An enzyme-free glucose sensor based on hydrophobic substrate and its preparation method and application

Abstract

The application belongs to the field of glucose detection, and particularly relates to an enzyme-free glucose sensor based on a hydrophobic substrate and a preparation method and application thereof. The application can realize glucose detection in various pH solution environments, reduces the dependence on high OH ‑ concentration of a solution; and the oxygen reduction reaction can be carried out at a lower reduction potential, which provides convenience for low-energy consumption use of the sensor.

Description

Technical Field

[0001] This invention belongs to the field of glucose detection, specifically relating to an enzyme-free glucose sensor based on a hydrophobic substrate, its preparation method, and its application. Background Technology

[0002] Diabetes is a chronic disease that seriously threatens people's health, affecting more than 537 million people worldwide and claiming more than 1.5 million lives each year, and the number of patients continues to rise. When blood glucose levels are below or above the range of 3.3 to 7.8 mmol / L, it is essential to prevent diabetes-related emergencies. Therefore, developing rapid and accurate blood glucose monitoring methods is crucial for enabling diabetic patients to better manage their condition. Although enzyme-based electrochemical glucose sensors have been widely researched and applied due to their high selectivity and sensitivity, the instability of biological enzymes is easily affected by factors such as temperature, pH, and ions, thus hindering the stability and range of enzyme biosensors.

[0003] Non-enzymatic glucose sensors based on noble metals, metal alloys, metal oxides, and carbon-related materials have attracted attention due to their longer lifespan compared to enzyme sensors. Significant efforts have been made in the preparation of high-performance electrocatalysts, resulting in various enzyme-free glucose sensors with high detection performance. However, the electrochemical oxidation of glucose consumes a large amount of OH groups. - Enzyme-free glucose detection often requires a strongly alkaline solution to achieve ideal sensitivity and linear detection range. Although existing techniques achieve OH- ionization in the detection region... - While the concentration is increased, the generation of hydrogen bubbles (adhering to the electrode surface) and excessive energy consumption (high electrolysis potential) reduce the accuracy and practicality of the method. Summary of the Invention

[0004] Existing methods involve developing electrodes with large specific surface areas to achieve detection performance under near-neutral detection conditions; however, due to OH... - The lack of [specific technology / resources] results in low detection sensitivity; additionally, it relies on water splitting, through H [method / method / process]. + The reduction generates H2 to raise the pH of the detection area, providing sufficient OH- for the smooth execution of enzyme-free detection. - The main problem is that an irregular amount of air bubbles will adhere to the electrode surface, which will change the detection area and reduce the accuracy and reproducibility of the detection results. Secondly, the high potential required for water splitting will significantly increase the energy consumption of the detection process and reduce the economic efficiency of actual use.

[0005] (1) First, an electrocatalyst with oxygen reduction and glucose detection properties is modified on the surface of a hydrophobic substrate; (2) Then, taking advantage of the hydrophobic properties of the substrate, a large amount of air is captured in the cavities of the porous substrate when it comes into contact with an aqueous solution; (3) Finally, a negative potential is applied to the electrode to reduce oxygen in the air to OH. - Then, a positive potential is applied for glucose detection, achieving efficient glucose detection.

[0006] The purpose of this invention is to (1) eliminate the dependence on the strongly alkaline environment of the detection solution in existing enzyme-free detection; and (2) avoid the influence of lysed water on the detection solution and the generation of H2, thereby improving the accuracy and reproducibility of the detection.

[0007] To address the aforementioned technical problems, this application provides the following technical solution:

[0008] This invention provides a method for preparing an enzyme-free glucose sensor based on a hydrophobic substrate, comprising the following steps:

[0009] S1: Preparation of hydrophobic substrate;

[0010] The hydrophobic substrate is selected from PTFE (polytetrafluoroethylene) coated carbon cloth, carbon fiber, PTFE (polytetrafluoroethylene) porous film, PE (polyethylene) hydrophobic film, PVDF (polyvinylidene fluoride) porous hydrophobic film or low surface energy modified material.

[0011] The low surface energy modified material is obtained by immersing a porous or arrayed material in an organic solution containing the low surface energy material; the porous or arrayed material is selected from TiO2 nanowire arrays, graphene arrays, hydrophilic carbon fibers, hydrophilic PVDF porous films, or hydrophilic PE porous films.

[0012] S2: Modify the surface of the hydrophobic substrate with an oxygen reduction catalyst and a glucose oxidation catalyst to obtain the enzyme-free glucose sensor based on the hydrophobic substrate;

[0013] The oxygen reduction catalyst is selected from Fe, Pt, Co, Ni or Cu, and the glucose oxidation catalyst is selected from Pt, Au, Pd, Cu, Co, Ni, CuO, Co3O4 or alloys; the alloy is selected from Ni-Co, Pt-Cu or Pd-Co.

[0014] Preferably, in step S1, the contact angle between the substrate with the hydrophobic surface and water is greater than 130°.

[0015] Preferably, the low surface energy material is selected from PDMS (polydimethylsilane), perfluorooctyltrichlorosilane, or octadecyltrichlorosilane.

[0016] Preferably, the organic solution is toluene.

[0017] Preferably, in step S1, the soaking time is 25-35 minutes.

[0018] Preferably, in step S1, the product is dried after soaking.

[0019] Furthermore, the drying temperature is 100-180℃ and the time is 0.5-2.5h.

[0020] Preferably, in step S2, the modification method is electrodeposition, PVD (physical vapor deposition), or sol-gel method.

[0021] Preferably, in step S2, the deposition sites of the oxygen reduction catalyst and the glucose oxidation catalyst can overlap (contact each other) or be interleaved in a non-contact manner.

[0022] The present invention also provides an enzyme-free glucose sensor based on a hydrophobic substrate prepared by the above preparation method.

[0023] The present invention also provides the application of the above-mentioned enzyme-free glucose sensor based on a hydrophobic substrate in glucose detection, comprising the following steps: using a three-electrode system, the enzyme-free glucose electrode as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl as the reference electrode, glucose detection is performed by step potential method; during glucose detection, the current signal at the positive potential is recorded at -0.8 to -0.4V (vs. Ag / AgCl) for 20s, and then at +0.4 to +0.7V for 15s.

[0024] The technical solution of the present invention has the following advantages compared with the prior art:

[0025] 1. It can detect glucose in solutions with various pH levels, reducing the impact of high OH content in the solution. - Concentration dependence;

[0026] 2. The oxygen reduction reaction can be carried out at a relatively low reduction potential, which facilitates the low-energy use of the sensor. Attached Figure Description

[0027] Figure 1 This is a top view of the graphene array using SEM (scanning electron microscopy).

[0028] Figure 2 This is a top view of the hydrophobic graphene after Pt deposition.

[0029] Figure 3 This is a step detection curve for an enzyme-free glucose electrode.

[0030] Figure 4 Hydrophobic / hydrophilic enzyme-free glucose sensor in OH -The it curve and linear fitting curve for glucose after the generation step are obtained. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0032] Example 1

[0033] 1. Using arrayed graphene ( Figure 1 The graphene array was used as the electrode substrate. First, it was immersed in a 5% polydimethylsilane (PDMS) toluene solution for 30 min, and then removed and placed in an oven at 120 °C for 2 h to obtain an array of graphene substrates with a hydrophobic surface and a contact angle with water of 150 ± 2°.

[0034] 2. Using electrodeposition, platinum (Pt) electrocatalysts with oxygen reduction and glucose oxidation capabilities are deposited on the electrode surface. A three-electrode system is used: Pt wire as the counter electrode, Ag / AgCl (3M) as the reference electrode, and graphene as the working electrode. The deposition potential is -0.3V (vs. Ag / AgCl). The deposition solution is 10g / L H2PtCl6·6H2O:H2O:1mol / L H2SO4 = 1:1:2, and the deposition time is 60s. Figure 2 As shown, Pt particles are uniformly deposited on the surface of the graphene array, with a size of approximately 0.2–2 μm;

[0035] 3. The prepared enzyme-free glucose sensor was used for electrochemical measurement of glucose. Electrochemical measurement was performed using a CHI 660E electrochemical workstation with a three-electrode system. The enzyme-free glucose electrode was used as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. Glucose detection was performed using a step potential method, first at -0.6V for 20s, then at +0.4V for 15s. The current signal at +0.4V was recorded, and the detection curve is shown below. Figure 3 .

[0036] Example 2

[0037] This invention provides a method for preparing an enzyme-free glucose electrode. The experimental steps are similar to those in Example 1, except that the substrate material is polyethylene film (PE), and Pt is sputtered onto its surface using a plasma sputtering instrument to prepare the enzyme-free electrode.

[0038] Example 3:

[0039] This invention provides a method for preparing an enzyme-free glucose electrode. The experimental steps are similar to those in Example 1, except that the substrate material is a hydrophobic polyvinylidene fluoride (PVDF) film, and Pt is sputtered onto its surface using a plasma sputtering instrument to prepare the enzyme-free electrode.

[0040] Comparative Example 1

[0041] Compared with traditional two-phase electrodes, its preparation method is similar to that of the electrode in Example 1. The difference is that the hydrophobic porous conductive substrate is replaced with a hydrophilic graphene array.

[0042] Effect Evaluation 1

[0043] Figure 3 In the step detection curve of the enzyme-free glucose electrode, the first potential is -0.6V for 20s, and the second potential is +0.4V for 15s.

[0044] Figure 4 Hydrophobic / hydrophilic enzyme-free glucose sensor in OH - After the generation step, the it curve and linear fitting curve for glucose were obtained. (a, b) Hydrophobic / hydrophilic enzyme-free glucose sensor in OH - The it curve of glucose after the generation step, working potential: +0.4V; (c) Linear fitting curves at 6s in Figures a and b.

[0045] The enzyme-free glucose sensor obtained in Example 1 and the glucose detection in Comparative Example 1 were compared.

[0046] The enzyme-free glucose sensor obtained in Example 1 and Comparative Example 1 were used to test glucose concentrations of 0 mM, 1 mM, 3 mM, 5 mM, 7 mM, 10 mM, 15 mM, 20 mM, 25 mM, 30 mM, 35 mM, and 40 mM. The experimental results are shown in [Figure number missing]. Figure 4 .

[0047] Figure 4 Figure 'a' is a graph showing the response current of the enzyme-free glucose sensor of this invention. The glucose concentrations from top to bottom in the graph are 0 mM, 1 mM, 3 mM, 5 mM, 7 mM, 10 mM, 15 mM, 20 mM, 25 mM, 30 mM, 35 mM, and 40 mM, respectively. Figure 4 As can be seen from 'a', it can be used to detect glucose, and the response current increases accordingly as the glucose concentration increases.

[0048] from Figure 4 As can be seen from c, the upper limit of detection of the electrochemical enzyme sensor prepared in Example 1 of the present invention is as high as 40 mM, while through Figure 4 As can be seen from b and c, Control Example 1 did not show any detection performance after the oxygen reduction step.

[0049] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing an enzyme-free glucose sensor based on a hydrophobic substrate, characterized in that, Includes the following steps: S1: Preparation of a hydrophobic substrate; the hydrophobic substrate is selected from low surface energy modified materials; the low surface energy modified materials are obtained by immersing a graphene array in an organic solution containing PDMS; S2: Modify the surface of the hydrophobic substrate with an oxygen reduction catalyst and a glucose oxidation catalyst to obtain the enzyme-free glucose sensor based on the hydrophobic substrate; The oxygen reduction catalyst is selected from Fe, Co, Ni or Cu, and the glucose oxidation catalyst is selected from Pt, Au, Pd, Cu, Co, Ni, CuO, Co3O4 or alloys; the alloy is selected from Ni-Co, Pt-Cu or Pd-Co; in step S1, the contact angle between the hydrophobic substrate and water is greater than 130°.

2. The preparation method according to claim 1, characterized in that, The organic solution is toluene.

3. The preparation method according to claim 1, characterized in that, In step S1, the soaking time is 25-35 minutes.

4. The preparation method according to claim 1, characterized in that, In step S1, the product is dried after soaking.

5. The preparation method according to claim 4, characterized in that, The drying temperature is 100-180℃, and the time is 0.5-2.5 h.

6. The preparation method according to claim 1, characterized in that, In step S2, the modification method is electrodeposition, PVD, or sol-gel method.

7. An enzyme-free glucose sensor based on a hydrophobic substrate prepared by the preparation method according to any one of claims 1-6.

8. The application of the enzyme-free glucose sensor based on a hydrophobic substrate as described in claim 7 in glucose detection, characterized in that, The procedure includes the following steps: using a three-electrode system, with the enzyme-free glucose electrode as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl as the reference electrode, glucose is detected by step potential method; during glucose detection, the current signal at the positive potential is recorded after 20 s at -0.8 to -0.4 V and then 15 s at +0.4 to +0.7 V.

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