Download or read book Process Dependent Properties in Colloidally Synthesized Giant Core Shell Nanocrystal Quantum Dots written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to their characteristic bright and stable photoluminescence, semiconductor nanocrystal quantum dots (NQDs) have attracted much interest as efficient light emitters for applications from single-particle tracking to solid-state lighting. Despite their numerous enabling traits, however, NQD optical properties are frustratingly sensitive to their chemical environment, exhibit fluorescence intermittency ('blinking'), and are susceptible to Auger recombination, an efficient nonradiative decay process. Previously, we showed for the first time that colloidal CdSe/CdS core/shell nanocrystal quantum dots (NQDs) comprising ultrathick shells (number of shell monolayers, n,> 10) grown by protracted successive ionic layer adsorption and reaction (SILAR) leads to remarkable photostability and significantly suppressed blinking behavior as a function of increasing shell thickness. We have also shown that these so-called 'giant' NQDs (g-NQDs) afford nearly complete suppression of non-radiative Auger recombination, revealed in our studies as long biexciton lifetimes and efficient multiexciton emission. The unique behavior of this core/shell system prompted us to assess correlations between specific physicochemical properties - beyond shell thickness - and functionality. Here, we demonstrate the ability of particle shape/faceting, crystalline phase, and core size to determine ensemble and single-particle optical properties (quantum yield/brightness, blinking, radiative lifetimes). Significantly, we show how reaction process parameters (surface-stabilizing ligands, ligand:NQD ratio, choice of 'inert' solvent, and modifications to the SILAR method itself) can be tuned to modify these function-dictating NQD physical properties, ultimately leading to an optimized synthetic approach that results in the complete suppression of blinking. We find that the resulting 'guiding principles' can be applied to other NQD compositions, allowing us to achieve non-blinking behavior in the near-infrared. Lastly, in addition to realizing novel light-emission properties by refining nanoscale architectures at the single-NQD level, we also investigate collective properties by assembling our core/shell NQDs into larger scale arrays.

Download or read book Semiconductor Nanocrystal Quantum Dots written by Andrey Rogach and published by Springer Science & Business Media. This book was released on 2008-09-02 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first book to specifically focus on semiconductor nanocrystals, and address their synthesis and assembly, optical properties and spectroscopy, and potential areas of nanocrystal-based devices. The enormous potential of nanoscience to impact on industrial output is now clear. Over the next two decades, much of the science will transfer into new products and processes. One emerging area where this challenge will be very successfully met is the field of semiconductor nanocrystals. Also known as colloidal quantum dots, their unique properties have attracted much attention in the last twenty years.

Download or read book Core Shell Quantum Dots written by Xin Tong and published by Springer Nature. This book was released on 2020-07-01 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book outlines various synthetic approaches, tuneable physical properties, and device applications of core/shell quantum dots (QDs). Core/shell QDs have exhibited enhanced quantum yield (QY), suppressed photobleaching/blinking, and significantly improved photochemical/physical stability as compared to conventional bare QDs. The core-shell structure also promotes the easy tuning of QDs’ band structure, leading to their employment as attractive building blocks in various optoelectronic devices. The main objective of this book is to create a platform for knowledge sharing and dissemination of the latest advances in novel areas of core/shell QDs and relevant devices, and to provide a comprehensive introduction and directions for further research in this growing area of nanomaterials research.

Download or read book Nanocrystal Quantum Dots written by Victor I. Klimov and published by CRC Press. This book was released on 2017-12-19 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Colloidal Semiconductor Nanocrystals Synthesis Properties and Applications written by Vladimir Lesnyak and published by Frontiers Media SA. This book was released on 2020-01-06 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Structure of Colloidal Quantum Dots written by Ingrid Joylyn Paredes and published by American Chemical Society. This book was released on 2023-06-15 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology is an interdisciplinary field comprising materials scientists, chemists, physicists, and engineers dedicated to understanding the chemistry behind the associated synthesis, purification, modification, and applications. Already, nanotechnology has been instrumental to advances in medicine, electronics, catalysis, and cosmetics. The work of nanotechnologists has enabled society to move from the current “Silicon Age” into a new “Nano Age.” These alternatives to Si-based technologies are expected to combine the optoelectronic properties of bulk inorganic semiconductors with the benefits of additive device manufacturing—low cost, large area, and solution-based processes. This primer focuses on a class of nanomaterials known as colloidal quantum dots. Known for their solution processability and size-dependent optoelectronic properties, the study of colloidal quantum dots has garnered significant attention from the research community. The goal of this primer is to equip newcomers with the introductory knowledge and tools necessary to enter the field. As such, the scope of our work focuses on the synthesis and characterization of quantum dots; where possible, we point the reader to further reading specific to applications.

Download or read book Relationships Between Processing Structure And Properties Of Nanocrystal Quantum Dots And Superlattices written by Kaifu Bian and published by . This book was released on 2015 with total page 421 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystal quantum dots are novel materials of great scientific and technological interests. The attractive features of quantum dots include size-tunable optoelectronic properties, high optical absorption cross section and ease of synthesis and deposition. These unique features qualify quantum dots as a promising material platform for emerging technological applications such as photovoltaic devices, sensors, light emitting diodes and bioimaging. In most of the proposed applications, individual quantum dots cannot be utilized until they form macroscopic assemblies. Under proper conditions quantum dots self-assemble into periodical superlattices. The properties and performance of quantum dot assemblies depend on not only the intrinsic properties of isolated dots but also their spatial arrangement or ordering. Consequently the relationships between processing, structure and properties of quantum dots and superlattices are of great importance in guiding the design and fabrication of novel nanomaterials with advantageous features using quantum as building blocks. In this dissertation, I present my graduate research studying such trilateral relationships in lead chalcogenide quantum dot systems. The first half of this dissertation discusses the relationship between processing and structure of self-assembled superlattices. An overview of how the ligand-ligand interaction as the major driving force along with factors including particle size, shape, ligand morphology, solvents and interfaces determine superlattice morphology is provided and followed by specific examples. (1) By tuning surface ligand morphology of PbS quantum dots and growth conditions, the effective particles shape was altered and therefore different symmetries (fcc, bcc and bct) of superlattice were achieved. (2) The translational and orientational orderings in an fcc superlattice of cuboctahedron PbS quantum dots was decoded by small and wide angle x-ray scatterings. The dots showed two distinct orientations as a result of the interplay between particle shape and ligand attractions. (3) Study of the nucleation, orientational alignment and symmetry transformations of PbS nanocubes at solvent-air and solvent-substrate interfaces is presented to demonstrate the role of interfaces as templates in guiding superlattice formation. Presented in the second half of this dissertation are my research works using high pressure, which efficiently tunes both superlattice and atomic structures without altering chemistry, to probe the relationships between structure and properties of quantum dots systems. (1) Difference in the pressure-induced atomic phase transition pressure indicated that dots in bcc superlattice are more mechanically stable than those in fcc due to translational and orientational orderings. (2) Elastic stiffness of PbS quantum dots were found to show size-dependence which is explained by a core-shell model. (3) Size-dependent variation of band gap of PbS quantum dot under elevated pressure was observed and correlated to changes of atomic structure. (4) Quantum dots were innovatively used as a nano-scaled tool to uniaxially compress organic molecule chains and measure the force-length relationship of single molecules.

Download or read book Colloidal Quantum Dot Optoelectronics and Photovoltaics written by Gerasimos Konstantatos and published by Cambridge University Press. This book was released on 2013-11-07 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: Captures the most up-to-date research in the field, written in an accessible style by the world's leading experts.

Download or read book Ternary Quantum Dots written by Oluwatobi Samuel Oluwafemi and published by Woodhead Publishing. This book was released on 2021-07-02 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ternary Quantum Dots: Synthesis, Properties, and Applications reviews the latest advances in ternary (I-III-VI) chalcopyrite quantum dots (QDs), along with their synthesis, properties and applications. Sections address the fundamental key concepts of ternary quantum dots, progress in synthesis strategies (i.e., organic and aqueous synthesis), and characterization methods (i.e., transmission electron microscopy, dynamic light scattering, etc.). Properties of ternary quantum dots are comprehensively reviewed, including optical, chemical and physical properties. The factors and mechanisms of the cytotoxicity of ternary quantum dot-based nanomaterials are also described. Since ternary chalcopyrite quantum dots are less toxic and more environmentally benign than conventional binary II-VI chalcogenide quantum dots, they are being investigated to replace conventional quantum dots in a range of applications. Thus, this book reviews QDs in various applications, such as solar cells, photocatalytic, sensors and bio-applications. Reviews fundamental concepts of ternary quantum dots and quantum dot-nanocomposites including the most relevant synthesis strategies, key properties, and characterization techniques Delves into the cytotoxicity of quantum dots looking at the factors and mechanisms that influence cytotoxicity including demonstration of cytotoxicity assays for in vitro and in vivo tests Touches on the many applications of ternary quantum dots including biomedical applications, applications in solar cells, sensing applications, and photocatalytic applications

Download or read book Photoactive Semiconductor Nanocrystal Quantum Dots written by Alberto Credi and published by Springer. This book was released on 2017-01-20 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Current Chemistry Collections presents critical reviews from the journal Topics in Current Chemistry organized in topical volumes. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field.

Download or read book Aggregative Growth of Colloidal Semiconducting Nanocrystals for Nanoshell Quantum Dots and Quantum Dot Molecules written by James Cassidy and published by . This book was released on 2022 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: With continuing progress in the chemical synthesis of colloidal semiconductor nanocrystals (NC), one property that remains elusive to the rational design is the ensemble photoluminescence (PL) line width. Given the growing demand for NC-based light-emitting materials, substantial research effort has been dedicated to this issue. Here, we demonstrate a postsynthetic strategy that allows reducing emission line widths of CdSe and CdS NCs to near single-particle levels while enhancing the PL quantum yield. The key idea behind the synthetic approach lies in employing a nonclassical coalescence growth mechanism, which leads to size focusing irrespective of the initial sample morphology. Numerical simulations accurately predict the observed particle size evolution, confirming the ability of coalescence growth to promote size focusing of semiconductor colloids. Ultimately, we expect that the demonstrated coalescence growth strategy could enable a rational control of nanocrystal size distributions and corresponding spectral line widths in many types of semiconductor NCs. The optoelectronic properties of colloidal semiconductor nanocrystals (NCs) can be manipulated by changing their geometric shape. The precise synthetic control over particle morphologies, however, has remained elusive. Conventional growth techniques rely on the kinetic assembly of atomic units, where supersaturation and precipitation processes can lead to a broad distribution of particle shapes. In this paper, we demonstrate that replacing atomic precursors with small-size nanocrystals as building blocks for larger colloids offers an easier, more predictive control over nanoparticle shape evolution. The reported growth strategy is illustrated via shape-selective syntheses of CdSe and CdS NC cubes, spheres, rods, as well as iv unprecedented "donut" and ring-like structures. Different particle morphologies were obtained through a thermodynamically driven growth, using a distinct combination of coordinating compounds that minimize the surface free energy. The demonstrated aggregative growth is explained using a thermodynamic model for interacting viscous colloids. Auger decay of multiple excitons represents a significant obstacle to photonic applications of semiconductor quantum dots (QDs). This nonradiative process is particularly detrimental to the performance of QD-based electroluminescent and lasing devices. Here, we demonstrate that semiconductor quantum shells with an "inverted" QD geometry inhibit Auger recombination, allowing substantial improvements to their multiexciton characteristics. By promoting a spatial separation between multiple excitons, the quantum shell geometry leads to ultralong biexciton lifetimes (>10 ns) and a large biexciton quantum yield. Furthermore, the architecture of quantum shells induces an exciton-exciton repulsion, which splits exciton and biexciton optical transitions, giving rise to an Auger-inactive single-exciton gain mode. In this regime, quantum shells exhibit the longest optical gain lifetime reported for colloidal QDs to date (>6 ns), which makes this geometry an attractive candidate for the development of optically and electrically pumped gain media.

Download or read book Temperature Dependent Optical Properties of Colloidal IV VI Quantum Dots Composed of Core Shell Heterostructures with Alloy Components written by Efrat Lifshitz and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Temperature-Dependent Optical Properties of Colloidal IV-VI Quantum Dots, Composed of Core/Shell Heterostructures with Alloy Components.

Download or read book Semiconductor Nanocrystals written by Alexander L. Efros and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: A physics book that covers the optical properties of quantum-confined semiconductor nanostructures from both the theoretical and experimental points of view together with technological applications. Topics to be reviewed include quantum confinement effects in semiconductors, optical adsorption and emission properties of group IV, III-V, II-VI semiconductors, deep-etched and self assembled quantum dots, nanoclusters, and laser applications in optoelectronics.

Download or read book Methods of Synthesis of Colloidal Nanoparticles written by Jeffrey A. Gerbec and published by . This book was released on 2006 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Anisotropic and Shape Selective Nanomaterials written by Simona E. Hunyadi Murph and published by Springer. This book was released on 2017-07-14 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews recent advances in the synthesis, characterization, and physico-chemical properties of anisotropic nanomaterials. It highlights various emerging applications of nanomaterials, including sensing and imaging, (bio)medical applications, environmental protection, plasmonics, catalysis, and energy. It provides an excellent and comprehensive overview of the effect that morphology and nanometric dimension has on the physico-chemical properties of various materials and how this leads to novel applications.

Download or read book Synthesis Photophysics and Applications of Colloidal Semiconductor Quantum Dots written by Kelly Loraine Sowers and published by . This book was released on 2016 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Colloidal semiconductor nanocrystals, commonly known as quantum dots (QDs), have been the source of much interest recently, as three-dimensional quantum confinement allows for size-dependent optical properties. Since particle size, shape, composition, and surface passivation are all easily controlled (and thus, particle photophysics) in the initial synthesis and post-synthetic reactions, the made-to-order nature of QDs allows them to be potentially useful in a wide range of applications, particularly in photocatalyitic systems. This work will touch on some of the fundamental synthetic methods of cadmium chalcogenide QDs, the resulting photophysics of surface composition, and efficacy as a photosensitizer. QDs are synthesized and subsequently shelled using secondary phosphine chalcogens, which enables particular control over the surface composition of CdSe/CdS core/shell QDs. Interestingly, this surface tuning can be used to control the fluorescence properties of the QD in a precise manner, wherein sulfur-rich surfaces demonstrate quenched fluorescence quantum yields, and cadmiumrich surfaces reversibly recover fluorescence. DFT calculations demonstrate that hole trap states arising on sulfur-rich surfaces act to diminish radiative recombination processes. The surface effects on trap states provide constructive insight into necessary features of QDs for various applications, including use in a solar hydrogen generation scheme."--Page vii.

Download or read book Quantum Dots written by Inamuddin and published by Materials Research Forum LLC. This book was released on 2021-04-05 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book provides a thorough survey of current research in quantum dots synthesis, properties, and applications. The unique properties of these new nanomaterials offer multifunctional applications in such fields as photovoltaics, light-emitting diodes, field-effect transistors, lasers, photodetectors, solar cells, biomedical diagnostics and quantum computing. Keywords: Quantum Dots (QD), Photovoltaics, Light-emitting Diodes, Field-effect Transistors, Lasers, Photodetectors, Solar Cells, Biomedical Diagnostics, Quantum Computing, QD Synthesis, Carbon QDs, Graphene QDs, QD Sensors, Supercapacitors, Magnetic Quantum Dots, Cellular/Molecular Separation, Chromatographic Separation Column, Photostability, Luminescence of Carbon QDs, QD Materials for Water Treatment, Semiconductor Quantum Dots, QD Drug Delivery, Antibacterial Quantum Dots.