Application of a naphthylphenylpropynone fluorescent probe in detection of mercury ions, iron ions and iodine ions

Abstract

This invention provides an application of a naphthalenepyridone fluorescent probe in the detection of mercury, iron, and iodide ions, belonging to the field of fluorescence analysis technology. Different metal cations were added to the CH3CN / H2O solution containing the fluorescent probe, and it was found that only Hg was detected. 2+ This can enhance the fluorescence of the fluorescent probe, while Fe... 3+ The addition of [a specific ingredient] can quench the fluorescence of the fluorescent probe. Furthermore, [the following is an example of a specific ingredient]: A3-Hg. 2+ When different anions were added to a CH3CN / H2O solution containing Ion, it was found that only Ion... ‑ The addition of A3-Hg can make 2+ The fluorescence is weakened, therefore this fluorescent probe can recognize Fe with high sensitivity and high selectivity. 3+ Hg 2+ and I ‑ In addition, this fluorescent probe can also be used to treat Hg in traditional Chinese medicine. 2+ Quantitative detection.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fluorescence analysis, and relates to application of a naphthalene benzopropyl pyranone fluorescent probe in detection of mercury ions, iron ions and iodine ions. BACKGROUND

[0002] Mercury ions (Hg 2+ ) are common metals and are widely used by people. For a long time, mercury ions have been considered as toxic elements, and recent researches further reveal the toxicity of mercury ions to human bodies. Mercury ions have strong toxicity to human brains, kidneys, intestines and stomachs and nervous systems. Once the mercury ions enter human bodies, they will soon enter enzymes or proteins in the bodies and combine with many negative groups, so that many metabolic pathways in cells are affected. Therefore, detection of mercury ions has important application value.

[0003] Iron (Fe 3+ ) ions are important elements for maintaining body health and are one of main raw materials for synthesizing hemoglobin. Although iron ions are not toxic by themselves, iron ion poisoning can be caused when excessive or insufficient iron is taken in. For example, excessive intake can cause liver cirrhosis or gastrointestinal reactions, and insufficient intake can not only cause anemia in infants and young children, but also affect immune function, digestive absorption capacity and muscle movement function. Therefore, rapid detection of iron ions is very important.

[0004] Iodine ions (I - ) are closely related to human health, and iodine is one of essential trace elements for human bodies and is called "intelligence element". Iodine is an element necessary for maintaining normal functions of human thyroid glands, and when human bodies lack iodine, goiter will occur. It is worth noting that excessive intake of iodine by human bodies is also harmful, and excessive iodine in daily diet can also cause "hyperthyroidism".

[0005] At present, a variety of ion detection methods have been developed, and fluorescence method has become a main detection means in the field of ion detection due to advantages such as simple operation, rapidness, high sensitivity and the like. SUMMARY

[0006] The application aims to provide application of a naphthalene benzopropyl pyranone fluorescent probe in detection of mercury ions, iron ions and iodine ions.

[0007] I. Fluorescent probe and preparation thereof

[0008] The fluorescent probe 3-carboxylic acid naphthopyranone A3 of the application has a molecular formula of C 14 H8O4 and a structural formula as shown in the following formula:

[0009] .

[0010] The synthesis method of the fluorescent probe comprises the following steps:

[0011] (1) Synthesis of 3-carboxyethyl benzopyrone: 2-hydroxy-1-naphthaldehyde and diethyl malonate are dissolved in anhydrous ethanol, and piperidine is added as a catalyst, and heated to reflux at 80-90 ℃ for 3-5 h, after the reaction is completed, cooled to room temperature, adjust pH to 5-6 with hydrochloric acid, after cooling, filter and dry, recrystallized with methanol to obtain 3-carboxyethyl benzopyrone. Among them, the molar ratio of 2-hydroxy-1-naphthaldehyde and diethyl malonate is 1:1-1:1.5; the molar ratio of piperidine and 2-hydroxy-1-naphthaldehyde is 1:1-1:1.5.

[0012] (2) 3-carboxyethyl benzopyrone and NaOH are dissolved in an ethanol aqueous solution, heated to reflux at 80-90 ℃ for 8 h, after the reaction is completed, add water and adjust pH to 1-2 with 1M HCl, a light yellow precipitate is generated, filter and dry to obtain a crude product, recrystallized with glacial acetic acid to obtain naphthalene benzopyranone fluorescent probe. Among them, the molar ratio of 3-carboxyethyl benzopyrone and sodium hydroxide is 1:1.5-1:2.

[0013] The synthesis route is as follows:

[0014]

[0015] The hydrogen spectrum and mass spectrum of A3 are as follows: Figure 1 And Figure 2 .

[0016] II. Application of fluorescent probe in detection of Hg 2+

[0017] 1. Fluorescent performance of fluorescent probe A3

[0018] The research on the fluorescent performance of probe A3 shows that the fluorescent probe A3 has good solubility in acetonitrile solution. When the excitation wavelength is 362 nm, the probe molecule A3 has good fluorescence emission performance, and the fluorescence intensity is 370 (as shown in Figure 3 ).

[0019] 2. Fluorescent probe A3 recognizes Hg 2+ and Fe 3+

[0020] In the CH3CN / H2O (1:9, v / v) solution (C A3 =2×10 -5 M) of the fluorescent probe A3, 5 equivalent (relative to the fluorescent probe A3) of Cu 2+ , Pb 2+ , Cr 3+ , Co 2+ ​Ni 2+ Cd 2+ Zn 2+ Ag 2+ Ca 2+ Mg 2+ Al 3 + Hg 2+ Fe 3+ An aqueous solution. The results showed that Hg... 2+ The addition of Fe significantly enhances the fluorescence of the CH3CN / H2O (1:9, v / v) solution of A3. 2+ The addition of [a specific substance] can quench the fluorescence of the A3 CH3CN / H2O (1:9, v / v) solution, while the addition of other metal cations cannot significantly change the fluorescence of the A3CH3CN / / H2O (1:9, v / v) solution (e.g.) Figure 3 As shown in the figure, this indicates that fluorescent probe A3 can be used for Hg 2+ Fe 3+ Selective fluorescence recognition.

[0021] Anti-interference experiments showed that the presence of other metal cations affected the recognition of Hg by the fluorescent probe A3. 2+ Fe 3+ Without any interference (such as) Figure 4 , 5 (As shown).

[0022] Fluorescent titration experiments showed that fluorescent probe A3 was effective against Hg. 2+ Fe 3+ The lowest detection limits are 2.21 × 10⁻⁶. -6 M, 2.99 × 10 -6 M (as) Figure 6 , 7 (As shown in Figures 8 and 9), high sensitivity.

[0023] 3. Fluorescent probe A3-Hg 2+ Fluorescent Recognition I -

[0024] In the fluorescent probe A3-Hg 2+ CH3CN / H2O (1:9, v / v) solution (C A3-Hg 2+ =2×10 -5 Add 10 equivalents (relative to fluorescent probe A3) of F to M). - , Cl - , Br - , I - AC - H2PO4 -, HSO4 - , ClO4 - , NO3 - ,N3 - , SO3 - aqueous solution. It was found that the addition of I - can significantly weaken the fluorescence of A3-Hg 2+ CH3CN / H2O(1:9, v / v) solution, while the addition of other anion ions cannot significantly change the fluorescence of A3-Hg 2+ CH3CN / H2O(1:9, v / v) solution (as shown in Figure 10 ), indicating that the fluorescent probe A3-Hg 2+ can be used for selective fluorescence recognition of I - .

[0025] Anti-interference experiment results show that the presence of other metal cations has no interference on the recognition of I - by fluorescent probe A3-Hg 2+ (as shown in Figure 11 ).

[0026] Fluorescence titration experiments show that the minimum detection limit of fluorescent probe A3-Hg 2+ for I - is 4.10 × 10 -6 M (as shown in Figure 12 , 13 ), which has high sensitivity.

[0027] 4、Mechanism analysis of fluorescent probe A3 recognizing Hg 2+

[0028] In the CH3CN / H2O(1:9, v / v) solution of fluorescent probe A3, Hg 2+ was added, and the solvent was dried for solid-state infrared spectrum test. By comparing the infrared spectrum of fluorescent probe A3 (as shown in Figure 18 ), it can be seen that a complex is formed between fluorescent probe A3 and Hg 2+ , resulting in fluorescence enhancement. And through high resolution mass spectrometry, A3 and Hg 2+ working curve, it can be known that the ratio of fluorescent probe A3 and Hg 2+ forming complex is 1:1 (as shown in Figure 14 , 19 ).

[0029] 5、Mechanism analysis of fluorescent probe A3 recognizing Fe 3+

[0030] In the CH3CN / H2O(1:9, v / v) solution of fluorescent probe A3, Fe​​3+ The solvent was dried, and solid-state infrared spectroscopy was performed. Comparison with the infrared spectrum of fluorescent probe A3 showed that (e.g.) Figure 18 As shown), fluorescent probe A3 and Fe 3+ A complex was formed between them, leading to fluorescence quenching. Furthermore, high-resolution mass spectrometry and analysis of A3 and Fe... 3+ The working curves show that the fluorescent probe A3 and Fe 3+ The ratio of complexes formed is 2:3 (e.g.) Figure 15 , 20 (As shown).

[0031] 6. Fluorescent probe A3-Hg 2+ Identify - Mechanism analysis

[0032] In the fluorescent probe A3-Hg 2+ Add I to the CH3CN / H2O (1:9, v / v) solution - The solvent was dried, and solid-state infrared spectroscopy was performed. The results were obtained by comparing the sample with the fluorescent probe A3-Hg. 2+ A comparison of the infrared spectra reveals (e.g.) Figure 7 (As shown), fluorescent probe A3-Hg 2+ with I - A complex formed between them, leading to decreased fluorescence. Furthermore, high-resolution mass spectrometry and analysis of A3 and A3-Hg... 2+ The working curve shows that the fluorescent probe A3-Hg 2+ with I - The ratio of complexes formed is 1:4 (e.g.) Figure 16 , 21 (As shown).

[0033] 7. Detection of Hg using fluorescent probe A3 2+ Practical applications

[0034] 7.1 By immersing the silica gel plate in an A3 CH3CN / H2O (1:9, v / v) solution (C A3 =2×10 -5 In M), and then dried in air to prepare a thin film. When Hg 2+ When dropped onto a thin film, a noticeable color change was observed under 365nm UV light (e.g., ...). Figure 17 (As shown), therefore, this thin film can be used to detect Hg. 2+ Convenient testing reagent kits.

[0035] 7.2 Application in the determination of trace copper in traditional Chinese medicine

[0036] Parallel measurements were taken of the CH3CN / H2O (1:9, v / v) solution of fluorescent probe A3 (C A3=2×10 -5 M) Several portions, with different concentrations of Hg added. 2+ Standard solution, detection of added Hg 2+ The fluorescence intensity of the fluorescent probe after adding Hg is determined based on the standard solution. 2+ The fluorescence intensity at the emission peak of the subsequent system and Hg 2+ Establish a linear formula for the concentration (e.g.) Figure 22 ), Hg 2+ Concentration at 1.0 × 10 -5 ~5.0×10 - 5 Fluorescence intensity F and Hg in the range of mol / L 2+ The concentration C exhibits a good linear relationship, with the linear equation being F = 66.385 + 312.7642 C, R 2 =0.9908, where F is the fluorescence intensity and C is Hg. 2+ Concentration, in mol / L; under the same conditions, the fluorescence intensity of the probe was measured after adding the digestion solution of the Chinese medicinal materials, and the Hg concentration in the Chinese medicinal materials was calculated according to the linear formula. 2+ The specific content.

[0037] Wash the Chinese herbs (rhubarb, codonopsis, astragalus, angelica, and licorice) with deionized water, dry them at 90℃, pulverize them, pass them through a 200-mesh sieve, and store them in a desiccator for later use. Accurately weigh 1.0 g of the above Chinese herbal sample and place it in a beaker. Add 5 mL of nitric acid solution and 1 mL of perchloric acid, cover with a watch glass, and let it stand overnight. The next day, heat it on a hot plate until it boils. Keep the solution boiling until it becomes clear. Continue heating until white smoke appears and then dissipates. The solution becomes colorless and transparent. After cooling, rinse the watch glass and the inner wall of the beaker with ultrapure water, transfer it to a 25 mL volumetric flask, and dilute to 25 mL with ultrapure water to obtain the Chinese herbal sample solution for later use.

[0038] Then, the concentration of mercury ions in the traditional Chinese medicine sample solution was obtained according to the regression equation F = 66.385 + 312.7642 C, and the mercury ion content in the traditional Chinese medicine was calculated based on the mass of the sample. The linear range of this method is 1.0 × 10⁻⁶. -5 ~5.0×10 -5 mol / L, detection limit is 4.77×10 -6 M, recovery rate greater than 95.0%.

[0039] 8. Fluorescent probe A3-Hg 2+ Test I - Practical applications

[0040] By immersing the silicone plate in A3-Hg 2+ CH3CN / H2O (1:9, v / v) solution (C A3-Hg2+ =2x10 -5 M) and then dried in air to prepare a thin film. When I - was dropped onto the thin film, a significant color change (as shown in Figure 17 ) was observed under irradiation at 365 nm using a UV lamp, so the thin film can be used in a convenient detection kit for detecting I - .

[0041] 9. Practical application of fluorescent probe A3 for detecting Fe 3+

[0042] A thin film was prepared by immersing a silica gel plate in a CH3CN / H2O (1:9, v / v) solution (C A3 =2x10 -5 M) of A3 and then drying it in air. When Fe 3+ was dropped onto the thin film, a significant color change (as shown in Figure 17 ) was observed under irradiation at 365 nm using a UV lamp, so the thin film can be used in a convenient detection kit for detecting Fe 3+ .

[0043] In summary, the present application synthesizes a benzylpyranyl ketone small molecule fluorescent probe. In a CH3CN / H2O solution of the fluorescent probe, different metal cations are added respectively, and it is found that only Hg 2+ can enhance the fluorescence of the fluorescent probe, and the addition of Fe 3+ can quench the fluorescence of the fluorescent probe. In addition, in a CH3CN / H2O solution with A3-Hg 2+ as the main body, different anions are added respectively, and it is found that only the addition of I - can weaken the fluorescence of A3-Hg 2+ . Therefore, the fluorescent probe can recognize Fe 3+ , Hg 2+ and I - with high sensitivity and high selectivity, and the recognition process is not disturbed by other metal cations. In addition, the fluorescent probe has good application prospects in detecting the concentration of Hg 2+ in traditional Chinese medicinal materials. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is the hydrogen spectrum of the probe molecule A3 of the present application.

[0045] Figure 2 is the mass spectrum of the probe molecule A3 of the present application.

[0046] Figure 3 ​Full fluorescence scans of probe molecule A3 of this invention with different metal cations added to a CH3CN / H2O (1:9, v / v) solution were performed. Lambda ex =362 nm).

[0047] Figure 4 Hg was added to a CH3CN / H2O (1:9, v / v) solution of probe molecule A3 of the present invention. 2+ Based on this, fluorescence anti-interference diagrams of different metal cations were added respectively.

[0048] Figure 5 Fe was added to a CH3CN / H2O (1:9, v / v) solution of probe molecule A3 of the present invention. 3+ Based on this, fluorescence anti-interference diagrams of different metal cations were added respectively.

[0049] Figure 6 Hg was added to the CH3CN / H2O (1:9, v / v) solution of probe molecule A3 of the present invention. 2+ The fluorescence titration diagram.

[0050] Figure 7 Fe was added to a CH3CN / H2O (1:9, v / v) solution of probe molecule A3 of the present invention. 3+ The fluorescence titration diagram.

[0051] Figure 8 , 9 These are the Hg-related properties of probe molecule A3 of the present invention. 2+ and Fe 3+ The fluorescence titration fitting curve.

[0052] Figure 10 The probe molecule of this invention is A3-Hg. 2+ Fluorescence full scan of CH3CN / H2O (1:9, v / v) solution with different anions added ( Lambda ex =362 nm).

[0053] Figure 11 The probe molecule of this invention is A3-Hg. 2+ I was added to the CH3CN / H2O (1:9, v / v) solution. - Based on this, fluorescence anti-interference diagrams of different anions were added respectively.

[0054] Figure 12 The probe molecule of this invention is A3-Hg. 2+ Add I to the CH3CN / H2O (1:9, v / v) solution -The fluorescence titration curve of the probe molecule A3-Hg

[0055] Figure 13 The working curve of the probe molecule A3 and Hg 2+ - The fluorescence titration fitting curve of the probe molecule A3-Hg

[0056] Figure 14 , 15 The working curve of the probe molecule A3 and Hg 2+ 3+

[0057] Figure 16 The working curve of the probe molecule A3 and I -

[0058] Figure 17 The probe molecule A3 is made into a thin film to detect Hg 2+ 3+ -

[0059] Figure 18 The infrared spectrum of the probe molecule A3 and A3-Hg 2+ 3+ 2+ -I -

[0060] Figure 19 The mass spectrum of the probe molecule A3-Hg 2+

[0061] Figure 20 The mass spectrum of the probe molecule A3-Fe 3+

[0062] Figure 21 The mass spectrum of the probe molecule A3-Hg 2+ +I -

[0063] Figure 22 The linear formula of the probe molecule A3 with the change of Hg 2+ concentration DETAILED DESCRIPTION

[0064] The preparation of the probe molecule A3 and the application of the fluorescence recognition of Hg 2+ 3+ are further illustrated below through specific examples.

[0065] Example 1, fluorescence probe A3

[0066] ​​​​​​​​​​​​​​(1) Take 2-hydroxy-1-naphthaldehyde 3.44 g (20 mmol) and diethyl malonate 3.2 g (20 mmol) dissolved in 50 mL of anhydrous ethanol in a 250 mL round-bottom flask, and add 1 mL of piperidine as a catalyst, heat to reflux at 80~90 ℃ for 4 h, after the reaction is completed, cool the reaction mixture to room temperature, adjust the pH to 5~6 with 4M hydrochloric acid, precipitate, suction filtration, and oven dry to obtain the crude product, recrystallize from methanol to obtain product a.

[0067] (2) Take compound a 2.69 g (10 mmol) and NaOH 1.6 g (10 mmol) dissolved in 40 mL of 95% ethanol and 30 mL of water in a 250 mL round-bottom flask, heat to reflux at 80~90 ℃ for 8 h, after the reaction is completed, add 20 mL of water and adjust the pH to 1~2, a light yellow precipitate is produced, suction filtration, oven dry to obtain the crude product, recrystallize from glacial acetic acid to obtain probe A3.

[0068] Example 2, fluorescent probe A3 recognizes Hg 2+ , Fe 3+

[0069] Respectively, 2 mL of CH3CN / H2O (1:9, v / v) solution of fluorescent probe A3 (C A3 =2×10 -5 M) was taken in a series of colorimetric tubes, and Cu 2+ , Pb 2+ , Cr 3+ , Co 2+ , Ni 2+ , Cd 2+ , Zn 2+ , Ag 2+ , Ca 2+ , Mg 2+ , Al 3+ ,Hg 2+ , Fe 3+ aqueous solution (C=0.1M) was added, if the fluorescence of the CH3CN / H2O solution of fluorescent probe A3 is significantly enhanced, it means that Hg 2+ is added; if the fluorescence of the CH3CN / H2O solution of fluorescent probe A3 is quenched, it means that Fe 3+ is added; if the fluorescence of the CH3CN / H2O solution of fluorescent probe A3 does not change significantly, it means that other metal cations are added.

[0070] Example 3, fluorescent probe A3-Hg 2+ recognizes I -

[0071] Respectively take 2 mL fluorescent probe A3-Hg 2+ CH3CN / H2O (1:9, v / v) solution (C A3-Hg =2×10 2+ - 5 M) in a series of colorimetric tubes, respectively, F - , Cl - , Br - , I - , AC - , H2PO4 - , HSO4 - , ClO4 - , NO3 - , N3 - ,SO3 - aqueous solution (C=0.1M), if the fluorescence of the CH3CN / H2O solution of fluorescent probe A3-Hg 2+ is significantly weakened, it means that I - is added; if the fluorescence of the CH3CN / H2O solution of fluorescent probe A3-Hg 2+ does not change significantly, it means that other anions are added.

[0072] Example 4, fluorescent probe A3 detects mercury in traditional Chinese medicine 2+

[0073] (1) The drawing of standard curve

[0074] Parallelly take several portions of the CH3CN / H2O (1:9, v / v) solution (C A3 =2×10 -5 M) of fluorescent probe A3, add different known concentrations of Hg 2+ standard solution in 5 mL colorimetric tube, place at 30℃ for 40 min, measure the fluorescence intensity with 1cm×1cm quartz sample cell under the condition that the width of incident and emission slit is 5nm and the voltage is 500V. In the range of 1.0×10 -5 ~5.0×10 -5 mol / L, the fluorescence intensity shows good linear relationship with mercury ion, and the regression equation is F=66.385+312.7642 C

[0075] (2) Detecting mercury ion in traditional Chinese medicine

[0076] The to-be-tested traditional Chinese medicine is washed with deionized water, dried at 90°C, and then crushed and sieved through a 200-mesh sieve and stored in a desiccator for standby. 1 g of the above traditional Chinese medicine sample is accurately weighed and placed in a beaker, 5 mL of nitric acid solution and 1 mL of perchloric acid solution are added, and a surface dish is covered and left overnight. The next day, it is placed on an electric heating plate and heated to boiling, and the solution is kept boiling until it is clear. Continue heating until white smoke appears and disappears, and the solution becomes colorless and transparent. After cooling, wash the surface dish and the inner wall of the beaker with ultrapure water, transfer to a 25-mL volumetric flask, and dilute to 25 mL with ultrapure water to obtain a traditional Chinese medicine sample solution for standby. Take the CH3CN / H2O (1:9, v / v) solution of fluorescent probe A3 (C A3 = 2 x 10 -5 M) into a 5-mL cuvette, add the traditional Chinese medicine sample solution, and place it at 30°C for 40 min. Measure the fluorescence intensity at 465 nm with a 1-cm x 1-cm quartz sample cell, an incident and exit slit width of 5 nm, an excitation wavelength of 362 nm, and a voltage of 500 V. Then, according to the regression equation: F = 66.385 + 312.7642 C, the concentration of mercury ions in the traditional Chinese medicine sample solution is obtained as shown in the table below, and the content of mercury ions in the traditional Chinese medicine is calculated according to the mass of the traditional Chinese medicine sample.

[0077] The results of the determination by the fluorescence method proposed in the present application are shown in the table below, and each group of experiments was repeated 6 times. The results show that the fluorescence method proposed in the present application is successfully used for the determination of Hg 2+ in traditional Chinese medicine, and is accurate, reliable, and feasible.

[0078]

Claims

1. The use of naphthobirpiryranone fluorescent probe in detecting mercury ions, iron ions, characterized in that: The structure of the naphthalene benzopyranone fluorescent probe is: ； In the CH3CN / H2O solution of the naphthalene benzyl propyl pyranone fluorescent probe, the aqueous solution of Cu 2+ , Pb 2+ , Cr 3+ , Co 2+ , Ni 2+ , Cd 2+ , Zn 2+ , Ag 2+ , Ca 2+ , Mg 2+ , Al 3+ , Hg 2+ , Fe 3+ was added respectively, only the addition of Hg 2+ can make the fluorescence of the CH3CN / H2O solution of the fluorescent probe significantly enhanced; only the addition of Fe 3+ can make the fluorescence of the CH3CN / H2O solution of the fluorescent probe quenched; in the CH3CN / H2O solution, the volume ratio of CH3CN to H2O is 1:

9.

2. The use of naphthopyranone fluorescent probe in the continuous detection of iodine ions, characterized in that: The structure of the naphthalene benzopyranone fluorescent probe is: ； In the CH3CN / H2O solution of the naphthalene benzyl propyl pyranone fluorescent probe, Hg 2+ was added - , Cl - , Br - , I - , AC - , H2PO4 - , HSO4 - , ClO4 - , NO3 - ,N3 - , SO3 - aqueous solution was added to the CH3CN / H2O solution of the fluorescent probe, only the addition of I - can significantly weaken the fluorescence of the CH3CN / H2O solution of the fluorescent probe; the volume ratio of CH3CN to H2O in the CH3CN / H2O solution is 1:

9.

3. The application of naphthalene phenyl propynone fluorescent probe in detecting Hg 2+ concentration in traditional Chinese medicine, characterized in that: The structure of the naphthalene benzopyranone fluorescent probe is: ； The traditional Chinese medicine includes rhubarb, dangshen, astragalus, angelica and licorice; Hg 2+ Concentration in 1.0 x 10 -5 ~5.0 x 10 -5 mol / L range, the fluorescence intensity and the linear equation of Hg 2+ Concentration in traditional Chinese medicine: F = 66.385 + 312.7642 C, R 2 = 0.9908, where F is the fluorescence intensity, C is the Hg 2+ concentration, in mol / L.

4. The preparation method of the naphthalene benzopyranone fluorescent probe according to any one of claims 1-3, comprising the following steps: (1) synthesis of 3-carboxylic acid ethyl benzopyranone: 2-hydroxy-1-naphthaldehyde and malonic acid diethyl ester are dissolved in anhydrous ethanol, and piperidine is added as a catalyst, and heated to reflux at 80-90 ℃ for 3-5 h, after the reaction is completed, cooled to room temperature, and pH is adjusted to 5-6 with hydrochloric acid, after cooling, filtered and dried, and recrystallized with methanol to obtain 3-carboxylic acid ethyl benzopyranone; (2) 3-carboxylic acid ethyl benzopyranone and NaOH are dissolved in an ethanol aqueous solution, heated to reflux at 80-90 ℃ for 8 h, after the reaction is completed, water is added and pH is adjusted to 1-2 with HCl, a light yellow precipitate is generated, filtered and dried to obtain a crude product, and recrystallized with glacial acetic acid to obtain the naphthalene benzopyranone fluorescent probe.

5. The method for preparing a naphthylphenylpyranone fluorescent probe as described in claim 4, characterized in that: In step (1), the molar ratio of 2-hydroxy-1-naphthaldehyde and malonic acid diethyl ester is 1:1-1:1.5; the molar ratio of piperidine and 2-hydroxy-1-naphthaldehyde is 1:1-1:1.

5.

6. The method for preparing a naphthylphenylpyranone fluorescent probe as described in claim 4, characterized in that: In step (2), the molar ratio of 3-carboxylic acid ethyl benzopyranone and sodium hydroxide is 1:1.5-1:2.

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