Nanoplasmin for detecting phenolic compounds, quantitative detection method of phenolic compounds

Abstract

This invention discloses a nanozyme for the detection of phenolic compounds and a quantitative detection method for phenolic compounds. The nanozyme comprises an organometallic framework material and copper loaded on the surface of the organometallic framework material, possessing a core-shell structure. The active metal catalytic center is loaded on the material surface, which helps to improve the utilization efficiency and catalytic activity of the active center, thereby enhancing the detection capability of large molecular weight phenolic compounds. Based on the standard addition method, the nanozyme of this invention can be used for the quantitative analysis of BPA in environmental water and thermal paper, exhibiting high accuracy and sensitivity, and strong anti-interference ability. The quantitative detection method of this invention can be used in conjunction with an image acquisition device for quantitative calculation of phenolic compounds, further simplifying the detection of phenolic compounds.

Description

Technical Field

[0001] This invention relates to a colorimetric analysis reagent, and more particularly to a nanozyme for the detection of phenolic compounds, as well as a method for preparing the nanozyme and a method for the quantitative detection of phenolic compounds. Background Technology

[0002] Bisphenol A (BPA) is a typical endocrine disruptor compound. Because it mimics the activity of endogenous estrogen, it can interfere with reproductive development, immune regulation, and metabolic balance by binding to estrogen receptors. BPA is widely used in the production of polycarbonate plastics, and its unreacted monomers are also present as key color-developing additives in thermal paper. Thermal paper products, such as receipts, tickets, and shipping labels, are ubiquitous in commercial activities. Routine analysis of BPA typically requires complex instruments, such as high-performance liquid chromatography (HPLC) and chromatography-mass spectrometry (GC-MS, LC-MS), limiting its use due to reliance on bulky and expensive equipment and complex pretreatment procedures.

[0003] Colorimetric analysis is a method that converts color changes into detectable signals. It offers advantages such as low cost, ease of operation, and wide applicability. Methods for analyzing phenolic pollutants using colorimetry have been reported in the literature. For example, Professor Yang Yi's research group reported on a bioinspired Cu / Zn-ZIF nanozyme with excellent laccase-like activity for selective colorimetric detection of phenolic pollutants (Talanta, 2025, 127862). This method involves doping Cu, the active component that catalyzes the oxidation of phenolic compounds, into the Zn-ZIF framework, forming a nanozyme with laccase-like activity. The detection of phenolic pollutants utilizes the principle that "the Cu / Zn-ZIF nanozyme oxidizes phenolic compounds, condenses with an amino-containing chromogenic agent, causing a color change, and triggering a change in absorbance." However, because Cu exists in a doped form, the structural size of the phenolic compound being detected needs to match the size of the Zn-ZIF framework; otherwise, the catalytic ability of the nanozyme is not as good as that of natural laccase.

[0004] BPA has a bisphenol structure, and its molecular structure and size differ from those of monophenylcyclic phenols. Therefore, it is crucial to develop reliable methods for the detection and monitoring of BPA. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a nanozyme for the detection of phenolic compounds; another purpose of this invention is to provide a quantitative detection method for phenolic compounds.

[0006] Technical solution: The present invention provides a nanozyme for the detection of phenolic compounds. The nanozyme has a core-shell structure, comprising an organometallic framework material and copper loaded on the surface of the organometallic framework material, wherein the organometallic framework material is ZIF-8.

[0007] Preferably, the nanozyme is spherical with a particle size range of 176.35±17.06 nm.

[0008] The aforementioned method for synthesizing nanozymes involves mixing water-soluble zinc salt and 2-methylimidazole, reacting at room temperature for at least 1 hour; then adding water-soluble copper salt and reacting for at least 1 hour; finally adding N2H4·H2O and reacting for at least 4 hours to obtain nanozyme ZIF-8@Cu.

[0009] Preferably, the mass ratio of the water-soluble zinc salt to 2-methylimidazole is 0.4~0.6:1, and the addition ratio of the water-soluble copper salt and N2H4·H2O relative to 2-methylimidazole is 0.9~1.1 μmmol / mg.

[0010] The present invention provides a method for the quantitative detection of phenolic compounds, comprising the following steps:

[0011] Take the sample to be tested, add the amino colorimetric reagent, the aforementioned nanozyme ZIF-8@Cu, and the target phenolic compound standard, and carry out the colorimetric reaction. Calculate the concentration of the phenolic compound based on the change in absorbance of the reaction solution or the change in RGB data in computer-readable form.

[0012] Preferably, the amino colorimetric agent is 4-aminoantipyridine.

[0013] Preferably, the final concentration of the nanozyme ZIF-8@Cu in the reaction solution is 75~125 μg / mL. More preferably, the final concentration of the nanozyme ZIF-8@Cu is 90~110 μg / mL.

[0014] Preferably, the reaction solution for the colorimetric reaction has a pH of 6.5 to 8, the reaction temperature is 20 to 70°C, and the reaction duration is 50 to 70 minutes.

[0015] Preferably, in the reaction solution for the colorimetric reaction, the concentration of sodium chloride is less than 110 mmol / L and the volume concentration of ethanol is less than 20%.

[0016] Preferably, the method for calculating the concentration of phenolic compounds using RGB value changes in a computer-readable format is as follows: obtain a photograph of the reaction solution after color development, import it into DeepSeek image design software (GRB image color picking software), obtain the R, G, and B values, and fit a working curve with the concentration of phenolic compounds and the (R+G) / B ratio as the coordinate axes, respectively.

[0017] Preferably, the pH of the reaction solution is maintained using MES buffer and / or HEPES buffer.

[0018] Beneficial Effects: Compared with the prior art, the present invention has the following beneficial effects: 1. A core-shell nanozyme (ZIF-8@Cu) was designed and synthesized. The active ingredient copper, which catalyzes the oxidation of phenolic compounds, is dispersed on the surface of ZIF-8 by in-situ deposition to improve its catalytic efficiency and avoid the limitation of the size of the organometallic framework material on the contact of the active ingredient with the analyte. This allows the nanozyme to detect larger biphenyl ring phenolic compounds and can be used for quantitative analysis of BPA in thermal paper; 2. The quantitative detection of BPA using nanozymes has high accuracy and sensitivity, strong anti-interference ability, a linear range of 2.5–400 μM, and a detection limit of 0.516 μM; 3. The apparatus required for quantitative BPA detection is greatly simplified, and the applicability is wide: quantitative BPA detection can be completed by analyzing and extracting the RGB signal of the reaction solution using a handheld image acquisition device, without the need for a spectrophotometer. Attached Figure Description

[0019] Figure 1 Characterization images of ZIF-8@Cu prepared in Example 1: (A) Transmission electron microscope image of ZIF-8; (B) Particle size distribution of ZIF-8; (C) Transmission electron microscope image of ZIF-8@Cu; (D) Dark-field transmission electron microscope image of ZIF-8@Cu; (E) Particle size distribution of ZIF-8@Cu; (F) Elemental mapping image of ZIF-8@Cu;

[0020] Figure 2 Example 2 experimental characterization diagrams: (A) Reaction principle of 2,4-DP and 4-AP catalyzed by ZIF-8@Cu enzyme; (B) UV-Vis absorption spectra of 2,4-DP, 4-AP, their mixture and ZIF-8@Cu mixture; (C) Statistical graph of absorbance at 510 nm of 2,4-DP+4-AP+ZIF-8@Cu reaction mixture as a function of ZIF-8@Cu concentration; (D) Spectrum of absorbance of ZIF-8@Cu catalyzed oxidation of 2,4-DP and 4-AP as a function of reaction time; (E) UV-Vis spectra of 2,4-DP+4-AP + ZIF-8@Cu solution in saturated oxygen, air and saturated nitrogen buffer; (F) Confirmation of ZIF-8@Cu laccase activity: 1. Reaction of ZIF-8@Cu with 2,4-DP; 2. Adding supernatant of HRP and TMB after centrifugation of solution; 3. Adding H2O2 to solution 2.

[0021] Figure 3The effects of different conditions on the catalytic activity of ZIF-8@Cu nanozymes were investigated: (A) temperature; (B) pH; (C) NaCl content; (D) ethanol content; (E) type of buffer solution; and (F) storage time.

[0022] Figure 4 ZIF-8@Cu nanozyme for BPA detection: (A) Feasibility analysis of BPA detection; (B) Absorption spectra of BPA at different concentrations; (C) Absorbance values ​​of BPA at different concentrations; (D) Linear calibration graph of BPA absorption at different concentrations; (E) Anti-interference analysis; (F) Selectivity analysis;

[0023] Figure 5 A schematic diagram of the RGB analysis method for detecting BPA: (A) Heatmap of R, G and B values ​​after the reaction of mixed solutions of BPA + 4-AP + ZIF-8@Cu with different concentrations; (B) Color changes and corresponding R, G and B color extraction; (C) Fitting curve of (R + G) / B value versus BPA concentration. Detailed Implementation

[0024] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0025] Reagents, materials, and instruments: Bisphenol A (BPA), 2,4-dichlorophenol (2,4-DP), 4-aminoantipyrrolidone (4-AP), dimethylimidazolium (2-MeIM), hydrazine hydrate (N2H4·H2O), hydrogen peroxide (H2O2), 3,3′,5,5′-tetramethylbenzidine (TMB), 2-(N-morpholine)acetic acid (MES), N-(2-hydroxyethyl)piperazine-N′-2-ethanesulfonic acid (HEPES), Zn(NO3)2, CuCl2, etc., were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. All other chemicals and reagents were commercially available analytical grade (AR). All buffers and solutions were prepared using ultrapure water during the experiments. Transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) were performed on a JEM-2800 (JEOLLtd., Japan). UV-vis absorbance measurements were performed using an Infinite-200PRO multi-functional microplate reader (Tecan, Switzerland). Water bath heating was performed using a DK-S26 electric thermostatic water bath (Shanghai Jinghong Experimental Equipment Co., Ltd.).

[0026] Example 1: Preparation and characterization of nanozyme ZIF-8@Cu

[0027] (1) Synthesis of ZIF-8: 2.5 mL of 2-methylimidazole solution with a concentration of 4 mg / mL was added to a glass reaction flask, and then 2.5 mL of Zn(NO3)2·6H2O solution with a concentration of 2 mg / mL was added. The reaction was carried out at room temperature for 1 h to obtain ZIF-8.

[0028] (2) Continue to add 100 μL of 0.1 M CuCl2 solution to the mixed solution obtained in step (1), and after reacting for 1 h, add 100 μL of N2H4·H2O and continue to react for 4 h.

[0029] (3) After the reaction is complete, the product is collected by centrifugation. The product is washed three times each with ultrapure water and methanol, dried, and stored in a refrigerator at 4°C.

[0030] The characterization results of the synthesized nanozyme ZIF-8@Cu in this embodiment are as follows: Figure 1 As shown, Figure 1 Parts A and B, 2-methylimidazole solution and Zn 2+ The synthesized ZIF-8 exhibits a distinctly spherical shape with a particle size of approximately 110.38 nm; Figure 1 In portions C, D, and E, ZIF-8@Cu maintains a spherical morphology, and the particle size gradually increases to 176.35 nm, as shown below. Figure 1 Elemental analysis of the F portion of ZIF-8@Cu shows that O, Cu, Zn and N elements are present, with Cu mainly distributed on the surface of the material.

[0031] In this embodiment, Cu ions were successfully deposited on the surface of ZIF-8 using an in-situ deposition method to prepare ZIF-8@Cu nanozyme.

[0032] Example 2: Verification of ZIF-8@Cu Laccase Activity

[0033] ZIF-8@Cu was dispersed in ultrapure water to prepare a 1 mg / mL solution. The catalytic activity of ZIF-8@Cu was determined using 100 μL of 10 mM 2,4-dichlorophenol (2,4-DP) as the substrate and 100 μL of 10 mM 4-aminoantipyridine (4-AP) as the colorimetric reagent. The amount of ZIF-8@Cu added was 100 μL, and the final volume of different reaction solutions was limited to 1 mL. If the volume of the reaction solution was insufficient, it was supplemented with 30 mM MES buffer.

[0034] like Figure 2In Part B, after reacting at 25℃ for 1 hour, no obvious characteristic absorption peak was observed at 510 nm in the UV absorption spectra of the reaction solutions containing ZIF-8@Cu, 2,4-DP, and 4-AP alone, as well as the mixed reaction solutions containing 2,4-DP + ZIF-8@Cu, 4-AP + ZIF-8@Cu, and 2,4-DP + 4-AP. When the three components 2,4-DP, 4-AP, and ZIF-8@Cu were present simultaneously, the solution color turned dark pink, and a characteristic absorption peak appeared at 510 nm, indicating that the ZIF-8@Cu nanozyme can mimic laccase activity and catalyze the oxidation of 2,4-DP. Figure 2 Part A is a schematic diagram of the principle of ZIF-8@Cu catalysis for 2,4-DP and 4-AP color development.

[0035] Example 3: Optimization of ZIF-8@Cu nanozyme catalytic conditions

[0036] 3.1 Final Concentration Optimization: The procedure was as follows: Based on Section 2.1, 100 μL of 10 mM 2,4-DP and 100 μL of 10 mM 4-AP were added simultaneously to the reaction solution. The amount of ZIF-8@Cu added was varied to achieve a final concentration range of 25–100 µg / mL. The absorbance change at 510 nm of the reaction solution was then measured. The results are as follows: Figure 2 As shown in section C, the catalytic activity of ZIF-8@Cu nanozymes increases in a concentration-dependent manner within the range of 25–100 µg / mL, reaching its optimum at a concentration of 100 µg / mL.

[0037] 3.2 Reaction Time Optimization: 100 μL of 10 mM 2,4-DP, 100 μL of 10 mM 4-AP, and 100 μL of 1 mg / mL ZIF-8@Cu were simultaneously added to the reaction solution. The absorbance change at 510 nm was measured within the reaction time range of 0–60 min. The results are as follows: Figure 2 As shown in part D, the absorbance at 510 nm increases continuously with the extension of reaction time, indicating that the substrate oxidation products gradually increase over time.

[0038] 3.3 Optimization of the Reaction Environment: The presence of O2 is essential for the catalytic oxidation of laccase. To further confirm that ZIF-8@Cu possesses catalytic properties similar to laccase, 100 μL of 10 mM 2,4-DP, 100 μL of 10 mM 4-AP, and 100 μL of 1 mg / mL ZIF-8@Cu were simultaneously added to the reaction solution. The reaction atmosphere was changed to air, N2, and O2, respectively, and the absorbance changes were measured. Figure 2In the E part, the N2-treated group had the lowest absorbance, while the O2-treated group had the highest absorbance. This indicates that O2 plays an important role in the ZIF-8@Cu catalytic reaction, a characteristic similar to that of laccase.

[0039] 3.4 Determination of Optimal Temperature: Similar to the procedure in Section 3.2, change the temperature from 20 °C to 80 °C and measure the change in absorbance. The test results are as follows: Figure 3 As shown in Part A, the activity significantly increases with increasing temperature in the range of 20 °C to 60 °C, reaching a maximum at 60 °C, indicating that this temperature is the optimal reaction temperature for the nanozyme. When the temperature exceeds 60 °C, the activity shows a slow decreasing trend, but still remains at a high level, demonstrating excellent thermal stability.

[0040] 3.5 Determination of Optimal pH: 100 μL of 2,4-DP (10 mM), 100 μL of 4-AP (10 mM), and 700 μL of MES buffer (30 mM, pH adjusted to 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10, 11) were added to the reaction solution. Then, 100 μL of ZIF-8@Cu (1 mg / mL) was added, and the reaction was carried out at 25 ℃ for 1 h. The test results are as follows: Figure 3 As shown in Part B, the activity of ZIF-8@Cu gradually increased as the pH rose from 2.0 to 7.0, and reached its optimal activity at pH 7.0.

[0041] 3.6 Optimal Ionic Strength Test: Similar to the procedure in Section 3.2, but with the sodium chloride concentration in the reaction system varied from 0-500 mM using 1M sodium chloride solution. The test results are as follows: Figure 3 As shown in section C, the catalytic activity of ZIF-8@Cu increases slowly with increasing sodium chloride concentration. This may be because the presence of salt increases the ionic strength of the solution and produces a "salting-out" effect, thereby enhancing the catalytic performance of ZIF-8@Cu, consistent with the salt-promoted nanozyme catalytic behavior reported in the literature.

[0042] 3.7 Optimal Organic Solvent Concentration Test: Similar to the procedure in Section 3.2, replace part of the MES buffer with ethanol to achieve an ethanol volume ratio of 0-100% v / v. The test results are as follows: Figure 3 As shown in section D, the addition of ethanol significantly reduced the catalytic activity of the nanozyme, and it was completely inhibited when its concentration reached 80%.

[0043] 3.8 Buffer Type Test: Similar to the procedure in Section 3.2, replace MES with different types of buffers such as PBS, H2O, and HEPES. The test results are as follows: Figure 3As shown in section E, ZIF-8@Cu exhibits higher catalytic activity in MES buffer solution than in other buffer systems.

[0044] In summary, 60 ℃ was selected as the optimal reaction temperature and 7.0 as the optimal pH for the catalytic reaction in subsequent experiments.

[0045] Example 4: Validation of reaction mechanism and test of nanozyme storage time

[0046] 4.1 The catalytic product is a key factor in evaluating the properties of laccase, which can directly reduce O2 to water. In the catalytic reaction, the supernatant obtained after centrifugation of the reaction mixture of 2,4-DP and ZIF-8@Cu is as follows: Figure 2 In the F portion, horseradish peroxidase (HRP) and TMB were added to the supernatant, labeled 1 and 2 respectively. No color change was observed, indicating that the system did not contain H2O2. When additional H2O2 was added to reaction solution 2, the solution immediately turned blue, indicating that O2 was reduced to water instead of H2O2. These results confirm that the ZIF-8@Cu nanozyme exhibits laccase-like properties.

[0047] 4.2 Storage time test: such as Figure 3 The F portion of the nanozyme maintained high catalytic activity after being stored at 4°C for 15 days, indicating that the nanozyme has high structural stability and highlighting its practical application prospects.

[0048] Example 5: Verification of BPA activity and BPA detection using ZIF-8@Cu

[0049] 5.1 As Figure 4 In part A, 100 μL of 10 mM BPA and 100 μL of 1 mg / mL ZIF-8@Cu were added separately, as well as a mixed reaction solution containing 100 μL of 10 mM BPA, 100 μL of 10 mM 4-AP, 100 μL of 1 mg / mL ZIF-8@Cu, and 100 μL of 10 mM 4-AP. The mixture was heated to 60 °C and reacted for 1 h. No obvious characteristic absorption peak was observed at 510 nm. However, when the three-component reaction solution containing BPA, 4-AP, and ZIF-8@Cu was added, an obvious characteristic absorption peak was observed at 510 nm.

[0050] 5.2 Anti-interference capability test

[0051] To verify the feasibility and accuracy of this method in detecting bisphenol A in actual thermal paper samples, its anti-interference ability and selectivity were systematically evaluated. Potential interfering substances, such as metal ions, anions, and other substances that may exist in the thermal paper, were selected. Figure 4The results of the E and F sections showed that the constructed ZIF-8@Cu nanozyme exhibited excellent selectivity for BPA, and the presence of other substances did not elicit a significant signal response, indicating that the system has good anti-interference ability. Furthermore, this method does not require complex pretreatment steps, further highlighting its practical potential in BPA detection.

[0052] 5.3 Colorimetric Working Curve

[0053] Establish a working curve for the analytical test: Prepare BPA gradient standard solutions (0 mM, 0.025 mM, 0.1 mM, 0.25 mM, 0.5 mM, 0.75 mM, 1.0 mM, 1.5 mM, 2.0 mM, 3.0 mM, 4.0 mM, 5.0 mM, 7.5 mM, 10 mM). Add 100 μL of each concentration of BPA solution, 100 μL of ZIF-8@Cu (1 mg / mL), and 100 μL of 4-AP (10 mM) to 700 μL of LME ES buffer (30 mM). The reaction system is 1 mL. After thorough mixing, perform the colorimetric reaction under optimized conditions (60 ℃, pH=7, 60 min). Measure the absorbance of the reaction system at characteristic wavelengths using a microplate reader. Plot a standard working curve with BPA concentration on the x-axis and absorbance on the y-axis. The results are shown below. Figure 4 As shown in sections B, C, and D, the absorbance at 500 nm gradually increases with increasing BPA concentration within the range of 2.5–1000 μM. Further analysis indicates that absorbance exhibits a good linear relationship with BPA concentration in the range of 2.5–400 μM (R0). 2 =0.997), and the detection limit was 0.516 μM.

[0054] 5.4 RGB Three Primary Color Analysis Method Working Curve

[0055] Following the same procedures as in Section 5.3, reaction solutions with different BPA concentrations were obtained. After the colorimetric reaction, images of the reaction solutions were captured using an image acquisition device to obtain RGB mixed data. In this invention, the image acquisition device was a Honor 300 smartphone.

[0056] like Figure 5 In the A, B, and C sections, image color sampling software (ecjson.com / image_color#ea1a5e) was used to separate the acquired RGB mixed data, obtaining R, G, and B channel data respectively. BPA concentration was plotted on the x-axis, and the (R+G) / B ratio on the y-axis to analyze whether a linear relationship existed between the two. Within the 5-100 μM concentration range, the (R+G) / B ratio showed a good linear relationship with BPA concentration, with a linear correlation coefficient R0. 2 =0.996.

[0057] 5.5 BPA Analysis in Actual Samples

[0058] Thermal paper, river water, and tap water were selected as actual samples to verify the actual performance of the detection method. The thermal paper sample preparation method was as follows: 2 g of thermal paper sample was weighed, cut into small pieces, and 40 mL of methanol was added. The sample was then placed on a shaker for 10 minutes for extraction, followed by ultrasonic-assisted extraction for another 10 minutes. The supernatant was collected after centrifugation.

[0059] Take 10 mL of supernatant, river water, and tap water respectively, divide them into several equal portions, and add different amounts of bisphenol A (BPA) standard solution to each portion to prepare BPA-spiked samples of different concentrations. Mix 100 μL of the spiked sample solution with 100 μL of 1 mg / mL ZIF-8@Cu nanozyme and 100 μL of 10 mM chromogenic reagent, and make up the volume to 1 mL with 30 mM MES buffer. After reacting at 60℃ for 60 min, measure the absorbance at 510 nm wavelength, or acquire RGB data using an image acquisition module, and calculate the spike recovery rate using both analytical methods.

[0060] As shown in Table 1, the spiked recoveries of BPA using the colorimetric method ranged from 98.28% to 103.30%, with relative standard deviations (RSDs) as low as 1.07% to 4.24%, indicating that the method has good accuracy and precision. As shown in Table 2, the RGB analysis method exhibited analytical performance comparable to the colorimetric method, with spiked recoveries ranging from 97.22% to 105.22% and RSDs of 1.27% to 4.33%.

[0061] The above results demonstrate that the detection system constructed in this invention is suitable for the reliable determination of BPA in various real-world samples, and is simple to operate, requiring no complex pretreatment, thus possessing good potential for practical application. Using RGB values ​​to convert color signals into digital indicators simplifies the sensing process, enabling on-site quantitative analysis of BPA without the need for large instruments or spectrophotometers, providing a practical solution for the accurate and sensitive detection of BPA in real-world environmental samples.

[0062] Table 1: Recovery of Bisphenol A from Real Samples (Thermal Paper, River Water, Tap Water) Using Colorimetric Detection Method

[0063]

[0064] Table 2: Recovery of BPA from real samples (thermal paper, river water, tap water) using RGB analysis.

[0065]

[0066] This invention successfully prepared ZIF-8@Cu with a core-shell structure and laccase-like activity. ZIF-8@Cu exhibits high catalytic efficiency and environmental stability for phenolic compounds. When applied to the detection of phenolic pollutants, particularly BPA in thermal paper, ZIF-8@Cu demonstrates good accuracy and precision.

[0067] Furthermore, the phenolic pollutant analysis method of the present invention can be further simplified: by directly using a handheld image acquisition device, such as a smartphone, to extract and analyze RGB values ​​and calculate the BPA concentration in the sample, this simplified analysis method shows good prospects in different environmental monitoring applications.

Claims

1. A nanozyme for the detection of phenolic compounds, characterized in that, The nanozyme has a core-shell structure, comprising an organometallic framework material and copper loaded on the surface of the organometallic framework material, wherein the organometallic framework material is ZIF-8.

2. The nanozyme according to claim 1, characterized in that, The nanozyme is spherical with a particle size range of 176.35±17.06 nm.

3. The method for synthesizing nanozymes according to claim 1 or 2, characterized in that, Mix water-soluble zinc salt and 2-methylimidazole, and react at room temperature for at least 1 hour; then add water-soluble copper salt and react for at least 1 hour; finally add N2H4·H2O and continue reacting for at least 4 hours to obtain nanozyme ZIF-8@Cu.

4. The synthesis method according to claim 3, characterized in that, The mass ratio of the water-soluble zinc salt to 2-methylimidazole is 0.4 to 0.6:1, and the addition ratio of the water-soluble copper salt and N2H4·H2O relative to 2-methylimidazole is 0.9 to 1.1 μmmol / mg.

5. A method for the quantitative detection of phenolic compounds, characterized in that, Includes the following steps: Take the sample to be tested, add the amino colorimetric reagent, the nanozyme as described in claim 1 or 2, and the target phenolic compound standard sample, and carry out a colorimetric reaction. Calculate the concentration of the phenolic compound based on the change in absorbance of the reaction solution or the change in RGB data in computer-readable form.

6. The quantitative detection method according to claim 5, characterized in that, The amino colorimetric agent is 4-aminoantipyridine, and the final concentration of the nanozyme ZIF-8@Cu in the reaction solution is 75~125μg / mL.

7. The quantitative detection method according to claim 5, characterized in that, The reaction solution for the colorimetric reaction has a pH of 6.5 to 8, the reaction temperature is 20 to 70°C, and the reaction time is 50 to 70 minutes.

8. The quantitative detection method according to claim 5, characterized in that, In the reaction solution for the colorimetric reaction, the concentration of sodium chloride is less than 110 mmol / L and the volume concentration of ethanol is less than 20%.

9. The quantitative detection method according to claim 5, characterized in that, The method for calculating the concentration of phenolic compounds using RGB value changes in a computer-readable format is as follows: acquire a photo of the reaction solution after color development, import it into image color picking software, obtain the R, G, and B values, and fit a working curve with the concentration of phenolic compounds and the (R+G) / B ratio as the coordinate axes, respectively.

10. The quantitative detection method according to any one of claims 5 to 9, characterized in that, The pH of the reaction solution is maintained using MES buffer and / or HEPES buffer.

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