Fluorescent paper-based sensor for visually detecting ratio of spermine in meat food as well as preparation and application of fluorescent paper-based sensor

Abstract

The invention relates to a preparation method and application of a fluorescent paper-based sensor for visually detecting the ratio of spermine in meat food, belongs to the technical field of rapid detection of food safety, and mainly aims to rapidly obtain information of the putrefaction degree of the meat food and provide a basis for market supervision departments, manufacturers and consumers. The invention provides a novel method for rapidly detecting the concentration of a biogenic amine representative spermine in meat products. The technical key points of the invention are as follows: on the basis of a'double response-switch 'ratio fluorescence principle, a filter paper chip is taken as a carrier, a G-BCQDs / Zr-MOFs ratio fluorescence probe is used, a ratio fluorescence paper-based sensor for rapidly detecting the concentration of a biogenic amine representative substance spermine in food is researched and developed, and the ratio fluorescence paper-based sensor is successfully applied to quantitative detection of spermine in an actual food sample in combination with a mobile phone APP. The problem that the quantitative detection accuracy of a ratio fluorescent paper-based sensor is not high is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of rapid food safety detection, and in particular relates to a ratio fluorescence paper-based sensor for visually detecting spermine in meat food. Background Art

[0002] Biogenic amines (BA) are a general term for a class of low-molecular-weight organic compounds containing amino groups that are biologically active. Due to the potential toxic effects of biogenic amines and their role as indicators of food spoilage, research on biogenic amine detection methods has attracted attention in food hygiene. Biogenic amines can be divided into three types according to their structure: aliphatic amines, aromatic amines, and heterocyclic amines. Spermine belongs to the aliphatic amine type of biogenic amines. Spermine can react with nitrite to produce carcinogenic nitrosamines.

[0003] The production of biogenic amines in meat and meat products is related to the presence of microorganisms. These microorganisms may be natural microorganisms in meat or may come from the surrounding environment during processing. High concentrations of biogenic amines in aquatic products are usually caused by improper storage. Illegal merchants sell spoiled meat products, which harms people's physical and mental health and has attracted great attention from market supervision departments. Therefore, it is very important to quickly detect the concentration of biogenic amines in spoiled meat products.

[0004] At present, the main methods for determining biogenic amines include liquid chromatography, enzyme sensor array, high performance liquid chromatography, gas chromatography, gas chromatography-mass spectrometry, etc. Although these methods can accurately detect the concentration of biogenic amines, they also have disadvantages such as cumbersome sample preparation, poor stability, interference from byproducts, complex instrument operation, long analysis time, and these methods cannot be used outside the laboratory. Therefore, a rapid, visual, and on-site quantitative method for detecting biogenic amines in food is needed.

[0005] Since the change direction of the fluorescence emission peak in the "dual response-off" ratio fluorescence paper-based sensor is consistent, the slope of the standard working curve of the ratio fluorescence probe is small, the detection linear range is narrow, and the visual effect contrast is not obvious. Therefore, it is necessary to develop a "dual response-on / off" biomass carbon quantum dot ratio fluorescence paper-based sensor. Metal organic frameworks (MOFs) are skeleton structures with unique porous crystal characteristics made by coordination self-assembly between functional organic ligands and metal ions (or clusters). In recent years, MOFs have attracted widespread attention as a new type of sensing material for detecting different volatile organic compounds and gases. Compared with other sensing materials, porous MOFs have the advantages of large specific surface area, high reversibility, large functionalized sites, adjustable pore size, and good chemical and thermal stability. At present, MOFs are widely used in the field of food analysis as a detection material.

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

[0007] Purpose of the invention:

[0008] The main purpose of the present 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 of biogenic amines, in meat products. The main features of this method are (1) a "dual response-switch" ratio fluorescence paper-based sensor based on p-aminobenzoic acid-modified lignin biomass carbon quantum dots and Zr-MOFs is constructed and used to visually detect the concentration of spermine, a representative of biogenic amines, in food. This method has the characteristics of reducing background interference, sensitive visual detection effect, and easy to distinguish. (2) Based on the "dual response-switch" ratio fluorescence principle, a ratio fluorescence paper-based sensor for quickly detecting the concentration of spermine, a representative of biogenic amines in food, was developed, and successfully used in conjunction with a mobile phone APP for quantitative detection of spermine in actual food samples, solving the problem of low quantitative detection accuracy of ratio fluorescence paper-based sensors.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] A method for preparing a ratiometric fluorescent paper-based sensor for visually detecting spermine in meat food comprises the following steps:

[0011] 1. Preparation of Biomass Carbon Quantum Dots

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

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

[0014] 2. Preparation of Zr-MOFs

[0015] Weigh 174.02 mg ZrCl4 and dissolve it in 15 mL N,N-dimethylformamide (DMF), add 1 mL concentrated hydrochloric acid until the solution is clear. Subsequently, weigh a certain amount of 2,5-dihydroxyterephthalic acid (146.6 mg) and add it to the above solution. The obtained mixture was transferred to a polytetrafluoroethylene autoclave 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, which was washed three times with DMF and anhydrous ethanol respectively. Then, the obtained yellow precipitate was dried in a vacuum oven at 50 °C and prepared into a 2.00 mg / mL Zr-MOFs solution for further use.

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

[0017] 1.00 mg / mL of G-BCQDs (1.50 mL) and 2.00 mg / mL of Zr-MOFs (0.75 mL) were mixed and diluted to 3 mL with ultrapure water and shaken for 2 h to obtain a ratiometric fluorescent probe (the volume ratio of G-BCQDs and Zr-MOFs was 1:2).

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

[0019] Use 7 cm qualitative filter paper (GB / T1914-2017) as a paper-based chip, and use a tablet press to cut the filter paper into 14 mm circular filter paper chips. Use tweezers to clamp the 14 mm circular filter paper chip and immerse it in the ratiometric fluorescent probe G-BCQDs / Zr-MOFs solution obtained in step 3 for 5 s. After natural drying, the ratiometric fluorescent paper-based sensor is obtained and stored in a refrigerator.

[0020] 5. Preparation of linear equation of working curve

[0021] Under 365 nm ultraviolet light, the fluorescent paper-based sensor gradually changes from green to yellow in different concentrations of spermine SPM solution. The R' value in the RGB value and the SPM concentration (C SPM ) 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); at the same time, when the concentration of SPM is between 220.00-510.0 μM, it also has a linear relationship with R′, and its linear equation is R′=0.0982C SPM +202.07 (R 2 =0.9999).

[0022] 6 Actual sample analysis

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

[0024] The pretreated shrimp samples were subjected to spike recovery experiments with spiked SPM concentrations of 100.00, 220.00 and 350.00 mol / L, respectively. The spermine SPM concentration in the pretreated samples was detected using a ratiometric fluorescent paper-based sensor in conjunction with a mobile phone APP.

[0025] Fresh shrimp and ratiometric fluorescent paper-based sensors were placed in a watch dish, sealed with plastic wrap, and placed in a 365 nm dark box UV analyzer at room temperature for different periods of time to observe the color changes of the ratiometric fluorescent paper-based sensors to determine whether the shrimp were corrupt and produced biogenic amines.

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

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

[0028] Figure 2 shows the FT-IR images of G-BCQDs and Zr-MOFs.

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

[0030] Figure 4 Fluorescence color changes of the fluorescent paper-based sensor on the first day (A), the second day (B), and the third day (C) DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with 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) Sawdust pretreatment: Weigh 4.00 g of sawdust and 60 mL of 2 mol / L sodium hydroxide, pour into a 100 mL polytetrafluoroethylene autoclave, and heat at 180 °C for 3 h. After cooling naturally to room temperature, adjust the pH value to 2 with a 5% hydrochloric acid solution to precipitate lignin. Finally, extract with 10 mL of ethyl acetate and dry in a vacuum oven at 60 °C to obtain lignin solid 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 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 autoclave, and heat at 240 °C for 24 h. After cooling to room temperature, filter with a 0.2 μm organic microporous filter membrane to obtain a yellow solution, then dialyze with a 1000 Da dialysis membrane for 1 d, collect the internal solution, freeze-dry, and use ultrapure water to prepare a 1.00 mg / mL p-aminobenzoic acid modified biomass carbon quantum dot G-BCQDs solution, and store it in a refrigerator for later use.

[0036] 2. Preparation of Zr-MOFs

[0037] Weigh 174.02 mg ZrCl4 and dissolve it in 15 mL N,N-dimethylformamide DMF, add 1 mL concentrated hydrochloric acid until the solution is clear. Subsequently, weigh 146.6 mg 2,5-dihydroxyterephthalic acid and add it to the above solution. The obtained mixture was transferred to a polytetrafluoroethylene autoclave 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. After washing three times with DMF and anhydrous ethanol respectively, the obtained yellow precipitate was dried in a vacuum oven at 50 °C and prepared into a 2.00 mg / mL Zr-MOFs solution for further use.

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

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

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

[0041] Use 7 cm qualitative filter paper (GB / T1914-2017) as a paper-based chip, and cut the filter paper into 14 mm circular filter paper chips using a tablet press. Use tweezers to clamp the 14 mm circular filter paper chip and immerse it in the G-BCQDs / Zr-MOFs ratio fluorescence probe solution obtained in step 3 for 5 s. After natural drying, the ratio fluorescence paper-based sensor is obtained and stored in a refrigerator for later use.

[0042] 5. Preparation of linear equation of working curve

[0043] Under a 365 nm ultraviolet lamp, 200 uL of spermine SPM solutions of different concentrations were added to the ratiometric fluorescent paper-based sensor obtained in step 4 and dried naturally. The fluorescent paper-based sensor gradually changed from green to yellow. Observed under a 365 nm ultraviolet lamp, the RGB value of the fluorescent color on the ratiometric fluorescent paper-based sensor, the R′ value in the RGB value, and the SPM concentration (C SPM ) 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); at the same time, when the concentration of SPM is between 220.00-510.0 μM, it also has a linear relationship with R′, and its linear equation is R′=0.0982CSPM +202.07 (R 2 =0.9999).

[0044] 6. Actual Sample Analysis

[0045] (1) Shrimp sample pretreatment: Add 2.00 g of fresh shrimp to 20 mL of acetonitrile and disperse by ultrasonication for 30 min. Then, add 1.00 g of activated carbon and shake for 30 min for dispersion and purification. Centrifuge at 4000 rpm / min, filter with a 0.2 μm organic microporous filter membrane, evaporate at 55 °C, and dilute to 60 mL with ultrapure water to obtain the pretreated sample solution, which is then stored in a refrigerator.

[0046] (2) Spiked recovery experiment: The pretreated shrimp sample solution was subjected to a spiked recovery experiment. The concentrations of spiked spermine SPM were 100.00, 220.00 and 350.00 mol / L, respectively. A total volume of 200uL of spiked spermine SPM solution was added dropwise to the ratiometric fluorescent paper-based sensor solution obtained in step 4, dried naturally, and photographed and extracted under a 365nm UV analyzer to obtain the RGB value of its color. The RGB value was substituted into the linear equation obtained in step 5 to calculate the SPM concentration, as well as the recovery rate and relative standard deviation of SPM. The results are shown in Table 1. As can be seen from Table 1, the recovery rate of SPM in shrimp samples is in the range of 90.97-101.14%, and the relative standard deviation is less than 2.15%. The above results show that the ratiometric fluorescent paper-based sensor can be used for SPM concentration detection in actual samples.

[0047] Table 1 Visual ratiometric fluorescence paper-based sensor for detecting SPM in actual samples (n=3)

[0048]

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

[0050] 1. Preparation of Biomass Carbon Quantum Dots

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

[0052] (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 in 60 mL of ultrapure water, heat in an oil bath at 90 °C for 2 h, and filter with filter paper to obtain a filtrate. Pour the filtrate into a 100 mL polytetrafluoroethylene autoclave and heat at 240 °C for 24 h. After cooling to room temperature, filter with a 0.2 μm organic microporous filter membrane to obtain a yellow solution, and then dialyze with a 1000 Da dialysis membrane for 1 d, collect the internal solution, freeze-dry, and use ultrapure water to prepare a 1.00 mg / mL p-aminobenzoic acid modified biomass carbon quantum dot G-BCQDs solution, and store it in a refrigerator for later use.

[0053] 2. Preparation of Zr-MOFs

[0054] Weigh 174.02 mg ZrCl4 and dissolve it in 15 mL N,N-dimethylformamide DMF, add 1 mL concentrated hydrochloric acid until the solution is clear. Subsequently, weigh 146.6 mg 2,5-dihydroxyterephthalic acid and add it to the above solution. The obtained mixture was transferred to a polytetrafluoroethylene autoclave 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. After washing three times with DMF and anhydrous ethanol respectively, the obtained yellow precipitate was dried in a vacuum oven at 50 °C and prepared into a 2.00 mg / mL Zr-MOFs solution for further use.

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

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

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

[0058] Use 7 cm qualitative filter paper (GB / T1914-2017) as a paper-based chip, and cut the filter paper into 14 mm circular filter paper chips with a tablet press. Use tweezers to hold the 14 mm circular filter paper chip and immerse it in the G-BCQDs / Zr-MOFs ratio fluorescence probe solution obtained in step 3 for 5 s, then dry it naturally to obtain a ratio fluorescence paper-based sensor, which is stored in a refrigerator for later use.

[0059] 5. Actual sample analysis

[0060] Place fresh shrimp and the ratiometric fluorescent paper-based sensor obtained in step 4 in a watch glass, seal it with plastic wrap, and place it in a 365 nm dark box UV analyzer at room temperature for different periods of time to observe the color changes of the ratiometric fluorescent paper-based sensor to determine whether spermine is produced in the shrimp sample and whether it is corrupt. The experimental results are shown in the attached Figure 4 (A), (B) and (C), the results show that the shrimp meat samples began to spoil on the second day, indicating the production of spermine, proving that the ratiometric fluorescent paper-based sensor can be used to monitor the degree of spoilage of shrimp samples.

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

[0062] Figure 2 shows the infrared spectra of G-BCQDs and Zr-MOFs of the present invention. As shown in Figure 2, G-BCQDs has an infrared spectrum of 3438 cm -1 The strong absorption peak at 2923 cm -1 The absorption peaks of 1637, 1556, 1492, 1378 and 1130 cm -1 The peaks at 3267, 1235, 2922, and 1653 cm represent the stretching vibration of C=C, C=ONR, and NH2, the bending vibration of CN, and the bending vibration of CN-. In addition, the infrared spectrum of Zr-MOFs shows that there are absorption peaks at 3267, 1235, 2922, and 1653 cm, which are the stretching vibrations of OH and CN, respectively. -1 The strong peaks nearby belong to the asymmetric and symmetric carboxylic acid (COO-) bonds in the organic linker, which coordinate to the metal center via O- during deprotonation. -1 The absorption peaks near 795, 658, and 565 cm are attributed to the stretching vibration of the aromatic ring. -1 It is due to the characteristic band vibration of Zr-O bond.

[0063] Figure 3 is an XRD diagram of G-BCQDs and Zr-MOFs of the present invention. As shown in Figure 3, 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 (111), (200), (222) and (600) crystal planes, respectively.

Claims

1. A method for preparing a ratiometric fluorescent paper-based sensor for visually detecting spermine in meat products, characterized in that The following steps are involved: (1) Sawdust pretreatment: Weigh 4.00 g of sawdust and 60 mL of 2 mol / L sodium hydroxide, pour into a 100 mL polytetrafluoroethylene autoclave, heat at 180 °C for 3 h, cool naturally to room temperature, adjust the pH value to 2-7 with 5% hydrochloric acid solution, precipitate lignin, finally extract with 10 mL of ethyl acetate, dry in a vacuum 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 obtained in step (1) above and 0.3 g of p-aminobenzoic acid, dissolve 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 autoclave, heat at 240 °C for 24 h, cool to room temperature, filter with a 0.2 μm organic microporous filter membrane to obtain a yellow solution, dialyze with a 1000 Da dialysis membrane for 1 d, collect the internal solution, freeze-dry, and use ultrapure water to prepare a 1.00 mg / mL p-aminobenzoic acid modified biomass carbon quantum dot G-BCQDs solution, and store in a refrigerator for later use; (3) Preparation of zirconium-based metal organic framework material Zr-MOFs: Weigh 174.02 mg ZrCl4 and dissolve it in 15 mL N,N-dimethylformamide DMF, add 1 mL concentrated hydrochloric acid, and after the solution is clarified, weigh 146.6 mg 2,5-dihydroxyterephthalic acid and add it to the above solution. Transfer the obtained mixture to a polytetrafluoroethylene autoclave and heat it at 80 °C for 24 h. After cooling to room temperature, centrifuge it at 8000 rpm / min for 5 min to obtain a yellow precipitate. After washing it three times with DMF and anhydrous ethanol respectively, the obtained yellow precipitate is dried in a vacuum oven at 50 °C and prepared into a 2.00 mg / mL zirconium-based metal organic framework material Zr-MOFs solution for use. (4) Preparation of G-BCQDs / Zr-MOFs ratio fluorescent probe: 1.50 mL of 1.00 mg / mL G-BCQDs obtained in step (2) and 0.75 mL of 2.00 mg / mL Zr-MOFs obtained in step (3) were weighed, mixed thoroughly, diluted to 3 mL with ultrapure water, and shaken for 2 h to obtain a G-BCQDs / Zr-MOFs ratio fluorescent probe; (5) Preparation of G-BCQDs / Zr-MOFs ratiometric fluorescent paper-based sensor: Use 7 cm qualitative filter paper of specification GB / T1914-2017 as paper-based chip, cut the filter paper into 14 mm circular filter paper chips with a tablet press, use tweezers to clamp the 14 mm circular filter paper chip and immerse it in the G-BCQDs / Zr-MOFs ratiometric fluorescent probe solution obtained in the above step (4), take it out after 5 s and let it dry naturally to obtain the ratiometric fluorescent paper-based sensor, which is then stored in a refrigerator for future use.

2. The ratiometric fluorescent paper-based sensor according to claim 1 can be used for rapid visual detection of spermine in meat products, characterized in that The steps include: 200uL of the test solution was dropped into the G-BCQDs / Zr-MOFs ratio fluorescence paper-based sensor according to claim 1, dried naturally, observed under a 365 nm ultraviolet lamp, and the RGB value of the fluorescence color on the ratio fluorescence paper-based sensor was identified and extracted using a smartphone.

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