Developing a fundamental understanding of the interactions of chemical warfare agents (CWAs) with surfaces is essential for the rational design of new sorbents, sensors, and decontamination strategies. The interactions of chemical warfare agent simulants, molecules which retain many of the same chemical or physical properties of the agent without the toxic effects, with amorphous silica were conducted to investigate how small changes in chemical structure affect the overall chemistry. Experiments investigating the surface chemistry of two classes of CWAs, nerve and blister agents, were performed in ultrahigh vacuum to provide a well-characterized system in the absence of background gases. Transmission infrared spectroscopy and temperature-programmed desorption techniques were used to learn about the adsorption mechanism and to measure the activation energy for desorption for each of the simulant studied. In the organophosphate series, the simulants diisopropyl methylphosphonate (DIMP), dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), dimethyl chlorophosphate (DMCP), and methyl dichlorophosphate (MDCP) were all observed to interact with the silica surface through the formation of a hydrogen bond between the phosphoryl oxygen of the simulant and an isolated hydroxyl group on the surface. In the limit of zero coverage, and after defect effects were excluded, the activation energies for desorption were measured to be 57.9 ± 1, 54.5 ± 0.3, 52.4 ± 0.6, 48.4 ± 1, and 43.0 ± 0.8 kJ/mol for DIMP. DMMP, TMP, DMCP, and MDCP respectively. The adsorption strength was linearly correlated to the magnitude of the frequency shift of the ν(SiO-H) mode upon simulant adsorption. The interaction strength was also linearly correlated to the calculated negative charge on the phosphoryl oxygen, which is affected by the combined inductive effects of the simulants’ different substituents. From the structure-function relationship provided by the simulant studies, the CWA, Sarin is predicted to adsorb to isolated hydroxyl groups of the silica surface via the phosphoryl oxygen with a strength of 53 kJ/mol. The interactions of two common mustard simulants, 2-chloroethyl ethyl sulfide (2-CEES) and methyl salicylate (MeS), with amorphous silica were also studied. 2-CEES was observed to adsorb to form two different types of hydrogen bonds with isolated hydroxyl groups, one via the S moiety and another via the Cl moiety. The desorption energy depends strongly on the simulant coverage, suggesting that each 2-CEES adsorbate forms two hydrogen bonds. MeS interacts with the surface via a single hydrogen bond through either its hydroxyl or carbonyl functionality. While the simulant work has allowed us to make predictions agent-surface interactions, actual experiments with the live agents need to be conducted to fully understand this chemistry. To this end, a new surface science instrument specifically designed for agent-surface experiments has been developed, constructed, and tested. The instrument, located at Edgewood Chemical Biological Center, now makes it possible to make direct comparisons between simulants and agents that will aid in choosing which simulants best model live agent chemistry for a given system. These fundamental studies will also contribute to the development of new agent detection and decontamination strategies. / Ph. D.

Developing a fundamental understanding of the interactions between catalytic surfaces and adsorbed molecules is imperative to the rational design of new materials for catalytic, sorption and gas separation applications. Experiments that probed the chemistry at the gas-surface interface were employed through the utilization of in situ infrared spectroscopic measurements in high vacuum conditions to allow for detailed and systematic investigations into adsorption and reactive processes. Specifically, the mechanistic details of propene epoxidation on the surface of nanoparticulate Au supported on TiO2 and dimethyl chlorophosphate (DMCP) decomposition on the surface of TiO2 aerogel-supported Cu nanoparticles were investigated. In situ infrared spectroscopy illustrates that TiO2-supported Au nanoparticles exhibit the unprecedented ability to produce the industrially relevant commodity chemical, propene oxide, through the unique adsorption configuration of propene on the surface of Au and a hydroperoxide intermediate (-OOH) in the presence of gaseous hydrogen and oxygen. Whereas, TiO2-supported Cu aerogels oxidize the organophosphate-based simulant, DMCP, into adsorbed CO at ambient environments. Through a variety of spectroscopic methods, each step in these oxidative pathways was investigated, including: adsorption, oxidation and reactivation of the supported-nanoparticle systems to develop full mechanistic pictures. Additionally, the perturbation of vibrational character of the probe molecule, CO, was employed to characterize the intrinsic µ3-hydroxyls and molecular-level defects associated with the metal-organic framework (MOF), UiO-66. The adsorption of CO onto heterogeneous surfaces effectively characterizes surfaces because the C-O bond vibrates differently depending on the nature of the surface site. Therefore, CO adsorption was used within the high vacuum environment to identify atomic-level characteristics that traditional methods of analysis cannot distinguish. / Doctor of Philosophy / The interaction between small gas molecules and solid surfaces is important for environmental, industrial and military applications. In order to chemically change molecules, surfaces act to lower activation barriers and provide a low energy plane to create new chemical bonds. To study the fundamental interactions that occur between gas molecules and surfaces, we employ infrared spectroscopy in order to probe the vibrations of bonds at the gas–surface interface. By tracking the chemical bonds that break and form on the surface of different materials, we can develop surface reaction pathways for a variety of different chemical reactions. We focus our efforts on two different applications: the conversion of propene to propene oxide for industrial applications and the decomposition of chemical warfare agents. Using the techniques described above, we were able to develop reaction pathways for both propene oxidation and chemical warfare agent simulant degradation. Our work is critical to the further development of catalysts that harness the specific structural and chemical properties we identify as important and exploit them for further use.

Comme l’a montré l’utilisation de sarin en Syrie en 2013, les agents chimiques de guerre restent une menace. L’exposition de populations est une situation d’urgence qui nécessite des moyens rapides et efficaces. La décontamination et le soin des personnes exposées restent une priorité. Les cheveux représentent une matrice couramment utilisée dans le domaine médico-légal. Dans ce travail, notre intérêt se porte sur la capacité du cheveu à capter et libérer des composés dans l’air, notamment l’ypérite, ainsi que sur l’efficacité de décontamination de cette matrice. Pour ce travail, nous avons utilisé deux composés aux propriétés physiques/chimiques proches de celles de l’ypérite : le salicylate de méthyle et le 2-chloroéthyl éthyl sulfure. Les deux similis ont été retenus par le cheveu avec une plus grande affinité pour le salicylate de méthyle. Nous avons observé une corrélation entre l’intensité d’exposition (influence de la dose et du temps) et la teneur en contaminants retrouvés sur les cheveux. Ces résultats montrent qu’il est possible d’utiliser le cheveu pour détecter une exposition individuelle. Après exposition, la teneur dans des cheveux laissés à désorber a été mesurée avec le salicylate de méthyle. Les résultats obtenus ont montré que les cheveux contaminés sont susceptibles de libérer les toxiques. Cela peut poser un problème sanitaire, qui implique donc que la décontamination des cheveux soit étudiée. Les protocoles de décontamination testés montrent une efficacité partielle (élimination de 40 à 80%). Ces résultats impliquent la nécessité d’optimiser les procédures actuelles ou de définir de nouveaux outils pour la décontamination du cheveu après exposition. / As shown by sarin use in Syria (2013), chemical warfare agents remain a threat. Chemical exposure of populations is an emergency situation, where quick and efficient means are mandatory. Decontamination and care of the victims are a priority. Scalp hair is routinely used as a biological matrix in forensic sciences. In this thesis work, interest focuses on hair capacity to trap and release compounds from atmosphere, especially sulphur mustard, as well as decontamination of this matrix. For this work, two molecules with similar physical/chemical properties to sulphur mustard were used: methyl salicylate and 2-chloroethyl ethyl sulphide. Both simulants were trapped by scalp hair, with higher affinity towards methyl salicylate. We observed a correlation between exposure intensity (influence from dose and time) and simulant content recovered from hair analysis. Results suggest that hair can be used to assess individual contamination. After exposure, evolution of methyl salicylate hair content has been measured. Results pointed out that contaminated hair can thereafter release the simulants. This can lead to health issue, highlighting the fact that hair decontamination must be investigated. Tested decontamination protocols showed a partial efficacy (40-80% removal). Those results evidenced the need to optimise current procedures or define new tools for hair decontamination after chemical exposure.

Chemical warfare agents are a toxic class of compounds that are incredibly harmful to human health. Methods of detoxification and decontamination currently exist, however they all suffer from problems that involve logistical transport or involve technologies that directly address liquid threats instead of vapors. One promising method of detoxification involves the oxidation of these compounds into less-harmful species. The relatively large chemical size and complexity of modern-day chemical warfare agents, however, precludes a straightforward analysis of the chemical transformations that take place on novel decontaminating materials. Additionally, a fundamental understanding of reaction mechanisms that occur on novel material surfaces is required before improved materials can be developed. To this end, the oxidation of three simpler, smaller organic molecules were studied over a variety of materials in order to build up a chemical understanding of the systems under study. The photoepoxidation of propene into propene oxide was observed to readily occur over an in-house developed dual titania-silica catalyst created by atomic layer deposition. The subsequent photoinduced degradation of produced propene oxide was observed to occur over the novel catalyst. Next, the oxidation of CO was studied over a Pt/TiO2 catalyst while in the presence of humidity. The addition of water was shown to enable an alternative, low energy pathway that closely followed the water gas shift, but ended upon the production of stable surface-bound formates. Gaseous oxygen was found to subsequently oxidize these surface formates into the full oxidation product, CO2. Next, the oxidation of methanol was studied over the same Pt/TiO2 catalyst. It was discovered that the water produced when methanol initially adsorbs to the catalyst surface is responsible for unlocking the oxidative capacity of the material. Finally, a custom packedbed reactor was designed and built that enabled unique experimental capabilities not yet available in commercial systems, and will be used in the future to directly test the oxidative capabilities of novel materials for chemical warfare agent destruction. / Doctor of Philosophy / The chemical interactions and reactions that occur between gases and surfaces are incredibly important for a multitude of technologies employed by governments, militaries, and citizens alike. The precise methods in which these gases interact with materials of interest determine whether said material can be used in a catalytic fashion. Much like how an automobile catalytic converter does not have to be replaced each time the vehicle is started; a catalyst is able to be used repeatedly without loss of function. Catalysts in general are unique in that they function to create or allow for chemical reactions to proceed through alternative, lower energy pathways that are more likely to occur under milder environmental conditions. In order to understand the chemical reactions that occur on a catalyst, a combination of specialized spectroscopic methods was used that allowed for tracking the precise chemical bonds that were formed or broken during reaction. A few different model chemical reactions are explored in this work, ranging from the conversion of carbon monoxide into CO2, and the oxidation of methanol, a small alcohol commonly found in fuel cells. The experimental techniques employed herein allowed for precise chemical mechanisms to be tracked, and the information gained will certainly be useful for the design of next-generation materials by future research.

Les agents chimiques de guerre et leurs dérivés pesticides sont des molécules toxiques qui provoquent une incapacité temporaire ou des dommages permanents allant jusqu’à la mort de l’individu. Une des voies majeures de la contamination est la pénétration cutanée. La protection de la peau semble donc importante pour prévenir de ces dangers. Cette thèse concerne l’élaboration de nouveaux topiques protecteurs cutanés contenant des polymères HASE fluorés greffés avec des nanoparticules de silice, cérine ou titane. Dans un premier temps les actifs ont été synthétisés en grosse quantité et leurs propriétés de mouillabilité améliorées. Les tests toxicologiques ont montré que les actifs n’étaient pas irritants pour la peau et non toxiques pour l’environnement. La formulation de ces polymères a permis le développement de deux nouvelles crèmes barrières contre la pénétration du paraoxon dont l’efficacité est dépendante de la présence des nanoparticules. Le greffage des nanoparticules à un polymère HASE fluoré et leur formulation a donc permis le développement de nouveaux topiques efficaces. L’évaluation de l’efficacité a été réalisée sur membranes artificielles et confirmée sur explants de peaux humaines. Enfin, le peu de disponibilité des explants de peaux humaines a motivé le développement d’un modèle d’efficacité utilisant des épidermes humains reconstruits. / Chemical warfare agents and pesticides are toxic molecules causing temporary incapacitation or permanent harms leading to the death of people. One of the major routes of contamination is the percutaneous penetration. Skin protection is important to prevent these dangers. The aim of this thesis is to develop new active topical skin protectants based on nanoparticular networks containing fluorinated HASE polymers grafting with silica, cerium or titanium nanoparticles. First, polymers were synthesized in larger quantity and their wettability properties improved. Toxicological studies have showed that these compounds are non-irritant and non-toxic for the environment. The formulation of these polymers has led to the elaboration of two new barrier creams against paraoxon penetration whose efficiency is dependent on the presence of nanoparticles. Therefore, the grafting of nanoparticles to fluorinated HASE polymer and their formulation have enabled the development of new active topical skin protectant. Efficiency evaluation was done using artificial membranes and was confirmed on ex vivo human skin. The limited availability of human skin explants has motivated the development of a new efficiency model using reconstructed human epidermis.

Les neurotoxiques organophosphorés sont appelés agents chimiques de guerre car ils sont une menace à la fois pour les militaires et pour les populations civiles. La voie percutanée est l’une des principales voies d’entrée pour ces agents, et plus particulièrement pour le VX, très peu volatil. La décontamination des surfaces exposées est alors cruciale afin d’éviter l’intoxication des victimes. En cas d’attentat terroriste, le cuir chevelu humain pourrait être un site préférentiel d’exposition. Cette partie du corps, riche en follicules pileux, pourrait nécessiter des produits et des processus de décontamination adaptés. Ce travail est divisé en 4 parties : 1) Validation d’un modèle de peau in vitro pour le cuir chevelu humain ; 2) Détermination des stratégies de décontamination ; 3) Formulation de nouveaux systèmes de décontamination ; 4) Évaluation de leur efficacité de décontamination. La peau d’oreille de porc est un modèle pertinent pour l’étude de la pénétration percutanée in vitro du VX à travers le cuir chevelu humain. La peau de dessus de tête de porc représente un bon modèle de cuir chevelu humain pour l’étude de l’affinité du VX avec la tige pilaire. L’étude de distribution du VX selon différents temps d’exposition a montré que la majorité du toxique reste à la surface de la peau jusqu’à 2h d’exposition. Il est donc intéressant de décontaminer la peau même après 2h d’exposition aux agents chimiques de guerre. Les microémulsions comprenant un actif détoxifiant (oxime) sont les systèmes les plus efficaces car ils pénètrent en profondeur afin de venir détruire le toxique in situ dans la peau. Les poudres et les émulsions de Pickering ont une action de surface et permettent d’extraire le toxique présent à la surface de la peau et dans les couches superficielles. Les résultats de nos études in vitro ont montré que ces formulations sont significativement plus efficaces que la terre à foulon pour une décontamination après 45 min d’exposition au VX / Organophosphorous nerve agents are designed as chemical warfare agent because they represent a threat both for the military and the civilians. Due to its low volatility, VX mainly remains in its liquid form and mostly presents a contamination by skin contact. Decontamination of exposed body surface is therefore crucial to prevent victims' poisoning. In case of terrorist acts, civilian human scalp could be a preferential site of exposure. This body region, rich in hair follicles, may require adapted decontamination products and procedures. The aims of this work are: 1) Validation of a relevant in vitro human scalp skin model; 2) Determination of decontamination strategies; 3) Formulation of new decontamination systems; 4) Evaluation of their decontamination efficacy. Pig ear skin is a relevant model when studying the in vitro percutaneous penetration of VX through human scalp. Pig skull roof skin could be used when studying the affinity of VX for hair. This study has shown that most of the nerve agent remains on the skin surface up to 2h of exposure, which means that it is worth decontaminating even if contamination occurred 2h before. Microemulsions loading a detoxifying agent (oxime) are the most efficient systems because they are able to penetrate deeper into the skin to neutralize the agent in situ. Adsorbing powders and Pickering emulsions could interact with the agent present on the skin surface and in the superficial layers. Our results from the in vitro experiments have demonstrated that these formulations are more efficient than Fuller's earth for skin decontamination after 45 min of VX exposure

This study addressed five key applications of paper spray mass spectrometry (PS-MS): (i) comparative analysis of the microporous substrate with the cellulose-based substrate in drug detection; (ii) detection of more than 190 fentanyl analogs with their fragmentation pattern can be implemented in the future reference for quicker, accurate and sensitive determination; (iii) exploring sweat in a fingerprint to be considered an alternate method to recognize non-invasive markers of metabolites, lipids, narcotics, and explosive residues that can be used in forensic testing applications; (iv) extending and improving better, cost-effective and quick real-time monitoring of the diseased stage using biofluid samples to obtain vastly different lipid information in viral infection such as COVID-19; and (v) mass spectral detection in chemical warfare agent (CWA) stimulant gas exposure with microporous structure absorbency capabilities in air quality monitoring. This novel synthetic material is known as Teslin® (PPG Industries), consisting of a microporous polyolefin single-layered silica matrix, can be used for precise, sensitive, selective, and rapid sample analysis with PS-MS. The Teslin® substrate provided longer activation time for samples and an active signal with a higher concentration of ion formation and mobility compared to cellulose-based papers. Direct analysis of multiple samples showed that, besides being more sensitive to the study and highly efficient with less sample size and spray solvent needed, Teslin® had less interaction with paper source molecules. For less than 60 seconds of processing time, PS-MS can be used as a rapid detection tool, with limited sample preparation requiring less than one microgram of the sample. Overall, the data in this analysis indicate the capacity of the PS-MS as an alternative approach for direct chemical analysis in many applications. Specifically, the waterproof and microporosity characteristics of Teslin® have proven its usefulness in detecting a variety of chemical components in liquid, solid, and gaseous phases without requiring any chemical treatment or substrate alteration.