CN116037917A - MOF-AuNRs-NG composite material for simultaneous detection of dopamine, uric acid and vitamin C - Google Patents

Abstract

The invention belongs to the technical field of biological detection, and particularly relates to a MOF-AuNRs-NG composite material for simultaneously detecting dopamine, uric acid and vitamin C. The MOF-AuNRs-NG composite material provided by the invention comprises the following materials in parts by weight: 0.1 to 0.12 part of MOF-AuNRs compound which is a core-shell structure compound taking an Au nano rod as a core and CU-BTC as a shell; 0.03 to 0.05 portion of carbon material. The electrode prepared from the MOF-AuNRs-NG composite material can be used as an electrochemical sensor, and can be used for simultaneously detecting dopamine, uric acid and vitamin C. The method for simultaneously detecting the dopamine, the uric acid and the vitamin C by using the electrode has the advantages of wide linear range, low detection limit, good anti-interference capability, good reproducibility and high stability, and the respective detection of the dopamine, the uric acid and the vitamin C can not be influenced, so that the purpose of simultaneously and accurately detecting three substances can be realized, and the application prospect is good.

Description

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

technical field

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

Background technique

Dopamine (DA) is a neurotransmitter in the nervous system of mammals and plays an important role in the body. When the content of DA is changed, the chances of people suffering from depression, schizophrenia and Parkinson's disease will be greatly increased. Since the content of DA in the human body is correlated with various diseases, the detection of DA has very important clinical value.

Uric acid (UA) is the product of purine metabolism in the human body. When the intake of purine substances exceeds the metabolic level of the human body, uric acid will accumulate in the body, leading to problems such as gout, hyperemia, and cardiovascular diseases. Determining the level of uric acid in the human body can correctly evaluate whether the body's metabolism is normal or not and the status of immune function, which is of great significance to human health.

Vitamin C, also known as ascorbic acid (AA), is an important water-soluble vitamin. AA has good antioxidant properties, can effectively remove free radicals in the human body, maintain enzyme activity in the body, and protect the human body from damage by strong oxidants. At the same time, AA plays an important role in the metabolism of substances in the living body. When the intake of AA is seriously insufficient, it will cause scurvy, bleeding gums, bad breath, cataracts and other diseases.

The abnormal content of these three biological small molecules, DA, UA and AA, in the human body will lead to some related diseases. The construction of a new technology that can quickly and sensitively detect the concentration of DA, UA and AA has great clinical value and research for the protection of human health. significance. Since the three substances of DA, UA and AA are all electrochemically active, and these three substances often coexist in living organisms, the simultaneous detection of a single substance or three substances using electrochemical detection methods has attracted much attention in recent years. .

However, it is very difficult to perform electrochemical detection of DA, UA and AA at the same time. This is because the reducibility of the three molecules of DA, UA and AA is similar, and the redox potential is very close in the electrochemical test. Therefore, when conventional electrode materials are used for electrochemical testing, the redox peaks of the three are difficult to separate, so that the detection of these three substances cannot be realized. Based on this difficulty, the Chinese invention patent application "CN108344785A A method for preparing a composite material modified electrode that can be used to simultaneously detect ascorbic acid, dopamine and uric acid" provides a zinc oxide-copper oxide/porous carbon sphere composite material, DA, UA and The three substances AA have different overpotentials on the electrode of the composite material, so when the composite material is used as the electrode to perform electrochemical tests on the three substances DA, UA and AA, the oxidation peaks of the three substances can be effectively separated. Therefore, in this patent application, a method for simultaneously detecting DA, UA and AA three substances by using an electrochemical test has been realized. However, the zinc oxide-copper oxide/porous carbon sphere composite is mainly composed of oxides and carbon materials, and its adsorption to DA, UA and AA is relatively limited, which limits its sensitivity to the detection of these three molecules. . Therefore, it is very necessary to further develop new electrode materials, construct highly selective, highly sensitive modified electrodes and realize simultaneous detection of DA, UA and AA.

Contents of the invention

Aiming at the defects of the prior art, the present invention provides a MOF-AuNRs-NG composite material for the simultaneous detection of dopamine, uric acid and vitamin C, the purpose of which is to provide a new composite material which can simultaneously detect DA, UA and AA detection.

A composite material comprising the following components by weight:

0.1-0.12 parts of MOF-AuNRs composite, the MOF-AuNRs composite is a core-shell structure composite with Au nanorod as the core and CU-BTC as the shell;

0.03-0.05 parts of carbon material.

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.

Preferably, the shell layer further includes 0.0026-0.003 parts of chitosan.

Preferably, the MOF-AuNRs composite is made of 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;

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

Preferably, the carbon material is nitrogen-doped graphene.

The present invention also provides the preparation method of above-mentioned composite material, comprises the following steps:

(1) Au nanorods were prepared by seed crystal growth method;

(2) wrapping the CU-BTC material on the Au nanorod to obtain the MOF-AuNRs composite;

(3) Mixing the MOF-AuNRs composite obtained in step (2) with a carbon material to obtain.

Preferably, in step (1), _the seed crystal growth method comprises the following steps: (1.1) using CTAB as a protective agent, reducing HAuCl with NaBH ₄ to make a seed crystal;

And/or, in the step (2), the specific step of wrapping the CU-BTC material on the Au nanorods is: after stabilizing the Au nanorods obtained in the step (1) with PVP, adding them to a concentration of 7-7.5mmol/ In the n-caproic acid solution of L; then adding concentration is 8～8.3mmol/l cupric chloride solution and concentration is the trimesic acid solution of 7～7.5mmol/L, reacts, separates, vested; Described n-caproic acid solution , The volume ratio of copper chloride solution and trimesic acid solution is 0.8～1.2:0.8～1.2:0.8～1.2;

And/or, in step (3), the MOF-AuNRs composite is mixed with the carbon material in solvent ethanol to obtain the composite material;

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.

The present invention also provides an electrode made of the above-mentioned composite material.

The present invention also provides a method for simultaneously detecting dopamine, uric acid and vitamin C, which uses the above-mentioned electrodes to conduct electrochemical tests on samples.

Preferably, the following steps are included:

(A) Use the above electrodes to perform differential pulse voltammetry on the standard solutions of dopamine, uric acid and vitamin C, respectively, and obtain the current-concentration standard curves of dopamine, uric acid and vitamin C; wherein, dopamine is 0.4463 ~ 0.4465Vvs.Ag/AgCl (3M KCl), take the current at 0.0720～0.0723V vs.Ag/AgCl(3M KCl) for uric acid, and take the current at -0.2190～-0.2193V vs.Ag/AgCl(3M KCl) for vitamin C;

(B) Using the above electrode to perform differential pulse voltammetry on the sample, and obtain the contents of dopamine, uric acid and vitamin C in the sample according to the current-concentration standard curve obtained in step (A). nitrogen doping

In the present invention, the MOF material CU-BTC used is composed of copper ions and trimesic acid, which has most of the general performance advantages of MOFs materials, such as large surface area, high porosity, controllable pore size, ordered crystal structure and excellent mechanical stability. The "MOF-AuNRs composite" is a composite obtained by wrapping CU-BTC with Au nanorods as the core. The "MOF-AuNRs-NG composite material" refers to a composite material composed of MOF-AuNRs composite and nitrogen-doped graphene, and other components such as chitosan can also be added to the preferred solution. The "MOF-AuNRs-NG@GCE modified electrode" refers to an electrode obtained by loading or modifying a MOF-AuNRs-NG composite material on a glassy carbon electrode. The "CTAB" is cetyltrimethylammonium bromide. The "V vs.Ag/AgCl (3M KCl)" is a potential unit, and its meaning is the potential value calculated with the electrode potential of the Ag/AgCl electrode in the 3M KCl solution system as 0 point.

After adopting the technical scheme of the present invention, the following beneficial effects can be obtained:

1. The present invention provides a new composite material MOF-AuNRs-NG. In this composite material, the biggest advantage of MOFs material lies in its unique adsorption performance; the functionalization of AuNRs can further affect the electronics and internal structure of MOF, making It has stronger catalytic activity, which makes the MOF-AuNRs composite material have more excellent electrochemical performance and stability. Therefore, the composite material of the present invention has enhanced electrocatalytic activity and electron transfer rate, and can simultaneously detect dopamine, uric acid and vitamin C with high selectivity and high sensitivity, providing a new option for the detection of the three.

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

3. In the preferred scheme, 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 was added to the composite material to increase Its adhesion and film-forming properties on GCE effectively improve the stability of sensing and detection.

Apparently, according to the above content of the present invention, according to common technical knowledge and conventional means in this field, without departing from the above basic technical idea of the present invention, other various forms of modification, replacement or change can also be made.

The above-mentioned content of the present invention will be further described in detail below through specific implementation in the form of examples. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following examples. All technologies realized based on the above contents of the present invention belong to the scope of the present invention.

Description of drawings

Figure 1 is a schematic diagram of the synthesis and detection of MOF-AuNRs-NG composite materials;

Figure 2 is the SEM images of AuNRs, CU-BTC and MOF-AuNRs-NG composites, where (A) is the TEM images of AuNRs, (B) and (C) are the SEM images of CU-BTC, (D ) and (E) are scanning electron micrographs of MOF-AuNRs-NG composites, (F) are transmission electron micrographs of MOF-AuNRs-NG composites;

Figure 3 shows the cyclic voltammetry curve (A) and AC impedance (B) test results of the MOF-AuNRs-NG@GCE electrode and the control electrode;

Figure 4 is the cyclic voltammetry curves (A-C) of AA, DA and UA on different electrodes, and the cyclic voltammetry curves (D) of different concentrations of AA, DA and UA on MOF-AuNRs-NG@GCE electrodes;

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

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

Fig. 7 is the experimental result of interference research of AA;

Figure 8 shows the experimental results of the interference research of DA;

Figure 9 shows the experimental results of UA interference research;

Figure 10 shows the results of DPV detection of 0.01M 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;

Figure 11 shows the use of twelve MOF-AuNRs-NG@GCE electrodes containing 300.0 μM AA (A), 40.0 μM DA (B) and 40.0 μM UA on days 1, 2, 4, 6, 8, and 10, respectively. (C) 0.01MPBS solution for DPV detection results.

Detailed ways

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

Example 1 MOF-AuNRs-NG composite material and its preparation method

This embodiment provides a MOF-AuNRs-NG composite material, the preparation method is shown in Figure 1, and the specific steps are:

1. Preparation of Au nanorods (AuNRs)

a. Mix HAuCl ₄ solution (250 μL, 10 mmol L ^-1 ) and CTAB solution (7.5 mL, 100 mmol L ^-1 );

b. Quickly add freshly prepared, ice-cold NaBH ₄ (600 μL, 10 mmol L ⁻¹ ) solution into the above mixed solution under 800 r magnetic stirring and stir for 2 min;

c. Store the obtained brown-yellow solution at 30° C. for aging and growth for 2 hours to obtain a seed solution of AuNRs;

d. Mix CTAB solution (40.0 mL, 100 mmol L ^-1 ), HAuCl ₄ solution (1.7 mL, 10 mmol L ^-1 ) and AgNO ₃ solution (250 μL, 10 mmol L ^-1 ) evenly;

e. Slowly add 270 μL of AA to the mixed solution of step d, after adding AA, the color of the mixed solution gradually changes from orange yellow to colorless to obtain a growth solution;

f. Add 300 μL seed solution dropwise to the above growth solution to promote the growth of AuNRs. After adding the AuNRs seed solution for 10-20 minutes, the color of the solution gradually changed from colorless to blue-purple; keep the above growth solution at 30°C for 16 hours;

g. Centrifuge (10000rpm, 10min) to remove excess CTAB from the solution to obtain AuNRs; the preservation method of AuNRs is to redisperse in deionized water and store in a refrigerator at 4°C for later use.

2. Preparation of MOF-AuNRs-NG composites

a. After stabilizing the above AuNRs with PVP, add 5.0mL 7.5mmol/L n-hexanoic acid solution; after shaking for 6-8 seconds, mix 5.0mL 8.3mmol/l copper chloride solution, 5.0mL 7.5mmol/L The trimesic acid solution was added to the above mixture at one time, and shaken again for 30 minutes. After the transparent mixed solution was left at room temperature for 5 hours, the obtained product was centrifuged and washed 3 to 4 times with n-caproic acid. In this step, the mass ratio of AuNRs to copper chloride solution and trimesic acid is 1:1:1.

b. Sonicate the final product after washing in a above for 3 hours using an ultrasonic instrument to form a stable MOF-AuNRs complex;

c. Precipitate and disperse nitrogen-doped graphene (NG, product number XF047) purchased from Nanjing Xianfeng Nano Co., Ltd. in ethanol, and exfoliate it into a single layer by ultrasonication for 2 hours; then, disperse the above MOF-AuNRs composite in ethanol Neutralize and sonicate for 1 h; mix the above 0.03 part of NG suspension and 0.1 part of MOF-AuNRs composite suspension and stir at room temperature for 2 h. Quilted composite material;

d. The suspension (0.05g/mL) of the composite material obtained in step c and the chitosan solution with a mass percent concentration of 0.1% are fully mixed in a vortexer at a volume ratio of 1:1 to obtain MOF-AuNRs- NG composites.

The SEM images of the AuNRs prepared in this example, the CU-BTC used and the prepared MOF-AuNRs-NG composite are shown in Figure 2. Figure 2(A) is a transmission electron microscope image of AuNRs. It can be seen from the figure that the dispersion of AuNRs is good, the length is about 25nm, and has a good shape, which can play a supporting role in the growth of CU-BTC. Figure 2(B) and (C) are SEM images of CU-BTC at different magnifications. Figure 2(D) and (E) are the SEM images of MOF-AuNRs-NG composites under different magnifications. It can be seen from the figure that the light and thin lamellar structure of NG is successfully coated on the surface of CU-BTC. Figure 2(F) is the TEM 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.

Example 2 Preparation of MOF-AuNRs-NG@GCE Modified Electrode

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

a. Grinding and polishing: Wet the polishing cloth with pure water, take an appropriate amount of Al ₂ O ₃ powder in the order of 1.0 μm and 0.05 μm particle size, draw the GCE electrode on the polishing cloth in the order of “8” and polish it for 40 times. After finishing, the surface of GCE electrode is mirror surface;

b. Cleaning: Rinse the dirt on the surface of the electrode with pure water after each polishing, put the electrode into a small beaker filled with an appropriate amount of pure water, move it into an ultrasonic water bath for cleaning, and repeat three times for 1 minute each time until it is cleaned; Wash thoroughly with ethanol, acetone, and pure water respectively for 1 min to obtain a smooth and clean GCE electrode surface;

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

Embodiment 3 detects the method for DA, UA and AA simultaneously

a. The MOF-AuNRs-NG/GCE modified electrode prepared in Example 2 is used as the working electrode, Ag/AgCl (3M KCl) is the reference electrode, and the platinum wire electrode is the counter electrode, respectively for the standards of dopamine, uric acid and vitamin C The solution was tested by differential pulse voltammetry to obtain the current-concentration standard curve of dopamine, uric acid and vitamin C; wherein, the current at 0.4467Vvs.Ag/AgCl(3M KCl) was taken for dopamine, and 0.0723V vs.Ag/AgCl( The current at 3M KCl), vitamin C takes the current at -0.2193Vvs.Ag/AgCl (3M KCl);

The parameters of the differential pulse voltammetry test are set as follows: the scanning speed is 50mv/s, and the pulse time is 0.02S.

b. Use the method of step a to carry out differential pulse voltammetry test on the sample to be tested, and obtain the contents of dopamine, uric acid and vitamin C in the sample according to the current-concentration standard curve obtained in step (A).

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

Conductivity of Experimental Example 1 Electrode

1. Preparation of the reference electrode

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

Preparation of MOF-NG@GCE: MOF is also prepared by the method of Example 1, except that PVP-stabilized AuNRs are not added, then nitrogen-doped graphene (NG) is precipitated and dispersed in ethanol, and it is exfoliated into a single layer by ultrasonication for 2h ; Next, the above-mentioned MOF was dispersed in ethanol and ultrasonicated for 1 h; the above-mentioned NG suspension (30 mL, 1 mg/mL) and MOF (30 mL, 0.1 g/mL) composite suspension were mixed and stirred at room temperature for 2 h, and finally Obtained MOF-NG material; MOF-NG material is prepared into MOF-NG@GCE electrode according to the method of Example 2;

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.

2. Cyclic voltammetry curve

For the AuNRs@GCE electrode (Fig. 3Aa), the MOF-AuNRs-NG@GCE electrode of Example 2 (Fig. 3Ab), the MOF-NG@GCE electrode (Fig. 3Ac), the MOF@GCE (Fig. 3Ad) and the GCE electrode (Fig. 3Ae) Cyclic voltammetry scans were performed in solutions containing 0.1 M KCl, 2.5 mM [Fe(CN) ₆ ] ^4- and 2.5 mM [Fe(CN) ₆ ] ^3- . The scanning parameters are set as follows: the scanning speed is 50mv/s, and the scanning voltage range is +0.6V～-0.2V. The results are shown in Figure 3A. 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 can enhance surface electron transport compared with CU-BTC, AuNRs and MOF-NG composites speed.

3. AC impedance test

For the AuNRs@GCE electrode (Fig. 3Ba), the MOF-AuNRs-NG@GCE electrode of Example 2 (Fig. 3Bb), the MOF-NG@GCE electrode (Fig. 3Bc), the MOF@GCE (Fig. 3Bd) and the GCE electrode (Fig. 3Be) An AC impedance test was performed in a solution containing 2.5 mM [Fe(CN) ₆ ] ^4- and 2.5 mM [Fe(CN) ₆ ] ^3- . The test conditions are: the test frequency is from 0.0001Hz-0.1Hz. The obtained EIS map is shown in Figure 3B. From the figure, it can be seen that the curve curvature of the MOF-AuNRs-NG@GCE electrode is the largest, and the diameter of the semicircle is the smallest, indicating that the resistance of the MOF-AuNRs-NG composite material is the smallest.

This experimental example shows that compared with CU-BTC, AuNRs and MOF-NG composites, MOF-AuNRs-NG composites have better electrical conductivity, which provides a good material basis for them to be used as electrochemical detection sensors.

Experimental example 2 Overpotential of AA, UA, DA on MOF-AuNRs-NG@GCE electrode

1. Preparation of the reference electrode

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

2. Electrochemical test

1. Use 0.01M PBS (pH=7.0) to prepare solutions with concentrations of 5mM AA, 2mM DA, and 2mM UA. Cyclic voltammetry scanning was performed in the above three solutions, and the scanning parameters were set as follows: the scanning speed was 100mv/s, and the scanning voltage range was +0.8-0.8V.

The test results of AuNRs@GCE electrode (a), MOF-AuNRs-NG@GCE electrode (b) and GCE electrode (c) of Example 2 are shown in Fig. 4(A)-(C). It can be seen from the figure that although there are redox peaks on the AuNRs@GCE electrode, there is no selectivity, and the overpotential of the target detection substances (AA, UA and DA) cannot be distinguished; while MOF-AuNRs-NG@GCE On the electrodes, the overpotentials of the target detection substances (AA, UA, and DA) are different, and the overpotential positions where the three are different from each other can be clearly found.

2. Prepare the coexistence system of four different concentrations of AA, DA and UA according to the following table:

test group AA concentration (mM) DA concentration (mM) Concentration of UA (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

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 100mv/s, and the scanning voltage range was +0.8～-0.8V .

The results are shown in Figure 4D. It can be seen from the figure that the corresponding overpotentials of AA, UA and DA are -0.2193V, ﹢0.0723V and ﹢0.4467V, respectively, which have good discrimination and can realize simultaneous detection.

Embodiment 3 is to the linear investigation of the differential pulse voltammetry (DPV) detection of different concentrations AA, DA, UA

The purpose of this experiment example is to further explore the influence of the three target detection substances on each other when they co-exist.

1. Investigate the linear relationship of the other target detection substance when the concentration of the two target detection substances is kept constant:

Using the MOF-AuNRs-NG@GCE electrode of Example 2, the DPV method was used for testing, and the testing conditions were: the scanning speed was 50mv/s, and the pulse time was 0.02S. The solution used is: in 0.01M PBS (PH=7.0) buffer solution, the concentrations of UA, DA, and AA are respectively controlled to be constant, and the other target detection substance is changed according to a certain concentration gradient.

The results are shown in Figure 5. It can be seen from the figure that the concentration of UA, DA, and AA is controlled arbitrarily, and the concentration and current of the other target detection substance maintain a good linear relationship.

Calculated by the method of three-fold signal-to-noise ratio, the detection limits of AA can be determined to be 0.128 μM, 0.025 μM and 0.019 μM, respectively.

2. Investigate the linear relationship when the concentrations of the three target detection substances change at the same time:

Using the MOF-AuNRs-NG@GCE electrode of Example 2, the DPV method was used for testing, and the testing conditions were: the scanning speed was 50mv/s, and the pulse time was 0.02S. . The solution used is: in 0.01M PBS (PH=7.0) buffer, the concentrations of UA, DA, and AA are changed at the same time, the concentration range of AA is 20-450μM, the concentration range of DA is 10-200μM, and the concentration range of AA is 10～450μM.

The results are shown in Figure 6. It can be seen from the figure that when the concentrations of UA, DA, and AA are changed at the same time, the concentrations and currents of the three maintain a good linear relationship.

Through this experimental example, it can be shown that the three target detection substances will not affect the accuracy of the quantitative detection of their respective contents.

Experimental example 4 selectivity, reproducibility and stability investigation

1. Selective inspection

In order to verify the anti-interference ability of MOF-AuNRs-NG@GCE prepared in Example 2, several potential interferers (lysine, glycine, glucose, citric acid, K ⁺ , Cl ^- , Na ⁺ , NO ^3- , CO ₃ ^2- and SO ₄ ^2- ) were added step by step to 0.01M PBS (pH 7.0) containing AA, DA and UA respectively, and determined by it method. The parameters of it method test are set as follows: the voltage is set at 0.2V, and the pulse time is 0.1S.

The results are shown in Figures 7-9, among which, Figure 7 shows the addition of 0.2mM lysine, glycine, glucose, citric acid, K ⁺ , Cl ^- , Na ⁺ , NO ^3- , CO ₃ ^2- in the presence of 20 μM AA , SO ₄ ^2- current response; Figure 8 shows the addition of 0.2mM lysine, glycine, glucose, citric acid, K ⁺ , Cl ^- , Na ⁺ , NO ^3- , CO ₃ ^2- , SO in the presence of 20 μM DA ₄ ^2- current response; Fig. 7 shows the addition of 0.2mM lysine, glycine, glucose, citric acid, K ⁺ , Cl ^- , Na ⁺ , NO ^3- , CO ₃ ^2- , SO ₄ ² in the presence of 20 μM UA ^- current response.

It can be seen from the figure that these potential interferers 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.

2. Reproducibility investigation

In order to verify the reproducibility, five MOF-AuNRs-NG@GCE electrodes were used as a parallel group to perform DPV on a 0.01M PBS solution containing 300.0 μM AA (A), 40.0 μM DA (B) and 40.0 μM UA (C). For detection, the detection parameters are set as follows: the scanning speed is 50mv/s, and the pulse time is 0.02S.

The results are shown in Figure 10, the calculated RSDs are 4.30%, 4.51% and 4.64% for AA, DA and UA, respectively. Shows good reproducibility.

3. Stability inspection

In order to verify the stability of MOF-AuNRs-NG@GCE electrodes, twelve MOF-AuNRs-NG@GCE electrodes were used on the 1st, 2nd, 4th, 6th, 8th, and 10th day, respectively. The 0.01MPBS solution of 40.0μM DA(B) and 40.0μM UA(C) was used for DPV detection, and the detection parameters were set as follows: the scanning speed was 50mv/s, and the pulse time was 0.02S.

The results are shown in Figure 11. The calculated RSDs are 99.13%, 114.6% and 94.14% for AA, DA and UA, respectively. It shows that the stability of MOF-AuNRs-NG@GCE electrode is good.

It can be seen from the above examples and experimental examples that the present invention provides a MOF-AuNRs-NG composite material, which has good electrical conductivity and has high selectivity to AA, DA and UA after being made into an electrode. Response, and it can distinguish the three overpotentials, and can accurately detect AA, DA and UA simultaneously. Therefore, the MOF-AuNRs-NG composite material and detection method of the present invention have good application prospects in the detection of AA, DA and UA.

Claims (10)

1. A composite material, characterized in that: it comprises the following components by weight: 0.1-0.12 parts of MOF-AuNRs composite, the MOF-AuNRs composite is a core-shell structure composite with Au nanorod as the core and CU-BTC as the shell; 0.03-0.05 parts of carbon material. 2. The composite material according to claim 1, characterized in that: the composite material is a core-shell structure, the core of the core-shell structure comprises the MOF-AuNRs composite, and the shell layer of the core-shell structure comprises the carbon material. 3. The composite material according to claim 2, characterized in that: the shell layer further includes 0.0026-0.003 parts of chitosan. 4. The composite material according to claim 1, characterized in that: the MOF-AuNRs composite is made of 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; And/or, the aspect ratio of the Au nanorods is 2-4, and the length of the Au nanorods is 25-35nm. 5. The composite material according to claim 1, characterized in that: the carbon material is nitrogen-doped graphene. 6. The preparation method of the composite material described in any one of claims 1-5, is characterized in that, comprises the steps: (1) Au nanorods were prepared by seed crystal growth method; (2) wrapping the CU-BTC material on the Au nanorod to obtain the MOF-AuNRs composite; (3) Mixing the MOF-AuNRs composite obtained in step (2) with a carbon material to obtain. 7. the preparation method described in claim 6 is characterized in that: In step ( _{1), the seed crystal growth method comprises the following steps: (1.1) using CTAB as a protective agent, reducing HAuCl with NaBH 4 to} make a seed crystal; And/or, in the step (2), the specific step of wrapping the CU-BTC material on the Au nanorods is: after stabilizing the Au nanorods obtained in the step (1) with PVP, adding them to a concentration of 7-7.5mmol/ In the n-caproic acid solution of L; then adding concentration is 8～8.3mmol/l cupric chloride solution and concentration is the trimesic acid solution of 7～7.5mmol/L, reacts, separates, vested; Described n-caproic acid solution , The volume ratio of copper chloride solution and trimesic acid solution is 0.8～1.2:0.8～1.2:0.8～1.2; And/or, in step (3), the MOF-AuNRs composite is mixed with the carbon material in solvent ethanol to obtain the composite material; 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. 8. An electrode made of the composite material according to any one of claims 1-5. 9. A method for simultaneously detecting dopamine, uric acid and vitamin C, characterized in that: it adopts the electrode described in claim 8 to carry out an electrochemical test on the sample. 10. according to the described method of claim 9, is characterized in that, comprises the steps: (A) adopt the electrode described in claim 8 to carry out differential pulse voltammetry test to the standard solution of dopamine, uric acid and vitamin C respectively, obtain the current-concentration standard curve of dopamine, uric acid and vitamin C; Wherein, dopamine takes 0.4463～0.4465 The current at V vs.Ag/AgCl (3M KCl), the current at 0.0720～0.0723V vs.Ag/AgCl(3M KCl) for uric acid, the current at -0.2190～-0.2193V vs.Ag/AgCl(3M KCl) for vitamin C ) at the current; (B) adopt the electrode described in claim 8 to carry out differential pulse voltammetry test to sample, obtain the content of dopamine, uric acid and vitamin C in the sample according to the current-concentration standard curve that step (A) obtains.

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