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
Author: John Donegan
Publisher: CRC Press
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 development of novel optoelectronic devices such as light-emitting diodes, solar cells, and lasers. Moreover, the demand for water-compatible light emitters and the most common biological buffers give CdTe quantum dots fields a veritable edge in biolabeling and bioimaging. Cadmium Telluride Quantum Dots: Advances and Applications focuses on CdTe quantum dots and addresses their synthesis, assembly, optical properties, and applications in biology and medicine. It makes for a very informative reading for anyone involved in nanotechnology and will also benefit those scientists who are looking for a comprehensive account on the current state of quantum dot–related research.
The higher-level theoretical analysis finds the general existence of a threshold diameter, above which dot and wire band gaps converge. The origin and magnitude of this threshold diameter is discussed.
High-quality colloidal CdTe quantum wires having purposefully controlled diameters in the range of 5-11 nm are grown by the solution-liquid-solid (SLS) method, using Bi-nanoparticle catalysts, cadmium octadecylphosphonate and trioctylphosphine telluride as precursors, and a TOPO solvent. The wires adopt the wurtzite structure, and grow along the  direction (parallel to the c axis). The size dependence of the band gaps in the wires are determined from the absorption spectra, and compared to the experimental results for high-quality CdTe quantum dots. In contrast to the predictions of an effective-mass approximation, particle-in-a-box model, and previous experimental results from CdSe and InP dot-wire comparisons, the band gaps of CdTe dots and wires of like diameter are found to be experimentally indistinguishable. The present results are analyzed using density functional theory under the local-density approximation by implementing a charge-patching method. The higher-level theoretical analysis finds the general existence of a threshold diameter, above which dot and wire band gaps converge. The origin and magnitude of this threshold diameter is discussed.
This paper gives an overview of molecular beam epitaxy (MBE) growth of and the optical properties of Cadmium Telluride (CdTe) quantum dots grown on Zinc Telluride (ZnTe) by self-assembly.
Author: Sebastian Mackowski
This paper gives an overview of molecular beam epitaxy (MBE) growth of and the optical properties of Cadmium Telluride (CdTe) quantum dots grown on Zinc Telluride (ZnTe) by self-assembly. It is shown that quantum dots in this material system can be obtained either by depositing CdTe at a high substrate temperature or by subjecting CdTe layer to a healing process, up to 70 seconds long before its capping or, eventually, by applying these two methods simultaneously. Moreover, it is found that one can also use the atomic layer epitaxy method to achieve the formation. From optical measurements performed on large quantum dot ensembles it is found that the quantum dot emission is much broader than that of quantum wells, and that it is observable up to much higher temperatures, which indicates strong exciton localization. The latter is also evidenced by an insensitivity of the decay time of the exciton recombination (^3O0 ps) to the temperature. From the presence of a second, very long decay time (^5 ns) and from disappearance of the sharp lines related to recombination in single dots, the acoustic phonon scattering of excitons is found to play an important role in these quantum dot structures. From a magnetic field dependence of the single dot emission energy, the exciton effective g-factor and spatial extension of the exciton wave function are deduced to be equal to -3 and 3 nanometers, respectively. Both the g-factor and the value of the diamagnetic shift are found to be independent of the energy of the quantum dot emission at Beta=Omicron Tau and of the in-plane symmetry of its potential. (11 figures, 35 refs.).
Charge separation, transport, and recombination represent fundamental processes for electrons and holes in semiconductor photovoltaic devices.
Author: Paul Roland
Category: Photovoltaic cells
Charge separation, transport, and recombination represent fundamental processes for electrons and holes in semiconductor photovoltaic devices. Here, two distinct materials systems, based on lead sulfide quantum dots and on polycrystalline cadmium telluride, are investigated to advance the understanding of their fundamental nature for insights into the material science necessary to improve the technologies. Lead sulfide quantum dots QDs have been of growing interest in photovoltaics, having recently produced devices exceeding 10% conversion efficiency. Carrier transport via hopping through the quantum dot thin films is not only a function of inter-QD distance, but of the QD size and dielectric media of the surrounding materials. By conducting temperature dependent transmission, photoluminescence, and time resolved photoluminescence measurements, we gain insight into photoluminescence quenching and size-dependent carrier transport through QD ensembles. Turning to commercially relevant cadmium telluride (CdTe), we explore the high concentrations of self-compensating defects (donors and acceptors) in polycrystalline thin films via photoluminescence from recombination at defect sites. Low temperature (25 K) photoluminescence measurements of CdTe reveal numerous radiative transitions due to exciton, trap assisted, and donor-acceptor pair recombination events linked with various defect states. Here we explore the difference between films deposited via close space sublimation (CSS) and radio frequency magnetron sputtering, both as-grown and following a cadmium chloride treatment. The as-grown CSS films exhibited a strong donor-acceptor pair transition associated with deep defect states. Constructing photoluminescence spectra as a function of time from time-resolved photoluminescence data, we report on the temporal evolution of this donor-acceptor transition. Having gained insight into the cadmium telluride film quality from low temperature photoluminescence measurements, we now turn to completed devices, evaluating the influence of back contact transport versus temperature. Cadmium telluride photovoltaic devices are known to form a Schottky junction when simply using a metal back contact. Our group previously reported on the attempted application of iron pyrite nanocrystals as a back contact material due to their high conductivity and doping concentration. These devices, however, exhibited non-ideal current-voltage curves where an S-Kink restricted current collection and reduced efficiency. Here we employ temperature dependent current-voltage measurements to gain insight into the S-Kink behavior and attempt to replicate the current-voltage curves using circuit modeling. We develop a modified diode circuit model where an anti-parallel diode pair serves to limit the current flow at voltages near VOC. This model successfully reproduces the experimental data and provides a means to extract diode parameters from current-voltage plots exhibiting S-Kink behavior.
Improved performance Quantum dot light emitting of silicon nanowire/cadmium telluride electrochemical cell hybrid device ... Size of CdTe quantum dots controls the CdTe quantum dots decorated n-ZnO nanorods/p-GaN light-emitting diodes.
Author: Simona Clichici
Publisher: BoD – Books on Demand
Category: Technology & Engineering
In the last decade, nanomaterials have become a double-edged sword. On one hand, nanomaterials have proven their limitless potential not only for technological applications, but also for medical ones. On the other hand, the increasing use of these nanomaterials has raised concerns regarding their safety for environmental and human health, due to their potential toxicity. The toxic effects of nanomaterials depend on their type, surface geometry, diameter, length and function. This book intends to provide a comprehensive evidence-based overview of nanomaterial toxicity, from their synthesis and characterization, environmental impact, tests to assess their toxicity in vitro and in vivo, ways to modulate their impact on living organisms, to their beneficial use in biomedical applications.
Quantum dots (QDs) are hybrid organic/inorganic nanoparticles with novel physical properties. QDs have two components: an inorganic core and an optically active coated shell. Moreover, surface coatings can be applied to QDs to modify the particle as needed for experiments. Hydrophilic coatings prevent leaking of metal cargo from the core, enhancing the solubility in biological contexts and bind molecules, such as receptor–ligands, antibodies, therapeutic, and diagnostic macromolecules for enhanced effects. Their high surface-to-volume ratio allows multiple functional groups to attach onto the surface of the particles at constant surface volume. Silicon-, gallium-, indium-, or germanium-based; cadmium-based; and carbon-based QDs have already been used in many applications, such as imaging probes for the engineering of multifunctional nanodevices. Superior properties of QDs make them an excellent system in technology and biotechnology. This book describes electroanalytical applications of QD-based nanobiosensors, including brief information about the synthesis and characterization of QDs and basics of electroanalytical methods, followed by QDs in electrochemical biomimetic sensors, QDs in microchips, inorganic materials doped QDs, QD-based electrochemical DNA biosensors, electroluminescence for biomarker analysis using aptamer-based QDs, QD-based photoelectrochemical techniques, enzyme-based nanobiosensors using QDs, QD-based electrochemical immunosensors, and QD-modified nanosensors in drug analysis. Outlines QD-based applications for drug, food, clinical, and environmental science Shows how the properties of QDs make them effective ingredients in biosensing applications Assesses the major challenges in integrating QDs in biosensing systems
As a multipotent tool for scientific exploration, semiconductor nanoparticles, or quantum dots (QDs), have gained enormous interest in nanoscience in the past two decades.
Author: Shohei Taniguchi
Category: Imaging systems in biology
As a multipotent tool for scientific exploration, semiconductor nanoparticles, or quantum dots (QDs), have gained enormous interest in nanoscience in the past two decades. The research presented here focused on cadmium telluride (CdTe) QDs: novel synthetic methodologies were used to prepare previously inaccessible nanomaterials based on CdTe QDs. -- CdTe/CdSe/ZnSe core/shell/shell QDs were prepared by a one-pot synthesis. The resulting QDs exhibited near infrared emission, were readily dispersed in aqueous media and applied to deep tissue imaging where emission through the skin indicated the gradual transition of the QDs via the lymphatic tract. -- Using a different synthetic approach, CdTe QDs, which were dispersed in organic media, were exposed to mercury cations in a toluene/methanol solution, resulting in CdHgTe nanoalloy formation. The optical characteristics of the resulting materials were substantially red-shifted from those of the original CdTe QDs. Structural changes were also examined and the influence of the addition of metal cations to other colloidal QDs. -- The organometallic compound Cd(TeC6H5)2 was synthesised and used as a single-source precursor for CdTe QDs. Products isolated after thermal decomposition of the single-source precursors showed strong emission of various wavelengths depending on the reaction time. The underlying chemistry on QDs formation was investigated, and CdTe/ZnS QDs were prepared using only single-source precursors. -- To make the QDs useful in biology, the surface of organically synthesised CdTe/ZnS QDs was modified with an amphiphilic protein (hydrophobin) to phase transfer the particles into aqueous solution. The QDs exhibited bright emission after phase transfer, and were applied to cell imaging in order to examine the validity as a fluorophore and the influence on a cell.
Charge transport in a quantum dot supercrystal. J. Phys. Chem. C 115, 21409 (2011). 72. C. de Mello Donegá, and R. Koole. Size dependence of the spontaneous emission rate and absorption cross section of CdSe and CdTe quantum dots.
Author: Joachim Piprek
Publisher: CRC Press
Optoelectronic devices are now ubiquitous in our daily lives, from light emitting diodes (LEDs) in many household appliances to solar cells for energy. This handbook shows how we can probe the underlying and highly complex physical processes using modern mathematical models and numerical simulation for optoelectronic device design, analysis, and performance optimization. It reflects the wide availability of powerful computers and advanced commercial software, which have opened the door for non-specialists to perform sophisticated modeling and simulation tasks. The chapters comprise the know-how of more than a hundred experts from all over the world. The handbook is an ideal starting point for beginners but also gives experienced researchers the opportunity to renew and broaden their knowledge in this expanding field.
Synthesis and characterization of surface-modified colloidal cadmium telluride quantum dots. The Journal of Physical Chemistry. 1993;97:1199912003 Available from: http://pubs.acs.org/doi/abs/10.1021/j100148a026 Oluwafemi OS, ...
Author: Vasilios N. Stavrou
Publisher: BoD – Books on Demand
The book entitled Nonmagnetic and Magnetic Quantum Dots is divided into two sections. In Section 1, the chapters are related to nonmagnetic quantum dots and their applications. More specifically, exact models and numerical methods have been presented to describe the analytical solution of the carrier wave functions, the quantum mechanical aspects of quantum dots, and the comparison of the latter to experimental data. Furthermore, methods to produce quantum dots, synthesis techniques of colloidal quantum dots, and applications on sensors and biology, among others, are included in this section. In Section 2, a few topics of magnetic quantum dots and their applications are presented. The section starts with a theoretical model to describe the magnetization dynamics in magnetic quantum dot array and the description of dilute magnetic semiconducting quantum dots and their applications. Additionally, a few applications of magnetic quantum dots in sensors, biology, and medicine are included in Section 2.
Ananth, D.A., Rameshkumar, A., Jeyadevi, R., Jagadeeswari, S., Nagarajan, N., Renganathan, R., Sivasudha, T., Antibacterial potential of rutin conjugated with thioglycolic acid capped cadmium telluride quantum dots (TGA-CdTe QDs).
Author: Suvardhan Kanchi
Publisher: John Wiley & Sons
Category: Technology & Engineering
The use of biological sources such as microbes and plants can help in synthesizing nanoparticles in a reliable and eco-friendly way. The synthesis of nanoparticles by these natural sources is characterized by processes that take place near to ambient temperature and pressures and also near neutral pH. This edited volume authored by subject specialists, provides all the latest research and builds a database of bioreduction agents to various metal nanoparticles using different precursor systems. The book also highlights the different strategies such as simplicity, cost-effectiveness, environment-friendly and easily scalable, and includes parameters for controlling the size and shape of the materials developed from the various greener methods. In order to exploit the utmost potential metal nanoparticles synthesis from the different sources such as agricultural waste, flora and fauna, food waste, microbes and biopolymer systems, it is also crucial to recognize the biochemical and molecular mechanisms of production of nanoparticles and their characterization.
Author: Ines Batinić-HaberlePublish On: 2016-10-13
Fluorescence plate reader for quantum dot-protein bioconjugation analysis. J Nanosci Nanotechnol. 2014;14(5):3320–7. 23. Tenório DPLA, et al. CdTe quantum dots conjugated to concanavalin A as potential fluorescent molecular probes for ...
Author: Ines Batinić-Haberle
This essential volume comprehensively discusses redox-active therapeutics, focusing particularly on their molecular design, mechanistic, pharmacological and medicinal aspects. The first section of the book describes the basic aspects of the chemistry and biology of redox-active drugs and includes a brief overview of the redox-based pathways involved in cancer and the medical aspects of redox-active drugs, assuming little in the way of prior knowledge. Subsequent sections and chapters describe more specialized aspects of central nervous system injuries, neurodegenerative diseases, pain, radiation injury and radioprotection (such as of brain, lungs, head and neck and erectile function) and neglected diseases (e.g., leishmaniasis). It encompasses several major classes of redox-active experimental therapeutics, which include porphyrins, salens, nitrones, and most notably metal-containing (e.g., Mn, Fe, Cu, Zn, Sb) drugs as either single compounds or formulations with nanomaterials and quantum dots. Numerous illustrations, tables and figures enhance and complement the text; extensive references to relevant literature are also included. Redox-Active Therapeutics is an invaluable addition to Springer’s Oxidative Stress in Applied Basic Research and Clinical Practice series. It is essential reading for researchers, clinicians and graduate students interested in understanding and exploring the Redoxome—the organism redox network—as an emerging frontier in drug design, redox biology and medicine.
T. Rajh, O.I. Micic and A. J. Nozik, Synthesis and characterization of surface-modified colloidal cadmium telluride quantum dots, J Phys Chem 97, 11999–12003 (1993). A. Rogach, L. Katsikas, A. Kornowski, D. Su, A. Eychmüller and H.
Publisher: World Scientific
This two-part multivolume set provides a comprehensive overview of current achievements in biomedical applications of nanotechnology, including stem cell based regenerative medicine, medical imaging, cell targeting, drug delivery, and photothermal/photodynamic cancer therapy. New approaches in early cancer diagnosis and treatment are introduced with extensive experimental results. In particular, some novel materials have been synthesized with new properties that are most effective in cancer therapy. Some of the key issues are also addressed with these recent discoveries such as bio safety and bio degradability, that are essential in the success of nano medicine. An important aspect of this book set is the introduction of nanotechnology to the medical communities that are searching for new treatments of cancer. It may also break the barriers between the physical and medical sciences so that more MDs will be able to appreciate the new discoveries and establishments in medical diagnosis and therapy that will allow the effective handling of major clinical issues. This major reference publication will be important as the field of nanomedicine has been rapidly developing with a great deal of new information. It is anticipated that the research will soon advance into the pre-clinical stage. Therefore, this reference set can serve as valuable background information for future clinical studies.
Author: Margarita Sanchez-DominguezPublish On: 2016-03-09
Microcalorimetric, Spectroscopic and Microscopic Investigation on the Toxic Effects of CdTe Quantum Dots on Halobacterium halobium R1. Nanotechnology 2010, 21 (47). Xiao, Q.; et al. Evaluate the Potential Toxicity of Quantum ...
Author: Margarita Sanchez-Dominguez
Category: Technology & Engineering
Nanocolloids: A Meeting Point for Scientists and Technologists presents an easy-to-read approach to current trends in nanoscale colloid chemistry, which offers relatively simple and economically feasible ways to produce nanomaterials. Nanocolloids have been the subjects of major development in modern technology, with many current and future applications. The book helps scientists and technologists to understand the different aspects of modern nanocolloid science. It outlines the underlying fundamental principles of nanocolloid science and covers applications ranging from emulsions to dispersions and suspensions. You will find details on experimental techniques and methods for the synthesis and characterization of nanocolloids, including the latest developments in nanoemulsions and nanoparticles. Edited by leading academics with over 10 years’ experience in the field of colloid and surfactant science. Each chapter is authored by recognized experts in the field. Outlines the underlying fundamental science behind nanocolloids. Provides comprehensive coverage of current topics and potential applications in nanocolloid science. Presents a multidisciplinary approach to help chemical engineers, chemists, physicists, materials scientists and pharmacologists, form an in-depth understanding of nanocolloid science.
... Rogach, A.L. Luminescent CdTe nanocrystals as ion probes and pH sensors in aqueous solutions. Colloids Surf. A 2006, 281,40–43. [CrossRef) Wang, Y.; Ye, C.; Zhu, Z.H.; Hu, YZ. Cadmium telluride quantum dots as pH-sensitive probes ...
Author: Jose María Lagaron
Food quality, safety, and fortification are key aspects to guarantee that foods reach consumers in optimal conditions from the point of view of freshness, microbiology, and health promotion. This book overviews the most recent fundamental and oriented efforts by multidisciplinary researchers and technologists on the application of nanoscience and nanotechnology to generate new added value solutions for the food industry. Nanomaterials to Enhance Food Quality, Safety, and Health Impact provides a valuable guide for both industry and academic researchers interested in the production of healthier, safer, and sustainable food products.
Rajh, T., Micic, O.I., Nozik, A.J.: Synthesis and characterization of surface-modified colloidal cadmium telluride quantum dots. J. Phys. Chem. 97(46), 11999–12003 (1993) 112. Rogach, A., et al.: Colloidally prepared HgTe nanocrystals ...
Author: Xin Tong
Publisher: Springer Nature
Category: Technology & Engineering
This book presents a comprehensive overview of state-of-the-art quantum dot photodetectors, including device fabrication technologies, optical engineering/manipulation strategies, and emerging photodetectors with building blocks of novel quantum dots (e.g. perovskite) as well as their hybrid structured (e.g. 0D/2D) materials. Semiconductor quantum dots have attracted much attention due to their unique quantum confinement effect, which allows for the facile tuning of optical properties that are promising for next-generation optoelectronic applications. Among these remarkable properties are large absorption coefficient, high photosensitivity, and tunable optical spectrum from ultraviolet/visible to infrared region, all of which are very attractive and favorable for photodetection applications. The book covers both fundamental and frontier research in order to stimulate readers' interests in developing novel ideas for semiconductor photodetectors at the center of future developments in materials science, nanofabrication technology and device commercialization. The book provides a knowledge sharing platform and can be used as a reference for researchers working in the fields of photonics, materials science, and nanodevices.
Thiolcapping of CdTe nanocrystals: an alternative to organometallic synthetic routes. J Phys Chem B 2002;106:7177–85. He Y, Zhong YL, Su YY, Lu YM, Jiang ZY, Peng F, et al. Water-dispersed near-infrared-emitting quantum dots of ...
Nanotechnology is considered the next big revolution in medicine and biology. For the past 20 years, research groups have been involved in the development of new applications of novel nanomaterials for biotechnological applications. Nanomaterials are also becoming increasingly important in medical applications, with new drugs and diagnostic tools based on nanotechnology. Every year, hundreds of new ideas using nanomaterials are applied in the development of biosensors. An increasing number of new enterprises are also searching for market opportunities using these technologies. Nanomaterials for biotechnological applications is a very complex field. Thousands of different nanoparticles could potentially be used for these purposes. Some of them are very different; their synthesis, characterization and potentiality are very diverse. This book aims to establish a route guide for non-erudite researchers in the field, showing the advantages and disadvantages of the different kind of nanomaterials. Particular attention is given to the differences, advantages and disadvantages of inorganic nanoparticles versus organic nanoparticles when used for biotechnological applications. A tutorial introduction provides the basis for understanding the subsequent specialized chapters. Provides an overview of the main advantages and disadvantages of the use of organic and inorganic nanoparticles for use in biotechnology and nanomedicine Provides an excellent starting point for research groups looking for solutions in nanotechnology who do not know which kind of materials will best suit their needs Includes a tutorial introduction that provides a basis for understanding the subsequent specialized chapters