Porphyrin metal organic framework composite material, preparation method and biogenic amine SERS (Surface Enhanced Raman Scattering) array sensor

Abstract

The invention relates to a porphyrin metal organic framework composite material, a preparation method and a biogenic amine SERS (Surface Enhanced Raman Scattering) array sensor. The preparation method of the composite material comprises the steps that a copper precursor solution is added into a surfactant, heating reaction is conducted, a reducing agent is added, heating reaction is conducted, and copper nanoparticles are obtained; the preparation method comprises the following steps: adding a transition metal salt and a surfactant into an organic solvent, adding a porphyrin ligand, carrying out a solvothermal reaction, carrying out centrifugal separation, washing and drying to obtain a porphyrin metal organic framework material, and dispersing the porphyrin metal organic framework material into the organic solvent to obtain a dispersion liquid A; and dispersing copper nanoparticles in the dispersion liquid A, carrying out a second heating reaction, and carrying out centrifugal separation, washing and drying to obtain the porphyrin metal organic framework composite material. The invention also provides the porphyrin metal organic framework composite material prepared by the preparation method, and the application of the porphyrin metal organic framework composite material as a biogenic amine SERS array sensor. The invention solves the problem that the accuracy of the detection result is influenced because the traditional biogenic amine detection method is difficult to realize field detection.

Description

Technical Field

[0001] This invention relates to the field of food detection technology, and more specifically, to a porphyrin metal-organic framework composite material, its preparation method, and a biogenic amine SERS array sensor. Background Technology

[0002] Biogenic amines are a class of nitrogen-containing low-molecular-weight organic compounds widely found in natural foods and processed products. Their formation and accumulation mainly stem from the metabolic activities of microorganisms. During storage, protein-rich foods such as meat and fish, if contaminated by microorganisms, will have their proteins hydrolyzed into amino acids by proteases secreted by the microorganisms. These amino acids are then further decarboxylated by decarboxylases to generate biogenic amines. For example, histamine is produced by the decarboxylation of histidine and is commonly found in stale fish; putrescine and cadaverine are produced by the decarboxylation of ornithine and lysine, respectively, and are hallmark substances of meat spoilage; tyramine is produced by the decarboxylation of tyrosine and is often found in fermented dairy products or soy products.

[0003] Biogenic amines are both chemical signaling molecules for food spoilage and safety risk factors. Excessive biogenic amines can cause food poisoning, with symptoms including headache, palpitations, and vomiting; tyramine can cause a sudden rise in blood pressure in hypertensive patients, which can be life-threatening in severe cases. Polyamines such as putrescine and cadaverine are important indicators of food spoilage, and their levels are positively correlated with the degree of microbial contamination, and can be used to assess food freshness.

[0004] The mainstream method for detecting biogenic amines is chromatographic analysis, such as high-performance liquid chromatography (HPLC). This method utilizes the polarity differences of biogenic amines for chromatographic separation, combined with ultraviolet, fluorescence, or mass spectrometry detectors for quantification. It has advantages such as a wide linear range. However, this method also has many drawbacks, such as complex pretreatment (requiring derivatization and solid-phase extraction), long detection time, expensive equipment, and unsuitability for rapid on-site detection.

[0005] Surface-enhanced Raman scattering (SERS) sensing is a spectroscopic analysis technique based on the enhancement effect of localized electromagnetic fields on the surface of metal nanostructures. Its core principle is that when molecules adsorb onto a metal surface, the electromagnetic field generated by localized surface plasmon resonance (LSPR) can enhance the Raman scattering signal of the molecules by 10-1. 4 ~10 14 This allows for trace detection at the single-molecule level. SERS sensors, by resolving the characteristic Raman spectra of molecules ("chemical fingerprints") and combining this with signal-enhancing substrate design, can achieve highly sensitive identification and quantification of target analytes (such as biogenic amines). However, traditional SERS sensors are limited in their practical application due to limitations in substrate material properties, interfacial interaction mechanisms, and detection modes when detecting biogenic amines. Summary of the Invention

[0006] One objective of this invention is to provide a porphyrin metal-organic framework composite material, its preparation method, and its application, in order to solve the problem that traditional biogenic amine detection methods are difficult to implement on-site detection, thus affecting the accuracy of the detection results. Another objective of this invention is to provide a biogenic amine SERS array sensor, in order to solve the problem that traditional SERS sensors are limited by the characteristics of the substrate material, the interfacial interaction mechanism, and the detection mode when detecting biogenic amines.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a porphyrin metal-organic framework composite material includes the following steps:

[0009] The copper precursor solution was added to the first surfactant solution for the first heating reaction, then the reducing agent solution was added, the temperature was increased, the reaction was centrifuged, and the precipitate was washed and purified to obtain copper nanoparticles.

[0010] A transition metal salt and a second surfactant are added to a first organic solvent, followed by the addition of a porphyrin ligand. A solvothermal reaction is then carried out, followed by centrifugation. The precipitate is washed and dried to obtain a porphyrin metal-organic framework material.

[0011] The porphyrin metal-organic framework material is dispersed in a second organic solvent to obtain dispersion A; the copper nanoparticles are dispersed in dispersion A, and then a second heating reaction is carried out. After centrifugation, the precipitate is washed and dried to obtain the porphyrin metal-organic framework composite material.

[0012] Based on the aforementioned technical methods, the introduction of copper nanoparticles provides more active sites for the detection of biogenic amines. Their unique physicochemical properties, such as surface plasmon resonance, enhance the interaction with biogenic amine molecules, thereby improving detection sensitivity. Simultaneously, the regular porous structure of the porphyrin metal-organic framework provides numerous adsorption sites for biogenic amine molecules, enabling them to contact the detection system more effectively and further improving detection sensitivity. This composite material preparation method, by combining copper nanoparticles with porphyrin metal-organic frameworks, fully leverages the advantages of both, achieving highly sensitive detection of biogenic amines and solving the problems of traditional detection methods that hinder on-site detection and affect the accuracy of results.

[0013] Preferably, the copper precursor solution is selected from copper chloride solution.

[0014] Preferably, the transition metal salt is selected from at least one of cobalt salt, nickel salt, zinc salt, iron salt, and copper salt.

[0015] Preferably, the cobalt salt is selected from at least one of cobalt nitrate, cobalt nitrate hexahydrate, cobalt chloride, cobalt acetate, and cobalt sulfate.

[0016] Preferably, the nickel salt is selected from at least one of nickel nitrate, nickel nitrate hexahydrate, nickel chloride, nickel acetate, and nickel sulfate.

[0017] Preferably, the zinc salt is selected from at least one of zinc nitrate, zinc nitrate hexahydrate, zinc chloride, zinc acetate, and zinc sulfate.

[0018] Preferably, the iron salt is selected from at least one of ferric nitrate, ferric nitrate hexahydrate, ferric chloride, ferric acetate, and ferric sulfate.

[0019] Preferably, the copper salt is selected from at least one of copper nitrate, copper nitrate hexahydrate, copper chloride, copper acetate, and copper sulfate.

[0020] Preferably, the porphyrin ligand is selected from at least one of tetra(4-carboxyphenyl)porphyrin (TCPP), 5,10,15,20-tetra(4-carboxyphenyl)porphyrin (H6TCPP), 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetra(4-bromophenyl)porphyrin (TBPP), and 5,10,15,20-tetra(4-methoxyphenyl)porphyrin (TMPP).

[0021] Preferably, the first surfactant is selected from a mixture of hexadecyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP).

[0022] Preferably, the reducing agent is selected from ascorbic acid.

[0023] Preferably, the first organic solvent is selected from a mixture of dimethylformamide (DMF) and anhydrous ethanol.

[0024] Preferably, the second surfactant is selected from polyvinylpyrrolidone (PVP).

[0025] Preferably, the second organic solvent is selected from dimethylformamide (DMF).

[0026] Preferably, the temperature of the first heating reaction is 55-65°C and the time is 5-15 min.

[0027] Preferably, the temperature of the heating reaction is 95–105°C, and the time is 50–70 min.

[0028] Preferably, the temperature of the solvothermal reaction is 70–90°C and the time is 22–26 h.

[0029] Preferably, the temperature of the second heating reaction is 75-85°C, and the time is 22-26 hours.

[0030] Preferably, the mass ratio of the copper nanoparticles to the porphyrin metal-organic framework material is 1:5 to 1:10.

[0031] The present invention also provides a porphyrin metal-organic framework composite material prepared by the preparation method described herein.

[0032] This invention also provides an application of the porphyrin metal-organic framework composite material prepared by the method described herein as a sensor.

[0033] This invention also provides an application of the porphyrin metal-organic framework composite material prepared by the method described herein as a SERS sensor.

[0034] The SERS sensor of this invention is composed of different combinations of metal ions and porphyrin ligands with nanomaterials, forming corresponding array combinations. This SERS sensor array achieves highly sensitive and selective detection of biogenic amines in food through a triple mechanism of "specific adsorption of porphyrin MOFs + efficient SERS enhancement by MNPs + array pattern recognition." Its core advantage lies in utilizing the structural tunability of MOFs and the optical properties of nanomaterials to transform molecular recognition into a resolvable spectral signal array. The Raman signal of the sensor changes after reacting with biogenic amine molecules and is converted into analyzable multidimensional data. Combined with image processing and partial least squares regression, a multivariate prediction model (PLS, SVM) is established, providing a new method for the rapid detection of multi-component biogenic amines in complex food matrices. The resulting sensor array has a wider range of applications, suitable for the detection of various amine substances, expanding the application scope of sensor arrays and meeting the needs of food freshness and safety detection.

[0035] The present invention also provides a bioamine SERS array sensor, comprising a porphyrin metal-organic framework composite material prepared by the preparation method described in the present invention.

[0036] Traditional SERS sensors are typically based on noble metal nanoparticles (such as gold and silver), but these materials suffer from problems such as easy aggregation and poor stability, limiting their application in complex environments. This invention effectively solves this problem by introducing MOF materials as the SERS substrate: the high specific surface area and tunable structure of MOFs can effectively adsorb and enrich target molecules, thereby improving the intensity of the SERS signal. MOF materials can synergistically interact with metal nanoparticles (such as CuNPs), significantly enhancing the Raman signal through surface plasmon resonance, thus improving detection sensitivity. MOF materials possess good chemical and thermal stability, effectively protecting metal nanoparticles from external environmental influences, thereby improving the repeatability and lifespan of the SERS sensor. Traditional SERS sensors typically employ a single detection mode, making it difficult to achieve simultaneous detection of multiple target biogenic amines. This invention achieves simultaneous detection of multiple target biogenic amines by constructing a SERS sensor array: Array Design: The SERS sensor array consists of multiple tiny detection units, each capable of detecting different biogenic amine molecules, thus achieving simultaneous multi-target detection. This effectively solves the problem that traditional SERS sensors are limited by the characteristics of the substrate material, the interfacial interaction mechanism, and the detection mode when detecting biogenic amines.

[0037] The present invention also provides a method for preparing a bioamine SERS array sensor, comprising the following steps: depositing at least two of the porphyrin metal-organic framework composite material solutions onto a nylon filter membrane, placing it in an oven, and vacuum drying it for 10 min at a temperature of 50°C to obtain a bioamine SERS array sensor.

[0038] Porphyrin metal-organic frameworks (MOFs) offer single-function sensing, but they suffer from several drawbacks, including insufficient selectivity, low sensitivity, limited functionality, and poor environmental adaptability. The metal center of porphyrin MOFs (such as Cu)... 2+ Zn 2+ The coordination of porphyrin MOFs with biogenic amines has a certain degree of universality, but the differences in molecular structure (e.g., functional groups, hydrophobicity) among different biogenic amines (such as histamine, putrescine, and tyramine) may lead to overlap in the recognition capabilities of a single material for multiple amines. When low concentrations of biogenic amines are adsorbed onto the surface of a single material, the Raman signal is easily overwhelmed by noise due to insufficient molecular numbers or random adsorption orientation, resulting in a relatively high detection limit. A single sensor can only be designed for one type or class of biogenic amines. If multiple targets need to be detected, multiple independent sensors need to be prepared, which is time-consuming and costly. Different food matrices (such as meat, dairy products, and alcoholic beverages) have significant differences in pH, ionic strength, and protein content, making it difficult for the pore microenvironment (e.g., polarity, pore size) of a single porphyrin MOF to maintain stable adsorption performance under complex conditions.

[0039] Array sensing can effectively solve the above problems. Each sensor unit acts as an independent "encoder," generating a unique response to biogenic amines (such as Raman peak intensity and peak position shift), forming a multidimensional signal matrix. The array can simultaneously detect multiple biogenic amines, and the response intensity of each amine on different units forms a unique "fingerprint." Combined with machine learning algorithms (PCA, SVM), multivariate calibration models (PLS, OPLS-DA, SVM) can be constructed, enabling the simultaneous detection and analysis of more than five biogenic amines, reducing the detection time to less than 10 minutes, and achieving detection limits at the nanomolar or picomolar level.

[0040] Raman spectroscopy can provide the chemical bond vibration characteristics of biogenic amine molecules. By analyzing the position and intensity of characteristic peaks, the type and concentration of biogenic amines can be directly identified. The high specific surface area and ordered pores of porphyrin MOFs provide a large number of adsorption sites for biogenic amines, increasing the molecular concentration per unit area and thus enhancing the SERS signal. The metal ions in porphyrin MOFs can form coordination bonds with the amino groups of biogenic amines, directionally enriching the target molecules. At the same time, the surface plasmon properties of metal nanoparticles (such as CuNPs) can be modulated to further enhance the enhancement efficiency. With the dual advantages of surface enhancement effect and molecular fingerprint recognition, SERS technology is perfectly matched with the polar structure and coordination ability of biogenic amines. It not only achieves highly sensitive detection of trace biogenic amines, but also further improves adsorption efficiency and signal stability through the design and optimization of substrate materials (such as porphyrin MOFs).

[0041] Preferably, the biogenic amine SERS array sensor is used to detect biogenic amines in food.

[0042] The beneficial effects of this invention are as follows:

[0043] The preparation method of the porphyrin metal-organic framework composite material of the present invention, by introducing copper nanoparticles, provides more active sites for the detection of biogenic amines. Its unique physicochemical properties, such as surface plasmon resonance, enhance the interaction with biogenic amine molecules, thereby improving detection sensitivity. Simultaneously, the regular porous structure of the porphyrin metal-organic framework material provides numerous adsorption sites for biogenic amine molecules, enabling them to contact the detection system more effectively, further improving detection sensitivity. Therefore, through the synergistic effect of copper nanoparticles and the porphyrin metal-organic framework material, highly sensitive detection of biogenic amines is achieved.

[0044] The biogenic amine SERS array sensor of the present invention uses multiple independent sensors to form an array sensor. Each sensor unit acts as an independent "code" and generates a unique response to biogenic amines (such as Raman peak intensity and peak position shift), forming a multidimensional signal matrix. This allows for the simultaneous detection of multiple biogenic amines. The response intensity of each amine on different units forms a unique "fingerprint," enabling the detection and analysis of more than 5 biogenic amines in a single operation. This significantly shortens the detection time and has practical application value in the field of food detection technology. Attached Figure Description

[0045] Figure 1 SVM images of bioamine recognition using a single sensor (a) and a sensor array (b), respectively;

[0046] Figure 2 PLS regression curve for SERS detection of mixed biogenic amines;

[0047] Figure 3 The XRD pattern of CuNPs@porphyrin MOF prepared in Example 3;

[0048] Figure 4 The FTIR spectrum of CuNPs@porphyrin MOF prepared in Example 3;

[0049] Figure 5 TEM image of CuNPs@porphyrin MOF prepared in Example 3;

[0050] Figure 6 The XPS spectrum of the CuNPs@porphyrin MOF prepared in Example 3;

[0051] Figure 7 The image shows the UV-VIS pattern of the CuNPs@porphyrin MOF prepared in Example 3.

[0052] Figure 8 The SERS spectrum of the metalloporphyrin MOF prepared in Example 3 is shown below.

[0053] Figure 9 OPLS-DA plot of pork;

[0054] Figure 10 The SERS superspectrum of biogenic amine molecules;

[0055] Figure 11 PCA diagram (a) and OPLS-DA diagram (b) for SERS recognition of biogenic amines;

[0056] Figure 12 This is a graph showing the trend of TVB-N in pork samples.

[0057] Figure 13This is an SVM model built based on pork TVB-N. Detailed Implementation

[0058] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0059] Example 1

[0060] A method for fabricating a SERS sensor includes the following steps:

[0061] Preparation of S1, porphyrin metal-organic framework composites: from Ni 2+ SERS sensor prepared by binding porphyrin ligands to copper nanoparticles:

[0062] S11. Weigh 0.12g of copper chloride into 10mL of deionized water and stir until completely dissolved to obtain a copper precursor solution; weigh 0.048g of CTAB and 0.048g of PVP and dissolve them in 20mL of deionized water, then heat and stir at 60℃ until transparent to obtain a first surfactant solution; weigh 0.32g of ascorbic acid and dissolve it in 10mL of deionized water to obtain a reducing agent solution.

[0063] The copper precursor solution was slowly added dropwise to the first surfactant solution, and the mixture was stirred and heated for 10 minutes at a constant temperature of 60°C to form a blue-green transparent solution. Nitrogen or argon gas was then introduced into the blue-green transparent solution for 10 minutes, followed by the rapid addition of the reducing agent solution. At this point, the solution color gradually changed from blue-green to reddish-brown (Cu). 2+ →Cu 0 The mixture was heated to 100℃ and stirred for 1 hour until the reaction was completely colorless. During this period, an inert gas protection was maintained. The resulting mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of deionized water was added to the precipitate and ultrasonically dispersed for 5 minutes. The mixture was then centrifuged again at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of anhydrous ethanol was added to the precipitate (to remove residual organic matter). The mixture was ultrasonically dispersed and centrifuged at 10,000 rpm. The supernatant was discarded. If the supernatant was still turbid, the mixture was washed with ethanol once more and the supernatant was discarded. The precipitate was copper nanocubes, which are copper nanoparticles.

[0064] 0.4 mmol of Ni(NO3)2·6H2O and 20.0 mg of PVP were added to 16 mL of a first organic solvent containing DMF and ethanol in a volume ratio of 3:1. After complete dissolution, 12 mg of TCPP was added, and the mixture was sonicated for 15 minutes. The sonicated solution was then poured into a 20 mL stainless steel autoclave lined with Teflon. The autoclave was placed in a constant temperature oven and subjected to a solvothermal reaction at 80 °C for 24 hours. During the reaction, metal ions coordinate with porphyrin ligands to gradually form porphyrin MOF crystals. After the reaction, the reaction vessel is allowed to cool naturally to room temperature. The product in the reaction vessel is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes. The precipitate is collected and washed three times with DMF. After each wash, the precipitate is centrifuged at 8000 rpm for 10 minutes to remove unreacted metal salts, ligands and other impurities. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain dried Ni-TCPP MOF material, which is then sealed and stored for later use.

[0065] Accurately weigh the prepared Ni-TCPP MOF material (metalloporphyrin MOF material) and add it to 10 mL of DMF. Sonicate the mixture for 30 minutes to ensure that the Ni-TCPP MOF material is uniformly dispersed in the DMF, thus obtaining dispersion A. Take an appropriate amount of the prepared copper nanocubes and add them to dispersion A. Sonicate the mixture for 30 minutes to ensure that the copper nanocubes are uniformly dispersed in the system containing Ni-TCPP MOF material. Control the mass ratio of copper nanocubes to porphyrin MOF to be 1:10 to obtain a mixed solution. Transfer the mixed solution to a 50 mL beaker and react it with magnetic stirring in a water bath at 80 °C for 24 hours. In this process, copper nanocubes are loaded onto the surface or pores of Ni-TCPP MOF materials through surface coordination or electrostatic adsorption, forming copper nanocubes@Ni-TCPP MOF composite materials. After the reaction, the mixture is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes to collect the precipitate. The precipitate is washed three times alternately with DMF and anhydrous ethanol, and centrifuged at 8000 rpm for 10 minutes after each wash to remove unloaded copper nanocubes and other impurities. The washed precipitate is then placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain copper nanocubes@Ni-TCPP MOF composite materials, i.e., porphyrin metal-organic framework composite materials, which are then sealed and stored for later use.

[0066] S2. Take 0.005g of the above copper nanocubes@Ni-TCPP MOF composite material and ultrasonically disperse it in 1ml of anhydrous ethanol. Add 50ul of the solution and deposit it on the nylon filter membrane. Dry it under vacuum at 50℃ to obtain the SERS sensor.

[0067] S3. Optimization of SERS detection time: 50 μL of the target biogenic amine was incubated with the sensor. Raman spectroscopy was performed every 10 minutes until the Raman signal no longer changed. This experiment was repeated three times. The 241 and 410 cm⁻¹ values ​​before and after the reaction between the sensor and the target biogenic amine were calculated. -1 The ratio of the intensity of Raman characteristic peaks, expressed as I 410 / I 241 The time with the largest ratio is the optimal detection time.

[0068] S4. Detection of biogenic amines: Ten biogenic amines closely related to food spoilage were selected (spermine, spermidine, cadaverine, putrescine, tyramine, tryptamine, histamine, phenylethylamine, dimethylamine, cystamine, etc., with a uniform concentration of 10 μM). Two parallel samples were set up for each biogenic amine, and five replicate tests were performed. Data range: 150–1650 cm⁻¹ -1 The obtained spectral data will be used to construct a multi-model analysis system encompassing PCA, OPLS-DA, and SVM. The results are as follows: Figure 1 As shown in figure a, the accuracy of a single SERS sensor is only 85%, making it difficult to distinguish between different biogenic amines and prone to misjudgment.

[0069] Example 2

[0070] A method for preparing a bio-amine SERS array sensor includes the following steps:

[0071] This embodiment provides a 2×1 SERS sensor array composed of two metals, Co and Ni, combined with porphyrin ligands and then with copper nanoparticles:

[0072] S11. Weigh 0.12g of copper chloride into 10mL of deionized water and stir until completely dissolved to obtain a copper precursor solution; weigh 0.048g of CTAB and 0.048g of PVP and dissolve them in 20mL of deionized water, then heat and stir at 60℃ until transparent to obtain a first surfactant solution; weigh 0.32g of ascorbic acid and dissolve it in 10mL of deionized water to obtain a reducing agent solution.

[0073] The copper precursor solution was slowly added dropwise to the first surfactant solution, and the mixture was stirred and heated for 10 minutes at a constant temperature of 60°C to form a blue-green transparent solution. Nitrogen or argon gas was then introduced into the blue-green transparent solution for 10 minutes, followed by the rapid addition of the reducing agent solution. At this point, the solution color gradually changed from blue-green to reddish-brown (Cu). 2+ →Cu 0The mixture was heated to 100℃ and stirred for 1 hour until the reaction was completely colorless. During this period, an inert gas protection was maintained. The resulting mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of deionized water was added to the precipitate and ultrasonically dispersed for 5 minutes. The mixture was then centrifuged again at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of anhydrous ethanol was added to the precipitate (to remove residual organic matter). The mixture was ultrasonically dispersed and centrifuged at 10,000 rpm. The supernatant was discarded. If the supernatant was still turbid, the mixture was washed with ethanol once more and the supernatant was discarded. The precipitate was copper nanocubes, which are copper nanoparticles.

[0074] 0.4 mmol of Co(NO3)2·6H2O and 20.0 mg of PVP were added to 16 mL of a first organic solvent containing DMF and ethanol in a volume ratio of 3:1. After complete dissolution, 12 mg of TCPP was added, and the mixture was sonicated for 15 minutes. The sonicated solution was then poured into a 20 mL stainless steel autoclave lined with Teflon. The autoclave was placed in a constant temperature oven and subjected to a solvothermal reaction at 80 °C for 24 hours. During the reaction, metal ions coordinate with porphyrin ligands to gradually form porphyrin MOF crystals. After the reaction, the reaction vessel is allowed to cool naturally to room temperature. The product in the reaction vessel is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes. The precipitate is collected and washed three times with DMF. After each wash, the precipitate is centrifuged at 8000 rpm for 10 minutes to remove unreacted metal salts, ligands and other impurities. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain dried Co-TCPP MOF material, which is then sealed and stored for later use.

[0075] Accurately weigh the prepared Co-TCPP MOF material (metalloporphyrin MOF material) and add it to 10 mL of DMF. Sonicate and disperse for 30 minutes to ensure that the Co-TCPP MOF material is uniformly dispersed in the DMF, thus obtaining dispersion A. Take an appropriate amount of the prepared copper nanocubes and add them to dispersion A. Sonicate for 30 minutes to ensure that the copper nanocubes are uniformly dispersed in the system containing the Co-TCPP MOF material. Control the mass ratio of copper nanocubes to porphyrin MOF to be 1:10 to obtain a mixed solution. Transfer the mixed solution to a 50 mL beaker and react with magnetic stirring in a water bath at 80 °C for 24 hours. In this process, copper nanocubes are loaded onto the surface or pores of the Co-TCPP MOF material through surface coordination or electrostatic adsorption, forming a copper nanocube@Co-TCPP MOF composite material. After the reaction, the mixture is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes to collect the precipitate. The precipitate is washed three times alternately with DMF and anhydrous ethanol, and centrifuged at 8000 rpm for 10 minutes after each wash to remove unloaded copper nanocubes and other impurities. The washed precipitate is then placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain the copper nanocube@Co-TCPP MOF composite material, i.e., porphyrin metal-organic framework composite material, which is then sealed and stored for later use.

[0076] S12. Weigh 0.12g of copper chloride into 10mL of deionized water and stir until completely dissolved to obtain a copper precursor solution; weigh 0.048g of CTAB and 0.048g of PVP and dissolve them in 20mL of deionized water, then heat and stir at 60℃ until transparent to obtain a first surfactant solution; weigh 0.32g of ascorbic acid and dissolve it in 10mL of deionized water to obtain a reducing agent solution.

[0077] The copper precursor solution was slowly added dropwise to the first surfactant solution, and the mixture was stirred and heated for 10 minutes at a constant temperature of 60°C to form a blue-green transparent solution. Nitrogen / argon gas was then introduced into the blue-green transparent solution for 10 minutes, followed by the rapid addition of the reducing agent solution. At this point, the solution color gradually changed from blue-green to reddish-brown (Cu). 2+ →Cu 0The mixture was heated to 100℃ and stirred for 1 hour until the reaction was completely colorless. During this period, an inert gas protection was maintained. The resulting mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of deionized water was added to the precipitate and ultrasonically dispersed for 5 minutes. The mixture was then centrifuged again at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of anhydrous ethanol was added to the precipitate (to remove residual organic matter). The mixture was ultrasonically dispersed and centrifuged at 10,000 rpm. The supernatant was discarded. If the supernatant was still turbid, the mixture was washed with ethanol once more and the supernatant was discarded. The precipitate was copper nanocubes, which are copper nanoparticles.

[0078] 0.4 mmol of Ni(NO3)2·6H2O and 20.0 mg of PVP were added to 16 mL of a first organic solvent containing DMF and ethanol in a volume ratio of 3:1. After complete dissolution, 12 mg of TCPP was added, and the mixture was sonicated for 15 minutes. The sonicated solution was then poured into a 20 mL stainless steel autoclave lined with Teflon. The autoclave was placed in a constant temperature oven and subjected to a solvothermal reaction at 80 °C for 24 hours. During the reaction, metal ions coordinate with porphyrin ligands to gradually form porphyrin MOF crystals. After the reaction, the reaction vessel is allowed to cool naturally to room temperature. The product in the reaction vessel is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes. The precipitate is collected and washed three times with DMF. After each wash, the precipitate is centrifuged at 8000 rpm for 10 minutes to remove unreacted metal salts, ligands and other impurities. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain dried Ni-TCPP MOF material, which is then sealed and stored for later use.

[0079] Accurately weigh the prepared Ni-TCPP MOF material (metalloporphyrin MOF material) and add it to 10 mL of DMF. Sonicate the mixture for 30 minutes to ensure that the Ni-TCPP MOF material is uniformly dispersed in the DMF, thus obtaining dispersion A. Take an appropriate amount of the prepared copper nanocubes and add them to dispersion A. Sonicate the mixture for 30 minutes to ensure that the copper nanocubes are uniformly dispersed in the system containing Ni-TCPP MOF material. Control the mass ratio of copper nanocubes to porphyrin MOF to be 1:10 to obtain a mixed solution. Transfer the mixed solution to a 50 mL beaker and react it with magnetic stirring in a water bath at 80 °C for 24 hours. In this process, copper nanocubes are loaded onto the surface or pores of Ni-TCPP MOF materials through surface coordination or electrostatic adsorption, forming copper nanocubes@Ni-TCPP MOF composite materials. After the reaction, the mixture is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes to collect the precipitate. The precipitate is washed three times alternately with DMF and anhydrous ethanol, and centrifuged at 8000 rpm for 10 minutes after each wash to remove unloaded copper nanocubes and other impurities. The washed precipitate is then placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain copper nanocubes@Ni-TCPP MOF composite materials, i.e., porphyrin metal-organic framework composite materials, which are then sealed and stored for later use.

[0080] S2. Take 0.005g of each of the two composite materials and ultrasonically disperse them in 1ml of anhydrous ethanol. Add 50ul of solution to each and deposit them on a nylon filter membrane. Dry them under vacuum at 50℃ to obtain a 2×1 bioamine SERS array sensor.

[0081] S3. Optimization of SERS detection time: 50 μL of the target biogenic amine was incubated with the sensor. Raman spectroscopy was performed every 10 minutes until the Raman signal no longer changed. This experiment was repeated three times. The 241 and 410 cm⁻¹ values ​​before and after the reaction between the sensor and the target biogenic amine were calculated. -1 The ratio of the intensity of Raman characteristic peaks, expressed as I 410 / I 241 The time with the largest ratio is the optimal detection time.

[0082] S4. Detection of biogenic amines: Ten biogenic amines closely related to food spoilage (cadaverine, putrescine, histamine, etc., all at a uniform concentration of 10 μM) were selected. Two parallel samples were used for each biogenic amine, and five replicate tests were performed. Data range: 150-1650 cm⁻¹ -1 The obtained spectral data will be used to construct a multi-model analysis system including PCA, OPLS-DA, and SVM.

[0083] Example 3

[0084] A method for preparing a bio-amine SERS array sensor includes the following steps:

[0085] This embodiment provides a 2×2 SERS sensor array composed of three metals (Fe, Zn, and Zr) combined with different porphyrin ligands and then combined with copper nanoparticles.

[0086] S11. Weigh 0.12g of copper chloride into 10mL of deionized water and stir until completely dissolved to obtain a copper precursor solution; weigh 0.048g of CTAB and 0.048g of PVP and dissolve them in 20mL of deionized water, then heat and stir at 60℃ until transparent to obtain a first surfactant solution; weigh 0.32g of ascorbic acid and dissolve it in 10mL of deionized water to obtain a reducing agent solution.

[0087] The copper precursor solution was slowly added dropwise to the first surfactant solution, and the mixture was stirred and heated for 10 minutes at a constant temperature of 60°C to form a blue-green transparent solution. Nitrogen or argon gas was then introduced into the blue-green transparent solution for 10 minutes, followed by the rapid addition of the reducing agent solution. At this point, the solution color gradually changed from blue-green to reddish-brown (Cu). 2+ →Cu 0 The mixture was heated to 100℃ and stirred for 1 hour until the reaction was completely colorless. During this period, an inert gas protection was maintained. The resulting mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of deionized water was added to the precipitate and ultrasonically dispersed for 5 minutes. The mixture was then centrifuged again at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of anhydrous ethanol was added to the precipitate (to remove residual organic matter). The mixture was ultrasonically dispersed and centrifuged at 10,000 rpm. The supernatant was discarded. If the supernatant was still turbid, the mixture was washed with ethanol once more and the supernatant was discarded. The precipitate was copper nanocubes, which are copper nanoparticles.

[0088] Add 0.4 mmol of anhydrous Fe(NO3)2 and 20.0 mg of PVP to 16 mL of a first organic solvent containing DMF and ethanol in a volume ratio of 3:1. After complete dissolution, add 12 mg of TCPP and sonicate for 15 minutes. Then pour the sonicated solution into a 20 mL stainless steel autoclave lined with Teflon. Place the autoclave in a constant temperature oven and carry out a solvothermal reaction at 80 °C for 24 hours. During the reaction, metal ions coordinate with porphyrin ligands to gradually form porphyrin MOF crystals. After the reaction, the reaction vessel is allowed to cool naturally to room temperature. The product in the reaction vessel is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes. The precipitate is collected and washed three times with DMF. After each wash, the precipitate is centrifuged at 8000 rpm for 10 minutes to remove unreacted metal salts, ligands and other impurities. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain dried Fe-TCPP MOF material, which is then sealed and stored for later use.

[0089] Accurately weigh the prepared Fe-TCPP MOF material (metalloporphyrin MOF material) and add it to 10 mL of DMF. Sonicate the mixture for 30 minutes to ensure that the Fe-TCPP MOF material is uniformly dispersed in the DMF, thus obtaining dispersion A. Take an appropriate amount of the prepared copper nanocubes and add them to dispersion A. Sonicate the mixture for 30 minutes to ensure that the copper nanocubes are uniformly dispersed in the system containing the Fe-TCPP MOF material. Control the mass ratio of copper nanocubes to porphyrin MOF to be 1:10 to obtain a mixed solution. Transfer the mixed solution to a 50 mL beaker and react it with magnetic stirring in a water bath at 80 °C for 24 hours. In this process, copper nanocubes are loaded onto the surface or pores of Fe-TCPP MOF materials through surface coordination or electrostatic adsorption, forming copper nanocubes@Fe-TCPP MOF composite materials. After the reaction, the mixture is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes to collect the precipitate. The precipitate is washed three times alternately with DMF and anhydrous ethanol, and centrifuged at 8000 rpm for 10 minutes after each wash to remove unloaded copper nanocubes and other impurities. The washed precipitate is then placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain copper nanocubes@Fe-TCPP MOF composite materials, i.e., porphyrin metal-organic framework composite materials, which are then sealed and stored for later use.

[0090] S12. Weigh 0.12g of copper chloride into 10mL of deionized water and stir until completely dissolved to obtain a copper precursor solution; weigh 0.048g of CTAB and 0.048g of PVP and dissolve them in 20mL of deionized water, then heat and stir at 60℃ until transparent to obtain a first surfactant solution; weigh 0.32g of ascorbic acid and dissolve it in 10mL of deionized water to obtain a reducing agent solution.

[0091] The copper precursor solution was slowly added dropwise to the first surfactant solution, and the mixture was stirred and heated for 10 minutes at a constant temperature of 60°C to form a blue-green transparent solution. Nitrogen or argon gas was then introduced into the blue-green transparent solution for 10 minutes, followed by the rapid addition of the reducing agent solution. At this point, the solution color gradually changed from blue-green to reddish-brown (Cu). 2+ →Cu 0 The mixture was heated to 100℃ and stirred for 1 hour until the reaction was completely colorless. During this period, an inert gas protection was maintained. The resulting mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of deionized water was added to the precipitate and ultrasonically dispersed for 5 minutes. The mixture was then centrifuged again at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of anhydrous ethanol was added to the precipitate (to remove residual organic matter). The mixture was ultrasonically dispersed and centrifuged at 10,000 rpm. The supernatant was discarded. If the supernatant was still turbid, the mixture was washed with ethanol once more and the supernatant was discarded. The precipitate was copper nanocubes, which are copper nanoparticles.

[0092] Add 0.4 mmol of ZnSO4 and 20.0 mg of PVP to 16 mL of a first organic solvent containing DMF and ethanol in a volume ratio of 3:1. After complete dissolution, add 12 mg of TCPP and sonicate for 15 minutes. Then pour the sonicated solution into a 20 mL stainless steel autoclave lined with Teflon. Place the autoclave in a constant temperature oven and carry out a solvothermal reaction at 80 °C for 24 hours. During the reaction, metal ions coordinate with porphyrin ligands to gradually form porphyrin MOF crystals. After the reaction, the reaction vessel is allowed to cool naturally to room temperature. The product in the reaction vessel is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes. The precipitate is collected and washed three times with DMF. After each wash, the precipitate is centrifuged at 8000 rpm for 10 minutes to remove unreacted metal salts, ligands and other impurities. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain dried Zn-TCPPMOF material, which is then sealed and stored for later use.

[0093] Accurately weigh the prepared Zn-TCPP MOF material (metalloporphyrin MOF material) and add it to 10 mL of DMF. Sonicate the mixture for 30 minutes to ensure that the Zn-TCPP MOF material is uniformly dispersed in the DMF, thus obtaining dispersion A. Take an appropriate amount of the prepared copper nanocubes and add them to dispersion A. Sonicate the mixture for 30 minutes to ensure that the copper nanocubes are uniformly dispersed in the system containing Zn-TCPP MOF material. Control the mass ratio of copper nanocubes to porphyrin MOF to be 1:10 to obtain a mixed solution. Transfer the mixed solution to a 50 mL beaker and react it with magnetic stirring in a water bath at 80 °C for 24 hours. In this process, copper nanocubes are loaded onto the surface or pores of the Zn-TCPP MOF material through surface coordination or electrostatic adsorption, forming copper nanocubes@Zn-TCPP MOF composite materials. After the reaction, the mixture is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes to collect the precipitate. The precipitate is washed three times alternately with DMF and anhydrous ethanol, and centrifuged at 8000 rpm for 10 minutes after each wash to remove unloaded copper nanocubes and other impurities. The washed precipitate is then placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain the copper nanocubes@Zn-TCPP MOF composite material, i.e., porphyrin metal-organic framework composite material, which is sealed and stored for later use.

[0094] S13. Weigh 0.12g of copper chloride into 10mL of deionized water and stir until completely dissolved to obtain a copper precursor solution; weigh 0.048g of CTAB and 0.048g of PVP and dissolve them in 20mL of deionized water, then heat and stir at 60℃ until transparent to obtain a first surfactant solution; weigh 0.32g of ascorbic acid and dissolve it in 10mL of deionized water to obtain a reducing agent solution.

[0095] The copper precursor solution was slowly added dropwise to the first surfactant solution, and the mixture was stirred and heated for 10 minutes at a constant temperature of 60°C to form a blue-green transparent solution. Nitrogen or argon gas was then introduced into the blue-green transparent solution for 10 minutes, followed by the rapid addition of the reducing agent solution. At this point, the solution color gradually changed from blue-green to reddish-brown (Cu). 2+ →Cu 0The mixture was heated to 100℃ and stirred for 1 hour until the reaction was completely colorless. During this period, an inert gas protection was maintained. The resulting mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of deionized water was added to the precipitate and ultrasonically dispersed for 5 minutes. The mixture was then centrifuged again at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of anhydrous ethanol was added to the precipitate (to remove residual organic matter). The mixture was ultrasonically dispersed and centrifuged at 10,000 rpm. The supernatant was discarded. If the supernatant was still turbid, the mixture was washed with ethanol once more and the supernatant was discarded. The precipitate was copper nanocubes, which are copper nanoparticles.

[0096] Add 0.4 mmol of Zr(NO3)4·5H2O and 20.0 mg of PVP to 16 mL of a first organic solvent with a DMF and ethanol volume ratio of 3:1. After complete dissolution, add 12 mg of TCPP and sonicate for 15 minutes. Then pour the sonicated solution into a 20 mL stainless steel autoclave lined with Teflon. Place the autoclave in a constant temperature oven and carry out a solvothermal reaction at 80 °C for 24 hours. During the reaction, metal ions coordinate with porphyrin ligands to gradually form porphyrin MOF crystals. After the reaction, the reaction vessel is allowed to cool naturally to room temperature. The product in the reaction vessel is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes. The precipitate is collected and washed three times with DMF. After each wash, the precipitate is centrifuged at 8000 rpm for 10 minutes to remove unreacted metal salts, ligands and other impurities. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain dried Zr-TCPP MOF material, which is then sealed and stored for later use.

[0097] Accurately weigh the prepared Zr-TCPP MOF material (metalloporphyrin MOF material) and add it to 10 mL of DMF. Sonicate the mixture for 30 minutes to ensure that the Zr-TCPP MOF material is uniformly dispersed in the DMF, thus obtaining dispersion A. Take an appropriate amount of the prepared copper nanocubes and add them to dispersion A. Sonicate the mixture for 30 minutes to ensure that the copper nanocubes are uniformly dispersed in the system containing Zr-TCPP MOF material. Control the mass ratio of copper nanocubes to porphyrin MOF to be 1:10 to obtain a mixed solution. Transfer the mixed solution to a 50 mL beaker and react it with magnetic stirring in a water bath at 80 °C for 24 hours. In this process, copper nanocubes are loaded onto the surface or pores of Zr-TCPP MOF materials through surface coordination or electrostatic adsorption, forming copper nanocubes@Zr-TCPP MOF composite materials. After the reaction, the mixture is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes to collect the precipitate. The precipitate is washed three times alternately with DMF and anhydrous ethanol, and centrifuged at 8000 rpm for 10 minutes after each wash to remove unloaded copper nanocubes and other impurities. The washed precipitate is then placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain copper nanocubes@Zr-TCPP MOF composite materials, i.e., porphyrin metal-organic framework composite materials, which are then sealed and stored for later use.

[0098] S14. Weigh 0.12g of copper chloride into 10mL of deionized water and stir until completely dissolved to obtain a copper precursor solution; weigh 0.048g of CTAB and 0.048g of PVP and dissolve them in 20mL of deionized water, then heat and stir at 60℃ until transparent to obtain a first surfactant solution; weigh 0.32g of ascorbic acid and dissolve it in 10mL of deionized water to obtain a reducing agent solution.

[0099] The copper precursor solution was slowly added dropwise to the first surfactant solution, and the mixture was stirred and heated for 10 minutes at a constant temperature of 60°C to form a blue-green transparent solution. Nitrogen or argon gas was then introduced into the blue-green transparent solution for 10 minutes, followed by the rapid addition of the reducing agent solution. At this point, the solution color gradually changed from blue-green to reddish-brown (Cu). 2+ →Cu 0The mixture was heated to 100℃ and stirred for 1 hour until the reaction was completely colorless. During this period, an inert gas protection was maintained. The resulting mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of deionized water was added to the precipitate and ultrasonically dispersed for 5 minutes. The mixture was then centrifuged again at 10,000 rpm for 10 minutes. The supernatant was discarded. 10 mL of anhydrous ethanol was added to the precipitate (to remove residual organic matter). The mixture was ultrasonically dispersed and centrifuged at 10,000 rpm. The supernatant was discarded. If the supernatant was still turbid, the mixture was washed with ethanol once more and the supernatant was discarded. The precipitate was copper nanocubes, which are copper nanoparticles.

[0100] Add 0.4 mmol of anhydrous Fe(NO3)2 and 20.0 mg of PVP to 16 mL of a first organic solvent containing DMF and ethanol in a volume ratio of 3:1. After complete dissolution, add 12 mg of TBPP and sonicate for 15 minutes. Then pour the sonicated solution into a 20 mL stainless steel autoclave lined with Teflon. Place the autoclave in a constant temperature oven and carry out a solvothermal reaction at 80 °C for 24 hours. During the reaction, metal ions coordinate with porphyrin ligands to gradually form porphyrin MOF crystals. After the reaction, the reaction vessel is allowed to cool naturally to room temperature. The product in the reaction vessel is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes. The precipitate is collected and washed three times with DMF. After each wash, the precipitate is centrifuged at 8000 rpm for 10 minutes to remove unreacted metal salts, ligands and other impurities. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain dried Fe-TBPP MOF material, which is then sealed and stored for later use.

[0101] Accurately weigh the prepared Fe-TBPP MOF material (metalloporphyrin MOF material) and add it to 10 mL of DMF. Sonicate the mixture for 30 minutes to ensure that the Fe-TBPP MOF material is uniformly dispersed in the DMF, thus obtaining dispersion A. Take an appropriate amount of the prepared copper nanocubes and add them to dispersion A. Sonicate the mixture for 30 minutes to ensure that the copper nanocubes are uniformly dispersed in the system containing the Fe-TBPP MOF material. Control the mass ratio of copper nanocubes to porphyrin MOF to be 1:10 to obtain a mixed solution. Transfer the mixed solution to a 50 mL beaker and react it with magnetic stirring in a water bath at 80 °C for 24 hours. In this process, copper nanocubes are loaded onto the surface or pores of Fe-TBPP MOF material through surface coordination or electrostatic adsorption, forming copper nanocubes@Fe-TBPP MOF composite material. After the reaction, the mixture is transferred to a centrifuge tube and centrifuged at 8000 rpm for 10 minutes to collect the precipitate. The precipitate is washed three times alternately with DMF and anhydrous ethanol, and centrifuged at 8000 rpm for 10 minutes after each wash to remove unloaded copper nanocubes and other impurities. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 12 hours to obtain the copper nanocubes@Fe-TBPP MOF composite material, i.e., porphyrin metal-organic framework composite material, which is sealed and stored for later use.

[0102] S2. Take 0.005g of each of the above four composite materials and ultrasonically disperse them in 1ml of anhydrous ethanol. Add 50ul of solution to each and deposit them on the nylon filter membrane. Dry them under vacuum at 50℃ to obtain a 2×2 bioamine SERS array sensor.

[0103] S3. Optimization of SERS detection time: 50 μL of the target biogenic amine was incubated with the sensor. Raman spectroscopy was performed every 10 minutes until the Raman signal no longer changed. This experiment was repeated three times. The 241 and 410 cm⁻¹ values ​​before and after the reaction between the sensor and the target biogenic amine were calculated. -1 The ratio of the intensity of Raman characteristic peaks, expressed as I 410 / I 241 The time with the largest ratio is the optimal detection time.

[0104] S4. Detection of biogenic amines: Ten biogenic amines closely related to food spoilage (cadaverine, putrescine, histamine, etc., all at a uniform concentration of 10 μM) were selected. Two parallel samples were used for each biogenic amine, and five replicate tests were performed. Data range: 150-1650 cm⁻¹ -1 The obtained spectral data will be used to construct a multi-model analysis system encompassing PCA, OPLS-DA, and SVM. The results are as follows: Figure 1 As shown, confusion matrix analysis reveals that the SERS sensor array ( Figure 1b) has an overall recognition accuracy of 91%, which is higher than that of a single sensor ( Figure 1 a) An 85% improvement in accuracy, representing a 6 percentage point increase. Experiments demonstrate that the SERS array combined with hyperspectral analysis can accurately identify unknown biogenic amines. Furthermore, a calibration map was constructed using PLS-R to compare the quantitative accuracy and precision between the sensor array and the AgNPs@HOF sensor. Figure 2 As shown, the SERS sensor array exhibits better linear correlation (RL). 2 >0.980), and its root mean square error is 0.130.

[0105] Detection and Analysis

[0106] 1) XRD analysis

[0107] The copper nanocubes@Fe-TCPP MOF composite material prepared in Example 3 was subjected to XRD analysis, and the results are as follows: Figure 3 As shown.

[0108] from Figure 3 Analysis shows that 2θ appears at 43.3°, 50.4°, and 74.1°, which corresponds to the crystal structure of face-centered cubic Cu, and corresponds to the (111)(200)(220) crystal planes of Cu, respectively.

[0109] 2) FTIR analysis

[0110] The copper nanocubes@Zn-TCPP MOF composite material prepared in Example 3 was subjected to FTIR spectroscopy analysis, and the results are as follows: Figure 4 As shown.

[0111] from Figure 4 Analysis revealed that the sensor surface contains groups such as C=C, C=O, CH, C=N, and Cu-O.

[0112] 3) TEM analysis

[0113] The copper nanocubes@Zn-TCPP MOF composite material prepared in Example 3 was subjected to TEM analysis, and the results are as follows: Figure 5 As shown.

[0114] from Figure 5 Analysis revealed that CuNPs@Zn-TCPP consists of spherical copper nanoparticles coated with sheet-like ZnTCPP.

[0115] 4) XPS Analysis

[0116] XPS analysis was performed on the copper nanocubes@Zr-TCPP MOF composite material prepared in Example 3, and the results are as follows: Figure 6 As shown.

[0117] from Figure 6 Analysis shows that the peaks at 183.00, 285.00, 531.00, 399.00, and 935.00 eV correspond to the electron binding energies of Zr3d, C1s, O1s, N1s, and Cu2p in CuNPs@Zr-TCPP MOF, respectively.

[0118] 5) UV-VIS analysis

[0119] The copper nanocubes@Zn-TCPP MOF composite material prepared in Example 3 was subjected to UV-VIS analysis, and the results are as follows: Figure 7 As shown.

[0120] from Figure 7 Analysis shows that porphyrin-based MOF materials such as Zn-TCPP typically exhibit a strong absorption peak (Soret band) around 400 nm, accompanied by multiple Q-band absorption peaks. Therefore, Figure 4 Similar absorption peaks can be observed in the composite material, indicating the presence of a typical porphyrin structure.

[0121] 6) SERS spectral analysis

[0122] The copper nanocubes@Fe-TCPP MOF composite material prepared in Example 3 (corresponding to...) Figure 8 CuNP@FeTCPP), copper nanocubes@Zr-TCPP MOF composites (corresponding to...) Figure 8 CuNP@ZrTCPP and copper nanocubes@Zn-TCPP MOF composites (corresponding to...) Figure 8 SERS spectral analysis was performed on CuNP@ZnTCPP, and the results are as follows: Figure 8 As shown.

[0123] from Figure 8 Analysis revealed that the SERS spectra of the three composite materials all exhibited strong enhancement effects due to the surface plasmon resonance of copper nanoparticles. However, due to the different metal nodes (Fe, Zr, and Zn) in the three composite materials, their MOF structures differed in chemical composition and physical properties, leading to different Raman peak positions and intensities in the SERS spectra.

[0124] 7) Detection of biogenic amines in real samples and construction of a freshness detection model.

[0125] (1) Preparation of pork samples: Different parts of pork, including tenderloin and hind leg, were selected and stored at 4℃ and 25℃. Starting from the fresh state, samples were taken every 24 hours for 7 consecutive days to monitor the changes in volatile basic nitrogen (TVB-N) content. In addition, pork tissue homogenate was taken, acidic extraction solution was added, and after centrifugation, the supernatant was collected and the pH was adjusted to 7.0-8.5 to optimize biogenic amine adsorption.

[0126] (2) Detection of volatile gases: Pork samples were placed at the bottom of a sealed container, and the 2×2 biogenic amine SERS array sensor prepared in Example 3 was placed on top of the container. To verify the excellent performance of the array gas sensor in identifying and grading the freshness of meat products, VOCs hyperspectral data of pork samples with different storage times (0, 12h, 1d, 2d, 3d, 4d, 5d, 6d, 7d) were constructed and analyzed. Orthogonal partial least squares discriminant analysis (OPLS-DA) model was used as a reference unsupervised classification technique to analyze the spectral data collected from each sensor. The results are as follows: Figure 9 As shown.

[0127] from Figure 9 Analysis shows that meat stored at 25°C for different times exhibits good differentiation. The clear separation between these confidence ellipses indicates that the constructed SERS platform effectively distinguishes meat samples.

[0128] (3) Acquisition and feature extraction of SERS sensor array images: The 2×2 biogenic amine SERS array sensor prepared in Example 3 was used to detect and identify different types of biogenic amines. This was achieved by combining SERS hyperspectral images (…). Figure 10 ) and PCA ( Figure 11 a) OPLS-DA ( Figure 11 b) Data analysis verified the accuracy of the biogenic amine SERS array sensor in distinguishing biogenic amines.

[0129] from Figure 12 , 13 It can be seen that different types of biogenic amines can be distinguished very well.

[0130] (4) Pork Freshness Testing: After volatile gas testing, the volatile basic nitrogen (TVB-N) content of the pork was determined using the national standard method for TVB-N testing. The results are as follows: Figure 12 As shown, the TVB-N content gradually increased during storage, and the difference in variation between samples from the same batch was less than 0.3 mg / 100g. According to national standards, the threshold between freshness and staleness of pork is 15 mg / 100g; after reaching this critical point, the TVB-N content increases rapidly.

[0131] (5) The 2×2 biogenic amine SERS array sensor prepared in Example 3 was placed on the top layer of a transparent glass petri dish without contacting the food sample placed on the bottom layer. It was stored for 7 days at 5°C and 25°C. Based on the TVB-N content, all obtained SERS spectra were classified into different freshness categories (fresh, not fresh, and spoiled), resulting in a total of 160 SERS hyperspectral data to construct a dataset for SVM evaluation. A machine learning model based on the SVM algorithm was used to grade the meat freshness.

[0132] 6) Verification of the actual detection effect of the prediction model

[0133] When the spectral data of the sample is imported into the SVM model, it gives the most likely freshness category to which the meat belongs. For example... Figure 13 As shown, the diagonal of the confusion matrix displays the accuracy of correctly classified samples, indicating that the overall accuracy of the SVM model is improved by the dimension of the VOC fingerprint of the sensor array, achieving a discrimination accuracy of 90%. This demonstrates that the constructed SVM prediction model has ideal performance.

[0134] In summary, this study developed a specific array sensor for volatile gases in food based on SERS sensing and machine learning algorithms. By analyzing the changes in SERS signals caused by the reaction of biogenic amines with each sensor unit, biogenic amines were analyzed, and a corresponding predictive model was established to determine food freshness. The results show that the model has stable and efficient predictive performance. This invention is universally applicable to food detection. When using the sensor array to detect other meat products such as beef, lamb, chicken, duck, and fish, only a new model needs to be built based on the sensor array data and the TVB-N value.

[0135] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for preparing a porphyrin metal-organic framework composite material, characterized in that, Includes the following steps: The copper precursor solution was added to the first surfactant solution for the first heating reaction, then the reducing agent solution was added, the temperature was increased, the reaction was centrifuged, and the precipitate was washed and purified to obtain copper nanoparticles. A transition metal salt and a second surfactant are added to a first organic solvent, followed by the addition of a porphyrin ligand. A solvothermal reaction is then carried out, followed by centrifugation. The precipitate is washed and dried to obtain a porphyrin metal-organic framework material. The porphyrin metal-organic framework material is dispersed in a second organic solvent to obtain dispersion A; the copper nanoparticles are dispersed in dispersion A, and then a second heating reaction is carried out. After centrifugation, the precipitate is washed and dried to obtain the porphyrin metal-organic framework composite material.

2. The method for preparing the porphyrin metal-organic framework composite material according to claim 1, characterized in that, The copper precursor solution is selected from copper chloride solution; And / or, the transition metal salt is selected from at least one of cobalt salts, nickel salts, zinc salts, iron salts, and copper salts; And / or, the porphyrin ligand is selected from at least one of tetra(4-carboxyphenyl)porphyrin (TCPP), 5,10,15,20-tetra(4-carboxyphenyl)porphyrin (H6TCPP), 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetra(4-bromophenyl)porphyrin (TBPP) and 5,10,15,20-tetra(4-methoxyphenyl)porphyrin (TMPP).

3. The method for preparing the porphyrin metal-organic framework composite material according to claim 1, characterized in that, The first surfactant is selected from a mixture of hexadecyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP); And / or, the reducing agent is selected from ascorbic acid; And / or, the first organic solvent is selected from a mixture of dimethylformamide (DMF) and anhydrous ethanol; And / or, the second surfactant is selected from polyvinylpyrrolidone (PVP); And / or, the second organic solvent is selected from dimethylformamide (DMF).

4. The method for preparing the porphyrin metal-organic framework composite material according to claim 1, characterized in that, The temperature of the first heating reaction is 55~65℃, and the time is 5~15min; And / or, the temperature of the heating reaction is 95~105℃ and the time is 50~70min; And / or, the temperature of the solvothermal reaction is 70~90℃ and the time is 22~26h; And / or, the temperature of the second heating reaction is 75~85℃, and the time is 22~26h.

5. The method for preparing the porphyrin metal-organic framework composite material according to claim 1, characterized in that, The mass ratio of the copper nanoparticles to the porphyrin metal-organic framework material is 1:5 to 1:

10.

6. A porphyrin metal-organic framework composite material prepared by the preparation method according to any one of claims 1 to 5.

7. The application of a porphyrin metal-organic framework composite material prepared by the preparation method according to any one of claims 1 to 5 as a sensor.

8. A bioamine SERS array sensor, characterized in that, Including porphyrin metal-organic framework composites prepared by the preparation method according to any one of claims 1 to 5.

9. The method for preparing a biogenic amine SERS array sensor according to claim 8, characterized in that, Includes the following steps: At least two of the porphyrin metal-organic framework composite solutions were deposited on a nylon filter membrane and vacuum dried at 50°C for 10 min to obtain a bioamine SERS array sensor.

10. The application according to claim 9, characterized in that, The biogenic amine SERS array sensor is used to detect biogenic amines in food.

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