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Decontamination of sensitive electronics exposed to chemical contaminants such as chemical warfare agents (CWA) is incompatible with existing water-based/corrosive methods. The development of new chemistries to tackle this challenge is of great interest. In this paper we investigate the effectiveness of metal–organic frameworks (MOFs) to degrade organophosphorus compounds in non-aqueous environments, via a combined experimental-molecular modeling study. Emphasis is placed on understanding the effect of framework characteristics (metal identity and linker functional group) on the methanolysis of these toxic chemicals, along with identifying reactivity trends for relevant sarin (GB) simulants. Several representative materials based on a hexanuclear metal cluster were judiciously selected, including the well-known catalytically active MOF, UiO-66. Complementary insights into the vibrational and structural properties of these materials were provided by periodic density functional theory (DFT) calculations. Findings indicate that Zr is a more effective metal center to support the degradation of organophosphorus compounds in methanol, as compared to Eu and Y. Detailed investigation into the reactivity of three relevant simulant candidates (diethyl chlorophosphate, DECP, dimethyl 4-nitrophenylphosphate, DMNP, and diisopropyl fluorophosphate, DFP), revealed that nitro- and fluorophosphates are better surrogates to mimic the reactivity of GB in methanol, as compared to chlorophosphate-based molecules. Importantly, experimental results on the MOF based degradation of GB in methanol are reported here for the first time. Additionally, this is the first study that systematically investigates the effectiveness of using MOFs for the solvolysis of organophosphorus compounds, providing valuable insights for materials design and simulant downselection.

Recently, lithium nitride (Li3N) has been proposed as a chemical warfare agent (CWA) neutralization reagent for its ability to produce nucleophilic ammonia molecules and hydroxide ions in aqueous solution. Quantum chemical calculations can provide insight into the Li3N neutralization process that has been studied experimentally. Here, we calculate reaction-free energies associated with the Li3N-based neutralization of the CWA VX using quantum chemical density functional theory and ab initio methods. We find that alkaline hydrolysis is more favorable to either ammonolysis or neutral hydrolysis for initial P-S and P-O bond cleavages. Reaction-free energies of subsequent reactions are calculated to determine the full reaction pathway. Notably, products predicted from favorable reactions have been identified in previous experiments.

We performed ab initio molecular dynamics (AIMD) simulations to benchmark bulk liquid structures and to evaluate results from all-atom force field molecular dynamics (FFMD) simulations with the generalized Amber force field (GAFF) for organophosphorus (OP) and organochlorine (OC) compounds. Our work also addresses the current and important topic of force field validation, applied here to a set of nonaqueous organic liquids. Our approach differs from standard treatments, which validate force fields based on thermodynamic data. Utilizing radial distribution functions (RDFs), our results show that GAFF reproduces the AIMD-predicted asymmetric liquid structures moderately well for OP compounds that contain bulky alkyl groups. Among the OCs, RDFs obtained from FFMD overlap well with AIMD results, with some offsets in position and peak structuring. However, re-parameterization of GAFF for some OCs is needed to reproduce fully the liquid structures predicted by AIMD. The offsets between AIMD and FFMD peak positions suggest inconsistencies in the developed force fields, but, in general, GAFF is able to capture short-ranged and long-ranged interactions of OPs and OCs observed in AIMD. Along with the local coordination structure, we also compared enthalpies of vaporization. Overall, calculated bulk properties from FFMD compared reasonably well with experimental values, suggesting that small improvements within the FF should focus on parameters that adjust the bulk liquid structures of these compounds.

The effect of the dielectric medium between the particles on plasmon coupling was studied experimentally and theoretically. Two-dimensional arrays of silver nanoparticles adsorbed on glass slides were immobilized using poly(methylmethacrylate). The method provides an efficient way for stabilization of particles on surfaces. It was concluded that increasing the dielectric function of the surrounding medium promotes plasmon coupling between silver nanoparticles. On the basis of the quasi-crystalline approximation, the optimum refractive index was calculated that yielded the strongest and highest Q extinction band due to coherent plasmon coupling.

Analysis of surface enhanced Raman scattering spectra from 20 different molecules adsorbed on substrates composed of silver nanoparticles immobilized on silver mirror films revealed competitive Raman enhancement from different types of molecules simultaneously present on the surface. The observed SERS behavior could not be explained using local field enhancement or charge-transfer models. A different SERS mechanism is proposed based on plasmon-induced electronic coupling between the oscillating electrons in the metal and the electronic system of adsorbed molecules. It is suggested that this mechanism has general applicability to other SERS-exhibiting systems.

The primary goals of the Enhanced Micellar Catalysis project were to gain an understanding of the micellar environment of DF-200, or similar liquid CBW surfactant-based decontaminants, as well as characterize the aerosolized DF-200 droplet distribution and droplet chemistry under baseline ITW rotary atomization conditions. Micellar characterization of limited surfactant solutions was performed externally through the collection and measurement of Small Angle X-Ray Scattering (SAXS) images and Cryo-Transmission Electron Microscopy (cryo-TEM) images. Micellar characterization was performed externally at the University of Minnesota's Characterization Facility Center, and at the Argonne National Laboratory Advanced Photon Source facility. A micellar diffusion study was conducted internally at Sandia to measure diffusion constants of surfactants over a concentration range, to estimate the effective micelle diameter, to determine the impact of individual components to the micellar environment in solution, and the impact of combined components to surfactant phase behavior. Aerosolized DF-200 sprays were characterized for particle size and distribution and limited chemical composition. Evaporation rates of aerosolized DF-200 sprays were estimated under a set of baseline ITW nozzle test system parameters.

Particle size effects of nano- and polycrystalline metal tungstate MWO4 (M = Ca, Pb, Cd) scintillators were examined through a comparison of commercially available powders and solution precipitation prepared nanoscaled materials. The scintillation behaviors of nanoparticles and commercial powders were examined with ion beam induced luminescence (IBIL), photoluminescence (PL), and cathodoluminescence (CL) spectroscopy techniques. For commercial microns sized MWO4 powders, spectral emission differences between CL and PL were only observed for Cd and Pb tungstates when compared to reported single crystals. The IBIL wavelength emissions also differed from the commercial MWO4 CL and PL data and were red shifted by 28 and 14 nm for CaWO4 and CdWO4; respectively, while PbWO4 had no significant change. IBIL analysis on CaWO4 nanoparticles produced a 40 nm blue shift from the commercial powder emission. These preliminary results suggest that both size and cation Z may affect the emission properties of the MWO4 scintillators.

Several silver compounds were reduced by low-pressure air plasma to produce porous nanostructured surfaces as surface-enhanced Raman scattering (SERS) substrates. This method is advantageous because substrates are easy to prepare and the silver metal surface is inherently clean without spectroscopic background. Silver compounds were melted into 1–2 mm slugs on quartz slides and plasma treated for different lengths of time. Silver chloride was found to be the best compound to make reproducible and stable SERS substrates. SERS activity of the substrates was tested using L-tryptophan, 4-mercaptobenzoic acid, and adenine.

We report a straightforward method for preparation of freestanding transparent polymer film containing 2D silver nanoparticle arrays and possessing polarization-sensitive optical properties.

Polyoxoniobates are exceptional amongst polyoxometalates in that they can potentially perform base catalysis in water, a process in which a proton is bonded to an oxo ligand, and a hydroxyl is released. Catalytic decomposition of chemical warfare agents such as organofluorophosphates that were used recently in the infamous civilian attacks in Syria is one opportunity to employ this process. Upon evaluation of the polyoxoniobate Lindqvist ion, [Nb6O19]8–, fast neutralization kinetics was discovered for the breakdown of the nerve agent simulant diisopropyl fluorophosphate (DFP). The polyoxoniobates were also tested against the nerve agents Sarin (GB) and Soman (GD). It was determined that different Lindqvist countercations (Li, K, or Cs) affect the rate of decomposition of the organophosphate compounds in both aqueous media (homogeneous reaction), and in the solid state (heterogeneous reaction). Small-angle X-ray scattering analysis of solutions of the Li, K, and Cs salts of [Nb6O19]8– for concentrations at which the experiments were performed revealed distinct differences that could be linked to their relative reaction rates. This study represents the first demonstration of exploiting the unique alkaline reactivity of polyoxoniobates for nerve agent decontamination.

Single crystal, silver particles of 215 +/- 10 nm size were synthesized in solution using the hydrogen reduction method and were characterized by UV-visible extinction spectroscopy and electron microscopy. The extinction spectra reveal the presence of higher order multipoles of the plasmon resonance, such as quadrupole, octupole, and hexadecapole, in addition to the dipole. The formation of higher order multipoles was continuously monitored during the particles growth. Mie extinction calculations were performed and are in good agreement with the measured extinction spectra. The frequency shift of all plasmon modes was measured as a function of the refractive index of the surrounding dielectric medium.

We report surface patterning on the nanolevel with the “grafting to” approach carried out at relatively low temperatures (40 °C). Low grafting temperatures were achieved viasolvent-assisted grafting and allowed the use of the developed approach for surface templating in a variety of ways. Specifically, two examples of the patterning are discussed. A poly-2-vinylpyridine, P2VP surface pattern was created by a combination of capillary force lithography and the solvent-assisted grafting. Silver nanoparticle arrays were created and transferred into a silicon matrix employing the P2VP pattern. Solvent-assisted grafting was also a suitable technique for manipulating thermolabile objects, e.g.proteins. Protein molecules were imprinted via the grafting. Rebinding experiments showed preferential protein adsorption onto the imprinted surface relative to a non-imprinted control sample.