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Author: Adam Biacchi Publisher: ISBN: Category : Languages : en Pages :
Book Description
Solution methods of materials synthesis have found application in a variety of fields due to the diversity of products accessible, facility of process scalability, and the ease of tuning their properties through prudent selection of reaction conditions. Control of experimental variables during the formation of colloidally stable nanoscale solids within a liquid matrix allows for tailoring of the particles' characteristics, including shape, size, composition, and surface chemistry. In this dissertation, I will discuss how the manipulation of reaction chemistries can be used to synthesize shape-controlled metal and semiconductor colloidal nanocrystals. Further, I will elaborate on the mechanisms by which these particles form from molecular precursors and describe how their properties can differ from their bulk analogues through extensive characterization, especially using transmission electron microscopy. These studies contribute to the continued development of chemical routes to nanocrystals and their application as functional materials.First, I will review recent advances in the synthesis and characterization of shape-controlled nanocrystals, as well as highlight their promising applicability in a number of emerging technologies. These principles will then be leveraged to the specific case of catalytically-active rhodium nanocrystals, which can be synthesized with morphological and dimensional control using a polyol solution-mediated strategy. I describe an innovative shape-controlled synthesis to monodisperse colloidal rhodium icosahedra, cubes, triangular plates, and octahedra using this route. Additionally, new insights into the important role of the polyol reducing solvent on the synthesis of these nanocrystals are revealed, and how these might be exploited to engender superior reaction control and novel products.Next, I will describe how a crystallization mechanism was established for the synthesis of numerous morphologies of noble metal nanocrystals. I present a thorough analysis of the synthesis of shape-controlled rhodium nanocrystals, using extensive transmission electron microscopy characterization, and relate these findings to one of the primary synthetic levers available in the polyol synthesis: the anionic ligands present. Further, I show that the crystallization process proceeds by a nonclassical mechanism in which cluster particles serve as a stable intermediate between molecular precursors and the final product. I then apply these principles to the shape-controlled synthesis of other noble metal nanocrystals before expounding a generalized formation mechanism in the polyol synthesis of colloidal metal nanocrystals. Finally, I will highlight my efforts in the designed synthesis and characterization of colloidal tin(II) sulfide (SnS) semiconducting "quantum dot" nanocrystals. I describe a route for the solution synthesis of monodisperse colloidal SnS nanosheets, nanocubes, and nanospherical polyhedra in high yield. Further, detailed crystallographic characterization of these nanocrystals using transmission electron microscopy indicates that their atomic structure possesses a previously-unreported nanoscale deviation from the bulk phase. Additionally, I show that their electronic and photocatalytic properties of these quantum dots are both shape-dependent and distinct from bulk SnS.
Author: Adam Biacchi Publisher: ISBN: Category : Languages : en Pages :
Book Description
Solution methods of materials synthesis have found application in a variety of fields due to the diversity of products accessible, facility of process scalability, and the ease of tuning their properties through prudent selection of reaction conditions. Control of experimental variables during the formation of colloidally stable nanoscale solids within a liquid matrix allows for tailoring of the particles' characteristics, including shape, size, composition, and surface chemistry. In this dissertation, I will discuss how the manipulation of reaction chemistries can be used to synthesize shape-controlled metal and semiconductor colloidal nanocrystals. Further, I will elaborate on the mechanisms by which these particles form from molecular precursors and describe how their properties can differ from their bulk analogues through extensive characterization, especially using transmission electron microscopy. These studies contribute to the continued development of chemical routes to nanocrystals and their application as functional materials.First, I will review recent advances in the synthesis and characterization of shape-controlled nanocrystals, as well as highlight their promising applicability in a number of emerging technologies. These principles will then be leveraged to the specific case of catalytically-active rhodium nanocrystals, which can be synthesized with morphological and dimensional control using a polyol solution-mediated strategy. I describe an innovative shape-controlled synthesis to monodisperse colloidal rhodium icosahedra, cubes, triangular plates, and octahedra using this route. Additionally, new insights into the important role of the polyol reducing solvent on the synthesis of these nanocrystals are revealed, and how these might be exploited to engender superior reaction control and novel products.Next, I will describe how a crystallization mechanism was established for the synthesis of numerous morphologies of noble metal nanocrystals. I present a thorough analysis of the synthesis of shape-controlled rhodium nanocrystals, using extensive transmission electron microscopy characterization, and relate these findings to one of the primary synthetic levers available in the polyol synthesis: the anionic ligands present. Further, I show that the crystallization process proceeds by a nonclassical mechanism in which cluster particles serve as a stable intermediate between molecular precursors and the final product. I then apply these principles to the shape-controlled synthesis of other noble metal nanocrystals before expounding a generalized formation mechanism in the polyol synthesis of colloidal metal nanocrystals. Finally, I will highlight my efforts in the designed synthesis and characterization of colloidal tin(II) sulfide (SnS) semiconducting "quantum dot" nanocrystals. I describe a route for the solution synthesis of monodisperse colloidal SnS nanosheets, nanocubes, and nanospherical polyhedra in high yield. Further, detailed crystallographic characterization of these nanocrystals using transmission electron microscopy indicates that their atomic structure possesses a previously-unreported nanoscale deviation from the bulk phase. Additionally, I show that their electronic and photocatalytic properties of these quantum dots are both shape-dependent and distinct from bulk SnS.
Author: Kallum M. Koczkur Publisher: American Chemical Society ISBN: 0841299013 Category : Science Languages : en Pages : 164
Book Description
Our society depends heavily on metals. They are ubiquitous construction materials, critical interconnects in integrated circuits, common coinage materials, and more. Excitingly, new uses for metals are emerging with the advent of nanoscience, as metal crystals with nanoscale dimensions can display new and tunable properties. The optical and photothermal properties of metal nanocrystals have led to cancer diagnosis and treatment platforms now in clinical trials, while, at the same time, the ability to tune the surface features of metal nanocrystals is giving rise to designer catalysts that enable more sustainable use of precious resources. These are just two examples of how metal nanocrystals are addressing important social needs.
Author: Celso de Mello Donegá Publisher: Springer ISBN: 3662448238 Category : Technology & Engineering Languages : en Pages : 303
Book Description
This book can be roughly divided into three parts: fundamental physico-chemical and physical principles of Nanoscience, chemistry and synthesis of nanoparticles, and techniques to study nanoparticles. The first chapter is concerned with the origin of the size dependence of the properties of nanomaterials, explaining it in terms of two fundamental nanoscale effects. This chapter also serves as a general introduction to the book, briefly addressing the definition and classification of nanomaterials and the techniques used to fabricate and study them. Chapter 2 lays out the theoretical framework within which to understand size effects on the properties of semiconductor nanocrystals, with particular emphasis on the quantum confinement effect. The optical properties of metal nanoparticles and metal nanostructures (periodic lattices) are discussed in Chapter 3. Chapter 4 is devoted to nanoporous materials, treating in detail their synthesis, structure and functional properties, as well as the physical properties of liquids confined in nanopores. The preparation methods, characterization techniques, and applications of supported nanoparticles are covered in Chapter 5. The sixth Chapter presents the essential physical-chemical concepts needed to understand the preparation of colloidal inorganic nanoparticles, and the remarkable degree of control that has been achieved over their composition, size, shape and surface. The last four Chapters are dedicated to a few selected characterization techniques that are very valuable tools to study nanoparticles. Chapter 7 concentrates on electron microscopy techniques, while Chapter 8 focuses on scanning probe microscopy and spectroscopy. Electron paramagnetic resonance (EPR) based spectroscopic techniques and their application to nanoparticles are explored in Chapter 9. Finally, Chapter 10 shows how solution Nuclear Magnetic Resonance (NMR) spectroscopic techniques can be used to unravel the surface chemistry of colloidal nanoparticles.
Author: Venkatesham Tallapally Publisher: ISBN: Category : Alloys Languages : en Pages :
Book Description
Nanomaterials, typically less than 100 nm size in any direction have gained noteworthy interest from scientific community owing to their significantly different and often improved physical properties compared to their bulk counterparts. Semiconductor nanoparticles (NPs) are of great interest to study their tunable optical properties, primarily as a function of size and shape. Accordingly, there has been a lot of attention paid to synthesize discrete semiconducting nanoparticles, of where Group III-V and II-VI materials have been studied extensively. In contrast, Group IV and Group IV-V based nanocrystals as earth abundant and less-non-toxic semiconductors have not been studied thoroughly. From the class of Group IV, Ge1-xSnxalloys are prime candidates for the fabrication of Si-compatible applications in the field of electronic and photonic devices, transistors, and charge storage devices. In addition, Ge1-xSnx alloys are potentials candidates for bio-sensing applications as alternative to toxic materials. Tin phosphides, a class of Group IV-V materials with their promising applications in thermoelectric, photocatalytic, and charge storage devices. However, both aforementioned semiconductors have not been studied thoroughly for their full potential in visible (Vis) to near infrared (NIR) optoelectronic applications. In this dissertation research, we have successfully developed unique synthetic strategies to produce Ge1-xSnxalloy quantum dots (QDs) and tin phosphide (Sn3P4, SnP, and Sn4P3) nanoparticles with tunable physical properties and crystal structures for potential applications in IR technologies. Low-cost, less-non-toxic, and abundantly-produced Ge1-xSnxalloys are an interesting class of narrow energy-gap semiconductors that received noteworthy interest in optical technologies. Admixing of Îł-Sn into Ge results in an indirect-to-direct bandgap crossover significantly improving light absorption and emission relative to indirect-gap Ge. However, the narrow energy-gaps reported for bulk Ge1-xSnxalloys have become a major impediment for their widespread application in optoelectronics. Herein, we report the first colloidal synthesis of Ge1-xSnxalloy quantum dots (QDs) with narrow size dispersity (3.3±0.5 -- 5.9±0.8 nm), wide range of Sn compositions (0--20.6%), and composition-tunable energy-gaps and near infrared (IR) photoluminescence (PL). The structural analysis of alloy QDs indicates linear expansion of cubic Ge lattice with increasing Sn, suggesting the formation of strain-free nanoalloys. The successful incorporation of Îł-Sn into crystalline Ge has been confirmed by electron microscopy, which suggests the homogeneous solid solution behavior of QDs. The quantum confinement effects have resulted in energy gaps that are significantly blue-shifted from bulk Ge for Ge1-xSnxalloy QDs with composition-tunable absorption onsets (1.72±0.84 eV for x=1.5--20.6%) and PL peaks (1.62--1.31 eV for x=1.5--5.6%). Time-resolved PL (TRPL) spectroscopy revealed microsecond and nanosecond timescale decays at 15 K and 295 K, respectively owing to radiative recombination of dark and bright excitons as well as the interplay of surface traps and core electronic states. Realization of low-to-non-toxic and silicon-compatible Ge1-xSnxQDs with composition-tunable near IR PL allows the unprecedented expansion of direct-gap Group IV semiconductors to a wide range of biomedical and advanced technological studies. Tin phosphides are a class of materials that received noteworthy interest in photocatalysis, charge storage and thermoelectric devices. Dual stable oxidation states of tin (Sn2+ and Sn4+) enable tin phosphides to exhibit different stoichiometries and crystal phases. However, the synthesis of such nanostructures with control over morphology and crystal structure has proven a challenging task. Herein, we report the first colloidal synthesis of size, shape, and phase controlled, narrowly disperse rhombohedral Sn4P3, hexagonal SnP, and amorphous tin phosphide nanoparticles (NPs) displaying tunable morphologies and size dependent physical properties. The control over NP morphology and crystal phase was achieved by tuning the nucleation/growth temperature, molar ratio of Sn/P, and incorporation of additional coordinating solvents (alkylphosphines). The absorption spectra of smaller NPs exhibit size-dependent blue shifts in energy gaps (0.88--1.38 eV) compared to the theoretical value of bulk Sn3P4 (0.83 eV), consistent with quantum confinement effects. The amorphous NPs adopt rhombohedral Sn4P3 and hexagonal SnP crystal structures at 180 and 250 ̊C, respectively. Structural and surface analysis indicates consistent bond energies for phosphorus across different crystal phases, whereas the rhombohedral Sn4P3 NPs demonstrate Sn oxidation states distinctive from those of the hexagonal and amorphous NPs owing to complex chemical structure. All phases exhibit N(1s) and ʋ(N-H) energies suggestive of alkylamine surface functionalization and are devoid of tetragonal Sn impurities.
Author: Victor I. Klimov Publisher: CRC Press ISBN: 0203913264 Category : Science Languages : en Pages : 505
Book Description
The vast technological potential of nanocrystalline materials, as well as current intense interest in the physics and chemistry of nanoscale phenomena, has led to explosive growth in research on semiconductor nanocrystals, also known as nanocrystal quantum dots, and metal nanoparticles. Semiconductor and Metal Nanocrystals addresses current topics impacting the field including synthesis and assembly of nanocrystals, theory and spectroscopy of interband and intraband optical transitions, single-nanocrystal optical and tunneling spectroscopies, electrical transport in nanocrystal assemblies, and physical and engineering aspects of nanocrystal-based devices. Written by experts who have contributed pioneering research, this reference comprises key advances in the field of semiconductor nanocrystal quantum dots and metal nanoparticles over the past several years. Focusing specifically on nanocrystals generated through chemical techniques, Semiconductor and Metal Nanocrystals Merges investigative frontiers in physics, chemistry, and engineering Documents advances in nanocrystal synthesis and assembly Explores the theory of electronic excitations in nanoscale particles Presents comprehensive information on optical spectroscopy of interband and intraband optical transitions Reviews data on single-nanocrystal optical and tunneling spectroscopies Weighs controversies related to carrier relaxation dynamics in ultrasmall nanoparticles Discusses charge carrier transport in nanocrystal assemblies Provides examples of lasing and photovoltaic nanocrystal-based devices Semiconductor and Metal Nanocrystals is a must read for scientists, engineers, and upper-level undergraduate and graduate students interested in the physics and chemistry of nanoscale semiconductor and metal particles, as well as general nanoscale science.
Author: Khan Maaz Publisher: Intechopen ISBN: 1789234786 Category : Technology & Engineering Languages : en Pages : 290
Book Description
Silver nanoparticles are the subject of immense interest because of their distinct chemical and physical properties that are different from their bulk counterpart. This makes these nanoparticles very important in many fields including antimicrobial applications, biosensor materials, composite fibers, cryogenic superconducting materials, cosmetic products, and electronic components. This book aims to provide in-depth study and analysis of various fabrication, characterization, and application techniques of silver nanoparticles that lead these nanoparticles very important in the recent technology. This book presents deep understanding of the new techniques from basic to the advanced level. This book addresses scientists, engineers, doctoral and postdoctoral fellows, and technical professionals working in specialized fields.
Author: Nabraj Bhattarai Publisher: ISBN: 9781321194531 Category : Languages : en Pages : 138
Book Description
The properties of metal nanoparticles are controlled by their composition, shape, size and crystalline structure. Nanoparticles and nanoclusters with controlled shape and size were synthesized and investigated using atomic resolution images from aberration corrected scanning/transmission electron microscopy (STEM) and mass spectrometry (MS). Gold-palladium (Au-Pd) core-shell nanocube and triangular nanoparticles were prepared by a seed-mediated growth process and the growth mechanism was studied by varying the volume of Pd precursors added to the Au seed solution. The atomic resolution STEM images revealed that the nanocube is formed from a single-crystal Au seed with rapid growth along 111 directions while the triangular nanoparticles were obtained with growth preferentially along 110 directions rather than 111 direction. The strain generated by the lattice mismatch between fcc -Au and fcc -Pd, is released by Shockley partial dislocations (SPD), combined with stacking faults (SF) that appear at the final (outer) Pd layer. Then, as the shell grows the SPDs and SFs appear at the interface and combine with misfit dislocations, which finally diffuse to the free surfaces due to the alloying of Au into the Pd shell. In related work, magneto-plasmonic gold-cobalt (Au-Co) nanoparticles of diameter 4-nm were generated by a phase-transfer process and investigated by STEM, where the Z-contrast imaging and energy dispersive x-ray spectroscopy (EDS) showed inhomogeneous alloying between Au and Co at the nanoscale. The observed ferromagnetic behavior carries significance in biomedical applications. In addition, selected metallic (Au144 (SR)60 ) and bimetallic (CuAu144 ) nanoclusters were obtained with thiolate-ligand protection and characterized using optical, MS, and STEM techniques. The optical spectrum and MS results established the monodispersity and purity of the nanoclusters. Another important aspect is that the emergence of broad strong plasmonic band centered near 520 nm (2.3-eV), by incorporation of single Cu atom into Au 144 nanoclusters, contrasts to the conventional view of 'non-plasmonic' response of sub-2.0-nm (Au,Cu) clusters. The high resolution STEM images and diffraction patterns, obtained from aberration corrected STEM, were used as an alternative technique to study the crystal structure of atomically defined Au 144 (SR)60 nanoclusters, where the images and diffraction patterns obtained, before they were altered by electron beam, were compared with theoretically simulated STEM images and diffraction patterns obtained from atomistic structural models derived from first principles density functional theory (DFT) calculations and confirmed the structure of Au 144 (SR) 60 as one featuring icosahedral shell packing. Finally, dodecane-thiolate protected gold (Au) nanoparticles of diameter ~ 4 ± 0.5 nm were prepared, in order to grow an ultrathin ordered film or superlattice of these nanocrystal-cores for investigation using STEM. The STEM imaging showed long-range hexagonally ordered superlattices of the nanocrystals, separated by the thiolate groups where the lattice constant determined by direct imaging are in good agreement with those determined by small-angle electron diffraction.
Author: Challa S.S.R. Kumar Publisher: Springer Science & Business Media ISBN: 3642389341 Category : Science Languages : en Pages : 718
Book Description
Third volume of a 40volume series on nanoscience and nanotechnology, edited by the renowned scientist Challa S.S.R. Kumar. This handbook gives a comprehensive overview about Transmission electron microscopy characterization of nanomaterials. Modern applications and state-of-the-art techniques are covered and make this volume an essential reading for research scientists in academia and industry.
Author: Kathy Lu Publisher: John Wiley & Sons ISBN: 1118408950 Category : Technology & Engineering Languages : en Pages : 379
Book Description
Serving as the only systematic and comprehensive treatment on the topic of nanoparticle-based materials, this book covers synthesis, characterization, assembly, shaping and sintering of all types of nanoparticles including metals, ceramics, and semiconductors. A single-authored work, it is suitable as a graduate-level text in nanomaterials courses.
Author: Adam Biacchi
Author: Adam Biacchi
Author: Kallum M. Koczkur
Author: Celso de Mello Donegá
Author: Jing Zhao
Author: Venkatesham Tallapally
Author: Victor I. Klimov
Author: Khan Maaz
Author: Nabraj Bhattarai
Author: Challa S.S.R. Kumar
Author: Kathy Lu