A rapid-response and highly sensitive fluorescent probe for detecting Hg 2+ and its preparation method

Abstract

The present invention discloses a fast-responsive and highly sensitive fluorescent probe for detecting Hg<supgt;2+< / supgt> and a preparation method thereof. The method includes the steps: 1. Take 4-(diethylamino)-2-hydroxybenzaldehyde and ethyl cyanoacetate and add them to an ionic liquid composed of 2-hydroxy-N,N,N-trimethylethylammonium chloride and urea, heat and react fully, add deionized water and filter by suction to obtain 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile; 2. Take 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile and Lawesson's reagent and add them to toluene in sequence, heat and react fully, evaporate to remove toluene by rotary evaporation and perform silica gel column chromatography to obtain 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile; 3. Take 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile and add it to a NaOH solution, heat and react fully, cool, dropwise add concentrated hydrochloric acid until the precipitate is completely precipitated, filter and dry to obtain a coumarin-based fluorescent probe, which has the advantages of high detection sensitivity, short response time and strong anti-interference ability to Hg<supgt;2+< / supgt>, and can be used for the detection of Hg<supgt;2+< / supgt> in food and the environment.

Description

Technical Field

[0001] The present invention relates to heavy metal detection, and specifically to a rapid-response and highly sensitive fluorescent probe for detecting Hg 2+ and a preparation method thereof. Background Art

[0002] Mercury is a highly toxic non-essential element. Since mercury is not easily metabolized and excreted in organisms and has a biological enrichment effect along the food chain, its harm is long-term and latent. Once the harm breaks out, it will cause long-term and difficult-to-recover hidden dangers and consequences. Long-term exposure of the human body to a mercury vapor environment will cause involuntary tremors in the limbs, and there will also be symptoms such as irritability, agitation, forgetfulness, shyness, depression, stuttering, timidity, anxiety, restlessness, instability, excitability, inattention, memory loss, and mental depression. Moreover, a series of symptoms can occur in the gastrointestinal tract, urinary system, skin, and eyes. The symptoms of acute mercury poisoning are hepatitis, nephritis, proteinuria, hematuria, and uremia. Therefore, the real-time, rapid, and sensitive detection of mercury content in food and environmental samples has become a highly regarded task and has extremely important scientific research and practical significance.

[0003] Traditional methods for detecting mercury content are mainly achieved through atomic fluorescence spectrometry and atomic absorption spectrometry. However, these methods all rely on large-scale instruments, which are expensive and complex to operate, and require professional testing personnel to operate. The molecular fluorescence probe technology has the characteristics of strong specificity, high sensitivity, simple operation, strong time-space resolution ability, good membrane penetration, etc., and can be used for fluorescence detection research of cells and living tissues. Therefore, it has broad application prospects in the fields of analytical detection and bioimaging.

[0004] A fluorescent probe molecule generally consists of a fluorophore with a signal output function and a functional group with a reaction recognition function. When the probe molecule encounters a specific ion or small molecule, the functional group undergoes specific recognition with the recognition ion, and then a signal conversion from the recognition group to the signal output group occurs to identify and detect the recognition ion. Coumarin compounds are an important part of fluorescent dyes. They can be used in fields such as fluorescent dyes, laser dyes, and optoelectronic materials. They are a class of molecules with a benzopyran structure and have a high fluorescence quantum yield large Stokes shift, adjustable photophysical and photochemical properties, and good photostability, and are considered the preferred fluorophore in the design of fluorescent sensor molecules. Therefore, synthesizing a probe molecule with coumarin as the fluorescent mother nucleus and applying it to the detection of Hg 2+ in food and environmental samples has broad application prospects. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for detecting Hg 2+A rapid-response and highly sensitive fluorescent probe and its preparation method for Hg 2+ It has the advantages of high detection sensitivity, short response time, and strong anti-interference ability.

[0006] To achieve the above object, the present invention is implemented by the following technical solutions:

[0007] A preparation method of a rapid-response and highly sensitive fluorescent probe for detecting Hg 2+ comprises the following steps:

[0008] Step 1: Take 0.05 - 0.5 g of 4-(diethylamino)-2-hydroxybenzaldehyde and 0.025 - 0.3 g of ethyl cyanoacetate and add them to 10 mL of ionic liquid. Heat to 80 - 120 °C and react fully. After the reaction, add deionized water to dissolve the ionic liquid fully, and then filter off the deionized water and ionic liquid to obtain a yellow solid product 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile;

[0009] The ionic liquid is composed of 2-hydroxy-N,N,N-trimethylethylammonium chloride and urea mixed in a mass ratio of (1 - 3):(3 - 1);

[0010] Step 2: Take 0.08 - 0.56 g of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile and 0.2 - 0.8 g of Lawesson's reagent and add them to 50 - 150 mL of toluene in sequence. Heat to 100 - 150 °C and react fully, then rotary evaporate to remove toluene, and perform silica gel column chromatography to obtain 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile;

[0011] Step 3: Take 0.1 - 0.6 g of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile and add it to 10 mL of NaOH solution with a mass fraction of 8 - 20%. Heat to 80 °C and react fully. After the reaction, let it cool naturally, and then dropwise add concentrated hydrochloric acid until the yellow precipitate is completely precipitated. Filter and dry to obtain a coumarin-based fluorescent probe, and its structural formula is as follows:

[0012]

[0013] Further, the reaction time in Step 1 is 6 - 8 h.

[0014] Further, the reaction time in Step 2 is 6 - 12 h.

[0015] Further, the eluent used in the silica gel column chromatography in Step 2 is composed of petroleum ether and ethyl acetate mixed in a volume ratio of 7:1.

[0016] Further, the reaction time in Step 3 is 4 - 8 h.

[0017] Furthermore, the drying temperature in the step 3 is 25 - 80 °C.

[0018] A rapid-response and highly sensitive fluorescent probe for detecting Hg 2+

[0019] Compared with the prior art, the present invention has the following technical effects:

[0020] The fluorescent probe prepared by the present invention has excellent selectivity and fluorescent response performance for Hg 2+ It shows specific recognition ability for water-soluble solutions containing Hg 2+ Moreover, this fluorescent probe has the advantages of excellent water solubility, high detection sensitivity, short response time, strong anti-interference ability proven by experiments, wide pH application range, low detection limit, and wide detection concentration range. It can be used for the detection and analysis of the Hg 2+ content in food and environmental samples, and has strong application prospects. Description of the Drawings

[0021] Figure 1 It is the ion-selective fluorescence spectrogram of the fluorescent probe of the present invention in the EtOH-H2O (5:5, v / v) solvent;

[0022] Figure 2 It is the fluorescence emission spectrogram of the anti-interference ability of the fluorescent probe of the present invention in the EtOH-H2O (5:5, v / v) solvent;

[0023] Figure 3 It is the graph of the change of the fluorescence emission intensity of the fluorescent probe of the present invention with pH in the EtOH-H2O (5:5, v / v) solvent;

[0024] Figure 4 It is the time-response fluorescence emission spectrogram of the fluorescent probe of the present invention in the EtOH-H2O (5:5, v / v) solvent after adding Hg 2+

[0025] Figure 5 It is the graph of the change of the fluorescence intensity of the fluorescent probe of the present invention with the Hg 2+ concentration in the EtOH-H2O (5:5, v / v) solvent;

[0026] Figure 6 It is the linear relationship graph of the fluorescence intensity of the fluorescent probe of the present invention with the Hg 2+ concentration in the EtOH-H2O (5:5, v / v) solvent;

[0027] Figure 7 ​​UV lamp photos of the fluorescent probe of the present invention in EtOH-H2O (5:5, v / v) solutions containing different metal ions;

[0028] Figure 8 Synthetic route diagrams of the coumarin-based fluorescent probes in Examples 1 to 6 of the present invention. Detailed implementation manners

[0029] The following further elaborates on the specific content of the present invention in conjunction with examples.

[0030] Example 1

[0031] Step 1: Take 0.2 g of 4-(diethylamino)-2-hydroxybenzaldehyde and 0.15 g of ethyl cyanoacetate, add them to 10 mL of ionic liquid, heat to 100 °C and react for 6 h. After the reaction, add deionized water to fully dissolve the ionic liquid, and then remove the deionized water and ionic liquid by suction filtration to obtain the yellow solid product 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile, where: the ionic liquid is composed of 2-hydroxy-N,N,N-trimethylethylammonium chloride and urea mixed in a mass ratio of 1:3;

[0032] Step 2: Take 0.24 g of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile and 0.5 g of Lawesson's reagent, add them to 50 mL of toluene in sequence, heat to 110 °C and react for 10 h. After the reaction, then remove toluene by rotary evaporation to obtain mixture A; use a mixture of petroleum ether and ethyl acetate with a volume ratio of 7:1 as the eluent for silica gel column chromatography of mixture A to obtain 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile;

[0033] Step 3: Take 0.26 g of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile, add it to 10 mL of 10% NaOH solution by mass, heat to 80 °C and react for 4 h. After natural cooling, drop in concentrated hydrochloric acid until the yellow precipitate is completely precipitated, filter and dry to obtain the coumarin-based fluorescent probe, and its structural formula is as follows:

[0034]

[0035] In Example 1, the yield of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile is 92%, the yield of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile is 33.7%, and the yield of the fluorescent probe molecule is 85%.

[0036] Example 2

[0037] Step 1: Take 0.05 g of 4-(diethylamino)-2-hydroxybenzaldehyde and 0.25 g of ethyl cyanoacetate and add them to 10 mL of ionic liquid. Heat to 80 °C and react for 7 h. After the reaction is completed, add deionized water to fully dissolve the ionic liquid, and then remove the deionized water and ionic liquid by suction filtration to obtain the yellow solid product 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile, where: the ionic liquid is composed of 2-hydroxy-N,N,N-trimethylethylammonium chloride and urea mixed in a mass ratio of 2:3;

[0038] Step 2: Take 0.08 g of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile and 0.2 g of Lawesson's reagent and add them to 70 mL of toluene in turn. Heat to 120 °C and react for 6 h. After the reaction is completed, then rotary evaporate to remove toluene to obtain mixture A; Mix petroleum ether and ethyl acetate in a volume ratio of 7:1 as the eluent and perform silica gel column chromatography on mixture A to obtain 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile;

[0039] Step 3: Take 0.1 g of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile and add it to 10 mL of 8% NaOH solution by mass. Heat to 80 °C and react for 5 h. After natural cooling, drop in concentrated hydrochloric acid until the yellow precipitate is completely precipitated, filter and dry to obtain the coumarin-based fluorescent probe, and its structural formula is as follows:

[0040]

[0041] In Example 2, the yield of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile is 60%, the yield of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile is 15%, and the yield of the fluorescent probe molecule is 80%.

[0042] Example 3

[0043] Step 1: Take 0.28 g of 4-(diethylamino)-2-hydroxybenzaldehyde and 0.16 g of ethyl cyanoacetate and add them to 10 mL of ionic liquid. Heat to 90 °C and react for 8 h. After the reaction is completed, add deionized water to fully dissolve the ionic liquid, and then remove the deionized water and ionic liquid by suction filtration to obtain the yellow solid product 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile, where: the ionic liquid is composed of 2-hydroxy-N,N,N-trimethylethylammonium chloride and urea mixed in a mass ratio of 1:1;

[0044] Step 2: Take 0.32 g of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile and 0.3 g of Lawesson's reagent and add them to 90 mL of toluene in turn. Heat the mixture to 100 °C and react for 8 h. After the reaction is completed, then rotary evaporate to remove toluene to obtain mixture A; Use a mixture of petroleum ether and ethyl acetate with a volume ratio of 7:1 as the eluent for silica gel column chromatography of mixture A to obtain 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile;

[0045] Step 3: Take 0.25 g of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile and add it to 10 mL of a NaOH solution with a mass fraction of 14%. Heat the mixture to 80 °C and react for 6 h. After natural cooling, dropwise add concentrated hydrochloric acid until the yellow precipitate is completely precipitated. Filter and dry to obtain the coumarin-based fluorescent probe, and its structural formula is as follows:

[0046]

[0047] In Example 3, the yield of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile was 75%, the yield of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile was 20%, and the yield of the fluorescent probe molecule was 90%.

[0048] Example 4

[0049] Step 1: Take 0.1 g of 4-(diethylamino)-2-hydroxybenzaldehyde and 0.23 g of ethyl cyanoacetate and add them to 10 mL of ionic liquid. Heat the mixture to 110 °C and react for 6 h. After the reaction is completed, add deionized water to fully dissolve the ionic liquid, and then remove the deionized water and the ionic liquid by suction filtration to obtain the yellow solid product 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile, where: the ionic liquid is composed of 2-hydroxy-N,N,N-trimethylethylammonium chloride and urea mixed in a mass ratio of 1:2;

[0050] Step 2: Take 0.95 g of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile and 0.4 g of Lawesson's reagent and add them to 110 mL of toluene in turn. Heat the mixture to 130 °C and react for 9 h. After the reaction is completed, then rotary evaporate to remove toluene to obtain mixture A; Use a mixture of petroleum ether and ethyl acetate with a volume ratio of 7:1 as the eluent for silica gel column chromatography of mixture A to obtain 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile;

[0051] Step 3: Take 0.4 g of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile and add it to 10 mL of a NaOH solution with a mass fraction of 16%. Heat the mixture to 80 °C and react for 7 h. After natural cooling, dropwise add concentrated hydrochloric acid until the yellow precipitate is completely precipitated. Filter and dry to obtain the coumarin-based fluorescent probe, and its structural formula is as follows:

[0052]

[0053] In Example 4, the yield of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile was 85%, the yield of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile was 25%, and the yield of the fluorescent probe molecule was 82%.

[0054] Example 5

[0055] Step 1: Take 0.35 g of 4-(diethylamino)-2-hydroxybenzaldehyde and 0.3 g of ethyl cyanoacetate and add them to 10 mL of ionic liquid. Heat to 120 °C and react for 8 h. After the reaction is completed, add deionized water to fully dissolve the ionic liquid, and then remove the deionized water and ionic liquid by suction filtration to obtain the yellow solid product 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile, where: the ionic liquid is composed of 2-hydroxy-N,N,N-trimethylethylammonium chloride and urea mixed in a mass ratio of 3:2;

[0056] Step 2: Take 0.45 g of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile and 0.6 g of Lawesson's reagent and add them to 130 mL of toluene in turn. Heat to 140 °C and react for 11 h. After the reaction is completed, then remove the toluene by rotary evaporation to obtain mixture A; Use a mixture of petroleum ether and ethyl acetate in a volume ratio of 7:1 as the eluent for silica gel column chromatography of mixture A to obtain 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile;

[0057] Step 3: Take 0.5 g of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile and add it to 10 mL of a 18% NaOH solution by mass. Heat to 80 °C and react for 8 h. After natural cooling, drop in concentrated hydrochloric acid until the yellow precipitate is completely precipitated, filter and dry to obtain the coumarin-based fluorescent probe, and its structural formula is as follows:

[0058]

[0059] In Example 5, the yield of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile was 95%, the yield of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile was 45%, and the yield of the fluorescent probe molecule was 95%.

[0060] Example 6

[0061] Step 1: Take 0.5 g of 4-(diethylamino)-2-hydroxybenzaldehyde and 0.85 g of ethyl cyanoacetate and add them to 10 mL of ionic liquid. Heat the mixture to 100 °C and react for 7 h. After the reaction is completed, add deionized water to fully dissolve the ionic liquid, and then remove the deionized water and ionic liquid by suction filtration to obtain the yellow solid product 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile, where: the ionic liquid is composed of 2-hydroxy-N,N,N-trimethylethylammonium chloride and urea mixed in a mass ratio of 3:1;

[0062] Step 2: Take 0.56 g of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile and 0.8 g of Lawesson's reagent and add them to 150 mL of toluene in sequence. Heat the mixture to 150 °C and react for 12 h. After the reaction is completed, then remove the toluene by rotary evaporation to obtain mixture A; Use a mixture of petroleum ether and ethyl acetate with a volume ratio of 7:1 as the eluent for silica gel column chromatography of mixture A to obtain 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile;

[0063] Step 3: Take 0.6 g of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile and add it to 10 mL of 20% NaOH solution by mass fraction. Heat the mixture to 80 °C and react for 4 h. After natural cooling, drop concentrated hydrochloric acid until the yellow precipitate is completely precipitated, filter and dry to obtain the coumarin-based fluorescent probe, and its structural formula is as follows:

[0064]

[0065] In Example 6, the yield of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile is 90%, the yield of 7-(diethylamino)-2-thioxo-2H-chromene-3-carbonitrile is 30%, and the yield of the fluorescent probe molecule is 93%.

[0066] See Figure 8 For the synthesis route of the coumarin-based fluorescent probe, the probes prepared in Examples 1 to 6 appear as a yellow solution when dissolved in an EtOH-H2O (5:5, v / v) solvent and have blue-green fluorescence. The optimal excitation and optimal emission wavelengths are 410 nm and 475 nm respectively. When a solution containing Hg 2+ is added to the solution, the S atom on the probe molecule coordinates with Hg 2+ to occur a coordination effect. The yellow solution quickly turns into a red suspension. After a few minutes, the red coordination complex precipitates, and the supernatant becomes colorless. At the same time, the blue-green fluorescence of the probe molecule disappears. As Figure 7 shown, after adding a solution containing Hg 2+After the solution, when the EtOH-H2O (5:5, v / v) solution containing the fluorescent probe prepared in Example 1 was used, the fluorescence was quenched, while when other metal ions were added to the EtOH-H2O (5:5, v / v) solution containing the fluorescent probe prepared in Example 1, the fluorescence hardly changed. Therefore, Hg in the analyte can be detected by measuring the change in fluorescence intensity of the probe solution before and after the reaction with Hg 2+ to achieve the purpose of determining the concentration and content of Hg 2+ in the analyte.

[0067] For the performance tests of the coumarin-based fluorescent probe prepared in Example 1, see Examples 7 to 12 in detail.

[0068] Example 7

[0069] Determine the ion selectivity of the fluorescent probe prepared in Example 1:

[0070] First, use EtOH-H2O (5:5, v / v) as the solvent to accurately prepare a 1 μM fluorescent probe stock solution. Then, dilute the fluorescent probe stock solution with EtOH-H2O (5:5, v / v) and prepare several equal-volume probe test solutions with a concentration of 50 nM as needed. Add metal ion aqueous solutions to each probe test solution, and the metal ion aqueous solutions added to each probe test solution are different. After adding the metal ion aqueous solutions, the molar concentration of the metal ion in each final solution is the same as that of the probe. Measure its fluorescence emission spectrum at an excitation wavelength of 410 nm. The measurement results are as Figure 1 shown. It can be seen that the fluorescent probe prepared in Example 1 only shows an obvious selective response to Hg 2+ and has no obvious response to other metal ions.

[0071] Example 8

[0072] Determine the anti-interference ability of the fluorescent probe prepared in Example 1:

[0073] First, use EtOH-H2O (5:5, v / v) as the solvent and prepare several equal-volume fluorescent probe test solutions with a concentration of 50 nM as needed. Add 5 μL of interference metal ion solutions with the same molar concentration to each test solution, and then add 5 μL of Hg 2+ solution to each test solution. Finally, several mixed solutions B with the same concentration are obtained. Measure the fluorescence emission spectra of each test solution before adding the Hg 2+ solution and each mixed solution B after adding the Hg 2+ solution at an excitation wavelength of 410 nm. The measurement results are as Figure 2 shown. It can be seen that in the presence of interfering ions, the fluorescent probe prepared in Example 1 shows a response to Hg2+ The determination is basically not interfered by other coexisting metal ions.

[0074] Example 9

[0075] Determine the molecular response performance of the fluorescent probe prepared in Example 1 at different pH values:

[0076] Accurately prepare several solutions C with different pH values using EtOH-H2O (5:5, v / v) as the solvent. Using solution C as the solvent, prepare several equal-volume probe test solutions with a concentration of 50 nM. Then, add Hg with the same concentration as the probe test solution to each probe test solution. 2+ solution, and respectively measure the fluorescence emission intensity of the test solution before and after adding Hg 2+ solution at an excitation wavelength of 410 nm. The measurement results are as Figure 3 shown. It can be seen that the probe has good response ability to Hg in the pH range of 1.5 - 12.1. 2+ All have good response ability.

[0077] Example 10

[0078] Determine the response time of the fluorescent probe prepared in Example 1:

[0079] Prepare a 50 nM probe test solution using EtOH-H2O (5:5, v / v) as the solvent. Add Hg three times the concentration of the probe to the probe solution. 2+ solution, and respectively measure the fluorescence emission spectrum of the solution at an excitation wavelength of 410 nm at certain time intervals. The measurement results are as Figure 4 shown. It can be seen that the fluorescence intensity value rapidly drops to the lowest value and tends to be stable 2 minutes after adding Hg 2+ solution. Therefore, the fluorescent probe prepared in Example 1 can achieve accurate determination of Hg after 2 minutes. 2+ accurate determination.

[0080] Example 11

[0081] Determine the titration and detection range of the fluorescent probe prepared in Example 1:

[0082] Prepare several probe test solutions with a concentration of 50 nM using EtOH-H2O (5:5, v / v) as the solvent. Add Hg to each probe test solution. 2+ solution to make the concentration of the mixed system solution within 0 - 30 nM, and measure its fluorescence emission spectrum at an excitation wavelength of 410 nm. The measurement results are as Figure 5 shown. It can be seen that the fluorescence emission intensity of the probe prepared in Example 1 gradually decreases with the increase of Hg 2+ concentration. The measurement results are as Figure 6As shown, when the concentration of Hg in the mixed solution 2+ is in the range of 0 - 1.0 nmol·L -1 , an obvious linear relationship is shown (R 2 = 0.9984). The detection limit concentration of Hg 2+ is 0.008 nmol·L -1 .

[0083] Example 12

[0084] The fluorescent probe prepared in Example 1 was used to measure the actual samples and the spiked recovery samples:

[0085] Several portions of the probe test solution with a concentration of 50 nM were prepared using EtOH-H2O (5:5, v / v) as the solvent. Rice and surface water were digested with nitric acid and diluted to a constant volume with ultrapure water to obtain the actual samples D and E. The spiked recovery samples of the actual samples D and E were respectively prepared. The actual samples D and E and their spiked recovery samples were respectively added to the probe test solution, and the fluorescence emission spectra of the probe test solution at an excitation wavelength of 410 nm were measured. A standard curve was established by preparing a series of concentration mercury ion solutions. The measurement results are shown in Table 1. It can be seen that the measurement results of the fluorescent probe are similar to those of the atomic fluorescence method, and the spiked recovery rate of the fluorescent probe is in the range of 102.2% - 111.5%, meeting the requirements of food and environmental detection.

[0086] Table 1 Measurement results of the mercury content in actual samples and spiked recovery experiments of the fluorescent probe prepared in Example 1

[0087]

[0088] Note: Nd = Not detected.

Claims

1. A preparation method of a fast-response and highly sensitive fluorescent probe for detecting Hg 2+ , characterized in that The steps include: Step 1, taking 0.05-0.5 g of 4-(diethylamino)-2-hydroxybenzaldehyde and 0.025-0.3 g of ethyl cyanoacetate, adding them to 10 mL of ionic liquid, heating to 80-120° C. and fully reacting, after the reaction is completed, adding deionized water to fully dissolve the ionic liquid, and then filtering off the deionized water and the ionic liquid to obtain a yellow solid product 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile; The ionic liquid is prepared by mixing 2-hydroxy-N,N,N-trimethylethylammonium chloride and urea in a mass ratio of (1-3):(3-1); Step 2, taking 0.08-0.56 g of 7-(diethylamino)-2-oxo-2H-chromene-3-carbonitrile and 0.2-0.8 g of Lawesson's reagent, sequentially adding them into 50-150 mL of toluene, heating to 100-150° C. and fully reacting, then removing toluene by rotary evaporation, and performing silica gel column chromatography to obtain 7-(diethylamino)-2-thio-2H-chromene-3-carbonitrile; Step 3, take 0.1-0.6g 7-(diethylamino)-2-thio-2H-chromene-3-carbonitrile and add it to 10mL of 8-20% NaOH solution, heat it to 80°C and react it fully, let it cool naturally after the reaction is completed, then add concentrated hydrochloric acid dropwise until the yellow precipitate is completely precipitated, filter and dry to obtain a coumarin-based fluorescent probe, the structural formula of which is as follows:

2. The preparation method of the fast-response and highly sensitive fluorescence probe for detecting Hg 2+ is characterized in that The reaction time in step 1 is 6 to 8 hours.

3. The preparation method of a rapid-response and highly sensitive fluorescent probe for detecting Hg 2+ , characterized in that The reaction time in step 2 is 6 to 12 hours.

4. A method for preparing a rapid-response and highly sensitive fluorescence probe for detecting Hg 2+ , characterized in that The eluent used in the silica gel column chromatography in step 2 is a mixture of petroleum ether and ethyl acetate in a volume ratio of 7:

1.

5. The preparation method of a fast-response and highly sensitive fluorescence probe for detecting Hg 2+ , characterized in that The reaction time in step 3 is 4 to 8 hours.

6. The preparation method of the fast-responsive and highly sensitive fluorescence probe for detecting Hg 2+ , characterized in that The drying temperature in step 3 is 25-80°C.

7. A rapid-response and highly sensitive fluorescent probe for detecting Hg prepared by the method according to any one of claims 1 to 6 2+ ​

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