Sensor for detecting nitroaromatic explosives in gas as well as preparation method and application of sensor

Abstract

The invention provides a sensor for detecting gas nitroaromatic explosives and a preparation method and application thereof.The sensor comprises a gas sampling system, a sensing system and a processing system, a sensing module in the sensing system is composed of a substrate, a sensitive layer and an interdigital electrode, the sensitive layer is formed by compounding amino-modified graphene quantum dots and a metal organic framework material. The sensor realizes high-sensitivity and rapid detection of nitro-aromatic explosives (such as TNT and DNT) gas through a specific molecular recognition effect and synergistic enhancement of a high-specific-surface-area material. The preparation method comprises the steps of substrate pretreatment, sensitive layer construction and interdigital electrode patterning. The lowest detection limit of the sensor can reach ppb level, the response time is short, the selectivity is good, and the sensor is suitable for trace explosive detection in scenes such as public safety, anti-terrorist law enforcement and border patrol.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and particularly to a sensor for detecting gas nitroaromatic explosives, a preparation method thereof, and an application thereof. Background Art

[0002] Nitroaromatic compounds are a typical type of explosive components containing nitro groups. Representative substances include trinitrotoluene (TNT), dinitrotoluene (DNT), etc. Because they contain both nitro functional groups and aromatic rings in their structures, they have relatively high explosive properties. These compounds are widely used in military weapons, industrial explosives, and civil blasting and other fields. Nitroaromatic explosives also have a certain volatility and can release trace gas molecules at room temperature. Therefore, with the increasingly complex global security situation, timely and accurately detecting trace explosive gases present in the environment is of extremely important significance for fields such as public place safety monitoring, anti-terrorism and anti-explosion, border control, major event security checks, and crime scene investigation.

[0003] Currently, the methods for detecting gas nitroaromatic explosives mainly include mass spectrometry, gas chromatography, ion mobility spectrometry, fluorescence analysis, and electrochemical detection methods, etc. Although these methods have a certain application basis in the field of precision detection, most of them rely on large-scale instrument equipment, the detection process is complex, and it is difficult to meet the requirements of portable and real-time monitoring. Therefore, researchers have begun to focus on constructing sensor arrays through functional materials for on-site detection and trace analysis of explosive gas molecules. However, the existing sensors for detecting nitroaromatic gas explosives still have many problems. For example, some sensors have insufficient detection sensitivity and cannot detect target gases at low concentrations; some sensors have a slow response speed and are difficult to meet the rapid identification requirements in emergency scenarios; there are also some sensors with poor selectivity and are easily interfered by other volatile organic compounds or humidity changes in the environment, resulting in false alarms or missed alarms.

[0004] Based on the above problems, there is an urgent need to develop a sensor for detecting gas nitroaromatic explosives with high sensitivity, fast response speed, and good selectivity to meet the rapid identification requirements of trace explosive gases in complex environments. Summary of the Invention

[0005] In view of the above-mentioned technical problems, a sensor for detecting gaseous nitroaromatic explosives, its preparation method and application are provided, aiming to effectively improve the detection performance and expand its practical and portable application scenarios by optimizing the sensitive material system and device structure. The present invention mainly utilizes a sensitive layer composed of amino-modified graphene quantum dots and metal-organic framework materials in the sensing module, which is in close contact with the pre-constructed interdigital electrode structure to form a sensing module with stable response signals and high structural integration. Together with the gas sampling system and processing system arranged outside the sensor, real-time monitoring and data feedback of the target gas are achieved.

[0006] The technical means adopted in the present invention are as follows:

[0007] A sensor for detecting gaseous nitroaromatic explosives, comprising a gas sampling system, a sensing system and a processing system, which work together to achieve the detection of gaseous nitroaromatic explosives;

[0008] Among them, the sensing system includes a sensing module, and the sensing module includes a substrate, a sensitive layer and interdigital electrodes. The substrate is used to provide support for the sensor. The sensitive layer is coated on the surface of the substrate, and the interdigital electrodes are located below the sensitive layer and are in close contact with it.

[0009] Furthermore, the substrate is a silicon wafer or a quartz wafer. The sensitive layer is composed of a composite of amino-modified graphene quantum dots and metal-organic framework materials. The interdigital electrodes are made of gold or platinum.

[0010] Furthermore, the thickness of the sensitive layer is 100 nm - 500 nm. The finger width of the interdigital electrodes is 10 μm to 50 μm, and the finger spacing is 10 μm to 30 μm.

[0011] Furthermore, the particle size of the graphene quantum dots in the sensitive layer is less than 10 nm, and the mass ratio of the metal-organic framework material to the graphene quantum dots is 2:1 - 5:1. Among them, the metal-organic framework material is UiO-66-NH2 or MIL-101(Cr), which is used to enhance the adsorption and recognition of nitroaromatic molecules.

[0012] Furthermore, the gas sampling system includes a housing. An air inlet hood is arranged on one side of the housing, and an air inlet pump is arranged on the other side. The air inlet end of the air inlet pump penetrates into the interior of the housing. A filter screen is arranged outside the air inlet hood.

[0013] Furthermore, the processing system includes a circuit signal processing module, which includes a microprocessor, a signal amplifier, a filter and a wireless transmission module. The microprocessor is used to collect the Raman signal generated by the sensor module and convert it into a digital signal. After amplification by the signal amplifier, filtering by the filter and noise reduction processing, the processed data is sent to the terminal device through the wireless transmission module.

[0014] The present invention also discloses a method for preparing the above-mentioned sensor for detecting gaseous nitroaromatic explosives, comprising the following steps:

[0015] Step 1: pretreatment of the substrate, ultrasonically cleaning the substrate with acetone, ethanol and deionized water in sequence, and then drying it in a nitrogen atmosphere for later use;

[0016] Step 2: preparing the sensitive layer, mixing the amino-modified graphene quantum dots and the metal organic framework material in a preset mass ratio in a solution, forming a uniform mixed solution by ultrasonic dispersion, coating the mixed solution on the surface of the substrate by spin coating or chemical vapor deposition, and drying to form a sensitive layer;

[0017] Step three: preparing the interdigitated electrodes, using photolithography technology to make a mask for the interdigitated electrodes on the surface of the substrate, using a sputtering process to deposit metal material on the mask to form the interdigitated electrodes, and finally removing the mask.

[0018] The present invention also discloses a method for detecting gaseous nitroaromatic explosives using the above-mentioned sensor, comprising:

[0019] The calibration step is to place the sensor in a standard gas environment containing nitroaromatic explosive gas of different concentrations, record the electrical signal output by the sensor, and establish a calibration curve between the electrical signal and the explosive gas concentration;

[0020] The actual detection steps are to place the sensor in the test environment, and determine the concentration of nitroaromatic explosive gas in the test environment based on the electrical signal output by the sensor and the calibration curve, with a detection limit of less than 100ppt.

[0021] Furthermore, the electrical signal is a change in the intensity of a Raman signal, with a response time of less than 30 seconds and a recovery time of less than 60 seconds.

[0022] The present invention also discloses the application of the above-mentioned sensor in public place security detection, which is used for rapid detection of trace amounts of nitroaromatic explosive gases such as TNT and DNT in the air in scenes such as subways, airports, and border inspection stations.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. The present invention uses a composite of amino-modified graphene quantum dots and metal-organic framework materials to form a sensitive layer. The two cooperate to form a large specific surface area and high-density active sites, which can have strong molecular recognition and electronic interactions with nitroaromatic molecules (such as TNT, DNT), significantly enhancing the response ability to trace explosive gases. The lowest detection limit can reach the ppb level or even lower (the detection sensitivity is related to the material structure and response system, and the actual detection limit can reach the ppb level or even lower than 100 ppt according to the optimized parameters).

[0025] 2. The nanomaterials used in the present invention have excellent gas diffusion performance and rapid adsorption ability, and the thickness of the sensitive layer is controlled in the order of hundreds of nanometers, which can accelerate the mass transfer process of target gas molecules, achieve rapid capture and signal conversion, and shorten the response time to within dozens of seconds, meeting the rapid early warning requirements for sudden explosive gases.

[0026] 3. The amino functional groups in the sensitive material of the present invention can specifically have hydrogen bond, electrostatic or charge transfer interactions with nitroaromatic molecules. At the same time, the unique molecular sieve structure of the metal-organic framework material provides size-matching pores and chemical affinity selectivity, enabling the sensor to exhibit good recognition ability for nitroaromatic gases in complex environments and reducing false responses to interference sources such as water vapor and organic volatiles.

[0027] In summary, the present invention uses a sensitive layer composed of a composite of amino-modified graphene quantum dots and metal-organic framework materials as the sensing element of the sensing system, forms an integrated structure with interdigital electrodes, and cooperates with a gas sampling system and a circuit processing system. The overall structure is compact, facilitating preparation and integration. The present invention realizes highly selective, highly sensitive and rapid response detection of trace nitroaromatic explosive gases, and has the advantages of a compact structure, short response time, low detection limit, easy integration and on-site deployment, etc. It is particularly suitable for the explosive screening requirements in high-security level scenarios such as security inspection, anti-terrorism, and border law enforcement, and has broad practical prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 It is a schematic structural diagram of the sensor for detecting nitroaromatic explosive gases of the present invention.

[0030] Figure 2 It is an overall cross-sectional view of the sensor for detecting nitroaromatic explosive gases of the present invention.

[0031] Figure 3 This is a schematic structural diagram of the sensing module in the present invention.

[0032] In the figure: 1. Housing; 2. Air inlet hood; 201. Filter screen; 3. Air inlet pump; 4. Sensing module; 401. Substrate; 402. Sensitive layer; 403. Interdigitated electrode; 5. Circuit signal processing module. Specific embodiments

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Embodiment 1

[0035] As Figure 1 and Figure 2 shown, a sensor for detecting gas nitroaromatic explosives provided by the present invention includes a gas sampling system, a sensing system, and a processing system, and the three work together to achieve the detection of gas nitroaromatic explosives.

[0036] Specifically, the sensing system includes a sensing module 4 (as Figure 3 shown), the sensing module 4 includes a substrate 401, a sensitive layer 402, and an interdigitated electrode 403. The substrate 401 is used to provide support for the sensor. The sensitive layer 402 is coated on the surface of the substrate 401. The interdigitated electrode 403 is located below the sensitive layer 402 and is in close contact with it to form an efficient signal transmission interface.

[0037] Among them, the substrate 401 is made of a material with excellent mechanical properties, heat resistance, and chemical stability, such as a high-purity single-crystalline silicon wafer or a quartz wafer, and the surface is finely polished to provide ideal flatness and stability. The sensitive layer 402 is prepared on the surface of the substrate 401 by chemical vapor deposition CVD or spin coating. The material of the sensitive layer 402 is a functionalized nanocomposite material that specifically recognizes nitroaromatic molecules, such as a composite of amino-modified graphene quantum dots (NH2-GQDs) and metal-organic frameworks (MOF). The interdigitated electrode 403 is prepared on the substrate 401 by high-precision lithography and magnetron sputtering processes. The interdigitated electrode 403 is made of a noble metal with excellent electrical conductivity and high chemical stability, such as gold or platinum. The interdigitated electrode 403 is in close contact with the sensitive layer 402 to transmit electrical signals.

[0038] Preferably, the thickness of the sensitive layer is 100 nm - 500 nm, which is conducive to the rapid diffusion of the target gas into the sensitive material and full contact with the active sites, thereby improving the sensitivity and response speed. The finger width of the interdigital electrode is 10 μm to 50 μm, and the finger spacing is 10 μm to 30 μm, which can effectively control the resistance, facilitate the amplification of the electrical signal, reduce the risk of crosstalk, and is suitable for multi-point arrays.

[0039] It should be noted that the particle size of the graphene quantum dots in the sensitive layer is less than 10 nm, which effectively improves the density of surface active sites and the electron transport efficiency of the material, enabling the target gas molecules to interact with the sensitive layer more quickly; the mass ratio of the metal-organic framework material to the graphene quantum dots is 2:1 - 5:1, which helps to provide a rich pore structure and chemical adsorption sites on the basis of ensuring sufficient conduction paths. Among them, the metal-organic framework material is selected from UiO-66-NH2 or MIL-101(Cr) with a high specific surface area, strong thermal stability, and affinity selectivity for aromatic nitro-containing molecules, which is used to enhance the adsorption and recognition of nitroarene molecules.

[0040] In addition, the gas sampling system includes a housing 1 made of antistatic polycarbonate. An air intake hood 2 with an aerodynamic optimization design is provided on the left side of the housing 1. A multi-layer composite filter screen 201 is provided on the outside of the air intake hood 2, which can effectively filter interfering substances such as dust and water droplets in the environment; a micro high-efficiency air intake pump 3 is provided on the right side of the housing 1. The intake end of the air intake pump 3 penetrates into the interior of the housing 1 to ensure that sufficient gas samples pass through the sensing module 4.

[0041] The processing system includes a circuit signal processing module 5. The circuit signal processing module 5 includes a microprocessor, a signal amplifier, a filter, and a wireless transmission module. The microprocessor is used to collect the Raman signals generated by the sensing module 4, convert them into digital signals, and after being amplified by the signal amplifier and filtered and noise-reduced by the filter, the processed data is sent to a mobile phone, a tablet, or a dedicated terminal device in real time through a Bluetooth 5.0 / WiFi / 4G multi-mode wireless transmission module to achieve remote monitoring and data analysis.

[0042] In practical applications of the present invention, the sensor is placed in the environment to be detected, and the switch of the intake pump 3 is turned on. After the environmental gas is efficiently filtered by the filter screen 201, it is uniformly introduced into the interior of the housing 1 through the intake hood 2. When trace gas molecules containing nitroaromatic explosives come into contact with the sensing module 4, specific interactions occur between the gas molecules and the NH2-GQDs / MOF composite material in the sensitive layer 402, that is, hydrogen bonding and charge transfer occur between the nitro group in the gas molecules and the amino group in the sensitive layer 402, resulting in changes in the electrical properties of the sensitive layer 402, such as a significant change in conductivity. This change is converted into an electrical signal by the interdigital electrode 403, and then the microprocessor in the circuit signal processing module 5 is responsible for collecting these electrical signals and converting them into digital signals. After being amplified and optimized by the signal amplifier, filtered and noise-reduced by the filter, the processed data is sent to the terminal device through the wireless transmission module, realizing the detection and analysis of explosive gases.

[0043] Example 2

[0044] The present invention also provides a preparation method for a sensor for detecting nitroaromatic explosives in gases. Based on the sensor for detecting nitroaromatic explosives in gases in Example 1, the preparation method of the sensing module includes the following steps:

[0045] Step 1: Substrate pretreatment:

[0046] The substrate 401 of the silicon wafer is successively ultrasonically cleaned with acetone, ethanol, and deionized water for 15 - 30 minutes to remove surface impurities, then dried in a nitrogen atmosphere, and subsequently heat-treated in a vacuum oven at 120°C for 20 minutes to completely remove adsorbed water molecules on the surface;

[0047] Step 2: Sensitive layer preparation:

[0048] Amino-functionalized graphene quantum dots are prepared by chemical synthesis. The prepared amino-functionalized graphene quantum dots and the metal-organic framework material are mixed in a mass ratio of 1:3 in an N,N-dimethylformamide solvent, and a uniform mixed solution is formed by ultrasonic dispersion for 40 minutes. The mixed solution is spin-coated on the surface of the pretreated substrate 401 and dried at 60 - 80°C to form the sensitive layer 402;

[0049] Step 3: Interdigital electrode preparation:

[0050] A mask for the interdigital electrode 403 is fabricated on the surface of the substrate 401 by photolithography technology, and then a metal such as gold or platinum is deposited on the mask by magnetron sputtering to form the interdigital electrode 403. Finally, the mask is removed by a degluing process of soaking in an acetone solution for 15 minutes.

[0051] Example 3

[0052] The present invention also provides a method for preparing a sensor for detecting gaseous nitroaromatic explosives. Based on Example 2, the difference from Example 2 in Step 2 is that the prepared amino-modified graphene quantum dots and the metal-organic framework material are mixed in a mass ratio of 1:5 in N,N-dimethylformamide solvent, and ultrasonic dispersion is carried out for 60 minutes to form a uniform mixed solution. The mixed solution is coated on the surface of the pretreated substrate 401 by chemical vapor deposition (CVD), and dried at 60-80 °C for 2 hours to form the sensitive layer 402.

[0053] Example 4

[0054] The present invention also provides a method for detecting gaseous nitroaromatic explosives. Based on a sensor for detecting gaseous nitroaromatic explosives in Example 1, it includes the following steps:

[0055] Step 1: Calibration:

[0056] The sensor is placed in a standard gas environment containing gaseous nitroaromatic explosives with different concentrations (such as TNT, DNT, RDX, etc.). Each concentration point is measured 3-5 times to ensure data reliability; the electrical signal parameters output by the sensor are recorded, including the resistance change rate, current change value or capacitance change amount; the calibration curve between the electrical signal and the concentration of the explosive gas is established by least squares fitting, and performance parameters such as the correlation coefficient, detection limit and linear range are calculated; at the same time, the influence of environmental factors such as temperature and humidity on the calibration curve is evaluated, and a necessary compensation model is established.

[0057] Step 2: Actual detection:

[0058] The sensor is preheated to stabilize the baseline signal; the sensor is placed in the environment to be detected, and the gas sampling system is started for sampling, and the sampling time is 30 seconds to 2 minutes; according to the electrical signal output by the sensor, the concentration of gaseous nitroaromatic explosives in the environment is determined in combination with the calibration curve; the detection result is displayed and recorded in real time through the processing system. When the detected explosive concentration exceeds the preset threshold, the system automatically issues an alarm; after the detection is completed, the sensor is cleaned and regenerated, and the sensitive layer is restored to its initial state by heating or passing a clean air stream for the next detection.

[0059] Specifically, when gas molecules containing nitroaromatic explosives come into contact with the sensitive layer 402, specific interactions occur between the gas molecules and the material of the sensitive layer 402. Taking the composite material of amino-modified graphene quantum dots and metal-organic framework as an example, hydrogen bonding and charge transfer occur between the amino group and the nitro group, resulting in changes in the electrical properties of the sensitive layer 402, such as resistance, capacitance, etc. The interdigital electrode 403 converts this change in electrical property into a measurable electrical signal. By detecting the change in the electrical signal, qualitative and quantitative detection of gas nitroaromatic explosives is achieved; secondly, the microprocessor is responsible for collecting these electrical signals, converting them into digital signals, and after being amplified by a signal amplifier, filtered by a filter, and noise-reduced, the processed data is sent to the terminal device through a wireless transmission module.

[0060] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the present invention; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A sensor for detecting gas nitroaromatic explosives, characterized in that, It includes a gas sampling system, a sensor system and a processing system, which work together to detect gaseous nitroaromatic explosives; The sensing system includes a sensing module, which includes a substrate, a sensitive layer and interdigital electrodes. The substrate is used to provide support for the sensor, the sensitive layer is coated on the surface of the substrate, and the interdigital electrodes are located below the sensitive layer and in close contact with it.

2. The sensor according to claim 1, wherein, The substrate is a silicon wafer or a quartz wafer, the sensitive layer is a composite of amino-modified graphene quantum dots and metal organic framework materials, and the interdigital electrodes are made of gold or platinum.

3. The sensor according to claim 2, wherein, The thickness of the sensitive layer is 100nm-500nm, the finger width of the interdigitated electrode is 10μm to 50μm, and the finger spacing is 10μm to 30μm.

4. The sensor according to claim 3, wherein, The particle size of the graphene quantum dots in the sensitive layer is less than 10 nm, and the mass ratio of the metal organic framework material to the graphene quantum dots is 2:1-5:1; wherein the metal organic framework material is UiO-66-NH2 or MIL-101 (Cr), which is used to enhance the adsorption and recognition of nitroaromatic molecules.

5. The sensor according to claim 1, characterized in that, The gas sampling system comprises a shell, an air intake hood is arranged on one side of the shell, and an air intake pump is arranged on the other side, the air intake end of the air intake pump penetrates into the interior of the shell; a filter screen is arranged on the outer side of the air intake hood.

6. The sensor according to claim 1, characterized in that, The processing system includes a circuit signal processing module, which includes a microprocessor, a signal amplifier, a filter and a wireless transmission module. The microprocessor is used to collect the Raman signal generated by the sensor module and convert it into a digital signal. After amplification by the signal amplifier, filtering by the filter and noise reduction processing, the processed data is sent to the terminal device through the wireless transmission module.

7. A method for preparing a sensor for detecting nitroaromatic explosives in gas according to any one of claims 1-6, characterized in that, The following steps are involved: Step 1: pretreatment of the substrate, ultrasonically cleaning the substrate with acetone, ethanol and deionized water in sequence, and then drying it in a nitrogen atmosphere for later use; Step 2: preparing the sensitive layer, mixing the amino-modified graphene quantum dots and the metal organic framework material in a preset mass ratio in a solution, forming a uniform mixed solution by ultrasonic dispersion, coating the mixed solution on the surface of the substrate by spin coating or chemical vapor deposition, and drying to form a sensitive layer; Step three: preparing the interdigitated electrodes, using photolithography technology to make a mask for the interdigitated electrodes on the surface of the substrate, using a sputtering process to deposit metal material on the mask to form the interdigitated electrodes, and finally removing the mask.

8. A method for detecting gas nitroaromatic explosives using the sensor according to any one of claims 1-6, characterized in that include: The calibration step is to place the sensor in a standard gas environment containing nitroaromatic explosive gas of different concentrations, record the electrical signal output by the sensor, and establish a calibration curve between the electrical signal and the explosive gas concentration; The actual detection steps are to place the sensor in the test environment, and determine the concentration of nitroaromatic explosive gas in the test environment based on the electrical signal output by the sensor and the calibration curve, with a detection limit of less than 100ppt.

9. The method according to claim 8, wherein The electrical signal is a change in the intensity of the Raman signal, with a response time of less than 30 seconds and a recovery time of less than 60 seconds.

10. Use of the sensor according to any one of claims 1-6 in public place safety detection, characterized in that, Used for rapid detection of trace amounts of nitroaromatic explosive gases such as TNT and DNT in the air in scenes such as subways, airports, and border inspection stations.

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