium species Cr6+ are isolated and atomically dispersed on the alumina support as free chromate CrO
4
2–
while on silica, dichromate or polychromate species like Cr2O
7
2–
or Cr3O
10
2–
predominate. Chromium oxide exhibits a better catalytic properties for paraxylene partial oxidation, when it is supported on alumina. The difference of oxidation states and degree of oligomerisation of chromium on the two supports affects the catalytic properties. 相似文献
62.
Shemseddine Fessi Abdelhamid Ghorbel 《Journal of Sol-Gel Science and Technology》2000,19(1-3):417-420
The chemical reactivity of the aluminium-sec-butoxide (ASB) and the palladium acetylacetonate Pd(acac)2, used as precursors for the preparation of the alumina supported palladium catalysts by sol-gel method was investigated by the spectroscopic study of the precursor mixture during ageing, using FTIR, UV-VIS and 27Al NMR. The obtaind results showed that acetylacetonate ligands were linked to aluminum when the mixture was aged at 40°C. This was proved by the bands observed at 1530 and 1600 cm–1 in the FTIR spectra, the band obtained at 289 nm in the UV-VIS spectra and the 27Al NMR sharp peak at 3 ppm. Furthermore, in order to avoid the Pd(acac)2 reduction to metallic palladium by the SB occurring when the mixture is aged for 3 h, an optimum ageing time should be selected. The precursors modification and the preservation of the palladium oxidation state during ageing could be the required conditions to create a bond between palladium and aluminium during the gelation step. This should be the reason of the thermal stability improvement of the alumina supported palladium catalyst prepared by the sol-gel method. 相似文献
63.
Fares Zouaoui Saliha Bourouina-Bacha Mustapha Bourouina Nadia Zine Abdelhamid Errachid Nicole Jaffrezic-Renault 《Molecules (Basel, Switzerland)》2022,27(2)
The massive and careless use of glyphosate (GLY) in agricultural production raises many questions regarding environmental pollution and health risks, it is then important to develop simple methods to detect it. Electrochemical impedance spectroscopy (EIS) is an effective analytical tool for characterizing properties at the electrode/electrolyte interface. It is useful as an analytical procedure, but it can also help in the interpretation of the involved fundamental electrochemical and electronic processes. In this study, the impedance data obtained experimentally for a microsensor based on molecularly imprinted chitosan graft on 4-aminophenylacetic acid for the detection of glyphosate was analyzed using an exact mathematical model based on physical theories. The procedure for modeling experimental responses is well explained. The analysis of the observed impedance response leads to estimations of the microscopic parameters linked to the faradic and capacitive current. The interaction of glyphosate molecules with the imprinted sites of the CS-MIPs film is observed in the high frequency range. The relative variation of the charge transfer resistance is proportional to the log of the concentration of glyphosate. The capacitance decreases as the concentration of glyphosate increases, which is explained by the discharging of the charged imprinted sites when the glyphosate molecule interacts with the imprinted sites through electrostatic interactions. The phenomenon of adsorption of the ions in the CMA film is observed in the low frequency range, this phenomenon being balanced by the electrostatic interaction of glyphosate with the imprinted sites in the CS-MIPs film. 相似文献
64.
Abdou O. Abdelhamid Sobhi M. Gomha Waleed A. M. A. El‐Enany 《Journal of heterocyclic chemistry》2019,56(9):2487-2493
Sodium salt of 3‐hydroxy‐1‐(1‐aryl‐5‐methylpyrazolyl)propenone derivatives was used as a precursor for synthesis of various fused azolopyrimidine ring systems as pyrazolopyrimidines, triazolopyrimidines, and pyrimidobenzimidazoles following many procedures. The identity of the prepared compounds was elucidated by their spectral data and elemental analyses. The in vitro antimicrobial activity of 13 new compounds was evaluated, and many derivatives showed good to moderate activity. 相似文献
65.
Imane Boubezari Ali Zazoua Franois Bessueille Abdelhamid Errachid Nicole Jaffrezic‐Renault 《Electroanalysis》2020,32(7):1642-1650
Instant determination of glucose levels is necessary to monitor the treatment of diabetes. The next generation of electrochemical sensors aims to eliminate the use of enzymes because of their lack of stability and the complex procedure to immobilize them on the electrode. In this paper Pr1.92Ba0.08Ni0.95Zn0.05O4+δ perovskite, a A2BO4+δ type, was tested, for the first time for non enzymatic detection of glucose. It was synthesized by a sol‐gel method. The obtained crystallized powder was structurally characterized by XRD, morphologically characterized by SEM and EDX and electrochemically characterized. A monoclinic crystallographic system was formed. The presence of Pr2O3 during synthesis and calcination is in agreement with the formation of defects in the crystalline network and the disproportionation of NiIII sites into NiII and NiIV, due to the substitution of Pr by Ba. The oxido‐reduction of NiII sites is observed by cyclic voltammetry. The electrocatalytic oxidation of glucose through the electrooxidized NiII site was observed on a gold electrode, at 481 mV. The analytical performance of this glucose sensor is good in comparison to previously published ABO3 perovskite modified electrodes, in terms of dynamic range (1.5 μM–7000 μM) and detection limit (0.5 μM). Its application to human serum shows that there is no interference for glucose detection. 相似文献
66.
Nancy Joumaa Prisca Toussay Muriel Lansalot Abdelhamid Elaissari 《Journal of polymer science. Part A, Polymer chemistry》2008,46(1):327-340
A new strategy relying on the use of a phosphate‐based macromonomer (PAM200) to modify the surface of iron oxide nanoparticles was developed for the synthesis of submicrometer polystyrene (PS) magnetic particles. First, iron oxide nanoparticles were synthesized using the coprecipitation of ferrous and ferric salts in alkaline medium. Besides the classical oleic acid (OA)/octane‐based ferrofluid, styrene‐based ferrofluids were elaborated with either OA or PAM200 as the stabilizer. In all cases, maghemite (γ‐Fe2O3) was clearly identified, with nanoparticles rather spherical in shape but exhibiting broad particle size distribution (PSD). Both OA and PAM200 led to stable maghemite‐based ferrofluids showing superparamagnetic properties. Further use of these ferrofluids in styrene miniemulsion polymerization resulted in inhomogeneous distribution of maghemite among and inside the polymer particles with OA‐based ferrofluids, whereas PAM200/styrene‐based ferrofluids led to magnetic particles with homogeneous distribution of maghemite inside PS particles. Broad PSD and small nonmagnetic particles were however observed. The true mechanisms operating in these systems are still to elucidate, but this study validates PAM200 as an efficient compatibilizing agent between hydrophilic maghemite and hydrophobic PS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 327–340, 2008 相似文献
67.
3-Ethoxycarbonyl-5-methyl-1-(4-methylphenyl)-4-pyrazoloylhydroximoyl chloride (1) reacted with o-phenylenediamine, o-aminothiophenol, o-aminophenol and methyl anthranilate to afford 3-nitrosoquinoxaline, benzothiadiazine, benzoxadiazine, and 3-hydroxyquinazoline, respectively. Imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine and isoxazole derivatives were obtained via the reaction of 1 with 2-aminopyridine, 2-aminopyrimidine and the appropriate active methylene compounds, respectively. Pyrazolo[3,4-d]pyridazines, and pyrrolidino[3,4-d]isoxazolines derivatives were also synthesized. The structures of the newly synthesized compounds were established on the basis of spectral data and alternate synthesis whenever possible. 相似文献
68.
反相微乳液合成30~100nm磁性聚合物纳米微球 总被引:12,自引:0,他引:12
利用反相微乳液一步法成功地制备了磁性聚合物纳米微球,微球粒径在30~100nm左右,均一性较好,研究表明,Fe(Ⅱ)浓度对微乳液和微胶乳的稳定性有很大影响,碱的种类、AOT和单体的含量能控制微球粒径,用振动探针式磁强仪(VSM)测定了不同比例的[Fe(Ⅱ)]/[Fe(Ⅲ)]所合成的聚合物微球的磁性,发现温度对合成高磁饱和强度和超顺磁性起关键作用,合成的磁性聚合物微胶乳透明且稳定性较好. 相似文献
69.
Hydroximoyl chlorides 3 react with acrylonitrile, N-arylmaleimide and maleic anhydride to give isoxazolines 5 , pyrrolidino[3,4-d]isoxazolines 8 , and furolidino[3,4-d]isoxazolines 9 , respectively. 3 reacted with 2-aminopyridine, 2-aminopyrimidine, o-phenylenediamine and o-aminothiophenol to yield 3-ni-trosoimidazo[1,2-α]pyridines 20 , 3-nitrosopyrimidines 22 , 3-naphthoyl-1,4-dihydrobenzo-1,2,4-triazines 24 , and 3-naphthoyl-4H-1,3,4-benzothiadiazine 27 , respectively. Compound 3 reacted with benzoylacetonitrile, acetoacetanilide, thiophenol, benzencsulfinic acid in ethanolic sodium ethoxide solution to give the corresponding isoxazoles 12–13 and oximes 16–17 , respectively. The structures of these products were confirmed by elemental analyses, spectral data and, wherever possible, alternative synthesis. 相似文献
70.
Said Ahmed Soliman Ghozlan Ismail Abdelshafy Abdelhamid Mohamed Hilmy Elnagdi Hatem Moustafa Gaber 《Journal of heterocyclic chemistry》2005,42(6):1185-1189
3‐Diethylaminoacrylonitrile ( 1 ) reacts with hydrazonyl halides ( 2a‐d ) to yield 1,3‐disubstituted pyrazole‐4‐carbonitriles 5a‐d. The acetyl 1‐p‐chlorophenylpyrazole‐4‐carbonitrile ( 5a ) condensed with hydrazine hydrate to yield the bishydrazone 10 and with dimethylformamide dimethylacetal to yield 1‐aryl‐3‐(3‐dimethylamino)acryloyl pyrazole‐4‐carbonitrile ( 11 ). This enamine reacts with hydrazine hydrate to yield the pyrazolylpyrazole ( 12 ) and with naphthoquinone to yield the 3‐naphthofuranoyl pyrazole 13. The pyra‐zolyl pyridine derivative 14 was obtained upon treatment of 11 with acetylacetone in the presence of ammonium acetate. Compound 11 was coupled with p‐chlorobenzene diazonium chloride to yield the hydrazone 16 that was coupled further with p‐chlorobenzenediazonium chloride to yield the formazane 18. 相似文献