Download or read book Two Step Nucleation and Growth of InP Quantum Dots Via Magic Sized Cluster Intermediates written by and published by . This book was released on 2015 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report on the role of magic-sized clusters (MSCs) as key intermediates in the synthesis of indium phosphide quantum dots (InP QDs) from molecular precursors. These observations suggest that previous efforts to control nucleation and growth by tuning precursor reactivity have been undermined by formation of these kinetically persistent MSCs prior to QD formation. The thermal stability of InP MSCs is influenced by the presence of exogenous bases as well as choice of the anionic ligand set. Addition of a primary amine, a common additive in previous InP QD syntheses, to carboxylate terminated MSCs was found to bypass the formation of MSCs, allowing for homogeneous growth of InP QDs through a continuum of isolable sizes. Substitution of the carboxylate ligand set for a phosphonate ligand set increased the thermal stability of one particular InP MSC to 400°C. The structure and optical properties of the MSCs with both carboxylate and phosphonate ligand sets were studied by UV-Vis absorption spectroscopy, powder XRD analysis, and solution 31P{1H} and 1H NMR spectroscopy. Finally, the carboxylate terminated MSCs were identified as effective single source precursors (SSPs) for the synthesis of high quality InP QDs. Employing InP MSCs as SSPs for QDs effectively decouples the formation of MSCs from the subsequent second nucleation event and growth of InP QDs. The concentration dependence of this SSP reaction, as well as the shape uniformity of particles observed by TEM suggests that the stepwise growth from MSCs directly to QDs proceeds via a second nucleation event rather than an aggregative growth mechanism.
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 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 Semiconductor Quantum Dots written by Mark Green and published by Royal Society of Chemistry. This book was released on 2014 with total page 285 pages. Available in PDF, EPUB and Kindle. Book excerpt: Postgraduates and experienced researchers will benefit from the comprehensive nature of the book, as will manufacturers of quantum dots and those wishing to apply them.
Download or read book Formation Mechanism of Monodisperse Colloidal Semiconductor Quantum Dots written by Matthew William Greenberg and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nevertheless, to address this relative dearth of conventional spectroscopic probes, here we explore the use of X-ray Total Scattering real space Pair Distribution Function (PDF) analysis and Small Angle X-ray Scattering (SAXS) techniques to directly probe the crystallization process in-situ. Time-resolved measurements of the small angle reciprocal space scattering data allow mapping of the time evolution of the colloidal size and concentration of the crystals during synthesis, while the Fourier transform of scattering data over a wide range of reciprocal space provides direct insight into the local structure. Through this approach, we compare direct observations of these nucleation and growth processes to the widely cited theoretical models of these processes (Classical Nucleation Theory and LaMer "Burst Nucleation") and find a number of stark differences between these widely cited theories and our experiments. The first two chapters cover the results of these ??-???? diffraction studies.
Download or read book Experimental and Theoretical Investigation of Indium Phosphide Quantum Dot Growth Mechanisms written by Lisi Xie (Ph. D.) and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Indium phosphide (InP) quantum dots (QDs) stand out as the most promising candidate to replace the currently commercialized cadmium-containing materials for optoelectronic applications. This thesis focuses on using experimental and theoretical methods to study growth mechanisms of InP QDs from precursor conversion to final nanocrystal formation. As the key experimental platform, a high temperature and high pressure microfluidic system was first applied to study the effect of group V precursor reactivity on the QD growth. High-pressure flow conditions allow for precise control of synthetic parameters and also the use of low-boiling-point solvents for synthesis with enhanced mixing. Results showed that lowering the precursor reactivity did not significantly improve the QD quality, contradicting the original hypothesis. The unexpected role of precursor chemistry motivated investigation into the early-stage QD growth mechanisms. First-principles approaches were used without any prior assumptions on reaction pathways. Simulations showed that small clusters with indium-rich surfaces form in the early-stage QD growth. In and P precursors have different roles, with P precursors controlling the reaction energy, and In precursors determining the reaction barrier. With clusters identified as important growth intermediates in both simulations and experiments, their role during the QD formation was then investigated with a one-solvent protocol, which combined flow synthesis, GPC purification and MALDI mass characterization. Experiments revealed that similar clusters exist during the late-stage nanocrystal growth, suggesting their role as a continuous supply for the QD formation. Lastly, a QD size tuning strategy was developed involving the use of weakly associated ligands to synthesize cluster-free InP QDs with different sizes and narrow size distributions. This synthetic approach enabled the construction of a correlation between the absorption features and the mass and concentration of InP QDs. The importance of In precursor quality became apparent after exploring effects of impurities and solvents. For example, when water and hydroxide/oxide species contaminate In precursors, the growth of InP QDs are inhibited and batch-to-batch variations are observed.
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 Semiconductor Quantum Dots II Volume 642 written by Rosa Leon and published by . This book was released on 2001-11-09 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners.
Download or read book Tuning Semiconducting and Metallic Quantum Dots written by Christian von Borczyskowski and published by CRC Press. This book was released on 2017-03-27 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology is one of the growing areas of this century, also opening new horizons for tuning optical properties. This book introduces basic tuning schemes, including those on a single quantum object level, with an emphasis on surface and interface manipulation of semiconducting and metallic quantum dots. There are two opposing demands in current forefront applications of quantum dots as optical labels, namely high luminescence stability (suppression of luminescence intermittency) and controllable intermittency and bleaching on a single-particle level to facilitate super-resolution optical microscopy (for which Eric Betzig, Stefan W. Hell, and William E. Moerner were awarded the 2014 Nobel Prize in Chemistry). The book discusses these contradictory demands with respect to both an understanding of the basic processes and applications. The chapters are a combination of scholarly presentation and comprehensive review and include case studies from the authors’ research, including unpublished results. Special emphasis is on a detailed understanding of spectroscopic and dynamic properties of semiconducting quantum dots. The book is suitable for senior undergraduates and researchers in the fields of optical nanoscience, materials science, and nanotechnology.
Download or read book Cadmium Telluride Quantum Dots written by John Donegan and published by CRC Press. This book was released on 2016-04-19 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last two decades, semiconductor quantum dots-small colloidal nanoparticles-have garnered a great deal of scientific interest because of their unique properties. Among nanomaterials, CdTe holds special technological importance as the only known II-VI material that can form conventional p-n junctions. This makes CdTe very important for the dev
Download or read book Quantum Dots Theory and Applications written by Rodolph Donovan and published by . This book was released on 2016-04-01 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: A quantum dot is a nanoparticle made of any semiconductor material such as silicon, cadmium selenide, cadmium sulfide, or indium arsenide. Quantum dots may be able to increase the efficiency of solar cells. In normal solar cells, a photon of light generates one electron. Experiments with both silicon quantum dots and lead sulfide quantum dots can generate two electrons for a single photon of light. Therefore, using quantum dots in solar cells could significantly increase their efficiency in producing electric power. Quantum dots (QD) are nanoscale semiconductor devices that tightly confine either electrons or electron holes in all three spatial dimensions. They can be made through several possible routes including colloidal synthesis, plasma synthesis, or mechanical fabrication. The electronic properties of the quantum dots fall between those of bulk semiconductors and those of discrete molecules of comparable size, and optoelectronic properties such as band gap, can be tuned as a function of particle size and shape for a given composition. Because of the high tunability of properties, QDs are of interest in many research applications such as transistors, solar cells, LEDs, and diode lasers. For instance, the ability of QDs to precisely convert and tune a spectrum makes them ideal for LCD displays. Previous LCD displays can waste energy converting red-green poor, blue-yellow rich white light into a more balanced lighting. By using QDs, only the necessary colors for ideal images are contained in the screen. The result is a screen that is brighter, clearer, and more energy-efficient. Researchers are also working on the use of quantum dots in displays for applications ranging from your cell phone to large screen televisions that would consume less power than current displays. By placing different size quantum dots in each pixel of a display screen, the red, green, and blue colors used to generate the full spectrum of colors would be available. The book Quantum Dots - Theory and Applications covers some new research results in the field of fundamental excitations, decoherence, charge states, epitaxial techniques and photoluminescence experiments related to devices made with quantum dots also includes numerous applications of quantum dots.
Download or read book Optics of Quantum Dots and Wires written by Garnett W. Bryant and published by Artech House Publishers. This book was released on 2005 with total page 574 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum technology is the key to next-generation optoelectronics and laser semiconductors, and this new cutting-edge book is an in-depth examination of how quantum dots and wires are fabricated and applied to optics. You find a solid tutorial on the optical properties of nanoscale dots and wires that explains the current state of this technology and why it is so promising. The book presents a detailed survey of techniques based on molecular beam epitaxial growth for fabricating semiconductor quantum dots and wires. You learn how to assess these growth strategies for insertion of dots and wires into devices.
Download or read book Quantum Dots written by Orion Ciftja and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanoscience and nanotechnology is continuously moving forward enabling the precise, controlled fabrication of structures and devices at atomic and molecular scales. Quantum dots are typically semiconductor nanocrystals that have gained tremendous attention due to their unique electronic, magnetic, chemical and optical properties. They have proven very useful in applications in many fields across the physical, engineering, chemical, biological and medical sciences. In this book, the authors give an overview of the progress and major research developments in the field of quantum dots over the past two decades. They specifically focus on discussing the cutting-edge applications in the fields of information technology, electronics, biotechnology, energy, medicine, cellular imaging and diagnostic bio-sensing.
Download or read book Kinetics based Investigation of ZnS Syntheses and Co product Evolution from Dual and Single source Precursors written by Kathryn Grace Woodburn and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanomaterials, the focus of an active area of materials chemistry research, have a multitude of uses ranging from efficiency improvement in lighting displays to photocatalysis and biological tagging for drug delivery. All such applications need nanomaterials with specific properties. This necessitates precise, reproducible control over their structure, which is currently limited by an incomplete understanding and of their syntheses. One method to better characterize nanocrystal syntheses is to improve knowledge of the mechanism and kinetics of precursor decomposition and nanocrystal nucleation and growth. This thesis explores the mechanisms and kinetics of the synthesis of zinc sulfide (ZnS) nanocrystals, both as a model binary metal chalcogenide species and because ZnS itself has many applications as a commonly-used large band-gap semiconducting quantum dot. This thesis presents a tandem study of traditional "dual" precursors and single-source precursors to serve as comparison and contrast agents in the development of a more holistic understanding of precursor decomposition and nanocrystal growth. The syntheses of dual and single-source precursors are first presented, followed by a discussion of their behavior in common hot-injection syntheses. The steric and electronic properties of the substituted thioureas used in dual precursor reactions and single-source precursor syntheses result in different precursor reactivity profiles. Understanding exactly how differing reactivity profiles impart control over nanocrystal structure and properties remains unanswered and is a promising query to direct future research. Following methodology development for replicable ZnS hot-injection syntheses, alternative approaches to ZnS synthesis are explored and the successful production of ZnS by microwave and ultraviolet irradiation is discussed.
Download or read book Synthesis and Characterization of Zinc Oxide Quantum Dots written by Scott. W. Russell and published by . This book was released on 2015 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Zinc oxide Nanoparticles, also known as quantum dots, have been synthesized with sizes ranging from 1 to 19 nm. Quantum dots are a developing form of semiconductor that have several possible advantages over traditional silicon based semiconductors. For example, instead of needing to undergo tedious and expensive doping procedures to generate wide and tunable band gap ranges as in the case of traditional silicon-based semiconductors, quantum dots can create wide and tunable band gap ranges based simply on their size. Furthermore, as a result of their band gaps quantum dots are capable of fluorescing different colors when excited by a UV light source. The one nanometer dots observed in my experiments, for instance, have a violet fluorescence with an ideal peak at 421 nm; whereas the violet semiconductor indium gallium nitride currently used in systems need up to 1000nm to peak. These zinc oxide dots were studied starting with the synthesis methods to determine the best way to produce a full range of fluorescence colors; then their size UV absorbance and fluorescence spectrums were taken and examined; and finally the sizes of the dots were measured with three different methods. The agreement of the results from the three methods used in my experiments provides greater understanding of the basic aspects of the dots and aid the development of a simple, but effective equation to relate the dot size to band gap size."--
Download or read book Quantum Dots written by Aleksandr Georgievich Tartakovskiĭ and published by . This book was released on 2012 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: "A comprehensive review of cutting-edge solid state research, focusing on its prominent example - quantum dot nanostructures, this book features a broad range of techniques for fabrication of these nano-structured semiconductors and control of their quantum properties. Written by leading researchers, the book considers advanced III-V and II-VI semiconductor quantum dots (QDs) realized by self-assembly, lithography and chemical synthesis; novel QD structures in nanowires and graphene; and transport and optical methods for control of single QDs"--
Download or read book Development of Zinc Oxide Nanowires and Quantum Dot Incorporation for Photovoltaic Applications written by Bita Janfeshan and published by . This book was released on 2015 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heterojunctions of metal oxide semiconductors with quantum dots (QD) have been deployed in a number of advanced electronic devices. Improvement in the devices' performance requires in-depth studies on charge carrier transfer dynamics. In this work, charge carrier dynamics, at the interface on zinc oxide nanowires (ZnO NW) with cadmium selenide QDs, were investigated. ZnO NWs were synthesized and characterized through the chemical vapor deposition (CVD) and hydrothermal methods. Both methods yielded highly crystalline ZnO structures. The hydrothermally grown NWs were doped with aluminum (Al) and the spectroscopy analyses showed that Al was successfully incorporated into the ZnO crystalline structure. Colloidal cadmium selenide/zinc sulfide (CdSe/ZnS) core/shell QDs were incorporated into synthesized ZnO NW arrays. The interaction and wettability of two different QD ligands (Octadecylamine and oleic acid) on the self-assembly of QDs in the NW spacing were investigated using electron microscopy. Afterwards, the charge carrier transfer dynamics at the heterojunction of NW/QD were studied employing time resolved photoluminescence spectroscopy (TRPL). A hypothesis on charge transfer kinetics, based on the experimental measurements, was provided. It was realized that photocharging of QDs is the main reason for substantial PL quench, when holes are not effectively removed from the photoexcited QDs by a hole-transporting medium. Furthermore, the TRPL measurements showed that the hole transfer rate by a polysulfide electrolyte is slower than that of an electron; one main reason in impeding the device performance in quantum dot-sensitized solar cells (QDSSC). The NW/QD heterojunction was deployed in the structure of a QDSSC. The current-voltage behavior of the cells under various conditions was characterized in both dark and light conditions. The underlying problems hindering the device performance were identified by these characterizations. Heterojunction of ZnO NWs with a GaN thin film was also deployed in the structure of an LED. The NWs were grown on GaN film using the hydrothermal method. The fabricated device exhibited light emission under both forward and reverse bias injection currents. The electroluminescence and PL characterizations revealed that the light emission from the fabricated device depends on the point defects and interface states of the two semiconductors.
