Download or read book Synthesis and Characterization of Infrared Quantum Dots written by Daniel Kelly Harris and published by . This book was released on 2014 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis focuses on the development of synthetic methods to create application ready quantum dots (QDs) in the infrared for biological imaging and optoelectronic devices. I concentrated primarily on controlling the size and size distribution of indium arsenide and cadmium arsenide QDs. In the nanocrystal community, classical nucleation and growth is often invoked to explain size focusing. However, this model lacks predictive power and contradicts what is known about the chemistry of QD growth. I try to relate my experimental approach and my conclusions to our understanding of the mechanism of particle growth. This approach led me to explore the role of precursor conversion rate in the growth of III-V QDs and to develop a continuous injection synthesis method that I used to make both III-V and cadmium arsenide QDs. Cadmium arsenide (Cd 3As 2 ) is a narrow gap semiconductor that can form QDs with tunable emission between 530nm and 2000nm. I developed a synthetic strategy to precisely control the size of Cd3As 2 QDs while maintaining a narrow size distribution. Continuous precursor injection was used to drive growth and suppress size broadening. The quantum yields of Cd3As 2 QDs produced using this method ranged as high as 80%, and their emission is tunable over a broad range with narrow linewidths. However, they were found to be unstable in ambient conditions. Nevertheless, by processing in inert conditions we were able to make a crude photodetector that demonstrates that Cd3As 2 QDs are sufficiently stable for use in optoelectronic devices. Although growth of a Cd3 P2 shell provided enough added stability to observe emission after ligand exchange into water, these core-shell structures do not seem to be robust enough for biological applications. Indium arsenide (InAs) QDs are more easily stabilized with a core-shell structure. However, the spectral linewidths are broad and existing synthetic techniques produce only small particles with limited spectral tunability. Models predicted that decreasing precursor reactivity would produce larger, more monodisperse particles. Therefore, I chemically modified the group-V precursor to reduce reactivity. I made a library of group-V precursors, and I developed a framework for comparing the QDs that they produced and measuring the kinetics of precursor conversion and particle growth. Although we successfully reduced precursor reactivity, we found that the effect on particle size was minimal and that the least reactive precursors produced particles with inferior size distributions. To find another way to try to improve III-V synthesis, I adapted the continuous injection method developed for making Cd3As 2. Using this strategy, I was able to produce InAs QDs with broadly tunable size and narrow spectral features. However, continuous injection ceases to drive particle growth beyond about 5nm in diameter. We examined why particle growth stops, and proposed a strategy to prolong growth and size focusing. Ultimately, the continuous injection technique allowed us to produce InAs QDs with infrared emission and narrow spectral features that were ideally suited for producing QDs optimized for deep tissue imaging in mice. By adding a shell of CdSe, CdS, or ZnSe, the quantum yield and stability were enhanced. These emitters allowed us to see biodistribution and biological processes occurring inside live mice. Although we found that precursor chemistry did not affect particle growth to the degree we hoped, we were able to produce application ready QDs via a continuous injection procedure. Continuous injection synthesis of QDs is a precise way to tune QD size while maintaining narrow size distributions. We have used this technique to produce QDs with the specifications required for high impact applications.

Download or read book Synthesis and Characterization of Colloidal Quantum Dots written by Melisa R. Greenberg and published by . This book was released on 2006 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Synthesis and Characterization of II IV Quantum Dots and Their Assembly Into 3D Quantum Dot Superlattices written by Christopher Bruce Murray and published by . This book was released on 1995 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.

Download or read book Synthesis and Characterization of Colloidal Lead Chalcogenide Quantum Dots and Progress Towards Single Photons On demand written by Keith Alexander Abel and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanometer-sized semiconductor crystals, termed 'quantum dots', are of fundamental interest because of their size-tunable properties. Three-dimensional quantum confinement of charge carriers by the small crystal size results in discrete atomic-like electronic states. This dissertation describes the synthesis and in-depth characterization of lead chalcogenide colloidal quantum dots for forthcoming applications as near-infrared single photon emitters. An efficient single photon source that operates at telecommunication wavelengths (between 1.3 and 1.6?m) is a basic requirement for many photonic quantum technologies, such as quantum computing and quantum cryptography. Chapters 1 and 2 of this work provide an introduction to colloidal quantum dots and their use as single photon emitters. It includes a description of photonic crystal microcavities and their ability to enhance the spontaneous emission rate of quantum dots. The synthesis and basic characterization of PbSe and PbS quantum dots is then discussed in chapter 3. In particular, a new synthetic method for the preparation of highly photoluminescent PbS quantum dots is presented. PbSe/CdSe core/shell quantum dots prepared by a cation exchange reaction are also described and a significant improvement in photo-stability is shown. Chapter 3 concludes with a description of three different surface modification techniques. PbSe core and PbSe/CdSe core/shell materials are investigated further in chapter 4 by advanced characterization techniques that include high-angle annular dark field (HAADF) imaging, energy-filtered transmission electron microscopy (EF-TEM) imaging, energy-dependent X-ray photo-electron spectroscopy (XPS), small angle X-ray scattering (SAXS), and small angle neutron scattering (SANS). The information obtained from these techniques is combined to form a structural model of the PbSe core and PbSe/CdSe core/shell quantum dots with greater complexity than previously reported. In chapter 5, the temperature-dependent photoluminescence from PbSe and PbSe/CdSe core/shell quantum dots is discussed and a thermal model is presented that accounts for the large (non-trivial) temperature dependence of the Stokes shift and photoluminescence lineshape over the entire temperature range (4.5 to 295 K). Chapter 6 examines two scalable methods to integrate the colloidal quantum dots into silicon two-dimensional photonic crystal slab microcavities (a requirement for efficient single photon emission). Finally, conclusions and possible future work are discussed in chapter 7.

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 Quantum Dots written by Yarub Al-Douri and published by . This book was released on 2024-09-11 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of Doped Core shell Quantum Dots written by Elizabeth J. Sodt and published by . This book was released on 2007 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The central theme of the research performed is the systematic modification of the optical properties of quantum dots by the formation of a shell of another quantum dot of a different band gap energy. Core/shell quantum dots such as CdS:Mn/CdS. CdS:Mn/ZnS, and ZnS:Mn/CdS with various concentrations of dopant Mn2 in the core and shell concentrations have been synthesized under mild conditions in the aqueous phase using stoichiometric amounts of the surfactant stabilizer dodecyl sulfate. These quantum dots exhibit UV-vis, emission, and electron paramagnetic resonance (EPR) spectral behavior that is dependent on the concentration of the shell and the dopant Mn2 in the core. The emission intensities of the core quantum dots do exhibit a systematic variation with Mn2 concentration. When a shell is added a systematic variation in the emission intensity and lifetime that are inversely proportional to the concentration of the shell is observed. When the large band gap ZnS is added as a shell to the small band gap CdS, the Mn2+ ions migrate from the core to the shell which is manifested in the emission and EPR spectra. Additionally the mixing of the valence and conduction band energy states of the large and small band gap shell and core respectively is also manifested in the emission spectra. In the reverse case, namely when CdS is added as a shell to ZnS the migration is not observed and the mixing of the valence and conduction band energy levels is minimum. The tunable optical properties of these core/shell quantum dots make them excellent platforms for the generation of nanosensors for nerve gas analogs.

Download or read book Synthesis and Characterization of PbS based Quantum Dots and Study on Their Optical Properties written by Yi-Ching Yang and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of Aqueous Quantum Dots for Biomedical Applications written by Hui Li and published by . This book was released on 2008 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of II VI and IV VI Colloidal Semiconductor Quantum Dots written by Li Guo and published by . This book was released on 2007 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of a New Sensitive Dye and Quantum Dots written by Jason Michael Horst and published by . This book was released on 2011 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of PbTe Quantum Dots written by Faiza Anwar and published by . This book was released on 2011 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of Alloyed Quaternary Quantum Dots written by Man-Lin Liao and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Synthesis and Characterization of Silicon Quantum Dots written by Richard Alan Bley and published by . This book was released on 1997 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: