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Situ Synthesis (situ + synthesis)
Selected AbstractsIn Situ Synthesis, Characterization of SiPMo-X, and Different Catalytic Properties of SiPMo-X and SiPW-XEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2006Chunfeng Shi Abstract SBA-15 frameworks with encapsulated Keggin type heteropolyacids (HPAs) were synthesized in situ under strongly acidic conditions (pH,<,0). During the hydrolysis of tetraethyl orthosilicate (TEOS), a P- and a Mo source were added into the initial sol,gel system to form Keggin type HPAs. The texture of the final products was studied by the N2 adsorption,desorption isotherms and transmission electron microscopy (TEM), and their structure was systematically characterized by X-ray diffraction (XRD), UV/Vis diffuse reflectance- (DRS), infrared- (IR), and 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Characterization results suggest that the samples show very ordered hexagonal mesostructure, and the HPAs that are incorporated into the framework of meso-silica are insoluble during catalysis. Results of catalytic tests indicate that the materials demonstrated catalytic activity comparable with or even surpassing those of the bulk HPAs in catalytic tests implementing chemical reactions of bulky molecules (1,3,5-triisopropylbenzene cracking, esterification of benzoic acid with tert -butyl alcohol, and 2,3,6-trimethylphenol hydroxylation with H2O2). Additionally, some other properties, such as easy separation and stability when recycled, ensure their potential applications in the chemical industries. Here, we report not only the in situ synthesis and characterization of SiPMo-X, but also the difference in the catalytic properties of SiPMo-X and SiPW-X. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Multicolor Polymer Nanocomposites: In Situ Synthesis and Fabrication of 3D Microstructures,ADVANCED MATERIALS, Issue 5 2008Z.-B. Sun The multiphoton polymerization of CdS,polymer nanocomposites is used to fabricate 3D luminescent structures such as the multicolor "microbull" shown in the figure. The CdS nanoparticles are synthesized in situ within the polymer matrices with their size controlled by the amount of added crosslinker. [source] In Situ Synthesis and Microstructures of Tungsten Carbide-Nanoparticle-Reinforced Silicon Nitride-Matrix CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2004Tateoki Iizuka A W2C-nanoparticle-reinforced Si3N4 -matrix composite was fabricated by sintering porous Si3N4 that had been infiltrated with a tungsten solution. During the sintering procedure, nanometer-sized W2C particles grew in situ from the reaction between the tungsten and carbon sources considered to originate mainly from residual binder. The W2C particles resided in the grain-boundary junctions of the Si3N4, had an average diameter of ,60 nm, and were polyhedral in shape. Because the residual carbon, which normally would obstruct sintering, reacted with the tungsten to form W2C particles in the composite, the sinterability of the Si3N4 was improved, and a W2C,Si3N4 composite with almost full density was obtained. The flexural strength of the W2C,Si3N4 composite was 1212 MPa, ,34% higher than that of standard sintered Si3N4. [source] In Situ Synthesis of an Imidazolate-4-amide-5-imidate Ligand and Formation of a Microporous Zinc,Organic Framework with H2 -and CO2 -Storage Ability,ANGEWANDTE CHEMIE, Issue 7 2010Franziska Debatin Enge Kanäle mit polaren Wänden bestimmen Struktur und Funktion eines Metall-organischen Gerüsts aus Zinkionen und einem Imidazolat-Amid-Imidat-Liganden (siehe Struktur: Zn,orange, N,blau, O,rot, C,dunkelgrau, H,hellgrau), das über eine hohe Aufnahmekapazität für H2 und CO2 verfügt. Der starre und stabile Chelatligand entsteht in situ durch partielle Hydrolyse eines Dicyanimidazols. [source] In Situ Synthesis of Trisubstituted Methanol Ligands and Their Potential as One-Pot Generators of Cubane-like Metal ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2006Brendan F. Abrahams Dr. Abstract Two different one pot routes to a variety of metal cubane compounds are reported; one route is based on an in situ benzilic acid type rearrangement and the other involves in situ nucleophilic attack at a ketone. Diketosuccinic acid in basic solution in the presence of certain divalent metal ions undergoes a benzilic acid type rearrangement to generate the carbon oxyanion, C(CO2,)3O,, which serves as a cubane-forming bridging ligand in a series of octanuclear complexes of composition [M8{C(CO2)3O}4](H2O)12 (M=Mg, Mn, Fe, Co, Ni, Zn). At the heart of each of these highly symmetrical aggregates is an M4O4 cubane core, each oxygen component of which is provided by the alkoxo centre of a C(CO2,)3O, ligand. Reaction of 2,2,-pyridil, (2-C5H4N)COCO(2-C5H4N), and calcium nitrate in basic alcoholic solution, which proceeds by a similar benzilic acid type rearrangement, gives the cubane compounds, [Ca4L4(NO3)4] in which L=(2-C5H4N)2C(COOR)O, (R=Me or Et). Nucleophilic attack by bisulfite ion at the carbonyl carbon atom of 2,2,-dipyridyl ketone in the presence of certain divalent metals generates the electrically neutral complexes, [{(C5H4N)2SO3C(OH)}2M] (M=Mn, Fe, Co, Ni, Zn and Cd). Cubane-like complexes [M4{(C5H4N)2SO3C(O)}4] (M=Zn, Mn) can be obtained directly from 2,2,-dipyridyl ketone in one-pot reaction systems (sealed tube, 120,°C) if a base as weak as acetate ion is present to deprotonate the OH group of the initial [(C5H4N)2SO3C(OH)], bisulfite addition compound; the [(C5H4N)2SO3C(O)]2, ligand in this case plays the same cubane-forming role as the ligands C(COO,)3O, and (2-C5H4N)2C(COOR)O, above. When excess sodium sulfite is used in similar one-pot reaction mixtures, the monoanionic complexes, [M3Na{(C5H4N)2SO3C(O)}4], (M=Zn, Mn, Co) with an M3NaO4 cubane core, are formed directly from 2,2,-dipyridyl ketone. [source] Synthesis and Characterization of MWNTs/Au NPs/HS(CH2)6Fc Nanocomposite: Application to Electrochemical Determination of Ascorbic AcidELECTROANALYSIS, Issue 16 2008Jian-Ding Qiu Abstract In this article, a detailed electrochemical study of a novel 6-ferrocenylhexanethiol (HS(CH2)6Fc) self-assembled multiwalled carbon nanotubes-Au nanoparticles (MWNTs/Au NPs) composite film was demonstrated. MWNTs/Au NPs were prepared by one-step in situ synthesis using linear polyethyleneimine (PEI) as bifunctionalizing agent. HS(CH2)6Fc, which acted as the redox mediator, was self-assembled to MWNTs/Au NPs via Au-S bond. Transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), Fourier transformed infrared absorption spectroscopy (FT-IR), UV-visible absorption spectroscopy, and cyclic voltammetry were used to characterize the properties of the MWNTs/Au NPs/HS(CH2)6Fc nanocomposite. The preparation of the nanocomposite was very simple and effectively prevented the leakage of the HS(CH2)6Fc mediator during measurements. The electrooxidation of AA could be catalyzed by Fc/Fc+ couple as a mediator and had a higher electrochemical response due to the unique performance of MWNTs/Au NPs. The nanocomposite modified electrode exhibited excellent catalytic efficiency, high sensitivity, good stability, fast response (within 3,s) and low detection limit toward the oxidation of AA at a lower potential. [source] In Situ Synthesis, Characterization of SiPMo-X, and Different Catalytic Properties of SiPMo-X and SiPW-XEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2006Chunfeng Shi Abstract SBA-15 frameworks with encapsulated Keggin type heteropolyacids (HPAs) were synthesized in situ under strongly acidic conditions (pH,<,0). During the hydrolysis of tetraethyl orthosilicate (TEOS), a P- and a Mo source were added into the initial sol,gel system to form Keggin type HPAs. The texture of the final products was studied by the N2 adsorption,desorption isotherms and transmission electron microscopy (TEM), and their structure was systematically characterized by X-ray diffraction (XRD), UV/Vis diffuse reflectance- (DRS), infrared- (IR), and 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Characterization results suggest that the samples show very ordered hexagonal mesostructure, and the HPAs that are incorporated into the framework of meso-silica are insoluble during catalysis. Results of catalytic tests indicate that the materials demonstrated catalytic activity comparable with or even surpassing those of the bulk HPAs in catalytic tests implementing chemical reactions of bulky molecules (1,3,5-triisopropylbenzene cracking, esterification of benzoic acid with tert -butyl alcohol, and 2,3,6-trimethylphenol hydroxylation with H2O2). Additionally, some other properties, such as easy separation and stability when recycled, ensure their potential applications in the chemical industries. Here, we report not only the in situ synthesis and characterization of SiPMo-X, but also the difference in the catalytic properties of SiPMo-X and SiPW-X. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis of Core,Shell Inorganic NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Ronen Kreizman Abstract New materials and techniques pertaining to the synthesis of inorganic nanotubes have been ever increasing since the initiation of the field in 1992. Recently, WS2 nanotubes, which are produced now in large amounts, were filled with molten lead iodide salt by a capillary wetting process, resulting in PbI2@WS2 core,shell nanotubes. This work features progress in the synthesis of new core,shell nanotubes, including BiI3@WS2 nanotubes produced in a similar same manner. In addition, two new techniques for obtaining core,shell nanotubes are presented. The first is via electron-beam irradiation, i.e., in situ synthesis within a transmission electron microscope. This synthesis results in SbI3 nanotubes, observed either in a hollow core of WS2 ones (SbI3@WS2 nanotubes), or atop of them (WS2@SbI3 nanotubes). The second technique involves a gaseous phase reaction, where the layered product employs WS2 nanotubes as nucleation sites. In this case, the MoS2 layers most often cover the WS2 nanotube, resulting in WS2@MoS2 core,shell nanotubes. Notably, superstructures of the form MoS2@WS2@MoS2 are occasionally obtained. Using a semi-empirical model, it is shown that the PbI2 nanotubes become stable within the core of MoS2 nanotubes only above a critical core diameter of the host (>12,nm); below this diameter the PbI2 crystallizes as nanowires. These model calculations are in agreement with the current experimental observations, providing further support to the growth mechanism of such core,shell nanotubes. [source] Micropatterning Layers by Flame Aerosol Deposition-Annealing,ADVANCED MATERIALS, Issue 16 2008Antonio Tricoli A flame process for in situ synthesis and micropatterned deposition of highly porous, self-assembled, lace-like nanostructured layers of pure or Pt-doped SnO2 is presented. These layers are stabilized in situ by rapid flame annealing that results in transparent cauliflower-like layers with strong adhesion to substrates containing integrated circuitry, while exhibiting high CO sensitivity (f). [source] Synthesis of CdS- and ZnS-modified bentonite nanoparticles and their applications to the degradation of eosin BJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2009M. Ghiaci Abstract BACKGROUND: In the present study, nanocomposites of cadmium sulphide (CdS) and zinc sulphide (ZnS) on a bentonite have been prepared via an in-situ precipitation route and their catalytic behaviour was evaluated in the degradation of eosin B. RESULTS: It was found that the basal space of bentonite increased from 1.23 to 1.49 nm after CdS or ZnS nanoparticles were deposited on layers of the bentonite. The resulting CdS,bentonite and ZnS,bentonite nanocomposites can degrade eosin B from aqueous solution after 2 h under UV irradiation. CONCLUSION: A soft method for in situ synthesis of monodispersed, CdS and ZnS nanoparticles, using a reverse micelle type procedure, is reported. The synthesized CdS- and ZnS,bentonite composites combined the adsorptive ability of bentonite and the catalytic degradation ability of CdS and ZnS to remove eosin B from its aqueous solution efficiently. Copyright © 2009 Society of Chemical Industry [source] Stereoregular P(MMA)-clay nanocomposites by metallocene catalysts: In situ synthesis and stereocomplex formationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2007Wesley R. Mariott Abstract This contribution reports the synthesis and characterization of stereochemically controlled, as well as crystalline stereocomplex, P(MMA)-clay nanocomposites using metallocene complexes and alane-intercalated clay activators. The ligand elimination and exchange reactions involving Lewis acids E(C6F5)3 (E = Al, B) and an organically modified montmorillonite clay were employed to synthesize the alane-intercalated clay activators. When combined with dimethyl metallocenes of various symmetries, these clay activators brought about efficient MMA polymerizations leading to in situ polymerized, stereochemically controlled P(MMA)-intercalated clay nanocomposites. The most noticeable thermal property enhancement observed for the clay nanocomposite P(MMA), when compared with the pristine P(MMA) having similar molecular weight and stereomicrostructure, has a considerable increase in Tg (,10 °C). Mixing of dilute THF solutions of two diastereomeric nanocomposites in a 1:2 isotactic to syndiotactic ratio, followed by reprecipitation or crystallization procedures, yielded unique double-stranded helical stereocomplex P(MMA)-clay nanocomposites with a predominantly exfoliated clay morphology. Remarkably, the resulting crystalline stereocomplex P(MMA) matrix is resistant to the boiling-THF extraction and its clay nanocomposites exhibit high Tm of 201 to 210 °C. Furthermore, the stereocomplex P(MMA)-clay nanocomposite shows a one-step, narrow decomposition temperature window and a single, high maximum rate decomposition temperature of 377 °C. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2581,2592, 2007 [source] Clay-PMMA Nanocomposites by Photoinitiated Radical Polymerization Using Intercalated Phenacyl Pyridinium Salt InitiatorsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2006Alper Nese Abstract Summary: In situ synthesis of poly(methyl methacrylate) (PMMA) nanocomposites by photopolymerization using organophilic montmorillonite (MMT) as the layered clay is reported. MMT clay was ion exchanged with N -phenacyl, N,N -dimethylanilinium hexafluoro phosphate (PDA) which acts as both suitable intercalant- and photo-initiator. These modified clays were then dispersed in methyl methacrylate (MMA) monomer in different loading degrees to carry out the in situ photopolymerization. Intercalation ability of the photoinitiator and exfoliated nanocomposite structure were evidenced by both X-ray diffraction (XRD) spectroscopy and transmission electron microscopy (TEM). Thermal properties and morphologies of the resultant nanocomposites were also studied. Schematic representation of clay-PMMA nanocomposites by photoinitiated radical polymerization. [source] Coherent random lasers from weakly scattering polymer films embedded with superfine silver nanoparticlesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S1 2009Xiangeng Meng Abstract Random lasers with coherent feedback have been obtained in highly transparent polymer films embedded with silver (Ag) nanoparticles. The hybrid materials were fabricated via in situ synthesis, through which Ag nanoparticles were precipitated by heat treatment. Sharp peaks with linewidth of ,0.3 nm emerge on a broad emission background when the pump energy reaches a threshold. Random lasers with coherent feedback induced by Ag nanoparticles have been little reported, and hence, we believe that this work brings about an important aspect to random lasers. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Use of recombinant rotavirus VP6 nanotubes as a multifunctional template for the synthesis of nanobiomaterials functionalized with metalsBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Germán Plascencia-Villa Abstract The structural characteristics and predefined constant size and shape of viral assemblies make them useful tools for nanobiotechnology, in particular as scaffolds for constructing highly organized novel nanomaterials. In this work it is shown for the first time that nanotubes formed by recombinant rotavirus VP6 protein can be used as scaffolds for the synthesis of hybrid nanocomposites. Rotavirus VP6 was produced by the insect cell-baculovirus expression vector system. Nanotubes of several micrometers in length and various diameters in the nanometer range were functionalized with Ag, Au, Pt, and Pd through strong (sodium borohydride) or mild (sodium citrate) chemical reduction. The nanocomposites obtained were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM) with energy dispersive spectroscopy (EDS), dynamic light scattering, and their characteristic plasmon resonance. The outer surface of VP6 nanotubes had intrinsic affinity to metal deposition that allowed in situ synthesis of nanoparticles. Furthermore, the use of preassembled recombinant protein structures resulted in highly ordered integrated materials. It was possible to obtain different extents and characteristics of the metal coverage by manipulating the reaction conditions. TEM revealed either a continuous coverage with an electrodense thin film when using sodium citrate as reductant or a discrete coverage with well-dispersed metal nanoparticles of diameters between 2 and 9,nm when using sodium borohydride and short reaction times. At long reaction times and using sodium borohydride, the metal nanoparticles coalesced and resulted in a thick metal layer. HRTEM-EDS confirmed the identity of the metal nanoparticles. Compared to other non-recombinant viral scaffolds used until now, the recombinant VP6 nanotubes employed here have important advantages, including a longer axial dimension, a dynamic multifunctional hollow structure, and the possibility of producing them massively by a safe and efficient bioprocess. Such characteristics confer important potential applications in nanotechnology to the novel nanobiomaterials produced here. Biotechnol. Bioeng. 2009; 104: 871,881. © 2009 Wiley Periodicals, Inc. [source] Surface-initiated nitroxide-mediated polymerization: a tool for hybrid inorganic/organic nanocomposites ,in situ' synthesisPOLYMER INTERNATIONAL, Issue 10 2006Leïla Ghannam Abstract Hybrid silica particles comprised of an inorganic core and an organic polymer shell can be synthesized by surface-initiated nitroxide-mediated polymerization (SINMP) in the presence of a grafted alkoxyamine as initiator. The layer of initiator molecules attached or adsorbed to the particles surface is based on a nitroxide group. The synthesis and characterization of these alkoxyamine structures are briefly described. The grafted initiator particles are studied in order to determine the nature of the anchorage sites and the grafting density. With a stable radical or nitroxide as chain-growth moderator tethered to the inorganic core, it was demonstrated that the grafting from or to SINMP exhibits a control character with a very low polydispersity and good agreement between theoretical/experimental molecular weights. A comparative review of different alkoxyamines with a bimolecular system based on a grafted azoic initiator in the presence of an acyclic ,-phosphonylated nitroxide called SG1 is also described. Moreover, original methods for the synthesis of alkoxyamine grafted surface by in situ trapping of carbon radicals and some new developments for colored pigments will be reported. These topics could be one of the directions of the field in the next years. Copyright © 2006 Society of Chemical Industry [source] | ||||||||||||||||||||||