Method for detecting sarin simulant diethyl chlorophosphate by using europium-based metal organic framework nano material

Abstract

The invention relates to a method for detecting sarin simulant diethyl chlorophosphate by using a europium-based metal organic framework nano material, and nano particles are the europium-based metal organic framework material of double ligands (1, 3, 5-tri (4-carboxyl phenyl) benzene and o-phenylenediamine tripolymer) uniformly grown on the surface of nano cellulose. The europium-based metal organic framework material taking o-phenylenediamine tripolymer as the ligand can weaken red fluorescence due to the fact that the antenna effect is hindered. Amino groups in the ligand can be subjected to nucleophilic addition reaction with diethyl chlorophosphate, so that an addition ligand with unstable coordination is generated, the addition ligand is separated from a material framework, red fluorescence is recovered, rapid and high-sensitivity fluorescence enhancement detection on sarin toxic agent simulant diethyl chlorophosphate atmosphere is realized, the detection limit is 2.88 ppb, and the response time is about 1 s. Meanwhile, the film material overcomes the interference of acid, realizes the specific detection of diethyl chlorophosphate, and provides an extensive design thought for the detection of functional metal organic framework materials and nerve toxic agents.

Description

Technical Field

[0001] The present invention belongs to the fields of crystal material synthesis and nerve agent detection, and provides a method for detecting diethyl chlorophosphate, a sarin nerve agent mimic, using europium-based metal-organic framework nanomaterials. Background Art

[0002] Europium-based metal-organic framework materials are multifunctional composite materials in which trivalent europium ions are used as the center and coordinated with organic molecular ligands through coordination to form crystals. The europium-based metal-organic framework materials with high coordination (≥8) and ligand-sensitizable properties have characteristic red fluorescence emission and extremely excellent fluorescence properties.

[0003] Carboxylated nanocellulose is a nanosized linear polymer in which part of the surface is carboxylated and is composed of glucose units connected by β-1,4-glycosidic bonds. It often plays roles such as regulating the morphology of materials and enhancing the properties of materials in material synthesis, and is a high-quality crystal regulating material that is natural, green, and biodegradable.

[0004] Nerve agents are a class of extremely toxic organophosphorus compounds. The phosphorus element in the phosphoryl group in their common structure has strong electrophilicity, and will nucleophilically attack acetylcholinesterase that regulates biological neurotransmitters, rendering it inactivated, thereby leading to disorders of the central nervous system, paralysis of the human body, difficulty in breathing, etc., and can cause death within a few minutes. Therefore, the development and reserve of rapid on-site highly sensitive nerve agent gas detection materials are of great significance.

[0005] Currently, existing detection methods for nerve agents include mass spectrometry, ion mobility spectrometry, surface-enhanced Raman scattering, flame photometry, etc. It is worth affirming that some of them have good selectivity and application value, but the equipment cost and cumbersome pretreatment are often not suitable for on-site immediate detection. In contrast, due to the unique sensitivity, designability, and visually observable sensing signals of fluorescence sensing, it has been widely applied to the field of nerve agent detection. The toxicity of nerve agents is too high for researchers to directly study, and their mimics are often used to test the detection performance. Taking the highly volatile sarin agent as an example, only 7 ppb can harm human health, and the lethal dose is only 75 mg·min / m 3, therefore, in the detection research of sarin nerve agents, diethyl chlorophosphate (DCP) with phosphoryl groups and halogen chlorine, which have the same common groups, is often used as its mimic. Among the currently common fluorescence detection materials, the detection rate of nitrogen-containing small molecule probes is the fastest and most sensitive. To further improve the fluorescence stability, the nitrogen-containing probe molecules are combined with metal centers in the form of ligands to prepare metal-organic framework materials (MOFs) for the rapid and sensitive detection of DCP, a mimic of sarin nerve agents. However, these materials often cannot distinguish between sarin nerve agents and common acid atmospheres. Therefore, it is important to develop a field detection material for sarin nerve agents with good fluorescence stability, high detection sensitivity, and anti-acid selectivity, and to exist in the form of popular products such as films or labels as a technical reserve in the field of public safety. Summary of the Invention

[0006] The object of the present invention is to provide a method for detecting diethyl chlorophosphate, a mimic of sarin, using europium-based metal-organic framework nanomaterials. This material can achieve highly sensitive and specific fluorescence detection of diethyl chlorophosphate gas, a mimic of sarin. The principle lies in the one-step synthesis of aromatic amine-functionalized europium-based metal-organic framework materials: First, carboxylated nanocellulose is used to fix trivalent europium ions on the fiber surface through coordination during the synthesis of europium-based metal-organic frameworks. Using the principle of heterogeneous nucleation, a large number of crystal nuclei are rapidly generated during the material synthesis process, thus reducing the europium-based metal-organic framework material to nanoscale. Also, the nanozyme response is used to oxidize and polymerize o-phenylenediamine into o-phenylenediamine trimer and coordinate with the unsaturated coordinated metal centers, finally forming aromatic amine-functionalized europium-based metal-organic framework nanoparticles. The detection principle is that after the material is functionalized, the antenna effect is blocked, and the red color of the europium-based metal-organic framework itself should be significantly weakened. Using the amino group in the ligand as the recognition site, after reacting with diethyl chlorophosphate gas, a complex ligand is formed. This complex has an unstable coordination structure and spontaneously dissociates from the metal-organic framework structure, thus restoring the blocked antenna effect and realizing fluorescence enhancement to detect diethyl chlorophosphate. Using the self-assembly principle, the material is vacuum-dried into a fluorescence sensing film. Under the excitation wavelength of 365 nm, the fluorescence of the film changes from light pink to positive red during the detection of diethyl chlorophosphate. By regulating the atmospheres of diethyl chlorophosphate with different volume concentrations and other interfering substances, the detection performance of the film is further evaluated. It is found that its detection limit is 2.88 ppb, the response time is about 1 s, and it can distinguish 14 interfering substances such as common organic solvents, acids, and diethyl chlorophosphate structure analogs, with high specificity, especially excluding the problem of common acid interference in the detection field of diethyl chlorophosphate (DCP).

[0007] A method for detecting diethyl chlorophosphate, a sarin mimic, using an europium-based metal-organic framework nanomaterial according to the present invention. The nanoparticles are europium-based metal-organic framework materials with 1,3,5-tris(4-carboxyphenyl)benzene and o-phenylenediamine trimer uniformly grown on the surface of nanocellulose. The specific operation is carried out according to the following steps:

[0008] Preparation of europium-based metal-organic framework particles:

[0009] a. Take carboxylated nanocellulose with a mass percentage of 1.17% and add it to 5 mL of pure water, stir well to disperse, and then add 5 mL of N,N-dimethylformamide solution and continue to stir evenly to obtain a carboxylated nanocellulose dispersion;

[0010] b. Dissolve europium nitrate hexahydrate solid in 5 mL of pure water, add the carboxylated nanocellulose dispersion obtained in step a, and stir for 2 - 4 h to obtain a mixture solution;

[0011] c. Dissolve 1,3,5-tris(4-carboxyphenyl)benzene solid and o-phenylenediamine solid in 5 mL of N,N-dimethylformamide solution to obtain a ligand solution;

[0012] d. Slowly drop the ligand solution obtained in step c into the mixture solution obtained in step b, stir well for 1 h until the mixture solution is homogeneous without stratification and the color is white-gray. Put the solution into the inner liner of the reaction kettle, at a temperature of 120 °C for 4 h, cool and let it stand. Centrifuge and wash repeatedly 3 times with N,N-dimethylformamide solution and pure water to obtain an europium-based metal-organic framework nanoparticle material in the form of a pale white-yellow gel;

[0013] Preparation of europium-based metal-organic framework nanoparticle fluorescence sensing film:

[0014] e. Add the europium-based metal-organic framework nanoparticle material obtained in step d to 15 mL of methanol, stir and sonicate until homogeneous, and perform vacuum filtration using a polyvinylidene fluoride membrane with a diameter of 50 mm and a pore size of 2 μm;

[0015] f. Fix the pre-product obtained by filtration in step e with neutral filter paper and a hard glass plate, at a temperature of 30 °C, vacuum dry for 12 h, and demold to obtain an europium-based metal-organic framework nanoparticle fluorescence sensing film, which is stored in the dark;

[0016] Or add the europium-based metal-organic framework nanoparticle material obtained in step d to 15 mL of methanol, stir and sonicate until homogeneous, and perform vacuum filtration using a polyvinylidene fluoride membrane with a diameter of 50 mm and a pore size of 0.45 μm;

[0017] Demold the pre-product obtained by filtration using a vacuum high-pressure device, at a temperature of 35 °C, 70 mbar for 5 min, to obtain an europium-based metal-organic framework nanoparticle fluorescence sensing film, which is stored in the dark;

[0018] Detection of diethyl chlorophosphate, a sarin simulant, by nanoparticle thin films:

[0019] g. Cut the thin film obtained in step f into pieces of size 0.5×0.5 cm, place them in a sealed quartz tube, and introduce atmospheres of diethyl chlorophosphate with different volume concentrations of 20 ppm, 15 ppm, 10 ppm, 5 ppm, 1 ppm, 0.75 ppm, 0.50 ppm, and 0.25 ppm respectively. Use a fluorescence spectrometer to perform fluorescence emission spectroscopy on the detected thin film, measure the fluorescence emission spectrum of the thin film under 380 nm laser emission, then take the fluorescence emission intensity at 617 nm as the ordinate and the volume concentration of diethyl chlorophosphate as the abscissa to obtain a fitting curve, and determine the fluorescence detection limit of the thin film material for detecting diethyl chlorophosphate atmosphere;

[0020] Or after cutting the thin film in step g, place it in a sealed space to contact with the atmosphere of diethyl chlorophosphate, a nerve agent simulant. Under the irradiation of a 365 nm ultraviolet lamp, the fluorescence of the red dots on the surface of the thin film is enhanced;

[0021] Or mix carboxyl nanocellulose and a europium-based metal-organic framework material with a double ligand in a mass ratio of 1:1 to form an off-white colloidal fluorescent ink, and apply the ink on the surface of non-woven fabric by screen printing and direct writing methods to obtain a fluorescent label for detecting diethyl chlorophosphate atmosphere; then cut the fluorescent label and place it in a sealed space to contact with the atmosphere of diethyl chlorophosphate, a nerve agent simulant. Under the irradiation of a 365 nm ultraviolet lamp, the fluorescence of the label changes from light yellow to red.

[0022] A method for detecting diethyl chlorophosphate, a sarin simulant, by a europium-based metal-organic framework nanomaterial according to the present invention. Through the nucleophilic addition reaction of tri-o-phenylenediamine ligand with diethyl chlorophosphate, the functionalized structure of the unstable ligand complex detaches from the europium-based metal-organic framework material, restoring the antenna effect originally hindered by the tri-o-phenylenediamine ligand, and realizing highly specific and sensitive on-site detection of the atmosphere of diethyl chlorophosphate, a nerve agent simulant. It provides a relatively solid research foundation for the morphology control and functional synthesis of metal-organic framework materials and the field of nerve agent detection.

[0023] Compared with the existing detection technologies, the present invention has the following advantages:

[0024] A method for detecting diethyl chlorophosphate, a sarin mimic, using europium-based metal-organic framework nanomaterials according to the present invention realizes the fluorescence turn-on detection of diethyl chlorophosphate in the atmosphere by regulating the surface morphology and antenna effect of the europium-based metal-organic framework material; in addition, this material has excellent selectivity, especially for the interference of common acid gases (hydrofluoric acid, hydrochloric acid, acetic acid, phosphoric acid), realizing the rapid response and on-site visual recognition of diethyl chlorophosphate (DCP) gas, providing an implementable strategy for the application of metal-organic framework functionalized materials, providing a theoretical basis and technical practice for the on-site detection of diethyl chlorophosphate, a nerve agent mimic, and providing a good basic research for the gas monitoring of nerve agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1H NMR spectrum of the functional ligand molecule of the europium-based metal-organic framework o-phenylenediamine trimer in Example 1 of the present invention;

[0026] Figure 2 Mass spectrum of the functional ligand molecule of the present invention, where the abscissa is the mass-to-charge ratio and the ordinate is the percentage of the mass-to-charge ratio;

[0027] Figure 3 Transmission electron microscope and elemental distribution of the europium-based metal-organic framework nanoparticle material in Example 1 of the present invention

[0028] Figure 4 Scanning electron microscope image of the europium-based metal-organic framework nanoparticle material in Example 1 of the present invention;

[0029] Figure 5 Physical picture of the thin film in Example 1 of the present invention;

[0030] Figure 6 Detection performance of the fluorescence sensing thin film of the present invention, where (a) change in the fluorescence intensity (617 nm) of the thin film after contacting with diethyl chlorophosphate gas at different volume concentrations and (b) corresponding physical picture (c) linear fitting of the fluorescence intensity (d) time response and physical picture, and R0 in ((R - R0) / R0) is the average value of the red values of the red highlights on the surface of the fluorescence thin film when it is not in contact with diethyl chlorophosphate (DCP);

[0031] Figure 7 Selectivity of the fluorescence thin film to diethyl chlorophosphate (DCP) atmosphere and its interferents and bar chart for extracting the red values of the surface particles in Example 3 of the present invention, where R0 in ((R - R0) / R0) is the average value of the red values of the red highlights on the surface of the fluorescence thin film when it is not in contact with diethyl chlorophosphate (DCP);

[0032] Figure 8For the (a) rheological properties of the fluorescent sensing ink and the contact angle, and (b) fluorescence changes of the cloth-based sensing label before and after detecting DCP atmosphere in Example 4 of the present invention. Detailed implementation manners

[0033] The present invention will be further described in detail below through specific embodiments:

[0034] Example 1

[0035] Preparation of europium-based metal-organic framework nanoparticles:

[0036] a. Take 1.2 g of carboxylated nanocellulose with a mass percentage of 1.17%, add 5 mL of pure water and stir well to disperse, then add 5 mL of N,N-dimethylformamide solution and continue to stir evenly to obtain a carboxylated nanocellulose dispersion;

[0037] b. Take 0.025 mol of europium nitrate hexahydrate solid and dissolve it in 5 mL of pure water, add it to the carboxylated nanocellulose dispersion, and stir for 2 - 4 h to obtain a mixture solution;

[0038] c. Take 0.025 mol of 1,3,5-tris(4-carboxyphenyl)benzene solid and 0.15 mol of o-phenylenediamine solid and dissolve them in 5 mL of N,N-dimethylformamide solution to obtain a ligand solution;

[0039] d. Slowly drop the ligand solution in step c into the mixture solution obtained in step b, and stir well for 1 h until the inside of the mixture solution is uniform and without stratification, and the color is white-gray. Put the solution into the inner liner of the reaction kettle, at a temperature of 120 °C for 4 h. After cooling and standing, use N,N-dimethylformamide solution and pure water to centrifuge and wash 3 times repeatedly to obtain pale yellowish-white jelly-like europium-based metal-organic framework nanoparticles;

[0040] Preparation of europium-based metal-organic framework nanoparticle fluorescent sensing film:

[0041] e. Add 15 mL of methanol to the europium-based metal-organic framework nanoparticle material obtained in step d, stir and ultrasonicate until uniform, and perform vacuum filtration using a polyvinylidene fluoride membrane with a diameter of 50 mm and a pore size of 2 μm;

[0042] f. Fix the pre-filtered product in e with neutral filter paper and a hard glass plate, at a temperature of 30 °C, vacuum dry for 12 h, and demold to obtain a europium-based metal-organic framework nanoparticle fluorescent sensing film, and store it in the dark;

[0043] Or add 15 mL of methanol to the europium-based metal-organic framework nanoparticle material obtained in step d, stir and ultrasonicate until uniform, and perform vacuum filtration using a polyvinylidene fluoride membrane with a diameter of 50 mm and a pore size of 0.45 μm;

[0044] The pre-product obtained by suction filtration was demolded using a vacuum high-pressure device at a temperature of 35°C, 70 mbar for 5 minutes to obtain a europium-based metal-organic framework nanoparticle fluorescent sensing film, which was stored in the dark.

[0045] Example 2

[0046] Detection of diethyl chlorophosphate, a sarin simulant:

[0047] Preparation of atmospheres with different volume concentrations of diethyl chlorophosphate and common interfering substances

[0048] The standard 95% purity diethyl chlorophosphate was successively diluted to 15.15%, 11.36%, 7.57%, 3.78%, 0.75%, 0.57%, 0.38%, 0.19%, 0.00% using methanol solution. 10 mL of each of the above solutions was taken and placed in a 500 mL glass bottle, which was sealed with a rubber stopper.

[0049] The sealed glass bottles in step a were placed in an oven at a temperature of 40°C for 12 hours to obtain diethyl chlorophosphate with volume concentrations of 20 ppm, 15 ppm, 10 ppm, 5 ppm, 1 ppm, 0.75 ppm, 0.50 ppm, 0.25 ppm, 0.00 ppm.

[0050] The film obtained in step f of Example 1 was cut into a size of 0.5×0.5 cm and placed in a sealed quartz tube. Atmospheres of diethyl chlorophosphate with volume concentrations of 20 ppm, 15 ppm, 10 ppm, 5 ppm, 1 ppm, 0.75 ppm, 0.50 ppm, 0.25 ppm were respectively introduced. The fluorescence emission spectrum of the film after detection was measured using a fluorescence spectrometer. The fluorescence emission spectrum of the film under 380 nm laser emission was determined. Then, with the fluorescence emission intensity at 617 nm as the ordinate and the volume concentration of diethyl chlorophosphate as the abscissa, a fitting curve was obtained to determine the fluorescence detection limit of the film material for detecting diethyl chlorophosphate atmosphere, which was 2.88 ppb.

[0051] Using an industrial camera and an external ultraviolet device, the film was exposed to 365 nm ultraviolet light irradiation. The fluorescence changes of the film material in contact with diethyl chlorophosphate (DCP) atmosphere were collected by the industrial camera. Using image processing software, the red values of the red bright spots on the material surface were extracted frame by frame, and an image of the relationship between the fluorescence red value change of the film and time was established, and the response time was obtained to be about 1 s.

[0052] Example 3

[0053] Detection of gases by the fluorescent film material:

[0054] Cut the thin film obtained in step f of Example 1 into a thin film of 0.5 cm × 0.5 cm, and seal both ends of it with rubber stoppers into a non-fluorescent transparent quartz tube;

[0055] Fix a needle A with a scale at the zero scale line at one end, use another identical needle B to draw 5 mL of unknown gas to be measured, draw the needle A to 5 mL and wait for the scale of needle B to be zero, then quickly pull out needle A;

[0056] After waiting for 10 s, irradiate the thin film in the quartz tube with an ultraviolet lamp. If obvious red bright spots appear on the surface of the thin film, the unknown gas is diethyl chlorophosphate (DCP) gas; otherwise, it is other gases.

[0057] Example 4

[0058] Stir and mix evenly the europium-based metal-organic framework nanoparticles obtained in step d of Example 1 and carboxyl nanocellulose with a mass fraction of 1.17% at a mass ratio of 1:1, and keep it in a slow-flowing semi-solid state, then europium-based metal-organic framework nanoparticle ink is obtained. Use the fluorescent ink on the non-woven fabric by screen printing or direct writing method, and put it into a constant temperature air-circulating oven at a temperature of 50 °C for 12 h to obtain a fluorescent sensing label, and store it in the dark;

[0059] Seal the fluorescent sensing label into a non-fluorescent transparent quartz tube; fix a needle A with a scale at the zero scale line at one end, use another identical needle B to draw 5 mL of unknown gas to be measured, draw the needle A to 5 mL and wait for the scale of needle B to be zero, then quickly pull out needle A; after the obtained fluorescent label is in contact with diethyl chlorophosphate (DCP) atmosphere in the device for 10 s, take it out, and use an external ultraviolet device and a digital camera to record the fluorescence change of the label.

Claims

1. A method for detecting diethyl chlorophosphate, a sarin simulant, using europium-based metal-organic framework nanomaterials, characterized in that, The nanoparticles are europium-based metal-organic framework materials of 1,3,5-tris(4-carboxyphenyl)benzene and o-phenylenediamine trimer uniformly grown on the surface of nanocellulose. The specific operation is carried out according to the following steps: Preparation of europium-based metal-organic framework particles: a. Add carboxylated nanocellulose with a mass percentage of 1.17% to 5 mL of pure water and stir well to disperse, then add 5 mL of N,N-dimethylformamide solution and continue to stir evenly to obtain a carboxylated nanocellulose dispersion; b. Dissolve europium nitrate hexahydrate solid in 5 mL of pure water, add the carboxylated nanocellulose dispersion obtained in step a, and stir for 2 - 4 h to obtain a mixture solution; c. Dissolve 1,3,5-tris(4-carboxyphenyl)benzene solid and o-phenylenediamine solid in 5 mL of N,N-dimethylformamide solution to obtain a ligand solution; d. Slowly drop the ligand solution obtained in step c into the mixture solution obtained in step b, stir well for 1 h until the mixture solution is homogeneous and without stratification, and the color is white-gray. Put the solution into the inner liner of the reaction kettle, at a temperature of 120 °C for 4 h, cool and let it stand. Centrifuge and wash repeatedly with N,N-dimethylformamide and pure water for 3 times to obtain a pale white-yellow jelly-like europium-based metal-organic framework nanoparticle material; Preparation of europium-based metal-organic framework nanoparticle fluorescence sensing film: e. Add the europium-based metal-organic framework nanoparticle material obtained in step d to 15 mL of methanol, stir and ultrasonicate until homogeneous, and perform vacuum filtration using a polyvinylidene fluoride membrane with a size of 50 mm and a pore size of 2 μm; f. Fix the pre-product obtained by vacuum filtration in step e with a neutral filter paper and a hard glass plate, at a temperature of 30 °C, vacuum dry for 12 h, and demold to obtain a europium-based metal-organic framework nanoparticle fluorescence sensing film, and store it in the dark; Or add the europium-based metal-organic framework nanoparticle material obtained in step d to 15 mL of methanol, stir and ultrasonicate until homogeneous, and perform vacuum filtration using a polyvinylidene fluoride membrane with a size of 50 mm and a pore size of 0.45 μm; Demold the pre-product obtained by vacuum filtration using a vacuum high-pressure device, at a temperature of 35 °C, 70 mbar for 5 min to obtain a europium-based metal-organic framework nanoparticle fluorescence sensing film, and store it in the dark; Detection of diethyl chlorophosphate, a sarin simulant: g. Cut the film obtained in step f into a size of 0.5×0.5 cm, put it into a sealed quartz tube, and introduce atmospheres of diethyl chlorophosphate with different volume concentrations of 20 ppm, 15 ppm, 10 ppm, 5 ppm, 1 ppm, 0.75 ppm, 0.50 ppm, and 0.25 ppm respectively. Use a fluorescence spectrometer to perform a fluorescence emission spectrum on the detected film, measure the fluorescence emission spectrum of the film under 380 nm laser emission, then use the fluorescence emission intensity at 617 nm as the ordinate and the volume concentration of diethyl chlorophosphate as the abscissa to obtain a fitting curve, and determine the fluorescence detection limit of the film material for detecting diethyl chlorophosphate atmosphere; Alternatively, after cutting the thin film in step g, it is placed in a sealed space to contact with the atmosphere of diethyl chlorophosphate, a nerve agent mimic. Under the irradiation of a 365 nm ultraviolet lamp, the fluorescence of the red bright spots on the surface of the thin film is enhanced; Alternatively, carboxylated nanocellulose and an europium-based metal-organic framework material with double ligands are mixed in a mass ratio of 1:1 to form a off-white colloidal fluorescent ink. The ink is applied to the surface of the non-woven fabric by screen printing and direct writing to obtain a fluorescent label for detecting the atmosphere of diethyl chlorophosphate. After cutting the fluorescent label, it is placed in a sealed space and contacted with the atmosphere of diethyl chlorophosphate, a nerve agent mimic. Under the irradiation of a 365 nm ultraviolet lamp, the fluorescence of the label changes from light yellow to red.

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