Glucose non-enzyme sensor prepared by depositing gold through multiple electrochemical reduction

Abstract

The invention discloses a glucose non-enzyme sensor prepared by depositing gold through multiple electrochemical reduction. An electrode system of the glucose non-enzyme sensor comprises a working electrode, a counter electrode and a reference electrode, the working electrode is modified with a functional layer, the functional layer is composed of a graphene oxide material and gold nanoparticles, and the gold nanoparticles are prepared and deposited on graphene oxide through a repeated electrochemical reduction method. The electrode material prepared by the invention is simple in preparation method, is used for non-enzyme glucose detection, is high in detection sensitivity and strong in anti-interference capability, and can be repeatedly used.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensing, and particularly relates to a glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold. Background Art

[0002] Diabetes is a metabolic disorder syndrome caused by multiple factors such as genetics and immunity, and its fundamental cause is the decline of islet function. Accurately measuring the blood glucose level of diabetic patients is crucial for effectively monitoring, treating, and controlling the condition. As an important energy substance in the body, the concentration level of glucose can reflect the health status of the body. The glucose level in diabetic patients is abnormally elevated, so the analysis and detection of glucose are of great significance for ensuring human health, disease diagnosis, and treatment. Currently, the glucose concentration is usually detected using sensors, among which electrochemical sensors are the most common and can be divided into two categories: enzyme-based and enzyme-free. In recent years, the number of diabetic patients has been increasing continuously, and the need for the detection and treatment of diabetes is urgent. Therefore, it is necessary to develop a glucose sensor that is fast, accurate, low-cost, and highly sensitive.

[0003] Electrochemical glucose sensors can be divided into enzyme-based and enzyme-free types. Enzyme-based sensors are widely used, but the inherent defects of enzymes (high cost, poor stability, and susceptibility to environmental influences) limit their development. Enzyme-free sensors have attracted much attention due to their simple preparation, low cost, and good stability. However, existing enzyme-free sensors still face challenges: low selectivity and susceptibility to interference; narrow linear range, even lower than the normal blood glucose concentration. Therefore, developing electrode materials with high selectivity, wide linear range, and high sensitivity is of great academic significance and application value for enzyme-free electrochemical glucose sensors. Summary of the Invention

[0004] Based on the deficiencies of the above-mentioned existing technologies, the present invention provides a glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold.

[0005] To solve the above problems, the present invention adopts the following technical solutions:

[0006] The glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold in the present invention has an electrode system including a working electrode, a counter electrode, and a reference electrode; a functional layer is modified on the working electrode, and the functional layer is composed of graphene oxide material and gold nanoparticles.

[0007] The modification method of the working electrode includes the following steps:

[0008] Step 1: Add graphene oxide to an ethanol solution, ultrasonically disperse it evenly, mix the obtained dispersion with purified water at a volume ratio of 1:1, and ultrasonically disperse it evenly to obtain a mixed solution; drop the mixed solution on the surface of the activated working electrode, and after drying, form a working electrode modified with graphene oxide material.

[0009] Step 2: Place the working electrode modified with the graphene oxide material obtained in Step 1 into chloroauric acid solution for multiple unidirectional electrochemical reduction electrodeposition, so as to modify gold nanoparticles on the graphene oxide, and obtain an electrode material containing a multi-level structure of graphene oxide and gold nanoparticles.

[0010] In Step 1, the concentration of the graphene oxide ethanol dispersion is 2 - 4 mg / mL.

[0011] In Step 2, the concentration of the chloroauric acid solution is 3 - 5 mM.

[0012] In Step 2, use unidirectional cyclic voltammetry for multiple controllable depositions of gold nanoparticles (Au NPs). Set the potential range from +0.8 V to -0.3 V (only reduction scan, no reverse oxidation), cycle and deposit 10 - 20 times at a scan rate of 50 mV / s, and control the temperature of the constant temperature water bath at 25 ± 1°C. After the deposition is completed, the electrode is washed with deionized water and dried for subsequent performance testing.

[0013] Furthermore, the counter electrode and the working electrode are formed by printing conductive carbon paste on a flexible substrate, and the reference electrode is formed by printing conductive silver paste on the flexible substrate. The flexible substrate uses polyethylene terephthalate PET.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] 1. The unidirectional scanning strategy of the present invention avoids the oxidation and dissolution of Au NPs in traditional bidirectional cycles, promotes the directional nucleation and growth of Au by successive reduction, and finally forms uniformly dispersed three-dimensional dendritic Au NPs on the surface of GO. This structure has a high specific surface area and abundant catalytic active sites, combined with the conductive network of GO, significantly enhancing the electron transfer efficiency and glucose oxidation reaction kinetics. The present invention has excellent sensitivity of 544.94 μA mM 3+ cm -1 cm -2 , a fast response time (3.7 s), a low detection limit (0.34 μM), and a wide linear range (4.69 μM - 25.8 mM).

[0016] 2. The present invention constructs a conductive substrate by drop-coating graphene oxide, combined with a multiple unidirectional electrodeposition process, to form a three-dimensional cross-linked gold nanocomposite structure. The synergistic effect of the high specific surface property of graphene oxide and the catalytic activity of gold nanoparticles significantly improves the adsorption capacity of glucose molecules and the electron transfer efficiency. This composite structure has a uniform pore distribution and stable interfacial properties, enabling the sensor to exhibit a good linear response in a wide concentration range, while avoiding the stability defects of enzyme-based sensors caused by protein denaturation.

[0017] 3. The present invention adopts a unidirectional reduction electrodeposition strategy, and through precise regulation of deposition kinetic parameters, realizes the directional assembly of gold nanoparticles on the surface of graphene oxide. This process effectively suppresses the defect of random growth of crystal planes in traditional bidirectional electrodeposition and enhances the chemical homogeneity of the electrode surface. Anti-interference experiments show that the sensor has excellent selectivity for common interferents such as uric acid and ascorbic acid, and exhibits good process repeatability and detection reliability. Description of the Drawings

[0018] Figure 1 It is a scanning electron microscope image of the electrode surface obtained in step 2 of Example 1 of the present invention.

[0019] Figure 2 It is a scanning electron microscope image of the electrode surface obtained in step 3 of Example 1 of the present invention.

[0020] Figure 3 It is a comparative scanning electron microscope image of the agglomeration of gold nanoparticles by potentiostatic electrodeposition of gold.

[0021] Figure 4 It is a comparative graph of the current responses of the working electrodes obtained in step 2 when the electrodeposition termination voltages are -0.5V, -0.4V, -0.3V, -0.2V, and -0.1V respectively.

[0022] Figure 5 It is a comparative graph of the current responses of the working electrodes obtained in step 3 at different numbers of electrodeposition cycles.

[0023] Figure 6 It is a stability graph of the glucose sensor prepared in Example 1 of the present invention.

[0024] Figure 7 It is an anti-interference performance graph of the glucose sensor prepared in Example 1 of the present invention.

[0025] Figure 8 It is a cyclic voltammogram of the glucose sensor prepared in Example 1 of the present invention. Figure 9 It is a comparison of the oxidation peak current values of the cyclic voltammetry tests of the glucose sensors prepared in Examples 1-3 and Comparative Example 1 in an electrolyte with a glucose concentration of 5 mM. Detailed Embodiments

[0026] The technical solutions of the present invention will be described in detail below through specific embodiments. The following embodiments are implemented on the premise of the technical solutions of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0027] Example 1:

[0028] The flexible enzymatic glucose sensor provided by this embodiment includes a flexible PET substrate and an electrode system disposed on the flexible substrate; the electrode system includes a working electrode, a counter electrode, and a reference electrode; the counter electrode and the working electrode are formed by printing conductive carbon paste on the flexible substrate, and the reference electrode is formed by printing conductive silver paste on the flexible substrate.

[0029] A functional layer is modified on the working electrode. The functional layer is obtained by first modifying the surface of the working electrode with a graphene oxide solution by the drop-coating method, and then depositing gold by using the multiple electrochemical reduction method to modify gold nanoparticles on the graphene oxide layer.

[0030] 1. Electrode activation: Immerse the electrode in a 0.05 mol / mL sulfuric acid solution for 2 hours, and then use the sulfuric acid solution as the electrolyte to scan by cyclic voltammetry for 20 cycles. After the peak values in the CV graph are basically stable, take it out, rinse it with pure water, dry it at room temperature, and store it at 4°C.

[0031] 2. Mix the graphene oxide dispersion (concentration 2 - 4 mg / mL) and purified water in a volume ratio of 1:1, and ultrasonically process for 30 minutes to obtain a uniform dispersion system. Take 4 μL of the above mixed solution and precisely drop-coat it on the surface of the pre-activated working electrode, and let it stand in a clean room temperature environment until the solvent completely volatilizes. Subsequently, place the electrode in a vacuum drying oven and heat-treat it at 40°C for 2 hours to form a dense and uniform graphene oxide functional layer modified electrode, and store it in a dry environment at 4°C for standby.

[0032] 3. Perform multiple unidirectional electrochemical reduction electrodeposition of gold on the graphene oxide modified working electrode obtained in step 2 in a 4 mM chloroauric acid solution. In the electrolyte, use the unidirectional cyclic voltammetry method to perform multiple controllable depositions of gold nanoparticles. Set the potential range to +0.8 V to -0.3 V (only reduction scan, no reverse oxidation), and cycle deposit 20 times at a scan rate of 50 mV / s. Control the temperature of the constant temperature water bath at 25 ± 1°C. After the deposition is completed, the electrode is washed with deionized water and dried for subsequent performance testing. This step modifies gold nanoparticles on the graphene oxide to obtain an electrode material containing a graphene oxide / gold nanoparticle multi-level structure.

[0033] Example 2:

[0034] The glucose enzyme-free sensor is prepared according to the same method steps as in Example 1, with the only difference being that: in step 3, the number of cyclic depositions in the unidirectional cyclic voltammetry method is changed to 10 times.

[0035] Example 3:

[0036] The glucose enzyme-free sensor is prepared according to the same method steps as in Example 1, with the only difference being that: in step 3, the number of cyclic depositions in the unidirectional cyclic voltammetry method is changed to 30 times.

[0037] Comparative Example 1:

[0038] The glucose enzyme-free sensor was prepared according to the same method steps as in Example 1, with the only difference being that: in Step 3, the deposition of gold by multiple unidirectional cyclic voltammetry was changed to the deposition of gold by the potentiostatic method.

[0039] Test characterization:

[0040] (I) Morphology characterization

[0041] Figure 1 - Figure 2 These are the scanning electron microscope images of the surface of the modified electrode prepared in Steps 2 and 3 of Example 1 of the present invention in sequence. After the modification process in Step 2, the graphene oxide sheets are loaded on the surface of the electrode substrate in a uniform and dense manner, forming an active interface with a high specific surface area. Figure 2 The microscopic morphology analysis further reveals that through the electrochemical deposition process in Step 3, gold nanoparticles with uniform particle size are obtained.

[0042] Figure 3 This is the scanning electron microscope image of the potentiostatic deposition of gold in Comparative Example 1, and its microscopic morphology shows that the gold nanoparticles agglomerate on the electrode surface. There is an obvious difference compared with the effect of the modification strategy of the present invention.

[0043] (II) Optimization of the electrodeposition voltage

[0044] The electrodeposition voltages in Step 3 of Example 1 were respectively set to -0.5, -0.4, -0.3, -0.2, -0.1 V to prepare electrode materials containing a multi-level structure of graphene oxide material and gold nanoparticles.

[0045] The modified electrode was tested by cyclic voltammetry on a CHI660E electrochemical workstation, and the electrolyte was a 0.2 M sodium hydroxide solution containing 5 mM glucose. Figure 4 This is the comparison chart of the current responses of the working electrodes obtained in Step 3 when the electrodeposition voltages are -0.5, -0.4, -0.3, -0.2, -0.1 V respectively. Among them, the sensor for depositing gold nanoparticles at a potential of -0.3 V has a higher current response to glucose detection.

[0046] (III) Optimization of the electrodeposition time

[0047] The number of electrodeposition cycles in Step 3 of Example 1 was respectively set to 10 cycles, 15 cycles, 20 cycles, 25 cycles, 30 cycles, 35 cycles to prepare electrode materials containing a multi-level structure of graphene oxide material and gold nanoparticles.

[0048] The modified electrode was tested by cyclic voltammetry on a CHI660E electrochemical workstation, and the electrolyte was a 0.2 M sodium hydroxide solution containing 5 mM glucose. Figure 5Figure showing the comparison of the current responses of the working electrodes obtained in Step 3 for different numbers of electrodeposition times. Among them, when the electrodeposition time is 30 cycles, the sensor has a higher current response to glucose detection.

[0049] (IV) Response of the sensor obtained in Example 1 to glucose

[0050] The sensor prepared in Example 1 was tested by cyclic voltammetry on a CHI660E electrochemical workstation. The electrolyte was 0.2 M sodium hydroxide solution containing 5 mM glucose. The starting voltage was set at 0.2 V, the voltage range was between -0.8 and 1.4 V, and the scanning rate was set at 0.05 v / s. Figure 6 Figure showing the reproducibility of the glucose sensor prepared in Example 1. It can be seen from the figure that after scanning 10 cycles, the curves basically overlap, showing good reproducibility.

[0051] The glucose sensor prepared in Example 1 of the present invention showed excellent detection specificity in the anti-interference performance test. Specifically, first, the response current value in a 5 mM glucose solution was detected. Subsequently, when 0.2 mM ascorbic acid and 0.3 mM uric acid, common interfering substances in the physiological environment, were added to the 5 mM glucose standard solution respectively, the response current value of the sensor did not change significantly ( Figure 7 ). This experimental data fully demonstrates that the sensor described in the present invention can effectively suppress the influence of typical interfering substances in biological samples and has a high selective recognition ability for glucose molecules.

[0052] Figure 8 Cyclic voltammogram of the glucose sensor prepared in Example 1 in the range of glucose concentration from 0 mM to 15 mM. From bottom to top are glucose concentrations of 0, 0.5, 1, 2.5, 5, 7.5, 10, 12.5, 15 mM respectively. It can be seen that the oxidation current increases with the increase of glucose concentration.

[0053] Figure 9 Comparison of the oxidation peak current values of the glucose sensors prepared in Examples 1-3 and Comparative Example 1 in a 5 mM glucose electrolyte during cyclic voltammetry testing.

[0054] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold, characterized in that: The electrode system of the glucose enzyme-free sensor includes a working electrode, a counter electrode and a reference electrode; a functional layer is modified on the working electrode, and the functional layer is composed of graphene oxide material and gold nanoparticles.

2. The glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold according to claim 1, characterized in that: The modification method of the working electrode includes the following steps: Step 1: Add graphene oxide to an ethanol solution, ultrasonically disperse it evenly, mix the obtained dispersion with purified water at a volume ratio of 1:1, and ultrasonically disperse it evenly to obtain a mixed solution; drop the mixed solution on the surface of the activated working electrode, and dry it to form a working electrode modified with graphene oxide material. Step 2: Place the working electrode modified with graphene oxide material obtained in Step 1 in a chloroauric acid solution for multiple unidirectional electrochemical reduction depositions, so that gold nanoparticles are modified on the graphene oxide to obtain an electrode material with a multi-level structure of graphene oxide and gold nanoparticles.

3. The glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold according to claim 2, characterized in that: In Step 1, the concentration of the graphene oxide ethanol dispersion is 2-4 mg / mL.

4. The glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold according to claim 2, characterized in that: In Step 2, the concentration of the chloroauric acid solution is 3-5 mM.

5. The glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold according to claim 4, characterized in that: In Step 2, a unidirectional cyclic voltammetry method is used for multiple controllable depositions of gold nanoparticles, the set potential range is from +0.8 V to -0.3 V, and the cyclic deposition is carried out at a scanning rate of 50 mV / s, and the temperature is controlled at 25±1°C by a constant temperature water bath.

6. The glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold according to claim 5, characterized in that: The number of cyclic depositions is 10-20 times.

7. The glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold according to claim 1, characterized in that: The counter electrode and the working electrode are formed by printing conductive carbon paste on a flexible substrate, and the reference electrode is formed by printing conductive silver paste on the flexible substrate.

8. The glucose enzyme-free sensor prepared by multiple electrochemical reduction depositions of gold according to claim 7, characterized in that: The flexible substrate uses polyethylene terephthalate PET.

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