Agent Simulation Research Articles

Thermocatalytic Decomposition of Dimethyl Methylphosphonate Based on CeO2 Catalysts with Different Morphologies

The catalytic performances of the catalysts and decomposition mechanisms of dimethyl methylphosphonate (DMMP), a commonly used nerve agent simulant, are well understood based on previous studies. However, the effects of the morphology of the catalyst on DMMP decomposition performance and mechanisms remain unexplored. Thus, in this work, experimental studies were conducted on the thermocatalytic decomposition of DMMP on CeO2 nanomaterials with different morphologies, e.g., irregular nanoparticles, nanorods, and nanocubes. From the performance evaluation, CeO2 nanorods exhibited higher DMMP thermocatalytic decomposition performance as compared to irregular nanoparticles and nanocubes. The primary reaction pathways were the same on all three morphologies of materials, according to in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study, whereas side reaction paths showed variable behaviors. According to the catalytic reaction mechanism study, the surface lattice oxygen played a vital role in the thermocatalytic decomposition of DMMP and the accumulation of phosphates, carbonates, and formates were the main factors for deactivation of the catalyst. The behavior of CeO2 catalyst with different morphologies in the thermocatalytic decomposition of DMMP was revealed in this work, and this will be useful for the future design of high-performing catalysts for the efficient degradation of chemical toxicant.

Oxime-Functionalized, Nonwoven Nanofabrics for Rapid, Inexpensive Decontamination of a Nerve Agent Simulant

Organophosphorous-based nerve agents remain one of the most toxic and accessible chemical warfare agents known to man. Herein, we report the development of novel, oxime-functionalized poly(4-vinylpyridine) (P4VP-Ox) materials as inexpensive, scalable polymeric substrates capable of rapid decontamination of nerve agents, as demonstrated using one nerve agent simulant, dimethyl-4-nitrophenyl phosphate (DMNP). The incorporated oximes adjacent to positively charged pyridinium salts remain deprotonated at neutral to slightly basic pH, providing super-nucleophilic materials to deactivate nerve agents and their simulants rapidly and irreversibly. These materials were electrospun to form nanofabrics, providing increased surface area and enhanced reactivity for degradation of DMNP. Nanofibers obtained from P4VP functionalized at 20 mol % pendants with ortho-pyridinium oximes moieties (P4VP-OOx20%) provided the fastest reaction kinetics. This substrate provided complete decomposition of DMNP within 1.5 h and calculated t1/2 = 14.4 min. The P4VP-Ox substrates were also found to be recyclable, allowing for quantitative DMNP degradation within 8 h over the course of four reaction cycles. Furthermore, to mimic real-life scenarios, we attempted solid-state DMNP degradation via applying small drops of DMNP directly on the nanofabric substrates and extracting with water for 31P NMR analysis. Overall, the P4VP-OOx20% substrate was found to retain its reactivity in the solid state, with the as-prepared nanofabric displaying >95% DMNP degradation after 6 h. When performed in different environments (i.e., 100% humidity, hexanes-rich atmosphere), the reactivity diminished slightly but still displayed >95% degradation after 24 h of reaction, establishing these materials for applications as reactive, economical, and easily scalable Chem-Bio protective materials.

Spontaneously super-hygroscopic MOF-gel microreactors for efficient detoxification of nerve agent simulant in atmospheric environments

We design a spontaneously super-hygroscopic alkaline microreactor by photoinduced integration of Zr-MOF catalyst and alkaline poly(dimethylaminoethyl acrylate) onto LiCl-salinized poly(N-isopropylacrylamide) gel, generating a microenvironment with non-volatile polymeric base and non-bulk water for detoxification of a typical nerve agent simulant, dimethyl 4-nitrophenyl phosphate (DMNP), in atmospheric environments. The super-hygroscopic gel with directional microchannels facilitates the absorption, transport and storage of water under different humidities, and exhibits fast hygroscopic efficiency with a high moisture absorption capacity of 6.4 g g−1. The integrated microreactor achieves simultaneous water uptake and catalytic hydrolysis of DMNP in an atmospheric environment with an initial half-life of ∼1.9 h and a final conversion of 95.5%, which is attributed to the synergistic catalytic microenvironment of the exposed Zr-MOF catalyst, the polymeric base, and the water from moist air. This work provides a feasible strategy for designing spontaneously hygroscopic microreactors for detoxifying nerve agent simulants in atmospheric environments.

Dual-State Fluorescent Probe for Ultrafast and Sensitive Detection of Nerve Agent Simulants in Solution and Vapor.

The development of fluorescent probes for detecting nerve agents has been the main concern focus of research because of their lethal toxicity for humans. Herein, a probe (PQSP) based on the quinoxalinone unit and the styrene pyridine group was synthesized and could visually detect a sarin simulant diethyl chlorophosphate (DCP) with excellent sensing properties in solution and solid states. Interestingly, PQSP showed an apparent intramolecular charge-transfer process by catalytic protonation after reacting with DCP in methanol, accompanied with the aggregation recombination effect. The sensing process was also verified by nuclear magnetic resonance spectra, scanning electron microscopy, and theoretical calculations. In addition, the papered test strips of loading probe PQSP exhibited an ultrafast response time within 3 s and high sensitivity with a limit of detection of 3 ppb for the detection of DCP vapor. Therefore, this research provides a designed strategy for developing the probes with dual-state emission fluorescence in solution and solid states for detecting DCP sensitively and rapidly, which can be fabricated as chemosensors to visually detect nerve agents in practice.

Progress of sensitive materials in chemiresistive sensors for detecting chemical warfare agent simulants: A review

Abstract Chemical warfare agents (CWAs) are chemical substances intended for use in military operations to kill, injure, or incapacitate an enemy. It is very important to detect toxic CWAs at trace levels on site. Compared with traditional CWA analysis instrument methods, chemiresistive gas sensors present advantages of being small, fast, and inexpensive. Chemiresistive gas sensors are still an important research topic with the development of nanofabrication technology and new kinds of sensing materials, including carbon nanotubes, graphene, and black phosphorus (BP). Chemiresistive gas sensors are divided into three categories according to the type of sensitive materials: carbon- and BP-based materials, conductive polymers, and metal oxide semiconductors. A brief analysis was carried out on fabrication strategies using sensitive materials, including hydrogen bonding strategies, nanostructures, morphology, doping effects, composite materials, and other material application methods, and the sensitive materials and detection effects are summarized in this study. This review aims to provide guidance in the development of chemiresistive sensors for the detection of CWAs.

Trustworthy agent-based simulation: the case for domain-specific modelling languages

Simulation is a key tool for researching complex system behaviour. Agent-based simulation has been applied across domains, such as biology, health, economics and urban sciences. However, engineering robust, efficient, maintainable, and reliable agent-based simulations is challenging. We present a vision for engineering agent simulations comprising a family of domain-specific modelling languages (DSMLs) that integrates core software engineering, validation and simulation experimentation. We relate the vision to examples of principled simulation, to show how the DSMLs would improve robustness, efficiency, and maintainability of simulations. Focusing on how to demonstrate the fitness for purpose of a simulator, the envisaged approach supports bi-directional transparency and traceability between the original domain understanding to the implementation, interpretation of results and evaluation of hypotheses.

Porphyrin-Moiety-Functionalized Metal–Organic Layers Exhibiting Catalytic Capabilities for Detoxifying Nerve Agent and Blister Agent Simulants

The development of very efficient bifunctional catalysts for the simultaneous detoxification of two kinds of the deadliest chemical warfare agents (CWAs), nerve agent and blister agent, is highly desirable. In this study, two porphyrin-based ligands [tetrakis(4-carboxyphenyl) porphyrin (TCPP) and protoporphyrin IX (PPIX)] are introduced into 2D Zr-1,3,5-tris(4-carboxyphenyl)benzene (BTB) metal-organic layers (MOLs), composed of six-connected Zr6 nodes and the tritopic carboxylate ligand BTB, by a solvent-assisted ligand incorporation method. The loads of TCPP and PPIX are 6.4 and 10.9 wt %, respectively. The detoxification of simulants of the nerve agent and the blister agent was conducted to investigate the catalytic activity of porphyrin-moiety-functionalized MOLs. The reaction half-life of optimal TCPP-functionalized MOL catalyzing the hydrolysis of a nerve agent simulant is only 2.8 min, meanwhile, the half-life of the selective catalytic oxidation of a blister agent simulant is only 1.2 min under LED illumination. More importantly, such a degradation half-life is only about 4 min under natural sunlight (∼60 mW/cm2). To our knowledge, TCPP-functionalized MOL is by far the most efficient catalyst for blister agent simulant degradation under solar light. Therefore, 2D ultrathin MOLs on demand appear to be a promising and efficient material platform for the development of bifunctional catalysts for CWA protection.

MOF–Polymer Mixed Matrix Membranes as Chemical Protective Layers for Solid-Phase Detoxification of Toxic Organophosphates

Zirconium-based metal-organic frameworks (Zr-MOFs) have been demonstrated as potent catalysts for the hydrolytic detoxification of organophosphorus nerve agents and their simulants. However, the practical implementation of these Zr-MOFs is limited by the poor processability of their powdered form and the necessity of water media buffered by a volatile liquid base in the catalytic reaction. Herein, we demonstrate the efficient solid-state hydrolysis of a nerve agent simulant (dimethyl-4-nitrophenyl phosphate, DMNP) catalyzed by Zr-MOF-based mixed matrix membranes. The mixed matrix membranes were fabricated by incorporating MOF-808 into the blending matrix of poly(vinylidene fluoride) (PVDF), poly(vinylpyrrolidone) (PVP), and imidazole (Im), in which MOF-808 provides highly active catalytic sites, the hydrophilic PVP helps to retain water for promoting the hydrolytic reaction, and Im serves as a base for catalytic site regeneration. Impressively, the mixed matrix membranes displayed excellent catalytic performance for the solid-state hydrolysis of DMNP under high humidity, representing a significant step toward the practical application of Zr-MOFs in chemical protective layers against nerve agents.

Dual-Function Detoxifying Nanofabrics against Nerve Agent and Blistering Agent Simulants

The development of functional materials that can detoxify multiple chemical warfare agents (CWAs) at the same time is of great significance to cope with the uncertainty of CWA use in real-world situations. Although many catalysts capable of detoxifying CWAs have been reported, there is still a lack of effective means to integrate these catalytic-active materials on practical fibers/fabrics to achieve effective protection against coexistence of a variety of CWAs. In this work, by a combination of electrospinning and in situ solvothermal reaction, PAN@Zr(OH)4@MOF-808 nanofiber membranes were prepared for detoxification of both nerve agent and blistering agent simulants dimethyl 4-nitrophenyl phosphate (DMNP) and 2-chloroethyl ethyl sulfide (CEES). Under the catalytic effect of the MOF-808 component, DMNP hydrolysis with a half-life as short as 1.19 min was achieved. Meanwhile, an 89.3% CEES removal rate was obtained within 12 h by adsorption and catalysis of MOF-808 and Zr(OH)4 components at ambient conditions, respectively. PAN@Zr(OH)4@MOF-808 nanofiber membranes also showed a superior blocking effect on CEES compared to bare PAN and PAN@Zr(OH)4 nanofiber membranes. Simultaneous protection against DMNP and CEES showed effective inhibition of both simulants for at least 2 h. The preparation method also imparted intrinsically good interfacial adhesion between the components, contributing to the excellent recycling stability of PAN@Zr(OH)4@MOF-808 nanofiber membranes. Therefore, the prepared composite nanofabrics have great application potential, which provides a new idea for the construction of broad-spectrum protective detoxification materials.

Infection Risk Assessment via Agent Simulation with Seat-Choice Behavior

The human behavior has much impact on the infectious desease spreading. The pathogen generation is not uniform for the residential area since the human have some preference on where to be. The purpose of the present study is to evaluate the impact of the human preference on the seat choice behavior on the pathogen concentration. The preference of the seat selections in a train was modelled and the agent simulation was performed in order to evaluate the non-uniformity of pathogen. The concentration was calculated with Wells-Riley model. The results of the agent simulation showed the preference of seat choice based on the experimental results in a train environment. The seats at the end were more selected than other seats. The concentration at the seats at the end kept increasing because the agent sat there by turns and that is why there was no recovery time. The double effect of the more seat selection and the less recovery time has much impact on the non-uniformity of the concentration.

A chemodosimetric approach for the visual detection of nerve agent simulant diethyl chlorophosphate (DCP) in liquid and vapour phase.

In this work, a novel fluorescent ratiometric switch, 8-((6-(1H-benzo[d]imidazol-2-yl)pyridin-2-yl)methoxy)quinoline (BIPQ), has been introduced for sensing an organophosphorus (OP) chemical vapor threat, diethyl chlorophosphate (DCP), the low-toxic mimic of the real nerve agent sarin (GB). BIPQ is efficient at detecting DCP in both solution and gaseous phase and has potential practical application with high sensitivity and selectivity. The probe shows significant ratiometric emission in the presence of DCP along with a distinct color change from blue to cyan under UV light. The sensing mechanism of the chemodosimeter is based on the generation of a new adduct, BIPQ-DCP, through a nucleophilic substitution reaction with DCP followed by a ring-closure process to form the final product. The detection limit of BIPQ for DCP was determined to be in the order of 10-8 (M) in the liquid state. DFT and TDDFT computational techniques were carried out in order to interpret the electronic properties theoretically.

Zirconium-based MOF nanocrystals confined on amphoteric halloysite nanotubes for promoting the catalytic hydrolysis of an organophosphorus nerve agent simulant.

Exploiting efficient and practical catalysts for hydrolyzing organophosphorus nerve agents is significant and highly desirable. Herein, a new class of self-detoxifying composites, namely, halloysite nanotubes@NU-912 (HNTs@NU-912), HNTs@NU-912-I and HNTs@UiO-66-NH2, is constructed by in situ synthesis of hexanuclear zirconium cluster-based metal-organic frameworks (Zr-MOFs) NU-912, NU-912-I and UiO-66-NH2, respectively, with HNTs, which are natural nanotubular materials consisting of Si-O-Si tetrahedral sheets on the outer surface and Al-OH octahedral sheets on the inner surface. The results show that crystalline Zr-MOFs uniformly cover the outer surface of HNTs and the particle size of Zr-MOFs is greatly reduced to less than 50 nm. Furthermore, HNTs@NU-912, HNTs@NU-912-I and HNTs@UiO-66-NH2 display much higher catalytic efficiency for the hydrolysis of dimethyl-4-nitrophenyl phosphate (DMNP) than the corresponding Zr-MOFs both in an aqueous N-ethylmorpholine (NEM) buffer solution and under ambient conditions. Specifically, HNTs@NU-912-I shows a turnover frequency (TOF) of 0.315 s-1 in aqueous buffer solution, placing it among the best Zr-MOF-based heterogeneous catalysts for the hydrolysis of DMNP. The composites show high stability, and more importantly, can replace the buffer solvent and control the pH to a certain degree by virtue of its acidic Si-O-Si sheets and alkaline Al-OH sheets. This work provides a certain reference for the subsequent development of personal protective equipment.

Immobilization of Brønsted basic hexaniobate on the Lewis acidic zirconia using an emulsion assisted self-assembly strategy for synergistic boosting of nerve agent simulant decontamination

The Brønsted basic hexaniobate is immobilized on the Lewis acidic zirconia by emulsion assisted self-assembly, the synergistic effect between the two components endows the C16N-Nb6/ZrO2 with remarkable performance for hydrolysis of Sarin simulant.

Agent simulation research of the impact of free market electricity trading on the power supply mix

Agent simulation research of the impact of free market electricity trading on the power supply mix

Synthesis of a trinuclear zinc(II) cluster composed of [4.4.3.01,5]tridecane cages: a rapid detection and degradation probe for the chemical warfare agent simulant diethyl cyanophosphonate in protein-rich food products.

Diethyl cyanophosphonate (DCNP), a simulant of Tabun, is a common pollutant in pharmaceutical waste and poses a high risk to living organisms. Herein, we demonstrate a compartmental ligand-derived trinuclear zinc(II) cluster [Zn3(LH)2(CH3COO)2] as a probe for the selective detection and degradation of DCNP. It consists of two pentacoordinated Zn(II) [4.4.3.01,5]tridecane cages bridged through a hexacoordinated Zn(II) acetate unit. The structure of the cluster has been elucidated by spectrometric, spectroscopic, and single-crystal X-ray diffraction studies. The cluster shows a two-fold increased emission as compared to the compartmental ligand (at λexc = 370 nm and λem = 463 nm) due to the chelation-enhanced fluorescence effect and acts as a turn-off signal in the presence of DCNP. It can detect DCNP at nano levels up to 186 nM (LOD). The direct bond formation between DCNP and Zn(II) via the -CN group degrades it to inorganic phosphates. The mechanism of the interaction and degradation is supported by spectrofluorimetric experiments, NMR titration (1H and 31P), time of flight mass spectrometry and density functional theory calculations. The applicability of the probe has been further tested by the bio-imaging of zebrafish larvae, analysis of high-protein food products (meat and fish) and vapour phase detection by paper strips.

A salicylaldoximate-based AIE probe for the detection of the nerve agent simulant DCP

A salicylaldoximate-based AIE probe TPE-D successively undergoes the formation of nitrile and the phosphorylation of phenolic hydroxyl group when detecting DCP, which will give a significant fluorescence ‘light-up’ response within minutes.

Visual and ratiometric fluorescent probe via an intramolecular charge transfer for detection of a nerve agent simulant in solutions and in the gas phase

A simple two-step synthesis was done to make a probe PPID for rapid detection of DCP in the solution and vapor phase. The mechanism involved in the sensing was enhanced ICT.

The preservation of sarin and O,O'-diisopropyl fluorophosphate inside coordination cage hosts.

The host-guest chemistry of O,O'-diisopropyl fluorophosphate (DFP), a phosphonofluoridate G-series chemical warfare agent simulant, was investigated in the presence of a number of octanuclear cubic coordination cage hosts. The aim was to demonstrate cage-catalysed hydrolysis of DFP at near neutral pH: however, two octanuclear coordination cages, HPEG (containing water-solubilising PEG groups) and HW (containing water-solubilising hydroxymethyl groups), were actually found to increase the lifetime of DFP in aqueous buffer solution (pH 8.7). Crystallographic analysis of DFP with a structurally related host cage revealed that DFP binds to windows in the cage surface, not in the internal cavity. The phosphorus-fluorine bond is directed into the cavity rather than towards the external environment, with the cage/DFP association protecting DFP from hydrolysis. Initial studies with the chemical warfare agent (CWA) sarin (GB) with HPEG cage in a buffered solution also showed a drastically reduced rate of hydrolysis for sarin when bound in the host cage. The ability of these cages to inhibit hydrolysis of these P-F bond containing organophosphorus guests, by encapsulation, may have applications in forensic sample preservation and analysis.

Boosted ability of ZIF-8 for early-stage adsorption and degradation of chemical warfare agent simulants.

Efficient adsorption of hazardous substances from the environment is crucial owing to the considerable risks they pose to both humans and ecosystems. Consequently, the development of porous materials with strong adsorption capabilities for hazardous substances, such as chemical warfare agents (CWAs), is pivotal for safeguarding human lives. Specifically, the early-stage adsorption proficiency of the adsorbents plays a vital role in determining their effectiveness as ideal adsorbents. Herein, we report the efficient adsorption of CWA simulants using thermally treated ZIF-8 (T-ZIF-8). The T-ZIF-8 samples were prepared by subjecting ZIF-8 to a simple thermal treatment, which resulted in a more positive surface charge with extra open metal sites. Although the pore volume of T-ZIF-8 decreased after thermal treatment, the positive surface charge of T-ZIF-8 proved advantageous for the adsorption of the CWA simulants. As a result, the adsorption capacity of T-ZIF-8 for the CWA simulants improved compared to that of pure ZIF-8. Notably, T-ZIF-8 exhibited a remarkably enhanced adsorption ability in the early stage of exposure to the CWA simulants, possibly due to the effective polar interactions between T-ZIF-8 and the simulants via the electron-rich components within the CWA simulants. Moreover, the enhanced adsorption capacity of T-ZIF-8 led to the fast degradation of simulant compared to pure ZIF-8. T-ZIF-8 also demonstrated excellent stability over three adsorption cycles. These findings highlight that T-ZIF-8 is an outstanding material for the early-stage adsorption and degradation of CWA simulants, offering high effectiveness and stability.

Instantaneous degradation of nerve agent simulants using zirconium-based metal–organic polyhedra

Metal–organic polyhedra (MOPs) are discrete molecules made of metal ions/clusters and organic ligands, and their crystal packing leads to the generation of intrinsic and extrinsic porosity.