A method for detecting putrescine using PtPd NPs@TPE fluorescent nanozymes

Abstract

A method for ratiometric detection of putrescine using PtPd NPs@TPE fluorescent nanozymes. This invention first utilizes mesoporous platinum-palladium nanoparticles (PtPd NPs) doped with tetraphenylethylene (TPE) to obtain fluorescent nanoparticles (PtPd NPs@TPE) with oxidase-like activity, which can produce blue fluorescence under 365 nm ultraviolet light excitation. Secondly, this invention utilizes the antioxidant properties of putrescine solution to inhibit the formation of 2,3-diaminophenazine (DAP), an oxidation product, during the oxidation of o-phenylenediamine (OPD) by PtPd NPs@TPE, thereby reducing the DAP content. Based on the relationship between putrescine concentration and the colorimetric intensity of DAP, and the ratio of the yellow fluorescence intensity of DAP at 552 nm to the blue fluorescence intensity of PtPd NPs@TPE at 442 nm, a novel ratiometric fluorescence method for detecting putrescine is constructed. This method can be used to detect actual samples such as dried bean curd, with a detection limit as low as 0.0025 μg / mL.

Description

Technical Field

[0001] This invention relates to a method for detecting putrescine using PtPd NPs@TPE fluorescent nanozymes, belonging to the field of pollutant detection technology. Background Technology

[0002] The freshness of soy products refers to the growth and decomposition process of microorganisms and enzymes within them. Its freshness directly affects the quality and safety of soy products, impacting food hygiene and potentially endangering human health. For both fresh and fermented soy products, rapid, accurate, and effective methods for detecting freshness remain crucial for ensuring food safety and health. Traditionally, freshness assessment relies heavily on personal sensory evaluations, such as the color, odor, and quality of soy products. However, this simple method often depends heavily on subjective judgment and suffers from insufficient confidence. In contrast, evaluating the freshness of soy products by measuring specific indicator substances within them is more accurate and faster. Biogenic amines are small molecules formed from protein molecules under the action of amino acid decarboxylases. They accumulate rapidly during the spoilage of soy products, making them an important indicator of freshness.

[0003] Biogenic amines are a general term for a class of low-molecular-weight nitrogen-containing organic compounds with biological activity. They can be considered as substances formed by replacing 1-3 hydrogen atoms in an ammonia molecule with alkyl or aryl groups. They are commonly found in animals and plants, and are also very prevalent in fermented foods. Biogenic amines are crucial for the normal physiological functions of cells and are essential components of biologically active cells. Different biogenic amines play different roles. Under normal circumstances, the body maintains normal biogenic amine concentrations in cells and tissues through continuous biosynthesis and catabolism. However, excessive exogenous intake can disrupt this balance. If the intake exceeds the body's metabolic capacity, obvious symptoms of biogenic amine poisoning will appear. For example, biogenic amines can enter various tissue systems of the body, leading to excessive secretion of adrenaline and gastric acid, increased blood sugar levels, or elevated blood pressure, causing allergic reactions such as headaches, nausea, palpitations, and respiratory disorders. In severe cases, it can even be life-threatening.

[0004] Currently, common methods for detecting biogenic amines in food include liquid chromatography, electrochemical detection, SERS, colorimetry, and fluorescence methods. While these methods can achieve quantitative detection of biogenic amines in food, they still have drawbacks such as complex sample pretreatment and the need for large and expensive instruments. Therefore, it is of great significance to construct a ratiometric fluorescence modal sensor for detecting the content of biogenic amines in soy products.

[0005] Compared with traditionally synthesized nanomaterials with enzyme activity, platinum-palladium particles, with their strong oxidizing properties, exhibit better enzyme activity and are simpler to synthesize. They also possess significant advantages such as water solubility, biocompatibility, and non-immunogenicity, demonstrating promising prospects for development and utilization. Summary of the Invention

[0006] The purpose of this invention is to provide a method for detecting putrescine using PtPd NPs@TPE fluorescent nanozymes.

[0007] To achieve the above and other related objectives, the technical solution provided by this invention is: a PtPd NPs@TPE fluorescent nanoparticle, wherein the preparation method of the PtPd NPs@TPE fluorescent nanoparticle includes the following steps:

[0008] Step 1: Synthesis of PtPd NPs

[0009] Pluronic F127 was ultrasonically dissolved in an aqueous solution containing H2PtCl6, Pd(CH3COO)2 and hydrochloric acid. After adding ascorbic acid, the mixture was ultrasonically treated. The final product was centrifuged to remove the supernatant, the precipitate was washed with acetone, and the final precipitate was dried and stored for later use.

[0010] Step 2: Synthesis of PtPd NPs@TPE

[0011] Tetraphenylethylene was added to the PtPd NPs solution, stirred, centrifuged, and the supernatant was washed with anhydrous ethanol and finally dissolved in deionized water to obtain the PtPd NPs@TPE fluorescent nanoparticle solution.

[0012] To achieve the above and other related objectives, the present invention provides a method for detecting putrescine, comprising the following steps:

[0013] S1: Measure the fluorescence spectra of standards of different concentrations under excitation at 365 nm wavelength.

[0014] The PtPd NPs@TPE fluorescent nanoparticle solution prepared according to claim 1 was transferred into a container, and different concentrations of putrescine samples to be tested dissolved in water were added. Then, o-phenylenediamine solution was added, and after mixing evenly, the reaction was carried out. After the reaction was completed, the sample was transferred to a cuvette, and the fluorescence spectrum under excitation at a wavelength of 365 nm was measured using a fluorescence spectrophotometer. The ratio of 442 nm to 552 nm was recorded as F1 = F442 nm / F552 nm.

[0015] S2: Constructing the standard curve equation

[0016] The F-value calculated based on fluorescence spectrophotometer measurements and the concentration C of putrescine standard. putrescineConstructing a linear equation, the regression equation for the ultraviolet spectrophotometer is F = aC. putrescine +b;

[0017] S3: Sample Detection

[0018] The F1 value is calculated by replacing the putrescine standard with the sample containing the contaminant and performing fluorescence spectrophotometry. The obtained F1 value is then substituted into the corresponding standard curve equation to calculate the putrescine concentration value of the sample.

[0019] The preferred technical solution is that, in S1, the concentration of the PtPd NPs@TPE fluorescent nanoparticle solution is 50.0 μg / mL; the concentration of the o-phenylenediamine solution is 10.0 mmol / L; and the volume ratio between the PtPd NPs@TPE fluorescent nanoparticle solution and putrescine, o-phenylenediamine solution, and aqueous solution is 10:10:20:160.

[0020] The preferred technical solution is that the regression equation for the fluorescence spectrophotometer is F = -0.0229C. putrescine +0.02613;

[0021] The preferred technical solution is that the sample to be tested is a liquid sample; the sample is filtered with filter paper or filter membrane with a pore size of 0.22μm before testing, and the filtrate is collected.

[0022] The advantages of this invention compared to the prior art are:

[0023] 1. This invention uses TPE with aggregation-induced emission properties to dope mesoporous platinum-palladium particles to form PtPdNPs@TPE fluorescent nanoparticles. This method for synthesizing PtPd NPs@TPE fluorescent nanoparticles is simple and exhibits good fluorescence properties. They can be used as an internal control in constructing ratiometric fluorescence detection methods, effectively avoiding interference from the external environment.

[0024] 2. This invention utilizes the antioxidant properties of putrescine as an inhibitor of the yellow fluorescent DAP produced by the oxidation of OPD. The antioxidant properties exhibited by putrescine reduce the production of the fluorescent product DAP. Based on the relationship between putrescine concentration and colorimetric intensity, and based on the yellow fluorescence of DAP at 552 nm and the blue fluorescence of PtPd NPs@TPE at 442 nm, a rapid method for determining putrescine using ratiometric fluorescence mode was established. This method was successfully applied to the detection of actual samples, with a detection limit as low as 0.014 μg / mL. The development of this method is of great significance for the rapid and accurate detection of putrescine concentration in food. Attached Figure Description

[0025] Figure 1Characterization data for PtPd NPs@TPE fluorescent nanoparticles are presented below. (A) represents the TEM image of PtPd NPs@TPE; (B) represents the EDX spectrum of PtPd NPs@TPE; (CE) represent the STEM images and elemental mappings of Pt and Pd in ​​PtPd NPs@TPE, respectively; (F) represents the fluorescence emission spectra of TPE (aqueous solution), PtPd NPs@TPE, and TPE (dichloromethane solution) at 365 nm, with insets showing their corresponding images under a 365 nm UV lamp; (G) represents the Zeta potential of PtPd NPs and PtPd NPs@TPE; and (H) represents the hydrated particle size of PtPd NPs and PtPd NPs@TPE.

[0026] Figure 2 The fluorescence stability of PtPd NPs@TPE fluorescent nanoparticles in acetate-sodium acetate buffer at different pH values ​​was evaluated.

[0027] Figure 3 Fluorescence spectra of PtPd NPs@TPE fluorescent nanoparticles to verify enzyme activity. (A, B) represent the verification of the oxidase activity mechanism of PtPd NPs@TPE, where 1 represents OPD, 2 represents PtPd NPs+OPD, 3 represents PtPd NPs+OPD+N2, 4 represents PtPd NPs@TPE+OPD, and 5 represents PtPd NPs@TPE+OPD+N2; (C) represents the EPR spectra of DMPO and DMPO+PtPd NPs@TPE alone; (D) represents the EPR spectra of TEMP and TEMP+PtPd NPs@TPE alone; (EF) represents the enzyme kinetic equation activity verification of PtPd NPs@TPE.

[0028] Figure 4 The optimization of various reaction conditions for the PtPd NPs@TPE-putrescine-AIE-OPD reaction is presented. (A) corresponds to the optimization of reaction temperature; (B) corresponds to the optimization of reaction time.

[0029] Figure 5The images show the fluorescence emission spectra of PtPd NPs@TPE-AIE-OPD after the reaction. (A) represents the fluorescence emission spectra of PtPd NPs@TPE-AIE-OPD reacting with different concentrations of putrescine; (B) represents the fluorescence emission spectra of PtPd NPs@TPE-AIE-OPD reacting with some common amino acids (such as methionine (Met), valine (Val), tyrosine (Tyr), serine (Ser), threonine (Thr), phenylalanine (Phe), tryptophan (Trp), leucine (Leu)) and other biogenic amines (such as cadaverine (Cad), putrescine (Put), spermidine (Spe), histamine (His)).

[0030] Figure 6 This is a standard curve for para-putramine concentrations in the range of 0-500 μg / mL using ratiometric fluorescence method.

[0031] Figure 7 A comparison of different detection methods for putrescine. Detailed Implementation

[0032] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in these embodiments.

[0033] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Please refer to... Figure 1-6 It should be noted that the structures, ratios, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the scope of the invention. Therefore, they have no substantial technical significance, and any modifications to the structure, changes in ratios, or adjustments to size are not permitted. The following embodiments are provided to better understand the invention, but are not intended to limit it. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the experimental materials used in the following embodiments were purchased from conventional biochemical reagent stores.

[0034] Unless otherwise specified, all reagents or materials described in the following examples are commercially available.

[0035] The technical solution of the present invention will be further described in detail below with reference to examples.

[0036] Example 1: A method for preparing PtPd NPs@TPE fluorescent nanoparticles

[0037] (1) Synthesis of PtPd NPs

[0038] 20.0 mg of Pluronic F127 was dissolved by sonication in an aqueous solution containing 1.8 mL of H2PtCl6 (20 mM), 0.2 mL of Pd(CH3COO)2 (20 mM), and 44 μL of HCl (6 M). 2.0 mL of ascorbic acid (100 mM) was added, and the mixture was sonicated for 4.0 h. The final product was centrifuged at 10,000 rpm for five minutes, the supernatant was discarded, the precipitate was washed three times with acetone, and the final precipitate was dried in an oven and stored for later use.

[0039] (2) Synthesis of PtPd NPs@TPE

[0040] Take 100 μL of 12.0 mg / mL TPE and add it to 1.0 mL of PtPd NPs (1.0 mg / mL). Stir for 6.0 h, centrifuge and take the supernatant. Wash three times with anhydrous ethanol aqueous solution and finally dissolve in DI water. Store for later use. The concentration of PtPd NPs@TPE is the same as the content of added PtPd NPs.

[0041] The PtPd NPs@TPE fluorescent nanoparticles prepared in this invention are a material that simultaneously possesses oxidase-like activity and fluorescence properties. See also... Figure 1 A. The PtPd NPs@TPE fluorescent nanoparticles of this invention can be clearly observed using TEM, revealing their nanostructure with a size of approximately 80.0 nm, indicating nanoscale dimensions; their EDX spectrum ( Figure 1 B) It can be found that it is composed of Pt and Pd elements; through its STEM and elemental mapping diagram ( Figure 1 CE (elemental chromatogram) can determine the elemental composition and mesoporous structure; while fluorescence spectroscopy (…) Figure 1 F) It can be observed that TPE exhibits relatively disordered fluorescence in water, but no fluorescence in dichloromethane solution, verifying that it is an aggregation-induced emission (AIE) fluorophore material. After doping into mesoporous PtPd NPs, the resulting PtPd NPs@TPE exhibits uniformly distributed blue fluorescence; its potential and particle size distribution (…) Figure 1 (G and 1H) results show that the surface potential and hydrated particle size of PtPd NPs did not change significantly after TPE doping, proving that TPE was doped into the interior of the mesoporous PtPd NPs. These results demonstrate the successful synthesis of this fluorescent nanomaterial.

[0042] See Figure 2The fluorescence stability of PtPd NPs@TPE fluorescent nanomaterials was demonstrated. Specifically, when PtPd NPs@TPE was added to acetate-sodium acetate buffer solutions at different pH values, its fluorescence remained almost unchanged, proving that PtPd NPs@TPE fluorescent nanomaterials possess strong fluorescence stability.

[0043] Example 2: Enzymatic activity and mechanism verification of PtPd NPs@TPE fluorescent nanoparticles

[0044] 50.0 μg / mL PtPd NPs@TPE was reacted with 10.0 mM OPD and 1.0 mM TMB, respectively. After the reaction, the fluorescence emission spectrum and UV absorption spectrum were measured. In addition, DMPO was used as a superoxide anion scavenger and TEMP as a singlet oxygen scavenger to verify the mechanism of the oxidase-like activity of PtPd NPs@TPE.

[0045] See Figure 3 The results demonstrate the enzymatic activity of PtPd NPs@TPE fluorescent nanomaterials reacting with OPD. In Figures A and B, 1 shows OPD alone without producing a fluorescence emission peak, while 2 shows PtPd NPs and OPD coexisting, with OPD being oxidized to DAP, producing a fluorescence emission peak at 552 nm. After introducing N2 into 2 (i.e., 3), a significant decrease in the fluorescence emission peak at 552 nm is observed. 4 shows the fluorescence emission spectrum after the reaction of PtPd NPs@TPE and OPD, revealing relatively obvious fluorescence emission peaks at both 442 nm and 552 nm. However, after introducing N2 (i.e., 5), a significant decrease in the fluorescence emission peak at 552 nm is observed. The results indicate that PtPd NPs in PtPd NPs@TPE primarily undertake oxidase activity. After incorporation with TPE, PtPd NPs@TPE exhibits a strong fluorescence emission peak at 442 nm, further confirming the successful synthesis of this fluorescent nanozyme PtPd NPs@TPE with oxidase-like activity. In Figures C and D, a relatively obvious superoxide anion signal can be observed (Figure C), while no singlet oxygen signal peak appears in Figure D. This further verifies that the oxidase-like activity of PtPd NPs@TPE involves reacting with dissolved oxygen in the solution to generate superoxide anions, which can then further oxidize OPD to produce DAP. Figures E and F represent the reaction rates of PtPd NPs@TPE with different concentrations of TMB, and the Mitchell constant (K) was calculated based on these rates. m (0.143) and maximum reaction rate (V max The value is 26.32, which proves that the synthesized PtPd NPs@TPE has strong enzyme activity.

[0046] Example 3: Optimization of conditions for detecting putrescine based on PtPd NPs@TPE fluorescence modality

[0047] To obtain the optimal detection conditions, we selected and optimized each reaction condition (such as reaction temperature and reaction time) to make the reaction optimal.

[0048] See Figure 4 (A) shows the fluorescence spectra of PtPd NPs@TPE (50ug / mL) + putrescine (0μg / mL) + OPD (10mmol / L) after reaction at different temperatures (25, 30, 35, 40, 45℃). It can be found that the fluorescence intensity reaches the highest at 552nm at 35℃, so we selected 35℃ as the reaction condition. (B) shows the fluorescence intensity F at 442nm of PtPd NPs@TPE (50ug / mL) + putrescine (0μg / mL) + OPD (10mmol / L) after reaction for different times (0, 5, 10, 15, 20, 25, 30min). 442nm The fluorescence intensity F at 552 nm 552nm The ratio F 442nm / F 552nm The reaction time gradually decreased over time, and then stabilized after 20 minutes. Therefore, we chose 20 minutes as the optimal reaction time.

[0049] Example 4: Construction of a method for detecting putrescine based on PtPd NPs@TPE ratio fluorescence modality

[0050] 10 μL of a 1 mg / mL PtPd NPs@TPE solution and 10 μL of putrescine solutions of different concentrations were added to 160 μL of ultrapure water, followed by 20 μL of a 100 mM OPD solution. The mixture was allowed to react for 20 min, and the fluorescence emission spectrum at 365 nm excitation was measured using a fluorescence spectrophotometer. The ratio of the fluorescence emission at 442 nm to 552 nm was recorded as F1 = F... 442nm / F 552 nm .

[0051] See Figure 5 A, Figure 6 And Table 1, the change in the ratio of fluorescence emission spectra at 442 nm to 552 nm (F = F 442 nm / F 552nmThere was a good linear relationship between the concentration of putrescine and the concentration of putrescine in the range of 0.01-500 μg / mL. The regression equation was F = 0.0269C + 0.2613, the correlation coefficient was 0.9940, and the detection limit was 0.014 μg / mL. The fitting process was as follows: the ratio of the fluorescence emission spectrum of the system at 442 nm to 552 nm under 365 nm excitation after adding 0-500 μg / mL putrescine to the system and the corresponding putrescine concentration were imported into Origin software. The linear equation F = 0.0269C + 0.2613 with a correlation coefficient of 0.9940 was obtained by fitting the addition of 0-500 μg / mL putrescine and the corresponding absorbance change. The detection limit was obtained by 3σ / k, where σ is the standard deviation of the ratio of the fluorescence emission spectrum of the PtPd NPs@TPE-OPD-Put system without putrescine at 365 nm excitation for 11 tests, and k is the slope of the obtained linear equation.

[0052] Table 1. Test values ​​of different concentrations of putrescine in Example 3.

[0053] Putrescine concentration (μg / mL) <![CDATA[F 442 nm / F 552 nm ]]> 0 0.250 0.01 0.257 0.05 0.259 0.1 0.263 0.5 0.271 1 0.288 5 0.395 10 0.573 25 0.827 50 1.281 100 2.623 250 6.026 500 7.839

[0054] Example 5: Selectivity Validation of a Method for Detecting Putrescine Based on TPE@PtPd Fluorescence Modal

[0055] 10 μL of a 1 mg / mL PtPd NPs@TPE solution and 10 μL of different amino acid solutions (e.g., methionine (Met), valine (Val), tyrosine (Tyr), serine (Ser), threonine (Thr), phenylalanine (Phe), tryptophan (Trp), leucine (Leu)) and different biogenic amine solutions (e.g., cadaverine (Cad), putrescine (Put), spermidine (Spe), histamine (His)) were added to 160 μL of ultrapure water. Then, 20 μL of a 100 mM OPD solution was added. The mixture was reacted for 20 min, and its fluorescence spectrum under 365 nm excitation was measured using a fluorescence spectrophotometer.

[0056] See Figure 5 B. Selective fluorescence spectrum of this method. This method can be used to detect biogenic amines, and in complex environmental systems, it shows excellent selectivity and accuracy in the detection of putrescine compared to other possible substances.

[0057] Example 6: Detection of putrescine in samples

[0058] (1) Sample pretreatment

[0059] Dried tofu purchased from surrounding markets was stored at 30-38℃ for more than three days to allow it to naturally rot, thus becoming a food sample containing putrescine. Before testing, the sample was chopped up, dissolved in ultrapure water, filtered through 0.22μm filter paper or membrane, and the filtrate was collected for testing.

[0060] (2) Test sample

[0061] Determine the fluorescence spectrum of the sample under 365 nm excitation.

[0062] Transfer ultrapure water to a container, add the sample to be tested dissolved in the ultrapure water, add PtPd NPs@TPE and OPD solution, mix well, and then transfer to a cuvette. Measure the fluorescence spectrum at 365 nm excitation using a fluorescence spectrophotometer, and record the ratio of 442 nm to 552 nm as F1 = F. 442 nm / F 552 nm .

[0063] (3) Calculate the putrescine concentration in the dried bean curd sample.

[0064] Substituting the calculated value F1 into the fluorescence spectroscopy regression equation F = 0.0269C + 0.2613, the concentration C of putrescine in the sample was obtained. putrescine The value is the putrescine concentration, which can be obtained as 8.4 μg / mL through the fluorescence spectrum regression equation.

[0065] Table 2. Relationship between putrescine content and freshness of soy products

[0066]

[0067] Example 7: Detection of putrescine in actual samples

[0068] (1) Sample pretreatment

[0069] Fresh dried tofu and non-rotten fermented dried tofu were used as references. Rotten dried tofu and expired fermented dried tofu (purchased from surrounding markets and stored at 30-38℃ for more than three days) were used as samples. Before testing, the samples were chopped with a knife, dissolved in ultrapure water, filtered through 0.22μm filter paper or filter membrane, and the filtrate was collected for testing.

[0070] (2) Test sample

[0071] Determine the fluorescence spectrum of the sample under 365 nm excitation.

[0072] Transfer ultrapure water to a container, add the sample to be tested dissolved in the ultrapure water, add PtPd NPs@TPE and OPD solution, mix well, and then transfer to a cuvette. Measure the fluorescence spectrum at 365 nm excitation using a fluorescence spectrophotometer, and record the ratio of 442 nm to 552 nm as F1 = F. 442 nm / F 552 nm ;

[0073] (3) Calculate the putrescine concentration in the dried bean curd sample.

[0074] Substituting the calculated value F1 into the fluorescence spectroscopy regression equation F = 0.0269C + 0.2613, the concentration C of putrescine in the sample was obtained. putrescine The value is the putrescine concentration, which can be obtained through the fluorescence spectrum regression equation.

[0075] The test results showed that no putrescine was detected in fresh dried tofu, and the putrescine content in rotten dried tofu was less than 40 ug / mL. Putrescine was detected in fresh dried tofu that had spoiled, with a content of 8.9 ug / mL, while the putrescine content in rotten dried tofu was 231.2 ug / mL.

[0076] Example 8: Comparison of detection methods for putrescine

[0077] like Figure 7 As shown, there are various methods for detecting putrescine, including fluorescence detection, liquid chromatography, gas chromatography, and capillary electrophoresis. Compared with the above methods, this method is simple to operate and does not require complex operation and large-scale instrumentation. In addition, compared with these methods, the detection results of this method are more accurate, have a wider linear range, and higher detection precision.

[0078] The above description is merely a preferred embodiment for explaining the present invention and is not intended to limit the present invention in any way. Therefore, any modifications or changes made to the present invention under the same inventive spirit should still be included within the scope of protection intended by the present invention.

Claims

1. A PtPd NPs@TPE fluorescent nanoparticle, characterized in that, The preparation method of the PtPd NPs@TPE fluorescent nanoparticles includes the following steps: Step 1: Synthesis of PtPd NPs Pluronic F127 was ultrasonically dissolved in an aqueous solution containing H2PtCl6, Pd(CH3COO)2 and hydrochloric acid. After adding ascorbic acid, the mixture was ultrasonically treated. The final product was centrifuged to remove the supernatant, the precipitate was washed with acetone, and the final precipitate was dried and stored for later use. Step 2: Synthesis of PtPd NPs@TPE Tetraphenylethylene was added to the PtPd NPs solution, stirred, centrifuged, and the supernatant was washed with anhydrous ethanol and finally dissolved in deionized water to obtain the PtPd NPs@TPE fluorescent nanoparticle solution.

2. A method for detecting putrescine, characterized in that, Includes the following steps: S1: Determine the fluorescence spectra of standards at different concentrations under excitation at 365 nm wavelength. The PtPd NPs@TPE fluorescent nanoparticle solution of claim 1 was transferred to a container, and different concentrations of putrescine samples to be tested dissolved in water were added. Then, o-phenylenediamine solution was added, and the mixture was stirred evenly before the reaction was carried out. After the reaction was completed, the mixture was transferred to a cuvette, and the fluorescence spectrum under excitation at a wavelength of 365 nm was measured using a fluorescence spectrophotometer. The ratio of 442 nm to 552 nm was recorded as F1=F 442 nm / F 552 nm ; S2: Constructing the standard curve equation The F1 value calculated based on fluorescence spectrophotometer measurements and the concentration C of putrescine standard. putrescine Constructing a linear equation, the regression equation for the fluorescence spectrophotometer is F1 = aC putrescine + b; S3: Sample Detection The F1 value is calculated by replacing the putrescine standard with the sample containing the contaminant and performing fluorescence spectrophotometry. The obtained F1 value is then substituted into the corresponding standard curve equation to calculate the putrescine concentration value of the sample.

3. The method for detecting putrescine according to claim 2, characterized in that, In S1, the concentration of the PtPd NPs@TPE fluorescent nanoparticle solution was 50.0 μg / mL; the concentration of the o-phenylenediamine solution was 10.0 mmol / L; and the volume ratio of the PtPd NPs@TPE fluorescent nanoparticle solution to putrescine, o-phenylenediamine solution, and aqueous solution was 10:10:20:

160.

4. The method for detecting putrescine according to claim 2, characterized in that, The regression equation for the fluorescence spectrophotometer is F1 = 0.0229C. putrescine + 0.02613.

5. The method for detecting putrescine according to claim 2, characterized in that, The sample to be tested is a liquid sample; the sample is filtered with 0.22 μm filter paper or filter membrane before testing, and the filtrate is collected.

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