<p> We have studied the pyrolysis of aromatic combustion intermediates using an array of detection techniques. The molecules investigated include cyclic aromatic molecules with hydrocarbon substituents (ethylbenzene, n-propylbenzene, isopropylbenzene, and styrene), oxygen-containing substituents (anisole and phenol), resonance stabilized radicals (benzyl radical and tropyl radical) and phenyl radical. At the exit of a resistively heated micro-reactor (1 mm inner diameter, 3 cm long), the pyrolysis fragments are detected using photoionization mass spectrometry (PIMS), matrix isolation vibrational spectroscopy, microwave spectroscopy, tunable VUV synchrotron-based PIMS, and tabletop VUV PIMS with photoelectron photoion coincidence spectroscopy (PEPICO). This array of detection methods allows for the identification of all possible fragments including metastables, radicals, and atoms. The findings allow for detailed mechanistic information regarding which pathways are active at different pyrolysis temperatures and can also be used to help identify products and individual isomers that are formed during the gas-phase thermal decomposition of aromatic systems. By providing direct experimental pyrolysis data, models for fuel decomposition and soot formation can be improved to help understand current combustion systems and eventually aid in the design of superior fuel sources in the near future.</p>

<p> Electrospray ionization (ESI) is a premier method for volatilizing and ionizing biological analytes for mass spectrometry. In conventional mass spectrometry (MS), the spectrum of mass-to-charge ratio (<i>m/z</i>) for an ensemble of ions is measured. ESI produces a distribution of charges for each ionized species, and the mass of each species is determined by assigning a charge state to each peak in the <i>m/z</i> spectrum. These peaks are difficult to resolve for species above the 100-kDa range because of peak broadening and shifting due to salt adducts, incomplete desolvation, and intrinsic heterogeneity. Without resolved charge states, the mass cannot be determined. Charge detection mass spectrometry (CDMS) offers a solution to this problem. </p><p> In CDMS, both the <i>m/z</i> and the charge are measured simultaneously for individual ions. Multiplying those measurements for each ion yields the mass. Thus, there is no need for charge state resolution in an m/z spectrum. CDMS can therefore be used to measure the masses of extremely heavy and heterogeneous analytes far beyond the capabilities of conventional MS. This comes at the cost of efficiency, since single ions are measured serially, and resolution, since the charge measurement historically has been imprecise in CDMS. </p><p> Here we report a nearly perfect charge measurement in CDMS by analyzing each ion for 3 s in an electrostatic ion trap and implementing a novel analysis method. Then we discuss spontaneous mass and charge losses of trapped ions. Finally, we discuss multiple applications of CDMS to bacteriophage P22. P22 capsids assemble into <i>T = 7</i> &lsquo;procapsids&rsquo; with the assistance of a distribution of scaffolding proteins; we report the typical width of that distribution. Next we report our observation of mass loss in P22 procapsids over the course of weeks due to precipitation of scaffolding proteins. Then we discuss how the charge on electrosprayed P22 capsids allows us to distinguish morphologies of P22 capsids. Finally, we report an accurate mass measurement of the infectious P22 phage, a >50 MDa particle containing nucleic acid and nine kinds of protein.</p>

<p> A novel concept to provide position-sensitivity to a microchannel plate (MCP) is described. While several designs exist to make MCPs position sensitive, all these designs are based upon collection of the electrons. In contrast, this approach utilizes an induced signal as the electron cloud emanates from an MCP and passes a wire plane. We demonstrate the validity of the concept by constructing a device that provides single electron detection with 98 &mu;m position resolution (FWHM) over an area of 50 mm &times; 50 mm. The characteristics of the detector are described through both bench-top tests and simulation. After characterization of the detector, the sense wire detector was utilized for slow-neutron radiography. Furthermore, we utilized our knowledge of position-sensitive techniques to realize a beam-imaging MCP detector useful for radioactive beam facilities.</p><p>

Ab initio calculations were utilized to demonstrate the theory behind molecular properties and were correlated to actual spectroscopic results in the infrared and Raman. Symmetrical aspects of small flexible molecules were examined to determine how symmetry coordinates mix in the potential energy distribution and whether these are infrared and Raman active. The difficulty is the spectroscopic landscape of the spectrum gets extremely complicated even in very small carbon chain dihalides. The example of 1,4-dichlorobutane is provided. The work here will provide a solid reference for future research as we have found in previous work that 1,2-dibromopropane, a sensitive compound, has in previous publications shown what looks to be degradation. Three other publications are in preparation allyldichlorosilane, n-butylgermane and n-butylsilane of which the two finial compounds have conformers with the same symmetry. Instrumentation has been updated to be continually maintained and upgraded to be viable and competitive. Times for crystallizations of spectroscopic compounds for the IR and Raman cold cells can exceed 50-60 hours of continuous annealing. Modification and development of equipment allowed a level of automation and a much more precise temperature control at lower temperatures that would not have been possible before.

<p> Over recent years, Ion Mobility&ndash;Mass Spectrometry (IMS&ndash;MS) measurements have become a widely used tool in a number of disciplines of scientific relevance, including, in particular, the structural characterization of mass-selected biomolecules such as proteins, peptides, or lipids, brought into the gas-phase using a variety of ionization methods. In these structural studies, the measured electrical mobilities are customarily interpreted in terms of a collision cross-section, based on the classic kinetic theory of ion mobility. For ideal ions interacting as smooth, rigid-elastic hard-spheres with also-spherical gas molecules, this <i>collision cross-section</i> (CCS) is identical to the <i>true</i>, geometric cross section. On the other hand, for real ions with non-perfectly spherical geometries and atomically-rough surfaces, subject to long-range interactions with the gas molecules, the expression for the CCS can become fairly intricate.</p><p> This complexity has frequently led to the use of helium as the drift gas of choice for structural studies, given its small size and mass, its low polarizability (minimizing long-range interactions), and its sphericity and lack of internal degrees of freedom, all of which contribute to reduce departures between measured and true cross-sections. Recently, however, a growing interest has arisen for using moderately-polarizable gases such as air, nitrogen, or carbon dioxide (among others) in these structural studies, due to a number of advantages they present over helium, including their higher breakdown voltages (allowing for higher instrument resolutions) and better pumping characteristics. This shift has, nevertheless, remained objectionable in the eye of those seeking to infer accurate structural information from ion mobility measurements and, accordingly, there is a critical need to study whether or not measurements carried out in such gases may be corrected for the finite size of the gas molecules and their long-range interactions with the ions, in order to provide cross-sections truly representative of ion geometry. A first step to address this matter is undertaken here for the special case of nearly-spherical, nanometer-sized ions.</p><p> In order to attain this goal, we have performed careful and accurate IMS&ndash;MS measurements of hundreds of electrospray-generated nanodrops of the ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF₄), in a variety of drift gases (air, CO₂, and argon), covering a wide range of temperatures (20-100 &deg;C, for both air and CO₂), and considering nanodrops of both positive and negative polarity (the latter in room-temperature air only). Thanks to the combined measurement of the mass and mobility of these nanodrops, we are able to simultaneously determine a mobility-based collision cross-section and a mass-based diameter (taking into account the finite compressibility of the IL matter) for each of them, which then allows us to establish a comparison between the two.</p><p> Over the entire range of experimental conditions investigated, our measurements show that the electrical mobilities of these nearly-spherical, multiply-charged IL nanodrops are accurately described by an adapted version of the well-known Stokes&mdash;Millikan (SM) law for the mobility of spherical ions, with the nanodrop diameter augmented by an effective gas-molecule collision diameter, and including a correction factor to account for the effect of ion&mdash;induced dipole (polarization) interactions, which result in the mobility decreasing linearly with the ratio between the polarization and thermal energies of the ion&ndash;neutral system at contact. The availability of this empirically-validated relation enables us, in turn, to determine true, geometric cross-sections for globular ions from IMS&mdash;MS measurements performed in gases other than helium, including molecular or atomic gases with moderate polarizabilities. In addition, the observed dependence of the experimentally-determined values for the effective gas-molecule collision diameter and the parameters involved in the polarization correction on drift-gas nature, temperature, and nanodrop polarity, is further evaluated in the light of the results of numerical calculations of the electrical mobilities, in the free-molecule regime, of spherical ions subject to different types of scattering with the gas molecules and interacting with the latter under an ion&ndash;induced dipole potential. Among the number of findings derived from this analysis, a particularly notable one is that nanodrop&ndash;neutral scattering seems to be of a <i>diffuse</i> (cf. elastic and specular) character in all the scenarios investigated, including the case of the monatomic argon, which therefore suggests that the atomic-level surface roughness of our nanodrops and/or the proximity between their internal degrees of freedom, rather than the sphericity (or lack of it) and the absence (or presence) of internal degrees of freedom in the gas molecules, are what chiefly determine the nature of the scattering process.</p>

<p> Energy generation via organic photovoltaic (OPV) cells provide many advantages over alternative processes including flexibility and price. However, more efficient OPVs are required in order to be competitive for applications. One way to enhance efficiency is through manipulation of exciton mechanisms within the OPV, for example by inserting a thin film of bathocuproine (BCP) and gold nanoparticles between the C₆₀/Al and ZnPc/ITO interfaces, respectively. We find that BCP increases efficiencies by 330% due to gains of open circuit voltage (<i>V_oc</i>) by 160% and short circuit current (<i>J_sc</i>) by 130%. However, these gains are complicated by the anomalous photovoltaic effect and an internal chemical potential. Exploration in the tuning of metallic nanoparticle deposition on ITO was done through four techniques. Drop casting Ag nanoparticle solution showed arduous control on deposited morphology. Spin-coating deposited very low densities of nanoparticles. Drop casting and spin-coating methods showed arduous control on Ag nanoparticle morphology due to clustering and low deposition density, respectively. Sputtered gold on glass was initially created to aid the adherence of Ag nanoparticles but instead showed a quick way to deposit aggregated gold nanoparticles. Electrodeposition of gold nanoparticles (AuNP) proved a quick method to tune nanoparticle morphology on ITO substrates. Control of deposition parameters affected AuNP size and distribution. AFM images of electrodeposited AuNPs showed sizes ranging from 39 to 58 nm. UV-Vis spectroscopy showed the presence of localized plasmon resonance through absorption peaks ranging from 503 to 614 nm. A linear correlation between electrodeposited AuNP size and peak absorbance was seen with a slope of 3.26 wavelength(nm)/diameter(nm).</p>

<p> The use of spectrofluorometers to examine nanomaterials is quite popular using either fluorescence or synchronous measurements. However, understanding how a material&rsquo;s optical properties can influence spectral acquisition are of great importance to accurately characterize nanomaterials. This dissertation presents a series of computational and experimental studies aimed at enhancing the quantitative understanding of nanoparticle interactions with matter and photons. This allows for more reliable spectrofluorometer based acquisition of nanoparticle containing solutions. </p><p> Chapter I presents a background overview of the works described in this dissertation. Correction of the gold nanoparticle (AuNP) inner filter effect (IFE) on fluorophore fluorescence using PEGylated AuNPs as an external reference method is demonstrated in Chapter II. The AuNP IFE is corrected to quantify tryptophan fluorescence for surface adsorbed proteins. We demonstrate that protein adsorption onto AuNPs will only induce ~ 20% tryptophan fluorescence reduction instead of the commonly assumed 100% reduction. </p><p> Using water Raman intensities to determine the effective path lengths of a spectrofluorometer for correction of fluorophore fluorescence is discussed in Chapter III. Using Ni(NO3)2 and K2Cr2O7 as Raman IFE references, the excitation and emission path lengths are found to exhibit chromophore and fluorophore independence, however path lengths are spectrofluorometer dependent. </p><p> Finally, ratiometric resonance synchronous spectroscopy (R2S2) is discussed in Chapter IV. Using a combination of UV-vis and R2S2 spectroscopy, the optical cross sections of a wide range of nanomaterials were determined. Also on-resonance fluorescence in solution is demonstrated for the first time. The nanoparticles discussed range from photon absorbers, scatterers, simultaneous photon absorbers and scatterers, all the way to simultaneous photon absorbers, scatterers, and emitters.</p>

An enclosed inductively coupled plasma (ICP) was designed to overcome the limitations of the conventional ICP torch for the analysis of toxic and reactive gases. In particular, the extreme toxicity of arsine prevents the safe application of a standard ICP torch and gas exhaust for the direct determination of impurities in arsine. The enclosed ICP provides containment of toxic gases in a quartz discharge container. The total volume of toxic gas consumed is minimized as well. Parameter characterization of a sealed ICP system was investigated. The choice and role of the additive gas, effect of flow rate, discharge container size and geometry, rf power, signal reproducibility, operating parameters, and procedures were determined. Modifiers were investigated to prevent deposition of arsenic and metallic impurities to the cooler container walls. The first reported direct qualitative analysis of semiconductor-grade arsine is described. Chlorine was found to be the most effective additive gas for arsenic vaporization for both flowing and static ICP operation. Chlorine addition to the argon stream extended the arsine introduction to concentrations of up to 10% into the discharge. An rf generator (40.68 MHz) power of 1.0 kW and 30% chlorine content for 7.11% arsine in a 65-mm diameter spherical container were applied to identify eight impurities qualitatively: C, Fe, Ge, Mg, Mo, Ni, Sn, and V. A vapor phase introduction system was developed to calibrate the SICP. Theoretical detection limits for tin in arsine and chlorine were calculated as 2.00 and 0.218 ppb, respectively. A hypothesis was formulated to describe the stability of the chlorine-containing arsine plasma. Proof of this hypothesis will require techniques to probe the presence and distribution of ion and atom species within the sealed discharge. The absolute noise power spectra of atomic emission signals from the SICP for flowing and static operation demonstrated that noise below 5 Hz was lower than observed in conventional ICP discharges. White noise levels were lower for the SICP than a conventional ICP. The implications of this result is the improvement in signal-to-noise ratio signal averaging techniques. This can provide very low analyte detection limits measured in the sealed inductively coupled plasma.

Diverse experimental techniques were used for the determination of acetaminophen (N-(p-Hydroxyphenyl)acetamide, N-acetyl-p-aminophenol) in aqueous and non-aqueous media. A study was performed on the electrochemical characterization of acetaminophen at a noble-metal electrode. A pretreatment procedure on the gold electrode was developed under basic conditions. The anodic peak current was the analytical parameter used. Spectrometric techniques were used as detection means, and their analytical potential was evaluated. Infrared techniques such as transmission and attenuated total internal reflection (ATR) were used for the quantitative determination of acetaminophen. The molar absorptivity of acetaminophen was calculated at the carbonyl infrared band from the calibration data obtained from the experiments performed in non-aqueous solvents using the transmission technique. The attenuated total internal reflection technique was used to overcome limitations on the use of the infrared transmission technique for aqueous based systems. A quantitative study was undertaken of the possibilities for the determination of acetaminophen in aqueous solutions by coupling flow injection analysis (FIA) with Fourier transform-infrared (FT-IR) spectrometry. Optimization of the basic flow injection FT-IR system was performed. The cylindrical internal reflection cell for liquid evaluation (CIRCLE$\sp\circler$) was used as the detector cell compatible with aqueous solutions. Applications to systems involving on-line chemical reactions by coupling the flow injection analysis technique with infrared spectrometric detection were described. Flow injection spectrophotometric and infrared detection methods were developed for the determination of acetaminophen based on its hydrolysis reaction with sodium hydroxide to form p-aminophenol and its oxidation with potassium ferricyanide to produce an orange-red species, p-benzoquinonemonoimine. The developed methods were evaluated by analysis of tablets of a commercial formulation. The ability of flow injection techniques for generating transient product profiles combined with the infrared mode for monitoring reaction species was investigated to help in the study of reaction mechanisms. Ab initio calculations were performed on acetaminophen at the 3-21G level of the theory. Structural parameters were optimized for the two conformations of acetaminophen. The calculated and experimental spectra were compared in terms of the infrared vibrational frequencies.