Browsing by Author "Bartels, Randy, committee member"
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Item Open Access Accessing molecular structure and dynamics of photoelectrochemical systems with nonlinear optical spectroscopy(Colorado State University. Libraries, 2022) Farah, Yusef Rodney, author; Krummel, Amber T., advisor; Szamel, Grzegorz, committee member; Barisas, B. George, committee member; Bartels, Randy, committee memberPhotoelectrochemical cells (PEC) are a class of solar energy device that have a variety of applications and can be used to directly generate electricity or convert the sun's energy in the form of chemical bonds through photosynthetic processes. The first PEC dates to Becquerel's discovery of the photovoltaic effect in 1839; and, after nearly 200 years of its first creation, the PEC is constantly evolving with the discovery of new fabrication techniques and materials. Sunlight harvesting materials are used in PECs to capture the sun's radiation and drive electron transfer and photocatalytic reactions. Understanding the photophysical properties of the materials used within PEC chemical systems informs on the development of high-performance, low-cost, and sustainable solar energy devices needed to address current global climate challenges and meet societal energy demands. Chemical systems in PEC architectures are nontrivial and often rely on several components working harmoniously in tandem with one another to stimulate photovoltaic or photocatalytic processes. Dye-sensitized solar cells (DSSCs) are a type of photovoltaic PEC that use molecular chromophores to absorb light, transfer electrons to a semiconductor, and accept electrons from an electrolyte. Local environmental structure of the chromophore can either promote or hinder these electron transfer events within a device. To this end, investigating the molecular structure of the chromophore, including the parameters that influence the structure, is necessary for fabricating DSSCs with optimal efficiency. The work presented in this dissertation utilizes the nonlinear optical spectroscopic technique of heterodyne-detected vibrational sum frequency generation (HD-VSFG) to investigate the interfacial structure of N3-dye, a popular chromophore used within DSSC devices. It is discovered that the interfacial structure of N3 is influenced by the substrate, pH conditions upon deposition to the substrate, and by the presence of an electrolyte. Additionally, the work presented herein investigates exciton dynamics of monolayer MoS2 photoanodes within an operational PEC. Monolayer transition metal dichalcogenides (TMDs), such MoS2, are two-dimensional semiconducting materials with fascinating photophysical properties. Only recently have monolayer TMDs been investigated for their integration within optoelectronic devices, such as PECs. By utilizing ultrafast transient absorption (TA) spectroscopy, unique exciton properties of the MoS2 photoanode are identified within operational conditions. Photocurrent generation via ultrafast hot carrier extraction is discovered, challenging the preconceived notions of the Shockley-Queisser limit; further, we explore the dynamic control of the exciton energy by tuning an external voltage bias to the PEC. PEC chemical environments are ubiquitous and the photophysical properties are dependent on many underlying parameters. Set forth in this dissertation is the foundation for applying the nonlinear optical techniques of HD-VSFG and TA across a variety of chemical systems pertaining to PECs and assessing data within an established theoretical framework to elucidate molecular structure and dynamics.Item Open Access Characterizing the diffusional behavior and trafficking pathways of Kv2.1 using single particle tracking in live cells(Colorado State University. Libraries, 2013) Weigel, Aubrey, author; Krapf, Diego, advisor; Tamkun, Michael, committee member; Bamburg, James, committee member; Bartels, Randy, committee memberStudying the diffusion pattern of membrane components yields valuable information regarding membrane structure, organization, and dynamics. Single particle tracking serves as an excellent tool to probe these events. We are investigating of the dynamics of the voltage gated potassium channel, Kv2.1. Kv2.1 uniquely localizes to stable, micro-domains on the cell surface where it plays a non-conducting role. The work reported here examines the diffusion pattern of Kv2.1 and determines alternate functional roles of surface clusters by investigating recycling pathways using single particle tracking in live cells. The movement of Kv2.1 on the cell surface is found to be best modeled by the combination of a stationary and non-stationary process, namely a continuous time random walk in a fractal geometry. Kv2.1 surface structures are shown to be specialized platforms involved in trafficking of Kv channels to and from the cell surface in hippocampal neurons and transfected HEK cells. Both Kv2.1 and Kv1.4, a non-clustering membrane protein, are inserted and retrieved from the plasma membrane at the perimeter of Kv2.1 clusters. From the distribution of cluster sizes, using a Fokker-Planck formalism, we find there is no evidence of a feedback mechanism controlling Kv2.1 domain size on the cell surface. Interestingly, the sizes of Kv2.1 clusters are rather governed by fluctuations in the endocytic and exocytic machinery. Lastly, we pinpoint the mechanism responsible for inducing Kv2.1 non-ergodic dynamics: the capture of Kv2.1 into growing clathrin-coated pits via transient binding to pit proteins.Item Open Access Combined multispectral/hyperspectral remote sensing of tropospheric aerosols for quantification of their direct radiative effect(Colorado State University. Libraries, 2013) McGarragh, Gregory R., author; Stephens, Graeme, advisor; Kreidenweis, Sonia, committee member; Vonder Haar, Thomas, committee member; Bartels, Randy, committee memberScattering and absorption of solar radiation by aerosols in the atmosphere has a direct radiative effect on the climate of the Earth. Unfortunately, according to the IPCC the uncertainties in aerosol properties and their effect on the climate system represent one of the largest uncertainties in climate change research. Related to aerosols, one of the largest uncertainties is the fraction of the incident radiation that is scattered rather than absorbed, or their single scattering albedo. In fact, differences in single scattering albedo have a significant impact on the magnitude of the cooling effect of aerosols (opposite to that of greenhouse gasses) which can even have a warming effect for strongly absorbing aerosols. Satellites provide a unique opportunity to measure aerosol properties on a global scale. Traditional approaches use multispectral measurements of intensity at a single view angle to retrieve at most two aerosol parameters over land but it is being realized that more detail is required for accurate quantification of the direct effect of aerosols, in particular its anthropogenic component, and therefore more measurement information is required. One approach to more advanced measurements is to use not only intensity measurements but also polarimetric measurements and to use multiple view angles. In this work we explore another alternative: the use of hyperspectral measurements in molecular absorption bands. Our study can be divided into three stages the first of which is the development of a fast radiative transfer model for rapid simulation of measurements. Our approach is matrix operator based and uses the Padé approximation for the matrix exponential to evaluate the homogeneous solution. It is shown that the method is two to four times faster than the standard and efficient discrete ordinate technique and is accurate to the 6th decimal place. The second part of our study forms the core and is divided into two chapters the first of which is a rigorous sensitivity and optimal estimation based information content study that explores the use of measurements made by a MODIS type instrument combined with measurements made by an instrument similar to GOSAT TANSO-FTS which supplies hyperspectral measurements of intensity and polarization in the O2 A-band and the 1.61- and 2.06-μm CO2 bands. It is found that the use of the hyperspectral bands provides a means to separate the effects of the surface and aerosol absorption from effects related to aerosol single scattering parameters. The amount of information increases significantly when the CO2 bands are included rather than just the more traditional O2 A-band, when polarization measurements are included, and when measurements are made at multiple view angles. We then present a retrieval using co-located observations of MODIS and GOSAT TANSO-FTS which are both also co-located with AERONET sites for validation purposes. We introduce an optimal estimation retrieval and perform this retrieval on our co-located observations. We choose a complete state vector to maximize the use of the information in our measurements and use an a priori constraint and regularization to arrive at a stable solution. In addition to the retrieved parameters, we also calculate a self contained estimation of the retrieval error. Validation with AERONET, for retrievals using MODIS plus TANSO-FTS measurements of intensity and polarization in all three bands indicate accuracies within 15% for optical thickness, 10% for fine mode mean radius, 35% for coarse mode mean radius, 15% for the standard deviation of fine mode mean radius, 25% for the standard deviation of the coarse mode mean radius, 0.04 for the real part of the index of refraction, and 0.05 for single scattering albedo. In addition to the retrieved parameters, we also validate the estimated retrieval error and find that the estimations have distributions that are tighter and within the broader distributions of real errors relative to AERONET. The third part of our study uses the retrieval results to calculate radiative fluxes, errors, and sensitivities at solar wavelengths along with aerosol radiative effect and effect efficiency. In addition, we outline how to propagate the errors in the retrieval through the flux calculations to provide an error estimation of the fluxes. These results are then validated against the corresponding AERONET products. It was found that the flux results were most sensitive to single scattering albedo while the size distribution and real part of the index of refraction also have significant effects. Relative to AERONET our fluxes are less accurate than an independent AERONET validation, due to uncertainties in our satellite based retrieval with accuracies within 13 Wm-2 for TOA upward, 9 Wm-2 for BOA upward, and 30 Wm-2 for BOA downward. The estimated errors also contained uncertainties but were in fact more conservative than the actual errors.Item Open Access Detection of small numbers of barium ions implanted in solid xenon for the EXO experiment(Colorado State University. Libraries, 2012) Cook, Shon, author; Fairbank, William, advisor; Lee, Siu Au, committee member; Roberts, Jacob, committee member; Bartels, Randy, committee memberIn an effort to discover the yet-unknown absolute masses of neutrinos, the goal of the Enriched Xenon Observatory is to observe neutrinoless double beta decay of 136Xe. Identification of this very rare decay may be difficult even with the best conventional efforts to reduce and reject radioactive background, thus requiring additional background rejection via detection of the daughter 136Ba nucleus. One method of detection is laser-induced fluorescence of the barium atom in solid xenon. Spectra of very small numbers of barium atoms in solid xenon, as few as 3 atoms, are reported for the first time. Demonstration of detection of Ba atoms with large fluorescence efficiencies gives promise for detecting single atoms in the near future. Results from experiments involving implantation of Ba+ ions in solid xenon are discussed. One narrow excitation peak was discovered from ion beam deposition that was not found in neutral deposits. Five new emission lines are found with this same excitation spectrum. Bleaching, annealing, and laser dependence of these lines are studied. The identification of the new Ba species as Ba+ or as a barium molecule is discussed.Item Open Access Experimental realization of two-isotope collision-assisted Zeeman cooling(Colorado State University. Libraries, 2013) Hamilton, Mathew, author; Roberts, Jacob, advisor; Lundeen, Stephen, committee member; Gelfand, Martin, committee member; Bartels, Randy, committee memberThe work presented in this thesis focuses on the demonstration and initial evaluation of a novel non-evaporative cooling method called collision-assisted Zeeman cooling. For this realization, an ultracold gas consisting of a mixture of 87Rb and 8Rb was used. Cooling was accomplished through interisotope inelastic spin-exchange collisions that converted kinetic energy into magnetic energy. Continual optical pumping spin polarized the 85Rb which ensured that only kinetic energy reducing collisions occurred and the scattered pump photons carried entropy out of the system. Thus, cooling of the ultracold gas can be achieved without requiring the loss of any atoms in order to do so. This represents a theoretical advantage over forced evaporative cooling, which is the current state-of-the-art cooling technique in most experiments. This thesis discusses the details of collision-assisted Zeeman cooling, as well as how the theory of the technique has been extended from cooling a single species to cooling with two species. There are many predicted advantages from using two rather than one species of atom in this type of cooling: greater flexibility in finding favorable spin-exchange collision rates, easier requirements on the magnetic fields that must be used, and an additional means to mitigate reabsorption (the primary limitation in many if not most non-evaporative cooling techniques). The experimental considerations needed to prepare a system that simultaneously trapped two isotopes to be able to perform collision-assisted Zeeman cooling are discussed. Because this cooling scheme is highly reliant on the initial conditions of the system, a focused experiment examining the loading of the optical trap with both isotopes of Rb was conducted and the results of that experiment are described here. The first experimental observations of spin-exchange collisions in an ultracold gas mixture of Rb are described as a part of this work. The experiments where collision-assisted Zeeman cooling were demonstrated are then described and evaluated. In this first implementation of the cooling technique the initial densities were too low and optical-pump-induced heating and loss too high for achieving the full predicted performance of the cooling technique. Through additional modeling, these limitations were understood and the necessary improvements for the next iteration of CAZ cooling experiments are laid out at the end of this work.Item Open Access Exploring model chemical systems through a new lens: combining novel microfluidic technology with infrared analysis techniques(Colorado State University. Libraries, 2016) Barich, Michael, author; Krummel, Amber T., advisor; Levinger, Nancy, committee member; Strauss, Steve, committee member; Kipper, Matt, committee member; Bartels, Randy, committee memberMultiple designer peptides, such as RADA-16, have been used as model systems to investigate the chemical parameters that influence protein folding and self-assembly processes. As such, the cause and effect relationship between folding outcomes and folding environmental factors have been extensively investigated. However, the mechanism of the folding process is largely unexplained due to the lack of an analysis technique that can capture structural changes on the time scale of the folding process. This thesis is the first step towards the ability to monitor the protein folding process with atomic structural resolution in real time. In this work, the sample handling capabilities of microfluidic devices are used to expand the experimental range of both infrared (IR) and two dimensional infrared (2D IR) measurement techniques. This includes the development of novel channel designs, overcoming IR compatibility issues, and setting precedent in monitoring chemical processes within microfluidic devices. Microfluidic channel geometries that perform microsecond mixing were developed to allow access to early reaction kinetics. A novel fabrication technique was developed to afford IR analysis methods to be utilized in microfluidic detection schemes. Lastly, model chemical reactions were studied in both Fourier transform IR microspectroscopy (FTIR microspectroscopy) and 2D IR spectroscopy experiments to highlight the applicability of the technology towards a broad range of chemical and biological systems, including the protein folding and self assembly processes.Item Open Access Femtosecond to nanosecond transient absorption studies of aqueous solvation and deprotonation dynamics in confinement(Colorado State University. Libraries, 2011) Cole, Richard Leo, author; Levinger, Nancy E., advisor; Bernstein, E. R. (Elliot R.), committee member; Ladanyi, Branka M., committee member; Van Orden, Alan K., committee member; Bartels, Randy, committee memberWe explore the use of logarithmic based optical delay in time-resolved data collection. We show that logarithmic spacing of data points provides an economical way to collect data over many decades of time which speeds data collection. We present a simple algorithm to generate time delay points for application in time-resolved data collection. We test the use of logarithmic vs. linear data collection over six orders of magnitude by measuring broadband femtosecond transient absorption (BFTA) spectra of HPTS in pH-7 water from femtoseconds to nanoseconds. Statistical analysis of logarithmic and linear data collection show that linear data collection shows a clear advantage by requiring a fewer number of time-delay points to achieve a given precision in subsequent data analysis. We investigate solvation dynamics (SD) via coumarin 343 (C343) in Aerosol OT (sodium bis(2-ethylhexyl) sulfosuccinate, AOT) reverse micelles with varying water content through broadband femtosecond transient absorption experiments. These studies build upon our previous studies of SD in the AOT reverse micelles through time-resolved fluorescence Stokes shift (TRFSS) experiments (J. Phys. Chem. B, 1998, 102, 2705) which limited data collection to approximately 100 ps. We extend the experimental time window to 2 nanoseconds and recover the entire solvation response. These results combined with steady-state spectra and reorientation dynamics indicate that C343 exists in two distinct populations within the reverse micelles which correlate with interfacial and core water. Our results suggest that translational motion of C343 may contribute to the total observed solvation response. We study excited state proton transfer (ESPT) of HPTS (8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt) in cationic (cetyltrimethylammonium bromide, CTAB), anionic (AOT), and nonionic (polyoxyethylene (5) isooctylphenyl ether, IGE) reverse micelles by BFTA. For larger AOT RM, ESPT dynamics are found to be approximately equal to the dynamics found in bulk water. As the size of the AOT RM approaches the size of the probe molecule, ESPT becomes increasingly quenched. For all sizes of CTAB RM, HPTS ESPT is found to be 10-20 times slower than HPTS ESPT in bulk water. This result combined with reorientation measurements suggest that HPTS resides at the interfacial region in CTAB RM and thus remains immobilized. In IGE RM, ESPT is 4-10 times slower than bulk water behavior which we contribute to immobilization of HPTS in the micelle interface. HPTS reorientational motion is hindered with respect to bulk HPTS motion. We measure the kinetic isotope effect (KIE) on HPTS ESPT dynamics and results suggest that the solvent plays a significant role in the observed dynamics only in the largest IGE reverse micelles. Steady-state absorption measurements show that HPTS exists in a unique environment within IGE RM which contrasts with HPTS in other nonionic reverse micelle systems.Item Open Access Precision measurement and symmetry properties of metastable hydrogen(Colorado State University. Libraries, 2022) Rasor, Cory M., author; Yost, Dylan, advisor; Roberts, Jacob, committee member; Mooney, Michael, committee member; Bartels, Randy, committee memberHydrogen has been an indispensable system to study during the development of quantum mechanics due to the simplicity of its atomic structure. Hydrogen maintains its utility today as an important tool for determining fundamental values such as the Rydberg and fine structure constants, as well as the proton charge radius. The work described in this thesis aims to use hydrogen for determining the proton Zemach radius, to search for anomalous spin-dependent forces, and to provide means for measuring the degree of parity violation within this simple system. An overview of a 2S1/2 hyperfine interval measurement is described, followed by a description of the apparatus used and finally a discussion of the systematic effects to be characterized. A proposed parity violation experiment is also described.Item Open Access Probing buried defects in zinc oxide nanoparticles using defect-mediated energy transfer(Colorado State University. Libraries, 2019) Beck, Lacey, author; Sambur, Justin, advisor; Prieto, Amy, committee member; Bartels, Randy, committee memberSemiconductor nanocrystals are actively explored as light harvesting materials for solar energy conversion and optoelectronic applications such as solar cells and light emitting diodes. The underlying processes in such systems include charge carrier generation, recombination, and transport. Defects influence these underlying processes by introducing energy levels inside the semiconductor bandgap that trap charge carriers. Despite their critical importance, the real space distribution of defect sites in semiconductor nanocrystals is often unknown. Here we demonstrate an ensemble-level energy transfer measurement approach to study the radiative defect states in a size series of ZnO nanocrystals. In this approach, ZnO defects that have energy levels inside the band gap engage in energy transfer with surface adsorbed AlexaFluor dye molecule acceptors. By quantifying the defect-mediated energy transfer efficiency as a function of nanocrystal size and reaction time, we determined that the radiative defect sites in ZnO are located between the nanocrystal core and surface (i.e., near surface sites) and the distance between the defect sites and the surface increases as the nanocrystals grow larger. The all-optical energy transfer approach represents a non-destructive characterization method to determine the spatial distribution of defects in semiconductor nanocrystals. The defect distributions can be correlated with optoelectronic or photocatalytic properties to elucidate structure/function relationships in a wide range of applications that involve light-matter interactions.Item Open Access Recovery of organ boundaries in electrical impedance tomography images using a priori data, optimization, and deep learning(Colorado State University. Libraries, 2019) Capps, Michael, author; Mueller, Jennifer, advisor; Cheney, Margaret, committee member; Pinaud, Olivier, committee member; Bartels, Randy, committee memberIn this thesis we explore electrical impedance tomography (EIT) and new aspects of the solutions to the inverse conductivity problem. Specifically we will focus on new methods for obtaining additional information from direct reconstructions on 2D domains using the D-bar method based on work by Nachmann in 1996 and Mueller and Siltanen in 2000. We cover the history of EIT as well as performing a review of relevant literature. Original work presented covers (1) an application of signal separation of cardiac and ventilation signals to the recovery of pulmonary measures and detection of air trapping in children with cystic fibrosis, (2) recovery of the boundaries of internal structures in EIT data sets using optimization of a priori data in the D-bar method, (3) recovery of the boundaries of internal structures in EIT data sets using deep neural networks applied to the scattering transform in the D-bar method. Results using both numerically simulated data and data collected on a tank with simulated organs made of agar are presented.Item Open Access Synthesis and characterization of fluorine-containing C60 derivatives and their charge transfer photophysics in organic photovoltaics(Colorado State University. Libraries, 2013) Larson, Bryon W., author; Strauss, Steven H., advisor; Rumbles, Garry, advisor; Rappé, Anthony, committee member; Bartels, Randy, committee member; Chen, Eugene, committee member; Robinson, Raymond S., committee memberTransformative advances in the science of new materials and technological solutions for energy conversion and storage require focused efforts from scientists across different disciplines. One of the major frontiers for modern chemistry is the molecular design of advanced materials from earth-abundant elements with finely tuned chemical, photophysical, and electronic properties. In this work, several highly efficient and, in some cases, highly regioselective synthetic methodologies have been developed for the first time that resulted in a wide array of versatile fullerene-based organic electron acceptors with highly tunable electronic properties. The classes of these newly synthesized and characterized materials include mono-perfluorocarbocyclic C60 derivatives, highly functionalizable ω-X-perfluoroalkylfullerenes (X = SF5, Br, I, COOEt), twenty one new isomers of deca-trifluoromethyl[60]fullerenes, and several new isomers of octa- and hexa-trifluoromethyl[60]fullerenes. Improved synthetic and separation techniques yielding up to multi-gram amounts of difluoromethylene[60]fulleroid and several other classes of technologically important perfluoroalkylfullerenes have also been developed, which enabled several organic photovoltaic-relevant studies using state-of-the art facilities at the National Renewable Energy Laboratory. This included the first experimental determination of an optimal driving force for the relative yield of free carrier generation in a family of polyfluorene polymers by using a series of trifluoromethylfullerene acceptors with a large range of electron affinities synthesized by the author. In another study, a judiciously selected series of acceptors was applied for a time-resolved microwave conductivity (TRMC) study that provided the first compelling experimental evidence that the yield for uncorrelated free charge generation in organic photovoltaic (OPV) device-relevant blends of donor:acceptor active layers is a function of carrier mobility. Finally, a new fullerene acceptor rivaling one of the champion fullerene derivatives, phenyl-C61-butyric acid methyl ester (PCBM), in OPV performance was studied by TRMC and in OPV devices.Item Open Access Theoretical and experimental investigation into the IR-VUV ion dip spectroscopy of amino acids and analogue systems(Colorado State University. Libraries, 2010) Clawson, Keven James, author; Bernstein, Elliot, advisor; Bartels, Randy, committee member; Fisher, Ellen, committee memberAmino acids are among the fundamental building blocks of life, and as such have been, and continue to be, of much interest for study. While gas phase spectroscopic studies can be very useful in obtaining information about molecular species (in this case various naturally occurring amino acids), the use of computational and theoretical methods can aid these studies in providing a more complete understanding of the properties and behaviors of these species. Here presented are the results of IR-VUV ion dip spectroscopy, coupled with a high-level theoretical examination of the spectroscopic results, including MP2 and CASSCF calculations. In IR-VUV ion dip spectroscopy, the isolated neutral molecules are ionized by a single photon of 10.5 eV energy 118 nm. If the neutral ground state amino acids are exposed to IR radiation prior to ionization, an IR spectrum can be determined by observation of the ion intensity of the different fragment mass channels. Species specifically studied include numerous naturally occurring aliphatic and aromatic amino acid species, and amino acid analogue species. In the case of the aliphatic amino acids, conformer specific decomposition pathways are observed spectroscopically, and further elucidated both through the study of III amino acid analogue species and through high level multiconfigurational CASSCF calculations. It is shown that upon ionization, the localized character of the charge, coupled with the geometry of the neutral parent molecule, directs the decomposition reaction of the molecule. In simple, small aliphatic amino acid and analogue species, these factors are unique to the conformation of the molecule, leading to conformer specific decomposition chemistry. In the amino acid species, the localized charge tends to occur either on one of the available moieties (carboxylic acid, amine, etc.), or on the carbon-carbon bond, depending on the conformer. The IR-VUV ion dip spectra obtained from the aromatic amino acid species, however, clearly demonstrate different photodecomposition behavior in the aromatic species when compared to the simple, smaller aliphatic species. The conformer specific chemistry which was observed in the smaller molecules was not evident in the aromatic species. This is likely due to the aromatic moiety containing the lowest energy, localized ion state for the molecule which does not lead to ion fragmentation. Thus, the conformer specific decomposition chemistry observed in the non-aromatic species is no longer observed in those species which contain an aromatic moiety.Item Open Access Transient absorption imaging of hemeprotein in fresh muscle fibers(Colorado State University. Libraries, 2022) Wang, Erkang, author; Wilson, Jesse, advisor; Bartels, Randy, committee member; Krapf, Diego, committee member; Tobet, Stuart, committee memberMitochondrial diseases affect 1 in 4000 individuals in the U.S. among adults and children of all races and genders. Nevertheless, these diseases are hard to diagnose because they affect each person differently. Meanwhile the gold standard diagnosis methods are usually invasive and time- consuming. Therefore, a non-invasive and in-vivo diagnosis method is highly demanded in this area. Our goal is to develop a non-invasive diagnosis method based on the endogenous nonlinear optical effect of the live tissues. Mitochondrial disease is frequently the result of a defective electron transport chain (ETC). Our goal is to develop a non-invasive way to measure redox within the ETC, specifically, of cytochromes. Cytochromes are iron porphyrins that are essential to the ETC. Their redox states can indicate cellular oxygen consumption and mitochondrial ATP production. So being able to differentiate the redox states of cytochromes will offer us a method to characterize mitochondrial function. Meanwhile, Chergui's group found out that the two redox states of cytochrome c have different pump-probe spectroscopic responses, meaning that the transient absorption (TA) decay lifetime can be a potential molecular contrast for cytochrome redox state discrimination. Their research leads us to utilize the pump-probe spectroscopic idea to develop a time-resolved optical microscopic method to differentiate not only cytochromes from other chemical compounds but also reduced cytochromes from oxidized ones. This dissertation describes groundbreaking experiments where transient absorption is used to reveal excited-state lifetime differences between healthy controls and an animal model of mitochondrial disease, in addition to differences between reduced and oxidized ETC in isolated mitochondria and fresh preparations of muscle fibers. For our initial experiments, we built a pump-probe microscopic system with a fiber laser source, producing 530nm pump and 490nm probe using a 3.5kHz laser scanning rate. The pulse durations of pump and probe are both 800fs. For the preliminary results, we have successfully achieved TA decay contrast between reduced and oxidized cytochromes in solution form. Then we have achieved SNR enhanced pump-probe image of BGO crystal particles with the help of the software- based adaptive filter noise canceling method. We also have installed a FPGA-based adaptive filter to enhance the pump-probe signals of the electrophoresis gels that contain different mitochondrial respiratory chain supercomplexes. However, because the noise floor was still 30 dB higher than shot noise limit, cytochrome imaging in live tissues was still problematic. We then built another pump-probe microscope with a solid- state ultrafast laser source. In that way, we do not need to worry about laser relative intensity noise (RIN) anymore, since the noise floor of the solid-state laser source can reach the shot noise limit at MHz region. One other advantage of the new laser source is that it can provide one tunable laser output that can be directly converted to the probe pulse with tunable center wavelength. Its tunability can cover the entire visible spectrum. We realized a pump-probe microscopy with a 520nm pump pulse and a tunable probe pulse. The tunability on the probe arm allows us to explore better pump-probe contrast between two redox states. What's more, I will introduce my preliminary results of utilizing supercontinuum generation in a photonic crystal fiber (PCF) to realize tunability on pump wavelength. In that way, more possibilities will be unlocked. And the hyperspectral pump-probe microscope will be able to distinguish more molecules.Item Embargo Transient phase microscopy using balanced-detection temporal interferometry and a compact piezoelectric microscope design with sparse inpainting(Colorado State University. Libraries, 2024) Coleal, Cameron N., author; Wilson, Jesse, advisor; Bartels, Randy, committee member; Levinger, Nancy, committee member; Adams, Henry, committee memberTransient phase detection, which measures the Re{∆N }, is the complement to transient absorption detection (Im{∆N }). This work extends transient phase detection from spectroscopy to microscopy using a fast-galvanometer point-scanning setup and compares the trade-offs in transient phase versus transient absorption microscopy for the same pump and probe wavelengths. The realization of transient phase microscopy in conjunction with transient absorption microscopy opens a new door to measure the excited-state kinetics with phase-based or absorption-based techniques; depending on the sample and the wavelengths in use, transient phase detection may provide a signal improvement over transient absorption. Up until this point, transient phase microscopy has been a neglected technique in ultrafast pump-probe imaging applications. Additionally, this work evaluates a miniature piezoelectric actuator to replace galvanometers in a compact point-scanning microscope design. Sparsity limitations present in the design are addressed by the construction of a Fourier-projections based inpainting algorithm which could enable faster imaging acquisition in future applications.