Biological fluid glucose detection electrode and preparation process thereof

Abstract

The invention discloses a biological fluid glucose detection electrode and a preparation process thereof, the biological fluid glucose detection electrode comprises a conductive substrate, the outer side of the conductive substrate is coated with a catalytic layer, and the catalytic layer is used for modifying the catalytic activity of the conductive substrate on glucose electrooxidation; the catalyst layer is an amorphous porous structure layer; the catalyst layer is formed by compounding an MOF material with an amorphous structure and one of nanoparticles, a polymer and graphene; the MOF material is amorphous MIL-101 (Cr)-NH2, and the amorphous MIL-101 (Cr)-NH2 is prepared from a metal precursor Cr and a terephthalic acid ligand into which an amino group is introduced as raw materials. On the basis of the directly synthesized amorphous MOF composite material, the electrocatalytic activity of the electrode on glucose electrooxidation is modified, so that the detection efficiency and precision of the electrode on glucose in biological fluid are improved.

Description

Technical Field

[0001] The invention relates to the technical field of glucose detection electrodes, in particular to a biological fluid glucose detection electrode and a preparation process thereof. Background Art

[0002] When diabetic patients test their blood sugar levels, they need to use a needle device to draw blood samples for analysis. The needle device can cause pain and wound infection. Therefore, using biological fluids such as tears, saliva, urine or sweat instead of blood as a sampling target is an urgent method to achieve non-invasive and painless blood sugar testing. At present, the electrochemical method is considered to be an effective detection method with greater applicability, and a large number of non-enzymatic electrochemical sensors for glucose detection have appeared on the market; with the development of metal organic framework materials, their porosity, uniform pore size and large surface area and other characteristics, in theory, have a beneficial effect on improving the efficiency of glucose detection, which makes the application of metal organic framework materials expected to be developed in the direction of glucose detection, however, MOF materials usually exhibit low electrical conductivity, which will affect the detection results of glucose; it has been found that the conductivity of the material will increase in the amorphous state, however, the amorphous MOF generated by processing the crystalline MOF by heat treatment, high pressure treatment and other methods, due to the reduction of porosity, the conductivity is not effectively improved, so it is of positive significance to develop electrodes modified by directly synthesized amorphous MOF materials and their derivatives for glucose detection in biological fluids. Summary of the invention

[0003] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a biological fluid glucose detection electrode and a preparation process thereof, based on the electrocatalytic activity of the electrode modified by a directly synthesized amorphous MOF composite material, to improve the electrode's detection efficiency and accuracy for glucose.

[0004] Technical solution: To achieve the above-mentioned purpose, the present invention provides a biological fluid glucose detection electrode and its preparation process, comprising a conductive substrate, the outer side of which is coated with a catalytic layer for modifying the catalytic activity of the conductive substrate for glucose electro-oxidation; the catalytic layer is an amorphous porous structure layer.

[0005] Furthermore, the catalytic layer is composited by an amorphous MOF material and one of nanoparticles, polymers and graphene.

[0006] Furthermore, the MOF material is amorphous MIL-101(Cr)-NH2, and the amorphous MIL-101(Cr)-NH2 is prepared from metal precursor Cr and terephthalic acid ligand introduced with amino groups as raw materials.

[0007] Further, the following steps are included:

[0008] Step I, dissolving Cr(NO3)3·9H2O in ultrapure water and stirring to obtain solution A;

[0009] Step II, dissolving BDC-NH2 in the solution A, and stirring to obtain solution B;

[0010] Step III, transferring the solution B into a reaction kettle and encapsulating it, and reacting it at 200° C. to obtain a solid C;

[0011] Step IV, washing the solid C with ethanol, centrifugally separating and drying it, and activating it under vacuum to obtain MIL-101(Cr)-NH2 powder;

[0012] Step V, the prepared MIL-101(Cr)-NH2 powder is first mixed with PVDF and NMP to obtain solution D, and then mixed with graphene at a volume ratio of 10:1 to obtain a MIL-101(Cr)-NH2 / graphene composite material solution after ultrasonic treatment;

[0013] Step VI, drop-casting the prepared MIL-101(Cr)-NH2 / graphene composite material solution on a stainless steel-316 electrode to form an amorphous porous structure layer;

[0014] Step VII, test in a three-electrode system, electrode F, Ag / AgCl (1M KCl) and platinum sheet are used as working electrode, reference electrode and auxiliary electrode respectively. Square wave voltammetry, cyclic voltammetry and impedance test are used to confirm the electrochemical performance of the composite electrode.

[0015] Furthermore, in the solution A prepared in step I, the concentration of Cr(NO3)3·9H2O is 0.2-0.3 g / mL; in the solution B prepared in step II, the concentration of BDC-NH2 is 0.08-0.15 g / mL; in steps I and II, the stirring speed is 500 rpm and the stirring time is 10 min.

[0016] Furthermore, in step III, the reaction time of solution B at 200° C. is 18 h; in step IV, solid C is washed with anhydrous ethanol at 70° C. for 3 h, dried at 80° C. for 24 h after separation, and vacuum activated at 150° C. for 24 h.

[0017] Furthermore, in step V, the concentration of MIL-101(Cr)-NH2 in solution D is 0.05-0.1 g / mL, and two drops of PVDF are added to every 1 mL of solution D.

[0018] Further, in step VI, every 1 cm 215 μL of MIL-101(Cr)-NH2 / graphene composite material solution was dropped onto the stainless steel-316 electrode and slowly heated to dryness.

[0019] Furthermore, in step VI, before adding the MIL-101(Cr)-NH2 / graphene composite material solution, the stainless steel-316 electrode is first cleaned in an ethanol ultrasonic bath for 3 minutes and then rinsed with deionized water for multiple times.

[0020] Beneficial effects: The biological fluid glucose detection electrode and its preparation process of the present invention directly synthesize the MIL-101(Cr)-NH2 / graphene composite material, which is drop-casted on the electrode surface to form a catalytic layer, and its amorphous structure is used to enhance the conductivity of the electrode, and the electrocatalytic activity of the electrode is modified, thereby catalyzing the electro-oxidation activity of glucose on the electrode surface. The composite added graphene further increases the surface area and conductivity of MIL-101(Cr)-NH2, and is suitable for the detection of glucose by SWV technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 SEM images of bare SS, MIL-101(Cr)-NH2 / SS and MIL101(Cr)-NH2 / graphene / SS;

[0022] Figure 2 It is a schematic structural diagram of an embodiment of a biological fluid glucose detection electrode of the present invention;

[0023] Figure 3 Electrochemical characterization using SWV, CV, and impedance spectroscopy was performed for bare SS, MIL-101(Cr)-NH2, and MIL101(Cr)-NH2 / graphene. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] As attached Figure 1-3 The biological fluid glucose detection electrode and its preparation process include a conductive substrate 1, the conductive substrate 1 is coated with a catalytic layer 2 on the outside, which is used to modify the catalytic activity of the conductive substrate 1 to glucose electro-oxidation; the catalytic layer 2 is an amorphous porous structure layer. The catalytic layer 2 is a composite of an amorphous MOF material and one of nanoparticles, polymers, and graphene.

[0026] The MOF material is amorphous MIL-101(Cr)-NH2, which is prepared from metal precursor Cr and amino-introduced terephthalic acid ligands as raw materials. The conductive substrate is a stainless steel-316 electrode, namely, a SS electrode.

[0027] This scheme directly synthesizes an amorphous MOF structure by selecting suitable metal precursors and organic ligands and introducing amino groups into the ligands without subsequent treatment of the prepared MOF, so that the prepared MOF material has structural characteristics such as porosity, high surface area, random distribution of metal ions and ligands within the framework, and lack of any long-range order. The MOF material can improve conductivity by providing additional structural defect sites and unsaturated coordination sites, thereby improving the conductivity of the electrode without adding other conductive materials. On this basis, conductive materials such as nanoparticles, polymers, and graphene are also compounded to further improve the conductive properties of the modified electrode.

[0028] Among them, it is preferred to add graphene material, because the surface area of ​​the material is further increased after the amorphous MIL-101(Cr)-NH2 of this scheme is compounded with graphene.

[0029] The large specific surface area of ​​graphene is used to load amorphous MIL-101(Cr)-NH2, and amorphous MIL-101(Cr)-NH2 is inserted between graphene sheets, thereby reducing the interaction force between graphene sheets and avoiding adsorption and aggregation between graphene sheets, thereby increasing the porosity and surface area, and enhancing the activity of amorphous MIL-101(Cr)-NH2.

[0030] Amorphous MIL-101(Cr)-NH2 is randomly arranged along the graphene surface, and multiple layers are superimposed to construct a three-dimensional irregular network space structure. This structure is laid flat on the electrode surface. The current is quickly transmitted within the sheet along the network structure of graphene, and is quickly transmitted between the sheets through amorphous MIL-101(Cr)-NH2. This enables the SS electrode modified by this material to effectively catalyze the electro-oxidation activity of glucose and improve the conductivity. When any position on the electrode surface contacts biological fluids such as sweat, the glucose in the sweat will undergo an electro-oxidation reaction on the electrode surface, thereby generating current. The current seeks the nearest path to quickly transmit to the electrode along the spatial three-dimensional irregular network constructed by graphene and MIL-101(Cr)-NH2, and then is transmitted to the detection equipment along the wire to reflect real-time detection data.

[0031] It not only maintains a high porosity and surface area, but also constructs multiple optional conductive paths to quickly find the shortest conductive path to improve conductivity. It also catalyzes the electro-oxidation activity of glucose, increases the current generation speed and current peak, and thus improves the sensitivity and accuracy of the electrode. It avoids the reduction in conductivity caused by the reduction in porosity, so as to improve the detection efficiency and accuracy of the electrode for glucose.

[0032] The electrode modified by MIL-101(Cr)-NH2 / graphene composite material was used for voltammetric oxidation and chronoamperometric oxidation of glucose, based on the reaction mechanism of glucose oxidation to glucose lactone on the surface of MIL-101(Cr)-NH2 / graphene / SS electrode, thus forming a current for glucose detection. Among them, the peak current generated by the SS electrode modified by MIL-101(Cr)-NH2 / graphene (10:1) was doubled compared with the bare SS electrode, and the detection effect was better.

[0033] The preparation process of the biological fluid glucose detection electrode specifically comprises the following steps:

[0034] Step I, dissolving Cr(NO3)3·9H2O in ultrapure water, stirring to obtain solution A; in solution A, the concentration of Cr(NO3)3·9H2O is 0.2-0.3 g / mL; the stirring speed is 500 rpm, and the stirring time is 10 min.

[0035] Step II, dissolving BDC-NH2 in the solution A, stirring to obtain solution B; in solution B, the concentration of BDC-NH2 is 0.08-0.15 g / mL; the stirring speed is 500 rpm, and the stirring time is 10 min.

[0036] Step III, transferring the solution B to a Teflon autoclave or a tetrafluoroethylene reactor for packaging, and autoclaving at 200° C. for 18 h to obtain a solid C.

[0037] Experimental verification shows that at lower temperatures, such as 140°C autoclave for 24 hours, the synthesized MIL-101(Cr)-NH2 has enhanced its crystallization performance to a certain extent, and three broad peaks appear at 16.60°, 8.95° and 5.05° in the XRD diffraction peak. However, at 200°C, the synthesized MIL-101(Cr)-NH2 has only one broad peak at 8.69° in the XRD diffraction peak, confirming that at 200°C, MIL-101(Cr)-NH2 is more likely to form an amorphous structure.

[0038] Step IV, the solid C is washed with anhydrous ethanol at 70° C. for 3 h, centrifuged, dried at 80° C. for 24 h, and activated in a vacuum environment at 150° C. for 24 h to obtain MIL-101(Cr)-NH2 powder.

[0039] According to the above preparation process, in order to confirm the synthesis of amorphous MIL-101(Cr)-NH2, the material synthesized in step IV was studied by FT-IR. This is because amorphous MOF is a random distribution of metal ions and ligands within the framework, lacking any long-range order. Therefore, amorphous MOF only shows diffuse scattering in the x-ray instrument. The XRD pattern shows that the lack of medium and long-range order in MIL-101(Cr)-NH2 makes the characterization process difficult, so FT-IR and SEM studies are used to ensure the synthesis of the MOF structure.

[0040] FT-IR studies have revealed the surface chemical properties of MIL-101(Cr) and its derivatives. -1 The OH stretching vibration band was detected at 1400 cm -1 and 1590cm -1 The bands at 1259, 160 and 770 cm-1 indicate the presence of carboxylic acid groups and C=C stretching vibrations of the benzene ring. -1 The band detected nearby is generated by CH deformation vibration. The aromatic CN stretching vibration of MIL-101(Cr)-NH2 is generated by 1254cm -1 The peak detected at 1600 cm indicates that for MIL-101(Cr)-NH2, C=N appears at 1600 cm -1 In addition, 590cm -1 The peak at refers to the symmetric stretching of Cr-O in the MOF structure. The synthesis of amorphous MIL-101(Cr)-NH2 was confirmed.

[0041] Step V, the prepared MIL-101 (Cr) -NH2 powder is first mixed with PVDF and NMP to obtain solution D; after ultrasonic treatment of solution D, it is mixed with graphene in a volume ratio of 10:1 to obtain a MIL-101 (Cr) -NH2 / graphene composite material solution; the concentration of MIL-101 (Cr) -NH2 in solution D is 0.05 ~ 0.1g / mL, and two drops of the PVDF are added to every 1mL of the solution D.

[0042] Step VI, drop-casting the prepared MIL-101(Cr)-NH2 / graphene composite material solution onto a stainless steel-316 electrode; before dropping the MIL-101(Cr)-NH2 / graphene composite material solution, first clean the stainless steel-316 electrode in an ethanol ultrasonic bath for 3 minutes, then rinse with deionized water for several times; then, at every 1 cm 2 15 μL of MIL-101(Cr)-NH2 / graphene composite material solution was dropped onto the stainless steel-316 electrode and slowly heated to dryness, eventually forming an amorphous porous structure layer on the stainless steel-316 electrode.

[0043] Since PVDF is thermoplastic, PVDF is first mixed with MIL-101(Cr)-NH2, and then the two are mixed with graphene, so that relatively ordered PVDF and disordered MIL-101(Cr)-NH2 are located between graphene sheets; the composite of graphene and MIL-101(Cr)-NH2 forms a three-dimensional irregular network space. During the process of drop casting on the electrode surface and drying, the PVDF located between the graphene sheets is thermoplastic and fixed to form an irregular network space, making the structure more stable and durable. , will not lose activity quickly, thus extending the service life; at the same time, the thermoplasticity of PVDF is conducive to the rapid film formation of MIL-101(Cr)-NH2 / graphene composite materials on the electrode surface, and the formed film is hydrophobic and filterable, which can block most interference factors, including urea, lactic acid, sodium chloride, etc., so that the interference factors have little effect on the current peak. Excluding the small amount of protein interference that may exist in body fluids, glucose can be better adsorbed and fixed by the formed catalytic film, which is conducive to catalyzing the electro-oxidation activity of glucose. The addition of NMP is conducive to the uniform mixing of PVDF and MIL-101(Cr)-NH2, ensuring the uniformity of the support effect after film formation and the overall stability of the catalytic film.

[0044] Step VII, test in a three-electrode system, electrode F, Ag / AgCl (1M KCl) and platinum sheet are used as working electrode, reference electrode and auxiliary electrode respectively. Square wave voltammetry, cyclic voltammetry and impedance test are used to confirm the electrochemical performance of the composite electrode.

[0045] According to the above preparation process, two electrodes, MIL-101(Cr)-NH2 / SS and MIL-101(Cr)-NH2 / graphene / SS, were prepared respectively. The surfaces of bare SS, MIL-101(Cr)-NH2 / SS and MIL-101(Cr)-NH2 / graphene / SS were detected by scanning electron microscopy.

[0046] As attached Figure 1 As shown in the figure, from left to right, the surface morphology scanning results of bare SS, MIL-101(Cr)-NH2 / SS and MIL-101(Cr)-NH2 / graphene / SS are shown. The SEM images confirm the presence of corresponding amorphous MIL-101(Cr)-NH2 and amorphous MIL-101(Cr)-NH2 / graphene on the surface of SS electrode.

[0047] Subsequently, the electrochemical properties of bare SS, MIL-101(Cr)-NH2 / SS and MIL-101(Cr)-NH2 / graphene / SS were studied using SWV, CV and impedance spectroscopy.

[0048] As attached Figure 3 As shown in the figure, from left to right, bare SS, MIL-101(Cr)-NH2 and MIL-101(Cr)-NH2 / graphene were electrochemically characterized using SWV, CV and impedance spectroscopy. Among them, SWV conditions: scan rate, 0.05mV / s; step potential, 0.005mV; amplitude, 0.05V. CV conditions: scan rate, 0.05V. Among them, the amplitude of 0.05V can produce the highest peak current. In addition, the incubation time of 150 seconds can effectively improve the immobilization of glucose on the modified electrode; it can be seen from the figure that the SWV results confirm that the electrocatalytic activity of the SS electrode modified by amorphous MIL-101(Cr)-NH2 and amorphous MIL-101(Cr)-NH2 / graphene is enhanced.

[0049] In addition, CV and EIS analysis were performed with potassium ferrocyanide (5 mM) dissolved in KCL (0.1 M). The CV results showed that after SS modification, the redox peaks of the redox probe were enhanced and the peak separation (ΔEp) was reduced. These observations confirmed the enhancement of electron transfer and catalytic activity of the modified electrode. MIL-101(Cr)-NH2 / graphene showed the highest oxidation peak current, which was due to the excellent catalytic activity of the conductive amorphous MOF and graphene.

[0050] In EIS, the electron transfer resistance (Ret) (estimated by the semicircle diameter of the Nyquist plot) decreased after the SS electrode was modified with MIL-101(Cr)-NH2 and MIL-101(Cr)-NH2 / graphene, confirming the reduced impedance and enhanced electron transfer on the SS electrode surface.

[0051] In summary, the SS electrode modified with MIL-101(Cr)-NH2 / graphene material prepared by this scheme exhibits high catalytic activity for the electro-oxidation of glucose in biological fluids, and can realize efficient and accurate detection of the glucose content in biological fluids.

[0052] In addition, when choosing to introduce clusters, in addition to amino groups, nitro groups are also considered.

[0053] According to the above preparation process steps Ⅰ to Ⅳ, four material samples of MIL-101(Cr), MIL-101(Cr)-NO2, semi-crystalline MIL-101(Cr)-NH2, and amorphous MIL-101(Cr)-NH2 were prepared respectively. According to experimental analysis, the specific surface areas of the four materials are 2332.8, 1578.9, 1699.9 and 340.1 m 2 / g. It can be seen that the introduction of nitro or amino groups in the ligand can form a MOF structure with a small specific surface area, but the introduction of nitro groups in the MOFs material has only a slight effect on its mesoporous structure, while the introduction of amino groups has a greater impact on the amorphous MOF structure. It can also be seen from the SEM image that MIL-101(Cr)-NO2 contains only some defects. Therefore, the MIL-101(Cr)-NH2 prepared by introducing amino groups and taking corresponding reaction conditions can have the ideal amorphous structure characteristics.

[0054] Example 1: 2.21 g of Cr(NO3)3·9H2O was dissolved in 10 ml of ultrapure water at room temperature, stirred for 10 min, and magnetically stirred at a speed of 500 rpm to obtain solution A1; 1 g of BDC-NH2 was dissolved in solution A1 at room temperature, stirred for 10 min, and magnetically stirred at a speed of 500 rpm to obtain solution B1; solution B1 was transferred to a polytetrafluoroethylene liner and packaged in a reactor, and reacted at 200°C for 18 h to obtain solid C1; solid C1 was washed with anhydrous ethanol at 70°C for 3 h, centrifuged and dried in an oven at 80°C for 24 h, and finally vacuum activated at 150°C for 24 h to obtain MIL-101(Cr)-NH2 powder. 0.05 g of MIL-101(Cr)-NH2 powder was mixed with two drops of PVDF and 1 ml of NMP to obtain solution D1, which was ultrasonically treated for 10 min. Then, solution D1 was mixed with graphene at a volume ratio of 10:1 between MIL-101(Cr)-NH2 powder and graphene to obtain the composite material MIL-101(Cr)-NH2 / graphene. Finally, 15 μL of the composite material was dropped on a 1 cm 2 The sheet of stainless steel-316 electrode was heated until dry to obtain a 1 cm 2 The size of a sheet-shaped glucose detection electrode.

[0055] For larger sheet electrode surfaces, the drop casting surface is evenly divided into grids, with the middle part divided into several 1 cm 2 The drop casting area of ​​​​the size can be divided into several parts less than 1cm 2 The drop casting area is 1 cm in the middle 2 15 μL of composite material is dripped into the drop casting area, and the corresponding volume of composite material is dripped into the drop casting area at the edge in proportion to the area of ​​each area. The solution is dripped into the center of the corresponding area to form liquid beads, and the liquid beads in each area are diffused until they contact each other through vibration, and the liquid surface tension is used to make multiple liquid beads merge, and under continuous vibration, a uniformly flat liquid layer is formed on the electrode plane, and then gradually heated to dry to form a uniform composite material coating. It can effectively control the coating thickness value on the electrode surface and ensure the uniformity of the coating thickness on the motor coating surface.

[0056] Example 2, based on the synthesis basis of the composite material in Example 1, finally, the needle-shaped SS electrode is vertically immersed in the composite material for 15-30 seconds, then lifted up at a uniform speed and heated to dryness to obtain a needle-shaped glucose detection electrode.

[0057] The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the above principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A biological fluid glucose detection electrode, characterized in that: It comprises a conductive substrate (1), the outer side of which is coated with a catalytic layer (2) for modifying the catalytic activity of the conductive substrate (1) for glucose electro-oxidation; the catalytic layer (2) is an amorphous porous structure layer.

2. A biological fluid glucose detection electrode according to claim 1, characterized in that: The catalytic layer (2) is composed of a composite of an amorphous MOF material and one of nanoparticles, polymers and graphene.

3. A biological fluid glucose detection electrode according to claim 2, characterized in that: The MOF material is amorphous MIL-101(Cr)-NH2, and the amorphous MIL-101(Cr)-NH2 is prepared from metal precursor Cr and terephthalic acid ligand introduced with amino groups as raw materials.

4. A process for preparing a biological fluid glucose detection electrode according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step I, dissolving Cr(NO3)3·9H2O in ultrapure water and stirring to obtain solution A; Step II, dissolving BDC-NH2 in the solution A, and stirring to obtain solution B; Step III, transferring the solution B into a reaction kettle and encapsulating it, and reacting it at 200° C. to obtain a solid C; Step IV, washing the solid C with ethanol, centrifugally separating and drying it, and activating it under vacuum to obtain MIL-101(Cr)-NH2 powder; Step V, the prepared MIL-101(Cr)-NH2 powder is first mixed with PVDF and NMP to obtain solution D, and then mixed with graphene at a volume ratio of 10:1 to obtain a MIL-101(Cr)-NH2 / graphene composite material solution after ultrasonic treatment; Step VI, drop-casting the prepared MIL-101(Cr)-NH2 / graphene composite material solution on a stainless steel-316 electrode to form an amorphous porous structure layer; Step VII, test in a three-electrode system, electrode F, Ag / AgCl (1M KCl) and platinum sheet are used as working electrode, reference electrode and auxiliary electrode respectively. Square wave voltammetry, cyclic voltammetry and impedance test are used to confirm the electrochemical performance of the composite electrode.

5. The process for preparing a biological fluid glucose detection electrode according to claim 4, characterized in that: In the solution A prepared in step I, the concentration of Cr(NO3)3·9H2O is 0.2-0.3 g / mL; in the solution B prepared in step II, the concentration of BDC-NH2 is 0.08-0.15 g / mL; in steps I and II, the stirring speed is 500 rpm and the stirring time is 10 min.

6. The process for preparing a biological fluid glucose detection electrode according to claim 5, characterized in that: In step III, the reaction time of solution B at 200° C. is 18 h; in step IV, solid C is washed with anhydrous ethanol at 70° C. for 3 h, dried at 80° C. for 24 h after separation, and vacuum activated at 150° C. for 24 h.

7. The process for preparing a biological fluid glucose detection electrode according to claim 6, characterized in that: In step V, the concentration of MIL-101(Cr)-NH2 in solution D is 0.05-0.1 g / mL, and two drops of PVDF are added to every 1 mL of solution D.

8. The process for preparing a biological fluid glucose detection electrode according to claim 7, characterized in that: In step VI, every 1 cm 2 15 μL of MIL-101(Cr)-NH2 / graphene composite material solution was dropped onto the stainless steel-316 electrode and slowly heated to dryness.

9. The process for preparing a biological fluid glucose detection electrode according to claim 8, characterized in that: In step VI, before adding the MIL-101(Cr)-NH2 / graphene composite material solution, the stainless steel-316 electrode was cleaned in an ethanol ultrasonic bath for 3 minutes and then rinsed with deionized water several times.

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