A donor-acceptor type fluoroboron dipyrrolidine fluorescent compound and its preparation method and application

Abstract

The present invention discloses a donor-acceptor type fluoroboron dipyrrolidine fluorescent compound, its preparation method and application. The fluorescent compound is composed of an 8-position modified cholesterol fragment as an assembly unit, a 2,6-position modified triphenylamine as an electron donor, and fluoroboron dipyrrolidine as an electron acceptor and luminescent unit. Its molecular structure is shown below. The preparation method of the fluorescent compound of the present invention is simple and the reaction conditions are mild. The donor-acceptor type fluoroboron dipyrrolidine with a 2,6-position modified electron donor substituent has an intramolecular charge transfer process, its Stokes shift is significantly broadened, and the excited state has microenvironment-sensitive characteristics. At the same time, it has an assembly unit of a cholesterol fragment and can be co-assembled with a dicholesterol compound to prepare a fluorescent sensing film with high luminescence efficiency and large specific surface area. Based on the polarity-sensitive characteristics, the fluorescent sensing film can realize pattern recognition of 7 toxic and harmful gases with different polarities by a single fluorescent species. #imgabs0#

Description

Technical Field

[0001] The present invention belongs to the technical field of donor-acceptor type fluorescent thin film materials, and specifically relates to a fluoroboron dipyrrole fluorescent compound with an intramolecular charge transfer process, a preparation method thereof, and an application of the compound in the technical field of fluorescent sensing thin films. Background Art

[0002] Volatile organic compounds (VOCs) generally refer to organic compounds with a boiling point below 250°C at atmospheric pressure. Most VOCs are toxic to some degree and pose health risks to all living things, including humans. For example, when the concentration of alkane gases in the air exceeds the explosive concentration limit, it can cause public safety hazards, and long-term exposure to alkane gases can also cause systemic damage to the human nervous system. Inhalation of chloroform gas can paralyze the nervous system and have an anesthetic effect, while acetone gas may cause damage to the liver, kidneys, and pancreas. Furthermore, many VOCs are precursors to the formation of ozone in the air. Therefore, sensing and monitoring VOC levels is essential in air quality monitoring and industrial production processes.

[0003] In recent years, the sensor field has seen significant growth, driven by the rapid development of the Internet of Things. Thin-film-based fluorescence sensors, in particular, have garnered increasing attention due to their rich signal acquisition capabilities, high sensitivity, and ability to detect in situ and online. They have already played a crucial role in the detection of explosives, chemical warfare agents, addictive drugs, and volatile organic compounds. The core of thin-film-based fluorescence sensing lies in the creation of thin-film materials. The design and synthesis of fluorescent species, the preparation strategy for thin-film materials, and the choice of film substrate all play a crucial role in the development of high-performance thin-film materials.

[0004] With the growing demand for complex sample detection, multi-parameter, high-throughput detection has greatly increased the difficulty of designing and synthesizing sensor units. To achieve efficient and differentiated detection of multiple analytes while minimizing the synthesis difficulty, it is necessary to design fluorescent molecules with extremely sensitive excited states and diverse detection parameters. Fluoroboron dipyrrolidines substituted with 2,6-position electron donors have shown promise for multi-parameter, high-throughput detection due to their high molar extinction coefficients, large Stokes shifts, and sensitivity to the excited-state microenvironment. However, these molecules are prone to aggregation-induced quenching in the solid state, which affects the sensing performance of fluorescent films. Summary of the Invention

[0005] In view of the shortcomings of current technology, the purpose of the present invention is to provide a donor-acceptor type fluoroboron dipyrrolidine fluorescent compound and its preparation method, as well as a co-assembled fluorescent sensing film prepared based on the compound and its application in sensing and detecting volatile organic compounds.

[0006] To achieve the purpose of this invention, the molecular structure of the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound used in the present invention is as follows:

[0007]

[0008] The preparation method of the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound comprises the following steps:

[0009] Step 1: Adding a compound of Formula I and L-phenylalanine cholesteryl ester primary amine to an organic solvent, reacting under the catalysis of 4-dimethylaminopyridine and in the presence of a dehydrating agent to produce a compound of Formula II; the dehydrating agent is dicyclohexylcarbodiimide or 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride;

[0010] The structural formula of the compound of formula I is as follows:

[0011]

[0012] The structural formula of the L-phenylalanine cholesterol ester primary amine is as follows:

[0013]

[0014] The structural formula of the compound of formula II is as follows:

[0015]

[0016] Step 2: Under N2 protection, the compound of formula II is added to the reaction solvent, and under the alkaline conditions provided by anhydrous potassium carbonate and the catalysis of triphenylphosphine palladium, a Suzuki coupling reaction is carried out with 4-(diphenylamino)phenylboronic acid to obtain a donor-acceptor type fluoroborane dipyrrolidine fluorescent compound.

[0017] In the above step 1, the molar ratio of the compound of formula I to L-phenylalanine cholesterol ester primary amine, dehydrating agent, and 4-dimethylaminopyridine is preferably 1:1.5-2.5:1-2:0.1-0.5.

[0018] In the above step 1, it is preferred to first react in an ice bath for 0.5 to 1 h, and then react at 20 to 40° C. for 16 to 24 h.

[0019] In the above step 1, the organic solvent is preferably any one of dichloromethane, tetrahydrofuran, and N,N-dimethylformamide.

[0020] In the above step 2, the molar ratio of the compound of formula II to 4-(diphenylamino)phenylboronic acid, anhydrous potassium carbonate, and triphenylphosphine palladium is preferably 1:3-4:10-20:0.15-0.3.

[0021] In the above step 2, the Suzuki coupling reaction is preferably carried out at the reflux temperature of the reaction solvent for 18 to 24 hours; the reaction solvent is a mixed solvent of 1,4-dioxane and water or a mixed solvent of tetrahydrofuran and water, and the volume ratio of 1,4-dioxane or tetrahydrofuran to water in the mixed solvent is 1:0.02 to 0.04.

[0022] The co-assembled fluorescent sensing film provided by the present invention is prepared by mixing the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound and the dicholesterol compound in a solvent at a molar ratio of 1:35 to 50 to form a gel precursor solution, uniformly coating the gel precursor solution on a clean glass substrate surface, and drying to form a film with a nanofiber structure; wherein the dicholesterol compound has the following structural formula:

[0023]

[0024] In the gel precursor solution, the concentration of the dicholesterol compound is preferably 4 to 25 mg / mL, and the concentration of the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound is preferably 200 to 800 mM.

[0025] In the gel precursor solution, it is further preferred that the concentration of the dicholesterol compound is 15 to 25 mg / mL, and the concentration of the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound is 300 to 600 mM.

[0026] The solvent used to form the gel precursor solution is any one of toluene, chloroform and benzene.

[0027] The co-assembled fluorescent sensor film of the present invention can be used to detect volatile organic compounds, wherein the volatile organic compounds include any one of n-pentane gas, n-hexane gas, n-heptane gas, chloroform gas, tetrahydrofuran gas, acetone gas, acetonitrile gas, etc. The specific detection method is as follows: (1) placing the co-assembled fluorescent sensor film in air without volatile organic compounds, using a sensing platform to measure the fluorescence emission intensity I0 of the sensor film, then placing the co-assembled fluorescent sensor film in volatile organic compounds of different concentrations, using the sensing platform to measure the fluorescence emission intensity I corresponding to the different concentration systems, and drawing a standard curve of I-I0 value changing with gas concentration; wherein the emission wavelength of the sensing unit is 520nm, and the central wavelength of the detection light source is 630nm; (2) using the co-assembled fluorescent sensor film according to the method (1) to measure the fluorescence emission intensity of the gas to be measured, and combining the linear equation of the standard curve to achieve qualitative and quantitative detection of the gas to be measured.

[0028] Compared with the existing technology, the present invention has the following beneficial effects:

[0029] 1. This invention synthesizes a donor-acceptor type fluoroboron dipyrrolidine fluorescent compound containing assembly units, using a fluoroboron dipyrrolidine main molecule as an electron acceptor and luminescent unit, a 2,6-substituted triphenylamine as an electron donor, and an 8-modified cholesterol fragment as an assembly unit. The molecule undergoes intramolecular charge transfer in the excited state, significantly broadening the Stokes shift and promising thin-film device implementation. Furthermore, the non-planar propeller-like structure of triphenylamine reduces the degree of close packing during molecular aggregation. The introduction of a dicholesterol compound into the co-assembly process simultaneously orderly arranges the fluorescent molecules and minimizes aggregation-induced quenching, resulting in a co-assembled fluorescent sensing film with high luminescence efficiency and a large specific surface area.

[0030] 2. The nanofiber fluorescent sensing film constructed by co-assembling the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound with the dicholesterol compound of the present invention has a large specific surface area and high porosity. At the same time, the utilization rate of the fluorescent species is high, which improves the gas mass transfer efficiency. Therefore, the prepared co-assembled fluorescent sensing film has good stability, fast response speed, long service life, and the detection limit of the detected gas is far lower than the concentration that threatens human life and health.

[0031] 3. Based on the microenvironment-sensitive properties of the excited state of the fluoroboron dipyrrolidine fluorescent compound in the co-assembled fluorescent sensing film, the present invention realizes multi-analyte pattern recognition of the thin film sensor and uses a single fluorescent species to perform high-throughput detection of seven toxic and harmful gases, including n-pentane, n-hexane, n-heptane, chloroform, tetrahydrofuran, acetone and acetonitrile. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 1 is the ultraviolet absorption spectrum of the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound in Example 1 in solvents of different polarities.

[0033] Figure 2 1 is the fluorescence emission spectrum of the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound in Example 1 in solvents of different polarities.

[0034] Figure 3 This is the SEM image test of the co-assembled fluorescent sensing film in Example 2.

[0035] Figure 4 1 is a comparison of the fluorescence emission spectra of the co-assembled fluorescence sensing film and the solid-state fluorescence sensing film in Example 2.

[0036] Figure 5 The stability of the co-assembled fluorescent sensing film in sensing test 1.

[0037] Figure 6 It is the signal change of the co-assembled fluorescent sensing film in response to different gases in sensing test 2.

[0038] Figure 7 This is the principal component analysis of seven volatile organic compounds by the co-assembled fluorescent sensing film in sensing test 3.

[0039] Figure 8 This is the detection limit test of n-pentane gas by the co-assembled fluorescent sensing film in sensing test 4.

[0040] Figure 9 This is the detection limit test of chloroform gas by the co-assembled fluorescent sensing film in sensing test 4.

[0041] Figure 10 The response recovery time test of the assembled fluorescent sensing film to n-pentane gas in the sensing test 5 is

[0042] Figure 11 This is the response recovery time test of the co-assembled fluorescent sensing film to chloroform gas in sensing test 5.

[0043] Figure 12 This is a 100-cycle test of n-pentane gas on the assembled fluorescent sensing film in sensing test 5.

[0044] Figure 13 This is a 100-cycle test of chloroform gas on the assembled fluorescent sensing film in sensing test 5. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further illustrated below by the accompanying drawings and examples. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0046] Example 1

[0047] Step 1: 0.453 g (0.73 mmol) of the compound of formula I was dissolved in 150 mL of dichloromethane (DCM), 0.151 g (0.73 mmol) of dicyclohexylcarbodiimide (DCC) and 0.009 g (0.073 mmol) of 4-dimethylaminopyridine (DMAP) were weighed and dissolved in 10 mL of dichloromethane and added to the above reaction system, and then 0.779 g (1.46 mmol) of L-phenylalanine cholesterol was added. The alcohol ester primary amine was stirred for 30 minutes under ice bath conditions and then continued to stir at room temperature for 20 hours. After the reaction was completed, the resulting mixture was filtered and the filtrate was washed twice with 0.01 mol / L hydrochloric acid (100 mL × 3), 0.01 mol / L sodium hydroxide aqueous solution (100 mL × 3) and ultrapure water (100 mL × 3), respectively. The dichloromethane layer was dried over anhydrous magnesium sulfate and the dichloromethane was removed by vacuum distillation to obtain a crude product. The crude product was obtained by filtration with a mixed solvent of dichloromethane and petroleum ether (V 二氯甲烷 ∶V 石油醚=5:1) as the mobile phase and silica gel as the stationary phase for column chromatography to purify the crude product. The red solid obtained after vacuum drying is the compound of formula II with a yield of 50%.

[0048]

[0049] The obtained compound of formula II 1 H NMR δ H (600MHz, CDCl3, Me4Si): 7.84-7.86 (d, 2H, phenyl ring), 7.28-7.30 (d, 2H, phenyl ring) ring), 7.23-7.31 (m, 5H, benzyl), 6.31-6.33 (d, 1H, NH), 5.34 (s, 1H, alkenyl), 4.99-5.03 (m, 1H, CONH), 4.59-4.63 (m, 1H, CH2), 3. 21-3.24(m, 2H, CH2(C6H5)), 2.58(s, 6H, CCH3), 1.29(s, 6H, CCH3), 0.62-2.31(m, 43H, cholesterylprotons); mass spectrum MALDI-TOF-MS, molecular formula C 56 H 70 BF2I2N3O3, theoretical value: 1136.3568 ([M+H] + ); experimental value: 1136.3637([M+H] + ).

[0050] Step 2: After 50 mL of 1,4-dioxane was deoxygenated with N2 for 30 min, 0.341 g (0.3 mmol) of compound II, 0.347 g (1.2 mmol) of 4-(diphenylamino)phenylboronic acid, 0.829 g (6.0 mmol) of anhydrous potassium carbonate, 0.087 g (0.075 mmol) of triphenylphosphine palladium, and 2 mL of ultrapure water were added in sequence. The mixture was heated under reflux at 110°C for 24 h to stop the reaction. 1,4-dioxane was removed by distillation under reduced pressure, and the mixture was dissolved in 80 mL of dichloromethane and washed with ultrapure water (100 mL×3). The organic phase was dried over anhydrous sodium sulfate and dichloromethane was removed by distillation under reduced pressure to obtain a crude product. A mixed solvent of ethyl acetate and petroleum ether was used as the mobile phase (V 乙酸乙酯 ∶V 石油醚 =1:7), and the crude product was purified by column chromatography using silica gel as the stationary phase, and dried in vacuo to obtain a purple solid, i.e., a donor-acceptor type fluoroboron dipyrrolidine fluorescent compound, with a yield of 33%.

[0051]

[0052] The nuclear magnetic resonance of the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound 1 H NMR δ H (600MHz, CD2Cl2, Me4Si): 7.92-7.93(d, 2H, phenyl ring), 7.52-7.53(d, 2H, phenyl ring) ring), 7.06-7.35 (m, 33H, benzyl, triphenylamine), 6.71-6.73 (d, 1H, NH), 5.44 (s, 1H, alkenyl), 5.02-5.05 (m, 1H, CONH), 4.64-4.70(m,1H,CH2), 3.25-3.33(m,2H,CH2(C6H5)), 2.57(s,6H,CCH3), 1.24(s,6H,CCH3), 0.73-2.41(43H,m,cholesteryl protons); mass spectrometry MALDI-TOF-MS, molecular formula C 92 H 98 BF2N5O3, theoretical value: 1370.7731 ([M+H] + ); experimental value: 1370.7818 ([M+H] + ).

[0053] The donor-acceptor type fluoroboron dipyrrolidine fluorescent compound was added to organic solvents of different polarities to prepare dilute solutions with a concentration of 10 μM. The UV-visible absorption spectra of the different solvents were collected using a U-3900 UV spectrophotometer at room temperature. Figure 1 As shown in the figure, the maximum absorption peaks of the compound in solvents of different polarities are all around 540nm, and the solvent properties have little effect on the compound's ultraviolet absorption spectrum, that is, the ground state properties of the compound are basically not affected by the solvent polarity.

[0054] Subsequently, the fluorescence emission spectra of the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound in different solvents were tested using an FLS980 single-photon counting time-resolved fluorescence spectrometer with 520 nm as the excitation light source, such as Figure 2 As shown in the figure, the luminescence properties of this compound have a significant solvent effect. As the solvent polarity increases, the Stokes shift is continuously broadened, indicating that the solvent polarity can regulate its excited state to the intramolecular charge transfer state.

[0055] Example 2

[0056] Preparation of co-assembled fluorescent sensing film

[0057] 0.68 mg (0.5 μmol) of donor-acceptor type fluoroboron dipyrrolidine fluorescent compound and 25 mg (23.2 μmol) of dicholesterol compound were added to 1 mL of toluene and heated for 10 min to dissolve the dicholesterol compound to form a gel precursor solution; 20 μL of the gel precursor solution was evenly coated on the surface of a clean glass substrate, dried in an oven at 50°C for 12 h, taken out to obtain a co-assembled fluorescent sensing film, and sealed for later use.

[0058] In addition, 20 μL of a 500 μmol / L toluene solution of a donor-acceptor type fluoroboron dipyrrolidine fluorescent compound was transferred and evenly dropped onto the surface of a clean glass substrate. The film was dried in an oven at 50°C for 12 h, and then taken out to obtain a solid fluorescent film as a control film, which was then sealed for later use.

[0059] The co-assembled fluorescent sensing film was characterized by SEM morphology, such as Figure 3 As shown in the figure, the microstructure of the co-assembled fluorescent sensing film is a network structure of fibers with a diameter of about 300 nm, indicating that the film material has a large specific surface area and porosity, and the utilization rate of the fluorescent species is extremely high.

[0060] At room temperature, with 520 nm as the excitation light source, the fluorescence emission spectra of the co-assembled fluorescent sensing film and the solid-state fluorescent film were measured using an FLS980 single-photon counting time-resolved fluorescence spectrometer. Figure 4 As shown in the figure, the fluorescence intensity of the co-assembled fluorescent sensing film is stronger than that of the solid-state fluorescent film, indicating that co-assembly can avoid fluorescence quenching of molecules in the aggregated state, and the film has good luminescence efficiency.

[0061] The above co-assembled fluorescent sensing film was subjected to a sensing test, as follows:

[0062] Sensing test 1: The co-assembled fluorescent sensing film was placed in air without the analyte and irradiated continuously for 12 hours under the sensor device with 520nm as the excitation light source to explore the photostability of the film. The results are as follows: Figure 5 As shown in the figure, after continuous irradiation for 12 hours, the fluorescence intensity of the film only decreased by 3.6%, indicating that the film material has good light stability.

[0063] Sensing test 2: Place the co-assembled fluorescent sensing film in air without the analyte to be analyzed and test its fluorescence spectrum. Then place the co-assembled fluorescent sensing film in the saturated vapor of n-pentane, n-hexane, n-heptane, chloroform, tetrahydrofuran, acetone and acetonitrile respectively. After 30 minutes, test the changed fluorescence spectrum and plot the changes in fluorescence intensity and emission peak position. The results are shown in the figure. Figure 6As shown in the figure, the non-polar gases n-pentane, n-hexane, and n-heptane have a sensitizing effect on the fluorescence intensity of the co-assembled fluorescent sensing film, and the spectrum is blue-shifted; while the polar gases chloroform, tetrahydrofuran, acetone, and acetonitrile have a quenching effect on its fluorescence intensity, and the spectrum is red-shifted.

[0064] Sensing test 3: Based on the fluorescence intensity of the co-assembled fluorescent sensor film under different analytes, the change value of the fluorescence emission position, and the response time of the co-assembled fluorescent sensor film to different analytes, the principal component analysis was performed. The results are as follows: Figure 7 As shown in the figure, each type of dot represents an analyte. As can be seen from the figure, dots of different shapes can be well distinguished, indicating that the co-assembled fluorescent sensing film can well distinguish seven toxic and harmful gases from the two dimensions of sensing thermodynamics and kinetics.

[0065] Sensing test 4: Place the co-assembled fluorescent sensor film in air without the analyte to test its fluorescence emission intensity I0. Then place the co-assembled fluorescent sensor film in different concentrations of the analyte vapor to test the fluorescence emission intensity I at different concentrations. Taking n-pentane and chloroform as examples, multiple measurements are made and a scatter plot of the fluorescence intensity change value I-I0 versus concentration is drawn. The results are shown in the figure. Figure 8 Figure 9 The inset shows the linear relationship between fluorescence intensity change and concentration in the low-concentration range. The figure shows that the detection limits of the co-assembled fluorescent sensing film for n-pentane and chloroform are 758 ppm and 259 ppm, respectively, both far below the concentrations that immediately threaten life and health (1500 ppm for n-pentane and 500 ppm for chloroform).

[0066] Sensing Test 5: The co-assembled fluorescent sensor film was placed in air without the analyte and its fluorescence emission intensity, I0, was measured. The co-assembled fluorescent sensor film was then placed in saturated n-pentane or chloroform vapor. When the fluorescence intensity, I, ceased to change, the analyte was removed. The fluorescence intensity of the co-assembled fluorescent sensor film gradually recovered, completing one test cycle when it ceased to change. The time it took for the film's response intensity to decrease from the initial intensity, I0, to 90.0% of the maximum response intensity was recorded as the film's response time to the analyte; the time it took for the signal to decrease from the maximum response intensity to 90.0% was recorded as the film's recovery time to the analyte. Figure 10 、 Figure 11The response and recovery time of the co-assembled fluorescent sensor film to n-pentane and chloroform gas are shown in the figure. As can be seen from the figure, the film's response time to n-pentane gas is only 3.3s, and the recovery time is only 27.6s. Similarly, the response time to chloroform gas is only 8.1s, and the recovery time is only 19.9s, indicating that the film has a very fast response speed. Repeat the above operation and perform 100 test cycles on the co-assembled fluorescent sensor film. The test results for n-pentane and chloroform are shown in the figure. Figure 12 、 13 The results show that the film has no performance degradation after being used 100 times, indicating that the film has good reversibility.

Claims

1. A donor-acceptor type fluoroborane dipyrrolidine fluorescent compound, characterized in that The molecular structure of the fluorescent compound is shown below: 。 2. A method for preparing the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound according to claim 1, characterized in that The steps include: Step 1: Adding a compound of Formula I and L-phenylalanine cholesteryl ester primary amine to an organic solvent, reacting them under the catalysis of 4-dimethylaminopyridine and in the presence of a dehydrating agent to produce a compound of Formula II; the dehydrating agent is dicyclohexylcarbodiimide or 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride; The structural formula of the compound of formula I is as follows: The structural formula of the L-phenylalanine cholesterol ester primary amine is as follows: The structural formula of the compound of formula II is as follows: Step 2: Under N2 protection, add the compound of formula II to the reaction solvent and carry out a Suzuki coupling reaction with 4-(diphenylamino)phenylboronic acid under the alkaline conditions provided by anhydrous potassium carbonate and the catalysis of triphenylphosphine palladium to obtain a donor-acceptor type fluoroboranedipyrrolidine fluorescent compound.

3. The method for preparing the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound according to claim 2, wherein: In step 1, the molar ratio of the compound of formula I to L-phenylalanine cholesterol ester primary amine, dehydrating agent, and 4-dimethylaminopyridine is 1:1.5-2.5:1-2:0.1-0.5; the reaction is first carried out in an ice bath for 0.5-1 h, and then at 20-40°C for 16-24 h; the organic solvent is any one of dichloromethane, tetrahydrofuran, and N,N-dimethylformamide.

4. The method for preparing the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound according to claim 2, wherein: In step 2, the molar ratio of the compound of formula II to 4-(diphenylamino)phenylboronic acid, anhydrous potassium carbonate, and triphenylphosphine palladium is 1:3-4:10-20:0.15-0.3; the Suzuki coupling reaction is carried out at the reflux temperature of the reaction solvent for 18-24 hours; the reaction solvent is a mixed solvent of 1,4-dioxane and water or a mixed solvent of tetrahydrofuran and water, and the volume ratio of 1,4-dioxane or tetrahydrofuran to water in the mixed solvent is 1:0.02-0.

04.

5. A co-assembled fluorescent sensing film for detecting volatile organic compounds, characterized by: The donor-acceptor type fluoroboron dipyrrolidine fluorescent compound according to claim 1 and the dicholesterol compound are mixed in a solvent at a molar ratio of 1:35-50 to form a gel precursor solution, the gel precursor solution is evenly coated on the surface of a clean glass substrate, and dried to obtain a co-assembled fluorescent sensing film with a nanofiber structure; The structural formula of the dicholesterol compound is as follows: The concentration of the dicholesterol compound in the gel precursor solution is 4 to 25 mg / mL, and the concentration of the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound is 200 to 800 mM; The solvent is any one of toluene, chloroform and benzene.

6. The co-assembled fluorescent sensing film for detecting volatile organic compounds according to claim 5, characterized in that: The concentration of the dicholesterol compound in the gel precursor solution is 15-25 mg / mL, and the concentration of the donor-acceptor type fluoroboron dipyrrolidine fluorescent compound is 300-600 mM.

7. Use of the co-assembled fluorescent sensor film according to claim 5 in detecting volatile organic compounds, wherein the volatile organic compound is any one of n-pentane gas, n-hexane gas, n-heptane gas, chloroform gas, tetrahydrofuran gas, acetone gas, and acetonitrile gas.

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