MOF-AuNRs-NG composites for simultaneous detection of dopamine, uric acid, and vitamin C

Abstract

The present invention belongs to the field of biological detection technology, and in particular to a MOF-AuNRs-NG composite material for the simultaneous detection of dopamine, uric acid and vitamin C. The MOF-AuNRs-NG composite material provided by the present invention includes the following materials by weight: 0.1 to 0.12 parts of a MOF-AuNRs composite, wherein the MOF-AuNRs composite is a core-shell structure composite with Au nanorods as a core and CU-BTC as a shell; and 0.03 to 0.05 parts of a carbon material. The MOF-AuNRs-NG composite material of the present invention is made into an electrode that can be used as an electrochemical sensor and can be used for the simultaneous detection of dopamine, uric acid and vitamin C. The method for simultaneously detecting dopamine, uric acid and vitamin C using the electrode has the advantages of a wide linear range, a low detection limit, good anti-interference ability, good reproducibility and high stability, and dopamine, uric acid and vitamin C do not affect each other's detection, and can achieve the purpose of accurately detecting the three substances simultaneously, with good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of biological detection, and in particular relates to a MOF-AuNRs-NG composite material for the simultaneous detection of dopamine, uric acid and vitamin C. Background Art

[0002] Dopamine (DA) is a neurotransmitter in the mammalian nervous system and plays a vital role in the body. Altered DA levels significantly increase a person's risk of developing depression, schizophrenia, and Parkinson's disease. Because DA levels in the human body are correlated with a variety of diseases, its detection has significant clinical value.

[0003] Uric acid (UA) is a product of purine metabolism in the human body. When purine intake exceeds the body's metabolic capacity, uric acid accumulates in the body, leading to problems such as gout, hyperhematuria, and cardiovascular disease. Measuring uric acid levels in the human body can accurately assess the body's metabolic health and immune function, and is of great significance to human health.

[0004] Vitamin C, also known as ascorbic acid (AA), is an important water-soluble vitamin. AA possesses excellent antioxidant properties, effectively scavenging free radicals in the body, maintaining enzyme activity, and protecting the body from damage by strong oxidants. AA also plays a vital role in metabolism. Severely insufficient AA intake can lead to conditions such as scurvy, bleeding gums, bad breath, and cataracts.

[0005] Abnormal levels of three biomolecules, DA, UA, and AA, in the human body can lead to related diseases. Developing new technologies that can rapidly and sensitively detect DA, UA, and AA concentrations has significant clinical value and research significance for safeguarding human health. Because DA, UA, and AA are all electrochemically active and often coexist in living organisms, the use of electrochemical detection methods for the simultaneous detection of individual or all three substances has attracted considerable attention in recent years.

[0006] However, it is very difficult to perform electrochemical detection of the three substances DA, UA and AA at the same time. This is because the reducibility of the three molecules DA, UA and AA is similar, and the redox potentials in the electrochemical test are very close. Therefore, when using conventional electrode materials for electrochemical testing, the redox peaks of the three are difficult to separate, making it impossible to detect the three substances. Based on this difficulty, the Chinese invention patent application "CN108344785A A method for preparing a composite material modified electrode that can be used for the simultaneous detection of ascorbic acid, dopamine and uric acid" provides a zinc oxide-copper oxide / porous carbon ball composite material. The three substances DA, UA and AA have different overpotentials on the electrode of the composite material. Therefore, when using the composite material as an electrode to perform electrochemical testing on the three substances DA, UA and AA, the oxidation peaks of the three substances can be effectively separated. Therefore, this patent application realizes a method for simultaneously detecting the three substances DA, UA and AA using electrochemical testing. However, the zinc oxide-copper oxide / porous carbon sphere composite material is mainly composed of oxides and carbon materials, and its adsorption effect on DA, UA, and AA is relatively limited, which limits its sensitivity in detecting these three molecules. Therefore, it is very necessary to further develop new electrode materials to construct highly selective and sensitive modified electrodes and achieve simultaneous detection of DA, UA, and AA. Summary of the Invention

[0007] In view of the defects of the existing technology, the present invention provides a MOF-AuNRs-NG composite material for the simultaneous detection of dopamine, uric acid and vitamin C, with the aim of providing a new composite material to achieve the simultaneous detection of DA, UA and AA.

[0008] A composite material comprising the following components by weight:

[0009] 0.1 to 0.12 parts of a MOF-AuNRs composite, wherein the MOF-AuNRs composite is a core-shell structure composite with Au nanorods as the core and CU-BTC as the shell;

[0010] 0.03-0.05 parts of carbon material.

[0011] Preferably, the composite material is a core-shell structure, the core of the core-shell structure includes the MOF-AuNRs composite, and the shell layer of the core-shell structure includes the carbon material.

[0012] Preferably, the shell layer further comprises 0.0026 to 0.003 parts of chitosan.

[0013] Preferably, the MOF-AuNRs composite is prepared from the following raw materials in parts by weight: 0.5-0.7 parts of Au nanorods; 0.4-0.5 parts of copper chloride; 0.5-0.6 parts of trimesic acid;

[0014] And / or, the aspect ratio of the Au nanorods is 2-4, and the length of the Au nanorods is 25-35 nm.

[0015] Preferably, the carbon material is nitrogen-doped graphene.

[0016] The present invention also provides a method for preparing the composite material, comprising the following steps:

[0017] (1) Au nanorods were prepared by seed growth method;

[0018] (2) wrapping the CU-BTC material outside the Au nanorods to obtain a MOF-AuNRs composite;

[0019] (3) The MOF-AuNRs composite obtained in step (2) is mixed with carbon material to obtain.

[0020] Preferably, in step (1), the seed crystal growth method comprises the following steps: (1.1) using CTAB as a protective agent and reducing HAuCl4 with NaBH4 to prepare seed crystals;

[0021] And / or, the specific steps of wrapping the CU-BTC material outside the Au nanorods in step (2) are: stabilizing the Au nanorods obtained in step (1) with PVP, adding the Au nanorods to a 7-7.5 mmol / L n-hexanoic acid solution; then adding a 8-8.3 mmol / L copper chloride solution and a 7-7.5 mmol / L trimesic acid solution, reacting, and separating to obtain the Au nanorods; the volume ratio of the n-hexanoic acid solution, the copper chloride solution, and the trimesic acid solution is 0.8-1.2:0.8-1.2:0.8-1.2;

[0022] and / or, in step (3), the MOF-AuNRs composite and the carbon material are mixed in an ethanol solvent to obtain the composite material;

[0023] And / or, in step (3), the MOF-AuNRs composite is mixed with the carbon material and then mixed with the chitosan solution to obtain the composite material.

[0024] The present invention also provides an electrode made of the composite material.

[0025] The present invention also provides a method for simultaneously detecting dopamine, uric acid and vitamin C, which uses the above-mentioned electrode to perform electrochemical testing on the sample.

[0026] Preferably, the method comprises the following steps:

[0027] (A) Differential pulse voltammetry was performed on standard solutions of dopamine, uric acid, and vitamin C using the above-mentioned electrodes to obtain current-concentration standard curves for dopamine, uric acid, and vitamin C. The current at 0.4463–0.4465 V vs. Ag / AgCl (3 M KCl) was used for dopamine, the current at 0.0720–0.0723 V vs. Ag / AgCl (3 M KCl) was used for uric acid, and the current at -0.2190–-0.2193 V vs. Ag / AgCl (3 M KCl) was used for vitamin C.

[0028] (B) Perform differential pulse voltammetry on the sample using the above electrodes, and obtain the content of dopamine, uric acid and vitamin C in the sample according to the current-concentration standard curve obtained in step (A).

[0029] The MOF material CU-BTC used in this invention is composed of copper ions and trimesic acid. It possesses most of the general performance advantages of MOFs, including a large surface area, high porosity, controllable pore size, an ordered crystal structure, and excellent mechanical stability. The "MOF-AuNRs composite" is a composite formed by encapsulating CU-BTC with Au nanorods as the core. The "MOF-AuNRs-NG composite" refers to a composite material composed of a MOF-AuNRs composite and nitrogen-doped graphene. In preferred embodiments, other components such as chitosan may also be added. The "MOF-AuNRs-NG@GCE modified electrode" refers to an electrode obtained by loading or modifying a MOF-AuNRs-NG composite onto a glassy carbon electrode. "CTAB" is cetyltrimethylammonium bromide. "V vs. Ag / AgCl (3M KCl)" is a potential unit, representing the potential value calculated with the electrode potential of an Ag / AgCl electrode in a 3M KCl solution as the zero point.

[0030] After adopting the technical solution of the present invention, the following beneficial effects can be achieved:

[0031] 1. This invention provides a novel composite material, MOF-AuNRs-NG. The greatest advantage of MOFs lies in their unique adsorption properties. The functionalization of AuNRs further influences the electronic and internal structure of MOFs, enhancing their catalytic activity and resulting in superior electrochemical performance and stability. This composite material exhibits enhanced electrocatalytic activity and electron transfer rate, enabling highly selective and sensitive simultaneous detection of dopamine, uric acid, and vitamin C, offering a new option for their detection.

[0032] 2. The method of the present invention for simultaneous detection of dopamine, uric acid and vitamin C has good discrimination of the overpotentials of the three. When the three exist at the same time, they will not affect the accurate detection of each other. The detection method of the present invention has a wide linear range, low detection limit, good anti-interference ability, good reproducibility and high stability, and can achieve accurate detection.

[0033] 3. In the preferred solution, in order to increase the composite ability between CU-BTC, Au nanorods and carbon materials and reduce the loss of CU-BTC during electrochemical detection, a small amount of chitosan is added to the composite material to increase its adhesion and film-forming properties on GCE, effectively improving the stability of sensing detection.

[0034] Obviously, based on the above contents of the present invention, according to common technical knowledge and customary means in this field, without departing from the above basic technical ideas of the present invention, other various forms of modifications, replacements or changes can be made.

[0035] The following further describes the above content of the present invention in detail through specific embodiments in the form of examples. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the synthesis and detection of MOF-AuNRs-NG composite materials;

[0037] Figure 2 Electron micrographs of AuNRs, CU-BTC and MOF-AuNRs-NG composite materials, wherein (A) is a transmission electron micrograph of AuNRs, (B) and (C) are scanning electron micrographs of CU-BTC, (D) and (E) are scanning electron micrographs of MOF-AuNRs-NG composite materials, and (F) is a transmission electron micrograph of MOF-AuNRs-NG composite materials;

[0038] Figure 3 Cyclic voltammetry (A) and electrochemical impedance spectroscopy (EIS) test results of the MOF-AuNRs-NG@GCE electrode and the control electrode.

[0039] Figure 4 Cyclic voltammetry curves (AC) of AA, DA, and UA on different electrodes, and cyclic voltammetry curves (D) of AA, DA, and UA at different concentrations on MOF-AuNRs-NG@GCE electrode;

[0040] Figure 5DPV detection of AA by MOF-AuNRs-NG@GCE electrode in the presence of DA and UA (A); DPV detection of DA in the presence of AA and UA (B); DPV detection of UA in the presence of AA and DA (C); (D), (E), and (F) are the fitting curves of peak current versus concentration in (A), (B), and (C), respectively;

[0041] Figure 6 DPV detection (A) of MOF-AuNRs-NG@GCE electrode in AA, DA and UA solutions with different concentrations and the fitting curve of peak current versus concentration (BD);

[0042] Figure 7 This is the experimental result of AA's interference research;

[0043] Figure 8 The results of the DA interference study experiment are as follows;

[0044] Figure 9 The results of the UA interference research experiment are as follows;

[0045] Figure 10 Results of DPV detection of 0.01 M PBS solution containing 300.0 μM AA (A), 40.0 μM DA (B), and 40.0 μM UA (C) using five MOF-AuNRs-NG@GCE electrodes as a parallel group;

[0046] Figure 11 The results of DPV detection of 0.01 M PBS solution containing 300.0 μM AA (A), 40.0 μM DA (B), and 40.0 μM UA (C) using twelve MOF-AuNRs-NG@GCE electrodes on days 1, 2, 4, 6, 8, and 10, respectively. DETAILED DESCRIPTION

[0047] The reagents and materials used in the following examples and experimental examples are all commercially available.

[0048] Example 1 MOF-AuNRs-NG composite material and preparation method thereof

[0049] This embodiment provides a MOF-AuNRs-NG composite material, the preparation method is as follows Figure 1 As shown, the specific steps are:

[0050] 1. Preparation of Au Nanorods (AuNRs)

[0051] a. HAuCl4 solution (250 μL, 10 mmol L -1 ) and CTAB solution (7.5 mL, 100 mmol L-1 )mix;

[0052] b. Freshly prepared, ice-cold NaBH4 (600 μL, 10 mmol L) was stirred at 800 r. -1 ) solution was quickly added to the above mixed solution and stirred for 2 minutes;

[0053] c. The obtained brown-yellow solution was stored at 30°C for aging growth for 2 h to obtain a seed solution of AuNRs;

[0054] d. CTAB solution (40.0 mL, 100 mmol L -1 ), HAuCl4 solution (1.7 mL, 10 mmol L -1 ) and AgNO3 solution (250 μL, 10 mmol L -1 ) mix well;

[0055] e. Slowly add 270 μL AA to the mixed solution in step d. After adding AA, the color of the mixed solution gradually changes from orange to colorless to obtain a growth solution.

[0056] f. Add 300 μL of seed solution dropwise to the above growth solution to promote the growth of AuNRs. After 10-20 minutes of adding the AuNRs seed solution, the color of the solution gradually changes from colorless to blue-purple. Keep the above growth solution at 30°C and react for 16 hours.

[0057] g. Centrifuge (10,000 rpm, 10 min) to remove excess CTAB from the solution to obtain AuNRs. The AuNRs were preserved by redispersing them in deionized water and placing them in a refrigerator at 4°C until use.

[0058] 2. Preparation of MOF-AuNRs-NG Composite Materials

[0059] a. After stabilizing the AuNRs with PVP, add them to 5.0 mL of 7.5 mmol / L n-hexanoic acid solution. After shaking for 6–8 seconds, add 5.0 mL of 8.3 mmol / L copper chloride solution and 5.0 mL of 7.5 mmol / L trimesic acid solution to the mixture all at once and shake again for 30 minutes. The resulting transparent mixture is allowed to stand at room temperature for 5 hours, then centrifuged and washed three to four times with n-hexanoic acid. In this step, the mass ratio of AuNRs to copper chloride solution and trimesic acid is 1:1:1.

[0060] b. The final product after washing in step a was sonicated for 3 hours to form a stable MOF-AuNRs complex;

[0061] c. Nitrogen-doped graphene (NG, product number XF047) purchased from Nanjing Xianfeng Nano Co., Ltd. was precipitated and dispersed in ethanol and sonicated for 2 hours to exfoliate it into a monolayer. Next, the MOF-AuNRs composite was dispersed in ethanol and sonicated for 1 hour. 0.03 parts of the NG suspension and 0.1 parts of the MOF-AuNRs composite suspension were mixed and stirred at room temperature for 2 hours. The resulting suspension contained a composite material with CU-BTC grown on AuNRs as the core and NG coated.

[0062] d. The suspension of the composite material obtained in step c (0.05 g / mL) was thoroughly mixed with a chitosan solution having a mass percentage concentration of 0.1% in a vortexer at a volume ratio of 1:1 to obtain a MOF-AuNRs-NG composite material.

[0063] The electron microscopy images of the AuNRs, CU-BTC and MOF-AuNRs-NG composite materials prepared in this example are shown in FIG. Figure 2 shown. Figure 2 (A) is a transmission electron microscopy image of AuNRs. It can be seen from the image that AuNRs are well dispersed, about 25 nm in length, have good morphology, and can play a supporting role in the growth of CU-BTC. Figure 2 (B) and (C) are scanning electron micrographs of CU-BTC at different magnifications. Figure 2 (D) and (E) are scanning electron micrographs of the MOF-AuNRs-NG composite material at different magnifications. It can be seen from the images that the thin lamellar structure of NG is successfully coated on the surface of CU-BTC. Figure 2 (F) is the transmission electron microscopy image of the MOF-AuNRs-NG composite material, which further confirms that the CU-BTC grown with AuNRs as the core in the composite material is wrapped by NG.

[0064] Example 2 Preparation of MOF-AuNRs-NG@GCE modified electrode

[0065] In this example, the MOF-AuNRs-NG composite material prepared in Example 1 was modified on a glassy carbon electrode (GCE) to prepare an electrode for simultaneous detection of DA, UA, and AA. The specific steps are as follows:

[0066] a. Grinding and polishing: Wet the polishing cloth with pure water, take an appropriate amount of Al2O3 powder in the order of 1.0μm and 0.05μm particle size, and draw an "8-shaped" polishing on the polishing cloth 40 times. After polishing, the surface of the GCE electrode is mirror-like;

[0067] b. Cleaning: After each polishing, rinse the electrode surface with pure water to remove dirt. Place the electrode in a small beaker filled with an appropriate amount of pure water and move it to an ultrasonic water bath for 1 minute each time. Repeat three times until it is clean. Finally, thoroughly clean the electrode surface with ethanol, acetone, and pure water for 1 minute each to obtain a smooth and bright GCE electrode surface.

[0068] c. After the GCE electrode was dried, 7 μL of MOF-AuNRs-NG composite material (0.05 g / mL) was added dropwise to the electrode surface to prepare a MOF-AuNRs-NG / GCE modified electrode.

[0069] Example 3 Method for Simultaneous Detection of DA, UA, and AA

[0070] a. The MOF-AuNRs-NG / GCE modified electrode prepared in Example 2 was used as the working electrode, Ag / AgCl (3M KCl) was used as the reference electrode, and a platinum wire electrode was used as the counter electrode. Standard solutions of dopamine, uric acid, and vitamin C were subjected to differential pulse voltammetry to obtain current-concentration standard curves of dopamine, uric acid, and vitamin C; wherein, the current at 0.4467V vs.Ag / AgCl (3M KCl) for dopamine, the current at 0.0723V vs.Ag / AgCl (3M KCl) for uric acid, and the current at -0.2193V vs.Ag / AgCl (3M KCl) for vitamin C were taken;

[0071] The parameters of the differential pulse voltammetry test were set as follows: scan rate of 50 mV / s and pulse time of 0.02 s.

[0072] b. Perform differential pulse voltammetry on the sample to be tested using the method of step a, and obtain the content of dopamine, uric acid and vitamin C in the sample according to the current-concentration standard curve obtained in step (A).

[0073] In order to further illustrate the technical effect of the present invention, further experiments are carried out using the MOF-AuNRs-NG@GCE modified electrode of Example 2.

[0074] Experimental Example 1 Conductivity of Electrodes

[0075] 1. Preparation of reference electrode

[0076] Preparation of AuNRs@GCE: The AuNRs prepared in Example 1 were prepared into AuNRs@GCE electrodes according to the method of Example 2;

[0077] Preparation of MOF-NG@GCE: MOF was prepared using the method of Example 1, except that PVP-stabilized AuNRs were not added. Nitrogen-doped graphene (NG) was then precipitated and dispersed in ethanol and exfoliated into a monolayer by ultrasonication for 2 h. Subsequently, the MOF was dispersed in ethanol and ultrasonicated for 1 h. The NG suspension (30 mL, 1 mg / mL) and the MOF (30 mL, 0.1 g / mL) composite suspension were mixed and stirred at room temperature for 2 h to obtain the MOF-NG material. The MOF-NG material was then prepared into a MOF-NG@GCE electrode according to the method of Example 2.

[0078] Preparation of MOF@GCE: The CU-BTC used in Example 1 was prepared into a MOF@GCE electrode according to the method of Example 2.

[0079] 2. Cyclic voltammetry curve

[0080] For AuNRs@GCE electrode ( Figure 3 Aa), MOF-AuNRs-NG@GCE electrode of Example 2 ( Figure 3 Ab), MOF-NG@GCE electrode ( Figure 3 Ac)、MOF@GCE( Figure 3 Ad) and GCE electrodes ( Figure 3 Ae) in the presence of 0.1 M KCl, 2.5 mM [Fe(CN)6] 4- and 2.5 mM [Fe(CN)6] 3- Cyclic voltammetry was performed in the solution. The scanning parameters were set as follows: scanning speed was 50mv / s, and scanning voltage range was +0.6V~-0.2V. The results are shown in Figure 2. Figure 3 A, it can be seen from the figure that the current of the MOF-AuNRs-NG@GCE electrode is the largest, indicating that the MOF-AuNRs-NG composite material can enhance the surface electron transfer speed compared with the CU-BTC, AuNRs and MOF-NG composites.

[0081] 3. AC impedance test

[0082] For AuNRs@GCE electrode ( Figure 3 Ba), MOF-AuNRs-NG@GCE electrode of Example 2 ( Figure 3 Bb), MOF-NG@GCE electrode ( Figure 3 Bc)、MOF@GCE( Figure 3 Bd) and GCE electrode ( Figure 3 Be) in the presence of 2.5 mM [Fe(CN)6] 4- and 2.5 mM [Fe(CN)6] 3-The EIS graph is shown in Figure 1. Figure 3 As shown in Figure B, it can be seen that the curve curvature of the MOF-AuNRs-NG@GCE electrode is the largest and the semicircle diameter is the smallest, indicating that the resistance of the MOF-AuNRs-NG composite material is the smallest.

[0083] This experimental example shows that compared with CU-BTC, AuNRs and MOF-NG composites, MOF-AuNRs-NG composite material has better conductive properties, which provides a good material basis for it as an electrochemical detection sensor.

[0084] Experimental Example 2 Overpotential of AA, UA, and DA on MOF-AuNRs-NG@GCE electrode

[0085] 1. Preparation of reference electrode

[0086] Preparation of AuNRs@GCE: The AuNRs prepared in Example 1 were prepared into AuNRs@GCE electrodes according to the method of Example 2.

[0087] 2. Electrochemical testing

[0088] 1. Prepare solutions of 5 mM AA, 2 mM DA, and 2 mM UA in 0.01 M PBS (pH 7.0). Perform cyclic voltammetry scans in these three solutions with a scan rate of 100 mV / s and a voltage range of +0.8 to -0.8 V.

[0089] The test results of AuNRs@GCE electrode (a), MOF-AuNRs-NG@GCE electrode (b) and GCE electrode (c) of Example 2 are shown in Figure 2. Figure 4 As shown in (A)-(C), the AuNRs@GCE electrode exhibits redox peaks, but lacks selectivity, and the overpotentials of the target analytes (AA, UA, and DA) cannot be distinguished. However, the MOF-AuNRs-NG@GCE electrode exhibits distinct overpotentials for the target analytes (AA, UA, and DA), and their distinct overpotential positions can be clearly identified.

[0090] 2. Prepare four coexistence systems of AA, DA and UA with different concentrations according to the table below:

[0091] Experimental group AA concentration (mM) DA concentration (mM) UA concentration (mM) a 20.0 2.5 1 b 25.0 4.0 2 c 30.0 5.5 3 d 35.0 7.0 5

[0092] In the above four experimental groups, the MOF-AuNRs-NG@GCE electrode of Example 2 was used for cyclic voltammetry scanning, and the scanning parameters were set as follows: the scanning speed was 100 mv / s, and the scanning voltage range was +0.8 to -0.8 V.

[0093] The results are as follows Figure 4 As shown in Figure D, it can be seen from the figure that the overpotentials corresponding to AA, UA and DA are -0.2193V, +0.0723V and +0.4467V respectively, which have good discrimination and can be detected simultaneously.

[0094] Example 3 Linearity Investigation of Differential Pulse Voltammetry (DPV) Detection of Different Concentrations of AA, DA, and UA

[0095] The purpose of this experimental example is to further explore the mutual influence of the three target detection objects when they coexist.

[0096] 1. Examine the linear relationship of another target analyte while keeping the concentrations of the two target analytes constant:

[0097] The MOF-AuNRs-NG@GCE electrode from Example 2 was tested using the DPV method at a scan rate of 50 mV / s and a pulse duration of 0.02 s. The solution used was a 0.01 M PBS (pH 7.0) buffer solution, with the concentrations of UA, DA, and AA held constant while the concentration of the other target analyte was varied according to a specific concentration gradient.

[0098] The results are as follows Figure 5 As shown in the figure, it can be seen that when the concentrations of two of UA, DA, and AA are arbitrarily controlled to remain unchanged, the concentration of the other target detection object and the current maintain a good linear relationship.

[0099] By calculating using the three-fold signal-to-noise ratio method, the detection limits of AA were determined to be 0.128 μm, 0.025 μM, and 0.019 μM, respectively.

[0100] 2. Examine the linear relationship when the concentrations of the three target analytes change simultaneously:

[0101] The MOF-AuNRs-NG@GCE electrode from Example 2 was tested using the DPV method at a scan rate of 50 mV / s and a pulse duration of 0.02 s. The solution used was a 0.01 M PBS (pH 7.0) buffer solution with varying concentrations of UA, DA, and AA. The concentrations of AA ranged from 20 to 450 μM, DA from 10 to 200 μM, and AA from 10 to 450 μM.

[0102] The results are as follows Figure 6 As shown in the figure, it can be seen that when the concentrations of UA, DA, and AA change simultaneously, the concentrations and currents of the three maintain a good linear relationship.

[0103] This experimental example shows that the three target detection substances will not affect the accuracy of the quantitative detection of their respective contents.

[0104] Experimental Example 4: Investigation of selectivity, reproducibility and stability

[0105] 1. Selective inspection

[0106] In order to verify the anti-interference ability of MOF-AuNRs-NG@GCE prepared in Example 2, several potential interfering substances (lysine, glycine, glucose, citric acid, K + 、Cl - 、Na + 、NO 3- 、CO3 2- and SO4 2- ) were added sequentially to 0.01 M PBS (pH 7.0) containing AA, DA, and UA, and the assay was performed using the IT method. The parameters for the IT method were: voltage at 0.2 V, pulse time at 0.1 s.

[0107] The results are as follows Figure 7-9 As shown, Figure 7 In the presence of 20 μM AA, 0.2 mM lysine, glycine, glucose, citric acid, K + 、Cl - 、Na + 、NO 3- 、CO3 2- 、SO4 2- The current response; Figure 8 In the presence of 20 μM DA, 0.2 mM lysine, glycine, glucose, citric acid, K + 、Cl - 、Na + 、NO 3- 、CO3 2- 、SO4 2- The current response; Figure 7 In the presence of 20 μM UA, 0.2 mM lysine, glycine, glucose, citric acid, K + 、Cl - 、Na + 、NO 3- 、CO3 2- 、SO4 2- The current response.

[0108] As can be seen from the figure, these potential interferents have no effect on the test of AA, DA and UA, indicating that the MOF-AuNRs-NG@GCE electrode of the present invention has good selectivity.

[0109] 2. Reproducibility study

[0110] To verify the reproducibility, five MOF-AuNRs-NG@GCE electrodes were used as a parallel group to perform DPV detection on a 0.01 M PBS solution containing 300.0 μM AA (A), 40.0 μM DA (B) and 40.0 μM UA (C). The detection parameters were set as follows: scan speed of 50 mv / s and pulse time of 0.02 s.

[0111] The results are as follows Figure 10 As shown in the figure, the calculated RSDs were 4.30%, 4.51% and 4.64% for AA, DA and UA, respectively, indicating good reproducibility.

[0112] 3. Stability inspection

[0113] In order to verify the stability of the MOF-AuNRs-NG@GCE electrode, twelve MOF-AuNRs-NG@GCE electrodes were used to perform DPV detection on 0.01 M PBS solution containing 300.0 μM AA (A), 40.0 μM DA (B) and 40.0 μM UA (C) on the 1st, 2nd, 4th, 6th, 8th and 10th days respectively. The detection parameters were set as follows: scan speed of 50 mv / s and pulse time of 0.02 s.

[0114] The results are as follows Figure 11 As shown in Figure 3, the calculated RSDs for AA, DA, and UA are 99.13%, 114.6%, and 94.14%, respectively, indicating that the MOF-AuNRs-NG@GCE electrode has good stability.

[0115] As can be seen from the above embodiments and experimental examples, the present invention provides a MOF-AuNRs-NG composite material with excellent electrical conductivity. When fabricated into an electrode, this material exhibits highly selective electrochemical responses to AA, DA, and UA. Furthermore, it can distinguish the overpotentials of the three, enabling accurate and simultaneous electrochemical detection of AA, DA, and UA. Therefore, the MOF-AuNRs-NG composite material and detection method of the present invention have promising application prospects in the detection of AA, DA, and UA.

Claims

1. A method for simultaneously detecting dopamine, uric acid and vitamin C, characterized in that: It uses electrodes to perform electrochemical tests on samples; The electrode is made of a composite material; The composite material comprises the following components by weight: The composite material is a core-shell structure, wherein the core of the composite material core-shell structure comprises 0.1 to 0.12 parts of a MOF-AuNRs composite, and the MOF-AuNRs composite is a core-shell structure composite with Au nanorods as the core and CU-BTC as the shell; The shell layer of the composite material core-shell structure comprises 0.03-0.05 parts of carbon material and 0.0026-0.003 parts of chitosan; The MOF-AuNRs composite is prepared from the following raw materials in parts by weight: 0.5 to 0.7 parts of Au nanorods; 0.4 to 0.5 parts of copper chloride; 0.5 to 0.6 parts of trimesic acid; The aspect ratio of the Au nanorods is 2-4, and the length of the Au nanorods is 25-35 nm; The carbon material is nitrogen-doped graphene; The preparation method of the composite material comprises the following steps: (1) Au nanorods were prepared by seed growth method; (2) wrapping the CU-BTC material outside the Au nanorods to obtain a MOF-AuNRs composite; (3) mixing the MOF-AuNRs composite obtained in step (2) with a carbon material to obtain; In step (1), the seed crystal growth method comprises the following steps: (1.1) using CTAB as a protective agent and reducing HAuCl4 with NaBH4 to prepare seed crystals; The specific steps of wrapping the CU-BTC material outside the Au nanorods in step (2) are as follows: stabilizing the Au nanorods obtained in step (1) with PVP, and then adding them to a 7-7.5 mmol / L n-hexanoic acid solution; then adding a 8-8.3 mmol / L copper chloride solution and a 7-7.5 mmol / L trimesic acid solution, reacting, and separating to obtain the product; the volume ratio of the n-hexanoic acid solution, the copper chloride solution, and the trimesic acid solution is 0.8-1.2:0.8-1.2:0.8-1.2; In step (3), the MOF-AuNRs composite and the carbon material are mixed in an ethanol solvent to obtain the composite material; In step (3), the MOF-AuNRs composite is mixed with the carbon material and then mixed with the chitosan solution to obtain the composite material.

2. The method according to claim 1, characterized in that The steps include: (A) Using the electrode, differential pulse voltammetry was performed on standard solutions of dopamine, uric acid, and vitamin C to obtain current-concentration standard curves for dopamine, uric acid, and vitamin C, respectively; wherein, for dopamine, the current at 0.4463 to 0.4465 V vs. Ag / AgCl (3 M KCl) was taken; for uric acid, the current at 0.0720 to 0.0723 V vs. Ag / AgCl (3 M KCl) was taken; and for vitamin C, the current at -0.2190 to -0.2193 V vs. Ag / AgCl (3 M KCl) was taken; (B) performing differential pulse voltammetry on the sample using the electrode, and obtaining the contents of dopamine, uric acid, and vitamin C in the sample according to the current-concentration standard curve obtained in step (A).

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