A single-atom POD-mimicking enzyme nanomaterial, its preparation method, and food safety detection application

Abstract

The present invention belongs to the technical fields of nanomaterials, analytical detection, and food safety, and specifically relates to a single-atom POD-mimicking enzyme nanomaterial, a preparation method thereof, and a food safety detection application. The single-atom POD-mimicking enzyme nanomaterial comprises a noble metal Os and a defective metal oxide, wherein the defective metal oxide is an oxide of metal Cu, and the Os is anchored on the defective metal oxide in the form of single atoms. The present invention also relates to the use of the single-atom POD-mimicking enzyme nanomaterial in the preparation of a detection reagent having POD activity and in the colorimetric detection of hydrogen peroxide or nitrite.

Description

Technical Field

[0001] The invention belongs to the technical fields of nano materials, analysis and detection, and food safety, and specifically relates to a single-atom POD enzyme-mimicking nano material, a preparation method thereof, and food safety detection application. Background Art

[0002] Food safety has become a major challenge faced by the whole world. It not only causes great harm to human health, but also seriously restricts import and export trade and industrial development. Nitrite is usually used as a preservative and colorant in food processing and is widely present in daily life. Excessive intake of food additives such as nitrite can cause a series of adverse reactions, such as methemoglobinemia, headache, dizziness, rapid heartbeat, nausea, and in severe cases, poisoning and death. Due to the potential carcinogenicity of nitrite, the World Health Organization (WHO) has listed it as a highly toxic substance. The Food and Agriculture Organization of the United Nations (FAO) and WHO set the maximum limit of nitrite in drinking water at 3.0 mg / L and the maximum daily intake of nitrite in food at 0.06 mg / kg. China's national food safety standard (GB 2762-2024) limits the maximum content of nitrite in milk powder and formula milk powder to 2.0 mg / kg, bottled water to 0.1 mg / L, the maximum amount added to meat products to 0.5 g / kg, and the maximum residual amount does not exceed 30 mg / kg. Therefore, the development of efficient and accurate nitrite detection technology is crucial to ensure food safety. Chromatographic methods such as gas chromatography, high-performance liquid chromatography, gas chromatography-mass spectrometry and high-performance liquid chromatography-mass spectrometry, and electrochemical methods are the most commonly used detection technologies in current food safety monitoring. Although it has the advantages of high sensitivity and good accuracy, it also has disadvantages such as expensive equipment, long time consumption, relatively complex operation, and high professional requirements for technical personnel. It cannot meet the needs of real-time and effective monitoring of the entire chain of food production, processing, circulation and sales. Therefore, the development of simple, accurate and economical on-site rapid detection technology has become a research hotspot.

[0003] Natural enzymes (such as peroxidase (POD), oxidase (OXD), catalase (CAT), superoxide dismutase (SOD), etc.) have been proven to have advantages such as high catalytic activity and strong substrate specificity. As core recognition materials or markers, they play an important role in common rapid detection technologies such as enzyme inhibition and immunoassay. However, due to their own limitations, such as poor stability, easy inactivation, high cost, and difficulty in preparation and purification, they are difficult to be widely used in rapid food safety detection technology, which limits their application and promotion.

[0004] With the continuous progress of nanotechnology, researchers have gradually developed nanozymes that can mimic the catalytic activity of natural enzymes. These nanozyme preparations can not only mimic the catalytic processes of natural enzymes such as OXD, POD, and laccase, regulate the ROS-producing activity, but also have advantages such as high designability, multifunctionality, and stability, and are expected to be used as efficient and precise new enzyme-mimicking catalysts in the field of food safety detection technology. Bionic enzyme preparations represented by metal oxides (such as Fe3O4, CeO2, MoO3, Co3O4, MnO2, etc.), metal hydroxides (such as Cu(OH)2), metal nanoparticles (such as Ag and Au nanoparticles, Pd@Pt nanodendrites, etc.), and carbon-based single-atom materials (such as Fe, Co, Zn-N-C, etc.) show certain food safety detection activities, but still face challenges in food safety detection research: the energy substrate conversion efficiency of the metal active centers of nanozymes is relatively low, and the ROS-producing activity is insufficient. Often, a large dose is required to achieve efficient and rapid detection effects. However, high-concentration ROS-producing materials also increase the equipment cost, which greatly limits their application prospects in food safety detection. Therefore, designing sensors with high catalytic activity, high selectivity, and stability for nitrite content detection is the core and challenge of this project's research, and related research is of great significance for food safety monitoring. Summary of the Invention

[0005] In view of the above defects, the present invention provides a novel enzyme-mimicking nanosensor. The enzyme-mimicking nanomaterial includes noble metal Os and defective metal oxide (named Cu - O v ), that is, the noble metal is anchored on the Cu - O v precursor to form a peroxidase (POD) enzyme-mimicking nanomaterial; the enzyme-mimicking nanomaterial has POD activity, and thus can be used to accurately detect the content of substances such as nitrite (for example, in food safety detection).

[0006] The technical solution of the present invention:

[0007] The first technical problem to be solved by the present invention is to provide a single-atom POD-mimicking enzyme nanomaterial, which contains noble metal Os and defective metal oxide, wherein the defective metal oxide is an oxide of metal Cu, and the Os is anchored on the defective metal oxide in the form of single atoms.

[0008] Further, the defective metal oxide is an oxygen vacancy defective metal oxide.

[0009] Further, the particle size of the single-atom POD-mimicking enzyme nanomaterial is 2 - 20 nm.

[0010] The second technical problem to be solved by the present invention is to provide a method for preparing the single-atom POD enzyme-mimicking nanomaterial described herein, which comprises the following steps:

[0011] (1) Hydrothermally react a copper salt and an amine compound in water, wash and dry the resulting precipitate to obtain a defective metal oxide.

[0012] (2) Mix and stir the defective metal oxide obtained in step (1) with an Os salt in water so that Os is anchored on the defective metal oxide in the form of single atoms. After washing and drying the resulting precipitate, the single-atom POD enzyme-mimicking nanomaterial is obtained.

[0013] Further, the copper salt includes CuCl2·xH2O.

[0014] Further, the amine compound includes at least one of hexamethylenetetramine, urea, ammonium chloride, and ammonium nitrate.

[0015] Further, the mass ratio of the copper salt to the amine compound is 1:5 - 15.

[0016] Further, the conditions of the hydrothermal reaction are to react at 60 - 150 °C for 1 - 12 h.

[0017] Further, the Os salt includes OsCl3·xH2O.

[0018] Further, the mass ratio of the defective metal oxide to the Os salt is 50:1 - 25, preferably 5:2 to 10:1.

[0019] Further, the stirring includes stirring at 20 - 100 °C for 5 - 48 hours.

[0020] The third technical problem to be solved by the present invention is to provide the use of the single-atom POD enzyme-mimicking nanomaterial described herein or the single-atom POD enzyme-mimicking nanomaterial prepared by the method described herein in the preparation of a detection reagent having POD activity.

[0021] The fourth technical problem to be solved by the present invention is to provide the use of the single-atom POD enzyme-mimicking nanomaterial described herein or the single-atom POD enzyme-mimicking nanomaterial prepared by the method described herein in the colorimetric detection of hydrogen peroxide or nitrite (for example, in food safety detection).

[0022] The fifth technical problem to be solved by the present invention is to provide a sensor for detecting hydrogen peroxide or nitrite (for example, in food safety detection), wherein the sensor comprises the single-atom POD enzyme-mimicking nanomaterial described herein or the single-atom POD enzyme-mimicking nanomaterial prepared by the method described herein.

[0023] Advantages of the present invention:

[0024] In the present invention, a novel nanozyme material (named OsCu - O v ) was prepared by uniformly and stably anchoring noble metal Os on the Cu - O v precursor. It can serve as a POD - mimicking nano - reactor to replace natural enzymes for the highly efficient and selective colorimetric detection of various biomarkers. Due to the metal - O coordination, oxygen vacancies, and unique enzymatic properties of the noble metal existing in the obtained nanozyme material, the nanozyme material exhibits excellent and unique POD - mimicking activity, and thus shows excellent POD detection activity and good substrate selectivity.

[0025] The POD detection activity of the nanozyme material obtained in the present invention. TMB, as a novel chromogenic substrate, has been widely used in biochemical detection research. The chromogenic reaction of TMB oxidation is based on its core part: benzidine, which contains two easily oxidizable amino groups and can be oxidized into a blue product through a one - electron pathway. In the presence of H2O2, POD can catalyze the oxidation of TMB (colorless) to form blue oxTMB with a characteristic absorption peak at 652 nm. When nitrite is introduced, the generated blue oxTMB species will react specifically with nitrite to produce diazotized TMB, resulting in a color change from blue to green and finally to yellow, which enables accurate detection of nitrite.

[0026] In addition, systematic colorimetric tests show that the nano - reactor of the nanozyme material obtained in the present invention exhibits high - efficiency diagnostic activity and substrate selectivity for food additive nitrite, with a very low detection limit and a wide detection range: 1.48 mM for H2O2 in the range of 0 - 1350 μM and 2.23 μM for nitrite in the range of 0.2 - 120 μM. Meanwhile, the good stability of the Cu - O v structure also enables the nano - reactor to work efficiently under harsh conditions (such as different temperatures and different acidic conditions).

[0027] It can be seen that the present invention not only provides a highly sensitive and inexpensive colorimetric biosensor for food safety, but also provides a new approach for engineering - customized mimetic enzyme nano - reactors, serving as a powerful tool for rapid food detection. Brief Description of the Drawings

[0028] Figure 1 Synthesis schematic diagram of OsCu - O v in Example 1 of the present invention.

[0029] Figure 2 PXRD patterns of Cu - O v and OsCu - O v in Example 1 of the present invention.

[0030] Figure 3 SEM images of the material obtained in Example 1 of the present invention: (a) Cu - O v SEM image; (b) OsCu - O v SEM image.

[0031] Figure 4 HRTEM image of OsCu - O obtained in Example 1 of the present invention v

[0032] Figure 5 Aberration - corrected image of OsCu - O obtained in Example 1 of the present invention v

[0033] Figure 6 XPS spectra of the material obtained in Example 1: (a) survey spectrum; (b) high - resolution XPS C 1s; (c) high - resolution XPS O 1s; (d) high - resolution XPS Cu 2p; (e) high - resolution XPS Cl 1s; (f) high - resolution XPS Os 4f.

[0034] Figure 7 XAS image of OsCu - O obtained in Example 1 of the present invention v

[0035] Figure 8 Results of evaluating and comparing the POD and OXD mimetic enzyme activities of the material obtained in Example 1 of the present invention by TMB colorimetric method: (a) POD mimetic enzyme activity; (b) Michaelis - Menten curve and double - reciprocal curve with H2O2 as the substrate; (c) kinetic parameters with H2O2 as the substrate.

[0036] Figure 9 Results of the POD activity stability of the material obtained in Example 1: (a) POD activity of OsCu - O v at different temperatures and different pH values; (b) solution stability of OsCu - O v during the POD activity test

[0037] Figure 10 Results of product detection in the POD - catalyzed process of the material obtained in Example 1: (a) Free - radical quenching process using TBA, BQ, and NaN3 as quenchers during the POD mimic test; EPR results (b) ·OH, (c) ·O2 - and (d) 1 O2.

[0038] Figure 11 ​​​Results of detecting H2O2 for the material obtained in Example 1: (a) The absorbance spectra of the POD-like activity of OsCu-O v at different concentrations of H2O2; (b) The concentration-dependent curve of H2O2; (c) The linear correlation diagram of H2O2.

[0039] Figure 12 Results of detecting nitrite for the material obtained in Example 1: (a) The absorbance spectra of the POD-like activity of OsCu-O v at different concentrations of nitrite; (b) The linear correlation diagram of nitrite.

[0040] Figure 13 Results of the POD activity stability for the materials obtained in Examples 1-5. Detailed implementation manners

[0041] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0042] Example 1: Synthesis of single-atom POD-like enzyme nanomaterial (named OsCu-O v )

[0043] Cu-O v Precursor: 10 mL of deionized water containing 340.9 mg of CuCl2·xH2O was mixed with 15 mL of deionized water containing 3.154 g of HMT (hexamethylenetetramine, urotropine), then the mixture was shaken well and further hydrothermally treated in an autoclave at 95 °C for 5 h; then the precipitate was washed with deionized water and dried under vacuum.

[0044] Synthesis of nanosensor material OsCu-O v : 50 mg of Cu-O v was dispersed in a flask with 10 mL of deionized water and continuously sonicated for 10 min; then 0.5 mL of an OsCl3·xH2O aqueous solution (concentration of 10 mg mL -1 ) was poured into the above solution; stirred at room temperature for 24 h, the precipitate was collected and washed with H2O solution at least 3 times, and then dried overnight under vacuum at 60 °C to obtain OsCu-O v .

[0045] Example 2: Structure characterization of OsCu-O v

[0046] Cu-O v, with a Cu precursor and a hexamethylenetetramine ligand; in addition, based on the Os-O coordination, the Os catalytic site simulating POD activity can be uniformly anchored on the Cu-O by hydrothermal synthesis or impregnation method v support, and the synthesis schematic diagram of OsCu-O v is as shown in Figure 1 .

[0047] The X-ray diffraction pattern (XRD) shows that after the Os sites are anchored, the crystal structure of Cu-O v has no significant change (as shown in Figure 2 ). The scanning electron microscope (SEM) image shows that Cu-O v and OsCu-O v show typical spherical shapes with a diameter of about 30 nm (as shown in Figure 3 ). The high-resolution transmission electron microscope (HR-TEM) image shows that the lattice fringe spacings of 0.2614, 0.2763, and 0.3165 nm are consistent with the crystal planes (0 2 2), (1 2 1), and (0 2 1) of Cu-O v (as shown in Figure 4 ). The high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) and energy-dispersive spectroscopy (EDS) results further reveal that Os atoms are uniformly dispersed at the atomic level on the Cu-O v precursor (as shown in Figure 5 ).

[0048] The present invention further conducts X-ray photoelectron spectroscopy (XPS) tests to study the chemical composition and electronic state, and the results are as shown in Figure 6 and Table 1. The XPS full-spectrum and elemental analysis show that the Os element is successfully doped into Cu-O v . Compared with Cu-O v , there is an obvious peak shift in the O1s of OsCu-O v , indicating the formation of Os-O coordination. The Os 4f spectrum shows that the oxidation state in Os atoms is mainly composed of Ir 3+ and Ir 4+ , indicating the formation of atomically dispersed Os with O coordination. The Os L3-edge synchrotron radiation X-ray absorption spectroscopy ( Figure 7 ) is used to study the coordination structure of the enzyme-mimicking material. The white line peak oxidation state of OsCu-O v is closer to that of OsO2, and the valence state analysis shows that the average valence state of Os in OsCu-O v is 4.2, which is slightly higher than the Os valence state in OsO2. The R-space and wavelet transform results show that there is only Os-O in the coordination structure of OsCu-O v , and there is no Os-Os coordination structure, indicating that Os exists in the form of single atoms.

[0049] Table 1 Elemental content in the biocatalyst determined by XPS measurement.

[0050]

[0051] Example 3: OsCu-O v Performance test

[0052] Mimicking Enzyme and Colorimetric Detection Activity

[0053] After verifying the morphology and structure of Cu-O v and OsCu-O v the present invention further studied their enzyme-mimicking activity and the performance of detecting food additive content.

[0054] First, the activity of POD mimics was evaluated and compared using the typical 3,3′,5,5′-tetramethylbenzidine (TMB) colorimetric method. As Figure 8 shown in v a, OsCu-O v showed very efficient TMB oxidation activity with the highest characteristic absorption peak at 652 nm, while Cu-O m showed very poor POD mimic activity. The enzyme-mimicking POD activity was further revealed by kinetic parameters such as the catalytic constant (K max ), the maximum reaction rate (V Figure 8 ), and the turnover number (TON). The results are shown in Table 2 and v b-c. Using H2O2 as the substrate, the double-reciprocal plot of Michaelis–Menten kinetics for OsCu-O v showed a good linear fitting relationship; the results of the kinetic parameters indicated that the POD mimic activity of OsCu-O

[0055] Table 2 Kinetic parameters of OsCu-O v using H2O2 as the substrate

[0056] <![CDATA[E0(μM)]]> <![CDATA[V max (μM s -1 )]]> <![CDATA[K m (mM)]]> <![CDATA[TON(s -1 )]]> H2O2 5.44 1.41 18.5 259.9

[0057] Figure 9 a). Meanwhile, the nano-reactor obtained in the present invention still had high catalytic activity under different reaction conditions, such as within different temperature and different pH ranges ( Figure 9 a). At the same time, to verify the long-term structural stability of OsCu-O v v samples were left in NaOAc-HOAc buffer for different lengths of time (pH 4.5), and the POD mimic activity did not decrease, indicating its good POD mimic stability ( Figure 9 b).

[0058] Then, radical quenching experiments and EPR analysis were applied to identify the products during the POD-mimicking process with H2O2 as the substrate. After adding potassium tert-butoxide (TBA, a radical quencher for ·OH), benzoquinone (BQ, a radical quencher for ·O2 - , and sodium azide (NaN3, a radical quencher for 1 O2), the intensity value of oxTMB at 652 nm decreased, confirming that the main products generated were ·OH, ·O2 - , and 1 O2 ( Figure 10 a). Then, EPR further confirmed the generation of ·OH, ·O2 - , and 1 O2 ( Figure 10 b-d). In summary, the present invention has demonstrated that ·OH, ·O2 - , and 1 O2 are the main products during the POD-mimicking process.

[0059] Colorimetric Detection of H2O2

[0060] Due to the excellent POD-mimicking properties of OsCu-O v , it indicates that the obtained nanomaterials can be used for quantitative detection by evaluating the H2O2 level through colorimetry. As shown in Figure 11 a, the characteristic absorption peak at 652 nm gradually increased with the increase in the H2O2 concentration. The absorbance was linearly proportional to the H2O2 concentration (0 - 1350 μM) ( Figure 11 b). Meanwhile, after calculation, the LOD for H2O2 detection was 1.48 mM, indicating that the OsCu-O v obtained in the present invention exhibited high detection activity towards H2O2.

[0061] Colorimetric Detection of Nitrite

[0062] As shown in Figure 12 a, the characteristic absorption peak at 652 nm gradually decreased with the increase in the nitrite concentration, and the characteristic absorption peak at 445 nm gradually increased with the increase in the nitrite concentration. The ratio of A 652 / A 445 absorbance was linearly proportional to the nitrite concentration (0.2 - 120 μM) ( Figure 12 b). Meanwhile, after calculation, the LOD for nitrite detection was 2.23 μM, indicating that the OsCu-O v obtained in the present invention exhibited high detection activity towards nitrite.

[0063] Example 4: Changing Cu-O vPrepare OsCu-O with the mass ratio to Os v

[0064] Cu-O v Precursor: Mix 10 mL of deionized water containing 340.9 mg of CuCl2·xH2O with 15 mL of deionized water containing 3.154 g of HMT (hexamethylenetetramine, urotropine), then shake the mixture well and further perform hydrothermal treatment in an autoclave at 95 °C for 5 h; then wash the precipitate with deionized water and dry it under vacuum.

[0065] Nanosensor material OsCu-O v Synthesis: Disperse 50 mg of Cu-O v in a flask with 10 mL of deionized water and continuously sonicate for 10 min; then pour 1 mL of an OsCl3·xH2O aqueous solution (concentration 10 mg mL -1 ) into the above solution; stir at room temperature for 24 h, collect the precipitate and wash it with H2O solution at least 3 times, then dry it overnight under vacuum at 60 °C to obtain OsCu-O v (Cu-O v :Os = 5:1). It was found that the obtained OsCu-O v (Cu-O v :Os = 5:1) has good POD activity ( Figure 13 ).

[0066] Example 5: Change the mass ratio of Cu-O v to prepare OsCu-O with the mass ratio to Os v

[0067] Cu-O v Precursor: Mix 10 mL of deionized water containing 340.9 mg of CuCl2·xH2O with 15 mL of deionized water containing 3.154 g of HMT (hexamethylenetetramine, urotropine), then shake the mixture well and further perform hydrothermal treatment in an autoclave at 95 °C for 5 h; then wash the precipitate with deionized water and dry it under vacuum.

[0068] Nanosensor material OsCu-O v Synthesis: Disperse 50 mg of Cu-O v in a flask with 10 mL of deionized water and continuously sonicate for 10 min; then pour 2 mL of an OsCl3·xH2O aqueous solution (concentration 10 mg mL -1 ) into the above solution; stir at room temperature for 24 h, collect the precipitate and wash it with H2O solution at least 3 times, then dry it overnight under vacuum at 60 °C to obtain OsCu-O v (Cu-Ov :Os = 10:4). It was found that the obtained OsCu - O v (Cu - O v :Os = 10:4) had good POD activity ( Figure 13 ).

[0069] Example 6: Changing the mass ratio of Cu - O v and Os to prepare OsCu - O v

[0070] Cu - O v Precursor: Mix 10 mL of deionized water containing 340.9 mg of CuCl2·xH2O with 15 mL of deionized water containing 3.154 g of HMT (hexamethylenetetramine, urotropine), then shake the mixture well, and further hydrothermally treat it in an autoclave at 95 °C for 5 h; then wash the precipitate with deionized water and dry it under vacuum.

[0071] Synthesis of the nanosensor material OsCu - O v : Disperse 50 mg of Cu - O v in a flask with 10 mL of deionized water, and continuously sonicate for 10 min; then pour 0.2 mL of an OsCl3·xH2O aqueous solution (concentration of 10 mg mL -1 ) into the above solution; stir at room temperature for 24 h, collect the precipitate and wash it with H2O solution at least 3 times, and then dry it overnight under vacuum at 60 °C to obtain OsCu - O v (Cu - O v :Os = 25:1). It was found that the obtained OsCu - O v (Cu - O v :Os = 25:1) had poor POD activity ( Figure 13 ).

[0072] Comparative Example 1: Anchoring the noble metal Ru on Cu - O v to prepare RuCu - O v POD activity

[0073] Cu - O v Precursor: Mix 10 mL of deionized water containing 340.9 mg of CuCl2·xH2O with 15 mL of deionized water containing 3.154 g of HMT (hexamethylenetetramine, urotropine), then shake the mixture well, and further hydrothermally treat it in an autoclave at 95 °C for 5 h; then wash the precipitate with deionized water and dry it under vacuum.

[0074] Synthesis of the nanosensor material RuCu - O v : Disperse 50 mg of Cu - O vDispersed in a flask with 10 mL of deionized water and continuously ultrasonicated for 10 min; then 1 mL of an aqueous RuCl3·xH2O solution (concentration 10 mg mL -1 ) was poured into the above solution; stirred at room temperature for 24 h, the precipitate was collected and washed with H2O solution at least 3 times, and then dried overnight under vacuum at 60 °C to obtain RuCu-O v (Cu-O v :Ru = 5:1). It was found that the obtained RuCu-O v (Cu-O v :Ru = 5:1) had no POD activity ( Figure 13 ).

[0075] Comparative Example 2: The POD activity of FeCu-O v prepared by anchoring transition metal Fe on Cu-O v

[0076] Cu-O v Precursor: 10 mL of deionized water containing 340.9 mg of CuCl2·xH2O was mixed with 15 mL of deionized water containing 3.154 g of HMT (hexamethylenetetramine, urotropine), then the mixture was shaken well and further hydrothermally treated in an autoclave at 95 °C for 5 h; then the precipitate was washed with deionized water and dried under vacuum.

[0077] Synthesis of the nanosensor material FeCu-O v : 50 mg of Cu-O v was dispersed in a flask with 10 mL of deionized water and continuously ultrasonicated for 10 min; then 1 mL of an aqueous FeCl3 solution (concentration 10 mg mL -1 ) was poured into the above solution; stirred at room temperature for 24 h, the precipitate was collected and washed with H2O solution at least 3 times, and then dried overnight under vacuum at 60 °C to obtain FeCu-O v (Cu-O v :Fe = 5:1). It was found that the obtained FeCu-O v (Cu-O v :Fe = 5:1) had no POD activity ( Figure 13 ).

[0078] ​It should be noted that the description of the present invention provides preferred embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments do not serve as additional limitations to the content of the present invention. The purpose of providing these embodiments is to make the understanding of the disclosed content of the present invention more thorough and comprehensive. Moreover, the above technical features continue to be combined with each other to form various embodiments not listed above, which are all regarded as within the scope described in the specification of the present invention. Further, for those of ordinary skill in the art, improvements or transformations can be made based on the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A single-atom POD enzyme-mimicking nanomaterial, characterized in that, The single-atom POD enzyme-mimicking nanomaterial contains noble metal Os and defective metal oxide, wherein the defective metal oxide is an oxide of metal Cu, and the Os is anchored on the defective metal oxide in the form of single atoms; The single-atom POD enzyme-mimicking nanomaterial is prepared by the following method, and the preparation method includes the following steps: (1) Hydrothermally react a copper salt and an amine compound in water, and wash and dry the generated precipitate to obtain a defective metal oxide; the amine compound includes hexamethylenetetramine, and the conditions of the hydrothermal reaction are to react at 60-150 °C for 1-12 h; (2) Mix and stir the defective metal oxide obtained in step (1) with an Os salt in water so that Os is anchored on the defective metal oxide in the form of single atoms. After washing and drying the obtained precipitate, the single-atom POD enzyme-mimicking nanomaterial is obtained; The Os salt includes OsCl3•xH2O; The mass ratio of the defective metal oxide to the Os salt is 50:(2-25).

2. The single-atom POD enzyme-mimicking nanomaterial according to claim 1, characterized in that, The defective metal oxide is an oxygen vacancy defective metal oxide.

3. A method for preparing the single-atom POD enzyme-mimicking nanomaterial according to claim 1 or 2, characterized in that, Including the following steps: (1) Hydrothermally react a copper salt and an amine compound in water, and wash and dry the generated precipitate to obtain a defective metal oxide; the amine compound includes hexamethylenetetramine, and the conditions of the hydrothermal reaction are to react at 60-150 °C for 1-12 h; (2) Mix and stir the defective metal oxide obtained in step (1) with an Os salt in water so that Os is anchored on the defective metal oxide in the form of single atoms. After washing and drying the obtained precipitate, the single-atom POD enzyme-mimicking nanomaterial is obtained.

4. The method according to claim 3, wherein The copper salt includes CuCl2•xH2O; The mass ratio of the copper salt to the amine compound is 1:5-15.

5. The method according to claim 3, wherein The stirring includes stirring at 20-100 °C for 5-48 hours.

6. Use of the single-atom POD enzyme-mimicking nanomaterial according to claim 1 or 2 or the single-atom POD enzyme-mimicking nanomaterial prepared by the method according to any one of claims 3-5 in the preparation of a detection reagent having POD activity.

7. Use of the single-atom POD enzyme-mimicking nanomaterial according to claim 1 or 2 or the single-atom POD enzyme-mimicking nanomaterial prepared by the method according to any one of claims 3-5 in the colorimetric detection of hydrogen peroxide or nitrite.

8. A sensor for detecting hydrogen peroxide or nitrite, characterized in that, The sensor contains the single-atom POD enzyme-mimicking nanomaterial according to claim 1 or 2 or the single-atom POD enzyme-mimicking nanomaterial prepared by the method according to any one of claims 3-5.

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