High-activity ultrafine nanometer magnesium oxide composite material and preparation method thereof

Abstract

This invention discloses a highly active ultrafine nano-magnesium oxide composite material and its preparation method, belonging to the field of nanomaterial preparation technology. The method involves depositing ultrafine flower-like MgO on the surface of graphene nanosheets, followed by in-situ coating with MOF-Al and then carbonization. On one hand, MOF-Al is a porous and flexible framework that gradually pyrolyzes during high-temperature calcination, thus buffering thermal stress. On the other hand, the ultrafine flower-like MgO contains numerous mesopores and gaps. When the temperature rises, the expansion of the magnesium oxide sheets is offset by the compression of the pores and the minute slippage between the sheets. These two factors work together to prevent interfacial cracking between MgO and graphene due to differences in thermal shrinkage. Furthermore, the gradual pyrolysis of MOF-Al during high-temperature calcination allows Al to act as exogenous ions, doping the ultrafine flower-like MgO. These exogenous ions replace the original ion lattice positions, disrupting the integrity of the MgO lattice and facilitating the introduction of oxygen vacancies, thereby significantly improving the bactericidal effect.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation technology, specifically a highly active ultrafine nano magnesium oxide composite material and its preparation method. Background Technology

[0002] Magnesium oxide, as a typical alkaline earth metal oxide, has received increasing attention and application in recent years in fields such as high-grade lubricants, food, medicine, and silicon steel. Among the many magnesium oxide materials, nano-magnesium oxide has superior high-temperature resistance, thermal conductivity, and electrical insulation compared to ordinary magnesium oxide. Considering the small size effect, macroscopic quantum tunneling effect, and quantum size effect of nanomaterials, nano-magnesium oxide possesses special optical, electromagnetic, thermal, and mechanical properties. Currently, commonly used methods for preparing nano-magnesium oxide include co-precipitation, sol-gel, hydrothermal synthesis, and electrochemical methods. However, these methods all have some technical problems, mainly including: (1) the prepared nano-magnesium oxide particles are generally 20-100 nm in size, which are prone to aggregation during use, affecting efficiency; (2) the prepared nano-magnesium oxide usually exists in an amorphous form, which limits its application and makes it difficult to recycle; (3) the existing preparation process is complex and requires high-quality experimental equipment, making it difficult to achieve large-scale industrial production. Therefore, it is necessary to develop a method for preparing highly dispersed nano-magnesium oxide materials that can overcome the above shortcomings.

[0003] Chinese patent application CN107805427A discloses a method for preparing a magnesium oxide / graphene antibacterial coating. This method involves in-situ deposition of magnesium hydroxide nanosheets onto graphene oxide, followed by calcination to form a magnesium oxide / graphene composite material. However, magnesium oxide is a typical ceramic material with a cubic, dense structure, which undergoes significant thermal expansion and contraction with temperature changes. Furthermore, the in-situ deposition of nanosheets and the nanoscale grain boundary effect exacerbate its anisotropy in thermal expansion, potentially leading to interlayer delamination between magnesium oxide and graphene. Summary of the Invention

[0004] The purpose of this invention is to provide a highly active ultrafine nano-magnesium oxide composite material and its preparation method. The method involves depositing ultrafine flower-like MgO on the surface of graphene nanosheets, followed by in-situ coating with MOF-Al and then carbonization. On the one hand, MOF-Al is a porous and flexible framework that gradually pyrolyzes during high-temperature calcination, thus buffering thermal stress. On the other hand, the ultrafine flower-like MgO contains a large number of mesopores and gaps. When the temperature rises, the expansion of the magnesium oxide sheets is offset by the compression of the pores and the tiny slippage between the sheets. The two work together to prevent interfacial cracking between MgO and graphene due to differences in thermal shrinkage.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing a highly active ultrafine nano-magnesium oxide composite material includes the following steps: Step 1: In situ, flower-like MgO is grown on the surface of graphene oxide to obtain an ultrafine flower-like MgO / GO precursor. Then, MOF-Al structure is coated in situ on the surface of the ultrafine flower-like MgO / GO precursor to obtain MOF-Al@flower-like MgO / GO precursor.

[0006] Step 2: Place the MOF-Al@flower-like MgO / GO precursor in a muffle furnace and calcine it to 500-600℃ for 2-4 hours under a nitrogen atmosphere at a heating rate of 2-4℃ / min. Then, allow it to cool naturally to room temperature to obtain a highly active ultrafine nano-magnesium oxide composite material.

[0007] Furthermore, the specific preparation steps of the ultrafine flower-like MgO / GO precursor are as follows: Mixed solutions A, B, and C were added to a reaction vessel at a mass ratio of 1:2:1.2. The mixture was stirred for 3-5 minutes at 20-25°C and 1000-1300 r / min. The precipitate was then allowed to stand at 20-25°C for 50-60 minutes, filtered, and washed 2-4 times with deionized water and anhydrous ethanol, respectively. The precipitate was then vacuum dried at 60-70°C for 12-14 hours to obtain an ultrafine flower-like MgO / GO precursor.

[0008] Furthermore, the specific preparation steps for mixed solution A are as follows: Magnesium nitrate hexahydrate and deionized water were added to a reaction vessel at a ratio of 0.4-0.6 g to 500-600 mL. The mixture was stirred at 70-75 °C and 500-600 r / min for 40-50 min until dissolved, to obtain mixed solution A.

[0009] Furthermore, the specific preparation steps for mixed solution B are as follows: Anhydrous sodium carbonate and deionized water are added to a reaction vessel at a ratio of 0.4-0.6 g: 1000-1200 mL. The mixture is stirred at 50-55 °C and 500-600 r / min for 40-50 min to obtain mixed solution B.

[0010] Furthermore, the specific preparation steps for mixed solution C are as follows: Add hexadecyltrimethylammonium bromide and deionized water to a reaction vessel and stir for 40-50 min at 20-25℃ and 500-600 r / min. Then add graphene oxide dispersion with a concentration of 0.5-0.6 g / L and stir for 30-40 min at 1000-1100 r / min to obtain mixed solution C. Furthermore, the ratio of hexadecyltrimethylammonium bromide, deionized water, and graphene oxide dispersion is 10-12g: 200-220mL: 403-405mL.

[0011] Furthermore, the specific preparation steps of the MOF-Al@flower-like MgO / GO precursor are as follows: Aluminum chloride hexahydrate, terephthalic acid, ultrafine flower-like MgO / GO precursor, deionized water, and N,N-dimethylformamide were added to a polytetrafluoroethylene hydrothermal reactor and stirred at 220-230℃ and 500-600 r / min for 72-74 h. After the reaction was completed, the mixture was naturally cooled to room temperature, filtered, and the precipitate was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The precipitate was then vacuum dried at 60-70℃ for 12-14 h to obtain the MOF-Al@flower-like MgO / GO precursor.

[0012] Furthermore, the mass ratio of aluminum chloride hexahydrate, terephthalic acid, ultrafine flower-like MgO / GO precursor, deionized water, and N,N-dimethylformamide is 4.4-4.6:4.2-4.5:2-3:43-45:28-30.

[0013] The beneficial effects of this invention are: 1. The highly active ultrafine nano-magnesium oxide composite material prepared by this invention has abundant active sites on its surface. Structurally, it consists of ultrafine flower-like MgO deposited on the surface of graphene nanosheets, which is then carbonized after in-situ coating with MOF-Al. On the one hand, MOF-Al is a porous and flexible framework that gradually pyrolyzes during high-temperature calcination, thus buffering thermal stress. On the other hand, the ultrafine flower-like MgO contains a large number of mesopores and gaps. When the temperature rises, the expansion of the magnesium oxide sheets is offset by the compression of the pores and the tiny slippage between the sheets. The two work together to prevent interfacial cracking between MgO and graphene due to differences in thermal shrinkage.

[0014] 2. The highly active ultrafine nano-magnesium oxide composite material prepared by this invention has a special structure that can increase the specific surface area and the contact area with bacteria, thereby improving antibacterial properties. Furthermore, the gradual pyrolysis of MOF-AI during high-temperature calcination allows AI to act as an exogenous ion, doping the ultrafine flower-like MgO. The exogenous ions replace the original ion's lattice position, disrupting the integrity of the MgO lattice, thus making it easier to introduce oxygen vacancies, thereby significantly improving the bactericidal effect. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1: A method for preparing a highly active ultrafine nano-magnesium oxide composite material, comprising the following steps: S1: Add 0.4g of magnesium nitrate hexahydrate and 500mL of deionized water to a reaction vessel, and stir for 40min at 70℃ and 500r / min until dissolved, to obtain mixed solution A; add 0.4g of anhydrous sodium carbonate and 1000mL of deionized water to a reaction vessel, and stir for 40min at 50℃ and 500r / min, to obtain mixed solution B; add 10g of hexadecyltrimethylammonium bromide and 200mL of deionized water to a reaction vessel, and stir for 40min at 20℃ and 500r / min, then... Add 403 mL of 0.5 g / L graphene oxide dispersion and stir at 1000 r / min for 30 min to obtain mixed solution C. Add mixed solution A, mixed solution B and mixed solution C to the reaction vessel at a mass ratio of 1:2:1.2 and stir at 20℃ and 1000 r / min for 3 min. Then let the precipitate stand at 20℃ for 50 min, filter, wash the precipitate twice with deionized water and anhydrous ethanol, and dry it under vacuum at 60℃ for 12 h to obtain ultrafine flower-like MgO / GO precursor.

[0017] S2: 4.4 g aluminum chloride hexahydrate, 4.2 g terephthalic acid, 2 g ultrafine flower-like MgO / GO precursor, 43 g deionized water and 28 g N,N-dimethylformamide were added to a polytetrafluoroethylene hydrothermal reactor and stirred at 220 °C and 500 r / min for 72 h. After the reaction was completed, the mixture was naturally cooled to room temperature, filtered, and the precipitate was washed twice with deionized water and anhydrous ethanol, respectively. The precipitate was then dried under vacuum at 60 °C for 12 h to obtain MOF-Al@flower-like MgO / GO precursor.

[0018] S3: The MOF-Al@flower-like MgO / GO precursor was placed in a muffle furnace and calcined at 500℃ for 2h under a nitrogen atmosphere at a heating rate of 2℃ / min. It was then naturally cooled to room temperature to obtain a highly active ultrafine nano-magnesium oxide composite material.

[0019] Example 2: A method for preparing a highly active ultrafine nano-magnesium oxide composite material, comprising the following steps: S1: Add 0.5g of magnesium nitrate hexahydrate and 550mL of deionized water to the reaction vessel, and stir for 45min at 72.5℃ and 550r / min until dissolved, to obtain mixed solution A; add 0.5g of anhydrous sodium carbonate and 1100mL of deionized water to the reaction vessel, and stir for 45min at 52.5℃ and 550r / min, to obtain mixed solution B; add 11g of hexadecyltrimethylammonium bromide and 210mL of deionized water to the reaction vessel, and stir for 45min at 22.5℃ and 550r / min, then... Add 404 mL of 0.55 g / L graphene oxide dispersion and stir at 1050 r / min for 35 min to obtain mixed solution C. Add mixed solutions A, B and C to the reaction vessel at a mass ratio of 1:2:1.2 and stir at 22.5 °C and 1150 r / min for 4 min. Then let the precipitate stand at 22.5 °C for 55 min, filter, wash the precipitate three times with deionized water and anhydrous ethanol respectively, and dry it under vacuum at 65 °C for 13 h to obtain the ultrafine flower-like MgO / GO precursor.

[0020] S2: 4.5g aluminum chloride hexahydrate, 4.35g terephthalic acid, 2.5g ultrafine flower-like MgO / GO precursor, 44g deionized water and 29g N,N-dimethylformamide were added to a polytetrafluoroethylene hydrothermal reactor and stirred at 225℃ and 550r / min for 73h. After the reaction was completed, the mixture was naturally cooled to room temperature, filtered, and the precipitate was washed three times with deionized water and anhydrous ethanol, respectively. The precipitate was then dried under vacuum at 65℃ for 13h to obtain MOF-Al@flower-like MgO / GO precursor.

[0021] S3: The MOF-Al@flower-like MgO / GO precursor was placed in a muffle furnace and calcined at 550℃ for 3h under a nitrogen atmosphere at a heating rate of 3℃ / min. It was then naturally cooled to room temperature to obtain a highly active ultrafine nano-magnesium oxide composite material.

[0022] Example 3: A method for preparing a highly active ultrafine nano-magnesium oxide composite material, comprising the following steps: S1: Add 0.6g of magnesium nitrate hexahydrate and 600mL of deionized water to a reaction vessel, and stir for 50min at 75℃ and 600r / min until dissolved, to obtain mixed solution A; add 0.6g of anhydrous sodium carbonate and 1200mL of deionized water to a reaction vessel, and stir for 50min at 55℃ and 600r / min, to obtain mixed solution B; add 12g of hexadecyltrimethylammonium bromide and 220mL of deionized water to a reaction vessel, and stir for 50min at 25℃ and 600r / min, then... Add 405 mL of 0.6 g / L graphene oxide dispersion and stir at 1100 r / min for 40 min to obtain mixed solution C. Add mixed solution A, mixed solution B and mixed solution C to the reaction vessel at a mass ratio of 1:2:1.2 and stir at 25 °C and 1300 r / min for 5 min. Then let the precipitate stand at 25 °C for 60 min, filter, wash the precipitate four times with deionized water and anhydrous ethanol respectively, and vacuum dry at 70 °C for 14 h to obtain ultrafine flower-like MgO / GO precursor.

[0023] S2: 4.6g aluminum chloride hexahydrate, 4.5g terephthalic acid, 3g ultrafine flower-like MgO / GO precursor, 45g deionized water and 30g N,N-dimethylformamide were added to a polytetrafluoroethylene hydrothermal reactor and stirred at 230℃ and 600r / min for 74h. After the reaction was completed, the mixture was naturally cooled to room temperature, filtered, and the precipitate was washed four times with deionized water and anhydrous ethanol, respectively. The precipitate was then vacuum dried at 70℃ for 14h to obtain MOF-Al@flower-like MgO / GO precursor.

[0024] S3: The MOF-Al@flower-like MgO / GO precursor was placed in a muffle furnace and calcined at 600℃ for 4h under a nitrogen atmosphere at a heating rate of 4℃ / min. It was then naturally cooled to room temperature to obtain a highly active ultrafine nano-magnesium oxide composite material.

[0025] Comparative Example 1: Based on Example 3, the highly active ultrafine nano magnesium oxide composite material prepared in step S3 was replaced with the magnesium oxide / graphene composite material described in paragraph 20 of the specification of the preparation method of magnesium oxide / graphene antibacterial coating disclosed in Chinese Patent Application No. CN107805427A.

[0026] Comparative Example 2: Based on Example 3, the MOF-Al@flower-like MgO / GO precursor in step S3 was replaced with the ultrafine flower-like MgO / GO precursor prepared in step S1, while the other steps remained unchanged, to prepare a highly active ultrafine nano magnesium oxide composite material.

[0027] The performance of the highly active ultrafine nano-magnesium oxide composite materials prepared in Examples 1-3 and Comparative Examples 1-2 was tested: The antibacterial performance was quantitatively measured using the colony counting method. A concentration of 1 mg / mL of highly active ultrafine nano-magnesium oxide composite material was added to 30 mL of a 1×10⁻⁶ m³ / mL solution. 7 In an E. coli culture at CFU / mL, under the same conditions, a bacterial suspension without added materials was used as a negative control group. Both suspensions were placed in a constant temperature shaker and cultured at 37℃ and 150 rpm. Then, 100 μL of the bacterial suspension was diluted tenfold in a 900 μL PBS buffer solution. After spreading, the suspensions were incubated upside down in a 37℃ constant temperature incubator for 24 h, followed by colony counting. X represents the antibacterial rate, A represents the number of E. coli colonies on the negative control group's culture medium, and B represents the number of E. coli colonies on the experimental group's culture medium. The calculation formula is X = AB / B × 100%. The results are shown in Table 1. Table 1 As shown in Table 1, Comparative Example 1 lacks a flower-like multi-level structure and a MOF-Al coated framework. During calcination, the thermal shrinkage of MgO and graphene is mismatched, leading to easy interface cracking and detachment. The structure is extremely unstable, prone to agglomeration and deactivation, and its specific surface area and total pore volume are much lower than those of the Example. The material has a small contact area with bacteria, resulting in low adsorption and interaction efficiency and a significant decrease in antibacterial activity. Without Al ion doping, oxygen vacancies cannot be introduced into the MgO lattice, resulting in very few active sites and a decrease in antibacterial rate. It does not possess the synergistic effect of MOF pyrolysis buffering and flower-like pore pressure relief, and the material structure is easily damaged, resulting in poor long-term stability.

[0028] In Comparative Example 2, without MOF-Al coating and calcination, there was no exogenous Al ions to replace the Mg lattice, which could not destroy the MgO lattice or introduce oxygen vacancies. The number of active sites was significantly reduced, resulting in a decrease in antibacterial rate. Lacking the porous and flexible framework formed by MOF-Al pyrolysis, it could not buffer thermal stress, and the expansion of MgO sheets would still cause micro-cracks at the interface.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing high-activity ultrafine nanometer magnesium oxide composite material, characterized in that, Includes the following steps: Step 1: In situ, flower-like MgO is grown on the surface of graphene oxide to obtain an ultrafine flower-like MgO / GO precursor. Then, MOF-Al structure is coated in situ on the surface of the ultrafine flower-like MgO / GO precursor to obtain MOF-Al@flower-like MgO / GO precursor. Step 2: Place the MOF-Al@flower-like MgO / GO precursor in a muffle furnace and calcine it to 500-600℃ for 2-4 hours under a nitrogen atmosphere at a heating rate of 2-4℃ / min. Then, allow it to cool naturally to room temperature to obtain a highly active ultrafine nano-magnesium oxide composite material.

2. The method for preparing a highly active ultrafine nano-magnesium oxide composite material according to claim 1, characterized in that, The specific preparation steps of the ultrafine flower-like MgO / GO precursor are as follows: Mixed solutions A, B, and C were added to a reaction vessel at a mass ratio of 1:2:1.

2. The mixture was stirred for 3-5 minutes at 20-25°C and 1000-1300 r / min. The precipitate was then allowed to stand at 20-25°C for 50-60 minutes, filtered, and washed 2-4 times with deionized water and anhydrous ethanol, respectively. The precipitate was then vacuum dried at 60-70°C for 12-14 hours to obtain an ultrafine flower-like MgO / GO precursor.

3. The method for preparing a highly active ultrafine nano-magnesium oxide composite material according to claim 2, characterized in that, The specific preparation steps for the mixed solution A are as follows: Magnesium nitrate hexahydrate and deionized water were added to a reaction vessel at a ratio of 0.4-0.6 g to 500-600 mL. The mixture was stirred at 70-75 °C and 500-600 r / min for 40-50 min until dissolved, to obtain mixed solution A.

4. The method for preparing a highly active ultrafine nano-magnesium oxide composite material according to claim 2, characterized in that, The specific preparation steps for the mixed solution B are as follows: Anhydrous sodium carbonate and deionized water are added to a reaction vessel at a ratio of 0.4-0.6 g: 1000-1200 mL. The mixture is stirred at 50-55 °C and 500-600 r / min for 40-50 min to obtain mixed solution B.

5. The method for preparing a highly active ultrafine nano-magnesium oxide composite material according to claim 2, characterized in that, The specific preparation steps for the mixed solution C are as follows: Add hexadecyltrimethylammonium bromide and deionized water to a reaction vessel and stir for 40-50 min at 20-25℃ and 500-600 r / min. Then add graphene oxide dispersion with a concentration of 0.5-0.6 g / L and stir for 30-40 min at 1000-1100 r / min to obtain mixed solution C.

6. The method for preparing a highly active ultrafine nano-magnesium oxide composite material according to claim 5, characterized in that, The ratio of hexadecyltrimethylammonium bromide, deionized water, and graphene oxide dispersion is 10-12g: 200-220mL: 403-405mL.

7. The method for preparing a highly active ultrafine nano-magnesium oxide composite material according to claim 1, characterized in that, The specific preparation steps of the MOF-Al@flower-like MgO / GO precursor are as follows: Aluminum chloride hexahydrate, terephthalic acid, ultrafine flower-like MgO / GO precursor, deionized water, and N,N-dimethylformamide were added to a polytetrafluoroethylene hydrothermal reactor and stirred at 220-230℃ and 500-600 r / min for 72-74 h. After the reaction was completed, the mixture was naturally cooled to room temperature, filtered, and the precipitate was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The precipitate was then vacuum dried at 60-70℃ for 12-14 h to obtain the MOF-Al@flower-like MgO / GO precursor.

8. The method for preparing a highly active ultrafine nano-magnesium oxide composite material according to claim 7, characterized in that, The mass ratio of aluminum chloride hexahydrate, terephthalic acid, ultrafine flower-like MgO / GO precursor, deionized water, and N,N-dimethylformamide is 4.4-4.6:4.2-4.5:2-3:43-45:28-30.

9. A highly active ultrafine nano-magnesium oxide composite material, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

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