Ru / RuO2 nano foam enzyme as well as preparation method and application thereof

Abstract

The invention provides a Ru / RuO2 nano foam enzyme as well as a preparation method and application thereof, and belongs to the technical field of nano enzymes. The preparation method of the Ru / RuO2 nano foam enzyme comprises the following steps: uniformly mixing graphene, a ruthenium precursor and a solvent, carrying out reflux reaction, and collecting a solid product A; and mixing the solid product A and the molten salt 1, grinding, adding into the molten salt 2 in a molten state, preserving heat, and cooling, washing and drying after the heat preservation is finished to obtain the Ru / RuO2 nano foam enzyme. The preparation method disclosed by the invention does not need a tight inert atmosphere and a complex calcining process, and is simple; the colorimetric sensing method for glucose detection based on the nano-enzyme has extremely low detection limit, shows high specificity and sensitivity, and is suitable for accurate glucose detection.

Description

Technical Field

[0001] The present invention relates to the technical field of nanozymes, and particularly relates to a Ru / RuO2 nano-foam enzyme, a preparation method thereof, and an application thereof. Background Art

[0002] Hyperglycemia is one of the main inducements for the occurrence and development of diabetic nephropathy. It causes serious damage to the kidneys through mechanisms such as glomerular hyperperfusion, hyperfiltration, tubular injury, and inflammatory responses. Long-term hyperglycemia can lead to thickening of the glomerular basement membrane, interstitial fibrosis of the renal tubules, and a gradual increase in urinary protein, and may ultimately develop into diabetic nephropathy. The detection of blood glucose has important clinical significance in the prevention and management of diabetic nephropathy. By regularly monitoring blood glucose levels, abnormal blood glucose can be detected in a timely manner and intervened, thereby effectively preventing the occurrence of diabetic nephropathy. In addition, during the treatment of diabetic nephropathy, strict blood glucose control can relieve the further deterioration of the condition, delay the decline of renal function, and at the same time provide a good basis for the recovery of patients. Therefore, blood glucose detection is not only an important part of the daily management of diabetic patients, but also an important means to protect kidney health and improve the quality of life.

[0003] Common blood glucose monitoring techniques are realized based on natural glucose oxidase (GOx) sensors. Glucose can be decomposed into gluconic acid and hydrogen peroxide (H2O2) under the action of natural glucose oxidase, and then the concentration of hydrogen peroxide is detected by a colorimetric method to indirectly measure the blood glucose level. The advantage of this method is that it is easy to operate, has high sensitivity and specificity, and is suitable for the blood glucose monitoring needs of most patients. However, this detection technique also has some deficiencies, mainly including the following points: 1) The natural bio-enzyme in the traditional glucose oxidase sensor is sensitive to temperature and pH value, and is prone to losing activity during long-term storage and use, affecting the detection accuracy. 2) The extraction and purification process of natural bio-enzymes is complex and costly, which limits their large-scale application.

[0004] A good solution is to use nanozymes to replace traditional natural bio-enzymes. Nanozymes are a new generation of artificial mimetic enzymes, which are a class of nanomaterials with similar catalytic efficiency and enzyme-catalyzed reaction kinetics to natural enzymes. They are more stable than traditional natural enzymes and can maintain high activity under extreme conditions. Therefore, using nanozyme materials with peroxidase-like activity to replace natural enzymes and applying them to blood glucose detectors can greatly improve the service life of the detection instrument. However, the activity of currently used synthetic nanozymes for blood glucose detection is relatively low, which limits their application.

[0005] Constructing coherent grain boundaries can trigger significant charge redistribution, thereby establishing a metastable electronic state and significantly enhancing the catalytic activity of nanozymes. However, most heterogeneous interfaces have large lattice mismatches and multiple dangling bonds, often presenting an incoherent structure. Therefore, developing a simple and effective method to synthesize highly active nanozymes with abundant coherent grain boundaries to replace natural enzymes for glucose detection in blood has important clinical significance. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a Ru / RuO2 nanofoam enzyme and its preparation method and application. The graphene-confined Joule-heated molten salt calcination method proposed by the present invention can promote the uniform and rapid nucleation of different crystals, inhibit the aggregation and overgrowth of single crystals, and thus facilitate the formation of nanozymes with abundant coherent grain boundaries. This unique coherent grain boundary can trigger significant charge redistribution, thereby establishing a metastable electronic state and significantly enhancing the catalytic activity of nanozymes. When this Ru / RuO2 nanofoam enzyme with abundant coherent grain boundaries is applied to glucose detection, the detection limit (LOD) of this colorimetric sensor is as low as 28.5 μM, which is of great significance for the accurate and rapid determination of blood glucose.

[0007] To achieve the above object, the present invention provides the following technical solutions: One of the technical solutions of the present invention is a preparation method of a Ru / RuO2 nanofoam enzyme, comprising the following steps: After mixing graphene, a ruthenium precursor, and a solvent evenly, carry out a reflux reaction, and collect solid product A; After mixing the solid product A and molten salt 1 and grinding, then add it to molten molten salt 2 for heat preservation. After the heat preservation ends, cool it to room temperature, wash, and dry to obtain the Ru / RuO2 nanofoam enzyme.

[0008] In the present invention, the ruthenium precursor is ruthenium chloride, ruthenium acetylacetonate, or ruthenium oxalate; the mass ratio of graphene to the ruthenium precursor is 1:0.5 - 1.5.

[0009] In the present invention, the solvent is ethylene glycol. The present invention does not make special limitations on the dosage of ethylene glycol, and the dosage of the solvent known in the art that can meet the requirements of the reflux reaction can be selected. For example: add 1 - 5 mL of ethylene glycol per 1 mg of graphene.

[0010] The reason for setting the ratio of graphene and ruthenium chloride as the above parameters in the present invention is as follows: High proportion of graphene: on the one hand, it will cause waste, and on the other hand, too much metal adsorbed on the surface of graphene is prone to aggregation during calcination; low proportion of graphene: graphene cannot completely adsorb the metal in the solution.

[0011] In the present invention, the temperature of the reflux reaction is 150 to 180 °C, and the time is 1 to 10 h.

[0012] Further, the temperature of the reflux reaction is 170 to 180 °C, and the time is 1 to 5 h.

[0013] In the present invention, both the molten salt 1 and the molten salt 2 are potassium chloride or sodium chloride; the mass ratio of the solid product A to the molten salt 1 is 1:1 to 5.

[0014] The present invention does not make special limitations on the dosage of the molten salt 2, and the dosage can meet the requirements of the molten salt calcination method. For example, the mass ratio of Ru / RuO2 nanofoam enzyme to the molten salt 2 is 1:6 to 15. The preparation method of the molten salt 2 in the molten state in the present invention is: heating the molten salt 2 to the molten state at 800 °C.

[0015] In the present invention, the heat preservation time is 1 to 100 s.

[0016] Further, the heat preservation time is 1 to 50 s.

[0017] Further, the heat preservation time is 10 to 30 s.

[0018] Further, the heat preservation time is 10 s.

[0019] In the present invention, if the heat preservation time is too long, sintering is likely to occur, resulting in a decrease in the specific surface area of the product and a weakening of the performance.

[0020] The second technical solution of the present invention is a Ru / RuO2 nanofoam enzyme prepared by the above preparation method.

[0021] The third technical solution of the present invention is an application of the above Ru / RuO2 nanofoam enzyme in glucose detection.

[0022] The fourth technical solution of the present invention is a colorimetric sensing method for glucose detection, including the following steps: (1) Mixing buffer solution 1, glucose oxidase and glucose solution and incubating; then adding the above Ru / RuO2 nanofoam enzyme, 3,3',5,5'-tetramethylbenzidine (TMB) and buffer solution 2 to the incubated glucose solution, incubating, and measuring the absorbance of the reaction solution after the incubation ends; (2) Establishing a standard curve based on the concentration and absorbance of the glucose solution; (3) Mix buffer solution 1, glucose oxidase and the solution to be tested, and then incubate; after that, add the above-mentioned Ru / RuO2 nano-foam enzyme, TMB and buffer solution 2 to the incubated glucose solution, incubate, and after the incubation ends, measure the absorbance of the reaction solution, and then substitute the measured absorbance into the standard curve in step (2) to obtain the glucose concentration of the solution to be tested. That is: the difference between step (3) and step (1) is only that the glucose solution in step (1) is replaced with the solution to be tested.

[0023] In the present invention, the buffer solution 1 is a PBS solution with pH = 7; the buffer solution 2 is a sodium acetate buffer solution; the concentration of the buffer solution 2 is 0.2 M and pH = 4.5.

[0024] The present invention discloses the following technical effects: The present invention adopts the method of graphene anchoring and dispersing Ru ions, combined with the molten salt-assisted pyrolysis technology, to in-situ generate Ru / RuO2 nano-foam enzyme with rich coherent grain boundaries in an air atmosphere. This preparation process does not require a strict inert atmosphere and complex calcination process, significantly reducing the preparation cost and improving the production efficiency at the same time.

[0025] The nano-enzyme preparation method of the present invention is simple, with the advantages of high stability and low cost, and can effectively overcome the problems of easy inactivation and high price of natural enzymes in traditional blood glucose detection, providing a more economical and reliable solution for blood glucose detection.

[0026] The nano-enzyme prepared by the present invention has rich coherent grain boundaries and nano-foam characteristics. The coherent grain boundaries can optimize the coordination environment of Ru active sites, trigger the charge redistribution of interfacial Ru elements, thus significantly enhancing the catalytic activity of the nano-enzyme. In addition, the foam characteristics of the nano-enzyme are beneficial to the adsorption, activation and desorption of substrate molecules on the Ru active sites, thereby significantly improving the sensitivity and service life of the glucose sensor based on Ru / RuO2 nano-foam enzyme.

[0027] Based on the nano-enzyme prepared by the present invention, a colorimetric sensing method for glucose detection is constructed. This method has an extremely low detection limit, shows high specificity and sensitivity, and is suitable for accurate glucose detection. Brief Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1Powder X-ray diffraction pattern of Ru / RuO2-1 in Example 1; Figure 2 Scanning electron micrograph of Ru / RuO2-1 in Example 1; Figure 3 N2 adsorption-desorption isotherm curve of Ru / RuO2-1 in Example 1. The inset shows the pore size distribution diagram; Figure 4 High-resolution electron microscopy image of Ru / RuO2-1 in Example 1; Figure 5 Comparison chart of the peroxidase-like activity of the samples in Example 1 and Comparative Examples 1-3; Figure 6 UV absorption spectra of the Ru / RuO2 nanozyme system with different glucose concentrations; Figure 7 Relationship curve between the UV absorption value and the glucose concentration. Detailed implementation manners

[0030] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0031] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0032] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0033] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are only exemplary.

[0034] Terms such as "comprising", "including", "having", "containing", etc. used in this text are all open-ended terms, meaning including but not limited to.

[0035] The present invention respectively uses the following methods to detect the activity of Ru / RuO2 nanofoam enzyme and the detection sensitivity of Ru / RuO2 nanofoam enzyme to glucose.

[0036] (1) Activity evaluation of Ru / RuO2 nanofoam enzyme Prepare a suspension of coherent twin boundary-rich Ru / RuO2 nanofoam enzyme (5 mg / mL), TMB (1 mM), and H2O2 (100 mM) solutions with pure water respectively. Subsequently, mix 150 μL of Ru / RuO2 nanofoam enzyme suspension, 150 μL of H2O2 solution, and 150 μL of TMB solution in 2550 μL of sodium acetate - acetic acid (NaAc-Hac, pH = 4.5, 0.2 M) buffer solution. After incubating at room temperature for 5 min, measure the absorbance of the reaction solution at 652 nm with a UV-visible spectrophotometer to evaluate the activity of Ru / RuO2 nanofoam enzyme.

[0037] (2) Evaluation of detection sensitivity Add 200 μL of glucose solutions with different concentrations (0 - 15 mM) to 0.5 mL of PBS solution (pH = 7.4), and then add 100 μL of glucose oxidase (GOx, 2 mg / mL). After incubating at 37 °C for 10 min, subsequently add 150 μL of Ru / RuO2 nanofoam enzyme suspension (5 mg / mL), 200 μL of TMB solution (1 mM), and 1.85 mL of sodium acetate buffer (0.2 M, pH = 4.5) to the incubated glucose solution, and incubate at room temperature for 10 min. Finally, measure the absorbance of the reaction solution at 652 nm with a UV-visible spectrophotometer to detect the glucose content in the solution, and further evaluate the detection sensitivity of the colorimetric sensing method based on this nanozyme to glucose.

[0038] The technical solutions described in the present invention are all conventional solutions in the art unless otherwise specified. The reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0039] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments.

[0040] Example 1 Step S1: Add 120 mg of graphene, 120 mg of ruthenium trichloride, and 240 mL of ethylene glycol to a round-bottom flask. After ultrasonic dispersion, carry out a reflux reaction at 170 °C for 3 h, and then obtain the first solid A through centrifugation and washing; Step S2: Add 200 mg of the first solid substance A and 400 mg of potassium chloride into a mortar and grind for ten minutes to obtain the second solid substance B; Step S3: Place 5 g of potassium chloride in a muffle furnace and heat it to the molten state at 850 °C. Then add 600 mg of the second solid substance B into the molten potassium chloride. After keeping it warm for 10 s, take out the molten salt and pour it into a graphite cooling tank to cool rapidly to obtain the third solid substance C; Step S4: The third solid substance C is centrifugally washed three times with deionized water and then dried to obtain Ru / RuO2 nano-foam enzyme with rich coherent grain boundaries, named Ru / RuO2-1.

[0041] Example 2 The difference from Example 1 is only that in Step S1, 120 mg of ruthenium trichloride is replaced by 60 mg of ruthenium trichloride, and the reflux reaction condition is changed to reflux reaction at 180 °C for 1 h. The remaining steps and parameters are the same as those in Example 1. The obtained Ru / RuO2 nano-foam enzyme is denoted as Ru / RuO2-2.

[0042] Example 3 The difference from Example 1 is only that in Step S2, 400 mg of potassium chloride is replaced by 200 mg of potassium chloride. The remaining steps and parameters are the same as those in Example 1. The obtained Ru / RuO2 nano-foam enzyme is denoted as Ru / RuO2-3.

[0043] Example 4 The difference from Example 1 is only that sodium chloride is used instead of potassium chloride in the preparation process. The remaining steps and parameters are the same as those in Example 1. The obtained Ru / RuO2 nano-foam enzyme is denoted as Ru / RuO2-4.

[0044] Example 5 The difference from Example 1 is only that ruthenium oxalate of equal mass is used instead of ruthenium trichloride in the preparation process. The remaining steps and parameters are the same as those in Example 1. The obtained Ru / RuO2 nano-foam enzyme is denoted as Ru / RuO2-5.

[0045] Comparative Example 1 Step S1: The same as Step S1 in Example 1; Step S2: Place 200 mg of the first solid substance A in a muffle furnace and keep it warm at 850 °C for 20 s and then take it out. After cooling, obtain RuO2 nano-enzyme, named RuO2.

[0046] Comparative Example 2 Step S1: The same as Step S1 in Example 1; Step S2: Put 200 mg of the first solid substance A into a tube furnace. Under a reducing atmosphere (H2 / Ar: 5 / 95), with a heating rate of 5 °C / min, heat it to 850 °C, hold for 20 s, and after cooling, obtain Ru nanozyme, named Ru.

[0047] Comparative Example 3 Step S1: The same as Step S1 of Comparative Example 2; Step S2: The same as Step S2 of Comparative Example 2; Step S3: Place 200 mg of Ru nanozyme in a muffle furnace, hold at 300 °C for 0.5 h, then take it out, and after cooling, obtain Ru / RuO2 nanozyme, named Ru / RuO2-D.

[0048] Characterization and effect verification: 1. Figure 1 It is the powder X-ray diffraction pattern of Ru / RuO2-1 in Example 1. As can be seen from the figure, Example 1 is mainly composed of two phases of Ru and RuO2. It shows that the scheme of the present invention does not require a strict inert atmosphere and a complex calcination process, and directly generates a composite material of Ru and RuO2 in-situ under an air atmosphere. The synergistic effect between different components inside this composite material can significantly improve the catalytic activity of active sites, and thus exhibit higher nanozyme activity.

[0049] 2. Figure 2 It shows the scanning electron micrograph of Ru / RuO2-1 in Example 1. The results show that the Ru / RuO2 prepared in Example 1 mainly presents a porous foam-like structure of particle accumulation.

[0050] 3. N2 adsorption-desorption test further analyzes the pore structure of Ru / RuO2-1. As Figure 3 shown, the characteristic hysteresis loop indicates that Example 1 has a rich mesoporous structure. The Barrett-Joyner-Halenda (BJH) analysis results in the inset show that the pore size distribution of Example 1 is mainly concentrated in 5-40 nm. This rich pore structure further proves the nano-foam characteristics of Example 1, and this foam characteristic is beneficial to the adsorption, activation, and desorption of substrate molecules on the Ru active sites, and thus significantly improves the sensitivity and service life of the glucose sensor based on Ru / RuO2 nano-foam enzyme.

[0051] 4. Figure 4It is a high-resolution electron microscope image of Ru / RuO2-1 in Example 1. As can be seen from the figure, the coherent growth characteristics of Ru and RuO2 components in Example 1, and this coherent growth produces obvious coherent grain boundaries. The reason for the formation of this coherent characteristic is mainly due to the high-temperature potassium chloride molten salt oxidation of graphene in the process of uniformly adsorbing Ru ions. Graphene itself has a certain reducibility that can reduce part of the Ru element to Ru elemental substance, and the molten salt can isolate most of the air to avoid the complete oxidation of Ru elemental substance. At the same time, some of the Ru ions loaded on the graphene will also be oxidized by the oxygen inside the molten salt to form RuO2. In addition, the confinement effect of graphene and the rapid high-temperature oxidation of molten salt can promote the uniform and rapid nucleation of Ru and RuO2, inhibit the agglomeration and excessive growth of Ru and RuO2, and then facilitate the formation of Ru / RuO2 nanozymes with rich coherent grain boundaries. This coherent grain boundary can optimize the coordination environment of the Ru active site, trigger the charge redistribution of the interface Ru element, thereby significantly enhancing the intrinsic catalytic activity of the nanozyme.

[0052] 5. Use pure water to prepare coherent grain boundary-rich Ru / RuO2 nanofoam enzyme suspension (5 mg / mL), TMB (1 mM), and H2O2 (100 mM) solutions, respectively. Then, 150 µL of Ru / RuO2 nanofoam enzyme, 150 µL of H2O2, and 150 µL of TMB were mixed in 2550 µL of sodium acetate-acetic acid (NaAc-Hac, pH=4.5, 0.2 M) buffer solution. After incubation at room temperature for 5 min, the absorbance of the reaction solution was measured at 652 nm using a UV-visible spectrophotometer to evaluate the activity of the Ru / RuO2 nanofoam enzyme.

[0053] Figure 5The peroxidase-like activities of the samples of Example 1 and Comparative Examples 1-3 were compared. Example 1 exhibited the strongest absorption peak at 652 nm, which was stronger than that of Comparative Example 3, Comparative Example 2, and Comparative Example 1 in sequence. It was shown that the order of nanozyme activity was Example 1 > Comparative Example 3 > Comparative Example 2 > Comparative Example 1. Table 1 lists the phase compositions and pore structure information of Example 1 and Comparative Examples 1-3. It can be seen from Table 1 that Comparative Example 1 and Comparative Example 2 were composed of RuO2 and Ru respectively, while Comparative Example 3 was a mixed phase composed of RuO2 and Ru. In addition, the specific surface area and pore size distribution range of the comparative examples were much smaller than those of Example 1, especially Comparative Example 1 hardly had a pore-like structure. The above information indicates that the nanozymes with a mixed phase of RuO2 and Ru (Example 1 and Comparative Example 3) have much better activity than single-phase RuO2 (Comparative Example 1) and Ru (Comparative Example 2), indicating that the synergistic effect between RuO2 and Ru can significantly improve the catalytic activity of the nanozyme. In addition, the nanozyme activity of the Ru / RuO2 nanofoam enzyme with rich coherent grain boundaries (Example 1) was significantly better than that of Ru / RuO2-D prepared by the conventional method (Comparative Example 3). The high nanozyme activity of Example 1 was mainly due to its abundant coherent grain boundaries and porous nanofoam structure inside.

[0054] Table 1 Phase compositions and pore structure information of Example 1 and Comparative Examples 1-3

[0055] 6. Add 200 µL of glucose solutions with different concentrations (0, 0.75, 1.5, 3, 4.5, 6, 7.5, 9, 10.5, 12, 13, 15 mM) to 0.5 mL of PBS solution (pH = 7.4), and then add 100 µL of glucose oxidase (GOx, 2 mg / mL). After incubating at 37 °C for 10 min, subsequently add 150 µL of Ru / RuO2-1 nanofoam enzyme, 200 µL of TMB solution (1 mM), and 1.85 mL of sodium acetate buffer (0.2 M, pH = 4.5) to the incubated glucose solution, and incubate at room temperature for 10 min. Finally, measure the absorbance of the reaction solution at 652 nm with a UV-visible spectrophotometer to detect the glucose content in the solution, and further evaluate the detection sensitivity of the colorimetric sensing method for glucose based on this nanozyme.

[0056] The principle of glucose colorimetric detection relies on the oxidation reaction of glucose catalyzed by glucose oxidase (GOx) to generate hydrogen peroxide. Under the efficient catalysis of the Ru / RuO2 nanofoam enzyme with rich coherent grain boundaries, hydrogen peroxide reacts with the color reagent (TMB), thereby causing a significant change in the color of the solution. By precisely measuring the depth of the color (i.e., the subtle change in absorbance), we can accurately quantitatively analyze the concentration of glucose in the solution. Figure 6The UV-VIS absorption spectra of glucose solutions with different concentrations from 0 to 1 mM are presented. As the glucose concentration continuously increases, the color of the sample solution gradually changes from clear and colorless to deep blue, and at a wavelength of 652 nm, the absorbance gradually increases with the increase in glucose concentration.

[0057] Figure 7 It is the relationship curve between the ultraviolet absorption value and the glucose concentration. The data shows that within the concentration range of 0 to 0.5 mM, there is an almost perfect linear relationship between the two, and the linear equation is: y = 3.154x + 0.0047 (R² = 0.999). The detection limit of glucose is approximately 28.5 µM, indicating that the colorimetric sensing method based on the coherent twin-boundary Ru / RuO2 nanofoam enzyme exhibits excellent glucose detection sensitivity and has high scientific value.

[0058] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of Ru / RuO2 nano-foam enzyme, characterized in that, It includes the following steps: After uniformly mixing graphene, a ruthenium precursor and a solvent, carry out a reflux reaction, and collect solid product A; Mix the solid product A and molten salt 1 and grind them, then add them into molten molten salt 2 for heat preservation. After the heat preservation ends, cool to room temperature, wash and dry to obtain the Ru / RuO2 nano-foam enzyme.

2. The preparation method of the Ru / RuO2 nano-foam enzyme according to claim 1, characterized in that, The ruthenium precursor is ruthenium chloride, ruthenium acetylacetonate or ruthenium oxalate; the mass ratio of graphene to the ruthenium precursor is 1:0.5 - 1.

5.

3. The preparation method of the Ru / RuO2 nano-foam enzyme according to claim 1, characterized in that, The temperature of the reflux reaction is 150 - 180 °C, and the time is 1 - 10 h.

4. The preparation method of the Ru / RuO2 nano-foam enzyme according to claim 1, characterized in that, Both the molten salt 1 and the molten salt 2 are potassium chloride or sodium chloride; the mass ratio of the solid product A to the molten salt 1 is 1:1 - 5.

5. The preparation method of the Ru / RuO2 nano-foam enzyme according to claim 1, characterized in that, The heat preservation time is 1 - 100 s.

6. A Ru / RuO2 nano-foam enzyme prepared by the preparation method according to any one of claims 1 - 5.

7. An application of the Ru / RuO2 nano-foam enzyme according to claim 6 in the detection of glucose content.

8. A colorimetric sensing method for glucose detection, characterized in that, It includes the following steps: (1) Mix buffer solution 1, glucose oxidase and glucose solution and incubate; then add the Ru / RuO2 nano-foam enzyme, TMB and buffer solution 2 according to claim 6 to the incubated glucose solution, incubate, and measure the absorbance of the reaction solution after the incubation ends; (2) Establish a standard curve based on the concentration and absorbance of the glucose solution; (3) Mix buffer solution 1, glucose oxidase and the test solution and incubate; then add the Ru / RuO2 nano-foam enzyme, TMB and buffer solution 2 according to claim 6 to the incubated glucose solution, incubate, measure the absorbance of the reaction solution after the incubation ends, and then substitute the measured absorbance into the standard curve in step (2) to obtain the glucose concentration of the test solution.

9. The colorimetric sensing method for glucose detection according to claim 8, wherein The buffer solution 1 is a PBS solution; the buffer solution 2 is a sodium acetate buffer solution.

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