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21.
We report that nano‐emulsions can be creatively used as a morphology selective synthesis method to prepare not only nano‐grains but also nano‐fibers with high selectivity. Synthesis of the two different morphological materials was demonstrated using polyaniline synthesis as a model case. Polyaniline nano‐grains were synthesized from aniline molecules in nano‐size aqueous droplets as polymerization sites whose droplets were generated by inverse water‐in‐oil nano‐emulsion use, and polyaniline nano‐fibers were synthesized from aniline in aqueous nano‐dimensional channels as polymerization sites whose channels were generated by direct oil‐in‐water nano‐emulsion use containing high population of oil droplets. Using the approaches, we successfully synthesized nano‐fibers of 60 nm diameter with 0.5 µm length and also nano‐grains having diameter of 60–80 nm. The two different polymerization sites of nano‐scale dimension were made by changing the ratio among surfactant, aqueous aniline/HCl solution, and oil, i.e. organic solvent. We found the nano‐fibers synthesized from the channels formed by the direct oil‐in‐water nano‐emulsion have higher bulk electrical conductivity than the nano‐grains which were synthesized from the droplets formed by the inverse water‐in‐oil emulsion. We also found that the emulsion use allows us to use a room temperature synthesis unlike conventional synthesis methods which require to use ice bath temperature. Physical properties of both nano‐fibers and nano‐grains synthesized were characterized by Fourier transform infrared (FTIR), UV–Vis spectra, scanning electron microscopy (SEM), and four probes conductivity measurement. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
22.
Lin MJ Jouaiti A Grosshans P Kyritsakas N Hosseini MW 《Chemical communications (Cambridge, England)》2011,47(27):7635-7637
The combination of four enantiomerically pure organic tectons composed of a rigid chiral backbone bearing two terminal pyridyl coordinating sites with ZnSiF(6) behaving as an infinite pillar leads to the formation of tubular 2-D enantiomerically pure helical channels with controlled size and orientation. 相似文献
23.
Lalla Hasna Abdeljebbar Munir Humam Philippe Christen Damien Jeannerat Bruno Vitorge Saaid Amzazi Abdelaziz Benjouad Kurt Hostettmann Khalid Bekkouche 《Helvetica chimica acta》2007,90(2):346-352
From the leaves of Withania adpressa, a plant endemic to Sahara of Morocco and Algeria, the novel steroidal lactone (22R)‐14α,15α,17β,20β‐tetrahydroxy‐1‐oxowitha‐2,5,24‐trien‐26,22‐olide (= (15S,17S)‐14,15,17,20‐tetrahydroxy‐22,26‐epoxyergosta‐2,5,24‐triene‐1,26‐dione; 1 ), was isolated, along with three known compounds, withanolides F ( 2 ), J ( 3 ), and oleanolic acid. Their structures were mainly solved by in‐depth 1D‐ and 2D‐NMR (including ADEQUATE) experiments, as well as by HR‐MS analyses and chemical evidence. 相似文献
24.
Abdelaziz Maouche 《Monatshefte für Mathematik》1996,122(3):205-213
In this paper we study some questions related to spectral theory in Jordan-Banach algebras. Firstly, we introduce the notion of exponential spectrum and then we extend to Jordan-Banach algebras a theorem due to Robin Harte in the associative case. Secondly, these results are used to get a theorem on spectral perturbation by inessential elements in Jordan-Banach algebras. 相似文献
25.
In this paper, we are concerned with a coupled viscoelastic wave system with Balakrishnan-Taylor dampings, dynamic boundary conditions, source terms, and past histories. Under suitable assumptions on relaxation functions and source terms, we prove the global existence of solutions by potential well theory and we establish a more general decay result of energy, in which the exponential decay and polynomial decay are only special cases, by introducing suitable energy and perturbed Lyapunov functionals. 相似文献
26.
Slaheddine Chaabouni Slaheddine Kamoun Abdelaziz Daoud Tahar Jouini 《Journal of chemical crystallography》1997,27(7):401-404
The pentakis ethylenediammonium bis undecachlorodiantimonate(III) tetrahydrate salt is monoclinic with the following unit
cell dimensions:a=16.271(5) Å,b=13.004(4) Å,c=13.932(4) Å, β=111.72(2)°, space groupP21/c withZ=2. The structure was solved by Patterson methods and refined to a finalR value of 0.023 for 4435 reflections withF
0>4σ(F
0). The structure shows a layer arrangement perpendicular to thea axis: planes of the [Sb2Cl11]5− bioctahedra alternate with planes of [NH3(CH2)2NH3]2+ dications. The [Sb2Cl11]5− bioctahedra are connected through O−H...Cl hydrogen bonds, such that infinite chains of composition [Sb2Cl11(H2O]n
5n− are formed in the structure, parallel to the twofold axis. These chains are themselves interconnected by means of N−H...Cl
and O−H...Cl bonds originating from the [NH3(CH2)2NH3]2+ entities and the water molecules, respectively, and form a threedimensional network. 相似文献
27.
Slaheddine Chaabouni Slaheddine Kamoun Abdelaziz Daoud Tahar Jouini 《Journal of chemical crystallography》1991,27(7):401-404
The pentakis ethylenediammonium bis undecachlorodiantimonate(III) tetrahydrate salt is monoclinic with the following unit
cell dimensions:a=16.271(5) Å,b=13.004(4) Å,c=13.932(4) Å, β=111.72(2)°, space groupP21/c withZ=2. The structure was solved by Patterson methods and refined to a finalR value of 0.023 for 4435 reflections withF
0>4σ(F
0). The structure shows a layer arrangement perpendicular to thea axis: planes of the [Sb2Cl11]5− bioctahedra alternate with planes of [NH3(CH2)2NH3]2+ dications. The [Sb2Cl11]5− bioctahedra are connected through O−H...Cl hydrogen bonds, such that infinite chains of composition [Sb2Cl11(H2O]n
5n− are formed in the structure, parallel to the twofold axis. These chains are themselves interconnected by means of N−H...Cl
and O−H...Cl bonds originating from the [NH3(CH2)2NH3]2+ entities and the water molecules, respectively, and form a threedimensional network. 相似文献
28.
Pyrazolo[4,3‐d]pyrimidines, pyrazolo[4,3‐d]triazolino[4,3‐a]pyrimidines, 3‐(2‐thiazolyl)thiophenes, thiazolo[3,2‐a]pyridine and pyrazolo[1,5‐a]pyrimidines were synthesized from 2‐[4‐(3‐oxobenzo[f]‐2H‐chromen‐2‐yl)‐1,3‐thiazol‐2‐yl]ethanenitrile. The newly synthesized compounds were elucidated by elemental analysis, spectral data, chemical transformation and alternative synthesis route whenever possible. 相似文献
29.
The design, synthesis, and characterization of the 10 linear and bent acentric ligands 1 – 10 (tectons) based on the differentiation of two divergently disposed coordinating poles is reported. The nature of the two poles and their distance are varied by the use of different linear spacers. For these molecules, a monodentate coordinating site, i.e., a pyridine ring, and a tridentate coordinating site, i.e., a pyridine moiety bearing at the 2 and 6 positions either two thioether groups or two dimethylamino units (PySMe and PyN(Me2)2 type, resp.), a terpyridine, or a pyridine ring bearing two optically pure dihydrooxazole units, are combined. 相似文献
30.
Hamed EM Doai H McLaughlin CK Houmam A 《Journal of the American Chemical Society》2006,128(20):6595-6604
Important aspects of the electrochemical reduction of a series of substituted benzyl thiocyanates were investigated. A striking change in the reductive cleavage mechanism as a function of the substituent on the aryl ring of the benzyl thiocyanate was observed, and more importantly, a regioselective bond cleavage was encountered. A reductive alpha-cleavage (CH(2)-S bond) was seen for cyano and nitro-substituted benzyl thiocyanates leading to the formation of the corresponding nitro-substituted dibenzyls. With other substituents (CH(3)O, CH(3), H, Cl, and F), both the alpha (CH(2)-S) and the beta (S-CN) bonds could be cleaved as a result of an electrochemical reduction leading to the formation of the corresponding substituted monosulfides, disulfides, and toluenes. These final products are generated through either a protonation or a nucleophilic reaction of the two-electron reduction-produced anion on the parent molecule. The dissociative electron transfer theory and its extension to the formation/dissociation of radical anions, as well as its extension to the case of strong in-cage interactions between the produced fragments ("sticky" dissociative electron transfer (ET)), along with the theoretical calculation results helped rationalize (i) the observed change in the ET mechanism, (ii) the dissociation of the radical anion intermediates formed during the electrochemical reduction of the nitro-substituted benzyl thiocyanates, and more importantly (iii) the regioselective reductive bond cleavage. 相似文献