Adsorption and photodegradation of dimethyl methylphosphonate on mineral surfaces: A comparative study of titania and kaolin

Nylon- and cotton-based fabrics, particularly a 50:50 nylon-cotton blend ("NYCO"), are commonly used for military and workforce garments. Developing high-throughput methods to attach reactive or sorptive metal oxide or metal-organic framework (MOF) nanoparticles (NPs) is important for chemical protection. Open-air plasma treatment has been used to activate cotton, nylon, and NYCO such that they covalently bond to ca. 20 nm zinc oxide and UiO-66-NH2 MOF particles. For cotton, X-ray photoelectron spectroscopy (XPS) shows that plasma treatment partially oxidizes cellulose, with transformation of aliphatic carbons to hydroxyl and carbonyl groups. For nylon, XPS indicates the formation of additional hydroxyl groups and transformation of some amide groups to hydroxyamides. Plasma-treated fabrics and untreated controls were spray-coated with ethanolic suspensions of ZnO or UiO-66-NH2 particles, ultrasonicated in ethanol, and air-dried. In some cases, particle-covered fabrics were machine-washed to assess durability. For all three fabrics, scanning electron microscopy (SEM) and XPS demonstrated that plasma treatment significantly enhances the surface concentration of ZnO NPs that remain after ultrasonication. However, machine washing removes most of the ZnO NPs, with minimal differences between untreated and plasma-treated fabrics. In the case of UiO-66-NH2, particle sizes of ca. 200 and 500 nm were evaluated, and adhesion was significantly better on NYCO for the smaller particles due to more attachment sites per unit mass; a significant surface concentration of the smaller MOF remains on NYCO even after five wash cycles. To demonstrate the efficacy of the process for treating fabrics to impart chemical protection, permeation times of the nerve agent simulant dimethyl methylphosphonate were compared for bare and MOF-functionalized NYCO. The functionalized fabric exhibited a permeation time that was almost three times greater than for bare, plasma-treated fabric. These results demonstrate the practicality of the process for high-throughput preparation of metal oxide and UiO-66-NH2 functionalized NYCO for chemical protection.

Chemical forensic profiling of compounds related to the chemical weapons convention using 2D and 3D diffusion-ordered NMR spectroscopy.

Photoionization induced chemical ionization time-of-flight mass spectrometry for rapid and sensitive detection of trace gaseous chemical warfare agents.

Bilayer oxides chemiresistor design for highly selective detection of dimethyl methylphosphonate

We explore the performance of a chemiresistor sensorarray basedon thin layers of reduced graphene oxide (rGO). The rGO is depositedwith a spray coating technique to fabricate three samples of differentlayer thicknesses, which are characterized by atomic force microscopy(AFM) and Raman spectroscopy. We expose the chemiresistors to watervapor, three volatile organic compounds (VOC), ethanol, acetone, andformaldehyde, and two simulants of chemical warfare agents (CWA),dimethyl–methyl phosphonate (DMMP) and dipropylene glycol monomethylether (DPGME). The rGO-based sensors show noticeable changes in resistanceupon parts per million variations of the analyte concentrations. Thelargest detection sensitivity 0.02%/ppm is observed with DPGME. Furthermore,we investigate a thickness-dependent signal that depends on the natureof the analyte. We show that comparing the signal measured with onlya few rGO layers of different thicknesses can be used to distinguishformaldehyde from other VOC and DMMP from DPGME. Our findings representa step toward the development of practical sensor arrays based onlow cost, scalable graphene-based materials, enabling both sensitiveand selective detection of analytes.

Aluminum nanoparticles (Al NPs) were synthesized via catalyzed thermal reduction of an aluminum precursor in the presence of a capping ligand. A systematic study was conducted to examine the effect of dilution on nanoparticle synthesis by varying the volume of anhydrous toluene across four dilution factors while maintaining constant molar quantities of the aluminum precursor, catalyst, and ligand. This methodology is relevant for scale-up processes, where more dilute conditions can mitigate nanoparticle reactivity and enhance safety. The resulting Al NPs were characterized with respect to the yield, size distribution, chemical composition (bulk and surface), and morphology. Consistent and favorable yields were observed across all of the dilution conditions. The synthesized Al NPs were further evaluated as low-cost substrates for surface-enhanced Raman spectroscopy (SERS). While Au and Ag nanoparticles are known to exhibit SERS activity in the visible region for chemical warfare agent (CWA) surrogates, little is known about SERS performance in the ultraviolet (UV) region by using metallic substrates. Al NPs, with broadband optical absorption extending from the UV to the near-infrared (NIR), were investigated for this application. Rhodamine 6G (R6G), a standard dye, and dimethyl methylphosphonate (DMMP), a commonly used CWA surrogate, were analyzed by using 248.6 nm UV excitation. The Al NPs exhibited modest SERS activity for both analytes under these conditions. To the best of our knowledge, this is the first report to examine both the synthesis of Al NPs under varying reagent concentrations by changing the solvent volumes and their SERS performance in the UV region for CWA surrogates. Further efforts aimed at reducing particle agglomeration and tailoring surface chemistry are expected to improve sensitivity and enable the development of cost-effective SERS-based sensors for trace CWA detection.

There is a growing interest in developing safer and moreeffectivedecontaminating agents for organophosphate-based pesticides and nerveagents. In this study, we present an effective method for the nonaqueousdecontamination of these compounds using small-molecule-based decontaminatingagents under ambient conditions. Our approach utilizes aryl and heteroarylcarboxaldehyde hydrazones and hydrazides to effectively hydrolyzenerve agent simulants into their nontoxic degradation products. Theeffectiveness of this method was evaluated using a range of nerveagent simulants, including dimethyl 4-nitrophenyl phosphate (DMNP),dimethyl methylphosphonate (DMMP), and triphenyl phosphate (TPhP).In the presence of the heteroaryl hydrazone, the rate of hydrolysiswas enhanced by 116-, 1930-, and 2490-fold relative to the uncatalyzedhydrolysis of TPhP, DMNP, and DMMP, respectively. Our findings demonstratethe potential of aryl carboxaldehyde hydrazones and hydrazides forthe instantaneous and effective decontamination of nerve agents. Theseresults are further substantiated by GIAO–DFT calculations.Additionally, the regioselectivity of the nucleophiles in the degradationof simulants to nontoxic products at alkaline pH (≥9.5) iselucidated.

HighlightsThe mobile workstation integrates capillary electrophoresis with C4D on disposable PDMS chips, enabling rapid, sensitive organophosphate detection in the field.Optimised injection techniques, voltage settings, and a custom adaptor ensure reproducible separations and robust performance under challenging field conditions.The portable system reduces analytical turnaround times relative to laboratory methods, enabling rapid decisions in forensic and environmental scenarios.Its cost-effective, user-friendly design supports widespread on-site deployment, boosting emergency response and public safety.Timely detection of organophosphates in outdoor environments remains a critical challenge for forensic and environmental monitoring. Traditional methods often require transporting samples to centralised laboratories, delaying essential response actions. In this study, we present a novel mobile analytical chemistry workstation that integrates capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) on low-cost polydimethylsiloxane (PDMS) microfluidic chips, enabling rapid and accurate on-site analysis of organophosphates. The system features a streamlined workflow that includes in-field sample collection, microfluidic analysis, and the wireless transmission of data to a central command centre for immediate decision-making. The detection system demonstrates a linear range of 2.5 mM to 20 mM for dimethyl methylphosphonate (DMMP), with an estimated limit of detection (LOD) of 2.5 mM. We evaluate the feasibility of combining CE and C4D under field conditions, highlighting both the strengths and limitations of this integrated platform.

Inhibition effect and mechanism of micron-sized water mist containing dimethyl methylphosphonate in hydrogen explosions

Sarin is an extremely toxic and fast-acting chemical warfare nerve agent that poses a serious threat to human health, necessitating the development of appropriate sensing technologies. Dimethyl methylphosphonate (DMMP), which has a chemical structure similar to that of sarin but is non-toxic, is often used as a simulation agent in related research. Among promising gas-sensing materials, CuFe2O4 exhibits suitable thermal stability. It is easily produced and has low toxicity. Its performance can be enhanced using heterogeneous ion doping to increase the number of surface defects and content of adsorbed oxygen. Therefore, a solvothermal method was adopted in this study to prepare CuFe2O4 hollow microspheres that were subsequently doped with different ratios of Sn4+ or Sn2+. Detailed characterizations of the obtained materials were conducted, and the corresponding CuFe2O4-based gas sensors were fabricated. Their gas-sensing performance against DMMP was studied to analyze and discuss the gas-sensing and sensitization mechanisms associated with Sn4+ and Sn2+ doping. The CuFe2O4-based sensor doped with 2 mol% Sn2+ exhibited excellent gas-sensing performance in response to a 1 ppm concentration of DMMP, with response and recovery times of 12 and 63 s, respectively. Notably, its response to 1 ppm DMMP (16.27) was 3.3-fold higher than that to 1 ppm 2-CEES (4.98). The doped CuFe2O4 sensor exhibited superior response-recovery characteristics and enhanced moisture resistance compared to the undoped sensor.

A Pt@CeLaCoNiOx/Co@SnO2 laminated MOS sensor was prepared using Co@SnO2 as the gas-sensitive film material and Pt@CeLaCoNiOx as the catalytic film material. The sensor was verified to exhibit good sensing performances for dimethyl methylphosphonate, a simulant of Sarin, under a temperature modulation, and characteristic peaks appeared in the resistance response curves only for dimethyl methylphosphonate. The Article Swarm Optimization-Backpropagation Neural Network had a good ability to identify the resistance response data of dimethyl methylphosphonate. The identification accuracy increased as the concentration of dimethyl methylphosphonate increased. This scheme can effectively identify whether the test gas contained dimethyl methylphosphonate or not, which provided a reference for achieving the high selectivity of the MOS sensor for Sarin.

Dimethyl methylphosphonate (DMMP) and modified nano-silica were utilised to enhance the mechanical properties, thermal stability, and flame retardancy of waterborne polyurethane (WPU). Nano-silica modified with the silane coupling agent γ-aminopropyltriethoxysilane (KH550) exhibited excellent dispersibility and stability. Compared with pure WPU, the limiting oxygen index (LOI) of P/Si-WPU increased from 18.1% to 28.3%, and its UL-94 rating reached V-0, with a significant improvement in elongation at break. Furthermore, the peak heat release rate of P/Si-WPU decreased by 29.1%, while the total heat release was reduced by 6.8% in comparison to pure WPU. The synergistic flame-retardant mechanism of phosphorus and silicon was investigated through an analysis of the char residue of WPU and its composites. This study provides a potential approach for the development of WPU with superior flame retardancy and enhanced mechanical properties.

Accurate detection of dimethyl methylphosphonate (DMMP), a simulant for chemical warfare agents, is vital for both public safety and military defense. However, conventional detection methods suffer from low selectivity, owing to interference from structurally similar compounds. In this study, we present a highly sensitive and selective gas sensor utilizing a solid-mounted film bulk acoustic resonator based on carbon nanotubes functionalized with hexafluoroisopropanol (HFiP) to enhance DMMP detection. This approach leverages the strong hydrogen bonding between HFiP and DMMP molecules to significantly improve the sensor’s adsorption capacity and selectivity. To further refine selectivity and at the same time solve the cross-sensitivity problem of sensitive membranes, we introduce a virtual sensor array design, generated by modulating the input power to the resonator, which enables the sensor to operate in multiple response modes across varying vibrational amplitudes. These multimodal responses are subjected to linear discriminant analysis, allowing precise differentiation of DMMP from other volatile organic compounds such as tributyl phosphate and dimethyl phthalate. Our results demonstrate superior performance in terms of both sensitivity and selectivity, offering a robust solution for detecting low-concentration DMMP in complex environments.

The detection and identification of chemical warfare agents (CWAs) are critical to safeguarding global security, as these toxic substances pose significant threats to human health and the environment. Effective monitoring and control of CWAs are essential for compliance with the Chemical Weapons Convention. Contamination of water sources with CWAs or their degradation products can have long-lasting ecological and public health implications. Dimethyl methylphosphonate (DMMP), a chemical simulant with structural similarities to hazardous organophosphorus agents, was selected for this study due to its relevance in proficiency testing (PT) and method validation. Here, we present the development and validation of a gas chromatography-mass spectrometry technique for the determination of DMMP. The QuEChERS extraction method was utilized to enhance sample preparation efficiency. The results obtained from the validated method revealed excellent linearity (R² = 0.9998), a low limit of detection of 0.0167 ppm, and high accuracy and precision, with recovery values between 95.7% and 97.3%, and low relative standard deviations at 3.5% for intraday and 3.7% for interday. The method was successfully applied in an Organisation for the Prohibition of Chemical Weapons PT, achieving a recovery value of 95.6% for DMMP. These results demonstrate the reliability of the method, underscoring its potential for use in international efforts to monitor and control CWAs, thereby preventing their misuse.

Nerve agents, a highly toxic class of chemical warfare agents, pose serious risks to human health and social stability. Metal oxides are commonly used as catalysts to break down these agents through thermocatalytic decomposition. In particular, bimetallic oxide catalysts offer enhanced stability and catalytic efficiency due to their synergistic effects. In this study, CuO/ZrO2 composite catalysts with varying Cu/Zr ratios were synthesized using a secondary hydrothermal method, resulting in a hollow microsphere morphology. The catalytic efficiency of these composites in thermocatalytically decomposing dimethyl methylphosphonate (DMMP), a sarin simulant, was systematically evaluated. The findings revealed that the catalyst with a 10%Cu/Zr ratio exhibited the best performance, achieving the longest protection duration of 272 min. The hollow microsphere structure facilitated high dispersion of CuO on the ZrO2 surface, promoting strong interactions and generation of oxygen vacancies, which enhanced the catalytic activity. Furthermore, the catalytic reaction mechanism was explored by analyzing the surface characteristics of the catalyst and the resulting reaction products. This research addresses a gap in the application of CuO/ZrO2 catalysts for DMMP decomposition and provides valuable insights for the future development of catalysts for chemical warfare agent degradation.

This study reports the synthesis of plasmonic hot nanogap networks-in-triangular nanoframes (NITNFs), featuring narrow intraparticle nanogap networks embedded within triangular nanoframes. Starting from Au nanotriangles, Pt NITNFs are synthesized through a cascade reaction involving simultaneous Pt deposition and Au etching in a one-pot process. The Pt NITNFs are then transformed into plasmonically active Au NITNFs via Au coating. The near-field focusing capabilities of the Au NITNFs are tailored by fine-tuning the void area fraction down to 3.9%, resulting in the formation of narrow nanogaps of ≈1nm. This optimization enables the successful implementation of single-particle surface-enhanced Raman scattering (SERS) measurements. Then, monolayer Au NITNFs films on Al substrates are prepared, which enabled weakly adsorbing species to be positioned close to the hot spots of the NITNFs by anchoring them to the underlying Al substrates. As a representative sensing application, the SERS-based detection of gas-phase dimethyl methylphosphonate (DMMP) using a film of plasmonic NITNFs on an Al substrate exhibits outstanding performances, achieving a limit of detection of 5ppm and a detection time of 120 s.

Liquid crystals (LCs), when interfaced with chemically functionalized surfaces, can amplify a range of chemical and physical transformations into optical outputs. While metal cation-binding sites on surfaces have been shown to provide a basis for the design of chemoresponsive LCs, the cations have been found to dissociate from the surfaces and dissolve slowly into LCs, resulting in time-dependent changes in the properties of LC-solid interfaces (which impacts the reliability of devices incorporating such surfaces). Here, we explore the use of surfaces comprising metal-coordinating polymers to minimize the dissolution of metal cations into LCs and characterize the impact of the interfacial environment created by the coordinating polymer on the ordering and time-dependent properties of LCs. In particular, by combining theoretical (electronic structure calculations) and experimental (polarization-modulation infrared reflection-adsorption spectroscopy) results, we determine that the pyridine groups of a thin film of poly(4-vinylpyridine-co-divinylbenzene) (P(4VP-co-DVB)) coordinate with Ni2+ when Ni(ClO4)2 is deposited onto the film. We provide evidence that the Ni2+-pyridine coordination weakens the binding of Ni2+ with 4'-n-pentyl-4-biphenylcarbonitrile (5CB), a room-temperature nematic LC, as compared to Ni(ClO4)2 supported on glass, although binding is still sufficiently strong to induce a homeotropic (perpendicular) orientation of the LC. Exposure of the 5CB films supported on Ni(ClO4)2-decorated P(4VP-co-DVB) substrates to parts-per-million vapor concentrations of dimethylmethylphosphonate (DMMP) was found to trigger orientational transitions (to planar (parallel) orientations) in the LC films. In contrast, 5CB supported on Ni(ClO4)2-decorated glass surfaces exhibited no response, even though displacement of 5CB by DMMP is predicted by computations to be thermodynamically favored in both cases. We propose that the distinct LC responses measured on glass and the coordinating polymer substrates are governed by the kinetics of displacement of 5CB by DMMP, a proposal that is supported by measurements performed with increasing temperature. Importantly, by using Ni2+ supported on P(4VP-co-DVB), we measured the ordering of 5CB to be stable and long-lived (>7 days), in contrast to unstable LC ordering (<14 h) when using Ni2+ supported on glass under dry conditions and at room temperature. We further demonstrate the stability of Ni(ClO4)2 supported on P(4VP-co-DVB) toward higher temperatures and humidity using E7 as the LC. Overall, these results demonstrate that metal-coordinating polymer films are a promising class of substrates for fabricating robust and long-lived chemoresponsive LCs.

We report the exfoliation of ultrathin gallium oxide (Ga2O3) films from liquid metal balloons, formed by injecting air into droplets of eutectic gallium-indium alloy (eGaIn). These Ga2O3 films enable the selective adsorption of carbon nanotubes (CNTs) dispersed in water, resulting in the formation of a dense, percolating CNT network on their surface. The self-assembled CNT network on Ga2O3 provides a versatile platform for device fabrication. As an example application, we fabricated a chemiresistive gas sensor for detecting simulants of chemical warfare agents (CWAs), including diisopropyl methylphosphonate (DIMP), dimethyl methylphosphonate (DMMP), and triethyl phosphate (TEP). The sensor exhibited reversible responses, high sensitivity, and low limits of detection (13 ppb for DIMP, 28 ppb for DMMP, and 53 ppb for TEP). These findings highlight the potential of Ga2O3 films derived from liquid metal balloons for integrating CNTs into functional electronic devices.

Effect of ionic wind on the sample distribution in corona discharge ion mobility spectrometry