Author: Lauren Marie Forbes
Publisher:
ISBN: 9781303324000
Category :
Languages : en
Pages : 92
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Book Description
Heterogeneous catalysts have widespread industrial applications. Platinum nanomaterials in particular, due to their particularly high electrocatalytic activity and durability, are used to catalyze a wide variety of reactions, including oxygen reduction, which is frequently used as the cathode reaction in fuel cells. As platinum is a very expensive material, a high priority in fuel cell research is the exploration of less expensive, more efficient catalysts for the oxygen reduction reaction (ORR). We demonstrate here the use of phage display to identify peptides that bind to Pt (100) which were then used to synthesize platinum cubes in solution. However, while the peptides were able to control particle growth, the bio-synthesized Pt particles showed extremely poor activity when tested for ORR. This could be attributed to peptide coverage on the surface or strong interactions between particular amino acids and the metal that are detrimental for catalysis. To investigate this further, we decided to investigate the role of individual amino acids on Pt nanocrystal synthesis and catalysis. For this, we conjugated the R-groups of single amino acids to polyethylene glycol (PEG) chains. Through this work we have determined that the identity of the amino acid R-group is important in both the synthesis and the catalytic activity of the particles. For Pt nanoparticle synthesis, we found that the hydrophobicity of the functional groups affected their ability to interact well with the particles during nucleation and growth, and thus only the hydrophilic functional groups were capable of mediating the synthesis to produce well-defined faceted particles. With respect to ORR, we found distinct trends that showed that the inclusion of certain amino acids could significantly enhance catalysis- even at high polymer loadings. This work presents evidence that counters the common conception that organic capping ligands decrease catalytic activity; in fact activity may actually be improved over bare metal through judicious choice and design of ligands that inhibit Pt oxidation and control chain packing at the Pt surface. Therefore, it may be possible to have ligands on a nanoparticle surface that allow the particles to be well-dispersed on an electrode surface, while simultaneously enhancing catalysis.
Author: Varun Rawat
Publisher: CRC Press
ISBN: 1000555534
Category : Science
Languages : en
Pages : 249
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Book Description
As the broad challenges around energy and the environment have become the focus of much research, scientists and experts have dedicated their efforts to developing more active and selective catalytic systems for key chemical transformations. For many decades environmentally viable protocols for the synthesis of fine chemicals have been the crux of academic and industrial research. Heterogeneous Catalysis in Organic Transformations serves as an overview of this work, providing a complete description of role of heterogeneous catalysis in organic transformations and offering a review of the current and near future technologies and applications. Discusses the fundamentals of catalysis and compares the advantages and disadvantages of different types of catalyst systems Examines oxide nanoparticles and noble metal nanoparticles Consider organometallic compounds, solid-supported catalysts, and mesoporous materials Describes recent advances in metal-based heterogeneous catalysts and new reactions with possible mechanistic pathways Providing a comprehensive review of heterogeneous catalysis from the basics through recent advances, this book will be of keen interest to undergraduates, graduates, and researchers in chemistry, chemical engineering, and associated fields.
Author: Imann Mosleh
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Nanoparticles have received much attentions due to their unique properties that makes them suitable candidates for a broad range of applications. As the size of particles decreases, their surface area-to-volume ratio would increase which is the main cause of much attention. In addition to the size, their morphologies and compositions may also play important roles for defining unique properties. Nanoparticle synthesis include both bottom-up and top-down strategies. To control the process of inorganic nanoparticles synthesis one could follow the bottom-up approach to have atom-level control over their compositions, morphologies, phases, and sizes which is the subject of this work. Due to their specific sequence of amino acids, proteins and peptides has been demonstrated to be used for nanoparticle synthesis. The main obstacle to widespread development and commercialization of protein and peptide-directed nanoparticle synthesis platforms is their high cost when the peptide is obtained by traditional chemical synthesis. A promising approach for the cost-effective production of nanoparticles using protein/peptide derives from our effort to develop Escherichia coli into an expression platform. In contrast to most biochemical engineering applications, the purity of the fusion proteins and peptides may be less stringent for nanoparticle synthesis, demonstrating the fact that crude bacterial lysates containing fusion peptides may be used in lieu of expensive, pure peptide in nanoparticles synthesis while the nucleation and growth mechanism is consistent with traditional systems. Indeed, it is conceivable that simply concentrating the protein/peptide may be the only purification step necessary for nanoparticle synthesis. Additionally, catalytic activities of the fusion protein-directed nanoparticles were evaluated using the most popular and efficient routes for the formation of carbon- carbon bonds, Suzuki-Miyaura coupling and Stille coupling reactions. The unpurified fusion protein-directed nanoparticles showed slightly higher catalytic activity comparing to the chemically synthesized peptide counterparts. Moreover, fusion protein-directed nanoparticles presented high catalytic activities in green solvents as well as high stability and recyclability. They also could be utilized efficiently for the synthesis of Lapatinib precursor, an oral active anti breast cancer drug. The excel catalytic activity of the fusion protein-directed nanoparticles make them an excellent candidate for catalytic applications in the future.
Author: May Maung
Publisher:
ISBN: 9781339826233
Category : Allyl alcohol
Languages : en
Pages : 48
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Book Description
Abstract: This thesis presents the systematic evaluation of palladium nanoparticles functionalized with well-defined small organic ligands that can provide a spatial control in the surrounding environment of nanoparticle catalyst surfaces. Various thiolate ligand-capped palladium nanoparticles are produced by using different S-alkylthiosufate ligand precursors in a two-phase system composed of toluene and water. These palladium nanoparticles are then characterized using transmission electron microscopy, thermogravimetric analysis, NMR, FT-IR, and UV-vis spectroscopy. The catalysis studies on alkanethiolate-capped palladium nanoparticles with different ligand structures (linear alkyl vs cyclohexyl vs phenyl) show that the chemical and structural composition of a monolayer surrounding the palladium nanoparticles greatly influences the overall activity and selectivity of nanoparticle catalysts for the hydrogenation, isomerization, and hydrogenolysis of allylic alcohols. Especially, the effect of non-covalent interactions between surface ligands and incoming substrates in the near-surface environment is observed. Furthermore, the catalytic properties of & ohgr;-carboxylate-functionalized alkanethiolate-capped palladium nanoparticles are studied for the biphasic reactions of hydrophobic allylic alcohols that are immiscible in aqueous solution. The systematic investigations on the influence of pH and substrate size are performed to check the utility of structurally stable and water-soluble palladium nanoparticles as new micellar catalysts.
Author: Daniel L. Fedlheim
Publisher: CRC Press
ISBN: 9780585404394
Category : Science
Languages : en
Pages : 348
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Book Description
A state-of-the-art reference, Metal Nanoparticles offers the latest research on the synthesis, characterization, and applications of nanoparticles. Following an introduction of structural, optical, electronic, and electrochemical properties of nanoparticles, the book elaborates on nanoclusters, hyper-Raleigh scattering, nanoarrays, and several applications including single electron devices, chemical sensors, biomolecule sensors, and DNA detection. The text emphasizes how size, shape, and surface chemistry affect particle performance throughout. Topics include synthesis and formation of nanoclusters, nanosphere lithography, modeling of nanoparticle optical properties, and biomolecule sensors.
Author: Diego J. Gavia
Publisher:
ISBN: 9781303765926
Category : Allyl alcohol
Languages : en
Pages : 170
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Book Description
Abstract: This thesis presents systematic investigations on the relationship between the catalytic property and the surface ligand density/core size of thiolate ligand-capped Pd nanoparticles (PdNPs). The systematic variations in the two-phase synthesis of PdNPs generated from sodium S-dodecylthiosulfate and sodium co-carboxyl-S'-alkanethiosulfates were performed. The resulting PdNPs were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and *H NMR and UV Vis spectroscopy. The catalysis studies on various PdNPs with different surface ligand density and average core size showed a strong correlation between the PdNP composition and the turnover frequency (TOF) of the isomerization of allyl alcohol. Stable watersoluble Pd nanoparticles with the lower surface ligand density were further examined for the catalytic hydrogenation of allyl alcohol in both aqueous and organic solvents. The catalysis results showed that water-soluble Pd nanoparticles dissolved in water favored the hydrogenation product (1-propanol) whereas Pd nanoparticles dispersed in chloroform exhibited a low catalytic activity with some selectivity towards the isomerization product (propanal).
Author: John D. Attelah
Publisher:
ISBN:
Category : Nanostructured materials
Languages : en
Pages : 0
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Book Description
Author's abstract: Rational design of active and stable palladium nanoparticles using peptide is emerging field in nanomaterial technology. Nanoparticles are preferred as catalysts compared to their bulk counter-parts due to their large surface area-to-volume ratio making them more reactive. The use of peptide to facilitate the formation and stabilization of the inorganic nanoparticles such as palladium is desirable due to their less toxic nature, and desired products formed after the completion of the reaction. In addition, peptide is known to impart high level of control over size and shape in nanoparticles. In this work, peptide-driven fabrication of catalytically stable and reactive palladium was conducted in organic solvents and used in Heck reaction catalysis of iodobenzene and butyl acrylate to form butyl cinnamate. The use of a peptide ligands contrasts with the traditional toxic bulky phosphine ligands, which are conventionally used to stabilize and solubilize bulky palladium metal catalyst. The optimum temperature for maximum yield of butyl cinnamate was investigated in series of reactions set up from 25 to 80 °C with other reaction parameters kept constant. Heck coupling reaction is industrially important in synthesis of various pharmaceuticals We successfully conducted, characterized, and quantified the Heck coupling reaction in ethanol and DMSO at 80 °C using palladium-capped peptide nanoparticles and triethyl amine base. Different engineered and control peptides were used to fabricate palladium nanoparticles formation and for enhancing their colloidal and stability during the Heck reaction. The peptides used were engineered from the control Pd4 (TSNAVHPTLRHL) peptide, which is known to specifically bind palladium metal via the histidines at positions six and eleven. The S2 (AFILPTG) peptide, which is specific to silica, was attached at either ends of the Pd4 peptide to form S2Pd4, Pd4S2, and S2Pd4S2. The engineered peptide-capped palladium nanoparticles were investigated for their colloidal stability and catalytic activity.
Author: Emily A.. Groover
Publisher:
ISBN:
Category : Biotechnology
Languages : en
Pages : 0
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Book Description
Author's abstract: The synthesis of palladium nanoparticles (Pd NPs) using materials-directed peptides is a novel, nontoxic approach which exerts a high level of control over the particle size and shape. This biomimetic technique is environmentally benign, featuring nonhazardous ligands and ambient conditions. Nanoparticles are extremely reactive catalysts, boasting a large surface-to-volume ratio when compared to their bulk counterparts. The rational design of these nanoparticles using peptides has been very successful in aqueous environments, but no research has been done to apply it in organic systems. As such, the biomimetic synthesis of Pd NPs in an organic system is here investigated, with ethanol and dimethyl sulfoxide (DMSO) as solvents of interest. These systems adapt palladium-binding peptides to incorporate a hydrophobic region on the -N terminus, -C terminus, and both N and C termini to aid in solvent interaction during nanoparticle synthesis. These peptides proved to successfully synthesize colloidal nanoparticles in both ethanol and DMSO. Their subsequent application as catalysts in the Suzuki-Miyaura carbon cross-coupling reaction facilitated a comparison of the peptide-capped nanoparticles’ catalytic activity. Catalytic studies indicate that the S2Pd4S2 peptide, with two hydrophobic regions, produced nanoparticles with the highest catalytic activity as compared to the other major peptides, suggesting that materials-directed peptides may be adapted and tuned to operate effectively in organic solvents.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 7
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Book Description
The overall objective of the proposed research is to use fundamental advances in bionanotechnology to design powerful platinum nanocrystal electrocatalysts for fuel cell applications. The new economically-viable, environmentally-friendly, bottom-up biochemical synthetic strategy will produce platinum nanocrystals with tailored size, shape and crystal orientation, hence leading to a maximum electrochemical reactivity. There are five specific aims to the proposed bio-inspired strategy for synthesizing efficient electrocatalytic platinum nanocrystals: (1) isolate peptides that both selectively bind particular crystal faces of platinum and promote the nucleation and growth of particular nanocrystal morphologies, (2) pattern nanoscale 2-dimensional arrays of platinum nucleating peptides from DNA scaffolds, (3) investigate the combined use of substrate patterned peptides and soluble peptides on nanocrystal morphology and growth (4) synthesize platinum crystals on planar and large-area carbon electrode supports, and (5) perform detailed characterization of the electrocatalytic behavior as a function of catalyst size, shape and morphology. Project Description and Impact: This bio-inspired collaborative research effort will address key challenges in designing powerful electrocatalysts for fuel cell applications by employing nucleic acid scaffolds in combination with peptides to perform specific, environmentally-friendly, simultaneous bottom-up biochemical synthesis and patterned assembly of highly uniform and efficient platinum nanocrystal catalysts. Bulk synthesis of nanoparticles usually produces a range of sizes, accessible catalytic sites, crystal morphologies, and orientations, all of which lead to inconsistent catalytic activities. In contrast, biological systems routinely demonstrate exquisite control over inorganic syntheses at neutral pH and ambient temperature and pressures. Because the orientation and arrangement of the templating biomolecules can be precisely controlled, the nanocrystals boast a defined shape, morphology, orientation and size and are synthesized at benign reaction conditions. Adapting the methods of biomineralization towards the synthesis of platinum nanocrystals will allow effective control at a molecular level of the synthesis of highly active metal electrocatalysts, with readily tailored properties, through tuning of the biochemical inputs. The proposed research will incorporate many facets of biomineralization by: (1) isolating peptides that selectively bind particular crystal faces of platinum (2) isolating peptides that promote the nucleation and growth of particular nanocrystal morphologies (3) using two-dimensional DNA scaffolds to control the spatial orientation and density of the platinum nucleating peptides, and (4) combining bio-templating and soluble peptides to control crystal nucleation, orientation, and morphology. The resulting platinum nanocrystals will be evaluated for their electrocatalytic behavior (on common carbon supports) to determine their optimal size, morphology and crystal structure. We expect that such rational biochemical design will lead to highly uniform and efficient platinum nanocrystal catalysts for fuel cell applications.
Author: Claudia Altavilla
Publisher: CRC Press
ISBN: 1351833960
Category : Technology & Engineering
Languages : en
Pages : 885
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Book Description
Among the various nanomaterials, inorganic nanoparticles are extremely important in modern technologies. They can be easily and cheaply synthesized and mass produced, and for this reason, they can also be more readily integrated into applications. Inorganic Nanoparticles: Synthesis, Applications, and Perspectives presents an overview of these special materials and explores the myriad ways in which they are used. It addresses a wide range of topics, including: Application of nanoparticles in magnetic storage media Use of metal and oxide nanoparticles to improve performance of oxide thin films as conducting media in commercial gas and vapor sensors Advances in semiconductors for light-emitting devices and other areas related to the energy sector, such as solar energy and energy storage devices (fuel cells, rechargeable batteries, etc.) The expanding role of nanosized particles in the field of catalysis, art conservation, and biomedicine The book’s contributors address the growing global interest in the application of inorganic nanoparticles in various technological sectors. Discussing advances in materials, device fabrication, and large-scale production—all of which are urgently required to reduce global energy demands—they cover innovations in areas such as solid-state lighting, detailing how it still offers higher efficiency but higher costs, compared to conventional lighting. They also address the impact of nanotechnology in the biomedical field, focusing on topics such as quantum dots for bioimaging, nanoparticle-based cancer therapy, drug delivery, antibacterial agents, and more. Fills the informational gap on the wide range of applications for inorganic nanoparticles in areas including biomedicine, electronics, storage media, conservation of cultural heritage, optics, textiles, and cosmetics Assembling work from an array of experts at the top of their respective fields, this book delivers a useful analysis of the vast scope of existing and potential applications for inorganic nanoparticles. Versatile as either a professional research resource or textbook, this effective tool elucidates fundamentals and current advances associated with design, characterization, and application development of this promising and ever-evolving device.
