An electrochemical / colorimetric dual-mode metal-organic framework nanosenor and a preparation method thereof and application thereof in Hg 2+ detection

Abstract

The application discloses an electrochemical / colorimetric dual-mode metal organic framework nanosenor and a preparation method thereof and application of the nanosenor in Hg 2+ detection, and belongs to the technical field of environmental analysis and heavy metal ion detection. The Au-MOF material has weak enzyme-like activity in metal sites, and the enzyme-like activity is significantly excited in the presence of mercury ions, so that the oxidation reaction of a color developing substrate is catalyzed and obvious color change is generated, and colorimetric detection of mercury ions is realized. Meanwhile, the metal sites in the material have metal affinity for mercury ions, and can effectively enrich the mercury ions, so that the current response of mercury ions in the electrochemical detection process is enhanced, and electrochemical detection of mercury ions is realized. The method simultaneously obtains colorimetric signals and electrochemical signals under the same recognition mechanism, and realizes detection and analysis of mercury ions through the cooperative output of the dual signals. The method is simple in operation, rapid in response, and suitable for detection of mercury ions in water samples.

Description

Technical Field

[0001] This invention belongs to the fields of nanotechnology and environmental monitoring technology, specifically relating to a metal-organic framework nanozyme, its preparation method, and its application. Background Technology

[0002] Mercury ions (Hg) 2+ Hg is a highly toxic and bioaccumulative heavy metal ion, widely found in industrial wastewater, natural water bodies, and the ecological environment. 2+ Once inside the human body, Hg can accumulate through the food chain, causing serious damage to the nervous system, immune system, and kidney function, and even leading to irreversible health risks. Therefore, Hg... 2+ Sensitive and reliable detection is of great significance in fields such as environmental monitoring, public health and water quality safety.

[0003] In recent years, nanomaterials have attracted widespread attention in the field of heavy metal ion detection. Among them, metal-organic frameworks (MOFs), as a class of porous crystalline materials constructed from metal nodes and organic ligands, possess characteristics such as large specific surface area, tunable pore structure, abundant functional sites, and ease of structural design, showing promising application prospects in chemical sensing and analytical detection. Hg based on MOF materials... 2+ Detection methods have been extensively studied, among which colorimetric detection has gained attention due to its advantages such as ease of operation and intuitive response.

[0004] However, colorimetric detection is typically based on the analysis of color changes in solutions or materials under specific conditions. While colorimetric methods offer a degree of intuitiveness, accurate values ​​usually still require testing with instruments such as ultraviolet-visible absorption spectroscopy. Furthermore, colorimetric results can be affected by factors such as lighting conditions, sample background, and observer subjectivity; relying solely on a single colorimetric signal limits the accuracy and reliability of the results. Meanwhile, electrochemical detection methods, due to their high sensitivity, fast response speed, and ease of quantitative analysis, are widely used for Hg detection. 2+ Electrochemical detection research is being conducted. However, electrochemical detection typically relies on instruments such as electrochemical workstations to read and analyze signals, resulting in a lack of intuitive visualization of the detection results. Furthermore, under complex sample systems or environmental conditions, even a single electrochemical signal pattern can be subject to interference.

[0005] Against this backdrop, how can we fully leverage the structural and performance advantages of MOF materials as nanomaterials to construct Hg receptors that simultaneously output colorimetric and electrochemical signals based on the same recognition mechanism? 2+ The detection system has become a pressing issue in the current technological field. By coordinating the output of multiple detection signals, it is hoped that mutual verification of detection results can be achieved, thereby improving Hg levels.2+ The reliability and application value of the detection. Summary of the Invention

[0006] Based on the above problems, the purpose of this invention is to provide an Au-MOF material that can be used for Hg in water. 2+ Colorimetric detection can also be used for Hg in water. 2+ Electrochemical detection. This invention utilizes the Au active sites in Au-MOF and Hg... 2+ The metal-philic interaction between them specifically enhances the catalase-like activity (POD-like) of Au-MOF, efficiently catalyzing the oxidation of TMB by H2O2, thus achieving the oxidation of Hg. 2+ Colorimetric quantitative detection, simultaneously detecting Au active sites and Hg 2+ Metal-friendly interactions between them favor Hg 2+ The accumulation of Hg on the electrode surface increases the current response, thus enabling the control of Hg. 2+ Electrochemical detection.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution.

[0008] An electrochemical / colorimetric dual-mode detection of Hg 2+ An Au-MOF nanozyme sensor, wherein the Au-MOF nanozyme contains Au; the specific surface area of ​​the Au-MOF nanozyme sensor is 617.25 m². 2 g -1 The aperture distribution is mainly concentrated at 1.41 nm, and transmission electron microscopy shows ordered lattice fringes with a spacing of 1.09 nm.

[0009] The preparation method of the Au-MOF nanozyme sensor includes the following steps:

[0010] (1) Solution A: Mix 185.5 mg of 3,5-dimethyl-1H-pyrazole-4-carboxaldehyde (1.5 mmol) with 8.31 mL of anhydrous methanol and 437.5 μL of triethylamine until homogeneous;

[0011] (2) Solution B: Dissolve 350 mg of chloro(tetrahydrothiophene) gold (I) (1.09 mmol) in 8.31 mL of acetone;

[0012] (3) Add solution A dropwise into solution B and stir for 10 minutes;

[0013] (4) Filter and collect the white crystalline powder Au-CTC;

[0014] (5) In a Schlenk tube, add 96 mg Au-CTC (0.1 mmol), 42.35 mg 2,2'-(5'-(4-(cyanomethyl)phenyl)-[1,1':3',1''-terphenyl]-4,4''-diyl)diacetonitrile (0.1 mmol), 1 mL mesitylene, 1 mL 1,4-dioxane and 200 μL of 4 M NaOH solution;

[0015] (6) The tube was rapidly frozen in a liquid nitrogen bath at 77 °C and degassed by three thawing cycles using a refrigeration pump;

[0016] (7) After the mixture has returned to room temperature, it is ultrasonically treated for 30 minutes, and then heated at 100 °C for 72 hours;

[0017] (8) The Au-MOF nanozyme sensor is obtained by filtration, washing and solvent exchange with N,N-dimethylformamide and methanol.

[0018] Furthermore, the stirring time in step (3) is 5-60 minutes.

[0019] Furthermore, the 2,2'-(5'-(4-(cyanomethyl)phenyl)-[1,1':3',1''-terphenyl]-4,4''-diyl)diacetonitrile in step (5) may be selected from one of the following compounds: 1,3,5-tris(4-cyanophenyl)benzene, 2,2',2''-(1,3,5-triazine-2,4,6-triyl)tri(phenyl-4,1-diyl)triacetonitrile or terephthalic acid acetonitrile.

[0020] Furthermore, the heating temperature in step (7) is 80-150 ℃.

[0021] An electrochemical detection method for mercury ions in water includes an Au-MOF-modified working electrode, wherein the Au-MOF-modified working electrode employs any of the aforementioned Au-MOF nanozyme sensors; the modification method includes: mixing the Au-MOF nanozyme sensor with ethanol in a certain proportion to prepare a modification ink; drop-coating the modification ink onto the electrode surface; and drying to obtain the Au-MOF-modified electrode; immersing the modified electrode in a solution containing Hg 2+ Electrodeposition was performed in an acetic acid buffer solution at a specific potential, followed by detection of Hg using square wave anodic stripping voltammetry (SWASV). 2+ The content of.

[0022] Furthermore, the concentration of the modifying ink is 0.5-3 mg / mL; the amount of the modifying ink dropped onto the electrode is 5 μL to 10 μL; the pH range of the acetate buffer used in the test is 1-7; the voltage range of the electrodeposition is -1 to -1.5 V; and the electrodeposition time is 60-180 seconds.

[0023] Furthermore, the voltage range of the square wave anodic stripping voltammetry (SWASV) is 0-0.6 V.

[0024] A colorimetric detection method for mercury ions in water, employing the Au-MOF nanozyme sensor described in any of the preceding claims; the colorimetric detection method includes: dispersing Au-MOF in distilled water to prepare a solution with a concentration of 2 mg / mL. -1 Au-MOF stock solution was prepared and sonicated for 10 minutes; subsequently, 40 μL of Au-MOF stock solution was added to solutions containing different concentrations of Hg. 2+ The buffer solution was added; H2O2 (30 μL, 30%) and TMB (30 μL, 10 mM) were added sequentially; the reaction system was incubated at 30 °C for 10 minutes and then UV spectrophotometric measurements were performed.

[0025] Furthermore, the concentration of the Au-MOF stock solution is 0.5-3 mg / mL; the Hg 2+ The concentration range is 10-1000 nM; the amount of H2O2 added is 10-60 μL; the amount of TMB added is 10-60 μL.

[0026] By employing the above technical solution, the effective gains of the present invention are:

[0027] Au active sites in Au-MOF serve as Hg 2+ The identification unit is capable of interacting with Hg 2+ It specifically binds to and enhances its enzyme-like activity by accelerating electron transfer, efficiently catalyzing the oxidation of TMB by H2O2 and generating a significant colorimetric signal; simultaneously, Hg is enriched at the electrode interface. 2+ It can generate stable and quantitatively detectable electrochemical signals. Furthermore, the large specific surface area and hollow structure of Au-MOF not only provide abundant active sites but also offer unimpeded mass transfer channels for the diffusion and mass transfer of reactants and products, achieving effective signal amplification at the structural level. Benefiting from these mechanisms and structural advantages, this dual-mode sensor has been successfully applied to the detection of Hg in real-world environmental water samples. 2+ The tests demonstrated good accuracy and reliability. Attached Figure Description

[0028] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings:

[0029] Figure 1 Show the BET diagram and pore size diagram of Au-MOF provided by the embodiments of the present invention; wherein Figure 1 a is the BET diagram of Au-MOF; Figure 1 b is the pore size distribution diagram of Au-MOF;

[0030] Figure 2 Show the transmission electron microscope diagram of Au-MOF provided by the embodiments of the present invention; wherein Figure 2 a is the TEM diagram of Au-MOF; Figure 2 b is Figure 2 the partial enlarged view of a;

[0031] Figure 3 Show the SWAV response diagram of Hg 2+ by the embodiments of the present invention and the comparative example;

[0032] Figure 4 Show the ultraviolet absorption spectrum response diagram of Hg 2+ by the embodiments of the present invention and the comparative example;

[0033] Figure 5 Show the SWAV diagram and its corresponding linear relationship diagram of the electrochemical sensor based on Au-MOF provided by the embodiments of the present invention for different concentrations of Hg 2+ ; wherein Figure 5 a is the SWAV diagram of the Au-MOF electrode for different concentrations of Hg 2+ ; Figure 5 b is Figure 5 the calibration curve corresponding to Hg 2+ in a;

[0034] Figure 6 Show the ultraviolet absorption spectrum diagram and its corresponding linear relationship diagram of the colorimetric sensor based on Au-MOF provided by the embodiments of the present invention for different concentrations of Hg 2+ ; wherein Figure 6 a is the ultraviolet absorption spectrum diagram of Au-MOF for different concentrations of Hg 2+ ; Figure 6 b is Figure 6 the calibration curve corresponding to Hg 2+ in a;

[0035] Figure 7 Show the electrochemical and colorimetric detections of Hg 2+ by Au-MOF prepared using different organic ligands in the embodiments of the present invention; wherein Figure 7 a shows that the obtained electrochemical characteristic peak is located at 0.28 V; Figure 7 b shows that the obtained TMB oxidation characteristic peak is located at 652 nm. Detailed Implementation

[0036] To illustrate the present invention in more detail, the technical solution of the present invention will be further described below with reference to preferred embodiments and accompanying drawings.

[0037] Au-MOF-based colorimetric / electrochemical dual-mode detection of Hg 2+ The method includes the following steps:

[0038] Example 1: Preparation and Characterization of Au-MOF

[0039] 1. Preparation process:

[0040] (1) Solution A: Mix 185.5 mg of 3,5-dimethyl-1H-pyrazole-4-carboxaldehyde (1.5 mmol) with 8.31 mL of anhydrous methanol and 437.5 μL of triethylamine until homogeneous;

[0041] (2) Solution B: Dissolve 350 mg of chloro(tetrahydrothiophene) gold (I) (1.09 mmol) in 8.31 mL of acetone;

[0042] (3) Add solution A dropwise into solution B and stir for 10 minutes;

[0043] (4) Filter and collect the white crystalline powder Au-CTC;

[0044] (5) In a Schlenk tube, add 96 mg Au-CTC (0.1 mmol), 42.35 mg 2,2'-(5'-(4-(cyanomethyl)phenyl)-[1,1':3',1''-terphenyl]-4,4''-diyl)acetonitrile (0.1 mmol), 1 mL mesitylene, 1 mL 1,4-dioxane and 200 μL of 4 M NaOH solution;

[0045] (6) The tube was rapidly frozen in a liquid nitrogen bath at 77 °C and degassed by three thawing cycles using a refrigeration pump.

[0046] (7) After the mixture has returned to room temperature, it is ultrasonically treated for 30 minutes, and then heated at 100 °C for 72 hours.

[0047] (8) Au-MOF was obtained by filtration, washing and solvent exchange with N,N-dimethylformamide and methanol.

[0048] The Au-MOF nanozyme contains Au.

[0049] 2. Structural characterization:

[0050] (1) Pore structure characteristics: Figure 1 The BET test spectrum shows that the BET specific surface area of ​​Au-MOF is 617.25 m². 2 g -1 The pore size distribution is mainly concentrated around 1.41 nm. This combination of high specific surface area and concentrated micropore distribution is beneficial for maximizing the exposure of Au active sites, thereby providing a sufficient reaction interface for subsequent reaction processes.

[0051] (2) The orderliness of materials: Figure 2 The transmission electron microscope (TEM) images show ordered lattice fringes with a spacing of 1.09 nm, corresponding to the (200) crystal plane, indicating that the Au-MOF structure is ordered.

[0052] Example 2: Construction of an electrochemical sensor

[0053] Take 1.0 mg of Au-MOF prepared in Example 1, place it in a centrifuge tube, and add 1 mL of anhydrous ethanol. Sonicate the mixture for 10 minutes until a homogeneous and stable suspension is formed, thus obtaining the modified ink. The concentration of Au-MOF in the modified ink is 0.5 mg / mL to 3 mg / mL.

[0054] Using a micropipette, 3 to 10 μL of the modified ink, preferably 6 μL, is vertically drop-coated onto the surface of a polished and cleaned 3 mm diameter glassy carbon electrode (GCE), ensuring that the droplet completely covers the working surface of the electrode. The electrode is then allowed to air dry at room temperature until the solvent has completely evaporated, thus obtaining the Au-MOF / GCE modified electrode, which serves as the working electrode of the electrochemical sensor.

[0055] Example 3: Hg 2+ Electrochemical detection performance

[0056] Using the modified electrode constructed in Example 2 as the working electrode, a platinum wire electrode as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode, a three-electrode system was formed. The electrolyte was an acetate buffer solution at pH 5. Square wave anodic stripping voltammetry (SWASV) was used for detection, with an amplitude of 0.02 V, a frequency of 25 Hz, a potential step of 5 mV, and a voltage range of 0–0.6 V.

[0057] Square wave anodic stripping voltammetry (SWASV) was used to study Hg at different concentration gradients (5 nM-10 μM). 2+ The solution was tested, and the results were as follows: Figure 5 As shown in figure a, a distinct Hg peak appears at approximately 0.26 V. 2+ Oxidation peak, and peak current varies with Hg 2+ The effect increases with increasing concentration. (Using Hg) 2+A linear fit was performed using the concentration (C, μM) as the x-axis and the corresponding oxidation peak current (I, μA) as the y-axis, yielding a good linear relationship. Figure 5 b): I (μA) = 2.07 C (μM) + 1.54 (R² = 0.998). Based on a signal-to-noise ratio of 3 (S / N=3), the limit of detection (LOD) for DA using this method is 1.49 nM.

[0058] Example 4: Hg 2+ Colorimetric detection performance

[0059] The Au-MOF prepared in Example 1 was dispersed in distilled water to prepare a concentration of 2 mg / mL. -1 Au-MOF stock solution was prepared and sonicated for 10 minutes. Then, 40 μL of Au-MOF stock solution was added to solutions containing different concentrations of Hg. 2+ The buffer solution was added. H₂O₂ (30 μL, 30%) and TMB (30 μL, 10 mM) were then added sequentially. After incubating the reaction system at 30 °C for 10 minutes, the UV absorbance values ​​in the 500-750 nm range were measured.

[0060] Hg at different concentration gradients (10-1000 nM) were analyzed using ultraviolet spectroscopy. 2+ The solution was tested, and the results were as follows: Figure 6 As shown in Figure a, a distinct TMB oxidation peak appears at 652 nm, and the absorbance value increases with Hg. 2+ The effect increases with increasing concentration. (Using Hg) 2+ Using the concentration (C, μM) as the x-axis and the corresponding absorbance value as the y-axis, a linear fit was performed, yielding a good linear relationship. Figure 6 b): Y = 0.00066 C (nM) + 0.099 (R² = 0.996). Based on a signal-to-noise ratio of 3 (S / N=3), this method is effective for Hg. 2+ The limit of detection (LOD) is 7.9 nM.

[0061] Example 5: Synthesis of Au-MOF with different organic ligands

[0062] Following the preparation method of Example 1, only the 2,2'-(5'-(4-(cyanomethyl)phenyl)-[1,1':3',1''-terphenyl]-4,4''-diyl)acetonitrile in step (5) was replaced with an equal amount of 2,2',2''-(1,3,5-triazine-2,4,6-triyl)tri(phenyl-4,1-diyl)triacetonitrile, while keeping all other conditions unchanged, Au-MOF was prepared. The 3 μM Hg was then subjected to the same reaction as in Example 3. 2+Electrochemical detection was performed on 600 nM Hg according to the method in Example 4. 2+ Colorimetric analysis was performed. The results are as follows: Figure 7 As shown, Au-MOF can achieve Hg 2+ Colorimetric and electrochemical dual-mode detection.

[0063] The following is combined with Figure 3 and Figure 4 Explain the differences between the comparative examples and the present invention:

[0064] Comparative Example 1: Au-CTC vs. Hg 2+ Electrochemical and colorimetric detection performance

[0065] Au-CTC was prepared using the method described in Example 1. The electrode was modified according to the method described in Example 2. [The following text appears to be unrelated and possibly a separate sentence fragment:] ...containing 3 μM Hg 2+ SWAV testing was performed in the mixed solution, see Figure 3 The results showed that the oxidation peak current was weaker than that of Au-MOF. Colorimetric detection was performed according to the method in Example 4, and the results indicated that its enzyme activity was weaker than that of Au-MOF (…). Figure 4 The above results indicate that Au-CTC monomers can effectively interact with Hg. 2+ However, due to the accumulation of materials, the full release of Au-CT activity is limited.

[0066] Comparative Example 2: MOFD

[0067] In a Schlenk tube, 22.55 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 24.97 mg of 1,3,5-tris(4-formylphenyl)benzene, 1.5 mL of mesitylene, 0.5 mL of 1,4-dioxane, and 200 μL of 6 M acetic acid solution were added. The tube was rapidly frozen in a liquid nitrogen bath at 77 °C and degassed by three thawing cycles using a freeze pump. After returning to room temperature, the mixture was sonicated for 30 minutes, and then heated at 120 °C for 72 hours. The mixture was filtered and washed with anhydrous 1,4-dioxane to obtain MOFD. Its electrochemical response ( Figure 3 ) and enzyme properties ( Figure 4 The values ​​of ) are the lowest among all materials, further verifying that the main enzyme activity and electrochemical performance of Au-MOF originate from the Au active center.

[0068] The following is a more detailed explanation with reference to the accompanying drawings:

[0069] Figure 1 The BET spectrum of the Au-MOF obtained in this example shows that the synthesized Au-MOF exhibits a typical type I adsorption isotherm, indicating that the material is predominantly microporous. Its BET specific surface area is 617.25 m².2 g -1 The pore size distribution is mainly concentrated around 1.41 nm. This combination of high specific surface area and concentrated micropore distribution is beneficial for maximizing the exposure of Au active sites, thereby providing a sufficient reaction interface for subsequent reaction processes.

[0070] Figure 2 The image shows a transmission electron microscope (TEM) image of the Au-MOF obtained in this example. The TEM image shows ordered lattice fringes with a spacing of 1.09 nm, corresponding to the (200) crystal plane.

[0071] like Figure 3 As shown, the electrochemical responses of different materials were compared under the same conditions. The MOFD response of the pure organic framework was weak, indicating its limited recognition and charge transfer capabilities. The Au-CTC response was enhanced, originating from Au's charge transport and Hg... 2+ While metal-philic interactions exist, the lack of an ordered porous structure and low accessibility of active sites limit performance improvement. Au-MOF, however, exhibits the strongest response, attributed to the synergistic effect of its interconnected channels and uniformly distributed Au sites on Hg. 2+ Mass transfer and charge transfer significantly amplify the current signal.

[0072] like Figure 4 As shown, no Hg was added. 2+ At that time, none of the materials showed significant catalytic color development of TMB, indicating that their intrinsic POD-like activity was weak. The addition of Hg... 2+ Subsequently, all Au-containing materials were able to catalyze the blue transformation of TMB, indicating that Au is the catalytic center, and Hg... 2+ These components play a crucial activating role in catalytic activity. Au-CTC exhibits some activity, while Au-MOF shows significant color development with a strong absorption peak at 652 nm, corresponding to a high concentration of oxidized TMB. This is mainly attributed to the porous structure and high specific surface area of ​​Au-MOF, which facilitates the exposure of catalytic sites and promotes reactant mass transfer, thereby significantly improving catalytic efficiency.

[0073] Figure 5 The Au-MOF obtained in this example was tested with Hg containing different concentration gradients. 2+ The solution yielded Hg. 2+ The electrochemical characteristic peak is located near 0.26 V ( Figure 5 a), and Hg 2+ The peak current showed a linear relationship with concentration, and the detection limit was 1.49 nM ( Figure 5 b).

[0074] Figure 6 The Au-MOF obtained in this example was tested with Hg containing different concentration gradients. 2+The solution yielded an oxidation characteristic peak for TMB around 652 nm. Figure 6 a), and the oxidation peak intensity of TMB is similar to that of Hg. 2+ The concentration showed a linear relationship, and the detection limit was 7.9 nM ( Figure 6 b).

[0075] Figure 7 This embodiment uses Au-MOF prepared with different organic ligands to target Hg. 2+ Electrochemical and colorimetric detection yielded an electrochemical characteristic peak at 0.28 V ( Figure 7 a) The TMB oxidation characteristic peak obtained is located at 652 nm. Figure 7 a) This indicates that Au-MOF prepared by changing the organic ligand can still be effectively used for Hg. 2+ Electrochemical and colorimetric detection.

[0076] Finally, it should be noted that the above embodiments are merely preferred examples for clearly illustrating the present invention, but they are not intended to limit the implementation of the present invention. Those skilled in the art should understand that the technical features in the above solutions can be combined arbitrarily, and other modifications or equivalent substitutions can be made to some technical features based on the above specific implementation methods. It is impossible to exhaustively list all implementation methods here. Therefore, any modifications, improvements, equivalent substitutions, etc., derived from the technical solutions of the present invention within the spirit and principles of the present invention should be within the scope of protection claimed by the present invention.

Claims

1. An electrochemical / colorimetric dual-mode detection method for Hg 2+ The Au-MOF nanozyme sensor is characterized by, The Au-MOF nanozyme contains Au; the specific surface area of ​​the Au-MOF nanozyme sensor is 617.25 m². 2 g -1 The aperture distribution is mainly concentrated at 1.41 nm, and transmission electron microscopy shows ordered lattice fringes with a spacing of 1.09 nm. The preparation method of the Au-MOF nanozyme sensor includes the following steps: (1) Solution A: Mix 185.5 mg of 3,5-dimethyl-1H-pyrazole-4-carboxaldehyde (1.5 mmol) with 8.31 mL of anhydrous methanol and 437.5 μL of triethylamine until homogeneous; (2) Solution B: Dissolve 350 mg of chloro(tetrahydrothiophene) gold (I) (1.09 mmol) in 8.31 mL of acetone; (3) Add solution A dropwise into solution B and stir for 10 minutes; (4) Filter and collect the white crystalline powder Au-CTC; (5) In a Schlenk tube, add 96 mg Au-CTC (0.1 mmol), 42.35 mg 2,2'-(5'-(4-(cyanomethyl)phenyl)-[1,1':3',1''-terphenyl]-4,4''-diyl)diacetonitrile (0.1 mmol), 1 mL mesitylene, 1 mL 1,4-dioxane and 200 μL of 4 M NaOH solution; (6) The tube was rapidly frozen in a liquid nitrogen bath at 77 °C and degassed by three thawing cycles using a refrigeration pump; (7) After the mixture has returned to room temperature, it is ultrasonically treated for 30 minutes, and then heated at 100 °C for 72 hours; (8) The Au-MOF nanozyme sensor is obtained by filtration, washing and solvent exchange with N,N-dimethylformamide and methanol.

2. The Au-MOF nanozyme sensor according to claim 1, characterized in that, The stirring time in step (3) is 5-60 minutes.

3. The Au-MOF nanozyme sensor according to claim 1, characterized in that, In step (5), the 2,2'-(5'-(4-(cyanomethyl)phenyl)-[1,1':3',1''-terphenyl]-4,4''-diyl)diacetonitrile may be selected from one of the following compounds: 1,3,5-tris(4-cyanophenyl)benzene, 2,2',2''-(1,3,5-triazine-2,4,6-triyl)tri(phenyl-4,1-diyl)triacetonitrile, or terephthalic acid acetonitrile.

4. The Au-MOF nanozyme sensor according to claim 1, characterized in that, The heating temperature in step (7) is 80-150 ℃.

5. An electrochemical detection method for mercury ions in water, characterized in that, The invention includes an Au-MOF-modified working electrode, wherein the Au-MOF-modified working electrode employs the Au-MOF nanozyme sensor according to any one of claims 1-4; the modification method includes: mixing the Au-MOF nanozyme sensor with ethanol in a certain proportion to prepare a modification ink, drop-coating the modification ink onto the electrode surface, and drying to obtain the Au-MOF-modified electrode; immersing the modified electrode in a solution containing Hg 2+ Electrodeposition was performed in an acetic acid buffer solution at a specific potential, followed by detection of Hg using square wave anodic stripping voltammetry (SWASV). 2+ The content of.

6. The electrochemical detection method according to claim 5, characterized in that: The concentration of the modifying ink is 0.5-3 mg / mL; the amount of the modifying ink dropped onto the electrode is 5 μL to 10 μL; the pH range of the acetate buffer used in the test is 1-7; the voltage range of the electrodeposition is -1 to -1.5 V; and the electrodeposition time is 60-180 seconds.

7. The electrochemical detection method according to claim 5, characterized in that: The voltage range of the square wave anodic stripping voltammetry (SWASV) is 0-0.6 V.

8. A colorimetric detection method for mercury ions in water, characterized in that, The Au-MOF nanozyme sensor according to any one of claims 1-4 is used; the colorimetric detection method includes: dispersing the Au-MOF nanozyme sensor in distilled water to prepare a concentration of 2 mg / mL. -1 Au-MOF stock solution was prepared and sonicated for 10 minutes; subsequently, 40 μL of Au-MOF stock solution was added to solutions containing different concentrations of Hg. 2+ The buffer solution was added; H2O2 (30 μL, 30%) and TMB (30 μL, 10 mM) were added sequentially; the reaction system was incubated at 30 °C for 10 minutes and then UV spectrophotometric measurements were performed.

9. The colorimetric detection method according to claim 8, characterized in that: The concentration of the Au-MOF stock solution is 0.5-3 mg / mL; the Hg 2+ The concentration range is 10-1000 nM; the amount of H2O2 added is 10-60 μL; the amount of TMB added is 10-60 μL.

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