Fluorene-based polymer fluorescent probe as well as preparation method and application thereof

Abstract

The invention relates to a fluorene-based polymer fluorescent probe and a preparation method and application thereof, the preparation method comprises the following steps: 1, dissolving diborate fluorene, dibromo fluorene, dibromo heteroaromatic ring and dibromo benzothiadiazole monomers in an organic solvent, and adding a catalyst and a tetraethylammonium hydroxide aqueous solution for reaction; and 2, after the reaction is finished, cooling to room temperature, precipitating in methanol, filtering, performing Soxhlet extraction, and drying to obtain the fluorene-based polymer fluorescent probe. The application method comprises the following steps: 1, dissolving the fluorene-based polymer fluorescent probe in toluene to prepare a toluene solution, adding the toluene solution into N, N-dimethylacetamide, and filtering to obtain a fluorescent probe solution; and 2, taking the fluorescent probe solution, adding the to-be-detected water sample in batches, carrying out fluorescence emission spectrum determination under excitation of a light source with the excitation wavelength of 340-390nm, drawing a fluorescence intensity change curve, and calculating the fluorescence emission spectrum intensity change value delta I before and after the to-be-detected water sample is added into the fluorescent probe solution according to the curve.

Description

Technical Field

[0001] This invention relates to the field of chemical detection technology, specifically to a fluorene-based polymer fluorescent probe, its preparation method, and its application. Background Technology

[0002] Fe 3+ Fe is a common heavy metal ion, and when it accumulates in water exceeding 0.3 mg / L, it is harmful to human health and the natural aquatic environment. If Fe in the human body... 3+ Excessive levels of Fe in natural water can lead to methemoglobinemia, reducing the blood's oxygen-carrying capacity and harming human health. 3+ When the concentration is too high, the water will become noticeably darker and have a distinct metallic smell, causing water pollution.

[0003] Currently, the main methods for detecting ferric ions include atomic absorption spectrometry (AAS), ion chromatography, inductively coupled plasma atomic emission spectrometry (ICP-AES), and inductively coupled plasma mass spectrometry (ICP-MS). While these methods offer advantages in accuracy, they also suffer from drawbacks such as bulky and inconvenient instruments, complex operation, and high cost. Summary of the Invention

[0004] I. Technical problems to be solved This invention addresses the shortcomings of existing technologies by proposing a fluorene-based polymer fluorescent probe, its preparation method, and its application. This probe utilizes fluorene, S,S-dioxo-dibenzothiophene and its derivatives, and benzothiadiazole to construct a high-efficiency luminescent polymer, which can be used as a fluorescent probe to detect ferric ions in water. It has advantages such as fast detection speed and high selectivity.

[0005] II. Specific Technical Solutions A fluorene-based polymer fluorescent probe has the following chemical structure: In the formula: R1, R2, Z1, and Z2 independently represent H, D, F, CN, alkenyl, alkynyl, amino, nitro, acyl, alkoxy, carbonyl, sulfone, alkyl with 1-30 carbon atoms, cycloalkyl with 3-30 carbon atoms, aromatic hydrocarbon with 6-60 carbon atoms, or aromatic heterocyclic group with 3-60 carbon atoms; x, y, and z are the mole fractions of the unit components, satisfying: x + y + z = 1, 0.01 ≤ y ≤ 0.3, 0.01 ≤ z ≤ 0.2, n = 1-300; R1, R2, Z1, and Z2, as alkyl, alkoxy, and cycloalkyl, can adjust the solubility of the polymer, and as H, D, F, CN, alkenyl, alkynyl, amino, nitro, acyl, carbonyl, and sulfone, they may interact with the analyte to improve the detection performance. The existing technology section adds the advantages of fluorene, S,S-dioxo-dibenzothiophene and its derivatives and benzothiadiazole, where D refers to the isotope of hydrogen, deuterium (D). Ar is one of the following conjugated structural units containing sulfone-based aromatic heterocycles: 3,7-replace- S,S -dioxo-dibenzothiophene; 2,8-replacement- S,S -dioxo-dibenzothiophene; 4,6-replacement- S,S -dioxo-dibenzothiophene; 2,7-replace- S,S -dioxo-dibenzothiophene; 5,9-replace- S,S -dioxan-naphthalene-benzothiophene; 3,9-replace- S,S -dioxane-dibenzothiophene-indene; 3,8-replacement- S,S -dioxo-dibenzothiophenoindole; 3,10-substitute-double ( S,S -dioxo-dibenzothiophene)cyclopentadiene; 3,10-substitute-double ( S,S -dioxo-dibenzothiophene) and pyrrole; Wherein, R1 and R2 are independently represented as H, D, F, CN, alkenyl, alkynyl, amino, nitro, acyl, alkoxy, carbonyl, sulfone, alkyl with 1-30 carbon atoms, cycloalkyl with 3-30 carbon atoms, aromatic hydrocarbon group with 6-60 carbon atoms, or aromatic heterocyclic group with 3-60 carbon atoms.

[0006] A method for preparing a fluorene-based polymer fluorescent probe, comprising the following steps: Step 1: Dissolve diboron fluorene, dibromofluorene, dibromoaromatic heterocycle, and dibromobenzothiadiazole monomers in an organic solvent, add a catalyst and tetraethylammonium hydroxide aqueous solution to carry out the reaction; Step 2: After the reaction is complete, cool to room temperature, precipitate in methanol, filter, perform Soxhlet extraction, and dry to obtain fluorene-based polymer fluorescent probes.

[0007] As an optimization: the molar ratio of the diborate fluorene, dibromofluorene, dibromoaromatic heterocyclic compound, and dibromobenzothiadiazole monomer is 0.5:0-0.48:0.01-0.3:0.01-0.2; the organic solvent includes toluene or tetrahydrofuran; the reaction temperature is 80℃-90℃, and the reaction time is 40-120 min; the catalyst includes palladium acetate and tricyclohexylphosphine, the mass ratio of palladium acetate to diborate fluorene monomer is 1:80-100, the mass ratio of tricyclohexylphosphine to diborate fluorene monomer is 1:40-50; and the molar ratio of tetraethylammonium hydroxide to diborate fluorene monomer is 1:1-3.

[0008] A method for using a fluorene-based polymer fluorescent probe. Step 1: Dissolve the fluorene-based polymer fluorescent probe in toluene to prepare a 0.01 g / mL toluene solution, then take 20 μL and add it to 20 mL of the solution. N,N The fluorescent probe solution was obtained by filtration in dimethylacetamide. Step 2: Take 2 mL of fluorescent probe solution and add 10-20 μL of the water sample to be tested in portions. Under the excitation of a light source with an excitation wavelength of 340 nm-390 nm, perform fluorescence emission spectroscopy measurement and plot the fluorescence intensity change curve. Calculate the change value ΔI of fluorescence emission spectral intensity before and after adding the water sample to the fluorescent probe solution based on the curve.

[0009] The beneficial effects of this invention are as follows: Fluorene possesses high fluorescence quantum yield and wide bandgap, and its solubility, stability, quantum yield, and emission wavelength can be adjusted by modifying the 2,7 and C-9 positions. S,S-dioxo-dibenzothiophene and its derivatives, as well as benzothiadiazole, are all excellent electron-deficient units. Introducing them into the polyfluorene framework can achieve high luminescence efficiency through charge transfer states, demonstrating great potential as organic fluorescent probes. This invention utilizes fluorene, S,S-dioxo-dibenzothiophene and its derivatives, and benzothiadiazole to construct a high-efficiency luminescent polymer, which is then used as a fluorescent probe to detect ferric ions in water. This probe offers advantages such as rapid detection and high selectivity. The fluorescent probe of this invention can detect ferric ions in water with fast detection speed, high selectivity, and simple operation. Attached Figure Description

[0010] Figure 1 For P1 at 10 -5 UV-Vis absorption and photoluminescence spectra in mol / L toluene solutions (a, b) and in different solvents (c, d).

[0011] Figure 2 The fluorescence intensity of P1 under different metal ion concentrations: (a) alkali metal ions; (b) alkaline earth metal ions; (c, d) transition metal ions.

[0012] Figure 3 To add low concentration of Fe 3+ Photoluminescence spectrum of ion P1 (a); Stern-Wolmer curve (b).

[0013] Figure 4 The UV-Vis absorption spectra are of aqueous solutions of metal ions with concentrations of 0.001 M (a) and 0.01 M (b). Detailed Implementation

[0014] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0015] Example 1 Synthesis of 2,7-dibromo-9,9-dioctylfluorene (1) 2,7-Dibromofluorene (4.05 g, 12.5 mmol) and dimethyl sulfoxide (50 mL) were added to a two-necked flask, and the mixture was then protected with nitrogen. A 50 wt% aqueous solution of sodium hydroxide (5 g, 125 mmol) was slowly added. The mixture was stirred at room temperature for 1 hour, and then 1-bromo-n-octane (6.03 g, 31.25 mmol) was added. The reaction was continued for 12 hours. The mixture was extracted with dichloromethane and precipitated by column chromatography with petroleum ether as the eluent to give a white solid (6.1 g, 89% yield). 1 ¹³C NMR, ¹³C NMR, and elemental analysis results indicate that the obtained compound is the target product.

[0016] Example 2 Synthesis of 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (2) 2,7-Dibromo-9,9-dioctylfluorene (5.48 g, 10 mmol), pinacol diborate (6.35 g, 25 mmol), 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride (0.73 g, 0.1 mmol), potassium acetate (4.90 g, 50 mmol), and 1,4-dioxane (100 mL) were added to a two-necked flask and heated at 85 °C for 12 hours under nitrogen protection. After the reaction was complete, the mixture was cooled to room temperature, extracted with dichloromethane, and subjected to column chromatography using petroleum ether / dichloromethane as the developing solvent to give a white solid (5.1 g, 79%). 1 ¹³C NMR, ¹³C NMR, and elemental analysis results indicate that the obtained compound is the target product.

[0017] Example 3 Synthesis of 4,7-dibromo-benzothiadiazole (3) Benzothiadiazole (13.6 g, 100 mmol) and hydrobromic acid (24.5 mL, 47 wt%) were added to a two-necked flask, heated to 125 °C, and liquid bromine (11.3 mL, 220 mmol) was added dropwise. The mixture was then refluxed for 2.5 hours. The mixture was extracted with dichloromethane and purified by column chromatography using chloroform as the eluent to obtain pale yellow needle-like crystals (27.3 g, 93%). 1 ¹³C NMR, ¹³C NMR, and elemental analysis results indicate that the obtained compound is the target product.

[0018] Example 4 3,7-Dibromo- S,S Synthesis of -dioxo-dibenzothiophene (4) 3,7-Dibromodibenzothiophene (2.74 g, 8 mmol) was added to a round-bottom flask and dissolved in dichloromethane (80 mL). Then, m-chloroperoxybenzoic acid (13.8 g, 80 mmol) was added to the mixture. After reacting at room temperature for 12 hours, excess m-chloroperoxybenzoic acid was neutralized with 10% aqueous sodium hydroxide solution. The reaction mixture was extracted with dichloromethane, and recrystallized from tetrahydrofuran and n-hexane to give a white solid (2.39 g, 80%). 1 ¹³C NMR, ¹³C NMR, and elemental analysis results indicate that the obtained compound is the target product.

[0019] Example 5 Synthesis of 4,6-dibromo-S,S-dioxo-dibenzothiophene (5) 2,8-Dibromodibenzothiophene (2.74 g, 8 mmol) was added to a round-bottom flask and dissolved in dichloromethane (80 mL). Then, m-chloroperoxybenzoic acid (13.8 g, 80 mmol) was added, and the mixture was reacted at room temperature for 12 hours. Excess m-chloroperoxybenzoic acid was neutralized with 10% sodium hydroxide aqueous solution. The reaction mixture was extracted with dichloromethane, and recrystallized from tetrahydrofuran and n-hexane to give a white solid (2.39 g, 80%). 1 ¹³C NMR, ¹³C NMR, and elemental analysis results indicate that the obtained compound is the target product.

[0020] Example 6 Synthesis of 5,9-dibromo-S,S-dioxo-naphthalene-benzothiophene (10) (1) Synthesis of 5-bromo-2-iodo-ethimercaptobenzene (6) 4-Bromo-2-fluoro-1-iodobenzene (24.07 g, 80 mmol), potassium carbonate (22.08 g, 160 mmol), and N,N-dimethylformamide (250 mL) were added to a three-necked flask. Then, ethanethiol (5.76 mL, 80 mmol) was added to the reaction mixture, and the mixture was stirred at 100°C for 12 hours. The mixture was extracted with dichloromethane and purified by column chromatography using petroleum ether as eluent to give a colorless liquid (24.96 g, 91%).

[0021] (2) Synthesis of 5-bromo-2-iodo-ethyl sulfoxide benzene (7) 5-Bromo-2-iodo-ethimercaptobenzene (17.15 g, 50 mmol) was dissolved in acetic acid (150 mL) and stirred in an ice bath. Then, 30% hydrogen peroxide solution (5.1 mL) was added dropwise to the reaction solution. The reaction was allowed to proceed for 8 hours. The solution was extracted with dichloromethane and purified by column chromatography using a mixture of petroleum ether and tetrahydrofuran as eluent to give a white solid (5.43 g, 70%).

[0022] (3) Synthesis of 1-bromo-4-(4-bromo-2-(ethyl sulfoxide)phenyl)naphthalene (8) In a two-necked flask, 5-bromo-2-iodo-ethyl sulfoxide benzene (4.31 g, 12 mmol), 4-bromo-1-naphthylboronic acid (3.01 g, 12 mmol), and toluene (50 mL) were added and stirred until the solid was completely dissolved. Then, 2M potassium carbonate aqueous solution (30 mL, 8.28 g, 60 mmol), tetrakis(triphenylphosphine palladium) (0.69 g, 0.6 mmol), and tetra-n-butylammonium bromide (0.38 g, 1.2 mmol) were added sequentially, and finally, nitrogen gas was bubbled through the solution for protection. The reaction was carried out at 70 °C for 24 h, then cooled to room temperature, and extracted with dichloromethane. The crude product was preliminarily purified by column chromatography to give a pale yellow solid.

[0023] (4) Synthesis of 5,9-dibromo-naphthalene-benzothiophene (9) In a single-necked flask, 1-bromo-4-(4-bromo-2-(ethyl sulfoxide)phenyl)naphthalene (4.38 g, 10 mmol), trifluoromethanesulfonic acid (20 mL), and phosphorus pentoxide (7.1 g, 50 mmol) were added and stirred at room temperature in the dark for 24 hours. After the reaction was complete, the reaction solution was slowly added to ice water and filtered. The residue was added to a two-necked flask, dissolved with pyridine (50 mL), and refluxed for 12 hours. After cooling to room temperature, the pyridine was neutralized with dilute hydrochloric acid, extracted with dichloromethane, and purified by silica gel column chromatography using petroleum ether as the mobile phase to give a yellow solid (1.96 g, 49%).

[0024] (5) Synthesis of 5,9-dibromo-S,S-dioxo-naphthalene-benzothiophene (10) 5,9-Dibromo-naphthiophene (1.96 g, 5 mmol), dichloromethane (50 mL), and m-chloroperoxybenzoic acid (4.32 g, 25 mmol) were added to a single-necked flask and stirred at room temperature for 12 hours. The excess m-chloroperoxybenzoic acid was neutralized with a 10% (w / w) aqueous solution of sodium hydroxide, extracted with dichloromethane, and recrystallized from tetrahydrofuran and ethanol to give a pale yellow solid (1.65 g, 78%). 1 ¹³C NMR, ¹³C NMR, and elemental analysis results indicate that the obtained compound is the target product.

[0025] Example 7 Synthesis of 3,9-dibromo-S,S-dioxo-dibenzothiophene-indene (14) (1) Synthesis of 2-(4-bromo-2-(ethyl sulfoxide)phenyl)-9,9-dioctylfluorene (11) 5-Bromo-2-iodo-ethyl sulfoxide benzene (3.59 g, 10 mmol), 2-(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (4.69 g, 9.1 mmol), and tetrabutylammonium bromide (0.32 g, 0.91 mmol) were added to a three-necked flask, and the reactants were dissolved in toluene (80 mL). Then, potassium carbonate aqueous solution (2 M, 25 mL) and tetra(triphenylphosphine)palladium (0.53 g, 0.46 mmol) were added, and the reaction was stirred at 60°C for 24 hours under nitrogen protection. After the reaction was complete, the mixture was extracted with dichloromethane and purified by column chromatography using petroleum ether / dichloromethane as the eluent, yielding a yellow oily liquid (3.74 g, 66%).

[0026] (2) Synthesis of 3-bromo-dibenzothiophene-indene (12) 2-(4-bromo-2-(ethyl sulfoxide)phenyl)-9,9-dioctylfluorene (3.11 g, 5 mmol) and trifluoromethanesulfonic acid (20 mL) were added to a single-necked round-bottom flask, followed by phosphorus pentoxide (3.05 g, 25 mmol). The mixture was stirred at room temperature for 24 hours, and the reaction solution was slowly poured into ice water and filtered. The resulting solid was refluxed in pyridine (75 mL) for 12 hours. After cooling to room temperature, the pyridine was neutralized with hydrochloric acid. The solution was extracted with dichloromethane, washed with water, and purified by column chromatography using petroleum ether as eluent to obtain a colorless oil (2.19 g, 76%).

[0027] (3) Synthesis of 3-bromo-S,S-dioxo-dibenzothiophene-indene (13) 3-Bromo-dibenzothiophene-indene (1.44 g, 2.5 mmol) was added to a round-bottom flask, dissolved in dichloromethane (80 mL), and then m-chloroperoxybenzoic acid (4.3 g, 25 mmol) was added. The mixture was reacted at room temperature for 12 hours, and excess m-chloroperoxybenzoic acid was neutralized with 10% sodium hydroxide aqueous solution. The solution was extracted with dichloromethane and purified by column chromatography with petroleum ether / dichloromethane to give a white solid (1.37 g, 90%).

[0028] (4) Synthesis of 3,9-dibromo-S,S-dioxo-dibenzothiophene-indene (14) 3-Bromo-S,S-dioxo-dibenzothiophene-indene (1.0 g, 1.6 mmol) was dissolved in a mixed solvent of chloroform (3 mL) and trifluoroacetic acid (6 mL). Then, N-bromosuccinimide (0.37 g, 2.1 mmol) was dissolved in chloroform (1 mL) and added dropwise to the reaction mixture. The reaction was stirred at 60°C for 5 hours. After cooling to room temperature, the mixture was extracted with dichloromethane and purified by column chromatography using petroleum ether / dichloromethane as eluent to give a white solid (1.02 g, 90%). 1¹H NMR, ¹³C NMR, and elemental analysis results indicate that the obtained compound is the target product.

[0029] Example 8 Synthesis of poly(9,9-dioctylfluorene-co-3,7-S,S-dioxo-dibenzothiophene-co-benzothiadiazole) (P1-P3) Polymer P1: Under inert gas protection, 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 2,7-dibromo-9,9-dioctylfluorene (128.2 mg, 0.234 mmol), 3,7-dibromo-S,S-dioxo-dibenzothiophene (22.4 mg, 0.06 mmol), 4,7-dibromo-benzothiadiazole (1.8 mg, 0.006 mmol), palladium acetate (1 mg), tricyclohexylphosphine (2 mg), 9 mL of toluene, and 0.9 mL of 25 wt% tetraethylammonium hydroxide aqueous solution were added to a 25 mL two-necked flask. The reaction mixture was stirred at 95 °C for 1.5 hours. The reaction was stopped, and the polymer was precipitated in methanol. The mixture was filtered, and the residue was extracted using a Soxhlet extractor and dried to give a yellow flocculent solid with a yield of 79%. Mn: 36.5 kDa, PDI: 2.08. ¹H NMR (400 MHz, CDCl₃) δ (ppm): 8.22–8.17 (br, ArH), 8.04–7.97 (br, ArH), 7.96–7.91 (br, ArH), 7.90–7.79 (br, ArH), 7.76–7.60 (br, ArH), 2.30–1.90 (br, CH₂), 1.30–1.04 (br, CH₂), 0.88–0.76 (t, CH₃).

[0030] Polymer P2: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 2,7-dibromo-9,9-dioctylfluorene (65.8 mg, 0.12 mmol), 3,7-dibromo-S,S-dioxo-dibenzothiophene (44.8 mg, 0.12 mmol), 4,7-dibromo-benzothiadiazole (18 mg, 0.06 mmol). The preparation process was the same as P1, with a yield of 80%, Mn: 33.3 kDa, PDI: 2.11.

[0031] Polymer P3: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 3,7-dibromo-S,S-dioxo-dibenzothiophene (67.2 mg, 0.18 mmol), 4,7-dibromo-benzothiadiazole (36 mg, 0.12 mmol). The preparation process was the same as P1, with a yield of 78%, Mn: 32.2 kDa, and PDI: 1.91.

[0032] Example 9 Synthesis of poly(9,9-dioctylfluorene-co-4,6-S,S-dioxo-dibenzothiophene-co-benzothiadiazole) (P4-P6) Polymer P4: Under inert gas protection, 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 2,7-dibromo-9,9-dioctylfluorene (128.2 mg, 0.234 mmol), and 4,6-dibromo- S,S -dioxane-dibenzothiophene (22.4 mg, 0.06 mmol), 4,7-dibromo-benzothiadiazole (1.8 mg, 0.006 mmol), palladium acetate (1 mg), tricyclohexylphosphine (2 mg), 9 mL toluene, and 0.9 mL of 25 wt% tetraethylammonium hydroxide aqueous solution. The reaction was stirred at 95 °C for 1.5 hours. The reaction was stopped, and the polymer was precipitated in methanol. The mixture was filtered, and the residue was extracted using a Soxhlet extractor and dried to give a yellow flocculent solid with a yield of 70%. n 26.7 kDa, PDI: 1.88.

[0033] Polymer P5: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 2,7-dibromo-9,9-dioctylfluorene (65.8 mg, 0.12 mmol), 4,6-dibromo- S,S -dioxo-dibenzothiophene (44.8 mg, 0.12 mmol) and 4,7-dibromo-benzothiadiazole (18 mg, 0.06 mmol) were prepared using the same method as P4, with a yield of 72%. n 23.2 kDa, PDI: 1.97.

[0034] Polymer P6: 2,7-Di(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 4,6-dibromo- S,S-dioxo-dibenzothiophene (67.2 mg, 0.18 mmol) and 4,7-dibromo-benzothiadiazole (36 mg, 0.12 mmol) were prepared using the same method as P4, with a yield of 78%. n 22.2 kDa, PDI: 1.99.

[0035] Example 10 Synthesis of poly(9,9-dioctylfluorene-co-S,S-dioxon-naphthalene-benzothiophene-co-benzothiadiazole) (P7-P9) Polymer P7: Under inert gas protection, 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 2,7-dibromo-9,9-dioctylfluorene (128.2 mg, 0.234 mmol), 5,9-dibromo-S,S-dioxo-naphthalene-benzothiophene (25.4 mg, 0.06 mmol), 4,7-dibromo-benzothiadiazole (1.8 mg, 0.006 mmol), palladium acetate (1 mg), tricyclohexylphosphine (2 mg), 9 mL of toluene, and 0.9 mL of 25 wt% tetraethylammonium hydroxide aqueous solution were added to a 25 mL two-necked flask. The reaction was stirred at 95 °C for 1.5 hours. The reaction was stopped, and the polymer was precipitated in methanol. The precipitate was filtered, and the residue was extracted using a Soxhlet extractor and dried to give a yellow flocculent solid with a yield of 81%. n 36.7 kDa, PDI: 2.28.

[0036] Polymer P8: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 2,7-dibromo-9,9-dioctylfluorene (65.8 mg, 0.12 mmol), 5,9-dibromo-S,S-dioxo-naphthalene-benzothiophene (50.8 mg, 0.12 mmol), 4,7-dibromo-benzothiadiazole (18 mg, 0.06 mmol). The preparation process was the same as for P7, with a yield of 79%. n 33.2 kDa, PDI: 2.30.

[0037] Polymer P9: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 5,9-dibromo-S,S-dioxo-naphthalene-benzothiophene (76.2 mg, 0.18 mmol), 4,7-dibromo-benzothiadiazole (36 mg, 0.12 mmol). The preparation process was the same as for P7, with a yield of 78%. n 30.2kDa, PDI: 2.23.

[0038] Example 11 Synthesis of poly(9,9-dioctylfluorene-co-S,S-dioxo-dibenzothiophene-indene-co-benzothiadiazole) (P10-P12) Polymer P10: Under inert gas protection, 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 2,7-dibromo-9,9-dioctylfluorene (128.2 mg, 0.234 mmol), 3,9-dibromo-S,S-dioxo-dibenzothiophene indene (41.2 mg, 0.06 mmol), 4,7-dibromo-benzothiadiazole (1.8 mg, 0.006 mmol), palladium acetate (1 mg), tricyclohexylphosphine (2 mg), 9 mL of toluene, and 0.9 mL of 25 wt% tetraethylammonium hydroxide aqueous solution were added to a 25 mL two-necked flask. The reaction mixture was stirred at 95 °C for 1.5 h. The reaction was stopped, and the polymer was precipitated in methanol. The precipitate was filtered, and the residue was extracted using a Soxhlet extractor and dried to give a yellow flocculent solid with a yield of 81%. n 38.5 kDa, PDI: 2.26.

[0039] Polymer P11: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 2,7-dibromo-9,9-dioctylfluorene (65.8 mg, 0.12 mmol), 3,9-dibromo-S,S-dioxo-dibenzothiophene-indene (82.4 mg, 0.12 mmol), 4,7-dibromo-benzothiadiazole (18 mg, 0.06 mmol). The preparation process was the same as for P10, with a yield of 77%. n 30.7 kDa, PDI: 2.25.

[0040] Polymer P12: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-borylyl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol), 3,9-dibromo-S,S-dioxo-dibenzothiophene indene (123.6 mg, 0.18 mmol), 4,7-dibromo-benzothiadiazole (36 mg, 0.12 mmol), prepared using the same method as P10, with a yield of 78%. n 31.2 kDa, PDI: 2.03.

[0041] Example 12 Photophysical properties The UV-Vis absorption spectrum and photoluminescence (PL) spectrum of P1 in toluene solution are as follows: Figure 1 As shown in (a) and (b). By Figure 1 (a) It can be seen that P1 exhibits a strong absorption peak around 388 nm, which originates from the conjugated π-electron system in the PF backbone. Notably, although the SO unit content in P1 reaches 10%, its introduction has minimal impact on the position of the absorption peak in the PF backbone. Furthermore, no characteristic absorption peaks associated with the narrow bandgap BT unit were observed in the spectrum. Because the molar percentage of the BT unit in P1 is extremely low, its intrinsic characteristic absorption signal is masked by the strong absorption of the PF backbone, resulting in the inability to detect independent characteristic peaks in the spectrum. This result indirectly indicates that the contribution of different structural units in the polymer to the overall optical properties is closely related to their respective contents.

[0042] exist Figure 1 Three emission peaks can be observed in (b), located at 431 nm, 455 nm, and 522 nm, respectively. The emission peaks at 431 nm and 455 nm correspond to 0-0 and 0-1 vibrational transitions, respectively, originating from the vibrational structure of the fluorene backbone (fine-tuned by the SO unit), reflecting the rigidity and regularity of the conjugated backbone. In addition, the emission peak at 522 nm is attributed to the narrow bandgap characteristics of the BT unit and is also related to the Foster resonance energy transfer (FRET) from the PF-SO segment to the BT unit.

[0043] P1 in different polar solvents (toluene, tetrahydrofuran, chloroform and...) N,N The absorption and PL spectra of (-dimethylacetamide) are as follows: Figure 1 (c) and Figure 1 As shown in (d), when the solvent polarity increases from low-polarity toluene to high-polarity DMA, the absorption spectra of P1 show a slight red shift except for the DMA solution. Figure 1 (c), while its PL spectrum shows a significant redshift. Figure 1 (d) This indicates that the ground state exhibits a weaker intramolecular charge transfer effect due to its smaller dipole moment, while the excited state has a significantly increased dipole moment and a stronger intramolecular charge transfer effect. Furthermore, the main peak of the PL spectrum in the DMA solution is located at 552 nm, indicating that the polymer's fluorescence at this point mainly originates from the radiative transition of the BT unit. This is primarily due to the enhanced ICT effect and energy transfer between the PF-SO segment and the BT unit under a highly polar environment. This phenomenon also confirms that the BT unit has been successfully grafted into the PF backbone and participates in the luminescence process. The photoluminescence quantum yield (PLQY) of P1 in the DMA solution was measured to be 77.6%. This high fluorescence quantum yield suggests that this polymer has the potential to achieve fluorescence detection under low concentration conditions.

[0044] Example 13 Preparation of aqueous solutions of metal ions Accurately weigh 0.017 g NaNO3, 0.020 g KNO3, 0.051 g Mg(NO3)2·6H2O, 0.049 g BaCl2·2H2O, 0.047 g Ca(NO3)2·4H2O, 0.058 g ZnSO4·7H2O, 0.058 g Co(NO3)2·6H2O, 0.058 g Ni(NO3)2·6H2O, 0.062 g Cd(NO3)2·4H2O, 0.080 g Cr(NO3)3·9H2O, 0.048 g Cu(NO3)2·3H2O, 0.049 g MnSO4·7H2O, and 0.081 g Fe(NO3)3·9H2O. Add each ingredient separately to 20 mL of deionized water, shake to dissolve, and obtain 0.01 g of the solution. A mol / L aqueous solution of metal ions.

[0045] Example 14 Fluorescence response test of polymer fluorescent probes to different metal ions The procedure for the metal ion fluorescence response test is as follows: Add 20 μL of metal salt solution of different concentrations sequentially to 2 mL of DMA solution containing P1. After mixing thoroughly, measure the fluorescence spectrum, setting the excitation wavelength to 365 nm. The fluorescence intensity of the P1 solution increases with increasing metal ion concentration as follows: Figure 2 shown. ,Na + K + Ca² + Mn² + Zn² + The effect on P1 fluorescence was relatively small, with quenching percentages of 26.9%, 19.6%, 31.5%, 13.7%, and 0.014%, respectively. + Ba² + Cd² + The impact was second, with quenching percentages of 47.9%, 43.9%, and 49.1% respectively for Cu². + Cr³ + Co² + Ni² + Fe³ + The impact was quite significant, with quenching percentages reaching 57.1%, 56.9%, 61.2%, 55.9%, and 78.7%, respectively. Fe³ + It exhibited the highest quenching percentage among all studied ions, indicating its effect on Fe. 3+ It has a certain degree of selective recognition capability.

[0046] from Figure 1 (c) and Figure 4 (a) Comparison revealed that Fe 3+ The absorption spectrum of Fe partially overlaps with that of the fluorescent probe P1. Under 365 nm ultraviolet light excitation, Fe... 3+ They will competitively absorb and excite light energy. Therefore, with Fe... 3+ As the content increases, the excitation light energy applied to the fluorescent probe P1 gradually decreases, leading to a decrease in fluorescence intensity.

[0047] Example 15 Fe 3+ Detection limit calculation Dissolve 1 mg of fluorescent probe P1 in 100 μL of toluene, then take 20 μL of the toluene solution of P1 and add it to 20 mL of water. N,N In dimethylacetamide, filter and take 2 mL of the filtrate as the fluorescent probe solution. Utilize low concentrations of Fe... 3+ A dropwise addition experiment was conducted on P1, with 20 μL of 0.005 mol / L Fe being added in portions. 3+ The fluorescence emission spectrum of the aqueous solution was tested under excitation light at 365 nm as follows: Figure 3 (a). With (I0-I) / I as the ordinate, Fe 3+ Plot the Stern-Volmer curve with concentration on the x-axis, as shown below. Figure 3 (b), where I0 and I represent the absence of Fe, respectively. 3+ and containing Fe 3+ The fluorescence intensity of the fluorescent probe solution was then measured. The detection limit was calculated to be 776 μM using the formula LOD = 3δ / K, where LOD is the detection limit and δ is the value of the Fe-free value. 3+ The standard deviation of the blank solution is given by K, where K is the quenching constant.

[0048] Example 16 Quenching mechanism Depend on Figure 4 (a) It can be seen that Fe 3+ It exhibits a broad absorption band in the wavelength range of 225-500 nm, which is similar to the absorption spectrum of P1. Figure 1 (c) There is some overlap. Therefore, Fe 3+ Competitive absorption with P1 is likely the primary quenching mechanism. It is noteworthy that Mn² + Zn² + The fluorescence of P1 is minimally affected, a phenomenon that may be related to the type of anion in the metal salt—Mn². + Zn² + The aqueous solution was prepared using sulfates, while aqueous solutions of other metal ions were prepared using nitrates. From Figure 4(b) It can be observed that nitrate ions have an absorption band around 300 nm, which may have a certain quenching effect on the fluorescence of P1. Unfortunately, Fe... 3+ The overlap between the absorption spectra of P1 and P1 is still limited, resulting in P1 having a limited effect on Fe. 3+ The selectivity and sensitivity of the probe were unsatisfactory. This result can provide a key reference for the subsequent molecular structure design of fluorescent probes. By further optimizing the molecular structure, it is expected to improve the probe's selectivity for Fe. 3+ Detection performance.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims.

Claims

1. A fluorene-based polymer fluorescent probe, characterized in that: The chemical structural formula is In the formula: R1, R2, Z1, and Z2 independently represent H, D, F, CN, alkenyl, alkynyl, amino, nitro, acyl, alkoxy, carbonyl, sulfone, alkyl with 1-30 carbon atoms, cycloalkyl with 3-30 carbon atoms, aromatic hydrocarbon with 6-60 carbon atoms, or aromatic heterocyclic group with 3-60 carbon atoms; x, y, and z are the mole fractions of the unit components, satisfying: x + y + z = 1, 0.01 ≤ y ≤ 0.3, 0.01 ≤ z ≤ 0.2, and n = 1-300; Ar is one of the following conjugated structural units containing sulfone-based aromatic heterocycles: 3,7-replace- S,S -dioxo-dibenzothiophene; 2,8-replacement- S,S -dioxo-dibenzothiophene; 4,6-replacement- S,S -dioxo-dibenzothiophene; 2,7-replace- S,S -dioxo-dibenzothiophene; 5,9-replace- S,S -dioxan-naphthalene-benzothiophene; 3,9-replace- S,S -dioxane-dibenzothiophene-indene; 3,8-replacement- S,S -dioxo-dibenzothiophenoindole; 3,10-substitute-double ( S,S -dioxo-dibenzothiophene)cyclopentadiene; 3,10-substitute-double ( S,S -dioxo-dibenzothiophene) and pyrrole; Wherein, R1 and R2 are independently represented as H, D, F, CN, alkenyl, alkynyl, amino, nitro, acyl, alkoxy, carbonyl, sulfone, alkyl with 1-30 carbon atoms, cycloalkyl with 3-30 carbon atoms, aromatic hydrocarbon group with 6-60 carbon atoms, or aromatic heterocyclic group with 3-60 carbon atoms.

2. The method for preparing the fluorene-based polymer fluorescent probe according to claim 1, characterized in that, The specific steps are as follows: Step 1: Dissolve diboron fluorene, dibromofluorene, dibromoaromatic heterocycle, and dibromobenzothiadiazole monomers in an organic solvent, add a catalyst and tetraethylammonium hydroxide aqueous solution to carry out the reaction; Step 2: After the reaction is complete, cool to room temperature, precipitate in methanol, filter, perform Soxhlet extraction, and dry to obtain fluorene-based polymer fluorescent probes.

3. The method for preparing the fluorene-based polymer fluorescent probe according to claim 2, characterized in that: The molar ratio of the diborate fluorene, dibromofluorene, dibromoaromatic heterocyclic compound, and dibromobenzothiadiazole monomer is 0.5:0-0.48:0.01-0.3:0.01-0.2; the organic solvent includes toluene or tetrahydrofuran; the reaction temperature is 80℃-90℃, and the reaction time is 40-120 min; the catalyst includes palladium acetate and tricyclohexylphosphine, the mass ratio of palladium acetate to diborate fluorene monomer is 1:80-100, the mass ratio of tricyclohexylphosphine to diborate fluorene monomer is 1:40-50; and the molar ratio of tetraethylammonium hydroxide to diborate fluorene monomer is 1:1-3.

4. The method of using the fluorene-based polymer fluorescent probe according to claim 1, characterized in that: Step 1: Dissolve the fluorene-based polymer fluorescent probe in toluene to prepare a toluene solution, then add... N,N The fluorescent probe solution was obtained by filtration in dimethylacetamide. Step 2: Take the fluorescent probe solution and add it to the water sample to be tested in portions. Under the excitation of a light source with an excitation wavelength of 340nm-390nm, perform fluorescence emission spectroscopy measurement and plot the fluorescence intensity change curve. Calculate the change value ΔI of fluorescence emission spectral intensity before and after adding the water sample to the fluorescent probe solution based on the curve.

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