Fluorescent probe as well as synthesis method and application thereof

Abstract

The invention discloses a fluorescent probe and a synthesis method and application thereof.The synthesis method of the fluorescent probe comprises the following steps that 2, 5-dibromothiophene-3-formaldehyde and 2, 6-bis (trimethyltin) dithieno-cyclopentadiene derivatives are subjected to a Stille coupling reaction, and a polymer P1 is obtained; then the polymer P1 and thiosemicarbazide are subjected to the following reaction to obtain the fluorescent probe: the polymer P1 and THF are mixed to obtain a mixed solution, an ethanol solution of thiosemicarbazide is dropwise added into the mixed solution, stirring reaction is performed for 10-24 h at the temperature of 20-50 DEG C to obtain a reaction solution, the reaction solution is concentrated and then dropwise added into water, suction filtration, washing and drying are performed, and a purple solid, namely the fluorescent probe, is obtained, and the ratio of the polymer P1 to thiosemicarbazide in the ethanol solution of thiosemicarbazide is 1: (8-20) according to the amount of substance. The fluorescent probe disclosed by the invention is high in response speed (the response time is less than 1min), and can be used for rapidly detecting the concentration of Hg < 2 + > in a water sample.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescence sensing detection, and in particular relates to a fluorescent probe based on a conjugated polymer and a synthesis method and application thereof. Background Art

[0002] Mercury ion (Hg 2+ ) is widely present in various media such as industrial wastewater, soil, and crops. It can be converted into fat-soluble poisons under the action of microorganisms and enter the human body. It is enriched in human organs, causing damage to the human immune system, nervous system, and endocrine system, posing a serious threat to human life and health. In 2022, my country made special arrangements to strengthen the prevention and control of heavy metal pollution, and listed mercury as one of the key heavy metals under control. Therefore, the development of simple, fast, and reliable methods for detecting mercury ions is very important for maintaining human life and health and protecting the environment.

[0003] At present, the main methods for detecting mercury ions include atomic absorption spectroscopy, ultraviolet-visible spectrophotometry, inductively coupled plasma mass spectrometry, electrochemical method, etc. These methods usually require cumbersome pretreatment of the test samples, with complex steps and harsh detection conditions. In addition, the test results are easily affected by the detection environment, making it difficult to achieve real-time on-site detection of mercury ions. Compared with the above detection methods, fluorescent probe technology has the advantages of low detection cost, simple operation, and high sensitivity in detecting metal ions. In recent years, people have developed some mercury ion fluorescent probes based on organic small molecules, but there are relatively few reports on mercury ion fluorescent probes based on conjugated polymers, and these probes have disadvantages such as long response time and low sensitivity. Summary of the invention

[0004] In view of the deficiencies in the prior art, an object of the present invention is to provide a fluorescent probe, which has a fast response and high sensitivity and can detect mercury ion concentration quickly and in real time.

[0005] Another object of the present invention is to provide a method for synthesizing the fluorescent probe.

[0006] Another object of the present invention is to provide an application of the fluorescent probe in detecting mercury ion concentration.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] A fluorescent probe, the general structural formula of which is as follows:

[0009]

[0010] Wherein, the two R connected to the same five-membered ring are independent of each other (the two R connected to the same five-membered ring may be the same or different), R is a C1-C30 alkyl group, p is a natural number of 1-50, and q is a natural number of 1-50.

[0011] The synthesis method of the fluorescent probe comprises the following steps: mixing polymer P1 and THF to obtain a mixed solution, adding an ethanol solution of thiosemicarbazide dropwise to the mixed solution, stirring and reacting at 20-50° C. for 10-24 hours to obtain a reaction solution, concentrating the reaction solution and then adding it dropwise into water, filtering, rinsing, and drying to obtain a purple solid as a fluorescent probe (FP-Hg), wherein, in terms of the amount of substance, the ratio of thiosemicarbazide in the ethanol solution of polymer P1 and thiosemicarbazide is 1:(8-20), and the structural formula of the polymer P1 is:

[0012] In the above technical solution, the ratio of the amount of the polymer P1 to the volume of THF is 1:(50-100), the unit of the amount of the polymer P1 is mmol, and the unit of the volume is mL.

[0013] In the above technical solution, the ethanol solution of thiosemicarbazide is a mixture of thiosemicarbazide and ethanol, and the concentration of thiosemicarbazide in the ethanol solution of thiosemicarbazide is 0.3-0.8 mol / L.

[0014] In the above technical scheme, 2,5-dibromothiophene-3-carboxaldehyde and 2,6-di(trimethyltin)dithienocyclopentadiene derivative are subjected to Stille coupling reaction to obtain polymer P1. The method for the Stille coupling reaction of 2,5-dibromothiophene-3-carboxaldehyde and 2,6-di(trimethyltin)dithienocyclopentadiene derivative comprises: adding anhydrous toluene and Pd(PPh3)4 to 2,5-dibromothiophene-3-carboxaldehyde and 2,6-di(trimethyltin)dithienocyclopentadiene in a nitrogen atmosphere; The mixture of cyclopentadiene derivatives is stirred and reacted at 90-110° C. for 48-72 hours to obtain a reaction solution, and the reaction solution is added dropwise into methanol, filtered to obtain a solid, extracted, and the extract is collected. The solvent is removed by rotary evaporation to obtain a purple solid as polymer P1, wherein the ratio of the 2,5-dibromothiophene-3-carboxaldehyde to the 2,6-di(trimethyltin)dithienocyclopentadiene derivative is 1:1, and the structural formula of the 2,6-di(trimethyltin)dithienocyclopentadiene derivative is:

[0015]

[0016] In the above technical solution, the ratio of the volume fraction of anhydrous toluene to the amount fraction of 2,5-dibromothiophene-3-carboxaldehyde is 1:(0.05-0.3), the unit of the volume fraction is mL, and the unit of the amount fraction is mmol.

[0017] In the above technical solution, the ratio of Pd(PPh3)4 and 2,5-dibromothiophene-3-carboxaldehyde is (0.01-0.1):1 in terms of the amount of the substances.

[0018] In the above technical solution, the extraction is to place the solid in a Soxhlet extractor and extract it with methanol, n-hexane and chloroform in sequence.

[0019] In the above technical solution, the ratio of methanol to anhydrous toluene is (10-25):1 by volume.

[0020] The application of the fluorescent probe in detecting the concentration of mercury ions includes the following steps:

[0021] S1, preparing N portions of solution A having the same concentration of the fluorescent probe, each portion of solution A being: dissolving the fluorescent probe in THF to obtain solution A;

[0022] In S1, the concentration of the fluorescent probe in solution A is 1×10 -5 ~50×10 -5 M.

[0023] S2, preparing N portions of a standard aqueous solution containing mercury ions, wherein the N portions of the standard aqueous solution have different concentrations of mercury ions, and respectively adding a portion of the standard aqueous solution to N portions of solution A so that the concentration of the fluorescent probe is C1, to obtain N portions of standard spectrum test solutions, exciting each portion of the standard spectrum test solution with light of a wavelength of P1 nm, to obtain N fluorescence emission spectra, and drawing a linear relationship curve between the maximum fluorescence intensity of the fluorescence emission spectrum of the standard spectrum test solution and the concentration of mercury ions in the standard aqueous solution;

[0024] In S2, the mercury ion concentration in the N parts of the standard aqueous solution ranges from 0.015 to 0.5 mmol.

[0025] In S2, the ratio of solution A to the standard aqueous solution is 2000:(0-100) by volume.

[0026] S3, prepare a portion of solution A, add the test solution to solution A so that the concentration of the fluorescent probe is C1, obtain a spectral test solution, use light with a wavelength of P1 nm to excite the spectral test solution, obtain a fluorescence emission spectrum, substitute the maximum fluorescence intensity of the fluorescence emission spectrum of the spectral test solution into the linear relationship curve, and obtain the mercury ion concentration in the test solution.

[0027] In the above technical solution, P1=470-520 nm, and the wavelength of the maximum fluorescence intensity is located at 625-700 nm.

[0028] In the above technical solution, C1 is less than the concentration of the fluorescent probe in solution A.

[0029] A portable paper-type sensor comprises filter paper and a fluorescent probe loaded on the filter paper.

[0030] The preparation method of the portable paper sensor comprises: dissolving the fluorescent probe in THF to prepare a fluorescent probe concentration of 2×10 -5 ~10×10 -5 M's first solution, soaking the filter paper in the first solution for 10 to 24 hours, taking out the filter paper, and drying it to obtain a portable paper sensor.

[0031] The method for using the portable paper-type sensor comprises: preparing a plurality of mercury salt aqueous solutions as standard solutions, wherein the mercury ion concentrations in the plurality of mercury salt aqueous solutions are different, soaking a portable paper-type sensor in each mercury salt aqueous solution, taking it out to dry, and directly observing it under sunlight / exciting it with an ultraviolet lamp;

[0032] The colors of the portable paper sensors of all standard solutions observed directly in sunlight / excited by ultraviolet light are used as comparison standard cards; one of the portable paper sensors is immersed in the solution to be tested, taken out and dried, and directly observed in sunlight / excited by ultraviolet light to obtain the color of the portable paper sensor of the solution to be tested observed directly in sunlight / excited by ultraviolet light, and the comparison standard card to which the color of the portable paper sensor of the solution to be tested observed directly in sunlight / excited by ultraviolet light is close is determined, and the mercury ion concentration in the standard solution corresponding to the close comparison standard card is used as the mercury ion concentration in the solution to be tested.

[0033] In the above technical solution, the concentration of mercury ions in the standard solution includes: (1.8-2.2)×10 -6 、(3.8~4.2)×10 -6 、(5.8~6.2)×10 -6 、(7.8~8.2)×10 -6 and (9.8~10.2)×10 -6 M.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. The fluorescent probe of the present invention has a fast response speed (response time < 1 min) and can be used to detect Hg in water samples. 2+ Rapid detection of concentration;

[0036] 2. The fluorescent probe of the present invention has high sensitivity and a linear detection range of 0-10 μM, which meets the requirements of my country's standards for the detection of mercury content in drinking water (drinking water ≤ 0.001 mg / L);

[0037] 3. The fluorescent probe of the present invention can be made into a portable paper sensor to achieve real-time on-site naked eye detection of Hg 2+ content. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the principle of detecting mercury ion concentration using fluorescent probe;

[0039] Figure 2 is a fluorescence emission spectrum of N wavelengths in the range of 520-900 nm in the embodiment;

[0040] Figure 3 It is the linear relationship curve between the maximum fluorescence intensity of the fluorescence emission spectrum and the concentration of mercury ions in the standard aqueous solution;

[0041] Figure 4 The portable paper sensor is used to detect different Hg 2+ Response plots of concentrations;

[0042] Figure 5 Infrared spectra of the fluorescent probe and polymer P1. DETAILED DESCRIPTION

[0043] like Figure 1 As shown in the figure, the fluorescent probe can produce strong fluorescence under the excitation of light with a wavelength of 490nm, and the semicarbazide in the fluorescent probe structure acts as a mercury ion (Hg 2+ ) recognition site, which can bind to mercury ions (Hg 2+ ) binds to quench the fluorescence of the fluorescent probe.

[0044] The synthetic route of the present invention is:

[0045]

[0046] 2,5-Dibromothiophene-3-carboxaldehyde and 2,6-di(trimethyltin)dithienocyclopentadiene derivative were reacted through Stille coupling reaction to obtain polymer P1, and then polymer P1 was reacted with semicarbazide to obtain the target product fluorescent probe (FP-Hg).

[0047] Purity and purchase sources of the drugs in the following examples:

[0048] 2,6-Bis(trimethyltin)-4,4-di(2-ethylhexyl)dithienocyclopentadiene was purchased from Nanjing Zhiyan Technology Co., Ltd.; thiophene-3-carboxaldehyde, N-bromosuccinimide, semicarbazide and tetrakis(triphenylphosphine)palladium (Pd(PPh3)4) were purchased from Tianjin Xiensi Biochemical Technology Co., Ltd.; anhydrous sodium sulfate, N,N-dimethylformamide (DMF), tetrahydrofuran (THF), toluene, methanol, n-hexane and ethanol were all purchased from Tianjin Hengshan Chemical Technology Co., Ltd.; chloroform was purchased from Tianjin Bohai Chemical Reagent Co., Ltd.; mercuric perchlorate trihydrate was purchased from Nanjing Duobo Chemical Co., Ltd.

[0049] The models of the instruments involved in the following embodiments are as follows:

[0050] UV-visible spectrometer UV 2550; fluorescence spectrometer F4600 FL; nuclear magnetic resonance instrument Varian Unityplus400MHz NMR; Fourier transform infrared spectrometer ALPHA II FT-IR; electronic balance ML204 / 02.

[0051] The preparation of 2,5-dibromothiophene-3-carboxaldehyde in the following example comprises: adding thiophene-3-carboxaldehyde (1.1215 g, 10 mmol) and 10 mL of anhydrous DMF to a 50 mL three-necked round-bottom flask under an ice bath, stirring to completely dissolve the thiophene-3-carboxaldehyde, and in a nitrogen atmosphere and dark conditions, adding 15 mL of a DMF solution of N-bromosuccinimide (15 mL A DMF solution of N-bromosuccinimide containing 50 mmol (8.8995 g) of N-bromosuccinimide) was added dropwise to the above reaction solution. After the addition was completed, the reaction was continued to stir at room temperature for 48 hours. The reaction was stopped, and the reaction mixture was added dropwise to 250 mL of deionized water. The mixture was extracted with ether (50 mL, 3 times). The ether layers were combined, dried over anhydrous sodium sulfate, filtered, and the ether was removed by rotary evaporation to obtain an orange-yellow solid crude product. The orange-yellow solid crude product was recrystallized from n-heptane to obtain a light yellow needle-like solid of 2,5-dibromothiophene-3-carboxaldehyde (1.4255 g, yield 52%).

[0052] The NMR of 2,5-dibromothiophene-3-carboxaldehyde is: 1 H NMR (400MHz, Chloroform-d) δ9.79 (s, 1H), 7.34 (s, 1H).

[0053] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0054] Example 1

[0055] A method for synthesizing a fluorescent probe comprises the following steps: subjecting 2,5-dibromothiophene-3-carboxaldehyde and 2,6-di(trimethyltin)-4,4-di(2-ethylhexyl)dithienocyclopentadiene to Stille coupling reaction to obtain a polymer P1, and then subjecting the polymer P1 to the following reaction with thiosemicarbazide to obtain a fluorescent probe: dissolving the polymer P1 (150 mg, 0.3 mmol) in 20 mL THF was added to obtain a mixed solution, and an ethanol solution of thiocarbamide was added dropwise to the mixed solution (the ethanol solution of thiocarbamide was 6 mL, the concentration of thiocarbamide in the ethanol solution of thiocarbamide was 0.5 mol / L, and the ethanol solution of thiocarbamide in 6 mL of thiocarbamide was (266.1 mg, 3 mmol)). After the addition was completed, the reaction was carried out at 45° C. with magnetic stirring for 12 h, and the reaction was stopped to obtain a reaction solution. The reaction solution was concentrated to about 2 mL, and then added dropwise to 50 mL of deionized water, and filtered to obtain a filter cake. The filter cake was rinsed with ethanol for 3 times, and vacuum dried to obtain a purple solid as a fluorescent probe (FP-Hg). The yield of the fluorescent probe was 153.2 mg, and the yield was 89%. Among them, the structural formula of polymer P1 is:

[0056]

[0057] like Figure 5 As shown, 1669cm -1 The absorption peak at 1643 cm is the C=O functional group, which can be used as the characteristic peak of polymer P1. When polymer P1 reacts with thiosemicarbazide to generate FP-Hg, the characteristic peak of polymer P1 disappears, while the absorption peak at 1643 cm -1 A new absorption peak appears at the C=N functional group, which can be used as the characteristic peak of FP-Hg, proving the successful synthesis of the fluorescent probe.

[0058] In the above-mentioned synthesis method, the method for Stille coupling reaction of 2,5-dibromothiophene-3-carboxaldehyde and 2,6-bis(trimethyltin)-4,4-bis(2-ethylhexyl)dithienocyclopentadiene comprises: adding 5 mL of anhydrous toluene to a mixture of 2,5-dibromothiophene-3-carboxaldehyde (67.5 mg, 0.25 mmol) and 2,6-bis(trimethyltin)-4,4-bis(2-ethylhexyl)dithienocyclopentadiene (0.1821 g, 0.25 mmol) in a nitrogen atmosphere, stirring magnetically until complete. Dissolve, add Pd(PPh3)4 (0.0288 g, 0.025 mmol) to the above reaction solution, seal the reaction bottle, heat to 110°C, continue to react at 110°C with stirring for 48 hours, stop the reaction to obtain a reaction solution, add the reaction solution dropwise into 100 mL of methanol, filter to obtain a solid, place the obtained solid in a Soxhlet extractor, extract with methanol, n-hexane and chloroform in turn, collect the chloroform extract, and remove the solvent by rotary evaporation to obtain a purple solid as polymer P1. The yield of polymer P1 is 62 mg, and the yield is 48%.

[0059] The NMR of polymer P1 is: 1 H NMR(400MHz,THF-d8)δ10.15(s,1H),7.62(d,J=14.7Hz,2H),7.44(td,J=13.1,11 .1,5.4Hz,1H),2.51(s,4H),2.06(s,3H),1.05(s,14H),0.73(d,J=33.2Hz,13H).

[0060] The structural formula of 2,6-bis(trimethyltin)-4,4-bis(2-ethylhexyl)dithienocyclopentadiene is:

[0061]

[0062] Example 2

[0063] The application of the fluorescent probe in detecting the concentration of mercury ions includes the following steps:

[0064] S1, prepare N portions of solution A with the same concentration of fluorescent probe, each portion of solution A is: dissolve the fluorescent probe (FP-Hg) in THF to obtain a fluorescent probe concentration of 2×10 -5 M solution A, N = 13;

[0065] S2, prepare N portions of standard aqueous solutions containing mercury ions, the concentrations of mercury ions in the N portions of standard aqueous solutions are different, and the concentrations of mercury ions in the N portions of standard aqueous solutions are 0.015, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18 and 0.2 mmol, respectively. Take 2 mL of solution A and place it in a quartz cuvette. Add 4 μL of the standard aqueous solution to each portion of solution A so that the concentration of the fluorescent probe is C1 (C1 is the concentration of the fluorescent probe before the reaction with mercury ions), and obtain N portions of standard spectral test solution, C1 is slightly less than 2×10 -5 M, 1 minute later, use P1 nm (490 nm) wavelength light to excite each standard spectrum test solution to obtain N fluorescence emission spectra in the range of 520-900 nm, such as Figure 2 As shown, a linear relationship curve between the maximum fluorescence intensity of the fluorescence emission spectrum of the standard spectral test solution and the concentration of mercury ions in the standard aqueous solution is drawn, such as Figure 3 As shown, Hg in standard aqueous solution 2+ The concentration is the horizontal axis, and the maximum fluorescence intensity of the fluorescence emission spectrum is the vertical axis. The equation of the linear relationship curve is F = 1648.94-119[Hg 2+ ], R 2 =0.977, detection range: [Hg 2+ ]=0~10μM([Hg 2+ ] represents the concentration of mercury ions, and F is the fluorescence intensity);

[0066] S3, prepare a 2mL A solution, add 4μL of the test solution to 2mL of the A solution so that the concentration of the fluorescent probe is C1, and obtain a spectral test solution. After 1 minute, use light with a wavelength of P1 nm (490nm) to excite the spectral test solution to obtain a fluorescence emission spectrum. Substitute the maximum fluorescence intensity of the fluorescence emission spectrum of the spectral test solution into the equation of the linear relationship curve to obtain the mercury ion concentration in the test solution.

[0067] In order to verify the above method to detect Hg 2+ To determine the accuracy of the content, a Hg(ClO4)2 aqueous solution with a mercury ion concentration of 5 μM was prepared as the test solution, and operations were performed according to S1 to S3 to obtain a mercury ion concentration of 4.9 μM. The mercury ion concentration obtained by the equation of the linear relationship curve of this embodiment was consistent with the actual mercury ion concentration.

[0068] Example 3

[0069] A portable paper-type sensor comprises filter paper and a fluorescent probe loaded on the filter paper.

[0070] The preparation method of the portable paper sensor comprises: dissolving the fluorescent probe in THF to prepare a fluorescent probe concentration of 2×10 -5 The first solution of M was prepared, and white filter paper was cut into small rectangular pieces of paper of 0.6 cm × 2 cm and immersed in the first solution for 12 h. The small rectangular pieces of paper were taken out and dried to obtain a portable paper sensor.

[0071] The method for using the portable paper sensor comprises: preparing 5 portions of trihydrated mercuric perchlorate aqueous solution as standard solutions, wherein the trihydrated mercuric perchlorate aqueous solution is obtained by dissolving trihydrated mercuric perchlorate in ultrapure water, and the mercury ion concentrations in the 5 portions of trihydrated mercuric perchlorate aqueous solution are 2×10 -6 M, 4×10 -6 M, 6×10 -6 M, 8×10 -6 M, 10×10 -6 M, soak a portable paper sensor in each portion of trihydrate mercuric perchlorate aqueous solution for 5 minutes, take it out and dry it, observe it directly under sunlight / excite it with a UV lamp emitting at 365nm, and use the color of the portable paper sensors of all standard solutions directly observed under sunlight / excited by a UV lamp as a comparison standard card;

[0072] Soak a portable paper sensor in the solution to be tested, take it out and dry it, observe it directly in sunlight / excite it with ultraviolet light, obtain the color of the portable paper sensor of the solution to be tested under direct observation in sunlight / excited by ultraviolet light, determine the comparison standard card that the color of the portable paper sensor of the solution to be tested under direct observation in sunlight / excited by ultraviolet light is close to, and use the mercury ion concentration in the standard solution corresponding to the close comparison standard card as the mercury ion concentration in the solution to be tested. Real-time detection of mercury ion content by naked eye or by ultraviolet light excitation can be achieved according to the color change of the standard colorimetric card.

[0073] like Figure 4 As shown, the portable paper sensor soaked in deionized water is pink. It is used to detect aqueous solutions of mercury ions of different concentrations. When directly observed under sunlight, the color of the portable paper sensor changes from pink to white as the concentration of mercury ions in the trihydrate mercuric perchlorate aqueous solution increases. When excited by a purple light, the fluorescence of the portable paper sensor gradually dims as the concentration of mercury ions detected increases.

[0074] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A fluorescent probe, characterized in that Its general structure is as follows: The two Rs connected to the same five-membered ring are independent of each other, R is a C1-C30 alkyl group, p is a natural number of 1-50, and q is a natural number of 1-50.

2. A method for synthesizing a fluorescent probe, characterized in that: The following steps are involved: The polymer P1 and THF are mixed to obtain a mixed solution, and an ethanol solution of thiosemicarbazide is added dropwise to the mixed solution, and the mixture is stirred at 20-50° C. for 10-24 hours to obtain a reaction solution, and the reaction solution is concentrated and then added dropwise to water, filtered, rinsed, and dried to obtain a purple solid as a fluorescent probe, wherein the ratio of polymer P1 to thiosemicarbazide in the ethanol solution of thiosemicarbazide is 1:(8-20) in terms of the amount of substance, and the structural formula of the polymer P1 is:

3. The synthesis method according to claim 2, characterized in that The Stille coupling reaction of 2,5-dibromothiophene-3-carboxaldehyde and 2,6-di(trimethyltin)dithienocyclopentadiene derivative is carried out to obtain polymer P1. The method for carrying out Stille coupling reaction of 2,5-dibromothiophene-3-carboxaldehyde and 2,6-di(trimethyltin)dithienocyclopentadiene derivative comprises: adding anhydrous toluene and Pd(PPh3)4 to 2,5-dibromothiophene-3-carboxaldehyde and 2,6-di(trimethyltin)dithienocyclopentadiene in a nitrogen atmosphere; The mixture of the derivatives is stirred at 90-110° C. for 48-72 hours to obtain a reaction solution, the reaction solution is added dropwise into methanol, filtered to obtain a solid, extracted, the extract is collected, and the solvent is removed by rotary evaporation to obtain a purple solid as polymer P1, wherein the ratio of the 2,5-dibromothiophene-3-carboxaldehyde to the 2,6-di(trimethyltin)dithienocyclopentadiene derivative is 1:1, and the structural formula of the 2,6-di(trimethyltin)dithienocyclopentadiene derivative is:

4. The synthesis method according to claim 2, characterized in that The ratio of the amount of the polymer P1 to the volume of THF is 1:(50-100), the unit of the amount of the polymer P1 is mmol, the unit of the volume is mL, the ethanol solution of thiosemicarbazide is a mixture of thiosemicarbazide and ethanol, and the concentration of thiosemicarbazide in the ethanol solution of thiosemicarbazide is 0.3-0.8 mol / L.

5. The synthesis method according to claim 3, characterized in that The ratio of the volume fraction of the anhydrous toluene to the amount fraction of 2,5-dibromothiophene-3-carboxaldehyde is 1:(0.05-0.3), the unit of the volume fraction is mL, and the unit of the amount fraction is mmol.

6. The synthesis method according to claim 3, characterized in that Calculated by amount, the ratio of Pd(PPh3)4 to 2,5-dibromothiophene-3-carboxaldehyde is (0.01-0.1):1, and calculated by volume, the ratio of methanol to anhydrous toluene is (10-25:1).

7. The synthesis method according to claim 3, characterized in that The extraction is performed by placing the solid in a Soxhlet extractor and extracting with methanol, n-hexane and chloroform in sequence.

8. Use of one of the fluorescent probes obtained by the synthesis method of claims 2 to 7 and the fluorescent probe of claim 1 in detecting mercury ion concentration, characterized in that: The following steps are involved: S1, preparing N portions of solution A having the same concentration of the fluorescent probe, each portion of solution A being: dissolving the fluorescent probe in THF to obtain solution A; S2, preparing N portions of a standard aqueous solution containing mercury ions, wherein the N portions of the standard aqueous solution have different concentrations of mercury ions, and respectively adding a portion of the standard aqueous solution to N portions of solution A so that the concentration of the fluorescent probe is C1, to obtain N portions of a standard spectrum test solution, exciting each portion of the standard spectrum test solution with light of a wavelength of P1 nm, to obtain N fluorescence emission spectra, and drawing a linear relationship curve between the maximum fluorescence intensity of the fluorescence emission spectrum of the standard spectrum test solution and the concentration of mercury ions in the standard aqueous solution; S3, prepare a portion of solution A, add the test solution to solution A so that the concentration of the fluorescent probe is C1, obtain a spectral test solution, use light with a wavelength of P1 nm to excite the spectral test solution, obtain a fluorescence emission spectrum, substitute the maximum fluorescence intensity of the fluorescence emission spectrum of the spectral test solution into the linear relationship curve, and obtain the mercury ion concentration in the test solution.

9. The use according to claim 8, characterized in that: In S1, the concentration of the fluorescent probe in solution A is 1×10 -5 ~50×10 -5 M, in S2, the mercury ion concentration range in N parts of standard aqueous solution is 0.015~0.5mmol, in S2, the ratio of A solution to standard aqueous solution is 2000:(0~100) by volume, P1=470~520nm, the wavelength of maximum fluorescence intensity is at 625~700nm, and C1 is less than the concentration of fluorescent probe in A solution.

10. A portable paper sensor, characterized in that: include: Filter paper and fluorescent probe loaded on the filter paper.

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