Metal oxide sheet with spherical convex particles and oxygen vacancies enriched on surface, preparation method and application

Abstract

The invention relates to a metal oxide sheet with spherical convex particles and oxygen vacancies enriched on the surface, a preparation method and application. According to the sheet preparation method, metal oxide sheet xerogel is obtained through a heating bubbling method, and spherical convex particles and oxygen defects are enriched on the surface of the metal oxide sheet xerogel in combination with a staged annealing oxidation process. The diameter of the spherical convex particles on the surface of the thin sheet is 50-100 nm, the thickness of the thin sheet is 100-500 nm, the length and width size range of the thin sheet is not limited, and the thin sheet is suitable for various size specifications. The surface of the thin sheet is enriched with spherical convex particles and oxygen defects, so that adsorption sites with relatively high surface area / volume and high density can be provided, the surface electronic structure is improved, the electron transmission rate is accelerated, the sensing performance is enhanced, and the sensing stability is improved. The thin sheet has a wide application prospect in the fields of gas sensing, colorimetric sensing, fluorescence sensing, stress sensing, chemical sensing, photoelectric sensing and biological sensing.

Description

Technical Field

[0001] The present invention relates to a metal oxide flake with surface enriched spherical convex particles and oxygen defects, as well as its preparation method and application, belonging to the field of sensing technology. This invention relates to the design, modification, and application of function-oriented sensing micro-nanomaterials. The flake is prepared by synthesizing a metal oxide flake xerogel using a heated bubbling method, combined with a staged annealing and oxidation process, to enrich the spherical convex particles and oxygen defects on its surface. The flake can be applied in gas sensing, colorimetric sensing, fluorescence sensing, stress sensing, chemical sensing, photoelectric sensing, and biosensing. Background Art

[0002] In recent years, with the frequent occurrence of food safety issues internationally, the demand for faster and more accurate food freshness and safety monitoring has increased significantly. Traditional methods for detecting spoiled food and food contaminated with foodborne pathogens, such as sensory evaluation and PCR laboratory analysis, have significant shortcomings. Sensory testing is subject to significant subjectivity and struggles to detect early signs of spoilage. Laboratory analysis methods offer high accuracy but are complex and time-consuming (typically 2 to 48 hours), making them inadequate for rapid on-site testing.

[0003] Advances in sensor technology have provided new approaches and methods for addressing these issues, particularly the use of gas sensors for biomarker gas detection. During food spoilage, internal biochemical reactions continuously release characteristic spoilage gases such as ammonia and hydrogen sulfide. High-performance gas sensors can achieve highly sensitive detection of trace amounts (ppb concentrations) of these gases in the early stages of spoilage. Foodborne pathogens such as Pseudomonas aeruginosa, Salmonella, and Escherichia coli commonly metabolize biomarker gases such as 2-aminoacetophenone, 1-octen-3-ol, and indole. The development of high-performance sensing materials can enable accurate and early detection of these foodborne pathogens.

[0004] In current cutting-edge research, such sensing technologies often rely on the development of core sensing materials. For example, in 2022, the American journal ACS Sensors reported on a multi-walled carbon nanotube framework material modified with polypyrrole and modified with Pt nanodots. This material exhibited an ammonia detection limit as low as 5 ppb (ACS Sensors, 2022, 7, 874). In another example, in March 2025, an internationally recognized journal in the field of sensing reported on a polypyrrole-encapsulated iron vanadate nanorod material decorated with palladium nanoparticles, which successfully achieved chemiresistive detection of indole, a metabolite of Escherichia coli, exhibiting a stable sensing response in the concentration range of 1 to 50 ppm (Sensors and Actuators B: Chemical, 2025, 433, 137590). Although this type of research has made some progress, existing sensing materials have shortcomings in terms of long-term stability, sensing baseline, tolerance to corrosive gases, and selective detection of multiple marker gases. Currently, the design and regulation of such sensing materials is a technical problem that needs to be solved urgently. Summary of the Invention

[0005] In view of the technical shortcomings of existing sensing materials in terms of long-term stability, multi-gas selectivity and surface defect regulation, a metal oxide flake is provided that synergistically improves the sensing performance by constructing surface spherical convex particles and regulating oxygen defects, and a process method for its scalable preparation is provided to promote its application in the field of food health and safety monitoring. The flake is prepared by a heated bubbling method to obtain a metal oxide flake dry gel, and the spherical convex particles and oxygen defects are enriched on its surface through a staged annealing and oxidation process. The advantage of this flake is that the surface-enriched spherical convex particles and oxygen defects can provide a higher surface area / volume and high-density adsorption sites, improve the surface electronic structure, accelerate the electron transfer rate, enhance the sensing performance, and improve the sensing stability. The invention content of the metal oxide flake with surface enriched spherical convex particles and oxygen defects in the present invention is as follows: The diameter of the spherical convex particles on the surface of the thin slice is 50 to 100 nm, the thickness of the thin slice is 100 to 500 nm, and the length and width of the thin slice are not limited, and it is suitable for various sizes. The preparation steps are as follows: (1) Preparing a precursor solution: dissolving 0.01 to 1 M of a metal salt in a 0.01 to 1 M inorganic acid aqueous solution and stirring to obtain a solution A; dissolving 0.001 to 0.01 M of another heterogeneous metal salt in a 0.01 to 0.05 M inorganic acid aqueous solution and stirring to obtain a solution B, wherein the atomic ratio of the metal ion to the heterogeneous metal ion is (0.001 to 1):1; dissolving 0.001 to 0.01 M of the metal salt in water to obtain a solution C, wherein the atomic ratio of the rare earth ion to the metal ion is (0.001 to 1):1; adding solution C and solution B dropwise into solution A to obtain a precursor solution; (2) Synthesis of metal oxide thin sheet xerogel by bubbling method: 0.01 ~ 0.05 M alcohol compound is added to the precursor solution and stirred at room temperature for 1 ~ 10 hours for polymerization. The mixture is then placed in an environment of 100 ~ 200 °C for 1 ~ 10 hours. The product obtained by bubbling the solution is first washed with deionized water, and then frozen at -20 ~ -196 °C for 1 ~ 3 hours and freeze-dried to obtain metal oxide thin sheet xerogel; (3) Preparation of metal oxide flakes with surface enriched spherical convex particles and oxygen defects: The metal oxide flake dry gel is placed in a muffle furnace at 100 ~ 1000 ℃ for staged annealing, with a heating rate of 1 ~ 10 ℃ / min, annealing time of 0.5 ~ 5 hours, and a cooling rate of 1 ~ 10 ℃ / min, finally obtaining metal oxide flakes with surface enriched spherical convex particles and oxygen defects.

[0006] The method for preparing metal oxide flakes with surface enriched spherical protrusions and oxygen defects described in the present invention is characterized in that, in step (1), the metal salt in the solution A includes any one of copper chloride, zinc sulfate, ferric chloride, nickel nitrate, tin chloride, stannous chloride, indium nitrate and tungsten hexachloride, or a mixture of two or more thereof; the inorganic acid includes any one of sulfuric acid, hydrochloric acid, nitric acid, citric acid, boric acid and oxalic acid, or a mixture of two or more thereof; the heterogeneous metal salt in the solution B includes any one of aluminum sulfate, manganese sulfate, chromium chloride, molybdenum chloride, bismuth nitrate, iridium chloride and palladium chloride, or a mixture of two or more thereof; the rare earth salt includes any one of lanthanum chloride, cerium chloride, terbium chloride, samarium sulfate and yttrium chloride, or a mixture of two or more thereof; and in step (2), the alcohol compound includes any one of methanol, ethanol, ethylene glycol, propylene glycol, glycerol and isopropanol, or a mixture of two or more thereof.

[0007] The present invention provides applications for metal oxide flake sensing materials enriched with spherical convex particles and oxygen defects. These materials can be used in gas sensing, colorimetric sensing, fluorescence sensing, chemical sensing, photoelectric sensing, and biosensing for detecting early food spoilage and foodborne pathogens. The application of samarium aluminum co-doped tin oxide flakes enriched with spherical convex particles and oxygen defects in gas sensing is illustrated below: The samarium aluminum co-doped tin oxide thin-sheet sensing material, enriched with spherical convex particles and oxygen defects, exhibits excellent sensing performance for food spoilage marker gases and biomarker gases of foodborne pathogens. This is attributed to the synergistic effect of the surface spherical convex particles and the regulation of oxygen defects, which provide a high surface area / volume ratio and a high density of adsorption sites. This improves the surface electronic structure, accelerates electron transfer, enhances sensing performance, and improves sensing stability. This material has significant application prospects in the field of early warning of food safety and health. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a scanning electron microscope (SEM) image of a samarium aluminum co-doped tin oxide flake with surface enriched spherical convex particles and oxygen defects, showing that the surface of the flake is enriched with spherical convex particles with a diameter of 50 to 100 nm, and the flake thickness is 100 to 500 nm.

[0009] Figure 2 (a) X-ray diffraction pattern of samarium-aluminum co-doped tin oxide flakes with surface enriched spherical convex particles and oxygen defects, and (b) locally enlarged pattern, in which the absence of samarium and aluminum diffraction peaks and the shift of the diffraction peaks in (b) indicate the successful doping of samarium and aluminum in the prepared composite material.

[0010] Figure 3 This is the O 1s X-ray photoelectron spectrum of samarium aluminum co-doped tin oxide flakes with surface enriched spherical convex particles and oxygen defects. The prepared samarium aluminum co-doped tin oxide flakes with surface enriched spherical convex particles and oxygen defects are rich in defective oxygen.

[0011] Figure 4 The sensing response of samarium aluminum co-doped tin oxide thin films enriched with spherical convex particles and oxygen defects to various concentrations of H2S, a food spoilage marker gas, at 250 ℃.

[0012] Figure 5 The sensing response of samarium aluminum co-doped tin oxide thin films enriched with spherical convex particles and oxygen defects to 5 ppm concentration of foodborne pathogen metabolic biomarker gas at 250 °C. DETAILED DESCRIPTION

[0013] The present invention is described below by way of specific embodiments. Unless otherwise specified, the technical means used in the present invention are methods well known to those skilled in the art. In addition, the embodiments should be understood to be illustrative rather than limiting the scope of the present invention, the spirit and scope of the present invention being limited only by the claims. For those skilled in the art, various changes or modifications to the material components and dosages in these embodiments, without departing from the spirit and scope of the present invention, also fall within the scope of protection of the present invention. The raw materials and reagents used in the present invention are all commercially available.

[0014] Example 1 (1) Preparation of precursor solution. Dissolve 1 M copper chloride (CuCl2) in 1 M hydrochloric acid aqueous solution and stir to obtain solution A; dissolve 0.005 M aluminum sulfate (Al2(SO4)3) in 0.05 M hydrochloric acid (HCl) aqueous solution and stir to obtain solution B; dissolve 0.01 M lanthanum chloride (LaCl3) in water to obtain solution C. Add solution C and solution B dropwise to solution A to obtain a precursor solution; (2) Synthesis of lanthanum-aluminum co-doped copper oxide thin sheet xerogel by bubbling method. 0.01 M ethanol (C2H6O) was added to the precursor solution and stirred at room temperature for 6 hours to polymerize. The mixture was then placed in a 100 °C environment for 10 hours. The product obtained by bubbling the solution was then washed with deionized water and frozen at -20 °C for 3 hours before freeze-drying to obtain lanthanum-aluminum co-doped copper oxide thin sheet xerogel. (3) Preparation of lanthanum-aluminum co-doped copper oxide thin sheets with surface enriched spherical convex particles and oxygen defects. The lanthanum-aluminum co-doped copper oxide thin sheet xerogel was placed in a muffle furnace and annealed in stages at 300 °C and 1000 °C for 1 hour and 1 hour, respectively, with heating and cooling rates of 10 °C / min and 10 °C / min, respectively. Finally, lanthanum-aluminum co-doped copper oxide thin sheets with surface enriched spherical convex particles and oxygen defects were obtained.

[0015] Example 2 (1) Preparation of precursor solution. Dissolve 0.2 M zinc sulfate (ZnSO4) in 0.05 M sulfuric acid (H2SO4) aqueous solution and stir to obtain solution A; dissolve 0.001 M manganese sulfate (MnSO4) in 0.01 M hydrochloric acid aqueous solution and stir to obtain solution B; dissolve 0.01 M cerium chloride (CeCl3) in water to obtain solution C. Add solution C and solution B dropwise to solution A to obtain a precursor solution; (2) Synthesis of zinc oxide-supported manganese oxide / cerium oxide thin sheet xerogel by bubbling method. 0.01 M isopropyl alcohol (C3H8O) was added to the precursor solution and stirred at room temperature for 4 hours for polymerization. The mixture was then placed in a 120 °C environment for 3 hours. The product obtained by bubbling the solution was washed with deionized water and then frozen at -40 °C for 1.5 hours and freeze-dried to obtain zinc oxide-supported manganese oxide / cerium oxide thin sheet xerogel. (3) Preparation of zinc oxide / manganese oxide / cerium oxide thin sheets with surface enriched spherical convex particles and oxygen defects. The zinc oxide-supported manganese oxide / cerium oxide thin sheet xerogel was placed in a muffle furnace and annealed in stages at 350 °C, 400 °C, and 900 °C for 2 hours, 2 hours, and 2 hours, respectively, with heating and cooling rates of 3 °C / min and 5 °C / min, respectively. Finally, zinc oxide-supported manganese oxide / cerium oxide thin sheets with surface enriched spherical convex particles and oxygen defects were obtained.

[0016] Example 3 (1) Preparation of precursor solution. Dissolve 0.1 M ferric chloride (FeCl3) in 0.1 M boric acid (H3BO3) aqueous solution and stir to obtain solution A; dissolve 0.01 M chromium chloride (CrCl3) in 0.01 M boric acid (H3BO3) aqueous solution and stir to obtain solution B; dissolve 0.01 M terbium chloride (TbCl3) in water to obtain solution C. Add solution C and solution B dropwise into solution A to obtain a precursor solution; (2) Synthesis of chromium-doped iron oxide-supported terbium oxide thin sheet xerogel by bubbling method. 0.04M propylene glycol (C8H8O3) was added to the precursor solution and stirred at room temperature for 2 hours for polymerization. The mixture was then placed in an environment of 110°C for 9 hours. The product obtained by bubbling the solution was then washed with deionized water and then frozen at -25°C for 2 hours and freeze-dried to obtain chromium-doped iron oxide-supported terbium oxide thin sheet xerogel. (3) Preparation of chromium-doped iron oxide-supported terbium oxide thin sheets with surface enriched spherical convex particles and oxygen defects. The chromium-doped iron oxide-supported terbium oxide thin sheet xerogel was placed in a muffle furnace and annealed in stages at 200 °C, 300 °C, 500 °C, and 800 °C for 2 hours, 1 hour, 1 hour, and 3 hours, respectively, with heating and cooling rates of 5 °C / min and 8 °C / min, respectively. Finally, chromium-doped iron oxide-supported terbium oxide thin sheets with surface enriched spherical convex particles were obtained.

[0017] Example 4 (1) Preparation of precursor solution. Dissolve 0.02 M nickel nitrate (Ni(NO3)2) in 0.1 M citric acid (C6H8O7) aqueous solution and stir to obtain solution A; dissolve 0.002 M molybdenum chloride (MoCl5) in 0.02 M citric acid (C6H8O7) aqueous solution and stir to obtain solution B; dissolve 0.005 M samarium sulfate (Sm2(SO4)3) in water to obtain solution C. Add solution C and solution B dropwise into solution A to obtain a precursor solution; (2) Synthesis of samarium-doped nickel oxide-supported molybdenum oxide thin sheet xerogel by bubbling method. 0.02M propylene glycol (C3H8O2) was added to the precursor solution and stirred at room temperature for 1 hour for polymerization. The mixture was then placed in an environment of 180°C for 6 hours. The product obtained by bubbling the solution was then washed with deionized water and then frozen at -25°C for 2 hours and freeze-dried to obtain samarium-doped nickel oxide-supported molybdenum oxide thin sheet xerogel. (3) Preparation of samarium-doped nickel oxide-supported molybdenum oxide thin sheets with surface enriched spherical convex particles and oxygen defects. The samarium-doped nickel oxide-supported molybdenum oxide thin sheet xerogel was placed in a muffle furnace and annealed in stages at 100 °C, 500 °C, and 800 °C for 1 hour, 2 hours, and 3 hours, respectively, with heating and cooling rates of 10 °C / min and 10 °C / min, respectively. Finally, samarium-doped nickel oxide-supported molybdenum oxide thin sheets with surface enriched spherical convex particles and oxygen defects were obtained.

[0018] Example 5 (1) Preparation of precursor solution. Dissolve 0.4 M tin chloride (SnCl4) in 0.2 M oxalic acid (H2C2O4) aqueous solution and stir to obtain solution A; dissolve 0.008 M iridium chloride (IrCl3) in 0.01 M oxalic acid (H2C2O4) aqueous solution and stir to obtain solution B; dissolve 0.005 M yttrium chloride (YCl3) in water to obtain solution C. Add solution C and solution B dropwise into solution A to obtain a precursor solution; (2) Synthesis of tin oxide-supported iridium oxide / yttrium oxide thin sheet xerogel by bubbling method. 0.05M methanol (CH4O) was added to the precursor solution and stirred at room temperature for 3.5 hours to polymerize. The mixture was then placed in a 150°C environment for 6 hours. The product obtained by bubbling the solution was washed with deionized water and then frozen at -60°C for 1 hour and freeze-dried to obtain tin oxide-supported iridium oxide / yttrium oxide thin sheet xerogel. (3) Preparation of tin oxide-supported iridium oxide / yttrium oxide thin sheets with surface enriched spherical convex particles and oxygen defects. The tin oxide-supported iridium oxide / yttrium oxide thin sheet xerogel was placed in a muffle furnace and annealed in stages at 500 °C and 800 °C for 2 hours and 3 hours, respectively, with heating and cooling rates of 10 °C / min and 5 °C / min, respectively. Finally, tin oxide-supported iridium oxide / yttrium oxide thin sheets with surface enriched spherical convex particles and oxygen defects were obtained.

[0019] Example 6 (1) Preparation of precursor solution. Dissolve 0.1 M indium nitrate (In(NO3)3) in 0.2 M hydrochloric acid (HCl) aqueous solution and stir to obtain solution A; dissolve 0.009 M palladium chloride (PdCl2) in 0.05 M hydrochloric acid (HCl) aqueous solution and stir to obtain solution B; dissolve 0.01 M cerium chloride (CeCl3) in water to obtain solution C. Add solution C and solution B dropwise to solution A to obtain a precursor solution; (2) Synthesis of cerium-doped indium oxide-supported palladium oxide thin sheet xerogel by bubbling method. 0.015M isopropyl alcohol (C3H8O) was added to the precursor solution and stirred at room temperature for 3 hours to polymerize. The mixture was then placed in a 120°C environment for 6 hours. The product obtained by bubbling the solution was washed with deionized water and then frozen at -196°C for 1 hour and freeze-dried to obtain cerium-doped indium oxide-supported palladium oxide thin sheet xerogel. (3) Preparation of cerium-doped indium oxide-supported palladium oxide thin sheets with surface enriched spherical convex particles and oxygen defects. The cerium-doped indium oxide-supported palladium oxide thin sheet dry gel was placed in a muffle furnace and annealed in stages at 200 °C, 500 °C, and 800 °C for 3 hours, 3 hours, and 3 hours, respectively, with heating and cooling rates of 10 °C / min and 10 °C / min, respectively. Finally, cerium-doped indium oxide-supported palladium oxide thin sheets with surface enriched spherical convex particles and oxygen defects were obtained.

[0020] Example 7 (1) Preparation of precursor solution. Dissolve 0.4 M tungsten hexachloride (WCl6) in 1 M boric acid (H3BO3) aqueous solution and stir to obtain solution A; dissolve 0.005 M bismuth nitrate (Bi(NO3)3) in 0.03 M boric acid (H3BO3) aqueous solution and stir to obtain solution B; dissolve 0.005 M samarium sulfate (Sm2(SO4)3) in water to obtain solution C. Add solution C and solution B dropwise into solution A to obtain a precursor solution; (2) Synthesis of bismuth-samarium co-doped tungsten oxide thin sheet xerogel by bubbling method. 0.01 M isopropyl alcohol (C3H8O) was added to the precursor solution and stirred at room temperature for 2 hours to polymerize. The mixture was then placed in a 130 °C environment for 5 hours. The product obtained by bubbling the solution was washed with deionized water and then frozen at -100 °C for 1 hour and freeze-dried to obtain bismuth-samarium co-doped tungsten oxide thin sheet xerogel. (3) Preparation of bismuth-samarium co-doped tungsten oxide thin sheets with surface enriched spherical convex particles and oxygen defects. The bismuth-samarium co-doped tungsten oxide thin sheet xerogel was placed in a muffle furnace and annealed in stages at 300 ℃, 400 ℃ and 700 ℃ for 1 hour, 3 hours and 3 hours, respectively, with heating and cooling rates of 10 ℃ / min and 10 ℃ / min, respectively. Finally, bismuth-samarium co-doped tungsten oxide thin sheets with surface enriched spherical convex particles and oxygen defects were obtained.

[0021] Example 8 (1) Preparation of precursor solution. Dissolve 0.05 M tin chloride (SnCl4) in 0.05 M nitric acid (HNO3) aqueous solution and stir to obtain solution A; dissolve 0.001 M chromium chloride (CrCl3) and manganese sulfate (MnSO4) in 0.05 M boric acid (H3BO3) aqueous solution and stir to obtain solution B; dissolve 0.01 M cerium chloride (CeCl3) in water to obtain solution C. Add solution C and solution B dropwise into solution A to obtain a precursor solution; (2) Synthesis of manganese, chromium, and cerium co-doped tin oxide thin sheet xerogel by bubbling method. 0.01 M propylene glycol (C3H8O2) was added to the precursor solution and stirred at room temperature for 3 hours to polymerize. The mixture was then placed in a 120 °C environment for 3 hours. The product obtained by bubbling the solution was washed with deionized water and then frozen at -51 °C for 2 hours and freeze-dried to obtain manganese, chromium, and cerium co-doped tin oxide thin sheet xerogel. (3) Preparation of Mn / Cr / Ce co-doped tin oxide thin sheets with surface enriched spherical convex particles and oxygen defects. The Mn / Cr / Ce co-doped tin oxide thin sheet dry gel was placed in a muffle furnace and annealed in stages at 400°C, 500°C, and 600°C for 3 hours, 2 hours, and 3 hours, respectively, with heating and cooling rates of 3°C / min and 10°C / min, respectively. Finally, Mn / Cr / Ce co-doped tin oxide thin sheets with surface enriched spherical convex particles and oxygen defects were obtained.

[0022] Example 9 (1) Preparation of precursor solution. Dissolve 0.05 M zinc sulfate (ZnSO4) in 0.03 M nitric acid (HNO3) aqueous solution and stir to obtain solution A; dissolve 0.005 M aluminum sulfate (Al2(SO4)3) in 0.02 M boric acid (H3BO3) aqueous solution and stir to obtain solution B; dissolve 0.01 M lanthanum chloride (LaCl3) in water to obtain solution C. Add solution C and solution B dropwise into solution A to obtain a precursor solution; (2) Synthesis of lanthanum-doped zinc oxide-supported alumina thin sheet xerogel by bubbling method. 0.05M methanol (CH4O) and ethylene glycol (C2H6O2) were added to the precursor solution and stirred at room temperature for 2 hours for polymerization. The mixture was then placed in a 120°C environment for 10 hours. The product obtained by bubbling the solution was then washed with deionized water and then frozen at -196°C for 3 hours and freeze-dried to obtain lanthanum-doped zinc oxide-supported alumina thin sheet xerogel. (3) Preparation of lanthanum-doped zinc oxide-supported alumina sheets with surface enriched spherical convex particles and oxygen defects. The lanthanum-doped zinc oxide-supported alumina sheet dry gel was placed in a muffle furnace and annealed in stages at 200 °C, 300 °C, 600 °C, and 900 °C for 1 hour, 4 hours, 3 hours, and 3 hours, respectively, with heating and cooling rates of 10 °C / min and 10 °C / min, respectively. Finally, lanthanum-doped zinc oxide-supported alumina sheets with surface enriched spherical convex particles and oxygen defects were obtained.

Claims

1. A metal oxide flake having a surface enriched with spherical convex particles and oxygen defects, characterized in that: The thin slices are chemically composed of metal oxides; the diameter of the spherical convex particles on the surface of the thin slices is 50 to 100 nm, the thickness of the thin slices is 100 to 500 nm, and the length and width of the thin slices are not limited, and are suitable for various sizes. The preparation steps are as follows: (1) Preparing a precursor solution: dissolving 0.01 to 1 M of a metal salt in a 0.01 to 1 M inorganic acid aqueous solution and stirring to obtain a solution A; dissolving 0.001 to 0.01 M of another heterogeneous metal salt in a 0.01 to 0.05 M inorganic acid aqueous solution and stirring to obtain a solution B, wherein the atomic ratio of the metal ion to the heterogeneous metal ion is (0.001 to 1):1; dissolving 0.001 to 0.01 M of a rare earth salt in water to obtain a solution C, wherein the atomic ratio of the rare earth ion to the metal ion is (0.001 to 1):1; adding solution C and solution B dropwise into solution A to obtain a precursor solution; (2) Synthesis of metal oxide thin sheet xerogel by bubbling method: 0.01 ~ 0.05 M alcohol compound is added to the precursor solution and stirred at room temperature for 1 ~ 10 hours for polymerization. The mixture is then placed in an environment of 100 ~ 200 °C for 1 ~ 10 hours. The product obtained by bubbling the solution is first washed with deionized water, and then frozen at -20 ~ -196 °C for 1 ~ 3 hours and freeze-dried to obtain metal oxide thin sheet xerogel; (3) Preparation of metal oxide flakes with surface enriched spherical convex particles and oxygen defects: The metal oxide flake dry gel is placed in a muffle furnace at 100 ~ 1000 ℃ for staged annealing, with a heating rate of 1 ~ 10 ℃ / min, annealing time of 0.5 ~ 5 hours, and a cooling rate of 1 ~ 10 ℃ / min, finally obtaining metal oxide flakes with surface enriched spherical convex particles and oxygen defects.

2. The metal oxide flake having surface enriched spherical protrusions and oxygen defects according to claim 1, wherein the surface chemical state of the metal oxide flake is characterized by: the surface of the flake material is enriched with defective oxygen, wherein the atomic ratio of defective oxygen to the oxygen content in the material is 10% to 60%.

3. The chemical composition of the metal oxide flakes enriched with spherical protrusion particles and oxygen defects on the surface according to claim 1, characterized in that: The atomic ratio of heterogeneous metal ions to metal ions is (0.001 ~ 1):1; the atomic ratio of rare earth ions to metal ions is (0.001 ~ 1):

1.

4. The chemical composition of the metal oxide flakes enriched with spherical protrusion particles and oxygen defects on the surface according to claim 1, characterized in that: In step (1), the metal salt in the solution A includes any one of copper chloride, zinc sulfate, ferric chloride, nickel nitrate, tin chloride, stannous chloride, indium nitrate and tungsten hexachloride, or a mixture of two or more thereof; the inorganic acid includes any one of sulfuric acid, hydrochloric acid, nitric acid, citric acid, boric acid and oxalic acid, or a mixture of two or more thereof; the heterogeneous metal salt in the solution B includes any one of aluminum sulfate, manganese sulfate, chromium chloride, molybdenum chloride, bismuth nitrate, iridium chloride and palladium chloride, or a mixture of two or more thereof; the rare earth salt includes any one of lanthanum chloride, cerium chloride, terbium chloride, samarium sulfate and yttrium chloride, or a mixture of two or more thereof; in step (2), the alcohol compound includes any one of methanol, ethanol, ethylene glycol, propylene glycol, glycerol and isopropanol, or a mixture of two or more thereof.

5. The metal oxide flake having surface enriched spherical protrusion particles and oxygen defects according to claim 1, characterized in that: When using the bubbling method, the reaction temperature is controlled at 100 ~ 200 ° C and kept at this temperature for 1 to 10 hours; during the freeze-drying process, the product is first frozen at -20 ~ -196 ° C for 1 to 3 hours; the staged annealing includes 2 to 4 stages, and the annealing temperature is controlled at 100 ~ 1000 ° C.

6. The method for preparing a metal oxide flake having surface enriched spherical convex particles and oxygen defects according to any one of claims 1 to 5, wherein the prepared micro-nanostructured material has surface enriched spherical convex particles and oxygen defects.

7. The metal oxide flakes having surface-enriched spherical protrusions and oxygen defects according to claim 1 , wherein the metal oxide flakes are characterized in their microscopic geometric morphology by: the spherical protrusions being enriched on the surface of the metal oxide flakes; the spherical protrusions having a diameter of 50 to 100 nm; the thickness of the flakes being 100 to 500 nm; and the length and width of the flakes being unrestricted and applicable to a variety of sizes.

8. The metal oxide flakes with surface enriched spherical convex particles and oxygen defects according to claim 1, wherein the metal oxides include but are not limited to monovalent, divalent and polyvalent metal oxides, as well as metal oxides modified by monovalent, divalent and polyvalent heterogeneous metal doping.

9. Use of the metal oxide flakes enriched with spherical protrusion particles and oxygen defects on the surface as a sensing material according to claim 1, characterized in that: Used in the fields of gas sensing, colorimetric sensing, fluorescence sensing, stress sensing, chemical sensing, photoelectric sensing and biosensing, specifically including but not limited to harmful gas detection, biomolecule recognition, food spoilage monitoring, stress sensing monitoring, chemical reaction monitoring and photoelectric device manufacturing.

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