A metal-doped cerium-based nanozyme and its application

Abstract

This invention belongs to the field of nanozyme technology, specifically relating to a metal-doped cerium-based nanozyme and its applications. The preparation method of the metal-doped cerium-based nanozyme provided in this invention includes the following steps: dissolving a cerium salt solution and a transition metal salt solution in water to form solution A; mixing solution A with a sodium sulfide solution, and then performing a co-precipitation reaction, followed by static aging to obtain a precipitate, which is the metal-doped cerium-based nanozyme; wherein the metal nitrate is selected from one of the transition metal elements iron, copper, manganese, cobalt, nickel, zirconium, and lanthanum. Compared with pure cerium sulfide nanozymes, the metal-doped cerium-based nanozyme provided by this invention exhibits 1.5 to 9 times higher catalytic activity, enabling highly sensitive detection of hydrogen peroxide.

Description

Technical Field

[0001] This invention belongs to the field of nanozyme technology, specifically relating to a metal-doped cerium-based nanozyme and its applications. Background Technology

[0002] Hydrogen peroxide (H2O2, commonly known as hydrogen peroxide solution) is an intermediate product of some metabolic reactions in the human body. For example, glucose can be catalyzed by glucose oxidase to produce gluconic acid and hydrogen peroxide. However, excessively high levels of hydrogen peroxide in the body can lead to diseases such as cancer and cardiovascular disease. Currently, the main methods for detecting hydrogen peroxide include electrochemical methods, chromatography, and spectrophotometry. However, these methods all have certain limitations. For example, they require high-quality instruments and samples, and they cannot avoid interference from complex components in the blood, making it impossible to achieve rapid and accurate direct detection of hydrogen peroxide and related substances. Therefore, it is crucial to develop a simple and rapid method for detecting hydrogen peroxide.

[0003] Natural enzymes are a class of highly efficient biocatalysts, but their demanding operating conditions limit their applications, and the high cost of artificially synthesizing natural enzymes also restricts their use. Nanozymes derived from nanomaterials possess enzyme-like catalytic activity and, compared to natural enzymes, offer advantages such as lower cost, stronger resistance to biodegradation, and larger production volumes. However, compared to natural enzymes, most nanozymes still exhibit significant differences in specificity and catalytic efficiency, limiting their widespread application. Sulfide nanozymes are widely used in analytical detection and tumor diagnosis and treatment due to their excellent photothermal conversion properties and peroxide-mimicking enzyme performance. Cerium-based nanozymes typically contain both trivalent and tetravalent valence states, which can accelerate electron flow and enhance peroxide-mimicking enzyme performance. Furthermore, cerium-based nanozymes exhibit good biocompatibility in vivo. However, existing nanozymes have poor performance in detecting hydrogen peroxide; therefore, providing a nanozyme with superior hydrogen peroxide detection performance is extremely important. Summary of the Invention

[0004] To address the low catalytic efficiency of nanozymes in existing technologies, this invention provides a metal-doped cerium-based nanozyme and its application. By doping cerium sulfide with different metal ions, the prepared M / CeS2 nanozyme is used to achieve high-sensitivity detection of hydrogen peroxide.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] The first aspect of this invention provides a metal-doped cerium-based nanozyme, which is prepared according to the following steps:

[0007] A solution A is formed by dissolving a cerium salt solution and a transition metal salt solution in water.

[0008] Solution A is mixed with sodium sulfide solution to undergo a co-precipitation reaction. After standing and aging, a precipitate is obtained, which is the metal-doped cerium-based nanozyme.

[0009] The metal in the transition metal salt is selected from one of the transition metal elements: iron, copper, manganese, cobalt, nickel, zirconium, and lanthanum.

[0010] In some technical solutions of this invention, when the transition metal element is iron, lanthanum or cobalt, the metal-doped cerium-based nanozymes prepared have higher catalytic efficiency.

[0011] In some technical solutions of the present invention, the molar ratio of metal ions in the transition metal salt to cerium ions in the cerium salt is 0.05 to 0.3.

[0012] In some technical solutions of the present invention, the mass ratio of sodium sulfide to cerium salt is 4-6:4-6.

[0013] In some technical solutions of the present invention, the cerium salt includes: cerium halide, cerium sulfate, and cerium acetate;

[0014] The transition metal salts include: transition metal halides, transition metal sulfates, and transition metal acetates. The type of salt used in this invention has little effect on the co-precipitation reaction; however, because nitrates have high solubility and are easily dissolved, nitrate ions are easily washed away after the reaction. Preferably, cerium nitrate and transition metal nitrates are selected for the reaction.

[0015] In some technical solutions of the present invention, the coprecipitation reaction time is 30 min to 50 min; the static aging time is 1.5 h to 2.5 h.

[0016] In some technical solutions of this invention, the method further includes: washing and drying the precipitate to obtain metal-doped cerium-based nanozymes. The washing primarily removes unreacted ions, such as nitrate ions and sodium ions.

[0017] In some technical solutions of this invention, the washing process includes first using deionized water, and then using ethanol for washing.

[0018] In some technical solutions of the present invention, the number of times the deionized water is used for washing is 2 to 4.

[0019] In some technical solutions of the present invention, the ethanol is used for washing 2 to 4 times.

[0020] In some technical solutions of this invention, the drying temperature is 70℃~100℃.

[0021] In some technical solutions of this invention, the drying time is 12h to 36h.

[0022] A second aspect of the present invention provides the application of the aforementioned metal-doped cerium-based nanozyme in hydrogen peroxide detection.

[0023] A third aspect of the present invention provides a method for detecting hydrogen peroxide, comprising: adding a colorimetric reagent and the metal-doped cerium-based nanozyme solution to a sample to be tested, reacting for 8 min to 15 min to obtain a reaction product, then analyzing the absorbance of the reaction product and calculating the detection result of hydrogen peroxide in the sample to be tested.

[0024] In some technical solutions of this invention, the concentration of the metal-doped cerium-based nanozyme solution is 300 μg·mL. -1 ~500μg·mL -1 The concentration of hydrogen peroxide in the sample to be tested ranges from 3 μmol / L to 200 μmol / L, and the volume ratio of the metal-doped cerium-based nanozyme solution to the sample to be tested is 0.7 to 1.5.

[0025] In some technical solutions of this invention, the concentration of the metal-doped cerium-based nanozyme solution is 400 μg·mL. -1 .

[0026] In some technical solutions of the present invention, the colorimetric agent is a 3,3',5,5'-tetramethylbenzidine solution.

[0027] In some technical solutions of the present invention, the volume ratio of the colorimetric agent to the metal-doped cerium-based nanozyme solution is 0.8-1.2, and the concentration of the 3,3',5,5'-tetramethylbenzidine solution is 4mM-6mM.

[0028] In some technical solutions of this invention, the volume ratio of the colorimetric reagent to the metal-doped cerium-based nanozyme solution is 1.0, the concentration of the 3,3',5,5'-tetramethylbenzidine solution is 5 mM, and the concentration of the metal-doped cerium-based nanozyme solution is 400 μg·mL. -1 .

[0029] In some technical solutions of the present invention, the absorbance at a wavelength of 652 nm is subsequently recorded using an ultraviolet spectrophotometer.

[0030] In some technical solutions of this invention, the pH of the reaction system is 4.

[0031] In some technical solutions of this invention, the reaction temperature is 37°C.

[0032] In some technical solutions of the present invention, the reaction time is 8 min to 12 min.

[0033] In some technical solutions of the present invention, the reaction time is 10 minutes.

[0034] Compared with existing technologies, the advantages of this invention are:

[0035] This invention provides a metal-doped cerium-based nanozyme, which exhibits 1.5 to 9 times higher catalytic activity compared to pure cerium sulfide nanozymes.

[0036] The present invention also provides the application of the above-mentioned cerium sulfide nanozyme in the detection of hydrogen peroxide. This method has the advantages of visualization and simple operation, and has a good linear relationship in the range of 10 to 200 μmol / L, with a detection limit as low as 3 μmol / L, which can achieve high sensitivity detection of hydrogen peroxide.

[0037] The present invention also optimized the concentration of Fe / CeS2 nanozyme. 200 μL of Fe / CeS2 nanozyme at different concentrations were added to 50 mM hydrogen peroxide. The results showed that the catalytic efficiency of Fe / CeS2 was the highest when the concentration of Fe / CeS2 nanozyme was 400 μg / mL in 50 mM hydrogen peroxide.

[0038] The metal-doped cerium-based nanozymes provided by this invention have a simple preparation method. Different metal-doped cerium sulfide nanozymes were synthesized in one step using a co-precipitation method. By doping with transition metals, the aim was to obtain cerium sulfide nanozymes with optimal hydrogen peroxide detection performance. In this invention, cerium-based nanozymes doped with different transition metals were prepared, and the peroxidase performance of cerium-based nanozymes doped with different metals was tested. Metal-doped cerium-based nanozymes with higher catalytic efficiency were screened out. Attached Figure Description

[0039] Figure 1 Transmission electron microscopy images of CeS2 nanozymes doped with different metals; among them... Figure 1 A is a transmission electron microscope image of CeS2; Figure 1 B is a transmission electron microscope image of Fe / CeS2; Figure 1 The C is a transmission electron microscope image of Mn / CeS2; Figure 1 D is the transmission electron microscope image of La / CeS2; Figure 1 E is a transmission electron microscope image of Zr / CeS2; Figure 1 F is a transmission electron microscope image of Co / CeS2.

[0040] Figure 2 Figure 1 shows the POD test results of CeS2 nanozymes with different metal doping.

[0041] Figure 3 This is a standard curve for determining the concentration of H2O2.

[0042] Figure 4 The figure shows the results of the concentration optimization of Fe / CeS2 nanozyme in 50mM hydrogen peroxide. Detailed Implementation

[0043] The present invention will be described in detail below with reference to specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following embodiments can be obtained commercially unless otherwise specified.

[0044] Hydrogen peroxide (H2O2, commonly known as hydrogen peroxide solution) is an intermediate product of some metabolic reactions in the human body. For example, glucose can be catalyzed by glucose oxidase to produce gluconic acid and hydrogen peroxide. However, excessively high levels of hydrogen peroxide in the body can lead to diseases such as cancer and cardiovascular disease. Currently, the main methods for detecting hydrogen peroxide include electrochemical methods, chromatography, and spectrophotometry. However, these methods all have certain limitations. For example, they require high-quality instruments and samples, and they cannot avoid interference from complex components in the blood, making it impossible to achieve rapid and accurate direct detection of hydrogen peroxide and related substances. Therefore, it is crucial to develop a simple and rapid method for detecting hydrogen peroxide.

[0045] Natural enzymes are a class of highly efficient biocatalysts, but their demanding operating conditions limit their applications, and the high cost of artificially synthesizing natural enzymes also restricts their use. Nanozymes derived from nanomaterials possess enzyme-like catalytic activity and, compared to natural enzymes, offer advantages such as lower cost, stronger resistance to biodegradation, and larger production volumes. However, compared to natural enzymes, most nanozymes still exhibit significant differences in specificity and catalytic efficiency, limiting their widespread application. Cerium-based nanozymes typically contain both trivalent and tetravalent valence states, which can accelerate electron flow and promote peroxide-mimicking enzyme performance. Furthermore, nanozymes exhibit good biocompatibility in vivo. However, existing nanozymes show poor performance in detecting hydrogen peroxide; therefore, providing a nanozyme with superior hydrogen peroxide detection performance is extremely important.

[0046] This invention provides a metal-doped cerium-based nanozyme, which is prepared according to the following steps:

[0047] Cerium salt and transition metal salt are dissolved in water to form solution A;

[0048] Solution A is mixed with sodium sulfide to undergo a co-precipitation reaction. After static aging, a precipitate is obtained, which is the metal-doped cerium-based nanozyme.

[0049] The metal in the transition metal salt is selected from one of the transition metal elements: iron, copper, manganese, cobalt, nickel, zirconium, and lanthanum.

[0050] This invention provides a metal-doped cerium-based nanozyme, which exhibits 1.5 to 9 times higher catalytic activity compared to pure cerium sulfide nanozymes.

[0051] The present invention also provides the application of the above-mentioned cerium sulfide nanozyme in the detection of hydrogen peroxide. This method has the advantages of visualization and simple operation, and has a good linear relationship in the range of 10 to 200 μmol / L, with a detection limit as low as 3 μmol / L, which can achieve high sensitivity detection of hydrogen peroxide.

[0052] The metal-doped cerium-based nanozymes provided by this invention have a simple preparation method. Different metal-doped cerium sulfide nanozymes were synthesized in one step using a co-precipitation method. By doping with transition metals, the aim was to obtain cerium sulfide nanozymes with optimal hydrogen peroxide detection performance. In this invention, cerium-based nanozymes doped with different transition metals were prepared, and the peroxidase performance of cerium-based nanozymes doped with different metals was tested. Metal-doped cerium-based nanozymes with higher catalytic efficiency were screened out.

[0053] Example 1: Metal-doped cerium-based nanozymes

[0054] The specific preparation steps of metal-doped cerium-based nanozymes are as follows:

[0055] (1) Weigh out different metal nitrates (Fe(NO3)3·6H2O: 0.47g; Mn(NO3)2·6H2O: 0.29g; Cu(NO3)3·6H2O: 0.28g; La(NO3)3·6H2O: 0.51g; Zr(NO3)3·6H2O: 0.50g; Co(NO3)3·6H2O: 0.34g), and dissolve each weighed metal nitrate in 30mL of deionized water with 5.1g of Ce(NO3)3·6H2O to obtain solution A;

[0056] The molar ratio of metal ions Fe, Mn, Cu, La, Zr or Co to Ce is 0.1.

[0057] (2) Weigh 5.64g of Na2S·H2O and dissolve it in 100mL of deionized water to form solution B;

[0058] Solution A was added dropwise to solution B using a peristaltic pump while stirring to ensure that solutions A and B were mixed evenly. After the addition was complete, stirring was continued for 30 minutes to allow solutions A and B to react fully and form a precipitate. The precipitate was then aged and allowed to stand for 2 hours before being filtered to obtain the precipitate.

[0059] (3) Wash the precipitate three times with 20 mL of deionized water each time to remove unreacted ions such as nitrate and sodium ions. Collect the washed precipitate and wash it three times with anhydrous ethanol each time, using 20 mL. After washing, dry it rapidly at 80°C for 24 h to obtain the nanozyme, which is named M / CeS2, where M represents metal ions: Fe, Mn, Cu, La, Zr or Co.

[0060] Example 2: Metal-doped cerium-based nanozymes

[0061] The specific preparation steps of metal-doped cerium-based nanozymes are as follows:

[0062] (1) Weigh different metal nitrates (Fe(NO3)3·6H2O: 1.41g; Mn(NO3)2·6H2O: 0.87g; Cu(NO3)3·6H2O: 0.84g; La(NO3)3·6H2O: 1.53g; Zr(NO3)3·6H2O: 1.50g; Co(NO3)3·6H2O: 1.02g); Dissolve the weighed metal nitrates in 30mL of deionized water with 5.1g of Ce(NO3)3·6H2O to obtain solution A;

[0063] The molar ratio of metal ions Fe, Mn, Cu, La, Zr or Co to Ce is 0.3.

[0064] (2) Weigh 7g of Na2S·H2O and dissolve it in 100mL of deionized water to form solution B;

[0065] Solution A was added dropwise to solution B using a peristaltic pump while stirring to ensure that solutions A and B were mixed evenly. After the addition was complete, stirring was continued for 50 minutes to allow solutions A and B to react fully and form a precipitate. The precipitate was then aged and allowed to stand for 2.5 hours before being filtered to obtain the precipitate.

[0066] (3) Wash the precipitate three times with 20 mL of deionized water each time to remove unreacted ions such as nitrate and sodium ions. Collect the washed precipitate and wash it three times with 20 mL of anhydrous ethanol each time. After washing, dry it at 100°C for 12 h to obtain the nanozyme named M / CeS2, where M represents metal ions: Fe, Mn, Cu, La, Zr or Co.

[0067] Example 3:

[0068] The specific preparation steps of metal-doped cerium-based nanozymes are as follows:

[0069] (1) Weigh different metal nitrates (Fe(NO3)3·6H2O: 0.24g; Mn(NO3)2·6H2O: 0.15g; Cu(NO3)3·6H2O: 0.14g; La(NO3)3·6H2O: 0.26g; Zr(NO3)3·6H2O: 0.25g; Co(NO3)3·6H2O: 0.17g); Dissolve the weighed different metal nitrates with 5.1g Ce(NO3)3·6H2O in 30mL of deionized water to obtain solution A; wherein the molar ratio of metal ions Fe, Mn, Cu, La, Zr or Co to Ce is 0.05.

[0070] Weigh 3g of Na2S·H2O and dissolve it in 100mL of deionized water to form solution B;

[0071] (2) Add solution A to solution B dropwise using a peristaltic pump while stirring to mix solution A and solution B evenly. After the addition is complete, continue stirring for 30 minutes to allow solution A and solution B to react fully and form a precipitate. Then, let it age and stand for 1.5 hours, and then filter to obtain the precipitate.

[0072] (3) Wash the precipitate three times with 20 mL of deionized water each time to remove unreacted ions such as nitrate and sodium ions. Collect the washed precipitate and wash it three times with anhydrous ethanol each time, using 20 mL each time. After washing, dry it rapidly at 70°C for 36 h to obtain the nanozyme, which is named M / CeS2, where M represents metal ions: Fe, Mn, Cu, La, Zr or Co.

[0073] The preparation methods provided in Examples 1-3 can all produce metal-doped cerium-based nanozymes with similar structures and functions. Therefore, taking the metal-doped cerium-based nanozyme prepared in Example 1 as an example, M / CeS2 was observed using transmission electron microscopy (TEM), and the results are as follows. Figure 1 As shown in AF. From the TEM results, it can be found that the nanozymes prepared by different metal doping of CeS2 are all nanoscale in size, which is beneficial to the dispersion of nanozymes in solution, increases the specific surface area, and improves the catalytic efficiency.

[0074] Comparative Example 1: Preparation of cerium sulfide nanozymes:

[0075] 5.64 g of Na2S·H2O was weighed and dissolved in 100 mL of deionized water to form a Na2S·H2O solution. 5.1 g of Ce(NO3)3·H2O was weighed and dissolved in 30 mL of deionized water to form a Ce(NO3)3·H2O solution. The Ce(NO3)3·H2O solution was then added dropwise to the Na2S·H2O solution using a peristaltic pump while stirring. After the addition was complete, stirring was continued for 30 min. The mixture was then aged and allowed to stand for 1 h. It was then washed three times with deionized water and three times with anhydrous ethanol, each time using 20 mL. Finally, it was dried at 70 °C for 24 h. The nanozyme was named CeS2.

[0076] Example 5: Performance testing of different nanozymes and peroxidases

[0077] Add 1400 μL of HAc-NaAc buffer solution (pH=4) and 200 μL of the nanozyme suspension prepared in Example 1 (concentration 40 μg·mL) to the cuvette in sequence. -1 The nanozyme suspension prepared in Comparative Example 1 (concentration 40 μg·mL) or the nanozyme suspension prepared in Comparative Example 1 -1 200 μL H₂O₂ (50 mM) and 200 μL TMB (5 mM) were reacted. After reacting at 37 °C for 10 min, the absorbance values ​​were recorded. The results are shown in the figure below. Figure 2 As shown.

[0078] Depend on Figure 2 The results show that the POD activity of CeS2 was improved to varying degrees after different metals were doped, indicating that doping with transition metals can enhance the POD activity of CeS2. This may be due to the synergistic effect between metals. Among them, Fe doping has the greatest effect, and the POD activity of Fe / CeS2 is nearly 9 times that of CeS2.

[0079] 3. Detection of hydrogen peroxide using different nanozymes

[0080] In this embodiment, Fe / CeS2, which has the best POD activity, was selected for detecting hydrogen peroxide in the sample.

[0081] The concentration of Fe / CeS2 nanozyme was optimized. 200 μL of Fe / CeS2 nanozyme at different concentrations (50 μg / mL, 100 μg / mL, 200 μg / mL, 400 μg / mL, 800 μg / mL, 1000 μg / mL) and 200 μL of 5 mM TMB were added to 50 mM hydrogen peroxide. The catalytic reaction was carried out at pH 4 and 37 °C, and the absorbance at 652 nm was recorded using a UV spectrophotometer. In this invention, the volume ratio of Fe / CeS2 nanozyme solution to the sample can be 0.7–1.5 to achieve the detection of hydrogen peroxide. Specifically, in this embodiment, the volume ratio of Fe / CeS2 nanozyme solution to the sample is 1.0.

[0082] The measurement results are as follows Figure 3 As shown, the UV absorption intensity increases with the increase of Fe / CeS2 concentration of the nanozyme, indicating that the ability of the nanozyme to catalyze the oxidation of TMB by H2O2 is also enhanced. However, when the concentration is greater than 400 μg / mL, the increase in UV absorption intensity is not significant. This may be because the adsorption of H2O2 is already saturated, and further increasing the concentration of the nanozyme will not significantly improve the catalytic efficiency. Therefore, the concentration of the nanozyme was chosen to be 400 μg / mL.

[0083] Prepare hydrogen peroxide solutions of different concentrations (1, 2, 5, 10, 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300 μmol / L). Then, add 200 μL of a 5 mM solution of 3,3',5,5'-tetramethylbenzidine (TMB) and 200 μL of the Fe / CeS2 nanozyme prepared above (concentration 400 μg·mL). -1 The catalytic reaction was carried out for 10 minutes at pH 4 and temperature 37°C, and the absorbance at a wavelength of 652 nm was recorded using a UV spectrophotometer.

[0084] The measurement results are as follows Figure 4 As shown in the figure, the results indicate that the detection results exhibit a linear trend when the hydrogen peroxide concentration is between 10-200 μmol / L, with the detection limit as low as 3 μmol / L.

[0085] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0086] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. Application of a metal-doped cerium-based nanosensor in hydrogen peroxide detection, characterized in that, The metal-doped cerium-based nanoscale enzyme is prepared according to the following steps: The cerium salt and the transition metal salt are dissolved in water to form a solution A; the cerium salt is selected from cerium halide, cerium sulfate or cerium acetate; the transition metal salt is selected from transition metal halide, transition metal sulfate or transition metal acetate; The solution A is mixed with sodium sulfide to perform a co-precipitation reaction, and after standing and aging, a precipitate is obtained, which is the metal-doped cerium-based nanoscale enzyme; wherein the metal of the transition metal salt is selected from one of iron, copper, manganese, cobalt, nickel, zirconium and lanthanum of transition metal elements.

2. Use according to claim 1, wherein The transition metal element is iron, lanthanum or cobalt.

3. The use according to claim 1, wherein the compound is ###0002### The mass ratio of the metal ion in the transition metal salt to the cerium ion in the cerium salt is 0.05-0.

3.

4. Use according to claim 3, wherein the compound is ###0002### The mass ratio of sodium sulfide to the cerium salt is 4-6:4-6.

5. The use according to claim 1, wherein The co-precipitation reaction time is 30-50 minutes.

6. The use according to claim 1, wherein The standing and aging time is 1.5-2.5 hours.

7. A method of detecting hydrogen peroxide, characterized by, Comprising: The color developer and the solution of the metal-doped cerium-based nanoscale enzyme are added to the sample to be tested, and the reaction is performed for 8-15 minutes to obtain a reaction product, and then the absorbance of the reaction product is analyzed to calculate the detection result of hydrogen peroxide in the sample to be tested; The metal-doped cerium-based nanoscale enzyme is prepared according to the following steps: The cerium salt and the transition metal salt are dissolved in water to form a solution A; the cerium salt is selected from cerium halide, cerium sulfate or cerium acetate; the transition metal salt is selected from transition metal halide, transition metal sulfate or transition metal acetate; The solution A is mixed with sodium sulfide to perform a co-precipitation reaction, and after standing and aging, a precipitate is obtained, which is the metal-doped cerium-based nanoscale enzyme; wherein the metal of the transition metal salt is selected from one of iron, copper, manganese, cobalt, nickel, zirconium and lanthanum of transition metal elements.

8. The method of claim 7, wherein, The concentration of the solution of the metal-doped cerium-based nanoscale enzyme is 300-500 μg / mL; the concentration of hydrogen peroxide in the sample to be tested ranges from 3 μmol / L to 200 μmol / L, and the volume ratio of the solution of the metal-doped cerium-based nanoscale enzyme to the sample to be tested is 0.7-1.5.

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