Self-energized sensor, preparation method thereof and application of self-energized sensor in uric acid detection

Abstract

The invention relates to the technical field of sensor analysis and detection, in particular to a self-powered sensor and a preparation method and application thereof.The self-powered sensor is characterized in that a dual-MOF-derived iron-doped carbon nanotube catalyst is prepared through a solvothermal method and high-temperature calcination, and when the catalyst is applied to a cathode of a zinc-air battery, excellent power density, energy density and durability are shown; the performance is superior to that of a commercial Pt / C catalyst. Uurate oxidase UAO is loaded on a cathode catalyst to form a cathode sensing interface, and the UAO consumes oxygen to catalyze uric acid oxidation and competes with the oxygen reduction process of the cathode of the zinc-air battery to reduce an output signal, so that the zinc-air battery self-energized electrochemical sensor based on the oxygen competition model is constructed for uric acid detection. According to the invention, the application of the zinc-air battery in the self-energized sensor is broadened, and the constructed sensor has a wide linear range, high sensitivity and low detection limit when being used 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 and a preparation method thereof and application thereof in uric acid detection. Background Art

[0002] Uric acid is an important nitrogen-containing compound that is commonly found in biological fluids such as serum and urine. It is the main end product of purine metabolism. Abnormal uric acid levels in biological fluids can indicate diseases such as gout, metabolic syndrome and kidney disease. Therefore, uric acid is an effective biomarker for detecting purine metabolism disorders. Establishing a method for rapid and reliable detection of uric acid concentration is of great significance for the diagnosis and treatment of diseases.

[0003] At present, there are many different methods for uric acid detection, such as high performance liquid chromatography, spectrophotometry, ion chromatography, high performance liquid chromatography / isotope dilution mass spectrometry and electrochemical biosensor, etc. These methods use relatively expensive instruments and are complicated to operate. In order to achieve the purpose of real-time monitoring and facilitate people's convenient and quick use, it is very important to develop miniaturized and integrated sensors.

[0004] As an emerging and powerful analytical method, self-powered electrochemical sensors have attracted much attention recently because of their advantages such as no need for external power supply, simple structure, easy miniaturization and integration, etc. However, the low open circuit voltage and output power density lead to their narrow detection range and limited sensitivity, which to some extent restrict the application of self-powered sensors. Summary of the invention

[0005] In view of the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a self-powered sensor and a preparation method thereof and application in uric acid detection. The present invention replaces precious metals with Fe-N-CNTs as the cathode material of a zinc-air battery to reduce costs, designs a self-powered electrochemical sensor based on the coupling of Fe-N-CNTs cathode catalyst and UAO, and 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: A method for preparing a self-powered sensor comprises the following steps: 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.

[0007] Dissolve 2-methylimidazole in methanol, mix it with the precursor MIL-P, then add a soluble zinc salt to obtain a mixed solution. Let the mixed solution stand for growth, and after post-treatment, obtain MIL@ZIF. Calcinate and carbonize the MIL@ZIF under a protective atmosphere to obtain Fe-N-CNTs.

[0008] Disperse the Fe-N-CNTs in ethanol containing a perfluorosulfonic acid resin solution to obtain Fe-N-CNTs ink.

[0009] Drop the Fe-N-CNTs ink on the surface of a glassy carbon electrode to obtain Fe-N-CNTs / GCE. Drop a uricase solution on the surface of the Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE. Use UAO / Fe-N-CNTs / GCE as the cathode and a Zn sheet as the anode to construct a self-powered sensor based on a dual-MOF-derived Fe-based cathode catalyst.

[0010] In the present invention, a novel self-powered uric acid detection sensor is constructed 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 to provide energy for the sensor to achieve self-driven uric acid monitoring. The uricase at the cathode catalyzes the oxidation of uric acid by reacting with oxygen, consuming oxygen, resulting in a decrease in the oxygen participating in the battery chemical reaction, so the output voltage decreases. Thus, the change trend of uric acid concentration can be deduced by the magnitude of the output voltage. The smaller the output voltage, the higher 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, and the constructed sensor for uric acid detection has a wide linear range, high sensitivity, and low detection limit.

[0011] In a preferred embodiment of the present invention, the dosage ratio of 2-methylimidazole to methanol is 3.28 g to 4 g: 60 mL to 100 mL.

[0012] In a preferred embodiment of the present invention, the dosage ratio of 2-methylimidazole to the precursor MIL-P is 3.28 g to 4 g: 12 mL to 16 mL, and the mass ratio of the soluble zinc salt to 2-methylimidazole is 3 to 3.5: 3.28 to 4.

[0013] 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.

[0014] In a preferred embodiment of the present invention, the dosage ratio of the Fe-N-CNTs catalyst to ethanol is 1 mg to 3 mg: 0.5 mL to 1 mL, the dosage ratio of Fe-N-CNTs to the perfluorosulfonic acid resin solution is 1 mg to 3 mg: 5 μL to 10 μL, and the mass concentration of the perfluorosulfonic acid resin solution is 0.25%.

[0015] In a preferred embodiment of the present invention, the concentration of the urate oxidase solution is 400 U / mL to 500 U / mL.

[0016] 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 solvothermal reaction, and performing post-treatment on the solvothermal reaction product to obtain the MIL-101(Fe) metal-organic framework material.

[0017] In a preferred embodiment of the present invention, the mass ratio of the soluble iron salt to terephthalic acid is 0.337 to 1.35: 0.2075, the dosage ratio of the soluble iron salt to DMF is 0.337 g to 1.35 g: 15 mL, the solvothermal reaction temperature is 100 °C to 120 °C, and the solvothermal reaction time is 20 hours to 24 hours.

[0018] Another object of the present invention is to provide a self-powered sensor prepared by the preparation method described in any one of the above.

[0019] The third object of the present invention is to provide an application of the self-powered sensor described above in uric acid detection.

[0020] Compared with the prior art, the beneficial effects of the present invention are: 1. First, the metal-organic framework material MIL-101(Fe) is dissolved in methanol containing polyvinylpyrrolidone to obtain the 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. The ZIF in the mixed solution is allowed to grow statically on MIL-P, and after post-treatment, MIL@ZIF is obtained. The MIL@ZIF is calcined and carbonized under a protective atmosphere to obtain an Fe-N-CNTs catalyst. The Fe-N-CNTs catalyst is dispersed in ethanol containing a perfluorosulfonic acid resin solution to obtain Fe-N-CNTs ink. The Fe-N-CNTs ink is dropped onto the surface of a glassy carbon electrode to obtain Fe-N-CNTs / GCE. The uricase solution is dropped onto the surface of the Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE. Using UAO / Fe-N-CNTs / GCE as the cathode and a Zn sheet as the anode, a self-powered sensor is constructed. By assembling a Zn sheet anode and a UAO / Fe-N-CNTs / GCE cathode, the present invention constructs a novel self-powered sensor for uric acid detection. The cathode and anode of the battery generate electrical energy through a chemical reaction to provide energy for the sensor to achieve self-driven uric acid monitoring. The uricase on the cathode catalyzes the oxidation of uric acid by reacting with oxygen, consuming oxygen, resulting in a decrease in the oxygen participating in the battery chemical reaction, so the output voltage decreases. Thus, the change trend of uric acid concentration can be deduced by the magnitude of the output voltage. The smaller the output voltage, the higher 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, and the constructed sensor for uric acid detection has a wide linear range, high sensitivity, and low detection limit.

[0021] 2. The present invention prepares a dual-MOF-derived iron-doped carbon nanotube Fe-N-CNTs catalyst by solvothermal method and high-temperature calcination, and uses it as the cathode of a zinc-air battery. The zinc-air battery constructed using this catalyst shows excellent power density, energy density, and durability, and its performance is superior to that of commercial Pt / C catalysts. Uricase 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 at the cathode of the zinc-air battery, resulting in a decrease in the output signal. Furthermore, a self-powered electrochemical sensor for uric acid detection based on an oxygen competition model is constructed.

[0022] 3. Compared with traditional detection methods, the electrochemical detection method used in the present invention has the characteristics of simple and flexible operation, simple instrument equipment, high sensitivity, low detection cost, wide linear range, and low detection limit. Description of the Drawings

[0023] Figure 1Among them, (a) is the working mode diagram of the self-powered sensor composed of the cathode UAO / Fe-N-CNTs / GCE and the anode Zn sheet, and (b) is the open-circuit voltage diagram.

[0024] Figure 2 This is the scanning electron microscope image of ZIF@MIL and Fe-N-CNTs prepared in Example 1 of the present invention.

[0025] Figure 3 Among them, (a) is the optimization curve of the amount of iron salt in 0.1 M KOH solution, and (b) is the optimization curve of the amount of iron salt in 0.1 M PBS solution.

[0026] Figure 4 Among them, (a) is the ORR performance of Fe-N-CNTs and 20 wt% Pt / C measured in 0.1 M KOH solution, and (b) is the ORR performance measured in 0.1 M PBS solution.

[0027] Figure 5 It is the open-circuit voltage during the preparation of GCE, Fe-N-CNTs / GCE, and UAO / Fe-N-CNTs / GCE electrodes.

[0028] Figure 6 It is the open-circuit voltage of different concentrations of uric acid. The concentrations of uric acid are 0, 0.001 μM, 0.01 μM, 0.1 μM, 1 μM, 10 μM, 20 μM, 50 μM, and 100 μM in descending order according to the height of the curve.

[0029] Figure 7 It is the relationship curve between the open-circuit voltage after adding uric acid and the uric acid concentration. The inset in the figure is the linear relationship diagram between the open-circuit voltage and the logarithm of the uric acid concentration.

[0030] Figure 8 It is the (a) power density, (b) polarization curve, (c) specific capacity, and (d) durability test results of assembling a zinc-air battery in a neutral environment. Detailed implementation manners

[0031] The following combines the embodiments of the present invention and uses preferred embodiments and accompanying drawings for detailed description to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] It should be noted that all the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be obtained through market purchase or prepared by existing methods.

[0033] Weigh 0.5 times, 1 time and 2 times the amount of FeCl3·6H2O and 0.2075 g of terephthalic acid separately with a balance, dissolve them in 15 mL of DMF, and stir magnetically to disperse them evenly. LSV tests were carried out 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 as Figure 3 shown. The 1-time amount is the best condition with the largest half-wave potential. Therefore, 0.675 g of FeCl3·6H2O was selected as the best dosage to react with 0.2075 g of terephthalic acid to prepare the MIL-101(Fe) metal-organic framework material.

[0034] Example 1 A preparation method of a self-powered sensor based on a dual-MOF-derived Fe-based cathode catalyst includes the following steps: (1) Preparation of the precursor MIL-P Weigh 0.675 g of FeCl3·6H2O and 0.2075 g of terephthalic acid separately with a balance, dissolve them in 15 mL of DMF, stir with a magnetic stirrer for more than 35 minutes, and then carry out a solvothermal reaction at 110 °C for 20 hours. Wash the reaction product 5 times alternately with DMF and hot absolute ethanol at a rotation speed of 10000 r·min -1 , wash for 10 minutes each time, and vacuum dry at 60 °C to obtain yellow MIL-101(Fe).

[0035] Dissolve all the obtained MIL-101(Fe) in methanol containing 3 g of polyvinylpyrrolidone, stir magnetically for 12 hours, and then wash by centrifugation with methanol 5 times at a centrifugation speed of 10000 r·min -1 , with a centrifugation washing time of 5 minutes each time. Disperse the obtained solid evenly in 45 mL of methanol for standby to obtain the precursor MIL-P.

[0036] (2) Preparation of Fe-N-CNTs Dissolve 3.28 g of 2-methylimidazole in 60 mL of methanol, add 16 mL of the precursor MIL-P and stir vigorously for 5 minutes. Then add 3 g of Zn(NO3)2·6H2O and stir for 5 minutes. Let the obtained liquid stand for 24 hours to grow fully, then wash 5 times with methanol, vacuum dry at 60 °C for 12 hours, and grind into powder to obtain MIL@ZIF.

[0037] Place MIL@ZIF in a porcelain boat and calcine it for carbonization at 950 °C for 3 hours in a tube furnace protected by a nitrogen / argon atmosphere at a heating rate of 5 °C·min -1 and then let it cool naturally to obtain a black Fe-N-CNTs catalyst.

[0038] (3) Preparation of the self-powered sensor Thoroughly grind the obtained Fe-N-CNTs catalyst at room temperature. Weigh 3.0 mg of Fe-N-CNTs with an electronic balance, add 1.0 mL of ethanol for dispersion, and then add 10 μL of a 0.25 wt% perfluorosulfonic acid resin solution. Place it in an ultrasonic machine and ultrasonicate for more than 30 minutes to prepare Fe-N-CNTs ink.

[0039] Drop 15 μL of Fe-N-CNTs ink onto the surface of a glassy carbon electrode to obtain Fe-N-CNTs / GCE. Drop 10 μL of a UAO solution with a concentration of 500 U·mL -1 onto the surface of Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE. Use UAO / Fe-N-CNTs / GCE as the cathode and a zinc sheet as the anode to assemble a self-powered sensor.

[0040] Example 2 A preparation method of a self-powered sensor based on a dual-MOF-derived Fe-based cathode catalyst, comprising the following steps: (1) Preparation of the precursor MIL-P Weigh 0.675 g of FeCl3·6H2O and 0.2075 g of terephthalic acid with a balance and dissolve them in 15 mL of DMF. Stir with a magnetic stirrer for more than 35 minutes, and then carry out a solvothermal reaction at 100 °C for 24 hours. Wash the reaction product 5 times alternately with DMF and hot absolute ethanol at a rotation speed of 10000 r·min -1 for 10 minutes each time. After vacuum drying at 60 °C, yellow MIL-101(Fe) is obtained.

[0041] Dissolve all the obtained MIL-101(Fe) in methanol containing 3 g of polyvinylpyrrolidone, stir magnetically for 12 hours, and then wash it 5 times by centrifugation with methanol at a centrifugation speed of 10000 r·min -1 for 5 minutes each time. Uniformly disperse the obtained solid in 45 mL of methanol for standby to obtain the precursor MIL-P.

[0042] (2) Preparation of Fe-N-CNTs Dissolve 3.5 g of 2-methylimidazole in 80 mL of methanol, add 12 mL of precursor MIL-P and stir vigorously for 5 minutes. Subsequently, add 3.2 g of Zn(NO3)2·6H2O and stir for 5 min. Let the resulting liquid stand for 24 hours for sufficient growth, then wash it 5 times with methanol and dry it in vacuum at 60 °C for 12 hours, and grind it into powder to obtain MIL@ZIF.

[0043] Place MIL@ZIF in a porcelain boat and calcine it for carbonization at 900 °C for 3 hours in a tube furnace protected by a nitrogen / argon atmosphere at a heating rate of 5 °C·min -1 to obtain a black Fe-N-CNTs catalyst by natural cooling.

[0044] (3)Preparation of self-powered sensor Thoroughly grind the obtained Fe-N-CNTs catalyst at room temperature, weigh 1.0 mg of Fe-N-CNTs with an electronic balance, add 0.5 mL of ethanol for dispersion, and then add 10 μL of 0.25 wt% perfluorosulfonic acid resin solution, and place it in an ultrasonic machine for ultrasonic treatment for more than 30 minutes to prepare Fe-N-CNTs ink.

[0045] Drop 15 μL of Fe-N-CNTs ink on the surface of a glassy carbon electrode to obtain Fe-N-CNTs / GCE. Drop 5 μL of UAO solution with a concentration of 400 U·mL -1 onto the surface of Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE. Use UAO / Fe-N-CNTs / GCE as the cathode and a Zn sheet as the anode to assemble a self-powered sensor.

[0046] Example 3 A preparation method of a self-powered sensor based on a dual-MOF-derived Fe-based cathode catalyst, comprising the following steps: (1)Preparation of precursor MIL-P Weigh 0.675 g of FeCl3·6H2O and 0.2075 g of terephthalic acid with a balance and dissolve them in 15 mL of DMF, stir on a magnetic stirrer for more than 35 minutes, then carry out a solvothermal reaction at 120 °C for 22 hours, and wash the reaction product 5 times alternately with DMF and hot absolute ethanol at a rotation speed of 10000 r·min -1 , wash for 10 min each time, and dry in vacuum at 60 °C to obtain yellow MIL-101(Fe).

[0047] Dissolve all the obtained MIL-101(Fe) in methanol containing 3 g of polyvinylpyrrolidone, stir magnetically for 12 hours, and then wash it 5 times by centrifugation with methanol at a centrifugation speed of 10000 r·min -1, The centrifugal washing time is 5 min each time. The obtained solid is evenly dispersed in 45 mL of methanol for standby to obtain the precursor MIL-P.

[0048] (2) Preparation of Fe-N-CNTs Dissolve 4 g of 2-methylimidazole in 100 mL of methanol, add 14 mL of the precursor MIL-P and stir vigorously for 5 minutes. Subsequently, add 3.5 g of Zn(NO3)2·6H2O and stir for 5 min. After allowing the resulting liquid to stand for 24 hours for sufficient growth, wash it 5 times with methanol and dry it in vacuum at 60 °C for 12 hours, and grind it into powder to obtain MIL@ZIF.

[0049] Place MIL@ZIF in a porcelain boat and calcine it at 930 °C for 2.5 hours in a tube furnace protected by a nitrogen / argon atmosphere at a heating rate of 5 °C·min -1 to obtain a black Fe-N-CNTs catalyst after natural cooling.

[0050] (3) Preparation of self-powered sensor Grind the obtained Fe-N-CNTs catalyst thoroughly at room temperature. Weigh 2.0 mg of Fe-N-CNTs with an electronic balance, add 0.8 mL of ethanol for dispersion, and then add 10 μL of 0.25 wt% perfluorosulfonic acid resin solution, and place it in an ultrasonic machine for ultrasonic treatment for more than 30 minutes to prepare Fe-N-CNTs ink.

[0051] Drop 15 μL of Fe-N-CNTs ink on the surface of the glassy carbon electrode to obtain Fe-N-CNTs / GCE. Drop 8 μL of UAO solution with a concentration of 450 U·mL -1 on the surface of Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE. Use UAO / Fe-N-CNTs / GCE as the cathode and a Zn sheet as the anode to assemble a self-powered sensor.

[0052] Result analysis Figure 1 In (a), it is a working mode diagram of the self-powered sensor composed of the cathode UAO / Fe-N-CNTs / GCE and the anode Zn sheet. (b) is an open-circuit voltage diagram. The sensor includes a cathode coated with UAO / Fe-N-CNTs and a zinc sheet as the anode. The reaction occurring at the cathode involves oxygen in the solution, so it is called an air battery. The anode and cathode of the air battery generate electrical energy through a chemical reaction to provide energy for the sensor. The uricase at the cathode reacts with oxygen to catalytically oxidize uric acid, consuming the oxygen in the solution, resulting in a decrease in the oxygen participating in the chemical reaction of the battery, so the output voltage decreases. Thus, the change trend of uric acid concentration can be obtained from the magnitude of the output voltage. The smaller the output voltage, the higher the uric acid concentration.

[0053] Figure 2 Scanning electron microscope images of ZIF@MIL and Fe-N-CNTs prepared in Example 1 of the present invention. As can be seen from Figure 2 the figure, MIL@ZIF has a regular morphology, and carbon nanotubes grow on Fe-N-CNTs, which is beneficial to increasing the specific surface area and improving the electrochemical performance.

[0054] Using Fe-N-CNTs catalysts with 0.5 times, 1 time, and 2 times the iron salt content as the working electrode, silver-silver chloride electrode as the reference electrode, and carbon rod as the counter electrode, ORR performance tests were carried out using 0.1M KOH and 0.1M PBS as electrolytes respectively. As Figure 3 shown, in 0.1M KOH solution and 0.1M PBS solution, Fe-N-CNTs with 1 time the iron salt content exhibit the best E 1 / 2 , so 1 time the iron salt content was selected as the optimal addition amount.

[0055] Using the Fe-N-CNTs catalyst prepared in Example 1 and 20wt% Pt / C as the working electrode, silver-silver chloride electrode as the reference electrode, and carbon rod as the counter electrode, ORR performance tests were carried out using 0.1M KOH and 0.1M PBS as electrolytes respectively. As Figure 4 shown, in 0.1M KOH solution, the E1 / 2 of Fe-N-CNTs is 0.899V, 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, higher than that of 20wt% Pt / C (E 1 / 2 = 0.74V). This shows that Fe-N-CNTs have excellent electrochemical performance and can be used to replace 20wt% Pt / C as the cathode material of zinc-air batteries.

[0056] Using the bare electrode, Fe-N-CNTs prepared in Example 1, and UAO / Fe-N-CNTs as the cathode respectively, and zinc sheet as the anode to construct a self-powered system of zinc-air batteries. The open-circuit voltages corresponding to the three electrodes were measured in 0.1M PBS solution. As Figure 5 can be seen, when Fe-N-CNTs are used as the cathode to form a zinc-air battery with a zinc sheet, 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.

[0057] Using UAO / Fe-N-CNTs / GCE as the cathode and a zinc sheet as the anode, a self-powered sensor was assembled for the detection of uric acid. The self-powered system of the zinc-air battery was tested for the open-circuit voltage in a 0.1 M PBS buffer solution with a pH of 7.4. The open-circuit voltages at different uric acid concentrations are as Figure 7 shown, where the uric acid concentrations, from high to low according to the peak values of the curve, are: 0, 0.001 μM, 0.01 μM, 0.1 μM, 1 μM, 10 μM, 20 μM, 50 μM, and 100 μM. The corresponding open-circuit voltage values are as Figure 6 shown. The linear relationship between the open-circuit voltage and the logarithm of the uric acid concentration is as Figure 7 shown. The corresponding linear regression equation is: E OCP (V) = -0.02827 lg c UA (μM)] + 1.273, and the correlation coefficient R 2 = 0.991; the detection range of the linear regression equation is 0.001 μM to 100 μM, and the lowest detection limit is 0.34 nM.

[0058] Using the Fe-N-CNTs catalyst and 20 wt% Pt / C + RuO2, respectively, with a nickel mesh and carbon cloth to form the cathode and a zinc sheet as the anode, zinc-air batteries were assembled. The power density, polarization curve, specific capacity, and durability of the batteries were tested in a mixed solution of 4 M NH4Cl and 0.2 M ZnCl2. The results are as Figure 8 shown. The zinc-air battery assembled with Fe-N-CNTs has a higher peak power of 50.5 mW·cm -2 , a charge-discharge voltage bandgap similar to that of commercial Pt / C + RuO2, a higher specific capacity of 675.5 mA·h·g -1 , and better stability.

[0059] In summary, in the present invention, a novel self-powered sensor for uric acid detection was constructed by assembling a zinc sheet anode and a UAO / Fe-N-CNTs / GCE cathode. The cathode and anode of the battery generate electrical energy through chemical reactions to provide energy for the sensor to achieve self-driven uric acid monitoring. The uricase in the cathode reacts with oxygen to catalytically oxidize uric acid, consuming oxygen, which leads to a decrease in the oxygen participating in the chemical reaction of the battery, so the output voltage decreases. Therefore, the change trend of the uric acid concentration can be deduced by the magnitude of the output voltage. The smaller the output voltage, the higher the uric acid concentration, thus achieving sensitive detection of uric acid.

[0060] It should be noted that when the present invention involves 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 adopted step methods 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 can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended protection scope is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0061] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the present invention and its equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A preparation method of a self-powered sensor, characterized in that, It includes the following steps: Prepare MIL-101(Fe) metal-organic framework material, dissolve the MIL-101(Fe) metal-organic framework material in methanol containing polyvinylpyrrolidone, and after centrifugal washing, obtain the precursor MIL-P; Dissolve 2-methylimidazole in methanol, mix it with the precursor MIL-P, then add soluble zinc salt to obtain a mixed solution, allow ZIF to grow statically on MIL in the mixed solution, and after post-treatment, obtain MIL@ZIF. Calcinate and carbonize the MIL@ZIF under a protective atmosphere to obtain the Fe-N-CNTs catalyst; Disperse the Fe-N-CNTs catalyst in ethanol containing perfluorosulfonic acid resin solution to obtain Fe-N-CNTs ink; Drop the Fe-N-CNTs ink on the surface of a glassy carbon electrode to obtain Fe-N-CNTs / GCE, drop the uricase solution on the surface of the Fe-N-CNTs / GCE to obtain UAO / Fe-N-CNTs / GCE, and use UAO / Fe-N-CNTs / GCE as the cathode and a Zn sheet as the anode to construct a self-powered sensor based on a dual-MOF-derived Fe-based cathode catalyst.

2. The preparation method of the self-powered sensor according to claim 1, characterized in that, The dosage ratio of 2-methylimidazole to methanol is 3.28 g - 4 g: 60 mL - 100 mL.

3. The preparation method of the self-powered sensor according to claim 1, characterized in that, The dosage ratio of 2-methylimidazole to the precursor MIL-P is 3.28 g - 4 g: 12 mL - 16 mL, and the mass ratio of the soluble zinc salt to 2-methylimidazole is 3 - 3.5: 3.28 - 4.

4. The preparation method of the self-powered sensor according to claim 1, characterized in that, The calcination and carbonization temperature is 900 °C - 950 °C, and the calcination and carbonization time is 2 hours - 3 hours.

5. The preparation method of the self-powered sensor according to claim 1, characterized in that, The dosage ratio of the 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%.

6. The preparation method of the self-powered sensor according to claim 1, characterized in that, The concentration of the uricase solution is 400 U / mL - 500 U / mL.

7. The preparation method of the self-powered sensor according to claim 1, characterized in that The MIL-101(Fe) metal-organic framework material is prepared by the following method: dissolve soluble iron salt and terephthalic acid in DMF, carry out a solvothermal reaction, and perform post-treatment on the solvothermal reaction product to obtain the MIL-101(Fe) metal-organic framework material.

8. The preparation method of the self-powered sensor according to claim 7, characterized in that, The mass ratio of the soluble iron salt to terephthalic acid is 0.337 - 1.35: 0.2075, the dosage ratio of the soluble iron salt to DMF is 0.337 g - 1.35 g: 15 mL, the solvothermal reaction temperature is 100 °C - 120 °C, and the solvothermal reaction time is 20 hours - 24 hours.

9. A self-powered sensor prepared by the preparation method according to any one of claims 1 - 8.

10. An application of the self-powered sensor according to claim 9 in uric acid detection.

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