Dimethyl Methylphosphonate Molecules Research Articles

Adsorption of DMMP and water vapor on granular activated carbon: An experimental and molecular simulation study

The adsorption behavior of Dimethyl methylphosphonate (DMMP), as a simulant of sarin nerve agent, especially in the presence of water vapor, is crucial for the design of efficient chemical protection equipment. Experimental results reveal DMMP's adsorption isotherm on granular activated carbon (GAC) as a typical type I. The adsorption process was a spontaneous and exothermic physical adsorption process, and the adsorption mechanism was in accordance with Dubinin's micropore filling theory. In the relative humidity range of 10 % ∼ 90 %, the isotherm remained I-type, and the effect of water vapor on the equilibrium adsorption capacity and apparent adsorption rate was weak. Molecular simulations also show that DMMP adsorption on GAC follows a type I isotherm, primarily driven by van der Waals forces of physical adsorption. The adsorption potential energy between DMMP and GAC surpasses that of water molecules, resulting in negligible effects from water vapor on DMMP adsorption equilibrium. Meanwhile, water molecules had minimal effect on the diffusion of DMMP molecules in the GAC pores, and the positional distribution of DMMP multilayer adsorption was consistent under different relative humidity conditions. Furthermore, the presence of polar functional groups such as hydroxyl groups significantly affects the adsorption equilibrium of DMMP.

Hydrogen-bond acidic organic compound-sensitized ionic gel for dimethyl methylphosphonate detection

Due to the threat of chemical warfare agents (CWAs), there is a pressing need to develop miniaturized gas sensors with fast response, high sensitivity and good stability. Herein, hexafluoroisopropanol aniline (HFIPA), a hydrogen-bond acidic organic compound, is embedded into a cross-linked poly(ethylene glycol) diacrylate/ionic liquid (PEGDA/IL) matrix as a sensitive film for detecting sarin simulant dimethyl methylphosphonate (DMMP). We find that the IL in the film constructs efficient gas transport channels, improving the absorption-desorption kinetics of DMMP molecules. The introduction of HFIPA enhances selectivity and sensitivity to DMMP through hydrogen bonding interaction. As a result, the SAW gas sensor based on PEGDA/IL-HFIPA ionic gel exhibits a fast response/recovery time of 28/53 s to 20 ppm DMMP and a low detection limit of 0.2 ppm at room temperature. By comparing with PEGDA-HFIPA, PEGDA/IL-HFIPA shows excellent anti-humidity interference ability, which is also attributed to the stable gas transport channels constructed by IL. Overall, this work develops a novel strategy to improve the gas-sensing properties of organic polymer materials.

Photonic Liquid Crystal Polymer Absorbent for Immobilization and Detection of Gaseous Nerve Agent Simulants

Detection and sequestration of chemical warfare agents (CWAs), such as poisonous organophosphates, are highly desirable for both personal security and environmental protection. However, both sensing and absorption in a single device have been rarely reported. In this study, we describe a photonic absorbent based on a cholesteric liquid crystal polymer as a dual sensing and decontamination device for gas-type CWAs. Dimethyl methylphosphonate (DMMP) was used as a simulant compound. A blue reflective photonic polymer was fabricated that was able to detect DMMP vapor through absorption. Hydrogen bond interactions between DMMP and mesogenic carboxylic groups of the polymer allow selectivity and capture. A distinct optical change of the film from blue to bright green indicates the absorption of DMMP vapor molecules and confirms when full absorption of the polymer is achieved. The diffusion of DMMP vapor into the material was observed by the formation of a sharp boundary between swollen and unswollen material, as evidenced by scanning electron microscopy images and the structural color changes. In ambient conditions, DMMP molecules are retained in the photonic absorbent without release to the environment. Heating above approximately 60 °C releases the absorbed DMMP, leading to a reusable optical device. These results confirm the ability of photonic polymers to sense and immobilize dangerous vapor, paving the way for the realization of simple, battery-free optical devices able to simultaneously warn and protect.

Synthesis of Novel CuO/ZnFe2O4/NaA Zeolite Nanocomposite Adsorbent for the Decontamination of Nerve Agent Sarin Simulant

The aim of present research is to evaluate the decontamination of nerve agent sarin simulant dimethyl methyl phosphonate (DMMP) in water media using the CuO/ZnFe2 O4 /NaA zeolite as a novel ternary nanocomposite adsorbent. In this regard, the CuO and ZnFe2 O4 nanoparticles were successfully synthesized within the NaA zeolite applying the ultrasound-assisted hydrothermal route and characterized via XRD, FESEM, FTIR, EDAX, VSM and BET analyses. Then, the CuO/ZnFe2 O4 /NaA nanocomposite activity was investigated for the decontamination of DMMP molecule and monitored by a GC-FID and GC-MS analyses. Plus, the impacts of several parameters, including contact time, adsorbent dose and adsorbent type on the decontamination of DMMP were studied. The gained data from GC-FID analysis confirmed the maximum decontamination more than 98.4% for DMMP. The parameters including: adsorbent amount of 50 mg and contact time of 40 min were achieved as the optimized values for the decontamination reaction. In addition, the non-toxic methyl phosphoric acid (MPA) as the DMMP degradation product in the presence of CuO/ZnFe2 O4 /NaA adsorbent was characterized.

Hydrogen bonds-induced room-temperature detection of DMMP based on polypyrrole-reduced graphene oxide hybrids

The development of fast-response, high sensitivity and selectivity gas sensors for monitoring of organophosphorus is essential, where two dimensional graphene-based materials possessing exceptionsal carrier mobility are considered as promising candidates for room-temperature organophosphorus detection. However, it is challenging to fabrication of graphene-based gas sensors for detection of organophosphorus with excellent sensing performances. Herein, we develope a self-redox strategy to synthesize polypyrrole decorated-reduced graphene oxide hybrids (PPy-rGO) by redox reactions between pyrrole and GO during hydrothermal treatment process. This self-redox strategy results in the formation of perfact interfical strucutre between PPy and rGO through the π-π interactions without the impurity from the conventional oxidation/reducing agents. Most importantly, such PPy-rGO hybrids can be used as novel sensing materials for detection of dimethyl methylphosphonate (DMMP) at room temperature. Specially, the response of PPy-rGO-based sensor towards 100 ppm DMMP can reach 12.9 %, which is 3-fold higher than that pristine rGO-based sensor. Meanwhile, PPy-rGO-based sensor exhibits short response time/recovery time (43 s/75 s), low detection limit (5 ppm), excellent repeatability, and high selectivity. By combination of FT-IR and N2 sorption isotherms, the enhanced DMMP sensing performances of PPy-rGO hybrids are concluded as following two aspects. Firstly, the formation of hydrogen bonds between PPy-rGO hybrids and DMMP molecules regulates the adsorption/desorption of DMMP. Secondly, increasing BET surface area by introduction of PPy into rGO matrix is beneficial to DMMP diffusion among the sensing materials. Our work would offer a new strategy for rational development of graphene-based materials for detection of organophosphorus at room temperature.

Thermal Decomposition of Dimethyl Methylphosphonate on Size-Selected Clusters: A Comparative Study between Copper Metal and Cupric Oxide Clusters

Room temperature decomposition and thermal decomposition of dimethyl methylphosphonate (DMMP), a chemical warfare agent (CWA) simulant, on size-selected copper clusters have been studied via combined X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). Cu100 and (CuO)80, which have the same nominal masses, were chosen to present a direct comparison between the reactivity of metallic copper and that of cupric oxide with DMMP. Room temperature XPS results have shown that most of the DMMP molecules decompose completely and reductively into atomic phosphorus on Cu100, while almost all the DMMP molecules are only dissociatively adsorbed on (CuO)80 as methyl methylphosphonate (MMP). XPS and TPD have been carried out to analyze the thermal decomposition of adsorbed DMMP by identifying the surface species after annealing to certain temperatures and the gaseous products evolved during linear temperature ramps, respectively. Methanol, formaldehyde, and methane are the three most significant gaseous products for DMMP decomposition on both Cu100 and (CuO)80. Methanol and formaldehyde, which evolve in the low temperature region, are believed to originate from surface methoxy species. Methanol, formaldehyde, and methane evolved in the high temperature region are related to further decomposition of the phosphorus-containing surface species. A set of methanol-probed TPD experiments have also been carried out, which suggest that methane evolution originates from the methyl group within DMMP instead of the surface methoxy species.

Enhanced dimethyl methylphosphonate detection based on two-dimensional WSe2 nanosheets at room temperature.

Chemical warfare agents, particularly nerve agents such as sarin, are exceptionally harmful and incredibly perilous to people. Thus, the sensitive detection of these gases is indispensable for reducing the risk of chemical weapons. Herein, we fabricated a room-temperature chemiresistive gas sensor based on two-dimensional few-layer tungsten diselenide (WSe2) nanosheets, which were prepared through a facile liquid-phase exfoliation method. The WSe2-based sensor has demonstrated sensitive and selective detection of dimethyl methylphosphonate (DMMP), which is a well-known simulant of the nerve agent sarin. The sensor based on WSe2 nanosheets revealed a high response reaching 8.91% to 10 ppm DMMP with a fast response time of 100 s. Furthermore, the sensor displayed reliable stability, excellent selectivity, and a low theoretical limit of detection of about 122 ppb. The enhanced sensing performance of WSe2 nanosheets can be ascribed to the increase of the specific surface area, which provides more active adsorption sites for DMMP molecules, thereby facilitating the charge transfer process between DMMP molecules and WSe2 nanosheets. Overall, our results indicate that two-dimensional transition metal dichalcogenide materials have the potential for the design and fabrication of high-performance nerve agent sensing devices.

HFIP-Functionalized Co3 O4 Micro-Nano-Octahedra/rGO as a Double-Layer Sensing Material for Chemical Warfare Agents.

Semiconductor metal oxides (SMO)-based gas-sensing materials suffer from insufficient detection of a specific target gas. Reliable selectivity, high sensitivity, and rapid response-recovery times under various working conditions are the main requirements for optimal gas sensors. Chemical warfare agents (CWA) such as sarin are fatal inhibitors of acetylcholinesterase in the nerve system. So, sensing materials with high sensitivity and selectivity toward CWA are urgently needed. Herein, micro-nano octahedral Co3 O4 functionalized with hexafluoroisopropanol (HFIP) were deposited on a layer of reduced graphene oxide (rGO) as a double-layer sensing materials. The Co3 O4 micro-nano octahedra were synthesized by direct growth from electrospun fiber templates calcined in ambient air. The double-layer rGO/Co3 O4 -HFIP sensing materials presented high selectivity toward DMMP (sarin agent simulant, dimethyl methyl phosphonate) versus rGO/Co3 O4 and Co3 O4 sensors after the exposure to various gases owing to hydrogen bonding between the DMMP molecules and Co3 O4 -HFIP. The rGO/Co3 O4 -HFIP sensors showed high stability with a response signal around 11.8 toward 0.5 ppm DMMP at 125 °C, and more than 75 % of the initial response was maintained under a saturated humid environment (85 % relative humidity). These results prove that these double-layer inorganic-organic composite sensing materials are excellent candidates to serve as optimal gas-sensing materials.

Adsorptive removal of nerve-agent simulant with zirconium-based metal-organic frameworks modified by hydrophobic monocarboxylic acids

Abstract An isoreticular series of zirconium-based benzenetricarboxlyates (MOF-808) were successfully synthesized using different lengths of linear mono-carboxylic acids (i.e., formate, propionate, and valerate) as a charge-balancing ligand, and then were applied for removal of nerve-agent simulants. Removal of dimethyl methylphosphonate (DMMP) as a nerve-agent simulant of the MOF-808 analogues was conducted in dry and humid air. Tests demonstrated that the adsorption capacity of DMMP was considerably enhanced with increase in the carbon chain length of the incorporated mono-carboxylic acids of the MOF-808 (formate OH, or OH2). These could act as active sites to adsorb DMMP via hydrogen bonding with the P O of a DMMP molecule and then decompose it by hydrolysis. These results demonstrate that simple modulation of the surface environments of Zr-based MOFs can be adapted to tune their intrinsic efficiency for removal of toxic chemicals.

Temperature dependent time resolved mid-IR photoacoustic spectroscopy of a nerve gas simulant DMMP

The paper reports the temperature dependent pulsed photoacoustic spectroscopy of Dimethyl methylphosphonate (DMMP) a nerve gas simulant between 50 and 180 °C temperature range. The time domain PA spectra are recorded using two mid-IR wavelengths i.e. 3374 nm, 3495 nm of pulse duration 1.5 ns at 1 kHz repetition rate obtained from optical parametric oscillator. Two anti-symmetric stretching vibrational modes of (CH3P) and (CH3O) groups of DMMP molecules have very strong vibrational peaks at 2861.2 cm−1 (3495 nm) and 2963.8 cm−1 (3374 nm), respectively. In addition, we have also recorded the PA spectra of acetone at the vibrational frequency 3115.2 cm−1 (3210 nm), which is the strong vibrational mode of CH band. The comparison of two PA spectra of DMMP and acetone recorded using similar PA cavity help us to understand the effect of other functional groups with respect to different excitation wavelengths. The presence of additional acoustic modes in the PA spectra of DMMP (3374 nm) above the boiling point confirms the slow process of thermal decomposition. Finally, the low level detection limit of DMMP in air is of the of the order of 0.91 ppbV.

Sarin-simulant detection by phthalocyanine/palladium structures: From modeling to real sensor response

The full recognition of a sensing mechanism is a key issue in the gas sensors investigation. Therefore within presented work we proposed the new approach for the comprehensive sensing mechanism description: theoretical analysis and experimental investigation of the sensing structure. The object of our study was metal-free phthalocyanine/palladium structure utilized in sarin-simulant dimethyl methylphosphonate (DMMP) detection at room temperature. In the theoretical evaluation semi-empirical simulations have been performed revealing bonding energies between sensing materials and DMMP molecule. Different variants of metallic overlayer were considered in the modeling including bare palladium and palladium oxide (PdO). The results of the simulations indicated physisorption as a main sensing mechanism, especially enhanced in presence of PdO phase. Theoretical estimation of electron affinity and band bending changes during gas adsorption was conducted indicating strong impact of surface dipole effect. The experimental investigations was based on X-ray photoelectron spectroscopy (XPS) chemical characterization of DMMP exposed surface supported by atomic force microscopy imaging. The XPS results coincided with theoretical statements demonstrating no traces of chemical interaction with analyzed gas. Simultaneously, the presence of PdO was corroborated. Finally, the real sensor response was analyzed confirming outcome of the theoretical simulations and results of the experimental investigations.

Ultrafast coherent vibrational dynamics in dimethyl methylphosphonate radical cation.

Femtosecond pump-probe measurements of the nerve agent simulant dimethyl methylphosphonate (DMMP) demonstrate the preparation of a robust coherent vibrational state in the corresponding radical cation. The oscillations in the transient ion yields have a period of 45 fs (750 cm-1), which is at least 3 times faster than any previously observed oscillations in polyatomic radical cations. Use of 1200-1600 nm, as opposed to 800 nm, wavelengths for ionization increases the oscillation amplitude by a factor of 5 and doubles the number of visible oscillation periods from 6 to 12, indicating that an adiabatic ionization mechanism significantly enhances preparation of the coherent state. The coherent motion is assigned to a bending mode in DMMP+ with frequency in the range of 742.2-754.7 cm-1 based on the results of DFT calculations. The observation of coherent nuclear dynamics in the dissociation of DMMP+ suggests the potential utility of coherent control schemes for controlling the dissociation of DMMP and related molecules, which has important implications for developing detection and decontamination technologies for organophosphorus chemical warfare agents.

Hybrid Nanocomposite-Based QCM Sensor for Detecting DMMP

Taking a hybrid nanocomposite of nitrogen doped multiwalled carbon nanotube/cobalt oxide nanoparticle/gold nanoparticle as a sensing material, we developed a quartz crystal microbalance-based nerve simulant sensor. Thesensor was simply fabricated by a drop casting of a mixture of the nanocomposite and ethanol on the top of gold electrode in a quartz crystal microbalance (QCM). Dimethyl methylphosphonate (DMMP) vapor as a targeted nervesimulant was generated by a bubbler system and modulated by two mass flow controllers. The frequency shifts taken from QCM was linearly responded to DMMP concentrations, ranging from 20 to 120 ppm. The adsorption rate of DMMP molecules was relatively high, while the desorption rate was low. It reveals a high sensitivity to DMMP vapor. To investigate the selectivity various VOCs including ethanol, water, toluene, methanol, and n-hexane were tested at 120 ppm of targeted VOCs concentration. Interestingly, the targeted VOCs other than DMMP were relatively low detected by the QCM sensor, implying remarkable selectivity. In this regards, the developed hybrid nanocomposite is a potential material to be used for sensing nerve simulants.

Structure and stability of solvation complexes of trimethyl phosphate and dimethyl methyl phosphonate

AbstractThe presently used electrolytes in Lithium ion batteries, dimethyl carbonate (DMC), and ethylene carbonate are flammable. Trimethyl phosphate (TMP) and dimethyl methyl phosphonate (DMMP) have been shown to be potential nonflammable electrolytes. Density functional theory is used to calculate the structure and stability of the solvation complexes of TMP and DMMP. The calculations indicate that TMP and DMMP can form a solvation complex of the form Li+(X)4 where X is the TMP or DMMP molecule. Calculations of the solvation energy and bond dissociation energies to remove one TMP and DMMP from the solvation complexes are compared with the same calculations on DMC. The results indicate that TMP and DMMP are considerably more stable than DMC.

Adsorption and decomposition of dimethyl methylphosphonate on pristine and mono-vacancy defected graphene: A first principles study

Here we report the adsorption and decomposition behavior of dimethyl methyl-phosphonate (DMMP) on pristine and defected graphene using the first principles theory. The primary objective of this study is to highlight the importance of a vacancy defect on the adsorption mechanism of a molecule. In order to account for the weak forces involved between the molecule and graphene, we have used dispersion corrected total energy calculations along with generalized gradient approximation scheme for the exchange correlation energy. Among various possible configurations, the most stable geometry shows oxygen atom of the DMMP molecule favors to be close to the surface plane and bind with one of the unsaturated carbon atoms at the defect site. The molecule-substrate interaction energy is stronger for defected graphene than pristine graphene. The decomposition of the DMMP molecule at the vacancy site of the defected graphene has been investigated. For the dissociative adsorption, it is seen that the CH bond of the DMMP breaks and H atom is transferred to one of the low-coordinated C-atoms at the vicinity of the defect, forming new CH bond. In addition, the CC bond formation between graphene and DMMP occurs. Finally, the nature of bonding and electronic structure at the interface was interpreted through site projected electronic density of states analysis.

Influence of hydrocarbon moiety of DMMP on flame propagation in lean mixtures

Phosphorus-containing compounds (PCCs) have been found to be significantly more effective than CF3Br for reducing burning velocity when added to stoichiometric hydrocarbon-air flames. However, when added to lean flames, DMMP (dimethylmethylphosphonate) is predicted to increase the burning velocity. The addition of DMMP to lean mixtures apparently increases the equivalence ratio (fuel/oxidizer) and the combustion temperature, as a result of hydrocarbon content of DMMP molecule. Premixed flames studies with added DMMP, OP(OH)3, and CF3Br are used to understand the different behavior with varying equivalence ratio and agent loading. Decrease of the equivalence ratio leads to the decrease of inhibition effectiveness of PCCs relative to bromine-containing compounds. For very lean mixtures CF3Br becomes more effective inhibitor than PCCs. Calculations of laminar burning velocities for pure DMMP/air mixtures predict the maximum burning velocity of 10.5cm/s at 4.04% of DMMP in air and at an initial temperature of 400K. Adiabatic combustion temperature is 2155K at these conditions.

Decontamination of toxic chemical warfare sulfur mustard and nerve agent simulants by NiO NPs/Ag-clinoptilolite zeolite composite adsorbent

The present investigation describes the performance of NiO NPs/Ag-clinoptilolite zeolite as a novel composite adsorbent for the decontamination of two most known sulfur mustard and nerve agent simulants; chloroethyl ethyl sulfide (CEES) and dimethyl methyl phosphonate (DMMP). The reactions were carried out in both methanol and n-hexane solvents and monitored by GC-FID, 31PNMR and GC–MS analyses subsequently. Moreover, the SEM/EDAX, XRD and FT-IR techniques were applied for characterization of the as-prepared samples. The GC-FID results denoted that CEES was decontaminated on the composite in n-hexane solvent after 12h at room temperature with a yield more than 86%. Besides, 31PNMR data illustrated that more than 89% of DMMP was decontaminated after 8h under similar conditions. It seems that non-polar solvent aids the material transfer to the reactive sites on the surface of the composite without blocking them. The rate constant and half-life have been calculated 3.8194×10−5s−1 and 7.3055×10−5s−1, and 1.8640×104s and 9.4860×103s for CEES and DMMP, respectively. The hydrolysis products; hydroxyl ethyl sulfide (HEES) and methyl phosphonic acid (MPA) were also identified by GC–MS analysis. It was emphasized that NiO NPs/Ag-clinoptilolite zeolite composite has a high capacity and potential for the decontamination of CEES and DMMP molecules.

Detection of dimethyl methylphosphonate by thin water film confined surface-enhanced Raman scattering method

It is important and necessary to effectively detect the chemical warfare agents, such as highly toxic never agent sarin. However, based on the surface-enhanced Raman scattering (SERS) effect, detection of nerve agent simulant dimethyl methylphosphonate (DMMP) which is weakly interacted with SERS-active substrate has been the most challenge for the routine SERS detection method. To overcome this challenge, we put forward a thin water film confined SERS strategy. Under the space-confinement of water film, Raman measurements are carried out in the water evaporation process. The subsequent water evaporation induces concentrating of the DMMP molecules, which are thus successfully restricted within the strong electromagnetic field enhanced area above the SERS substrates, leading to the enhancement of their Raman signals. This study provides a new way to achieve the efficient SERS-based detection of the target molecules weakly interacted with the metal substrates.

System Identification, Design, and Implementation of Amplitude Feedback Control on a Nonlinear Parametric MEM Resonator for Trace Nerve Agent Sensing

In this paper, we develop and experimentally verify a novel amplitude feedback control scheme on a silicon microbeam for real-time sensing of parts-per-trillion (ppt) nerve agent concentrations. Utilizing the nonlinear dynamics resulting from parametric excitation of the microbeam for sensing at atmospheric pressure has demonstrated superior performance compared with conventional linear forced sensing. The microbeam is coated with a molecularly imprinted polymer that selectively adsorbs dimethyl methylphosphonate (DMMP) a precursor to G-series nerve agents including sarin. When the molecules attach to the microbeam and increase its mass, the amplitude response described by the nonlinear dynamics shifts in frequency. In tracking this frequency shift, information about the mass load, and, therefore, the nerve agent concentration, can be extracted. Previous sensing schemes have successfully applied this concept while relying on experimentally designed controllers. This paper features a model-based approach starting with the nonlinear dynamics and system parameter identification. After linearization, a control designed with the Glover–McFarlane $\mathcal {H}_\infty $ loop-shaping procedure robustly stabilizes the system. The control scheme is implemented on a LabView field-programmable gate array. Water vapor and trace DMMP real-time experiments at atmospheric pressure demonstrate the control’s functionality. A limit of detection of 13.3 ppt DMMP molecules in nitrogen is established. [2014-0330]

Effect of polydimethylsiloxane (PDMS) coating on TiO2-based MALDI matrix for dimethyl methylphosphonate (DMMP) analysis

TiO2 nanoparticles were used as MALDI matrix for detecting dimethyl methylphosphate (DMMP) and its efficiency, in terms of DMMP signal intensity in the MALDI-MS analysis, was compared with that of polydimethylsiloxane (PDMS)-coated TiO2 matrix. Intensity of the DMMP signal in the MALDI-MS analysis was significantly increased by using PDMS-coated TiO2 matrix instead of bare ones. It was verified using FT-IR that the enhanced DMMP signal upon PDMS coating on TiO2 matrix is a result of weaker interactions between DMMP molecule and the PDMS-covered surface than that of bare TiO2. A weaker DMMP-matrix interaction can facilitate desorption of DMMP from the matrix surface in the MALDI process, yielding a higher sensitivity to DMMP in the MALDI-MS.