A xanthine electrochemical sensing electrode based on cobalt-iron Prussian blue analogue / ferrocene functionalized MXene

Abstract

An electrochemical sensing electrode based on a cobalt iron Prussian blue analogue / ferrocene functionalized MXene. The present invention belongs to the technical field of electrochemical sensors, and specifically relates to an electrochemical sensing electrode based on a cobalt iron Prussian blue analogue / ferrocene functionalized MXene complex. The purpose of the present invention is to solve the problems of narrow linear range, high detection limit and slow response time of the electrochemical sensors currently used to detect xanthine. The product: consists of a GCE electrode and a cobalt iron Prussian blue analogue / ferrocene functionalized MXene complex wrapped around the GCE electrode; the electrochemical sensor constructed based on this electrochemical sensing electrode exhibits excellent electrochemical sensing performance in xanthine detection, including a fairly wide linear range (3×10 ‑8 ~1.007×10 ‑3 M), extremely low detection limit (2×10 ‑9 M), a higher surface area (6.69 cm 2 ), excellent repeatability, good reproducibility and superior stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensors, and in particular relates to a xanthine electrochemical sensing electrode based on cobalt-iron Prussian blue analogues / ferrocene functionalized MXene. Background Art

[0002] Xanthine (3,7-dihydropurine-2,6-dione) is a key compound in biological systems, produced by guanine deaminase and hypoxanthine oxidase, respectively (both produced by the degradation of ATP). Xanthine oxidase converts xanthine to uric acid, which is excreted in the urine. Furthermore, xanthine is a key metabolite of adenine nucleotides and serves as a biomarker for diseases such as gout, renal failure, acute hypoxic stress, and adult respiratory distress syndrome. Measuring xanthine in serum and urine is crucial for the diagnosis and treatment of these diseases. Therefore, efficient and accurate determination of xanthine content in biological samples is crucial for disease diagnosis and prevention. However, due to the complexity of the matrix and the low concentration of the target compound, xanthine analysis in samples is a daunting task. Numerous methods exist for xanthine determination, including capillary electrophoresis, liquid chromatography, spectrophotometry, chemiluminescence, and enzymatic methods. Compared to the aforementioned methods, electrochemical methods offer advantages such as high sensitivity, rapid signal response, low cost, and convenient operation. Currently, various methods are used for xanthine determination. However, xanthine-based biosensors suffer from low stability, complex preparation, slow electron transfer, and susceptibility to environmental influences. Therefore, the development of low-cost, simple, highly sensitive, and fast-response non-enzymatic electrochemical methods is a promising option.

[0003] Prussian blue analogues are compounds obtained by replacing FeII or FeIII in Prussian blue molecules with transition metals during the research of Prussian blue. The general formula is A x M y In the formula [M'(CN)6]nH2O, A is an alkali metal, primarily derived from the reaction starting materials. It may or may not be present in a Prussian blue analog. M and M' are transition metals, which can be the same or different elements. If they are the same metal, the valence states of M and M' can be the same or different. Generally, M is defined as the external transition metal, while M' is the internal transition metal. The wide variety of Prussian blue analogs has resulted from the diverse nature of these metals. PBs and PBAs, with their three-dimensional (3D) framework structures, are also considered metal-organic frameworks (MOFs). Due to their unique microstructure, tunable composition, excellent electrochemical and photoelectrochemical properties, high stability, and ease of preparation, they are widely used in electrochemical fields such as sensors, electrocatalysis, and energy storage.

[0004] Ferrocene is the full name of dicyclopentadienyl iron, and its structure is an iron atom sandwiched between two cyclopentadienyl groups. Ferrocene has excellent electrochemical properties and is easy to functionalize, so it is often used to prepare electrode materials for electrochemical sensors. In addition, ferrocene has a unique sandwich structure. The two aromatic rings on the outer layer give it stable chemical properties, while the iron atom in the middle has multiple valence states, which gives it good catalytic ability. At the same time, ferrocene, as an aromatic compound, has the characteristics of easy substitution and is relatively easy to prepare derivatives. The ring of ferrocene can be substituted with both single rings and double rings at the same time, and a variety of derivatives can be prepared. Therefore, based on its own high redox activity, good biocompatibility, and as a good electron transfer mediator for biosensors, ferrocene and its derivatives have been widely used in various fields such as medicine, biology, and electrochemistry.

[0005] MXene is a new type of two-dimensional material, including transition metal carbides, carbonitrides and nitrides, with the chemical formula M n+1 X n T x , M represents a transition metal (such as Ti, V, Nb, Cr, Mo, etc.), X is carbon and / or nitrogen, T x Indicates surface terminations (such as OH, O, and F). MXene was first proposed by the Gogotsi team in 2011 and has recently sparked a wave of multidisciplinary research. Interestingly, it has many similarities with 2D graphene nanosheets in structure and properties. The most common MXene is Ti3C2T x , Ti3C2T x It is fabricated by etching aluminum with hydrofluoric acid (HF) using Ti3AlC2 with surface end groups (Tx) containing F, O, and OH. Among the various MXenes reported, MXenes have been widely used in electrochemical sensors due to their excellent electron conductivity, chemical stability, outstanding biocompatibility, large surface area, hydrophilicity, and numerous active groups. In addition to these properties, MXenes also possess strong reducing ability, making them highly popular in composite material construction and showing broad application prospects in a wide range of fields, including sensing, catalysis, microelectronics, and lithium-ion batteries. However, pure MXene exhibits poor oxidation resistance and is easily oxidized under heating conditions and in air, resulting in a decrease in conductivity. The impact on device performance remains to be studied. Furthermore, MXene-based xanthine electrochemical sensors that simultaneously achieve high sensitivity and a wide operating range have yet to be developed. Therefore, effective functionalization of MXenes is crucial for their electrochemical applications. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems of narrow linear range, high detection limit, slow response time, complex operation, high labor and instrument costs, and difficulty in meeting the demand for rapid detection of traditional sensors currently used to detect xanthine. The present invention provides a xanthine electrochemical sensing electrode based on cobalt-iron Prussian blue analogue / ferrocene functionalized MXene.

[0007] The present invention is a xanthine electrochemical sensing electrode based on a cobalt iron Prussian blue analogue / ferrocene functionalized MXene, which is characterized in that the xanthine electrochemical sensing electrode based on a cobalt iron Prussian blue analogue / ferrocene functionalized MXene is composed of a GCE electrode and a cobalt iron Prussian blue analogue / ferrocene functionalized MXene complex wrapped around the GCE electrode.

[0008] In the cobalt-iron Prussian blue analog / ferrocene-functionalized MXene composite, the MXene is obtained by etching LiF, HCl, and Ti3AlC2MAX powder in a polytetrafluoroethylene reactor. The mass ratio of LiF to Ti3AlC2MAX powder is (1.5-2.5):1.

[0009] In the ferrocene-functionalized MXene composite, the mass ratio of ferrocene is 14%.

[0010] The xanthine electrochemical sensing electrode based on cobalt-iron Prussian blue analogue / ferrocene functionalized MXene is obtained by sampling 9 to 11 μL using a drop coating method, applying the sample on a GCE electrode, and allowing it to dry naturally.

[0011] The present invention utilizes a three-electrode system to comprehensively characterize and analyze the electrochemical properties of the prepared composite material and the electrochemical detection effect of the material on xanthine through methods such as cyclic voltammetry, electrochemical impedance spectroscopy, and current-time method.

[0012] Beneficial effects of the present invention:

[0013] Compared to traditional electrochemical sensors, this invention constructs a xanthine electrochemical sensing electrode based on a cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene. This overcomes the narrow linear range, high detection limit, and slow response time issues currently encountered in xanthine electrochemical sensors. This is primarily due to the synergistic effect of the cobalt-iron Prussian blue analogue and the ferrocene-functionalized MXene. Both possess porous structures, which increase the sensor's specific surface area and the number of active adsorption sites for small biomolecules on the electrode surface, significantly improving its electrocatalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1This is a scanning electron micrograph of the cobalt-iron Prussian blue analogue obtained in Experiment 1;

[0015] Figure 2 Ti3C2T obtained in experiment 1 x Scanning electron microscope image of Mxene;

[0016] Figure 3 This is the scanning electron microscopy image of the cobalt-iron Prussian blue analogue / ferrocene functionalized MXene obtained in experiment 1;

[0017] Figure 4 This is a scanning electron micrograph of the xanthine electrochemical sensing electrode surface of the cobalt-iron Prussian blue analog / ferrocene-functionalized MXene obtained in Experiment 1;

[0018] Figure 5 Transmission electron microscopy image of the cobalt-iron Prussian blue analogue / ferrocene functionalized MXene obtained in experiment 1;

[0019] Figure 6 This is a magnified transmission electron microscope image of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene obtained in Experiment 1;

[0020] Figure 7 X-ray diffraction spectra of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene, cobalt-iron Prussian blue analogue, and MXene obtained in experiment 1;

[0021] Figure 8 This is the X-ray photoelectron spectrum of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene obtained in experiment 1 at 540 eV~526 eV;

[0022] Figure 9 This is the X-ray photoelectron spectrum of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene obtained in experiment 1 at 688 eV~681 eV;

[0023] Figure 10 This is the X-ray photoelectron spectrum of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene obtained in experiment 1 at 730 eV~702 eV;

[0024] Figure 11 This is the X-ray photoelectron spectrum of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene obtained in experiment 1 at 776 eV~816 eV;

[0025] Figure 12 This is the X-ray photoelectron spectrum of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene obtained in experiment 1 at 282 eV~300 eV;

[0026] Figure 13 This is the X-ray photoelectron spectrum of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene obtained in experiment 1 at 450 eV~470 eV;

[0027] Figure 14 The UV-visible spectra of the five active component solutions described in Experiment 1 are ferrocene, cobalt iron Prussian blue analogue / ferrocene functionalized MXene, ferrocene functionalized MXene, cobalt iron Prussian blue analogue and Ti3C2T x MXene;

[0028] Figure 15 The infrared-visible spectra of the five substances obtained in Experiment 1 are iron, Ti3C2T x MXene, ferrocene-functionalized MXene, cobalt-iron Prussian blue analogs, and cobalt-iron Prussian blue analogs / ferrocene-functionalized MXene;

[0029] Figure 16 The differential pulse voltammograms of the xanthine catalytic activities of the four materials involved in the experiment 1 are: Cobalt iron Prussian blue analogue / ferrocene functionalized MXene, ferrocene functionalized MXene, Ti3C2T x MXene and cobalt-iron Prussian blue analogs;

[0030] Figure 17 The differential pulse voltammograms of the catalytic ability of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene electrode obtained in experiment 1 for different concentrations of xanthine;

[0031] Figure 18 To verify that the response current of the cobalt iron Prussian blue analogue / ferrocene functionalized MXene electrode obtained in the catalysis of xanthine is linear with the added xanthine concentration, the concentration range is 3×10 -8 ~1.007×10 -3 M, the detection limit was 2.0 × 10 -9 M;

[0032] Figure 19 The differential pulse voltammogram of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene electrode obtained in Experiment 1 for the catalytic activity of xanthine at different pH values ​​is shown in the figure. As shown in the figure, the catalytic effect is best at pH = 6.

[0033] Figure 20 The differential pulse voltammograms of the cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene electrode obtained in Experiment 1 for the catalytic activity of xanthine at different scan rates are shown in the figure. The scan rate range from bottom to top is 10~60mV / s.

[0034] Figure 21 The anti-interference ability of the cobalt-iron Prussian blue analogue / ferrocene functionalized MXene electrode obtained in Experiment 1 to xanthine catalysis in the presence of uric acid and guanine was tested. The results showed that the sensor had strong recognition ability for xanthine, uric acid and guanine.

[0035] Figure 22 Electrochemical impedance spectroscopy of electrodes prepared from four materials obtained in Experiment 1: Ti3C2TxMXene, ferrocene-functionalized MXene, cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene, and cobalt-iron Prussian blue analogue;

[0036] Figure 23 This is the repeatability test of the xanthine electrochemical sensing electrode of the cobalt-iron Prussian blue analog / ferrocene functionalized MXene obtained in experiment 1. DETAILED DESCRIPTION

[0037] Specific embodiment 1: This embodiment is a xanthine electrochemical sensing electrode based on cobalt iron Prussian blue analogue / ferrocene functionalized MXene, characterized in that a xanthine electrochemical sensing electrode based on cobalt iron Prussian blue analogue / ferrocene functionalized MXene is composed of a GCE electrode and a cobalt iron Prussian blue analogue / ferrocene functionalized MXene complex wrapped around the GCE electrode.

[0038] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the xanthine electrochemical sensing electrode based on cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene is characterized in that the ferrocene-functionalized MXene is composed of two-dimensional MXene sheets with a thickness of 0.98~0.48nm. The other steps and parameters are the same as those in specific embodiment 1.

[0039] Specific embodiment 3: This embodiment differs from specific embodiments 1 or 2 in that the mass ratio of MXene to ferrocene in the cobalt-iron Prussian blue analog / ferrocene functionalized MXene composite is 20:3. Other steps and parameters are the same as those in specific embodiments 1 and 2.

[0040] Specific Embodiment 4: This embodiment differs from Specific Embodiments 1-3 in that the MXene is produced by etching LiF, HCl, and Ti3AlC2MAX powder in a polytetrafluoroethylene reactor. The mass ratio of LiF to Ti3AlC2MAX powder is 2:1. All other steps and parameters are the same as Specific Embodiments 1-3.

[0041] Specific Embodiment 5: This embodiment differs from Specific Embodiments 1 to 4 in that the cobalt-iron Prussian blue analog is synthesized from Co(NO3)2·6H2O and K3[Fe(CN)6] via a hydrothermal method, wherein the concentration ratio of Co(NO3)2·6H2O to K3[Fe(CN)6] is 3:2. Other steps and parameters are the same as those of Specific Embodiments 1 to 4.

[0042] Specific embodiment 6: This embodiment differs from Specific embodiments 1 to 5 in that the cobalt-iron Prussian blue analog / ferrocene-functionalized MXene composite is deposited by drop-coating 9 μL to 11 μL onto a GCE electrode and allowing to dry naturally. Other steps and parameters are the same as Specific embodiments 1 to 5.

[0043] Specific embodiment seven: In this embodiment, a method for preparing a xanthine electrochemical sensing electrode based on cobalt-iron Prussian blue analogue / ferrocene functionalized MXene is carried out by the following steps:

[0044] I. Preparation of Cobalt-Iron-Prussian Blue Analog Nanosheets: ① Dissolve 0.5-0.7 mmol Co(NO₃)₂·6H₂O and 0.8-1.0 mmol sodium citrate in 18-22 mL of deionized water under stirring, labeled as Solution A. ② Then, dissolve 0.3-0.5 mmol K₃[Fe(CN)₆] in 18-22 mL of deionized water, labeled as Solution B. ③ Rapidly add Solution B to Solution A and stir at 26-30°C for 18-22 min. Allow to stand at room temperature for 6-8 days. Collect the precipitate by centrifugation and freeze-dry to obtain Cobalt-Iron-Prussian Blue Analog Nanosheets.

[0045] The stirring time described in step 1 (3) is 18 to 22 minutes;

[0046] The placement time described in step 1③ is 6 to 8 days;

[0047] 2. Preparation of ferrocene functionalized MXene: ① Dissolve 1-2 g of lithium fluoride in a polytetrafluoroethylene container containing 38-42 mL of 9M hydrochloric acid solution under stirring and continue stirring for 28-32 min, labeled as solution A; ② Then slowly add 1.4-1.6 g of titanium aluminum carbide MAX phase powder to solution A at 38-42 °C and continue stirring for 38-42 h to obtain solution B; ③ Ultrasonicate solution B for 28-32 min, wash with 18-22 mL of 1M hydrochloric acid solution and then with distilled water and centrifuge until the pH is 6; ④ Add 98 mL-102 mL of distilled water and 0.8-1.2 mL of ethanol to the precipitate obtained in the previous step and ultrasonicate in an ice bath under argon atmosphere for 58-62 min, then collect the upper layer and freeze-dry to obtain solid Ti3C2Tx MXene; ⑤ Prepare 0.08~0.12 gTi3C2T x MXene was added to 40 mL of distilled water / ethanol solution (volume ratio of 1:1) and ultrasonicated for 1 h to obtain a uniform suspension. Then, 2-4 mL of 5 mg / mL ferrocene solution was added to it. After ultrasonication for 1 h, the suspension was freeze-dried to obtain ferrocene-functionalized MXene material.

[0048] The concentration of the hydrochloric acid solution in step 2① is 8-10 mol / L;

[0049] The mass ratio of ferrocene in step 2⑤ is 13%;

[0050] 3. Preparation steps of ferrocene functionalized MXene composite based on cobalt-iron Prussian blue analogue: ① Prepare 0.08~0.12 g Ti3C2T x MXene was added to 38-42 mL of distilled water / ethanol solution (volume ratio of 1:1) and sonicated for 1 h. Then, 1-2 mL of 5 mg / mL ferrocene solution was added to the obtained suspension, and solution C was obtained after sonication for 1 h. ② First, 0.5-0.7 mmol of cobalt nitrate hexahydrate was added to solution C and stirred continuously at room temperature for 11-13 h. ③ 18-22 mL of K3[Fe(CN)6] solution (0.4 mmol) was quickly poured into the above solution, stored at room temperature for seven days, and the precipitate was collected by centrifugation and freeze-dried to obtain a cobalt-iron Prussian blue analogue / ferrocene functionalized MXene complex.

[0051] 4. Preparation of xanthine electrochemical sensing electrode based on ferrocene-functionalized MXene as a cobalt-iron-Prussian blue analogue: ① Take 1-3 mg of sample and mix it with 230-250 μL of ethanol / naphthol solution (volume ratio 24:1), sonicate for 25-35 min, and after uniformity, take 9-11 μL and drop it on the GCE electrode by drop coating method. Let it dry naturally to obtain a xanthine electrochemical sensing electrode based on ferrocene-functionalized MXene as a cobalt-iron-Prussian blue analogue.

[0052] The linear range of the xanthine electrochemical sensor working electrode prepared in this embodiment is 3×10 -8 ~1.007×10 -3 M, the detection limit was 2.0 × 10 -9 M, with a higher surface area (6.69 cm 2), it has a wide linear range, fast detection speed and low detection limit. In addition, the working electrode prepared by the method of this embodiment has the advantages of good repeatability, reproducibility and stability, and is more sensitive to the detection of xanthine. This is mainly attributed to the cobalt iron Prussian blue analogue, ferrocene and Ti3C2T x The synergistic effect of the three MXenes promotes the electron transfer rate on the electrode surface and expands the active adsorption sites of hydrogen peroxide small molecules on the electrode surface, thereby greatly improving its electrocatalytic xanthine activity.

[0053] Specific embodiment eight: This embodiment differs from specific embodiment seven in that the amounts of cobalt nitrate hexahydrate and sodium citrate used in step one (1) are 0.6 mmol and 0.9 mmol, respectively. Other steps and parameters are the same as those in specific embodiment seven.

[0054] Specific embodiment nine: This embodiment differs from specific embodiment seven or eight in that the amounts of K3[Fe(CN)6] and deionized water used in step 1② are 0.4 mmol and 20 mL, respectively, and the other steps and parameters are the same as those in specific embodiment seven or eight.

[0055] Specific embodiment ten: This embodiment differs from specific embodiments seven to nine in that the stirring time in step one (3) is 20 min, the placement time is 7 days, and the other steps and parameters are the same as those in specific embodiments seven to nine.

[0056] Specific embodiment eleven: This embodiment differs from specific embodiments seven to ten in that the concentration of the hydrochloric acid solution in step two (1) is 9 mol / L, and the other steps and parameters are the same as those in specific embodiments seven to ten.

[0057] Specific embodiment 12: This embodiment differs from specific embodiments 7 to 11 in that the concentration of the ferrocene solution in step 2② is 5 mg / mL, and the other steps and parameters are the same as those of specific embodiments 7 to 11.

[0058] Specific embodiment 13: This embodiment differs from any one of specific embodiments 7 to 12 in that: the Ti3C2T x The mass ratio of MXene to ferrocene is 20:3; other steps and parameters are the same as those in Specific Embodiments 7 to 12.

[0059] Specific embodiment 14: This embodiment differs from specific embodiments 7 to 13 in that the lithium fluoride and 9M hydrochloric acid solution taken in step 3① are 3 g and 40 mL respectively, and the other steps and parameters are the same as those of specific embodiments 7 to 13.

[0060] Specific embodiment 15: This embodiment differs from specific embodiments 7 to 14 in that: in step 3②, the titanium aluminum carbide MAX added is 1.5 g, and stirred at 40°C for 40 h. The other steps and parameters are the same as those of specific embodiments 7 to 14.

[0061] Specific embodiment 16: This embodiment differs from specific embodiments 7 to 15 in that: in step 3③, solution B is ultrasonicated for 30 min, washed with 20 mL of 1M hydrochloric acid solution and then washed with distilled water and centrifuged until the pH is 6. The other steps and parameters are the same as those of specific embodiments 7 to 15.

[0062] Specific embodiment seventeen: This embodiment differs from specific embodiments seven to sixteen in that: in step three (4), 5 mL of ferrocene solution is added to the ethanol solution, and the mixture is allowed to stand for 30 min. Other steps and parameters are the same as those of specific embodiments seven to sixteen.

[0063] Specific embodiment 18: This embodiment differs from the specific embodiments 7 to 17 in that the Ti3C2T x The amounts of MXene and distilled water / ethanol solution (volume ratio of 1:1) were 0.1 g and 40 mL, respectively. The other steps and parameters were the same as those in Specific Embodiments 7 to 17.

[0064] Specific embodiment 19: This embodiment differs from any one of specific embodiments 7 to 18 in that in step 3⑤, the amount of ferrocene solution (5 mg / mL) added to the distilled water / ethanol solution is 1.5 mL, and the other steps and parameters are the same as those of any one of specific embodiments 7 to 18.

[0065] Specific embodiment 20: This embodiment differs from specific embodiments 7 to 19 in that: in step 3⑥, the amount of cobalt nitrate hexahydrate added to solution C is 0.6 mmol, the stirring time at room temperature is 12 h, and the other steps and parameters are the same as those of specific embodiments 7 to 19.

[0066] Specific embodiment 21: This embodiment differs from specific embodiments 7 to 21 in that the amount of K3[Fe(CN)6] solution (0.4 mmol) added in step 3⑦ is 20 mL, and the other steps and parameters are the same as those in specific embodiments 7 to 21.

[0067] Specific embodiment 22: This embodiment differs from specific embodiments 7 to 21 in that: in step 4, 2 mg of sample is mixed with 240 μL of ethanol / naphthol solution (volume ratio of 24:1), ultrasonicated for 30 min, 10 μL is taken out, drop-coated on the CGE electrode, and naturally dried to obtain a xanthine electrochemical sensing electrode based on cobalt-iron Prussian blue analogue / ferrocene functionalized MXene.

[0068] The following experiments were used to verify the effect of the present invention.

[0069] Experiment 1: The preparation method of a xanthine electrochemical sensing electrode based on cobalt-iron Prussian blue analogue / ferrocene functionalized MXene was carried out as follows:

[0070] I. Preparation of a Cobalt-Iron Prussian Blue Analog: ① Dissolve 0.6 mmol of cobalt nitrate hexahydrate and 0.9 mmol of anhydrous sodium citrate in 20 mL of deionized water with stirring, labeled as Solution A. ② Then, dissolve 0.4 mmol of K3[Fe(CN)6] in 20 mL of deionized water, labeled as Solution B. ③ Rapidly add Solution B to Solution A and stir at 28°C for 20 min. Allow to stand at room temperature for 7 days. Collect the precipitate by centrifugation and freeze-dry to obtain a Cobalt-Iron Prussian Blue Analog.

[0071] The stirring time described in step 1 (3) is 20 min;

[0072] The placement time described in step 1③ is 7 days;

[0073] 2. Preparation of MXene functionalized by ferrocene: ① 3 g of lithium fluoride was dissolved in a polytetrafluoroethylene container containing 40 mL of 9 M hydrochloric acid solution under stirring for 30 min, which was labeled as solution A; ② Then 1.5 g of titanium aluminum carbide MAX phase powder was slowly added to solution A at 40 ° C and stirred for 40 h to obtain solution B; ③ Solution B was ultrasonicated for 30 min, washed with 20 mL of 1 M hydrochloric acid solution and then washed with distilled water and centrifuged until the pH was 6; ④ 100 mL of distilled water and 1 mL of ethanol were added to the precipitate obtained in the previous step and ultrasonicated in an ice bath under argon atmosphere for 60 min, after which the upper layer was collected and freeze-dried to obtain solid Ti3C2Tx MXene; ⑤ 0.1 g of the prepared Ti3C2T x MXene was added to 40 mL of a mixture of distilled water and ethanol in a volume ratio of 1:1 and sonicated for 1 h. Then, 3 mL of ferrocene solution (5 mg / mL) was added to the obtained suspension. After sonication for 1 h, the suspension was freeze-dried to obtain ferrocene-functionalized MXene material.

[0074] The concentration of the hydrochloric acid solution in step 2① is 9 mol / L;

[0075] The mass ratio of ferrocene in step 2⑤ is 13%;

[0076] 3. Preparation steps of ferrocene functionalized MXene composite based on cobalt-iron Prussian blue analogue: ① 0.1 g of prepared Ti3C2T x MXene was added to 40 mL of a mixture of distilled water and ethanol in a volume ratio of 1:1, and ultrasonicated for 1 h to obtain a uniform suspension. Then 3 mL of 5 mg / mL ferrocene solution was added, and ultrasonicated for another 1 h to obtain solution C; ② First, 0.6 mmol of cobalt nitrate hexahydrate was added to solution C and stirred continuously at room temperature for 12 h; ③ 20 mL of K3[Fe(CN)6] (0.4 mmol) solution was quickly poured into the above solution, stored at room temperature for seven days, and then the precipitate was collected by centrifugation and freeze-dried to obtain a cobalt-iron Prussian blue analog ferrocene functionalized MXene complex.

[0077] 4. Preparation of xanthine electrochemical sensing electrode based on cobalt iron Prussian blue analogue / ferrocene functionalized MXene: ① Take 2 mg of sample and mix it with 240 μL ethanol / naphthol solution (volume ratio of 24:1), sonicate for 30 min, take 10 μL after uniformity, and drop it on the GCE electrode by drop coating method. Let it dry naturally to obtain a xanthine electrochemical sensing electrode based on cobalt iron Prussian blue analogue ferrocene functionalized MXene.

[0078] (I) Morphological characterization of the ferrocene-functionalized MXene composite based on the cobalt-iron Prussian blue analogue on the GCE electrode obtained in Experiment 1

[0079] Get as Figure 1 The scanning electron micrograph of the cobalt iron Prussian blue analogue obtained in Experiment 1 is shown in FIG. Figure 2 The scanning electron microscope magnified image of the cobalt iron Prussian blue analogue obtained in experiment 1 is shown. It can be seen from the figure that the thickness of the cobalt iron Prussian blue analogue nanosheet is 24 nm. It can be seen that the cobalt iron Prussian blue analogue particles are structured and evenly distributed. Figure 3 The scanning electron micrograph of a cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene on the GCE electrode obtained in Experiment 1 is shown in FIG. Figure 4 The cross-sectional view of the scanning electron micrograph of the xanthine electrochemical sensing electrode of the cobalt-iron Prussian blue analogue / ferrocene functionalized MXene obtained in Experiment 1 is shown as follows: Figure 5 The transmission electron microscopy image of the cobalt-iron Prussian blue analogue / ferrocene functionalized MXene obtained in experiment 1 is shown in FIG. Figure 6The transmission electron microscope magnified image of the cobalt-iron Prussian blue analogue / ferrocene functionalized MXene obtained in experiment 1 is shown. Figures 3 to 6 It can be seen that a cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene composite is composed of ferrocene-modified MXene and cobalt-iron Prussian blue analogue uniformly distributed inside and outside the MXene.

[0080] (II) Characterization of a Co-Fe-Prussian Blue analogue / ferrocene functionalized MXene composite, Co-Fe-Prussian Blue analogue, and MXene on the GCE electrode obtained in Experiment 1 using X-ray diffractometer and X-ray photoelectron spectroscopy

[0081] Get as Figure 7 The X-ray diffraction (XRD) patterns shown and Figures 8 to 13 The X-ray photoelectron spectroscopy (XPS) spectrum of the CoFePrussian blue analog / ferrocene-functionalized MXene composite on the GCE electrode obtained in Experiment 1 is shown. The XRD pattern shows that the characteristic diffraction peaks of the CoFePrussian blue analog / ferrocene-functionalized MXene composite sample only partially correspond to the crystal planes of the CoFePrussian blue analog and MXene. This indicates that the composite with the ferrocene-functionalized MXene disrupts the crystalline structure of the CoFePrussian blue analog and MXene, which facilitates the emergence of more active sites. The peak positions of oxygen, fluorine, iron, cobalt, carbon, and titanium in the XPS pattern indicate that ferrocene, the CoFePrussian blue analog, and the MXene were all successfully incorporated into the composite.

[0082] (III) Verification of the xanthine electrochemical sensing performance of a GCE electrode modified with a cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene complex obtained in Experiment 1 of this application

[0083] 1. Preparation of electrochemical sensors

[0084] A GCE electrode modified with a cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene complex obtained in Experiment 1 of this application was used as the working electrode, an Ag / AgCL electrode was used as the reference electrode, and a platinum wire electrode was used as the auxiliary electrode. The three-electrode system formed was the xanthine electrochemical sensor.

[0085] 2. Detection of xanthine using the electrochemical sensor obtained in step 1

[0086] Conclusion: We can get Figure 16 The differential pulse voltammograms of xanthine catalyzed by xanthine electrochemical sensors prepared with different materials are shown in Fig. Figure 17The differential pulse voltammograms of the xanthine electrochemical sensor based on the cobalt-iron Prussian blue analogue / ferrocene functionalized MXene composite for the catalytic ability of xanthine at different concentrations are shown, as well as Figure 18 The relationship between the response current of the cobalt iron Prussian blue analogue / ferrocene functionalized MXene electrode and the added xanthine concentration during the catalysis of xanthine is shown; Figure 16 The concentration range from bottom to top is 0.02~1000 μM. Figure 16 、 17 It can be seen that after the addition of xanthine, the xanthine electrochemical sensor based on the cobalt iron Prussian blue analogue / ferrocene functionalized MXene complex showed an irreversible oxidation peak at 0.84V, which is the catalytic potential of xanthine. As the xanthine concentration continued to increase, the catalytic peak current value at the catalytic potential of 0.84V also increased linearly. This is due to the catalytic oxidation reaction of xanthine by the ferrocene functionalized MXene complex based on the cobalt iron Prussian blue analogue, which caused the corresponding change in peak current. Figure 18 It can be seen that after catalyzing xanthine, the response current changes linearly with the concentration of added xanthine. This further demonstrates that the xanthine electrochemical sensor constructed based on the ferrocene-functionalized MXene complex of the cobalt-iron Prussian blue analog has an attractive detection performance for xanthine.

[0087] In summary, a xanthine electrochemical sensing electrode based on cobalt-iron Prussian blue analogue / ferrocene functionalized MXene was successfully prepared, and the xanthine electrochemical sensor constructed based on this sensing electrode has excellent and fast sensing performance.

Claims

1. A xanthine electrochemical sensing electrode based on cobalt-iron Prussian blue analogue / ferrocene functionalized MXene, characterized in that A xanthine electrochemical sensing electrode based on a cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene is composed of a GCE electrode and a cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene complex wrapped around the GCE electrode. The preparation method of the xanthine electrochemical sensing electrode based on a cobalt-iron Prussian blue analogue / ferrocene-functionalized MXene is completed by the following steps:

1. Preparation of Cobalt-Iron Prussian Blue Analogues ① Dissolve 0.6 mmol of cobalt nitrate hexahydrate and 0.9 mmol of sodium citrate anhydrous in 20 mL of deionized water under stirring, labeled as solution A; In step 1①, the volume ratios of cobalt nitrate hexahydrate and anhydrous sodium citrate to water are 3 mmol:100 mL and 4.5 mmol:100 mL, respectively; ② Dissolve 0.4mmol of K3[Fe(CN)6] in 20mL of deionized water, labeled as solution B. In step 1②, the volume ratio of K3[Fe(CN)6] to water is 1 mmol:50 mL; ③ Solution B was quickly added to solution A and stirred at 28°C for 20 minutes. The mixture was then placed at room temperature for 7 days. The precipitate was collected by centrifugation and freeze-dried to obtain cobalt-iron Prussian blue analog nanoparticles with an average particle size of approximately 100 nm. The stirring time in step 1 (3) is 20 min; The placement time described in step 1③ is 7 days; ④ The cobalt-iron Prussian blue analog nanoparticles prepared above have a uniform particle size distribution and an average particle size of 100 nm; 2. Preparation of Ferrocene-Functionalized Mxene ① Dissolve 3 g of lithium fluoride in 40 mL of 9 M hydrochloric acid solution in a polytetrafluoroethylene container under stirring for 30 min. This is labeled Solution A. The concentration of the hydrochloric acid solution in step 2① is 9 mol / L; In step 2①, the mass ratio of lithium fluoride to 9 mol / L hydrochloric acid is 3:40; ② Then, 1.5 g of titanium aluminum carbide MAX phase powder was slowly added to solution A at 40°C and stirred for 40 h to obtain solution B; The stirring time in step 2② is 40h; ③ Ultrasonicate solution B for 30 minutes, wash with 20 mL of hydrochloric acid solution and then with distilled water and centrifuge until the pH is 6; In step 2 (3), the concentration of the hydrochloric acid solution is 1 mol / L; ④ The bottom layer Ti3C2T obtained after centrifugation x 100 mL of distilled water and 1 mL of ethanol were added to the MXene compound, and then ultrasonicated in an ice bath for 60 min under an argon atmosphere to collect the upper black Ti3C2T x MXene suspension, and finally freeze-dried to obtain solid Ti3C2T x MXene; In step 2④, the volume ratio of ethanol to distilled water is 1:100; ⑤ Prepare 0.1g Ti3C2T x MXene was added to 40 mL of a mixture of distilled water and ethanol in a volume ratio of 1:

1. After ultrasonication for 1 h, 3 mL of ferrocene solution was added to the obtained suspension. After ultrasonication for 1 h, the suspension was freeze-dried. Obtain ferrocene functionalized MXene materials; Step 2⑤ Ti3C2T x The mass ratio of MXene to ferrocene is 20:3; ⑥ The ferrocene functionalized MXene material prepared above has a two-dimensional sheet structure; 3. Preparation of Cobalt-Iron Prussian Blue Analog / Ferrocene-Functionalized MXene Composites ① Prepare 0.1g Ti3C2T x MXene was added to 40 mL of a mixture of distilled water and ethanol in a volume ratio of 1:1 and sonicated for 1 h to obtain a uniform suspension. 3 mL of ferrocene solution was then added, and then sonicated for another 1 h to obtain solution C. The concentration of ferrocene in step 3① is 5 mg / mL; Step 3① Ti3C2T x The mass ratio of MXene to ferrocene is 20:3; ② First, 0.6 mmol of cobalt nitrate hexahydrate was added to solution C and stirred at room temperature for 12 h to obtain solution D; The stirring time in step 3② is 12h; ③ 20 mL of a solution containing 0.4 mmol of K3[Fe(CN)6] was quickly poured into solution D and stored at room temperature for seven days. The precipitate was then collected by centrifugation and freeze-dried to obtain a cobalt-iron Prussian blue analogue ferrocene-functionalized MXene complex, which exhibited a three-dimensional porous structure with multiple overlapping layers, and the nanoparticles were evenly distributed on the layer structure; ④ The cobalt-iron Prussian blue analogue ferrocene functionalized MXene complex prepared above is a three-dimensional porous structure with multiple overlapping layers, and CoFe-PBA nanoparticles are evenly distributed on the surface of the layers; 4. Preparation of Xanthine Electrochemical Sensing Electrode Based on Cobalt-Iron Prussian Blue Analog / Ferrocene-Functionalized MXene ① Mix 2 mg of the cobalt-iron Prussian blue analogue ferrocene-functionalized MXene composite with 240 μL of ethanol / naphthol solution; In step 4①, the volume ratio of ethanol / naphthol solution to sample is 24:1; ② The mixed solution was ultrasonicated for 30 minutes. After it was uniform, 10 μL was taken and dropped on the GCE electrode by drop coating method. It was naturally dried to obtain a xanthine electrochemical sensing electrode based on cobalt iron Prussian blue analogue / ferrocene functionalized MXene.

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