Covalent organic polymer fluorescent probe and method for detecting-OH-containing nitro explosives

Abstract

A preparation method of the covalent organic polymer fluorescent probe comprises the following steps: adding 2, 7-dibromopyrene and 1, 2, 3, 4, 5, 6-hexa (4-bromophenyl) benzene into an organic solvent for dissolving, adding a Ni (0) catalyst, and heating overnight for reaction. And after the reaction is finished, cooling to room temperature, adding an HCl aqueous solution, filtering the generated precipitate, and washing with an organic solvent to finally obtain the covalent organic polymer fluorescent probe. The fluorescent probe is synthesized through a nickel-catalyzed Yamamoto reaction, has an obvious quenching effect on-OH-containing nitro explosives, can observe obvious color change through naked eyes, and is high in sensitivity and low in detection limit; the method has no obvious response to-OH-free nitro explosives. Therefore, the fluorescent probe can be used as a specific fluorescent probe for high-selectivity detection of-OH nitro-containing explosives.

Description

Technical Field

[0001] The invention relates to the technical field of fluorescent probes, and in particular to a covalent organic polymer fluorescent probe and a method for detecting -OH-containing nitro explosives by using the probe. Background Art

[0002] As a powerful explosive, nitro explosives are widely used in military and civilian fields. However, it causes soil and water pollution, affects the survival of animals and plants, and seriously threatens the living environment and human health, and even national security. Therefore, it is particularly important to quickly develop sensitive nitro explosive detection technology.

[0003] Many detection methods have been reported, such as surface-enhanced Raman spectroscopy, mass spectrometry, and X-ray diffraction. However, these methods have certain limitations, such as the complexity and high cost of the required equipment, as well as insufficient sensitivity and accuracy. In addition, detecting low-concentration nitro explosives and distinguishing their different types remain major technical barriers and challenges.

[0004] Fluorescence sensing is a very effective method for detecting nitro explosives. It uses the interaction between specific fluorescent materials and nitro explosives for identification and measurement. It has the advantages of high sensitivity, rapid response and simple operation. Although fluorescence sensing technology has made some progress in the field of nitro explosive detection, most current research still focuses on the detection of a single explosive. In practical applications, due to the wide variety of nitro explosives and the fact that different explosives may have similar chemical structures and physical properties, the development of a fluorescent probe that can specifically identify a certain category of nitro explosives is of great significance for improving the accuracy and efficiency of detection. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of low accuracy and efficiency in the detection of nitro explosives in the prior art, and to provide a covalent organic polymer fluorescent probe and a method for detecting nitro explosives containing -OH groups.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: a method for preparing a covalent organic polymer fluorescent probe comprises the following steps:

[0007] S1. Dissolve bis-(1,5-cyclooctadiene) nickel ([Ni(cod)2]) and 2,2'-bipyridine in an organic solvent in a glove box, add 1,5-cyclooctadiene (cod) after heating and stirring to dissolve, and prepare a mixed solution;

[0008] S2, add 2,7-dibromopyrene and 1,2,3,4,5,6-hexa(4-bromophenyl)benzene to the mixed solution of S1 and dissolve them, then add Ni(0) catalyst, react at 60-120° C. for 10-24 hours, cool to room temperature after the reaction, and move the reactants out of the glove box;

[0009] S3. Add HCl aqueous solution to the reactants removed from the glove box in S2, continue stirring for 3 to 6 hours, filter the precipitate, wash it with chloroform, tetrahydrofuran, methanol, and deionized water in sequence, and then dry it in a vacuum drying oven at 120°C for 12 to 20 hours to obtain an apricot powder covalent organic polymer fluorescent probe.

[0010] Preferably, the molar ratio of bis-(1,5-cyclooctadiene)nickel ([Ni(cod)2]) to 2,2'-bipyridine in S1 is 1:1 to 3:1.

[0011] Preferably, the molar ratio of the two monomers 2,7-dibromopyrene to 1,2,3,4,5,6-hexa(4-bromophenyl)benzene in S2 is 1:1 to 4:1.

[0012] Preferably, the concentration of the HCl aqueous solution in S3 is 1 to 5 mol / L, and the molar amount is 2 to 3 times the molar amount of the Ni(0) catalyst.

[0013] More preferably, the organic solvent is N,N-dimethylformamide.

[0014] The present invention also provides a covalent organic polymer fluorescent probe prepared by the above preparation method.

[0015] The present invention also provides a method for detecting -OH-containing nitro explosives, using the above-mentioned covalent organic polymer fluorescent probe, dissolving the covalent organic polymer fluorescent probe in a DMF solution, adding a sample to be tested to the solution; measuring the change in fluorescence intensity; and judging the fluorescence sensing performance of the fluorescent probe to the -OH-containing nitro explosives based on the change in fluorescence intensity.

[0016] Preferably, the sample to be tested is one of soil, water or air.

[0017] The beneficial effects of the present invention are:

[0018] 1. The covalent organic polymer fluorescent probe in the present invention adopts the Yamamoto reaction, and the preparation process is simple and easy to operate, which is convenient for industrial large-scale production.

[0019] 2. The present invention utilizes a covalent organic polymer fluorescent probe to detect the sample to be tested. The probe has an obvious quenching effect only on nitro explosives containing -OH, and has no response to other nitro explosives not containing -OH, and has high selectivity; it can respond quickly, has high sensitivity, and has a low detection limit. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The invention discloses an infrared spectrum of a covalent organic polymer fluorescent probe synthesized by the invention for detecting nitro explosives containing -OH groups.

[0021] Figure 2 This is a SEM image of a covalent organic polymer fluorescent probe for detecting nitro explosives containing -OH groups.

[0022] Figure 3 This is a thermogravimetric analysis under N2 conditions.

[0023] Figure 4 It is a covalent organic polymer fluorescent probe for detecting -OH-containing nitro explosives. The room temperature photoluminescence (PL) spectrum under the excitation of λex=λex-max has a maximum emission peak of 426.8nm, showing a double emission peak.

[0024] Figure 5 It is the fluorescence intensity after adding different nitro explosives into the DMF solution of COP.

[0025] Figure 6 This is a titration experiment result diagram of a covalent organic polymer fluorescent probe for detecting -OH-containing nitro explosives. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0027] Example 1 Preparation of covalent organic polymer fluorescent probe for detecting -OH-containing nitro explosives

[0028] In a glove box, weigh 0.56g of bis-(1,5-cyclooctadiene) nickel ([Ni(cod)2]) and 0.32g of 2,2'-bipyridine and put them into a 150ml pressure bottle; add 40mL of DMF, dissolve it, and use a pipette to drop 0.25mL of 1,5-cyclooctadiene (cod) into the above solution, stir at 40°C for half an hour to completely dissolve the mixture, and obtain a dark purple solution. Add 0.324g of 2,7-dibromopyrene and 0.302g of 1,2,3,4,5,6-hexa(4-bromophenyl)benzene to the above solution, continue stirring until dissolved, start heating, the reaction temperature is 90°C, and react in anhydrous and oxygen-free environment for 10h. After the reaction is completed, stop heating and cool naturally to room temperature.

[0029] Add 20 mL of 3 mol / L HCl aqueous solution and continue stirring for 3 hours to obtain a suspension. After standing, the solution is separated into layers. The product is filtered and washed with chloroform, tetrahydrofuran, methanol, and deionized water (5×5 ml each) to obtain a solid sample. The solid sample is vacuum dried at 120°C for 12 hours to obtain the covalent organic polymer fluorescent probe of the present invention. The FT-IR infrared spectrum at 500 cm -1 The changes in the C-Br bonds on the left and right prove that the synthesis of the covalent organic polymer fluorescent probe (COP) was successful.

[0030] Example 2 Performance Detection of Covalent Organic Polymer Fluorescent Probe

[0031] 1. The performance of the covalent organic polymer fluorescent probe prepared in Example 1 was tested. The infrared spectrum, SEM image and thermogravimetric analysis results are shown in the attached table. Figure 1-3 shown.

[0032] in Figure 1 This is the infrared spectrum of the covalent organic polymer fluorescent probe synthesized by the present invention for detecting -OH-containing nitro explosives. The FTIR can confirm the successful coupling of phenyl-phenyl in COP. The infrared spectrum is at 500cm -1 The stretching peaks of left and right C-Br disappeared or weakened, indicating that the Br functional group in the reactant had been consumed by the phenyl-phenyl coupling reaction.

[0033] Figure 2 This is a SEM image of a covalent organic polymer fluorescent probe for detecting -OH-containing nitro explosives. The morphology of COP was characterized by SEM as a multi-layered petal-like structure.

[0034] Figure 3 This is the thermogravimetric analysis under N2 conditions. The results show that the COP loses about 5% of its mass when heated to 400°C, proving that it has good thermal stability.

[0035] 2. Fluorescence intensity test of the covalent organic polymer fluorescent probe prepared in Example 1

[0036] 3 mg COP was dissolved in 20 mL DMF solution, 3 mL was added to a cuvette, and the maximum excitation / emission wavelength of the material was measured using a fluorescence spectrometer. The maximum excitation wavelength of the COP was 345.2 nm, the maximum excitation wavelength was 426.8 nm, and the fluorescence intensity was 4870. The results are as follows Figure 4 As shown, the covalent organic polymer fluorescent probe ex =λ ex-max The room temperature photoluminescence (PL) spectrum under excitation has a maximum emission peak at 426.8nm, showing a double emission peak.

[0037] Example 2 Method for detecting -OH-containing nitro explosives

[0038] The covalent organic polymer fluorescent probe (COP) prepared in Example 1 was used to detect -OH-containing nitro explosives, as follows:

[0039] 1. Detection of -OH-containing nitro-explosives: Sensing properties of covalent organic polymer fluorescent probes for different nitro-explosives

[0040] After adding 30 μL of different nitro explosives (1 mM) to the DMF solution of COP (3 mg / 20 mL), the fluorescence intensity after adding the nitro explosives was measured to obtain the detection results of COP for different nitro explosives. This example tested 10 nitro explosives, including o-nitrophenol (oNP), p-nitrophenol (pNP), m-nitrophenol (mNP), m-dinitrobenzene (mDNB), o-dinitrobenzene (oDNB), m-nitrotoluene (mNT), p-nitrotoluene (pNT), 2,4-dinitrotoluene (2,4-DNT, 2,6-dinitrophenol (2,6-DNP), and trinitrophenol (TNP). The results are shown in the attached figure. Figure 5 As shown in Figure (a), the COP synthesized by the present invention has a good quenching effect on all nitro explosives containing -OH groups. Then, phenol and resorcinol, two organic substances containing -OH but not containing -NO2, were added to the DMF solution of COP as test substances, and their fluorescence intensity was detected. The results are shown in Figure (b). This shows that the covalent organic polymer fluorescent probe for detecting nitro explosives containing -OH has no quenching effect on substances containing only -OH (phenol and resorcinol), proving that the quenching of nitro explosives containing -OH by the COP is the result of the combined action of -OH and -NO2.

[0041] 2. Titration experiment of different nitro explosives using covalent organic polymer fluorescent probes to detect -OH-containing nitro explosives

[0042] During the titration, 6 μL of nitro explosive solution was added to the COP solution each time (a total of ten times). After each addition, the solution was mixed thoroughly. After mixing evenly, the fluorescence intensity was measured to monitor the change in fluorescence intensity. The recorded data was fitted to the Stern-Volmer equation to calculate the fluorescence quenching constant (K sv ), which explains the quenching kinetics and interaction of COP with nitro explosives.

[0043]

[0044] I0 is the fluorescence intensity before adding the analyte; I is the fluorescence intensity after adding the analyte, and [C] is the solution concentration.

[0045] The results are attached Figure 6As shown in the figure, taking the titration experiment of detecting TNP as an example, the left figure is the fluorescence spectrum of adding different concentrations of TNP to COP. As the concentration of TNP increases, the fluorescence of COP is gradually quenched. The right figure is the fluorescence quenching result fitted by the Stern-Volmer equation, and the slope is calculated to obtain K sv Reach 10 4 This indicates that the covalent organic polymer fluorescent probe for detecting -OH-containing nitro explosives has a high sensitivity for detecting TNP.

[0046] The specification and drawings of the present invention are considered to be illustrative rather than restrictive. On the basis of the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features according to the disclosed technical content without creative labor, all of which are within the protection scope of the present invention.

Claims

1. A method for preparing a covalent organic polymer fluorescent probe, characterized in that: The following steps are involved: S1. Dissolve bis-(1,5-cyclooctadiene) nickel ([Ni(cod)2]) and 2,2'-bipyridine in an organic solvent in a glove box, add 1,5-cyclooctadiene (cod) after heating and stirring to dissolve, and prepare a mixed solution; S2, add 2,7-dibromopyrene and 1,2,3,4,5,6-hexa(4-bromophenyl)benzene to the mixed solution of S1 and dissolve them, then add Ni(0) catalyst, react at 60-120° C. for 10-24 hours, cool to room temperature after the reaction, and move the reactants out of the glove box; S3. Add HCl aqueous solution to the reactants removed from the glove box in S2, continue stirring for 3 to 6 hours, filter the precipitate, wash it with chloroform, tetrahydrofuran, methanol, and deionized water in sequence, and then dry it in a vacuum drying oven at 120°C for 12 to 20 hours to obtain an apricot powder covalent organic polymer fluorescent probe.

2. The preparation method according to claim 1, characterized in that: The molar ratio of bis-(1,5-cyclooctadiene)nickel ([Ni(cod)2]) and 2,2'-bipyridine in S1 is 1:1 to 3:

1.

3. The preparation method according to claim 1, characterized in that: The molar ratio of the two monomers 2,7-dibromopyrene and 1,2,3,4,5,6-hexa(4-bromophenyl)benzene in S2 is 1:1 to 4:

1.

4. The preparation method according to claim 1, characterized in that: The concentration of the HCl aqueous solution in the S3 is 1-5 mol / L, and the molar amount is 2-3 times the molar amount of the Ni(0) catalyst.

5. The preparation method according to claim 1, characterized in that: The organic solvent is N,N-dimethylformamide.

6. A covalent organic polymer fluorescent probe prepared by the preparation method according to any one of claims 1 to 5.

7. A method for detecting -OH-containing nitro explosives, characterized in that: Using the covalent organic polymer fluorescent probe as described in claim 6, the covalent organic polymer fluorescent probe is dissolved in a DMF solution, and a sample to be tested is added to the solution; the change in fluorescence intensity is measured; and the fluorescence sensing performance of the fluorescent probe to nitro explosives containing -OH is determined based on the change in fluorescence intensity.

8. The method according to claim 7, characterized in that The sample to be tested is one of soil, water or air.

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