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Nanocrystals research has been an area of significant interest lately, due to the wide variety of potential applications in semiconductor, optical and biomedical fields. This book consists of a collection of research work on nanocrystals processing and characterization of their structural, optical, electronic, magnetic and mechanical properties. Various methods for nanocrystals synthesis are discussed in the book. Size-dependent properties such as quantum confinement, superparamagnetism have been observed in semiconductor and magnetic nanoparticles. Nanocrystals incorporated into different material systems have proven to possess improved properties. A review of the exciting outcomes nanoparticles study has provided indicates further accomplishments in the near future.
Alloying and doping have been widely used for band gap engineering and property tuning of semiconductor nanocrystals, providing novel composition and structure dependent properties. Ternary I-III-VI semiconductors represent one of the best heavy-metal-free optoelectronic materials. Here, efforts are devoted to improving the optical and electrical properties of the semiconductor nanocrystals and photophysical studies of related mechanisms. AgInS2 nanocrystals with tunable sizes and optical properties were synthesized in toluene at low temperature. The role of surface and intrinsic defects were studied using time-resolved photoluminecence and femtosecond transient absorption spectroscopies. Extremely long-lived excitons were observed in the AgInS2 nanocrystals, which can benefit potential phototovoltaic applications by increasing charge separation. Series of AgInS2-ZnS nanocrystals were synthesized by heating a Ag/In/Zn/S solution showing tunable PL which initially exhibits a red shift but ultimately finishes with blue shifted emission with increasing temperature. The incorporation of Zn and the increased cation exchange of silver by zinc at higher temperatures strongly influences the PL behavior. Systematic investigation by time-resolved spectroscopy showed distinguishable PL behaviors between developing and fully grown AgInS2-ZnS nanocrystals. We also synthesized near-infrared emitting AgInS2/ZnS nanocrystals with a thin layer of ZnS by carefully controlling the growing condition. The unexpected PL red shift and band gap reduction was ascribed to the local structural ordering in the thin gradient alloyed surface layer. Zinc concentration and growth temperatures played important roles in the formation of the near-infrared emitting nanocrystals, which are promising for bioimaging applications. For the self-doped Cu2-xS nanocrystals, several methods were explored to tune the free carrier plasmon absorption properties, which showed dramatic change with the amount of hole doping resulted from copper deficiency. X-ray photoelectron spectroscopy was used to identify the copper oxidation stayes and the origin of the valence band vacancies. Detailed analysis suggested an interesting partially oxidized layer on the nanocrystal surface. The last section is devoted to improving the thermoelectric performance of nanostructured ternary Bi0̣5Sb1̣5Te3. Sintering was found to increase ZT as a function of sintering temperature by increasing the charge carrier mobility more than the lattice thermal conductivity, resulting in an overall increase of thermoelectric performance
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
The current climate crisis is a great concern to humankind due to the devastating effects of the consistent rise of anthropogenic greenhouse gases. A viable alternative to reducing greenhouse gas emissions is the development of solar harvesting technologies. The need to develop new semiconductor materials with more capacity to absorb light and convert it into electricity is rapidly growing. A promising class of materials for this purpose are copper-based ternary chalcogenides such as CuCrS2, CuSb1-xBixS2, and Cu3VS4.The synthesis and characterization of copper-based ternary chalcogenides nanocrystals (NCs) have gained popularity in the scientific community due to their novel, physical, chemical, optical, electronic, magnetic, and mechanical properties. NCs can be precursors to the next-generation nanoparticle-based thin film solar cells. This generation of thin film solar cells is advantageous in terms of the compounding benefits. Materials in the forms of NCs offer size, and morphology-dependent properties, high absorption coefficients, and tunable bandgaps. Nanoparticle-based thin film solar cells use very thin layers of material, lowering their production cost while making the systems flexible, more efficient, and compatible with new and existing infrastructure.This dissertation addresses several challenging issues and realizes the successful fabrication of novel CuCrS2, CuSb1-xBixS2 (x=1, 0.18), and Cu3VS4 NCs-based thin films. These systems were synthesized using two different thermal decomposition methods: heat-up (HU) and hot-injection (HI). This dissertation presents a detailed study involving the synthesis and characterization of the above-mentioned semiconductors by applying the developed nano-to-thin film approach. Their optical and electrical properties were explored, and their respective optical bandgaps were determined using UV-vis and electron energy loss spectroscopy (EELS). The ability of the fabricated thin films to generate a photocurrent under sunlight irradiation was explored, reporting their responsivities and current conversion efficiencies.
Approaches to colloidal synthesis have rapidly developed to control the size, shape, and composition of various semiconductors, offering cost reductions, controllability, and scalability. Of semiconductor materials, germanium nanomaterials are known to be the most difficult to synthesize in solution-based methods because of their high crystallization temperature. Zero-dimensional germanium nanocrystals were synthesized by the heat-up method, without any strong reducing agent. Subsequently, finely controlled size-selective precipitation narrowed size distributions, and size-selected nanocrystals successfully created a monolayer germanium nanocrystals superlattice. One-dimensional germanium nanorods were synthesized by the solution–liquid–solid method using tin nanoparticles as seeds. By forming a liquid alloy with the tin seed at the eutectic temperature, which is much lower than the crystallization temperature, germanium nanorods were grown from the tin seed. A monophenylsilane enhanced the yield of germanium nanorods by promoting the phenyl redistribution of diphenylgermane, a germanium precursor. Using a mixture of HCl and HF, tin seeds were completely removed from the tips of the germanium nanorods, leaving germanium crystalline nanorods. Nonvolatile memories, a key component in various electronics and portable systems, include phase-change memory, a leading technology that has seen exponential growth in demand over the last decade. One important class of phase change materials are compounds on the GeTe–Sb2Te3 tie line. Despite interesting properties of the nanomaterials, colloidal synthesis of phase change material nanocrystals has only been rarely reported. In the present study, three representative phase change material nanocrystals, GeTe, Sb2Te3, and Ge2Sb2Te5, were successfully synthesized using the hot-injection method. A poly(vinylpyrrolidinone)–hexadecane (PVP–HDE) polymer was essential for the nanocrystal dispersion and making ternary Ge2Sb2Te5 nanocrystals. Two solvents, oleylamine and trioctylphosphine, were studied for synthesizing all three nanocrystals and reveal the conversion chemistry of phase change material precursors
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.
Characterization of Nanomaterials: Advances and Key Technologies discusses the latest advancements in the synthesis of various types of nanomaterials. The book's main objective is to provide a comprehensive review regarding the latest advances in synthesis protocols that includes up-to-date data records on the synthesis of all kinds of inorganic nanostructures using various physical and chemical methods. The synthesis of all important nanomaterials, such as carbon nanostructures, Core-shell Quantum dots, Metal and metal oxide nanostructures, Nanoferrites, polymer nanostructures, nanofibers, and smart nanomaterials are discussed, making this a one-stop reference resource on research accomplishments in this area. Leading researchers from industry, academia, government and private research institutions across the globe have contributed to the book. Academics, researchers, scientists, engineers and students working in the field of polymer nanocomposites will benefit from its solutions for material problems. Provides an up-to-date data record on the synthesis of all kinds of organic and inorganic nanostructures using various physical and chemical methods Presents the latest advances in synthesis protocols Presents latest techniques used in the physical and chemical characterization of nanomaterials Covers characterization of all the important materials groups such as: carbon nanostructures, core-shell quantumdots, metal and metal oxide nanostructures, nanoferrites, polymer nanostructures and nanofibers A broad range of applications is covered including the performance of batteries, solar cells, water filtration, catalysts, electronics, drug delivery, tissue engineering, food packaging, sensors and fuel cells Leading researchers from industry, academia, government and private research institutes have contributed to the books