Dimethyl Methylphosphonate Detection Research Articles

Synthesis and characterization of nitrogen-doped-MWCNT@cobalt oxide for nerve agent simulant detection

Organophosphorus nerve agents are toxic compounds that disrupt neuromuscular transmission by inhibiting the neurotransmitter enzyme, acetylcholinesterase, leading to rapid death. A hybrid composite was synthesized using a hydrothermal process for the early detection of dimethyl methyl phosphonate (DMMP), a simulant of the G-series nerve agent, sarin. Quartz crystal microbalance (QCM) and surface acoustic wave (SAW) sensors were used as detectors. Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs), cobalt oxide (Co3O4), and N-MWCNT@Co3O4 were compared to detect DMMP concentrations of 25–150 ppm. At 25 ppm, the differential frequencies (Δf) of the N-MWCNT, Co3O4, and N-MWCNT@Co3O4 sensors were 5.8, 2.3, and 99.5 Hz, respectively. The selectivity results revealed a preference for the DMMP rather than potential interference. The coefficients of determination (R2) of the N-MWCNT, Co3O4, and N-MWCNT@Co3O4 sensors for detecting 25–150 ppm DMMP were 0.983, 0.986, and 0.999, respectively. The response times of the N-MWCNT, Co3O4, and N-MWCNT@Co3O4 sensors for detecting 100 ppm DMMP were 25, 27, and 34 s, respectively, while the corresponding recovery times were 85, 105, and 181 s. The repeatability results revealed the reversible adsorption and desorption phenomena for the fixed DMMP concentration of 100 ppm. These unique findings show that synthesized materials can be used to detect organophosphorus nerve agents.

Fiber-optic Michelson interferometric trace dimethyl methyl phosphate sensor based on MnO2/ZnO composites film

Abstract A dimethyl-methyl phosphonate (DMMP) sensor based on MnO2/ZnO composite film integrated fiber-optic Michelson interference structure is proposed. The sensing structure is formed by a thick taper between a single-mode fiber (SMF) and a four-core fiber (FCF), and then the no-core fiber (NCF) is spliced at the other end of the FCF. To enhance reflection, the silver film was coated on the end of the NCF, and the fiber optic Michelson interference structure is formed. MnO2/ZnO composite sensing film was coated on the FCF surface, and the structure, morphology, and properties of the sensing material were analyzed by X-ray diffraction, Scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, etc. The sensitivity and the response time of the sensor are 0.3413 dB/ppm and 180 s, respectively. The sensor has good selectivity and stability, and it has a good application prospect in trace DMMP detection with high sensitivity.

Detection of Dimethyl methylphosphonate (DMMP) with an Interband Cascade Laser Sensor

Detection of Dimethyl methylphosphonate (DMMP) with an Interband Cascade Laser Sensor

Cupric ion-functionalized polyaniline/single-walled carbon nanotube hybrids for dimethyl methylphosphonate detection

Cupric ion-functionalized polyaniline/single-walled carbon nanotube hybrids for dimethyl methylphosphonate detection

Hierarchical Nanoheterostructure of HFIP-Grafted α-Fe2O3@Multiwall Carbon Nanotubes as High-Performance Chemiresistive Sensors for Nerve Agents

New and efficient sensors of nerve agents are urgently demanded to prevent them from causing mass casualties in war or terrorist attacks. So, in this work, a novel hierarchical nanoheterostructure was synthesized via the direct growth of α-Fe2O3 nanorods onto multiwall carbon nanotube (MWCNT) backbones. Then, the composites were functionalized with hexafluoroisopropanol (HFIP) and successfully applied to detect dimethyl methylphosphonate (DMMP)-sarin simulant gas. The observations show that the HFIP-α-Fe2O3@MWCNT hybrids exhibit outstanding DMMP-sensing performance, including low operating temperature (220 °C), high response (6.0 to 0.1 ppm DMMP), short response/recovery time (8.7 s/11.9 s), as well as low detection limit (63.92 ppb). The analysis of the sensing mechanism demonstrates that the perfect sensing performance is mainly due to the synergistic effect of the chemical interaction of DMMP with the heterostructure and the physical adsorption of DMMP by hydrogen bonds with HFIP that are grafted on the α-Fe2O3@MWCNTs composite. The huge specific surface area of HFIP-α-Fe2O3@MWCNTs composite is also one of the reasons for this enhanced performance. This work not only offers a promising and effective method for synthesizing sensitive materials for high-performance gas sensors but also provides insight into the sensing mechanism of DMMP.

Adsorptive stripping voltammetric sensor based on Cd zeolitic imidazole framework-67 for electrochemical detection of sarin simulant

A selective and reliable modified glassy carbon sensor, based on a 1.0% Cd zeolitic imidazole framework-67 modified glassy carbon sensor (GCS2), has been developed for ultrasensitive detection of dimethyl methyl phosphonate (DMMP) in human biological fluid. The synthesis of porous nanoparticles of Cd zeolitic imidazole framework-67 (Cd ZIF-67) was carried out via the hydrothermal method. The resulting Cd ZIF-67 powder emerges with good crystallinity, a rhombic dodecahedral morphology with particle size in the range 300 ~ 500 nm, and a specific surface area of 1780 m2·g−1. Furthermore, the fabricated sensor exhibited superior performance in the detection of DMMP with two linearity ranges of 0.02–2.0 nM and 2.0–9.0 nM and a limit of detection (LOD) of 0.06 pM. The fabricated sensor exhibited good reliability, long-term stability, and repeatability, which are favourable attributes for electroanalytical detection. In addition, the fabricated sensor displayed superior performance without significant interference during the assay of DMMP in a biological fluid (human serum sample) within two linearity ranges of 0.1–1.0 nM and 1.0–6.0 nM and a LOD of 0.03 nM.Graphical

Highly Sensitive and Selective Detection of Dimethyl Methyl Phosphonate with Copolymer‐Based QCM Sensors

AbstractIn this work, the volatile organic compounds (VOCs) sensing properties of a quartz crystal microbalance (QCM) transducer coated with six different poly(3‐methylthiophene) (P3MT) copolymerized with polypyrrole (PPy) are investigated. The sensor preparation involves the electrochemical deposition of P3MT, PPy, and P3MT‐co‐PPy on Au‐coated QCM transducers by electrochemical deposition techniques with a three‐electrode cell. The structural properties of the copolymer films are characterized using scanning electron microscopy, and their oxidation/reduction behavior is investigated through cyclic voltammetry. The copolymer‐based QCM sensors exhibit high sensitivity and selectivity to dimethyl methyl phosphonate and benzonitrile, even at low concentrations (<1 ppm) at room temperature. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich adsorption isotherms are studied to understand the VOCs sensing mechanism machine learning classification algorithms including quadratic discriminant (QD), neural nets, K‐nearest neighbors, linear discriminant, and support vector machines are applied to classify the sensor responses for the 12 different analytes. With the help of machine learning algorithms, tested analytes are successfully classified into their groups. The highest accuracy of 97.34% is achieved using the QD method. The developed sensor, combined with machine learning algorithms, shows promising potential for accurate and reliable detection and classification of VOCs.

In-situ copolymerization Ion-Gel-based flexible sensor for wearable dimethyl methylphosphonate detection

Flexible electronics have been extensively investigated in recent years due to their convenient and wearable properties. Considering the practical applications in the external environment, the demand for portable and miniaturized sensing systems is prominent, for example, detecting harmful and toxic gases. Flexible sensors provide a potential novel solution for achieving the above goals, which is wearable sensing. In this paper, we develop a flexible sensor based on the ionic gel (Ion-Gel) for the detection of dimethyl methylphosphonate (DMMP). DMMP is a kind of organophosphorus gas, which may cause pollution to the environment and harm to biology. The Ion-Gel sensitive film is prepared through in-situ copolymerization of the polymer monomer poly(ethylene glycol) diacrylate (PEGDA), ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) and gas-sensing group hexafluoroisopropyl alcohol (HFIPA) under 365 nm ultraviolet light. The sensitive film can be patterned through a shadow mask on the interdigital electrodes ultimately. The sensor exhibits good sensitivity to the DMMP, with a lower limit of detection reaching 100 ppb under room temperature. Noteworthily, the sensor’s detecting upper limit is successfully extended to high gas concentrations at 800 ppm and maintains good linearity. A flexible print board circuit (FPCB) front-end is developed for the flexible DMMP sensor to construct a wearable platform that can be attached to the hand to achieve real-time detection. When the alarm threshold is set to 2 ppm DMMP, the proposed wearable detection platform can successfully give an alarm signal within 15 s

A Nanoporous Polymer Modified with Hexafluoroisopropanol to Detect Dimethyl Methylphosphonate.

The increasing threat of nerve agents has prompted the need for gas sensors with fast response, high sensitivity, and good stability. In this work, the hexafluoroisopropanol functional group was modified on a porous aromatic framework material, which served as a sensitive material for detecting dimethyl methylphosphonate. A nerve agent sensor was made by coating sensitive materials on a surface acoustic wave device. Lots of pores in sensitive materials effectively increase the specific surface area and provide channels for diffusion of gas molecules. The introduction of hexafluoroisopropanols enables the sensor to specifically adsorb dimethyl methylphosphonate and improves the selectivity of the sensor. As a result, the developed gas sensor was able to detect dimethyl methylphosphonate at 0.8 ppm with response/recovery times of 29.8/43.8 s, and the detection limit of the gas sensor is about 0.11 ppm. The effects of temperature and humidity on the sensor were studied. The results show that the baseline of the sensor has a linear relationship with temperature and humidity, and the temperature and humidity have a significant effect on the response of the sensor. Furthermore, a device for real-time detection of nerve agent is reported. This work provides a new strategy for developing a gas sensor for detecting nerve agents.

Graphene based Mo6 cluster hybrid for detecting simulant nerve agent DMMP

Nerve agents are highly toxic chemical compounds that pose significant threats to human health and safety. Detecting and identifying these agents quickly is crucial for preventing their exposure and providing timely treatment. This study proposes the use of nanohybrids comprising crystalline octahedral molybdenum iodide cluster material supported on graphene (Mo6@Graphene) as a novel sensing material for the detection of dimethyl methylphosphonate (DMMP), a simulant of sarin nerve agent. The electrical sensing performance towards different concentrations of DMMP and at room temperature demonstrated fast and sensitive responses to DMMP, with almost full recovery of the sensor baseline in a few minutes. The calibration curve obtained showed a linear relationship between the sensor response and DMMP concentration, enabling the estimation of the limit of detection (LOD) of 270 ppb. The robustness of the Mo6@Graphene nanomaterial towards DMMP was assessed using various techniques, including Raman spectroscopy, X-ray diffraction and photoelectron spectroscopy. The binding energies (BEs) between DMMP and the supported Mo6 clusters determined by DFT calculations revealed H-bonding interactions involved in the sensing mechanism. The excellent sensing performance of the Mo6@Graphene film, combined with its low power consumption and high stability, makes it a promising candidate for the detection of nerve agents and their simulants.

A multisite strategy to improve room-temperature DMMP sensing performances on reduced graphene oxide modulated by N-doped carbon nanoparticles and copper ions

Development of room-temperature gas sensors with excellent sensing performances for detection of dimethyl methylphosphonate (DMMP, a simulant of organophosphate) has aroused considerable attention. However, the weak adsorption ability of sensing materials toward DMMP molecules causes poor sensing performances. In this work, a multisite strategy for enhancing sensitivity was proposed by introduction of both N-doped carbon nanoparticles (N-CNPs) and copper ions onto the surface of rGO (designated as GNC). Impressively, optimal GNC-3 exhibits the response value of 10.2% toward 100 ppm DMMP, which is 5.3 times higher than that of pristine rGO. This mechanism for multisite-assisted enhanced DMMP sensing performances was investigated by combined characterizations of Fourier-transform infrared spectra, UV-Vis spectra, photoluminescence spectra and Mott-Schottky curves. Besides the construction of multisite, improvement of hydrogen bonding interactions between DMMP molecules and N-CNPs in hybrids assisted by copper ions, and decrease of conduction band potential by formation of ternary hybrids also contribute to enhance the sensitivity of DMMP sensors. These findings not only provided new insights into designing high-performance room-temperature gas sensors, but also promoted the fundamental research on sensing mechanism for room-temperature gas sensors.

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.

Ppb-level mid-IR quartz-enhanced photoacoustic sensor for sarin simulant detection using a T-shaped tuning fork

A ppb-level mid-IR quartz-enhanced photoacoustic sensor for the highly sensitive detection of dimethyl methyl phosphonate (DMMP) —the sarin simulant—is developed using a T-shaped tuning fork. The sensor employs a narrow-linewidth mid-IR quantum cascade laser (QCL) to target a strong, interference-free DMMP absorption band. A custom quartz tuning fork with 800-μm prong spacing is employed to avoid significant photothermal noise, thus removing the requirement for an optical spatial filter. The performance of the photoacoustic sensor was optimized in terms of exciting power, modulation frequency, and gas pressure. A minimum detection limit of 6 ppb was achieved at an integration time of 300 ms, which can be further improved to 0.45 ppb at the optimal integration time of 20 s

Light-activated SAW sensor structures with photoconductive polymer films for DMMP detection

We report the light-activated surface acoustic wave (SAW) investigations of DMMP (dimethyl methylphosphonate) sensing based on photoconductive polymer films such as: (rr)P3HT (regio-regular Poly-3-hexylthiophene) and SilPEG1.4. These SAW sensor structures were composed of ∼205 MHz quartz dual delay lines with a novel switchable digital generator set-up and a thin (∼50–100 nm) polymer films created by means of a simple spray coating method. The white light, low power laser LED (blue, green, red) and seven LED’s sources were applied for light activation of the SAW structures. The relative sensitivity increase (frequency shifts in light vs. the non activated state) at 2 ppm of DMMP is ∼275 for SilPEG1.4 with a blue LED (∼460 nm), to even ∼340 for (rr)P3HT with a yellow LED (∼585 nm) activation. This last structure has also acceptable stability and repeatability with the limit of detection ∼133 ppb, the response/recovery times ∼5–100 s / ∼240 s, and sensitivity coefficient ∼1.013 kHz/ppm in ppb ranges. The observed substantially enhanced light-activated SAW sensitivity should be interpreted in category of the acoustoelectric interactions, because the acoustoelectric parameter, estimated by resistive transducer results, has the greatest value for a yellow and blue LED light illumination.

High Performance and Reusable SAW Sensor Coated with Thiourea-Decorated POSS with Different Functional Groups for DMMP Detection

A colorless, odorless G nerve agent, a type of chemical transfer agent (CWA) that causes significant loss of life, is being studied for quick and accurate detection. In this study, detection materials with different functional groups were synthesized based on thiourea (TU)-decorated polyhedral oligomeric silsesquioxane (POSS) to study the most suitable material for the detection of dimethyl methylphosphonate (DMMP), a simulant of neural agents. The sensing material was coated on a SAW sensor with a resonance frequency of 250 MHz based on ST-quartz, the DMMP exposure experiment was conducted, and the performance of the sensing material was compared through frequency shift before and after exposure. Coating materials with excellent reactivity with DMMP and appropriate coating concentration for each material were identified at a concentration of 10 ppm. Among them, POSS-TU with 3,5-bis(trifluoromethyl)phenyl as a functional group showed the largest frequency shift characteristics, and it was used in low concentration (1, 5, and 10 ppm) DMMP detection experiments to confirm linear frequency shift characteristics according to low concentration. Finally, through a selectivity experiment with other gases, it was confirmed that the amount of frequency shift in other gases except DMMP was small, making it an excellent DMMP sensing material.

Application of Cotton Swab–Ag Composite as Flexible Surface-Enhanced Raman Scattering Substrate for DMMP Detection

It is both important and required to quickly and accurately detect chemical warfare agents, such as the highly toxic nerve agent sarin. Surface-enhanced Raman scattering (SERS) has received considerable attention due to its rapid results, high sensitivity, non-destructive data acquisition, and unique spectroscopic fingerprint. In this work, we successfully prepared SERS cotton swabs (CSs) for the detection of the sarin simulant agent dimethyl methyl phosphonate (DMMP) by anchoring N1-(3-trimethoxysilylpropyl) diethylenetriamine (ATS)/silver nanoparticle (AgNP) nanocomposites on CSs using ATS as the stabilizer and coupling agent. Simultaneously, the binding mode and reaction mechanics between the AgNP, ATS, and CS were confirmed by XPS. The modified CSs exhibited good uniformity, stability, and adsorption capability for SERS measurements, enabling the adsorption and detection of DMMP residue from an irregular surface via a simple swabbing process, with a detection limit of 1 g/L. The relative standard deviations (RSDs) of RSD710 = 5.6% had high reproducibility. In this research, the fabrication method could easily be extended to other cellulose compounds, such as natural fibers and paper. Furthermore, the versatile SERS CSs can be used for the on-site detection of DMMP, particularly in civil and defense applications, to guarantee food security and the health of the population.

A smart chitosan-graphite molecular imprinted composite for the effective trapping and sensing of dimethyl methylphosphonate based on changes in resistance.

A molecular imprinted polymer (MIP) fabricated from a chitosan doped with graphite to create a conductive composite (CG-MIC) with the ability to trap and detect dimethyl methylphosphonate (DMMP) through a change in resistance of the material has been successfully manufactured. The GC-MIC presented a maximum trapping capacity of 96 ppm (0.096 mg g-1) of DMMP. A similar non-imprinted composite made of chitosan-graphite (CG-NIC) had a surface adsorption of 48 ppm (0.048 mg g-1) of DMMP. The manufacturing process was tested for consistency and there were no significant differences in resistance between batches of CG-MIC before (around 450 Ω) and after (around 70 Ω) DMMP extraction, representing a homogeneous manufacturing process. Although Atomic Force Microscopy studies revealed that the graphite was not homogenously distributed throughout the chitosan matrix, the response was consistent. The changes in the concentration of DMMP within the self-sensing material, being proportional to those in gas concentration, could be followed by the changes in resistance. The inclusion of common interferents: Acetic acid, acetone, ethanol, ammonium hydroxide and 2-propanol, equivalent in concentration to the DMMP, caused a change in the resistance of the material but did not substantially affect the specific resistance response of the composite material. Based on this data, the CG-MIC could be used as a smart material with sensing capabilities to monitor trapping levels of DMMP.

GO-HFIPPH covered a-IGZO thin film transistor for gate tunable DMMP detection

Field-effect transistor (FET) type gas sensors are showing their great attractions to researchers due to their miniature size, gate tunable sensitivity and compatibility with CMOS technology. Amorphous indium gallium zinc oxide (a-IGZO) thin film transistors have the advantage of simple preparation method, high mobility and potential for large-scale integration, which has been widely investigated in recent years. The traditional method of obtaining selectivity of semiconductor sensing materials is to make chemical decorations directly to the semiconductor active layer, which may damage the material’s properties. In this paper, we decorate graphene oxide (GO) with p-hexafluoroisopropanol phenyl (HFIPPH) to form GO-HFIPPH, and then use GO-HFIPPH to physically modify a-IGZO TFT through self-assembly to prepare a FET-type dimethyl methylphosphonate (DMMP) sensor. The proposed sensor shows good sensitivity and selectivity to DMMP, and has a 61.1 nA response to 200 ppb DMMP with 42 s and 26 s response/recovery time. In addition, the sensing mechanism is explained based on hydrogen bond theory, heterojunction and charge transportation of the a-IGZO transistor. We believe our GO-HFIPPH/a-IGZO TFT DMMP sensor will show a significant value for FET-type gas sensor design.

Fabrication of Fast Response and Recovery NiFeAl3+ Nanocomposite Gas Sensor for Detection of Dimethyl Methyl Phosphonate

Fabrication of Fast Response and Recovery NiFeAl3+ Nanocomposite Gas Sensor for Detection of Dimethyl Methyl Phosphonate

Part per trillion level DMMP gas sensor based on calixarene modified organic thin film transistor

Dimethyl methylphosphonate (DMMP) is a simulant of nerve agent sarin, which still remains a great challenge to detect due to lack of sensitive, selective and stable sensor. In this work, calixarenes are designed to apply on organic thin film transistor (OTFT) to form a high-performance gas sensor for DMMP detection. The theoretical calculation indicates that the binding energy between calixarene (4-tert-Butylcalix[6]arene, denote as TB6) and DMMP is stronger (–25.34 kcal/mol) than that of poly(3-hexylthiophene-2,5-diyl) (semiconductor layer of this OTFT sensor, denote as P3HT) (–10.83 kcal/mol), which could bring significant improvement to the sensitivity of this sensor. The experimental result confirms that the limit of detection (LOD) of TB6-P3HT based sensor can be as high as 10 ppt which is about four orders of magnitude higher than pristine P3HT. The drain current changes after exposure to 50 ppm DMMP, ethyl acetate, toluene, isopropanol and nitrogen dioxide are 39.0%, 2.9%, 2.7%, 2.1% and 1.3%, which also suggests the good selectivity of this sensor. Besides, the TB6-P3HT based sensor exhibits a better stability (14.1% degradation after one month) than pristine P3HT (55.8%) because of the better antioxidant capacity of this bilayer structure. Further, this sensor shows its ability to work in different relative humidity and temperatures, which demonstrates the potential application in complex environment. We anticipate this general approach could offer solutions for high performance gas detection.