Chemical Warfare Agent Simulants Research Articles

High performance methyl salicylate gas sensor based on noble metal (Au, Pt) decorated WO3 nanofibers

Methyl salicylate (MeSa) is known as a volatile plant pathogen biomarker and a chemical warfare agent simulant. Herein, high performance MeSa gas sensors were developed by optimizing morphology and composition of noble metal decorated tungsten trioxide (WO3) nanofibers. Using optimized nanofibers, 100 ppb of MeSa were readily sensed in dry air whereas the calculated low limit of detection (LLOD) is expected to be in a few tens of ppb. Pt-WO3 (1.1 at% Pt) nanofibers also show an excellent selectivity over other volatile organic compounds including aromatic compounds (i.e., benzene, toluene, ethyl benzene, p-xylene). Systematic characterization of sensors in environments with different oxygen contents indicated that surface carrier concentration significantly altered as a function of Au and Pt content. Although 1.7 at% Au-WO3 nanofibers based sensor has higher sensing response toward MeSa, 1.1 at% Pt-WO3 nanofibers were found to be a more promising sensing material for MeSa detection because of higher selectivity over other VOCs and lower calculated LLOD ( ∼41 ppb).

Mechanically Enhanced Detoxification of Chemical Warfare Agent Simulants by a Two-Dimensional Piezoresponsive Metal-Organic Framework.

Chemical warfare agents (CWAs) refer to toxic chemical substances used in warfare. Recently, CWAs have been a critical threat for public safety due to their high toxicity. Metal-organic frameworks have exhibited great potential in protecting against CWAs due to their high crystallinity, stable structure, large specific surface area, high porosity, and adjustable structure. However, the metal clusters of most reported MOFs might be highly consumed when applied in CWA hydrolysis. Herein, we fabricated a two-dimensional piezoresponsive UiO-66-F4 and subjected it to CWA simulant dimethyl-4-nitrophenyl phosphate (DMNP) detoxification under sonic conditions. The results show that sonication can effectively enhance the removal performance under optimal conditions; the reaction rate constant k was upgraded 45% by sonication. Moreover, the first-principle calculation revealed that the band gap could be further widened with the application of mechanical stress, which was beneficial for the generation of 1O2, thus further upgrading the detoxification performance toward DMNP. This work demonstrated that mechanical vibration could be introduced to CWA protection, but promising applications are rarely reported.

In-situ adsorption and detoxification of chemical warfare agent simulants by biocompatible Zr-MOFs immobilized ionic liquids composites: Mechanisms, degradation pathways and DFT calculations

Detoxicating materials of chemical warfare agents (CWAs) and their simulants play a critical role in reducing pollution contamination and environmental renovation. In this work, we present a simple strategy to prepare a core–shell structure Fe3O4/UiO-66-NH2/ILs@mSiO2 using hydrogen bonding association and electrostatic forces. We performed disinfection studies on dimethyl 4-nitrophenyl phosphate (DMNP) and 2-chloroethyl ethyl sulfide (2-CEES). The synergistic effects of catalytic activations for CWAs, which reduce the electron transport distance and lower the reaction energy barrier, lead to an increase in hydrolysis and Fenton-like reactions efficiency. Eliminationing tests of DMNP and 2-CEES showed that the half-lives of the degradation reactions were 128.36 and 1.12 min, respectively, and the degradation efficiency did not decrease significantly after 4 cycles. This new type of structure could be magnetically separated within 60 s to facilitate material recovery and reuse. Moreover, the presence of a mesoporous silica shell made the catalyst particles to become biocompatible and environmentally friendly. The degradation pathways of the intermediates were revealed based on nuclear magnetic resonance spectroscopy (NMR), gaschromatography-mass spectrometry (GC–MS) and density functional theory (DFT) calculations. The effective combination of catalysts provided a facile strategy for developing multi-effect synergistic catalysts for the elimination of CWAs and other pollutants.

Thermodynamic Insights into Phosphonate Binding in Metal-Azolate Frameworks.

Organophosphorus chemicals, including chemical warfare agents (CWAs) and insecticides, are acutely toxic materials that warrant capture and degradation. Metal-organic frameworks (MOFs) have emerged as a class of tunable, porous, crystalline materials capable of hydrolytically cleaving, and thus detoxifying, several organophosphorus nerve agents and their simulants. One such MOF is M-MFU-4l (M = metal), a bioinspired azolate framework whose metal node is composed of a variety of divalent first-row transition metals. While Cu-MFU-4l and Zn-MFU-4l are shown to rapidly degrade CWA simulants, Ni-MFU-4l and Co-MFU-4l display drastically lower activities. The lack of reactivity was hypothesized to arise from the strong binding of the phosphate product to the node, which deactivates the catalyst by preventing turnover. No such study has provided detailed insight into this mechanism. Here, we leverage isothermal titration calorimetry (ITC) to monitor the binding of an organophosphorus compound with the M-MFU-4l series to construct a complete thermodynamic profile (Ka, ΔH, ΔS, ΔG) of this interaction. This study further establishes ITC as a viable technique to probe small differences in thermodynamics that result in stark differences in material properties, which may allow for better design of first-row transition metal MOF catalysts for organophosphorus hydrolysis.

Enhancing the degradation efficiency of dimethyl nitrophenyl Phosphate, a chemical warfare agent Simulant, through acid sites in bimetallic Metal-Organic framework Ti-MOF-808(Zr): Synergistic roles of Lewis and Brønsted acids

Nerve agents pose an immediate and severe threat to human health, emphasizing the critical need for catalysts that can rapidly and effectively degrade these agents. Herein, we synthesized Ti-MOF-808(Zr) materials with varying Ti/Zr molar ratio using microwave-assisted solvothermal method. Characterization techniques, including BET analysis, TEM, and TG-DTA, confirmed their outstanding properties, such as a high surface area (1756 m2/g), 100 nm particle size, cubic shape, and remarkable thermal stability exceeding 500 °C. The coexistence of Ti4+ and Zr4+ in the secondary building units or inorganic nodes significantly elevates the number of Lewis and Brønsted acid sites in the bimetallic Ti-MOF-808(Zr), as determined through the TPD-NH3 and FTIR-CD3CN methods. We harnessed the potential of MOF-808(Zr) and Ti-MOF-808(Zr) materials as catalysts for the swift degradation of dimethyl nitrophenyl phosphate (DMNP). Remarkably, 4 %Ti-MOF-808(Zr) could degrade DMNP with a half-life of 14.95 s, achieving a complete degradation time within 80 s. We conducted a comprehensive investigation into various factors affecting the DMNP degradation process, including the Ti/Zr molar ratio, catalyst mass, pH, and buffer solution concentration. Notably, our findings reveal that the efficiency of DMNP degradation is profoundly influenced by both the total number of Lewis acid sites and the average acid sites ratio.

Toward Remote Detection of Chemical Warfare Simulants Using a Miniature Potentiostat

A miniaturized electrochemical sensor was developed for the remote detection of chemical warfare agent (CWA) simulants. To facilitate drone-based remote sensing, this present study focuses on advancing the miniaturized and compact electrochemical sensor for monitoring two CWA simulants, diisopropyl fluorophosphate (DFP) and O,S-diethylmethylphosphonothioate (O,S-DEMPT). The differential pulse voltammetry (DPV) signal was processed, and the DPV signature features were extracted on the basis of the redox properties associated with the absence and the presence of DFP and O,S-DEMPT. Upon the addition of 0.10 equivalence of DFP or O,S-DEMPT, a shift in potential (E) of ~0.13 V was recorded. The limit of detection (LOD) was calculated to be 0.25 µM (0.046 ppm) and 0.10 µM (0.017 ppm) for DFP and O,S-DEMPT, respectively. These results were validated using a portable Palmsens Emstat HR potentiostat, which corroborated the results obtained using a lab benchtop potentiostat. Additionally, Boolean logic (“AND” operation) was implemented for future drone technology deployment. This advancement enables the fabrication of a networked device capable of autonomously executing tasks without constant oversight.

Decontamination coupled with dynamic adsorption of sulfur mustard (CEES) and nerve agent-sarin simulants (DMMP) on synthesized zeolite-alpha with its metal oxide composites

Chemical warfare agents (CWAs) are the most feared toxic chemicals intended to debilitate the general human population and regional civilians. Therefore, prompt and urgent decontamination is needed to protect millions of lives and the associated hazardous implications. In this present study, our main goal is to evaluate the performance of Zeolite-Alpha and its various metal oxide composites as novel adsorbents for the decontamination of CWA simulants, 2-chloroethyl ethyl sulfide (CEES), and dimethyl methyl phosphonate (DMMP). Synthesized Zeolite-Alpha and their composites were characterized by XRD, FTIR, SEM-EDS, and BET analysis techniques. The CWA simulants’ decontamination (adsorption and desorption) was monitored using GC-FID and GC-MS analysis techniques. A possible reaction mechanism toward the adsorption and destruction of CWA simulants, CEES, and DMMP was also proposed. Nanocrystalline Zeolite-Alpha and its metal oxide composites are powerful adsorbents, and they showed more significant decontamination potential toward the above CWA simulants. The Cr-O-Alpha and Ag-O-Alpha showed promising results (93–98% decontamination) among all other synthesized metal oxide composites.

Three-Dimensional Au Octahedral Nanoheptamers: Single-Particle and Bulk Near-Field Focusing for Surface-Enhanced Raman Scattering.

Herein, we present a synthetic approach to fabricate Au nanoheptamers composed of six individual Au nanospheres interconnected through thin metal bridges arranged in an octahedral configuration. The resulting structures envelop central Au nanospheres, producing Au nanosphere heptamers with an open architectural arrangement. Importantly, the initial Pt coating of the Au nanospheres is a crucial step for protecting the inner Au nanospheres during multiple reactions. As-synthesized Au nanoheptamers exhibit multiple hot spots formed by nanogaps between nanospheres, resulting in strong electromagnetic near-fields. Additionally, we conducted surface-enhanced Raman-scattering-based detection of a chemical warfare agent simulant in the gas phase and achieved a limit of detection of 100 ppb, which is 3 orders lower than that achieved using Au nanospheres and Au nanohexamers. This pseudocore-shell nanostructure represents a significant advancement in the realm of complex nanoparticle synthesis, moving the field one step closer to sophisticated nanoparticle engineering.

Green synthesis of MOF-based textile composites for the degradation of a chemical warfare agent simulant.

A green synthesis of UiO-66-NH2 embedded in chitosan and deposited on textiles has been investigated for the degradation of chemical warfare agents. This method requires no heating or use of toxic solvents. The composite synthesized presents an interesting efficiency in detoxifying common simulants of chemical warfare agents, such as DMNP. In parallel, resistance and permeability tests were also realized in order to confirm the suitability of the composites for further applications.

Self-driven microplasma decontaminates chemical warfare agent simulant in different gas environments

To develop and refine a self-driven plasma decontamination system, this study investigated the effect of different gas environments (air, Ar, Ar/O2, and Ar/O2/H2O) on the degradation efficiency of 2-chloroethyl ethyl sulfide (2-CEES). A dielectric-dielectric rotating triboelectric nanogenerator (dd-rTENG) was constructed to mechanically induce atmospheric plasma. The dominant active species of different plasmas were identified through spectroscopic and chemical probe diagnostic methods. The results revealed that Ar/O2 and Ar/O2/H2O plasmas generated higher levels of reactive Ox species (O3, O2-, and 1O2) and OH radicals, respectively. Notably, the Ar/O2 and Ar/O2/H2O plasmas exhibited significantly higher decontamination efficiencies than the other plasmas. Moreover, the Ar/O2/H2O plasma featured an energy utilization efficiency of 0.962 μg/J, which is nearly twice that of the previously reported study. However, the Ar plasma exhibited minimal decontamination effect owing to its low electron energy and absence of active species. Further studies have indicated the vital role of reactive oxygen species in the 2-CEES decontamination process. Active Ox can promote the oxidation of 2-CEES, while OH can effectively mitigate the peroxidation process. Furthermore, the system exhibited low electron energy, which might play small role for 2-CEES decontamination. This study is vital for developing self-driven plasma decontamination devices and provides significant clues for understanding the 2-CEES decontamination mechanism.

Rapid Oxidative Detoxification of Mustard Simulant by the Multisite Synergistic Catalytic Action of {PMoVI11MoVO40CuI8} Units.

Under hydrothermal and solvent-thermal conditions, we synthesized two novel polyoxometalate (POM)-based hybrids: [CuI4(Pz)2(H2O)8(PMoVI11MoVO40)]·3.5H2O (1, Pz = pyrazine) and [(C2H8N)5(HPMoVI9MoV3O40)]·DMF·4H2O (2). Single-crystal X-ray diffraction indicates that compound 1 is a three-dimensional structure consisting of Cu (I), {PMo12} anions, Pz, and water, where Cu (I) can be considered as Lewis acid sites. Furthermore, both compounds 1 and 2 possess favorable catalysis activity in catalyzing the conversion of chemical warfare agent simulant 2-chloroethylethyl sulfide (CEES) to nontoxic production of 2-chloroethylethyl sulfoxide (CEESO) under ambient temperature. Significantly, 1 could realize 98% conversion and 100% selectivity of CEES owing to the multisite synergy in the {PMoVI11MoVO40CuI8} units in which the tricoordinated Cu (I) could interact with S and O atoms from CEES and H2O2, respectively. This interaction not only decreases the distance of CEES from peroxomolybdenum species formed by H2O2 but also activates CEES.

A high-performance standalone planar FAIMS system for effective detection of chemical warfare agents via TSPSO algorithm

A high-performance standalone planar field asymmetric waveform ion mobility spectrometry (p-FAIMS) system with a deconvolution algorithm (two-step particle swarm optimization algorithm, TSPSO) for overlapping peaks was developed to effectively detect chemical warfare agents (CWAs). Four CWA simulants were applied in this study to systemically evaluate the performance of the standalone p-FAIMS system. The experimental results showed that each CWA simulant in the mixture can be positively identified by carefully comparing the compensation voltage (CV) value of each peak in the FAIMS spectra for the mixture to the ones in the spectra acquired by using the same FAIMS system for the pure CWA simulant standards. The FAIMS spectrum of the CWA simulant mixture might consist of multiple overlapping peaks, which would be difficult to accurately determine the CV value for each CWA simulant peak. This problem has been effectively resolved in this study by deconvoluting the overlapping peaks via the TSPSO algorithm. As the effective peak deconvolution via TSPSO requires the degree of overlap between each FAIMS peak to be lower than a specific value, the flow rate of FAIMS carrier gas was decreased to further improve the resolution of the p-FAIMS system. After the accurate deconvolution, the resolution of original FAIMS spectrum can also be enhanced to achieve baseline separation by using TSPSO algorithm to narrow the peak width of each peak. The experimental results in this study demonstrated the possibility of using TSPSO algorithm to achieve high-resolution on a typically low-resolution standalone FAIMS. The concept in this study can potentially be applied to any low-resolution instruments to achieve high-resolution results.

Enhanced early‐stage adsorption of chemical warfare agent simulant by MIL‐68‐(X%OH)

AbstractThe development of porous adsorbents for removing hazardous chemicals is of paramount significance in mitigating the risks posed by these substances. Among these hazardous chemicals, chemical warfare agents (CWAs) are of primary concern due to their significant threat. Here, we report the development of porous metal–organic framework‐based adsorbents designed to efficiently adsorb CWA simulant, particularly during the early stages of exposure. We selected MIL‐68, which has a rigid Kagomé structure, as a model system for investigating the adsorption of 2‐chloroethyl ethyl sulfide (CEES). The introduction of a dangling hydroxyl (OH) group within the MIL‐68 framework significantly enhances CEES adsorption during the early stages of exposure to CEES vapors. However, it is crucial to note that an excessive presence of dangling OH groups can negatively impact adsorption ability. Therefore, it is imperative to carefully control the amount of dangling OH groups introduced into the MIL‐68 framework to optimize CEES adsorption performance.

Smoothing Methods for Continuous Permeation Data Measured Discretely Designated for Quick Evaluation of Barrier Materials

Information concerning barrier properties of materials used for production of personal protective equipment fundamentally not only affects their useful properties, but also supports the end users’ decisions. Data obtained from measurements by standardized methods have to be processed by appropriate statistical methods. The article deals with numerical and statistical methods of reconstruction of a continuous curve out of discretely measured data. These mathematical models are proposed as an extension to the manual measurement of a conductometric method. Behaviour of these models is demonstrated on two chemical warfare agent simulants, however, the proposed methodology is universal and can be applied also to chemicals which have no conductivity. The parametric and nonparametric models are studied in the curve reconstruction, as well as in the calculation of subsequent characteristics, for example, a lag-time. The nonparametric model shows the best results which are in accordance with an expert’s estimate.

Cross-Linked Fluorinated Polyurethanes against Chemical Warfare Agent Simulants: Properties Affected by the Structure of Diisocyanate

Cross-Linked Fluorinated Polyurethanes against Chemical Warfare Agent Simulants: Properties Affected by the Structure of Diisocyanate

Solar-thermally enhanced catalytic hydrolysis of chemical warfare agent simulant with UiO-66-NCS decorated reduced graphene oxide aerogels

As chemical warfare agent (CWA) is one of deadly chemicals with strong toxicity and fast action, it is imperative to develop catalytic protective materials that can quickly adsorb and efficiently detoxify CWAs. Herein, reduced graphene oxide (RGO) aerogels are decorated with UiO-66-NCS metal–organic framework with high catalytic activity by in situ growing UiO-66-NH2 inside the RGO hydrogels, converting the UiO-66-NH2 to more active UiO-66-NCS, and freeze-drying for realizing solar-thermally enhanced catalytic hydrolysis of dimethyl 4-nitrophenyl phosphate (DMNP), a chemical warfare agent simulant. Compared with UiO-66-NH2, the UiO-66-NCS is more efficient in catalytically hydrolyzing DMNP with a 30 % accelerated half-life, and the in situ decoration of the RGO aerogel with UiO-66-NCS further improves the catalytic hydrolysis efficiency because of the more exposed active sites of the UiO-66-NCS. Furthermore, the excellent solar-thermal conversion effect of the RGO porous substrate can rapidly generate heat and transfer it to the UiO-66-NCS catalyst, thereby promoting the catalytic activity of the catalyst. The UiO-66-NCS decorated RGO aerogel exhibits a great detoxification efficiency of DMNP under simulated solar light irradiation with a turnover frequency of as high as 0.0531 s−1, ∼2.3 times higher than that under room light, and 1.5 times better than that of UiO-66-NCS powder. The solar-thermally enhanced catalytic hydrolysis of DMNP with the UiO-66-NCS decorated RGO aerogel is demonstrated by the quick detoxification of CWA simulant with great recyclability.

Detection of chemical warfare agent simulants based on luminescent distributed Bragg reflector porous silicon

Detection of chemical warfare agent simulants based on luminescent distributed Bragg reflector porous silicon

Demonstration of High Detoxification Efficiency of Glassy Polymer–Metal Hydroxide Composites toward Chemical Warfare Agent Simulants

Demonstration of High Detoxification Efficiency of Glassy Polymer–Metal Hydroxide Composites toward Chemical Warfare Agent Simulants

Enhanced adsorption capacity of ZIF-8 for chemical warfare agent simulants caused by its morphology and surface charge

The effective separation of toxic chemicals, including chemical warfare agents (CWAs), from the environment via adsorption is of great importance because such chemicals pose a significant threat to humans and ecosystems. To this end, the development of effective porous adsorbents for CWA removal has received significant attention. Understanding the specific interactions between adsorbents and CWAs must precede for the development of effective adsorbents. Herein, we report the relationship between the adsorption capacity of porous ZIF-8 and its morphological and surface characteristics. Four types of ZIF-8, which have different morphologies (such as cubic, rhombic dodecahedron, and leaf- and plate-shaped samples), were selectively prepared. The four types of ZIF-8 were found to have different surface charges owing to dissimilarly exposed components on the surfaces and additionally incorporated components. The specific surface charges of ZIF-8 were found to be closely related to their adsorption capacities for CWA simulants such as 2-chloroethyl ethyl sulfide (CEES) and dimethyl methyl phosphonate (DMMP). Cubic ZIF-8, with the most positive surface charge among four ZIF-8 samples, exhibited the highest adsorption capacity for CEES and DMMP via the effective polar interaction. Moreover, ZIF-8 exhibited excellent recyclability without losing its adsorption capacity and without critical morphological or structural changes.

Self‐Diffusion of a Chemical Warfare Agent Simulant and Water in Nafion by Pulsed Field Gradient NMR

AbstractPulsed field gradient (PFG) NMR at high magnetic field was used to study microscopic diffusion of dimethyl methyl phosphonate (DMMP), a common chemical warfare agent (CWA) simulant, and water in Nafion membranes. PFG NMR measurements were performed for a broad range of molecular displacements. The self‐diffusivities were measured as a function of the DMMP concentration for several fixed water concentrations. The measured data suggest that DMMP and water diffuse in different regions of Nafion. While water mostly diffuses in hydrophilic regions of the membrane, viz. water channels, DMMP diffusion is mostly limited to interfacial perfluoroether regions between these water channels and the semi‐crystalline matrix.