Adsorption and Destruction of the G-Series Nerve Agent Simulant Dimethyl Methylphosphonate on Zinc Oxide

Construction of imidazole@defective hierarchical porous UiO-66 and fibrous composites for rapid and nonbuffered catalytic hydrolysis of organophosphorus nerve agents

Hydrolytic destruction of toxic organophosphorus nerve agents by metal-organic framework (MOF) catalysts is commonly reliant on bulk water and volatile liquid base, preventing real-world implementation. Poor accessibility to MOF-based active sites in heterogeneous catalysis is also a crucial factor since reactants diffusion is limited by inherently small micropores. To overcome these practical limitations, a ligand-selective pyrolysis strategy was used to construct unsaturated Zr defects and additional mesopores in UiO-66(Zr). Owing to synergistic effect of Zr defects and hierarchical pores, hydrolysis rate constant (k) of nerve agent simulant DMNP (dimethyl 4-nitrophenyl phosphate) on optimal DHP-UiO-30% (defective hierarchical porous UiO-66) is 3.2 times higher than counterpart UiO-30% in N-ethylmorpholine buffer. Encapsulating imidazole (Im) into DHP-UiO-30% affords Im@DHP-UiO, mimicking phosphotriesterase. Im-72@DHP-UiO exhibits rapid DMNP detoxification with 99% conversion in 12 min and initial half-life (t1/2) of 1.8 min in nonbuffered water. As the first example of 'three-in-one' detoxifier, Im@DHP-UiO is further integrated onto nonwoven fabric to construct Im@DHP/Fiber, achieving solid-phase detoxification at ambient humidity with t1/2 of 19.6 min and final conversion of 91%. This is comparable to many powdered catalysts in aqueous solution buffered by volatile bases. This unified strategy is critical and viable to efficiently hydrolyze nerve agents in practical settings.

Metal-Organic Framework Gels for Adsorption and Catalytic Detoxification of Chemical Warfare Agents: A Review

Chemical warfare agents (CWAs) have brought great threats to human life and social stability, and it is critical to investigate protective materials. MOF (metal-organic framework) gels are a class with an extended MOF architecture that are mainly formed using metal-ligand coordination as an effective force to drive gelation, and these gels combine the unique characteristics of MOFs and organic gel materials. They have the advantages of a hierarchically porous structure, a large specific surface area, machinable block structures and rich metal active sites, which inherently meet the requirements for adsorption and catalytic detoxification of CWAs. A series of advances have been made in the adsorption and catalytic detoxification of MOF gels as chemical warfare agents; however, overall, they are still in their infancy. This review briefly introduces the latest advances in MOF gels, including pure MOF gels and MOF composite gels, and discusses the application of MOF gels in the adsorption and catalytic detoxification of CWAs. Meanwhile, the influence of microstructures (pore structures, metal active site, etc.) on the detoxification performance of protective materials is also discussed, which is of great significance in the exploration of high-efficiency protective materials. Finally, the review looks ahead to next priorities. Hopefully, this review can inspire more and more researchers to enrich the performance of MOF gels for applications in chemical protection and other purification and detoxification processes.

Surface Tension of Organophosphorus Compounds: Sarin and its Surrogates

While the production and stockpiling of organophosphorus chemical warfare agents (CWAs), such as sarin, was banned three decades ago, CWAs have remained a threat. New approaches for decontamination and destruction of CWAs require detailed knowledge of their various physicochemical properties. In particular, surface tension is needed to describe the formation and evolution of hazardous aerosols when CWA liquids are dispersed in the air. Due to the extreme toxicity of sarin, most experimental studies are carried out using its surrogates─organophosphorus compounds which, while having similar structures, are much less toxic, e.g., dimethyl methylphosphonate (DMMP) and diisopropyl methylphosphonate (DIMP). However, not only for sarin, but also for its surrogates, literature data on the surface tension are scarce. Here we present experimental measurements and computational predictions of the surface tension of DMMP and DIMP. Classical molecular dynamics simulations using the Transferable Potentials for Phase Equilibria (TraPPE) force field produced an excellent agreement with the experimental results in the temperature range from 3 to 60 °C, validating the predictive capability of TraPPE. Consequently, we applied the TraPPE force field to sarin. Our modeled values for the sarin surface tension cover the range of temperatures from 0 to 85 °C, and the four experimental data points from the literature measured between 20 and 35 °C agree perfectly with our predictions. The temperature-dependent surface tension values for sarin and its surrogates obtained in our study can be used in models predicting the formation and evolution of aerosols made of these chemicals. Furthermore, our results justify the use of the TraPPE force field to derive the thermodynamic properties of other organophosphorus compounds with structures similar to the ones studied here.

Interfacial engineered superelastic metal-organic framework aerogels with van-der-Waals barrier channels for nerve agents decomposition

Chemical warfare agents (CWAs) significantly threaten human peace and global security. Most personal protective equipment (PPE) deployed to prevent exposure to CWAs is generally devoid of self-detoxifying activity. Here we report the spatial rearrangement of metal-organic frameworks (MOFs) into superelastic lamellar-structured aerogels based on a ceramic network-assisted interfacial engineering protocol. The optimized aerogels exhibit efficient adsorption and decomposition performance against CWAs either in liquid or aerosol forms (half-life of 5.29 min, dynamic breakthrough extent of 400 L g^-1) due to the preserved MOF structure, van-der-Waals barrier channels, minimized diffusion resistance (~41% reduction), and stability over a thousand compressions. The successful construction of the attractive materials offers fascinating perspectives on the development of field-deployable, real-time detoxifying, and structurally adaptable PPE that could be served as outdoor emergency life-saving devices against CWAs threats. This work also provides a guiding toolbox for incorporating other critical adsorbents into the accessible 3D matrix with enhanced gas transport properties.

Ruthenium nanoclusters modified by zinc species towards enhanced electrochemical hydrogen evolution reaction

Ruthenium (Ru) has been considered a promising electrocatalyst for electrochemical hydrogen evolution reaction (HER) while its performance is limited due to the problems of particle aggregation and competitive adsorption of the reaction intermediates. Herein, we reported the synthesis of a zinc (Zn) modified Ru nanocluster electrocatalyst anchored on multiwalled carbon nanotubes (Ru-Zn/MWCNTs). The Ru-Zn catalysts were found to be highly dispersed on the MWCNTs substrate. Moreover, the Ru-Zn/MWCNTs exhibited low overpotentials of 26 and 119 mV for achieving current intensities of 10 and 100 mA cm−2 under alkaline conditions, respectively, surpassing Ru/MWCNTs with the same Ru loading and the commercial 5 wt% Pt/C (47 and 270 mV). Moreover, the Ru-Zn/MWCNTs showed greatly enhanced stability compared to Ru/MWCNTs with no significant decay after 10,000 cycles of CV sweeps and long-term operation for 90 h. The incorporation of Zn species was found to modify the electronic structure of the Ru active species and thus modulate the adsorption energy of the Had and OHad intermediates, which could be the main reason for the enhanced HER performance. This study provides a strategy to develop efficient and stable electrocatalysts towards the clean energy conversion field.

Zinc Phthalocyanine Sensing Mechanism Quantification for Potential Application in Chemical Warfare Agent Detectors

Rapid and accurate detection of lethal volatile compounds is an emerging requirement to ensure the security of the current and future society. Since the threats are becoming more complex, the assurance of future sensing devices' performance can be obtained solely based on a thorough fundamental approach, by utilizing physics and chemistry together. In this work, we have applied thermal desorption spectroscopy (TDS) to study dimethyl methylophosphate (DMMP, sarin analogue) adsorption on zinc phthalocyanine (ZnPc), aiming to achieve the quantification of the sensing mechanism. Furthermore, we utilize a novel approach to TDS that involves quantum chemistry calculations for the determination of desorption activation energies. As a result, we have provided a comprehensive description of DMMP desorption processes from ZnPc, which is the basis for successful future applications of sarin ZnPc-based sensors. Finally, we have verified the sensing capability of the studied material at room temperature using impedance spectroscopy and took the final steps towards demonstrating ZnPc as a promising sarin sensor candidate.

Spectroscopic studies of methyl paraoxon decomposition over mesoporous Ce-doped titanias for toxic chemical filtration

The ever-constant threat of chemical warfare agents (CWA) motivates the design of materials to provide better protection to warfighters and civilians. Cerium and titanium oxide are known to react with organophosphorus compounds such Sarin and Soman. To study the decomposition of methyl paraoxon (CWA simulant) on such materials, we synthesized ordered mesoporous metal oxides (MMO) TiO₂, Ce_xTi_1-xO₂ (x = 0.005, 0.5, 0.10, 0.15) and CeO₂. We fully characterized TiO₂ and Ce-doped TiO₂ and found phase-pure oxides with cylindrical hexagonally packed pores and high surface areas (176-252 m²/g). Methyl paraoxon decomposition was tracked through UV/Vis and found Ce_0.15Ti_0.85O₂ to decompose the most methyl paraoxon, but CeO₂ to be the most reactive when normalized to surface area. The surface area normalized rate constant (k_SA) for CeO₂ was 3-4.6 times larger than that of TiO₂ and the Ce_xTi_1-xO₂ series. While TiO₂ and Ce_xTi_1-xO₂ for 0.05 ≤ x ≤ 0.10 displayed no significant differences in the kinetics, the mostly amorphous Ce_0.15Ti_0.85O₂ displayed a slight increase in reactivity. Our findings indicate that the nature of the cation, Ce⁴⁺ vs Ti⁴⁺, is less important to methyl paraoxon reactivity on these MMOs compared to other factors such as crystal structure type.

Superelastic and Photothermal RGO/Zr-Doped TiO2 Nanofibrous Aerogels Enable the Rapid Decomposition of Chemical Warfare Agents

To date, the reckless use of deadly chemical warfare agents (CWAs) has posed serious risks to humanity, property, and ecological environment. Therefore, necessary materials able to rapidly adsorb and securely decompose these hazardous toxics are in urgent demand. Herein, three-dimensional (3D) reduced graphene oxide/Zr-doped TiO₂ nanofibrous aerogels (RGO/ZT NAs) are synthesized by feasibly combining sol-gel electrospinning technology and a unidirectional freeze-drying approach. Benefiting from the synergetic coassembly of flexible ZT nanofibers and pliable RGO nanosheets, the hierarchically entangled fibrous frameworks feature ultralow density, superior elasticity, and robust fatigue resistance over 10⁶ compressive cycles. In particular, the RGO incorporation is attributed to the achieved increased surface area, stronger light absorption, and decreased recombination of charge-carriers for photocatalysis. The highly porous 3D RGO/ZT NAs deliver enhanced photothermal catalytic activity for CWA degradation as well as excellent recyclability and good photostability. This work opens fresh horizons for developing advanced 3D aerogel-based photocatalysts in a controlled fashion.

Antimicrobial Activity and Degradation Ability Study on Nanoparticle-Enriched Formulations Specially Designed for the Neutralization of Real and Simulated Biological and Chemical Warfare Agents

The present work reveals a comprehensive decontamination study on real and simulated biological and chemical warfare agents (BCWA). The emphasis was on evaluating the antimicrobial activity against real biological warfare agents, such as Bacillus anthracis, and also the capacity of neutralizing real chemical warfare agents, such as mustard gas or soman, by employing three different types of organic solutions enriched with ZnO, TiO₂, and zeolite nanoparticles, specially designed for decontamination applications. The capacity of decontaminating BCWA was evaluated through specific investigation tools, including surface monitoring with the swabs method, minimum inhibitory (MIC) and minimum bactericidal concentration (MBC) evaluations, time-kill tests for microorganisms, and GC-MS for monitoring chemical agents on different types of surfaces (glass, painted metal, rubber, and cotton butyl rubber). These tests revealed high decontamination factors for BCWA even after only 10 min, accomplishing the requirements imposed by NATO standards. At the completion of the decontamination process, the formulations reached 100% efficacy for Bacillus anthracis after 10–15 min, for soman after 20–30 min, and for mustard gas in an interval comprised between 5 and 24 h depending on the type of surface analyzed.

Understanding Dimethyl Methylphosphonate Adsorption and Decomposition on Mesoporous CeO2

The increased risk of chemical warfare agent usage around the world has intensified the search for high-surface-area materials that can strongly adsorb and actively decompose chemical warfare agents. Dimethyl methylphosphonate (DMMP) is a widely used simulant molecule in laboratory studies for the investigation of the adsorption and decomposition behavior of sarin (GB) gas. In this paper, we explore how DMMP interacts with the as-synthesized mesoporous CeO₂. Our mass spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy measurements indicate that DMMP can dissociate on mesoporous CeO₂ at room temperature. Two DMMP dissociation pathways are observed. Based on our characterization of the as-synthesized material, we built the pristine and hydroxylated (110) and (111) CeO₂ surfaces and simulated the DMMP interaction on these surfaces with density functional theory modeling. Our calculations reveal an extremely low activation energy barrier for DMMP dissociation on the (111) pristine CeO₂ surface, which very likely leads to the high activity of mesoporous CeO₂ for DMMP decomposition at room temperature. The two reaction pathways are possibly due to the DMMP dissociation on the pristine and hydroxylated CeO₂ surfaces. The significantly higher activation energy barrier for DMMP to decompose on the hydroxylated CeO₂ surface implies that such a reaction on the hydroxylated CeO₂ surface may occur at higher temperatures or proceed after the pristine CeO₂ surfaces are saturated.

Nanoflake-Engineered Zirconic Fibrous Aerogels with Parallel-Arrayed Conduits for Fast Nerve Agent Degradation

Chemical warfare agents (CWAs) pose huge threats to ecological environments, agriculture, and human health due to the turbulent international situation in contemporary society. Zirconium hydroxide (Zr(OH)₄) has captured the prime focus as an effective candidate for CWA decomposition but is often hindered by the isolated powder form. Here, we demonstrate a scalable three-dimensional space-confined synthetic strategy to fabricate nanoflake-engineered zirconic fibrous aerogels (NZFAs). Our strategy enables the stereoscopic Zr(OH)₄ nanoflakes vertically and evenly in situ grown on the interconnected fibrous framework, remarkably enlarging the surface area and providing rich active sites for CWA catalysis. The as-synthesized NZFAs exhibit intriguing properties of ultralow density (>0.37 mg cm^-3), shape-memory behavior under 90% strain, and robust fatigue resistance over 10⁶ compression cycles at 40% strain. Meanwhile, the high air permeability, prominent adsorptivity, and reusability make them state-of-the-art chemical protective materials. This work may provide an avenue for developing next-generation aerogel-based catalysts and beyond.

Recent progress in decontamination system against chemical and biological materials: challenges and future perspectives

Environmental contamination is one of the key issues of developing countries in recent days, and several types of methods and technologies have been developed to overcome these issues. This paper highlights the importance of decontamination in a contaminated environment that normally precedes protection, detection and identification followed by medical support. Further, this paper especially focuses on individual and collective NBC decontamination required on navy ships and correspondingly presents solutions (viable and economical) through the use of indigenously developed decontamination equipment. The paper also highlights the integration of various decontamination technologies with pre-existing ship decontamination systems, indicating the need for various decontaminants. Finally, we will also focus on new decontamination systems based on nanomaterials and enzymes and their utilization.

3D Core-Shell TiO2@MnO2 Nanorod Arrays on Microcantilevers for Enhancing the Detection Sensitivity of Chemical Warfare Agents

Nanostructured microcantilevers have shown promise for sensing application of molecules in the vapor phase. Nanostructures have improved the molecule capture ability of microcantilevers by highly enhancing the surface of capture. Here, to improve the sensitivity and selectivity of a commercial microcantilever without functionalization, we developed 3D core-shell titanium dioxide@manganese dioxide (TiO₂@MnO₂) nanorod arrays on a microcantilever, which exhibited a high enhancement in the sensing performance beyond that of 1D nanostructures for the detection of dimethyl methylphosphonate, a simulant of sarin.

Ultrathin Zirconium Hydroxide Nanosheet-Assembled Nanofibrous Membranes for Rapid Degradation of Chemical Warfare Agents

Organophosphorus-based chemical warfare agents (CWAs) are highly poisonous, and recent attacks using nerve agents have stimulated researchers to develop breakthrough materials for their fast degradation. Zr-based materials have been identified as the most effective catalysts for breaking down CWAs, but in their powdered form, their practical application in personal protective equipment is limited. Herein, a surface-confined strategy for the direct growth of vertically aligned zirconium hydroxide (Zr(OH)₄ ) nanosheets with ultrathin and tortuous structures on nanofibers is reported. The freestanding Zr(OH)₄ nanosheet-assembled nanofibrous membranes (NANMs) show superior catalytic performance to degrade dimethyl methylphosphonate, a nerve agent simulant, with a half-life of 4 min. In addition, intriguing membrane-type NANMs feature integrated properties of exceptional breathability, prominent flexibility, and robust fatigue resistance over one million buckling loads. This facile strategy provides a novel route to manufacture new classes of nanosheet-supported membranes for chemical-protective materials, in particular for gas filters, protective suits, and clothing.

Freestanding and Flexible β-MnO2@Carbon Sheet for Application as a Highly Sensitive Dimethyl Methylphosphonate Sensor

Research on wearable sensor systems is mostly conducted on freestanding polymer substrates such as poly(dimethylsiloxane) and poly(ethylene terephthalate). However, the use of these polymers as substrates requires the introduction of transducer materials on their surface, which causes many problems related to the contact with the transducer components. In this study, we propose a freestanding flexible sensor electrode based on a β-MnO₂-decorated carbon nanofiber sheet (β-MnO₂@CNF) to detect dimethyl methylphosphonate (DMMP) as a nerve agent simulant. To introduce MnO₂ on the surface of the substrate, polypyrrole coated on poly(acrylonitrile) (PPy@PAN) was reacted with a MnO₂ precursor. Then, phase transfer of PPy@PAN and MnO₂ to carbon and β-MnO₂, respectively, was induced by heat treatment. The β-MnO₂@CNF sheet electrode showed excellent sensitivity toward the target analyte DMMP (down to 0.1 ppb), as well as high selectivity, reversibility, and stability.

Degradation of Fatal Toxic Nerve Agents on Dry TiO2

Despite a recent dramatically increased risk of using chemical warfare agents in chemical attacks and assassinations, fundamental interactions of toxic chemicals with other materials are poorly understood, and micromechanisms of their chemical degradation are yet to be established. This represents an outstanding challenge in both fundamental science and practical applications in combat against chemical weapons. One of the most versatile and multifunctional oxides, TiO₂, has been suggested as a promising material to quickly adsorb and effectively destroy toxins. In this paper, we explore how sarin (also known as GB) adsorbs and decomposes on dry nanoparticles of TiO₂ anatase and rutile phases. We found that both anatase and rutile readily adsorb sarin gas molecules because of a strong electrostatic attraction between the phosphoryl oxygen and surface titanium atoms. The sarin decomposition most likely proceeds via a propene elimination; however, the reaction is exothermic on the rutile (110) surface and endothermic on the anatase (101) surface. High energy barriers suggest that sarin would hardly decompose on pristine dry surfaces of TiO₂, and degradation reactions can be triggered by defects or contaminants under realistic operational conditions.

SAW Chemical Array Device Coated with Polymeric Sensing Materials for the Detection of Nerve Agents

G nerve agents are colorless, odorless, and lethal chemical warfare agents (CWAs). The threat of CWAs, which cause critical damage to humans, continues to exist, e.g., in warfare or terrorist attacks. Therefore, it is important to be able to detect these agents rapidly and with a high degree of sensitivity. In this study, a surface acoustic wave (SAW) array device with three SAW sensors coated with different sensing materials and one uncoated sensor was tested to determine the most suitable material for the detection of nerve agents and related simulants. The three materials used were polyhedral oligomeric silsesquioxane (POSS), 1-benzyl-3-phenylthiourea (TU-1), and 1-ethyl-3-(4-fluorobenzyl) thiourea (TU-2). The SAW sensor coated with the POSS-based polymer showed the highest sensitivity and the fastest response time at concentrations below the median lethal concentration (LCt₅₀) for tabun (GA) and sarin (GB). Also, it maintained good performance over the 180 days of exposure tests for dimethyl methylphosphonate (DMMP). A comparison of the sensitivities of analyte vapors also confirmed that the sensitivity for DMMP was similar to that for GB. Considering that DMMP is a simulant which physically and chemically resembles GB, the sensitivity to a real agent of the sensor coated with POSS could be predicted. Therefore, POSS, which has strong hydrogen bond acid properties and which showed similar reaction characteristics between the simulant and the nerve agent, can be considered a suitable material for nerve agent detection.

Multimodal Characterization of Materials and Decontamination Processes for Chemical Warfare Protection

This Review summarizes the recent progress made in the field of chemical threat reduction by utilizing new in situ analytical techniques and combinations thereof to study multifunctional materials designed for capture and decomposition of nerve gases and their simulants. The emphasis is on the use of in situ experiments that simulate realistic operating conditions (solid-gas interface, ambient pressures and temperatures, time-resolved measurements) and advanced synchrotron methods, such as in situ X-ray absorption and scattering methods, a combination thereof with other complementary measurements (e.g., XPS, Raman, DRIFTS, NMR), and theoretical modeling. The examples presented in this Review range from studies of the adsorption and decomposition of nerve agents and their simulants on Zr-based metal organic frameworks to Nb and Zr-based polyoxometalates and metal (hydro)oxide materials. The approaches employed in these studies ultimately demonstrate how advanced synchrotron-based in situ X-ray absorption spectroscopy and diffraction can be exploited to develop an atomic- level understanding of interfacial binding and reaction of chemical warfare agents, which impacts the development of novel filtration media and other protective materials.

A protein nanocomposite for ultra-fast, efficient and non-irritating skin decontamination of nerve agents

In recent assassinations reported in London and Malaysia, nerve agents were used to cause death, by skin poisoning. Skin decontamination is the ultimate and most important defense against nerve agent poisoning, because no effective antidote currently exists. However, almost no existing material can achieve effective and rapid decontamination without irritating the skin. This study links proteins that exhibit no decontamination ability with polymers to form a nanocomposite. This creates a nanospace on the surface of the protein that attracts and traps organic molecules, effectively adsorbing the nerve agent Soman within several seconds, without irritating the skin. Analysis of the different components of proteins and polymers reveals that the decontamination efficiency is considerably affected by the thickness of the coated polymer. Moreover, the thickness of the layer is predominantly determined by the size and species of the core and the crosslinking method. Further in vivo experiments on rats poisoned with Soman verify the efficiency and safety of the nanocomposite. These results could be used to design and synthesize more multi-functional and effective decontamination materials.

Chitosan-Derived Porous Activated Carbon for the Removal of the Chemical Warfare Agent Simulant Dimethyl Methylphosphonate

Methods for the rapid removal of chemical warfare agents are of critical importance. In this work, a porous activated carbon material (C-PAC) was prepared from chitosan flakes via single-step potassium carbonate (K2CO3) activation for the prompt adsorption of dimethyl methylphosphonate (DMMP). C-PAC samples were prepared using different carbonization temperatures (350, 550, and 750 °C) at a constant K2CO3/chitosan ratio (1:2) and using different activator ratios (K2CO3/chitosan ratios of 1:0.5, 1:1, 1:2, and 1:3) at 750 °C. Furthermore, we evaluated the effect of preparation conditions on the adsorption capacities of the various C-PAC materials for DMMP under ambient conditions (25 °C). Notably, for the C-PAC material prepared at 750 °C using a K2CO3/chitosan ratio of 1:2, the DMMP adsorption was saturated at approximately 412 mg·g-1 carbon after 48 h. The good performance of this material makes it a potential candidate for use in remedial applications or protective gear.

Spectroscopically Resolved Binding Sites for the Adsorption of Sarin Gas in a Metal-Organic Framework: Insights beyond Lewis Acidity

Here we report molecular level details regarding the adsorption of sarin (GB) gas in a prototypical zirconium-based metal-organic framework (MOF, UiO-66). By combining predictive modeling and experimental spectroscopic techniques, we unambiguously identify several unique bindings sites within the MOF, using the P═O stretch frequency of GB as a probe. Remarkable agreement between predicted and experimental IR spectrum is demonstrated. As previously hypothesized, the undercoordinated Lewis acid metal site is the most favorable binding site. Yet multiple sites participate in the adsorption process; specifically, the Zr-chelated hydroxyl groups form hydrogen bonds with the GB molecule, and GB weakly interacts with fully coordinated metals. Importantly, this work highlights that subtle orientational effects of bound GB are observable via shifts in characteristic vibrational modes; this finding has large implications for degradation rates and opens a new route for future materials design.