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This study is divided into three parts. Part I deals with the mechanism of the self-initiated polymerization (or thermal polymerization) of styrene in the gas phase. In this work, we present the first direct evidence for the thermally self-initiated polymerization of styrene in the gas phase. Our approach is based on on-line analysis of the gas phase Oligomers by mass-selected ion mobility. The mobility measurements provide structural information on the ionized oligomers based on their collision cross-sections (Ω) which depend on the geometric shapes of the ions. Theoretical calculations of possible structural candidates of the Oligomers ions are then used to compute angle averaged Ω for comparison with the measured ones. The agreement between the measured and calculated Ω of the candidate structures provides reliable assignments to the structures of the oligomers. Furthermore, collisional-induced dissociations of the mass-selected oligomer ions provide further support for the structures obtained from the mobility measurements. Our results indicate that the gas phase polymerization of styrene proceeds via essentially the same initiation mechanism (the Mayo mechanism) as in condensed phase polymerization. The structural evidence, the mechanism of formation and the observed fragmentation pathway of the growing dimers and trimers in the gas phase are presentedIn Part II the solvation of a variety of metal cations by benzene clusters have been studied using laser vaporization, cluster beam and time-of-flight mass spectrometry techniques. In this work strong magic numbers were observed for clusters containing 10, 13 and 14 benzene molecules depending on the nature of the metal cation involved. The metal cations exhibiting preference solvation by 14 benzene molecules show a strong tendency to form sandwich structures with two benzene molecules. The interpretation of these results in view of the proposed structures and the growth patterns of the clusters are presented. In Part III, the work is focused on the investigation of the intracluster ion molecule reactions following the generation of Mg+ within the polar clusters (water, methanol, ether and acetonitrile).

In this work, the Drift Tube Ion Mobility technique is used to study the hydrophobic hydration and solvation of organic ions and measure the thermochemistry and kinetics of ion-molecule reactions. Furthermore, an exploratory study of the intracluster polymerization of isoprene will be presented and discussed. The ion hydration study is focused on the C3H3+ cation1 and Pyridine▪+ radical cation.2 The chemistry of the cyclic C3H3+ cation1 has received considerable attention and continues to be an active area of research.3-7 The binding energies of the first 5 H2O molecules to c-C3H3+ were determined by equilibrium measurements. The measured binding energies of the hydrated clusters of 9-12 kcal/mol are typical of carbon-based CH+•••X hydrogen bonds. The ion solvation with the more polar CH3CN molecules results in stronger bonds consistent with the increased ion-dipole interaction. Ab initio calculations show that the lowest energy isomer of the c-C3H3+(H2O)4 cluster consists of a cyclic water tetramer interacting with the c-C3H3+ ion, which suggests the presence of orientational restraint of the water molecules consistent with the observed large entropy loss. The c-C3H3+ ion is deprotonated by 3 or more H2O molecules, driven energetically by the association of the solvent molecules to form strongly hydrogen bonded (H2O)nH+ clusters. The kinetics of the associative proton transfer (APT) reaction C3H3+ + nH2O → (H2O)nH+ + C3H2• exhibits an unusually steep negative temperature coefficient of k = cT(sup>63±4 (or activation energy of -32 ± 1 kcal mol-1). The behavior of the C3H3+/water system is exactly analogous to the benzene+• /water system8,9, suggesting that the mechanism, kinetics and large negative temperature coefficients may be general to multibody APT reactions. These reactions can become fast at low temperatures, allowing ionized polycyclic aromatics to initiate ice formation in cold astrochemical environments.The solvation energies of the pyridine•+ radical cation by 1- 4 H2O molecules are determined by equilibrium measurements in the drift cell. The binding energies of the pyridine•+(H2O)n clusters are similar to the binding energies of protonated pyridineH+(H2O)n clusters that involve NH+∙∙OH2 bonds, and different from those of the solvated radical benzene•+(H2O)n ions that involve CHδ+∙∙OH2 bonds. These relations indicate that the observed pyridine•+ ions have the distonic •C5H4NH+ structure that can form NH+∙∙OH2 bonds. The observed thermochemistry and ab initio calculations show that these bonds are not affected significantly by an unpaired electron at another site of the ion. The distonic structure is also consistent with the reactivity of pyridine•+ in H atom transfer, intra-cluster proton transfer and deprotonation reactions. The results present the first measured stepwise solvation energies of distonic ions, and demonstrate that cluster thermochemistry can identify distonic structures.The gas phase clustering of small molecules around the hydronium ion is of fundamental interest and is relevant to important atmospheric and astrophysical processes. In this work, the equilibrium constants for the formation of the H3O+(X)n clusters with X = H2, N2 and CO and n = 1-3 at different temperatures are measured using the drift tube technique10. The arrival time distributions (ATDs) of the injected H3O+ and the H3O+(X)n clusters formed inside the cell are measured under equilibrium conditions. The resulting binding energies for the addition of one and two hydrogen molecules are similar [3.4 and 3.5 kcal/mol, respectively). For the N2 clustering with n = 1-3, the measured binding energies are 7.9, 6.9 and 5.4 kcal/mol, respectively. The clustering of CO on the H3O+ ion exhibits a relatively strong binding energy (11.5 kcal/mol) consistent with the dipole moment and polarizability of the CO molecule. Theoretical calculations of the lowest energy structures are correlated to the experimental results. Finally, intracluster polymerization leading to the formation of covalent bonded oligomer ions has been investigated following the ionization of neutral isoprene clusters. The results indicate that isoprene dimer cation has a structure similar to that of the limonene radical cation. Mass-selected mobility and dissociation studies also indicate that the larger isoprene cluster ions have covalent bonded structures. The conversion of molecular clusters into size-selected oligomers is an important process not only for detailed understanding of the early stages of polymerization but also for practical applications such as the formation of new polymeric materials with controlled and unusual properties.

In this study, we have developed a novel way of generating and exposing biological organisms (both prokaryotic and eukaryotic) to silver nanoparticles (AgNPs) and studying the biochemical changes induced by these particles. We analyzed the various organs of Wistar rats for localization and quantification of these particles using mass spectrometric and molecular biological techniques. Highest levels of AgNP was found in the lung tissue in addition to being present in the liver and kidneys. Analysis of the of the blood plasma from AgNP exposed rats revealed elevated levels of glutathione-disulfide, which is indicative of reactive oxygen species (ROS) generation, which was further validated using ROS specific immunofluorescence staining of liver tissue. Quantification of blood lactate levels of the AgNP exposed rats showed increased lactate levels, which is indicative of anaerobic respiration and may result from AgNP-induced oxidative stress. Further analysis of bone marrow cells from AgNP exposed rats showed a higher number of micronuclei formation in developing erythrocytes and bone marrow cytotoxicity. Finally, analysis of the genes involved in the renin-angiotensin system (RAS) and inflammatory response revealed upregulation in transcript levels of many of these important genes in the liver tissue. Taken together, our study provides an initial road map for the identification of different signaling pathways that are altered by the AgNP exposure and contributes to a comprehensive understanding of the mechanism involved in silver nanoparticle-induced toxicity.

Neste trabalho é apresentada uma nova geometria e os critérios de projeto para dispositivos de espectrometria de mobilidade iônica, com objetivo de aumentar a relação entre sinal e ruído detectados pelos eletrômetros que compõem a região de detecção, quando associado à ionização baseada em descargas elétricas que tipicamente emitem maior interferência eletromagnética em relação a outros tipos de ionização. A geometria e os critérios de projeto foram estabelecidos com o auxílio do simulador de trajetórias iônicas SIMION versão 8.1 e comparada com espectrômetros de mobilidade iônica do estado-da-arte. Os resultados das simulações dos dispositivos foram avaliados por meio dos testes estatísticos não-paramétricos de Iman-Davenport e Holm. O resultado indicou que a geometria proposta apresentou compatibilidade com as melhores características dos espectrômetros atuais com confiança estatística a 95 %. Na sequência a geometria proposta foi simulada, fabricada e testada para detecção dos íons de: tolueno - C7H8 (C5H5+, C6H5+, C7H7+), propanol - C3H8O (CH3+, CH3O+, C2H3+, C2H4O+, C2H5O+, C3H6+, C3H7+, C3H7O+) e água - H2O (H+, HO+, H2+, O+). Os picos de corrente iônica detectada nos eletrômetros indicaram coerência com as trajetórias simuladas para estes conjuntos de íons. Além disso, os resultados experimentais apresentaram um aumento na relação entre sinal e ruído para a nova geometria proposta que foi validada pelo teste de comparação pareada não-paramétrico de Wilcoxon a 95 % de confiança estatística. / In this work, a new geometry and a design criteria for ion mobility spectrometry devices was presented, aiming to increase the signal-to-noise ratio detected by electrodes of the detection region, when associated with ionization based on electrical discharges. The new geometry and the design criteria were established in the SIMION version 8.1 (an ionic trajectory simulator) and compared with the state-of-art ion mobility spectrometers. The results from device simulations were evaluated using the non-parametric statistical test of Iman-Davenport and Holm. The result indicated that the proposed design criteria presented compatibility with the best characteristics of current spectrometers with statistical evidence at 95%. The proposed geometry was simulated, fabricated and tested for the following solvents: toluene - C7H8 (C5H5+, C6H5+, C7H7+), propanol - C3H8O (CH3+, CH3O+, C2H3+, C2H4O+, C2H5O+, C3H6+, C3H7+, C3H7O+) and water - H2O (H+, HO+, H2+, O+). The peaks of ion current detected in the electrometers occurred at approximate positions of the simulated trajectories for these sets of ions. In addition, the experimental data showed an increase in the signal-to-noise ratio for the proposed new geometry that was validated by the test statistic of Wilcoxon signed rank at 95% statistical confidence.

Neste trabalho é apresentada uma nova geometria e os critérios de projeto para dispositivos de espectrometria de mobilidade iônica, com objetivo de aumentar a relação entre sinal e ruído detectados pelos eletrômetros que compõem a região de detecção, quando associado à ionização baseada em descargas elétricas que tipicamente emitem maior interferência eletromagnética em relação a outros tipos de ionização. A geometria e os critérios de projeto foram estabelecidos com o auxílio do simulador de trajetórias iônicas SIMION versão 8.1 e comparada com espectrômetros de mobilidade iônica do estado-da-arte. Os resultados das simulações dos dispositivos foram avaliados por meio dos testes estatísticos não-paramétricos de Iman-Davenport e Holm. O resultado indicou que a geometria proposta apresentou compatibilidade com as melhores características dos espectrômetros atuais com confiança estatística a 95 %. Na sequência a geometria proposta foi simulada, fabricada e testada para detecção dos íons de: tolueno - C7H8 (C5H5+, C6H5+, C7H7+), propanol - C3H8O (CH3+, CH3O+, C2H3+, C2H4O+, C2H5O+, C3H6+, C3H7+, C3H7O+) e água - H2O (H+, HO+, H2+, O+). Os picos de corrente iônica detectada nos eletrômetros indicaram coerência com as trajetórias simuladas para estes conjuntos de íons. Além disso, os resultados experimentais apresentaram um aumento na relação entre sinal e ruído para a nova geometria proposta que foi validada pelo teste de comparação pareada não-paramétrico de Wilcoxon a 95 % de confiança estatística. / In this work, a new geometry and a design criteria for ion mobility spectrometry devices was presented, aiming to increase the signal-to-noise ratio detected by electrodes of the detection region, when associated with ionization based on electrical discharges. The new geometry and the design criteria were established in the SIMION version 8.1 (an ionic trajectory simulator) and compared with the state-of-art ion mobility spectrometers. The results from device simulations were evaluated using the non-parametric statistical test of Iman-Davenport and Holm. The result indicated that the proposed design criteria presented compatibility with the best characteristics of current spectrometers with statistical evidence at 95%. The proposed geometry was simulated, fabricated and tested for the following solvents: toluene - C7H8 (C5H5+, C6H5+, C7H7+), propanol - C3H8O (CH3+, CH3O+, C2H3+, C2H4O+, C2H5O+, C3H6+, C3H7+, C3H7O+) and water - H2O (H+, HO+, H2+, O+). The peaks of ion current detected in the electrometers occurred at approximate positions of the simulated trajectories for these sets of ions. In addition, the experimental data showed an increase in the signal-to-noise ratio for the proposed new geometry that was validated by the test statistic of Wilcoxon signed rank at 95% statistical confidence.

Gas phase molecular clusters present an ideal medium for observing factors that drive chemical reactions without outside interferences from excessive solvent molecules. Introducing an ion into the cluster promotes ion-molecule interactions that may manifest in a variety of non-covalent or even covalent binding motifs and are of significant importance in many fields including atmospheric and astronomical sciences. For instance, in outer space, molecules are subject to ionizing radiation where ion-molecule reactions become increasingly competitive to molecule-molecule interactions. To elucidate individual ion-molecule interaction information, mass spectrometry was used in conjunction with appropriate theoretical calculations. Three main categories of experiment were conducted in this dissertation. The first of which were thermochemical equilibrium measurements where an ion was introduced to an ion mobility drift cell wherein thermalizing collisions occur with helium buffer gas facilitating a reversible reaction with a neutral molecule allowing the standard changes in enthalpy and entropy to be determined. The second type of experiment was an ion mobility experiment where an ionized homo- or hetero-cluster was injected into the drift cell at specific conditions allowing the reduced mobility and collisional cross-section to be evaluated. Thirdly, kinetics measurements were taken following injection of an ion into the drift cell were an irreversible reaction ensued with the neutral species hindering equilibrium, but prompting rate constant assessment. Previous research has laid the groundwork for this dissertation as the results and discussion contained herein will build upon existing data while maintaining originality. For example, past work has given support for ion-molecule reactions involving precursor species such as acetylene and hydrogen cyanide to form more complex organics, perhaps leading to biologically relevant species. The chemical systems studied for this research are either ionized substituted benzenes like phenylacetylene and benzonitrile or polycyclic aromatic nitrogen-containing hydrocarbons like quinoline and quinoxaline interacting with a variety of neutral species. Hydrogen bonding and its many sub-sections are of the utmost importance to the kinds of reactions studied here. Past work has shown the tendency of organic radical cations to form conventional and unconventional ionic hydrogen bonds with gas phase solvents. Other non-covalent modes of interaction have also been detected in addition to the formation of covalently bound species. Gas phase reactions studied here will explore, via mass-selected ion mobility, reversible and irreversible reactions leading to binding enthalpy and entropy and rate constant determination, respectively, in addition to collisional cross-section determination.

Solid phase microextraction (SPME), needle trap device (NTD), and membrane extraction with a sorbent interface (MESI) are solvent-free sample preparation techniques that were developed to perform the rapid routine analysis of organic compounds (VOCs) in various environmental matrices by integrating sampling, extraction, preconcentration and sample introduction procedures into one step. A portable ion mobility spectrometry (IMS) analyzer has some advantages, such as small size, light weight, operability under ambient pressure, air as carrier gas, and sensitivity, all of which make IMS suitable for on-site monitoring for low concentration of analytes. The aforementioned sampling and preconcentration techniques were coupled with a portable IMS analyzer, as well as a thermal desorption unit that can accommodate SPME, NTD and MESI, which was modified and combined with IMS for on-site monitoring of volatile organic compounds (VOCs) from human breath and plant emissions. Experimental results demonstrated that low detection limits were achievable for gaseous analytes, (25 ng/L for acetone (SPME-IMS), 43 ng/mL (NTD-IMS) and 2.3 ng/mL (MESI-IMS) for α-pinene). These three analytical systems were applied for on-site rapid determination of acetone in human breath and α-pinene from plant emissions respectively. The salient features of these systems that make them suitable for on-site monitoring of volatile organic compounds in different sources are: small size, simple operation, fast and/or on-line sampling, rapid analysis.

Solid phase microextraction (SPME), needle trap device (NTD), and membrane extraction with a sorbent interface (MESI) are solvent-free sample preparation techniques that were developed to perform the rapid routine analysis of organic compounds (VOCs) in various environmental matrices by integrating sampling, extraction, preconcentration and sample introduction procedures into one step. A portable ion mobility spectrometry (IMS) analyzer has some advantages, such as small size, light weight, operability under ambient pressure, air as carrier gas, and sensitivity, all of which make IMS suitable for on-site monitoring for low concentration of analytes. The aforementioned sampling and preconcentration techniques were coupled with a portable IMS analyzer, as well as a thermal desorption unit that can accommodate SPME, NTD and MESI, which was modified and combined with IMS for on-site monitoring of volatile organic compounds (VOCs) from human breath and plant emissions. Experimental results demonstrated that low detection limits were achievable for gaseous analytes, (25 ng/L for acetone (SPME-IMS), 43 ng/mL (NTD-IMS) and 2.3 ng/mL (MESI-IMS) for α-pinene). These three analytical systems were applied for on-site rapid determination of acetone in human breath and α-pinene from plant emissions respectively. The salient features of these systems that make them suitable for on-site monitoring of volatile organic compounds in different sources are: small size, simple operation, fast and/or on-line sampling, rapid analysis.

Molecular ionization is owed much of its development from the early implementation of electron ionization (EI). Although dramatically increasing the library of compounds discovered, an inherent problem with EI was the low abundance of molecular ions detected due to high fragmentation leading to the difficult task of the correct chemical identification after mass spectrometry (MS). These problems stimulated the research into new ionization methods which sought to "soften" the ionization process. In the late 1980s the advancements of ionization techniques was thought to have reached its pinnacle with both electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI). Both ionization techniques allowed for "soft" ionization of large molecular weight and/or labile compounds for intact characterization by MS. Albeit pervasive, neither ESI nor MALDI can be viewed as "magic bullet" ionization techniques. Both techniques require sample preparation which often included native sample destruction, and operation of these techniques took place in sealed enclosures and often, reduced pressure conditions. New open-air ionization techniques termed "ambient MS" enable direct analysis of samples of various physical states, sizes and shapes. One particular technique named Direct Analysis In Real Time (DART) has been steadily growing as one of the ambient tools of choice to ionize small molecular weight (< 1000 Da) molecules with a wide range of polarities. Although there is a large list of reported applications using DART as an ionization source, there have not been many studies investigating the fundamental properties of DART desorption and ionization mechanisms. The work presented in this thesis is aimed to provide in depth findings on the physicochemical phenomena during open-air DART desorption and ionization MS and current application developments. A review of recent ambient plasma-based desorption/ionization techniques for analytical MS is presented in Chapter 1. Chapter 2 presents the first investigations into the atmospheric pressure ion transport phenomena during DART analysis. Chapter 3 provides a comparison on the internal energy deposition processes during DART and pneumatically assisted-ESI. Chapter 4 investigates the complex spatially-dependent sampling sensitivity, dynamic range and ion suppression effects present in most DART experiments. New implementations and applications with DART are shown in Chapters 5 and 6. In Chapter 5, DART is coupled to multiplexed drift tube ion mobility spectrometry as a potential fieldable platform for the detection of toxic industrial chemicals and chemical warfare agents simulants. In Chapter 6, transmission-mode DART is shown to be an effective method for reproducible sampling from materials which allow for gas to flow through it. Also, Chapter 6 provides a description of a MS imaging platform coupling infrared laser ablation and DART-like phenomena. Finally, in Chapter 7 I will provide perspective on the work completed with DART and the tasks and goals that future studies should focus on.