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This book offers a comprehensive overview of ZnO-nano carbon core shell hybrid issues. There is significant interest in metal oxide/nanocarbon hybrid functional materials in the field of energy conversion and storage as electrode materials for supercapacitors, Li ion secondary battery, electrocatalysts for water splitting, and optoelectronic devices such as light emitting diodes and solar photovoltaic cells. Despite efforts to manipulate more uniform metal oxide-nanocarbon nanocomposite structures, they have shown poor performance because they are randomly scattered and non-uniformly attached to the nanocarbon surface. For higher and more effective performance of the hybrid structure, 3D conformal coating on metal oxides are highly desirable. In the first part of the book, the physical and chemical properties of ZnO and nanocarbons and the state-of-the-art in related research are briefly summarized. In the next part, the 3D conformal coating synthetic processes of ZnO templated nanocarbon hybrid materials such as ZnO-graphene,-C60, single-walled (SWCNT) are introduced with the aid of schematic illustrations. Analysis of their chemical bonding and structure are also presented. In the final section, several applications are presented: UV photovoltaic cells and photoelectrochemical anodes for water splitting using ZnO-C60 and ZnO-graphene, white-light-emitting diodes based on ZnO-graphene quantum dots(GQDs), inverted solar cells using ligand-modified ZnO-graphene QDs, and P(VDF-TrFE) copolymer with mixed with nano-ring SWCNT. The book describes how strong anchoring bonds between a ZnO core and carbon nanomaterial shell will ultimately prevail over the main drawbacks of ZnO with high charge recombination and poor electrochemical stability in liquid solutions. Due to the moderate energy states and excellent electric properties of the nanocarbons, ultrafast charge carrier transport from the ZnO core to the nanocarbon shell is guaranteed with the use of the photoluminescence (PL) lifetime measurement. Given the growing interest and significance of future research in optoelectronic and electrochemical devices applications, the contents are very timely. This book is targeted towards researchers looking for highly efficient metal oxide-nanocarbon hybrid functional materials in the fields of nano-optoelectronics, photoelectrochemistry, energy storage and conversion.
Graphene for Next Generation Lighting and Displays provides readers with a comprehensive overview of graphene, flexible graphene electrodes, and graphene-based next-generation display and lighting. The book covers a wide range of information, including the basic physics of graphene and recent trends in technical developments for graphene-based flexible and stretchable light-emitting devices. In addition, it discusses future prospects and suggests further directions for research on graphene-based next-generation displays and lightings. In addition, the book includes sections on the fundamental properties of graphene, synthetic methods of graphene, preparation of graphene electrodes and composite electrodes, and doping methods for graphene electrodes. Potential applications are also addressed including graphene-based flexible electrodes, buffer layer, emitters, and graphene-based stretchable electrodes. Reviews the most promising applications, including OLEDs, graphene-based buffer layers for LEDs, quantum dot emitters, and stretchable graphene electrodes Describes practical approaches in modifying the properties of graphene for the purpose of optoelectronic applications
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.
A hybrid, nanostructured solar cell architecture has been designed, described, fabricated and characterized. ZnO nanowires were synthesized using thermal chemical vapor deposition to act as a high energy photon absorber scaffold and electron transport pathway. InP-ZnS core-shell quantum dots were attached to the nanowires via surface chemistry to act as a high-efficiency sensitizing absorption medium. A ligand exchange procedure was performed to cap the quantum dots with mercaptopropionic acid for improved adhesion to ZnO nanowires and improved electrical properties. Experimentation was performed to optimize the surface chemistry adhesion of the ligand exchange and quantum dot-nanowire adhesion. A thoroughly-filled P3HT matrix was drop coated selectively and annealed into the quantum dot sensitized nanowire array to serve as a hole capture and transport, absorption, and planarizing medium. Characterization was performed throughout device fabrication using SEM, TEM, XRD, PL spectroscopy, Raman spectroscopy, UV-Vis spectroscopy, and electrical measurements. A dense monolayer of quantum dots was deposited and imaged via HRTEM. PL quenching of quantum dots in P3HT was observed. The viability and advantages of quantum dot sensitization of a hybrid ZnO nanowire-P3HT hybrid were shown via PL, UV-Vis and device electrical measurements.
Quantum dots: Emerging materials for versatile applications is an introduction to the fundamentals and important advances of research of this important category of semiconductor nanostructured materials. After a brief review of relevant nanotechnology concepts and the unique properties of nanomaterials, the book describes the fundamentals of quantum dots with definitions of the primary classifications of quantum dots. There is an emphasis on practical considerations of the commercial translation of quantum dots such as their toxicity, stability, and disposal. Moreover, the book focuses on a review of the advances in research in emerging quantum dot materials along with the latest innovations in materials design and fabrication methods. Quantum Dots is suitable for materials scientists and engineers in academia or industry R&D who are looking for an introduction to this research topic or a key reference on the latest advances and applications. Introduces the primary classifications, properties, synthesis, characterization and fabrication strategies of quantum dots Reviews the latest applications of quantum dots for LEDs, displays, energy storage devices, photovoltaic cells, medicine, and more Discusses the practical barriers to commercial translation of quantum dots, including toxicity, stability, and their safe disposal
This chapter provides a broad review of the latest research activities focused on the synthesis and application of ZnO nanowires (NWs) for dye-sensitized solar cells (DSCs) and composed of three main sections. The first section briefly introduces DSC-working principles and ZnO NW application advantages and stability issues. The next section reviews ZnO NW synthesis methods, demonstrating approaches for controlled synthesis of different ZnO NW morphology and discussing how this effects the overall efficiency of the DSC. In the last section, the methods for ZnO NW interface modification with various materials are discussed, which include ZnO core-shell structures with semiconductive or protective layers, ZnO NW hybrid structures with other materials, such as nanoparticles, quantum dots and carbon nanomaterials and their benefit for charge and light transport in DSCs. The review is concluded with some perspectives and outlook on the future developments in the ZnO nanowire application for DSCs.
Nanotechnologie ist eine multidisziplinäre Technologie, welche unterschiedliche Aspekte der Wissenschaft und Ingenieurwesen im Nanobereich umfasst. Es ist mehr als das Herstellen von sehr geordneten Nanostrukturen durch die gleichzeitige Verschmelzung von Nanomaterialien und es verlang nach gebrauchstauglichen Möglichkeiten einer präzisen Manipulation und Überwachung der entwickelten Nanostrukturen. Mit anderen Worten, die größte Herausforderung in der Nanotechnologie ist es, dass wir mehr über die Materialien und ihre Eigenschaften lernen und herausfinden müssen. Zinkoxid (ZnO) ist ein Halbleiter mit großer Bandlücke (3.37 eV) mit ausgezeichneten elektrischen, optischen, katalytischen und sensorischen Eigenschaften und hat eine Vielzahl von Verwendungsmöglichkeiten. Andererseits hat Zinksulfid (ZnS) eine hohe chemische Stabilität im alkalischen sowie schwach sauren Milieu. Die einzigartigen Eigenschaften der Kombination beider Materialien, ZnO und ZnS, können den Weg ebnen zur Realisierung von zukünftigen Devices (z.B. optoelektronische Bauteile, Sensoren, Wandler, Biomedizintechnik, usw.). Der Hauptbestandteil der in dieser Dissertation gezeigten Studien hat den Schwerpunkt des Designs von sehr geordneten Nanostrukturen aus ZnO und ZnO/ZnS Nanotubes die mithilfe von anodischen Aluminiumoxid (AAO) als feste Template hergestellt wurden. Die Dissertation bezieht sich besonders auf nanostruktur-basierte elektrochemische Sensoren und photoelektrochemische (PEC) Anwendungen zur Wasserspaltung bzw. Wasserstofferzeugung. In dieser Arbeit wurden ZnO/ZnS Nanotubes erfolgreich synthetisiert durch die Kombination von 3 Methoden: (i) AAO Template (ii) Atomlagenabscheidung (ALD) und (iii) schnelles thermischen Abscheiden. Es wurde festgestellt, dass AAO Template ohne weitere zusätzliche Behandlungen durch schnelles thermisches Abscheiden komplett während des Wachstums der ZnS-Ummantelung entfernt werden konnte. Die gleichmäßig angeordneten ZnO/ZnS Nanotube-Arrays mit hoher Kristallqualität zeigten eine verbesserte optische und elektrische Leistungsfähigkeit im Vergleich zu den ZnO Nanotubes. Somit erweist sich dies als kosteneffektive Möglichkeit für die Herstellung von röhrenartigen Core/Shell-Strukturen mit unterschiedlicher Zusammensetzung mittels AAO Template ohne weitere notwendige Prozesse zur Entfernung der Template. Im Gegensatz zu konventionellen Untersuchungen mit dem Fokus auf die Veränderung der optischen Absorptionsbandkante eines aus einen einzigen Material durch sog. Quantum Confinement Effects, wurden die optischen Absorptionseigenschaften von geordneten ZnO/ZnS Core/Shell Nanotubearrays, d.h. Quantum Confinement Effects über Materialgrenzen hinaus, untersucht. Die Daten zeigen, dass das Profil des Absorptionsspektrum der ZnO/ZnS Nanoarrays durch beide Komponenten und ihre geometrischen Parameter bestimmt wird. Beide Materialein zeigen eine Verringerung der optischen Bandlücke bei Erhöhung der ZnS Manteldicke und der Durchmesser der Nanotube-Arrays, was interessant ist bzgl. Der Erklärung in Bezug auf Aspekte des Materials. Nachfolgende Finite-Difference-Time-Domain (FDTD) Simulationen unterstützten die Beobachtungen und zeigten, dass die geometrischen und periodischen Parameter die optische Absorption der Core/Shell Nanostrukturarrays beeinflussen, sogar ohne Quanteneffekte. Diese Ergebnisse liefern eine neue Sichtweise auf die Verschiebung der optischen Bandlücke, was von Bedeutung für die Forschung in der Photoelektronik ist. Des Weiteren wurde der in dieser Arbeit hergestellte und charakterisierte Sensor angewandt um Veränderungen von chemischen und biochemischen Stoffen zu erkennen. Messungen mit dem Devices als primärere Sensoren wurden erfolgreich durchgeführt und zur Erkennung als Glukose-Biosensoren verwendet. Die Untersuchungen zeigen, dass die heterogene Elektronentransferratenkonstante (ks) von ZnO/ZnS gegenüber Glukose (1.69 s^-1) höher ist als die von reinem ZnO (0.95 s^-1), was für die Verbesserung der Leistungsfähigkeit und die höhere Empfindlichkeit verantwortlich ist. Zusätzlich haben Experimente eine Verbesserung der PEC Wasserstofferzeugung mit den hergestellten Nanostrukturen gezeigt, mit höheren Sättigungsphotostromdichten (1,02 mA/cm^2) und höheren Wirkungsgraden bei der Photokonversion (62%) bei ZnO/ZnS als bei den ZnO-Strukturen ohne jegliche Ummantelung (entsprechend 0,23mA/cm^2 und 55%).
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.
A crucial overview of the cutting-edge in nanocarbon research and applications In Synthesis and Applications of Nanocarbons, the distinguished authors have set out to discuss fundamental topics, synthetic approaches, materials challenges, and various applications of this rapidly developing technology. Nanocarbons have recently emerged as a promising material for chemical, energy, environmental, and medical applications because of their unique chemical properties and their rich surface chemistries. This book is the latest entry in the Wiley book series Nanocarbon Chemistry and Interfaces and seeks to comprehensively address many of the newly surfacing areas of controversy and development in the field. This book introduces foundational concepts in nanocarbon technology, hybrids, and applications, while also covering the most recent and cutting-edge developments in this area of study. Synthesis and Applications of Nanocarbons addresses new discoveries in the field, including: · Nanodiamonds · Onion-like carbons · Carbon nanotubes · Fullerenes · Carbon dots · Carbon fibers · Graphene · Aerographite This book provides a transversal view of the various nanocarbon materials and hybrids and helps to share knowledge between the communities of each material and hybrid type.