Synthesis and Characterization of Core-shell Upconversion Nanoparticles Containing Anisotropic Interfacial Strain PDF Download

Author: 趙劍雄
Publisher:
ISBN:
Category : Materials science
Languages : en
Pages : 90

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Author:
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ISBN:
Category :
Languages : en
Pages : 6

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Core-shell nanostructures have attracted much attention due to their unique and tunable properties relative to bulk structures of the same materials, making core-shell nanoparticles candidates for a variety of applications with multiple functionalities.[1,2] Intriguing magnetic behavior can be tailored by variation of size, interface, crystal orientation, and composition, and core-shell nanostructures with noble-metal shells yield novel optical responses[3] and enhanced electrocatalytic activity.[4].

Author: Jonathan G. McGrath
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ISBN:
Category :
Languages : en
Pages : 236

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This dissertation describes the use of spherical core/shell type micro- and nanoparticles as building blocks for the fabrication of colloidal crystals. The polymer component used in all of the projects that are described herein is poly-N-isopropylacrylamide (pNIPAm). The polymeric identity of particles composed of this soft, hydrogel material, which is also thermoresponsive, contributes to the self-assembly of such particles to form ordered structures. Chapter 2 examines a characterization technique using fluorescence resonance energy transfer (FRET) to investigate the structure of particles that possess a core/shell topology. Chapters 4-6 investigate strategies to impart both hard (dense core) and soft (flexible shell) properties to the particles by using styrene as the main component in a copolymer synthesis with pNIPAm (pS- co-NIPAm particles). The resulting crystal assemblies, which could be formed by simple drying procedures, were demonstrated to be robust and their application as processable, photonic inks is also investigated. Chapter 7 examines the ability to crosslink these crystals together by simple heating methods to produce robust films, and the optical properties of these crystal films could be tuned by simple rehydration. Chapters 3 and 5 examine the synthesis and self-assembly strategies of core/shell particles using the properties of pNIPAm shell layers that have been added to different types of core particles (silver or pS-co-NIPAm) for the purposes of fabricating colloidal crystals using thermal annealing procedures. Chapter 8 explores the use of silver particles as tracers for the characterization of colloidal crystals composed of thermally annealed colloidal crystals composed of pNIPAm hydrogel particles.

Author: Ryan Evan Schwarb
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ISBN:
Category : Fuel
Languages : en
Pages : 80

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Recent advances in the science of nanoparticle synthesis have resulted in new core-shell nanoparticles displaying novel, unique, and potentially valuable properties for their use in propellants, fuels, and explosives. This research was conducted in support of the Propulsion Directorate of the Air Force Research Laboratory aimed at the development of functional reactive nanoparticles as fuel additives for improved thermal stability. In this work, oxidation of highly reactive zero-valent iron nanoparticles coated to prevent agglomeration and early reaction was studied as a novel approach to remove oxygen from the fuels. The particles were synthesized using sonochemistry, a well-established technique to self assemble core-shell nanoparticles, where the solution of pentacarbonyl Fe(CO)5 in dodecane was sonciated in the presence of an encapsulating compound, or shell material, to produce core-shell nanoparticles (CSNPs). The nanoparticles were stable at the temperatures below 120°C; at elevated temperatures, the shell material allows oxygen to permeate and react with the iron core depleting the oxygen from solution. It was observed that altering the structure of the shell material significantly influences the temperature-controlled oxidation of CSNPs over a range from 130°C to 188°C. This thesis investigates various shell material parameters including chain length, structural perturbation, and functional group to protect the iron core from oxidation at low temperatures and enable temperature-controlled oxidation of the iron core at higher temperatures. The impact of shell material parameters on CSNP solubility, particle diameter and temperature-controlled oxidation are investigated and reported.

Author: Saheel Dilip Bhana
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ISBN:
Category :
Languages : en
Pages :

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Hybrid nanomaterials possessing dual magnetic/optical properties are of considerable interest to many areas, ranging from material science to medicine and biology. They are promising for a broad range of applications including catalysis, energy conversion, biological separation, medical diagnosis and treatment. Anisotropic magnetic-optical nanoparticles give better or new properties compared to spherical ones due to their high curvature and polarization-sensitive geometry. However, the engineering of compact and uniform anisotropic magnetic-optical core-shell nanoparticles remains a major challenge. The work in this thesis is aimed at the preparation and characterization of magnetic-optical core-shell hybrid NPs in different shapes and sizes. Iron oxide-gold core-shell nanoparticles in spherical, oval and pin shapes were prepared. Our studies have shown that iron oxide-gold core-shell nanoparticles, despite the shapes, exhibit 10 times better absorption properties compared to solid gold nanoparticles. The availability of these nanoparticles would make an important impact in biomedicine, material science and other fields.

Author: Selma Nacak
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Category :
Languages : en
Pages :

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Author: Jorge L. Chávez Benavides
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Category :
Languages : en
Pages :

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These studies suggested that the sequestered probes could interact with each other producing a dynamic quenching of the donor. Finally, we covalently attached another hydrophobic fluorescent probe to the particles to study the level of interaction with the solvent, observing that the probe preferred to react in the interior pores of the particles to reduce interaction with the polar media.

Author: Mark Douglas Edmundson
Publisher:
ISBN:
Category :
Languages : en
Pages : 280

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Author: He Li
Publisher:
ISBN: 9780549490159
Category : Nanostructured materials
Languages : en
Pages : 138

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Fe, Co, FexCo(1-x) and AuxFe (1-x) alloy nanoparticles encapsulated by graphitic carbon are synthesized by chemical vapor deposition. Transmission electron microscopy (TEM) reveals that the nanoparticles are mostly about 10 nm in diameter and each nanoparticle is enclosed by at least one layer of graphitic carbon. Phase identification by high resolution TEM indicates the metallic phases were indeed obtained and preserved, even after three years of exposure to ambient conditions. The Fe-containing nanoparticles were found to be either BCC or FCC or Fe 3C, the Co nanoparticles being FCC, the FexCo(1-x) (0.1

Author: Sriya Sanyal
Publisher:
ISBN:
Category : Composite materials
Languages : en
Pages : 186

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Nanoparticles are ubiquitous in various fields due to their unique properties not seen in similar bulk materials. Among them, core-shell composite nanoparticles are an important class of materials which are attractive for their applications in catalysis, sensing, electromagnetic shielding, drug delivery, and environmental remediation. This dissertation focuses on the study of core-shell type of nanoparticles where a polymer serves as the core and inorganic nanoparticles are the shell. This is an interesting class of supramolecular building blocks and can "exhibit unusual, possibly unique, properties which cannot be obtained simply by co-mixing polymer and inorganic particles". The one-step Pickering emulsion polymerization method was successfully developed and applied to synthesize polystyrene-silica core-shell composite particles. Possible mechanisms of the Pickering emulsion polymerization were also explored. The silica nanoparticles were thermodynamically favorable to self-assemble at liquid-liquid interfaces at the initial stage of polymerization and remained at the interface to finally form the shells of the composite particles. More importantly, Pickering emulsion polymerization was employed to synthesize polystyrene/poly(N-isopropylacrylamide) (PNIPAAm)-silica core-shell nanoparticles with N-isopropylacrylamide incorporated into the core as a co-monomer. The composite nanoparticles were temperature sensitive and could be up-taken by human prostate cancer cells and demonstrated effectiveness in drug delivery and cancer therapy. Similarly, by incorporating poly-2-(N, N)-dimethylamino)ethyl methacrylate (PDMA) into the core, pH sensitive core-shell composite nanoparticles were synthesized and applied as effective carriers to release a rheological modifier upon a pH change. Finally, the research focuses on facile approaches to engineer the transition of the temperature-sensitive particles and develop composite core-shell nanoparticles with a metallic shell.