A benzothiazole fluorescent probe for detecting picric acid, and its preparation method and application

Abstract

The present invention belongs to the technical field of picric acid detection, and provides a benzothiazole fluorescent probe for detecting picric acid, and a preparation method and application thereof. The method of the present invention comprises the following steps: under a protective atmosphere, compound 1 and sodium amide are subjected to a first reaction in a solvent, and the first reaction product and para-acetaminobenzaldehyde are further reacted to obtain a benzothiazole fluorescent probe. The probe N-BPA of the present invention has a large Stokes shift of 148 nm, which can avoid the self-quenching phenomenon in the fluorescence imaging process; the probe N-BPA can be used to detect picric acid and exhibits a quenched fluorescence response; the probe N-BPA can recognize picric acid and is not interfered with by other nitro compounds, and has good anti-interference ability; the detection limit is 5.42×10 ‑ 4 mol / L, and can be used as a fluorescent probe for detecting low concentrations of picric acid.

Description

Technical Field

[0001] The present invention relates to the technical field of picric acid detection, and in particular to a benzothiazole fluorescent probe for detecting picric acid, and a preparation method and application thereof. Background Art

[0002] Picric acid (PA, TNP), also known as 2,4,6-trinitrophenol, is a white or light yellow needle-shaped crystal with a bitter taste. It is non-hygroscopic and explosive when dry. Picric acid is commonly used in dyes, leather, explosives, and pesticides; in medicine, it is used as a surgical astringent. Besides its explosive properties, picric acid is also an environmental pollutant and toxic to organisms, such as respiratory damage and skin irritation. Its partially reduced form, picramic acid, is 10 times more mutagenic than simple TNP, making its detection of picric acid of great significance. In recent years, numerous methods have been developed for the detection of picric acid, including gel permeation chromatography, gas chromatography-mass spectrometry, ion mobility spectrometry, X-ray diffraction, and Raman spectroscopy. However, these methods often suffer from limitations such as bulky instrumentation, time-consuming procedures, and complex procedures.

[0003] Therefore, it is of great significance to develop a benzothiazole fluorescent probe with high sensitivity and simple operation for detecting picric acid. Summary of the Invention

[0004] The purpose of the present invention is to provide a benzothiazole fluorescent probe for detecting picric acid and a preparation method and application thereof in order to overcome the deficiencies of the prior art.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a benzothiazole fluorescent probe for detecting picric acid, wherein the structural formula of the benzothiazole fluorescent probe is:

[0007]

[0008] The present invention also provides a method for preparing the benzothiazole fluorescent probe for detecting picric acid, comprising the following steps:

[0009] Under a protective atmosphere, compound 1 and sodium amide are reacted in a solvent for a first reaction, and the first reaction product is further reacted with p-acetylaminobenzaldehyde to obtain a benzothiazole fluorescent probe;

[0010] The structural formula of compound 1 is:

[0011]

[0012] Preferably, the molar ratio of compound 1 to sodium amide is 0.63-0.72:0.9-1.1; the molar ratio of compound 1 to p-acetaminobenzaldehyde is 0.63-0.72:1.25-1.45.

[0013] Preferably, the molar volume ratio of the compound 1 to the solvent is 0.63-0.72 mmol: 25-35 mL; and the solvent is N,N'-dimethylformamide.

[0014] Preferably, the temperature of the first reaction and the continued reaction is 20-30° C., the time of the first reaction is 0.8-1.2 h, and the time of the continued reaction is 46-50 h.

[0015] Preferably, the product after the reaction is completed is subjected to quenching reaction, extraction, washing of organic phase, and drying in sequence to obtain a crude product, which is then pulped to obtain a benzothiazole fluorescent probe.

[0016] Preferably, the reagent for quenching the reaction is aqueous ammonium chloride solution, the reagent for extraction is dichloromethane, the reagent for washing the organic phase is saturated brine, and the reagent for drying is anhydrous sodium sulfate.

[0017] Preferably, the pulping is carried out using a mixture of petroleum ether and ethyl acrylate, and the volume ratio of petroleum ether to ethyl acrylate is 0.5-1.5:0.5-1.5.

[0018] The present invention also provides the use of the benzothiazole fluorescent probe for detecting picric acid in detecting picric acid.

[0019] The beneficial effects of the present invention include:

[0020] The fluorescent probe N-BPA of the present invention is a benzothiazole fluorescent probe formed by connecting ene-yne ​​double unsaturated bonds. The probe N-BPA has a large Stokes shift of 148 nm, which can avoid self-quenching in the fluorescence imaging process. The probe N-BPA can be used to detect picric acid (PA) and exhibits a quenched fluorescence response. The probe N-BPA can recognize picric acid and is not interfered by other nitro compounds, and has good anti-interference ability. The detection limit of the probe N-BPA is 5.42×10 -4 mol / L, indicating that the probe N-BPA can be used as a fluorescent probe for detecting low concentrations of picric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the UV-visible absorption spectrum of the probe prepared in Example 1;

[0022] Figure 2 The excitation spectrum and emission spectrum of the probe prepared in Example 1;

[0023] Figure 3 Fluorescence emission spectra of the probe prepared in Example 1 in different solvents;

[0024] Figure 4 The selectivity of the probe prepared in Example 1 for metal ions, wherein a is a spectrum and b is a histogram;

[0025] Figure 5 The selectivity of the probe prepared in Example 1 for anions, wherein a is a spectrum and b is a histogram;

[0026] Figure 6 The selectivity of the probe of Example 1 for nitro compounds, wherein a is a spectrum and b is a histogram;

[0027] Figure 7 The anti-interference test results of the probe of Example 1 on nitro compounds, wherein a is a spectrum and b is a histogram;

[0028] Figure 8 This is the fluorescence titration spectrum of the probe of Example 1 to picric acid;

[0029] Figure 9 The titration curve (a) and linear regression curve (b) of the probe of Example 1 for picric acid;

[0030] Figure 10 The color change of the probe in Example 1 before and after the reaction with picric acid;

[0031] Figure 11 is the UV-visible absorption spectrum of the probe of Example 1 and picric acid;

[0032] Figure 12 The Job's curve spectrum (a) and Job's curve (b) of the probe of Example 1 and picric acid;

[0033] Figure 13 This is the mass spectrum of the probe N-BPA in Example 1 after responding to picric acid;

[0034] Figure 14 IR spectra of the probe N-BPA in Example 1 before and after the reaction with picric acid;

[0035] Figure 15 The mode of action of the probe N-BPA of the present invention and picric acid;

[0036] Figure 16 The fluorescence emission spectrum of the probe in Example 1 and the ultraviolet absorption spectrum of picric acid. DETAILED DESCRIPTION

[0037] The present invention provides a benzothiazole fluorescent probe for detecting picric acid, wherein the structural formula of the benzothiazole fluorescent probe is:

[0038]

[0039] The present invention also provides a method for preparing the benzothiazole fluorescent probe for detecting picric acid, comprising the following steps:

[0040] Under a protective atmosphere, compound 1 and sodium amide are reacted in a solvent for a first reaction, and the first reaction product is further reacted with p-acetylaminobenzaldehyde to obtain a benzothiazole fluorescent probe;

[0041] The structural formula of compound 1 is:

[0042]

[0043] In the present invention, the synthesis route of the benzothiazole fluorescent probe for detecting picric acid is:

[0044]

[0045] In the present invention, the molar ratio of compound 1 to sodium amide is preferably 0.63-0.72:0.9-1.1, more preferably 0.65-0.70:0.95-1.05, and more preferably 0.67-0.68:1.0; the molar ratio of compound 1 to acetaminobenzaldehyde is preferably 0.63-0.72:1.25-1.45, more preferably 0.65-0.70:1.3-1.4, and more preferably 0.67-0.68:1.35-1.36.

[0046] In the present invention, the molar volume ratio of the compound 1 to the solvent is preferably 0.63-0.72 mmol: 25-35 mL, more preferably 0.65-0.70 mmol: 28-32 mL, and more preferably

[0047] 0.67~0.68mmol: 29~30mL; the solvent is preferably N,N'-dimethylformamide.

[0048] In the present invention, the temperature of the first reaction and the continued reaction is preferably 20-30°C, more preferably 22-28°C, and more preferably 24-25°C; the time of the first reaction is preferably 0.8-1.2h, more preferably 1h; the time of the continued reaction is preferably 46-50h, more preferably 47-49h, and more preferably 48h.

[0049] In the present invention, the product after the reaction is completed is preferably subjected to quenching reaction, extraction, washing of the organic phase, and drying in sequence to obtain a crude product, and the crude product is pulped to obtain a benzothiazole fluorescent probe.

[0050] In the present invention, the reagent for quenching the reaction is preferably an aqueous solution of ammonium chloride, the reagent for extracting is preferably dichloromethane, the reagent for washing the organic phase is preferably saturated brine, and the drying reagent is preferably anhydrous sodium sulfate.

[0051] In the present invention, the beating preferably uses a mixture of petroleum ether and ethyl acrylate, and the volume ratio of petroleum ether to ethyl acrylate is preferably 0.5-1.5:0.5-1.5, more preferably 0.8-1.2:0.8-1.2, and more preferably 1:1.

[0052] The present invention also provides the use of the benzothiazole fluorescent probe for detecting picric acid in detecting picric acid (2,4,6-trinitrophenol).

[0053] In the embodiment, the structural formula of compound 1 is:

[0054]

[0055] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] 0.68 mmol of compound 1 was dissolved in 30 mL of anhydrous N,N'-dimethylformamide, and 1.0 mmol of sodium amide was added. The reaction was allowed to proceed at 25°C under nitrogen for 1 hour. 1.36 mmol of p-acetaminobenzaldehyde was added to the reaction system and the reaction was continued. The reaction progress was monitored by TLC. After 48 hours of reaction, the starting materials were completely reacted to obtain the reaction product.

[0058] The reaction product was quenched by adding 100 mL of aqueous NH4Cl solution. The product was then poured into 400 mL of water and extracted with 300 mL of dichloromethane (100 mL each). The organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure at -0.01 MPa for 30 minutes to obtain the crude product. Finally, the product was slurried three times with a 1:1 (volume ratio) mixture of petroleum ether and ethyl acrylate to obtain the probe N-BPA.

[0059] The probe N-BPA in this example is 78 mg, MS (ESI+) m / z = 438.3 (M+H), NMR: 1H NMR (400MHz, CDCl3) δ7.98(s,1H),7.90(d,J=8.5Hz,1H),7.59(s,1H),7.56(d,J=3.1Hz,3H),7.49(s,1H),7.45(d, J=4.5Hz,1H),7.42(s,1H),7.35(s,1H),7.22(s,1H),6.68(d,J=8.9Hz,2H),5.30(s,1H),3.01(s,6H),2.21(s,3H). 13 C NMR (101MHz, DMSO) δ 169.10, 168.70 (d, J = 79.6Hz), 168.31, 153.29, 153.29, 150.67, 150.67, 141.28, 141.28, 138.17, 138.17, 134. 90,134.90,132.93,130.18,129.88,128.98,124.92,122.82,120.48(d,J=19.7Hz),119.44,112.38,108.75,92.37,87.73,24.59.

[0060] Example 2

[0061] 0.65 mmol of compound 1 was dissolved in 28 mL of anhydrous N,N'-dimethylformamide, and 0.95 mmol of sodium amide was added. The reaction was allowed to proceed under nitrogen at 24°C for 1.2 h. 1.3 mmol of p-acetaminobenzaldehyde was added to the reaction system and the reaction was continued. The reaction progress was monitored by TLC. After 49 h of reaction, the starting material was completely reacted to obtain the reaction product.

[0062] The reaction product was quenched by adding 95 mL of aqueous NH4Cl solution. The product was then poured into 400 mL of water and extracted with 300 mL of dichloromethane (100 mL each). The organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure at -0.01 MPa for 30 minutes to obtain a crude product. Finally, the product was slurried three times with a mixture of petroleum ether and ethyl acrylate in a volume ratio of 0.8:1.2 to obtain the probe N-BPA.

[0063] Example 3

[0064] 0.70 mmol of compound 1 was dissolved in 32 mL of anhydrous N,N'-dimethylformamide, and 1.05 mmol of sodium amide was added. The reaction was allowed to proceed at 28°C under nitrogen for 1 hour. 1.4 mmol of p-acetaminobenzaldehyde was added to the reaction system and the reaction was continued. The reaction progress was monitored by TLC. After 47 hours of reaction, the starting materials reacted completely to obtain the reaction product.

[0065] The reaction product was quenched by adding 105 mL of aqueous NH4Cl solution. The product was then poured into 400 mL of water and extracted with 300 mL of dichloromethane (100 mL each). The organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure at -0.01 MPa for 30 minutes to obtain the crude product. Finally, the product was slurried three times with a mixture of petroleum ether and ethyl acrylate in a volume ratio of 1.2:0.8 to obtain the probe N-BPA.

[0066] The probe N-BPA of Example 1 was dissolved in anhydrous ethanol to obtain a mother solution with a concentration of 0.001 mol / L, and spectral testing was performed. The fluorescence data was measured by a Perkin Elmer LS-55 fluorescence spectrophotometer, and the UV absorption spectrum data was measured by a Lambda 950 UV-visible spectrophotometer.

[0067] (1) UV-visible absorption spectrum and fluorescence properties

[0068] The mother solution with a concentration of 0.001 mol / L was diluted with anhydrous ethanol to a concentration of 1.0×10 -6 ~5.0×10 -5 mol / L of the test solution, and the UV-visible absorption spectrum was detected. The UV-visible absorption spectrum of the probe prepared in Example 1 is shown in FIG. Figure 1 As shown. Figure 1 It can be seen that the maximum absorption peak of the probe N-BPA shows a blue shift phenomenon, which is caused by the electron transition of the probe from π* to π. It is found that when the concentration of the probe N-BPA is 5.0×10 -5 mol / L, the maximum absorption peak blue-shifted to 385nm.

[0069] 2 mL of the mother solution with a concentration of 0.001 mol / L was subjected to fluorescence spectrum analysis test (Slit: 10*5, Scan: 300). The excitation spectrum and emission spectrum of the probe prepared in Example 1 are as follows: Figure 2 As shown. Figure 2 It can be seen that the excitation wavelength of the probe N-BPA is between 382 and 387 nm, the emission wavelength is around 535 nm, and the Stokes shift is as high as 148 nm, which can prevent spectral overlap between the excitation spectrum and the emission spectrum, thereby avoiding self-quenching during the test process.

[0070] (2) Solvent effect of probe

[0071] 10 μL of the mother solution with a concentration of 0.001 mol / L was dissolved in 2 mL of methanol, anhydrous ethanol, deionized water, ethyl acetate, carbon disulfide, pyridine, 1,4-dioxane, dimethyl sulfoxide, carbon tetrachloride, acetonitrile, nitrobenzene, acetone, dichloromethane, N,N'-dimethylformamide, triethylamine or aniline for fluorescence testing (E X =385nm, Slit:10*5, Scan:300), the fluorescence emission spectra of the probe prepared in Example 1 in different solvents are as follows Figure 3 As shown. Figure 3 It can be seen that the fluorescence response of probe N-BPA is the strongest in 1,4-dioxane solution. The fluorescence of probe N-BPA red-shifts with the increase of solvent acidity. The stronger the acidity, the lower the fluorescence intensity, and even fluorescence quenching effect occurs in protic solvents.

[0072] (3) Probe recognition of metal ions and non-metal ions

[0073] The probe N-BPA of Example 1 was dissolved in 1,4-dioxane to obtain a concentration of 1×10 -6 mol / L mother liquor.

[0074] Dissolve cobalt nitrate, chromium nitrate, calcium nitrate, lead nitrate, zinc nitrate, aluminum nitrate, copper nitrate, manganese nitrate, potassium nitrate, nickel nitrate, silver nitrate, and ferric nitrate in deionized water to prepare different metal ion test solutions with a concentration of 0.01 mol / L. Add 10 μL of different metal cation test solutions with a concentration of 0.01 mol / L to 2 mL of the mother solution and measure the corresponding fluorescence emission spectra (E X =385nm, Slit:10*5, Scan:300), the selectivity of the probe of Example 1 for anions is as follows Figure 4 As shown, a is the spectrum graph and b is the histogram. Figure 4 It can be seen that when water or metal ion solution is added to the probe N-BPA solution, the fluorescence intensity of the probe does not change significantly, which indicates that the probe N-BPA has almost no recognition effect on metal ions.

[0075] Dissolve potassium dichromate, sodium bromide, sodium fluoride, sodium bicarbonate, sodium sulfite, potassium chlorate, sodium nitrite, potassium iodide, potassium nitrate, sodium carbonate, dipotassium hydrogen phosphate, sodium acetate, sodium bisulfite, sodium sulfate, sodium thiosulfate, potassium permanganate, sodium trifluorosulfonate, and sodium periodate in deionized water to prepare test solutions of different anions with a concentration of 0.01 mol / L. -6 10 μL of the test solution of different anions was added to the mother solution of 1 mol / L, and the corresponding fluorescence emission spectra (E X=385nm, Slit:10*5, Scan:300), the selectivity of the probe of Example 1 for anions is as follows Figure 5 As shown, a is the spectrum graph and b is the histogram. Figure 5 It can be seen that when water or anion solution is added to the probe N-BPA solution, the fluorescence intensity of the probe does not change much, proving that the probe N-BPA also has no recognition effect on anions.

[0076] (4) Selectivity of the probe for nitro compounds

[0077] The probe N-BPA of Example 1 was dissolved in 1,4-dioxane to obtain a concentration of 1×10 -6 mol / L mother liquor.

[0078] 2,4,6-trinitrophenol, 2,4-dinitrophenol, p-nitrophenol, 1,4-dinitrobenzene, o-nitrophenol, m-dinitrobenzene, p-nitrotoluene, 3-nitrophenol, 2,4-dinitrobenzene, and nitrobenzene were dissolved in N,N'-dimethylformamide to prepare different nitro compound test solutions with a concentration of 0.01 mol / L. 50 μL of the different nitro compound test solutions with a concentration of 0.01 mol / L were added to 2 mL of the mother solution and fluorescence spectrum detection (E X =385nm, Slit:10*5, Scan:300), the selectivity of the probe of Example 1 for nitro compounds is as follows Figure 6 As shown, a is the spectrum graph and b is the histogram. Figure 6 It can be seen that the probe N-BPA has a good recognition effect on picric acid. The probe has a quenching effect on o-nitrophenol, 2,4-dinitrophenol, and 2,4,6-trinitrophenol (picric acid, PA), but only picric acid achieves a complete quenching effect.

[0079] Anti-interference ability of probe N-BPA for picric acid detection: Equal amounts of PA (50 μL) and equal amounts of interfering substances were added to 2 mL of the mother solution, and the changes in fluorescence response intensity were compared. The anti-interference test of the probe of Example 1 for nitro compounds (E X =385nm, Slit:10*5, Scan:300) The results are as follows Figure 7 As shown, a is the spectrum of the anti-interference experiment, and b is the histogram of the anti-interference experiment. Figure 7It can be seen that after the addition of picric acid, the fluorescence intensity of the probe decreased from 460 to 80, and the fluorescence intensity was attenuated by 83%. Since the interferor itself has a certain quenching effect on the fluorescence of the fluorescent substance, the addition of the interferor will cause the fluorescence intensity of the probe to decrease slightly, but it does not interfere with the detection of picric acid. This shows that the fluorescent probe N-BPA of the present invention has specific recognition ability for picric acid, is not easily affected by other nitro compounds, and has good anti-interference performance.

[0080] (5) Fluorescence titration test of the probe on picric acid (EX = 385 nm, Slit: 10*5, Scan: 300)

[0081] The probe N-BPA of Example 1 was dissolved in 1,4-dioxane to obtain a concentration of 1×10 -6 mol / L mother liquor.

[0082] The fluorescence spectrum of the probe of Example 1 titrated to picric acid is shown in FIG. Figure 8 As shown, the titration curve of the probe to picric acid and the titration linear regression diagram are shown as follows: Figure 9 As shown in a and b, the color change of the probe before and after the response to picric acid is as follows Figure 10 As shown. Figure 8 It can be seen that with the increase of picric acid concentration, the fluorescence intensity at 503nm decreases, and under 365nm ultraviolet light, it can be observed that the solution changes from strong light to very weak light. When the concentration of PA increases to 2.0×10 -4 mol / L, the probe fluorescence is quenched. Figure 9 It can be seen that picric acid is 5×10 -6 ~5×10 -5 In the mol / L concentration range, the titration fluorescence emission spectrum data is calculated by entering the Benesi-Hildebrand equation: I0 / I=1+K SV* [PA] (I0 and I are the fluorescence intensities when the picric acid concentration is 0 and [PA], respectively). The titration curve shows a good linear relationship. The linear regression equation is: y = 0.97432 + 12850*x, and the linear correlation coefficient is: R 2 =0.997, and the fitting constant of probe N-BPA was 1.285×10 4 L / mol, substituting the detection limit calculation formula LOD = 3σ / Ksv [σ:σ = 2.32 (standard deviation of the fluorescence response value of the blank sample)], the detection limit of the probe N-BPA is 5.42×10 -4 mol / L. The results show that the fluorescent probe N-BPA of the present invention has high detection sensitivity for low-concentration picric acid, low detection limit and wide linear detection range. Therefore, the fluorescent probe N-BPA can be used as a potential fluorescent probe to detect picric acid in the environment.

[0083] (6) Mechanism of action between probe and PA

[0084] The probe N-BPA of Example 1 was dissolved in 1,4-dioxane to obtain a concentration of 1×10 -6 mol / L mother solution, UV-visible absorption spectrum of test probe and picric acid and Job's curve (E X =385nm, Slit:10*5, Scan:300). The UV-visible absorption spectra of the probe of Example 1 and picric acid are as follows: Figure 11 As shown, the Job's curve is as follows Figure 12 As shown, where a is the curve spectrum and b is the curve graph. Figure 11 It can be seen that with the increase of picric acid concentration, the absorption intensity of the UV-visible absorption spectrum of the probe N-BPA at 335 nm is significantly enhanced. The molar extinction coefficients (ε) of the probes N-BPA and N-BPA+PA are calculated by the Beer-Lambert law and are 2.4×10 3 M -1 cm -1 and 8.0×10 5 M -1 cm -1 The increased absorption intensity of probe N-BPA+PA at 335nm and the more significant molar extinction coefficient are due to the effective electrostatic interaction between probe N-BPA and PA. A Job's plot was drawn to explore the mechanism of action of probe N-BPA and PA. The value of [PA]+[N-BPA]=1×10 -5 Mol / L is constant, [PA] / {[PA]+[N-BPA]} is used as the variable, and fluorescence intensity is used as the dependent variable to draw the Job's plot curve, such as Figure 12 As shown in a and b, the experimental results show that when the probe [PA] / {[PA]+[N-BPA]}≈0.5, the Job's plot curve has an inflection point, indicating that the probe N-BPA and PA are combined in a molar ratio of 1:1.

[0085] The mass spectrum of the probe N-BPA and PA in Example 1 after binding at a molar ratio of 1:1 is shown in FIG. Figure 13 As shown, Figure 13 The MS (ESI+) m / z = 730.34, which is consistent with the theoretical value of 730.66, can further prove that the probe N-BPA binds to PA in a molar ratio of 1:1.

[0086] The infrared spectra of the probe N-BPA and the combination of N-BPA and PA at a molar ratio of 1:1 were compared. The infrared spectra of the probe N-BPA before and after the reaction with picric acid (N-BPA+PA is the reaction after) are shown in Figure 2. Figure 14As shown, the probe N-BPA is at 3285 cm -1 The NH stretching vibration peak at 1658 cm -1 The C=O stretching vibration peak disappears, but the original C=N shifts. This is because the probe N-BPA has tautomerism similar to the keto and enol forms under the influence of PA, which causes this change in the infrared spectrum of the probe molecule. It is speculated that the probe N-BPA structure has undergone tautomerism similar to the keto and enol forms under the influence of PA, and a hydrogen bond interaction is formed between the probe N-BPA and PA, which causes the fluorescence quenching of the probe N-BPA. Based on the above data, it is speculated that the interaction between the probe N-BPA and PA is as follows: Figure 15 shown.

[0087] The fluorescence emission spectrum of the probe N-BPA in Example 1 and the ultraviolet absorption spectrum of PA are as follows: Figure 16 As shown by Figure 16 It can be seen that there is partial overlap between the ultraviolet absorption spectrum of PA and the fluorescence excitation spectrum of the probe N-BPA, which further proves that the probe N-BPA produces the above-mentioned tautomerism under the influence of PA, forms hydrogen bonds with PA, and competes to absorb the energy of the probe molecule, resulting in fluorescence quenching.

[0088] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A benzothiazole fluorescent probe for detecting picric acid, characterized in that: The structural formula of the benzothiazole fluorescent probe is:

2. The method for preparing the benzothiazole fluorescent probe for detecting picric acid according to claim 1, wherein: The following steps are included: Under a protective atmosphere, compound 1 and sodium amide are reacted in a solvent for a first reaction, and the first reaction product is further reacted with p-acetylaminobenzaldehyde to obtain a benzothiazole fluorescent probe; The structural formula of compound 1 is:

3. The preparation method according to claim 2, characterized in that The molar ratio of the compound 1 to sodium amide is 0.63-0.72:0.9-1.1; the molar ratio of the compound 1 to p-acetaminobenzaldehyde is 0.63-0.72:1.25-1.

45.

4. The preparation method according to claim 2 or 3, characterized in that The molar volume ratio of the compound 1 to the solvent is 0.63-0.72 mmol: 25-35 mL; the solvent is N,N'-dimethylformamide.

5. The preparation method according to claim 4, characterized in that The temperature of the first reaction and the continued reaction is 20-30° C., the time of the first reaction is 0.8-1.2 h, and the time of the continued reaction is 46-50 h.

6. The preparation method according to claim 4, characterized in that The product after the reaction is completed is subjected to quenching reaction, extraction, washing of organic phase and drying in sequence to obtain a crude product, which is then pulped to obtain a benzothiazole fluorescent probe.

7. The preparation method according to claim 6, characterized in that The reagent for quenching the reaction is an aqueous solution of ammonium chloride, the reagent for extracting is dichloromethane, the reagent for washing the organic phase is saturated brine, and the reagent for drying is anhydrous sodium sulfate.

8. The preparation method according to claim 6, characterized in that The beating process uses a mixture of petroleum ether and ethyl acrylate, and the volume ratio of petroleum ether to ethyl acrylate is 0.5-1.5:0.5-1.

5.

9. Use of the benzothiazole fluorescent probe for detecting picric acid according to claim 1 in detecting picric acid.

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