CN108680543B - A kind of method for detecting nitroaromatic explosives - Google Patents

Abstract

The invention discloses a method for detecting nitroaromatic hydrocarbon explosives. A fluorescent sensor based on amino-modified polystyrene is used to place it at a position to be measured, and the fluorescence of the fluorescent sensor based on amino-modified polystyrene is detected at regular intervals. intensity, and obtain the quenching efficiency of the amino-modified polystyrene-based fluorescence sensor, wherein the amino-modified polystyrene-based fluorescence sensor includes an aminated glass sheet and a sensing layer, and the sensing layer is placed on the surface of the aminated The surface of the glass sheet, the sensing layer is an electrospinning film prepared by blending amino-modified polystyrene and pyrene, and the structural formula of the amino-modified polystyrene is:

Wherein, m:n=8～12:1, the weight average molecular weight of amino-modified polystyrene is (4～5)×10 ⁴ g/mol, and the relative mass distribution index is 1.3～1.4. The detection method of the present invention has higher sensitivity for the detection of NACs.

Description

A kind of method for detecting nitroaromatic explosives

technical field

The invention relates to a method for detecting nitroaromatic explosives.

Background technique

There are many types of explosives that you hear about every day. A large number of explosive materials can be classified into six categories according to their structures: nitroalkanes (such as 2,3-dimethyl-2,3-dinitrobutane DMNB, nitroanthracene NM), nitroaromatic hydrocarbons (such as 2-nitrotoluene, 3-nitrotoluene, 4-nitrotoluene NT, 2,4-dinitrotoluene, 2,4-dinitrotoluene DNT, 2,4,6-trinitrotoluene TNT , 2,4,6-trinitrophenol PA, nitrobenzene DNB), nitroamines (such as cyclotrimethylene trinitroamine RDX, 1,3,5,7-tetranitro-1,3,5, 7-tetraazacyclooctane HMX, 2,4,6-trinitrobenzyl nitramine Tetryl), nitrates (such as nitroglycerin NG, pentaerythritol tetranitrate PETN), peroxides (such as hydrogen peroxide HP , Triacetone triperoxide TATP, hexamethylene triperoxide diamine HMTD).

Most of the explosives contain nitroaromatic compounds (NACs), and the detection of these compounds mainly includes bulk detection technology (Bulk Detection) and trace detection technology (Trace Detection). The volume detection technology mainly includes imaging detection and nuclear detection. The trace detection technology is to detect explosive particles or gases that are difficult to detect with the naked eye. Generally, explosives are volatile to a certain extent, and explosives will be attached to the surrounding of the storage location or the surface of people or objects that come into contact with the explosives. Micro-trace detection methods mainly include chemiluminescence method, redox method, ion mobility spectrometry, chemical reagent method, surface acoustic wave method, gas-mass spectrometry method, chemical sensor and canine animal analysis method. Among them, the most sensitive detection method for explosives is gas-mass spectrometry (10 ^-4 g/cm ^-1 ). In addition, the sensitivity of ion mobility spectrometry for explosive detection can also reach 10 ^-3 g/cm ^-1 , but the wide application of this method is limited due to the expensive and bulky instruments and the need for professional operation.

Due to the limitations of common detection methods, it is difficult to be widely used. It becomes more urgent to find a simple, fast, low-cost and high-sensitivity detection method to meet the actual needs.

SUMMARY OF THE INVENTION

In order to solve the deficiencies of the prior art, one of the purposes of the present invention is to provide an application of a fluorescent sensor of amino-modified polystyrene in detecting nitroaromatic explosives, and the fluorescent sensor used in the present invention can effectively enrich Nitroaromatic compounds have higher sensitivity for the detection of NACs.

In order to achieve the above object, the technical scheme of the present invention is:

其中，m:n＝8～12:1，氨基改性聚苯乙烯的重均分子量为(4～5)×10⁴g/mol，相对质量分布指数为1.3～1.4。An application of an amino-modified polystyrene fluorescent sensor in detecting nitroaromatic explosives, the amino-modified polystyrene fluorescent sensor comprises a surface aminated glass sheet and a sensing layer, and the sensing layer is provided with On the surface of the surface aminated glass sheet, the sensing layer is an electrospinning film spun from amino-modified polystyrene and pyrene, and the structural formula of the amino-modified polystyrene is:

Wherein, m:n=8～12:1, the weight average molecular weight of amino-modified polystyrene is (4～5)×10 ⁴ g/mol, and the relative mass distribution index is 1.3～1.4.

其中，m:n＝8～12:1，氨基改性聚苯乙烯的重均分子量为(4～5)×10⁴g/mol，相对质量分布指数为1.3～1.4。The second object of the present invention is to provide a method for detecting nitroaromatic compounds in explosives. The fluorescence intensity of the fluorescence sensor is obtained, and the quenching time of the fluorescence sensor of amino-modified polystyrene is obtained, wherein the fluorescence sensor of amino-modified polystyrene includes a glass sheet with surface amination and a sensing layer, and the sensing layer is arranged On the surface of the surface aminated glass sheet, the sensing layer is an electrospinning film spun from amino-modified polystyrene and pyrene, and the structural formula of the amino-modified polystyrene is:

Wherein, m:n=8～12:1, the weight average molecular weight of amino-modified polystyrene is (4～5)×10 ⁴ g/mol, and the relative mass distribution index is 1.3～1.4.

The beneficial effects of the present invention are:

1. The sensor of the present invention is prepared by electrospinning. The sensing layer has the advantages of large specific surface area, high porosity, good gas permeability, and controllable morphology. These advantages are all conducive to the rapid contact between the object to be tested and the sensing material; at the same time, the sensing layer prepared by the present invention is amino-modified polystyrene, and the glass sheet carrier used is surface aminated, and a large amount of amino It will interact with nitroaromatic compounds through hydrogen bonds, so that nitroaromatic compounds can be effectively enriched on the sensor surface. This enrichment greatly improves the sensitivity of the sensor to trace amounts of nitroaromatic compounds.

2. The sensor of the present invention has better selectivity for DNT, TNT and PA, and its quenching efficiency for DNT, TNT and PA is 91%, 82% and 36% respectively, while for other organic or inorganic interfering substances such as 3,5-dinitroaniline, commercial fragrances, urea, ammonium nitrate and sodium nitrite, etc., the sensor of the present invention has almost no response.

3. The sensor of the present invention has good reusability.

4. The present invention can detect trace amounts of nitroaromatic compounds in the air. When placed in 10ppb TNT vapor for 150s, the quenching rate can reach 65.4%.

Description of drawings

The accompanying drawings that constitute a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation of the present application.

Fig. 1 is the step schematic diagram of the functionalization of glass sheet carrier;

Fig. 2 is the synthetic route diagram of amino-functionalized polystyrene;

Fig. 3 Contact angles of secondary water of aminated glass flakes after different treatments, G: blank glass flakes, G-OH: hydroxylated glass flakes, G-NH ₂ : aminated glass flakes are two the contact angle of secondary water;

Figure 4 is the XPS photoelectron spectrum of the aminated glass sheet carrier after different treatments, G: blank glass sheet, G-NH ₂ : surface aminated glass sheet;

Figure 5 is an infrared spectrum, (a) 4-vinylbenzylamine and styrene; (b) PS-NH ₂ and PS;

Figure 6 is a 1H NMR spectrum, (a) 4-vinylbenzylphthalamide (b), 4-vinylbenzylamine, (c) PS-NH ₂ ;

Figure 7 shows the thermal stability analysis of PS and PS- _NH2 , (a) TGA, (b) DTG

Fig. 8 is the electron microscope photograph of PS- _NH2 electrospinning nanofiber membrane, (a) SEM, (b) TEM;

Figure 9 is a comparison diagram of the quenching efficiency of TNT gas for sensors prepared by (PS-NH ₂ /pyrene) electrospinning films with different receiving times (λ _ex =333 nm);

Figure 10 shows the fluorescence stability of (PS-NH ₂ /pyrene)/G-NH ₂ sensor in air (λ _ex =333 nm);

Figure 11a is the fluorescence quenching spectrum of TNT (λ _ex =333 nm) by (PS-NH ₂ /pyrene)/G-NH ₂ sensor, and Figure 11b is (PS-NH ₂ /pyrene)/G-NH ₂ sensor against TNT Fluorescence image before quenching, Fig. 11c shows the fluorescence image after quenching TNT by (PS-NH ₂ /pyrene)/G-NH ₂ sensor, Fig. 11d shows (PS/pyrene)/G, (PS/pyrene)/ Comparison of TNT quenching efficiency of G-NH ₂ , (PS-NH ₂ /pyrene)/G and (PS-NH ₂ /pyrene)/G-NH ₂ sensors;

Figure 12 shows the fluorescence images of different sensors placed in saturated TNT vapor for 150 s, before and after quenching, where a is (PS/pyrene)/G sensor, b is (PS/pyrene)/G _- NH sensor, c is (PS-NH ₂ /pyrene)/G sensor, d is (PS-NH ₂ /pyrene)/G-NH ₂ sensor, (1) is before quenching, (2) is after quenching;

Figure 13 is a photo of the quenching performance of PS-NH ₂ /pyrene electrospun nanofiber film, where a is the quenching characteristic of the sensor on DNT, b is the quenching characteristic of the sensor on TNT, and c is the quenching characteristic of the sensor on PA Extinction is characterized, 1 and 3 are ultraviolet light (λ _ex =254nm), 2 and 4 are fluorescent lamps;

Figure 14 is a histogram of fluorescence quenching of (PS-NH ₂ /pyrene)/G-NH ₂ sensor for different analytes;

Figure 15 is a comparison diagram of the reuse of (PS-NH ₂ /pyrene)/G-NH ₂ sensor for saturated TNT detection.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

As described in the background art, the prior art has the disadvantage that the existing sensors are difficult to detect NACs in micro-trace gas phase. In order to solve the above technical problems, the present application proposes a method for detecting nitroaromatic explosives.

其中，m:n＝8～12:1，氨基改性聚苯乙烯的重均分子量为(4～5)×10⁴g/mol，相对质量分布指数为1.3～1.4。A typical embodiment of the present application provides an application of an amino-modified polystyrene fluorescence sensor in detecting nitroaromatic explosives, wherein the amino-modified polystyrene fluorescence sensor includes a surface aminated A glass sheet and a sensing layer, the sensing layer is placed on the surface of the aminated glass sheet, the sensing layer is an electrospinning film spun from amino-modified polystyrene and pyrene, and the amino-modified polystyrene The structural formula of styrene is

Wherein, m:n=8～12:1, the weight average molecular weight of amino-modified polystyrene is (4～5)×10 ⁴ g/mol, and the relative mass distribution index is 1.3～1.4.

其中，m:n＝8～12:1，氨基改性聚苯乙烯的重均分子量为(4～5)×10⁴g/mol，相对质量分布指数为1.3～1.4。Another embodiment of the present application provides a method for detecting nitroaromatic explosives. A fluorescent sensor of amino-modified polystyrene is used to place it at the position to be measured, and the amino-modified polystyrene is detected at regular intervals. The fluorescence intensity of the fluorescence sensor is obtained, and the quenching time of the amino-modified polystyrene fluorescence sensor is obtained, wherein the amino-modified polystyrene fluorescence sensor comprises a surface aminated glass sheet and a sensing layer, the sensing layer It is placed on the surface of the surface aminated glass sheet, the sensing layer is an electrospinning film spun by amino-modified polystyrene and pyrene, and the structural formula of the amino-modified polystyrene is:

Wherein, m:n=8～12:1, the weight average molecular weight of amino-modified polystyrene is (4～5)×10 ⁴ g/mol, and the relative mass distribution index is 1.3～1.4.

Preferably, the thickness of the sensing layer is 0.5-1.5 μm. Further preferably, the thickness of the sensing layer is 1.0 μm.

Preferably, the mass ratio of amino-modified polystyrene to pyrene is 2-10:1.

Preferably, for the preparation method of the amino-modified polystyrene fluorescence sensor, the amino-modified polystyrene and pyrene are mixed uniformly to prepare a spinning solution, and the spinning solution is electrospun on the surface of the surface aminated glass sheet. Electrospinning films were spun to obtain sensors.

Further preferably, adding amino-modified polystyrene and pyrene to the mixed solution of N,N-dimethylformamide and tetrahydrofuran and stirring at room temperature for 12±1h can move the spinning solution.

Further preferably, the conditions for electrospinning are that the spinning voltage is 20 kV, the injection speed of the syringe is 0.04 mm/min, the receiving distance is 18-22 cm, and the receiving time is 1-8 min. More preferably, the receiving time is 5min.

Further preferably, the preparation method of the amino-modified polystyrene is as follows: dissolving styrene, 4-vinylbenzylamine and azobisisobutyronitrile (AIBN) in a solvent, heating to 70±5° C. Polymerization reaction 20 ± 5h. More preferably, the purification step of amino-modified polystyrene is to dissolve the product after the polymerization reaction in dichloromethane, and then add ice methanol for precipitation. Ice methanol mentioned in this application means that methanol is placed in an environment below 0°C for 5 to 24 hours.

The 4-vinylbenzylamine used in this application can be purchased directly or synthesized by itself.

The present application preferably provides a method for synthesizing 4-vinylbenzylamine, wherein potassium phthalimide and 4-chloromethylstyrene are reacted to obtain 4-vinylbenzylphthalamide, and the 4-Vinylbenzyl phthalamide can be obtained by reacting 4-vinylbenzylphthalamide with hydrazine hydrate. The reaction process is as follows:

More preferably, the conditions for preparing 4-vinylbenzylphthalamide are heating to 55±1°C under nitrogen atmosphere for 15-16 hours.

More preferably, the reaction conditions of 4-vinylbenzylphthalamide and hydrazine hydrate are refluxing under nitrogen atmosphere for 5±0.5h.

The surface-aminated glass flakes used in the present application can be prepared by conventional glass flakes using known methods.

The present application preferably provides a method for preparing a surface aminated glass flake. The glass flake is put into a mixed solution of concentrated sulfuric acid and hydrogen peroxide and treated at 95-100° C. for a period of time to obtain a surface hydroxylated glass flake. The hydroxylated glass flakes are added to the solution of 3-aminopropyltriethoxysilane and heated under reflux for a period of time to obtain surface aminated glass flakes.

In order to enable those skilled in the art to understand the technical solutions of the present application more clearly, the technical solutions of the present application will be described in detail below with reference to specific embodiments.

Reagents:

3-Aminopropyltriethoxysilane (98%), supplied by Aladdin Reagent Company;

p-Chloromethylstyrene (98%), provided by Jiuding Chemical (Shanghai) Technology Co., Ltd.;

Phthalimide potassium salt (98%), provided by Sarn Chemical Technology (Shanghai) Co., Ltd.;

Hydrazine hydrate (80%), dichloromethane (AR), methanol (AR), sodium hydroxide, toluene (AR), hydrochloric acid (AR, 37%), azobisisobutyronitrile (AIBN, recrystallized from methanol) , chloroform (AR), acetone (AR), ethanol (AR), provided by Tianjin Fuyu Fine Chemical Co., Ltd.

Example 1

Preparation of Amino-functionalized Glass Flakes (G-NH ₂ )

The schematic diagram of the preparation steps of G- _NH2 is shown in Figure 1. The cover glass was cut into 10×20 mm, and calcined at a high temperature of 500° C. in a muffle furnace for the purpose of removing organic impurities on the surface to obtain a blank glass slide (G). Then, the calcined glass flakes were put into a flask containing a mixed solution of concentrated sulfuric acid and hydrogen peroxide (7:3), and the reaction was stirred at 98 °C for 1 h, and then the reaction was stopped. After cooling to about 25 °C, take out the Ultrasonic washing in deionized water for 10 min was repeated 3 times to ensure that the sulfuric acid and hydrogen peroxide were cleaned. The cleaned glass flakes were placed in a vacuum drying oven at 40° C. to remove water to obtain hydroxylated glass flakes (G-OH).

1mL of 3-aminopropyltriethoxysilane was dropped into a three-necked flask containing 10mL of toluene. After mixing evenly, the hydroxylated glass flakes were placed in the mixture and heated under reflux for 12h. After the reaction was stopped, wait for it to cool. After reaching about 25°C, the glass pieces were taken out and ultrasonically cleaned with chloroform, acetone, and absolute ethanol in sequence for 10 min each. Make sure to remove the unreacted siloxane adhering to the glass sheet, and finally place the cleaned glass sheet in a drying oven to dry for use to obtain the aminated glass sheet (G-NH ₂ ).

Example 2

Preparation of Amino-Modified Polystyrene (PS-NH ₂ )

The synthetic route of (PS-NH ₂ ) is shown in FIG. 2 . Potassium phthalimide (5.075 g, 27.4 mmol) and 4-chloromethylstyrene (4.06 g, 26.6 mmol) were dissolved in 30 mL of dry DMF. After stirring the reaction at 55 °C for 15 h under _N2 protection, the solvent in the reaction solution was removed, and the residue was dissolved in chloroform. The solution was washed with 0.2M aqueous sodium hydroxide, then several times with water, then dried over anhydrous _MgSO4 , filtered, and evaporated to give the crude product. The crude product was purified several times by recrystallization from methanol solution to give 4-vinylbenzylphthalamide. The product was white crystals (yield: 5.46 g, 78%). ¹ H NMR (CDCl ₃ , ppm): 7.9-7.7 (m, 4H), 7.4-7.2 (m, 4H), 6.7 (dd, 1H), 5.8-5.2 (d, 2H), 4.8 (s, 2H) .

4-Vinylbenzylphthalimide (5.1 g, 19.3 mmol) and 80% hydrazine hydrate (1.6 g, 32 mmol) were dissolved in 50 mL of ethanol. The reaction was stirred at reflux for 5 hours under nitrogen protection. The solvent was then removed under reduced pressure and the solid residue was extracted with 50 mL of chloroform and treated with 20% aqueous NaOH (50 mL). The aqueous phase was then separated, extracted with chloroform, the extracts were combined, dried over anhydrous _MgSO4 , filtered and evaporated. The obtained crude oil was purified by column chromatography (silica gel, methanol:ethyl acetate=1:3) to obtain a transparent oil (yield: 1.78 g, 69%). ¹ H NMR (CDCl ₃ , ppm): 7.4-7.2 (m, 4H), 6.7 (dd, 1H), 5.8-5.2 (d, 2H), 3.8 (s, 2H).

Under nitrogen protection, styrene (3.95 g, 38 mmol), 4-vinylbenzylamine (0.51 g, 3.8 mmol) and AIBN (0.045 g, 0.27 mmol) were dissolved in DMF in a constant temperature oil bath at 70 °C The reaction was stirred for 20 hours. The reaction mixture was then cooled to room temperature and the crude polymer product was dissolved in dichloromethane and purified by precipitation in cold methanol. The product was vacuum dried at 40° C. for 24 hours to obtain PS-NH ₂ (yield: 2.9 g, 65%). ¹ H NMR (CDCl ₃ , ppm): 6.3-7.2 (C ₆ H ₄ and C ₆ H ₅ ); 4.4 (C ₆ H ₄ CH ₂ NH ₂ ); 1.1-2.2 (polymer backbone). The weight-average molecular weight of amino-modified polystyrene was 4.580×10 ^-4 g/mol, and the relative mass distribution index was 1.38.

Example 3

Preparation of (PS-NH ₂ /pyrene)/G-NH ₂ Electrospinning Thin Film Sensor

0.4 g of pyrene and 1.6 g of amino-modified polystyrene (PS-NH ₂ ) were dissolved in 10 mL of a mixed solution of N,N-dimethylformamide and tetrahydrofuran (DMF:TNF=3:1), 25 Stir at °C for 12 h to obtain a pyrene-doped PS- _NH2 electrospinning solution. This spinning solution was placed in a syringe, the air bubbles in it were discharged, the needle was connected to the positive high-voltage line, the glass sheet was stuck on the receiving roller, the spinning voltage was 20KV, the receiving distance was 20cm, and the syringe was injected with a bolus of 0.04mm/min speed, 25°C, and received for a certain time to prepare electrospinning films. The prepared electrospinning film sensor was placed in a vacuum drying oven and dried at 60 °C for 12 h to remove residual organic solvents.

Example 4

Detection of gas phase TNT by sensors

First, place 100 g of the nitroaromatic compound to be tested on the bottom of the cuvette, and cover the object to be tested with a piece of filter paper of a suitable size to prevent the sensor from directly touching the object to be tested. Then, the cuvette was sealed and placed at room temperature for 12 hours to ensure that the nitroaromatic hydrocarbons in the cuvette reached the saturated vapor pressure. After that, the cuvette was placed in the F-4600 fluorescence spectrophotometer, and the prepared sensor was placed in the cuvette facing the excitation light source for testing, and data was collected every 30s.

Example 5

The PS-NH ₂ /pyrene mixed solution was used as the spinning solution, and the nanofiber film was prepared by electrospinning technology. The spinning time was 10 hours, and the spinning film was peeled off for use. Then take three identical petri dishes and fill them with sand. Take 0.5 g of DNT, TNT and PA respectively and bury them in soil at a depth of 1 cm. At 40°C for 24 hours, the purpose is to allow the nitroaromatic explosive gas diffusion to simulate the real environment. Afterwards, the PS- _NH2 fluorescent nanofiber membranes were covered on the soil surfaces of the three petri dishes and left at room temperature for 5 hours. Then, the petri dish was placed under UV light to observe the detection of nitroaromatic explosives by PS-NH ₂ /pyrene electrospinning membrane.

The characterization results of Examples 1 to 5 are as follows:

1. Characterization of amino-grafted glass flakes (G-NH ₂ )

It can be seen from Figure 3 that the contact angle of the glass sheet to water shows corresponding regular changes after different treatment processes. For the blank glass flake (G) with surface organic impurities removed after high temperature calcination, its water contact angle is 34.9±0.2°. When G was hydroxylated by the mixed solution of concentrated sulfuric acid and hydrogen peroxide, its water contact angle was 27.06±0.2°. The decrease in the contact angle may be due to the increase in the number of hydroxyl groups on the surface of the glass sheet, resulting in its enhanced hydrophilicity. The water contact angle of the amino-grafted glass flakes (G-NH ₂ ) was 77.51±0.2°. Compared with the first two glass flakes, the contact angle of the glass flakes is significantly larger. The main reason may be that the hydroxylated glass flakes (G-OH) are grafted with aminopropyltriethoxysilane to remove alcohol in toluene solution. The hydroxyl groups and the silane chains on the glass surface increase significantly, which greatly enhances the hydrophobicity of the glass sheet (G-NH ₂ ) surface and increases the contact angle significantly. The regular variation of the contact angle test indicates that the corresponding chemical reaction has indeed occurred on the surface of the glass sheet.

It can be seen from Figure 4 that, compared with the blank glass piece, the glass piece after amino modification has an obvious nitrogen peak (N1s) at 401ev. This further confirmed the occurrence of the grafting reaction on the surface of the glass flakes. Figures 3 and 4 are combined to illustrate the successful grafting of amino groups on the surface of the glass flakes.

Synthesis of PS-NH ₂ and its ¹ H NMR, FT-IR and Thermal Stability Analysis

Figure 5(a) is the infrared spectrum of PS-NH ₂ and PS. Compared with the infrared spectrum of PS, the stretching vibration absorption peaks of saturated hydrocarbons of 4-vinylbenzylamine were observed near 2854-2918 cm ^{- 1} in PS- _NH2 , and 4- The NH stretching vibration absorption peak in vinylbenzylamine and the CN stretching vibration absorption peak at 1241cm ^-1 are all evidences of the structure of 4-vinylbenzylamine. Figure 5(b) is the infrared contrast image of PS- _NH2 and PS. Compared with PS, the appearance of the strong absorption peak at ³⁴³⁵ cm in PS _- NH is mainly due to the stretching vibration of NH. The CN stretching vibration absorption peak at 1253 cm ^-1 proves the synthesis of PS- _NH2 .

Figure 6 shows the ¹ HNMR spectra of the products of each step in the preparation of PS-NH ₂ . The hydrogen chemical shifts of aromatic ring CH and double bond CH in 4-vinylbenzylphthalamide and 4-vinylbenzylamine are 7.4-7.2 ppm and 6.8-5.2 ppm, respectively. No aromatics were observed in phthalimide at 7.7 and 7.9 ppm in the 4-vinylbenzylamine spectrum compared to the ¹ HNMR spectrum of 4-vinylbenzylphthalamide H signal, but the chemical shift of the methylene hydrogen at the ortho position of the benzene ring was observed at 3.8 ppm. The hydrogen chemical shift of the methylene group was observed at 4.4 ppm in the ¹ H NMR spectrum of PS-NH ₂ . These results strongly demonstrate the structure of the products of each step.

Figure 7 shows the TGA and DTG plots of PS and PS-NH ₂ . The decomposition temperature (Ti) at 5% weight loss of PS in Figure 7(a) is ~315°C. While the decomposition temperature of PS- _NH2 at 5% weight loss increased to ~369 °C. The reason for the higher thermal decomposition temperature of PS- _NH2 is that _-NH2 in its molecule can enhance the structural stability through hydrogen bonding interaction. In addition, as shown in Fig. 7(b), the fastest decomposition temperature of PS- _NH2 is higher than that of PS, showing better thermal stability.

Morphology analysis of electrospun nanofibers

Figure 8 presents the micromorphology of the electrospun nanofiber films of PS- _NH2 . It can be seen from Fig. 8(a) that the PS- _NH2 electrostatic fibers exhibit a uniform and smooth morphology. Figure 8(b) is a projection image taken under an optical microscope. It can be seen from Figure 8(b) that the prepared electrospinning membrane as a whole has good porosity, which is beneficial to the detection of the object in the nanofiber membrane. diffusion.

Characterization of (PS-NH ₂ /pyrene)/G-NH ₂ sensor for TNT sensing performance

According to the different receiving time of the electrospun nanofibers, the influence of the detection film thickness on the detection results of the sensor is shown in Figure 9. Eight nanofiber thin film sensors with different receiving time (1min～8min) were prepared and quenched by saturated TNT vapor respectively. It can be seen from Figure 9 that within a certain detection time, it is not that the thicker the film, the better the detection effect, but as the thickness increases, the quenching of saturated TNT first increases and then weakens. When the receiving time is 5min, the film The sensor has the highest quenching efficiency for saturated TNT. Therefore, the receiving time of the tested nanofiber film was selected to be 5 min (its thickness was 1 μm).

As shown in Fig. 10, the fluorescence intensity of the (PS- _NH2 /pyrene)/G- _NH2 sensor was slightly reduced within 1200 s in the air, indicating that the (PS- _NH2 /pyrene)/G- _NH2 nanofiber film The fluorescence stability of the sensor in air is good, and the possibility of self-quenching is ruled out in the quenching study of p-nitroarene explosives.

–Lowry酸，可以通过碱性胺在甲基处被去质子化。TNT阴离子上的负电荷通过三个吸电子硝基的共振稳定作用分布在整个分子中，因此导致形成酸-碱配对相互作用。所以，这种含有大量氨基的荧光传感器对硝基芳烃有富集效果，有利于检测痕量的NACs。The fluorescence quenching spectrum of the sensor to saturated 2,4,6-trinitrotoluene vapor is shown in Fig. 11a. In TNT saturated steam, the sensor has better response to TNT. Figure 11b and Figure 11c are comparative images of the nanofiber sensor before and after quenching TNT under a fluorescence microscope. It can be clearly seen with the naked eye that the fluorescence intensity of the nanofiber in the sensor is significantly reduced after quenching. In this part of the characterization, four sensors were prepared as (PS/pyrene)/G, (PS/pyrene)/G- _NH2 , (PS- _NH2 /pyrene)/G and (PS- _NH2 /pyrene) )/G-NH ₂ . Four kinds of sensors were used for fluorescence sensing detection of saturated TNT vapor. Figure 11d shows four thin film sensors of (PS/pyrene)/G, (PS/pyrene)/G- _NH2 , (PS- _NH2 /pyrene)/G and (PS- _NH2 /pyrene)/G- _NH2 Fluorescence quenching efficiency comparison chart. It can be seen from Fig. 11d that at 150s, (PS/pyrene)/G, (PS/pyrene)/G- _NH2 , (PS- _NH2 /pyrene)/G and (PS- _NH2 /pyrene) The fluorescence quenching efficiencies of )/G-NH ₂ were 18.8%, 51.1%, 40.8% and 65.4%, respectively. By comparison, it can be seen that the quenching effect of (PS-NH ₂ /pyrene)/G-NH ₂ sensor is the best, because the fluorescent sensor contains a large number of amino groups, which can indeed enrich nitroarenes through hydrogen bonds , thereby increasing the quenching rate. Two types of strong interactions may occur between the electron-deficient aromatic ring of TNT and the electron-rich amino group: (i) Charge transfer from the amino group to the aromatic ring leads to the formation of Meisenheimer complexes between TNT and primary amine groups. (ii) As a generally accepted mechanism, TNT molecules are

– Lowry acid, which can be deprotonated at the methyl group by basic amines. The negative charge on the TNT anion is distributed throughout the molecule by resonance stabilization of the three electron-withdrawing nitro groups, thus leading to the formation of acid-base pairing interactions. Therefore, this fluorescent sensor containing a large number of amino groups has an enrichment effect on nitroaromatics, which is beneficial to detect trace amounts of NACs.

In order to observe the detection rate of saturated TNT gas by the prepared four kinds of thin film sensors more intuitively, the fluorescence microscope was used to observe (PS/pyrene)/G, (PS/pyrene)/G-NH ₂ , (PS-NH ₂ /pyrene) respectively. )/G and (PS-NH ₂ /pyrene)/G-NH ₂ sensors before and after vapor quenching of saturated TNT. First, the prepared four thin-film sensors were placed in a fluorescence microscope to observe the fluorescence images of the four sensors when they were not quenched, and then the four sensors were placed in saturated TNT vapor for 150 s, and then the four sensors that had been quenched were placed They were placed in a fluorescence microscope, and the fluorescence images after quenching were observed, as shown in Figure 12. Fig. 12a(1), Fig. 12b(1), Fig. 12c(1), Fig. 12d(1) represent (PS/pyrene)/G, (PS/pyrene)/G-NH ₂ , (PS-NH ₂ / Fluorescence images of the four sensors before quenching, Fig. 12a(2), Fig. 12b(2), Fig. 12c( ₂ ), Fig. 12d( ₂ ) ) represent (PS/pyrene)/G, (PS/pyrene)/G-NH ₂ , (PS-NH ₂ /pyrene)/G and (PS-NH ₂ /pyrene)/G-NH ₂ sensors, respectively Fluorescence image after extinction. It can be seen that the four sensors all emit strong bright blue fluorescence before quenching. After being placed in saturated TNT steam for 150s, the quenching effects are different. It can be clearly seen from the comparison that the best quenching effect is shown in Figure 12d (2), namely (PS-NH ₂ /pyrene)/G-NH ₂ sensors. The possible reason is that both the sensor carrier and the nanofibers contain a large number of amino groups, which have a strong enrichment effect on nitro compounds, which greatly improves the quenching efficiency of the sensor. From the fluorescence images in Fig. 12b(2) and Fig. 12c(2), it can be seen that the quenching effect of the (PS/pyrene)/G- _NH2 sensor is better than that of the (PS- _NH2 /pyrene)/G sensor, possibly The reason is that the amino group-modified glass sheet has a large number of amino groups on both sides, and the amino group content in the nanofibers is less than that on the glass sheet, so the quenching effect of the (PS-NH ₂ /pyrene)/G sensor is relatively poor. Compared with the quenching effect of the (PS/pyrene)/G sensor, the fluorescence quenching effect of the sensor modified with amino groups is better than that of the sensor without amino group. Therefore, the introduction of the electron-rich amino group can greatly improve the detection effect of the sensor for NACs.

To simulate the detection of nitroaromatic compounds by PS-NH ₂ /pyrene electrospinning nanofiber film in a practical environment, three identical petri dishes were prepared and filled with sand, and then DNT, TNT and PA 0.5g were taken and buried In soil, the depth is 1 cm. Afterwards, the three petri dishes were placed at 40 °C for 24 h, and then the pyrene-doped PS- _NH2 fluorescent nanofiber membranes were respectively covered on the soil surfaces of the three petri dishes and placed at room temperature for 5 h for nitroaromatics. detection. Columns a, b, and c in Figure 13 are for detecting DNT, TNT, and PA, respectively, Figure 13a(1), Figure 13b(1), Figure 13c(1), Figure 13a(3), Figure 13b(3), Figure 13c (3) are the contrast images of PS-NH ₂ /pyrene fluorescent nanofiber membrane before and after quenching under UV irradiation (λ _ex =254 nm), respectively, showing bright blue when not initially quenched. After 5 hours, the PS-NH ₂ /pyrene fluorescent nanofiber membrane was quenched, and the quenching point in the figure indicated the position of the buried nitroaromatic compound under the soil in the petri dish, compare Fig. 13a(3), Fig. 13b( 3), Figure 13c(3) shows that the quenching effect of PS-NH ₂ /pyrene nanofiber film on these three nitroarene compounds is: DNT>TNT>PA, and the quenching effect on DNT is the best as shown. This is because DNT has a higher saturated vapor pressure (1.1×10 ^-4 Torr ⁾ , which is 18 times that of TNT (5.8×10 ^-6 Torr). However, PA has a smaller saturated vapor pressure (5.8×10 ^{- 9} Torr), which results in an unsatisfactory detection effect. Comparing Fig. 13a(2), Fig. 13b(2), Fig. 13c(2) with Fig. 13a(4), Fig. 13b(4), Fig. 13c(4), it can be seen that PS-NH ₂ /pyrene nanometers under fluorescent lamp The fiber film is white, and there is no obvious difference between the three under fluorescent light.

Fluorescence quenching characterization of sensors for different analytes

Fluorescence quenching of the (PS- _NH2 /pyrene)/G- _NH2 sensor for some chemicals such as TNT, DNT, PA, 3,5-dinitroaniline, commercial fragrances, urea, ammonium nitrate and sodium nitrite Figure 14 shows the comparison chart of the off and off. As can be seen from Fig. 14, the (PS- _NH2 /pyrene)/G- _NH2 sensor exhibited fluorescence responsiveness to DNT, TNT and PA with corresponding quenching efficiencies of 91%, 82% and 36%, respectively. %. However, other organic or inorganic interfering substances such as 3,5-dinitroaniline, commercial fragrances, urea, ammonium nitrate and sodium nitrite, etc., the (PS- _NH2 /pyrene)/G- _NH2 sensor showed little response.

The sensors show different quenching efficiencies for different NACs, mainly due to the different saturated vapor pressures of the explosives. At room temperature, the vapor pressures of DNT, TNT and PA were 280 ppb, 10 ppb and 0.0077 ppb, respectively. The vapor pressure of DNT is much higher than that of TNT, so the quenching efficiency for DNT (91%) is much higher than that for TNT (82%). Although there are three strongly electron-withdrawing nitro groups on the benzene ring of TNT, the saturated vapor pressure of the analyte plays a major role in this process. Relatively low quenching efficiency (36%) was shown for PA due to its too low vapor pressure. Additionally, since 3,5-dinitroaniline and commercial fragrances are electron-rich aromatic compounds, they do not cause significant fluorescence quenching. Commonly used nitrogen fertilizers such as ammonium nitrate, urea, sodium nitrite, etc. cause only negligible quenching. Combining all the above results further proves that the (PS-NH ₂ /pyrene)/G-NH ₂ sensor has higher sensitivity and better selectivity for NACs in the gas phase.

(PS-NH ₂ /pyrene)/G-NH ₂ Sensor Recyclability Characterization

The test and research process for the reusable performance of the (PS-NH ₂ /pyrene)/G-NH ₂ sensor is as follows: first, 100 g of the nitroaromatic compound TNT to be tested is placed on the bottom of the cuvette, and a sheet of TNT is covered on it. A suitable size filter paper to avoid direct contact of the sensor with the object to be measured. Then, seal the cuvette and place it at room temperature for 12 hours for later use to ensure that the gas phase in the cuvette reaches the saturated vapor pressure of the object to be tested. In addition, the prepared (PS-NH ₂ /pyrene)/G-NH ₂ sensor was placed in a clean empty cuvette and placed in a fluorescence detection instrument, so that the sensor film was facing the excitation light source, and the sensor burst was measured. The original fluorescence intensity before extinction. Next, the sensor was placed in the previously prepared cuvette filled with saturated TNT vapor for 0.5 hours, and the fluorescence intensity of the sensor was detected at this time. The (PS- _NH2 /pyrene)/G- _NH2 sensor was then removed and treated with nitrogen flow for 0.5 h to remove TNT from the sensor. Place the processed sensor in a clean empty cuvette to re-detect the fluorescence intensity. Repeat this process 5 times, and the result is shown in Figure 15. After the first cycle of fluorescence quenching and recovery, the fluorescence intensity of the (PS-NH ₂ /pyrene)/G-NH ₂ sensor decreased by approximately 10%. During the following 4 cycles, the signal intensity of the sensor did not decrease significantly, which indicates that the sensor has good reusability.

Summarize

(PS/pyrene)/G, (PS/pyrene)/G-NH ₂ , (PS-NH ₂ /pyrene)/G and (PS-NH ₂ /pyrene)/G- The morphology of the NH ₂ sensing film and its quenching performance against saturated TNT vapor, it is found that the (PS-NH ₂ /pyrene)/G-NH ₂ sensor has the best quenching effect. In this fluorescence sensing system, a large number of electron-rich amino groups were introduced, because the amino groups can interact with electron-deficient nitroarenes (NACs) through hydrogen bonding, so that NACs can be efficiently enriched. The (PS-NH ₂ /pyrene)/G-NH ₂ fluorescence sensor achieves a quenching rate of 65.4% for TNT vapor (~10 ppb) at 150 s.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims (6)

1. A method for detecting nitro-aromatic explosives is characterized in that a fluorescence sensor based on amino-modified polystyrene is placed at a position to be detected, the fluorescence intensity of the fluorescence sensor based on amino-modified polystyrene is detected at intervals, and the quenching efficiency of the fluorescence sensor based on amino-modified polystyrene is obtained; the fluorescence sensor based on the amino modified polystyrene comprises a glass sheet with an aminated surface and a sensing layer, wherein the sensing layer is arranged on the surface of the aminated glass sheet, the sensing layer is an electrostatic spinning film prepared by blending the amino modified polystyrene and pyrene, and the structural formula of the amino modified polystyrene is shown in the specification

Wherein m: n is 8 to 12:1, and the amino-modified polystyrene has a weight average molecular weight of 4 to 5 x 10⁴ g/mol, the relative mass distribution index is 1.3-1.4; the thickness of the sensing layer is 1.0 mu m; the mass ratio of the amino modified polystyrene to the pyrene is 2-10: 1; the electrostatic spinning conditions are that the spinning voltage is 20kV, the injection speed of the injector is 0.04mm/min, the receiving distance is 18-22 cm, and the receiving time is 5 min.

2. The method of claim 1, wherein the fluorescence sensor based on amino-modified polystyrene is prepared by uniformly mixing amino-modified polystyrene and pyrene to prepare a spinning solution, and spinning the spinning solution into an electrospun film on the surface of the aminated glass sheet by an electrospinning method, thereby obtaining the sensor.

3. The method for detecting nitroaromatic explosives in accordance with claim 2, wherein the spinning solution is obtained by adding amino-modified polystyrene and pyrene to a mixed solution of N, N-dimethylformamide and tetrahydrofuran, and stirring at room temperature for 12 ± 1 h.

4. The method for detecting nitroaromatic explosives in accordance with claim 2, wherein the preparation method of the amino-modified polystyrene comprises the following steps: dissolving styrene, 4-vinylbenzylamine and azobisisobutyronitrile in a solvent, and heating to 70 +/-5 ℃ to perform polymerization reaction for 20 +/-5 hours.

5. The method for detecting nitroaromatic explosives in accordance with claim 2, wherein the synthesis method of 4-vinylbenzylamine comprises the following steps: the method comprises the following steps of reacting potassium phthalimide with 4-chloromethyl styrene to obtain 4-vinyl benzyl phthalic diamide, and reacting the 4-vinyl benzyl phthalic diamide with hydrazine hydrate to obtain 4-vinyl benzyl amine.

6. The method for detecting nitroaromatic explosives in accordance with claim 2, wherein the surface aminated glass sheet is prepared by: and (2) putting the glass sheet into a mixed solution of concentrated sulfuric acid and hydrogen peroxide, treating for a period of time at 95-100 ℃ to obtain a surface hydroxylated glass sheet, adding the surface hydroxylated glass sheet into a solution of 3-aminopropyltriethoxysilane, and heating and refluxing for a period of time to obtain the surface aminated glass sheet.

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