A fluorescent probe for selectively and quantitatively detecting 4-nitroaniline, and a preparation method and application thereof

Abstract

The application discloses a fluorescent probe for selectively and quantitatively detecting 4-nitroaniline as well as a preparation method and application thereof. The fluorescent probe is a nanomicelle formed by self-assembly of an anion conjugated polymer and poloxamer, and has the functions of enhancing the fluorescence quantum yield of the conjugated polymer and water solubility. The fluorescent probe has a specific and obvious color response to the concentration of 4-nitroaniline, can exclude the interference of other biological molecules in a complex environment, and realizes selective and quantitative detection of 4-nitroaniline. In addition, the fluorescent probe can be made into a portable paper sheet sensor by a simple method, so that rapid and on-site real-time detection of 4-nitroaniline is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorescent probes and relates to a fluorescent probe for selectively and quantitatively detecting 4-nitroaniline and a preparation method and application thereof. Background Art

[0002] With the development of industry and the increase in population, the discharge of organic wastewater and other chemical wastes has increased dramatically, becoming an environmental and health issue of concern. 4-Nitroaniline (4-NA) is a key precursor to many chemical products, primarily used in the synthesis of pesticides, azo dyes, pharmaceuticals, light stabilizers, antioxidants, and more. 4-Nitroaniline degrades slowly, resulting in its long-term presence in the environment, adversely affecting water quality, soil fertility, wildlife, and other areas. 4-Nitroaniline is highly toxic and can cause more severe blood poisoning than aniline. Even trace amounts of 4-nitroaniline can cause significant harm to the human body, leading to health problems such as respiratory arrest, diarrhea, skin eczema, and anemia. Therefore, efficient and accurate detection of 4-nitroaniline is of great significance for national security, military applications, medical research, and environmental protection.

[0003] Traditional methods for the detection of 4-nitroaniline include colorimetry, high-performance liquid chromatography (HPLC), and electrochemical methods. HPLC offers high accuracy but is relatively time-consuming. Electrochemical methods offer high sensitivity and rapid detection, but are relatively complex. These methods, due to drawbacks such as high equipment investment, time consumption, and complex sample pretreatment, hinder real-time detection. Fluorescence detection methods, based on their superior optical properties, offer promising applications in rapid detection due to their low detection limits, high sensitivity, and portability. Currently reported fluorescence detection methods for 4-nitroaniline are primarily based on fluorescent dyes and quantum dots, but these materials pose significant challenges in terms of toxicity and dye leakage. Conjugated polymers (CPs) are a novel class of fluorescent organic materials that combine the properties of polymers and semiconductors. Due to their diverse properties, including high photoluminescence quantum yield (PLQY), good photostability, and excellent sensitivity, conjugated polymers are widely used in fluorescence sensing. However, most conjugated polymers are hydrophobic, and their limited water solubility severely limits their applications in sensing. By nano-micelle-forming conjugated polymers, not only their water solubility is improved, but also their fluorescence quantum yield is greatly increased. Therefore, it is considered to be a detection strategy with simple operation and high applicability.

[0004] At present, there are no reports on the detection of 4-nitroaniline using conjugated polymer nanomicelles. Therefore, designing a fluorescent probe that can effectively eliminate the interference of other analytes and achieve rapid, sensitive and efficient detection of 4-nitroaniline is very necessary for the protection of the ecological environment and human health. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a fluorescent probe for selective and quantitative detection of 4-nitroaniline, as well as its preparation method and application. The probe can selectively identify 4-nitroaniline in complex environments, has high sensitivity, low detection limit, good selectivity, and is convenient and quick to operate. At the same time, the probe can be prepared into a portable paper-type sensor, which is more suitable for on-site detection.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention discloses a fluorescent probe for selective and quantitative detection of 4-nitroaniline. The fluorescent probe is a nanomicelle formed by self-assembly of an anionic conjugated polymer and poloxamer. The structural formula of the anionic conjugated polymer is as follows:

[0008]

[0009] The present invention also discloses the use of the fluorescent probe for selectively and quantitatively detecting 4-nitroaniline in preparing a sensor for selectively and quantitatively detecting 4-nitroaniline.

[0010] Preferably, the sensor is a portable paper sensor.

[0011] The present invention also discloses a method for preparing the fluorescent probe for selectively and quantitatively detecting 4-nitroaniline, wherein the anionic conjugated polymer PF-DBT-COONa is mixed with poloxamer F127 and then self-assembled to obtain the fluorescent probe PF-Plu-Mic for selectively and quantitatively detecting 4-nitroaniline; wherein:

[0012] The molar ratio of the anionic conjugated polymer PF-DBT-COONa to poloxamer is (5-50): (0.1-1).

[0013] Preferably, the anionic conjugated polymer PF-DBT-COONa is synthesized according to the following method, comprising the following steps:

[0014] 1) Di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene) dipropyl ester, 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-bis(n-butyl 3-propionate) fluorene, and 4,7-bis(2-bromo-5-thienyl)-2,1,3-benzothiadiazole were mixed, and a tetrahydrofuran solution was added to obtain solution A;

[0015] 2) Potassium carbonate and ultrapure water are mixed and added to solution A, degassed, and then tetrakis(triphenylphosphine)palladium is added as a catalyst, nitrogen is introduced, and then heated under reflux to carry out a polymerization reaction. After the polymerization reaction is completed, separation and purification are carried out to obtain a precursor polymer PF-DBT-COOtBut;

[0016] 3) The precursor polymer PF-DBT-COOtBut was dissolved in dichloromethane, degassed, and then trifluoroacetic acid was added. The reaction was allowed to react at room temperature for 24 hours. A sodium carbonate solution was added and the reaction was continued for 6 to 24 hours. After the reaction was completed, the anionic conjugated polymer PF-DBT-COONa was separated and purified to obtain the anionic conjugated polymer PF-DBT-COONa.

[0017] Further preferably, in step 1), the amount ratio of di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene) dipropyl ester, 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-bis(n-butyl 3-propionate) fluorene, 4,7-bis(2-bromo-5-thienyl)-2,1,3-benzothiadiazole and tetrahydrofuran is (0.1-0.5) g: (0.2-1) g: (0.05-0.5) g: (15-100) mL;

[0018] In step 2), the ratio of potassium carbonate to ultrapure water is (0.5-2.5) g: (2-10) mL; the mass ratio of the added tetrakis(triphenylphosphine)palladium catalyst to potassium carbonate is 1:10;

[0019] In step 3), the ratio of the precursor polymer PF-DBT-COOtBut, trifluoroacetic acid and dichloromethane is (10-100) mg: (0.5-5) mL: (5-45) mL.

[0020] More preferably, in step 2) and step 3), the degassing time is 20 to 40 minutes, and the nitrogen introduction time is 30 to 40 minutes.

[0021] More preferably, in step 2), the heating reflux temperature is 40 to 100° C., and the polymerization reaction time is 12 to 96 hours.

[0022] Further preferably, in step 2), the separation and purification operation is as follows: after the reaction is completed, solid impurities are filtered out, the solvent is removed, water and chloroform are added for extraction, the organic phase is taken, dried with anhydrous sodium sulfate, filtered, the organic solvent is removed, and repeatedly precipitated in a methanol solution to obtain a precursor polymer PF-DBT-COOtBut.

[0023] Further preferably, in step 3), the separation and purification operation is as follows: after the reaction is completed, the dichloromethane is removed, and then the remaining solution is transferred to a dialysis bag with a molecular weight of 2 kDa and dialyzed for 48 hours, and the residual liquid is removed by rotary evaporation and vacuum drying to obtain an anionic conjugated polymer PF-DBT-COONa.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The fluorescent probe for selective and quantitative detection of 4-nitroaniline disclosed in the present invention is a nanomicelle formed by self-assembly of an anionic conjugated polymer with a novel structure and poloxamer. The degree of polymerization of the left chain of the anionic conjugated polymer is selected to be 80, and the degree of polymerization of the right chain is selected to be 20. The conjugated polymer (PF-DBT-COONa) in this ratio contains a polyfluorene fluorophore (415 nm) and a DBT fluorophore (635 nm), and can emit bright blue. The conjugated polymer self-assembles with F127 to form the nanomicelle fluorescent probe PF-Plu-Mic for selective and quantitative detection of 4-nitroaniline. Compared with a single polymer probe, the water solubility, fluorescence quantum yield and detection sensitivity for 4-nitroaniline are greatly improved.

[0026] The method for preparing the fluorescent probe for selective and quantitative detection of 4-nitroaniline disclosed in the present invention is very simple to operate. It only needs to be mixed with poloxamer F127 and then self-assembled to obtain the fluorescent probe PF-Plu-Mic for selective and quantitative detection of 4-nitroaniline. Poloxamer not only effectively improves the solubility of the conjugated polymer in water but also can convert the liquid probe into a portable gel solid device by adjusting the concentration, thereby realizing portable and on-site detection.

[0027] The fluorescent probe prepared by the present invention exhibits bright blue emission as a whole and has excellent selectivity for 4-nitroaniline. As the concentration of 4-nitroaniline increases, the probe is quenched, causing its fluorescence intensity to decrease significantly, and the bright blue fluorescence gradually fades. It can selectively identify 4-nitroaniline in complex environments, with high sensitivity, low detection limit, good selectivity, and convenient and quick operation. The probe can also be prepared into a portable paper-type sensor, which is more suitable for on-site detection.

[0028] Figure 1 The synthetic route of the fluorescent probe PF-DBT-COONa for selective quantitative detection of 4-nitroaniline of the present invention is shown in FIG.

[0029] Figure 2 This is a hydrogen nuclear magnetic resonance spectrum of the fluorescent probe PF-DBT-COONa capable of selectively and quantitatively detecting 4-nitroaniline in Example 1 of the present invention;

[0030] Figure 3This is a fluorescence response spectrum of PF-Plu-Mic to different concentrations of 4-nitroaniline in Example 7 of the present invention;

[0031] Figure 4 This is a graph showing the response of the paper-type PF-Plu-Mic sensor to different concentrations of 4-nitroaniline in Example 7 of the present invention. (a) shows the color of the test paper after immersion in a 1 mM 4-NA solution under UV light. (b) shows the color change of the test paper after adding various concentrations of 4-NA solution.

[0032] Figure 5 This is a bar graph showing the selectivity test of PF-Plu-Mic for 4-nitroaniline in Example 8 of the present invention, i.e., a graph showing the relationship between the response of PF-Plu-Mic and various potential interferents. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] The present invention is described in further detail below with reference to the accompanying drawings:

[0036] See also Figure 1 , is a roadmap for synthesizing the anionic conjugated polymer PF-DBT-COONa of the present invention, comprising the following steps:

[0037] 1) Mix di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene)dipropylate, 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-di(n-butyl 3-propionate)fluorene, 4,7-bis(2-bromo-5-thienyl)-2,1,3-benzothiadiazole, and then add a tetrahydrofuran solution to obtain solution A;

[0038] 2) Mix potassium carbonate and ultrapure water, add to solution A, degas, then add tetrakis(triphenylphosphine)palladium as a catalyst, introduce nitrogen, then heat to reflux, and perform a polymerization reaction. After the polymerization reaction is complete, separate and purify to obtain precursor polymer PF-DBT-COOtBut;

[0039] 3) Dissolve the precursor polymer PF-DBT-COOtBut in dichloromethane, degas, then add trifluoroacetic acid, and react at room temperature for 24 h. Add a sodium carbonate solution to continue the reaction for 6-24 h. After the reaction is complete, separate and purify to obtain an anionic conjugated polymer PF-DBT-COONa.

[0040] Example 1

[0041] Take 0.1 g of di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene)dipropylate (M1), 0.2 g of 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-di(n-butyl 3-propionate)fluorene (M2), and 0.05 g of 4,7-bis(2-bromo-5-thienyl)-2,1,3-benzothiadiazole (M3) in a three-necked flask, add 15 mL of a tetrahydrofuran solution to obtain solution A. Mix 0.5 g of potassium carbonate with 2 mL of ultrapure water, and add to solution A using a syringe. Degas for 30 min, add 0.005 g of tetrakis(triphenylphosphine)palladium as a catalyst, introduce nitrogen for 30 min, and heat to reflux at 40°C for 12 h to perform a polymerization reaction. After the polymerization reaction is complete, filter to remove solid impurities, remove the solvent using a rotary evaporator, extract with water and dichloromethane, dry the organic phase with anhydrous sodium sulfate, and filter. Repeat the precipitation in a methanol solution to obtain precursor polymer PF-DBT-COOtBut. Mix 10 mg of PF-DBT-COOtBut, 0.5 mL of trifluoroacetic acid, and 5 mL of dichloromethane, and react at room temperature for 12 h. After the reaction is complete, remove the dichloromethane using a rotary evaporator, add 25 mL of a 0.2M sodium carbonate solution, and react at room temperature for 6 h. After the reaction is complete, transfer the solution to a dialysis bag with a molecular weight of 2 kDa, and dialyze for 2 days. After removing the solvent by rotary evaporation and vacuum drying, an anionic conjugated polymer PF-DBT-COONa is obtained.

[0042] PF-DBT-COONa was characterized by H NMR spectroscopy. Figure 2 As shown. Figure 2 The test results can be attributed to the proton characteristic peaks: 1 H NMR (400 MHz, d4-Methanol, δ): 7.96-7.58 (m), 2.49 (b), 1.50 (b), 1.25 (b), 0.85 (b). The synthesized product was confirmed to be PF-DBT-COONa.

[0043] 5 μM PF-DBT-COONa and 0.1 μM poloxamer (F127) were self-assembled to form nanomicelles, obtaining the ratiometric fluorescent probe PF-Plu-Mic for selective and quantitative detection of 4-nitroaniline.

[0044] Example 2

[0045] 0.15 g of di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene)dipropyl ester (M1), 0.3 g of 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-bis(n-butyl 3-propionate)fluorene (M2), and 0.08 g of 4,7-bis(2-bromo-5-thienyl)-2,1,3-benzothiadiazole (M3) were placed in a three-necked flask and 25 mL of tetrahydrofuran solution was added to obtain solution A. 1.382 g of potassium carbonate was mixed with 3 mL of ultrapure water and added to solution A via syringe. The mixture was degassed for 30 minutes, and 0.015 g of tetrakis(triphenylphosphine)palladium was added as a catalyst. Nitrogen was introduced for 30 minutes, and the mixture was heated at reflux at 70°C for 48 hours to carry out the polymerization reaction. After the polymerization reaction is completed, solid impurities are filtered to remove the solvent, and water and chloroform are added for extraction. The organic phase is taken, dried over anhydrous sodium sulfate, and filtered; the organic solvent is removed by rotary evaporation, and the precursor polymer PF-DBT-COOtBut is repeatedly precipitated in a methanol solution to obtain. 50 mg of PF-DBT-COOtBut, 3 mL of trifluoroacetic acid, and 30 mL of dichloromethane are mixed and reacted at room temperature for 12 hours. After the reaction is completed, the dichloromethane is removed by rotary evaporation, and 25 ml of 0.2 M sodium carbonate solution is added and reacted at room temperature for 24 hours. After the reaction is completed, the solution is transferred to a dialysis bag with a molecular weight of 2 kDa and dialyzed for 2 days; after rotary evaporation and vacuum drying to remove the solvent, the anionic conjugated polymer PF-DBT-COONa is obtained. The characterization results of the fluorescent compound obtained in this example are the same as those in Example 1.

[0046] 9 μM of PF-DBT-COONa and 0.2 μM of poloxamer (F127) were formed into nanomicelles by self-assembly method to obtain a ratiometric fluorescent probe PF-Plu-Mic capable of selectively and quantitatively detecting 4-nitroaniline.

[0047] Example 3

[0048] Take 0.5 g of di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene)dipropylate (M1), 0.3 g of 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-di(n-butyl 3-propionate)fluorene (M2), 0.1 g of 4,7-bis(2-bromo-5-thienyl)-2,1,3-benzothiadiazole (M3) in a three-necked flask, add 60 mL of tetrahydrofuran solution to obtain solution A. Mix 2 g of potassium carbonate with 10 mL of ultrapure water, add solution A with a syringe, degas for 30 min, add 0.005 g of tetrakis(triphenylphosphine)palladium as catalyst, introduce nitrogen for 30 min, heat at 50°C for 48 h for polymerization. After the polymerization is completed, filter out the solid impurities, remove the solvent with a rotary evaporator, add water and chloroform for extraction, take the organic phase, dry with anhydrous sodium sulfate, filter; remove the organic solvent by rotary evaporation, and repeatedly precipitate in a methanol solution to obtain the precursor polymer PF-DBT-COOtBut. Mix 40 mg of PF-DBT-COOtBut, 2 mL of trifluoroacetic acid and 35 mL of dichloromethane, and react at room temperature for 12 h. After the reaction is completed, remove the dichloromethane by rotary evaporation, add 25 ml of 0.2M sodium carbonate solution and react at room temperature for 12 h. After the reaction is completed, transfer the solution to a dialysis bag with a molecular weight of 2 kDa and dialyze for 2 days; after removing the solvent by rotary evaporation and vacuum drying, the anionic conjugated polymer PF-DBT-COONa is obtained. The characterization of the fluorescent compound obtained in this example is the same as the characterization result in Example 1.

[0049] 5 μM of PF-DBT-COONa and 1 μM of poloxamer (F127) were formed into nanomicelles by self-assembly method to obtain a ratiometric fluorescent probe PF-Plu-Mic capable of selectively and quantitatively detecting 4-nitroaniline.

[0050] Example 4

[0051] Take 0.32 g of di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene) dipropyl ester (M1), 0.5 g of 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-di(3-n-butyric acid) fluorene (M2), 0.3 g of 4,7-bis(2-bromo-5-thiophenyl)-2,1,3-benzothiadiazole (M3) in a three-necked flask, add 100 mL of tetrahydrofuran solution to obtain solution A. Mix 2.5 g of potassium carbonate with 10 mL of ultrapure water, add solution A with a syringe, degas for 30 min, add 0.03 g of tetrakis(triphenylphosphine)palladium as catalyst, pass nitrogen for 30 min, heat at 80°C for 12 h for polymerization. After the polymerization reaction is completed, filter out the solid impurities, remove the solvent with a rotary evaporator, add water and chloroform to extract, take the organic phase, dry with anhydrous sodium sulfate, filter; remove the organic solvent by rotary evaporation, and repeatedly precipitate in a methanol solution to obtain the precursor polymer PF-DBT-COOtBut. Mix 100 mg of PF-DBT-COOtBut, 5 mL of trifluoroacetic acid and 45 mL of dichloromethane, and react at room temperature for 12 h. After the reaction is completed, remove the dichloromethane by rotary evaporation, add 25 ml of 0.2M sodium carbonate solution and react at room temperature for 24 h. After the reaction is completed, transfer the solution to a dialysis bag with a molecular weight of 2 kDa and dialyze for 2 days; after removing the solvent by rotary evaporation and vacuum drying, the anionic conjugated polymer PF-DBT-COONa is obtained. The characterization of the fluorescent compound obtained in this example is the same as the characterization result in Example 1.

[0052] Form nanomicelles by self-assembly of 25 μM of PF-DBT-COONa and 0.1 μM of poloxamer (F127) to obtain a ratiometric fluorescent probe PF-Plu-Mic that can selectively and quantitatively detect 4-nitroaniline.

[0053] Example 5

[0054] Take 0.48 g of di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene) dipropyl ester (M1), 0.35 g of 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-di(3-n-butyric acid) fluorene (M2), 0.05 g of 4,7-bis(2-bromo-5-thiophenyl)-2,1,3-benzothiadiazole (M3) in a three-necked flask, add 65 mL of tetrahydrofuran solution to obtain solution A. Mix 1.5 g of potassium carbonate with 8 mL of ultrapure water, add solution A with a syringe, degas for 30 min, add 0.009 g of tetrakis(triphenylphosphine)palladium as catalyst, pass nitrogen for 30 min, heat at 50°C for 96 h for polymerization. After the polymerization is completed, filter out the solid impurities, remove the solvent with a rotary evaporator, add water and chloroform to extract, take the organic phase, dry with anhydrous sodium sulfate, filter; remove the organic solvent by rotary evaporation, and repeatedly precipitate in a methanol solution to obtain the precursor polymer PF-DBT-COOtBut. Mix 50 mg of PF-DBT-COOtBut, 4 mL of trifluoroacetic acid and 5 mL of dichloromethane, and react at room temperature for 12 h. After the reaction is completed, remove the dichloromethane by rotary evaporation, add 25 ml of 0.2M sodium carbonate solution and react at room temperature for 6 h. After the reaction is completed, transfer the solution to a dialysis bag with a molecular weight of 2 kDa and dialyze for 2 days; after removing the solvent by rotary evaporation and vacuum drying, the anionic conjugated polymer PF-DBT-COONa is obtained. The characterization of the fluorescent compound obtained in this example is the same as the characterization result in Example 1.

[0055] Form nanomicelles by self-assembly of 25 μM of PF-DBT-COONa and 0.3 μM of poloxamer (F127) to obtain a ratiometric fluorescent probe PF-Plu-Mic that can selectively and quantitatively detect 4-nitroaniline.

[0056] Example 6

[0057] Take 0.1 g of di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene)dipropyl ester (M1), 0.8 g of 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-di(n-butyl 3-propionate) fluorene (M2), 0.45 g of 4,7-bis(2-bromo-5-thienyl)-2,1,3-benzothiadiazole (M3) in a three-necked flask, add 30 mL of tetrahydrofuran solution to obtain solution A. Mix 0.8 g of potassium carbonate with 8 mL of ultrapure water, add solution A with a syringe, degas for 30 min, add 0.01 g of tetrakis(triphenylphosphine)palladium as a catalyst, introduce nitrogen for 30 min, heat at 68°C for 36 h to carry out the polymerization reaction. After the polymerization reaction is completed, filter out the solid impurities, remove the solvent with a rotary evaporator, add water and chloroform to extract, take the organic phase, dry with anhydrous sodium sulfate, filter; remove the organic solvent by rotary evaporation, and repeatedly precipitate in a methanol solution to obtain the precursor polymer PF-DBT-COOtBut. Mix 25 mg of PF-DBT-COOtBut, 4.5 mL of trifluoroacetic acid and 40 mL of dichloromethane, and react at room temperature for 12 h. After the reaction is completed, remove the dichloromethane by rotary evaporation, add 25 ml of 0.2M sodium carbonate solution and react at room temperature for 20 h. After the reaction is completed, transfer the solution to a dialysis bag with a molecular weight of 2 kDa and dialyze for 2 days; after removing the solvent by rotary evaporation and vacuum drying, the anionic conjugated polymer PF-DBT-COONa is obtained. The characterization of the fluorescent compound obtained in this example is the same as the characterization results in Example 1.

[0058] Form nanomicelles by self-assembly of 40 μM of PF-DBT-COONa and 0.5 μM of poloxamer (F127) to obtain a ratiometric fluorescent probe PF-Plu-Mic that can selectively and quantitatively detect 4-nitroaniline.

[0059] Fluorescent detection performance test on 4-nitroaniline:

[0060] 1. Fluorescent detection on different concentrations of 4-nitroaniline

[0061] The fluorescent probe PF-Plu-Mic prepared by the present application (take Example 2 as an example) is used for fluorescent detection on different concentrations of 4-nitroaniline. During testing, PF-Plu-Mic is always maintained at 30 μM, and the concentration of 4-nitroaniline is 0 μM, 10 μM, 20 μM, 30 μM, 40 μM, 50 μM, 60 μM, 70 μM, and 80 μM. The total amount of the test system is 1 mL, the test temperature is 25°C, the excitation wavelength is 370 nm, and the measured fluorescence spectrum is as shown in Figure 3 As the concentration of 4-nitroaniline increases, the fluorescence intensity at 413 nm gradually decreases. As shown in Figure 3It can be seen that the fluorescence intensity ratio and the concentration of 4-nitroaniline show a good linear relationship. Figure 4 In order to make the PF-Plu-Mic into a portable paper sheet sensor, the fluorescence response graph of the PF-Plu-Mic to 4-nitroaniline is obtained. Figure 4 It is proved that the PF-Plu-Mic has the ability to sensitively, quickly and real-time detect 4-nitroaniline.

[0062] 2, Selectivity test of 4-nitroaniline in the presence of different potential interferents The selectivity test of 4-nitroaniline in the presence of different potential interferents is carried out by using the PF-Plu-Mic fluorescent probe prepared by the present application (taking Example 2 as an example). The fluorescence of the complex system in the presence of potential interferents is detected by using the PF-Plu-Mic fluorescent probe with a concentration of 30 μM. The test system, 4-nitroaniline (4-NA), 2,6-dichloro-4-nitroaniline (DCNA), toluene (Toluene), triethylamine (TEA), nitrobenzene (NB), aniline (AN), 4-nitrotoluene (4-NT), 3-nitroaniline (3-NA), benzoic acid (BA), trimethylamine (TMA), 3,3',5,5'-tetramethylbenzidine (TMB) and tetramethyl ethylenediamine (TMEDA). The concentration of each analyte is 0.8 mM, the total amount of the test system is 1 mL, the test temperature is 25°C, the excitation wavelength is 370 nm, and the measured fluorescence spectrum is as shown in Figure 5 It can be seen that the fluorescence intensity ratio and the concentration of 4-nitroaniline show a good linear relationship. Figure 5 It can be seen that the fluorescence probe of the present application has excellent selectivity for 4-nitroaniline.

[0063] In summary, the fluorescent probe for selectively and quantitatively detecting 4-nitroaniline disclosed by the present application is a nanomicelle formed by self-assembly of a new anion conjugated polymer and poloxamer, which has the functions of enhancing the fluorescence quantum yield of the conjugated polymer and water solubility. The fluorescent probe of the present application has a specific and significantly enhanced color response to the concentration of 4-nitroaniline, can exclude other biological molecules in a complex environment, and realizes selective and quantitative detection of 4-nitroaniline. In addition, the fluorescent probe can be made into a portable paper sheet sensor by a simple method, realizing rapid, on-site and real-time detection of 4-nitroaniline.

[0064] The above content is only for illustrating the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical solution falls within the protection scope of the claims of the present application.

Claims

1. A fluorescent probe for selective quantitative detection of 4-nitroaniline, characterized in that: The fluorescent probe is a nanomicelle formed by a self-assembly method of an anionic conjugated polymer and poloxamer; wherein the structural formula of the anionic conjugated polymer is as follows:

2. Use of the fluorescent probe for selective and quantitative detection of 4-nitroaniline according to claim 1 in the preparation of a sensor for selective and quantitative detection of 4-nitroaniline.

3. The use according to claim 2, characterized in that The sensor is a portable paper sensor.

4. The method for preparing the fluorescent probe for selective quantitative detection of 4-nitroaniline according to claim 1, characterized in that: The anionic conjugated polymer PF-DBT-COONa and poloxamer F127 were mixed and self-assembled to obtain the fluorescent probe PF-Plu-Mic for selective quantitative detection of 4-nitroaniline; wherein: The molar ratio of the anionic conjugated polymer PF-DBT-COONa to poloxamer is (5-50): (0.1-1).

5. The method for preparing a fluorescent probe for selective quantitative detection of 4-nitroaniline according to claim 4, wherein: The anionic conjugated polymer PF-DBT-COONa is synthesized according to the following method, comprising the following steps: 1) Di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene) dipropyl ester, 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-bis(n-butyl 3-propionate) fluorene, and 4,7-bis(2-bromo-5-thienyl)-2,1,3-benzothiadiazole were mixed, and a tetrahydrofuran solution was added to obtain solution A; 2) Potassium carbonate and ultrapure water are mixed and added to solution A, degassed, and then tetrakis(triphenylphosphine)palladium is added as a catalyst, nitrogen is introduced, and then heated under reflux to carry out a polymerization reaction. After the polymerization reaction is completed, separation and purification are carried out to obtain a precursor polymer PF-DBT-COOtBut; 3) The precursor polymer PF-DBT-COOtBut was dissolved in dichloromethane, degassed, and then trifluoroacetic acid was added. The reaction was allowed to react at room temperature for 24 hours. A sodium carbonate solution was added and the reaction was continued for 6 to 24 hours. After the reaction was completed, the anionic conjugated polymer PF-DBT-COONa was separated and purified to obtain the anionic conjugated polymer PF-DBT-COONa.

6. The method for preparing a fluorescent probe for selective quantitative detection of 4-nitroaniline according to claim 5, characterized in that: In step 1), the usage ratio of di-tert-butyl 3,3-(2,7-dibromo-9H-fluorene-9,9-ylidene) dipropyl ester, 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-bis(n-butyl 3-propionate) fluorene, 4,7-bis(2-bromo-5-thienyl)-2,1,3-benzothiadiazole and tetrahydrofuran is (0.1-0.5) g:(0.2-1) g:(0.05-0.5) g:(15-100) mL; In step 2), the ratio of potassium carbonate to ultrapure water is (0.5-2.5) g: (2-10) mL; the mass ratio of the added tetrakis(triphenylphosphine)palladium catalyst to potassium carbonate is 1:10; In step 3), the ratio of the precursor polymer PF-DBT-COOtBut, trifluoroacetic acid and dichloromethane is (10-100) mg: (0.5-5) mL: (5-45) mL.

7. The method for preparing a fluorescent probe for selective quantitative detection of 4-nitroaniline according to claim 5, characterized in that: In step 2) and step 3), the degassing time is 20 to 40 minutes, and the nitrogen introduction time is 30 to 40 minutes.

8. The method for preparing a fluorescent probe for selective quantitative detection of 4-nitroaniline according to claim 5, characterized in that: In step 2), the heating reflux temperature is 40 to 100° C., and the polymerization reaction time is 12 to 96 hours.

9. The method for preparing a fluorescent probe for selective quantitative detection of 4-nitroaniline according to claim 5, characterized in that: In step 2), the separation and purification operation is as follows: after the reaction is completed, solid impurities are removed by filtration, the solvent is removed, water and chloroform are added for extraction, the organic phase is taken, dried with anhydrous sodium sulfate, filtered, the organic solvent is removed, and repeatedly precipitated in a methanol solution to obtain a precursor polymer PF-DBT-COOtBut.

10. The method for preparing a fluorescent probe for selective quantitative detection of 4-nitroaniline according to claim 5, characterized in that: In step 3), the separation and purification operation is as follows: after the reaction is completed, the dichloromethane is removed, and then the remaining solution is transferred to a dialysis bag with a molecular weight of 2 kDa and dialyzed for 48 hours. The residual liquid is removed by rotary evaporation and vacuum drying to obtain an anionic conjugated polymer PF-DBT-COONa.

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