A fluorescent probe and a preparation method and application thereof

Abstract

The application belongs to the field of detection, and specifically discloses a fluorescent probe, a preparation method and application thereof; the fluorescent probe comprises a compound shown in formula (I). 2+ The fluorescent probe has high sensitivity and selectivity, is not interfered by other metal ions, has a short detection time, can be detected within 30 min, can be detected completely within 30 s at most, can realize visual detection when applied to a test strip, and can be applied to the detection of Hg 2+ in environmental samples, such as actual water samples and soil samples.

Description

Technical Field

[0001] This invention belongs to the field of detection, specifically relating to a fluorescent probe, its preparation method, and its application. Background Technology

[0002] Mercury is a highly toxic, non-degradable metallic pollutant that poses a significant threat to biological and ecosystem systems. Traditional methods for detecting Hg... 2+ The main analytical methods include atomic absorption spectrometry, inductively coupled plasma mass spectrometry, and electrochemical detection. Compared with traditional detection methods, organic small molecule fluorescent probes have advantages such as structural diversity, good reproducibility, ease of modification, and clear sensing mechanisms.

[0003] Based on the relevant mechanisms of action, common small organic molecules such as Hg 2+ Fluorescent probes are generally classified into two categories: (1) fluorescent probes based on simple coordination without significant bond cleavage; and (2) fluorescent probes based on chemical reactions involving significant bond cleavage (such as C / S bonds, C=S bonds, etc.). Compared to the former, fluorescent probes based on chemical reactions are generally more effective against Hg. 2+ It exhibits better selectivity and higher sensitivity.

[0004] More and more Hg based on chemical reactions 2+ Fluorescent probes were designed, especially thioacetal Hg. 2+ Fluorescent probes. However, most thioacetal Hg 2+ Fluorescent probes tend to function better in organic solvents because in solutions with high water content, their aggregated state easily undergoes π-π stacking, leading to severe fluorescence attenuation or even quenching, i.e., aggregation-induced fluorescence quenching (ACQ). Clearly, this ACQ phenomenon is relevant for many real-world samples containing Hg. 2+ Monitoring is disadvantageous as it cannot accurately detect Hg in water-containing samples. 2+ content. Summary of the Invention

[0005] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide a fluorescent probe.

[0006] The second objective of this invention is to provide a method for preparing a fluorescent probe.

[0007] A third objective of this invention is to provide the application of the aforementioned fluorescent probe in the detection of mercury ions.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A first aspect of the present invention provides a fluorescent probe comprising a compound represented by formula (I),

[0010]

[0011] R1 is selected from

[0012] Each R2 is independently selected from C 1～5 Alkyl groups.

[0013] In some embodiments of the present invention, C 1～5 The alkyl group is selected from -CH3, -CH2CH3, -CH(CH3)2, -CH2CH2CH3, -CH2CH2CH2CH3, -CH2CH(CH3)2, -CH(CH3)CH2CH3, -C(CH3)3, -CH2CH2CH2C H2CH3, -CH2CH2CH(CH3)2, -CH2CH(CH3)CH2CH3, -CH(CH3)CH2CH2CH3, -C(CH3)2CH2CH3, -CH2C(CH3)3 or -CH(CH3)CH(CH3)2.

[0014] In some embodiments of the present invention, R1 is selected from...

[0015] In some embodiments of the present invention, each R2 is independently selected from C. 1～3 Alkyl groups.

[0016] In some embodiments of the present invention, the compound represented by formula (I) is selected from...

[0017] In some embodiments of the present invention, the fluorescent probe further includes a carrier.

[0018] In some embodiments of the present invention, the carrier includes at least one of filter paper and porous materials. In some embodiments of the present invention, the porous material is selected from at least one of sponge, activated carbon, and molecular sieve.

[0019] In some embodiments of the present invention, the fluorescent probe further includes a solvent.

[0020] In some embodiments of the present invention, the solvent includes water.

[0021] The second aspect of the present invention provides a method for preparing the fluorescent probe described in the first aspect of the present invention, comprising the following steps:

[0022] The N-(4-benzaldehyde)carbazole is prepared by reacting compound A or compound B.

[0023] The compound A is

[0024] Compound B is n is an integer selected from 2 to 5.

[0025] In some embodiments of the present invention, the reaction is carried out with the participation of elemental iodine.

[0026] In some embodiments of the present invention, the reaction is carried out in the presence of a solvent.

[0027] In some embodiments of the present invention, the reaction time is 1 to 24 hours.

[0028] The third aspect of the present invention provides the application of the fluorescent probe described in the first aspect of the present invention in the field of mercury ion detection.

[0029] The beneficial effects of this invention are: the fluorescent probe of this invention exhibits high brightness and stable fluorescence emission characteristics in the liquid state, and is effective against Hg. 2+ It possesses high sensitivity and selectivity, is unaffected by interference from other metal ions, and requires a short detection time, completing the test within 30 minutes, with the fastest detection taking approximately 30 seconds. When applied to test strips, it enables visual detection and can be used on environmental samples, such as actual water and soil samples, for detecting Hg. 2+ The detection.

[0030] The method for preparing the fluorescent probe in this invention has advantages such as simple synthesis, low environmental pollution, easy operation, wide availability of raw materials, and low cost. This method eliminates the need for expensive catalysts, customized reagents, and instruments; the reaction is easily controlled; the yield can reach over 70%; and the material structure is... 1 H NMR, 13 Verification was performed using analytical methods such as C NMR, HRMS, and X-ray single-crystal diffraction. Attached Figure Description

[0031] Figure 1 This is the X-ray single-crystal diffraction pattern of the fluorescent probe 4a in Example 1.

[0032] Figure 2 The image shows the fluorescence emission intensity test results of fluorescent probe 4a in Example 1 after the addition of different metal ions.

[0033] Figure 3 Hg was added to the aqueous solution of fluorescent probe 4a in Example 1. 2+ Fluorescence images before and after.

[0034] Figure 4 The image shows the fluorescence emission intensity test results of fluorescent probe 4b after the addition of different metal ions in Example 2.

[0035] Figure 5 Hg was added to the aqueous solution of fluorescent probe 4b in Example 2. 2+ Fluorescence images before and after.

[0036] Figure 6 The fluorescent probe 4a in Example 1 is used to target Hg. 2+ The response time test graph.

[0037] Figure 7 The fluorescent probe 4b in Example 2 is used to target Hg. 2+ The response time test graph.

[0038] Figure 8 Test paper loaded with fluorescent probe 4a from Example 1 for Hg 2+ The detection image.

[0039] Figure 9 The fluorescent probe 4a in Example 1 was used to detect Hg in an actual water sample. 2+ The image shows the test results.

[0040] Figure 10 The fluorescent probe 4a in Example 1 was used to detect Hg in soil samples. 2+ The image shows the test results. Detailed Implementation

[0041] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0042] Example 1

[0043] This example provides a fluorescent probe, denoted as 4a, with the following structural formula:

[0044]

[0045] The synthesis route of the fluorescent probe in this example is as follows:

[0046]

[0047] The synthesis steps of the fluorescent probe in this example are as follows:

[0048] Weigh 167.2 mg of carbazole 1 and 40.0 mg of sodium hydroxide and add them to a reaction flask. Add 15 mL of anhydrous N,N-dimethylformamide, heat with stirring, and then add 124.1 mg of 4-fluorobenzaldehyde 2. Stir the reaction mixture in an oil bath at 130 °C for 6 hours. Stop the reaction, cool to room temperature, pour the mixture into distilled water, and extract with ethyl acetate. Dry the organic layer with anhydrous magnesium sulfate and concentrate by vacuum evaporation. Purify the crude product by column chromatography using a mixture of petroleum and dichloromethane (3:1 v / v) as eluent to give a white solid crude product, which is recrystallized from anhydrous ethanol to give pure intermediate 3.

[0049] Weigh 67.8 mg of intermediate 3 and 5.0 mg of elemental iodine, add 20 mL of anhydrous dichloromethane, then add 106.1 mg of methyl mercaptoacetate. After stirring at room temperature for 4 hours, the reaction was terminated by continuously adding 15 mL of 0.1 mol / L Na₂S₂O₃ aqueous solution and 15 mL of NaOH solution (10% by mass). The mixture was then extracted with CH₂Cl₂, the organic layer was separated, dried over anhydrous Na₂SO₄, and concentrated under vacuum. The solution was then purified by column chromatography (eluent: petroleum ether / ethyl acetate, volume ratio = 10 / 1) to obtain a yellow oil. Recrystallization from CH₂Cl₂ and n-hexane yielded pale yellow crystals 4a with a melting point of mp = 76.3℃–76.6℃.

[0050] The structural formula and related characterization data of fluorescent probe 4a are shown below:

[0051]

[0052] 1 H NMR(600MHz,DMSO-d6),δ,ppm:3.48-3.62(dd,J1=15.0Hz,J2=15.0Hz,4H,CH2-20,CH2-23),3.63(s,6H,OCH3-22,25),5.46(s,1H,CH-19),7.29-7.32(m ,2H,ArH-4,9),7.47-7.40(m,4H,ArH-2,3,10,11),7.66(d,J=8.4Hz,2H,ArH -14,18),7.69(d,J=8.4Hz,2H,ArH-15,17),8.26(d,J=7.8Hz,2H,ArH-5,8);

[0053] 13C NMR(150MHz,DMSO-d6),δ,ppm:34.12(C-20,23),52.67(C-22,25),53.09(C-19),110.14(C-2,11),120.67(C-4,9),121.04(C-5,8),123 .25(C-14,18),126.78(C-6,7),127.21(C-3,10),129.79(C-15,17),137.08(C-16),138.60(C-13),140.42(C-1,12),170.39(C-21,24);

[0054] ESI-MS, m / z (%): calculated as C 25 H 24 NO4S2([M+H)) + ):466.1141(100), 466.1133 was detected.

[0055] The X-ray single-crystal diffraction pattern of the fluorescent probe 4a in this example is as follows: Figure 1 As shown in the figure. The results of proton NMR, carbon NMR, high-resolution mass spectrometry, and X-ray single-crystal diffraction all indicate that the molecular structure of compound 4a is consistent with its expectations.

[0056] Example 2

[0057] This example provides a fluorescent probe, denoted as 4b, with the following structural formula:

[0058]

[0059] The synthesis route of the fluorescent probe in this example is as follows:

[0060]

[0061] The synthesis steps of the fluorescent probe in this example are as follows:

[0062] Weigh 167.2 mg of carbazole 1 and 40.0 mg of sodium hydroxide and add them to a reaction flask. Add 15 mL of anhydrous N,N-dimethylformamide, heat with stirring, and then add 124.1 mg of 4-fluorobenzaldehyde 2. Stir the reaction mixture in an oil bath at 130 °C for 6 hours. Stop the reaction, cool to room temperature, pour the mixture into distilled water, and extract with ethyl acetate. Dry the organic layer with anhydrous magnesium sulfate and concentrate by vacuum evaporation. Purify the crude product by column chromatography using a mixture of petroleum and dichloromethane (3:1 v / v) as eluent to give a white solid crude product, which is recrystallized from anhydrous ethanol to give pure intermediate 3.

[0063] Weigh 54.2 mg of intermediate 3 and 8.0 mg of elemental iodine, add 15 mL of anhydrous dichloromethane, then add 48.7 mg of 1,3-propanedithiol, and reflux the reaction mixture for 10 h. After cooling, terminate the reaction by continuously adding 15 mL of 0.1 mol / L Na₂S₂O₃ aqueous solution and 15 mL of 10% NaOH solution. Extract the resulting mixture with CH₂Cl₂, separate the organic layer, dry with anhydrous Na₂SO₄, and concentrate under vacuum. Purify by column chromatography (eluent: petroleum ether / ethyl acetate v / v = 15 / 1), evaporate to dryness to obtain an oily substance, recrystallize from CH₂Cl₂ and n-hexane to give white crystals 4b, with a melting point of mp = 207.7℃-208.8℃.

[0064] The structural formula and related characterization data of the fluorescent probe 4b in this example are shown below:

[0065]

[0066] 1 H NMR (600MHz, CDCl3), δ, ppm: 1.95-2.25 (m, 2H, CH2-21), 2.95-3.01 (m, 2H, SCH2-22), 3.13 (t, 2H, J=12.0Hz, SCH2-20), 5.30 (s, 1H, CH-19), 7.27-7.32 (m ,2H,ArH-4,9),7.38-7.46(m,4H,ArH-2,3,10,11),7.56(d,J=8.4Hz,2H,ArH -14,18),7.71(d,J=8.4Hz,2H,ArH-15,17),8.14(d,J=7.8Hz,2H,ArH-5,8);

[0067] 13 C NMR(150MHz,DMSO-d6),δ,ppm:25.23(C-21),31.52(C-20,22),49.89(C-19),110.20(C-2,11),120.68(C-4,9),121.03(C-5, 8),123.24(C-14,18),126.81(C-6,7),127.27(C-3,10),129.84(C-15,17),137.19(C-16),139.17(C-13),140.37(C-1,12);

[0068] ESI-MS, m / z (%): calculated as C 22 H 19 NS2([M+H] +):362.1032(100), Detection found 362.1029.

[0069] The results of proton nuclear magnetic resonance (NMR) spectroscopy, carbon nuclear magnetic resonance (NMR) spectroscopy, and high-resolution mass spectrometry all indicate that the molecular structure of compound 4b is consistent with its expectations.

[0070] Performance testing:

[0071] (1) Liquid sensing performance

[0072] Fifteen aqueous solutions of fluorescent probe 4a with a concentration of 10 μmol / L were prepared. In 14 of these solutions, 50 μmol / L of different metal ions (specifically Na+) were added. + Mg + Ca 2+ Cr 3+ Co 2+ Ni 2+ Cu 2+ Zn 2+ Cd 2+ Pb 2+ Fe 2+ Fe 3+ Al 3+ Hg 2+ Each group contains one type of metal ion for later use; then, a fluorescence spectrometer is used to analyze the fluorescence at λ. ex At a wavelength of 296 nm (slit width set to 5 nm) and a voltage of 500 V, the fluorescence emission spectra of 15 solutions were measured. Specific test results are as follows: Figure 2 and Figure 3 As shown, where, Figure 3 (a) in the image is the fluorescence spectrum of the aqueous solution of fluorescent probe 4a; Figure 3 (b) in the text refers to the addition of Hg. 2+ The fluorescence spectrum of the aqueous solution of the fluorescent probe 4a. From Figure 2 and Figure 3 It can be observed that the aqueous solution of fluorescent probe 4a exhibits strong fluorescence, and when Al is added... 3+ Na + Mg 2+ Ca 2+ Zn 2+ Cu 2+ Co 2+ Cr 3+ Cd 2+ Ni 2+ Pb 2+ Fe 2+ and Fe 3+ The fluorescence of the solution did not change significantly, and the fluorescence response was negligible. However, after adding Hg... 2+When ions are present, the fluorescence intensity of the emission peak at 435 nm decreases significantly, and the absorption peak red-shifts to 455 nm. This indicates that the fluorescent probe 4a is effective against Hg. 2+ It has high selectivity and can be used as a target for Hg. 2+ Ion-specific "off" probes.

[0073] Fifteen aqueous solutions of the fluorescent probe 4b with a concentration of 10 μmol / L were prepared. In 14 of these solutions, 50 μmol / L of different metal ions (specifically Na+) were added. + Mg + Ca 2+ Cr 3+ Co 2+ Ni 2+ Cu 2+ Zn 2+ Cd 2+ Pb 2+ Fe 2+ Fe 3+ Al 3+ Hg 2+ Each group contains one type of metal ion for later use; then, a fluorescence spectrometer is used to analyze the fluorescence at λ. ex At a wavelength of 296 nm (slit width set to 5 nm) and a voltage of 500 V, the fluorescence emission spectra of 15 solutions were measured. Specific test results are as follows: Figure 4 and Figure 5 As shown, where, Figure 5 (a) in the image is the fluorescence spectrum of the aqueous solution of fluorescent probe 4b; Figure 5 (b) in the text refers to the addition of Hg. 2+ The fluorescence spectrum of the aqueous solution of the fluorescent probe 4b. From Figure 4 and Figure 5 It can be observed that the aqueous solution of fluorescent probe 4b exhibits strong fluorescence, and when Al is added... 3+ Na + Mg 2+ Ca 2+ Zn 2+ Cu 2+ Co 2+ Cr 3+ Cd 2+ Ni 2+ Pb 2+ Fe 2+ and Fe 3+ The fluorescence of the solution did not change significantly, and the fluorescence response was negligible. However, after adding Hg... 2+ When ions are present, the fluorescence emission peak intensity at 430 nm decreases significantly, and the absorption peak red-shifts to 435 nm. This indicates that the fluorescent probe 4b is effective against Hg. 2+It has high selectivity and can also be used as a target for Hg. 2+ Ion-specific "off" probes.

[0074] (2) For Hg 2+ Response time

[0075] Prepare two sets of 10 μmol / L aqueous solutions of fluorescent probe 4a. Add one set of solutions to a quartz cuvette, place it in a fluorescence spectrometer, and rapidly add 50 μmol / L Hg. 2+ The solution was tested, and the relationship between the maximum intensity and time was recorded. Another set of samples was directly placed in a fluorescence spectrometer to test its fluorescence intensity. The testing conditions were: at λ... ex Fluorescence intensity was measured at 296 nm (slit width set to 5 nm) and 500 V. Specific test results are as follows: Figure 6 As stated. From Figure 6 It can be observed that the rapid addition of Hg to the solution of fluorescent probe 4a... 2+ Solution, compound 4a with Hg 2+ The reaction was essentially quenched completely within 30 seconds, and the maximum fluorescence intensity did not change significantly with extended testing time. This indicates that fluorescent probe 4a holds promise as a method for detecting Hg. 2+ Real-time sensors.

[0076] Prepare two sets of 10 μmol / L aqueous solutions of the fluorescent probe 4b. Add one set of solutions to a quartz cuvette, place it in a fluorescence spectrometer, and rapidly add 50 μmol / L Hg. 2+ The solution was tested, and the relationship between the maximum intensity and time was recorded. Another set of samples was directly placed in a fluorescence spectrometer to test its fluorescence intensity. The testing conditions were: at λ... ex Fluorescence intensity was measured at 296 nm (slit width set to 5 nm) and 500 V. Specific test results are as follows: Figure 7 As stated. From Figure 7 It can be observed that adding Hg to the solution of fluorescent probe 4b... 2+ After solution, compound 4b reacts with Hg 2+ The reaction was essentially quenched within 25 minutes. This may be due to the more stable six-membered ring structure of compound 4b, Hg 2+ The reaction requires the opening of the six-membered ring, which takes a relatively long time.

[0077] (3) The test paper loaded with compound 4a showed a positive effect on Hg. 2+ Detection applications

[0078] Cut four blank filter paper strips of the same size and set aside; prepare 10 mL of compound 4a (solvent: dichloromethane, concentration: 1×10⁻⁶). -3A solution of compound 4a (mol / L) was prepared; then the filter paper was soaked in the compound 4a solution for half an hour, removed and dried to complete the preparation of the portable test strip; different concentrations (1×10) were prepared. -3 mol / L to 1×10 -5 Hg (mol / L) 2+ For each aqueous solution, take 10 μL of the solution and drop it onto the test paper. Let it stand for five minutes to dry, then observe the change in fluorescence intensity under a 365 nm UV lamp. Specific test results are as follows: Figure 8 As shown, by Figure 8 It can be seen that different concentrations of Hg 2+ The solutions had varying effects on the quenching of the test strips, while the fluorescence of the blank control test strips remained unchanged. Therefore, the experimental results indicate that these test strips can be developed into portable, visual methods for detecting Hg. 2+ Sensing tools.

[0079] (4) The effect of compound 4a on Hg in actual water samples 2+ Detection

[0080] Distilled water, tap water, and river water were used as research subjects, and the Hg content in the samples was determined by spiking. 2+ Perform fluorescence emission spectroscopy testing and fluorescence analysis to calculate Hg 2+ The content of Hg was determined by adding different concentrations of Hg to different water samples. 2+ (0 μmol / L, 0.1 μmol / L, 0.5 μmol / L, 1 μmol / L) The above water samples were added to 1 mL of a 10 μmol / L aqueous solution of 4a, and then the maximum fluorescence intensity was measured using a fluorescence spectrometer. The specific test results are as follows: Figure 9 As shown. By Figure 9 It can be seen that the fluorescence intensity of compound 4a will change with Hg 2+ The concentration gradually decreased with increasing concentration. This invention determined the recovery rate and relative standard deviation (RSD) through three parallel tests to characterize the detection effect of the fluorescent probe 4a. The specific test results are shown in Table 1 below.

[0081] Table 1. Determination of Hg in actual water samples by fluorescent probe 4a. 2+

[0082]

[0083] Table 1 shows that compound 4a is effective against low concentrations of Hg. 2+ (concentration is 10) -6 The recoveries of Hg (mol / L) ranged from 95.9% to 107.2%, with RSDs less than 3%. These results indicate that compound 4a is suitable for the detection of Hg in real water samples. 2+ .

[0084] (5) Compound 4a's effect on Hg in soil samples 2+ Detection

[0085] Weigh out four 0.1g samples of laboratory soil and then soak them in 1mL of Hg at different concentrations. 2+ The solutions (with concentrations of 0 μmol / L, 0.1 μmol / L, 0.5 μmol / L, and 1 μmol / L) were placed at room temperature for 5 hours. Then, centrifugation and microporous membrane filtration were used to obtain Hg of different concentrations after treatment. 2+ Solution. Add the above Hg to 1 mL of 4a with a concentration of 10 μmol / L. 2+ The solution was then subjected to fluorescence emission spectroscopy testing and fluorescence analysis calculations. The fluorescence emission spectroscopy test results are as follows: Figure 10 As shown in Table 2, the fluorescence analysis calculation results are as follows.

[0086] Table 2. Determination of Hg in soil samples by compound 4a. 2+

[0087]

[0088] Depend on Figure 10 It can be seen that adding different concentrations of Hg to soil samples... 2+ The fluorescence intensity of compound 4a will change with Hg 2+ The concentration gradually decreased as it increased. Table 2 shows that compound 4a had an effect on Hg levels in the soil samples. 2+ The recovery rate ranges from 96.9% to 107%, with an RSD of less than 1.5%, making it suitable for detecting Hg in soil samples. 2+ Therefore, compound 4a can be used for the qualitative and quantitative detection of Hg in actual soil samples. 2+ And the recovery rate is relatively high.

[0089] In summary, this invention modifies a carbazole fluorophore with a thioacetal structure to construct a method for detecting Hg. 2+ Fluorescent probes 4a and 4b, both of which are sensitive to Hg 2+ It exhibits high selectivity and sensitivity, and has been successfully applied to the detection of Hg in actual water and soil samples. 2+ The fluorescent probes 4a and 4b in this invention can be used for the detection of Hg. 2+ The sensing material overcomes the ACQ effect and exhibits aggregation-induced emission (AIE) characteristics. When loaded into a test strip for Hg testing... 2+ Rapid detection can achieve visual recognition of Hg. 2+ The level of concentration.

[0090] Furthermore, this invention enables the synthesis of fluorescent probes 4a and 4b without the need for expensive catalysts, customized reagents, or instruments. The synthesis reaction is easily controlled, with a yield of up to 70%, and the material structure is adaptable. 1 H NMR, 13 Verification was performed using analytical methods such as C NMR, HRMS, and X-ray single-crystal diffraction.

[0091] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A fluorescent probe, characterized in that: Including the compounds shown in formula (I), ， R1 is selected from , ; Each R2 is independently selected from C 1~5 Alkyl groups.

2. The fluorescent probe according to claim 1, characterized in that: Each R2 is independently selected from C 1~3 Alkyl groups.

3. The fluorescent probe according to claim 1, characterized in that: The compound represented by formula (I) is selected from or .

4. The fluorescent probe according to any one of claims 1 to 3, characterized in that: The fluorescent probe also includes a carrier.

5. The fluorescent probe according to claim 4, characterized in that: The carrier includes at least one of filter paper and porous materials.

6. The fluorescent probe according to any one of claims 1 to 3, characterized in that: The fluorescent probe also includes a solvent.

7. The fluorescent probe according to claim 6, characterized in that: The solvent includes water.

8. The method for preparing the fluorescent probe according to any one of claims 1 to 7, characterized in that: Includes the following steps: The N-(4-benzaldehyde)carbazole is prepared by reacting compound A or compound B. The compound A is Compound B is n is an integer selected from 2 to 5.

9. The application of the fluorescent probe according to any one of claims 1 to 7 in the field of mercury ion detection, wherein the detection is not for disease diagnosis and treatment purposes.

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