Fluorescence detection method for detecting histamine, hydrogel as well as preparation method and application of hydrogel
By using a fluorescent sensor composed of copper nanoclusters and carbon dots, the problems of complexity and time consumption in existing histamine detection methods have been solved, enabling rapid and sensitive histamine detection, especially for in-situ visual detection of food samples.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANDONG ACADEMY OF AGRICULTURAL SCIENCES
- Filing Date
- 2026-02-03
- Publication Date
- 2026-05-12
AI Technical Summary
Existing histamine detection methods suffer from problems such as complex equipment, long processing time, high cost, photobleaching, and complex preparation processes, which hinder their practical application in food testing.
A fluorescent sensor composed of copper nanoclusters and carbon dots was developed. Histamine was detected by mixing copper nanocluster solution, carbon dot solution and histamine solution and using fluorescence spectroscopy. This process enabled the rapid and sensitive detection of histamine.
It enables rapid, simple, sensitive and specific histamine detection with a linear range of 40-120 μM and a detection limit of 0.37 μM, and can detect histamine in food samples in situ with visualization.
Smart Images
Figure CN122016746A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of bioamine detection technology, specifically relating to a fluorescence detection method for histamine, a hydrogel and its preparation method and application. Background Technology
[0002] Food safety is a critical global issue. During processing, storage, and transportation, aquatic products can be contaminated by internal and external microorganisms, leading to spoilage and the release of biogenic amines. Histamine is one of the most common biogenic amines, produced from histidine through a decarboxylation reaction under the action of endogenous decarboxylases. Ingesting food containing excessive histamine is associated with food poisoning, causing adverse reactions such as headaches, skin problems, arterial dilation, and low blood pressure, and can even pose a threat to human life. The histamine content in food reflects the metabolic activity of microorganisms and can serve as a key indicator for assessing food quality and safety. Therefore, developing simple and efficient histamine detection strategies is crucial.
[0003] Currently, various analytical methods have been developed for histamine detection, including gas chromatography, mass spectrometry, high-performance liquid chromatography, colorimetry, electrochemical methods, and immunoassays. However, some of these methods, such as chromatography, often require complex instruments and time-consuming sample preparation processes. Fluorescent sensors are favored due to their high sensitivity, low cost, rapid response, and ease of operation. In recent years, many metal-based fluorescent nanomaterials, such as semiconductor quantum dots and metal nanoclusters, have been used as specific units in various fluorescent sensors. However, these materials often encounter challenges, including poor performance in solid-state luminescence applications, photobleaching, the need for toxic precursors, complex preparation processes, and high costs, thus hindering their practical application in detection. Therefore, it is essential to develop simple and sensitive rapid fluorescence and visualization detection methods. Summary of the Invention
[0004] To address the shortcomings of existing technologies, this invention provides a fluorescence detection method for histamine, a hydrogel and its preparation method and application.
[0005] The technical solution of the present invention is as follows: A fluorescence detection method for histamine includes the following steps: Copper nanocluster solutions, carbon dot solutions, and histamine solutions of different concentrations were mixed and brought to a final volume. After the reactions were allowed to stand, mixed solutions of each system were obtained. The fluorescence emission spectra of each system at an excitation wavelength of 365 nm were measured, and the ratio F of the fluorescence intensity at emission wavelengths of 437 nm and 605 nm was used as the analytical term. 437 / F 605A standard curve is constructed with the histamine concentration in each system as the x-axis and the histamine concentration in each system as the y-axis. This curve is used to detect the histamine concentration in the sample to be tested.
[0006] According to a preferred embodiment of the present invention, in the fluorescence detection method, deionized water is used to bring the volume to the same level, and the mixture is allowed to stand at room temperature for more than 90 minutes to obtain a mixed solution of each system. The solvent for the copper nanocluster solution is ethanol; The final concentration of copper nanoclusters added to each system was 180-200 μg / mL; When preparing the standard curve, the final concentration of histamine is 40-120 μM; The volume of carbon dot solution added to each system is the same; The ratio of the volume of carbon dot solution added to the volume of the final volume in each system is 1:(15-20). The concentration of histamine in the test sample was determined using the standard curve method. Specifically, the copper nanocluster solution, carbon dot solution, and test sample solution were mixed using the same method as for preparing the standard curve. The mixture was then diluted to the same volume with deionized water. After the reaction was allowed to stand, a mixed solution of each system was obtained. The fluorescence emission spectra at the excitation wavelength of 365 nm were detected and recorded. The ratio F of the fluorescence intensity at the emission wavelengths of 437 nm and 605 nm was used as the analytical term. 437 / F 605 The histamine content in the sample was calculated using the prepared standard curve.
[0007] According to a preferred embodiment of the present invention, the fluorescence detection method includes the following steps: 100 μL of a 3 mg / mL copper nanocluster solution, 100 μL of a carbon dot solution, and histamine solutions of different concentrations were mixed and diluted to 1.5 mL with deionized water. After standing for 90 min, the mixtures were obtained. The fluorescence emission spectra of each system at an excitation wavelength of 365 nm were measured, and the ratio F of the fluorescence intensity at emission wavelengths of 437 nm and 605 nm was used as the analytical term. 437 / F 605 A standard curve is constructed with the histamine concentration in each system as the x-axis and the histamine concentration in each system as the y-axis. This curve is used to detect the histamine concentration in the sample to be tested.
[0008] According to a preferred embodiment of the present invention, the linear range of the detection method is 40-120 μM, and the detection limit is 0.37 μM.
[0009] A hydrogel comprising: copper nanoclusters, carbon dot solution and polyvinyl alcohol.
[0010] The preparation method of the above-mentioned hydrogel includes the following steps: A mixture of copper nanoclusters, carbon dot solution, and polyvinyl alcohol solution was prepared by repeated freeze-thaw cycles to obtain a hydrogel.
[0011] According to a preferred embodiment of the present invention, the method for preparing the hydrogel includes the following steps: Copper nanoclusters, carbon dot solution, and 10% polyvinyl alcohol solution were mixed at a mass-volume ratio of (3-4):1:(9-10) mg / mL / mL for 30-40 minutes at 85-90°C to obtain a homogeneous mixture. The mixture was then frozen at -18 to -20°C and thawed at room temperature. This freeze-thaw process was repeated more than three times to obtain a hydrogel. Alternatively, the hydrogel can be molded into different shapes for use.
[0012] The above-described method for detecting histamine, the above-described hydrogel, or the hydrogel prepared by the above method, and its application in any of the following: ① Detect histamine in the sample; ② Evaluate the freshness of the sample.
[0013] According to a preferred embodiment of the present invention, the sample is an aquatic product.
[0014] A method for detecting histamine in a sample using hydrogels includes the following steps: The hydrogel described above or prepared by the above method is placed in contact with the sample to be tested or immersed in the sample to be tested. The hydrogel is then irradiated with ultraviolet light, and the change in histamine in the sample is determined based on the color change.
[0015] According to a preferred embodiment of the present invention, the wavelength of the ultraviolet light irradiation is 365 nm. In the method described, as the histamine content in the sample increases, the hydrogel color gradually changes from yellow to orange-red.
[0016] In the above-mentioned fluorescence detection method for histamine, and the preparation method of hydrogel or hydrogel, The preparation method of copper nanoclusters includes the following steps: Copper nitrate, 3,5-bis(trifluoromethyl)benzylthiophenol and dichloromethane were mixed at a mass-volume ratio of (0.36-0.50):1:(120-140) g / mL / mL, stirred at room temperature for more than 8 h, the precipitate was collected by centrifugation, washed with ethanol more than 3 times, and dried below 100℃ to obtain copper nanoclusters. The preparation method of carbon dot solution includes the following steps: Glutathione, sodium citrate dihydrate, and deionized water were mixed and dissolved in a mass-volume ratio of (0.10-0.12):(1.00-1.03):(27-30) g / g / mL. The mixture was reacted at 180-200°C for 4-5 h, cooled to room temperature, and the product was collected. The product was then purified by dialysis in deionized water with a molecular weight cutoff of 500 Da for more than 24 h to obtain a carbon dot solution.
[0017] The beneficial effects of the present invention include at least the following: 1. This invention is the first to use 3,5-bis(trifluoromethyl)thiophenol as a ligand to prepare and synthesize a novel fluorescent copper nanocluster. It was found that by using copper nanoclusters, carbon dots and histamine to form a reaction system, histamine can be detected by fluorescence spectroscopy, and the detection of histamine is highly selective and specific.
[0018] 2. This invention is the first to synthesize a copper nanocluster / carbon dot-polyvinyl alcohol hydrogel sensor, which has specificity for histamine detection and can realize in-situ visual detection of food samples.
[0019] 3. The fluorescence detection method for histamine provided by this invention is rapid and simple to operate, highly sensitive, specific, has a low detection limit, and good repeatability; the linear range of the fluorescence method of this invention is 40-120 μM, and the detection limit is 0.37 μM (S / N = 3). Attached Figure Description
[0020] Figure 1 Electron microscopy characterization images of copper nanoclusters, carbon dots, and hydrogel sensors; In the figure: A is a transmission electron microscope image of copper nanoclusters, with a scale bar of 200 nm; B is a transmission electron microscope image of carbon dots, with a scale bar of 10 nm; C is a cryo-scanning electron microscope image of hydrogel, with a scale bar of 1 μm.
[0021] Figure 2 Spectral diagrams showing the selection of excitation and emission wavelengths for detection conditions; In the figure: A shows the excitation and emission spectra of copper nanoclusters; B shows the emission spectra of copper nanoclusters at different excitation wavelengths. C shows the excitation and emission spectra of carbon dots; D shows the emission spectra of carbon dots at different excitation wavelengths.
[0022] Figure 3 This is a graph showing the effect of different conditions on histamine detection. In the figure: A shows the effect of different copper nanocluster concentrations on histamine detection; B shows the effect of different reaction times on histamine detection.
[0023] Figure 4 Fluorescence spectra for detecting different histamine concentrations.
[0024] Figure 5 This is a standard curve showing the fluorescence intensity versus histamine concentration.
[0025] Figure 6 The diagram shows the selective detection results of the detection method provided by this invention.
[0026] Figure 7 Images of hydrogels and samples of shrimp stored at -20°C, 4°C, 25°C, and 30°C for different times under UV irradiation. Detailed Implementation
[0027] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.
[0028] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0029] All chemical reagents were of analytical grade.
[0030] Experimental Example 1 Preparation of materials and morphology characterization Preparation of copper nanoclusters: 0.0938 g of copper nitrate and 250 μL of 3,5-bis(trifluoromethyl)benzylthiophenol were mixed in 35 mL of dichloromethane and stirred at room temperature for 8 h. After centrifugation at 13000 rpm for 10 min, the yellow precipitate was collected, washed three times with ethanol, and dried at 50 °C to obtain copper nanoclusters. Ethanol was used as the solvent in the copper nanocluster solutions described below.
[0031] Preparation of carbon dot solution: 0.12 g glutathione and 1.03 g sodium citrate dihydrate were added to 27 mL of deionized water and sonicated until completely dissolved. The mixture was then transferred to an autoclave and reacted at 200°C for 4 h. After cooling to room temperature, the product was collected. The product was purified in deionized water using a dialysis bag (molecular weight cutoff: 500 Da) for 24 h. The product in the dialysis bag was the carbon dot solution.
[0032] Preparation of the hydrogel: 3 g of polyvinyl alcohol (degree of hydrolysis 98.0-99.0 mol%, viscosity 54.0-66.0 mPa.s, CAS No.: 9002-89-5) was dissolved in 27 mL of deionized water (90°C) and stirred until homogeneous to obtain a polyvinyl alcohol solution. At 90°C, 10 mg of copper nanoclusters and 3 mL of carbon dot solution were mixed with the above polyvinyl alcohol solution and stirred for 30 min to obtain a homogeneous mixture. The mixture was poured into a 48-well plate. The plate was frozen at -20°C for 20 h and then thawed at room temperature for 4 h. This freeze-thaw process was repeated three times to finally obtain a cylindrical hydrogel with a height of 1.5 cm and a diameter of 1.0 cm, which is the hydrogel sensor.
[0033] The inventors discovered during the preparation of the above-mentioned hydrogel that the hydrogel formed by one or two freeze-thaw cycles was not dense, too soft and easily broken.
[0034] The inventors characterized the prepared copper nanoclusters, carbon dots, and hydrogel using transmission and scanning electron microscopy. The experimental results are shown in [Figure number missing]. Figure 1 .like Figure 1 As shown in Figure A, the copper nanoclusters exhibit a banded structure with a width of approximately 20-30 nm and a length of approximately 200-400 nm. Compared with copper nanoclusters described in the prior art, the copper nanoclusters prepared by this method have better dispersion performance and more uniform morphology. Figure 1 The B in the figure indicates that the carbon dots are spherical and have good monodispersity. The lattice spacing of 0.21 nm corresponds to the (100) crystal plane of graphite, which indicates that there is a graphite-like structure in the carbon dots. Figure 1 The results of the C-test show that the hydrogel prepared in this invention has a distinct porous structure. Compared with previously reported hydrogels, the synthesis process of this hydrogel is more convenient, and the prepared product has a dense texture, making it easy to store and carry, and more conducive to the construction of portable sensing systems.
[0035] Experiment Example 2 Selection of the optimal excitation wavelength for detection conditions The experimental method was as follows: fluorescence spectroscopy was used to record the excitation spectra of copper nanoclusters and carbon dots, and the emission spectra at the optimal excitation wavelength. The experimental results are shown in [Figure number missing]. Figure 2 ,Depend on Figure 2 As shown in section A, the excitation spectrum of copper nanoclusters has a peak at 350 nm, and the emission peak is located at 605 nm; from Figure 2 As shown in section B, the emission spectrum of copper nanoclusters remains almost unchanged under different excitation wavelengths, and the emission peak is relatively complete when excited at 365 nm; from Figure 2As shown in C and D, the maximum excitation peak and corresponding emission peak of the carbon dots are located at 350 nm and 437 nm, respectively. The emission wavelength position of the carbon dots hardly changes under different excitation wavelengths. The inventors discovered that choosing an excitation wavelength of 365 nm as the optimal excitation wavelength for the detection system ensures both the integrity of the emission spectrum of the copper nanoclusters at this wavelength and a certain fluorescence emission intensity, while also ensuring that the carbon dots have good luminescence properties and do not overlap with the emission spectrum of the copper nanoclusters.
[0036] Selection of optimal experimental conditions for histamine detection The experimental method was as follows: the carbon dot concentration and reaction time were fixed, while the copper nanocluster concentration was changed; the carbon dot concentration and copper nanocluster concentration were fixed, while the reaction time was changed. The copper nanocluster solution, carbon dot solution and histamine solution were mixed and diluted to 1.5 mL with deionized water. After the reaction was allowed to stand, the mixed solutions of each system were obtained, and the fluorescence emission spectra at the excitation wavelength of 365 nm were detected and recorded.
[0037] The experimental results are shown in Figure 3 , Figure 3 Figure A shows the detection results when different concentrations of copper nanocluster solutions (50, 100, 150, 200, 250, 300, 400, 500 μg / mL) were added to the above system (after adjusting the volume to 1.5 mL). Figure 3 Figure B shows the effect of different reaction times on histamine detection; Figure 3 As shown in A and B, the curve gradually stabilizes with the addition of copper nanoclusters or the extension of reaction time. The detection results for different concentrations and reaction times are as follows: the optimal experimental conditions for histamine detection are a copper nanocluster concentration of 200 μg / mL and a reaction time of 90 min at room temperature.
[0038] Experimental Example 3 Linear range and detection limit of ratio fluorescence detection The experimental conditions were as follows: 100 μL of a 3 mg / mL copper nanocluster solution, 100 μL of a carbon dot solution, and histamine solutions of different concentrations were mixed, and each solution was brought to a final volume of 1.5 mL with deionized water. After the reaction was allowed to stand for 90 min, the mixed solutions of each system were obtained, and the fluorescence emission spectra of each system at an excitation wavelength of 365 nm were detected. Figure 4 ),Depend on Figure 4 It can be seen that the emission spectrum of carbon dots (437 nm) remains almost unchanged, while the fluorescence intensity of the emission spectrum of copper nanoclusters (605 nm) gradually decreases with the increase of histamine content. Using the fluorescence emission of carbon dots as a reference, histamine fluorescence detection can be achieved. The ratio F of the fluorescence intensity at the emission wavelengths of 437 nm and 605 nm at an excitation wavelength of 365 nm is... 437 / F 605A standard curve was constructed with the histamine concentrations (40, 60, 80, 100, and 120 μM) in the reaction system as the ordinate and the concentrations of histamine in the reaction system as the abscissa. Figure 5 (This is used to detect the concentration of histamine in the sample to be tested).
[0039] The experimental results are shown in Figure 4 , Figure 5 As can be seen, the linear range of this method is 40-120 μM, and the detection limit is 0.37 μM (S / N=3).
[0040] Experiment Example 4 Selectivity analysis of detection methods The experimental conditions were as follows: A copper nanocluster solution (100 μL, 3 mg / mL), a carbon dot solution (100 μL), and a histamine solution (or a blank water sample, or interfering substances of the same concentration, including tyramine, tryptamine, 2-phenylethylamine, putrescine, and spermidine) were mixed. The mixture was brought to a final volume of 1.5 mL with deionized water, allowed to stand at room temperature for 90 min, and then the fluorescence emission spectrum at an excitation wavelength of 365 nm was measured. The ratio F of the fluorescence intensity at emission wavelengths of 437 nm and 605 nm was used as the analytical term. 437 / F 605 A bar chart is plotted with histamine and other interfering substances at different concentrations (final concentrations of 40, 60, 80, 100, and 120 μM) on the ordinate to determine the specificity of the method for histamine response.
[0041] See results Figure 6 As can be seen from the figure, this method has strong selectivity and good specificity for the detection of histamine.
[0042] Example 1 Spiking test of histamine in shrimp meat Copper nanoclusters and carbon dot solutions were prepared using Experiment Example 1.
[0043] Construction of fluorescence analysis method and histamine spiked detection: 0.5 g of shrimp meat sample was mixed with 10 mL of 5% trichloroacetic acid, sonicated for 30 min, centrifuged (8000 rpm, 10 min), and the supernatant was collected. Hexane was added to remove fat, and the aqueous phase at the bottom was collected after phase separation. 100 μL of 3 mg / mL copper nanocluster solution, 100 μL of carbon dot solution, and the sample solution (with histamine solution added to final concentrations of 40, 50, and 100 μM, respectively) were mixed and diluted to 1.5 mL with deionized water. After reacting at room temperature (20℃-25℃) and standing for 90 min, the fluorescence emission spectrum at an excitation wavelength of 365 nm was detected, and the ratio F of the fluorescence intensity at emission wavelengths of 437 nm and 605 nm was obtained. 437 / F 605A standard curve was prepared using histamine solution, and the results of the spiked experiments were calculated using the prepared standard curve (see Table 1). The recoveries of the shrimp meat solution spiked with histamine ranged from 99.3% to 109.8%, with relative standard deviations (RSDs) of 0.2% to 0.8%, indicating that the method has good practicality and repeatability, and has the potential to detect histamine in food samples.
[0044] Table 1. Analysis results of histamine in shrimp meat (n=3)
[0045] Example 2 Rapid fluorescence-guided detection of histamine in fresh shrimp Preparation of hydrogel sensor and visualization detection of histamine in fresh shrimp samples: The hydrogel sensor prepared in Example 1 and a single whole river shrimp were placed in a sealed glass petri dish and incubated at -20°C, 4°C, 25°C, and 30°C, respectively. After different reaction times, the detection system was photographed under 365 nm ultraviolet light (UV lamp) using a smartphone (or camera). Obvious changes in fluorescence color were related to the histamine content and degree of deterioration. Experimental results are shown below. Figure 7 After 8 hours at 30°C, histamine levels increased, and the fluorescence image of the hydrogel sensor began to change from yellow to orange-red. At 25°C and 4°C, spoilage took 24 hours and 48 hours, respectively. However, when shrimp were stored at a lower temperature of -20°C, the fluorescence image showed almost no change within 48 hours, indicating that they could be preserved for a longer period at -20°C. These results demonstrate that this copper nanocluster / carbon dot-polyvinyl alcohol hydrogel sensor can enable the visual monitoring of seafood spoilage processes.
[0046] This invention is the first to synthesize a novel fluorescent copper nanocluster using 3,5-bis(trifluoromethyl)thiophenol as a ligand. The reaction system, consisting of copper nanoclusters, carbon dots, and histamine, enables the detection of histamine using fluorescence spectroscopy, exhibiting high selectivity, specificity, sensitivity, and low detection limit. Furthermore, this invention is the first to synthesize a copper nanocluster / carbon dot-polyvinyl alcohol hydrogel sensor, which is specific for histamine detection and enables in-situ visual detection of food samples.
Claims
1. A fluorescence detection method for histamine, characterized in that, Includes the following steps: Copper nanocluster solutions, carbon dot solutions, and histamine solutions of different concentrations were mixed and brought to a final volume. After the reactions were allowed to stand, mixed solutions of each system were obtained. The fluorescence emission spectra of each system at an excitation wavelength of 365 nm were measured, and the ratio F of the fluorescence intensity at emission wavelengths of 437 nm and 605 nm was used as the analytical term. 437 / F 605 A standard curve is constructed with the histamine concentration in each system as the x-axis and the histamine concentration in each system as the y-axis. This curve is used to detect the histamine concentration in the sample to be tested.
2. The detection method as described in claim 1, characterized in that, In the fluorescence detection method described above, deionized water is used to bring the volume to the same level, and the mixture is allowed to stand at room temperature for more than 90 minutes to obtain a mixed solution of each system. The solvent for the copper nanocluster solution is ethanol; The final concentration of copper nanoclusters added to each system was 180-200 μg / mL; When preparing the standard curve, the final concentration of histamine is 40-120 μM; The volume of carbon dot solution added to each system is the same; The ratio of the volume of carbon dot solution added to the volume of the final volume in each system is 1:(15-20). The concentration of histamine in the test sample was determined using the standard curve method. Specifically, the copper nanocluster solution, carbon dot solution, and test sample solution were mixed using the same method as for preparing the standard curve. The mixture was then diluted to the same volume with deionized water. After the reaction was allowed to stand, the resulting mixed solutions were obtained. The fluorescence emission spectra at an excitation wavelength of 365 nm were detected and recorded. The ratio F of the fluorescence intensity at emission wavelengths of 437 nm and 605 nm was used as the analytical term. 437 / F 605 The histamine content in the sample was calculated using the prepared standard curve.
3. The detection method as described in claim 1, characterized in that, The fluorescence detection method includes the following steps: 100 μL of a 3 mg / mL copper nanocluster solution, 100 μL of a carbon dot solution, and histamine solutions of different concentrations were mixed and diluted to 1.5 mL with deionized water. After standing for 90 min, the mixtures were obtained. The fluorescence emission spectra of each system were detected at an excitation wavelength of 365 nm. The ratio F of the fluorescence intensity at emission wavelengths of 437 nm and 605 nm was used as the analytical term. 437 / F 605 A standard curve is constructed with the histamine concentration in each system as the x-axis and the histamine concentration in each system as the y-axis. This curve is used to detect the histamine concentration in the sample to be tested.
4. The detection method as described in claim 1, characterized in that, The linear range of the detection method is 40-120 μM, and the detection limit is 0.37 μM.
5. A hydrogel, characterized in that, The components include: copper nanoclusters, carbon dot solution, and polyvinyl alcohol.
6. The method for preparing the hydrogel according to claim 5, characterized in that, Includes the following steps: A mixture of copper nanoclusters, carbon dot solution, and polyvinyl alcohol solution was prepared by repeated freeze-thaw cycles to obtain a hydrogel.
7. The preparation method according to claim 6, characterized in that, Includes the following steps: Copper nanoclusters, carbon dot solution, and 10% polyvinyl alcohol solution were mixed at a mass-volume ratio of (3-4):1:(9-10) mg / mL / mL for 30-40 minutes at 85-90°C to obtain a homogeneous mixture. The mixture was then frozen at -18 to -20°C and thawed at room temperature. This freeze-thaw process was repeated more than three times to obtain a hydrogel. Alternatively, the hydrogel can be molded into different shapes for use.
8. The use of the detection method according to any one of claims 1-4, the hydrogel according to claim 5, or the hydrogel prepared by the method according to any one of claims 6-7, in any of the following: ① Detect histamine in the sample; ② Evaluate the freshness of the sample.
9. The application as described in claim 8, characterized in that, The sample was an aquatic product.
10. A method for detecting histamine in a sample using a hydrogel, characterized in that, Includes the following steps: The hydrogel of claim 5 or the hydrogel prepared by any one of claims 6-7 is placed in contact with the sample to be tested or the hydrogel is immersed in the sample to be tested. The hydrogel is irradiated with ultraviolet light, and the change of histamine in the sample to be tested is determined based on the color change.
11. The method as described in claim 10, characterized in that, The wavelength of the ultraviolet light irradiation is 365 nm; In the method described, as the histamine content in the sample increases, the hydrogel color gradually changes from yellow to orange-red.
12. The detection method according to any one of claims 1-4, the hydrogel according to claim 5, or the preparation method according to any one of claims 6-7, characterized in that, The preparation method of copper nanoclusters includes the following steps: Copper nitrate, 3,5-bis(trifluoromethyl)benzylthiophenol and dichloromethane were mixed at a mass-volume ratio of (0.36-0.50):1:(120-140) g / mL / mL, stirred at room temperature for more than 8 h, the precipitate was collected by centrifugation, washed with ethanol more than 3 times, and dried below 100℃ to obtain copper nanoclusters. The preparation method of carbon dot solution includes the following steps: Glutathione, sodium citrate dihydrate, and deionized water were mixed and dissolved in a mass-volume ratio of (0.10-0.12):(1.00-1.03):(27-30) g / g / mL. The mixture was reacted at 180-200°C for 4-5 h, cooled to room temperature, and the product was collected. The product was then purified by dialysis in deionized water with a molecular weight cutoff of 500 Da for more than 24 h to obtain a carbon dot solution.