Method for preparing micro-nano copper oxide powder through microwave method and application of micro-nano copper oxide powder

Abstract

The invention discloses a method for preparing micro-nano copper oxide powder through a microwave method and application of the micro-nano copper oxide powder. The method comprises the following steps: a) preparing a copper ion solution; b) adding a dispersing agent and a surfactant; c) adding urea; d) microwave heating reaction; e) separating and purifying a product; and f) drying and calcining. According to the preparation method, the rapid heating characteristic of microwave radiation is utilized, the effect of urea is combined, dispersing agents such as polyvinylpyrrolidone (PVP) and the like and surface active agents are added into a solution containing copper ions, the copper oxide nano-particles with the particle size distribution being 50-100 nanometers and even being controllable to be in the micron order are prepared, and the copper oxide nano-particles have good crystal structures and dispersity; the method is simple in process, high in reaction speed and low in energy consumption, and the obtained copper oxide nano particles can be used for preparing high-performance and high-purity copper oxide nano materials and have wide application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterial preparation, and particularly to a method for preparing micro-nano copper oxide powder by microwave method and its application. Background Art

[0002] Copper oxide (CuO) is an important transition metal oxide with unique physical and chemical properties, such as narrow bandgap semiconductor properties, excellent catalytic activity, optical properties, thermal stability, etc. Therefore, CuO nanomaterials have wide applications in the fields of photocatalysis, batteries, gas sensors, magnetic materials, and electronic devices.

[0003] Currently, the methods for preparing CuO nanomaterials include sol-gel method, hydrothermal / solvothermal method, microemulsion method, chemical precipitation method, thermal decomposition method, etc.

[0004] However, these traditional methods have the following problems:

[0005] 1. Harsh reaction conditions: High-temperature and high-pressure equipment is required, increasing the complexity and danger of experiments;

[0006] 2. Long reaction time: The preparation process takes a long time, affecting production efficiency;

[0007] 3. Difficult to control particle size: It is difficult to achieve precise control of the size and morphology of nanoparticles;

[0008] 4. Poor dispersibility: Agglomeration is likely to occur, affecting the material properties;

[0009] Therefore, developing a method for preparing CuO nanoparticles with mild reaction conditions, simple process, rapid reaction, and controllable particle size and morphology has important research value and practical significance, and is also a technical problem that the present invention urgently needs to solve. Summary of the Invention

[0010] In view of this, the present invention provides a method for preparing micro-nano copper oxide powder by microwave method and its application.

[0011] To solve the above technical problems, the present invention adopts the following technical solutions:

[0012] A method for preparing micro-nano copper oxide powder by microwave method, comprising the following steps:

[0013] a) Prepare a copper ion solution: Dissolve a soluble copper salt in deionized water to obtain a copper ion solution;

[0014] b) Add a dispersant and a surfactant: Add a dispersant and a surfactant to the copper ion solution in step a), stir evenly to form a clear solution;

[0015] c) Adding urea: Under stirring, add urea in proportion and continue stirring to obtain a reaction mixture;

[0016] d) Microwave heating reaction: Transfer the reaction mixture obtained in step c) to a microwave reaction vessel and heat;

[0017] e) Product separation and purification: After the reaction is completed, cool, centrifuge to separate the product, wash to remove impurities;

[0018] f) Drying and calcination: Dry the product at a low temperature and then calcine to obtain micro-nano copper oxide powder.

[0019] Preferably, in step a), the soluble copper salt is one or more of copper acetate, copper nitrate or copper sulfate.

[0020] Preferably, in step b), the dispersant is polyvinylpyrrolidone PVP or polyethylene glycol PEG.

[0021] Preferably, in step b), the surfactant is sodium dodecyl sulfate SDS or Tween 80.

[0022] Preferably, in step c), the molar ratio of urea to copper ions is 1:1 to 5:1.

[0023] Preferably, in step d), the microwave power is 400 - 800 W, the heating time under the microwave power is 1 - 10 minutes, and the temperature of microwave heating is 60 - 100 °C.

[0024] Preferably, in step e), the washing is to wash repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities.

[0025] Preferably, in step f), the drying temperature at low temperature is 60 - 70 °C, the drying time is 10 - 12 hours; the calcination temperature is 300 - 400 °C, and the calcination time is 2 hours.

[0026] Preferably, in step f), the particle size distribution of the copper oxide nanoparticles is 50 - 100 nanometers.

[0027] An application of a method for preparing micro-nano copper oxide powder by microwave method in a gas sensor. Using the copper oxide nanoparticles as a sensitive material, it can be used to detect toxic gases such as formaldehyde, carbon monoxide, and ammonia.

[0028] The present invention has achieved the following technical effects compared with the prior art:

[0029] (1) By the coordinated regulation of the molar ratio of urea addition of 1:1 - 5:1 and the microwave power of 400 - 800 W, the present invention realizes the continuous controllable synthesis of nanoparticles from 50 - 100 nm to micron-sized particles, breaks through the problem of wide particle size distribution in traditional methods, and can control the copper oxide nanoparticles to the micron scale, which have good crystal structure and dispersibility;

[0030] (2) The present invention adopts microwave-assisted synthesis and utilizes its characteristics of rapid and uniform heating. Compared with the traditional hydrothermal method, the reaction time is significantly shortened to 5 - 10 minutes, showing significant efficiency advantages. The method of the present invention has simple process, fast reaction speed and low energy consumption. The obtained copper oxide nanoparticles can be used for the preparation of high-performance and high-purity copper oxide nanomaterials, and have broad application prospects;

[0031] (3) The present invention utilizes the combination of PVP / SDS / PEG multi-component dispersants, and the particle dispersibility (PDI < 0.2) is better than that of a single dispersant system (PDI > 0.3);

[0032] (4) Urea in the present invention plays a dual role. Urea acts as a precipitant in the reaction to promote the precipitation of copper ions, and also generates OH- through hydrolysis to adjust the pH value of the solution, which is beneficial to the formation of copper oxide;

[0033] (5) The particle size and morphology of the present invention are controllable. By adjusting reaction conditions such as microwave power, reaction time, the ratio of urea and copper salt, and the type and dosage of dispersants, the controllability of the particle size and morphology of copper oxide nanoparticles is achieved;

[0034] (6) The process of the present invention is simple and environmentally friendly. The reaction conditions are mild and the process is simple. No high-temperature and high-pressure equipment is required, and no harmful substances are generated during the reaction, which conforms to the concept of green chemistry.

[0035] (7) The preparation method of the present invention has many industrial application values. For example, in the catalytic field, it can be used as a catalyst or co-catalyst in catalytic oxidation, methanol reforming and other catalytic reactions; in the gas sensor field, it has sensitive characteristics to certain gases and can be used to prepare highly sensitive gas sensors to detect toxic gases in the environment; in the field of lithium-ion battery materials, it can be used as the anode material of lithium-ion batteries, having high specific capacity and excellent cycle performance; in the field of optical materials, it has good absorption performance in the visible light region and can be used in photodetectors, solar cells and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of a method for preparing micro-nano copper oxide powder by a microwave method and its application according to the present invention.

[0037] Figure 2SEM image of nano - copper oxide prepared by a microwave method for a method of preparing micro - nano copper oxide powder of the present invention and its application. Detailed implementation manners

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0039] The present invention discloses a method for preparing micro - nano copper oxide powder by a microwave method, which includes the following steps:

[0040] a) Prepare a copper ion solution: Dissolve a soluble copper salt in deionized water to obtain a copper ion solution;

[0041] b) Add a dispersant and a surfactant: Add a dispersant and a surfactant to the copper ion solution in step a), stir evenly to form a clear solution;

[0042] c) Add urea: Add urea in proportion under stirring, and continue stirring to obtain a reaction mixture;

[0043] d) Microwave heating reaction: Transfer the reaction mixture in step c) to a microwave reaction vessel, the microwave power is 400 - 800 W, the heating time under the microwave power is 1 - 10 minutes, and the temperature of microwave heating is 60 - 100 °C;

[0044] e) Product separation and purification: After the reaction is completed, cool, centrifuge to separate the product, and wash it repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0045] f) Drying and calcination: Dry the product at a low temperature of 60 - 70 °C for 10 - 12 hours, and then calcine it at 300 - 400 °C for 2 hours to obtain micro - nano copper oxide powder with a particle size distribution of 50 - 100 nanometers.

[0046] The soluble copper salt is one or more of copper acetate, copper nitrate or copper sulfate.

[0047] The dispersant is polyvinylpyrrolidone PVP or polyethylene glycol PEG.

[0048] The surfactant is sodium dodecyl sulfate SDS or Tween 80.

[0049] The molar ratio of urea to copper ions is 1:1 - 5:1.

[0050] The present invention also discloses an application of a method for preparing micro-nano copper oxide powder by microwave method in a gas sensor. Using copper oxide nanoparticles as the sensitive material, it can be used to detect toxic gases such as formaldehyde, carbon monoxide, and ammonia.

[0051] Example 1: Using copper acetate as the copper source to prepare nano copper oxide powder

[0052] 1. Reagents and materials:

[0053] Copper source: Copper acetate monohydrate (Cu(CH3COO)2·H2O), analytical pure;

[0054] Urea: Analytical pure;

[0055] Dispersant: Polyvinylpyrrolidone (PVP, K30), analytical pure;

[0056] Solvent: Deionized water;

[0057] 2. Preparation steps:

[0058] a) Prepare a copper ion solution: Weigh 1.0 g of copper acetate and dissolve it in 100 mL of deionized water to obtain a copper ion solution of approximately 50 mmol / L;

[0059] b) Add the dispersant: Add 1.0 g of PVP to the copper ion solution in step a) and stir until completely dissolved to form a homogeneous blue solution;

[0060] c) Add urea: Under stirring, add 3.0 g of urea and continue stirring for 15 minutes. The solution remains clear to obtain a reaction mixture;

[0061] d) Microwave heating reaction: Transfer the reaction mixture in step c) to a microwave reaction vessel, place it in a microwave reactor, set the microwave power to 600 W, the reaction time to 5 minutes, and control the temperature at 90 °C.

[0062] e) Product separation and purification: After the reaction, naturally cool to room temperature, centrifuge at 8000 rpm for 10 minutes to separate the product, and wash it repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0063] f) Drying and calcination: Place the product in an oven and dry it at 60 °C for 12 hours; then calcine it in an air atmosphere at 300 °C for 2 hours to obtain black copper oxide nano powder.

[0064] 3. Result characterization:

[0065] Particle size analysis: Observed by transmission electron microscopy (TEM), it can be seen that the copper oxide nanoparticles are in regular rod shapes, with a length of about 80 - 100 nm and a width of about 20 - 30 nm.

[0066] Crystal structure: The X-ray diffraction (XRD) test shows that the product is monoclinic CuO with sharp peaks and high crystallinity.

[0067] Specific surface area: The specific surface area of the copper oxide nanopowder is 25 m 2 / g as shown in Table 1 and Table 2;

[0068] As shown in Table 1 and Table 2;

[0069] Table 1:

[0070] Parameter Testing method Typical value (Example 1) Initial pH of solution pH meter 3.2±0.1 pH at reaction end point pH meter 6.8±0.3 OH⁻ generation rate Acid-base titration method 0.12 mmol / min Nucleation time DLS (Dynamic Light Scattering) 90 ± 15 s

[0071] Table 2:

[0072] Performance index Testing conditions Data of Example 1 Literature comparison value (hydrothermal method) Specific surface area (BET) <![CDATA[N2 adsorption, 77K]]> <![CDATA[38.5m 2 / g]]> <![CDATA[25-30m 2 / g]]> Pore size distribution BJH method Mainly mesopores, 4 - 6 nm Irregular pore size Conductivity Four-probe method, 25°C <![CDATA[1.2×10 -3 S / cm]]> <![CDATA[5×10 -4 S / cm]]> Thermal stability (TGA) Air atmosphere, 10°C / min Weight loss < 2% @ 400 °C Weight loss 5 - 8% @ 400°C .

[0073] Example 2: Preparation of micron-sized copper oxide powder using copper nitrate as the copper source

[0074] 1. Reagents and materials:

[0075] Copper source: Copper nitrate trihydrate (Cu(NO3)2·3H2O), analytical grade;

[0076] Urea: Analytical grade;

[0077] Dispersant: Polyethylene glycol (PEG400), analytical grade;

[0078] Surfactant: Sodium dodecyl sulfate (SDS), analytical grade;

[0079] Solvent: Deionized water.

[0080] 2. Preparation steps:

[0081] a) Prepare a copper ion solution: Weigh 2.0 grams of copper nitrate and dissolve it in 200 milliliters of deionized water to obtain a copper ion solution of approximately 50 mmol / L;

[0082] b) Add the dispersant and surfactant: Add 2.0 grams of PEG400 and 0.5 grams of SDS to the copper ion solution in step a), and stir until completely dissolved to form a homogeneous blue solution;

[0083] c) Add urea: Under stirring, add 6.0 grams of urea and continue stirring for 10 minutes to obtain a reaction mixture;

[0084] d) Microwave heating reaction: Transfer the reaction mixture in step c) to a microwave reaction vessel, place it in a microwave reactor, set the microwave power to 700 W, the reaction time to 8 minutes, and control the temperature at 95 °C;

[0085] e) Product separation and purification: After the reaction, it is naturally cooled to room temperature and centrifuged at 8000 rpm for 10 minutes to separate the product, which is repeatedly washed 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0086] f) Drying and calcination: The product is placed in an oven and dried at 70 °C for 10 hours; then it is calcined at 400 °C for 2 hours in an air atmosphere to obtain micron-sized copper oxide powder.

[0087] 3. Result characterization:

[0088] Particle size analysis: Observed by scanning electron microscopy (SEM), the copper oxide particles are flaky with a particle size of about 12 microns and relatively uniform particle size.

[0089] Crystal structure: As shown by XRD test, the product is CuO in monoclinic system without impurity peaks and has good crystallinity;

[0090] Example 3: Preparation of micron-sized copper oxide powder using copper nitrate as the copper source

[0091] 1. Reagents and materials:

[0092] Copper source: Copper nitrate trihydrate (Cu(NO3)2·3H2O), analytical pure;

[0093] Urea: Analytical pure;

[0094] Dispersant: Polyethylene glycol (PEG400), analytical pure;

[0095] Solvent: Deionized water.

[0096] 2. Preparation steps:

[0097] a) Preparation of copper ion solution: Weigh 2.0 grams of copper nitrate and dissolve it in 200 ml of deionized water to obtain a copper ion solution of about 50 mmol / L;

[0098] b) Addition of dispersant and surfactant: Add 2.0 grams of PEG400 to the copper ion solution in step a) and stir until completely dissolved to form a uniform blue solution;

[0099] c) Addition of urea: Under stirring, add 6.0 grams of urea and continue stirring for 10 minutes to obtain a reaction mixture;

[0100] d) Microwave heating reaction: Transfer the reaction mixture in step c) to a microwave reaction vessel, place it in a microwave reactor, set the microwave power to 700 W, the reaction time to 8 minutes, and control the temperature at 95 °C;

[0101] e) Product separation and purification: After the reaction, it was naturally cooled to room temperature, centrifuged at 8000 rpm for 10 minutes to separate the product, and repeatedly washed 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0102] f) Drying and calcination: The product was placed in an oven and dried at 70 °C for 10 hours; then calcined at 400 °C for 2 hours in an air atmosphere to obtain micron-sized copper oxide powder.

[0103] It can be obtained from the above Examples 1 - 3 that different dispersants and surfactants have a significant impact on the morphology and dispersibility of particles. Among them, when using PVP, it is beneficial to form uniform nanoparticles and prevent agglomeration; when using PEG400, it can promote the growth of particles and form larger particles; when adding SDS, it can adjust the morphology of particles to form sheet or rod-like structures.

[0104] Thus, it can be seen that by selecting appropriate dispersants and surfactants, the morphology and particle size of copper oxide nanoparticles can be regulated.

[0105] Example 4: Influence of reaction conditions on the particle size of copper oxide particles

[0106] 1. Experimental design:

[0107] While keeping the copper salt concentration constant, the molar ratio of urea to copper ions was changed, and the change in particle size was observed.

[0108] 2. Preparation steps: (I)

[0110] a) Preparation of copper ion solution: Weigh 1.0 g of copper acetate and dissolve it in 100 mL of deionized water to obtain a copper ion solution of approximately 50 mmol / L;

[0111] b) Addition of dispersant and surfactant: Add 1.0 g of PVP and 0.3 g of SDS to the copper ion solution in step a), stir until completely dissolved to form a uniform blue solution;

[0112] c) Addition of urea: Under stirring, add 1.0 g of urea and continue stirring for 15 minutes to obtain a reaction mixture;

[0113] d) Microwave heating reaction: Transfer the reaction mixture in step c) to a microwave reaction vessel, place it in a microwave reactor, set the microwave power to 600 W, the reaction time to 5 minutes, and control the temperature at 90 °C.

[0114] e) Product separation and purification: After the reaction, it is naturally cooled to room temperature, centrifuged at 8000 rpm for 10 minutes to separate the product, and washed repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0115] f) Drying and calcination: The product is placed in an oven and dried at 60 °C for 12 hours; then it is calcined in an air atmosphere at 300 °C for 2 hours to obtain black copper oxide nano-powder. (II)

[0117] a) Preparation of copper ion solution: Weigh 1.0 g of copper acetate and dissolve it in 100 mL of deionized water to obtain a copper ion solution of approximately 50 mmol / L;

[0118] b) Addition of dispersant and surfactant: Add 1.0 g of PVP and 0.3 g of SDS to the copper ion solution in step a), stir until completely dissolved to form a homogeneous blue solution;

[0119] c) Addition of urea: Under stirring, add 2.0 g of urea and continue stirring for 15 minutes to obtain a reaction mixture;

[0120] d) Microwave heating reaction: Transfer the reaction mixture in step c) to a microwave reaction vessel, place it in a microwave reactor, set the microwave power to 600 W, the reaction time to 5 minutes, and control the temperature at 90 °C.

[0121] e) Product separation and purification: After the reaction, it is naturally cooled to room temperature, centrifuged at 8000 rpm for 10 minutes to separate the product, and washed repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0122] f) Drying and calcination: The product is placed in an oven and dried at 60 °C for 12 hours; then it is calcined in an air atmosphere at 300 °C for 2 hours to obtain black copper oxide nano-powder. (III)

[0124] a) Preparation of copper ion solution: Weigh 1.0 g of copper acetate and dissolve it in 100 mL of deionized water to obtain a copper ion solution of approximately 50 mmol / L;

[0125] b) Addition of dispersant and surfactant: Add 1.0 g of PVP and 0.3 g of SDS to the copper ion solution in step a), stir until completely dissolved to form a homogeneous blue solution;

[0126] c) Addition of urea: Under stirring, add 3.0 g of urea and continue stirring for 15 minutes to obtain a reaction mixture;

[0127] d) Microwave heating reaction: Transfer the reaction mixture from step c) to a microwave reaction vessel, place it in a microwave reactor, set the microwave power to 600 W, the reaction time to 5 minutes, and control the temperature at 90 °C.

[0128] e) Product separation and purification: After the reaction is completed, naturally cool to room temperature, centrifuge at a speed of 8000 rpm for 10 minutes to separate the product, and wash it repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0129] f) Drying and calcination: Place the product in an oven and dry it at 60 °C for 12 hours; then calcine it in an air atmosphere at 300 °C for 2 hours to obtain black copper oxide nanoparticles.

[0130] 3. Result analysis:

[0131] When the molar ratio of urea to copper ions is 1:1, where 1 g of urea and 1 g of copper ions are used, the particle size is about 30 - 50 nm, the particle size is smaller, but the dispersibility is slightly poor, and there is slight agglomeration;

[0132] When the molar ratio of urea to copper ions is 2:1, where 2 g of urea and 1 g of copper ions are used, the particle size is about 50 - 80 nm, the dispersibility is better, and the morphology is regular;

[0133] When the molar ratio of urea to copper ions is 3:1, where 3 g of urea and 1 g of copper ions are used, the particle size increases, about 80 - 100 nm, and the morphology is rod-shaped or flaky.

[0134] It can be seen that by adjusting the ratio of urea to copper ions, the size and morphology of copper oxide nanoparticles can be effectively controlled; appropriately increasing the amount of urea is beneficial to obtaining larger-sized particles.

[0135] Example 5: Application of copper oxide nanoparticles in gas sensors

[0136] 1. Preparation method steps of the sensor:

[0137] a) Disperse the copper oxide nanoparticles prepared in Example 1 in an ethanol solution and ultrasonically treat for 30 minutes to obtain a uniform suspension;

[0138] b) Coat the suspension on a ceramic substrate, dry it, and calcine it at 300 °C for 1 hour to form a copper oxide sensitive film;

[0139] 2. Sensing performance test:

[0140] In an environment of formaldehyde gas with a certain concentration, the gas sensor exhibits high sensitivity and fast response performance, indicating that the prepared copper oxide nanoparticles have excellent gas-sensing performance.

[0141] Example 6: Influence of Microwave Power on Copper Oxide Particles

[0142] 1. Experimental Design:

[0143] Under the condition that other conditions are the same, change the microwave power;

[0144] 2. Preparation Steps: (1)

[0146] a) Prepare copper ion solution: Weigh 1.0 g of copper acetate and dissolve it in 100 mL of deionized water to obtain a copper ion solution of about 50 mmol / L;

[0147] b) Add dispersant: Add 1.0 g of PVP to the copper ion solution in step a), and stir until completely dissolved to form a uniform blue solution;

[0148] c) Add urea: Under stirring, add 3.0 g of urea, and continue to stir for 15 minutes. The solution remains clear to obtain a reaction mixture;

[0149] d) Microwave heating reaction: Transfer the reaction mixture in step c) to a microwave reaction vessel, place it in a microwave reactor, set the microwave power to 400 W, the reaction time to 5 minutes, and control the temperature at 90 °C.

[0150] e) Product separation and purification: After the reaction is completed, naturally cool to room temperature, centrifuge at 8000 rpm for 10 minutes to separate the product, and wash it repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0151] f) Drying and calcination: Place the product in an oven and dry it at 60 °C for 12 hours; then calcine it in an air atmosphere at 300 °C for 2 hours to obtain black copper oxide nano-powder. (2)

[0153] a) Prepare copper ion solution: Weigh 1.0 g of copper acetate and dissolve it in 100 mL of deionized water to obtain a copper ion solution of about 50 mmol / L;

[0154] b) Add dispersant: Add 1.0 g of PVP to the copper ion solution in step a), and stir until completely dissolved to form a uniform blue solution;

[0155] c) Add urea: Under stirring, add 3.0 g of urea, and continue to stir for 15 minutes. The solution remains clear to obtain a reaction mixture;

[0156] d) Microwave heating reaction: Transfer the reaction mixture from step c) to a microwave reaction vessel, place it in a microwave reactor, set the microwave power to 600 W, the reaction time to 5 minutes, and control the temperature at 90 °C.

[0157] e) Product separation and purification: After the reaction is completed, cool it naturally to room temperature, centrifuge at a speed of 8000 rpm for 10 minutes to separate the product, and wash it repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0158] f) Drying and calcination: Place the product in an oven and dry it at 60 °C for 12 hours; then calcine it in an air atmosphere at 300 °C for 2 hours to obtain black copper oxide nano-powder. (III)

[0160] a) Preparation of copper ion solution: Weigh 1.0 g of copper acetate and dissolve it in 100 mL of deionized water to obtain a copper ion solution of approximately 50 mmol / L;

[0161] b) Addition of dispersant: Add 1.0 g of PVP to the copper ion solution in step a), stir until completely dissolved to form a homogeneous blue solution;

[0162] c) Addition of urea: Under stirring, add 3.0 g of urea and continue stirring for 15 minutes. The solution remains clear to obtain a reaction mixture;

[0163] d) Microwave heating reaction: Transfer the reaction mixture from step c) to a microwave reaction vessel, place it in a microwave reactor, set the microwave power to 800 W, the reaction time to 5 minutes, and control the temperature at 90 °C.

[0164] e) Product separation and purification: After the reaction is completed, cool it naturally to room temperature, centrifuge at a speed of 8000 rpm for 10 minutes to separate the product, and wash it repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0165] f) Drying and calcination: Place the product in an oven and dry it at 60 °C for 12 hours; then calcine it in an air atmosphere at 300 °C for 2 hours to obtain black copper oxide nano-powder.

[0166] 3. Result analysis:

[0167] When the microwave power is 400 W, the reaction is incomplete, and the generated copper oxide particles have a large particle size and uneven distribution;

[0168] When the microwave power is 600 W, nano-sized copper oxide particles with uniform particle size can be obtained, and the particle size is about 50 - 80 nm;

[0169] When the microwave power is 800 W, the reaction is too fast, which easily leads to particle agglomeration and the particle size increases to more than 100 nanometers;

[0170] Thus, by selecting an appropriate microwave power, such as 600 W, copper oxide nanoparticles with uniform particle size and good dispersibility can be obtained.

[0171] Example 7: Influence of Urea Dosage on Particle Size

[0172] 1. Experimental Design:

[0173] Under the condition that other conditions are the same, increase the dosage of urea;

[0174] 2. Preparation Steps: (1)

[0176] a) Prepare a copper ion solution: Weigh 1.0 g of copper acetate and dissolve it in 100 mL of deionized water to obtain a copper ion solution of about 50 mmol / L;

[0177] b) Add a dispersant: Add 1.0 g of PVP to the copper ion solution in step a) and stir until completely dissolved to form a uniform blue solution;

[0178] c) Add urea: Under stirring, add 1.0 g of urea and continue stirring for 15 minutes. The solution remains clear to obtain a reaction mixture;

[0179] d) Microwave heating reaction: Transfer the reaction mixture in step c) to a microwave reaction vessel, place it in a microwave reactor, set the microwave power to 600 W, the reaction time to 5 minutes, and control the temperature at 90 °C.

[0180] e) Product separation and purification: After the reaction is completed, naturally cool to room temperature, centrifuge at 8000 rpm for 10 minutes to separate the product, and wash it repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities;

[0181] f) Drying and calcination: Place the product in an oven and dry it at 60 °C for 12 hours; then calcine it in an air atmosphere at 300 °C for 2 hours to obtain black copper oxide nano powder. (2)

[0183] a) Prepare a copper ion solution: Weigh 1.0 g of copper acetate and dissolve it in 100 mL of deionized water to obtain a copper ion solution of about 50 mmol / L;

[0184] b) Add a dispersant: Add 1.0 g of PVP to the copper ion solution in step a) and stir until completely dissolved to form a uniform blue solution;

[0185] c) Addition of urea: Under stirring, 3.0 g of urea was added, and stirring was continued for 15 minutes. The solution remained clear, and a reaction mixture was obtained.

[0186] d) Microwave heating reaction: The reaction mixture from step c) was transferred to a microwave reaction vessel and placed in a microwave reactor. The microwave power was set at 600 W, the reaction time was 5 minutes, and the temperature was controlled at 90 °C.

[0187] e) Product separation and purification: After the reaction was completed, it was naturally cooled to room temperature, centrifuged at 8000 rpm for 10 minutes to separate the product, and repeatedly washed 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities.

[0188] f) Drying and calcination: The product was placed in an oven and dried at 60 °C for 12 hours; then it was calcined in an air atmosphere at 300 °C for 2 hours to obtain black copper oxide nanometer powder. (III)

[0190] a) Preparation of copper ion solution: 1.0 g of copper acetate was weighed and dissolved in 100 mL of deionized water to obtain a copper ion solution of about 50 mmol / L.

[0191] b) Addition of dispersant: 1.0 g of PVP was added to the copper ion solution from step a), and stirred until completely dissolved to form a uniform blue solution.

[0192] c) Addition of urea: Under stirring, 5.0 g of urea was added, and stirring was continued for 15 minutes. The solution remained clear, and a reaction mixture was obtained.

[0193] d) Microwave heating reaction: The reaction mixture from step c) was transferred to a microwave reaction vessel and placed in a microwave reactor. The microwave power was set at 600 W, the reaction time was 5 minutes, and the temperature was controlled at 90 °C.

[0194] e) Product separation and purification: After the reaction was completed, it was naturally cooled to room temperature, centrifuged at 8000 rpm for 10 minutes to separate the product, and repeatedly washed 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities.

[0195] f) Drying and calcination: The product was placed in an oven and dried at 60 °C for 12 hours; then it was calcined in an air atmosphere at 300 °C for 2 hours to obtain black copper oxide nanometer powder.

[0196] 3. Result analysis:

[0197] When the molar ratio of urea to copper ions is 1:1, the particle size is smaller, about 30 - 50 nm.

[0198] When the molar ratio of urea to copper ions is 3:1, the particle size increases to 80 - 100 nanometers;

[0199] When the molar ratio of urea to copper ions is 5:1, the particles further increase in size and it is possible to form micron-sized particles.

[0200] Thus, increasing the amount of urea can promote the growth of the crystal nuclei of copper oxide and increase the particle size; at the same time, the buffering effect of urea is enhanced, the pH value of the solution increases, which is beneficial to the formation of copper oxide; by adjusting the molar ratio of urea to copper ions, the particle size of copper oxide nanoparticles can be controlled.

[0201] The above description is only a preferred embodiment of the present invention and does not impose any limitation on the technical scope of the present invention. Therefore, any minor modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing micro-nano copper oxide powder by microwave method, characterized in that, It includes the following steps: a) Prepare a copper ion solution: Dissolve a soluble copper salt in deionized water to obtain a copper ion solution; b) Add a dispersant and a surfactant: Add a dispersant and a surfactant to the copper ion solution in step a), stir evenly to form a clear solution; c) Add urea: Add urea in proportion under stirring, and continue stirring to obtain a reaction mixture; d) Microwave heating reaction: Transfer the reaction mixture in step c) to a microwave reaction vessel and heat; e) Product separation and purification: After the reaction is completed, cool, centrifuge to separate the product, wash to remove impurities; f) Drying and calcination: Dry the product at a low temperature and then calcine to obtain micro-nano copper oxide powder.

2. The method for preparing micro-nano copper oxide powder by microwave method according to claim 1, characterized in that, In step a), the soluble copper salt is one or more of copper acetate, copper nitrate or copper sulfate.

3. The method for preparing micro-nano copper oxide powder by microwave method according to claim 1, characterized in that, In step b), the dispersant is polyvinylpyrrolidone PVP or polyethylene glycol PEG.

4. A method for preparing micro-nano copper oxide powder by microwave method according to claim 1, characterized in that, In step b), the surfactant is sodium dodecyl sulfate SDS or Tween 80.

5. A method for preparing micro-nano copper oxide powder by microwave method according to claim 1, characterized in that, In step c), the molar ratio of urea to copper ions is 1:1 to 5:

1.

6. A method for preparing micro-nano copper oxide powder by microwave method according to claim 1, characterized in that, In step d), the microwave power is 400 - 800 W, the heating time under the microwave power is 1 - 10 minutes, and the microwave heating temperature is 60 - 100 °C.

7. A method for preparing micro-nano copper oxide powder by microwave method according to claim 1, characterized in that, In step e), the washing is to wash repeatedly 3 times with deionized water and absolute ethanol to remove unreacted reagents and impurities.

8. A method for preparing micro-nano copper oxide powder by microwave method according to claim 1, characterized in that, In step f), the drying temperature at low temperature is 60 - 70 °C, the drying time is 10 - 12 hours; the calcination temperature is 300 - 400 °C, and the calcination time is 2 hours.

9. A method for preparing micro-nano copper oxide powder by microwave method according to claim 1, characterized in that, In step f), the particle size distribution of the copper oxide nanoparticles is 50 - 100 nanometers.

10. Application of a method for preparing micro-nano copper oxide powder by microwave method in a gas sensor, characterized in that, Taking the copper oxide nanoparticles as a sensitive material, it can be used to detect toxic gases such as formaldehyde, carbon monoxide, and ammonia.

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