Synthesis of Alkanethiolate-capped Metal Nanoparticles Using Alkyl Thiosulfate Ligand Precursors for Selective Catalytic Reactions PDF Download
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Author: Khin Aye San
Publisher:
ISBN: 9780355097511
Category : Catalysis
Languages : en
Pages : 64
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Book Description
Abstract: Stable and isolable alkanethiolate-stabilized Pt nanoparticles (PtNP) were synthesized using the two-phase thiosulfate method with sodium S-alkylthiosulfate as ligand precursor. The mechanistic formation of octanethiolate-capped PtNP (Pt-SC8) from both sodium S-octylthiosulfate and 1-octanethiol ligands was investigated by using 1H NMR and UV-vis spectroscopy, which revealed the formation of different Pt complexes as the reaction intermediates. The partially poisoned PtNP with thiolate monolayer ligands was further investigated for the hydrogenation of various alkynes to understand the organic ligands-induced geometric and electronic surface properties of colloidal Pt nanoparticle catalysts. In addition, alkanethiolate-capped Pd nanoparticles (PdNP) were prepared using reversed thiosulfate addition method with S-octylthiosulfate as ligand precursor. Various synthetic conditions were applied to the modified two-phase method in order to control the average core size and surface ligand density. The obtained nanoparticles were characterized by 1H NMR, UV-vis spectroscopy, infrared spectroscopy (IR), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM).
Author: Khin Aye San
Publisher:
ISBN: 9780355097511
Category : Catalysis
Languages : en
Pages : 64
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Book Description
Abstract: Stable and isolable alkanethiolate-stabilized Pt nanoparticles (PtNP) were synthesized using the two-phase thiosulfate method with sodium S-alkylthiosulfate as ligand precursor. The mechanistic formation of octanethiolate-capped PtNP (Pt-SC8) from both sodium S-octylthiosulfate and 1-octanethiol ligands was investigated by using 1H NMR and UV-vis spectroscopy, which revealed the formation of different Pt complexes as the reaction intermediates. The partially poisoned PtNP with thiolate monolayer ligands was further investigated for the hydrogenation of various alkynes to understand the organic ligands-induced geometric and electronic surface properties of colloidal Pt nanoparticle catalysts. In addition, alkanethiolate-capped Pd nanoparticles (PdNP) were prepared using reversed thiosulfate addition method with S-octylthiosulfate as ligand precursor. Various synthetic conditions were applied to the modified two-phase method in order to control the average core size and surface ligand density. The obtained nanoparticles were characterized by 1H NMR, UV-vis spectroscopy, infrared spectroscopy (IR), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM).
Author: Piet W.N.M. van Leeuwen
Publisher: Springer Nature
ISBN: 3030458237
Category : Science
Languages : en
Pages : 460
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Book Description
This book provides an overview of the latest developments in the field of nanoparticle catalysis. It not only discusses established topics in detail, but also explores several emerging topics. Catalysis with nanoparticles is expanding exponentially and is attracting significant interest due to the many exciting findings being reported. Mastering the synthesis, characterization, stabilization and use of these catalysts offers numerous possibilities that far exceed those of classic heterogeneous and homogeneous catalysis.
Author: Franklin (Feng) Tao
Publisher: Royal Society of Chemistry
ISBN: 1782620338
Category : Science
Languages : en
Pages : 285
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Book Description
An introduction to the synthesis and applications of different nanocatalysts.
Author: Ming Bao
Publisher: Springer Nature
ISBN: 981974573X
Category :
Languages : en
Pages : 228
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Book Description
Author: Meredith Joanne McMurdo
Publisher:
ISBN:
Category :
Languages : en
Pages : 152
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Book Description
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).
Author: Monika Rak
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"Recent research on metal nanoparticles (M NPs) has shown vast potential and rapid advancement in various applications such as luxury consumer goods, industrial catalysts, and public health products. This research has shown that the properties of M NPs are unique from those of the atomic or even bulk counterparts. While the properties of M NPs are very exciting and inspire many research groups, the impact of the synthesis of these materials on the environment is often neglected in the search for purer products. The application of Green Chemistry principles would help to ameliorate some of the negative impact that the development and application of nanomaterials might have on the environment and society. This thesis examines the synthesis of a variety of M NPs through a solid-state, bottom-up, mechanochemical means. An efficient and atom-economical method of synthesizing ultra-small gold NPs is presented whereby the gold (III) precursor is ground directly with the amine stabilizing ligand. It was shown that the stainless steel container used for the reaction proved to be essential for the metal precursor reduction and subsequent NP formation. A more general method of mechanochemical synthesis of M NPs was then presented, whereby lignin, a biomass waste product, was used as reducing agent, ligand, and support material for the NPs. We found the synthesis to be applicable to a wide range of metal precursors and allowed for control over the positioning of the M NPs in the support. We pursued studies on the antimicrobial properties of silver NPs created through this method and found it effective against various bacteria. Another application discussed in the thesis is the catalytic oxidation of styrene using molecular oxygen and a variety of iron and iron oxide NPs and nanoshells (NSs) as catalysts." --
Author: Kayla Mae Roeser
Publisher:
ISBN:
Category :
Languages : en
Pages : 108
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Book Description
Noble metals are the most sought after elements for catalysis because of their versatility, activity, and recyclability for a variety of applications; however they are limited as a resource and expensive. Noble metal nanoparticles offer a solution for use in catalysis because their high surface area to volume ratio maximizes their available surface sites while minimizing the amount of metal used. Additionally, particularly exposed facets of nanoparticles can increase surface energies for superior catalytic activity and induce novel electronic/physical properties. In the first chapter of my thesis, I synthesized palladium, platinum, and semiconductor titania nanoparticles through a biomimetic approach by using peptides to preferentially bind to and expose particular crystal facets of nanoparticles. Using a combinatorial approach called biopanning to find highly selective surface energy modifiers for particular facets of materials gave insight to unique binding motifs for materials as well as induced morphology controlled nanoparticles at ambient conditions. There are limitless combinations of solvents, capping agents, and inorganic precursors for inorganic nanoparticle synthesis. Understanding these systems in terms of more global trends would circumvent the current colossal approach of empirically screening systems. To do this, considering the inorganic-organic interfacial relationship is key. In the second chapter, I report unique aryl small molecules which preferentially bind to palladium surfaces through electrostatic potentials and epitaxial binding in nanoparticle synthesis. These results offer an understanding to the dynamic binding relationship between capping agents and nanoparticle surfaces. Lastly, I report on the synthesis of gold-palladium nanoparticles and their activity for the benzyl alcohol oxidation reaction. It was found that the (100) facets of gold-palladium were more catalytically active than the (111) surface. Details of the nanoparticle shape, size, and activity add to the understanding how this material behaves at the atomic level and will help to impact future advances in this field of catalysis. The syntheses described here are important because they are environmentally friendly, they offer information about the binding mechanisms at the organic-inorganic interface of the systems, and give insight to catalytic behavior. All of this work is necessary to further exploit nanoparticle synthesis, assembly and provide the precise engineering of nanostructured materials.
Author: Nathan Musselwhite
Publisher:
ISBN:
Category :
Languages : en
Pages : 135
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Book Description
Model materials consisting of metal nanoparticles loaded onto oxide supports were synthesized, characterized, and investigated in a number of catalytic chemical reactions. By varying the size, shape, and composition of nanoparticle, as well as the material used to support the nanoparticles, it was found that small changes to the catalyst can have enormous changes to the reaction activity and selectivity. Investigation of these carefully synthesized catalysts via in situ characterization, and reaction studies, leads to a deeper understanding of the molecular level parameters that govern catalysis. Through study of the properties of the nanoparticles it was discovered that nanoparticle size and shape have a dominant role in the chemoselective catalysis of furfural over platinum nanoparticles. When vapor phase furfural and hydrogen gas were passed over Pt nanoparticles ranging in size from 1.5 to 7.1 nm, the catalytic selectivity was found to be dominated by the size of the nanoparticle. Large nanoparticles promoted hydrogenation of furfural to furfuryl alcohol, while smaller nanoparticles favored decarbonylation to furan. The same size specific selectivity was found in the hydrogenative reforming (the transformation of hydrocarbons to branched isomers) of C6 hydrocarbons, in which Pt nanoparticle size controls isomerization selectivity. Methylcyclopentane was found to be extremely size dependent at lower temperatures (553 K). It was found that smaller sized nanoparticles favored isomer formation, while larger sizes catalyzed the aromatization reaction more efficiently. n-hexane was found to be much less dependent on particle size, but still showed an increase in isomerization with small particles over larger sized Pt nanoparticles. The composition of PtxRh1-x bimetallic nanoparticles was also studied. These catalysts were characterized under hexane reforming conditions with Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS), in order to find the actual surface atomic composition under real catalytic working conditions. By using AP-XPS and catalytic data in tandem, it was found that an optimum Rh loading occurred when the surface ensemble statistically favored one Rh atom surrounded by Pt atoms. By utilizing different oxide materials for catalytic supports the flow of charge can play a role in the reaction at the surface or interface in a phenomenon known as the strong metal-support interaction (SMSI). When Pt nanoparticles were loaded onto mesoporous supports made of Co3O4, NiO, MnO2, Fe2O3, and CeO2 it was found that their activity for carbon monoxide oxidation was greatly enhanced relative to the support alone or Pt loaded onto inert mesoporous silica. This finding demonstrates that the interface of the metallic Pt nanoparticle and the oxide support is able to produce turnovers that are orders of magnitude higher than the two materials separately. When the same type of experiments were investigated with n-hexane as the reactant and macroporous Al2O3, TiO2, Nb2O5, Ta2O5, and ZrO2 were utilized as supports, it was found that the reaction selectivity was greatly altered depending on the catalytic support material. TiO2, Nb2O5, and Ta2O5 (all of which are strong Lewis acids) were found to be much more selective for isomer production than the standard SiO2 mesoporous silica supported Pt nanoparticle catalyst. Finally, an acidified mesoporous silica material was utilized as the support. This material was synthesized by using AlCl3 to modify the surface of mesoporous silica. This support was found to have no activity for hexane isomerization alone. However, when Pt nanoparticles were supported on the material, the activity and isomer selectivity in hexane reforming was increased several orders of magnitude as compared to the same nanoparticles supported on unmodified mesoporous silica. This dissertation builds on the existing knowledge of known concepts in catalysis science such as structure sensitive reactions, the metal-support interaction, and acid-base chemistry. The results show how small changes in the active sites of a catalyst can create large changes in the catalytic chemistry. This research demonstrates how careful material control, characterization and reaction study can help to elucidate the molecular level components necessary to design efficient catalysts.
Author: Oksana Zaluzhna
Publisher:
ISBN:
Category : Chemistry
Languages : en
Pages : 400
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Book Description
Additionally, the prospective utilization of alkyl selenocyanates as the ligand precursors for synthesis of alkane selenolate - protected Au NPs is demonstrated in this dissertation. Although the successful formation of Au NPs was achieved, the existence of cyano species on the surface of the metal core was experimentally challenging to determine.
Author: John C. Bauer
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
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.
