Method for detecting dimethyl methylphosphonate at room temperature by using surface modified transition metal disulfide nano material

Abstract

The invention discloses a method for detecting dimethyl methylphosphonate at room temperature by using a surface modified transition metal disulfide nano material, and belongs to the technical field of biochemical safety monitoring. According to the technical scheme, the method comprises the following steps: 1) raw material pretreatment: adding 4-(hexafluoro-2-hydroxy isopropyl) aniline and water into a reaction bottle, and carrying out ultrasonic treatment; 2) acidification reaction: dropwise adding fluoboric acid into the system; 3) performing low-temperature diazotization: dropwise adding sodium nitrite into the reaction bottle; (4) crystallizing and purifying to obtain white powdery 4-hexafluoroisopropanol benzodiazepine tetrafluoroborate; 5) preparation of an activation solution: dissolving 4-hexafluoroisopropanol benzodiazepine tetrafluoroborate and potassium iodide in water; and 6) surface modification: immersing the two-dimensional transition metal dichalcogenide in the activation solution to obtain the surface-modified transition metal dichalcogenide nano material. According to the method, the specific adsorption capacity on dimethyl methylphosphonate is remarkably enhanced, and the detection limit reaches ppb level.

Description

Technical Field

[0001] The invention belongs to the technical field of biochemical safety monitoring, and particularly relates to a method for detecting dimethyl methylphosphonate at room temperature by utilizing surface-modified transition metal disulfide nanomaterials. Background Art

[0002] Dimethyl methylphosphonate (DMMP, chemical formula C3H9O3P, CAS number 756-79-6) is an organophosphorus compound containing 25% phosphorus. It is a colorless, transparent liquid with a distinctive odor at room temperature. Its molecular weight is 124.08 g / mol, density is 1.145 g / mL (25°C), boiling point is 181°C, water solubility is ≥10 g / 100 mL at 21°C, and flash point is approximately 69°C (156°F). It exhibits excellent water solubility and compatibility with organic solvents. The highly reactive phosphorus atom in its molecular structure imparts unique chemical properties, particularly the phosphonate group, which is highly similar to the nerve agent sarin (isopropyl methylphosphonate), making DMMP a valuable sarin simulant.

[0003] Sarin, a typical G-type nerve agent, inhibits cholinesterase activity, leading to excessive accumulation of acetylcholine in the synaptic cleft, causing pupil constriction, difficulty breathing, muscle spasms, and ultimately respiratory failure. It is highly toxic and rapidly lethal. Given the military dangers of sarin, DMMP, due to its structural similarity, is widely used in gas mask effectiveness testing, gas detector calibration, and counterterrorism emergency drills, providing key technical support for the development of personal protective equipment and early warning of chemical terrorist attacks. Furthermore, as a highly efficient internally added flame retardant, DMMP can significantly improve the flame retardant properties of materials, requiring only 50% of the dosage of traditional flame retardants. In the industrial field, it can also be used as an additive for lithium battery electrolytes and as an intermediate in the synthesis of pesticides and drugs, demonstrating its multi-faceted application value.

[0004] However, DMMP's toxicity and environmental risks cannot be ignored: it can cause acute poisoning through inhalation, skin contact, or oral administration, with high-dose exposure leading to respiratory failure and even death. As a sarin simulant, strictly regulated under the Chemical Weapons Convention (CWC), it is subject to international transport regulations and production and trade restrictions. Furthermore, its volatility and water solubility increase the risk of environmental pollution and industrial leaks, creating an urgent need for trace detection technologies.

[0005] Current detection technologies face significant bottlenecks: While laboratory-grade gas chromatography-mass spectrometry can achieve ppb-level accuracy, the equipment is expensive and complex to operate, making it inadequate for rapid on-site detection. Metal oxide semiconductor sensors require high temperatures of 200-400°C, resulting in high power consumption, low sensitivity to DMMP, and slow recovery. While polymer / graphene-based sensors can operate at room temperature, their reliance on hydrogen bonding results in weak response signals and poor selectivity. They are susceptible to interference from alcohols, alkanes, and humidity in complex environments, and their device stability is insufficient. All of these technologies struggle to achieve trace detection limits of <1 ppm, making them inadequate for precise monitoring of sarin-like agent simulants in counterterrorism scenarios, as well as for real-time early warning requirements for industrial safety and environmental emergencies.

[0006] In view of the high-risk properties of DMMP as a sarin simulant and the bottlenecks of existing detection technologies, the development of a portable detection device with ppb-ppm level high sensitivity, rapid response and recovery at room temperature, strong anti-interference ability and long life is of great significance for the effectiveness evaluation of chemical protective equipment, industrial safety monitoring and public safety emergency response. Summary of the Invention

[0007] The present invention provides a method for detecting dimethyl methylphosphonate at room temperature using surface-modified transition metal dichalcogenide nanomaterials. The present invention constructs a new gas sensor by surface-modifying transition metal dichalcogenide nanomaterials, breaking through the limitations of traditional detection technologies in sensitivity, selectivity and stability, and providing an innovative solution for the efficient detection of sarin-type agent simulants.

[0008] The technical solution of the present invention is:

[0009] First, a method for detecting dimethyl methylphosphonate at room temperature using surface-modified transition metal disulfide nanomaterials is disclosed. The transition metal disulfide nanomaterials are surface-modified, and a sensor is prepared using the surface-modified transition metal disulfide nanomaterials. The sensor is then used for the characteristic detection of dimethyl methylphosphonate at room temperature.

[0010] Preferably, the surface modification of the transition metal dichalcogenide nanomaterial comprises the following steps:

[0011] 1) Raw material pretreatment: 4-(hexafluoro-2-hydroxyisopropyl)aniline and water were added to a reaction flask and ultrasonicated to form a uniform dispersion;

[0012] 2) Acidification reaction: Add fluoroboric acid dropwise to the system and continue sonication until the solution becomes clear and transparent;

[0013] 3) Low-temperature diazotization: Cool the reaction system to 0°C, dissolve sodium nitrite in pre-cooled water, and add it dropwise to the reaction flask through a constant pressure dropping funnel;

[0014] 4) Crystallization purification: Maintain the reaction at 0°C with stirring until a white precipitate is formed. Collect the solid product, wash it, and dry it to obtain 4-hexafluoroisopropanolbenzodiazine tetrafluoroborate (4-HFBD) as a white powder.

[0015] 5) Preparation of activation solution: Dissolve 4-hexafluoroisopropanol benzodiazine tetrafluoroborate and potassium iodide in water and stir to form an activation solution;

[0016] 6) Surface modification: immersing the two-dimensional transition metal dichalcogenide in an activation solution, performing a grafting reaction, washing, and drying to obtain a surface-modified transition metal dichalcogenide nanomaterial.

[0017] Preferably, the molar ratio of 4-(hexafluoro-2-hydroxyisopropyl)aniline, fluoroboric acid and sodium nitrite is 1:(1-3):(1-2).

[0018] Preferably, the ultrasonication time in step 1) is 5-10 min.

[0019] Preferably, the sodium nitrite solution in step 3) is added at a rate of 1-5 mL / min.

[0020] Preferably, the crystallization purification time in step 4) is 30-40 min, and the vacuum drying is performed at 60-65° C. for 2-4 h.

[0021] Preferably, in step 5), the molar ratio of 4-hexafluoroisopropanol benzodiazine tetrafluoroborate to potassium iodide is (1-1.5): the concentrations of 1,4-hexafluoroisopropanol benzodiazine tetrafluoroborate and potassium iodide are both (0.25-1) mmol / L.

[0022] Preferably, the two-dimensional transition metal dichalcogenide in step 6) is MoS2, WSe2, In2Se3, MoSe2 and WS2; the two-dimensional transition metal dichalcogenide is a two-dimensional transition metal dichalcogenide (TMD) grown by CVD on the surface of a SiO2 / Si substrate.

[0023] In a second aspect, a surface-modified transition metal dichalcogenide nanomaterial prepared by the preparation method is disclosed.

[0024] The reaction equation for the preparation of 4-hexafluoroisopropanol benzodiazine tetrafluoroborate 4-HFBD is as follows:

[0025]

[0026] The surface modification process is as shown in the attached instructions. Figure 1 As shown, under KI catalysis, the diazo group (-N2 +) is cleaved, and the generated phenyl radical forms a CS / Se covalent bond with the sulfur / selenium vacancies on the TMD surface, simultaneously anchoring the HFIPPh functional group.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The nanomaterial prepared in this invention exhibits ultrahigh sensitivity when fabricated into a sensor: by modifying the surface of TMD (such as MoS2, WS2, etc.) with 4-hexafluoroisopropanol benzodiazine tetrafluoroborate (4-HFBD), a strongly electron-withdrawing fluorine group is introduced, significantly enhancing the specific adsorption capacity of dimethyl p-methylphosphonate. The sensor's detection limit for DMMP is as low as 42 ppb (parts per billion), two orders of magnitude higher than that of conventional metal oxide semiconductor sensors (ppm level), meeting the monitoring requirements of the Chemical Weapons Convention for trace agent leaks.

[0029] 2. The nanomaterials prepared by the present invention are made into sensors that can efficiently detect at room temperature without relying on high-temperature heating (traditional sensors require 200-400°C), and the power consumption is reduced to the μW level, which is suitable for the battery power supply needs of portable devices; the response / recovery time is shortened to 4.6 seconds and 10.4 seconds respectively (at a concentration of 160 ppb), realizing real-time early warning of toxic agents in scenarios such as battlefields and security checks.

[0030] 3. The selectivity is greatly improved, and the directional hydrogen bond network design enables the sensor to maintain high selectivity in complex gas environments (such as those containing interferents such as ethanol and acetone).

[0031] 4. The synthesis method is simple and low-cost. The raw material 4-(hexafluoro-2-hydroxyisopropyl)aniline is a commercial reagent. The synthesis steps are simple (only diazotization + crystallization is required). The preparation process is compatible with microelectronics processing technology and supports wafer-level mass production, greatly reducing the manufacturing cost of a single device.

[0032] 5. Enhanced environmental adaptability, maintaining stable performance under high humidity conditions, breaking through the failure bottleneck of traditional sensors caused by water molecule interference; the sensor has a long working life, reduces the frequency of operation and maintenance calibration, and reduces the cost of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram illustrating the molecular modification mechanism of the present invention.

[0034] Figure 2 Conceptual diagrams of the CVD-grown TMDs (using MoS2 as an example) of the present invention, including (a) an overall view of the chemical vapor deposition (CVD) growth of a MoS2 thin film. (b) a schematic diagram of the dual porcelain boats arranged in a tube furnace. (c) a conceptual diagram of a MoS2 thin film grown on a silicon wafer.

[0035] Figure 3It is a schematic diagram of the preparation process of the sensor of the present invention.

[0036] Figure 4 The following is a performance comparison of Fct-MoS2 prepared in Example 1 of the present invention and MoS2 prepared in Comparative Example 1: (a) Optical image of MoS2 nanosheets. (b) Raman spectra of MoS2 and Fct-MoS2. (c) PL spectra of MoS2 and Fct-MoS2. (d) and (g) are schematic diagrams of MoS2 and Fct-MoS2, respectively. (e) and (f) are two-dimensional and three-dimensional AFM images of MoS2, respectively. (h) and (i) are two-dimensional and three-dimensional AFM images of functionalized MoS2, respectively. (j) is a thickness comparison diagram of MoS2 and Fct-MoS2. (k) Comparison of surface roughness of MoS2 and Fct-MoS2.

[0037] Figure 5 Figures depict the performance of the Fct-MoS2 and MoS2 sensors of the present invention at different DMMP concentrations. (a) Optical image of the Fct-MoS2 sensor and a magnified image of the Fct-MoS2 sensor. (b) Responses of MoS2 and Fct-MoS2 to various gases at a concentration of 5 ppm. (c) Dynamic sensing performance of the Fct-MoS2 sensor at different DMMP concentrations. The figure shows the sensor response at low concentrations. (d) Dynamic sensing performance of Fct-MoS2 at low concentrations (from 100 ppb to 200 ppb). (e) Linear fit of the gas sensor response as a function of DMMP concentration. (f) Dynamic response-recovery time curves up to 160 ppb DMMP. (g) Cyclic response-recovery curves of the device exposed to 2 ppm DMMP vapor. (h) Response curve, baseline resistance, and response time constant of Fct-MoS2 exposed to 1 ppm DMMP under controlled relative humidity conditions (30%, 60%, and 90%). (i) The gas sensor is stable to 2 ppm DMMP over a long period of time.

[0038] Figure 6 Performance diagram of different TMDs materials, (a) WS2 and Fct-WS2, (b) MoSe2 and Fct-MoSe2, (e) WSe2 and Fct-WSe2, (g) In2Se3 and Fct-In2Se3 responses to different gases at 20 ppm. (c) Fct-WS2, (d) Fct-MoSe2, (f) Fct-WSe2, (h) Fct-In2Se3 dynamic sensing performance to different DMMP concentrations. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0040] Example 1

[0041] The preparation method of the surface-modified transition metal dichalcogenide nanomaterial includes the synthesis of 4-hexafluoroisopropanol benzodiazine tetrafluoroborate (4-HFBD) and a covalent grafting reaction on the TMD surface, as shown in the schematic diagram. Figure 3 As shown, specifically:

[0042] 1) Raw material pretreatment: 4-(Hexafluoro-2-hydroxyisopropyl)aniline (HFIPA, 2.0 g, 7.7 mmol) and deionized water (6 mL) were added to a 50 mL eggplant-shaped reaction flask and sonicated (power 100 W, frequency 40 kHz) for 10 min to form a uniform dispersion;

[0043] 2) Acidification reaction: Slowly add fluoroboric acid (HBF4, 2.3 mL, 18.5 mmol) to the system and continue sonication until the solution becomes clear and transparent;

[0044] 3) Low-temperature diazotization: Cool the reaction system to 0°C (using an ice-water bath), dissolve sodium nitrite (NaNO2, 0.6 g, 9.2 mmol) in pre-cooled deionized water (6 mL), and add the solution dropwise to the reaction flask via a constant pressure dropping funnel at a rate of 1 mL / min.

[0045] 4) Crystallization purification: The reaction was stirred at 0°C until a white precipitate was precipitated. The crystallization purification time was 30 min. The solid product was collected by filtration under reduced pressure, washed with pre-cooled deionized water (3 times 15 mL each), and dried in vacuo (60°C, 4 h) to obtain 4-HFBD as a white powder (1.2 g, 72% yield).

[0046] 5) Preparation of activation solution: Dissolve 4-HFBD (0.25 mmol / L) and potassium iodide (KI, 0.25 mmol / L) in deionized water at a molar ratio of 1:1 and stir magnetically (500 rpm) for 5 min to form an activation solution.

[0047] 6) Surface modification: Immerse the two-dimensional TMD material MoS2 in the activation solution to trigger the grafting reaction, and the reaction time is 3 minutes;

[0048] The two-dimensional TMD material MoS2, i.e., a two-dimensional transition metal dichalcogenide, is grown on a silicon dioxide substrate surface using CVD in a dual-temperature zone tube furnace. High-purity molybdenum trioxide powder (MoO3, 99.99%, alfa) and sulfur (S, 99.99%, alfa) are used as starting precursor materials for the growth of MoS2. MoS2 nanosheets ( Figure 2ab). Place 5 mg of MoO3 powder on the surface of the quartz plate, and place a SiO2 / Si substrate 3 cm away from the MoO3 powder. The quartz boat is placed in the downstream heating zone of the dual-zone furnace, and S is placed in the upstream heating zone. First, the dual-zone tubular furnace system is filled with argon. Next, the MoO3 powder and S powder are heated to 680°C and 225°C within 50 minutes, respectively, and maintained for 20 minutes. Argon (20 sccm) is used as a carrier gas during the growth process. Finally, the system is cooled to room temperature to obtain nanosheet-shaped two-dimensional TMD material MoS2. The conceptual diagram of chemical vapor deposition growth of TMDs is attached to the specification. Figure 2 shown.

[0049] 7) Post-treatment: The modified TMD material MoS2 was rinsed with anhydrous ethanol three times and dried by nitrogen purge to obtain the surface-modified transition metal dichalcogenide nanomaterial Fct-MoS2.

[0050] Example 2

[0051] The preparation method of the surface-modified transition metal dichalcogenide nanomaterial includes the synthesis of 4-hexafluoroisopropanol benzodiazine tetrafluoroborate (4-HFBD) and a covalent grafting reaction on the TMD surface, as shown in the schematic diagram. Figure 3 As shown, specifically:

[0052] 1) Raw material pretreatment: 4-(Hexafluoro-2-hydroxyisopropyl)aniline (HFIPA, 2.5 g, 9.625 mmol) and deionized water (6 mL) were added to a 50 mL eggplant-shaped reaction flask and sonicated (power 100 W, frequency 40 kHz) for 10 min to form a uniform dispersion;

[0053] 2) Acidification reaction: Slowly add fluoroboric acid (HBF4, 2.3 mL, 18.5 mmol) to the system and continue sonication until the solution becomes clear and transparent;

[0054] 3) Low-temperature diazotization: Cool the reaction system to 0°C (using an ice-water bath), dissolve sodium nitrite (NaNO2, 0.6 g, 9.2 mmol) in pre-cooled deionized water (6 mL), and add the solution dropwise to the reaction flask via a constant pressure dropping funnel at a rate of 1 mL / min.

[0055] 4) Crystallization purification: The reaction was stirred at 0°C until a white precipitate formed (approximately 30 min). The solid product was collected by filtration under reduced pressure, washed with pre-cooled deionized water (3 × 15 mL), and dried in vacuo (60°C, 4 h) to obtain 4-HFBD as a white powder (1.352 g, 65% yield).

[0056] 5) Preparation of activation solution: Dissolve 4-HFBD (0.25 mmol / L) and potassium iodide (KI, 0.25 mmol / L) in deionized water at a molar ratio of 1:1 and stir magnetically (500 rpm) for 5 minutes to form an activation solution.

[0057] 6) Surface modification: Immerse the two-dimensional TMD material WSe2 in the activation solution to trigger the grafting reaction for 3 minutes;

[0058] The specific synthesis method for the two-dimensional TMD material WSe2 is as follows: Synthesis is carried out in a two-zone tube furnace. 10 mg of tungsten trioxide precursor is loaded into an alumina combustion boat located in the second heating zone. A pre-cleaned SiO2 / Si substrate (300 nm oxide layer) is inverted onto the boat containing the precursor. Using the two-zone tube furnace system, selenium powder is placed in the upstream low-temperature zone. Tungsten trioxide powder and sodium chloride are mixed in a 5:1 weight ratio. Before thermal processing, the reactor chamber is purged with ultrahigh-purity argon (200 sccm, 30 minutes) to establish an oxygen-free environment. The temperature profile is programmed as follows: a ramp rate of 15°C / min is used in the primary zone to the target temperature (400°C for Se), while the secondary zone reaches 860°C. When thermal equilibrium is reached, sulfur vapor delivery is initiated via a computer-controlled push rod mechanism. Growth conditions are maintained for 10 minutes under a continuous gas flow (hydrogen:argon = 6:54 sccm), yielding the two-dimensional TMD material WSe2.

[0059] 7) Post-treatment: The modified TMD material was rinsed with anhydrous ethanol three times and dried with nitrogen to obtain the surface-modified transition metal dichalcogenide nanomaterial Fct-WSe2.

[0060] Example 3

[0061] Unlike Example 2, in this example, "two-dimensional TMD material WSe2" is replaced by "two-dimensional TMD material WS2". The specific synthesis method of the two-dimensional TMD material WS2 is as follows: 50 mg of tungsten trioxide precursor is loaded into an alumina combustion boat located in the second heating zone. A pre-cleaned SiO2 / Si substrate (300 nm oxide layer) is inverted on the boat containing the precursor. A dual-zone tubular furnace system is used to place the sulfur source in the upstream low-temperature zone. It should be noted that a small amount of NaCl is added to the oxidative precursor tungsten trioxide at a weight ratio of 5:1 between tungsten trioxide powder and sodium chloride. Before hot processing, the reactor chamber is purged with ultra-high purity argon (200 sccm, 30 min) to establish an oxygen-free environment. The temperature curve is programmed as follows: the gradient rate in the main zone is 15°C / min to the target temperature (S is 225°C), while the secondary zone reaches 860°C. When thermal equilibrium was reached, sulfur vapor delivery was initiated via a computer-controlled push rod mechanism, and growth conditions were maintained for 10 minutes under a continuous gas flow (hydrogen:argon = 6:54 sccm), yielding surface-modified transition metal dichalcogenide nanomaterial Fct-WS2.

[0062] Example 4

[0063] Different from Example 2, in this embodiment, the “two-dimensional TMD material WSe2” is replaced by “two-dimensional TMD material MoSe2”. The specific synthesis method of the two-dimensional TMD material MoSe2 is:

[0064] 10 mg of molybdenum trioxide precursor was loaded into an alumina combustion boat located in the second heating zone. A pre-cleaned SiO2 / Si substrate (300 nm oxide layer) was inverted onto the boat containing the precursor. A dual-zone tube furnace system was used to place selenium powder in the upstream low-temperature zone. Prior to thermal processing, the reactor chamber was purged with ultrahigh-purity argon (200 sccm, 30 min) to establish an oxygen-free environment. The temperature profile was programmed as follows: a ramp rate of 15°C / min was used in the primary zone to the target temperature (400°C for Se), while the secondary zone reached 680°C. When thermal equilibrium was reached, vapor delivery was initiated via a computer-controlled push-rod mechanism, and growth conditions were maintained for 10 minutes under a continuous gas flow (hydrogen:argon = 6:54 sccm). This resulted in surface-modified transition metal dichalcogenide nanomaterials, Fct-MoSe2.

[0065] Example 5

[0066] Different from Example 2, in this embodiment, the "two-dimensional TMD material MoSe2" is replaced by "two-dimensional TMD material In2Se3". The specific synthesis method of the two-dimensional TMD material InSe2 is:

[0067] In2Se3 was synthesized using a direct vapor delivery method. High-purity In2O3 powder (0.2 mg) was loaded into a custom-designed quartz crucible, topped with an inverted fluoromica substrate. A selenium source (500 mg) was placed in a primary heating zone set at 350°C, while the growth zone was heated to 680°C via a controlled gradient (15°C / min) after an argon purge (200 sccm, 30 min). Post-growth cooling occurred naturally under a continuous gas flow (hydrogen:argon = 3:27 sccm). Surface-modified transition metal dichalcogenide nanomaterials, Fct-In2Se3, were obtained.

[0068] Comparative Example 1

[0069] In this comparative example, MoS2 is grown on the surface of a silicon wafer by CVD technology, that is, the two-dimensional TMD material MoS2 prepared in Example 1 is directly used.

[0070] Comparative Example 2

[0071] In this comparative example, WSe2 is grown on the surface of a silicon wafer by CVD technology, and the two-dimensional TMD material WSe2 prepared in Example 2 is directly used.

[0072] Comparative Example 3

[0073] In this comparative example, WS2 is grown on the surface of a silicon wafer by CVD technology, and the two-dimensional TMD material WS2 prepared in Example 3 is directly used.

[0074] Comparative Example 4

[0075] In this comparative example, MoSe2 is grown on the surface of a silicon wafer by CVD technology, and the two-dimensional TMD material MoSe2 prepared in Example 4 is directly used.

[0076] Comparative Example 5

[0077] In this comparative example, In2Se3 is grown on the surface of a silicon wafer by CVD technology, and the two-dimensional TMD material In2Se3 prepared in Example 5 is directly used.

[0078] Comparative Example 6

[0079] 4-Nitrophenyl tetrafluoroborate (0.25 mmol / L) was used as an activation solution to directly adsorb the two-dimensional TMD material MoS2. Compared with Example 1, although it can be adsorbed on the surface of the transition metal dichalcogenide through chemical reaction, it lacks the functional group that directly reacts with DMMP, resulting in the inability to detect DMMP and lacks practical application value.

[0080] The materials prepared in Example 1 and Comparative Example 1 are respectively designated as Fct-MoS2 and MoS2. The morphologies and corresponding characterizations of Fct-MoS2 and MoS2 are shown in FIG. Figure 4 As shown, Figure 4a is an optical image of MoS2 synthesized by CVD process. MoS2 has a typical triangular shape. Raman spectroscopy was used to determine the effect of covalent grafting of 4-HFBD molecules on the structural properties of MoS2. Figure 4 As shown in b, the typical Raman spectrum of 2H-MoS2 is around 380 cm -1 and 401cm -1 There are two prominent Raman active modes at the center, which are generated by the E2g and A1g vibration modes. After MoS2 is modified with 4-HFBD, the out-of-plane vibration mode appears at 3.0 cm -1 The blue shift of the in-plane vibrational mode E2g remains essentially unchanged. Furthermore, the intensity ratio of E2g to A1g changes. The ratio for pristine MoS2 is approximately 0.65, while that for functionalized MoS2 is approximately 0.54. We further performed photoluminescence (PL) spectroscopy measurements to evaluate the effect of grafting on the band structure of MoS2. Figure 4 c shows the PL spectra of pristine MoS2 and Fct-MoS2. After functionalization, the PL intensity of Fct-MoS2 is significantly suppressed, red-shifting from 1.86eV to 1.81eV, a red shift of about 0.05eV. The thickness of the islands ( Figure 4 d, g). The original MoS2 is about 2.5nm, and Fct-MoS2 is about 4nm ( Figure 4 f). This increase in thickness can be attributed to the functionalization of MoS2 with 4-HFBD. The surface roughness before and after functionalization is as follows: Figure 4 e and Figure 4 h. It can be clearly observed that the roughness increases from 0.57nm to 1.44nm after modification ( Figure 4 i).

[0081] The materials Fct-MoS2 and MoS2 obtained in Example 1 and Comparative Example 1 were used to prepare sensors, which were respectively referred to as sensor Fct-MoS2 and sensor MoS2. The specific preparation methods are as follows: Figure 3 As shown, a surface-modified transition metal dichalcogenide nanomaterial, Fct-MoS2, was transferred to interdigitated electrodes using a wet transfer method with the aid of polymethyl methacrylate (PMMA) to fabricate a gas sensor. First, PMMA was spin-coated onto a substrate containing the surface-modified transition metal dichalcogenide nanomaterial, Fct-MoS2, and then cured by heating at 80°C for 5 minutes. Mica was etched with 5% hydrofluoric acid (HF), causing the grown surface-modified transition metal dichalcogenide nanomaterial, Fct-MoS2, to fall off the substrate and adhere to the PMMA. The resulting mixture was then removed using interdigitated electrodes for later use. The PMMA was then removed with acetone, and the resulting sensor, Fct-MoS2 / MoS2, was fabricated after rinsing with ultrapure water.

[0082] The sensor Fct-MoS2 and sensor MoS2 were tested for DMMP at different concentrations. The specific test method was to characterize the interaction between the two by causing the resistance change of the device through the chemical reaction between DMMP vapor and the device. The test results are as follows: Figure 5 As shown, the MoS2 sensor device is shown in Figure 5 In a. In the magnified image, it can be clearly observed that triangular nanosheets cover the channel electrode to form a conductive structure. Gas sensing performance is shown in Figure 4. Figure 5 b-5i. By exposing it to various analytes (5 ppm), including oxidizing gas (nitrogen dioxide, NO2), reducing gas (hydrogen, H2; ammonia, NH3), nerve agent simulant (DMMP) and reduced volatile organic compounds (triethylamine, TEA; formaldehyde; acetone, ACE; methanol), as shown in Figure 5b-5i. Figure 5 By comparing the selectivity of the original sensor MoS2 and the functionalized sensor Fct-MoS2, we found that the unmodified MoS2 exhibited intrinsic selectivity for NO2 while showing no response to low concentrations of other selected molecules, including DMMP. After modification with 4-HFBD, the response of the sensor to DMMP was significantly enhanced. Figure 5 c depicts the transient response curve of the Fct-MoS2 gas sensor when exposed to different concentrations of DMMP gas at ambient temperature (25°C). As the DMMP concentration increases from 0.2ppm to 50ppm, the sensor response also increases significantly. In addition, even at very low concentrations (from 100ppb to 200ppb), the sensor exhibits fast response and recovery ( Figure 5 d). The sensor response is linearly related to the DMMP concentration ( Figure 5 e). Through data analysis and calculation, we estimate that the LOD of the Fct-MoS2 sensor for DMMP is approximately 42.5 ppb. The limit of detection (LOD) is the lowest concentration of the target gas that a gas sensor can detect and is one of the most important characteristics of a gas sensor. LOD = 3σ / s, where σ is the standard deviation of the linear fit curve and s is the slope of the linear fit curve. Response and recovery time are key parameters for evaluating gas sensor performance. These times are defined as the duration required to reach 90% equilibrium. Figure 5As shown in Figure f, the sensor demonstrates a fast response (4.6 s) and recovery (10.4 s) to 160 ppb of DMMP at room temperature. Of course, as the DMMP concentration increases, both the response time and the recovery time decrease. The sensor exhibits relatively low response times (82.2 s) and recovery times (255.6 s) to 20 ppm of DMMP. To evaluate the stability of low-concentration operation, the device was subjected to five consecutive exposure (100 s)-recovery cycles ( Figure 5 g). This scheme yielded consistent response amplitudes and negligible signal attenuation, demonstrating robust cycling stability under simulated field detection scenarios. Furthermore, the humidity-dependent sensing performance of the Fct-MoS2 gas sensor was systematically investigated by 1 ppm DMMP exposure tests under controlled relative humidity (RH) levels of 30%, 60%, and 90%. Figure 5 h). We observed a typical volcano-type response pattern, where the sensor response initially increased and then decreased with increasing humidity. These results indicate that the Fct-MoS2 gas sensor maintains excellent sensing capabilities even in high humidity environments (RH>60%), highlighting its practical application potential in ambient atmospheric monitoring. In addition, the sensor showed consistent response to 2 ppm DMMP over a 4-week period ( Figure 5 i).

[0083] Figure 6 Figure 2 is a performance diagram of different TMDs materials. According to the preparation method of sensor Fct-MoS2, the materials of Examples 2-5 and Comparative Examples 2-5 were prepared into corresponding sensors, which were respectively recorded as sensors Fct-WSe2, Fct-WS2, Fct-MoSe2 and Fct-In2Se3 and sensors WSe2, WS2, MoSe2 and In2Se3. The gas sensing performance of the above sensors was evaluated, and the results are shown in Figure 2. Figure 6 As shown in the figure, all functionalized TMDs (Fct-WSe2, Fct-WS2, Fct-MoSe2, and Fct-In2Se3) exhibited significantly enhanced responses to 20 ppm of DMMP, while no baseline sensitivity was detected for the unmodified TMDs (WS2, MoSe2, and In2Se3). This is attributed to the improved surface modification of the device by our method, while Fct-In2Se3 exhibits exclusive selectivity for DMMP and no cross-sensitivity to common interferents. Furthermore, the devices exhibited good concentration-dependence on DMMP.

[0084] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and substance of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions are intended to fall within the scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for detecting dimethyl methylphosphonate at room temperature using surface-modified transition metal dichalcogenide nanomaterials, characterized in that: The surface of the transition metal dichalcogenide nanomaterials was modified and a sensor was prepared using the surface modified transition metal dichalcogenide nanomaterials, which was used for the characteristic detection of dimethyl methylphosphonate at room temperature.

2. The method for detecting dimethyl methylphosphonate at room temperature using surface-modified transition metal dichalcogenide nanomaterials according to claim 1, wherein: The surface modification method of transition metal dichalcogenide nanomaterials comprises the following steps: 1) Raw material pretreatment: 4-(hexafluoro-2-hydroxyisopropyl)aniline and water were added to a reaction flask and ultrasonicated to form a uniform dispersion; 2) Acidification reaction: Add fluoroboric acid dropwise to the system and continue sonication until the solution becomes clear and transparent; 3) Low-temperature diazotization: Cool the reaction system to 0°C, dissolve sodium nitrite in pre-cooled water, and add it dropwise to the reaction flask through a constant pressure dropping funnel; 4) Crystallization purification: Maintain the reaction at 0°C with stirring until a white precipitate is formed. Collect the solid product, wash it, and dry it to obtain 4-hexafluoroisopropanolbenzodiazine tetrafluoroborate (4-HFBD) as a white powder. 5) Preparation of activation solution: Dissolve 4-hexafluoroisopropanol benzodiazine tetrafluoroborate and potassium iodide in water and stir to form an activation solution; 6) Surface modification: immersing the two-dimensional transition metal dichalcogenide in an activation solution, performing a grafting reaction, washing, and drying to obtain a surface-modified transition metal dichalcogenide nanomaterial.

3. The method for detecting dimethyl methylphosphonate at room temperature using surface-modified transition metal dichalcogenide nanomaterials according to claim 2, wherein: The molar ratio of 4-(hexafluoro-2-hydroxyisopropyl)aniline, fluoroboric acid and sodium nitrite is 1:(1-3):(1-2).

4. The method for detecting dimethyl methylphosphonate at room temperature using surface-modified transition metal dichalcogenide nanomaterials according to claim 2, wherein: The ultrasonication time in step 1) is 5-10 min.

5. The method for detecting dimethyl methylphosphonate at room temperature using surface-modified transition metal dichalcogenide nanomaterials according to claim 2, wherein: In step 3), the sodium nitrite solution is added at a rate of 1-5 mL / min.

6. The method for detecting dimethyl methylphosphonate at room temperature using surface-modified transition metal dichalcogenide nanomaterials according to claim 2, wherein: In step 4), the crystallization purification time is 30-40 minutes, and the vacuum drying is performed at 60-65° C. for 2-4 hours.

7. The method for detecting dimethyl methylphosphonate at room temperature using surface-modified transition metal dichalcogenide nanomaterials according to claim 2, wherein: In step 5), the molar ratio of 4-hexafluoroisopropanol benzodiazine tetrafluoroborate and potassium iodide is (1-1.5): the concentrations of 1,4-hexafluoroisopropanol benzodiazine tetrafluoroborate and potassium iodide are both (0.25-1) mmol / L.

8. The method for detecting dimethyl methylphosphonate at room temperature using surface-modified transition metal dichalcogenide nanomaterials according to claim 2, wherein: In step 6), the two-dimensional transition metal dichalcogenides are MoS2, WSe2, In2Se3, MoSe2 and WS2.

9. A surface-modified transition metal dichalcogenide nanomaterial obtained by surface-modifying the transition metal dichalcogenide nanomaterial according to the method of any one of claims 2 to 8.

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