Rhodamine 6g schiff base fluorescent probe, and preparation method therefor and use thereof

Abstract

The present invention relates to a rhodamine 6G Schiff base fluorescent probe, which is a complex of Cd2+ and a rhodamine 6G Schiff base. After the fluorescent probe is mixed with an anion, hydrogen sulfite, the hydrogen sulfite and a carbon-nitrogen double bond in the probe are subjected to addition, and the vacant orbital of Cd2+ in the complex is coordinated with the hydrogen sulfite, thereby achieving selective recognition of the hydrogen sulfite. By using a colorimetric method, experimental results show that the hydrogen sulfite has a color response to the fluorescent probe and changes from colorless to pink; the fluorescence intensity of the fluorescent probe at 550 nm is very weak during a fluorescence recognition method, but is significantly enhanced after the addition of the hydrogen sulfite, with almost no interference from other anions at 550 nm; and the lowest detection limit of the hydrogen sulfite by the fluorescent probe is 2.247×10-7 mol / L.

Description

A rhodamine 6G Schiff base fluorescent probe and its preparation method and application Technical Field

[0001] The present invention belongs to the technical field of fluorescent probes, and in particular relates to a rhodamine 6G Schiff base fluorescent probe and a preparation method and application thereof. Background Art

[0002] Sulfur dioxide has been recognized in recent years as a serious environmental pollutant, known for its potential to harm human health, cause acid rain, and harm aquatic life. Its derivatives (bisulfites) are used as preservatives and antioxidants in food, wine, and pharmaceuticals because they inhibit microbial growth and prevent mold. However, high concentrations of sulfites can cause diarrhea, low blood pressure, allergies, and asthma. Modern industrial processes release large amounts of bisulfite, which can also cause serious environmental problems.

[0003] Given this, the development of analytical methods that can effectively detect bisulfite is extremely important and meaningful. Currently reported methods for bisulfite detection include volumetric analysis, optical analysis, ion chromatography (IC), bisulfite-selective electrodes, and online analysis. Among these detection methods, colorimetric and fluorescent probes have become a focus of research due to their unique advantages. Most existing fluorescent probes for bisulfite detection utilize an addition reaction between carbonyl-containing aldehydes and ketones and bisulfite. For example, patent CN109734738A discloses a fluorescent probe capable of rapid detection of bisulfite: 3-(4'-formyl-1',1'-biphenyl-4'-carbonyl) nopinone-fluoroboron complex. However, the presence of other ions, such as sulfate, bromide, sulfite, chloride, and carbonate, can potentially interfere with bisulfite detection, resulting in insufficient selectivity for these currently reported colorimetric and fluorescent probes.

[0004] Summary of the Invention

[0005] The present invention aims to provide a rhodamine 6G Schiff base fluorescent probe and its preparation method and application. The rhodamine 6G Schiff base fluorescent probe provided by the present invention can selectively recognize bisulfite.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a rhodamine 6G Schiff base fluorescent probe, wherein the rhodamine 6G Schiff base fluorescent probe is Cd 2+ and rhodamine 6G Schiff base complex.

[0008] Preferably, the rhodamine 6G Schiff base is a rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base, and the rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base has a chemical structure shown in Formula I:

[0009] The preparation method of the rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base comprises the following steps: firstly mixing rhodamine 6G hydrazide, terephthalaldehyde, a catalyst and a solvent to obtain a mixed solution; and then subjecting the mixed solution to an addition reaction to obtain the rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base.

[0010] Preferably, the catalyst is an acid.

[0011] Preferably, the catalyst is acetic acid.

[0012] Preferably, the addition reaction is carried out under heating conditions; the heating temperature is 70 to 90° C., and the heating time is 2 to 8 hours.

[0013] The present invention also provides a method for preparing the Rhodamine 6G Schiff base fluorescent probe described in the above technical solution, comprising the following steps: reacting a cadmium-containing compound, Rhodamine 6G Schiff base and a solvent to obtain the Rhodamine 6G Schiff base fluorescent probe.

[0014] Preferably, the specific operation of reacting the cadmium-containing compound, rhodamine 6G Schiff base and solvent comprises the following steps:

[0015] (1) mixing a cadmium-containing compound with a first solvent to obtain a mixed solution A;

[0016] (2) mixing rhodamine 6G Schiff base with a second solvent to obtain a mixed solution B;

[0017] (3) mixing the mixed solution A obtained in step (1) and the mixed solution B obtained in step (2) and reacting them to obtain a rhodamine 6G Schiff base fluorescent probe;

[0018] There is no order in which steps (1) and (2) are performed.

[0019] Preferably, the cadmium-containing compound in step (1) is cadmium acetate.

[0020] Preferably, the first solvent in step (1) and the second solvent in step (2) are different.

[0021] Preferably, the second solvent in step (2) is an organic solvent.

[0022] Preferably, in step (3), the ratio of the amount of cadmium ions in the mixed solution A to the amount of rhodamine 6G Schiff base in the mixed solution B is 1:1.

[0023] Preferably, the reaction time in step (3) is 10 to 30 minutes.

[0024] Preferably, the reaction time in step (3) is 20 min.

[0025] The present invention also provides the use of the Rhodamine 6G Schiff base fluorescent probe described in the above technical solution or the Rhodamine 6G Schiff base fluorescent probe prepared according to the preparation method described in the above technical solution in the selective recognition of bisulfite.

[0026] Preferably, the method for selectively recognizing bisulfite by the Rhodamine 6G Schiff base fluorescent probe includes a colorimetric method or a fluorescence recognition method.

[0027] The present invention provides a rhodamine 6G Schiff base fluorescent probe, wherein the rhodamine 6G Schiff base fluorescent probe is Cd 2+ The fluorescent probe provided by the present invention is mixed with the anion bisulfite, and the bisulfite and the carbon-nitrogen double bond in the probe are added, resulting in a ring-opening reaction of the rhodamine Schiff base. At the same time, the Cd 2+ The empty orbital of the fluorescent probe coordinates with bisulfite, achieving selective recognition of bisulfite. The experimental results show that when using the colorimetric method, bisulfite has a color response to the fluorescent probe, changing from colorless to pink. There is a weak color interference from other anions, but the color of bisulfite is clearly different from other anion solutions. When using the fluorescence recognition method, the fluorescence intensity of the fluorescent probe at 550nm is very weak. After adding various anions, the fluorescence intensity of the fluorescent probe is enhanced to varying degrees. Among them, the fluorescence intensity is enhanced very significantly after adding bisulfite. There is almost no interference from other anions at 550nm. The minimum detection limit of the fluorescent probe for bisulfite provided by this application is 2.247×10 -7 mol / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 shows the color response of the fluorescent probe prepared in Example 1 to various anions;

[0029] Figure 2 shows the fluorescent probe solution in Example 1 with the addition of MnO4 - and HSO3 - The UV absorption spectrum after ;

[0030] FIG3 is a fluorescence response curve of the fluorescent probe in Example 1 to different anions;

[0031] Figure 4 shows the fluorescence intensity of the fluorescent probe prepared in Example 1 at 550nm and the fluorescence intensity of HSO3 - Linear relationship of concentration;

[0032] Figure 5 shows the fluorescence intensity of the fluorescent probe prepared in Example 1 at 550nm as a function of HSO3 - Job curve with varying mole fraction. DETAILED DESCRIPTION

[0033] The present invention provides a rhodamine 6G Schiff base fluorescent probe, wherein the rhodamine 6G Schiff base fluorescent probe is Cd 2+ and rhodamine 6G Schiff base complex.

[0034] In the present invention, the rhodamine 6G Schiff base is preferably a rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base, and the rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base has a chemical structure shown in Formula I:

[0035] In the present invention, the Rhodamine 6G Schiff base adopts the above chemical structure and is combined with Cd 2+ The complex composed can further improve the selective recognition of bisulfite.

[0036] In the present invention, the preparation method of the rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base preferably comprises the following steps: firstly mixing rhodamine 6G hydrazide, terephthalaldehyde, a catalyst and a solvent to obtain a mixed solution; and then subjecting the mixed solution to an addition reaction to obtain the rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base.

[0037] In the present invention, rhodamine 6G hydrazide, terephthalaldehyde, a catalyst and a solvent are preferably mixed first to obtain a mixed solution.

[0038] The present invention has no particular limitation on the source of the rhodamine 6G hydrazide, and it can be prepared using a commercially available product or a preparation method well known to those skilled in the art.

[0039] The present invention has no particular limitation on the source of the terephthalaldehyde, and commercially available products known to those skilled in the art may be used.

[0040] In the present invention, the ratio of the amount of rhodamine 6G hydrazide to terephthalaldehyde is preferably ≥ 2. In the present invention, when the ratio of the amount of rhodamine 6G hydrazide to terephthalaldehyde is within the above range, sufficient reaction of terephthalaldehyde can be ensured.

[0041] In the present invention, the catalyst is preferably an acid, more preferably acetic acid. The catalyst should not be highly oxidizing to prevent oxidation of terephthalaldehyde and thus affect the reaction. The catalyst is preferably used in an amount of 5% to 20% by mass of rhodamine 6G hydrazide, more preferably 5% to 10%. The catalyst can significantly increase the reaction yield.

[0042] The present invention has no particular limitation on the type and amount of the solvent, as long as it can fully dissolve rhodamine 6G hydrazide and terephthalaldehyde. In the present invention, the solvent is preferably anhydrous ethanol.

[0043] The present invention has no particular limitation on the mixing operation of the rhodamine 6G hydrazide, terephthalaldehyde, catalyst and solvent, and a technical solution for preparing a mixed material well known to those skilled in the art can be used. In the present invention, the mixing operation of the rhodamine 6G hydrazide, terephthalaldehyde, catalyst and solvent is preferably to first mix the rhodamine 6G hydrazide, terephthalaldehyde and solvent, and then add the catalyst to obtain a mixed solution.

[0044] After obtaining the mixed solution, the present invention preferably performs an addition reaction on the mixed solution to obtain rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base.

[0045] In the present invention, the addition reaction is preferably carried out under heating conditions. The present invention does not particularly limit the heating method, and a heating method well known in the art can be used. In the present invention, the heating method is preferably heating with an electric heating mantle, heating with a magnetic heating stirrer, or heating in a water bath, more preferably heating in a water bath. In the present invention, the water bath heating temperature is easy to control, which is beneficial for maintaining a constant reaction temperature, reducing solvent volatilization, and fully mixing the reactants, thereby fully reacting.

[0046] In the present invention, the heating temperature is preferably 70 to 90° C., more preferably 80° C.; the heating time is preferably 2 to 8 hours, more preferably 3 hours.

[0047] After the heating is completed, the present invention preferably cools, filters, washes and dries the heated product in sequence to obtain rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base.

[0048] The present invention has no particular limitation on the cooling time, as long as the heated product can be cooled to room temperature.

[0049] The present invention has no particular limitation on the filtering operation, and any filtering operation well known to those skilled in the art may be used.

[0050] The present invention has no particular limitation on the washing operation, as long as it can wash away unreacted substances and reaction by-products. In the present invention, the washing operation is preferably first washed with an equal volume mixture of ethanol and ether, an equal volume mixture of chloroform and dioxane, or an equal volume mixture of benzene and acetonitrile, and then washed with ethanol or N,N-dimethylformamide. The present invention has no particular limitation on the number of washing times, as long as it can wash away unreacted substances and reaction by-products. In the present invention, the number of washing times of the two washing liquids is preferably 2 to 5 times independently, more preferably 3 times.

[0051] The present invention does not specifically limit the drying method; any drying method familiar to those skilled in the art may be employed. In the present invention, vacuum drying is preferably employed. In the present invention, the drying temperature is preferably 80°C to 100°C. The present invention does not specifically limit the vacuum drying pressure; a conventional drying oven connected to a vacuum pump may be employed.

[0052] After the fluorescent probe provided by the present invention is mixed with the anion bisulfite, the bisulfite and the carbon-nitrogen double bond in the probe are added, resulting in a ring-opening reaction of the rhodamine Schiff base. 2+ The empty orbital of is coordinated with bisulfite, achieving selective recognition of bisulfite.

[0053] The present invention also provides a method for preparing the Rhodamine 6G Schiff base fluorescent probe described in the above technical solution, comprising the following steps: reacting a cadmium-containing compound, Rhodamine 6G Schiff base and a solvent to obtain the Rhodamine 6G Schiff base fluorescent probe.

[0054] In the present invention, the specific operation of reacting the cadmium-containing compound, rhodamine 6G Schiff base and solvent preferably includes the following steps:

[0055] (1) mixing a cadmium-containing compound with a first solvent to obtain a mixed solution A;

[0056] (2) mixing rhodamine 6G Schiff base with a second solvent to obtain a mixed solution B;

[0057] (3) mixing the mixed solution A obtained in step (1) and the mixed solution B obtained in step (2) and reacting them to obtain a rhodamine 6G Schiff base fluorescent probe;

[0058] There is no order in which steps (1) and (2) are performed.

[0059] The present invention preferably mixes the cadmium-containing compound with a first solvent to obtain a mixed solution A. In the present invention, the cadmium-containing compound is required to have a certain water solubility, cannot have strong oxidizing properties, and does not interfere with anion recognition. In the present invention, the cadmium-containing compound is preferably cadmium acetate. The present invention has no special restrictions on the type of the first solvent, as long as it can dissolve the cadmium-containing compound. In the present invention, the first solvent is preferably water. The present invention has no special restrictions on the operation of mixing the cadmium-containing compound with the first solvent, and the technical solution for preparing the mixed material well known to those skilled in the art can be used.

[0060] The present invention preferably mixes rhodamine 6G Schiff base with a second solvent to obtain a mixed solution B. In the present invention, the second solvent is preferably different from the first solvent, more preferably an organic solvent, and more preferably dimethyl sulfoxide. The present invention does not specifically limit the operation of mixing the rhodamine 6G Schiff base with the second solvent, and a technical solution for preparing a mixed material well known to those skilled in the art can be used.

[0061] After obtaining the mixed solutions A and B, the present invention preferably mixes the mixed solution A with the mixed solution B and then reacts them to obtain a Rhodamine 6G Schiff base fluorescent probe.

[0062] In the present invention, the ratio of the amount of cadmium ions in the mixed solution A to the amount of rhodamine 6G Schiff base in the mixed solution B is preferably 1:1.

[0063] In the present invention, the reaction of the mixed solution A and the mixed solution B is preferably carried out while stirring. The present invention does not particularly limit the stirring rate; a rate well known in the art may be employed. In the present invention, the stirring time is preferably 10 to 30 minutes, more preferably 20 minutes. In the present invention, the stirring time within the above range allows for sufficient coordination between the cadmium ions and the rhodamine 6G Schiff base.

[0064] The preparation method of the fluorescent probe provided by the present invention is simple and convenient, and the fluorescent probe can be obtained by only mixing raw materials and reacting them.

[0065] The present invention also provides the use of the rhodamine 6G Schiff base fluorescent probe described in the above technical solution or the rhodamine 6G Schiff base fluorescent probe prepared according to the preparation method described in the above technical solution for selectively identifying bisulfite. In the present invention, the method for selectively identifying bisulfite with the rhodamine 6G Schiff base fluorescent probe preferably includes colorimetry or fluorescence recognition.

[0066] In the present invention, the operation of the colorimetric method is preferably to pipette the Rhodamine 6G Schiff base fluorescent probe and the solution containing bisulfite into a colorimetric tube with a pipette, and after complete complexation, observe the color change of the solution. In the present invention, the operation of the fluorescence recognition method is preferably to pipette the Rhodamine 6G Schiff base fluorescent probe and the solution containing bisulfite into a cuvette, and after complete complexation, perform ultraviolet-visible absorption spectrum detection. In the present invention, the molar ratio of bisulfite to Rhodamine 6G Schiff base fluorescent probe in the solution containing bisulfite in the colorimetric method and the fluorescence recognition method is preferably (1 to 25):1.

[0067] The application of the rhodamine 6G Schiff base fluorescent probe provided by the present invention realizes the selective recognition of bisulfite. When a colorimetric method is used, bisulfite has a color response to the fluorescent probe, changing from colorless to pink. Other anions have weak color interference, but the color of bisulfite is clearly different from that of other anion solutions. When a fluorescence recognition method is used, the fluorescence intensity of the fluorescent probe at 550 nm is very weak. After adding various anions, the fluorescence intensity of the fluorescent probe is enhanced to varying degrees. The fluorescence intensity enhancement after adding bisulfite is particularly obvious, and other anions have almost no interference at 550 nm.

[0068] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0069] Example 1

[0070] 1.1 Synthesis of Rhodamine 6G Hydrazide

[0071] Rhodamine 6G 1.9187 g (4 mmol) was fully dissolved in 20 mL of anhydrous ethanol and heated in a water bath at 75°C. During the heating process, 6 mL of hydrazine hydrate was slowly added dropwise to the mixed solution. After the addition of hydrazine hydrate was complete, the mixture was refluxed at 75°C until the solution color no longer changed. The reaction time was 2.5 h. The mixture was cooled to room temperature and filtered. The washing solvent was a V (ethanol): V (ether) solution in a ratio of 1:1. The filtration was repeated three times and the mixture was dried in an oven to obtain 1.2839 g of the product with a calculated yield of 66.9%. The reaction formula is as follows:

[0072] 1.2 Synthesis of Rhodamine 6G Hydrazide Terephthalaldehyde Bis-Schiff Base

[0073] 1.2853 g (3 mmol) of rhodamine 6G hydrazide and 0.2096 g (1.5 mmol) of terephthalaldehyde were placed in a 50 mL round-bottom flask and dissolved in 20 mL of anhydrous ethanol. Acetic acid (5% by weight of rhodamine 6G hydrazide) was added, and the water bath temperature was set to 80°C. The mixture was heated under reflux for 3 h, and allowed to cool to room temperature. A precipitate was observed and filtered. The precipitate was washed three times with a V (ethanol): V (ether) solution of 1:1, and then washed three times with ethanol. The solid product (0.7885 g) was obtained by vacuum drying until completely dry. The reaction formula is as follows:

[0074] 1.3 Preparation of Rhodamine 6G Schiff base fluorescent probe

[0075] 0.3174 g of cadmium acetate (0.0012 mol) was dissolved in 20 mL of water to obtain solution A, and 0.5097 g of rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base (0.0012 mol) was dissolved in 20 mL of dimethyl sulfoxide to obtain solution B. A and B were mixed and stirred thoroughly for 20 minutes to obtain a rhodamine 6G Schiff base fluorescent probe.

[0076] The Rhodamine 6G Schiff base fluorescent probe prepared in Example 1 was diluted with a solvent with a volume ratio of dimethyl sulfoxide: water = 99:1 to obtain a concentration of 4.615×10 -5 mol / L fluorescent probe solution for performance testing, the test is as follows:

[0077] Preparation of anionic solution

[0078] Prepared 9.23×10 -4 mol / L of various anion solutions (SiO3 2- 、Cl - 、SO3 2- 、CO3 2- 、S2O8 2- 、SO4 2- 、MnO4 - 、HSO3 - ) Set aside. Except for the permanganate cation which is a potassium ion, the other salts are sodium salts.

[0079] Colorimetry:

[0080] 2 mL of the prepared 4.615×10 -5 mol / L fluorescent probe solution and 2mL 9.23×10 -4 Place 0.5 mol / L anion solution in a colorimetric tube and observe the color change of the solution after complete complexation.

[0081] Figure 1 shows the color response of the fluorescent probe prepared in Example 1 to various anions. As can be seen from Figure 1, HSO3 - It has color response to fluorescent probes and changes from colorless to pink. There is weak color interference from other anions, but HSO3 - The color is obviously different from other anion solutions, so HSO3 can be identified by naked eyes. - .

[0082] Fluorescence identification method:

[0083] The selective response of the fluorescent probe to various ions was determined using UV-visible absorption spectroscopy. Equal volumes of the fluorescent probe solution and anion were pipetted into a cuvette, mixed evenly, and completely complexed before UV-visible absorption spectroscopy was performed.

[0084] Figure 2 shows the fluorescent probe solution in Example 1 with the addition of MnO4 - and HSO3 - The UV absorption spectrum was detected. As shown in Figure 2, HSO3 - There is a weak absorption peak around 260nm, MnO4 - There is no absorption peak in this range.

[0085] Pipette equal volumes of fluorescent probe solution and anion into a cuvette, mix evenly, and after complete complexation, perform fluorescence spectrum detection. Set the excitation wavelength to 350nm, the emission slit to 10nm, and the excitation slit to 5nm.

[0086] Figure 3 is the fluorescence response curve of the fluorescent probe in Example 1 to different anions. As shown in Figure 3, the fluorescence intensity of the fluorescent probe at 550nm is very weak. After adding various anions, the fluorescence intensity of the fluorescent probe is enhanced to varying degrees. - The fluorescence intensity is enhanced significantly, and other anions have almost no interference at 550nm, so the fluorescent probe can selectively identify HSO3 - .

[0087] HSO3 - Fluorescence titration of fluorescent probes

[0088] In the fluorescence spectrum detection experiment, the concentration of the fluorescent probe was kept at 4.615×10 -5 mol / L remains unchanged, and HSO3 with different concentration gradients is accurately prepared in sequence - (respectively 2.424×10 -6 mol / L, 2.727×10 -6 mol / L、3.978×10 -6 mol / L、7.957×10 -6 mol / L、1.035×10 -5 mol / L、1.846×10 -5 mol / L, 2.400×10 -5 mol / L、2.800×10 -5 mol / L、3.200×10 -5 mol / L、3.692×10 -5 mol / L), the fluorescence test excitation wavelength was 350 nm, the emission slit was 10 nm, and the excitation slit was 5 nm.

[0089] Using different concentrations of HSO3 - The fluorescent probe prepared in Example 1 was titrated to obtain a series of fluorescence emission spectra. It was found that the fluorescence intensity of the blank solution of the fluorescent probe at 550 nm was very weak. When different concentrations of HSO3 were added, the fluorescence intensity of the blank solution of the fluorescent probe was very weak at 550 nm.- After aqueous solution, the fluorescence intensity at 550nm increases with the increase of HSO3 - Increases with the increase of concentration.

[0090] Determination of the detection limit of fluorescent probes

[0091] Test the emission spectra of the fluorescent detection solution of 4 groups of blank solutions (4.615×10 -5 mol / L), and the test standard deviation of the fluorescence intensity at 550 nm was calculated to be σ=0.12025.

[0092] Figure 4 shows the fluorescence intensity of the fluorescent probe prepared in Example 1 at 550nm and HSO3 - As shown in Figure 4, based on the linear relationship in the fluorescence emission spectrum, the linear correlation coefficient R 2 =0.99154, the slope is 1.6056×10 6 According to the formula LOD=3σ / m, the fluorescence probe is HSO3 - The minimum detection limit was 2.247×10 -7 mol / L.

[0093] Fluorescent probe and HSO3 - Study on the complexation mechanism of

[0094] In order to determine the fluorescence probe and HSO3 - Complexation ratio, Job's experiment was performed. Fluorescent probe and HSO3 - The total concentration is 10 -6 mol / L, by changing the conditions to make HSO3 - The molar ratio of the fluorescent probe to HSO3 was increased from 0:10 to 9:1 to obtain a series of fluorescence spectra. FIG5 shows the fluorescence intensity of the fluorescent probe prepared in Example 1 at 550 nm as the HSO3 - Job curve of mole fraction change. The results show that when HSO3 - When the complexation ratio with the fluorescent probe is about 2:1, the fluorescence intensity of the system reaches its maximum value.

[0095] It can be seen from the above examples that the rhodamine 6G Schiff base fluorescent probe provided by the present invention can selectively recognize bisulfite.

[0096] The description of the above embodiments is only intended to help understand the method of the present invention and its core concept. It should be noted that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications may be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. Various modifications to these embodiments are obvious to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A rhodamine 6G Schiff base fluorescent probe, wherein the rhodamine 6G Schiff base fluorescent probe is Cd 2+ Complex with rhodamine 6G Schiff base.

2. The rhodamine 6G Schiff base fluorescent probe according to claim 1, characterized in that: The rhodamine 6G Schiff base is a rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base, and the rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base has a chemical structure shown in Formula I:

3. The rhodamine 6G Schiff base fluorescent probe according to claim 2, characterized in that: The preparation method of the rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base comprises the following steps: firstly mixing rhodamine 6G hydrazide, terephthalaldehyde, a catalyst and a solvent to obtain a mixed solution; and then subjecting the mixed solution to an addition reaction to obtain the rhodamine 6G hydrazide terephthalaldehyde bis-Schiff base.

4. The rhodamine 6G Schiff base fluorescent probe according to claim 3, characterized in that: The catalyst is an acid.

5. The rhodamine 6G Schiff base fluorescent probe according to claim 4, characterized in that: The catalyst is acetic acid.

6. The rhodamine 6G Schiff base fluorescent probe according to claim 3, characterized in that: The addition reaction is carried out under heating conditions; the heating temperature is 70 to 90° C., and the heating time is 2 to 8 hours.

7. The method for preparing the rhodamine 6G Schiff base fluorescent probe according to any one of claims 1 to 6, comprising the following steps: The cadmium-containing compound, rhodamine 6G Schiff base and solvent are reacted to obtain a rhodamine 6G Schiff base fluorescent probe.

8. The preparation method according to claim 7, characterized in that: The specific operation of the reaction of the cadmium-containing compound, the rhodamine 6G Schiff base and the solvent comprises the following steps: (1) mixing a cadmium-containing compound with a first solvent to obtain a mixed solution A; (2) mixing rhodamine 6G Schiff base with a second solvent to obtain a mixed solution B; (3) mixing the mixed solution A obtained in step (1) and the mixed solution B obtained in step (2) and reacting them to obtain a rhodamine 6G Schiff base fluorescent probe; There is no order of precedence for step (1) and step (2).

9. The preparation method according to claim 8, characterized in that: The cadmium-containing compound in step (1) is cadmium acetate.

10. The preparation method according to claim 8, characterized in that: The first solvent in step (1) and the second solvent in step (2) are different.

11. The preparation method according to claim 8, characterized in that: The second solvent in step (2) is an organic solvent.

12. The preparation method according to claim 8, characterized in that: In the step (3), the ratio of the amount of cadmium ions in the mixed solution A to the amount of rhodamine 6G Schiff base in the mixed solution B is 1:

1.

13. The preparation method according to claim 8, characterized in that: The reaction time in step (3) is 10 to 30 minutes.

14. The preparation method according to claim 13, characterized in that: The reaction time in step (3) is 20 min.

15. Use of the Rhodamine 6G Schiff base fluorescent probe according to any one of claims 1 to 6 or the Rhodamine 6G Schiff base fluorescent probe prepared by the preparation method according to any one of claims 7 to 14 in selective recognition of bisulfite.

16. The use according to claim 15, characterized in that The method for selectively recognizing bisulfite by the rhodamine 6G Schiff base fluorescent probe includes a colorimetric method or a fluorescent recognition method.

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