A fluorescent probe for detecting mercury ions, and a preparation method and application thereof

Abstract

The present application relates to a kind of fluorescent probe for detecting mercury ion and its preparation method and application, belong to fluorescent probe detection technical field.The fluorescent probe for detecting mercury ion of the present application contains benzothiazole unit and mercapto group, the fluorescent probe for detecting mercury ion of the present application under the action of mercury ion, mercapto group will hydrolyze into aldehyde, to cause the change of fluorescence property.Meanwhile, the fluorescent probe for detecting mercury ion of the present application has extremely strong selectivity and specificity when detecting mercury ion, has important significance in chemical analysis detection.

Description

Technical Field

[0001] This invention relates to a fluorescent probe for detecting mercury ions, its preparation method, and its application, belonging to the field of fluorescent probe detection technology. Background Technology

[0002] Mercury is a heavy metal that seriously endangers human health. Its persistence, high mobility, and high bioaccumulation properties have made it one of the major environmental pollutants. Industries such as PVC production via the calcium carbide process, non-ferrous metal (copper, lead, zinc) smelting, coal-fired power generation, cement production, natural gas production, and battery manufacturing all generate large amounts of mercury-containing waste. Mercury-containing waste is generally managed as hazardous solid waste; however, after metal recovery or mercury removal treatment, it can be managed as general solid waste. Therefore, rapid and accurate detection of mercury in mercury-containing waste can effectively improve the precise management of solid waste. Traditional mercury ion detection methods suffer from problems such as expensive instruments, long analysis cycles, complex sample pretreatment, and high testing costs, making them unsuitable for the requirements of rapid and efficient mercury ion detection.

[0003] Fluorescent probe analysis, as a highly selective and sensitive method for mercury ion detection, is widely used in life sciences, environmental sciences, and other fields, and represents an important development direction in the field of mercury ion detection research. Fluorescent probe analysis utilizes fluorescent molecular probes with selective specificity for mercury ions and fluorescent properties to achieve rapid and simple detection of mercury ions. There are two main types of small molecule fluorescent probes used for detecting mercury ions: (1) coordination fluorescent probes; and (2) reactive fluorescent probes. Both types of small molecule fluorescent probes can cause corresponding changes in the fluorescence spectrum, thereby achieving the purpose of detecting mercury ions. Due to defects such as poor selectivity, susceptibility to interference, and a strong solvation effect in water, the application of coordination fluorescent probes in environmental applications is greatly limited. Reactive fluorescent probes, based on the mechanism of specific chemical reactions induced by mercury ions, have fluorescence and colorimetric signal outputs that are only affected by mercury ions. Therefore, reactive fluorescent probes exhibit high selectivity and high sensitivity when detecting mercury ions, attracting widespread attention from researchers. For example, Chinese patent document CN102584808A discloses a fluorescent probe for detecting mercury ions containing a thienylbenzothiazole unit. The sulfur atoms on the thienyl ring and benzothiazole ring in this fluorescent probe exhibit good recognition ability for mercury ions, offering advantages such as high sensitivity and high selectivity. Because 2-mercaptobenzothiazole possesses a sulfur heterocycle and thiol group capable of complexing mercury ions, Chinese patent document CN105806794A uses 2-mercaptobenzothiazole as a colorimetric probe for mercury ions, offering advantages such as simple operation, environmental friendliness, rapid and sensitive response, and strong anti-interference capabilities. However, the fluorescent probes for detecting mercury ions disclosed in the above documents have poor selectivity for mercury ions and are susceptible to interference from other metal ions (e.g., copper ions), resulting in significant errors in the detection results. Therefore, they are unsuitable for detecting mercury ions in complex mercury-containing waste. Chinese patent document CN113045538A discloses a salicylaldehyde thioglycol-based fluorescent probe for detecting mercury ions. The fluorescent probe disclosed in this patent document has extremely strong selectivity and specificity for mercury ions and has high detection sensitivity. However, it has problems such as poor practicality and strong background interference (strong background interference refers to the strong fluorescence intensity of the probe itself). Summary of the Invention

[0004] The purpose of this invention is to provide a fluorescent probe for detecting mercury ions, which can solve the problem of strong background interference in current fluorescent probes for detecting mercury ions.

[0005] The second objective of this invention is to provide a method for preparing a fluorescent probe for detecting mercury ions, which can solve the problem that the currently prepared fluorescent probes for detecting mercury ions have large detection error.

[0006] The third objective of this invention is to provide an application of a fluorescent probe for detecting mercury ions, which can solve the problem of poor selectivity in the current method of detecting mercury ions using fluorescent probes.

[0007] To achieve the above objectives, the technical solution adopted by the fluorescent probe for detecting mercury ions in this invention is as follows:

[0008] A fluorescent probe for detecting mercury ions has the structure shown in Formula I:

[0009]

[0010] The fluorescent probe for detecting mercury ions of the present invention contains both a benzothiazole fluorescent group and a thiol reactive group linked by chemical bonds. In the presence of mercury ions, the thiol group hydrolyzes into an aldehyde, thereby causing a change in fluorescence properties. Furthermore, the fluorescent probe for detecting mercury ions of the present invention exhibits extremely high selectivity and specificity in the detection of mercury ions, which is of great significance in chemical analysis.

[0011] Compared with the probe for detecting mercury ions disclosed in Chinese patent document CN113045538A, the probe of the present invention exhibits enhanced fluorescence when detecting mercury ions, while the probe disclosed in Chinese patent document CN113045538A exhibits weakened fluorescence when detecting mercury ions. Therefore, the probe of the present invention provides clearer detection results when detecting mercury ions.

[0012] The technical solution adopted in the preparation method of the fluorescent probe for detecting mercury ions of the present invention is as follows:

[0013] A method for preparing a fluorescent probe for detecting mercury ions as described above includes the following steps: mixing and reacting the compound shown in Formula II and ethanethiol in an organic solvent under the action of a catalyst, and then purifying the system after the mixing reaction to obtain a fluorescent probe for detecting mercury ions.

[0014]

[0015]

[0016] The method for preparing the fluorescent probe for detecting mercury ions of the present invention is simple to operate and conducive to large-scale production.

[0017] Preferably, the mass ratio of the compound represented by Formula II to ethanethiol is (2.7–3):(4–4.5). For example, the mass ratio of the compound represented by Formula II to ethanethiol is 2.7:4. Controlling the mass ratio of the compound represented by Formula II to ethanethiol within the above range ensures a high conversion rate of the raw materials and prevents side reactions.

[0018] Preferably, the catalyst is boron trifluoride diethyl ether. Preferably, the mass ratio of the compound represented by Formula II, ethanethiol, and the catalyst is (2.7–3):(4–4.5):(1.85–2). For example, the mass ratio of the compound represented by Formula II, ethanethiol, and the catalyst is 2.7:4:1.85. Using boron trifluoride diethyl ether as a catalyst allows the mixed reaction to be completed at room temperature, and improves the purity and yield of the product, thus reducing preparation costs.

[0019] Preferably, the mixing reaction is carried out at room temperature. The endpoint of the mixing reaction can be determined by detecting the conversion rate of the raw materials; generally, the mixing reaction time is not less than 3 hours. Carrying the mixing reaction at room temperature avoids the use of additional heat or cold sources, reducing preparation costs.

[0020] Preferably, the purification method includes the following steps: adjusting the pH of the mixed reaction system to 8-9 using an alkaline pH adjuster to obtain a mixed solution; then extracting the organic components in the mixed solution using an organic extraction solvent; removing the solvent from the extracted organic phase to obtain a crude solid product; and then performing chromatographic separation on the crude solid product to obtain a fluorescent probe for detecting mercury ions. Preferably, the alkaline pH adjuster is an alkali metal carbonate and / or an alkali metal bicarbonate. For example, the alkaline pH adjuster is sodium carbonate and / or sodium bicarbonate. Preferably, the organic extraction solvent is a chlorinated hydrocarbon solvent. For example, the organic extraction solvent is dichloromethane or trichloromethane. Preferably, the eluent used in the chromatographic separation is a chlorinated hydrocarbon solvent. For example, the eluent used in the chromatographic separation is dichloromethane. The above purification method has the advantages of simple operation and good impurity removal effect, and is easy to implement industrially.

[0021] It is understood that the compound represented by Formula II can be prepared using existing techniques, such as the methods disclosed in Chinese Patent Document CN112812075A or Chinese Patent Document CN106749093B. For example, the preparation method of the compound represented by Formula II is as follows:

[0022] (1) 2-hydroxy-5-methylbenzaldehyde and 2-aminobenzylthiophenol were reacted in an organic solvent under the action of a catalyst, and then the reaction system was purified to obtain an intermediate product.

[0023] (2) The intermediate product and hexamethylenetetramine were mixed and reacted in trifluoroacetic acid, and then the mixture was purified to obtain the compound shown in Formula II.

[0024] The technical solution adopted in the application of the fluorescent probe for detecting mercury ions of the present invention is as follows:

[0025] Application of a fluorescent probe for detecting mercury ions as described above in the detection of mercury ions.

[0026] The fluorescent probe for detecting mercury ions of the present invention has extremely strong selectivity and specificity in detecting mercury ions, which is of great significance in chemical analysis and detection. Attached Figure Description

[0027] Figure 1 The fluorescence spectra obtained from fluorescence spectroscopy analysis of the initial test solution, the test solution containing interfering metal ions, and the test solution containing mercury ions in Experimental Example 1 of this invention are shown below.

[0028] Figure 2 This is a schematic diagram showing the fluorescence intensity of different test solutions at an emission wavelength of 560 nm in Experimental Example 2 of the present invention;

[0029] Figure 3 The fluorescence spectra obtained from fluorescence spectroscopy analysis of test solutions containing different concentrations of mercury ions in Experimental Example 3 of this invention are shown.

[0030] Figure 4 This is a schematic diagram showing the linear fitting results between the fluorescence intensity of the test solution and the mercury ion concentration in the test solution in Experimental Example 3 of the present invention. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0032] I. Specific embodiments of the fluorescent probe for detecting mercury ions and its preparation method of the present invention are as follows:

[0033] Example

[0034] The fluorescent probe for detecting mercury ions in this embodiment has the structure shown in Formula I:

[0035]

[0036] The method for preparing the fluorescent probe for detecting mercury ions in this embodiment includes the following steps:

[0037] (1) 2.0 g of 2-hydroxy-5-methylbenzaldehyde, 1.84 g of 2-aminothiophenol and 20 mL of N,N-dimethylacetamide (DMF) were added to the reaction flask and stirred until 2-hydroxy-5-methylbenzaldehyde and 2-aminothiophenol were completely dissolved. Then, 2.4 g of sodium metabisulfite was added to the reaction flask in batches. After the addition was completed, the material in the reaction flask was heated to 110 °C for reflux reaction. The reaction was monitored by TLC during the reaction. When the reflux reaction was 3 h, the TLC monitoring results showed that the raw material disappeared, indicating that the reaction was basically over. At this time, the material in the reaction flask was cooled to room temperature, and then 80 mL of water was added to the reaction flask. At this time, solid precipitated out. The material in the reaction flask was then filtered, and the filtered solid was dried to obtain intermediate product 1.

[0038] (2) 2.5 g of intermediate product 1, 4.5 g of hexamethylenetetramine (HMTA), and 50 g of trifluoroacetic acid were added to a reaction flask. The mixture in the reaction flask was then heated to 100 °C and refluxed. The reaction was monitored by TLC. After 6 hours of reflux, the TLC monitoring showed that the starting material disappeared, indicating that the reaction was basically completed. At this time, 10 mL of 4 mol / L hydrochloric acid was added to the reaction flask and stirred for 30 min. The organic components in the reaction flask were then extracted three times with dichloromethane. The extracted organic phase was washed three times with saturated brine and then evaporated to dryness to obtain a crude solid. Finally, the crude solid was purified by column chromatography (using dichloromethane as the eluent) to obtain a light yellow solid, which is compound II. The results of NMR analysis of compound II are as follows: 1 H NMR (CDCl3, 300MHz) δ (ppm): 12.74 (1H, s), 10.32 (1H, s), 8.20 (1H, d, J = 9.3Hz), 8.20 (1H, s), 8 .11(1H,d,J=8.7Hz),7.72(1H,s),7.59(1H,t,J=1.6Hz)),7.50(1H,t,J=1.7Hz),2.38(3H,s);

[0039] (3) 0.27 g of compound II, 0.4 g of ethanethiol and 30 mL of dichloromethane were added to the reaction flask. The air in the reaction flask was then replaced with nitrogen. Under nitrogen protection, 0.185 g of boron trifluoride diethyl ether was added to the reaction flask. The materials in the reaction flask were stirred at room temperature. The reaction was monitored by TLC. After stirring for 3 hours, the TLC monitoring results showed that the raw materials disappeared, indicating that the reaction was basically over. At this time, the pH of the system after stirring was adjusted to between 8 and 9 with saturated sodium bicarbonate solution to obtain a mixture. The organic components in the mixture were then extracted three times with dichloromethane. The extracted organic phase was collected and evaporated to dryness to obtain a solid crude product. Finally, the solid crude product was purified by column chromatography (the eluent used in column chromatography was dichloromethane) to obtain a fluorescent probe for detecting mercury ions. The fluorescent probe for detecting mercury ions prepared in this example was named HgI.

[0040] The results of NMR analysis of the fluorescent probe used to detect mercury ions are as follows: 1 H NMR (CDCl3, 300MHz) δ (ppm): 8.40 (1H, d, J = 6.0Hz), 7.93 (1H, d, J = 9.0Hz), 7.78 (1H, d, J = 3.0Hz), 7.67 (1H, t, J = 6.0Hz),7.57(1H,t,J=6.0Hz),7.35(1H,s),5.73(1H,s),2.60-2.72(4H,m),2.38(3H,s),1.30(6H,t,J=6.0Hz).

[0041] The reaction equation for preparing the fluorescent probe for detecting mercury ions in this embodiment is as follows:

[0042]

[0043] II. Specific embodiments of the application of the fluorescent probe for detecting mercury ions of the present invention in the detection of mercury ions are as follows:

[0044] The fluorescent probe used for detecting mercury ions in the examples can be used to detect mercury ions, and will not be described in detail here.

[0045] In addition, in order to investigate the effect of the amount of raw materials on the experimental results, the fluorescent probe was prepared again according to step (3) of the example. The difference was that the amount of compound II was kept constant, and the amounts of ethanethiol and catalyst (boron trifluoride diethyl ether) were adjusted. The mass ratio of compound II, ethanethiol and catalyst was adjusted from 2.7:4:1.85 to 3:4.5:2 or 2.8:4.2:1.9. Then the prepared fluorescent probe was structurally characterized. The results showed that the fluorescent probe prepared after changing the parameters had the same structure as the fluorescent probe prepared in the example.

[0046] Experimental Example 1

[0047] To test the selectivity of the fluorescent probe for detecting mercury ions of the present invention, fluorescence spectra of the fluorescent probe for detecting mercury ions in the examples were performed in the presence of different metal ions. The selectivity for detecting mercury ions was analyzed based on the changes in fluorescence intensity. The specific method is as follows:

[0048] (1) Prepare solutions containing a single metal ion separately. Specifically, add the metal nitrate to high-purity water to prepare a metal ion solution with a concentration of 10 mmol / L. The metal ion is Na+. + K + Cs + Ca 2+ Mg 2+ Al 3+ Mn 2+ Fe 3+ Ag + Cd 2+ Co 2+ Cr 3+ Hg 2+ Cu 2+ Sr 2+ Pb 2+ or Zn 2+ .

[0049] (2) The fluorescent probe for detecting mercury ions in the example was dissolved in dimethyl sulfoxide to obtain a fluorescent probe solution with a concentration of 1 mmol / L.

[0050] (3) Stir the fluorescent probe solution with a concentration of 1 mmol / L and the test solvent (the test solvent is prepared by mixing HEPES buffer and acetonitrile in a volume ratio of 1:1) until homogeneous to obtain a fluorescent probe solution with a concentration of 10 μmol / L. Name the fluorescent probe solution with a concentration of 10 μmol / L as the initial test solution.

[0051] Simultaneously, a fluorescent probe solution with a concentration of 1 mmol / L and a metal ion solution (the metal ion in the metal ion solution is Na) were added. + K+ Cs + Ca 2+ Mg 2+ Al 3+ Mn 2+ Fe 3+ Ag + Cd 2+ Co 2+ Cr 3+ Hg 2+ Cu 2+ Sr 2+ Pb 2+ or Zn 2+ The test solvent (prepared by mixing HEPES buffer and acetonitrile in a volume ratio of 1:1) is stirred evenly to obtain a test solution containing interfering metal ions. The concentration of the metal ions in the test solution containing interfering metal ions is 100 μmol / L, and the concentration of the fluorescent probe used to detect mercury ions is 1 mmol / L.

[0052] In addition, a fluorescent probe solution with a concentration of 1 mmol / L and a metal ion solution (the metal ion in the metal ion solution is Hg) were prepared. 2+ The test solvent (prepared by mixing HEPES buffer and acetonitrile in a volume ratio of 1:1) is stirred evenly to obtain a test solution containing mercury ions. The concentration of mercury ions in the test solution is 10 mmol / L, and the concentration of the fluorescent probe used to detect mercury ions is 1 mmol / L.

[0053] (4) Fluorescence spectroscopy analysis was performed on the initial test solution, the test solution containing interfering metal ions, and the test solution containing mercury ions using a fluorescence spectrometer (excitation wavelength during analysis was 463 nm). The results are as follows: Figure 1 As shown.

[0054] Depend on Figure 1 It can be seen that the initial test solution has a certain fluorescence intensity. The fluorescence intensity of the test solution containing interfering metal ions is close to that of the initial test solution, and the fluorescence intensity of the test solution containing interfering metal ions is slightly less than that of the initial test solution. However, the fluorescence intensity of the test solution containing mercury ions is enhanced, indicating that the fluorescent probe of the present invention for detecting mercury ions has good selectivity for mercury ions.

[0055] Experiment Example 2

[0056] To test the anti-interference capability of the fluorescent probe for detecting mercury ions according to the present invention, the anti-interference capability of the fluorescent probe for detecting mercury ions to metal cations was tested. The specific test methods are as follows:

[0057] (1) Prepare solutions containing a single metal ion separately. Specifically, add a metal chloride salt to high-purity water to prepare a metal ion solution with a concentration of 10 mmol / L. The metal ion is Na+. + K + Cs + Ca 2+ Mg 2+ Al 3+ Mn 2 + Fe 3+ Ag + Cd 2+ Co 2+ Cr 3+ Hg 2+ Cu 2+ Sr 2+ Pb 2+ or Zn 2+ .

[0058] (2) The fluorescent probe for detecting mercury ions in the example was dissolved in dimethyl sulfoxide to obtain a fluorescent probe solution with a concentration of 1 mmol / L.

[0059] (3) Stir the fluorescent probe solution with a concentration of 1 mmol / L and the test solvent (the test solvent is prepared by mixing HEPES buffer and acetonitrile in a volume ratio of 1:1) until homogeneous to obtain a fluorescent probe solution with a concentration of 10 μmol / L. Name the fluorescent probe solution with a concentration of 10 μmol / L as the initial test solution.

[0060] Additionally, a fluorescent probe solution with a concentration of 1 mmol / L and a metal ion solution (the metal ion in the metal ion solution is Na) were prepared. + K + Cs + Ca 2+ Mg 2+ Al 3+ Mn 2+ Fe 3+ Ag + Cd 2+ Co 2+ Cr 3+ Cu 2+ Sr 2+ Pb 2+ or Zn 2+ ), Hg 2+The solution and test solvent (prepared by mixing HEPES buffer and acetonitrile in a 1:1 volume ratio) were stirred thoroughly to obtain a test solution containing interfering ions. This test solution containing interfering ions was named Test Solution I. In Test Solution I, the concentration of mercury ions was 100 μmol / L, and the interfering ion (Na+) was... + K + Cs + Ca 2+ Mg 2+ Al 3+ Mn 2+ Fe 3+ Ag + Cd 2+ Co 2+ Cr 3+ Cu 2+ Sr 2+ Pb 2+ or Zn 2+ The concentration of the fluorescent probe used to detect mercury ions is 100 μmol / L, and the concentration of the fluorescent probe is 1 mmol / L.

[0061] Finally, a fluorescent probe solution with a concentration of 1 mmol / L and Hg were added. 2+ The solution and test solvent (the test solvent is prepared in a volume ratio of 1:1) are stirred evenly to obtain a test solution containing mercury ions. The test solution containing mercury ions is named test solution II. In test solution II, the concentration of mercury ions is 100 μmol / L, and the concentration of the fluorescent probe used to detect mercury ions is 1 mmol / L.

[0062] (4) Fluorescence spectroscopy analysis was performed on the initial test solution, test solution I, and test solution II using a fluorescence spectrometer (excitation wavelength of 463 nm). The fluorescence intensity of different test solutions at an emission wavelength of 560 nm was then recorded. The results are as follows: Figure 2 As shown. Figure 2 The horizontal axis represents the type of substance in the test solution. For example, HgI represents the test solution containing only a fluorescent probe for detecting mercury ions, i.e., the initial test solution; HgI+Hg(II) represents the test solution containing only a fluorescent probe and mercury ions, i.e., test solution II; HgI+Hg(II)+Ag(I) represents the test solution containing only a fluorescent probe, mercury ions and silver ions, i.e., test solution I containing a fluorescent probe, mercury ions and silver ions.

[0063] Depend on Figure 2 It can be seen that the fluorescence intensity of test solution I containing different interfering ions at 560 nm is basically the same as that of test solution II at 560 nm, indicating that the fluorescent probe of the present invention for detecting mercury ions has a strong ability to resist interference from metal cations when detecting mercury ions.

[0064] Experimental Example 3

[0065] To investigate the feasibility of the fluorescent probe for quantitative detection of mercury ions according to the present invention, the correlation between mercury ion concentration and fluorescence intensity was tested. The specific test method is as follows:

[0066] (1) Add mercuric nitrate to high-purity water to prepare Hg 2+ The concentration of Hg was 10 mmol / L 2+ Solution;

[0067] (2) The fluorescent probe for detecting mercury ions in the example was dissolved in dimethyl sulfoxide to obtain a fluorescent probe solution with a concentration of 1 mmol / L.

[0068] (3) Add a 1 mmol / L fluorescent probe solution and a 10 mmol / L Hg solution. 2+ The solution and test solvent (prepared by mixing HEPES buffer and acetonitrile in a 1:1 volume ratio) were stirred evenly to obtain test solutions containing different concentrations of mercury ions. In the test solutions, the concentration of the fluorescent probe used to detect mercury ions was 10 μmol / L, and the concentrations of mercury ions were 0, 1 μmol / L, 2 μmol / L, 3 μmol / L, 4 μmol / L, 5 μmol / L, 6 μmol / L, 7 μmol / L, 8 μmol / L, 9 μmol / L, 10 μmol / L, 11 μmol / L, 12 μmol / L, 13 μmol / L, 14 μmol / L, and 15 μmol / L.

[0069] (4) Fluorescence spectroscopy analysis was performed on the test solutions containing different concentrations of mercury ions using a fluorescence spectrometer (excitation wavelength during analysis was 463 nm). The results are as follows: Figure 3 As shown, Figure 3 The x-axis represents the fluorescence emission wavelength in nm, and the y-axis represents the fluorescence intensity. Then, a linear fit was performed between the fluorescence intensity of the test solution and the mercury ion concentration in the test solution. The resulting fitting equation is: y = 11.05263 + 34.32386 (where y is the fluorescence intensity and x is the mercury ion concentration), R = 0.99595, SD = 13.49408, N = 14, P < 0.0001. The fitting results were plotted as follows: Figure 4 As shown, Figure 4 The x-axis represents mercury ion concentration in μmol / L, and the y-axis represents fluorescence intensity.

[0070] Depend on Figure 3 and Figure 4It can be seen that when the concentration of mercury ions in the test solution is 0-12 μmol / L, the fluorescence intensity of the test solution has a good linear relationship with the concentration of mercury ions, indicating that the fluorescent probe of the present invention for detecting mercury ions can achieve quantitative detection of mercury ions.

Claims

1. A fluorescent probe for detecting mercury ions, characterized in that, It has the structure shown in Equation I:

2. A method for preparing a fluorescent probe for detecting mercury ions as described in claim 1, characterized in that, Includes the following steps: The compound shown in Formula II and ethanethiol were mixed and reacted in an organic solvent under the action of a catalyst. The system after the mixture was then purified to obtain a fluorescent probe for detecting mercury ions.

3. The method for preparing a fluorescent probe for detecting mercury ions as described in claim 2, characterized in that, The mass ratio of the compound shown in Formula II to ethanethiol is (2.7–3):(4–4.5).

4. The method for preparing a fluorescent probe for detecting mercury ions as described in claim 2, characterized in that, The catalyst is boron trifluoride diethyl ether.

5. The method for preparing a fluorescent probe for detecting mercury ions as described in claim 2, characterized in that, The mass ratio of the compound shown in Formula II, ethanethiol, and catalyst is (2.7–3):(4–4.5):(1.85–2).

6. The method for preparing a fluorescent probe for detecting mercury ions as described in any one of claims 2-5, characterized in that, The purification method includes the following steps: adjusting the pH of the system after the mixed reaction to 8-9 using an alkaline pH adjuster to obtain a mixed solution; then extracting the organic components in the mixed solution using an organic extraction solvent; removing the solvent from the extracted organic phase to obtain a crude solid product; and then performing chromatographic separation on the crude solid product to obtain a fluorescent probe for detecting mercury ions.

7. The method for preparing a fluorescent probe for detecting mercury ions as described in claim 6, characterized in that, The alkaline pH adjuster is an alkali metal carbonate and / or an alkali metal bicarbonate.

8. The method for preparing a fluorescent probe for detecting mercury ions as described in claim 6, characterized in that, The organic extraction solvent is a chlorinated hydrocarbon solvent; the eluent used in the chromatographic separation is a chlorinated hydrocarbon solvent.

9. The method for preparing a fluorescent probe for detecting mercury ions as described in claim 8, characterized in that, The organic extraction solvent is dichloromethane or trichloromethane; the eluent used in the chromatographic separation is dichloromethane.

10. The application of the fluorescent probe for detecting mercury ions as described in claim 1 in the detection of mercury ions.

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