A hydrogel film for visual detection of antibiotics in water bodies and a preparation method thereof

Abstract

The present invention discloses a hydrogel film for visual detection of antibiotics in water bodies and a preparation method thereof. The film is prepared by using a thickener, a metal-organic framework material and a solvent. The preparation includes: mixing the thickener and the solvent and stirring to obtain a hydrogel, adding the metal-organic framework material thereto, stirring evenly, taking an appropriate amount of the mixture and performing a scraping treatment on the surface of a glass slide to form a hydrogel film for portable visual detection of antibiotics in water bodies, photographing the fluorescence photos of the hydrogel film before and after soaking in antibiotic solutions with different concentrations, and establishing a visual detection method through the change of the film gray scale before and after soaking. The hydrogel film prepared by the present invention has a short detection time for antibiotic molecules and high detection sensitivity. The visual detection method established through the change of the hydrogel film gray scale solves the disadvantages of the traditional fluorescence detection method that requires specific instruments and complex operations, reduces the detection cost, and has good practical application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of chemical analysis and detection, and relates to a hydrogel film for visual detection of antibiotics in water bodies and a preparation method thereof. Background Art

[0002] Antibiotics play an important role in improving human health and treating infections in humans, animals, and plants. However, the abuse of antibiotics has led to their residues in water, soil, animals, and plants, and ultimately their spread in the ecological cycle. Long-term ingestion of these foods contaminated with antibiotics can lead to decreased immunity, genetic defects, allergic reactions, and various cancers. Currently, traditional detection methods such as capillary electrophoresis (CE), high-performance liquid chromatography (HPLC), ion mobility spectrometry (IMS), mass spectrometry, and fluorescence spectroscopy are costly, time-consuming, and even require sophisticated equipment. Therefore, there is an urgent need to develop a convenient, fast, sensitive, and accurate detection method for rapid detection of antibiotics in water bodies.

[0003] Compared with detection methods such as fluorescence spectroscopy, the visual detection method based on the change of film gray scale has received extensive attention from researchers due to its simple operation. In recent years, although fluorescence detection methods have made great progress in terms of accuracy and sensitivity, they still have the disadvantages of difficulty in miniaturization of instruments, low detection sensitivity, and poor practicability. This is because fluorescence detection methods cannot do without fluorescence spectrometers, that is, specific instruments are required to perform detection operations. Therefore, there is an urgent need to develop a portable detection method to fundamentally get rid of the limitations caused by instrument factors. In recent years, smartphones have been rapidly popularized. By using the built-in camera of the mobile phone to take pictures and obtaining the color information contained in the images through data analysis software, a portable visual detection method based on smartphones can be designed. This detection method can calculate the change of image gray scale by using formulas, and further measure the concentration of the analyte. While simplifying the detection process, it overcomes the limitations caused by the need for specific instruments in traditional detection methods, and is expected to realize the practical application of metal-organic framework materials in the field of visual detection.

[0004] Metal-organic framework materials are porous materials formed by the self-assembly of metal ions or metal clusters with organic ligands. They have the advantages of large specific surface area, modifiable functional sites on the pore surface, good stability, and simple synthesis conditions. In recent years, they have been widely used in the field of visual detection. Most of the reported visual detections of metal-organic framework materials are mainly achieved in the form of powders. Before detection, the metal-organic framework material powder is first dissolved in water or an organic solvent to form a suspension. Then, a part of the suspension is taken and mixed with an antibiotic solution in a cuvette, and then it is taken to a spectrometer in the laboratory for testing. In actual detection, due to the generally poor dispersion of the powder in the solution, the sedimentation of the powder will greatly reduce the sensitivity and accuracy of the detection. In addition, a part of the visual detection of metal-organic framework materials is achieved in the form of films, but the complex preparation process, poor mechanical properties, and light impermeability of the films at the present stage limit their practical application in the field of visual detection of antibiotics.

[0005] Based on the above problems, it is very meaningful to develop a film that is simple to synthesize and has a certain mechanical strength, and on this basis, design a simple and portable visual analysis and testing method. The present invention specifically provides a hydrogel film for visual detection of antibiotics in water. When detecting, the film only needs to be soaked in an aqueous solution containing antibiotics for a few minutes, and combined with devices such as mobile phones and a handheld ultraviolet lamp, visual detection can be quickly achieved. The entire detection process is simple to operate, highly sensitive, and time-consuming short, and has great potential for practical application. Summary of the Invention

[0006] The purpose of the present invention is to provide a hydrogel film for portable visual detection of antibiotics in water and its preparation method.

[0007] The present invention is realized by the following technical solutions:

[0008] A hydrogel film for visual detection of antibiotics in water is prepared by mixing a thickener and a solvent, adding a metal-organic framework material, stirring evenly, and then scraping and coating to form a film on a substrate. After taking it off, the hydrogel film is obtained; when used for visual detection of antibiotics in water, the hydrogel film is directly soaked in the water to be measured, and photos of the hydrogel film before and after soaking are taken. After collecting color information, the gray scale is obtained, and the antibiotic concentration in the water is determined based on the change in gray scale.

[0009] In the above technical solution, further, the metal ions in the metal-organic framework material are zinc, europium, terbium, cadmium or dysprosium, and the organic ligand is 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine, 4,4',4''-(benzene-1,3,5-triyltris(azanediyl))tribenzoic acid, 5'-(4-carboxy-3-hydroxyphenyl)-3,3''-dihydroxy-[1,1':3',1''-terphenyl]-4,4''-dicarboxylic acid or 4,4',4''-(benzene-1,3,5-tris(ethene-2,1-diyl)-tribenzoic acid. The particle size of the metal-organic framework material is 1 to 15 μm, and the thickener is agarose, sodium alginate, chitosan or a silk fibroin fiber / poly(n-isopropylacrylamide) mixture. The dosage ratio of the metal-organic framework material to the thickener is: 3 to 6 parts by weight: 5 to 10 parts by weight.

[0010] According to a specific example of the present invention, a method for preparing a hydrogel film for visual detection of antibiotics in water bodies of the present invention includes the following steps:

[0011] (1) Preparation of the metal-organic framework material: Add metal nitrate and organic ligand into deionized water and organic solvent to obtain a mixed solution, then add a certain amount of acid, put the obtained solution into a glass bottle, and heat it at 80 to 130 °C

[0012] for 24 to 72 h, centrifuge and wash to obtain the metal-organic framework material;

[0013] (2) Preparation of the hydrogel: Mix the thickener with water or organic solvent, stir for 10 to 30 min until the thickener is dissolved to obtain a hydrogel; mix the metal-organic framework material and the hydrogel and place it at room temperature and stir for 5 to 10 h to obtain a mixture of the metal-organic framework material and the hydrogel;

[0014] (3) Preparation of the film: Take the obtained mixture and perform a scraping treatment on a glass substrate to form a uniform film on the surface of the glass slide, and then rinse it with deionized water to obtain a hydrogel film for visual detection of antibiotics in water.

[0015] In the above preparation method, the organic solvent in the mixed solution in (1) is N,N-dimethylformamide or N,N-dimethylacetamide, any one; the acid is nitric acid, trifluoroacetic acid or acetic acid, and the volume ratio of the acid to the mixed solution is 0.01 to 0.5:1; the weight ratio of the thickener to water or organic solvent in (2) is 0.01 to 0.1:1; the thickness of the hydrogel film is 100 to 300 μm.

[0016] The principle of the present invention is:

[0017] Metal-organic framework materials are porous materials formed by the self-assembly of metal ions or metal clusters with organic ligands. They have the advantages of large specific surface area, modifiable functional sites on the pore surface, good stability, and simple synthesis conditions. In recent years, they have been widely used in the field of visual detection. However, most of the visual detection of metal-organic framework materials is mainly achieved in the form of powders. When used, the powders are extremely easy to settle, which will greatly reduce the sensitivity and accuracy of detection. The metal-organic framework material films prepared by the in-situ synthesis method and the mixed matrix membrane method are limited in their practical applications in the field of visual detection due to the complex preparation process, low mechanical properties, and light impermeability. The film of the present invention uses a commercial glass slide as a substrate. After mixing a thickening agent, a solvent, and a metal-organic framework material, it can be formed into a film by simple scraping. This film has good light transmittance and a certain mechanical strength, and also has the characteristics of simple process and low cost. The traditional fluorescence detection method requires specific equipment such as a fluorescence spectrometer, with high detection costs and complex operations. The visual detection method uses the camera of a mobile phone to take images and obtains the color information contained in the images through data analysis software. The change in the gray value of the film before and after soaking in different antibiotic aqueous solutions is calculated using a formula, and a standard curve of the change value of the film gray value / initial gray value of the film - concentration of the analyte is constructed. In the actual detection process, the color information of the fluorescence images of the film before and after soaking in the analyte solution is obtained through data analysis software, the gray value of the film before and after soaking is calculated using the formula, and then the change value of the film gray value / initial gray value of the film obtained is compared with the standard curve to determine the concentration of the analyte. This method simplifies the detection process while overcoming the limitations caused by the need for specific instruments in traditional detection methods, and is expected to realize the practical application of metal-organic framework materials in the detection field.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. The film of the present invention uses a commercial glass slide as a substrate, enabling the film to have good light transmittance and mechanical strength. After mixing a thickening agent, a solvent, and a metal-organic framework material, it can be formed into a film by scraping, with a simple preparation process, low preparation cost, good film uniformity, and greatly improving the accuracy when the film is applied to visual detection.

[0020] 2. In the film of the present invention, the thickening agent molecules are non-toxic, odorless, chemically stable, safe and hygienic, and will not cause secondary pollution to the water body during use.

[0021] 3. Compared with the metal-organic framework powder probe, the presence of the hydrogel skeleton in the film of the present invention increases the specific surface area of the film, avoids the aggregation between metal-organic framework material particles, exposes more active sites, reduces the aggregation-induced quenching phenomenon, increases the fluorescence intensity of the metal-organic framework material system, and improves the sensitivity and accuracy of detection.

[0022] 4. The thin film of the present invention is a composite material with a hydrogel as the continuous phase and a metal-organic framework material as the dispersed phase. The porous structure existing in the hydrogel skeleton endows it with certain swelling properties. Both this structure and the porous structure of the metal-organic framework material have an adsorption effect on the analyte solution, thereby generating an enrichment effect, greatly increasing the adsorption amount and adsorption speed of the analyte, and then accelerating the interaction between the analyte molecules and the metal-organic framework material. The detection time is greatly shortened and the sensitivity is greatly improved.

[0023] 5. The thin film of the present invention has a hydrogel as the continuous phase. The free organic groups in the hydrogel make the thin film carry a certain amount of charge, which has an electrostatic adsorption effect on the analyte molecules, thereby generating an enrichment effect, greatly reducing the detection limit and improving the detection sensitivity.

[0024] 6. The thin film of the present invention only needs to be immersed in the actual water body for 2 - 5 minutes, and then it can realize the real-time detection of antibiotics in the water body. Especially when used in combination with a handheld ultraviolet lamp, the actual detection process can be greatly simplified.

[0025] 7. When the thin film of the present invention is used for visual detection, its good light transmittance enables it to exhibit the original fluorescence of the metal-organic framework material under the irradiation of a handheld ultraviolet lamp, greatly improving the sensitivity and accuracy of visual detection.

[0026] 8. The visual detection calculation method of the present invention is combined with a smart phone. The ratio of the gray-scale change value of the thin film before and after immersion to the gray-scale value of the control group is used as a variable to correspond to the antibiotic concentration, realizing the application of a single-color material system in visual detection, reducing the errors caused by different models of mobile phones in the detection process, expanding the selection range of the material system, simplifying the detection process, overcoming the limitations caused by the need for specific instruments in traditional detection methods, and providing a method for applying the metal-organic framework material thin film to a mobile detection platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the emission spectrum of the hydrogel thin film for visual detection of antibiotics in water under ultraviolet light excitation in the present invention.

[0028] Figure 2 is the standard curve of the gray-scale change value of the thin film / the initial gray-scale value of the thin film - antibiotic concentration calculated after the hydrogel thin film for visual detection of antibiotics in water is immersed in antibiotic solutions with different concentrations in the present invention. DETAILED IMPLEMENTATION MANNER

[0029] The content of the present invention will be further explained below in conjunction with examples. However, these examples do not limit the protection scope of the present invention. Based on the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

[0030] Example 1:

[0031] The film for portable fluorescence detection and visualization detection of nitroimidazole antibiotics in water bodies in this example is prepared by using 300 parts by weight of H2O, 3 parts by weight of europium and terbium with a particle size of 10 μm, and a metal-organic framework material formed by coordinating 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine and 6 parts by weight of sodium alginate. The specific preparation method is as follows:

[0032] (1) Preparation of the metal-organic framework material: Dissolve 35.05 mg of terbium nitrate, 1.07 mg of europium nitrate, and 24 mg of 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine in a mixed solvent of 12 mL of DMF and 1.8 mL of H2O. Subsequently, add 210 mL of nitric acid, encapsulate the solution in a 20 mL glass bottle, and place it in an oven at 105 °C for reaction for 48 h. Cool to room temperature and wash three times with DMF to obtain the metal-organic framework material for detecting nitroimidazole antibiotics. (2) Preparation of the mixture of the metal-organic framework material and sodium alginate hydrogel: Mix 60 mg of sodium alginate and 3 mL of H2O in a 20 mL glass bottle, stir at room temperature for 20 min, and wait for all the sodium alginate to dissolve. Then, let it stand for 30 min to eliminate bubbles to obtain the hydrogel for standby. Mix 30 mg of the metal-organic framework material for detecting nitroimidazole antibiotics and 3 mL of the hydrogel in a 20 mL glass bottle, and then place it in a room temperature environment and stir for 5 h to obtain the mixture of the metal-organic framework material and the hydrogel.

[0033] (3) Preparation of the film: Take 500 μL of the mixture of the metal-organic framework material and the hydrogel on a glass slide, and then use a BGD 209 / 1 type film doctor to perform scraping treatment on the glass slide. Immerse the scraped film in a calcium nitrate solution with a concentration of 30 M / L for 1 min, and then rinse it with deionized water to obtain the film for portable fluorescence detection and visualization detection of nitroimidazole antibiotics in water bodies, and its thickness is 250 μm.

[0034] (4) Under the excitation of 365 nm ultraviolet light of the handheld ultraviolet lamp, the film shows the fluorescence of the metal-organic framework material. Since the ultraviolet absorption spectrum of nitroimidazole antibiotics and the excitation spectrum of 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine in the metal-organic framework material have a large overlap, there is a competitive absorption relationship between nitroimidazole antibiotics and ligands for the excitation light, resulting in a decrease in the fluorescence intensity of the film. Therefore, after soaking in water containing nitroimidazole antibiotics, the fluorescence intensity of the film decreases significantly with the increase of nitroimidazole antibiotics, indicating that this film has a good detection effect on nitroimidazole antibiotics in water.

[0035] (5) Visual detection calculation principle: Gray = R×0.3 + G×0.59 + B×0.11. Use a mobile phone to take pictures of the hydrogel film soaked in aqueous solutions containing different concentrations of nitroimidazole antibiotics, collect the color information of the pictures using MATLAB, calculate the change amount of the gray value of the hydrogel film before and after soaking through the formula, and construct a standard curve of film gray change value / film initial gray value - nitroimidazole antibiotic concentration.

[0036] (6) According to the constructed standard curve of film gray change value / film initial gray value - nitroimidazole antibiotic concentration, during actual detection, a mobile phone can directly be used to take fluorescence pictures of the film of the present invention before and after immersion in the water sample to be detected containing nitroimidazole antibiotics, directly extract the gray value in the corresponding processing software, and compare the obtained film gray change value / film initial gray value with the previously obtained standard curve to determine the concentration of nitroimidazole antibiotics. This method simplifies the detection process while overcoming the limitations caused by the need for specific instruments in traditional detection methods.

[0037] Example 2:

[0038] The film for portable fluorescence detection of tetracycline antibiotics in water in this example is prepared from 300 parts by weight of H2O, 5 parts by weight of zinc with a particle size of 5 μm coordinated with 4,4',4”-(benzene-1,3,5-triyltris(azanediyl))tribenzoic acid to form a metal-organic framework material, and 10 parts by weight of agarose. The specific preparation method is as follows:

[0039] (1) Preparation of the metal-organic framework material: Dissolve 29.6 mg of zinc nitrate and 18.6 mg of 4,4',4”-(benzene-1,3,5-triyltris(azanediyl)) in a mixed solvent of 3 mL of DMF and 3 mL of H2O, and then add 120 μL of nitric acid

[0040] The solution was encapsulated in a 20 mL glass bottle and reacted in an oven at 130 °C for 72 h. After cooling to room temperature, it was washed three times with DMF to obtain a metal-organic framework material for detecting tetracycline antibiotics.

[0041] (2) Preparation of the metal-organic framework material and agarose hydrogel mixture: 200 mg of agarose was mixed with 3 mL of H2O in a 20 mL glass bottle, and then heated in an oven at 60 °C for 20 min. After all the agarose was dissolved, the hydrogel was obtained for standby. 100 mg of the metal-organic framework material for detecting tetracycline antibiotics was mixed with 3 mL of the hydrogel in a 20 mL glass bottle, and then stirred at 60 °C for 5 h to obtain the mixture of the metal-organic framework material and the hydrogel.

[0042] (3) Preparation of the thin film: 500 μL of the mixture of the metal-organic framework material and the hydrogel was taken on a glass slide, and then a BGD 209 / 2 type film doctor was used to scrape and coat on the glass slide to form a uniform film on the surface of the glass slide. After that, it was rinsed with deionized water to obtain a thin film for portable fluorescence detection and visual detection of tetracycline antibiotics in water, and its thickness was 150 μm.

[0043] (4) Under the excitation of ultraviolet light with a wavelength of 365 nm from a handheld ultraviolet lamp, the thin film showed the fluorescence of the metal-organic framework material. After the thin film was soaked in water containing tetracycline antibiotics, the fluorescence intensity of the thin film showed a decreasing trend with the increase of the concentration of tetracycline antibiotics. Due to the large overlap between the ultraviolet absorption spectrum of tetracycline antibiotics and the emission spectrum of 4,4',4''-(benzene-1,3,5-tris(azanyldiyl))tribenzoic acid in the metal-organic framework material, there was a fluorescence resonance energy transfer phenomenon between the emission light of tetracycline antibiotics and the ligand, resulting in the decrease of the fluorescence intensity of the thin film. Therefore, after being soaked in water containing tetracycline, the fluorescence intensity of the thin film decreased significantly with the increase of tetracycline antibiotics, indicating that this thin film had a good detection effect on tetracycline antibiotics in water. In addition, the detection response time of this thin film to tetracycline antibiotics in water was prolonged, which took 10 min. The reason for the longer analysis and detection time might be that the increase in the agarose content led to fewer voids in the hydrogel skeleton, resulting in a slower diffusion and penetration rate of tetracycline antibiotic molecules inside the thin film during the soaking process, and thus a slower response rate was caused.

[0044] (5) Visual detection calculation principle: Gray = (R×30 + G×59 + B×11) / 100. Use a mobile phone to take pictures of the hydrogel film after soaking in aqueous solutions containing different concentrations of tetracycline antibiotics. Use Photoshop to collect the color information of the photos, calculate the change in the gray value of the hydrogel film before and after soaking through the formula, and construct a standard curve of film gray value change / film initial gray value - tetracycline antibiotic concentration.

[0045] (6) According to the constructed standard curve of film gray value change / film initial gray value - tetracycline antibiotic concentration, during actual detection, a mobile phone can be directly used to take fluorescence photos of the film of the present invention before and after immersion in the water sample containing tetracycline antibiotics. The gray value can be directly extracted in the corresponding processing software, and the obtained film gray value change / film initial gray value is compared with the pre-obtained standard curve to determine the concentration of tetracycline antibiotics. This method simplifies the detection process while overcoming the limitations caused by the need for specific instruments in traditional detection methods.

[0046] Example 3:

[0047] The film for portable fluorescence detection and visual detection of sulfonamide antibiotics in water in this example is prepared from 300 parts by weight of acetic acid, 4 parts by weight of cadmium with a particle size of 1 μm, a metal-organic framework material formed by coordinating 5'-(4-carboxy-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1':3',1”-terphenyl]-4,4”-dicarboxylic acid, and 8 parts by weight of chitosan. The specific preparation method is as follows: (1) Preparation of the metal-organic framework material: Dissolve 30 mg of cadmium nitrate and 19.54 mg of 5'-(4-carboxy-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1':3',1”-terphenyl]-4,4”-dicarboxylic acid in a mixed solvent of 5 mL of DMA and 1 mL of H2O, and then add 400 μL of trifluoroacetic acid. Seal the solution in a 20 mL glass bottle and place it in an oven at 120 °C for reaction for 48 h. Cool to room temperature and wash three times with DMA to obtain the metal-organic framework material for detecting sulfonamide antibiotics.

[0048] (2) Preparation of the metal-organic framework material and chitosan hydrogel mixture: Mix 100 mg of chitosan and 3 mL of acetic acid solution in a 20 mL glass bottle, and then heat in an oven at 60 °C for 40 min. After the chitosan is completely dissolved, a yellow transparent hydrogel is obtained for standby. Mix 50 mg of the metal-organic framework material for detecting sulfonamide antibiotics and 3 mL of the hydrogel in a 20 mL glass bottle, and then stir at 60 °C for 5 h to obtain a mixture of the metal-organic framework material and the hydrogel.

[0049] (3) Preparation of the thin film: Take 500 μL of the mixture of metal-organic framework material and hydrogel on a glass slide, and then use a BGD 209 / 4 type film doctor to scrape and coat on the glass slide to form a uniform film of the mixture on the surface of the glass slide. After that, rinse with deionized water to obtain a thin film for portable fluorescence detection and visualization detection of sulfonamide antibiotics in water, with a thickness of 100 μm.

[0050] (4) Under the excitation of ultraviolet light with a wavelength of 365 nm from a handheld ultraviolet lamp, the thin film shows the fluorescence of the metal-organic framework material. Since there is a large overlap between the ultraviolet absorption spectrum of sulfonamide antibiotics and the excitation spectrum of 5'-(4-carboxy-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1':3',1”-terphenyl]-4,4”-dicarboxylic acid in the metal-organic framework material, sulfonamide antibiotics and the ligand have a competitive absorption relationship for the excitation light, resulting in a decrease in the fluorescence intensity of the thin film. Therefore, after soaking in water containing sulfonamide antibiotics, the fluorescence intensity of the thin film decreases significantly with the increase of sulfonamide antibiotics, indicating that this thin film has a good detection effect on sulfonamide antibiotics in water.

[0051] (5) Visual detection calculation principle: Gray = (R + G + B) / 3. Use a mobile phone to take pictures of the hydrogel thin film soaked in aqueous solutions containing different concentrations of sulfonamide antibiotics, collect the color information of the photos using Photoshop, calculate the change amount of the gray value of the hydrogel thin film before and after soaking through the formula, and construct a standard curve of the change value of the thin film gray value / the initial gray value of the thin film - sulfonamide antibiotic concentration.

[0052] (6) According to the constructed standard curve of the change value of the thin film gray value / the initial gray value of the thin film - sulfonamide antibiotic concentration, during actual detection, a mobile phone can be directly used to take fluorescence photos of the thin film of the present invention before and after immersion in the water sample to be detected containing sulfonamide antibiotics, directly extract the gray value in the corresponding processing software, and compare the obtained change value of the thin film gray value /

[0053] the initial gray value of the thin film with the pre-obtained standard curve to determine the concentration of sulfonamide antibiotics.

[0054] This method simplifies the detection process and overcomes the limitations caused by the need for specific instruments in traditional detection methods.

[0055] Example 4:

[0056] The thin film for portable fluorescence detection and visualization detection of quinolone antibiotics in water in this embodiment is prepared from 300 parts by weight of H2O, 5 parts by weight of dysprosium with a particle size of 5 μm, a metal-organic framework material formed by coordinating with 4,4',4"-(benzene-1,3,5-tris(ethene-2,1-diyl)-tribenzoic acid), 5 parts by weight of silk fibroin fiber, and 4 parts by weight of a poly(n-isopropylacrylamide) mixture. The specific preparation method is as follows:

[0057] (1) Preparation of the metal-organic framework material: Dissolve 44.8 mg of dysprosium nitrate and 74.6 mg of 4,4',4"-(benzene-1,3,5-tris(ethene-2,1-diyl)-tribenzoic acid) in a mixed solvent of 2 mL of DMF and 5 mL of H2O, and then add 600 μL of acetic acid. Seal the solution in a 20 mL glass bottle and place it in an oven at 130 °C for reaction for 72 h. Cool to room temperature and wash three times with DMF to obtain the metal-organic framework material for detecting quinolone antibiotics.

[0058] (2) Preparation of the metal-organic framework material and silk fibroin / poly(n-isopropylacrylamide) composite hydrogel mixture: Stir 50 mg of silk fibroin fiber, 40 mg of poly(n-isopropylacrylamide), and 3 mL of H2O at room temperature for 30 min to obtain a silk fibroin / poly(n-isopropylacrylamide) composite hydrogel. Mix 50 mg of the metal-organic framework material for detecting quinolone antibiotics with 3 mL of the hydrogel in a 20 mL glass bottle, and then stir at 60 °C for 5 h to obtain a mixture of the metal-organic framework material and the hydrogel.

[0059] (3) Preparation of the thin film: Take 500 μL of the mixture of the metal-organic framework material and the hydrogel on a glass slide, and then use a BGD 209 / 1 type film doctor to perform scraping treatment on the glass slide to make the mixture form a uniform film on the surface of the glass slide. Then rinse with deionized water to obtain a thin film for portable fluorescence detection and visualization detection of quinolone antibiotics in water, and its thickness is 300 μm.

[0060] (4) Under the excitation of ultraviolet light with a wavelength of 365 nm from a handheld ultraviolet lamp, the thin film shows the fluorescence of the metal-organic framework material. Since there is a large overlap between the ultraviolet absorption spectrum of quinolone antibiotics and the excitation spectrum of 4,4',4"-(benzene-1,3,5-tris(ethene-2,1-diyl)-tribenzoic acid) in the metal-organic framework material, there is a competitive absorption relationship between quinolone antibiotics and the ligand for the excitation light, resulting in a decrease in the fluorescence intensity of the thin film. Therefore, after soaking in water containing quinolone antibiotics, the fluorescence intensity of the thin film decreases significantly with the increase of quinolone antibiotics, indicating that this thin film has a good detection effect on quinolone antibiotics in water.

[0061] (5)Visual detection calculation principle: Gray = G. Use a mobile phone to take pictures of the hydrogel film after soaking it in aqueous solutions containing different concentrations of quinolone antibiotics. Use MATLAB to collect the color information of the pictures, calculate the change in the gray value of the hydrogel film before and after soaking through a formula, and construct a standard curve of film gray value change / film initial gray value - quinolone antibiotic concentration.

[0062] (6)According to the constructed standard curve of film gray value change / film initial gray value - quinolone antibiotic concentration, during actual detection, a mobile phone can be directly used to take fluorescence pictures of the film of the present invention before and after immersing it in the water sample to be detected containing quinolone antibiotics. The gray value can be directly extracted in the corresponding processing software, and the obtained film gray value change / film initial gray value is compared with the pre-obtained standard curve to determine the concentration of quinolone antibiotics. This method simplifies the detection process and overcomes the limitations caused by the need for specific instruments in traditional detection methods.

Claims

1. A hydrogel film for visual detection of antibiotics in water, characterized in that: The method comprises mixing a thickener and a solvent, adding a metal-organic framework material, stirring evenly, and then applying a scraper coating on a substrate to form a film. The hydrogel film is then removed to obtain the film. When used for visual detection of antibiotics in water, the hydrogel film is directly immersed in the water to be tested, and photos of the hydrogel film before and after immersion are taken. The color information is collected to obtain the grayscale, and the concentration of a specific type of antibiotic in the water is determined based on the grayscale change. The metal ions in the metal-organic framework material are zinc, europium, terbium, cadmium or dysprosium, and the organic ligands are 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine, 4,4',4"-(benzene-1,3,5-triyltris(azadiyl))tribenzoic acid, 5'-(4-carboxy-3-hydroxyphenyl)-3,3"-dihydroxy-[1,1':3',1"-terphenyl]-4,4"-dicarboxylic acid or 4,4',4"-(benzene-1,3,5-tris(ethylene-2,1-diyl)-tribenzoic acid.

2. The hydrogel film for visual detection of antibiotics in water according to claim 1, characterized in that: The metal-organic framework material and the thickener are used in a ratio of 3 to 6 parts by weight and 5 to 10 parts by weight.

3. The hydrogel film for visual detection of antibiotics in water according to claim 1, characterized in that: The particle size of the metal-organic framework material is 1 to 15 μm.

4. The hydrogel film for visual detection of antibiotics in water according to claim 1, characterized in that The thickener is agarose, sodium alginate, chitosan or a silk fibroin fiber / poly n-isopropylacrylamide mixture.

5. The hydrogel film for visual detection of antibiotics in water according to claim 1, characterized in that: The software for collecting photo color information is MATLAB or Photoshop, and the corresponding grayscale information is obtained by any one of Gray = R×0.3+G×0.59+B×0.11, Gray = (R×30+G×59+B×11) / 100, Gray = (R+G+B) / 3 or Gray = G.

6. The hydrogel film for visual detection of antibiotics in water according to claim 1, characterized in that The metal-organic framework material is prepared by adding metal nitrate and organic ligand into deionized water and an organic solvent to obtain a mixed solution, then adding a certain amount of acid, reacting the obtained solution at 80-130°C for 24-72 hours, centrifuging, and washing. The organic solvent is either N,N-dimethylformamide or N,N-dimethylacetamide. The acid is nitric acid, trifluoroacetic acid, or acetic acid, and the volume ratio of the acid to the mixed solution is 0.01-0.5:

1.

7. The hydrogel film for visual detection of antibiotics in water according to claim 1, characterized in that: The thickener is mixed with a solvent, the solvent is H2O or acetic acid, and the weight ratio of the thickener to the solvent is 0.01-0.1:

1.

8. The hydrogel film for visual detection of antibiotics in water according to claim 1, characterized in that: The thickness of the prepared hydrogel film is 100 to 300 μm.

9. The hydrogel film for visual detection of antibiotics in water according to claim 1, characterized in that: The antibiotics are nitroimidazoles, tetracyclines, sulfonamides and quinolones.

Images