A fluorescent probe with AIE properties and its preparation method and its application in Al 3+ Application in Identification

Abstract

The present invention relates to a fluorescent probe with AIE properties. The chemical structural formula of the fluorescent probe with AIE properties is: #imgabs0# The preparation method of the fluorescent probe with AIE properties is as follows: using 2-aminothiazole as a starting material, performing condensation ring closure and reduction reaction with 2-bromo-4'-nitroacetophenone to obtain an intermediate 6-(4-aminophenyl)imidazo[2,1-b]thiazole, and then performing nucleophilic addition with 5-chlorosalicylaldehyde to obtain N-4-(imidazo[2,1-b]thiazole)-phenyl-2-hydroxy-5-chlorobenzene imine, which is a fluorescent probe with AIE properties, and the structure of the fluorescent probe is characterized by infrared and nuclear magnetic resonance. The fluorescent probe with AIE properties is sensitive to Al 3+ It has good selective recognition, good recognition sensitivity and anti-interference ability; Job's curve shows that its complexation ratio is 1:1.

Description

Technical Field

[0001] The present invention relates to the field of fluorescent probe detection technology, and in particular to a fluorescent probe with AIE properties, a preparation method thereof, and its application in Al 3+ Identification applications. Background Art

[0002] Aluminum is the most abundant metal element in the earth's crust and is widely used in aerospace, industrial manufacturing, agricultural production and daily life. For example, our common aluminum alloy products, aluminum-containing food additives, aluminum-containing medicines, aluminum utensils, aluminum packaging, etc., so aluminum is closely related to people's production and life. In the human body, if there are too many aluminum ions for a long time, it will cause many diseases in the human body. If the aluminum ion content in the soil and water source is too high, it will not only inhibit the growth of plants, but also cause great harm to the environment. Therefore, in order to better control the impact of aluminum ions on humans and the environment, Al 3+ The detection of Al is very important. 3+ Fluorescent sensors still have disadvantages such as complex synthesis, unsatisfactory selectivity and sensitivity. Therefore, the development of aluminum ion-containing compounds with simple synthesis methods, good selectivity and high sensitivity has important application value.

[0003] Schiff base compounds refer to a class of organic compounds containing imino groups (-HC=N-) or alkylimino groups (-RC=N-) formed by various chemical reactions of two substances containing active amino groups and carbonyl groups. The presence of C=N bonds in the molecules and the influence of intramolecular hydrogen bonds enable them to exhibit fluorescence enhancement (AIE) phenomena. Schiff base compounds usually contain electron-rich heteroatoms such as S, N, and O. These metal ions containing lone pairs of electrons have strong coordination capabilities, causing different fluorescence and ultraviolet changes through chelation, providing an effective solution for detecting metal ions in contaminated liquids. In addition, Schiff base compounds are widely used in various biological tests due to their low toxicity, good photostability, and strong cell penetration. Summary of the Invention

[0004] Technical Problems to be Solved: In view of the shortcomings of the prior art, the present invention provides a fluorescent probe with AIE properties and a preparation method thereof. 3+ The fluorescent probe with AIE properties is used in the identification of Al 3+ It has good selective recognition, good recognition sensitivity and anti-interference ability; Job's curve shows that its complexation ratio is 1:1.

[0005] Technical solution: A fluorescent probe with AIE properties, the chemical structure of the fluorescent probe with AIE properties is:

[0006]

[0007] The preparation method of the fluorescent probe with AIE properties is as follows:

[0008] Step 1, synthesis of intermediate Ⅰ:

[0009] 2-aminothiazole, 2-bromo-4'-nitroacetophenone, and ethanol were added to a round-bottom flask and refluxed in a water bath for 4 hours to obtain a yellow-brown precipitate. After cooling, sodium bicarbonate was added and the mixture was refluxed for another 2 hours. The crude product, a yellow solid, was filtered to obtain the crude product. The yellow solid was dried for 10 minutes and poured into water, stirred evenly, and filtered to obtain intermediate I. The weight ratio of 2-aminothiazole, 2-bromo-4'-nitroacetophenone, and sodium bicarbonate was 1:(2.67-3.65):(0.15-0.35), and each gram of 2-aminothiazole corresponded to 120-200 mL of ethanol and 100-180 mL of water, respectively.

[0010] Step 2, synthesis of intermediate II:

[0011] Place intermediate I and ethanol in a round-bottom flask, heat to dissolve, then add Pd / C catalyst, raise the temperature to 80°C, and add 85% by mass hydrazine hydrate dropwise to the flask three times. Heat and reflux for 9 hours, filter while hot to obtain a clear solution, rotary evaporate the clear solution to 3-5 mL, add water and filter to obtain a white solid, and dry to obtain intermediate II, wherein the weight ratio of intermediate I to Pd / C catalyst is 1:0.375, and each gram of intermediate I corresponds to 187.5 mL of ethanol and 11.25 mL of 85% by mass hydrazine hydrate, respectively;

[0012] Step 3: Synthesis of fluorescent probes with AIE properties:

[0013] Intermediate II was placed in a round-bottom flask, and a magnetic bar was placed in it. Ethanol was added and stirred to dissolve it. Then 5-chlorosalicylaldehyde was added and condensed and refluxed at 80°C. After reacting for 3 hours, the reaction was tracked by TLC. After stopping the reaction, the flask was removed and allowed to stand and cool until the solid was completely precipitated. The solid was filtered and dried to obtain a fluorescent probe with AIE properties. The weight ratio of intermediate II to 5-chlorosalicylaldehyde was 1.08:0.7, and every 1.08 g of intermediate II corresponded to 100 mL of ethanol.

[0014] The above-mentioned fluorescent probe with AIE properties is 3+ Identification applications.

[0015] Beneficial effect: The present invention provides a fluorescent probe with AIE properties and a preparation method thereof and its application in Al 3+ The application of identification has the following beneficial effects:

[0016] 1. The fluorescent probe with AIE properties of the present invention is 3+ It has good selective recognition, good recognition sensitivity and anti-interference ability;

[0017] 2. The Job's curve of the fluorescent probe with AIE property of the present invention shows that its complexation ratio is 1:1.

[0018] 3. The fluorescent probe with AIE properties of the present invention is 3+ The detection limit was 1.484×10 -2 μmol·L -1 , far below the limit of Al in drinking water 3+ The upper limit of concentration of α-hydroxy-1-pyrrolidone has good potential application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The UV-visible absorption spectra of probe L in seven solvents: benzene, dichloromethane, ethyl acetate, tetrahydrofuran, ethanol, acetonitrile and N,N-dimethylformamide.

[0020] Figure 2 The fluorescence spectra of probe L in seven solvents: benzene, dichloromethane, ethyl acetate, tetrahydrofuran, ethanol, acetonitrile and N,N-dimethylformamide.

[0021] Figure 3 a is the fluorescence spectrum of probe L in different proportions of ethanol / water mixed solvents; b is the curve of the fluorescence intensity of probe L changing with water content; c is the curve of the fluorescence intensity of probe L in ethanol (5×10 -5 M) and ethanol / water (40 / 60, v / v); d is the fluorescence photograph of probe L in different ethanol / water ratios.

[0022] Figure 4 The fluorescence effect diagram of probe L when adding various metal ions under 365nm ultraviolet light.

[0023] Figure 5 Fluorescence spectra of probe L when various metal ions are added.

[0024] Figure 6 For other coexisting metal ions, L is used as the probe for Al 3+ Identified interference graph.

[0025] Figure 7 To gradually add Al in proportion to the ethanol solution 3 Fluorescence change spectrum after PCR.

[0026] Figure 8 To gradually add Al in proportion to the ethanol solution 3Slope graph of the titration standard curve.

[0027] Figure 9 For probe L and Al 3+ Job'plot graph.

[0028] Figure 10 For probe L to Al 3+ Detection limit diagram of fluorescence spectrometry. DETAILED DESCRIPTION

[0029] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by professionals in this field based on the above-mentioned invention content still fall within the scope of protection of the present invention.

[0030] The materials and reagents used in the following examples are from the following sources:

[0031] 2-Aminothiazole, 2-bromo-4′-nitroacetophenone, and 5-chlorosalicylaldehyde were purchased from Anhui Zesheng Technology Co., Ltd. (Annaiji Chemical); hydrazine hydrate (85% by mass) and 10% palladium on carbon (containing approximately 55% water) were purchased from Sinopharm Chemical Reagent (Shanghai) Co., Ltd.; other reagents and solvents were of analytical or chemical grade unless otherwise specified.

[0032] X-5A micro melting point apparatus (temperature uncorrected), Bruker 400 Ultra-shield nuclear magnetic resonance spectrometer (CDCl3 as solvent, TMS as internal standard), WQF-510 Fourier transform infrared spectrometer (KBr pellet), TU-1901 double-beam UV-visible spectrophotometer, HITACHI-7000 fluorescence spectrometer.

[0033] Example 1

[0034] The synthesis route of the fluorescent probe with AIE properties in Example 1 is as follows:

[0035]

[0036] The preparation method is as follows:

[0037] Step 1, Synthesis of Intermediate I (6-(4-nitrophenyl)imidazo[2,1-b]thiazole):

[0038] Weigh 1.00 g (10.00 mmol) of 2-aminothiazole, 2.93 g (12.00 mmol) of 2-bromo-4'-nitroacetophenone and 150 mL of ethanol into a 250 mL round-bottom flask and reflux in a water bath for 4 h to obtain a light yellow precipitate; after cooling for 15 min, 0.21 g (2.5 mmol) of NaHCO3 was added, and the mixture was refluxed for another 2 h; after filtration, the crude product was obtained as a yellow solid; after drying for 10 min, the yellow solid was poured into 150 mL of water, stirred, and filtered to obtain 1.65 g of intermediate I.

[0039] The yield of intermediate I was 77.6%.

[0040] Step 2, synthesis of intermediate II (6-(4-aminophenyl)imidazo[2,1-b]thiazole):

[0041] 0.80 g (3.33 mmol) of intermediate I and 150 mL of ethanol were added to a 250 mL round-bottom flask and heated to dissolve; 0.30 g of Pd / C catalyst was added to the above system and the temperature was raised to 80°C; 9 mL of 85% by mass hydrazine hydrate was weighed and added dropwise to the flask in three portions, and heated under reflux for 9 h; filtered while hot to obtain a clear solution, which was rotary evaporated to 3-5 mL, water was added, and suction filtered to obtain a white solid, which was finally dried to obtain 0.658 g of intermediate II.

[0042] The yield of intermediate II was 70.64%.

[0043] Step 3: Synthesis of a fluorescent probe with AIE properties (N-4-(imidazo[2,1-b]thiazole)-phenyl-2-hydroxy-5-chlorophenylimine):

[0044] 1.08 g (5.00 mmol) of intermediate II was weighed and placed in a 250 mL round-bottom flask, and a magnetic bar was placed. 100 mL of ethanol was added and stirred to dissolve it, and then 0.70 g (5.00 mmol) of 5-chlorosalicylaldehyde was added. The reaction temperature was set to 80°C, condensed and refluxed, and after reacting for 3 h, a TLC plate was used to track the reaction and observe the reaction progress. After 3 h, the reaction was stopped, the flask was removed and allowed to cool until the solid was completely precipitated, and then filtered and dried to obtain 0.97 g of a fluorescent probe with AIE properties.

[0045] The yield of the fluorescent probe with AIE properties was 54.9%.

[0046] The hydrogen nuclear magnetic resonance spectra of the intermediate product and the final product in this example are as follows.

[0047] Intermediate I: 1H-NMR (400MHz, CDCl3) δ8.51 (s, 1H), 8.27 (dt, J=9.00, 2.52Hz, 2H), 8.10 (dt, J=9.00, 2.52Hz, 2H), 8.01 (d, J=4.52Hz, 1H), 7.36 (d, J=4.52Hz, 1H).

[0048] Intermediate II: 1 H-NMR (400MHz, CDCl3) δ7.92 (s, 1H), 7.87 (d, J=4.48Hz, 1H), 7.49 (dt, J=8.52, 2.6Hz, 2H), 7.18 (d, J=4.52Hz, 1H), 6.58 (dt, J=8.64, 2.48Hz, 2H), 5.17 (s, 1H).

[0049] Fluorescent probes with AIE properties: 1 H-NMR (400MHz, CDCl3) δ13.23 (s, 1H), 8.63 (s, 1H), 7.91 (d, J = 8.64Hz, 2H), 7.79 (s, 1H), 7.48 (d, J = 4.36Hz, 1H), 7.39 (d, J = 2.48Hz, 1H), 7.36 (dd, J=6.48, 2.00Hz, 2H), 7.32 (dd, J=8.88, 2.64Hz, 1H), 6.99 (d, J=8.76Hz, 1H), 6.88 (d, J=4.24Hz, 1H); 13 C-NMR (100MHz, CDCl3) δ162.35,159.20,154.27,140.59,136.23,133.24,131.56,1 30.75,128.86,126.44,122.01,121.58,120.29,117.69,112.9,108.78;IR(KBr,cm -1 )v: 3414 (w, OH), 1609 (s, HC = N), 1488 ~ 1500 (s, ArH), 1348 (s, CN), 1144 (w, CS), 757 (m, C-Cl).

[0050] The following tests were performed on the fluorescent probe with AIE properties prepared in Example 1 (hereinafter referred to as "probe L"), and the methods and results are as follows.

[0051] 1. Optical property testing

[0052] The concentration is 5×10 -3 mol·L -1DMF probe mother solution. Pipette 50 μL of the mother solution into seven 5 mL volumetric flasks. Dilute to the scale with seven solvents: benzene, dichloromethane, ethyl acetate, tetrahydrofuran, ethanol, acetonitrile, and N,N-dimethylformamide. Measure the UV-visible absorption and fluorescence emission spectra.

[0053] 2. Ion recognition test

[0054] 2.1 Selectivity Experiment

[0055] The concentration is 5×10 -3 mol·L -1 Nitrate aqueous solution (Ag + , Al 3+ , Ca 2+ , Cd 2+ ,Co 2+ , Li + , Mg 2+ , Na + , Ni 2+ , Cu 2+ , Sr 2+ , Zn 2+ , K + , Hg 2+ 50 μL of the probe L mother solution was taken into 14 5 mL volumetric flasks, and 150 μL of different metal ion solutions was added. Finally, the solution was diluted to the mark with ethanol and its fluorescence emission spectrum was tested.

[0056] 2.2 Fluorescence titration experiment

[0057] Pipette 100uL of 5×10 -3 mol·L -1 DMF probe L mother solution, then add n times 5uL of 5×10 -3 mol·L -1 Al(NO3)3 aqueous solution (n is the number), diluted to the scale line with anhydrous ethanol, and finally the fluorescence spectrum test is performed.

[0058] 2.3 Anti-interference experiment

[0059] Take 14 dry and clean 5mL volumetric flasks, add 50uL sample solution and 50μL Al(NO3)3 solution to each volumetric flask, and then add 150μL of the above-mentioned solution with a concentration of 5×10 -3 mol·L -1 The fluorescence emission spectra of 14 nitrate aqueous solutions were tested.

[0060] 2.4 Complexation ratio experiment

[0061] The total volume of the probe L sample solution and the Al(NO3)3 solution was kept constant at 200uL, and 11 different molar ratios of probe L and Al(NO3)3 were prepared from 10:0 to 0:10 for fluorescence spectrum testing.

[0062] 3. Results and Discussion

[0063] 3.1 Study on the optical properties of probe L

[0064] 3.1.1 Ultraviolet spectroscopy (UV-Vis) and fluorescence spectroscopy tests

[0065] The UV-visible absorption spectra of probe L in seven solvents including benzene, dichloromethane, ethyl acetate, tetrahydrofuran, ethanol, acetonitrile and N,N-dimethylformamide are shown in Figure 2. Figure 1 The fluorescence spectrum is shown in Figure 2 The UV-visible absorption spectrum and fluorescence spectrum data are shown in Table 1 below.

[0066] Table 1

[0067]

[0068]

[0069] In Table 1, a is the maximum absorption wavelength (concentration 5.0×10 -5 mol L -1 ), b is the molar extinction coefficient (10 4 mol -1 ·L·cm -1 ), c is the maximum fluorescence emission peak, d is the fluorescence intensity corresponding to the maximum fluorescence emission peak, and e is the Stokes shift (cm -1 ).

[0070] Depend on Figure 1 As shown in Table 1, with the increase of solvent polarity, the single-photon absorption spectrum of probe L basically does not undergo red shift, and there is no obvious solvation effect, indicating that the orbital energy level of the probe L molecule is basically unaffected by the solvent molecules, and the energy levels between the orbital energy levels hardly change. In addition, the probe L has an absorption peak near 370nm, and the molar extinction coefficient (ε) reaches 10 4 mol -1 ·L·cm -1 Therefore, the transition of this absorption peak can be attributed to the π→π* or intramolecular charge transfer (ICT) of the entire molecule. Figure 2The fluorescence spectra of probe L show that, except for the emission peak at 475nm in DMF solvent, the other six solvents all have two emission peaks, one at 450nm short-wave and the other at 540nm long-wave. The Stokes' shift of probe L in different solvents is calculated, and the largest Stokes' shift is 8841cm in acetonitrile solution. -1 This result shows that in acetonitrile solution, the non-radiative transition energy loss of this molecule is the largest in the excited state.

[0071] 3.1.2 Aggregate Emission Spectroscopy (AIE)

[0072] In order to study the aggregation-induced fluorescence properties of probe L, we added water, a poor solvent, into its DMF solution to prepare a solution with a water content (f w )0~95% mixed solvent solution, and then detect and compare their fluorescence changes. Figure 3 shown. Figure 3 a is the fluorescence spectrum of probe L in different proportions of ethanol / water mixed solvents; b is the curve of the fluorescence intensity of probe L changing with water content; c is the curve of the fluorescence intensity of probe L in ethanol (5×10 -5 M) and ethanol / water (40 / 60, v / v); d is the fluorescence photograph of probe L at different ethanol / water ratios. Figure 3 The fluorescence spectra of the a probe L in different ratios of ethanol / water mixed solvents and its Figure 3 c in ethanol (5×10 -5 Fluorescence images of probe L in DMF (ethanol / water, 40 / 60, v / v) and ethanol / water (40 / 60, v / v) show that with increasing water content, the fluorescence intensity of probe L first increases and then decreases. At 40% water content, the fluorescence intensity reaches its peak, 12.3 times that of pure DMF, and appears bright cyan. These phenomena can be explained by the following: in the good solvent DMF, the molecules are dispersed, with virtually no intermolecular interactions. Molecules can rotate freely about single bonds within the solution, resulting in non-radiative energy loss from the excited state, and thus weak fluorescence. With increasing amounts of poor solvent, organic molecules aggregate, generating multiple intermolecular forces that inhibit intramolecular rotation and enhance fluorescence. When the water content exceeds 40%, the fluorescence intensity begins to drop dramatically. This phenomenon has been observed in many compounds exhibiting AIE properties and is associated with the increased aggregation of solute molecules into amorphous nanoparticles.

[0073] 3.2 Study on the recognition of aluminum ions by probe L

[0074] 3.2.1 Selectivity Experiment

[0075] In order to study the recognition effect of probe L on different metal ions, 14 metal ions (Na + , Ag + , Cu 2+ , Mg 2+ , Al 3+ , K + , Li + , Cd 2+ , Ni 2+ , Ca 2+ , Zn 2+ ,Co 2+ , Sr 2+ , Hg 2+ ), investigate the color change of the probe solution and the corresponding fluorescence spectrum change. The solution color change is as follows Figure 4 The fluorescence spectrum is shown in Figure 5 The results show that the probe L solution emits bright cyan fluorescence only when aluminum ions are added, while the addition of other ions produces no or very weak fluorescence. Correspondingly, the probe L solution has a strong fluorescence emission peak at 491nm. 3+ The fluorescence intensity increased from 22.6 to 3660, an increase of 161.9 times. 3+ The fluorescence enhancement effect of probe L is obvious, which is due to the interaction between the probe and Al 3+ After binding, a chelation-enhanced fluorescence (CHEF) effect was produced. When 13 other metal ions were added, the color and fluorescence spectrum of the solution changed little or almost not. This shows that the probe L molecule can achieve the effect of Al 3+ Selective fluorescence recognition.

[0076] 3.2.2 Anti-interference experiment

[0077] In order to further investigate the role of probe L as an Al 3+ To investigate the effectiveness of the selective sensor, we conducted a competition experiment with coexisting ions. In the ethanol solution of probe L, an equimolar amount of Al(NO3)3 and a 3-fold molar amount of other nitrate solutions were added in sequence, and fluorescence spectra were tested, such as Figure 6 The results show that the fluorescence intensity of the system is almost unchanged when aluminum ions and other metal ions are added. 3+ The recognition of Al is less affected by coexisting cations, indicating that probe L has a certain anti-interference ability against these metal ions and can be used as a potential Al 3+ Fluorescent probe.

[0078] 3.2.3 Fluorescence titration experiment

[0079] In order to study the effect of probe L on Al 3+ The recognition sensitivity was improved. A fluorescence titration experiment was carried out in ethanol solution. After aluminum ions were gradually added in proportion, the fluorescence change spectrum was as shown in the figure below. Figure 7 As shown, the slope of the titration standard curve is as follows Figure 8 As shown. Figure 7 、 8 It can be seen that with the addition of Al in the probe L solution 3+ The fluorescence intensity of the solution gradually increased with the increase of the amount of Al added (0 to 1.5 equiv.). The fluorescence emission intensity (y) of probe L at λ = 491 nm was related to the 3+ (x) is between 0 and 1.0×10 -4 mol / L range, and the linear regression equation between them is y=87.54×10 6 x-82.53, and the linear correlation coefficient is 0.9847.

[0080] 3.2.4 Complexation ratio

[0081] In order to study the relationship between probe L and Al 3+ The binding ratio of probe L solution was tested by Al 3+ Equimolar titration experiments were performed to obtain probes L and Al 3+ The complex Job curve, such as Figure 9 As shown in the Job curve, as the amount of Al added 3+ As the molar ratio gradually increases, the fluorescence emission intensity of the probe at λ = 499 nm shows a trend of gradually increasing first and then gradually decreasing. The fitting straight line of the scattered points shows that when Al 3+ When the molar ratio is 0.506, the fluorescence emission intensity of probe L at λ=491 nm reaches a maximum, indicating that the complexation ratio of probe L to aluminum ions is 1:1.

[0082] 3.2.5 Calculation of detection limit

[0083] Using the linear relationship y = 87.54451x-82.53253 in the fluorescence titration experiment in 3.2.3, the detection limit of probe L was calculated according to LOD = 3σ / S, where σ is the standard deviation of 20 blank samples and S is the linear regression slope of the relationship between the fluorescence intensity of probe L at λ = 499 nm and the metal ion concentration. The calculated LOD is 1.484×10 -2 μmol / L, which is far below the detection limit specified by WHO (7.41 μmol / L). Figure 10 Therefore, compared with other Al3 + Compared with the probe, probe L has the advantages of low detection limit and simple synthesis route, and is suitable for detecting Al3 + potential application value.

[0084] 4. Conclusion

[0085] The fluorescent probe with AIE properties synthesized by the present invention can identify Al 3+ A new Schiff base fluorescent probe. In ethanol solution, ion selectivity experiments and fluorescence titration experiments showed that probe L has a strong affinity for Al 3+ It has good selective recognition and good recognition sensitivity and anti-interference; Job's curve shows that its complexation ratio is 1:1. According to the fluorescence titration method, the probe has good selectivity for Al 3+ The detection limit was 1.484×10 -2 μmol·L -1 , far below the limit of Al in drinking water 3+ The upper limit of concentration of α-hydroxy-1-pyrrolidone has good potential application value.

[0086] The above is a detailed introduction to the embodiments of the present invention. For those skilled in the art, according to the ideas of the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A fluorescent probe with AIE properties, characterized in that The chemical structure of the fluorescent probe with AIE properties is:

2. The method for preparing a fluorescent probe with AIE properties according to claim 1, wherein Here’s how: Step 1, synthesis of intermediate Ⅰ: 2-aminothiazole, 2-bromo-4'-nitroacetophenone, and ethanol were added to a round-bottom flask and refluxed in a water bath for 4 hours to obtain a yellow-brown precipitate. After cooling, sodium bicarbonate was added and the mixture was refluxed for another 2 hours. The crude product, a yellow solid, was filtered to obtain the crude product. The yellow solid was dried for 10 minutes and poured into water, stirred evenly, and filtered to obtain intermediate I. The weight ratio of 2-aminothiazole, 2-bromo-4'-nitroacetophenone, and sodium bicarbonate was 1:(2.67-3.65):(0.15-0.35), and each gram of 2-aminothiazole corresponded to 120-200 mL of ethanol and 100-180 mL of water, respectively. Step 2, synthesis of intermediate II: Place intermediate I and ethanol in a round-bottom flask, heat to dissolve, then add Pd / C catalyst, raise the temperature to 80°C, and add 85% by mass hydrazine hydrate dropwise to the flask three times. Heat and reflux for 9 hours, filter while hot to obtain a clear solution, rotary evaporate the clear solution to 3-5 mL, add water and filter to obtain a white solid, and dry to obtain intermediate II, wherein the weight ratio of intermediate I to Pd / C catalyst is 1:0.375, and each gram of intermediate I corresponds to 187.5 mL of ethanol and 11.25 mL of 85% by mass hydrazine hydrate, respectively; Step 3: Synthesis of fluorescent probes with AIE properties: Intermediate II was placed in a round-bottom flask, and a magnetic bar was placed in it. Ethanol was added and stirred to dissolve it. Then 5-chlorosalicylaldehyde was added and condensed and refluxed at 80°C. After reacting for 3 hours, the reaction was tracked by TLC. After stopping the reaction, the flask was removed and allowed to stand and cool until the solid was completely precipitated. The solid was filtered and dried to obtain a fluorescent probe with AIE properties. The weight ratio of intermediate II to 5-chlorosalicylaldehyde was 1.08:0.7, and every 1.08 g of intermediate II corresponded to 100 mL of ethanol.

3. A fluorescent probe with AIE properties as claimed in claim 1 3+ Identification applications.

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