Matching Items (56)
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Description
Accurate virus detection is important for diagnosis in a timely manner to facilitate rapid interventions and treatments. RNA viruses affect an extensive amount of the world’s population, particularly in tropical countries where emerging infectious agents often arise. Current diagnostic methods have three main problems: they are time consuming, typically not

Accurate virus detection is important for diagnosis in a timely manner to facilitate rapid interventions and treatments. RNA viruses affect an extensive amount of the world’s population, particularly in tropical countries where emerging infectious agents often arise. Current diagnostic methods have three main problems: they are time consuming, typically not field-portable, and expensive. My research goal is to develop rapid, field-portable and cost sensitive diagnostic methods for RNA viruses. Herein, two different approaches to detect RNA viruses were proposed: Conjugated gold nanoparticles for detection of viral particles or virus-specific antibodies by monitoring changes in their optical properties, and Tentacle Probes coupled with qPCR for detection and differentiation of closely-related viral strains. The first approach was divided into two projects: the study and characterization of the gold nanoparticle-antibody system for detection of virus particles using dynamic light scattering (DLS) and UV-Vis spectrophotometry, and development of a detection method for antibodies using static light scattering (SLS) and antigen-conjugated gold nanoparticles. Bovine serum albumin (BSA) conjugated gold nanoparticles could successfully detect BSA-specific antibodies in vitro, and protein E from Dengue Virus serotype 2 conjugated gold nanoparticles could detect Dengue-specific antibodies, both in vitro and in serum samples. This method is more accurate than currently used detection methods such as dot blots. The second approach uses Tentacle Probes, which are modified molecular beacons, to detect with high specificity two different strains of Lymphocytic Choriomeningitis Virus (LCMV), Armstrong and Clone-13, which differ in only one nucleotide at the target sequence. We successfully designed and use Tentacle Probes for detection of both strains of LCMV, in vitro and in serum from infected mice. Moreover, detection of as little as 10% of Clone-13 strain was possible when diluted in 90% Armstrong strain. This approach enables the detection of different strains of virus even within a mixed quasispecies and may be important for improving intervention strategies for reducing disease. The detection methods provide rapid detection of viruses, including viral strains within mixed populations, and should enhance our ability in providing early responses to emerging infectious diseases due to RNA viruses including Zika or Dengue virus.
ContributorsFranco, Lina Stella (Author) / Mujica, Vladimiro (Thesis advisor) / Blattman, Joseph N (Thesis advisor) / Garcia, Antonio A. (Committee member) / Fromme, Petra (Committee member) / Hayes, Mark (Committee member) / Arizona State University (Publisher)
Created2016
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Description
Sunlight, the most abundant source of energy available, is diffuse and intermittent; therefore it needs to be stored in chemicals bonds in order to be used any time. Photosynthesis converts sunlight into useful chemical energy that organisms can use for their functions. Artificial photosynthesis aims to use the essential chemistry

Sunlight, the most abundant source of energy available, is diffuse and intermittent; therefore it needs to be stored in chemicals bonds in order to be used any time. Photosynthesis converts sunlight into useful chemical energy that organisms can use for their functions. Artificial photosynthesis aims to use the essential chemistry of natural photosynthesis to harvest solar energy and convert it into fuels such as hydrogen gas. By splitting water, tandem photoelectrochemical solar cells (PESC) can produce hydrogen gas, which can be stored and used as fuel. Understanding the mechanisms of photosynthesis, such as photoinduced electron transfer, proton-coupled electron transfer (PCET) and energy transfer (singlet-singlet and triplet-triplet) can provide a detailed knowledge of those processes which can later be applied to the design of artificial photosynthetic systems. This dissertation has three main research projects. The first part focuses on design, synthesis and characterization of suitable photosensitizers for tandem cells. Different factors that can influence the performance of the photosensitizers in PESC and the attachment and use of a biomimetic electron relay to a water oxidation catalyst are explored. The second part studies PCET, using Nuclear Magnetic Resonance and computational chemistry to elucidate the structure and stability of tautomers that comprise biomimetic electron relays, focusing on the formation of intramolecular hydrogen bonds. The third part of this dissertation uses computational calculations to understand triplet-triplet energy transfer and the mechanism of quenching of the excited singlet state of phthalocyanines in antenna models by covalently attached carotenoids.
ContributorsTejeda Ferrari, Marely (Author) / Moore, Ana (Thesis advisor) / Mujica, Vladimiro (Thesis advisor) / Gust, John (Committee member) / Woodbury, Neal (Committee member) / Arizona State University (Publisher)
Created2016
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Description
Over the last few decades, homogeneous molybdenum catalysis has been a center of interest to inorganic, organic, and organometallic chemists. Interestingly, most of the important advancements in molybdenum chemistry such as non-classical dihydrogen coordination, dinitrogen reduction, olefin metathesis, and water reduction utilize diverse oxidation states of the metal. However, employment

Over the last few decades, homogeneous molybdenum catalysis has been a center of interest to inorganic, organic, and organometallic chemists. Interestingly, most of the important advancements in molybdenum chemistry such as non-classical dihydrogen coordination, dinitrogen reduction, olefin metathesis, and water reduction utilize diverse oxidation states of the metal. However, employment of redox non-innocent ligands to tune the stability and reactivity of such catalysts have been overlooked. With this in mind, the Trovitch group has developed a series of novel bis(imino)pyridine (or pyridine diimine, PDI) and diimine (DI) ligands that have coordinating phosphine or amine arms to exert coordination flexibility to the designed complexes. The research described in this dissertation is focused on the development of molybdenum catalysts that are supported by PDI and DI chelates and their application in small molecule activation.

Using the phosphine containing PDI chelate, Ph2PPrPDI, several low-valent molybdenum complexes have been synthesized and characterized. While the zerovalent monocarbonyl complex, (Ph2PPrPDI)MoCO, catalyzes the reduction of aldehyde C=O bonds, the C-H activated Mo(II) complex, (6-P,N,N,N,C,P-Ph2PPrPDI)MoH was found to be the first well-defined molybdenum catalyst for reducing carbon dioxide to methanol. Along with low- oxidation state compounds, a Mo(IV) complex, [(Ph2PPrPDI)MoO][PF6]2 was also synthesized and utilized in electrocatalytic hydrogen production from neutral water. Moreover, with the proper choice of reductant, an uncommon Mo(I) oxidation state was stabilized and characterized by electron paramagnetic resonance spectroscopy and single crystal X-ray diffraction.

While the synthesized (PDI)Mo complexes unveiled versatile reduction chemistry, varying the ligand backbone to DI uncovered completely different reactivity when bound to molybdenum. Unlike PDI, no chelate-arm C-H activation was observed with the propyl phosphine DI, Ph2PPrDI; instead, a bis(dinitrogen) Mo(0) complex, (Ph2PPrDI)Mo(N2)2 was isolated. Surprisingly, this complex was found to convert carbon dioxide into dioxygen and carbon monoxide under ambient conditions through a novel tail-to-tail CO2 reductive coupling pathway. Detailed experimental and theoretical studies are underway to gain further information about the possible mechanism of Mo mediated direct conversion of CO2 to O2.
ContributorsPal, Raja (Author) / Trovitch, Ryan J (Thesis advisor) / Buttry, Daniel (Committee member) / Seo, Don (Committee member) / Arizona State University (Publisher)
Created2016
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Description
Studying charge transport through single molecules is of great importance for unravelling charge transport mechanisms, investigating fundamentals of chemistry, and developing functional building blocks in molecular electronics.

First, a study of the thermoelectric effect in single DNA molecules is reported. By varying the molecular length and sequence, the charge transport in

Studying charge transport through single molecules is of great importance for unravelling charge transport mechanisms, investigating fundamentals of chemistry, and developing functional building blocks in molecular electronics.

First, a study of the thermoelectric effect in single DNA molecules is reported. By varying the molecular length and sequence, the charge transport in DNA was tuned to either a hopping- or tunneling-dominated regimes. In the hopping regime, the thermoelectric effect is small and insensitive to the molecular length. Meanwhile, in the tunneling regime, the thermoelectric effect is large and sensitive to the length. These findings indicate that by varying its sequence and length, the thermoelectric effect in DNA can be controlled. The experimental results are then described in terms of hopping and tunneling charge transport models.

Then, I showed that the electron transfer reaction of a single ferrocene molecule can be controlled with a mechanical force. I monitor the redox state of the molecule from its characteristic conductance, detect the switching events of the molecule from reduced to oxidized states with the force, and determine a negative shift of ~34 mV in the redox potential under force. The theoretical modeling is in good agreement with the observations, and reveals the role of the coupling between the electronic states and structure of the molecule.

Finally, conclusions and perspectives were discussed to point out the implications of the above works and future studies that can be performed based on the findings.
ContributorsLi, Yueqi, Ph.D (Author) / Tao, Nongjian (Thesis advisor) / Buttry, Daniel (Committee member) / Mujica, Vladimiro (Committee member) / Arizona State University (Publisher)
Created2017
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Description
This work describes the investigation of novel cathode and anode materials. Specifically, several mixed polyanion compounds were evaluated as cathodes for Li and Na-ion batteries. Clathrate compounds composed of silicon or germanium arranged in cage-like structures were studied as anodes for Li-ion batteries.

Nanostructured Cu4(OH)6SO4 (brochantite) platelets were synthesized using polymer-assisted

This work describes the investigation of novel cathode and anode materials. Specifically, several mixed polyanion compounds were evaluated as cathodes for Li and Na-ion batteries. Clathrate compounds composed of silicon or germanium arranged in cage-like structures were studied as anodes for Li-ion batteries.

Nanostructured Cu4(OH)6SO4 (brochantite) platelets were synthesized using polymer-assisted titration and microwave-assisted hydrothermal methods. These nanostructures exhibited a capacity of 474 mAh/g corresponding to the full utilization of the copper redox in an conversion reaction. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies were preformed to understand the mechanism and structural changes.

A microwave hydrothermal synthesis was developed to prepare a series compounds based on jarosite, AM3(SO4)2(OH)6 (A = K, Na; M = Fe, V). Both the morphology and electrochemical properties showed a compositional dependence. At potentials >1.5 V vs. Li/Li+, an insertion-type reaction was observed in Na,Fe-jarosite but not in K,Fe-jarosite. Reversible insertion-type reactions were observed in both vanadium jarosites between 1 – 4 V with capacities around 40 - 60 mAh/g. Below 1 V vs. Li/Li+, all four jarosite compounds underwent conversion reactions with capacities ~500 mAh/g for the Fe-jarosites.

The electrochemical properties of hydrogen titanium phosphate sulfate, H0.4Ti2(PO4)2.4(SO4)0.6 (HTPS), a new mixed polyanion material with NASICON structure was reported. A capacity of 148 mAh/g corresponding to2 Li+ insertion per formula unit was observed. XRD and XPS were used to characterize the HTPS before and after cycling and to identify the lithium sites. Evaluation of the HTPS in Na-ion cell was also performed, and a discharge capacity of 93 mAh/g was observed.

A systematic investigation of the role of the processing steps, such as ball-milling and acid/base etching, on the electrochemical properties of a silicon clathrate compound with nominal composition of Ba8Al16Si30 was performed. According to the transmission electron microscope (TEM), XPS, and electrochemical analysis, very few Li atoms can be electrochemically inserted, but the introduction of disorder through ball-milling resulted in higher capacity, while the oxidation layer made by the acid/base treatment prevented the reation. The electrochemical property of germanium clathrate was also investigated, unlike the silicon clathrate, the germanium one underwent a conversion reaction.
ContributorsZhao, Ran (Author) / Chan, Candace K. (Thesis advisor) / Buttry, Daniel (Committee member) / Yarger, Jeffery (Committee member) / Arizona State University (Publisher)
Created2017
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Description
This thesis is devoted to the theoretical and computational study of electron transport in molecular junctions where one or more hydrogen bonds are involved in the process. While electron transport through covalent bonds has been extensively studied, in recent work the focus has been shifted towards hydrogen-bonded systems due to

This thesis is devoted to the theoretical and computational study of electron transport in molecular junctions where one or more hydrogen bonds are involved in the process. While electron transport through covalent bonds has been extensively studied, in recent work the focus has been shifted towards hydrogen-bonded systems due to their ubiquitous presence in biological systems and their potential in forming nano- junctions between molecular electronic devices and biological systems.

This analysis allows us to significantly expand our comprehension of the experimentally observed result that the inclusion of hydrogen bonding in a molecular junc- tion significantly impacts its transport properties, a fact that has important implications for our understanding of transport through DNA, and nano-biological interfaces in general. In part of this work I have explored the implications of quasiresonant transport in short chains of weakly-bonded molecular junctions involving hydrogen bonds. I used theoretical and computational analysis to interpret recent experiments and explain the role of Fano resonances in the transmission properties of the junction.

In a different direction, I have undertaken the study of the transversal conduction through nucleotide chains that involve a variable number of different hydrogen bonds, e.g. NH···O, OH···O, and NH···N, which are the three most prevalent hydrogen bonds in biological systems and organic electronics. My effort here has fo- cused on the analysis of electronic descriptors that allow a simplified conceptual and computational understanding of transport properties. Specifically, I have expanded our previous work where the molecular polarizability was used as a conductance de- scriptor to include the possibility of atomic and bond partitions of the molecular polarizability. This is important because it affords an alternative molecular descrip- tion of conductance that is not based on the conventional view of molecular orbitals as transport channels. My findings suggest that the hydrogen-bond networks are crucial in understanding the conductance of these junctions.

A broader impact of this work pertains the fact that characterizing transport through hydrogen bonding networks may help in developing faster and cost-effective approaches to personalized medicine, to advance DNA sequencing and implantable electronics, and to progress in the design and application of new drugs.
ContributorsWimmer, Michael (Author) / Mujica, Vladimiro (Thesis advisor) / Wolf, George (Committee member) / Chizmeshya, Andrew (Committee member) / Arizona State University (Publisher)
Created2017
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Description
Complex samples, such as those from biological sources, contain valuable information indicative of the state of human health. These samples, though incredibly valuable, are difficult to analyze. Separation science is often used as the first step when studying these samples. Electrophoretic exclusion is a novel separations technique that differentiates species

Complex samples, such as those from biological sources, contain valuable information indicative of the state of human health. These samples, though incredibly valuable, are difficult to analyze. Separation science is often used as the first step when studying these samples. Electrophoretic exclusion is a novel separations technique that differentiates species in bulk solution. Due to its ability to isolate species in bulk solution, it is uniquely suited to array-based separations for complex sample analysis. This work provides proof of principle experimental results and resolving capabilities of the novel technique. Electrophoretic exclusion is demonstrated at a single interface on both benchtop and microscale device designs. The benchtop instrument recorded absorbance measurements in a 365 μL reservoir near a channel entrance. Results demonstrated the successful exclusion of a positively-charged dye, methyl violet, with various durations of applied potential (30 - 60 s). This was the first example of measuring absorbance at the exclusion location. A planar, hybrid glass/PDMS microscale device was also constructed. One set of experiments employed electrophoretic exclusion to isolate small dye molecules (rhodamine 123) in a 250 nL reservoir, while another set isolated particles (modified polystyrene microspheres). Separation of rhodamine 123 from carboxylate-modified polystyrene spheres was also shown. These microscale results demonstrated the first example of the direct observation of exclusion behavior. Furthermore, these results showed that electrophoretic exclusion can be applicable to a wide range of analytes. The theoretical resolving capabilities of electrophoretic exclusion were also developed. Theory indicates that species with electrophoretic mobilities as similar as 10-9 cm2/Vs can be separated using electrophoretic exclusion. These results are comparable to those of capillary electrophoresis, but on a very different format. This format, capable of isolating species in bulk solution, coupled with the resolving capabilities, makes the technique ideal for use in a separations-based array.
ContributorsKenyon, Stacy Marie (Author) / Hayes, Mark A. (Thesis advisor) / Ros, Alexandra (Committee member) / Buttry, Daniel (Committee member) / Arizona State University (Publisher)
Created2012
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Description
Understanding charge transport in single molecules covalently bonded to electrodes is a fundamental goal in the field of molecular electronics. In the past decade, it has become possible to measure charge transport on the single-molecule level using the STM break junction method. Measurements on the single-molecule level shed light on

Understanding charge transport in single molecules covalently bonded to electrodes is a fundamental goal in the field of molecular electronics. In the past decade, it has become possible to measure charge transport on the single-molecule level using the STM break junction method. Measurements on the single-molecule level shed light on charge transport phenomena which would otherwise be obfuscated by ensemble measurements of groups of molecules. This thesis will discuss three projects carried out using STM break junction. In the first project, the transition between two different charge transport mechanisms is reported in a set of molecular wires. The shortest wires show highly length dependent and temperature invariant conductance behavior, whereas the longer wires show weakly length dependent and temperature dependent behavior. This trend is consistent with a model whereby conduction occurs by coherent tunneling in the shortest wires and by incoherent hopping in the longer wires. Measurements are supported with calculations and the evolution of the molecular junction during the pulling process is investigated. The second project reports controlling the formation of single-molecule junctions by means of electrochemically reducing two axial-diazonium terminal groups on a molecule, thereby producing direct Au-C covalent bonds in-situ between the molecule and gold electrodes. Step length analysis shows that the molecular junction is significantly more stable, and can be pulled over a longer distance than a comparable junction created with amine anchoring bonds. The stability of the junction is explained by the calculated lower binding energy associated with the direct Au-C bond compared with the Au-N bond. Finally, the third project investigates the role that molecular conformation plays in the conductance of oligothiophene single-molecule junctions. Ethyl substituted oligothiophenes were measured and found to exhibit temperature dependent conductance and transition voltage for molecules with between two and six repeat units. While the molecule with only one repeat unit shows temperature invariant behavior. Density functional theory calculations show that at higher temperatures the oligomers with multiple repeat units assume a more planar conformation, which increases the conjugation length and decreases the effective energy barrier of the junction.
ContributorsHines, Thomas (Author) / Tao, Nongjian (Thesis advisor) / Li, Jian (Thesis advisor) / Mujica, Vladimiro (Committee member) / Allee, David (Committee member) / Arizona State University (Publisher)
Created2013
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Description
Locomotion of microorganisms is commonly observed in nature. Although microorganism locomotion is commonly attributed to mechanical deformation of solid appendages, in 1956 Nobel Laureate Peter Mitchell proposed that an asymmetric ion flux on a bacterium's surface could generate electric fields that drive locomotion via self-electrophoresis. Recent advances in nanofabrication have

Locomotion of microorganisms is commonly observed in nature. Although microorganism locomotion is commonly attributed to mechanical deformation of solid appendages, in 1956 Nobel Laureate Peter Mitchell proposed that an asymmetric ion flux on a bacterium's surface could generate electric fields that drive locomotion via self-electrophoresis. Recent advances in nanofabrication have enabled the engineering of synthetic analogues, bimetallic colloidal particles, that swim due to asymmetric ion flux originally proposed by Mitchell. Bimetallic colloidal particles swim through aqueous solutions by converting chemical fuel to fluid motion through asymmetric electrochemical reactions. This dissertation presents novel bimetallic motor fabrication strategies, motor functionality, and a study of the motor collective behavior in chemical concentration gradients. Brownian dynamics simulations and experiments show that the motors exhibit chemokinesis, a motile response to chemical gradients that results in net migration and concentration of particles. Chemokinesis is typically observed in living organisms and distinct from chemotaxis in that there is no particle directional sensing. The synthetic motor chemokinesis observed in this work is due to variation in the motor's velocity and effective diffusivity as a function of the fuel and salt concentration. Static concentration fields are generated in microfluidic devices fabricated with porous walls. The development of nanoscale particles that swim autonomously and collectively in chemical concentration gradients can be leveraged for a wide range of applications such as directed drug delivery, self-healing materials, and environmental remediation.
ContributorsWheat, Philip Matthew (Author) / Posner, Jonathan D (Thesis advisor) / Phelan, Patrick (Committee member) / Chen, Kangping (Committee member) / Buttry, Daniel (Committee member) / Calhoun, Ronald (Committee member) / Arizona State University (Publisher)
Created2011
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Description
Understanding cellular processes can provide insight into disease pathogenesis and reveal critical information for prevention, diagnosis, and treatment. As key executors and signaling regulators, proteins carry relevant information not available from genomics and transcriptomics. Cell-to-cell differences significantly affect disease incidence and drug responses, generating a need for protein analysis at

Understanding cellular processes can provide insight into disease pathogenesis and reveal critical information for prevention, diagnosis, and treatment. As key executors and signaling regulators, proteins carry relevant information not available from genomics and transcriptomics. Cell-to-cell differences significantly affect disease incidence and drug responses, generating a need for protein analysis at the single-cell level. However, quantitative protein analysis at the single-cell level remains challenging due to the low protein amount in a single cell and the proteome complexity. It requires sensitive detection techniques and appropriate sample preparation and delivery to the detection area. Here, a microfluidic platform in tandem with matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) has been developed for targeted intracellular protein analysis. The elastomeric multi-layer microfluidic platform, termed MIMAS, was designed as a series of 8.75 nL wells separated by pneumatic valves. The MIMAS platform allows cell loading, sample processing on-chip, and further in situ mass spectrometry analysis. The sample processing includes cell lysis, immunocapture, tryptic digestion and MALDI matrix solution loading for co-crystallization. This work demonstrates that the MIMAS approach is suitable for protein quantification by assessing the apoptotic protein Bcl-2 from MCF-7 breast cancer cells using an isotope-labeled peptide. The limit of detection was determined as 11.22 nM, equivalent to 5.91 x 10^7 protein molecules per well. Moreover, the MIMAS platform design was improved, allowing the successful quantification of Bcl-2 protein in small cell ensembles down to ~10 cells in 4 nL wells. Furthermore, the MIMAS platform was integrated with laser capture microdissection (LCM) for protein analysis from post-mortem human tissues. Intracellular amyloid-β peptide (Aβ), a hallmark of Alzheimer’s Disease, was assessed from human brain tissue using the LCM-MIMAS. The successful detection of Aβ from small cell ensembles (20 sliced pyramidal cells) demonstrated the LCM-MIMAS capability of assessing intracellular proteins from specific tissue cell subpopulations. The MIMAS approach is a promising tool for intracellular protein analysis from small cell ensembles, with the potential for single-cell analysis. It allows for protein analysis towards the understanding of biological phenomena for clinical and biological research.
ContributorsCruz Villarreal, Jorvani (Author) / Ros, Alexandra (Thesis advisor) / Borges, Chad R (Committee member) / Buttry, Daniel (Committee member) / Arizona State University (Publisher)
Created2022