Mountain Scholar :: Browsing by Author "Van Orden, Alan, committee member"

Browsing by Author "Van Orden, Alan, committee member"

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Open Access
Accessing a new molecular scaffold for Fe(II) spin state switching through first coordination changes
(Colorado State University. Libraries, 2021) Livesay, Brooke N., author; Shores, Matthew P, advisor; Rappé, Anthony K., committee member; Van Orden, Alan, committee member; Ross, Kathryn A., committee member
Presented in this dissertation are the syntheses and characterizations of iron spin state switching complexes. The magnetic properties are extremely sensitive to environmental changes such as ligand field, coordination environment, and crystal packing. These studies focus on developing a better understanding of how the magnetic properties of iron complexes can be controlled by environmental modifications. The first chapter provides a detailed introduction to spin state switching. The chapter includes the origins of the phenomenon and background into previous efforts to modify the spin switching event. This chapter highlights the challenges of designing a spin state switching complex and the different pathways used to induce spin switching events in the solid state and solution phase. Chapter 2 describes the procedures used to collect solution magnetic data. This chapter details the advantages of collecting solution data using a MPMS instrument compared to the Evans' (1H NMR) Method. The standard operating procedures for the method using a MPMS instrument are described for future researchers. Examples of solution magnetic data collected by both methods are described and compared. Chapter 3 discusses the challenges that were encountered during the synthesis of an iron(II) complex. The synthesis stopped producing the desired product after it was successful for several months. Investigations into the reproducibility, synthetic methods, and purification steps were performed to understand why the original synthetic procedure stopped working. This chapter describes how commercially-available starting materials can differ between lot numbers and manufacturers and how these small differences can lead to significant changes in the purity of the final product. Chapter 4 discusses the impact of speciation on the spin state switching properties of the neutral iron(II) compound synthesized in Chapter 3. Analysis in the solid state indicates the iron(II) complex is in the high spin state at all temperatures. When this compound is dissolved in strongly coordinating solvents the bound anions are replaced by the solvent resulting in a high spin species when the solvent is oxygen-donating and low spin species when the solvent is nitrogen-donating. In non-coordinating solvents the iron(II) complex loses one of the bound anions but remains high spin. However, in moderately coordinating solvents like acetone, the iron(II) loses the bound anions upon decreasing the temperature, resulting in a coordination induced spin state switching event. These studies highlight the sensitivity of solvent choice on the solution magnetic properties of iron(II) compounds. Chapter 5 discusses the thought process used to design the synthetic procedure for the post-synthetic modification of an iron(II) compound. The azide alkyne cycloaddition reaction was tested with several catalysts and deprotecting agents. Thoughtful consideration was taken to avoid the transmetallation reaction between the cycloaddition catalyst and the iron(II) compound. The successful reaction conditions for the post synthetic modification were found and resulted in the formation of the desired iron(II) triazole compound. Additional iron(II) triazole complex salts synthesized following the method described in Chapter 5 are described and characterized in Chapter 6. Electron-donating, electron-withdrawing, and oxidation-sensitive substituents are included on the iron(II) triazole ligand to show the scope of the post synthetic modification reaction and allow for investigation into how substituents effect the magnetic properties of the resulting compounds. Variable temperature solid state magnetic characterization indicates the resulting iron(II) compounds show a variety of magnetic behaviors. However, analysis of the crystallographic data and comparison to related previously published iron(II) triazole compounds indicate the differences in the magnetic properties are due to the solid state crystal packing effects. In Chapter 7 the solution magnetic properties of the iron(II) triazole compounds described in Chapter 6 are discussed. Removing the crystal packing effects by characterizing the compounds in solution allows for discovery of a relationship between the substituent properties and the magnetic behavior of the resulting compounds. The compounds were characterized in d4-CD4OD by Evans' 1H NMR method and show a thermal spin state switching event. However, no relationship between the Hammett parameter of the substituents and the spin state properties was observed. Chapter 8 summarizes the investigation of solvent induced spin state switching and post-synthetic modification. Additionally, I discuss some future work that would expand on the studies presented in this dissertation.
Open Access
Atomic force microscopy: more than surface imaging
(Colorado State University. Libraries, 2020) Bishop, Terrance Tyler, author; Krapf, Diego, advisor; Prasad, Ashok, committee member; Van Orden, Alan, committee member
Atomic Force Microscopy (AFM) is a powerful imaging tool that has capabilities that go beyond the abilities of most other microscopes. Here, three examples of these capabilities were considered. First, the AFM was operated in an image generating mode to determine the surface heterogeneity of polysaccharide membranes. Second, the AFM was used to record force-indentation curves, these curves were fit with a Hertzian model to determine the stiffness of murine smooth muscle cells. Finally a approach for attaching 10 µm and 2 µm polystyrene beads to tip-less AFM cantilevers was proposed, and a viscoelastic contact model was tested to determine the viability of the created probes.
Open Access
Barium tagging in solid xenon for the EXO experiment
(Colorado State University. Libraries, 2011) Mong, Brian, author; Fairbank, William, Jr., advisor; Lundeen, Stephen, committee member; Berger, Bruce, committee member; Van Orden, Alan, committee member
Neutrinoless double beta decay experiments are searching for rare decay modes never before observed to uncover the absolute mass of the neutrino, as well as to discover if it is a Majorana fermion. Detection of the daughter nucleus can help provide positive identification of this event over most radioactive backgrounds. The goal of the Enriched Xenon Observatory (EXO) is to measure the rate of 0νββ decay in 136Xe, incorporating 136Ba daughter identification by laser induced fluorescence spectroscopy. Here, we investigate a technique in which the 136Ba daughter is grabbed with a cryogenic probe by freezing it in solid xenon ice, and detected directly in the solid xenon. The absorption and fluorescence spectra of barium in solid xenon were observed for the first time in this work. Identification of the 6s2 1S0 → 6s6p 1P1 transition in both absorption (558 nm) and emission spectra (594 nm) were made. Additional blue absorption and emission lines were observed, but their transitions were not identified. Saturation of the 6s2 1S0 → 6s6p 1P1 transition was not observed with increased excitation rates using resonance excitation at 558 nm. From this a limit on the metastable decay rate was deduced to be greater than 104 s-1. Finally a fluorescence spectrum was obtained from a sample with only 20,000 atoms in the laser beam. With potential improvements of 107 in detection efficiency, single barium atom detection seems possible in solid xenon. A fiber probe detector based on a bare single mode fiber was also constructed and tested with fluorescing dye molecules. Successful detection of a few dye molecules in solution at the probe tip was demonstrated.
Open Access
Biologically active aromatic acids in phosphatidylcholine liposomes: benzoic and salicylic acids
(Colorado State University. Libraries, 2022) Sanders, Sarah Ivy, author; Crans, Debbie, advisor; Van Orden, Alan, committee member; Van Buiten, Charlene, committee member
The interactions of benzoic acid and salicylic acid with phosphatidylcholine liposomes were characterized to understand interfacial interactions of the two weak aromatic acids with the membrane. The liposomal system was comprised of soy l-ɑ-phosphatidylcholine (SPC) bilayers, which allowed the determination of interfacial interactions and position within the membrane using 1D 1H NMR. Benzoic acid was considered due to its effects as a food stabilizer, where salicylic acid was considered as a derivative due to its effects as an anti-acne agent. Both were found to penetrate the membrane interface deeper when in their protonated forms. The presence of the weak acids on the membrane surface allowed stabilization through hydrogen bonding with liposomal headgroups, which allowed deprotonation to occur. Broadening of aromatic peaks demonstrated a pH dependence for both benzoic acid and salicylic acid, showing a deeper penetration around the pKa values of the weak acids. This study offers justification for the antimicrobial activity of benzoic and salicylic acids in lower pH environments. Thus, this study provides the next piece in understanding the uptake of benzoic acid and salicylic acid in bacteria for microbial inhibition.
Open Access
Characterization and modification of carbon composite electrodes towards more affordable biosensing applications and integration into fluidic devices
(Colorado State University. Libraries, 2022) Clark, Kaylee M., author; Henry, Charles S., advisor; Van Orden, Alan, committee member; Prieto, Amy L., committee member; Volckens, John, committee member
Fast, accurate, and low-cost medical tests and platforms for biomolecule monitoring are essential to the diagnosis, management, and treatment of many diseases. Electrochemical detection allows for highly sensitive measurements with fast response times. Carbon composite electrodes are an attractive option for electrochemical detection due to their low cost, resistance to biological fouling, large electrochemical solvent windows, and ability to be patterned. However, they often suffer from poor electrocatalytic activity, inability to be molded, and need for complex modifications to effectively detect certain analytes. Combining electrochemistry with fluidics is attractive for a wide array of applications including multiplexing, automation, and high-throughput screening. However, fabrication of electrochemical fluidic devices with integrated carbon electrodes remains a challenge. Thermoplastic electrodes (TPEs) are a new class of composite electrodes discussed in this dissertation that exhibit superior electrochemical properties to typical carbon composite electrodes and can be easily molded into intricate structures. Overall, this dissertation aims to improve carbon composite materials for biosensing applications and integration of electrochemical sensors into fluidic devices. Chapter 2 introduces polycaprolactone (PCL) as a new binder material for TPEs and focuses on the electrochemical characterization of the new material. The PCL-based TPEs have excellent electrochemical activity towards a wide range of analytes as well as high electrical conductivity. Chapter 2 also introduces a simple technique for integrating PCL and carbon composite electrodes into microfluidics. The presented electrode-integrated microfluidic devices are quickly fabricated with a laser cutter using PCL as a bonding layer. As a proof-of-concept application, water-in-oil droplets are electrochemically analyzed. Chapter 3 focuses on use of PCL-based TPEs for enzymatic sensors. The simple fabrication of TPEs also allows catalysts and enzymes to be mixed directly into the material to enhance detection. In Chapter 3, the TPE material is bulk-modified with cobalt phthalocyanine, an electrocatalyst, and glucose oxidase, resulting in a robust glucose sensor that demonstrates long-term current response stability. These sensors can be molded into intricate shapes and sanded for surface renewal (without requiring additional steps to maintain the modification), allowing the sensors to be continuously reused even if damaged or fouled. Chapter 4 investigates the properties of TPEs using two different binders – polycaprolactone (PCL) and polystyrene (PS) – with sanded and heat-pressed surface treatment. XPS and SEM analysis suggested that sanded TPEs have a higher density of graphitic edge planes and improved electrochemistry as a result. Electrochemical detection of O2 and H2O2, which are typically difficult to detect on carbon composites without complex modification, was demonstrated on sanded PS-based TPEs. Additionally, Chapter 4 introduces a new 3D-printed TPE sensor module that is reversibly sealed with magnets. A proof-of-concept sensor for detecting H2O2 in flow with the sensor module is presented. Chapter 5 presents a low-cost flow device, made of inexpensive polyethylene terephthalate (PET) and adhesive films, developed to detect SARS-CoV-2 nucleocapsid (N) protein. Upon addition of a sample in the device, reagents and washes are sequentially delivered to an integrated screen-printed carbon electrode for detection thus automating a full sandwich immunoassay with a single end-user step. The modified electrodes are sensitive and selective for COVID-19 N protein and stable for over seven weeks. The flow device was also successfully applied to detect nine different SARS-CoV-2 variants, including Omicron. In summary, this dissertation presents work to improve carbon composite electrodes, their modification, and integration into fluidic devices for applications as biosensors and beyond. The TPEs presented show improved electrochemical and physical properties, that allow for simple modifications. This work also demonstrates simple electrode integration strategies in several types of fluidic devices for easier and more sensitive detection of biologically relevant analytes. Moreover, the platforms established in this dissertation can be easily adapted for a wide variety of analytes and applications. This work provides materials, methods, and platforms to create more affordable biosensors for medical and other biological sensing.
Open Access
Conversion of lipid biomass to liquid hydrocarbons via pericyclic decarboxylations of α,β- and β,γ-unsaturated fatty acids using polycyclic aromatic hydrocarbon (PAH) solvent systems
(Colorado State University. Libraries, 2014) Romanishan, Michelle, author; Crans, Debbie C., advisor; Henry, Charles S., committee member; Barisas, George, committee member; Van Orden, Alan, committee member; Reardon, Kenneth, committee member
Development of a new process for converting lipid biomass, containing α,β- and β,γ-unsaturated fatty acids, to liquid hydrocarbon fuels (LHF) of varying carbon number is described in this dissertation. The theme for LHF production at present revolves around utilizing a catalytic system that requires high temperatures and pressures as well as multiple processing steps. The cost attributed to these types of processes has been a hindrance in moving the economy towards a cost-effective renewable fuel. Investigating possible catalyst-free processing techniques has led to the discovery of a lower energy reaction that utilizes specific unsaturated fatty acids into a cheap, high boiling point solvent system that has the ability to produce pure alkenes as liquid hydrocarbon fuels when heated to reflux temperature of the fatty acid. This sustainable process has been proven to decarboxylate α,β- and β,γ-unsaturated fatty acids via a pericyclic rearrangement. Using a high boiling, polycyclic aromatic hydrocarbon (PAH) solvent, such as phenanthrene or pyrene, pure alkene products in high yields have been obtained from heating α,β- or β,γ-unsaturated fatty acids to a temperature no higher than reflux of the acid. The successful process development and subsequent conversion of lipid-like biomass will be discussed at length and confirmed by ¹H NMR and GC/MS.
Open Access
Coupling electrochemistry and microfluidics for biosensor development
(Colorado State University. Libraries, 2016) Feeny, Rachel M., author; Henry, Charles S., advisor; Van Orden, Alan, committee member; Sambur, Justin B., committee member; Kipper, Matthew J., committee member
Biosensors are valuable analytical tools across both scientific and medical fields. Improving and miniaturizing biosensors is an area of great interest in academic, medical, and diagnostic settings. There is a constant need to improve these systems by increasing accessibility through lower costs, greater portability, and enhanced ease-of-use. Interfacing microfluidics and electrochemical methods shows great potential to address these needs. The work described in this thesis aims to address gaps in biosensor development, including increasing accessibility and improving sensing capabilities such as sensitivity, selectivity, and resolution, by combining electrochemistry and microfluidics to develop new tools for use in a range of biosensor systems. The primary focus of this research was to couple electrochemical detection methods with microfluidic devices for bioanalytical applications. Two main topics are reported. The first is a fluid transport mechanism employing the gas permeability of poly(dimethylsiloxane) (PDMS). Degassed PDMS pumps provide a simple, portable, inexpensive method to generate controlled fluid flow in a microfluidic device to transport a sample to electrodes for electrochemical detection. The second topic reported does not aim to address cost or portability of the system, but rather focuses on improving the capabilities of electrode arrays as chemical imaging platforms. In this work, a platinum microelectrode system was developed for biomarker detection, primarily nitric oxide and norepinephrine. Microfluidic devices interfaced directly with the electrodes provided precise control of fluid delivery to the sensors enabling both localized control of chemical concentrations as well as selective chemical stimulation of living tissue. The microelectrodes, when arranged in a high-density array, provided a platform capable of achieving electrochemical biomarker detection and imaging from live tissue slices with high spatiotemporal resolution. Both technologies described required the effective interfacing of microfluidic devices with electrochemical sensors to generate biomarker detection platforms. Custom microfluidic systems were developed to directly integrate biological samples into the platforms, including dried serum spots on a filter paper matrix and live ex vivo murine adrenal slices embedded in agarose. To achieve reproducible biomarker detection in complex biological matrices, electrochemical cleaning methods were developed and utilized for electrode maintenance. All of the tools described in this thesis were designed to address specific applications, but were also intended to be translatable to other systems. The degassed PDMS pump could be used as a fluid transport mechanism for other microfluidic devices, improving the simplicity and portability of systems that could otherwise be limited by external pumping equipment. Similarly, the strategies described for interfacing microfluidic devices with the reported electrode arrays and platinum microelectrodes could be applied to other silicon microchips to accomplish precise control of fluid delivery to the electrodes. The technology developed to generate an electrochemical imaging platform could be further pursued to achieve a high level of chemical selectivity by employing alternative waveforms, such as fast scan cyclic voltammetry, or electrode modifications to better elucidate the role of chemical gradients in biological systems. All of these tools, when applied to other bioanalytical platforms, could continue to advance the field of biomarker detection using microfluidic systems.
Open Access
Determination of reliable minimum, disproof-based particle formation mechanisms: investigation of a second-generation Ir(0)n nanoparticle system
(Colorado State University. Libraries, 2021) Whitehead, Christopher Breck, author; Finke, Richard, advisor; Neilson, Jamie, committee member; Van Orden, Alan, committee member; Shipman, Patrick, committee member
A long-sought goal in particle formation is an understanding of the chemical reaction mechanism. The complete understanding of the associated processes (nucleation, growth, and agglomeration) will yield particle size and distribution control. Mechanistic control and knowledge will yield improvements in the development of renewable energy and catalytic materials. The current state of chemical reaction mechanisms and the direct methods to study them are presented in an in-depth literature review in Chapter II. The best, state-of-the-art case studies are examined and the minimum criteria for a reliable, disproof-based chemical mechanism are presented. The experimental work presented in this dissertation centers on a second-generation {[(1,5-COD)IrI•HPO4]2}2– precursor to Ir(0)~150(HPO42–)x nanoparticle system. The exhaustive investigation of the reaction speciation and the dependence of IrI and HPO42– concentrations on the reaction kinetics are presented in Chapter III. Based on the reaction kinetics and there experimentally determined nucleation step, the molecular mechanism of Ir(0)~150(HPO42–)x nanoparticle formation is elucidated. Next, in Chapter IV, the second-generation {[(1,5-COD)IrI•HPO4]2}2– precursor to Ir(0)~150(HPO42–)x nanoparticle system is monitored directly by X-ray absorption spectroscopy and small-angle X-ray scattering and indirectly by in-house cyclohexene reporter reaction, gas-liquid chromatography, proton nuclear magnetic resonance, and transmission electron microscopy. A total of 6 physical methods are used to follow the particle formation kinetics. Finally, mechanism-enabled population balance modeling is applied as a final test of the proposed mechanism.
Open Access
Developing high-performance microfluidic paper-based analytical devices
(Colorado State University. Libraries, 2018) Nguyen, Michael Paul, author; Henry, Charles S., advisor; Van Orden, Alan, committee member; Strauss, Steven H., committee member; Marchese, Anthony J., committee member
Small-scale systems to manipulate fluids, also referred to as microfluidics, have proven effective at reducing analytical costs by increasing the portability of diagnostic devices. Microfluidic paper-based analytical devices (μPADs) have also proven to be cost-effective while remaining disposable, possessing the capacity to store reagents, and producing quantitative diagnostic results. These benefits have lead the field to increase exponentially since the seminal publication, with 63 review articles currently published on the subject. Most articles in the field focus on three topics: 1) new applications, 2) new methods of analysis with broad applicability, and 3) new ways to manipulate fluids in devices. A host of new analytes and clever architectures are being developed for a variety of applications, including environmental analysis and diagnostics. However, several critical obstacles remain for μPADs including improving detection limits, reducing analysis time, increasing selectivity, and increasing the range of measurable analytes. The work described in this dissertation presents three studies that address these issues. The first study examines simple factors to improve sample delivery through a cellulose channel that directly and significantly impact detection limits. Here I show how common μPAD designs lose roughly 50% of sample prior to quantification. This major challenge has been solved through geometry changes that led to a 94% increase in signal when compared to standard designs. While Ni(II) detection was used to study the system, the methods are translated to Mn(II) detection, antibiotic purity tests and determination of nitrite in saliva suggesting the broad applicability of the methods. The second study aimed at decreasing analysis time by utilizing multiple layers of paper in μPADs. I present the ability to tune speed, distance, and time at which the fluid travels with the formation of a microchannel between the layers. By increasing both the number of paper layers and the distance between them, the solution flux is dramatically increased in agreement with theoretical predictions. However, experimental flow rates deviate from predictions at large spacings. The detailed characterization and current understanding of the fast flow properties allow us to design assays that take seconds to complete instead of minutes along with improved analytical performance.Developing a selective test for Al(III) in food, mining and water samples is the goal of the last study. To address this need, a fluorescent ligand selective for Al(III) was synthesized and characterized on a μPAD for the first time. A distance-based μPAD for Al(III) exhibited a linear response from 2–55 ppm and a limit of detection of 2 ppm. This chemistry was also further developed with a radial uPAD that measures diameter of a color response as opposed to distance. Despite a smaller linear range with this radial device, the limit of detection is 0.9 ppm, which is below the concentration relevant to plant health. All three of these studies highlight improving the analytical performance of μPADs with carefully selected assays and deliberate device design.
Open Access
Development of electrochemical imaging methods using micro-electrode arrays and microfluidic networks
(Colorado State University. Libraries, 2016) Wydallis, John B., author; Henry, Charles S., advisor; Van Orden, Alan, committee member; Barisas, B. George, committee member; McNaughton, Brian R., committee member; Dandy, David S., committee member
Distribution of molecules over space and time drive a multitude of macroscopic and microscopic biological processes. There is a need to design novel imaging techniques that can map molecular distributions with spatiotemporal resolution. In this thesis, new electrochemical approaches to provide spatiotemporal imaging are presented. The bulk of this work utilizes high-density platinum micro-electrode arrays fabricated using complementary metal oxide semiconductor (CMOS) fabrication techniques as well as microfluidics and carbon-based electrodes fabricated using soft lithography fabrication techniques. The systems described in this dissertation focus on quantification of biologically relevant neurotransmitters, mainly catecholamines and nitric oxide with concentration ranges from nM to mM. The pitch, or resolution between two "pixels" of electrochemical data, was 250 µm for microfluidic based sampling methods and 12.5 µm for the CMOS based sensors. Descriptions of fabrication methods for the carbon based electrodes and CMOS electrodes are described in this work. Finally, potential future directions of this technology is discussed in the final chapter.
Embargo
Development of low-cost capillary driven immunoassays for improved medical diagnostics
(Colorado State University. Libraries, 2023) Link, Jeremy S., author; Henry, Charles S., advisor; Van Orden, Alan, committee member; Ackerson, Christopher J., committee member; Kipper, Matt J., committee member
Rapid medical diagnostics are a crucial part of an effective healthcare system. While traditional laboratory diagnostic methods are well established and sensitive, they are also time consuming and expensive. Point of care (POC) diagnostics offer an attractive alternative to traditional testing for more affordable, fast results. Their simplicity allows for POC devices to be run quickly by untrained personnel, but the simplicity often limits their detection range and sensitivity. In this dissertation I discuss affordable, capillary-driven immunoassay devices that are capable of passively delivering reagents associated with a traditional well-plate enzyme linked immunosorbent assay (ELISA) to test strips. These devices are made of patterned and laser cut double-sided adhesive. When stacked and laminated together, the patterns cut from the layers form hollow microfluidic channels that can passively transport fluids through capillary action. The devices in this dissertation require only a single end-user step to perform a sandwich immunoassay, and signal from the enzyme/substrate reaction is detectable in under 30 min. Chapter 2 discusses the first application for visual detection of SARS-CoV-2 in these affordable capillary-driven immunoassay devices. The device in this chapter uses the enzyme horseradish peroxidase (HRP) and the substrate 3,3',5,5'-tetramethylbenzydine (TMB) to produce signal at the test line. Upon sample addition, the device channels fill, rehydrating the detection antibody and substrate dried on conjugate release pads that are stored in the channels of the device. Within 20 min, target, reagents, and washing steps are passively delivered to a nitrocellulose test strip containing a capture antibody test line. The device performance was compared to a well-plate ELISA, and the detection limits for inactivated SASR-CoV-2 were 86 PFU/mL and 8 PFU/mL for the device and ELISA respectively. A dose response curve was also generated for spiked nasal swab samples with a detection limit of 222 PFU/mL, demonstrating the device's use with complex biological samples. Chapter 3 expands on the work in Chapter 2 by demonstrating an alternative detection method. Chemiluminescent immunoassays are highly sensitive assays that rely on the energy provided by a chemical reaction to excite electrons. When the electrons move back to the ground state, they produce light that can be detected with an imager. In Chapter 3, I demonstrate the first example of a one-step, capillary driven immunoassay for chemiluminescent detection. The device is similar to that in Chapter 2, but the detection system relies on the reaction between HRP and a luminol based substrate to detect SARS-CoV-2 antigen. This work was done in collaboration with Burst Diagnostics Inc. and will be published when the appropriate patents and protections are in place. Chapter 4 introduces the first capillary driven enzyme-linked immunoassay for the simultaneous detection of multiple biomarkers. This multiplexed device is made of the same inexpensive materials as the previous chapters, but the microfluidic channels are designed in such a way that reagents are delivered to two, spatially separated test strips. This separation allows for simultaneous detection of two targets without cross-reactivity between reagents, reducing the chance of false positives. To demonstrate the purpose of this device, they were used to detect SARS-CoV-2 antigen on one test strip, and influenza antigen on the other. The illnesses caused by these two viruses lead to very similar symptoms, so distinguishing between the two illnesses from a single device would be beneficial. Dose response curves were gathered for both antigens, and the device was able to detect both diseases visually without false positives on the other test strip. Another form of multiplexed detection is simultaneous detection of two targets. To demonstrate this, SARS-CoV-2 and influenza antigen were detected simultaneously. Additionally, SARS-CoV-2 virus and c-reactive protein (CRP), a biomarker that can be used to determine the severity of COVID-19 cases, were detected simultaneously. This multiplexed assay has the potential to tell a healthcare provider 1) if an infection is or is not SARS-CoV-2, and 2) what level of care might be needed. This dissertation introduces three capillary driven immunoassay devices primarily for the use of detecting communicable diseases. The devices all run from a single end-user step, and fully automate the steps required for a more time consuming and expensive ELISA. Although the focus of this dissertation was on detecting communicable diseases, these devices can (and are) being further developed for chronic illnesses. In the future, by swapping the antibodies used in the immunoassay, the applications of these devices are innumerable. Additionally, different detection methods, such as fluorescent, electrochemical, and further chemiluminescent work could continue to push the detection limit down, widening the application of these devices even further.
Open Access
Effect of additives on laser ignition and compression ignition of methane and hydrocarbons in a rapid compression machine
(Colorado State University. Libraries, 2016) Boissiere, Andrew, author; Marchese, Anthony, advisor; Yalin, Azer, advisor; Van Orden, Alan, committee member
Despite recent efforts to develop new energy systems that do not rely on combustion of fossil fuels, internal combustion (IC) engines powered on fossil fuels (i.e. gasoline, diesel or natural gas) will remain as an integral component of the global energy portfolio for years to come and increasing the efficiency of IC engines will be a necessary means to reduce fossil fuel consumption and greenhouse gas emissions. In this study, the effect of fuel additives on natural gas and gasoline spark ignited engines were investigated using laser ignition and compression ignition experiments performed in a rapid compression machine (RCM). The goal of the laser ignition study was to examine the effect of additives to extend the lean limit of natural gas engines, while the goal of the compression ignition experiments were to examine the ability of fuel additives to decrease knock propensity of gasoline fuels. For the laser ignition study, methane/air mixtures containing various fuel additives at temperatures and pressures representative of the compressed conditions inside an internal combustion engine were ignited in the RCM. An Nd:YAG laser operating at a wavelength of 1064 nm was used to ignite methane/air mixtures ranging in equivalence ratio from stoichiometric down to 0.4 using a rapid compression machine (RCM). Experiments were conducted to determine the lean limit, minimum spark energy (MSE), and minimum ignition energy (MIE). Three different fuel additives at varying concentrations were tested. The results show that laser ignition exhibits a stochastic behavior which must be interpreted statistically. A 90% probability of occurrence is used to evaluate the MSE and MIE which resulted in MSE90=2.3 mJ and MIE90=7.2 mJ for methane/air mixtures of equivalence ratio equal to 0.4. The lean limit, defined as greater than 90% of the theoretically possible heat release, was found as equivalence ratio of 0.47 for methane/air mixtures. All three fuel additives resulted in a reduction of the baseline methane/air MIE, while only DTBP and NM resulted in a reduction of the lean limit. For the compression ignition study, the effects of various fuel additives on the auto-ignition characteristics of gasoline reference fuels were studied in the RCM. Fuel additives were added to stoichiometric fuel/air mixtures of liquid gasoline surrogate fuels and were auto-ignited in a RCM. Experiments were conducted to determine the ignition delay, heat release rate, and net heat release of the gasoline surrogate/air mixtures with and without fuel additives. Five different gasoline fuel additives were tested in an Iso-Octane and Toluene Reference base fuel. The results show that the majority of the additives increased the reactivity and decreased the ignition delays of the base fuels. However, a select few of the tested additives decreased the reactivity and increased the ignition delays of the base fuel at select conditions, which could be beneficial to increasing the efficiency of internal combustion engines.
Open Access
Energy storage and conversion materials: Part 1, Synthesis and characterization of ruthenium tris-bipyridine based fullerene charge transfer salts as a new class of tunable thermoelectric materials; Part 2, Synthesis and characterization of polymer thin films for use as a lithium ion battery separator
(Colorado State University. Libraries, 2013) Bates, Daniel James, author; Elliott, C. Michael, advisor; Prieto, Amy L., advisor; Finke, Richard G., committee member; Van Orden, Alan, committee member; Crans, Debbie C., committee member; Dandy, David S., committee member
To view the abstract, please see the full text of the document.
Open Access
Fundamental insights into the alloy miscibility and surface chemistry of metal nanoclusters
(Colorado State University. Libraries, 2022) Anderson, Ian David, author; Ackerson, Christopher J., advisor; Shores, Matthew P., committee member; Van Orden, Alan, committee member; Prenni, Jessica E., committee member
The fascinating and varied properties of metals have captured people's imaginations long before the advent of modern chemistry. Basic metallurgy, dating as far back as the fourth millennium BC, remains one of the most consequential processes in human history. Today we enjoy an effective mastery over metals in their continuous bulk state, complete with alloy phase diagrams which describe properties as a function of temperature and percent composition. The coordination chemistry of single-metal complexes is similarly well-studied, initiated by the pioneering work of Alfred Werner in 1893. Size-dependent properties found at these two extremes (continuous bulk versus discrete molecular) have facilitated a myriad of applications in nearly every aspect of society through the development of unique materials. Between bulk metals and coordination complexes exists a new and rapidly growing area of chemistry concerned with clusters containing several to hundreds of metal atoms. Although there are commonalities shared with both molecular and bulk systems, these clusters also exhibit notable behavioral differences which can often not be explained through simple classical interpretations. The challenge of working with these species has been considerably eased within the past fifteen years from advancements in synthesis and characterization, in particular for monolayer-protected clusters (MPCs) of gold. These MPCs can be synthesized to precise monodispersity and are therefore defined by a molecular formula instead of the more general average size and dispersity used to define larger (typically > 3 nm) colloidal nanoparticles. Minor adjustments to the nuclearity, metal atom identity, or surface chemistry of gold MPCs have been shown to induce extensive changes in their observed properties and overall stability. Complete regiochemical control over both the metal core composition and surface ligand environment is therefore of immediate interest. This goal is especially important for potential applications in catalysis, electronics, biolabeling, energy conversion/storage, and theranostics. The work described herein covers two overarching themes: i) examining the alloying ability of gold MPCs with various late transition metals, and ii) an investigation of MPC surface chemistry through the introduction of multidentate ligands. Synthesis and analysis of the classically-immiscible rhodium-gold system using Au25(SR)18 as a template offers a fresh perspective of alloy gold MPCs containing metals with an open d-shell, alongside an updated framework for understanding MPC stability. Acetylide-for-thiolate, thiolate-for-acetylide, and intercluster exchange between acetylide- and thiolate-protected gold MPCs reveal lability which cannot be adequately rationalized through traditional MPC ligand exchange arguments. The first example of a thiolated gold MPC co-protected by several oxygen-containing diglyme ligands is described, which exhibits enhanced thermal stability as a result of the robust gold-diglyme, thiolate-diglyme, and diglyme-diglyme interactions. A straightforward synthetic pathway to fully dithiolate-protected gold MPCs is also described, as well as a post-synthetic ligand exchange study showcasing their resistance against incoming monodentate thiol exchange. Lastly we provide a series of vignettes detailing our efforts towards the synthesis of various MPCs using metals such as osmium, iridium, and bismuth. Overall these studies afford fundamental advancements in the understanding of soluble, air-stable metal nanoclusters and open up new opportunities for their applications.
Open Access
Fundamental studies of reverse micellear aggreagates by multinuclear and multidimensional NMR spectroscopy
(Colorado State University. Libraries, 2012) Sedgwick, Myles, author; Levinger, Nancy, advisor; Crans, Debbie, advisor; Henry, Chuck, committee member; Roess, Deborah, committee member; Van Orden, Alan, committee member
Self-assembled reverse micellar aggregates using cationic, anionic and non-ionic surfactants have been investigated by multinuclear and multidimensional NMR. By utilizing 51V NMR chemical shifts and line widths of decavanadate, the local proton concentration and characteristics of the reverse micellar environment are measured. There is a distinct environmental change on the interior of the reverse micelle depending on the surfactant used. 51V NMR signals for decavanadate inside an Igepal CO-520, non-ionic surfactant, reverse micelle display sharp signals indicating the decavanadate experiences water like environment. Conversely, 51V NMR signals for decavanadate inside an Igepal CO-610/430 mixed reverse micelle show significant broadening of the decavanadate signal indicating that the environment inside the reverse micelle in which the decavanadate resides is more viscous. These data provide a description in that the water pool of non-ionic surfactants can be compared. Time resolved anisotropy decays, ultrafast time-resolved transient absorption, and 2D NMR spectroscopy have been used to study proton transfer reactions in the interiors of Igepal-CO 520, CTAB and AOT reverse micelles. For ѡ0 = 10 reverse micelles formed with anionic AOT surfactant, the HPTS proton transfer dynamics are similar to dynamics in bulk aqueous solution, and the corresponding 1H 2D NOESY NMR spectra display no cross peaks between HPTS and AOT consistent with the HPTS residing, well-hydrated by water, in the interior of the reverse micelle water pool. In contrast, ultrafast transient absorption experiments show no evidence for HPTS photoinduced proton transfer reaction in reverse micelles formed with the cationic CTAB surfactant. In CTAB reverse micelles, clear cross peaks between HPTS and CTAB in the 2D NMR spectra show that HPTS embeds in the interface. Similar behavior is observed for HPTS in Igepal reverse micelles as in CTAB reverse micelles and we interpret the slowed dynamics in the same manner. The 2D NMR spectra for HPTS in Igepal-CO 520 reverse micelles shows interaction that imply the HPTS molecule is rested near the interface inside the reverse micelle. Dynamic light scattering (DLS) and 1H NMR spectroscopic experiments suggest that the assembly of the reverse micellar aggregates depends on non-polar solvent and co-surfactant used. Two different self-assembled particles form in the AOT/cholesterol /water in cyclohexane, where in the similar system of AOT/cholesterol /water in 1-octanol there is only one particle present. In microemulsions employing 1-octanol as the continuous medium, AOT reverse micelles form in a dispersed solution of cholesterol in 1-octanol. Although the size distribution of self-assembled particles is well-known for many different systems, evidence for simultaneous formation of two distinctly sized particles in solution that are chemically different is unprecedented. By utilizing optical spectroscopic techniques, 2D NMR, and DLS, the structure of the non-ionic reverse micelles have been characterized. The impact of adding cholesterol, a biologically relevant molecule, has on the structure of the reverse micellar solutions has also been shown.
Open Access
Hot injection synthesis and characterization of copper antimony selenide non-canonical nanomaterials toward earth-abundant renewable energy conversion
(Colorado State University. Libraries, 2018) Agocs, Daniel B., author; Prieto, Amy L., advisor; Buchanan, Kristen, committee member; Sambur, Justin, committee member; Sites, James R., committee member; Van Orden, Alan, committee member
Renewable and carbon-free energy generation has become a critically important field as the global population continues to increase. Further, the ample supply afforded by natural resources such as sunlight and geothermal heat are attractive options that can be harnessed using technologies like photovoltaics and thermoelectrics. There is a growing interest in searching for novel materials that exhibit high efficiencies in these devices, ideally composed of earth abundant, non-toxic materials. This search is aided by theory, which has identified several families of compounds with interesting structure types that may exhibit properties amenable to incorporation in high efficiency devices. However, many of these materials have not yet been thoroughly evaluated for photovoltaics or thermoelectrics. This dissertation is focused on developing the synthesis and describing the basic characterization of nanoparticles of members of the compounds in the Cu-Sb-Se series, of which syntheses have been developed for Cu3SbSe4 and Cu3SbSe3 and are described in this dissertation. Herein, we describe a hot-injection route for the formation of Cu3SbSe4 and Cu3SbSe3 nanocrystals. In order to place this work in context, the first chapter of this dissertation provides a detailed summary of the literature investigating the Cu-Sb-Se family of compounds. Here, the highest thermoelectric efficiencies have been achieved for Cu3SbSe4 while Cu3SbSe3 is not yet comparable thermoelectrically to Cu3SbSe4 nor as efficient as the photovoltaic material CuSbSe2. The second chapter details the development of a hot injection synthesis of Cu3SbSe4 nanocrystals. In order for these materials to be applied as electronic materials in real devices, their stability and function under ambient conditions is of interest. Therefore, we studied the changes in electronic conductivity as a function of exposure to atmosphere. The conductivity increase was attributed to a hole mobility increase, and this was further correlated to structural oxidations. Chapter 3 details development of a synthesis for phase-pure Cu3SbSe3 nanodiscs. This material has become of interest recently for photovoltaic applications due to its acceptable band gap for solar absorption. While the synthesis of nanoscale Cu3SbSe3 has been reported, these results have not been reproduced, and property measurements among these limited works vary. Therefore, a robust synthesis was developed and initial optical and photoelectrochemical properties were measured and are reported in this dissertation that demonstrate photoactivity in thin films of the Cu3SbSe3 nanodiscs. In the fourth chapter, a more vigorous exploration of the nanodisc morphology observed in Cu3SbSe3 is reported. As a degree of self-assembly is observed in stacks of the nanodiscs, the morphology is investigated to understand how tuning nanocrystal morphology, size, and surface might affect the resulting particle interactions. To this end, a double injection synthesis was developed wherein the products exhibit optoelectronic properties similar to those of the original single injection reaction. Chapter 5 entails the electrochemical investigation of the copper antimony selenide nanostructures. Electrochemical measurements to experimentally elucidate the electronic structure are reported, and a photovoltaic architecture is proposed for a Cu3SbSe3-absorber layer device. Further, the presence of a thiol has been demonstrated to be critical to not only morphology within the Cu3SbSe3 synthesis but also the product phase formation. Therefore, initial measurements and challenges with in-situ electrochemical exploration of precursor reactivity are reported. Finally, chapter 6 briefly emphasizes the major findings within this dissertation. The experimental results for both Cu3SbSe4 and Cu3SbSe3 syntheses are reiterated. Further, additional directions for future work with this system are suggested. These primarily focus on fabrication of a Cu3SbSe3 photovoltaic cell to begin understanding photogenerated carrier transport. This can be extended through applying knowledge gained by understanding disc stacking to improve film deposition and electronic properties within Cu3SbSe3 materials. Finally, development of an electrochemical measurement system for use in oleylamine media would allow a new perspective on investigation of colloidal nanocrystalline formation. These proposed experiments would contribute to their respective fields in the broader context of expanding search criteria for novel photovoltaic materials, addressing the challenge of grain boundary recombination sites in photovoltaic nanocrystals, and providing tools for exploring nanoparticle synthesis.
Open Access
I. Ground-state association between phenothiazine and tris(diimine)ruthenium(II) complexes: its role in highly efficient photoinduced charge separation. II. Ligand modifications of cobalt complexes to increase efficiency of electron-transfer mediators in dye-sensitized solar cells
(Colorado State University. Libraries, 2012) Weber, John, author; Elliott, C. Michael, advisor; Rappe, Anthony, committee member; Levinger, Nancy, committee member; Woody, Robert, committee member; Van Orden, Alan, committee member
Supramolecular triad assemblies consisting of a central trisbipyridineruthenium(II) chromophore (C2+), with one or more appended phenothiazine electron donors (D) and a diquat-type electron acceptor (A2+) have been shown to form long-lived photoinduced charge separated states (CSS) with unusually high quantum efficiency. Up to now, there has been no explanation for why such large efficiencies (often close to unity) are achieved from these systems when other, seemingly similar, systems are often much less efficient. In the present study, using a bimolecular system consisting of chromophore-acceptor diad (C2+-A2+) and an N-methylphenothiazine donor we demonstrate that a ground-state association exists between the RuL32+ and the phenothiazine prior to photoexcitation. It is this association process that is responsible for the efficient CSS formation in the bimolecular system and, by inference, also must be an essential factor in the fully intramolecular process occurring with the D-C2+-A2+ triad analogs. Alkyl-substituted bipyridine ligands in cobalt II/III complexes were modified in order to serve as efficient electron-transfer mediators in dye-sensitized solar cells. Attempts at halogen substitution reactions are described. Ultimately isopropyl groups appended to bipyridine ligands were modified by introducing a hydroxyl group at the benzylic position. The electrochemical behavior of the modified ligand is described, as well as its performance as part of a cobalt complex electron-transfer mediator in dye-sensitized solar cells.
Open Access
Imaging individual barium atoms in solid xenon by scanning of a focused laser for use in the nEXO experiment
(Colorado State University. Libraries, 2019) Chambers, Christopher, author; Fairbank, William, advisor; Lee, Siu Au, committee member; Wilson, Robert J., committee member; Van Orden, Alan, committee member
Neutrinoless double beta decay (0νββ) is a non-standard model decay process in which two simultaneous beta decays occur, with no emission of neutrinos. This decay is of great interest. If observed, it will demonstrate that the neutrino and anti-neutrino are not distinct. This decay also violates lepton number conservation, a requirement for some theories seeking to explain the matter-antimatter asymmetry of the universe. A measurement of the decay half-life will also give information on the absolute mass scale of the neutrinos. EXO-200 and nEXO use liquid xenon (LXe) time projection chambers (TPC) to search for 0νββ decay. EXO-200 first observed two neutrino double beta decay (2νββ) in xenon-136, the rarest decay ever observed. A low background measurement is vital to maximizing sensitivity to the 0νββ decay mode, yet to be observed. In this dissertation, research and development of a technique for positive identification of the barium-136 daughter (barium tagging) is presented. It is desirable to incorporate barium tagging into the future nEXO detector, as it provides discrimination against all background except for the 2νββ decay mode. The scheme being developed in this work involves extraction of the barium daughter in solid xenon with a cryogenic probe, followed by matrix-isolation fluorescence spectroscopy to tag the barium atom. This work focuses on the detection of individual barium atoms in a prepared solid xenon sample. Single atom sensitivity has been achieved, and a method for imaging of individual atoms by scanning of a focused laser has been demonstrated.
Open Access
Imaging single barium atoms in solid xenon for barium tagging in the nEXO neutrinoless double beta decay experiment
(Colorado State University. Libraries, 2016) Walton, Timothy, author; Fairbank, William M., advisor; Berger, Bruce, committee member; Van Orden, Alan, committee member; Wilson, Robert, committee member
The nEXO experiment will search for neutrinoless double beta decay of the isotope 136Xe in a ton-scale liquid xenon time projection chamber, in order to probe the Majorana nature of neutrinos. Detecting the daughter 136Ba of double beta decay events, called barium tagging, is a technique under investigation which would provide a veto for a background-free measurement. This would involve detecting a single barium ion from within a macroscopic volume of liquid xenon. One proposed barium tagging method is to trap the barium ion in solid xenon at the end of a cold probe, and then detect it by its fluorescence in the solid xenon. In this thesis, new studies on the spectroscopy of deposits of Ba and Ba+ in solid xenon are presented. Imaging of barium atoms in solid xenon is demonstrated with sensitivity down to the single atom level. Achievement of this level of sensitivity is a major step toward barium tagging by this method.
Open Access
Insights into the biosphere-atmosphere exchange of organic gases from seasonal observations over a ponderosa pine forest
(Colorado State University. Libraries, 2020) Fulgham, S. Ryan, author; Farmer, Delphine, advisor; Ham, Jay M., committee member; Ravishankara, Akkihebbal R., committee member; Van Orden, Alan, committee member
The biosphere-atmosphere exchange of organic gases over forests contributes to the formation of air pollution and the availability of forest nutrients. Forests can be both sources and sinks of volatile and semi-volatile organic compounds to the atmosphere. The role that forests play in controlling organic acid concentrations remains poorly understood, with multiple model-measurement comparisons reporting missing sources of formic acid. Large, missing sources of organic acids have been identified over different forested environments. Despite substantial seasonal variability in forest productivity and environmental conditions, a paucity of observations, during seasons other than summertime, is available. Although forest fires are a major source of hazardous organic gases and particulate matter, few measurements of semi-volatile organic compounds emitted by forest fires are available from within 1 km of the fire. Detection further-afield cannot disambiguate between chemistry at the source of the fire and chemical aging as a smoke plume traverses the atmosphere. Near-field observations are needed to characterize emissions attributable to combustion and pyrolysis processes. To improve understanding of processes that control the atmospheric budgets of organic acids, water-soluble pollutants with physicochemical properties similar to organic acids, and fire-emitted phenolic compounds, this dissertation reports measurements of the biosphere-atmosphere exchange of a suite of organic gases over a Rocky Mountain ponderosa pine forest in Colorado over four, seasonally-representative measurement campaigns. First, we report seasonally persistent, upward fluxes of organic acids, which are neither explained by direct emissions nor secondary production. Second, we present evidence for equilibrium partitioning into and out of water films on forest surfaces as both a missing source and sink of isocyanic acid and small alkanoic acids. Finally, we report significant enhancement of organic acids, phenolic compounds, and other nitrogen containing compounds during initiation of a controlled forest fire compared with the remainder of the burn. Nitrated phenols are rapidly produced and enhanced more than phenolic precursors during initial, higher temperature conditions. We attribute greater enhancement of nitrated phenols to high NOx emissions under higher temperature conditions.