Enzyme-free Glucose Sensor Electrode Based on CuCo Bimetallic Organic Framework Material and Its Preparation and Application

Abstract

The present invention belongs to the field of electrochemical biosensor technology, and discloses a non-enzyme glucose sensor electrode based on CuCo bimetallic organic framework material and its preparation and application. The electrode includes a foam copper substrate and a multi-walled carbon nanotube material (MWCNTs), a nanogold material and a CuCo bimetallic organic framework material sequentially loaded on the surface of the foam copper substrate. Its preparation method includes the steps of: mixing an aqueous solution of a divalent copper salt and a divalent cobalt salt and a dimethylformamide solution of trimesic acid, performing a hydrothermal reaction to prepare a CuCo bimetallic organic framework material (CuCo‑BTC), sequentially coating a multi-walled carbon nanotube (MWCNT) dispersion, a nanogold dispersion and a CuCo bimetallic organic framework material (CuCo‑BTC) dispersion on a foam copper (CF) surface to obtain a non-enzyme glucose sensor electrode (CuCo‑BTC / Au / MWCNT / CF). The non-enzyme glucose sensor prepared by the present invention has a wide detection range, high sensitivity, and has good anti-interference performance for uric acid, dopamine, ascorbic acid and cysteine.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical biosensor technology and relates to an enzyme-free glucose sensor for qualitative and quantitative detection of glucose, and in particular to an enzyme-free glucose sensor electrode based on a CuCo bimetallic organic framework material and its preparation and application. Background Art

[0002] Diabetes is a metabolic syndrome caused by various genetic, immune, and other pathogenic factors acting on the body, leading to decreased pancreatic function. Accurately measuring blood glucose levels in diabetic patients can effectively monitor, treat, and control diabetes. Electrochemical glucose sensors primarily use a working electrode as a recognition element. They specifically recognize glucose, react with it electrochemically, and then convert the chemical signal into a corresponding electrical signal, thereby achieving the purpose of qualitative and quantitative glucose analysis.

[0003] Electrochemical glucose sensors are divided into two types: enzyme-containing glucose sensors and non-enzyme glucose sensors. The enzymes in enzyme-containing glucose sensors are expensive to produce, unstable, easily affected by the environment, and require high reaction conditions, which in turn limits their development. Currently, non-enzyme electrochemical glucose sensors can overcome the shortcomings of the above-mentioned enzyme sensors and have gradually become a research hotspot. However, the electrode materials of non-enzyme electrochemical glucose sensors are easily affected by other interferences during the glucose detection process and have low selectivity. In addition, the linear range of glucose detection of existing sensors is relatively narrow, which is lower than the normal blood glucose concentration range of the human body (4.4-6.6mmol / L). Therefore, it is of great significance to develop an electrochemical glucose sensor electrode material with high selectivity, wide linear range, and high sensitivity.

[0004] Metal-organic frameworks (MOFs) are a type of coordination polymer that has seen rapid development in recent years. They typically use metal ions as connecting points, supported by organic ligands to form a three-dimensional structure. Transition metal MOFs are used in non-enzymatic glucose sensors. Research has found that the electrochemical performance of glucose sensors based on single-metal MOFs is still limited. Therefore, there is a need to research non-enzymatic electrochemical glucose sensors based on bimetallic MOFs, which exploit the synergistic effect between different metals to improve electrochemical performance. However, the electrical conductivity of MOFs is not very good and needs further improvement. Summary of the Invention

[0005] The purpose of the present invention is to address the technical defects of existing non-enzymatic electrochemical glucose sensors and provide an enzyme-free glucose sensor electrode based on CuCo bimetallic organic framework material and its preparation and application.

[0006] The main technical solution of the present invention is to provide a method for preparing an enzyme-free glucose sensor electrode based on CuCo bimetallic organic framework material. This method uses MWCNTs, nanogold and CuCo bimetallic organic framework materials to modify the foam copper surface to obtain an electrochemical sensor electrode with good stability, high conductivity and sensitivity for glucose detection.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention is to provide an enzyme-free glucose sensor electrode based on a CuCo bimetallic organic framework material, characterized in that the electrode comprises a foam copper substrate and multi-walled carbon nanotubes (MWCNTs), nanogold materials and CuCo bimetallic organic framework materials sequentially loaded on the surface of the foam copper substrate.

[0009] Preferably, the curved tubular MWCNTs on the multi-walled carbon nanotube material (MWCNTs) are coated in the bulk and granular CuCo bimetallic organic framework material to form a loose porous structure.

[0010] Preferably, the loading amount of the multi-walled carbon nanotube material (MWCNTs) is 0.5-1.0 mg / cm 2 The loading amount (dry weight) of the nano-gold material is 1.796-2.987 μg / cm 2 The loading amount (dry weight) of the CuCo bimetallic organic framework material is 1.25-3.75 mg / cm 2 .

[0011] The second aspect of the present invention is to provide a method for preparing an enzyme-free glucose sensor electrode based on a CuCo bimetallic organic framework material, comprising the following steps:

[0012] (1) An aqueous solution of a divalent copper salt and a divalent cobalt salt, a solution of trimesic acid (BTC) in N,N-dimethylformamide (DMF), and anhydrous ethanol are mixed and subjected to a hydrothermal reaction at a certain temperature. The precipitate is washed with purified water and an ethanol solution in sequence, centrifuged, and vacuum-dried to obtain CuCo-BTC powder;

[0013] (2) Dispersing CuCo-BTC powder in a mixture of purified water and ethanol, and ultrasonically dispersing the mixture to obtain a CuCo-BTC dispersion;

[0014] (3) Sodium citrate and polyvinylpyrrolidone (PVP) solution were added to the HAuCl4 solution, stirred and heated to obtain a nano-gold dispersion;

[0015] (4) dispersing MWCNTs powder (multi-walled carbon nanotubes) in a mixture of a perfluorinated resin solution (Nafion) and ethanol, and then ultrasonically dispersing the mixture to obtain a MWCNTs dispersion;

[0016] (5) MWCNTs dispersion, nanogold dispersion, and CuCo-BTC dispersion were sequentially coated on the surface of the foam copper and dried in sequence to prepare an electrochemical glucose sensor electrode.

[0017] Preferably, in step (1), the divalent copper salt is selected from CuSO 4. 5H2O, Cu(NO3) 2. 3H2O, CuCl 2. 2H2O; the divalent cobalt salt is selected from CoSO 4. 7H2O、Co(NO3) 2. 6H2O, CoCl 2. Any one of 6H2O.

[0018] Preferably, in step (1), the total concentration of the aqueous solution of the divalent copper salt and the divalent cobalt salt is 4-8 mM; the concentration of the trimesic acid is 4-8 mM;

[0019] The molar ratio of copper to cobalt in the aqueous solution of the divalent copper salt and the divalent cobalt salt is 0.5-2:1, and the volume ratio of the purified water, DMF and ethanol is 1:1:1.

[0020] More preferably, in step (1), the total concentration of the aqueous solution of the divalent copper salt and the divalent cobalt salt is 6 mM; the concentration of the trimesic acid is 6 mM;

[0021] The molar ratio of copper to cobalt in the aqueous solution of the divalent copper salt and the divalent cobalt salt is 1-1.5:1, and the volume ratio of the purified water, DMF and ethanol is 1:1:1.

[0022] Preferably, in step (1), the temperature of the hydrothermal reaction is 90-110° C., and the time of the hydrothermal reaction is 10-14 h; the vacuum drying temperature is 60-80° C., and the vacuum drying time is 10-14 h.

[0023] More preferably, in step (1), the temperature of the hydrothermal reaction is 100° C., and the time of the hydrothermal reaction is 12 h; the vacuum drying temperature is 70° C., and the vacuum drying time is 12 h.

[0024] Preferably, in step (2), the volume ratio of ethanol to purified water is 1:3; and the concentration of the CuCo-BTC dispersion is 50-150 mg / mL.

[0025] Preferably, in step (3), the particle size of the nanogold in the nanogold dispersion is 1-5 nm, and the concentration of the nanogold dispersion is 0.03585-0.05975 mg / mL.

[0026] Preferably, in step (4), the length of the MWCNTs is 10-30 μm and the outer diameter is 20-30 nm; the concentration of the Nafion solution is 5% (w / w), the volume ratio of the Nafion solution to ethanol is 1:9; and the concentration of the MWCNTs dispersion is 6.6-13.3 mg / mL.

[0027] Preferably, in step (5), the coating amount of the MWCNTs dispersion on the surface of the foam copper is 0.5-1.0 mg / cm 2 The coating amount (dry weight) of the nano-gold dispersion is 1.796-2.987 μg / cm 2 The coating amount (dry weight) of the CuCo-BTC dispersion is 1.25-3.75 mg / cm 2 .

[0028] Preferably, in step (5), the drying temperature after sequentially coating the MWCNTs dispersion, the nanogold dispersion and the CuCo-BTC dispersion is 50-60° C., and the drying time is 60 min, 30 min and 20 min, respectively.

[0029] The third aspect of the present invention is to provide a use of the non-enzyme glucose sensor electrode as described above and / or the non-enzyme glucose sensor electrode prepared by the method as described above in the manufacture of a glucose sensor.

[0030] A fourth aspect of the present invention is to provide an enzyme-free glucose sensor, which is made using the above-mentioned enzyme-free glucose sensor electrode and / or the enzyme-free glucose sensor electrode prepared by the above-mentioned method, and is used for qualitative and quantitative detection of glucose.

[0031] The present invention adopts the above technical solution, which has the following technical effects compared with the prior art:

[0032] (1) The present invention uses MWCNTs, nano-gold and CuCo bimetallic organic framework materials to modify foam copper, wherein MWCNTs can increase the specific surface area and conductivity of the electrode, nano-Au can improve the conductivity and sensitivity of the electrode, and CuCo-BTC can increase the catalytic activity of the electrode. Therefore, after the composite, the catalytic oxidation performance of the electrode for glucose is effectively improved.

[0033] (2) The enzyme-free glucose sensor electrode of the present invention is modified sequentially on the surface of copper foam by MWCNTs, nano-gold and CuCo-BTC. The preparation method is simple, the conditions are mild, and the whole process does not involve medium or high temperature heat treatment. It is energy-saving and environmentally friendly, has low production cost, and is suitable for large-scale production.

[0034] (3) The electrochemical glucose sensor electrode prepared by the present invention reacts rapidly to glucose solution, with a linear range of 0.01-5mM and 5-9mM, a detection limit of 3.4μM, and good anti-interference performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a scanning electron microscope image of the non-enzyme glucose sensor electrode provided in Example 1 of the present invention.

[0036] Figure 2 This is the energy spectrum of the non-enzyme glucose sensor electrode provided in Example 1 of the present invention.

[0037] Figure 3 TEM images of the non-enzymatic glucose sensor electrode (a) and nano-gold (b) provided in Example 1 of the present invention.

[0038] Figure 4 The cyclic voltammograms of the non-enzymatic glucose sensor electrode provided in Example 1 of the present invention in the presence and absence of glucose (a), the cyclic voltammograms at different scan rates (b), and the relationship between the anodic peak current density and the cathodic peak current density and the scan rate (c) are shown.

[0039] Figure 5 (a) is a time-current density curve of the non-enzymatic glucose sensor electrode provided in Example 1 of the present invention when detecting continuously added glucose of different concentrations, and (b) is a linear relationship diagram between glucose concentration and current density.

[0040] Figure 6 This is a time-current density response diagram of the non-enzymatic glucose sensor electrode provided in Example 1 of the present invention to different interferents.

[0041] Figure 7 The non-enzymatic glucose sensor electrode provided in Example 1 of the present invention detects the current density value of 0.5 mM glucose at different times.

[0042] Figure 8 This is the cyclic voltammetry curve of the five parallel non-enzymatic glucose sensor electrodes provided in Example 1 of the present invention in 0.5 mM glucose.

[0043] Figure 9 These are the cyclic voltammetry curves of the non-enzymatic glucose sensor electrodes provided in Examples 1, 6, and 8 of the present invention in 0.5 mM glucose. DETAILED DESCRIPTION

[0044] The present invention will be described in detail and specifically below through specific examples to provide a better understanding of the present invention, but the following examples do not limit the scope of the present invention.

[0045] Example 1 Preparation of Non-enzymatic Glucose Sensor Electrode

[0046] (1) Weigh 0.750 g of copper sulfate pentahydrate and 0.843 g of cobalt sulfate heptahydrate, dissolve them in 10 mL of deionized water to obtain a mixed solution I; weigh 1.2608 g of 1,3,5-trisic acid, dissolve them in 10 mL of DMF and 10 mL of anhydrous ethanol to obtain a mixed solution II; mix the mixed solutions I and II, stir at room temperature for 10 min, react at 100°C for 12 h, cool to room temperature, wash the precipitate with ethanol and deionized water in sequence, centrifuge, and dry the precipitate in a vacuum drying oven at 70°C for 12 h to obtain CuCo-BTC powder;

[0047] (2) Weigh 0.1 g of CuCo-BTC powder and dilute it to 1 mL with a mixture of water and ethanol (the volume ratio of ethanol to water is 1:3). Ultrasonic dispersion is performed for 10 min to obtain a CuCo-BTC dispersion with a concentration of 100 mg / mL.

[0048] (3) Add 50 mL of 0.01% HAuCl4 into a three-necked flask and heat with stirring until boiling. Then, quickly inject 1.7 mL of 1% sodium citrate solution and 0.5 mL of 1% PVP solution into the three-necked flask in sequence. Continue heating and stirring for 30 min, then stop heating and cool to room temperature to prepare a nano-gold dispersion with a concentration of 0.0478 mg / mL.

[0049] (4) Weigh 0.01 g of MWCNTs (length 10-30 μm, outer diameter 20-30 nm) powder and dilute to 1 mL with a mixture of perfluorinated resin solution (Nafion) solution (5% w / w) and ethanol (volume ratio of Nafion solution to ethanol is 1:9). Ultrasonic dispersion is performed for 10 min to obtain a MWCNTs dispersion with a concentration of 10 mg / mL.

[0050] (5) Take 60 μL MWCNTs dispersion, 40 μL nanogold dispersion and 20 μL CuCo-BTC dispersion and evenly coat them on the surface of the foam copper (coating area 0.8 cm) 2 ), each time the solution to be coated was dried before coating other solutions, the drying temperature was 50 ° C, the drying time was 60 min, 30 min, and 20 min respectively, to obtain the final electrode, and the final electrode was recorded as (CuCo-BTC / Au / MWCNTs / CF)1.

[0051] Example 2 Preparation of Non-enzyme Glucose Sensor Electrode

[0052] (1) Weigh 0.750 g of copper sulfate pentahydrate and 0.843 g of cobalt sulfate heptahydrate, dissolve them in 10 mL of deionized water to obtain a mixed solution I; weigh 1.2608 g of 1,3,5-trisic acid, dissolve them in 10 mL of DMF and 10 mL of anhydrous ethanol to obtain a mixed solution II; mix the mixed solutions I and II, stir at room temperature for 10 min, react at 100°C for 12 h, cool to room temperature, wash the precipitate with ethanol and deionized water in sequence, centrifuge, and dry the precipitate in a vacuum drying oven at 70°C for 12 h to obtain CuCo-BTC powder;

[0053] (2) Weigh 0.05 g of CuCo-BTC powder and dilute it to 1 mL with a mixture of water and ethanol (the volume ratio of ethanol to water is 1:3). Ultrasonic dispersion is performed for 10 min to obtain a CuCo-BTC dispersion with a concentration of 50 mg / mL.

[0054] (3) Add 50 mL of 0.005% HAuCl4 into a three-necked flask and heat with stirring until boiling. Then, add 1.7 mL of 1% sodium citrate solution and 0.5 mL of 1% PVP solution into the three-necked flask in sequence. Continue heating and stirring for 30 min, then stop heating and cool to room temperature to prepare a nano-gold dispersion with a concentration of 0.0239 mg / mL.

[0055] (4) Weigh 0.0066 g of MWCNTs (length 10-30 μm, outer diameter 20-30 nm) powder and dilute to 1 mL with a mixture of Nafion solution (5% w / w) and ethanol (volume ratio of Nafion solution to ethanol is 1:9). Ultrasonic dispersion is performed for 10 min to obtain a MWCNTs dispersion with a concentration of 6.6 mg / mL.

[0056] (5) Take 60 μL MWCNTs dispersion, 40 μL nanogold dispersion and 20 μL CuCo-BTC dispersion and evenly coat them on the surface of the foam copper (coating area 0.8 cm) 2 ), each time the solution to be coated was dried before coating other solutions, the drying temperature was 50 ° C, the drying time was 60 min, 30 min, and 20 min respectively, to obtain the final electrode, and the final electrode was recorded as (CuCo-BTC / Au / MWCNTs / CF)2.

[0057] Example 3 Preparation of Non-enzyme Glucose Sensor Electrode

[0058] (1) Weigh 0.750 g of copper sulfate pentahydrate and 0.843 g of cobalt sulfate heptahydrate, dissolve them in 10 mL of deionized water to obtain a mixed solution I; weigh 1.2608 g of 1,3,5-trisic acid, dissolve them in 10 mL of DMF and 10 mL of anhydrous ethanol to obtain a mixed solution II; mix the mixed solutions I and II, stir at room temperature for 10 min, react at 100°C for 12 h, cool to room temperature, wash the precipitate with ethanol and deionized water in sequence, centrifuge, and dry the precipitate in a vacuum drying oven at 70°C for 12 h to obtain CuCo-BTC powder;

[0059] (2) Weigh 0.15 g of CuCo-BTC powder and dilute it to 1 mL with a mixture of water and ethanol (the volume ratio of ethanol to water is 1:3). Ultrasonic dispersion is performed for 10 min to obtain a CuCo-BTC dispersion with a concentration of 150 mg / mL.

[0060] (3) Add 50 mL of 0.0125% HAuCl4 into a three-necked flask and heat with stirring until boiling. Then, quickly inject 1.7 mL of 1% sodium citrate solution and 0.5 mL of 1% PVP solution into the three-necked flask in sequence. Continue heating and stirring for 30 min, then stop heating and cool to room temperature to prepare a nano-gold dispersion with a concentration of 0.0597 mg / mL.

[0061] (4) Weigh 0.0133 g of MWCNTs (length 10-30 μm, outer diameter 20-30 nm) powder and dilute to 1 mL with a mixture of Nafion solution (5% w / w) and ethanol (volume ratio of Nafion solution to ethanol is 1:9). Ultrasonic dispersion is performed for 10 min to obtain a MWCNTs dispersion with a concentration of 13.3 mg / mL.

[0062] (5) Take 60 μL MWCNTs dispersion, 40 μL nanogold dispersion and 20 μL CuCo-BTC dispersion and evenly coat them on the surface of the foam copper (coating area 0.8 cm) 2 ), each time the solution to be coated was dried before coating other solutions, the drying temperature was 50 ° C, the drying time was 60 min, 30 min, and 20 min respectively, to obtain the final electrode, and the final electrode was recorded as (CuCo-BTC / Au / MWCNTs / CF)3.

[0063] Example 4 Preparation of Non-enzyme Glucose Sensor Electrode

[0064] In this Example 4, step (1) uses 0.5 g of copper sulfate pentahydrate and 1.124 g of cobalt sulfate heptahydrate, and the other steps are the same as in Example 1. The final electrode obtained is recorded as (CuCo-BTC / Au / MWCNTs / CF)4.

[0065] Example 5 Preparation of Non-enzyme Glucose Sensor Electrode

[0066] In Example 5, step (1) used 1.0 g of copper sulfate pentahydrate and 0.562 g of cobalt sulfate heptahydrate, and the other steps were the same as in Example 1. The final electrode was recorded as (CuCo-BTC / Au / MWCNTs / CF)5.

[0067] Example 6 Preparation of Non-enzyme Glucose Sensor Electrode

[0068] (1) Weigh 0.75 g of copper sulfate pentahydrate and 0.843 g of cobalt sulfate heptahydrate, dissolve them in 10 mL of deionized water to obtain a mixed solution I; weigh 1.2608 g of 1,3,5-trisic acid, dissolve them in 10 mL of DMF and 10 mL of anhydrous ethanol to obtain a mixed solution II; mix the mixed solutions I and II, stir at room temperature for 10 min, react at 100°C for 12 h, cool to room temperature, wash the precipitate with ethanol and deionized water in sequence, centrifuge, and dry the precipitate in a vacuum drying oven at 70°C for 12 h to obtain CuCo-BTC powder;

[0069] (2) Weigh 0.1 g of CuCo-BTC powder and dilute it to 1 mL with a mixture of water and ethanol (the volume ratio of ethanol to water is 1:3). Ultrasonic dispersion is performed for 10 min to obtain a CuCo-BTC dispersion with a concentration of 100 mg / mL.

[0070] (3) Weigh 0.01 g of MWCNTs (length 10-30 μm, outer diameter 20-30 nm) powder and dilute to 1 mL with a mixture of Nafion solution (5% w / w) and ethanol (volume ratio of Nafion solution to ethanol is 1:9). Ultrasonic dispersion is performed for 10 min to obtain a MWCNTs dispersion with a concentration of 10 mg / mL.

[0071] (4) Take 60 μL MWCNTs dispersion and 20 μL CuCo-BTC dispersion and evenly coat them on the surface of the foam copper (coating area 0.8 cm 2 ), each time the solution to be coated was dried before coating other solutions, the drying temperature was 50 ° C, the drying time was 60 min and 20 min respectively, and the final electrode was obtained, which was recorded as CuCo-BTC / MWCNTs / CF.

[0072] Example 7 Preparation of Non-enzyme Glucose Sensor Electrode

[0073] (1) Weigh 0.75 g of copper sulfate pentahydrate and 0.843 g of cobalt sulfate heptahydrate, dissolve them in 10 mL of deionized water to obtain a mixed solution I; weigh 1.2608 g of 1,3,5-trisic acid, dissolve them in 10 mL of DMF and 10 mL of anhydrous ethanol to obtain a mixed solution II; mix the mixed solutions I and II, stir at room temperature for 10 min, react at 100°C for 12 h, cool to room temperature, wash the precipitate with ethanol and deionized water in sequence, centrifuge, and dry the precipitate in a vacuum drying oven at 70°C for 12 h to obtain CuCo-BTC powder;

[0074] (2) Weigh 0.1 g of CuCo-BTC powder and dilute it to 1 mL with a mixture of water and ethanol (the volume ratio of ethanol to water is 1:3). Ultrasonic dispersion is performed for 10 min to obtain a CuCo-BTC dispersion with a concentration of 100 mg / mL.

[0075] (3) Add 50 mL of 0.0125% HAuCl4 into a three-necked flask and heat with stirring until boiling. Then, quickly inject 1.7 mL of 1% sodium citrate solution and 0.5 mL of 1% PVP solution into the three-necked flask in sequence. Continue heating and stirring for 30 min, then stop heating and cool to room temperature to prepare a nano-gold dispersion with a concentration of 0.0597 mg / mL.

[0076] (4) Take 40 μL of gold nanoparticles dispersion and 20 μL of CuCo-BTC dispersion and evenly coat them on the surface of the foam copper (coating area 0.8 cm) 2 ), each time the solution to be coated was dried before coating other solutions, the drying temperature was 50 ° C, the drying time was 30 min and 20 min respectively, and the final electrode was obtained, which was recorded as CuCo-BTC / Au / CF.

[0077] Example 8 Preparation of Non-enzyme Glucose Sensor Electrode

[0078] (1) Weigh 0.750 g of copper sulfate pentahydrate and 0.843 g of cobalt sulfate heptahydrate, dissolve them in 10 mL of deionized water to obtain a mixed solution I; weigh 1.2608 g of 1,3,5-trisic acid, dissolve them in 10 mL of DMF and 10 mL of anhydrous ethanol to obtain a mixed solution II; mix the mixed solutions I and II, stir at room temperature for 10 min, react at 100°C for 12 h, cool to room temperature, wash the precipitate with ethanol and deionized water in sequence, centrifuge, and dry the precipitate in a vacuum drying oven at 70°C for 12 h to obtain CuCo-BTC powder;

[0079] (2) Weigh 0.1 g of CuCo-BTC powder and dilute it to 1 mL with a mixture of water and ethanol (the volume ratio of ethanol to water is 1:3). Ultrasonic dispersion is performed for 10 min to obtain a CuCo-BTC dispersion with a concentration of 100 mg / mL.

[0080] (3) Take 20 μL of CuCo-BTC dispersion and evenly coat it on the surface of the foam copper (coating area 0.8 cm 2 ), drying temperature 50 ℃, drying for 20 min, to obtain the final electrode, recorded as (CuCo-BTC).

[0081] Example 9 Preparation of Non-enzyme Glucose Sensor Electrode

[0082] (1) Weigh 1.5 g of copper sulfate pentahydrate and dissolve it in 10 mL of deionized water to obtain a mixed solution I; weigh 1.2608 g of 1,3,5-trimethylbenzene trimesic acid and dissolve it in 10 mL of DMF and 10 mL of anhydrous ethanol to obtain a mixed solution II; mix the mixed solutions I and II, stir them at room temperature for 10 min, react them at 100°C for 12 h, cool them to room temperature, wash the precipitate with ethanol and deionized water in sequence, centrifuge the precipitate, and dry it in a vacuum drying oven at 70°C for 12 h to obtain Cu-BTC powder;

[0083] (2) Weigh 0.1 g of Cu-BTC powder and dilute it to 1 mL with a mixture of water and ethanol (the volume ratio of ethanol to water is 1:3). Ultrasonic dispersion is performed for 10 min to obtain a Cu-BTC dispersion with a concentration of 100 mg / mL.

[0084] (3) Add 50 mL of 0.01% HAuCl4 into a three-necked flask and heat with stirring until boiling. Then, quickly inject 1.7 mL of 1% sodium citrate solution and 0.5 mL of 1% PVP solution into the three-necked flask in sequence. Continue heating and stirring for 30 min, then stop heating and cool to room temperature to prepare a nano-gold dispersion with a concentration of 0.0478 mg / mL.

[0085] (4) Weigh 0.01 g of MWCNTs (length 10-30 μm, outer diameter 20-30 nm) powder and dilute to 1 mL with a mixture of Nafion solution (5% w / w) and ethanol (volume ratio of Nafion solution to ethanol is 1:9). Ultrasonic dispersion is performed for 10 min to obtain a MWCNTs dispersion with a concentration of 10 mg / mL.

[0086] (5) Take 60 μL MWCNTs dispersion, 40 μL nanogold dispersion and 20 μL Cu-BTC dispersion and evenly coat them on the surface of the foam copper (coating area 0.8 cm) 2 ), each time the solution to be coated was dried before coating other solutions, the drying temperature was 50 ° C, and the drying time was 60 min, 30 min, and 20 min respectively, to obtain the final electrode, which was recorded as Cu-BTC / Au / MWCNTs / CF.

[0087] Example 10 Preparation of Non-enzyme Glucose Sensor Electrode

[0088] (1) Weigh 1.686 g of cobalt sulfate heptahydrate and dissolve it in 10 mL of deionized water to obtain a mixed solution I; weigh 1.2608 g of 1,3,5-trisic acid and dissolve it in 10 mL of DMF and 10 mL of anhydrous ethanol to obtain a mixed solution II; mix the mixed solutions I and II, stir them at room temperature for 10 min, react them at 100°C for 12 h, cool them to room temperature, wash the precipitate with ethanol and deionized water in sequence, centrifuge and dry the precipitate in a vacuum drying oven at 70°C for 12 h to obtain Co-BTC powder;

[0089] (2) Weigh 0.1 g of Co-BTC powder and dilute it to 1 mL with a mixture of water and ethanol (the volume ratio of ethanol to water is 1:3). Ultrasonic dispersion is performed for 10 min to obtain a Co-BTC dispersion with a concentration of 100 mg / mL.

[0090] (3) Add 50 mL of 0.01% HAuCl4 into a three-necked flask and heat with stirring until boiling. Then, quickly inject 1.7 mL of 1% sodium citrate solution and 0.5 mL of 1% PVP solution into the three-necked flask in sequence. Continue heating and stirring for 30 min, then stop heating and cool to room temperature to prepare a nano-gold dispersion with a concentration of 0.0478 mg / mL.

[0091] (4) Weigh 0.01 g of MWCNTs (length 10-30 μm, outer diameter 20-30 nm) powder and dilute to 1 mL with a mixture of Nafion solution (5% w / w) and ethanol (volume ratio of Nafion solution to ethanol is 1:9). Ultrasonic dispersion is performed for 10 min to obtain a MWCNTs dispersion with a concentration of 10 mg / mL.

[0092] (5) Take 60 μL MWCNTs dispersion, 40 μL nanogold dispersion and 20 μL Co-BTC dispersion and evenly coat them on the surface of the foam copper (coating area 0.8 cm) 2 ), each time the solution to be coated was dried before coating other solutions, the drying temperature was 50 ° C, and the drying time was 60 min, 30 min, and 20 min respectively, to obtain the final electrode, which was recorded as Co-BTC / Au / MWCNTs / CF.

[0093] Example 11 Preparation of Non-enzymatic Glucose Sensor Electrode

[0094] In Example 10, step (1) used 0.723 g of copper nitrate trihydrate and 0.606 g of cobalt chloride hexahydrate, and the other steps were the same as in Example 1. The final electrode was recorded as (CuCo-BTC / Au / MWCNTs / CF)6.

[0095] Performance Testing

[0096] Taking the (CuCo-BTC / Au / MWCNTs / CF)1 electrode prepared in Example 1 as an example, performance tests were conducted as follows:

[0097] 1. Material Characterization

[0098] (1) The morphology of the prepared electrode (CuCo-BTC / Au / MWCNTs / CF)1 was observed using scanning electron microscopy (SEM).

[0099] like Figure 1 As shown, the lower layer of the electrode is a curved tubular MWCNT, which is covered with block and granular CuCo-BTC materials. The electrode material is loose and porous, and can provide a large specific surface area.

[0100] Figure 2 This is the EDS image of electrode (CuCo-BTC / Au / MWCNTs / CF) 1. The results show that copper, cobalt, carbon, gold, and oxygen elements are evenly distributed on the electrode surface.

[0101] (2) The morphology of the prepared electrode (CuCo-BTC / Au / MWCNTs / CF) 1 was observed using a transmission electron microscope (TEM). In order to obtain the morphology of Au nanoparticles, the TEM image of the gold nanoparticles was tested separately. Figure 3 (a) Strip-shaped MWCNT materials and granular MOF materials can be seen. Figure 3 (b) shows that the size of gold nanoparticles is uniform, ranging from 1 to 5 nm.

[0102] 2. Electrochemical Performance Test of Glucose Sensor Containing (CuCo-BTC / Au / MWCNTs / CF)1 Electrode

[0103] The prepared (CuCo-BTC / Au / MWCNTs / CF)1 electrode was used as the working electrode, the platinum sheet as the counter electrode, and the Ag / AgCl electrode as the reference electrode to construct a glucose three-electrode system, and the test was carried out using 0.1M NaOH solution as the electrolyte.

[0104] (1) Electrocatalytic activity towards glucose

[0105] At a potential of -0.2-0.8 V, 0.5 mM glucose was added to the electrolyte, and the cyclic voltammetry curves of the electrode were tested in the presence or absence of glucose. Figure 4 a shows that when glucose is added, an obvious catalytic current is exhibited, indicating that the electrode has good catalytic activity for glucose.

[0106] At a potential of 0-0.8 V, the scan rate was gradually increased to perform cyclic voltammetry scans and observe the current response of the electrode to glucose. Figure 4b shows the CV graphs of the electrode in an electrolyte containing 0.5 mM glucose at different scan rates (20-120 mV / s).

[0107] like Figure 4 As shown in c, with the increase of scan rate, the cathode and anode peak current densities show a good linear relationship with v, and the linear correlation coefficients are R pa 2 =0.99647, R pc 2 =0.99719, indicating that the electrochemical reaction process of the electrode is controlled by surface adsorption.

[0108] (2) Linear range, detection limit and sensitivity

[0109] Under 0.6V constant potential scanning, glucose solution with a concentration gradient from low to high was added to the electrolyte with a sampling interval of 50s, and the time-current curve of the electrode response to different concentrations of glucose was tested. The results are shown in the figure. Figure 5 As shown in a, the electrode has a good response to different concentrations of glucose.

[0110] according to Figure 5 As can be seen from b, the current density increases linearly with the glucose concentration from 0.01 mM to 9 mM. The corresponding linear equation when the glucose concentration is in the range of 0.01-5 mM is: y = 1.0214x + 0.1058 (R 2 =0.992), the sensitivity is 1021.4μA·mM -1 cm -2 When the glucose concentration is in the range of 5.0-9.0 mM, the corresponding linear equation is: y = 0.5119x + 2.3388 (R 2 =0.998), the sensitivity is 511.9μA·mM -1 cm -2 , with a detection limit of 3.4 μM.

[0111] (3) Anti-interference performance

[0112] At a constant potential of 0.6 V, 0.1 mM glucose, 0.01 mM uric acid, 0.01 mM ascorbic acid, 0.01 mM dopamine hydrochloride, 0.01 mM L-cysteine solution and 0.1 mM glucose were added to the electrolyte in sequence to test the anti-interference performance of the electrode.

[0113] The results are as follows Figure 6 It was shown that the current responses of these interferents were negligible compared with the current response of 0.1 mM glucose, indicating that the electrode had excellent selectivity.

[0114] (4) Reproducibility and stability

[0115] At a voltage of 0.6 V and constant stirring, 0.5 mM glucose solution was added to the test system, and the current response values of the electrode at different times were tested. Figure 7 As shown in Figure 2, the current value on the 28th day can still maintain 99.59% of the current value on the first day, indicating that the electrochemical glucose sensor has good stability. Five identical sensors were prepared and the same concentration of glucose was added to the test system. Figure 8 As shown in the figure, the relative standard deviation (RSD) of the peak current response value is less than 5%, indicating that the constructed enzyme-free glucose sensor has good reproducibility.

[0116] 3. Collaborative capabilities

[0117] At a potential of -0.2-0.8 V, 0.5 mM glucose was added to the electrolyte, and the cyclic voltammetry curves of the different electrodes prepared in Examples 1, 6, and 8 were tested in the presence of glucose. Figure 9 As shown in the figure, by comparison, it can be seen that the overall peak current response of CuCo-BTC / CF, CuCo-BTC / MWCNTs / CF and (CuCo-BTC / Au / MWCNTs / CF)1 electrodes gradually increases, indicating that the prepared (CuCo-BTC / Au / MWCNTs / CF)1 sensor electrode has good catalytic activity for glucose, and there is an obvious synergistic effect between the CuCo-BTC, MWCNTs and nanogold in the electrode.

[0118] Under a constant potential scan at 0.6 V, a glucose solution with a concentration gradient from low to high was added dropwise to the electrolyte with a sample addition interval of 50 seconds. The linear range, detection limit, and sensitivity of the electrodes prepared in Examples 1-11 for glucose detection were tested. The results are shown in Table 1.

[0119] As can be seen from Table 1, compared with Examples 1, 6, 7, and 8, the linear range of the sensor electrode (CuCo-BTC / Au / MWCNTs / CF)1 is significantly increased and the sensitivity is higher than that of CuCo-BTC / CF, CuCo-BTC / MWCNTs / CF, and CuCo-BTC / Au / CF, which further illustrates the synergistic effect between CuCo-BTC, MWCNTs, and gold nanoparticles in the electrode.

[0120] Comparing Examples 1, 9, and 10, the linear range of (CuCo-BTC / Au / MWCNTs / CF) 1 is significantly wider and the sensitivity is higher than that of Co-BTC / Au / MWCNTs / CF and Cu-BTC / Au / MWCNTs / CF, indicating that the CuCo bimetallic organic framework electrode has better catalytic activity than the single metal organic framework electrode (Cu or Co).

[0121] Comparative Examples 1, 4, and 5 show that when the Cu / Co molar ratio is 1:1, the electrode has better catalytic activity for glucose; Comparative Examples 1, 2, and 3 show that when the MWCNTs dispersion, nano-Au dispersion, and CuCo-BTC

[0122] The amount of dispersion was 0.75 mg / cm 2 , 2.39μg / cm 2 , 2.5mg / cm 2 When the reaction temperature is 0.5 ℃, the prepared (CuCo-BTC / Au / MWCNTs / CF)1 has good electrocatalytic activity towards glucose.

[0123] Comparison with Examples 1 and 11 shows that the types of the three divalent copper salts and divalent cobalt salts have little effect on the catalytic activity of the sensor electrode.

[0124] Table 1 Linear range, sensitivity and detection limit of glucose detected by electrodes prepared in Examples 1-11

[0125] In summary, the preparation method of the enzyme-free glucose sensor electrode provided by the present invention is to modify the foam copper surface with a certain amount of MWCNT solution, nano-gold solution and CuCo-BTC solution in sequence to obtain a high

[0126] The electrode has high selectivity, high sensitivity, anti-interference and wide linear range, and effectively improves the catalytic oxidation performance of the electrode for glucose 10; and its preparation method is simple, the conditions are mild, and it is suitable for large-scale production.

[0127] While the specific embodiments of the present invention have been described in detail above, these are merely exemplary and the present invention is not limited thereto. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, any equivalent changes and modifications made without departing from the spirit and scope of the present invention are intended to be encompassed within the scope of the present invention.

Claims

1. Enzyme-free glucose sensor electrode based on CuCo bimetallic organic framework material, characterized in that: The electrode comprises a foam copper substrate and multi-walled carbon nanotubes (MWCNTs), nano-gold materials and CuCo bimetallic organic framework materials sequentially loaded on the surface of the foam copper substrate; The loading amount of the multi-walled carbon nanotube material (MWCNTs) is 0.5-1.0 mg / cm 2 The loading amount of the nano-gold material is 1.796-2.987 μg / cm 2 The loading amount of the CuCo bimetallic organic framework material is 1.25-3.75 mg / cm 2 ; The CuCo bimetallic organic framework material uses trimesic acid (BTC) as an organic ligand, and the molar ratio of copper to cobalt in an aqueous solution of a divalent copper salt and a divalent cobalt salt is 1:

1.

2. The non-enzyme glucose sensor electrode according to claim 1, characterized in that The bent tubular MWCNTs on the multi-walled carbon nanotube material (MWCNTs) are coated in the bulk and granular CuCo bimetallic organic framework material to form a loose porous structure.

3. The method for preparing an enzyme-free glucose sensor electrode based on a CuCo bimetallic organic framework material according to any one of claims 1 to 2, characterized in that: The steps include: (1) An aqueous solution of a divalent copper salt and a divalent cobalt salt, a solution of trimesic acid (BTC) in N,N-dimethylformamide (DMF) and anhydrous ethanol are mixed and subjected to a hydrothermal reaction at a certain temperature. The precipitate is washed with purified water and an ethanol solution in sequence, centrifuged and vacuum dried to obtain CuCo-BTC powder; (2) Dispersing CuCo-BTC powder in a mixture of purified water and ethanol, and then ultrasonically dispersing the mixture to obtain a CuCo-BTC dispersion; (3) Add sodium citrate and polyvinyl pyrrolidone solution to the HAuCl4 solution, stir and heat to obtain a nano-gold dispersion; (4) Dispersing multi-walled carbon nanotube (MWCNT) powder in a mixture of perfluorinated resin solution (Nafion) and ethanol, and then ultrasonically dispersing to obtain a MWCNT dispersion; (5) MWCNTs dispersion, nanogold dispersion and CuCo-BTC dispersion were sequentially coated on the surface of copper foam and dried in sequence to prepare an electrochemical glucose sensor electrode.

4. The method for preparing an enzyme-free glucose sensor electrode according to claim 3, wherein: In step (1), the divalent copper salt is selected from CuSO4 . 5H2O, Cu(NO3)2 . 3H2O, CuCl2 . 2H2O; the divalent cobalt salt is selected from CoSO4 . 7H2O、Co(NO3)2 . 6H2O, CoCl2 . Any one of 6H2O.

5. The method for preparing the non-enzyme glucose sensor electrode according to claim 3, characterized in that: In step (1), the total concentration of the aqueous solution of the divalent copper salt and the divalent cobalt salt is 4-8 mM; the concentration of the trimesic acid is 4-8 mM; The volume ratio of the purified water, N,N-dimethylformamide (DMF) and ethanol is 1:1:

1.

6. The method for preparing the non-enzyme glucose sensor electrode according to claim 3, characterized in that: In step (2), the volume ratio of ethanol to purified water is 1:3; the concentration of the CuCo-BTC dispersion is 50-150 mg / mL.

7. The method for preparing an enzyme-free glucose sensor electrode according to claim 3, wherein: In step (3), the particle size of the nanogold in the nanogold dispersion is 1-5 nm, and the concentration of the nanogold dispersion is 0.03585-0.05975 mg / mL.

8. The method for preparing an enzyme-free glucose sensor electrode according to claim 3, wherein: In step (4), the length of the multi-walled carbon nanotube material (MWCNTs) is 10-30 μm and the outer diameter is 20-30 nm; the concentration of the perfluorinated resin solution (Nafion) is 5% (w / w), the volume ratio of the perfluorinated resin solution (Nafion) to ethanol is 1:9; and the concentration of the MWCNTs dispersion is 6.6-13.3 mg / mL.

9. Use of the non-enzyme glucose sensor electrode according to any one of claims 1 to 2 and / or the non-enzyme glucose sensor electrode prepared by the method according to any one of claims 3 to 8 in the manufacture of a glucose sensor.

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