Synthesis and Characterization of Colloidal Superstructures from Core-shell Nanocrystals with High Quantum Yield PDF Download

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

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Author: Jeffrey A. Gerbec
Publisher:
ISBN: 9780542571671
Category :
Languages : en
Pages : 356

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Book Description
Colloidal semiconductor nanocrystals, with unique size-dependent optical properties, have great promise for integration into next generation technologies including solid-state lighting and biological labeling. A general method of reproducible, large scale and environmentally safe synthetic preparation becomes crucial for integration in commercial devices. In addition to the synthetic protocol, an understanding of the surfaces of the as prepared material is critical for obtaining a high quantum yield that is stable for long periods of time in ambient conditions. In this dissertation, a new synthetic approach to general colloidal nanocrystals is presented. Microwave heating of molecular precursors increases the rate of reaction from days to minutes for a host of nanomaterials. The most relevant for the study of inorganic phosphors is CdSe and InP and their respective ternary analogs. Post synthetic surface treatment of the as prepared material show a tremendous increase in the QY for as prepared InP and InGaP. Post synthetic surface treatment is carried out by photoactivated etching with dilute HF. In the case of InGaP, the QY reaches 0.80 from 0.05 in a matter of minutes. Other surface treatment strategies that address the stability is carried out by forming epitaxial core shell structures. It is shown that using ZnS as a wide band gap shelling material, the QY of InP reaches 0.42 in solution and is stable for months. These are significant steps toward the engineering of semiconductor quantum dot phosphors for solid state lighting and biological labeling.

Author: Gerasimos Konstantatos
Publisher: Cambridge University Press
ISBN: 0521198267
Category : Science
Languages : en
Pages : 329

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Captures the most up-to-date research in the field, written in an accessible style by the world's leading experts.

Author: Vladimir Lesnyak
Publisher: Frontiers Media SA
ISBN: 2889632695
Category :
Languages : en
Pages : 110

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Author: Jessica Annette Sammons
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 59

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Author: Jonathan G. McGrath
Publisher:
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: José Manuel Cordero Hernández
Publisher:
ISBN:
Category :
Languages : en
Pages : 145

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Over the last decade, the synthesis methods of colloidal nanocrystals have advanced at an astonishing rate, producing particles that are chemically stable, monodisperse, and, in the case of semiconductor quantum dots (QDs), immensely bright. Inorganic nanocrystals linked to functional organic or biological molecules have recently emerged as a new class of nanomaterials for generating highly efficient devices, and sensing agents for a broad range of advanced applications. A key step in the synthesis of these constructs involves transforming the chemistry of the surface from that generated by the nanocrystals synthesis conditions (high boiling-point and hydrophobic solvent environment) to one possessesing the appropriate functional groups for derivatization and that is compatible with the intended final application. Here, we describe the synthesis of a series of organic ligands that modify the surface in that manner. The first ligand exhibits a norbornene functional group and binds strongly to the surface of colloidal nanocrystallites during particle synthesis, eliminating the need for ligand exchange and enabling large-scale production of high quality derivatizable nanomaterials. This ligand is compatible with state-of-the-art synthesis methods of a large variety of semiconductor nanocrystallites, including PbS, CdSe/CdS, and InAs/CdSe/CdS core/shell nanoparticles. Applications that make use of the norbornene click-chemistry functionality will be presented, along with efforts to preserve the high quantum yield and colloidal stability in water. We also introduce a bidentate carboxylate-based ligand as part of an effort to enhance the quality of QDs through the chelate effect. This ligands enhances the PLQY at high temperature, as a result of surface-related trap state passivation. Finally, we describe the synthesis of a new functional group for generating derivatizable-QDs that can be easily copolymerized with the polyimidazole ligand (PIL), and that is reactive with tetrazine and, upon thermal activation, with thiols to form stable bioconjugates.

Author: Victor I. Klimov
Publisher: CRC Press
ISBN: 1351834525
Category : Technology & Engineering
Languages : en
Pages : 584

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Book Description
A review of recent advancements in colloidal nanocrystals and quantum-confined nanostructures, Nanocrystal Quantum Dots is the second edition of Semiconductor and Metal Nanocrystals: Synthesis and Electronic and Optical Properties, originally published in 2003. This new title reflects the book’s altered focus on semiconductor nanocrystals. Gathering contributions from leading researchers, this book contains new chapters on carrier multiplication (generation of multiexcitons by single photons), doping of semiconductor nanocrystals, and applications of nanocrystals in biology. Other updates include: New insights regarding the underlying mechanisms supporting colloidal nanocrystal growth A revised general overview of multiexciton phenomena, including spectral and dynamical signatures of multiexcitons in transient absorption and photoluminescence Analysis of nanocrystal-specific features of multiexciton recombination A review of the status of new field of carrier multiplication Expanded coverage of theory, covering the regime of high-charge densities New results on quantum dots of lead chalcogenides, with a focus studies of carrier multiplication and the latest results regarding Schottky junction solar cells Presents useful examples to illustrate applications of nanocrystals in biological labeling, imaging, and diagnostics The book also includes a review of recent progress made in biological applications of colloidal nanocrystals, as well as a comparative analysis of the advantages and limitations of techniques for preparing biocompatible quantum dots. The authors summarize the latest developments in the synthesis and understanding of magnetically doped semiconductor nanocrystals, and they present a detailed discussion of issues related to the synthesis, magneto-optics, and photoluminescence of doped colloidal nanocrystals as well. A valuable addition to the pantheon of literature in the field of nanoscience, this book presents pioneering research from experts whose work has led to the numerous advances of the past several years.

Author: Frederic Victor Mikulec
Publisher:
ISBN:
Category :
Languages : en
Pages : 149

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Author: Adam Biacchi
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Solution methods of materials synthesis have found application in a variety of fields due to the diversity of products accessible, facility of process scalability, and the ease of tuning their properties through prudent selection of reaction conditions. Control of experimental variables during the formation of colloidally stable nanoscale solids within a liquid matrix allows for tailoring of the particles' characteristics, including shape, size, composition, and surface chemistry. In this dissertation, I will discuss how the manipulation of reaction chemistries can be used to synthesize shape-controlled metal and semiconductor colloidal nanocrystals. Further, I will elaborate on the mechanisms by which these particles form from molecular precursors and describe how their properties can differ from their bulk analogues through extensive characterization, especially using transmission electron microscopy. These studies contribute to the continued development of chemical routes to nanocrystals and their application as functional materials.First, I will review recent advances in the synthesis and characterization of shape-controlled nanocrystals, as well as highlight their promising applicability in a number of emerging technologies. These principles will then be leveraged to the specific case of catalytically-active rhodium nanocrystals, which can be synthesized with morphological and dimensional control using a polyol solution-mediated strategy. I describe an innovative shape-controlled synthesis to monodisperse colloidal rhodium icosahedra, cubes, triangular plates, and octahedra using this route. Additionally, new insights into the important role of the polyol reducing solvent on the synthesis of these nanocrystals are revealed, and how these might be exploited to engender superior reaction control and novel products.Next, I will describe how a crystallization mechanism was established for the synthesis of numerous morphologies of noble metal nanocrystals. I present a thorough analysis of the synthesis of shape-controlled rhodium nanocrystals, using extensive transmission electron microscopy characterization, and relate these findings to one of the primary synthetic levers available in the polyol synthesis: the anionic ligands present. Further, I show that the crystallization process proceeds by a nonclassical mechanism in which cluster particles serve as a stable intermediate between molecular precursors and the final product. I then apply these principles to the shape-controlled synthesis of other noble metal nanocrystals before expounding a generalized formation mechanism in the polyol synthesis of colloidal metal nanocrystals. Finally, I will highlight my efforts in the designed synthesis and characterization of colloidal tin(II) sulfide (SnS) semiconducting "quantum dot" nanocrystals. I describe a route for the solution synthesis of monodisperse colloidal SnS nanosheets, nanocubes, and nanospherical polyhedra in high yield. Further, detailed crystallographic characterization of these nanocrystals using transmission electron microscopy indicates that their atomic structure possesses a previously-unreported nanoscale deviation from the bulk phase. Additionally, I show that their electronic and photocatalytic properties of these quantum dots are both shape-dependent and distinct from bulk SnS.