Phosphorus magnetic resonance spectroscopy (31P-MRS) permits the measurement of high-energy phosphates in the gastrocnemius muscle at rest and during recovery from exercise. This examination is a powerful non-invasive method to evaluate muscle mitochondrial function in vivo. Data analysis, however, can be both time-consuming and user-dependent. I designed a fully-automated system to quantify both resting and recovery spectra, followed by quantification of metabolite recovery kinetics. This included quantifying the recovery kinetics of adenosine diphosphate (ADP), an index of mitochondrial function which previously had not been properly characterized. I modeled the transition from ischemic-exercise to perfused-recovery as a step function, and fitted the ADP recovery with a second-order step-response function. Furthermore, I used nearest-neighbour methods to account for the effects of physical conditioning and metabolic work on the recovery kinetics. This fully-automated method of analyzing 31P-MRS data provides comprehensive results relevant to the diagnosis and monitoring of patients with metabolic myopathies.

The use of ion-selective field-effect transistors (ISFETs) as potentiometric microsensors was investigated. In the first stage, an instrument was designed and built to operate an array of ISFETs. A microcomputer was used for instrument control and acquisition of data. / The second phase of research focussed on the development of a pH sensitive radiotelemetric device that could eventually be used for the noninvasive monitoring of gastric pH. The first attempt used an ISFET as a variable resistor in a simple telemetry circuit. The drift in the pH dependent signal from this device was significant. The use of a differential sensor was studied as a possible way to minimize the effect of signal drift. This system measured the differential output of a pH ISFET and a pH insensitive ISFET. The pH insensitivity was due to an alkanethiol monolayer at the ISFET$ vert$solution interface. / It was shown that ISFETs are well suited for use as sensors in telemetry devices. The union of these previously independent research areas has been achieved.

The goal of this study was to design, characterize and test a flow-through extraction cell for rapid determination of toxic metals present in soil and sediment samples. / Based on a design elaborated by Jean Bouffard, a Teflon cell was first machined, but it appeared to be leaky and hard to disassemble without breaking the fritted glass discs. To overcome these difficulties, a poly ether ether ketone (PEEK) cell was machined and several parts were modified. Even though the shape and seal of the components seemed to be affected when heated, the cell was working at room temperature and proved promising for future work. / Finally, the EPA (Environmental Protection Agency) method 1311 was applied on some real samples, and the extracts were analyzed in order to get reference results that could eventually be compared to results given by extracts obtained with the flow-through cell.* / *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office.

<p> Commercially available Ga⁺ focused ion beam (FIB) instruments with nanometer size probe allows for in situ materials removal (sputtering) and addition (deposition) on a wide range of material. These spatially precise processes have enabled a wide range of nanofacbrication operations (e.g. specimen preparation for analysis by scanning electron microscope, transmission electron microscope, and secondary ion mass spectrometer). While there exists an established knowledge of FIB methods for sample preparation of hard materials, but FIB methodology remain underdeveloped for soft materials such as biological and polymeric materials. </p><p> As FIB is increasingly utilized for specimen preparation of polymeric materials, it is becoming necessary to formulate an information base that will allow established FIB techniques to be generalized to this spectrum of materials. A thorough understanding of the fundamental ion-solid interactions that govern the milling process can be instrumental. Therefore, in an effort to make the existing procedures more universally applicable, the interrelationships between target material, variable processing parameters, and process efficiency of the milling phenomena are examined. The roles of beam current, distance (i.e. step size) between successive FIB beam dwell and the time it spent at each dwell point (i.e. pixel dwell time) are considered as applied to FIB nanomachining of four different thermoplastic polymers: 1. low density polyethylene (LDPE), 2. high density polyethylene (HDPE), 3. Polystyrene (PS), and 4. nylon 6 (PA6). Careful characterization of such relationships is used to explain observed phenomena and predict expected milling behaviors, thus allowing the FIB to be used more efficiently with reproducible results. Applications involving different types of polymer composite fiber are presented.</p>

<p> The development of better energy conversion and storage devices, such as fuel cells and batteries, is crucial for reduction of our global carbon footprint and improving the quality of the air we breathe. However, both of these technologies face important challenges. The development of lower cost and better electrode materials, which are more durable and allow more control over the electrochemical reactions occurring at the electrode/electrolyte interface, is perhaps most important for meeting these challenges. Hence, full characterization of the electrochemical processes that occur at the electrodes is vital for intelligent design of more energy efficient electrodes. </p><p> X-ray absorption spectroscopy (XAS) is a short-range order, element specific technique that can be utilized to probe the processes occurring at operating electrode surfaces, as well for studying the amorphous materials and nano-particles making up the electrodes. It has been increasingly used in recent years to study fuel cell catalysts through application of the &Delta;&mgr; XANES technique, in combination with the more traditional X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) techniques. The &Delta;&mgr; XANES data analysis technique, previously developed and applied to heterogeneous catalysts and fuel cell electrocatalysts by the GWU group, was extended in this work to provide for the first time space resolved adsorbate coverages on both electrodes of a direct methanol fuel cell. Even more importantly, the &Delta;&mgr; technique was applied for the first time to battery relevant materials, where bulk properties such as the oxidation state and local geometry of a cathode are followed.</p>

This thesis represents the development of the first laser spectroscopy based trace-gas sensors with sensor characteristics which simultaneously satisfy low cost, handheld footprint, low power, and long term autonomous operation while still providing part-per-billion detection sensitivity and negligible interference to enable trace gas sensor networks and wearable sensors. In order to realize these demanding criteria, this work describes the development of a complete laser spectroscopic sensor platform from the ground up to determine all of the tradeoffs inherent to photonic chemical sensing, and presents a sensor platform with a configuration to meet as many application requirements as possible. Specifically, complete photonic sensor integration and design optimization (e.g. digital signal processing, low power analog, digital control technology, high speed digital design, efficient programming, infrared laser technology, mechanical design) provides sensor characteristics which are significantly improved over the current sensor technology. These sensors can permit the portable deployment of trace gas sensors and enable applications previously unattainable with any other gas sensing method. A performance comparison of the various different types of sensors measured according to these new metrics of cost, size, power consumption in addition to standard metrics (such as sensitivity and specificity) will provide a complete description of advantages and disadvantages of each trace gas sensing technique. Performance characteristics of an open-access handheld sensor platform also provide the baseline for comparison in terms of all of these new criteria. This work will also detail the development path of each major sensor component to allow new technologies to update the original modules. This thesis also describes a scalable network of high sensitivity trace gas sensors, something which has not been achieved to-date. Additionally, issues such as variable-power consumption sensor management and gas sensor data harvesting and analysis will be addressed. Several new applications will be described which may be performed with the optimized sensors which were difficult to perform previously. Finally, this thesis will extrapolate future optimal sensor configurations based on current research in MEMS, photonics, networking, integration, and sensing and will conclude with a discussion of the impact of the various advances achieved in this work.

Significant effort has centered on improving methods for producing single-walled carbon nanotubes (SWCNTs) in large quantities because of their unique electrical, mechanical, and thermal characteristics. Most production methods yield many diverse SWCNT structures, which are defined by the imaginary rolling up of a graphene sheet. The discovery of intrinsic band-gap fluorescence from semiconducting SWCNTs suspended in surfactant solutions and the subsequent assignment of the various excitation-emission features for specific SWCNT structures has opened the door to a broad range of experimental endeavors previously unavailable. This thesis describes recent progress in developing fluorimetric analysis methods and applying them to chemical problems. First, a unique turn-key SWCNT fluorescence analyzer was built and novel data analysis method was implemented for the bulk characterization of carbon nanotube samples. The instrument and analysis are illustrated by comparing deduced diameter and chirality distributions for a typical SWCNT suspension against those obtained from a general purpose spectrofluorometer system. Secondly, the use of rationally designed peptide sequences as biocompatible solubilizing agents for SWCNTs is demonstrated. This study illustrates how these peptides can be tailored to either shift the average diameter of bulk suspended SWCNTs or improve sustainable nanotube solubilization through the use of peptide crosslinking. Finally, a project is described in which the addition of diazonium salts to SWCNT suspensions quenches the intrinsic near-infrared fluorescence of the semiconducting SWCNTs through sidewall chemical reactions. Structure dependent reactivities of SWCNT species were observed in bulk measurements and variations of diazonium salt, suspending agent, and/or pH were used to moderate the reactivity trends.

The physicochemical and engineering performance properties of several API class G and H ordinary Portland cements (OPCs) from various foreign and domestic sources have been investigated. The engineering performance properties are found to vary from sample to sample, and sources for this variation were sought out and identified. Magic angle spinning (MAS) 29Si nuclear magnetic resonance (NMR) experiments were marked by unusual relaxation behavior due to paramagnetism inherent in OPCs. A model system was created to mimic the paramagnetism of the cements and the system's relaxation behavior was analyzed. The iron in the calcium aluminoferrite (C4AF) provides the paramagnetism sufficient to substantially increase the relaxation rates of the 29Si in the tricalcium silicate (C3S) and dicalcium silicate (C2S) of cement. Several relaxation techniques were evaluated for analyzing cement relaxation, and saturation recovery was identified as the preferred technique. Correlations of data from the saturation recovery experiments with engineering performance properties, especially the strength development of cement pastes, were obtained facilely. An error analysis of the NMR and engineering performance testing techniques was conducted, which indicated that NMR measurements produced less error than the engineering performance tests. A best practice, modified from the saturation recovery experiment, is proposed for use in property correlations. Additionally, 13C MAS NMR was used to characterize various fluorinated single-walled carbon nanotubes (F-SWNTs), which proved surprisingly effective in attenuating 13C-19F dipolar interactions and quantifying the extent of functionalization present at high degrees of reaction. The mixed-metal nanocluster known as FeMoC was also characterized by MAS NMR. The impact of the paramagnetic Fe3+ in the Keplerate cage on the 31P nuclei in the caged Keggin ion of FeMoC was evident in the greatly reduced relaxation times measured.

The limitations of zero quantum NMR pulse sequences reported in the literature are discussed. Several new pulse sequences which improve and extend the scope of the currently available pulse sequences are described. A modified double quantum filtered proton zero quantum 2D-NMR pulse sequence which employs a potentially more efficient and chemical shift independent excitation scheme is described. Results obtained with the modified experiment are illustrated using the complex alkaloid gelsemine. Two new pulse sequences which provide $F\sb1$ homonuclear decoupling double quantum filtered zero quantum 2D-NMR spectra are introduced. One of the pulse sequences uses a chemical shift dependent excitation scheme while the second uses a chemical shift independent sequence. The effects of composite 180$\sbsp{y}{o}$ pulses during the excitation and evolution of zero quantum coherences are explored. The effectiveness of a magnetic field homogeneity spoiling pulses on the signal intensity of zero quantum resonances is investigated as is the effect of the tip angle of the radio frequency conversion pulse, $\alpha$. Double quantum filtered, $F\sb1$ proton homodecoupled zero quantum relayed coherence transfer is discussed and a new pulse sequence described. The pulse sequence provides a mechanism for exploring remote proton-proton connectivities. The mapping of the two four spin systems of the helicene derived phenanthro (3$\sp\prime$,4$\sp\prime$:3,4) phenanthro (2,1-b) thiophene is discussed in the context of zero quantum relay. A remote 5-bond "W" connectivity is observed for phenanthro (4,3-a) dibenzothiophene. Heteronuclear $\sp{13}$C-$\sp{31}$P chemical shift correlation via heteronuclear multiple quantum coherence is described. Enhanced sensitivity is afforded by the inverse detection of $\sp{31}$P rather than detection of the much less abundant $\sp{13}$C spin. Correlations via $\sp1J\sb{CP}$ and $\sp{n}J\sb{CP}$ where n = 2, 3, are observed with minor variations in the pulse sequence. A description of the laboratory built probes and X-band decoupler is also presented.

Macroscopic synthetic techniques for producing fullerene molecules have been developed which include the carbon arc and laser vaporization approaches. The "pentagon rule" kinetic growth mechanism for the fullerenes is proposed to explain this facile process. The reactor technology for generating fullerene molecules is generalized. Resonant two-photon ionization measurements have yielded the triplet state lifetimes and electronic spectroscopy of C$\sb{60}$ and C$\sb{70}$ in a supersonic molecular beam. The technique and results are described in detail. An unusual type of C$\sb{60}$ $\cdot$ Ar$\sp{+}$ complex has been detected through fragmentation studies in a tandem time-of-flight mass spectrometer. Rotational stabilization is proposed as the mechanism leading to the long lifetime of this and similar species.