Download or read book Synthesis of Ferromagnetic Nanoparticles Formic Acid Oxidation Catalyst Nanocomposites and Late transition Metal boride Intermellatics by Unique Synthetic Methods and Single source Precursors written by Matthew S. Wellons and published by . This book was released on 2008 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nanoparticles in Catalysis written by Shū Kobayashi and published by Springer Nature. This book was released on 2020-11-06 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume discusses the great potential of metal nanoparticle catalysts for complicated molecular synthesis and reviews the current progress of this field. The development of highly active and stable heterogeneous catalysts is a crucial subject in modern science. However, development of heterogeneous catalysts for fine chemical synthesis has lagged far behind those for bulk chemical process. In recent years metal nanoparticle catalysts have been of great interest in this area due to their unique activity, ease of heterogenization, and robustness. Therefore, metal nanoparticle catalysts are an excellent candidate for the above-mentioned active and robust heterogeneous catalysts and this book provides an overview of this area. The present volume summarizes recent progress on nanoparticle catalysis for various organic transformations from simple redox reactions to complex asymmetric C–C bond forming reactions and also presents seminal studies on new technologies. It comprehensively summarizes advances in metal nanoparticle catalysis across several aspects including reaction manners, mechanistic investigations and new synthetic methodologies to encourage the use of metal nanoparticle catalysts for future organic synthesis. This volume will be of interest to students, researchers and professionals focused on the next-generation of fine chemical synthesis.

Download or read book Synthetic Applications written by Rajender S. Varma and published by Walter de Gruyter GmbH & Co KG. This book was released on 2022-05-09 with total page 578 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic nanocatalysts are becoming an important tool for greener catalytic processes in chemical transformations in view of the ease of their removal from a reaction medium. This book explores assorted magnetic nanocatalysts, their deployment in synthesis, chemical transformation and their recovery and reuse. Various thematic topics embodied include magnetic nanocatalysts for S-S bond formation, N-heterocycle formation, C-heteroatom bond formation, silica-supported catalysts, multicomponent reactions, including their recyclability; another available volume emphasizes the utility of magnetic nanocatalysts in industrial appliances.

Download or read book Metal Oxide Nanocomposites written by B. Raneesh and published by John Wiley & Sons. This book was released on 2021-02-17 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal Oxide Nanocomposites: Synthesis and Applications summarizes many of the recent research accomplishments in the area of metal oxide-based nanocomposites. This book focussing on the following topics: Nanocomposites preparation and characterization of metal oxide nanocomposites; synthesis of core/shell metal oxide nanocomposites; multilayer thin films; sequential assembly of nanocomposite materials; semiconducting polymer metal oxide nanocomposites; graphene-based metal and metal oxide nanocomposites; carbon nanotube–metal–oxide nanocomposites; silicon mixed oxide nanocomposites; gas semiconducting sensors based on metal oxide nanocomposites; metal ]organic framework nanocomposite for hydrogen production and nanocomposites application towards photovoltaic and photocatalytic.

Download or read book The Synthesis of Novel Metal and Metal Oxide Nanoparticles with Applications Towards Catalysis written by Meredith Joanne McMurdo and published by . This book was released on 2010 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the synthesis of novel nanoparticles that are interesting for catalytic applications. The decomposition of RhCp(C2H4)2 and Rh(hfacac)(CO)2 were investigated, and the complex RhCp(C2H4)2 was successfully shown to decompose to rhodium nanoparticles. Analysis of the decomposition chemistry was used to control nanoparticle seed formation and growth. New stabilizer ligands, both polymeric and molecular, were attempted for the synthesis of rhodium nanoparticles. Polymeric stabilizers were screened as replacements for the widely used polyvinylpyrollidone (PVP) surfactant, however none afforded the high degree of control exhibited by PVP. However, molecular stabilizers were screened and small, monodisperse rhodium nanoparticles were synthesized with the stabilizer octadecylphosphonic acid, with a size and size dispersity of 1.92 +/-0.16 nm. A concurrent hydrogenation catalytic process was also utilized for the synthesis of small rhodium seed particles. In this nanoparticle synthesis, a rhodium precursor and a stabilizer were combined in the presence of an olefin and hydrogen, which aids in decomposition of the rhodium precursor to nanoparticles, and also catalytically converts the olefin to a saturated compound. The rate of hydrogen uptake was monitored and fit to a two-step autocatalytic mechanism correlated to nanoparticle formation and growth. Two new rhodium complexes were synthesized that contained a stabilizer ligand, however the most successful attempt to produce small, monodisperse rhodium nanoparticles by this process was with the rhodium source [(COD)Rh(NCCH3)2]BF4, and the stabilizer (Bu4N)2HPO4 in the presence of an equivalent of Proton Sponge0. Rhodium nanoparticles synthesized by this process have a size and size distribution of 1.88 +/-0.27 nm. The presence of olefin and hydrogen pressure of 42 psi was found to be ideal for the stabilization of nanoparticles during their formation. Also, reactant concentrations and the rate of the cyclohexene consumption are crucial to yield nanoparticles with this excellent size dispersity. Growth reactions with these small rhodium nanoparticles have been successful the synthesis of larger nanoparticles under conditions involving alternate stabilizers. The small nanoparticles were then tested and found to be useful as seed particles in the synthesis of larger rhodium nanoparticles. For each procedure, a mixture of 1-hexadecylamine, adamantane carboxylic acid, and 1,2-hexadecanediol was used to stabilize the nanoparticles. The use of synthesized seed particles allowed for the formation of tetrahedral (average edge length: 4.77 +/- 0.72 nm) or icosahedral shaped particles, depending on reaction temperature. Subsequent characterization revealed that approximately half of the tetrahedrally shaped nanoparticles are in fact triangular flat rafts, where one corner of the tetrahedron appears to be "cut off." However, the use of in situ seeds resulted in the formation of multipod structures. The multipods are single crystals with 2-8 arms per multipod, that propagate both the (110) and (111) directions. The synthesis and characterization of mixed-metal oxide spinel nanoparticles was then attempted for water oxidation catalysis. Nanoparticles of the compositions MnFe2O4 and CoFe2O4 (5.7 nm and 6.1 nm respectively) were synthesized according to a literature procedure with the stabilizers oleic acid and oleylamine, however they were characterized by ICP-OES to have low M:Fe (M = Mn, Co) ratios of 1:5 and 1:4 respectively. Nanoparticles of NiFe2O4 (8.0 nm) were also synthesized by a similar approach, and had the expected Ni:Fe ratio of 1:2 by ICP-OES. Cubic nanoparticles of Co3O4 were also synthesized, and through a subsequent cation exchange reaction with this material, CuxCo3-xO4 and NixCo3-xO4 nanoparticles could be synthesized with varying degrees of copper or nickel incorporation. Linear scan voltammograms were conducted on anodes modified with these nanoparticle materials. For the mixed-metal ferrites, CoFe2O4 showed the lowest overpotentials in the water oxidation reaction in the range of 0-100 mA cm-2. Copper modified Co3O4 nanoparticles had a lower onset potential than Co3O4 and performed with lower overpotentials at low current densities (20 mA cm-2). The nickel modified Co3O4 nanoparticles were superior to the other MxCo3-xO4 materials at all current densities measured (0-100 mA cm-2).

Download or read book Nanostructure of Transition Metal and Metal Oxide for Electrocatalysis written by Yanjuan Gu and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Nanostructure of Transition Metal and Metal Oxide for Electrocatalysis" by Yanjuan, Gu, 谷艳娟, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled NANOSTRUCTURE OF TRANSITION METAL AND METAL OXIDE FOR ELECTROCATALYSIS Submitted by Gu Yan Juan for the degree of Doctor of Philosophy at The University of Hong Kong in August 2006 Pd, Pt, and Ru nanoparticles that were uniformly dispersed on multi-walled carbon nanotubes (MWNTs) were synthesized by vacuum pyrolysis using metal acetylacetonate as metal precursor, and the nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X- ray diffraction (XRD). The size and distribution of the nanoparticles were strongly affected by the reaction time, temperature, and the initial mass ratio of the metal precursors to MWNTs. The higher temperature, the smaller Pd nanoparticles were formed at the range of 250 to 500 C. The average size of the Pd nanoparticles increased with the increase in mass ratio of the metal precursors to MWNTs. The particle size of Pt and Ru showed little change with the change in mass ratio. Pt and Ru nanoparticles had the mean diameters of 3.00.6 and 2.50.4 nm when the mass ratio of Pt(acac) and Ru(acac) to 2 3 MWNTs was both 2:1 at 500 C. The electrocatalytic activity of Pt/MWNTs and PtRu/MWNTs was investigated at room temperature by cyclic voltammetry and chronoamperometry. All of the electrochemical results showed that the PtRu/MWNTs catalyst exhibit high activity for methanol oxidation that resulted from the high surface area of carbon nanotubes and the platinum/ruthenium nanoparticles. Compared with Pt/MWNTs, the onset potential is much lower and the ratio of forward anodic peak current to reverse anodic peak current is much higher for methanol oxidation. Pt Ru /MWNTs displayed the best electrocatalytic 45 55 activities among all carbon nanotubes supported Pt and PtRu catalysts. Hyperbranched RuO nanostructures can be formed through the oxidation of Ru nanoparticles at relatively low temperatures in air, which is a very simple and low cost method. The morphology of the RuO nanostructure is closely associated with the dispersivity of the Ru nanoparticles on the MWNTs. Cu, Pt and Pd nanoparticles are very effective catalysts in the formation of RuO hyperbranched nanostructures. The electrochemical studies of these nanorods demonstrated that they display characteristic properties of RuO (110) surface. The successful attachment of Pt nanoparticles to RuO surface through a simple, two-step chemically controlled procedure is reported. The effect of the single crystal structure of RuO nanorods on the electrocatalytic activity of Pt nanoparticles was investigated, showing that the presence of the RuO nanorods greatly increases the electrochemical activity of electrodes toward methanol oxidation, not only increasing the current density but also shifting the onset potential of methanol electrooxidation to over 200 mV lower than that on the Pt nanoparticle electrode. The results described here also demonstrate the ability of metal oxide nanorods to serve as a conductive support for fuel cell applications. DOI: 10.5353/th_b3777439 Subjects: Electrocatalysis Transition metals Nanoparticles Nanostructured materials Methanol - Oxidation

Download or read book Synthesis and Optimization of the Transition Metal Boride Nanoparticles and Their Possible Magnetic hybrid Composite Applications written by Sina Khoshsima and published by . This book was released on 2020 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nanoparticles as Reactive Precursors written by John C. Bauer and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Alloys, intermetallic compounds and multi-metal oxides are generally made by traditional solid-state methods that often require melting or grinding/pressing powders followed by high temperature annealing (> 1000 degrees C) for days or weeks. The research presented here takes advantage of the fact that nanoparticles have a large fraction of their atoms on the surface making them highly reactive and their small size virtually eliminates the solid-solid diffusion process as the rate limiting step. Materials that normally require high temperatures and long annealing times become more accessible at relatively low-temperatures because of the increased interfacial contact between the nanoparticle reactants. Metal nanoparticles, formed via reduction of metal salts in an aqueous solution and stabilized by PVP (polyvinylpyrrolidone), were mixed into nanoparticle composites in stoichometric proportions. The composite mixtures were then annealed at relatively low temperatures to form alloy and intermetallic compounds at or below 600 degrees C. This method was further extended to synthesizing multi-metal oxide systems by annealing metal oxide nanoparticle composites hundreds of degrees lower than more traditional methods. Nanoparticles of Pt (supported or unsupported) were added to a metal salt solution of tetraethylene glycol and heated to obtain alloy and intermetallic nanoparticles. The supported intermetallic nanoparticles were tested as catalysts and PtPb/Vulcan XC-72 showed enhanced catalytic activity for formic acid oxidation while Pt3Sn/Vulcan XC-72 and Cu3Pt/y-Al2O3 catalyzed CO oxidiation at lower temperatures than supported Pt. Intermetallic nanoparticles of Pd were synthesized by conversion chemistry methods previously mentioned and were supported on carbon and alumina. These nanoparticles were tested for Suzuki cross-coupling reactions. However; the homocoupled product was generally favored. The catalytic activity of Pd3Pb/y-Al2O3 was tested for the Heck reaction and gave results comparable to Pd/y-Al2O3 with a slightly better selectivity. Conversion chemistry techniques were used to convert Pt nanocubes into Ptbased intermetallic nanocrystals in solution. It was discovered that aggregated clusters of Pt nanoparticles were capable of converting to FePt3; however, when Pt nanocubes were used the intermetallic phase did not form. Alternatively, it was possible to form PtSn nanocubes by a conversion reaction with SnCl2.

Download or read book Precursor directed Synthesis of Inorganic and Organic Nanomaterials for Photocatalytic Applications written by Sweta Gahlot and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The inorganic titanium dioxide TiO2 and metal-free graphitic carbon nitride (g-C3N4) are the two most important photocatalysts owing to their low cost, non-toxicity, high thermal and chemical stability, as well as high reactivity. However, these two materials also suffer from certain drawbacks such as a relatively high rate of electron-hole pair recombination, a slightly large bandgap that requires UV-light for activation (TiO2), and a relatively small surface area (g-C3N4).This thesis focuses to overcome above drawbacks by combining TiO2 with low bandgap metal chalcogenide semiconducting nanoparticles as a strategy to create an efficient charge separation at the interface of the heterojunctions and to extend the absorption to visible region. This thesis also attempts to improve the photocatalytic efficiency of g-C3N4 by synthesizing it with high surface area and, finely, by combining it with TiO2. After describing briefly the motivation behind the work and the existing literature on the subject matter in the first chapter, the Chapter 2 describes precursor-mediated synthesis and photocatalytic activity of binary coinage metal chalcogenide nanoparticles and their composites with TiO2 under mild conditions. We successfully isolate and characterize kinetically and/or thermally unstable molecular species during the reactions, thus providing an insight into the molecule-to-nanoparticle mechanisms. The metal chalcogenide-titania nanocomposites show superior activity for the photodegradation of formic acid under ultraviolet light, as compared to titania (P25), which is a well-established benchmark for photocatalysis under UV light. Chapter 3 describes the synthesis of ternary coinage metal chalcogenides and their composites with titania. A direct room temperature reaction of tBu2Se with copper and silver trifluoroacetates gives copper-silver-selenide nanoparticles that are formed via a highly reactive intermediate molecular species [Ag2Cu(TFA)4(tBu2Se)4]. We also employed the pre-formed copper chalcogenide NPs as precursors and reacted it with di-tertiary butyl chalcogenide to obtain ternary metal chalcogenide nanoparticles and their composites with TiO2 in pure phase and with high yield. Photocatalytic studies for the degradation of formic acid under ultraviolet radiations show that the ternary CuAgSe-TiO2 nanocomposites are even better photocatalysts than the binary chalcogenide-TiO2 nanocomposites described in Chapter 2. The second part of this thesis described in Chapter 4 diverges from the earlier chapters to concentrate on the coupling of titania with graphitic carbon nitride. In the first step, we develop a simple single-step calcination approach to synthesize graphitic nanoparticles with a high surface area (200 m2/g). We test the prepared photocatalyst for the degradation of formic acid and phenol under visible light, and analyze the effect of factors such as surface area, irradiance and concentration of carbon nitride on the photocatalytic performance. Results show that the performance increases linearly with surface area and irradiance, whereas it first increases and gradually reaches plateau as concentration of the photocatalyst is increased. In the second step, we couple carbon nitride with titania using mechanical mixing. The prepared nanocomposites are then evaluated for the photodegradation of formic acid under both ultraviolet and visible lights. Finally, the Chapter 5 describes the experimental details of the synthesis and characterization of the molecular precursors, metal chalcogenide nanoparticles, g-C3N4 nanosheets as well as their composites with TiO2. It also describes in detail the experimental setup for the photocatalytic studies.

Download or read book SIZE CONTROLLED SYNTHESIS OF TRANSITION METAL NANOPARTICLES THROUGH CHEMICAL AND PHOTO CHEMICAL ROUTES written by Behzad Tangeysh and published by . This book was released on 2015 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: The central objective of this work is developing convenient general procedures for controlling the formation and stabilization of nanoscale transition metal particles. Contemporary interest in developing alternative synthetic approaches for producing nanoparticles arises in large part from expanding applications of the nanomaterials in areas such as catalysis, electronics and medicine. This research focuses on advancing the existing nanoparticle synthetic routes by using a new class of polymer colloid materials as a chemical approach, and the laser irradiation of metal salt solution as a photo-chemical method to attain size and shape selectivity. Controlled synthesis of small metal nanoparticles with sizes ranging from 1 to 5nm is still a continuing challenge in nanomaterial synthesis. This research utilizes a new class of polymer colloid materials as nano-reactors and protective agents for controlling the formation of small transition metal nanoparticles. The polymer colloid particles were formed from cross-linking of dinegatively charged metal precursors with partially protonated poly dimethylaminoethylmethacrylate (PDMAEMA). Incorporation of [PtCl6]2- species into the colloidal particles prior to the chemical reduction was effectively employed as a new strategy for synthesis of unusually small platinum nanoparticles with narrow size distributions (1.12 ± 0.25nm). To explore the generality of this approach, in a series of proof-of-concept studies, this method was successfully employed for the synthesis of small palladium (1.4 ±0.2nm) and copper nanoparticles (1.5 ±0.6nm). The polymer colloid materials developed in this research are pH responsive, and are designed to self-assemble and/or disassemble by varying the levels of protonation of the polymer chains. This unique feature was used to tune the size of palladium nanoparticles in a small range from 1nm to 5nm. The procedure presented in this work is a new convenient room temperature route for synthesis of small nanoparticles, and its application can be extended to the formation of other transition metals and alloy nanoparticles. This research also focuses on developing new photo-chemical routes for controlling the size and shape of the nanoparticles through high-intensity ultra-fast laser irradiation of metal salt solution. One of the core objectives of this work is to explore the special capabilities of shaped laser pulses in formation of metal nanoparticles through irradiation of the solutions by using simultaneous spatial and temporal focusing (SSTF). Femtosecond laser irradiation has not yet been widely applied for nanoparticle synthesis, and offers new regimes of energy deposition for synthesis of nanomaterials. Photo-reduction of aqueous [AuCl4]- solution to the gold nanoparticles (AuNPs) has been applied as a model process for optimizing the experimental procedures, and evaluating the potential of shaped laser pulses in the synthesis of AuNPs. Systematic manipulation of the laser parameters and experimental conditions provided effective strategies to control the size of Au nanoparticles in strong laser fields. Varying the concentration of polyethylene glycol (PEG45) as a surfactant effectively tuned the size of AuNPs from 3.9 ±0.7nm to 11.0 ±2.4nm, and significantly increased the rate of Au(III) reduction during irradiation. Comparative studies revealed the capability of shaped laser pulses in the generation of smaller and more uniform AuNPs (5.8 ±1.1nm) relative to the other conventional laser irradiation methods (7.2 ±2.9nm). Furthermore, a new laser-assisted approach has been developed for selective formation of triangular Au nanoplates in the absence of any surfactant molecule. This method relies on rapid energy deposition by using shaped, ultra-intense laser pulses to generate Au seeds in aqueous [AuCl4]- solution, and the slow post-irradiation reduction of un-reacted [AuCl4]- species by using H2O2 as a mild reducing agent. Variation of the laser irradiation-time was found as an effective strategy to tune the morphology of Au nanomaterials from nanospheres to triangular nanoplates. The surfactant-free Au nanoplates produced in this research can be readily functionalized with a variety of target molecules or surfactants for desirable applications such as biomedicine. The concept of rapid laser processing followed by in situ chemical reduction can be expanded as a general methodology for high-yield production of nanomaterials, and provides a series of new laser dependent parameters for controlling the nanoparticle formation.