Pt-cu hydrogel enzyme-free electrochemical sensor for glucose, and preparation method therefor and use thereof

Abstract

A Pt-Cu hydrogel enzyme-free electrochemical sensor for glucose, and a preparation method therefor and the use thereof. The preparation method comprises: (1) preparation of a Pt-Cu hydrogel, involving: dissolving H2PtCl6 and CuCl2 in water to form a first solution, dissolving a weak reducing agent and sodium carbonate in water to form a second solution, mixing the first solution and the second solution to obtain a mixture, performing an ultrasonic treatment on the mixture, leaving same to stand at 60-80°C for a first period of time, then cooling the solution to room temperature, adding NaBH4, then leaving same to stand at 30-50°C for a second period of time, finally leaving same to age and stand at room temperature for at least 24 h, and then washing same to obtain the Pt-Cu hydrogel; and (2) placing the Pt-Cu hydrogel on an electrode, and immobilizing same, so as to obtain a Pt-Cu hydrogel enzyme-free electrochemical sensor for glucose. The sensor can achieve the enzyme-free detection of glucose in a neutral serum environment, with the detection range being 0-6 mM, which falls within the required linear detection range for the physiological concentration of glucose in a human body; moreover, the consumption of energy is reduced.

Description

Pt-Cu hydrogel non-enzyme glucose electrochemical sensor and preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202410990990.1, filed on July 23, 2024, and entitled "Pt-Cu hydrogel non-enzyme glucose electrochemical sensor and preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of non-enzyme glucose detection, in particular to a Pt-Cu hydrogel non-enzyme glucose electrochemical sensor and a preparation method and application thereof. BACKGROUND

[0003] Due to the high sensitivity and good selectivity of glucose oxidase to glucose, it is widely used in the construction of various biological sensors for glucose detection. However, enzyme modified electrodes have a series of shortcomings such as instability, high cost, complex immobilization process, and high requirements for operating environment, so how to develop a non-enzyme modified electrode to solve these problems has attracted widespread attention.

[0004] Electrochemical non-enzyme glucose sensors have high sensitivity, rapid reaction, good long-term storage performance, and relatively low price in the process of glucose sensing, which has aroused the research interest of a large number of researchers. The research of electrochemical non-enzyme glucose sensors mainly focuses on using metal mesoporous or nanoparticles (such as noble metals Pt, Pd, Au, non-noble metals Cu, Ni), metal oxides (such as Co, Fe, Cu, Ni oxides), bimetallic (metal-metal, metal-oxide, oxide-oxide), composite (such as Pt-Pb, Pt-Cu, Au-Pd, Au-Ni, Ni-Cu) and carbon-based composite materials such as carbon nanotubes or graphene as glucose sensing elements.

[0005] Hydrogel is a typical porous material with ultra-low density, high specific surface area, good flexibility and extremely high porosity. Among them, the new type of noble metal hydrogel derived from nanoparticles not only shows the physical and chemical properties common to traditional gels and nanoparticles, but also has its unique properties, which can be well applied in flexible electrodes. However, these excellent properties of hydrogel mainly rely on noble metals, and since the high cost of noble metals is a well-known problem, it greatly limits the application of hydrogel.

[0006] The research of the extraction of the enzyme-free electrode in the glucose electrochemical sensor mainly focuses on the following two directions: i) metal Pt and its alloy, ii) nano metal / metal oxide particle modified carbon nanotube array. Among them, most of the enzyme-free electrodes need to be tested in strong alkaline conditions, however, human blood is weakly alkaline, which cannot achieve accurate detection, and recently, it has been found that glucose can be detected through sweat, which is weakly acidic, and the current enzyme-free electrode cannot detect glucose in weakly acidic body fluids without external additives. Moreover, most of the reported glucose sensors have a low linear detection range, which cannot meet the linear detection range required by the physiological concentration of human glucose. In addition, most of the electrodes need a high working voltage when working, which consumes a lot of energy. SUMMARY

[0007] In order to solve the above problems, the application provides a preparation method of a Pt-Cu hydrogel enzyme-free glucose electrochemical sensor, which adopts a two-step reduction of Pt and Cu to obtain Pt-Cu hydrogel. The enzyme-free glucose electrochemical sensor prepared by placing the Pt-Cu hydrogel on the electrode can realize enzyme-free detection of glucose in a neutral and serum environment, the detection range is 0-6mM, which meets the linear detection range required by the physiological concentration of human glucose and reduces the energy consumption.

[0008] According to one aspect of the application, a preparation method of a Pt-Cu hydrogel enzyme-free glucose electrochemical sensor is provided, comprising the following steps:

[0009] (1) Preparation of Pt-Cu hydrogel: dissolve H2PtCl6 and CuCl2 in water to form a first solution, dissolve a weak reducing agent and sodium carbonate in water to form a second solution, mix the first solution and the second solution to obtain a mixture, and ultrasonic the mixture, stand at 60-80℃ for a first time, then cool the solution to room temperature and add NaBH4, and then stand at 30-50℃ for a second time, and finally age and stand at room temperature for at least 24h, and then wash to obtain Pt-Cu hydrogel;

[0010] (2) Place the Pt-Cu hydrogel on the electrode and fix it, and the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor is obtained.

[0011] In order to enable the enzyme-free electrode to test in neutral, weak alkaline or weak acidic environment, the Pt-Cu hydrogel prepared in the application has the characteristics of porous structure, good flexibility and high specific surface area, and a two-step reduction method is used to reduce Pt and Cu in the preparation process: in the first step, a weak reducing agent and sodium carbonate are added to reduce the metal salt to metal nanoparticles, and in the second step, sodium borohydride is added to induce the nanoparticles to assemble into a gel network, so that the medium can be quickly transmitted in the gel without hindrance, the catalytic efficiency is improved, and the hydrogel formed by the two-step method is more compact and not easy to scatter, the storage stability of the hydrogel is improved, and the service life of the sensor is prolonged.

[0012] In the above preparation method, the strong reducing agent sodium borohydride can provide an alkaline environment for the hydrogel, so that the hydrogel can exhibit good electrocatalytic activity for the oxidation of glucose under neutral conditions; the introduction of the abundant and low-cost transition metal Cu can reduce the cost while improving the active sites inside the hydrogel, improving the catalytic efficiency and catalytic activity, so that the detection range of the electrochemical sensor is 0-6mM, which meets the linear detection range required by the physiological concentration of human glucose; and the working voltage during the operation of the electrode is reduced, thereby reducing the energy consumption.

[0013] Optionally, the specific surface area of the Pt-Cu hydrogel is 15-50m 2 g -1 .

[0014] Optionally, the specific surface area of the Pt-Cu hydrogel is 24-46m 2 g -1 .

[0015] Optionally, the molar ratio of H2PtCl6 and CuCl2 is 0.5-3:1.

[0016] Optionally, the molar ratio of H2PtCl6 and CuCl2 is 2:1.

[0017] The above molar ratio determines the proportion of Pt and Cu in the Pt-Cu hydrogel, if CuCl2 is too much, the oxidation current of the hydrogel for detecting glucose will decrease, which may be due to the fact that the three-dimensional porosity of the platinum-copper hydrogel generated by too much CuCl2 is small, which is not conducive to the conduction and exposure of the active center, and if CuCl2 is too little, the production cost of the hydrogel will increase, and the lack of the synergistic effect of copper will also reduce the oxidation current of the hydrogel for detecting glucose.

[0018] Optionally, the weak reducing agent is glyoxylic acid, and the molar ratio of the glyoxylic acid and CuCl2 is 0.036-0.072:1;

[0019] The molar ratio of the sodium carbonate and CuCl2 is 1.26-2.52:1.

[0020] Optionally, the weak reducing agent is glyoxylic acid, and the molar ratio of the glyoxylic acid to CuCl2 is 0.054:1.

[0021] The molar ratio of the sodium carbonate to CuCl2 is 1.89:1.

[0022] The weak reducing agent and the sodium carbonate achieve one-step reduction, in which the metal salt is partially reduced to metal nanoparticles. If the amount of the glyoxylic acid and the sodium carbonate is too small, the metal nanoparticles produced by reduction are too small, and the hydrogel produced is relatively loose and not easy to shape. If the amount of the glyoxylic acid and the sodium carbonate is too large, it does not play a greater role because the amount of the embodiment 1 has reached the threshold value for the generation of the hydrogel.

[0023] Optionally, the concentration of CuCl2 in the first solution is 2.5 mM.

[0024] The volume ratio of water in the first solution to water in the second solution is 1:1.

[0025] Optionally, the molar ratio of NaBH4 to CuCl2 is 0.25-0.5:1.

[0026] Optionally, the molar ratio of NaBH4 to CuCl2 is 0.37:1.

[0027] NaBH4 achieves two-step reduction, which is to continue to reduce the remaining part of the metal salt in one-step reduction to metal nanoparticles and to induce the assembly of the metal nanoparticles into a gel network. If the amount of NaBH4 is too large, the hydrogel is easy to scatter, which may be caused by the generation of too many bubbles due to the strong reaction, the instability of the hydrogel, the inability to maintain the 3D cross-linked structure, and the easy powder particle shape. If the amount of NaBH4 is too small, part of the metal salt is not reduced to metal nanoparticles, and the hydrogel is not easy to shape.

[0028] Optionally, the ultrasonic time of the mixture is 10-15 min.

[0029] The first time is 0.5-1.5 h.

[0030] The second time is 2.5-3.5 h.

[0031] Optionally, the first time is 1 h.

[0032] The second time is 3 h.

[0033] Ultrasonic treatment of the mixture is to improve the uniformity of the raw materials. In the first time of standing, the metal salt is gradually reduced to metal nanoparticles. The second time of standing is to induce the assembly of the nanoparticles into a network of ultra-fine linear structures with many branches and mutual connections, to improve the number and exposure of active centers.

[0034] Optionally, the thickness of the Pt-Cu hydrogel placed on the electrode is 0.15-0.2 mm.

[0035] The thickness of the hydrogel determines the detection performance of the electrochemical sensor. If the thickness is less than 0.15 mm, the amount of hydrogel is too small, the detection current is too small, and the detection linearity is not good. If the thickness is greater than 0.2 mm, the amount of hydrogel is too much, it is not easy to fix the hydrogel on the electrode, and the detection linearity is not good.

[0036] According to another aspect of the present application, there is provided a Pt-Cu hydrogel enzyme-free glucose electrochemical sensor prepared by the preparation method of the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor according to any one of the above.

[0037] According to another aspect of the present application, there is provided a Pt-Cu hydrogel enzyme-free glucose electrochemical sensor prepared by the preparation method of the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor according to any one of the above.

[0038] Due to the use of the above scheme, the present application has the following advantages and effects compared with the prior art:

[0039] 1. The preparation method of the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor of the present application adjusts the proportion of the metal precursor to design a double-structured Pt-Cu hydrogel at room temperature, which has a porous structure, good flexibility and high specific surface area characteristics, and can exhibit good electrocatalytic activity for the oxidation of glucose under neutral conditions.

[0040] 2. The preparation method of the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor of the present application introduces the abundant and low-cost transition metal Cu, which reduces the proportion of the noble metal Pt, and the porous network structure of Cu can increase the contact between the internal active sites and the medium, so that the medium can be transported quickly and unobstructed in the internal, thereby improving the catalytic efficiency; and the internal network structure formed by the mutual connection of the metal hydrogel can also promote the electron transmission and transfer in the reaction, thereby further improving the catalytic activity.

[0041] 3. The preparation method of the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor of the present application is simple, the raw materials are easy to obtain and the production cost is low, has universality, and is convenient for large-scale production and processing.

[0042] 4. The Pt-Cu hydrogel enzyme-free glucose electrochemical sensor of the present application can detect glucose without enzyme in 0.1M PBS solution (pH 7.4) and serum environment, the detection range is 0-6mM, the working voltage of the electrode is reduced, and thereby the working energy consumption is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0043] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

[0044] Figure 1 is a flow chart of the preparation of Pt-Cu hydrogel according to Example 1 of the present application.

[0045] Figure 2 is a schematic diagram of the preparation of an enzyme-free glucose electrochemical sensor using the electrode and Pt-Cu hydrogel according to Example 1 of the present application.

[0046] Figure 3 is a SEM image of the hydrogel prepared according to Example 1, Example 4-5, Comparative Example 1-2, wherein (A) is a SEM image of the hydrogel prepared according to Example 4, (B) is a SEM image of the hydrogel prepared according to Example 5, (C) and (D) are SEM images of the hydrogel prepared according to Example 1, (E) is a SEM image of the hydrogel prepared according to Comparative Example 1, and (F) is a SEM image of the hydrogel prepared according to Comparative Example 2.

[0047] Figure 4 is an EDS image of the hydrogel prepared according to Example 1.

[0048] Figure 5 is an XRD test image of the hydrogel prepared according to Example 1 and Comparative Example 1.

[0049] Figure 6 is an XPS test image of the hydrogel prepared according to Example 1 and Comparative Example 1.

[0050] Figure 7 is a schematic diagram of the principle of the enzyme-free detection of glucose using Pt-Cu hydrogel.

[0051] Figure 8 is a cyclic voltammetry test curve of Example 1, Example 4, Example 6 and Comparative Example 1.

[0052] Figure 9 is an i-t graph of the enzyme-free glucose electrochemical sensor prepared according to Example 1 when a voltage of 0.2 V is applied in a 0.1 M PBS solution (pH 7.4) and the corresponding fitting curve.

[0053] Figure 10 is an i-t graph of the enzyme-free glucose electrochemical sensor prepared according to Example 1 when a voltage of 0.2 V is applied in serum and artificial sweat and the corresponding fitting curve. DETAILED DESCRIPTION

[0054] In order to make the above objectives, characteristics and advantages of the present application more apparent, a detailed description of the specific embodiments of the present application will be given below with reference to the drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in many different ways beyond the specific embodiments described and it is therefore contemplated that the present application covers any and all modifications of the present application within the scope of the present application.

[0055] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "linking", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, can be detachable connection, or integral; can be mechanical connection, can be direct connection, or indirect connection through intermediate medium, can be internal communication of two elements or interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0056] In the present application, the terms "upper", "lower", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0057] In addition, the term "and / or" in the present application means that three parallel schemes are included, for example, "A and / or B" includes A scheme, or B scheme, or A and B schemes are satisfied at the same time.

[0058] The present application will be described in detail below with reference to the examples, but the present application is not limited to these examples.

[0059] Unless otherwise specified, the raw materials in the examples and comparative examples of the present application are purchased through commercial channels.

[0060] Unless otherwise specified, the methods used in the examples and comparative examples of the present application are conventional methods in the prior art.

[0061] Example 1

[0062] The present embodiment relates to a preparation method of a Pt-Cu hydrogel enzyme-free glucose electrochemical sensor, comprising the following steps:

[0063] (1) Preparation of Pt-Cu hydrogel: Referring to FIG. 1, 5 mM of H2PtCl6 and 2.5 mM of CuCl2 were dissolved in 10 ml of water to form a first solution, 10 mg of glyoxylic acid and 500 mg of sodium carbonate were dissolved in 10 ml of water to form a second solution, the first solution and the second solution were mixed to obtain a mixture, and the mixture was ultrasonically treated for 10 min, and then was left to stand at 70°C for 1 h, after which the solution was cooled to room temperature, 35 mg of NaBH4 was added, and then the solution was left to stand at 40°C for 3 h, and finally was left to stand at room temperature for aging for 24 h, to obtain the Pt-Cu hydrogel after washing;

[0064] (2) Referring to FIG. 2, the 0.15 mm thick Pt-Cu hydrogel was placed on the electrode formed by the carbon paste, and was fixed by 5 microliters of 2 wt% Nafion, to obtain the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor.

[0065] Example 2

[0066] This example relates to a method for preparing a Pt-Cu hydrogel enzyme-free glucose electrochemical sensor, comprising the following steps:

[0067] (1) Preparation of Pt-Cu hydrogel: 5 mM of H2PtCl6 and 2.5 mM of CuCl2 were dissolved in 10 ml of water to form a first solution, 6.7 mg of glyoxylic acid and 333.87 mg of sodium carbonate were dissolved in 10 ml of water to form a second solution, the first solution and the second solution were mixed to obtain a mixture, and the mixture was ultrasonically treated for 10 min, and then was left to stand at 80°C for 0.5 h, after which the solution was cooled to room temperature, 47.29 mg of NaBH4 was added, and then the solution was left to stand at 50°C for 2.5 h, and finally was left to stand at room temperature for aging for 24 h, to obtain the Pt-Cu hydrogel after washing;

[0068] (2) The 0.2 mm thick Pt-Cu hydrogel was placed on the electrode formed by the carbon paste, and was fixed by 5 microliters of 2 wt% Nafion, to obtain the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor.

[0069] Example 3

[0070] This example relates to a method for preparing a Pt-Cu hydrogel enzyme-free glucose electrochemical sensor, comprising the following steps:

[0071] (1) Preparation of Pt-Cu hydrogel: 5 mM H2PtCl6 and 2.5 mM CuCl2 were dissolved in 10 ml water to form a first solution, 13.3 mg glyoxylic acid and 667.74 mg sodium carbonate were dissolved in 10 ml water to form a second solution, the first solution and the second solution were mixed to obtain a mixture, and the mixture was ultrasonicated for 15 min, and then was left to stand at 60 °C for 1.5 h, after which the solution was cooled to room temperature, 23.64 mg NaBH4 was added, and then it was left to stand at 30 °C for 3.5 h, and finally it was left to stand at room temperature for 24 h after aging, and after washing, Pt-Cu hydrogel was obtained;

[0072] (2) The 0.2 mm thick Pt-Cu hydrogel was placed on the electrode formed by the carbon paste, and was fixed with 5 microliters of 2 wt% Nafion to obtain the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor.

[0073] Example 4

[0074] The difference between this example and Example 1 is that in step (1), H2PtCl6 is 2.5 mM, and the rest is the same as Example 1.

[0075] Example 5

[0076] The difference between this example and Example 1 is that in step (1), H2PtCl6 is 1.25 mM, and the rest is the same as Example 1.

[0077] Example 6

[0078] The difference between this example and Example 1 is that in step (1), H2PtCl6 is 7.25 mM, and the rest is the same as Example 1.

[0079] Comparative Example 1

[0080] The difference between this comparative example and Example 1 is that CuCl2 is not added, and the rest is the same as Example 1.

[0081] Comparative Example 2

[0082] The difference between this comparative example and Example 1 is that H2PtCl6 is not added, and the rest is the same as Example 1.

[0083] Comparative Example 3

[0084] The difference between this comparative example and Example 1 is that in step (1), NaBH4 is not added, and only glyoxylic acid and sodium carbonate are used for one-step reduction, and the rest is the same as Example 1. Under this preparation method, hydrogel cannot be obtained, and thus the sensor cannot be obtained.

[0085] Comparative Example 4

[0086] The comparative example is different from example 1 in that no second solution of glyoxylic acid and sodium carbonate is added in step (1), the first solution is ultrasonically treated for 10 min, and then is left to stand at 70°C for 1 h, and then the solution is cooled to room temperature and NaBH4 is added to perform one-step reduction to obtain a hydrogel, and the rest is the same as example 1.

[0087] Test Example 1

[0088] The specific surface area of the hydrogel prepared in examples 1-3 above is tested after freeze-drying into powder, and the test results are shown in Table 1.

[0089] Table 1

[0090] Test Example 2

[0091] The morphology and structure of the hydrogels prepared in example 1, example 4, example 5, comparative example 1 and comparative example 2 are analyzed by SEM scanning electron microscope, and the test results are shown in FIG. 3, wherein (A) is the SEM image of the hydrogel prepared in example 4, (B) is the SEM image of the hydrogel prepared in example 5, (C) and (D) are the SEM images of the hydrogel prepared in example 1, (E) is the SEM image of the hydrogel prepared in comparative example 1, and (F) is the SEM image of the hydrogel prepared in comparative example 2.

[0092] As can be seen from FIG. 3, the Pt-Cu hydrogel prepared in the present application has a typical metal hydrogel nanowire network, which is composed of a network of ultra-fine linear structures connected to each other, has a large number of three-dimensional porous self-supporting structures and many bifurcations inside, and these structures are all helpful for the conduction and exposure of active centers, thereby improving the catalytic efficiency and catalytic activity of the hydrogel and improving the detection efficiency and detection accuracy of the sensor.

[0093] Test Example 3

[0094] The element distribution of the hydrogel in example 1 is tested by EDS energy dispersive X-ray spectroscopy of SEM, as shown in FIG. 4, wherein FIG. 4(A) is a qualitative analysis, proving that the hydrogel contains platinum and copper, FIG. 4(B) is a distribution map of Pt element, and FIG. 4(C) is a distribution map of Cu element. According to the test results, it can be seen that in the hydrogel of example 1, Pt and Cu are uniformly distributed in the three-dimensional network structure of nanowires.

[0095] Test Example 4

[0096] The crystallinity of the hydrogels prepared in example 1 and comparative example 1 is analyzed by powder X-ray diffractometer (XRD), and the test method is that the hydrogel is placed in a freeze dryer for freeze-drying for one day to become powder, and then XRD characterization is performed, and the test results are shown in FIG. 5.

[0097] According to FIG. 5, the X-ray diffraction peaks of the pure Pt hydrogel powder of Comparative Example 1 are consistent with the diffraction peaks of Pt (PDF #87-0640), indicating that the Pt hydrogel has a high degree of crystallinity. The three characteristic peaks of 39.9°, 46.4° and 67.7° of the Pt-Cu hydrogel of Example 1 correspond to the (111), (200) and (220) crystal planes of face-centered cubic Pt, respectively. Compared with the hydrogel of Comparative Example 1, the three characteristic peaks of the hydrogel of Example 1 slightly move to a higher diffraction angle, indicating that the crystal lattice of the hydrogel of Example 1 shrinks with the addition of Cu content. The reason for the slight shrinkage of the crystal lattice can be explained as the smaller Cu atoms penetrating into the Pt lattice, resulting in a smaller unit cell. At the same time, no diffraction of Cu is observed, which indicates that a bimetallic nanostructure composed of highly crystalline Pt and amorphous Cu is formed, and therefore the XRD results confirm that the PtCu hydrogel has been successfully synthesized.

[0098] Test Example 5

[0099] The surface composition and element state of the hydrogel powders of Example 1 and Comparative Example 1 were analyzed by X-ray photoelectron spectroscopy (XPS). The results are shown in FIG. 6.

[0100] FIG. 6(A) shows the scanning spectra of the hydrogel powders of Example 1 and Comparative Example 1. The presence of Pt and Cu can be clearly observed in the hydrogel of Example 1. FIG. 6(B) is the Pt4f core level photoelectron spectrum of the two hydrogels, and it can be seen that both hydrogels are deconvoluted into two pairs of peaks, which belong to 4f 5 / 2 and 4f 7 / 2 . The deconvolution analysis of the contained metal Pt shows that the contained metal Pt has two strong peaks at 70.9 eV and 74.3 eV, which belong to Pt4f 7 / 2 and Pt4f 5 / 2 , and the double peaks at 71.8 (Pt4f 7 / 2 ) and 75.5 (Pt4f 5 / 2 ) may be related to Pt 2+ species such as PtO and Pt(OH)2. Compared with the hydrogel powder of Comparative Example 1, the double peaks of the hydrogel powder of Example 1 at 70.9 eV (Pt4f 7 / 2 ) and 74.3 eV (Pt4f 5 / 2 ) are shifted to a certain extent.

[0101] FIG. 6(C) is the Cu2p core level photoelectron spectrum of the hydrogel powder of Example 1, which can be seen to be also deconvoluted into two pairs of peaks: two valence states at 932.2 eV and 934.4 eV, which are related to Cu and Cu 2+ valence states, respectively. The two obvious double peaks with binding energies of 951.9 eV and 954.1 eV constitute the 2p1 / 2 peaks can be attributed to Cu 2+ . The doublet at 932.2 eV and 951.9 eV is related to Cu, and the peaks at 934.4 and 954.1 eV can be attributed to Cu 2+ species.

[0102] Test Example 6

[0103] The principle of the hydrogel for non-enzyme detection of glucose is shown in Fig. 7. The sensors of Examples 1-6 and Comparative Examples 1-4 were tested by cyclic voltammetry (CV), using PBS solution as a blank group and 5 mM glucose solution as a control group. The results of the oxidation current at 0.2 V are shown in Table 2.

[0104] Table 2

[0105] Comparative Example 3 failed to generate a gel, and thus no test results were obtained.

[0106] Fig. 8(A) is a CV result diagram of the carbon electrodes in the electrochemical sensors of Example 1 (named Pt2Cu1), Example 4 (named Pt1Cu1), Example 6 (named Pt3Cu1), and Comparative Example 1 (named Pt) in PBS solution (blank) and PBS solution containing 5 mM glucose, respectively. As can be seen from Fig. 8(A), the carbon electrodes modified by the platinum-copper hydrogels with different proportions all have an increased oxidation current at 0.2 V after the addition of 5 mM glucose, which is probably due to the electrochemical oxidation of glucose on the electrode. After the addition of 5 mM glucose, the oxidation current has the largest increase when the platinum-copper ratio is 2:1. This is because the distribution of the platinum-copper hydrogel in the platinum and copper ratio of 2:1 makes the platinum and copper bimetallic alloy have a better synergistic effect. It can also be seen from Fig. 8(A) that the addition of copper metal increases the double-electron layer of the platinum-copper hydrogel, and the surface platinum-copper hydrogel can expand the specific surface area of the electrode.

[0107] Since the hydrogel-modified electrode of Example 1 has a higher oxidation current, it is selected for subsequent glucose detection experiments. Fig. 8(B) shows the CV results of the platinum-copper hydrogel electrode in PBS solution containing 0, 2, and 5 mM glucose. The results show that the oxidation peak current of glucose increases with the increase of the glucose concentration. Specifically, the oxidation peak at a potential of -0.1 V to 0.3 V is attributed to the electroadsorption of glucose on Pt, forming an incompletely oxidized adsorption intermediate (C6H 11 O6Pt). With the increase of the scanning potential, the intermediate is further oxidized to a glucose lactone, which is rapidly hydrolyzed in the solution to form gluconic acid.

[0108] The sensor of Example 1 was applied with a 0.2 V voltage in 0.1 M PBS solution (pH 7.4) and the current response was recorded for 60 s to obtain the i-t plot and the corresponding fitting curve. The test plot is shown in Figure 9(A). As can be seen from the i-t plot of Figure 9(A), the electrochemical oxidation current of glucose increased with the increase of glucose concentration, and the linear fitting curve in the range of 0-6 mM was consistent with the equation: y = 0.22298 + 1.0522X, R 2 The calculated results showed that the lowest detection limit of the sensor of Example 1 for glucose in PBS was 137 μM (S / N = 3).

[0109] The sensor of Example 1 was tested for selectivity by chronoamperometry. Common interfering species, such as dopamine, creatinine, lactic acid, and urea, were added to the sensor at their respective physiological concentration levels. As shown in Figure 9(B), 6 μM dopamine, 30 μM creatinine, 5 mM lactic acid, and 50 mM urea were added to a 3 mM glucose solution, respectively. As can be seen from Figure 9(B), there was no significant change in the current, and the sensor showed specific response to the target detection substance glucose. The current response was negligible with the addition of interfering species. This indicates that the enzyme-free glucose sensor has good selectivity.

[0110] Test Example 7

[0111] The sensor of Example 1 was used to detect samples of serum and artificial sweat to verify the feasibility of the sensor.

[0112] The serum detection method was as follows: serum samples were obtained from a volunteer at a hospital. The obtained serum was first diluted with a PBS solution to obtain a diluted 100-fold serum sample. 50 uL of the diluted serum was dropped onto the electrode surface, and then different concentrations of glucose (0, 1, 2, 3, 4, 5, and 6 mM) were added to the electrode surface. As shown in Figure 10(A), when the added glucose concentration increased from 0 to 10 mM, the chronoamperometric response of the enzyme-free glucose sensor also increased. Figure 10(B) shows the linear fitting curve obtained from the chronoamperometric response of the sensor to glucose. The relationship between the response in the actual sample (diluted 100-fold serum) and the added glucose concentration followed the equation: I (uA) = 1.03668 x c (Gu) (mM + 0.29946, R = 0.99306.

[0113] The artificial sweat detection method is: using pH 7.4 artificial sweat to test the simulated sweat sample. First, 50 μL of pH 7.4 artificial sweat is dropped on the electrode surface, and then different concentrations of glucose (0, 1, 2, 3, 4, 5, 6 mM) are added to the electrode surface for glucose spiking. As shown in FIG. 10(C), when the added glucose concentration increases from 0 to 6 mM, the chronoamperometric response of the enzyme-free glucose sensor increases accordingly. FIG. 10(D) shows the linear fitting curve obtained from the chronoamperometric response of the sensor to glucose. The response of the sensor to glucose in pH 7.4 artificial sweat follows the equation: I (uA) = 0.01256 x c (Gu) (mM) - 0.02064, R = 0.98943.

[0114] According to the above test, for additional glucose, the linear detection range of the enzyme-free sensor in serum (0-6 mM) and artificial sweat (0-6 mM) can cover the concentration of glucose in serum and sweat under physiological conditions, proving that the enzyme-free glucose sensor prepared in the present application has good feasibility in actual sample detection.

[0115] Test Example 8

[0116] The sensors of Examples 1-6 and Comparative Examples 1-4 were subjected to anti-interference tests, using PBS solution as a blank group, 3 mM glucose solution as a control group, and 5 mM lactic acid interferent was added to the 3 mM glucose solution for testing. The same chronoamperometry method as in Example 6 was used for testing, and the measured current data is shown in Table 3.

[0117] Table 3

[0118] According to the data in Table 3, the current difference of the blank group, the control group and after adding lactic acid of Example 5 and Comparative Example 2 is not large, proving that the sensor has no response to glucose. Comparative Example 3 cannot generate a gel, so no test results can be obtained.

[0119] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and it cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application should be covered within the protection scope of the present application.

Claims

1. A method for preparing a Pt-Cu hydrogel enzyme-free glucose electrochemical sensor, characterized in that, comprising the following steps: (1) Preparation of Pt-Cu hydrogel: dissolving H2PtCl6 and CuCl2 in water to form a first solution, dissolving a weak reducing agent and sodium carbonate in water to form a second solution, mixing the first solution and the second solution to obtain a mixture, and ultrasonicating the mixture, standing at 60-80℃ for a first time, then cooling the solution to room temperature and adding NaBH4, and standing at 30-50℃ for a second time, and finally aging at room temperature for at least 24 h, and washing to obtain the Pt-Cu hydrogel; (2) placing the Pt-Cu hydrogel on an electrode and fixing it, to obtain the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor.

2. The production method according to claim 1, characterized by, The specific surface area of the Pt-Cu hydrogel is 15-50 m 2 g -1 .

3. The production method according to claim 1, characterized by, The molar ratio of H2PtCl6 to CuCl2 is 0.5-3:

1.

4. The production method according to claim 3, characterized by, The molar ratio of H2PtCl6 to CuCl2 is 2:

1.

5. The preparation method according to claim 3, characterized in that, The weak reducing agent is glyoxylic acid, and the molar ratio of glyoxylic acid to CuCl2 is 0.036-0.072:

1. The molar ratio of sodium carbonate to CuCl2 is 1.26-2.52:

1.

6. The production method according to claim 5, wherein The molar ratio of glyoxylic acid to CuCl2 is 0.054:

1.

7. The preparation method according to claim 5, characterized in that, The molar ratio of sodium carbonate to CuCl2 is 1.89:

1.

8. The preparation method according to claim 5, characterized in that, The concentration of CuCl2 in the first solution is 2.5 mM. The volume ratio of water in the first solution to water in the second solution is 1:

1.

9. The method of claim 1, wherein, The molar ratio of NaBH4 to CuCl2 is 0.25-0.5:

1.

10. The method of claim 9, wherein, The molar ratio of NaBH4 to CuCl2 is 0.37:

1.

11. The method of claim 1, wherein, The ultrasonicating time of the mixture is 10-15 min. The first time is 0.5-1.5 h. The second time is 2.5-3.5 h.

12. The method of claim 11, wherein, The first time is 1 h. The second time is 3 h.

13. The method of claim 1, wherein, The thickness of the Pt-Cu hydrogel placed on the electrode is 0.15-0.2 mm.

14. The Pt-Cu hydrogel enzyme-free glucose electrochemical sensor prepared by the method of any one of claims 1-13.

15. The use of the Pt-Cu hydrogel enzyme-free glucose electrochemical sensor prepared by the method of any one of claims 1-13 in continuous blood glucose monitoring.

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