Naphthalimide fluorescent probe as well as preparation method and application thereof

Abstract

The invention relates to a naphthalimide fluorescent probe as well as a preparation method and application thereof, the chemical name of the naphthalimide fluorescent probe is 2-butyl-1, 3-dioxo-5-(thiophenyl)-2, 3-dihydro-1H-benzo [de] isoquinoline-6-formamide, and the structural formula of the naphthalimide fluorescent probe is as follows: 1, 3-dioxo-5-(thiophenyl)-2, 3-dihydro-1H-benzo [de] isoquinoline-6-formamide.

Description

Technical Field

[0001] This invention relates to the field of hypochlorous acid detection, and in particular to a naphthimide fluorescent probe, its preparation method, and its application. Background Technology

[0002] As an emerging analytical tool, fluorescent molecular probes exhibit significant technical advantages over traditional detection methods, such as high sensitivity, excellent selectivity, real-time dynamic monitoring capabilities, in-situ visualization, high spatiotemporal resolution, and good biocompatibility, making them a research hotspot in this field.

[0003] hypochlorous acid (ClO) - ClO₂, as a highly oxidizing reactive oxygen species (ROS), plays an indispensable role in living organisms. It is mainly generated by the reaction of hydrogen peroxide and chloride ions catalyzed by myeloperoxidase (MPO) and is widely involved in physiological processes such as immune defense and cell signaling. However, excessive ClO₂... - It can trigger a series of physiological diseases, such as rheumatoid arthritis, acute lung injury, atherosclerosis, cardiovascular disease, neurodegenerative diseases, Alzheimer's disease, and cancer. Furthermore, in daily life, hypochlorous acid (ClO₂)... - It also plays an important role in sterilization, disinfection, food preservation, and odor removal. ClO - As an important reactive oxygen species (H2O2, O2·) in the body - , 1 O2、·OH、ONOO - One of the key technologies is to accurately detect changes in hypochlorous acid concentration. This not only helps to reveal the mechanism of action of hypochlorous acid in physiological and pathological processes, but also provides new ideas and methods for the early diagnosis and treatment of related diseases.

[0004] In summary, the development of novel ClO₂ with high specificity and excellent biocompatibility is crucial. - Fluorescent probes have become a research hotspot in fields such as environmental monitoring and medical diagnosis. Summary of the Invention

[0005] To solve the above technical problems and achieve the control of ClO - To address the shortcomings of existing technologies, such as cumbersome synthesis steps and harsh reaction conditions, this application discloses a naphthimide-based fluorescent probe, chemically named 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide, with the following structural formula:

[0006]

[0007] According to another aspect of this application, this application provides a method for preparing the naphthalimide fluorescent probe as described above, the method comprising the following steps:

[0008] S101, using N-butyl-3-nitro-4-cyano-1,8-naphthioimide as the starting material, was dissolved together with sodium thiophene in the first solvent. Under a nitrogen atmosphere, triethylamine was added to the reaction system, and the reaction mixture was placed in an oil bath and stirred continuously. After the reaction was terminated, a yellow solid 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile was finally obtained.

[0009] In step S102, 2-Butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile was dissolved in a second mixed solvent, and potassium hydroxide was added. The reaction solution was heated to strong reflux under a nitrogen atmosphere. After the reaction was completed, a light yellow solid, 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide, was finally obtained.

[0010] In a preferred embodiment, the molar volume ratio of N-butyl-3-nitro-4-cyano-1,8-naphthalimide, sodium thiophene, triethylamine and the first solvent in step S101 is (1-3) mmol:(3-5) mmol:(1-3) mmol:(30-50 ml).

[0011] In a preferred embodiment, the molar volume ratio of 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile, potassium hydroxide, and the first solvent in step S102 is (1-3) mmol:(20-22) mmol:(10-20 ml).

[0012] In a preferred embodiment, the preparation method satisfies at least one of the following conditions:

[0013] The reaction time described in step S101 is 4 hours;

[0014] The reaction temperature in step S101 is 50℃;

[0015] The reaction time described in step S102 is 4 hours;

[0016] The reaction temperature in step S102 is 110℃.

[0017] One use of the naphthalimide fluorescent probe as described above, wherein the naphthalimide fluorescent probe is used to detect hypochlorous acid in an aqueous solution.

[0018] Furthermore, the fluorescent probe was dissolved in a DMF:H2O (7:3) solution to test hypochlorous acid.

[0019] It is worth mentioning that the fluorescent probe in this application uses naphthalimide as the fluorophore and phenyl sulfide as the reaction moiety. The study investigated the effects of adding different ClO groups to the fluorescent probe under the conditions of a DMF:H2O (7:3) buffer solution as the solvent. - The UV absorption spectrum at the specified concentration shows a maximum absorption peak at 393 nm. After the addition of hypochlorous acid, a new absorption peak appears at 428 nm (redshifted by 35 nm). In the fluorescence spectrum, due to the PET effect of the sulfur atom of the thioether towards the naphthaleneimide fluorophore, the probe itself initially does not exhibit fluorescence, but reacts with ClO... - After the reaction, ClO - Disruption of the NH···S hydrogen bond (IHB) interaction and the generation of a sulfoxide moiety with enhanced electron-withdrawing ability leads to inhibition of the photoinduced electron transfer (PET) process, triggering an "on" response and a significant increase in fluorescence intensity at 550 nm. The addition of other anions does not significantly change the fluorescence spectrum of this fluorescent probe. In the presence of interference from other ions, the addition of ClO... - Even after that, there is still a significant fluorescence intensity at 550 nm, almost unaffected by other ions.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The fluorophore of this fluorescent probe has not been designed to recognize hypochlorous acid, and the compound is relatively novel;

[0022] (2) The probe has good specificity, mainly because only hypochlorous acid can oxidize sulfide, thereby causing changes in optical signal.

[0023] It is worth mentioning that naphthalimide is a recognized high-quality fluorophore in the field of two-photon microscopy (TPM) due to its excellent photophysical properties (including a large Stokes shift, high molar extinction coefficient, and excellent photostability), which has made it highly favored by researchers. However, the small conjugated surface of the naphthalimide fluorophore, short excitation wavelength, and small Stokes shift result in poor recognition performance as a fluorescent probe for analyte detection, preventing its direct application in practical applications. By molecularly modifying the structure of naphthalimide, a series of naphthalimide-based fluorescent probes were designed. An intramolecular amide NH···S (thioether) hydrogen bond regulation system was constructed at the ortho position of the fluorophore and recognition site, successfully synthesizing probes with an intramolecular hydrogen bond regulation mechanism, resulting in excellent fluorescence optical properties. Attached Figure Description

[0024] Figure 1The image shows the UV-Vis spectra of the fluorescent probe in Example 1 with different ClO- concentrations added to a DMF:H2O (7:3) solution; the inset shows: photographs of the probe (left) and probe + ClO- (right); and a schematic diagram of the linear relationship between the UV absorption intensity ratio (A347 / A428) of the probe and ClO- concentrations (0-32.0 equiv.).

[0025] Figure 2 The fluorescence emission spectra of the fluorescent probe in Example 1 with different ClO- concentrations added to the DMF:H2O (7:3) solution are shown; inset: photographs of the probe (left) and probe + ClO- (right); schematic diagram of the linear relationship between the fluorescence intensity of the probe and the ClO- concentration (0-32.0 equiv.).

[0026] Figure 3 The curves show the relationship between fluorescence intensity and ClO- (150-200 μM) concentration.

[0027] Figure 4 The fluorescent emission spectra of the fluorescent probe in Example 1 when different anions are added to the DMF:H2O (7:3) solution are shown in the inset. The inset shows the fluorescence changes of the probe solution containing different anions under UV light (365nm) irradiation.

[0028] Figure 5 The bar chart shows the fluorescence emission changes at 538 nm of the fluorescent probe in Example 1 when different anions were added to DMF:H2O (7:3) and when it coexisted with other anions, in response to ClO-. This indicates that other anions do not interfere with the response of hypochlorous acid. Detailed Implementation

[0029] The preferred embodiments described below are merely examples, and other obvious variations will be apparent to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0030] A preferred embodiment of the present application of a naphthalimide-based fluorescent probe molecule will be described in detail below, wherein the structural formula of the fluorescent probe for detecting hypochlorous acid is:

[0031]

[0032] Example 1

[0033] The synthesis of the naphthimide fluorescent probe molecules in this application uses N-butyl-3-nitro-4-cyano-1,8-naphthimide as a starting material, obtained through nucleophilic substitution and hydrolysis. The synthetic method includes the following steps:

[0034] S1: Synthesis of 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile; specifically, in one embodiment, S1 comprises:

[0035] Starting with N-butyl-3-nitro-4-cyano-1,8-naphthalimide (1.00 g, 1.0 equiv), it was dissolved together with sodium thiophene (3.0 equiv) in 30 mL of ultra-dry N,N-dimethylformamide (DMF). Under a nitrogen atmosphere, triethylamine (0.31 g, 1.0 equiv) was added to the reaction system, and the reaction mixture was then placed in an oil bath at 50 °C and stirred continuously for 4 h. After the reaction was terminated, the reaction solution was slowly poured into 500 mL of deionized water, precipitating a yellow solid. The solid was collected by vacuum filtration and further purified by silica gel column chromatography (eluent: PE:EA = 5:1, v / v) to finally obtain the yellow solid 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile. The first solvent was N,N-dimethylformamide.

[0036] The yellow solid product obtained above was measured using a nuclear magnetic resonance instrument (Quantum-IPlus 400MHz), and the data are shown below:

[0037] 1 H NMR (400MHz, CDCl3) δ [ppm]: 8.57 (d, J = 7.2Hz, 1H), 8.47 (d, J = 8.4Hz, 1H), 8.12 (s, 1H), 7.91 (dd, J1 = J2 = 8.0Hz, 1H), 7.6 1-7.59(m,2H),7.50–7.49(m,3H),4.08(t,J=7.6Hz,2H),1.65-1.59(m,2H),1.41-1.36(m,2H),0.93(t,J1=7.4Hz,3H). 13 CNMR(101MHz, CDCl3)δ[ppm]:162.9,162.3,146.0,134.6,132.0,131.1,130.2,130.1,130.1,129.6 129.4,129.2,125.7,125.4,123.0,114.5,111.6,40.5,29.9,20.1,13.6.HRMS-ESI(m / z):[M+H] + Calcd.for(C 23 H 18 N2O2S):387.1167; Found:387.1165.

[0038] Analysis of the nuclear magnetic resonance spectroscopy data of the yellow solid product obtained above showed that the yellow solid product obtained above is 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile.

[0039] The synthesis method further includes: S2: synthesis of 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide; in one embodiment, step S2 includes:

[0040] 1 g of 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile (1.0 equiv) was dissolved in an ethanol-water mixture (10 mL, 1:1, v / v), and potassium hydroxide (20.0 equiv) was added. The reaction mixture was magnetically stirred at 110 °C for 4 h under a nitrogen atmosphere. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and 50 mL of 3M hydrochloric acid solution was slowly added for acidification. A yellow solid was observed to precipitate at this point. The precipitate was collected by Buchner funnel filtration, and the crude product was purified by silica gel column chromatography (eluent: DCM:MeOH = 100:1, v / v) to finally obtain a light yellow solid, 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide; the second solvent was ethanol and water; the obtained light yellow solid product was analyzed by nuclear magnetic resonance (NMR) instrument (Quantum-IPlus 400MHz), and the data are shown below:

[0041] 1 H NMR (400MHz, DMSO-d6) δ [ppm]: 8.49 (d, J = 7.6Hz, 1H), 8.39 (s, NH), 8.26 (d, J = 8.4Hz, 1H), 8.21 (s, NH), 8.07 (s, 1H), 7.95 (dd, J1 = 7.6Hz, J 2=8.0Hz,1H),7.54–7.51(m,2H),7.48–7.40(m,3H),3.97(t,J1=7.4Hz,2H),1.60-1.53(m,2H),1.35-1.26(m,2H),0.89(t,J=7.2Hz,3H). 13C NMR(101MHz,DMSO-d6)δ[ppm]:167.5,163.1,162.5,142.4,133.5,132.4,132.1,131.6,131.5,1 30.7,129.9,128.7,128.5,128.4,126.0,122.8,122.3,29.5,19.8,13.7.HRMS-ESI(m / z):[M+H] + Calcd.for(C 23 H 20 N2O3S):405.1273; Found:405.1266.

[0042] Analysis of the nuclear magnetic resonance (NMR) spectra of the obtained light yellow solid product showed that the obtained light yellow solid product was 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide.

[0043] Exemplary naphthalimide fluorescent probes for anion recognition performance

[0044] 1. Fluorescent probe titration experiment of hypochlorous acid

[0045] The fluorescent probe was dissolved in N,N-dimethylformamide to prepare a solution of 5000 μmol·L⁻¹. -1 The stock solution was prepared in N,N-dimethylformamide to form ClO - Stock solution, concentration 50000 μmol·L -1 Measure 100 μL of 5000 μmol·L⁻¹ -1 The fluorescent probe solution was placed in a 25 mL volumetric flask and diluted to 25 mL with N,N-dimethylformamide solution to prepare a 25 mL, 20 μmol·L⁻¹ solution. -1 Fluorescent probe solution in N,N-dimethylformamide solvent.

[0046] Titration experiment: 25 mL of 20 μmol·L⁻¹ solution was added. -1 The probe solution in N,N-dimethylformamide solvent was poured into a 100 mL wide-mouth conical flask, with 10.0 μL of 50000 μmol·L⁻¹ added dropwise each time. -1 (1 equivalent) ClO - After shaking the solution until it is homogeneous, its UV-Vis and fluorescence emission spectra are measured. This operation is repeated until 32 equivalents of hypochlorous acid solution are added.

[0047] The results show that, Figure 1The UV-Vis spectrum of the fluorescent probe is affected by the concentration of hypochlorous acid. As hypochlorous acid is gradually added, a new absorption peak appears at 428 nm (red shift 35 nm), and the solution color changes from colorless to yellow.

[0048] Next, its fluorescence spectrum was measured, such as... Figure 2 The fluorescence emission spectrum of the fluorescent probe is affected by the concentration of hypochlorous acid. With the gradual addition of hypochlorous acid, a significant bright green fluorescence signal is observed at 550 nm, until 30 equivalents of ClO are added. - When equilibrium is reached.

[0049] Titration experiment conclusion: Figure 3 The detection limit (LOD) of this probe is 4.9 nM, which is relatively low, indicating that the probe has high sensitivity for the detection of hypochlorous acid.

[0050] The aforementioned naphthalimide fluorescent probes are used to detect hypochlorous acid in aqueous solutions. During detection, the fluorescent probes are dissolved in N,N-dimethylformamide to test for hypochlorous acid.

[0051] 2. Selectivity study of fluorescent probes for hypochlorous acid

[0052] The fluorescent probe was prepared to a concentration of 20 μmol·L⁻¹ -1 A solution of N,N-dimethylformamide:water = 7:3 was prepared; F was prepared separately. – ,Cl – ,Br – ,I – P2O7 4- CN – NO3 – ,SH – H2PO4 – HSO4 – HSO3 – Ba 2+ Ca 2+ Mg 2+ ,K + Na + ,DTT,Cys,Hcy,GSH,H2O2,·OH,ONOO - And 5000 μmol·L of TBHP -1 A solution of N,N-dimethylformamide:water = 7:3 was prepared by measuring 0.8 mL of a 5000 μmol·L⁻¹ solution. -1 The fluorescent probe solution was prepared by diluting N,N-dimethylformamide and water to a final volume of 200 mL to obtain a 20 μmol·L⁻¹ solution. -1 The probe solution was divided into 25 groups (5 mL per group), and 32 equivalents (25 μL, 5000 μmol·L⁻¹) were added to each group. -1Various anion solutions were used to observe the response of fluorescent probes to various anions using fluorescence emission spectroscopy.

[0053] The results show that, Figure 4 As shown, only when ClO is added... - Only then will it activate its bright green fluorescence. For example... Figure 4 As shown, the fluorescent probe exhibits almost no fluorescence emission peak at 550 nm when N,N-dimethylformamide:water = 7:3 is used as the solvent. The addition of ClO... - Subsequently, the fluorescence emission peak at 550 nm was enhanced, while the addition of other anions did not significantly change the fluorescence emission peak of the fluorescent probe. This indicates that the fluorescent probe can specifically detect hypochlorous acid.

[0054] 3. Experimental study on the interference of other anions on hypochlorous acid

[0055] The above-prepared F – ,Cl – ,Br – ,I – P2O7 4- CN – NO3 – ,SH – H2PO4 – HSO4 – HSO3 – Ba 2+ Ca 2+ Mg 2+ ,K + Na + ,DTT,Cys,Hcy,GSH,H2O2,·OH,ONOO - And 5000 μmol·L of TBHP -1 The 25 solutions were observed by fluorescence emission spectroscopy, and then 32 equivalents (25 μL, 5000 μmol·L⁻¹) were added respectively. -1 The response of a fluorescent probe to hypochlorous acid in the presence of various anions was observed by fluorescence emission spectroscopy.

[0056] The results show that, Figure 5 As shown, when the fluorescent probe is used in a solvent of N,N-dimethylformamide:water = 7:3, the green bars indicate the presence of only F. – ,Cl – ,Br – ,I – P2O7 4- CN – NO3 – ,SH – H2PO4 –HSO4 – HSO3 – ,Ba 2+ Ca 2 + Mg 2+ ,K + Na + ,DTT,Cys,Hcy,GSH,H2O2,·OH,ONOO - And 5000 μmol·L of TBHP -1 Emission at 538 nm for anions. The yellow bar indicates the change that occurred upon subsequent addition of 32 equivalents of hypochlorous acid. This is derived from the emission at F... – ,Cl – ,Br – ,I – P2O7 4- CN – NO3 – ,SH – H2PO4 – HSO4 – HSO3 – Ba 2+ Ca 2+ Mg 2+ ,K + Na + ,DTT,Cys,Hcy,GSH,H2O2,·OH,ONOO - And 5000 μmol·L of TBHP -1 In the presence of anions, the interference with the detection of hypochlorous acid by the fluorescent probe in an N,N-dimethylformamide:water = 7:3 solution is minimal, with almost no effect.

[0057] Example 2

[0058] In another embodiment, this application provides a method for preparing a naphthalimide-based fluorescent probe, the method comprising the following steps:

[0059] S1: Synthesis of 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile; specifically, in one example, step S1 includes:

[0060] Starting with N-butyl-3-nitro-4-cyano-1,8-naphthalimide (1.00 g, 1.0 equiv), it was dissolved together with sodium thiophene (3.0 equiv) in an ultra-dry first solvent (30 mL). Under a nitrogen atmosphere, triethylamine (0.31 g, 1.0 equiv) was added to the reaction system, and the reaction mixture was then placed in an oil bath at 50 °C and stirred continuously for 4 h. After the reaction was terminated, the reaction solution was slowly poured into 500 mL of deionized water, precipitating a yellow solid. The solid was collected by vacuum filtration and further purified by silica gel column chromatography to give the product 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile (0.84 g, 70% yield), a yellow solid; the first solvent was N,N-dimethylformamide.

[0061] The preparation method of the naphthimide fluorescent probe further includes:

[0062] S2: Synthesis of 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide, specifically, in one embodiment, step S2 includes:

[0063] 2-Butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile (1 g, 1.0 equiv) was dissolved in a second solvent (10 mL, 1:1, v / v), and potassium hydroxide (20.0 equiv) was added. The reaction mixture was magnetically stirred at 110 °C for 4 h under a nitrogen atmosphere. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and 50 mL of 3M hydrochloric acid solution was slowly added for acidification. A yellow solid was observed to precipitate. The precipitate was collected by suction filtration using a Buchner funnel, and the crude product was purified by silica gel column chromatography to obtain 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide (0.74 g, 70% yield), which was a light yellow solid; the first solvent was ethanol and water.

[0064] Example 3

[0065] In yet another embodiment, this application provides a method for preparing a naphthalimide-based fluorescent probe, the method comprising the following steps:

[0066] S1: Synthesis of 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile, specifically in one example, step S1 includes:

[0067] Starting with N-butyl-3-nitro-4-cyano-1,8-naphthalimide (1.00 g, 1.0 equiv), it was dissolved together with sodium thiophene (3.0 equiv) in an ultra-dry first solvent (30 mL). Under a nitrogen atmosphere, triethylamine (0.31 g, 1.0 equiv) was added to the reaction system, and the reaction mixture was then placed in an oil bath at 50 °C and stirred continuously for 4 h. After the reaction was terminated, the reaction solution was slowly poured into 500 mL of deionized water, precipitating a yellow solid. The solid was collected by vacuum filtration and further purified by silica gel column chromatography to give the product 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile (0.84 g, 70% yield), a yellow solid; the first solvent was N,N-dimethylformamide.

[0068] The preparation method of the naphthalimide fluorescent probe further includes:

[0069] S2: Synthesis of 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide, specifically in another example, step S2 includes:

[0070] 2-Butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile (1 g, 1.0 equiv) was dissolved in a second solvent (10 mL, 1:1, v / v), and potassium hydroxide (20.0 equiv) was added. The reaction mixture was magnetically stirred at 110 °C for 4 h under a nitrogen atmosphere. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and 50 mL of 3M hydrochloric acid solution was slowly added for acidification. A yellow solid was observed to precipitate. The precipitate was collected by suction filtration using a Buchner funnel, and the crude product was purified by silica gel column chromatography to obtain 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide (0.74 g, yield 70%), a light yellow solid; the second solvent was ethanol and water.

[0071] The aforementioned naphthalimide fluorescent probes are used to detect hypochlorous acid in aqueous solutions. During detection, the fluorescent probes are dissolved in a DMF:H2O (7:3) solution to test for hypochlorous acid.

[0072] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A naphthalimide-based fluorescent probe, characterized in that, Its chemical name is 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide, and its structural formula is as follows:

2. A method for preparing a naphthalimide-based fluorescent probe, characterized in that, The method includes the following steps: S101, using N-butyl-3-nitro-4-cyano-1,8-naphthioimide as the starting material, was dissolved together with sodium thiophene in the first solvent. Under a nitrogen atmosphere, triethylamine was added to the reaction system, and the reaction mixture was placed in an oil bath and stirred continuously. After the reaction was terminated, a yellow solid 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile was finally obtained. In step S102, 2-Butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile was dissolved in a second mixed solvent, and potassium hydroxide was added. The reaction solution was heated to strong reflux under a nitrogen atmosphere. After the reaction was completed, a light yellow solid, 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxamide, was finally obtained.

3. The method for preparing the naphthalimide fluorescent probe according to claim 2, characterized in that, The molar volume ratio of N-butyl-3-nitro-4-cyano-1,8-naphthalimide, sodium thiophene, triethylamine and the first solvent in step S101 is (1-3) mmol: (3-5) mmol: (1-3) mmol: (30-50 ml).

4. The method for preparing the naphthalimide fluorescent probe according to claim 2, characterized in that, The molar volume ratio of 2-butyl-1,3-dioxo-5-(phenylthio)-2,3-dihydro-1H-benzo[de]isoquinoline-6-carboxynitrile, potassium hydroxide and the first solvent in step S102 is (1-3) mmol:(20-22) mmol:(10-20 ml).

5. The method for preparing the naphthalimide fluorescent probe according to claim 2, characterized in that, The preparation method satisfies at least one of the following conditions: The reaction time described in step S101 is 4 hours; The reaction temperature in step S101 is 50℃; The reaction time described in step S102 is 4 hours; The reaction temperature in step S102 is 110℃.

6. The use of a naphthalimide-based fluorescent probe as described above, characterized in that, The naphthalimide fluorescent probe is used to detect hypochlorous acid in aqueous solution.

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