Multifunctional ultra-high vacuum apparatus for studies of the interactions of chemical warfare agents on complex surfaces

Abstract

A fundamental understanding of the surface chemistry of chemical warfare agents is needed to fully predict the interaction of these toxic molecules with militarily relevant materials, catalysts, and environmental surfaces. For example, rules for predicting the surface chemistry of agents can be applied to the creation of next generation decontaminants, reactive coatings, and protective materials for the warfighter. Here, we describe a multifunctional ultra-high vacuum instrument for conducting comprehensive studies of the adsorption, desorption, and surface chemistry of chemical warfare agents on model and militarily relevant surfaces. The system applies reflection-absorption infrared spectroscopy, x-ray photoelectron spectroscopy, and mass spectrometry to study adsorption and surface reactions of chemical warfare agents. Several novel components have been developed to address the unique safety and sample exposure challenges that accompany the research of these toxic, often very low vapor pressure, compounds. While results of vacuum-based surface science techniques may not necessarily translate directly to environmental processes, learning about the fundamental chemistry will begin to inform scientists about the critical aspects that impact real-world applications.

Chemical Warfare Agent Surface Adsorption: Hydrogen Bonding of Sarin and Soman to Amorphous Silica

“…The custom multifunctional UHV chamber specifically designed to safely allow experiments with ultratoxic chemicals used for this work is described in a previous article 3 and is depicted schematically in Figure 5. The chamber combines multiple vacuum dosing methods for liquids and vapors and the ability to perform surface-sensitive IR spectroscopy and XPS as well as mass spectrometry (MS).…”

“…Experiments were performed in an UHV surface science instrument recently developed for the study of CWAs and other highly toxic compounds (see the Experimental Methods section). Located in a laboratory at the Aberdeen Proving Grounds, the instrument (Figure ) enables measurements of surface adsorption through infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS), while gas-phase products are monitored via a quadrupole mass spectrometer . Particulate silica surface samples were prepared by dispersing silica (200 m 2 /g, Aerosil fumed silica with a 12 nm average particle diameter) from a solution of isopropanol onto a reflective Au substrate, which served as an inert support and reflective mirror for performing IR spectroscopy of the silica during agent exposure.…”

“…Located in a laboratory at the Aberdeen Proving Grounds, the instrument (Figure 5) enables measurements of surface adsorption through infrared (IR) spectroscopy and Xray photoelectron spectroscopy (XPS), while gas-phase products are monitored via a quadrupole mass spectrometer. 3 Particulate silica surface samples were prepared by dispersing silica (200 m 2 /g, Aerosil fumed silica with a 12 nm average particle diameter) from a solution of isopropanol onto a reflective Au substrate, which served as an inert support and reflective mirror for performing IR spectroscopy of the silica during agent exposure. Once prepared, the surface samples were installed via a load-lock mechanism that couples the main chamber sample holder to a small transfer chamber located within the confines of a CWA-certified surety fume hood.…”

Di(hydroperoxy)cycloalkane Adducts of Triarylphosphine Oxides: A Comprehensive Study Including Solid-State Structures and Association in Solution

“…34−37 They are applied to probe surface acidities 38,39 warfare agents. 40 From an analytical point of view, phosphine oxides display interesting mobilities on surfaces that have recently been studied by solid-state NMR. 41−43 One of the most important features of phosphine oxides with respect to this contribution is their ability to form hydrogen bonds with a variety of different donors.…”

“…Phosphine oxides are important synthetic targets and intermediates. − For example, they are applied for Mitsunobu reactions and recently attracted attention as redox-free Mitsunobu organocatalysts . On the other hand, phosphine oxides are coproducts of Appel and Wittig reactions and unwanted byproducts of phosphine chemistry in general, especially when catalysts are immobilized on oxide supports via phosphine linkers. − They are applied to probe surface acidities , and receive attention in the decomposition of warfare agents . From an analytical point of view, phosphine oxides display interesting mobilities on surfaces that have recently been studied by solid-state NMR. − …”