A ratio fluorescent paper-based sensor for visual detection of spermine in meat products and preparation and use thereof

Abstract

The application relates to a preparation method and application of a visual detection spermine ratio fluorescent paper-based sensor in meat food, and belongs to the technical field of food safety rapid detection. The main purpose of the application is how to quickly obtain information about the corruption degree of meat food, and a new method for quickly detecting the concentration of a biological amine representative spermine in meat products is provided for market supervision departments, manufacturers and consumers. The technical points of the application are as follows: based on a "double response-switch" ratio fluorescent principle, a filter paper chip is used as a carrier, and a G-BCQDs / Zr-MOFs ratio fluorescent probe is used to develop a ratio fluorescent paper-based sensor for quickly detecting the concentration of a biological amine representative spermine in food, the ratio fluorescent paper-based sensor is combined with a mobile phone APP, and is successfully applied to quantitative detection of spermine in actual food samples, and the problem that the quantitative detection accuracy of the ratio fluorescent paper-based sensor is not high is solved.

Description

Technical Field

[0001] This invention belongs to the field of rapid food safety detection technology, specifically relating to a fluorescent paper-based sensor for visually detecting the ratio of spermine in meat products. Background Technology

[0002] Biogenic amines (BA) are a class of low-molecular-weight organic compounds containing amino groups that possess biological activity. The potential toxicity of biogenic amines and their role in indicating food spoilage have led to increased research into biogenic amine detection methods in food hygiene. Biogenic amines can be classified into three types based on their structure: aliphatic amines, aromatic amines, and heterocyclic amines. Spermine belongs to the aliphatic amine type of biogenic amines and can react with nitrites to produce the carcinogenic nitrosamines.

[0003] The formation of biogenic amines in meat and meat products is related to the microorganisms present. These microorganisms may be naturally occurring in the meat or originate from environmental contamination during processing. High concentrations of biogenic amines in aquatic products are usually due to improper storage. The sale of spoiled meat products by unscrupulous vendors harms public health and has drawn serious attention from market supervision departments. Therefore, rapid detection of biogenic amine concentrations in spoiled meat products is crucial.

[0004] Currently, methods for determining biogenic amines mainly include liquid chromatography, enzyme sensor arrays, high-performance liquid chromatography, gas chromatography, and gas chromatography-mass spectrometry. While these methods can accurately detect the concentration of biogenic amines, they also have drawbacks such as cumbersome sample preparation, poor stability, interference from byproducts, complex instrument operation, long analysis times, and inability to be used outside the laboratory. Therefore, a rapid, visualized, and on-site quantitative method for the determination of biogenic amines in food is needed.

[0005] Because the fluorescence emission peaks in "dual-response-off" ratiometric fluorescent paper-based sensors exhibit consistent direction of change, the standard working curve of the ratiometric fluorescent probe has a small slope, a narrow detection linear range, and unclear visual contrast. Therefore, developing a "dual-response-on" biomass carbon quantum dot ratiometric fluorescent paper-based sensor is essential. Metal-organic frameworks (MOFs) are framework structures with unique porous crystal characteristics, formed through the coordination self-assembly of functional organic ligands and metal ions (or clusters). In recent years, MOFs have attracted widespread attention as novel sensing materials for detecting various volatile organic compounds and gases. Compared with other sensing materials, porous MOFs have advantages such as large specific surface area, high reversibility, large functionalization sites, tunable pore size, and good chemical and thermal stability. Currently, MOFs are widely used as a detection material in the field of food analysis.

[0006] This patent relates to a dual-response-switch type ratiometric fluorescent paper-based sensor based on biomass carbon quantum dots (G-BCQDs) and Zr-MOFs (i.e., G-BCQDs / Zr-MOFs), used to detect the concentration of spermine (SPM), a representative biogenic amine. G-BCQDs and Zr-MOFs were characterized using TEM, SEM, XRD, FL, and XPS. A method for detecting spermine (SPM) concentration was established by combining the ratiometric fluorescent paper-based sensor with RGB recognition via a smartphone, and applied to the detection of spermine (SPM) concentration in actual food products. Summary of the Invention

[0007] Purpose of the invention:

[0008] The main purpose of this invention is to quickly obtain information on the degree of spoilage of meat products. This patent provides a new method for market supervision departments, manufacturers, and consumers to quickly detect the concentration of spermine, a representative biogenic amine in meat products. The main features of this method are: (1) A "dual-response-switch" ratiometric fluorescence paper-based sensor based on p-aminobenzoic acid-modified lignin biomass carbon quantum dots and Zr-MOFs is constructed and used for visual detection of the concentration of spermine, a representative biogenic amine in food. This method has the characteristics of reducing background interference, sensitive visual detection effect, and easy differentiation. (2) Based on the "dual-response-switch" ratiometric fluorescence principle, a ratiometric fluorescence paper-based sensor for quickly detecting the concentration of spermine, a representative biogenic amine in food, is developed and successfully used in conjunction with a mobile APP for quantitative detection of spermine in actual food samples, solving the problem of low accuracy of quantitative detection by ratiometric fluorescence paper-based sensors.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A method for preparing a fluorescent paper-based sensor for visually detecting the ratio of spermine in meat products includes the following steps:

[0011] 1. Preparation of biomass carbon quantum dots

[0012] Weigh 4.00 g of sawdust and measure 60 mL of 2 mol / L sodium hydroxide, then pour them into a 100 mL polytetrafluoroethylene high-pressure reactor. Heat at 180 °C for 3 h. After naturally cooling to room temperature, adjust the pH to 2-7 with 5% hydrochloric acid solution to precipitate lignin. Finally, extract with 10 mL of ethyl acetate and dry in a vacuum drying oven at 60 °C to obtain solid lignin for later use.

[0013] Weigh 0.15 g of lignin powder and 0.3 g of p-aminobenzoic acid, dissolve them in 60 mL of ultrapure water, heat in an oil bath at 90 °C for 2 h, and then filter the solution through filter paper to obtain the filtrate. Pour the filtrate into a 100 mL polytetrafluoroethylene high-pressure reactor and heat at 240 °C for 24 h. After cooling to room temperature, filter the solution through a 0.2 μm organic microporous membrane to obtain a yellow solution, then dialyze it through a 1000 Da dialysis membrane for 1 day. Collect the internal solution, freeze-dry it, and then prepare a 1.00 mg / mL biomass carbon quantum dot (G-BCQDs) solution using ultrapure water and store it in a refrigerator.

[0014] 2. Preparation of Zr-MOFs

[0015] 174.02 mg of ZrCl4 was weighed and dissolved in 15 mL of N,N-dimethylformamide (DMF), and 1 mL of concentrated hydrochloric acid was added until the solution became clear. Then, a certain amount of 2,5-dihydroxyterephthalic acid (146.6 mg) was weighed and added to the above solution. The resulting mixture was transferred to a polytetrafluoroethylene high-pressure reactor and heated at 80 °C for 24 h. After cooling to room temperature, it was centrifuged at 8000 rpm / min for 5 min to obtain a yellow precipitate. The precipitate was washed three times with DMF and anhydrous ethanol, respectively. The yellow precipitate was then dried in a vacuum oven at 50 °C and prepared as a 2.00 mg / mL Zr-MOFs solution for further use.

[0016] Preparation of 3 G-BCQDs / Zr-MOFs ratiometric fluorescent probes

[0017] Mix 1.00 mg / mL G-BCQDs (1.50 mL) and 2.00 mg / mL Zr-MOFs (0.75 mL), dilute with ultrapure water to 3 mL, and shake for 2 h to obtain a ratiometric fluorescent probe (the volume ratio of G-BCQDs to Zr-MOFs is 1:2).

[0018] 4. Fabrication of G-BCQDs / Zr-MOFs ratiometric fluorescent paper-based sensor

[0019] Using 7 cm qualitative filter paper (GB / T1914-2017) as the paper-based chip, the filter paper was cut into 14 mm circular filter paper chips using a tablet press. The 14 mm circular filter paper chips were held with tweezers and immersed in the ratiometric fluorescent probe G-BCQDs / Zr-MOFs solution obtained in step 3 for 5 s. After air drying, the ratiometric fluorescent paper-based sensor was obtained and stored in a refrigerator.

[0020] 5. Construction of the linear equation for the working curve

[0021] Under a 365 nm UV lamp, the fluorescent paper-based sensor gradually changed from green to yellow in spermine SPM solutions of different concentrations. The R′ value in the RGB values ​​corresponds to the SPM concentration (C). SPM It is proportional in the range of 0.0-220.0 μM, and its linear equation is R′=0.3740C. SPM +141.75(R 2 =0.9913); Simultaneously, when the SPM concentration is between 220.00 and 510.0 μM, it also exhibits a linear relationship with R′, with the linear equation being R′=0.0982C. SPM +202.07 (R) 2 =0.9999).

[0022] 6. Analysis of actual samples

[0023] First, the fresh shrimp sample was pretreated by adding 2.00 g of fresh shrimp to 20 mL of acetonitrile and ultrasonically dispersing for 30 min. Then, 1.00 g of activated carbon was added and shaken for 30 min for dispersion and purification. The mixture was centrifuged at 4000 rpm / min and then filtered through a 0.2 μm organic microporous membrane. The solution was then rotary evaporated at 55 ℃ and diluted with ultrapure water to 60 mL to obtain the pretreated sample solution, which was then refrigerated and stored.

[0024] Spiked recovery experiments were conducted on pretreated shrimp samples with SPM concentrations of 100.00, 220.00, and 350.00 mol / L. The concentration of spermine SPM in the pretreated samples was detected using a ratiometric fluorescence paper-based sensor coupled with a mobile app.

[0025] Fresh shrimp and a ratio fluorescence paper-based sensor were placed in a petri dish, sealed with plastic wrap, and placed in a 365 nm dark box UV analyzer at room temperature for different times. The color change of the ratio fluorescence paper-based sensor was observed to determine whether the shrimp had spoiled and produced biogenic amines.

[0026] The above-mentioned design of the spermine detection process is based on the fact that biomass carbon quantum dots play an "off" role in constructing ratiometric fluorescent probes. It is necessary to find a fluorescent material that plays an "on" role to construct a "dual-response-switch" ratiometric fluorescent probe, and spermine has an enhancing effect on the fluorescence emission of MOFs. Attached Figure Description

[0027] Figure 1(A) shows TEM and high-resolution TEM images (inset) of the G-BCQDs of this invention; (See attached image) Figure 1 (B) is a SEM image of the Zr-MOFs of the present invention.

[0028] Figure 2FT-IR plots of G-BCQDs and Zr-MOFs.

[0029] Figure 3 XRD patterns of G-BCQDs and Zr-MOFs.

[0030] Figure 4 The fluorescence color changes of the fluorescent paper-based sensor on day 1 (A), day 2 (B), and day 3 (C) Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] Example 1: Quantitative determination of spermine concentration in shrimp samples

[0033] 1. Preparation of biomass carbon quantum dots

[0034] (1) Pretreatment of sawdust: Weigh 4.00 g of sawdust and measure 60 mL of 2 mol / L sodium hydroxide, pour them into a 100 mL polytetrafluoroethylene high-pressure reactor, and heat at 180 ℃ for 3 h. After naturally cooling to room temperature, adjust the pH to 2 with 5% hydrochloric acid solution to precipitate lignin. Finally, extract with 10 mL of ethyl acetate and dry in a vacuum drying oven at 60 ℃ to obtain solid lignin for later use.

[0035] (2) Preparation of p-aminobenzoic acid modified biomass carbon quantum dots G-BCQDs: Weigh 0.15 g of lignin powder and 0.3 g of p-aminobenzoic acid, dissolve them in 60 mL of ultrapure water, heat in an oil bath at 90 ℃ for 2 h, filter, pour the filtrate into a 100 mL polytetrafluoroethylene high-pressure reactor, and heat at 240 ℃ for 24 h. After cooling to room temperature, filter through a 0.2 μm organic microporous membrane to obtain a yellow solution, dialyze through a 1000 Da dialysis membrane for 1 day, collect the internal solution, freeze-dry it, and prepare a 1.00 mg / mL p-aminobenzoic acid modified biomass carbon quantum dot G-BCQDs solution using ultrapure water, and store it in a refrigerator for later use.

[0036] 2. Preparation of Zirconium-based Organometallic Frameworks (Zr-MOFs)

[0037] 174.02 mg of ZrCl4 was weighed and dissolved in 15 mL of N,N-dimethylformamide (DMF). 1 mL of concentrated hydrochloric acid was added until the solution became clear. Subsequently, 146.6 mg of 2,5-dihydroxyterephthalic acid was weighed and added to the above solution. The resulting mixture was transferred to a polytetrafluoroethylene (PTFE) high-pressure reactor and heated at 80 °C for 24 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm / min for 5 min to obtain a yellow precipitate. The precipitate was washed three times with DMF and anhydrous ethanol, respectively. The yellow precipitate was then dried in a vacuum oven at 50 °C and prepared as a 2.00 mg / mL Zr-MOFs solution for further use.

[0038] Preparation of 3 G-BCQDs / Zr-MOFs ratiometric fluorescent probes

[0039] Mix 1.50 mL of 1.00 mg / mL G-BCQDs and 0.75 mL of 2.00 mg / mL Zr-MOFs, dilute with ultrapure water to 3 mL, and shake for 2 h to obtain a ratiometric fluorescent probe (the volume ratio of G-BCQDs to Zr-MOFs is 1:2).

[0040] 4. Fabrication of G-BCQDs / Zr-MOFs ratiometric fluorescent paper-based sensor

[0041] Using 7 cm qualitative filter paper (GB / T1914-2017) as the paper-based chip, the filter paper was cut into 14 mm circular filter paper chips using a tablet press. The 14 mm circular filter paper chips were held with tweezers and immersed in the G-BCQDs / Zr-MOFs ratiometric fluorescent probe solution obtained in step 3 for 5 seconds. After air drying, the ratiometric fluorescent paper-based sensor was obtained and stored in a refrigerator for later use.

[0042] 5. Construction of the linear equation for the working curve

[0043] Under a 365 nm UV lamp, 200 μL of succinamine SPM solutions of different concentrations were added dropwise to the ratiometric fluorescent paper-based sensor obtained in step 4. After air drying, the fluorescent paper-based sensor gradually changed from green to yellow. Observation was performed under a 365 nm UV lamp, and the RGB values ​​of the fluorescence color on the ratiometric fluorescent paper-based sensor were identified and extracted using a smartphone. The R′ value and SPM concentration (C) within the RGB values ​​were also analyzed. SPM It is proportional in the range of 0.0-220.0 μM, and its linear equation is R′=0.3740C. SPM +141.75(R 2 =0.9913); Simultaneously, when the SPM concentration is between 220.00 and 510.0 μM, it also exhibits a linear relationship with R′, with the linear equation being R′=0.0982C.SPM +202.07 (R) 2 =0.9999).

[0044] 6. Analysis of actual samples

[0045] (1) Shrimp sample pretreatment: 2.00 g of fresh shrimp was added to 20 mL of acetonitrile, ultrasonically dispersed for 30 min, 1.00 g of activated carbon was added, and the mixture was shaken for 30 min for dispersion and purification. The mixture was centrifuged at 4000 rpm / min, filtered through a 0.2 μm organic microporous membrane, rotary evaporated at 55 ℃, and then diluted with ultrapure water to 60 mL to obtain the pretreated sample solution, which was then stored under cold.

[0046] (2) Spiked Recovery Experiment: A spiked recovery experiment was conducted on the pretreated shrimp sample solution. The spiked concentrations of spermine (SPM) were 100.00, 220.00, and 350.00 mol / L. A total volume of 200 μL of spiked spermine (SPM) solution was added dropwise to the ratiometric fluorescent paper-based sensor solution obtained in step 4. After air drying, the RGB values ​​of the SPM were extracted using a 365 nm UV analyzer. These values ​​were then substituted into the linear equation obtained in step 5 to calculate the SPM concentration, as well as the SPM recovery rate and relative standard deviation. The results are shown in Table 1. As shown in Table 1, the SPM recovery rate in the shrimp sample was in the range of 90.97-101.14%, and the relative standard deviation was less than 2.15%. These results indicate that the ratiometric fluorescent paper-based sensor can be applied to the detection of SPM concentration in actual samples.

[0047] Table 1. Visualization of SPM in real samples (n=3) using a ratiometric fluorescent paper-based sensor.

[0048]

[0049] Example 2 Qualitative determination of spermine concentration in shrimp samples

[0050] 1. Preparation of biomass carbon quantum dots

[0051] (1) Pretreatment of sawdust: Weigh 4.00 g of sawdust and measure 60 mL of 2 mol / L sodium hydroxide, pour them into a 100 mL polytetrafluoroethylene high-pressure reactor, and heat at 180 ℃ for 3 h. After naturally cooling to room temperature, adjust the pH to 2 with 5% hydrochloric acid solution to precipitate lignin. Finally, extract with 10 mL of ethyl acetate and dry in a vacuum drying oven at 60 ℃ to obtain solid lignin for later use.

[0052] (2) Preparation of p-aminobenzoic acid modified biomass carbon quantum dots G-BCQDs: 0.15 g of lignin powder and 0.3 g of p-aminobenzoic acid were weighed and dissolved in 60 mL of ultrapure water. The mixture was heated in an oil bath at 90 °C for 2 h, and then filtered through filter paper to obtain the filtrate. The filtrate was poured into a 100 mL polytetrafluoroethylene high-pressure reactor and heated at 240 °C for 24 h. After cooling to room temperature, the solution was filtered through a 0.2 μm organic microporous membrane to obtain a yellow solution. The solution was then dialyzed through a 1000 Da dialysis membrane for 1 day. The internal solution was collected, freeze-dried, and then a 1.00 mg / mL p-aminobenzoic acid modified biomass carbon quantum dot G-BCQDs solution was prepared using ultrapure water and stored in a refrigerator for later use.

[0053] 2. Preparation of Zirconium-based Organometallic Frameworks (Zr-MOFs)

[0054] 174.02 mg of ZrCl4 was weighed and dissolved in 15 mL of N,N-dimethylformamide (DMF). 1 mL of concentrated hydrochloric acid was added until the solution became clear. Subsequently, 146.6 mg of 2,5-dihydroxyterephthalic acid was weighed and added to the above solution. The resulting mixture was transferred to a polytetrafluoroethylene (PTFE) high-pressure reactor and heated at 80 °C for 24 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm / min for 5 min to obtain a yellow precipitate. The precipitate was washed three times with DMF and anhydrous ethanol, respectively. The yellow precipitate was then dried in a vacuum oven at 50 °C and prepared as a 2.00 mg / mL Zr-MOFs solution for further use.

[0055] Preparation of 3 G-BCQDs / Zr-MOFs ratiometric fluorescent probes

[0056] Mix 1.50 mL of 1.00 mg / mL G-BCQDs and 0.75 mL of 2.00 mg / mL Zr-MOFs, dilute with ultrapure water to 3 mL, and shake for 2 h to obtain a ratiometric fluorescent probe (the volume ratio of G-BCQDs to Zr-MOFs is 1:2).

[0057] 4. Fabrication of G-BCQDs / Zr-MOFs ratiometric fluorescent paper-based sensor

[0058] Using 7 cm qualitative filter paper (GB / T1914-2017) as the paper-based chip, the filter paper was cut into 14 mm circular filter paper chips using a tablet press. The 14 mm circular filter paper chips were then held with tweezers and immersed in the G-BCQDs / Zr-MOFs ratiometric fluorescent probe solution obtained in step 3 for 5 seconds, followed by air drying to obtain the ratiometric fluorescent paper-based sensor. This sensor was then stored in a refrigerator for later use.

[0059] 5. Analysis of actual samples

[0060] Fresh shrimp and the ratiometric fluorescence paper-based sensor obtained in step 4 were placed in a petri dish, sealed with plastic wrap, and placed in a 365 nm darkroom UV analyzer at room temperature for different times. The color change of the ratiometric fluorescence paper-based sensor was observed to determine whether the shrimp sample produced spermine and whether it was spoiled. The experimental results are attached. Figure 4 (A), (B), and (C) indicate that the shrimp meat samples spoiled on the second day, indicating the production of spermine, proving that the ratio fluorescence paper-based sensor can be used to monitor the degree of spoilage of shrimp samples.

[0061] Figure 1(A) shows the TEM and high-resolution TEM images (inset) of the G-BCQDs of this invention; Figure 1 (B) is a SEM image of the Zr-MOFs of this invention. As shown in Figure (A) of the TEM image of G-BCQDs, the G-BCQDs are well dispersed, appearing as spherical dots with a lattice spacing of 0.22 nm, corresponding to the (100) crystal plane of graphene, with an average diameter of approximately 7 nm. As shown in Figure (B) of the SEM image of Zr-MOFs, the Zr-MOFs are dispersed crystals with a cubic close-packed structure and uniform morphology, similar to those reported in the literature.

[0062] From the appendix Figure 2 The infrared spectra of the G-BCQDs and Zr-MOFs of this invention are shown in the appendix. Figure 2 It can be seen that G-BCQDs are at 3438cm -1 The strong absorption peak is attributed to the stretching vibrations of OH and NH. At 2923 cm⁻¹ -1 The absorption peaks are consistent with the CH stretching vibrations. The peaks are at 1637, 1556, 1492, 1378, and 1130 cm⁻¹. -1 The peaks at these locations represent the stretching vibrations of C=C, C=ONR, and NH2, the bending vibration of CN, and the bending vibration of CN-, respectively. Furthermore, the infrared spectrum of Zr-MOFs shows absorption peaks at 3267, 1235, 2922, and 1653, corresponding to the stretching vibrations of OH and CN, respectively. Absorption peaks are also observed at 1598 and 1386 cm⁻¹. -1 The nearby strong peaks belong to the asymmetric and symmetric carboxylic acid (COO-) bonds in the organic linker, which coordinate with the metal center via O- during deprotonation. (1450–1600 cm⁻¹) -1 The nearby absorption peaks are attributed to the stretching vibrations of the aromatic ring, at 795, 658, and 565 cm⁻¹. -1 This is due to the characteristic band vibration of the Zr-O bond.

[0063] Appendix Figure 3 The images show the XRD patterns of the G-BCQDs and Zr-MOFs of this invention. (See attached diagram.) Figure 3 It can be seen that the broad peak at 2θ=23.6° is a characteristic diffraction peak of G-BCQDs, indicating that the carbon exists in the form of amorphous carbon. Zr-MOFs at 7.4, 8.5, 14.8 and 25.6° correspond to the (111), (200), (222) and (600) crystal planes, respectively.

Claims

1. A method for preparing a fluorescent paper-based sensor for visually detecting the ratio of spermine in meat products, characterized in that: Includes the following steps: (1) Pretreatment of sawdust: Weigh 4.00 g of sawdust and measure 60 mL of 2 mol / L sodium hydroxide, pour them into a 100 mL polytetrafluoroethylene high-pressure reactor, heat at 180 °C for 3 h, cool naturally to room temperature, adjust the pH value to 2-7 with 5% hydrochloric acid solution to precipitate lignin, finally extract with 10 mL of ethyl acetate, dry in a vacuum drying oven at 60 °C to obtain lignin powder for later use; (2) Preparation of p-aminobenzoic acid modified biomass carbon quantum dots G-BCQDs: Weigh 0.15 g of lignin powder and 0.3 g of p-aminobenzoic acid obtained in step (1) above, dissolve them in 60 mL of ultrapure water, heat in an oil bath at 90 °C for 2 h, filter, pour the filtrate into a 100 mL polytetrafluoroethylene high-pressure reactor, heat at 240 °C for 24 h, cool to room temperature, filter with a 0.2 μm organic microporous membrane to obtain a yellow solution, dialyze with a 1000 Da dialysis membrane for 1 day, collect the internal solution, freeze dry, and prepare a 1.00 mg / mL p-aminobenzoic acid modified biomass carbon quantum dot G-BCQDs solution with ultrapure water, and store it in a refrigerator for later use; (3) Preparation of zirconium-based organometallic framework material Zr-MOFs: 174.02 mg ZrCl4 was weighed and dissolved in 15 mL of N,N-dimethylformamide DMF. 1 mL of concentrated hydrochloric acid was added until the solution was clear. 146.6 mg of 2,5-dihydroxyterephthalic acid was weighed and added to the above solution. The resulting mixture was transferred to a polytetrafluoroethylene high-pressure reactor and heated at 80 °C for 24 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 5 min to obtain a yellow precipitate. The precipitate was washed three times with DMF and anhydrous ethanol, respectively. The yellow precipitate was dried in a vacuum oven at 50 °C and prepared as a 2.00 mg / mL zirconium-based organometallic framework material Zr-MOFs solution for later use. (4) Preparation of G-BCQDs / Zr-MOFs ratio fluorescent probe: Measure 1.50 mL of 1.00 mg / mL G-BCQDs obtained in step (2) above and 0.75 mL of 2.00 mg / mL Zr-MOFs obtained in step (3) above, mix thoroughly, dilute with ultrapure water to 3 mL, shake for 2 h to obtain G-BCQDs / Zr-MOFs ratio fluorescent probe; (5) Preparation of G-BCQDs / Zr-MOFs ratio fluorescence paper-based sensor: 7 cm qualitative filter paper of GB / T1914-2017 is used as paper-based chip. The filter paper is cut into 14 mm circular filter paper chips using a tablet press. The 14 mm circular filter paper chip is held with tweezers and immersed in the G-BCQDs / Zr-MOFs ratio fluorescence probe solution obtained in step (4) above. After 5 s, it is taken out and air-dried naturally to obtain the ratio fluorescence paper-based sensor. It is then stored in a refrigerator for later use.

2. The ratiometric fluorescent paper-based sensor obtained by the preparation method according to claim 1 is used for rapid visual detection of spermine in meat products, characterized in that... Includes the following steps: 200 μL of the test solution was added dropwise to the G-BCQDs / Zr-MOFs ratio fluorescent paper-based sensor as described in claim 1, allowed to air dry naturally, and observed under a 365 nm ultraviolet lamp. The RGB values ​​of the fluorescence color on the ratio fluorescent paper-based sensor were identified and extracted using a smartphone.

Images