Cellulose acetate based 1, 8-naphthalimide fluorescent probe for detecting Hg < 2 + > as well as preparation method and application of cellulose acetate based 1, 8-naphthalimide fluorescent probe

Abstract

The invention discloses a cellulose acetate based 1, 8-naphthalimide fluorescent probe for detecting Hg < 2 + > as well as a preparation method and application of the cellulose acetate based 1, 8-naphthalimide fluorescent probe. The preparation method comprises the following steps: by taking 4-bromo-1, 8-naphthalic anhydride as a raw material, carrying out condensation reaction on the 4-bromo-1, 8-naphthalic anhydride and 4-aminobutyric acid to prepare 4-(4-bromo-1, 8-naphthalic diimide) butyric acid (BNA-B); the BNA-B and piperazine are subjected to a substitution reaction, and a compound PNA-B is prepared; the PNA-B and 4-(bromomethyl) pyridine hydrochloride are subjected to a substitution reaction, and a compound PNA-B is prepared; and the PNA-B and cellulose acetate (CA) are subjected to an esterification reaction, such that the cellulose acetate-based 1, 8-naphthalimide fluorescent probe PNA-CA is prepared. The compound can specifically recognize Hg < 2 + >, after Hg < 2 + > is added into a PNA-CA acetonitrile / PBS buffer solution under 365nm ultraviolet irradiation, the fluorescence color of the solution is changed from colorless to yellow, the response time is 20s, the detection limit reaches 9.3 * 10 <-8 > M, and the probe has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of fluorescence detection technology and relates to a method for detecting Hg 2+ A cellulose acetate-based 1,8-naphthalimide fluorescent probe, a preparation method thereof, and an application thereof. Background Art

[0002] Mercury ions (Hg 2+ ) is a toxic heavy metal ion that is widely distributed in nature. 2+ Accumulation in the human body can cause damage to the nervous system, resulting in brain damage and other chronic diseases. 2+ It can spread through the biofilm in the human body, increasing its damage to the nervous system. In addition, Hg intake through diet 2+ In the aquatic environment, Hg 2+ Not only will it interfere with the shape of the embryo and the metabolic process of the fish, but when mercury ions accumulate excessively in the fish organs, it will also cause pathological changes. In addition, more and more studies have shown that Hg 2+ It will accumulate in plant roots and leaves. High concentrations of Hg 2+ It can be seen that mercury pollution poses a serious threat to ecosystems and human health. 2+ The detection method has important research significance. 2+ The main methods include electrochemical method, chemical titration method, spectrophotometry, etc. These methods have many limitations: cumbersome operation, insufficient practicality, low sensitivity, etc. In comparison, fluorescent probe technology has the advantages of easy operation and high sensitivity.

[0003] Cellulose is a natural polymer with a wide range of sources and abundant production. Each glucose ring of cellulose contains three hydroxyl groups, which can undergo reactions such as oxidation, etherification, cross-linking, and esterification, thereby achieving functional modification and application of cellulose and endowing cellulose with new properties. Cellulose acetate is the acetate ester of cellulose. As a cellulose derivative, it is more soluble in organic solvents than cellulose. In addition, it has the advantages of good biodegradability and mechanical properties, low cost, and non-toxicity. Therefore, cellulose acetate has been widely used in food packaging materials, biosensors, electrochemistry and other fields in recent years. 1,8-Naphthalimide is a small molecule fluorophore with excellent performance and is often used in the field of fluorescent probes. However, this type of small molecule fluorescent probe has some disadvantages: high cytotoxicity, low quantum yield, and poor processing performance. Grafting small-molecule fluorescent probes onto cellulose chains to create cellulose-based macromolecular fluorescent probes not only inherits the excellent properties of the cellulose polymer itself but also overcomes many of the limitations of small-molecule fluorescent compounds. Furthermore, the stable chemical bond between the small-molecule fluorophore and the cellulose backbone effectively overcomes the problem of easy loss of fluorescent molecules in materials prepared by physically mixing fluorescent small molecules with polymers. Therefore, the development of cellulose acetate-based macromolecular fluorescent probes is of great significance and has broad application prospects in fields such as bioimaging, detection and sensing, and information anti-counterfeiting. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a method for detecting Hg 2+ The cellulose acetate-based 1,8-naphthalene diimide fluorescent probe PPNA-CA has no fluorescence when exposed to 365nm ultraviolet light in acetonitrile / PBS buffer solution, but it emits no fluorescence when Hg is added. 2+ The solution then emits yellow fluorescence and can be used for Hg 2+ Another technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned cellulose acetate-based 1,8-naphthalene dicarboxylic acid imide fluorescent probe PPNA-CA. Another technical problem to be solved by the present invention is to provide an application of the above-mentioned cellulose acetate-based 1,8-naphthalene dicarboxylic acid imide fluorescent probe PPNA-CA.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for detecting Hg 2+ The cellulose acetate-based 1,8-naphthalene diimide fluorescent probe PPNA-CA has the structural formula:

[0007]

[0008] The preparation method of the cellulose acetate-based 1,8-naphthalimide fluorescent probe comprises the following steps:

[0009] (1) 4-Bromo-1,8-naphthalene dicarboxylic anhydride reacts with 4-aminobutyric acid to produce compound BNA-B;

[0010] (2) BNA-B undergoes a substitution reaction with piperazine to produce compound PNA-B;

[0011] (3) PNA-B undergoes a substitution reaction with 4-(bromomethyl)pyridine hydrochloride to prepare compound PPNA-B;

[0012] (4) Compound PPNA-B undergoes esterification reaction with the hydroxyl groups on cellulose acetate to produce cellulose acetate-based 1,8-naphthalene diimide fluorescent probe PPNA-CA.

[0013] The preparation steps of compound BNA-B in step (1) are as follows:

[0014] 1) To a 50 mL single-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 1 mmol of 4-bromo-1,8-naphthalene dicarboxylic anhydride, 1-2 mmol of 4-aminobutyric acid, and 20-40 mL of ethanol were added in sequence. The mixture was stirred and refluxed at 80°C for 4-6 hours. The reaction was monitored by TLC and stopped when the reaction was complete.

[0015] 2) After the reaction was cooled to room temperature, the precipitated solid was filtered and washed with distilled water, and then vacuum dried at 45° C. for 24 to 36 hours to obtain compound BNA-B.

[0016] The preparation steps of compound PNA-B in step (2) are as follows:

[0017] 1) To a 50 mL single-necked flask equipped with a stirrer, thermometer, and reflux condenser, 1 mmol of compound BNA-B, 20-30 mL of ethylene glycol monomethyl ether, and 3-4 mmol of piperazine were added in sequence. The mixture was stirred and refluxed at 123°C for 4-6 hours. The reaction was monitored by TLC and stopped when the reaction was complete.

[0018] 2) After the reaction solution was cooled to room temperature, the precipitated solid was filtered and washed with ethanol to obtain a crude product, which was then purified by silica gel column chromatography (dichloromethane:methanol=10:1) to obtain compound PNA-B.

[0019] The preparation steps of compound PPNA-B in step (3) are as follows:

[0020] 1) To a 50 mL single-necked flask equipped with a stirrer, thermometer, and reflux condenser, 1 mmol of compound PNA-B, 20-30 mL of acetonitrile, and 4-5 mmol of 4-(bromomethyl)pyridine hydrochloride were added in sequence. The mixture was stirred and refluxed at 80°C for 6-8 hours. The reaction was monitored by TLC and stopped when the reaction was complete.

[0021] 2) After the reaction solution was cooled to room temperature, the precipitated solid was filtered and washed with ethanol to obtain a crude product, which was then purified by silica gel column chromatography (dichloromethane:methanol=20:1) to obtain compound PPNA-B.

[0022] The preparation steps of the fluorescent probe PPNA-CA in step (4) are as follows:

[0023] 1) To a 100 mL three-necked flask equipped with a stirrer and a thermometer, 0.6-0.8 g CA, 1-2 mmol of compound PPNA-B, 0.4-0.6 mmol of 4-dimethylaminopyridine, and 50-70 mL of DMF were added in sequence and reacted in an ice bath under nitrogen for 20-40 min.

[0024] 2) Add 2-3 mmol of dicyclohexylcarbodiimide dissolved in 5 mL of DMF to the above reaction solution and continue the reaction at room temperature for 36-48 hours;

[0025] 3) After the reaction is completed, the reaction solution is poured into 200 mL of distilled water. The precipitate is filtered and washed with distilled water, and then vacuum-dried at 45° C. for 24 to 36 hours to obtain the fluorescent probe PPNA-CA.

[0026] The cellulose acetate-based 1,8-naphthalene diimide fluorescent probe is effective in detecting Hg 2+ The probe's acetonitrile / PBS buffer solution does not emit fluorescence under 365nm ultraviolet light. 2+ After that, the fluorescent color of the solution changes from colorless to yellow, which can be used for Hg 2+ Detection.

[0027] Beneficial effects: Compared with the prior art, the advantages of the present invention are as follows: Cellulose is the most widely distributed and most abundant natural polymer in nature, with a wide range of sources and low prices. 1,8-naphthalene dicarboximide is a fluorophore with excellent performance and is often used in the field of fluorescent probes. The cellulose-based fluorescent probe obtained by grafting 1,8-naphthalene dicarboximide derivatives onto the cellulose chain not only has the excellent performance of the cellulose polymer itself, but also overcomes many limitations of small molecule fluorescent compounds. The fluorescent probe PPNA-CA thus prepared has the characteristics of good luminescence performance and stable structure. The acetonitrile / PBS buffer solution of the probe was added with Hg under 365nm ultraviolet light irradiation. 2+After that, the fluorescent color of the solution gradually changes from colorless to yellow. 2+ The response time is 20s and the detection limit reaches 9.3×10 -8 M, as a detector for Hg 2+ Fluorescent probes have good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The infrared spectrum of CA, the infrared spectrum of the fluorescent probe PPNA-CA, and the infrared spectrum of the compound PPNA-B;

[0029] Figure 2 Add Hg to the fluorescent probe PPNA-CA solution (acetonitrile / PBS buffer solution = 5:5) 2+ Fluorescence spectra before and after;

[0030] Figure 3 The fluorescence spectra of the fluorescent probe PPNA-CA solution (acetonitrile / PBS buffer solution = 5:5) after adding different analytes;

[0031] Figure 4 Different concentrations of Hg were added to the fluorescent probe PPNA-CA solution (acetonitrile / PBS buffer solution = 5:5) 2+ Fluorescence spectrum of

[0032] Figure 5 Hg was added to the fluorescent probe PPNA-CA solution (acetonitrile / PBS buffer solution = 5:5) 2+ Response time graph after . DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0034] Example 1

[0035] The synthesis of the fluorescent probe PPNA-CA is as follows:

[0036]

[0037] The specific steps are as follows:

[0038] 1) To a 50 mL single-necked flask equipped with a stirrer, a thermometer, and a reflux condenser were added 1 mmol of 4-bromo-1,8-naphthalene dicarboxylic anhydride, 1.1 mmol of 4-aminobutyric acid, and 20 mL of ethanol, followed by stirring and reflux at 80°C for 4 hours; the reaction was monitored by TLC until completion, and the reaction was stopped. After cooling to room temperature, the precipitated solid was filtered, washed with distilled water, and dried under vacuum at 45°C for 24 hours to obtain compound BNA-B in a yield of 90%. 1 H NMR (600MHz, DMSO-d6) δ: 11.97 (s, 1H), 8.50 (dd, J=16.6, 7.9Hz, 2H), 8.27 (d, J=7.8Hz, 1H), 8.16 (d, J= 7.8Hz, 1H), 7.94 (t, J=7.9Hz, 1H), 4.03 (t, J=6.9Hz, 2H), 2.27 (t, J=7.3Hz, 2H), 1.85 (p, J=7.1Hz, 2H). 13 C NMR (150MHz, DMSO-d6) δ: 174.48, 163.4, 163.37, 132.91, 131.92, 131.72, 131.30, 130.16, 129.44, 129.16, 128.73, 123.23, 122.46, 31.81, 23.38.

[0039] 2) To a 50 mL single-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 1 mmol of compound BNA-B, 20 mL of ethylene glycol monomethyl ether, and 3 mmol of piperazine were added in sequence, and the mixture was stirred and refluxed at 123°C for 6 h. The reaction was monitored by TLC and stopped after completion. After the reaction solution was cooled to room temperature, the precipitated solid was filtered and washed with ethanol to obtain a crude product, which was then purified by silica gel column chromatography (dichloromethane:methanol = 10:1) to obtain compound PNA-B. 1 H NMR (600MHz, DMSO-d6) δ: 9.73 (s, 1H), 8.51 (d, J = 8.5Hz, 1H), 8.47 (d, J = 7.2Hz, 1H), 8.40 (d, J = 8.0Hz, 1H), 7.82 (t, J = 7.9Hz, 1 H), 7.41 (d, J=8.1Hz, 1H), 4.05 (t, J=7.0Hz, 2H), 3.48-3.37 (m, 8H), 2.28 (t, J=7.3Hz, 2H), 1.86 (p, J=7.3Hz, 2H), 1.21 (s, 1H). 13C NMR (150MHz, DMSO-d6) δ: 173.89, 163.64, 163.13, 154.39, 132.01, 130.76, 130.43, 1 29.00, 126.47, 125.37, 122.60, 116.71, 115.64, 49.28, 42.78, 42.71, 31.25, 22.99.

[0040] 3) To a 50 mL single-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, 1 mmol of compound PNA-B, 20 mL of acetonitrile, and 4 mmol of 4-(bromomethyl)pyridine hydrochloride were added in sequence, and the mixture was stirred and refluxed at 80°C for 8 h; the reaction was monitored by TLC and stopped after completion of the reaction; after the reaction solution was cooled to room temperature, the precipitated solid was filtered and washed with ethanol to obtain a crude product, which was then purified by silica gel column chromatography (dichloromethane:methanol = 20:1) to obtain compound PPNA-B. 1 H NMR (600MHz, DMSO-d6) δ: 11.99 (s, 1H), 8.52 (s, 1H), 8.45 (d, J=7.2Hz, 1H), 8.42 (d, J=8. 4Hz, 1H), 8.37 (d, J = 8.0Hz, 1H), 7.79 (dtd, J = 7.9, 4.9, 2.6Hz, 2H), 7.50 (d, J = 7.8Hz, 1H), 7.33 (d, J=8.2Hz, 1H), 7.29 (dd, J=7.5, 4.9Hz, 1H), 4.06 (t, J=7.0Hz, 2H), 3.75 (s, 2H), 3 .25 (d, J=4.9Hz, 4H), 2.77 (t, J=4.7Hz, 4H), 2.28 (t, J=7.3Hz, 2H), 1.87 (q, J=7.1Hz, 2H). 13 C NMR (150MHz, DMSO) δ: 174.44, 164.11, 163.58, 158.61, 156.01, 149.33, 137.02, 132.57, 131.02, 130.87, 12 9.59, 126.42, 125.73, 123.39, 123.04, 122.72, 116.06, 115.44, 64.16, 53.22, 53.13, 39.38, 31.81, 23.54.

[0041] 4) To a 100-mL three-necked flask equipped with a stirrer and a thermometer, 0.6 g of CA, 1 mmol of the compound PPNA-B, 0.4 mmol of 4-dimethylaminopyridine, and 50 mL of DMF were added sequentially and reacted in an ice bath under nitrogen for 30 min. Then, 2 mmol of dicyclohexylcarbodiimide dissolved in 5 mL of DMF was added to the reaction solution, and the reaction was continued at room temperature for 48 h. After the reaction, the reaction solution was poured into 200 mL of distilled water. The precipitate was filtered, washed with distilled water, and then vacuum-dried at 45°C for 24 h to obtain the fluorescent probe PPNA-CA.

[0042] Example 2

[0043] The structure of the fluorescent probe PPNA-CA was analyzed by FT-IR. Figure 1 The infrared spectra of CA, the infrared spectra of the fluorescent probe PPNA-CA, and the infrared spectra of the compound PPNA-B are shown in the figure. As can be seen from the figure, CA and PPNA-CA have a high fluorescence intensity at 3500 cm -1 There is an obvious characteristic absorption peak around 1700 cm, which belongs to the stretching vibration peak of the OH bond on the cellulose chain. -1 A new absorption peak appeared at 1500 nm, which belongs to the stretching vibration peak of C=O, indicating that CA and compound PPNA-B are connected through esterification reaction. In addition, the fluorescent probe PPNA-CA also showed some characteristic peaks belonging to the benzene ring, such as the skeleton vibration peak of C=C (1588, 1515 cm -1 ). Therefore, FT-IR analysis showed that the fluorescent probe PPNA-CA was successfully prepared.

[0044] Example 3

[0045] The fluorescent probe PPNA-CA was added to a solution (acetonitrile / PBS buffer solution = 5:5, v / v) to prepare a solution with a concentration of 0.05 mg / mL. The fluorescence emission spectrum was measured on a fluorescence spectrophotometer using a fluorescence spectrum titration method, as shown in FIG. Figure 2 The results showed that in acetonitrile / PBS buffer solution, the fluorescent probe PPNA-CA did not emit fluorescence at 533 nm, but when Hg 2+ After that, the fluorescence intensity at 533 nm increased sharply (excitation wavelength was 365 nm, excitation slit bandwidth was 6.0 nm, emission slit bandwidth was 10.0 nm).

[0046] Example 4

[0047] The fluorescent probe PPNA-CA was added to the solution (acetonitrile / PBS buffer solution = 5:5, v / v) to prepare a solution with a concentration of 0.05 mg / mL. One portion was used as a blank sample, and the other portions were added with other analytes, namely Ag + , Na + , K + , Ca 2+ , Mg 2+ , Cu 2+ , Fe 2+ , Zn 2+ , Mn 2+ , Pb 2+ ,Co 2+ , Ni 2+ , Fe 3+ , Al 3+ , Cr 3+ , measure the fluorescence emission spectrum of the solution, the results are as follows Figure 3 As shown. 2+ After adding Hg, the fluorescence intensity of the solution at 533 nm increased sharply, while when other analytes were added, the fluorescence intensity of the solution at 533 nm changed very little. This shows that the fluorescent probe PPNA-CA is sensitive to Hg 2+ The detection has good selectivity.

[0048] Example 5

[0049] The fluorescent probe PPNA-CA was added to the solution (acetonitrile / PBS buffer solution = 5:5, v / v) to prepare a solution with a concentration of 0.05 mg / mL. 2+ The fluorescence emission spectra after (0-100 μM) are as follows: Figure 4 The results show that as Hg 2+ With the gradual increase of concentration (0-100 μM), the fluorescence signal intensity of the fluorescent probe PPNA-CA at 533 nm gradually increased, indicating that the fluorescent probe PPNA-CA can be used to detect Hg in solution. 2+ The concentration of Hg 2+ The detection limit reached 9.3×10 -8 M.

[0050] Example 6

[0051] The fluorescent probe PPNA-CA was added to the solution (acetonitrile / PBS buffer solution = 5:5, v / v) to prepare a solution with a concentration of 0.05 mg / mL. 2+ The response time after Figure 5 The results show that the addition of Hg 2+After the addition of PPNA-CA, the fluorescence signal intensity at 533 nm increased sharply and reached the maximum value within 20 s, indicating that the probe can quickly detect Hg 2+ .

Claims

1. A method for detecting Hg 2+ The cellulose acetate-based 1,8-naphthalimide fluorescent probe is characterized in that: The structural formula is:

2. The method for preparing the cellulose acetate-based 1,8-naphthalimide fluorescent probe PPNA-CA according to claim 1, characterized in that: The steps include: (1) 4-Bromo-1,8-naphthalene dicarboxylic anhydride reacts with 4-aminobutyric acid to produce 4-(4-bromo-1,8-naphthalene dicarboximido)butyric acid (BNA-B); (2) Compound BNA-B undergoes a substitution reaction with piperazine to produce compound PNA-B; (3) Compound PNA-B undergoes a substitution reaction with 4-(bromomethyl)pyridine hydrochloride to prepare compound PPNA-B; (4) Compound PPNA-B undergoes esterification reaction with the hydroxyl groups on cellulose acetate to produce cellulose acetate-based 1,8-naphthalene diimide fluorescent probe PPNA-CA.

3. The method for preparing a cellulose acetate-based 1,8-naphthalimide fluorescent probe according to claim 2, wherein: The specific preparation steps of BNA-B in step (1) are as follows: 1) To a 50 mL single-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, add 1 mmol of 4-bromo-1,8-naphthalene dicarboxylic anhydride, 1-2 mmol of 4-aminobutyric acid, and 20-40 mL of ethanol in sequence. Stir and reflux at 80°C for 4-6 hours. Monitor by TLC until the reaction is complete. 2) After the reaction solution was cooled to room temperature, the precipitated solid was filtered, washed with distilled water, and then vacuum dried at 45° C. for 24 to 36 hours to obtain compound BNA-B.

4. The method for preparing a cellulose acetate-based 1,8-naphthalimide fluorescent probe according to claim 2, wherein: The specific preparation steps of PNA-B in step (2) are as follows: 1) To a 50 mL single-necked flask equipped with a stirrer, thermometer, and reflux condenser, 1 mmol of compound BNA-B, 20-30 mL of ethylene glycol monomethyl ether, and 3-4 mmol of piperazine were added in sequence. The mixture was stirred and refluxed at 123°C for 4-6 hours. The reaction was monitored by TLC and stopped when the reaction was complete. 2) After the reaction solution was cooled to room temperature, the precipitated solid was filtered and washed with ethanol to obtain a crude product, which was then purified by silica gel column chromatography (dichloromethane:methanol=10:1) to obtain compound PNA-B.

5. The method for preparing a cellulose acetate-based 1,8-naphthalimide fluorescent probe according to claim 2, wherein: The specific preparation steps of PPNA-B in step (3) are as follows: 1) To a 50 mL single-necked flask equipped with a stirrer, thermometer, and reflux condenser, 1 mmol of compound PNA-B, 20-30 mL of acetonitrile, and 4-5 mmol of 4-(bromomethyl)pyridine hydrochloride were added in sequence. The mixture was stirred and refluxed at 80°C for 6-8 hours. The reaction was monitored by TLC and stopped when the reaction was complete. 2) After the reaction solution was cooled to room temperature, the precipitated solid was filtered and washed with ethanol to obtain a crude product, which was then purified by silica gel column chromatography (dichloromethane:methanol=20:1) to obtain compound PPNA-B.

6. The method for preparing a cellulose acetate-based 1,8-naphthalene diimide fluorescent probe according to claim 2, wherein: The preparation steps of PPNA-CA in step (4) are as follows: 1) To a 100 mL three-necked flask equipped with a stirrer and a thermometer, 0.6-0.8 g CA, 1-2 mmol of compound PPNA-B, 0.4-0.6 mmol of 4-dimethylaminopyridine, and 50-70 mL of DMF were added in sequence and reacted in an ice bath under nitrogen for 20-40 min. 2) Add 2-3 mmol of dicyclohexylcarbodiimide dissolved in 5 mL of DMF to the above reaction solution and continue the reaction at room temperature for 36-48 hours; 3) After the reaction is completed, the reaction solution is poured into 200 mL of distilled water. The precipitate is filtered and washed with distilled water, and then vacuum-dried at 45° C. for 24 to 36 hours to obtain the fluorescent probe PPNA-CA.

7. The cellulose acetate-based 1,8-naphthalimide fluorescent probe according to claim 1 is used to detect Hg 2+ Application in.

8. The use according to claim 7, characterized in that Under 365nm UV irradiation, the acetonitrile / PBS buffer solution of the fluorescent probe PPNA-CA did not emit fluorescence. 2+ After that, the fluorescence color of the solution changed from colorless to yellow, the response time was 20s, and the detection limit reached 9.3×10 -8 M.

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