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Steric Effects On The Formation Of Manganese Oxide Clusters And 2-Dimensional Ammonium Formate Architectures, Carl Oberle 2018 University of Missouri, St. Louis

Steric Effects On The Formation Of Manganese Oxide Clusters And 2-Dimensional Ammonium Formate Architectures, Carl Oberle

Dissertations

It has been demonstrated by the Beatty group that altering the identity of the ortho-substituent of a dianiline counterion affects the assembly and dimensionality of a cadmium-chloride layer from 2-D to 0-D. This work seeks to extend this finding to metal oxide and organic hydrogen-bonded materials. By systematically increasing the ortho­-substituent’s size on the benzoate building block of reported manganese oxide clusters, of formula MnxOy(O2C-R)zLw (where R = Alkyl, L = neutral monodentate ligand), we aim to impact the self-assembly of these materials relative to their parent forms; establishing ...


From Flasks To Applications: Design And Optimization Of Giant Quantum Dots Using Traditional And Automated Synthetic Methods, Christina J. Hanson 2018 University of New Mexico

From Flasks To Applications: Design And Optimization Of Giant Quantum Dots Using Traditional And Automated Synthetic Methods, Christina J. Hanson

Nanoscience and Microsystems ETDs

Semiconducting nanocrystals, also known as quantum dots (QDs), that emit light with near-unity quantum yield and are extremely photostable are attractive options as down-conversion and direct electricity-to-light materials for a variety of applications including solid-state lighting, display technologies, bio-imaging and optical tracking. Standard QDs with a core/thin shell structure display fluorescence intermittency (blinking) and photobleaching when exposed to prolonged room temperature excitation for single dot measurements, as well as significant reabsorption and energy transfer when densely packed into polymers or at high solution concentrations.

We have developed thick shell “giant” QDs (gQDs), ultra-stable photon sources both at the ensemble ...


Evidence For Redox Mechanisms In Organometallic Chemisorption And Reactivity On Sulfated Metal Oxides, Rachel C. Klet, David M. Kaphan, Cong Liu, Frederic A. Perras, Marek Pruski, Adam S. Hock, Massimiliano Delferro 2018 Argonne National Laboratory

Evidence For Redox Mechanisms In Organometallic Chemisorption And Reactivity On Sulfated Metal Oxides, Rachel C. Klet, David M. Kaphan, Cong Liu, Frederic A. Perras, Marek Pruski, Adam S. Hock, Massimiliano Delferro

Ames Laboratory Accepted Manuscripts

The chemical and electronic interaction of organometallic species with metal oxide support materials is of fundamental importance for the development of new classes of catalytic materials. Chemisorption of Cp*(PMe3)IrMe2 on sulfated alumina (SA) and sulfated zirconia (SZ) led to an unexpected redox mechanism for deuteration of the ancillary Cp* ligand. Evidence for this oxidative mechanism was provided by studying the analogous homogeneous reactivity of the organometallic precursors toward trityl cation ([Ph3C]+), a Lewis acid known to effect formal hydride abstraction by one electron oxidation followed by hydrogen abstraction. Organometallic deuterium incorporation was found to be correlated with surface ...


Workflows For X-Ray And Neutron Interferometry/Tomography As Applied To Additive Manufacturing, Jumao Yuan 2018 Louisiana State University and Agricultural and Mechanical College

Workflows For X-Ray And Neutron Interferometry/Tomography As Applied To Additive Manufacturing, Jumao Yuan

LSU Doctoral Dissertations

Grating-based interferometry/tomography is being rapidly developed for non-destructive evaluation of additive manufacturing test articles. An application requiring an efficient workflow is extremely necessary for stress and fatigue testing samples.

At present, scientific workflows play an important role for computational experiments in additive manufacturing 3D printing and interferometry/tomography imaging analysis. A clear workflow template allows scientists to process experiments easier and faster. Work flow library grows, but to find an appropriate workflow for their task is challenging. In our research, there are mainly three portions in the workflow, interferometry analysis, image reconstruction and 3D visualization. Currently, the hierarchy of ...


Hyperpolarization Of Silicon Nanoparticles With Tempo Radicals, Jingzhe Hu, Nicholas Whiting, Pratip Bhattacharya 2018 University of Texas MD Anderson Cancer Center

Hyperpolarization Of Silicon Nanoparticles With Tempo Radicals, Jingzhe Hu, Nicholas Whiting, Pratip Bhattacharya

Nicholas Whiting

Silicon-based particles can be hyperpolarized via dynamic nuclear polarization to enhance 29Si magnetic resonance signals. Application of this technique to nanoscale silicon particles has been limited because of the low signal enhancements achieved; it is hypothesized that this is due to the low number of endogenous electronic defects inherent to the particles. We introduce a method of incorporating exogenous radicals into silicon nanoparticle suspensions in order to improve the hyperpolarization of 29Si nuclear spins to levels sufficient for in vivo MR imaging. Calibration of radical concentrations and polarization times are reported for a variety of silicon particle sizes (30−200 ...


Higher Energy Gap Control Of Fluorescence In Conjugated Polymers, Chien-Hung Chiang 2018 Louisiana State University and Agricultural and Mechanical College

Higher Energy Gap Control Of Fluorescence In Conjugated Polymers, Chien-Hung Chiang

LSU Doctoral Dissertations

Chemo- and biosensors based on fluorescent conjugated polymer benefit from greater detection sensitivity due to amplification of the electronic perturbations produced by analyte binding. This amplification stems from the exciton-transporting properties of conjugated polymers. A conventional design paradigm relies on the analyte binding events which generate sites of lower energy relative to the polymer energy: either fluorescence quenching sites (turn-off sensors) or bathochromically shifted fluorophores (turn-on sensors). In both type sensors, the excitons migrate to the lower-energy site created by analyte binding.

This dissertation primarily focused the investigation of an alternative paradigm when analyte binding creates higher energy gap sites ...


Multiresonant Anisotropic Nanostructures For Plasmon-Mediated Spectroscopies, Gregory Q. Wallace 2018 The University of Western Ontario

Multiresonant Anisotropic Nanostructures For Plasmon-Mediated Spectroscopies, Gregory Q. Wallace

Electronic Thesis and Dissertation Repository

To detect and analyze molecular species of interest, analytical sciences and technologies exploit the variation in the chemical properties associated with the analytes. Techniques involving vibrational spectroscopy rely on the unique response observed when a molecule interacts with light. Although these methods can provide the specificity needed for detection, they are traditionally hindered by the need for large quantities of material, and long acquisition times. To minimize these issues, advancements in plasmon-enhanced techniques, such as surface-enhanced Raman spectroscopy (SERS) and surface-enhanced infrared absorption (SEIRA) are being made. Such techniques make use of the strong interaction between an optical field and ...


Understanding The Functional Group-Dependent Self-Assembly And Cellular Entry Of Cationic Conjugated Polymer Nanoparticles, Prakash Manandhar 2018 Florida International University

Understanding The Functional Group-Dependent Self-Assembly And Cellular Entry Of Cationic Conjugated Polymer Nanoparticles, Prakash Manandhar

FIU Electronic Theses and Dissertations

Highly fluorescent conjugated polymers (CPs) are an important class of biomaterials used for various biological applications including labelling, sensing, and delivery of biological substances. Synthetic versatility and tunable emission make CPs a superior class of biomaterials. Understanding the structure-function relationship of CPs plays a vital role in designing high performing biomaterials. The cationic CPs are self-assembled to conjugated polymer nanoparticles (CPNs) in an aqueous environment due to their amphiphilicity. The physical and biophysical properties of CPNs are highly dependent on the chemical functionality and backbone structure of CPs. Modulation of the surface property and backbone structure of CPNs play an ...


Functionalized Nanoporous Carbon Scaffolds For Hydrogen Storage Applications, Christopher Carr 2018 University of Missouri, St. Louis

Functionalized Nanoporous Carbon Scaffolds For Hydrogen Storage Applications, Christopher Carr

Dissertations

Recent efforts have demonstrated confinement in porous scaffolds at the nanoscale can alter the hydrogen sorption properties of metal hydrides, though not to an extent feasible for use in onboard hydrogen storage applications, proposing the need for a method allowing further modifications. The work presented here explores how the functionalization of nanoporous carbon scaffold surfaces with heteroatoms can modify the hydrogen sorption properties of confined metal hydrides in relation to non-functionalized scaffolds (FS). Investigations of nanoconfined LiBH4and NaAlH4indicate functionalizing the carbon scaffold surface with nitrogen can shift the activation energy of hydrogen desorption in excess of ...


Nanoscale Mechanisms For High-Pressure Mechanochemistry: A Phase Field Study, Mahdi Javanbakht, Valery I. Levitas 2018 Isfahan University of Technology

Nanoscale Mechanisms For High-Pressure Mechanochemistry: A Phase Field Study, Mahdi Javanbakht, Valery I. Levitas

Aerospace Engineering Publications

Coupled evolution of a high-pressure phase (HPP) and dislocations, including dislocation pileups and dislocations generated due to phase transformation (PT), under compression and shear of a nanograined bicrystal, is considered as a model for high-pressure mechanochemistry. Recently developed phase field approach for the interaction between PTs and dislocations at large strains and a finite element analysis are utilized. Periodic boundary conditions for displacements are applied to the lateral surfaces. It is confirmed that the shear-induced dislocation pileups may reduce the PT pressure by an order of magnitude in comparison with hydrostatic loading, and even below phase equilibrium pressure, as it ...


Liquid-Like Thermal Conduction In Intercalated Layered Crystalline Solids, B. Li, H. Wang, Y. Kawakita, Q. Zhang, M. Feygenson, H. L. Yu, D. Wu, K. Ohara, T. Kikuchi, K. Shibata, T. Yamada, X. K. Ning, Y. Chen, J. Q. He, David Vaknin, R. Q. Wu, K. Nakajima, M. G. Kanatzidis 2018 Japan Atomic Energy Agency

Liquid-Like Thermal Conduction In Intercalated Layered Crystalline Solids, B. Li, H. Wang, Y. Kawakita, Q. Zhang, M. Feygenson, H. L. Yu, D. Wu, K. Ohara, T. Kikuchi, K. Shibata, T. Yamada, X. K. Ning, Y. Chen, J. Q. He, David Vaknin, R. Q. Wu, K. Nakajima, M. G. Kanatzidis

Ames Laboratory Accepted Manuscripts

As a generic property, all substances transfer heat through microscopic collisions of constituent particles1. A solid conducts heat through both transverse and longitudinal acoustic phonons, but a liquid employs only longitudinal vibrations2,3. As a result, a solid is usually thermally more conductive than a liquid. In canonical viewpoints, such a difference also serves as the dynamic signature distinguishing a solid from a liquid. Here, we report liquid-like thermal conduction observed in the crystalline AgCrSe2. The transverse acoustic phonons are completely suppressed by the ultrafast dynamic disorder while the longitudinal acoustic phonons are strongly scattered but survive, and are thus ...


Development Of A Semigraphitic Sulfur-Doped Ordered Mesoporous Carbon Material For Electroanalytical Applications, Jaqueline R. Maluta, Sergio A.S. Machado, Umesh Chaudhary, J. Sebastian Manzano, Lauro T. Kubota, Igor I. Slowing 2018 University of São Paulo

Development Of A Semigraphitic Sulfur-Doped Ordered Mesoporous Carbon Material For Electroanalytical Applications, Jaqueline R. Maluta, Sergio A.S. Machado, Umesh Chaudhary, J. Sebastian Manzano, Lauro T. Kubota, Igor I. Slowing

Ames Laboratory Accepted Manuscripts

The modification of traditional electrodes with mesoporous carbons is a promising strategy to produce high performance electrodes for electrochemical sensing. The high surface area of mesoporous carbons provides a large number of electroactive sites for binding analytes. Controlling the pore size and structure of mesoporous carbons and modifying their electronic properties via doping offers additional benefits like maximizing transport and tuning the electrochemical processes associated with analyte detection. This work reports a facile method to produce sulfur-doped ordered mesoporous carbon materials (S-OMC) with uniform pore structure, large pore volume, high surface area and semigraphitic structure. The synthesis used thiophenol as ...


Oxygen And Sulfur Adsorption On Vicinal Surfaces Of Copper And Silver: Preferred Adsorption Sites, Da-Jiang Liu, Patricia A. Thiel 2018 Ames Laboratory

Oxygen And Sulfur Adsorption On Vicinal Surfaces Of Copper And Silver: Preferred Adsorption Sites, Da-Jiang Liu, Patricia A. Thiel

Ames Laboratory Accepted Manuscripts

We present an extensive density functional theory (DFT) study of adsorption site energetics for oxygen and sulfur adsorbed on two vicinal surfaces of Cu and Ag, with the goal of identifying the most stable adsorption site(s), identifying trends and common themes, and comparing with experimental work in the literature where possible. We also present benchmark calculations for adsorption on the flat (111) and (100) surfaces. The first vicinal surface is the (211), and results are similar for both metals. We find that the step-doubling reconstruction is favored with both adsorbates and is driven by the creation of a special ...


Phonon Glass Behavior Beyond Traditional Cage Structures: Synthesis, Crystal And Electronic Structure, And Properties Of Kmg4sb3, Jian Wang, Lin-Lin Wang, Kirill Kovnir 2018 Iowa State University and Ames Laboratory

Phonon Glass Behavior Beyond Traditional Cage Structures: Synthesis, Crystal And Electronic Structure, And Properties Of Kmg4sb3, Jian Wang, Lin-Lin Wang, Kirill Kovnir

Ames Laboratory Accepted Manuscripts

Three new ternary antimonides, KMg4Sb3 and A(2)Mg(5)Sb(4) (A - Rb, Cs), were synthesized via high-temperature solid-state reactions and their crystal structures were determined by single crystal X-ray diffraction. All three compounds feature three-dimensional anionic frameworks composed of edge-shared MgSb4 tetrahedra with channels trapping the alkali metal cations. KMg4Sb3 crystallizes in beta-BaCu4S3 structure type (Pearson symbol oS32) while Rb2Mg5Sb4 and Cs2Mg5Sb4 are isostructural and crystallize in K2Zn5As4 structure type (Pearson symbol oC44). Band structure calculations predict KMg4Sb3 to be a direct bandgap semiconductor with E-g of similar to 1 eV. Characterizations of the transport properties indicate that ...


Synthesis Of Supported Pd-0 Nanoparticles From A Single-Site Pd2+ Surface Complex By Alkene Reduction, Aidan R. Mouat, Cassandra L. Whitford, Bor-Rong Chen, Shengsi Liu, Frederic A. Perras, Marek Pruski, Michael J. Bedzyk, Massimiliano Delferro, Peter C. Stair, Tobin J. Marks 2018 Northwestern University

Synthesis Of Supported Pd-0 Nanoparticles From A Single-Site Pd2+ Surface Complex By Alkene Reduction, Aidan R. Mouat, Cassandra L. Whitford, Bor-Rong Chen, Shengsi Liu, Frederic A. Perras, Marek Pruski, Michael J. Bedzyk, Massimiliano Delferro, Peter C. Stair, Tobin J. Marks

Ames Laboratory Accepted Manuscripts

A surface metal-organic complex, (-AlOx)Pd(acac) (acac = acetylacetonate), is prepared by chemically grafting the precursor Pd(acac)(2) onto gamma-Al2O3 in toluene at 25 degrees C. The resulting surface complex is characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and dynamic nuclear polarization surface-enhanced solid-state nuclear magnetic resonance spectroscopy (DNP SENS). This surface complex is a precursor in the direct synthesis of size-controlled Pd nanoparticles under mild reductive conditions and in the absence of additional stabilizers or pretreatments. Indeed, upon exposure to gaseous ethylene or liquid 1-octene at 25 degrees ...


Systematic Size Control In The Synthesis Of Zero-Valent Iron Nanoparticles, Grant C. Bleier 2018 University of New Mexico

Systematic Size Control In The Synthesis Of Zero-Valent Iron Nanoparticles, Grant C. Bleier

Chemistry ETDs

A novel synthetic method for the production of highly magnetic, low size-dispersity nanoparticles through reversible magnetic agglomeration is introduced and studied in detail. Initially, a weakly coordinating surfactant (3-octadecyl-2,4-pentanedione) is employed to produce a wide range of nanoparticle sizes ranging from 8 to 20 nm in diameter. The kinetics faced in these reactions by cheap and widely available iron complex precursors can be avoided in this method with the introduction of thermodynamic control, which occurs in the form of a magnetic precipitation event that essentially halts nanoparticle growth. Utilizing this synthetic method, the length of the alkyl chain on ...


Mechanochemistry Of The Libh4–Alcl3 System: Structural Characterization Of The Products By Solid-State Nmr, Takeshi Kobayashi, Oleksandr Dolotko, Shalbh Gupta, Vitalij K. Pecharsky, Marek Pruski 2018 Ames Laboratory

Mechanochemistry Of The Libh4–Alcl3 System: Structural Characterization Of The Products By Solid-State Nmr, Takeshi Kobayashi, Oleksandr Dolotko, Shalbh Gupta, Vitalij K. Pecharsky, Marek Pruski

Ames Laboratory Accepted Manuscripts

The double-cation metal borohydride, Li4Al3(BH4)(13), mechanochemically produced from a 13:3 mixture of lithium borohydride (LiBH4) and aluminum chloride (AlCl3), has a low hydrogen desorption temperature; however, the material's decomposition is accompanied by a large emission of toxic diborane (B2H6). We found that a decrease of the LiBH4:AICl(3) ratio in the starting mixture yields increased amounts of partially chlorinated products that also dehydrogenate at low temperature, but release negligibly small amounts of diborane. Extensive characterization by solid-state NMR spectroscopy (SSNMR) and powder X-ray diffraction (XRD) found that the 11:3 ratio product maintains the Li ...


Defect-Mediated, Thermally-Activated Encapsulation Of Metals At The Surface Of Graphite, Yinghui Zhou, Ann Lii-Rosales, Minsung Kim, Mark Wallingford, Dapeng Jing, Michael C. Tringides, Cai-Zhuang Wang, Patricia A. Thiel 2018 Ames Laboratory

Defect-Mediated, Thermally-Activated Encapsulation Of Metals At The Surface Of Graphite, Yinghui Zhou, Ann Lii-Rosales, Minsung Kim, Mark Wallingford, Dapeng Jing, Michael C. Tringides, Cai-Zhuang Wang, Patricia A. Thiel

Chemistry Publications

We show that 3 metals – Dy, Ru, and Cu – can form multilayer intercalated (encapsulated) islands at the graphite (0001) surface if 2 specific conditions are met: Defects are introduced on the graphite terraces to act as entry portals, and the metal deposition temperature is well above ambient. Focusing on Dy as a prototype, we show that surface encapsulation is much different than bulk intercalation, because the encapsulated metal takes the form of bulk-like rafts of multilayer Dy, rather than the dilute, single-layer structure known for the bulk compound. Carbon-covered metallic rafts even form for relatively unreactive metals (Ru and Cu ...


Biomedical Applications Of Hydrogels And Gumbos, Kelsey Elizabeth McNeel 2018 Louisiana State University and Agricultural and Mechanical College

Biomedical Applications Of Hydrogels And Gumbos, Kelsey Elizabeth Mcneel

LSU Doctoral Dissertations

Sodium deoxycholate (NaDC) is a small bile salt that was used in this dissertation to produce gelation of tris(hydroxymethyl)amino-methane (TRIS) solutions above, below, and near the pKa of NaDC. These solutions respectively yielded a neutral gelator, a charged gelator, and a mixture of each. Impacts of ionic interactions on gel formation were studied in detail and showed that pH can be used to modify many hydrogel properties including sol-gel temperature, crystallinity, and mechanical strength. It was also observed that pH modification of the hydrogels affected nanoparticle formation. Nanoparticles derived from a Group of Uniform Materials Based on Organic ...


Hybrid Electrochemical Capacitors: Materials, Optimization, And Miniaturization, Richa Agrawal 2018 Department of Mechanical and Materials Engineering, Florida International University

Hybrid Electrochemical Capacitors: Materials, Optimization, And Miniaturization, Richa Agrawal

FIU Electronic Theses and Dissertations

With the ever-advancing technology, there is an incessant need for reliable electrochemical energy storage (EES) components that can provide desired energy and power. At the forefront of EES systems are electrochemical capacitors (ECs), also known as supercapacitors that typically have higher power and superior cycle longevity but lower energy densities than their battery counterparts. One of the routes to achieve higher energy density for ECs is using the hybrid EC configuration, which typically utilizes a redox electrode coupled with a counter double-layer type electrode.

In this dissertation, both scale-up (coin-cell type) as well as scale-down (on-chip miniaturized) hybrid ECs were ...


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