A self-powered sensor and its preparation method and application in uric acid detection

Abstract

The present invention relates to the field of sensor analysis and detection technology, and in particular to a self-powered sensor and its preparation method and application. A dual-MOF-derived iron-doped carbon nanotube catalyst is prepared by a solvothermal method and high-temperature calcination. The catalyst is used for the cathode of a zinc-air battery to show excellent power density, energy density, and durability, with performance superior to that of a commercial Pt / C catalyst. Urate oxidase UAO is loaded on the cathode catalyst to form a cathode sensing interface. UAO consumes oxygen to catalyze the oxidation of uric acid, competing with the oxygen reduction process of the zinc-air battery cathode, resulting in a decrease in the output signal. A zinc-air battery self-powered electrochemical sensor based on an oxygen competition model is constructed for uric acid detection. The present invention broadens the application of zinc-air batteries in self-powered sensors, and the constructed sensor has a wide linear range, high sensitivity, and low detection limit for uric acid detection.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor analysis and detection, and in particular to a self-powered sensor, a preparation method thereof, and application in uric acid detection. Background Art

[0002] Uric acid, an important nitrogenous compound, is ubiquitous in biological fluids such as serum and urine and is the primary end product of purine metabolism. Abnormal uric acid levels in biological fluids can predict diseases such as gout, metabolic syndrome, and kidney disease. Therefore, uric acid is an effective biomarker for detecting disorders of purine metabolism. Establishing a rapid and reliable method for measuring uric acid concentration is of great significance for the diagnosis and treatment of diseases.

[0003] Currently, a variety of different uric acid detection methods have been developed, including high-performance liquid chromatography, spectrophotometry, ion chromatography, high-performance liquid chromatography / isotope dilution mass spectrometry, and electrochemical biosensors. These methods require relatively expensive instrumentation and are complex to operate. To achieve real-time monitoring and facilitate convenient and rapid use, it is crucial to develop miniaturized, integrated sensors.

[0004] Self-powered electrochemical sensors, as an emerging and powerful analytical method, have recently attracted considerable attention due to their advantages, such as requiring no external power supply, simple structure, and ease of miniaturization and integration. However, their low open-circuit voltage and output power density, resulting in a narrow detection range and limited sensitivity, have limited their application to some extent. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a self-powered sensor, a preparation method thereof, and its application in uric acid detection. The present invention replaces precious metals as the cathode material of a zinc-air battery by Fe-N-CNTs to reduce costs, and designs a self-powered electrochemical sensor based on the coupling of Fe-N-CNTs cathode catalyst and UAO, which realizes sensitive detection of uric acid through oxygen competition mode.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for preparing a self-powered sensor comprises the following steps:

[0008] The MIL-101(Fe) metal organic framework material is prepared by dissolving the MIL-101(Fe) metal organic framework material in methanol containing polyvinyl pyrrolidone, adsorbing organic molecules and metal ions, and obtaining a precursor MIL-P after centrifugal washing.

[0009] 2-Methylimidazole is dissolved in methanol and mixed with the precursor MIL-P, and then a soluble zinc salt is added to obtain a mixed solution. The mixed solution is allowed to stand for growth and post-treated to obtain MIL@ZIF. The MIL@ZIF is calcined and carbonized under a protective atmosphere to obtain Fe-N-CNTs.

[0010] The Fe-N-CNTs are dispersed in ethanol containing a perfluorosulfonic acid resin solution to obtain Fe-N-CNTs ink.

[0011] The Fe-N-CNTs ink was dropped onto the surface of the glassy carbon electrode to obtain Fe-N-CNTs / GCE, and the urate oxidase solution was dropped onto the surface of the Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE. UAO / Fe-N-CNTs / GCE was used as the cathode and Zn sheet as the anode to construct a self-powered sensor based on a dual-MOF-derived Fe-based cathode catalyst.

[0012] The present invention constructs a novel self-powered sensor for uric acid detection by assembling a Zn sheet anode and a UAO / Fe-N-CNTs / GCE cathode. The cathode and anode of the battery generate electrical energy through a chemical reaction, providing energy for the sensor to achieve self-driven uric acid monitoring. Urate oxidase at the cathode reacts with oxygen to catalyze the oxidation of uric acid, consuming oxygen, resulting in a decrease in the oxygen involved in the battery chemical reaction, thereby reducing the output voltage. The uric acid concentration change trend can be inferred from the output voltage. The smaller the output voltage, the greater the uric acid concentration, thereby achieving sensitive detection of uric acid. The present invention broadens the application of zinc-air batteries in self-powered sensors. The constructed sensor has a wide linear range, high sensitivity and low detection limit for uric acid detection.

[0013] In a preferred embodiment of the present invention, the usage ratio of 2-methylimidazole to methanol is 3.28 g~4 g:60 mL~100 mL.

[0014] In a preferred embodiment of the present invention, the usage ratio of 2-methylimidazole to precursor MIL-P is 3.28 g~4 g:12 mL~16 mL, and the mass ratio of soluble zinc salt to 2-methylimidazole is 3~3.5:3.28~4.

[0015] In a preferred embodiment of the present invention, the calcination and carbonization temperature is 900° C. to 950° C., and the calcination and carbonization time is 2 hours to 3 hours.

[0016] In a preferred embodiment of the present invention, the dosage ratio of Fe-N-CNTs catalyst to ethanol is 1 mg~3 mg: 0.5 mL~1 mL, the dosage ratio of Fe-N-CNTs to perfluorosulfonic acid resin solution is 1 mg~3 mg: 5 μL~10 μL, and the mass concentration of the perfluorosulfonic acid resin solution is 0.25%.

[0017] In a preferred embodiment of the present invention, the concentration of the uricase solution is 400 U / mL to 500 U / mL.

[0018] In a preferred embodiment of the present invention, the MIL-101(Fe) metal organic framework material is prepared by the following method: dissolving a soluble iron salt and terephthalic acid in DMF, performing a solvent thermal reaction, and post-treating the solvent thermal reaction product to obtain the MIL-101(Fe) metal organic framework material.

[0019] In a preferred embodiment of the present invention, the mass ratio of the soluble iron salt to terephthalic acid is 0.337~1.35:0.2075, the amount ratio of the soluble iron salt to DMF is 0.337g~1.35g:15mL, the solvent thermal reaction temperature is 100°C~120°C, and the solvent thermal reaction time is 20 hours~24 hours.

[0020] Another object of the present invention is to provide a self-powered sensor produced by any of the above-mentioned preparation methods.

[0021] The third object of the present invention is to provide an application of the above-mentioned self-powered sensor in uric acid detection.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention first dissolves the MIL-101 (Fe) metal organic framework material in methanol containing polyvinyl pyrrolidone to obtain a precursor MIL-P; dissolves 2-methylimidazole in methanol, mixes it with the precursor MIL-P, and then adds a soluble zinc salt to obtain a mixed solution, allowing the ZIF in the mixed solution to grow on the MIL-P, and obtains MIL@ZIF through post-treatment, and calcining and carbonizing the MIL@ZIF under a protective atmosphere to obtain a Fe-N-CNTs catalyst; Fe-N-CNTs catalyst is dispersed in ethanol containing perfluorosulfonic acid resin solution to obtain Fe-N-CNTs ink; the Fe-N-CNTs ink is added dropwise to the surface of a glassy carbon electrode to obtain Fe-N-CNTs / GCE; a urate oxidase solution is added dropwise to the surface of the Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE; a self-powered sensor is constructed using UAO / Fe-N-CNTs / GCE as the cathode and a Zn sheet as the anode. The present invention constructs a novel self-powered sensor for uric acid detection by assembling a Zn sheet anode and a UAO / Fe-N-CNTs / GCE cathode. The cathode and anode of the battery generate electrical energy through a chemical reaction, providing energy for the sensor to achieve self-driven uric acid monitoring. Urate oxidase at the cathode reacts with oxygen to catalyze the oxidation of uric acid, consuming oxygen, resulting in a decrease in the oxygen involved in the battery chemical reaction, thereby reducing the output voltage. The uric acid concentration change trend can be inferred from the output voltage. The smaller the output voltage, the greater the uric acid concentration, thereby achieving sensitive detection of uric acid. The present invention broadens the application of zinc-air batteries in self-powered sensors. The constructed sensor has a wide linear range, high sensitivity and low detection limit for uric acid detection.

[0024] 2. This invention prepares a dual-MOF-derived iron-doped carbon nanotube (Fe-N-CNT) catalyst via a solvothermal method and high-temperature calcination. This catalyst is then used as the cathode for zinc-air batteries. The resulting zinc-air battery demonstrates excellent power density, energy density, and durability, outperforming commercial Pt / C catalysts. Urate oxidase (UAO) is loaded onto the cathode catalyst to form the cathode sensing interface. UAO consumes oxygen to catalyze uric acid oxidation, competing with the oxygen reduction process at the zinc-air battery cathode, resulting in a reduced output signal. Furthermore, a self-powered electrochemical sensor for zinc-air batteries based on an oxygen competition model was constructed for the detection of uric acid.

[0025] 3. Compared with traditional detection methods, the electrochemical detection method used in the present invention has the characteristics of simple and flexible operation, simple instrumentation, high sensitivity, low detection cost, wide linear range and low detection limit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1In the figure, (a) is the working mode diagram of the self-powered sensor composed of cathode UAO / Fe-N-CNTs / GCE and anode Zn sheet, and (b) is the open circuit voltage diagram.

[0027] Figure 2 This is a scanning electron microscope image of ZIF@MIL and Fe-N-CNTs prepared in Example 1 of the present invention.

[0028] Figure 3 In the figure, (a) is the optimization curve of the amount of iron salt substance in 0.1 M KOH solution, and (b) is the optimization curve of the amount of iron salt substance in 0.1 M PBS solution.

[0029] Figure 4 In the figure, (a) is the ORR performance of Fe-N-CNTs and 20wt%Pt / C measured in 0.1M KOH solution, and (b) is the ORR performance measured in 0.1M PBS solution.

[0030] Figure 5 is the open circuit voltage during the preparation of GCE, Fe-N-CNTs / GCE and UAO / Fe-N-CNTs / GCE electrodes.

[0031] Figure 6 is the open circuit voltage of different concentrations of uric acid, where the concentration of uric acid is 0, 0.001 μM, 0.01 μM, 0.1 μM, 1 μM, 10 μM, 20 μM, 50 μM and 100 μM from high to low along the curve.

[0032] Figure 7 This is the relationship curve between the open circuit voltage and the uric acid concentration after the addition of uric acid. The illustration in the figure is the linear relationship diagram between the open circuit voltage and the logarithm of the uric acid concentration.

[0033] Figure 8 (a) Power density, (b) polarization curve, (c) specific capacity, and (d) durability test results of Zn-air batteries assembled in a neutral environment. DETAILED DESCRIPTION

[0034] The following is a detailed description of the technical solutions in the embodiments of the present invention, using preferred embodiments and accompanying drawings in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] It should be noted that all professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0036] 0.5 times, 1 times and 2 times of FeCl3·6H2O and 0.2075g of terephthalic acid were weighed and dissolved in 15mL DMF. The mixture was evenly dispersed by magnetic stirring. LSV test was performed using a rotating disk electrode to compare the oxygen reduction performance of Fe-N-CNTs under different multiple conditions in neutral and alkaline environments. The results are shown in Figure 2. Figure 3 As shown, 1 times the amount is the best condition and the half-wave potential is the largest. Therefore, 0.675g of FeCl3·6H2O is selected as the optimal amount to react with 0.2075g of terephthalic acid to prepare MIL-101(Fe) metal-organic framework material.

[0037] Example 1

[0038] A method for preparing a self-powered sensor based on a dual MOF-derived Fe-based cathode catalyst comprises the following steps:

[0039] (1) Preparation of precursor MIL-P

[0040] 0.675 g of FeCl3·6H2O and 0.2075 g of terephthalic acid were weighed and dissolved in 15 mL of DMF. The mixture was stirred on a magnetic stirrer for more than 35 minutes, and then subjected to solvent thermal reaction at 110°C for 20 hours. The reaction product was washed alternately with DMF and hot anhydrous ethanol five times at a speed of 10,000 r·min. -1 , washing for 10 min each time, and vacuum drying at 60°C to obtain yellow MIL-101(Fe).

[0041] The obtained MIL-101(Fe) was completely dissolved in methanol containing 3 g of polyvinyl pyrrolidone, fully stirred with magnetic stirring for 12 hours, and then centrifuged and washed 5 times with methanol at a centrifugal speed of 10000 r·min. -1 Each centrifugal washing time is 5 minutes, and the obtained solid is evenly dispersed in 45 mL of methanol for later use to obtain the precursor MIL-P.

[0042] (2) Preparation of Fe-N-CNTs

[0043] 3.28 g of 2-methylimidazole was dissolved in 60 mL of methanol, 16 mL of the precursor MIL-P was added and stirred vigorously for 5 minutes, followed by the addition of 3 g of Zn(NO3)2·6H2O and stirring for 5 minutes. The resulting liquid was allowed to stand for 24 hours for full growth, then washed with methanol five times, dried in a vacuum at 60°C for 12 hours, and ground into powder to obtain MIL@ZIF.

[0044] The MIL@ZIF was placed in a porcelain boat and heated in a tube furnace protected by nitrogen / argon atmosphere at 5°C·min -1 The temperature was raised to 950 °C and carbonized for 3 hours, and then naturally cooled to obtain a black Fe-N-CNTs catalyst.

[0045] (3) Preparation of self-powered sensors

[0046] The obtained Fe-N-CNTs catalyst was fully ground at room temperature. 3.0 mg of Fe-N-CNTs was weighed using an electronic balance and dispersed in 1.0 mL of ethanol. 10 μL of 0.25 wt% perfluorosulfonic acid resin solution was then added. The mixture was ultrasonicated in an ultrasonic machine for more than 30 minutes to prepare Fe-N-CNTs ink.

[0047] 15 μL of Fe-N-CNTs ink was added to the surface of the glassy carbon electrode to obtain Fe-N-CNTs / GCE. 10 μL of Fe-N-CNTs with a concentration of 500 U·mL was added. -1 The UAO solution was dropped onto the surface of Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE. UAO / Fe-N-CNTs / GCE was used as the cathode and the Zn sheet was used as the anode to assemble a self-powered sensor.

[0048] Example 2

[0049] A method for preparing a self-powered sensor based on a dual MOF-derived Fe-based cathode catalyst comprises the following steps:

[0050] (1) Preparation of precursor MIL-P

[0051] 0.675 g of FeCl3·6H2O and 0.2075 g of terephthalic acid were weighed and dissolved in 15 mL of DMF. The mixture was stirred on a magnetic stirrer for more than 35 minutes. The mixture was then subjected to solvent thermal reaction at 100°C for 24 hours. The reaction product was washed alternately with DMF and hot anhydrous ethanol five times at a speed of 10,000 r·min. -1 , washing for 10 min each time, and vacuum drying at 60°C to obtain yellow MIL-101(Fe).

[0052] The obtained MIL-101(Fe) was completely dissolved in methanol containing 3 g of polyvinyl pyrrolidone, fully stirred with magnetic stirring for 12 hours, and then centrifuged and washed 5 times with methanol at a centrifugal speed of 10000 r·min. -1 Each centrifugal washing time is 5 minutes, and the obtained solid is evenly dispersed in 45 mL of methanol for later use to obtain the precursor MIL-P.

[0053] (2) Preparation of Fe-N-CNTs

[0054] 3.5 g of 2-methylimidazole was dissolved in 80 mL of methanol, 12 mL of the precursor MIL-P was added and stirred vigorously for 5 minutes, followed by the addition of 3.2 g of Zn(NO3)2·6H2O and stirring for 5 minutes. The resulting liquid was allowed to stand for 24 hours for full growth, then washed with methanol five times, dried in a vacuum at 60°C for 12 hours, and ground into powder to obtain MIL@ZIF.

[0055] The MIL@ZIF was placed in a porcelain boat and heated in a tube furnace protected by nitrogen / argon atmosphere at 5°C·min -1 The temperature was raised to 900 °C and carbonized for 3 hours, and then naturally cooled to obtain a black Fe-N-CNTs catalyst.

[0056] (3) Preparation of self-powered sensors

[0057] The obtained Fe-N-CNTs catalyst was fully ground at room temperature. 1.0 mg of Fe-N-CNTs was weighed using an electronic balance and dispersed in 0.5 mL of ethanol. 10 μL of 0.25 wt% perfluorosulfonic acid resin solution was then added, and the mixture was ultrasonicated in an ultrasonic machine for more than 30 minutes to prepare Fe-N-CNTs ink.

[0058] 15 μL of Fe-N-CNTs ink was added to the surface of the glassy carbon electrode to obtain Fe-N-CNTs / GCE. 5 μL of Fe-N-CNTs ink with a concentration of 400 U·mL was added. -1 The UAO solution was dropped onto the surface of Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE. UAO / Fe-N-CNTs / GCE was used as the cathode and the Zn sheet was used as the anode to assemble a self-powered sensor.

[0059] Example 3

[0060] A method for preparing a self-powered sensor based on a dual MOF-derived Fe-based cathode catalyst comprises the following steps:

[0061] (1) Preparation of precursor MIL-P

[0062] 0.675 g of FeCl3·6H2O and 0.2075 g of terephthalic acid were weighed and dissolved in 15 mL of DMF. The mixture was stirred on a magnetic stirrer for more than 35 minutes, and then subjected to solvent thermal reaction at 120°C for 22 hours. The reaction product was washed alternately with DMF and hot anhydrous ethanol five times at a speed of 10,000 r·min. -1 , washing for 10 min each time, and vacuum drying at 60°C to obtain yellow MIL-101(Fe).

[0063] The obtained MIL-101(Fe) was completely dissolved in methanol containing 3 g of polyvinyl pyrrolidone, fully stirred with magnetic stirring for 12 hours, and then centrifuged and washed 5 times with methanol at a centrifugal speed of 10000 r·min. -1 Each centrifugal washing time is 5 minutes, and the obtained solid is evenly dispersed in 45 mL of methanol for later use to obtain the precursor MIL-P.

[0064] (2) Preparation of Fe-N-CNTs

[0065] 4 g of 2-methylimidazole was dissolved in 100 mL of methanol, 14 mL of the precursor MIL-P was added and stirred vigorously for 5 minutes, followed by the addition of 3.5 g of Zn(NO3)2·6H2O and stirring for 5 minutes. The resulting liquid was allowed to stand for 24 hours for full growth, then washed with methanol five times, dried in a vacuum at 60°C for 12 hours, and ground into powder to obtain MIL@ZIF.

[0066] The MIL@ZIF was placed in a porcelain boat and heated in a tube furnace protected by nitrogen / argon atmosphere at 5°C·min -1 The temperature was raised to 930 °C and carbonized for 2.5 hours, and then naturally cooled to obtain a black Fe-N-CNTs catalyst.

[0067] (3) Preparation of self-powered sensors

[0068] The obtained Fe-N-CNTs catalyst was fully ground at room temperature. 2.0 mg of Fe-N-CNTs was weighed using an electronic balance and dispersed in 0.8 mL of ethanol. 10 μL of 0.25 wt% perfluorosulfonic acid resin solution was then added, and the mixture was ultrasonicated in an ultrasonic machine for more than 30 minutes to prepare Fe-N-CNTs ink.

[0069] 15 μL of Fe-N-CNTs ink was added to the surface of the glassy carbon electrode to obtain Fe-N-CNTs / GCE. 8 μL of 450 U·mL -1 The UAO solution was dropped onto the surface of Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE. UAO / Fe-N-CNTs / GCE was used as the cathode and the Zn sheet was used as the anode to assemble a self-powered sensor.

[0070] Result Analysis

[0071] Figure 1 In the figure, (a) shows the operating mode of a self-powered sensor composed of a UAO / Fe-N-CNTs / GCE cathode and a Zn sheet anode, and (b) shows the open-circuit voltage. The sensor includes a UAO / Fe-N-CNTs-coated cathode and a Zn sheet anode. The reaction at the cathode is driven by oxygen in the solution, hence the name "air battery." The anode and cathode of an air battery chemically react to generate electricity, providing energy for the sensor. Urate oxidase at the cathode catalyzes the oxidation of uric acid, consuming oxygen in the solution. This reduces the oxygen available for the battery's chemical reactions, resulting in a decrease in the output voltage. The output voltage can be used to determine the uric acid concentration trend: a lower output voltage indicates a higher uric acid concentration.

[0072] Figure 2 The scanning electron microscope images of ZIF@MIL and Fe-N-CNTs prepared in Example 1 of the present invention are shown in FIG. Figure 2 It can be seen that MIL@ZIF has a regular morphology, and Fe-N-CNTs grow carbon tubes, which is beneficial to increase the specific surface area and improve the electrochemical performance.

[0073] The ORR performance was tested using Fe-N-CNTs catalysts with 0.5 times, 1 times and 2 times the iron salt content as working electrodes, silver-silver chloride electrodes as reference electrodes, carbon rods as counter electrodes, and 0.1 M KOH and 0.1 M PBS as electrolytes, respectively. Figure 3 As shown in Figure 2, in 0.1 M KOH solution and 0.1 M PBS solution, Fe-N-CNTs with one-fold iron salt content showed the best E 1 / 2 , so choose double the iron salt content as the optimal addition amount.

[0074] The Fe-N-CNTs catalyst prepared in Example 1 and 20 wt% Pt / C were used as working electrodes, silver-silver chloride electrode as reference electrode, carbon rod as counter electrode, 0.1 M KOH and 0.1 M PBS as electrolytes, respectively, to conduct ORR performance tests. Figure 4 As shown in the figure, in 0.1M KOH solution, the E1 / 2 of Fe-N-CNTs is 0.899V, which is higher than that of 20wt%Pt / C (E 1 / 2 =0.866V), in 0.1M PBS solution, the E1 / 2 of Fe-N-CNTs is 0.809V, which is higher than that of 20wt%Pt / C (E 1 / 2 =0.74 V), which shows that Fe-N-CNTs have excellent electrochemical properties and can be used to replace 20wt% Pt / C as the cathode material of zinc-air batteries.

[0075] A zinc-air battery self-powered system was constructed using a bare electrode, Fe-N-CNTs prepared in Example 1, and UAO / Fe-N-CNTs as cathodes and a zinc sheet as anode. The open circuit voltages of the three electrodes were measured in 0.1 M PBS solution. Figure 5 It can be seen that when Fe-N-CNTs is used as cathode and zinc sheet to form a zinc-air battery, the open circuit voltage is the largest. When UAO is loaded on the surface of Fe-N-CNTs, the open circuit voltage decreases slightly, and the open circuit voltage of GCE is the lowest.

[0076] UAO / Fe-N-CNTs / GCE was used as cathode and Zn sheet as anode to construct a self-powered sensor for uric acid detection. The open circuit voltage of the zinc-air battery self-powered system was tested in 0.1M PBS buffer with a pH of 7.4. Figure 7 As shown, the concentration of uric acid is as follows from high to low according to the peak value of the curve: 0, 0.001μM, 0.01μM, 0.1μM, 1μM, 10μM, 20μM, 50μM and 100μM, and the corresponding open circuit voltage values ​​are as follows Figure 6 As shown in the figure, the linear relationship between the open circuit voltage and the logarithm of uric acid concentration is obtained as follows: Figure 7 As shown, the corresponding linear regression equation is: E OCP (V)=-0.02827lg[ c UA (μM)] + 1.273, correlation coefficient R 2 =0.991; the detection range of the linear regression equation is 0.001μM~100μM, and the minimum detection limit is 0.34nM.

[0077] Zinc-air batteries were assembled using Fe-N-CNTs catalyst and 20wt% Pt / C+RuO2 with nickel mesh and carbon cloth as cathodes, and zinc sheets as anodes. The power density, polarization curve, specific capacity, and durability of the batteries were tested in a mixed solution of 4M NH4Cl and 0.2M ZnCl2. The results are shown in Figure 2. Figure 8 As shown, the zinc-air battery assembled with Fe-N-CNTs has a higher peak power of 50.5 mW·cm -2 , with a charge-discharge voltage band gap similar to that of commercial Pt / C+RuO2 and a higher specific capacity of 675.5 mA·h·g -1 , and better stability.

[0078] In summary, the present invention constructs a new self-powered sensor for uric acid detection by assembling a Zn sheet anode and a UAO / Fe-N-CNTs / GCE cathode. The cathode and anode of the battery generate electrical energy through chemical reactions, providing energy for the sensor to achieve self-driven uric acid monitoring; the urate oxidase at the cathode reacts with oxygen to catalyze the oxidation of uric acid, consuming oxygen, resulting in a decrease in the oxygen participating in the battery chemical reaction, so the output voltage decreases, and the uric acid concentration change trend is inferred by the output voltage. The smaller the output voltage, the greater the uric acid concentration, thereby achieving sensitive detection of uric acid.

[0079] It should be noted that when the present invention relates to numerical ranges, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the attached protection scope is intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0080] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the present invention and its equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a self-powered sensor, characterized in that: The following steps are involved: A MIL-101(Fe) metal organic framework material is prepared by dissolving the MIL-101(Fe) metal organic framework material in methanol containing polyvinyl pyrrolidone, and washing the mixture by centrifugation to obtain a precursor MIL-P; 2-Methylimidazole is dissolved in methanol and mixed with the precursor MIL-P, and then a soluble zinc salt is added to obtain a mixed solution. ZIF in the mixed solution is allowed to grow statically on MIL, and MIL@ZIF is obtained after post-treatment. The MIL@ZIF is calcined and carbonized under a protective atmosphere to obtain a Fe-N-CNTs catalyst; dispersing the Fe-N-CNTs catalyst in ethanol containing a perfluorosulfonic acid resin solution to obtain Fe-N-CNTs ink; The Fe-N-CNTs ink was dropped onto the surface of a glassy carbon electrode to obtain Fe-N-CNTs / GCE, and a urate oxidase solution was dropped onto the surface of the Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE. The UAO / Fe-N-CNTs / GCE was used as a cathode and a Zn sheet was used as an anode to construct a self-powered sensor based on a dual-MOF-derived Fe-based cathode catalyst; The dosage ratio of 2-methylimidazole to precursor MIL-P is 3.28 g ~ 4 g: 12 mL ~ 16 mL, and the mass ratio of soluble zinc salt to 2-methylimidazole is 3 ~ 3.5: 3.28 ~ 4; The concentration of urate oxidase solution is 400U / mL~500U / mL; The mixed solution was left to stand for 24 hours to allow for full growth; The MIL-101(Fe) metal organic framework material is prepared by the following method: dissolving a soluble iron salt and terephthalic acid in DMF, performing a solvothermal reaction, and post-treating the solvothermal reaction product to obtain the MIL-101(Fe) metal organic framework material; The mass ratio of the soluble iron salt to terephthalic acid is 0.337-1.35:0.2075, the amount ratio of the soluble iron salt to DMF is 0.337 g-1.35 g:15 mL, the solvent thermal reaction temperature is 100° C.-120° C., and the solvent thermal reaction time is 20 hours-24 hours.

2. The method for preparing a self-powered sensor according to claim 1, wherein: The usage ratio of 2-methylimidazole to methanol is 3.28g~4g:60mL~100mL.

3. The method for preparing a self-powered sensor according to claim 1, wherein: The calcination and carbonization temperature is 900°C to 950°C, and the calcination and carbonization time is 2 hours to 3 hours.

4. The method for preparing a self-powered sensor according to claim 1, wherein: The dosage ratio of Fe-N-CNTs catalyst to ethanol is 1 mg~3 mg: 0.5 mL~1 mL, the dosage ratio of Fe-N-CNTs to perfluorosulfonic acid resin solution is 1 mg~3 mg: 5 μL~10 μL, and the mass concentration of the perfluorosulfonic acid resin solution is 0.25%.

5. A self-powered sensor produced by the preparation method according to any one of claims 1 to 4.

6. Use of the self-powered sensor according to claim 5 in uric acid detection.

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