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

Abstract

The present invention discloses a covalent organic polymer fluorescent probe, and the preparation method is as follows: 2,7-dibromopyrene and 1,2,3,4,5,6-hexa(4-bromophenyl)benzene are added to an organic solvent to dissolve, a Ni(0) catalyst is added, and the reaction is heated overnight. After the reaction is completed, it is cooled to room temperature, an HCl aqueous solution is added, the resulting precipitate is filtered, and washed with an organic solvent to finally obtain the covalent organic polymer fluorescent probe. The fluorescent probe is synthesized by a nickel-catalyzed Yamamoto reaction, has a significant quenching effect on nitro explosives containing OH groups, can be observed with the naked eye to have a significant color change, has high sensitivity, and has a low detection limit; and has no significant response to nitro explosives containing OH groups. Therefore, this fluorescent probe can be used as a specific fluorescent probe for highly selective detection of nitro explosives containing OH groups.

Description

Technical Field

[0001] The present 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] Nitro explosives, as powerful explosives, are widely used in both military and civilian applications. However, they can cause soil and water pollution, impacting the survival of plants and animals, and seriously threatening the living environment, human health, and even national security. Therefore, the rapid development of sensitive nitro explosive detection technology is crucial.

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

[0004] Fluorescence sensing is a highly effective method for detecting nitro explosives. It utilizes the interaction between specific fluorescent materials and nitro explosives for identification and measurement. It offers advantages such as high sensitivity, rapid response, and ease of operation. Although fluorescence sensing technology has made progress in the field of nitro explosive detection, most current research 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, developing a fluorescent probe that can specifically identify a particular category of nitro explosives is crucial for improving detection accuracy and efficiency. 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] To solve the above technical problems, the present invention adopts the following technical solution: a method for preparing a covalent organic polymer fluorescent probe, comprising the following steps:

[0007] S1. In a glove box, dissolve bis-(1,5-cyclooctadiene) nickel ([Ni(cod)2]) and 2,2'-bipyridine in an organic solvent, heat and stir to dissolve, and then add 1,5-cyclooctadiene (cod) to 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 and react at 60-120°C for 10-24 hours. After the reaction is completed, cool to room temperature and remove the reactants from 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 powdery 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 nitro explosives containing -OH groups, 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 for nitro explosives containing -OH groups 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 a significant quenching effect only on nitro explosives containing -OH, and has no response to other nitro explosives that do not contain -OH, thus having high selectivity; and can respond quickly, with high sensitivity and 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 an 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 is the fluorescence intensity after adding different nitro explosives to the DMF solution of COP.

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

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

[0027] Example 1 Preparation of a 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 into a 150ml pressure bottle. Add 40mL of DMF and dissolve. Then, use a pipette to dropwise add 0.25mL of 1,5-cyclooctadiene (cod) to the solution. Stir at 40°C for half an hour to completely dissolve the mixture, yielding 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 solution. Continue stirring until dissolved. Heat the reaction to 90°C in an anhydrous and oxygen-free environment for 10 hours. After the reaction is complete, stop heating and allow the mixture to 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 and the product is filtered. It is 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 nitro explosives containing -OH groups. FTIR can confirm the successful coupling of phenyl-phenyl groups in COP. The infrared spectrum is at 500 cm -1 The C-Br stretching peaks on the left and right disappeared or weakened, indicating that the Br functional group in the reactant had been consumed through 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 SEM image shows that the COP morphology is a multilayered petal-like structure.

[0034] Figure 3 Thermogravimetric analysis under N2 conditions showed that the COP lost about 5% of its mass when heated to 400°C, proving its good thermal stability.

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

[0036] 3 mg of COP was dissolved in 20 mL of DMF solution, and 3 mL was added to a cuvette. 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 is ex =λ ex-max The room temperature photoluminescence (PL) spectrum under excitation shows a maximum emission peak at 426.8 nm, exhibiting a double emission peak.

[0037] Example 2 Method for Detecting -OH Nitro Explosives

[0038] The covalent organic polymer fluorescent probe (COP) prepared in Example 1 was used to detect nitro explosives containing -OH groups, 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 a DMF solution of COP (3 mg / 20 mL), the fluorescence intensity after the addition of the nitro explosives was measured to obtain the detection results of COP for different nitro explosives. In this example, 10 nitro explosives were tested, 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 in the present invention exhibits a strong quenching effect on all nitro explosives containing -OH groups. Furthermore, phenol and resorcinol, two organic compounds containing -OH but not -NO2, were added to a DMF solution of COP as test substances, and their fluorescence intensity was measured. The results are shown in Figure (b). This demonstrates that the covalent organic polymer fluorescent probe for detecting -OH-containing nitro explosives has no quenching effect on substances containing only -OH (phenol and resorcinol), demonstrating that the quenching of -OH-containing nitro explosives 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 additions). After each addition, the solution was thoroughly mixed. After mixing, 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 as attached Figure 6As shown in the figure: Taking the titration experiment of TNP detection 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 description 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 work, and all of them are within the scope of protection 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. In a glove box, dissolve bis-(1,5-cyclooctadiene) nickel ([Ni(cod)2]) and 2,2'-bipyridine in an organic solvent, heat and stir to dissolve, and then add 1,5-cyclooctadiene (cod) to 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 and react at 60-120°C for 10-24 hours. After the reaction is completed, cool to room temperature and remove the reactants from 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 powdery 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 S3 is 1 to 5 mol / L, and the molar amount is 2 to 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: The covalent organic polymer fluorescent probe as described in claim 6 is used, 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 for nitro explosives containing -OH groups is judged 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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