Mn2O3 / RuO2 / NCS composite nanosphere as well as preparation method and application thereof

Abstract

The invention discloses a Mn2O3 / RuO2 / NCS composite nano-sphere as well as a preparation method and application thereof, and belongs to the field of oxide-like enzymes. The invention aims to overcome the defects of single active site, low electron transfer efficiency, insufficient multifunctional synergy and the like of phase metal oxide nano-enzyme. According to the invention, Mn2O3 / RuO2 / NCS composite nano-enzyme with a yolk-shell structure is synthesized by adopting a hydrothermal method, and Mn2O3 and RuO2 nano-particles are loaded on a carbon-based material with high conductivity. The material disclosed by the invention has the structural characteristics of a microsphere structure, abundant pore channels, high specific surface area, multiple active sites, high conductivity, good hydrophilicity, tight electron contact between Mn2O3 and RuO2 and the like. Oxide-like enzyme activity experiments show that the Mn2O3 / RuO2 / NCS nano-composite has very excellent nano-enzyme activity, and shows excellent affinity (Km is equal to 0.1587 mM) and reaction speed Vmax is equal to 0.02987 uM / s).

Description

Technical Field

[0001] The present invention belongs to the field of peroxidase-like enzymes, and specifically relates to an Mn2O3 / RuO2 / NCS composite nanosphere and its preparation method and application. Background Art

[0002] Nanozymes are a class of nanomaterials with enzyme catalytic functions. They can combine the characteristics of nanomaterials and natural enzymes, catalyze reactions under normal temperature and pressure, and have the advantages of high efficiency, strong stability, low cost, and easy large-scale preparation. They show broad application prospects in the fields of environmental governance, food detection, chemical production, biomedicine, etc. In recent years, a large number of nanomaterials have been found to have nanozyme activity. Common nanozymes mainly include metal nanozymes (such as Au, Ag), metal oxide nanozymes (such as Fe3O4, CeO2), carbon-based nanozymes (such as graphene, fullerene), and composite nanozymes.

[0003] Among many nanozymes, metal oxide nanozymes have the advantages of simple structure, convenient preparation, and high catalytic activity, and are actually applied to highly sensitive colorimetric sensors for detecting biomarkers and hydrogen peroxide. However, these single-phase metal oxide nanozymes have defects such as single active sites, low electron transfer efficiency, and insufficient multi-functional synergy, which limit their applications. Summary of the Invention

[0004] The present invention provides an Mn2O3 / RuO2 / NCS composite nanosphere and its preparation method and application. The Mn2O3 / RuO2 / NCS composite metal oxide of the present invention is used as a nanozyme, and has the advantages of adjustable metal types, ratios, morphologies, and structures, synergistic effects of multiple active sites, and multiple functional bindings, making it superior to single-phase metal oxide nanozymes in terms of controllability, catalytic activity, stability, and application universality, and showing greater application potential.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The purpose of the present invention is to provide a preparation method of an Mn2O3 / RuO2 / NCS composite nanosphere, comprising the following steps:

[0007] Step 1. Completely dissolve CTAB (cetyltrimethylammonium bromide) in water, ultrasonically disperse it until it is clear, add glucose, stir until a colorless and transparent solution is formed, perform a hydrothermal reaction, cool to room temperature after the reaction is completed, wash with water, centrifuge, and dry to obtain carbon spheres (CS);

[0008] Step 2. Add urea into water, stir vigorously until it is completely dissolved, then add RuCl3 and MnSO4·H2O, stir until dissolved to form a brown transparent solution. Then add carbon spheres, stir for 30 min, disperse ultrasonically until uniform, conduct hydrothermal reaction. After the reaction is completed, cool down to room temperature, wash with water until the upper solution is clear and transparent, centrifuge, dry, and calcine in an air atmosphere to obtain Mn2O3 / RuO2 / NCS composite nanospheres with peroxidase-like activity.

[0009] Further defined, in step 1, the mass ratio of CTAB to the volume of water is 0.5 g∶70 mL.

[0010] Further defined, in step 1, the mass ratio of CTAB to glucose is 0.5∶3.5.

[0011] Further defined, in step 1, conduct hydrothermal reaction at 180 °C for 6 h.

[0012] Further defined, in step 1, dry at 60 °C.

[0013] Further defined, in step 2, the mass ratio of urea to the volume of water is 1 g∶10 mL.

[0014] Further defined, in step 2, the mass ratio of urea, RuCl3, MnSO4·H2O and carbon spheres is 1∶0.035∶0.012∶0.1.

[0015] Further defined, in step 2, conduct hydrothermal reaction at 140 °C for 8 h.

[0016] Further defined, in step 2, calcine at 400 °C for 8 h.

[0017] Further defined, in step 2, dry at 60 °C.

[0018] A kind of Mn2O3 / RuO2 / NCS composite nanospheres prepared by any of the above methods.

[0019] Further defined, in the composite nanospheres, Mn2O3 and RuO2 are uniformly dispersed in nitrogen-rich carbon spheres, Mn2O3 and RuO2 have a heterostructure, and C, N, O, Ru and Mn elements are uniformly distributed in the whole Mn2O3 / RuO2 / NCS material.

[0020] A kind of Mn2O3 / RuO2 / NCS composite nanospheres prepared by any of the above methods is used as peroxidase-like enzyme.

[0021] The present invention synthesizes a Mn2O3 / RuO2 / NCS composite nanozyme with a yolk-shell structure by a hydrothermal method, that is, loading Mn2O3 and RuO2 nanoparticles onto a carbon-based material with high electrical conductivity. The material of the present invention has a microsphere structure, with rich pores, a high specific surface area, many active sites, strong electrical conductivity, good hydrophilicity, and close electronic contact between Mn2O3 and RuO2. The peroxidase-like activity experiment shows that the Mn2O3 / RuO2 / NCS nano-composite has very excellent nanozyme activity, showing excellent affinity (Km = 0.1587 mM) and reaction rate Vmax = 0.02987 uM / s).

[0022] In order to further understand the features and technical content of the present invention, please refer to the following detailed description of the present invention and the attached drawings. However, the attached drawings are only for reference and illustration purposes and are not used to limit the present invention. Brief Description of the Drawings

[0023] Figure 1 a is the synthesis flow chart of Mn2O3 / RuO2 / NCS;

[0024] Figure 1 b is the TEM image of carbon spheres;

[0025] Figure 1 c is the TEM image of Mn-Ru-NCS;

[0026] Figure 1 d is the TEM image of Mn2O3 / RuO2 / NCS.

[0027] Figure 1 e is the HRTEM image of Mn2O3 / RuO2 / NCS;

[0028] Figure 1 f-k are the elemental distribution mapping diagrams of Mn2O3 / RuO2 / NCS;

[0029] Figure 2a is the X-ray diffraction (XRD) pattern of Mn2O3 / RuO2 / NCS;

[0030] Figure 2b is the X-ray photoelectron spectroscopy (XPS) of Mn2O3 / RuO2 / NCS;

[0031] Figure 2c is the XPS spectrum analysis of Ru 3p in Mn2O3 / RuO2 / NCS;

[0032] Figure 3 a is the actual result diagram of Mn2O3 / NCS catalyzing the substrate;

[0033] Figure 3b is the actual result diagram of the Mn2O3 / RuO2 / NCS-catalyzed substrate;

[0034] Figure 3 c is the absorbance curve of Mn2O3 / NCS at different substrate concentrations;

[0035] Figure 3 d is the absorbance curve of Mn2O3 / RuO2 / NCS at different substrate concentrations. Detailed implementation mode

[0036] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, and at the same time do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0037] Example 1: The preparation method of the Mn2O3 / RuO2 / NCS composite nanospheres in this example is prepared according to the following steps:

[0038] Preparation of the precursor CS: 0.5 g of CTAB (cetyltrimethylammonium bromide) was dispersed in 70 mL of water, stirred until completely dissolved, ultrasonically dispersed until clear, 3.5 g of glucose was added, and stirred until a colorless and transparent solution was formed. Then, it was loaded into a 100 mL hydrothermal reactor, hydrothermally reacted at 180 °C for 6 h, and after the reactor was cooled to room temperature, the obtained solution was washed with water, centrifuged at 10000 rpm for 5 min, and the obtained product was dried overnight at 60 °C to obtain carbon spheres (CS).

[0039] Preparation of the Mn2O3 / RuO2 / NCS composite nanospheres: 1 g of urea was added to 10 mL of water and stirred vigorously until completely dissolved. Subsequently, 0.035 g of RuCl3 and 0.012 g of MnSO4·H2O were added and stirred until dissolved to form a brown transparent solution. Then, 0.1 g of the precursor carbon spheres (CS) was added, stirred for 30 min, and ultrasonically dispersed until uniform. The above-mentioned uniformly mixed solution was loaded into a 50 mL reaction kettle, hydrothermally reacted at 140 °C for 8 h, and after the reaction kettle was cooled to room temperature, it was washed with water (10000 rpm, 5 min) until the upper solution was clear and transparent. The centrifuged sample was dried overnight at 60 °C to obtain Mn-Ru-NCS. The obtained brown powder Mn-Ru-NCS was calcined in an air atmosphere at 400 °C for 8 h to obtain the Mn2O3 / RuO2 / NCS composite nanospheres.

[0040] Determination of the pseudo-enzymatic activity of the Mn2O3 / RuO2 / NCS composite nanospheres:

[0041] 1) In the dark, dissolve TMB in dimethyl sulfoxide to obtain a TMB solution with a concentration of 10 mg / mL;

[0042] 2) Mix 74 mL of 0.2 mol / L acetic acid solution with 6 mL of 0.2 mol / L sodium acetate solution to obtain a NaAc-HAc solution with a pH of 3.6;

[0043] 3) The Mn2O3 / RuO2 / NCS composite nanospheres were ultrasonically dispersed in deionized water to obtain a material with a concentration of 1.5 mg / mL. 10 μL of the material was mixed with different volumes of TMB solution (0, 3.6, 7.2, 28.8, 50, 72 μL) and 0.2 mol / L NaAc-HAc buffer in a brown centrifuge tube to a total volume of 3 mL. The reaction was carried out for 4 min. The absorbance of the reaction system was detected at a wavelength of 652 nm. According to A = εcl (ε = 39000 M -1 cm -1 ) The absorbance A is converted to c, and then the reaction rate is calculated. By fitting the reaction velocity value v and substrate concentration to the Michaelis-Menten equation, the kinetic constants Vmax and Km can be calculated: Km = 0.1587 mM, and the reaction velocity Vmax = 0.02987 uM / s.

[0044] Structural and performance characterization

[0045] like Figure 1 As shown in a, the yolk-shell structure of Mn2O3 / RuO2 / NCS nanozyme can be prepared by a simple thermal oxidation method. First, glucose was used as the carbon source and cetyltrimethylammonium bromide (CTAB) was used as a surfactant to control the size of carbon spheres (CS). The uniformly dispersed carbon spheres with a size of about 300 nm were synthesized ( Figure 1 b) The metal cations (Mn 2+ Ru 3 + ) was impregnated into the interior and surface of the carbon spheres and pre-crystallized under hydrothermal conditions to form a Mn-Ru-CS precursor ( Figure 1 c). The subsequent oxidation process in a muffle furnace further leads to oxidative shrinkage of the Mn-Ru-CS precursor, ultimately forming a yolk-shell structured Mn2O3 / RuO2 / NCS nanocomposite (NCS represents N-doped carbon spheres) according to the Kirkendall effect. Figure 1d shows that the average diameter of the Mn2O3 / RuO2 / NCS yolk-shell spheres is about 150 nm. It is worth noting that after the oxidation treatment, the surface of the material becomes rough and porous due to the bubbling effect of the gaseous products generated by the pyrolysis of urea. This rich internal space, rough surface and porous yolk-shell structure are conducive to exposing more active sites and promoting mass transfer. At the same time, the outer shell can effectively prevent the corrosion of active sites in the acid-base system and maintain the stability of catalysis. Figure 1 The high-resolution TEM (HRTEM) image of e shows the (222) crystal plane of Mn2O3 and the (110) crystal plane of RuO2. There is an obvious heterointerface between the two crystals, indicating that the heterostructure of Mn2O3 and RuO2 has been successfully constructed. Figure 1 The EDS elemental mapping diagrams of f-k clearly confirm that Mn2O and RuO2 are uniformly dispersed in the nitrogen-rich carbon spheres, and the elements C, N, O, Ru and Mn are uniformly distributed throughout the Mn2O3 / RuO2 / NCS material.

[0046] The crystal structure of the synthesized Mn2O3 / RuO2 / NCS was studied by X-ray diffraction (XRD) patterns. As Figure 2a shown, the XRD peaks of Mn2O3 / RuO2 / NCS are in good agreement with the standard cards of Mn2O3 (JCPDS No. 41-1442) and RuO2 (JCPDS No. 43-1027), indicating the successful preparation of the Mn2O3 / RuO2 heterojunction structure. Figure 2b X-ray photoelectron spectroscopy (XPS) was used to further analyze the surface valence states of the components in Mn2O3 / RuO2 / NCS. Among them,

[0047] The XPS spectrum of Mn 2p can be divided into four binding energy peaks, located at 641.5, 642.6, 644.5 and 646.0 eV respectively, corresponding to Mn 2+ , Mn 3+ , Mn 4+ and satellite peaks. It is worth noting that compared with pure Mn2O3 / NCS, the characteristic peaks of Mn in Mn2O3 / RuO2 / NCS show a positive shift as a whole, indicating the escape of surface electrons after the coupling of Mn2O3 and RuO2. The XPS spectrum analysis of Ru 3p in Mn2O3 / RuO2 / NCS ( Figure 2c ) shows that the two peaks at 465.0 and 462.4 eV are attributed to Ru 4+ and Ru 3+, there is a slight negative shift of 0.2 eV compared with RuO2 / NCS. These results confirm that the formation energy of the Mn2O3 / RuO2 heterostructure can effectively trigger the redistribution of electrons at the surface / interface, and the direction of electron transfer should be from Mn to Ru. The electron transfer between active species will promote the catalytic reaction of the nanozyme-like.

[0048] Nanozyme activity test experiment

[0049] Mn2O3 / RuO2 / NCS catalyzes the substrate to undergo a redox reaction, producing a product with an absorption peak at 652 nm, and its peroxidase-like activity can be evaluated by measuring the absorbance and calculating. The experimental results show that the peroxidase-like activity of Mn2O3 / RuO2 / NCS is better than that of Mn2O3 / NCS, and this advantage is mainly manifested in higher catalytic efficiency and substrate affinity. During the experiment, as Figure 3 a, 3b show that the catalytic efficiency of Mn2O3 / RuO2 / NCS is better than that of Mn2O3 / NCS. As the test amount of the TMB solution increases, the color of the solution gradually deepens, and the color of Mn2O3 / RuO2 / NCS is deeper than that of Mn2O3 / NCS, which indicates that the yolk-shell structure, rich pores and high specific surface area of Mn2O3 / RuO2 / NCS can provide more active sites, accelerate the reaction process, and thus improve the efficiency of catalyzing the substrate. As Figure 3 c, 3d show that the absorbance measured by Mn2O3 / RuO2 / NCS increases significantly with the increase of the concentration of the substrate TMB solution. Although the absorbance measured by Mn2O3 / NCS also increases slightly, its absorbance is much smaller than that of Mn2O3 / RuO2 / NCS, and the change is not obvious and relatively messy. The higher reaction rate V of Mn2O3 / RuO2 / NCS indicates that it can have a higher catalytic efficiency at saturation or higher concentrations, and the lower Michaelis constant Km further indicates that it can bind tightly to the substrate and can efficiently catalyze the substrate at lower concentrations, which is of great significance. This characteristic reflects that Mn2O3 / RuO2 / NCS can maintain high-efficiency and good catalytic performance at different substrate concentrations, and its catalytic efficiency is much higher than that of Mn2O3 / NCS.

[0050] The specific embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A preparation method of Mn2O3 / RuO2 / NCS composite nanospheres, characterized in that, It includes the following steps: Step 1. Completely dissolve CTAB in water, ultrasonically disperse it until it becomes clear, add glucose, stir until a colorless and transparent solution is formed, perform hydrothermal reaction, after the reaction is completed, cool down to room temperature, wash with water, centrifuge, and dry to obtain carbon spheres; Step 2. Add urea to water, vigorously stir until it is completely dissolved, then add RuCl3 and MnSO4·H2O, stir until dissolved to form a brown transparent solution, then add carbon spheres, stir for 30 min, ultrasonically disperse until uniform, perform hydrothermal reaction, after the reaction is completed, cool down to room temperature, wash with water until the upper solution is clear and transparent, centrifuge, dry, and calcine in an air atmosphere to obtain the nanozyme-like Mn2O3 / RuO2 / NCS composite nanospheres.

2. The method according to claim 1, wherein The mass ratio of CTAB to the volume of water is 0.5 g∶70 mL, and the mass ratio of CTAB to glucose is 0.5∶3.

5.

3. The method according to claim 1, wherein In Step 1, perform hydrothermal reaction at 180 °C for 6 h.

4. The method according to claim 1, wherein The mass ratio of urea to the volume of water is 1 g∶10 mL, and the mass ratio of urea, RuCl3, MnSO4·H2O, and carbon spheres is 1∶0.035∶0.012∶0.

1.

5. The method according to claim 1, wherein In Step 2, perform hydrothermal reaction at 140 °C for 8 h.

6. The method according to claim 1, wherein Calcine at 400 °C for 8 h.

7. The method according to claim 1, wherein Both Step 1 and Step 2 are dried at 60 °C.

8. The Mn2O3 / RuO2 / NCS composite nanospheres prepared by the method according to any one of claims 1-7.

9. The composite nanospheres according to claim 8, wherein, In the said composite nanospheres, Mn2O3 and RuO2 are uniformly dispersed in the nitrogen-rich carbon spheres, Mn2O3 and RuO2 have a heterostructure, and the elements C, N, O, Ru, and Mn are uniformly distributed throughout the Mn2O3 / RuO2 / NCS material.

10. The Mn2O3 / RuO2 / NCS composite nanospheres prepared by the method according to any one of claims 1-7 are used as nanozymes.

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