Molybdenum-based ZIF-67 antibacterial nanoparticles as well as preparation method and application thereof

Abstract

The invention discloses molybdenum-based ZIF-67 antibacterial nanoparticles as well as a preparation method and application thereof, and belongs to the technical field of nano-drugs. The preparation method comprises the following steps: adding an ammonium molybdate tetrahydrate dispersion liquid into a cobalt nitrate hexahydrate dispersion liquid at 40-65 DEG C to obtain an organic ligand solution containing molybdenum and cobalt; the preparation method comprises the following steps: preparing a molybdenum-based ZIF-67 nano-particle, adding the molybdenum-based ZIF-67 nano-particle into a 2-methylimidazole dispersion liquid of polyvinylpyrrolidone, standing at 0-5 DEG C, adding triethylamine, stirring and reacting to obtain an initial reaction solution, further reacting under the ultrasonic action to obtain a Mo / ZIF-67 solution, and carrying out solid-liquid separation, washing and precipitating, filtering and drying to obtain the molybdenum-based ZIF-67 antibacterial nano-particle. According to the preparation method, efficient and controllable synthesis of the molybdenum-based ZIF-67 is achieved, and the molybdenum-based ZIF-67 antibacterial nanoparticle material which is good in crystallinity, uniform in particle size and obvious in antibacterial effect is obtained.

Description

Technical Field

[0001] This invention belongs to the field of nanomedicine technology, specifically relating to a molybdenum-based ZIF-67 antibacterial nanoparticle, its preparation method, and its antibacterial application. Background Art

[0002] Molybdenum (Mo) is a transition metal element with diverse applications in industrial metallurgy, chemical engineering and catalysis, electronics and semiconductors, and antibacterial fields due to its unique physicochemical properties and bioactivity. Studies have found that Mo possesses unique metal ion toxicity (Hazel Lin, et al. Comparative Effects of Graphene and Molybdenum Disulfideon Human Macrophage Toxicity, Small, 2020.). When present in aqueous solution as MoO42-, it can penetrate cell membranes, potentially achieving antibacterial effects. However, single molybdenum metal tends to aggregate, has a rapid release rate, poor biocompatibility, and limited antibacterial function, which to some extent restricts its application in nanomedicine.

[0003] ZIF-67 (zeolite imidazole ester framework material-67), as a typical metal-organic framework (MOF) material, has broad application prospects in many fields such as gas storage, catalysis, and sensing due to its unique structure and excellent performance. Due to its excellent biocompatibility and disintegration characteristics under acidic conditions, it is responsive to weakly acidic environments associated with various diseases such as malignant tumors, making it an ideal carrier for controlling drug transport and release.

[0004] Traditional methods for synthesizing ZIF-67 suffer from problems such as difficulty in controlling the synthesis process, poor product crystallinity, and uneven particle size distribution. Furthermore, the antibacterial effect of single zinc-based nanoparticles is limited, making it difficult to meet the high requirements for antibacterial performance in practical applications. Introducing molybdenum (Mo) into ZIF-67 to form molybdenum-based ZIF-67 can further expand its performance and application range.

[0005] Therefore, it is of great significance to develop a method for preparing molybdenum-based ZIF-67 with significant antibacterial effects that can achieve controllable synthesis and improve product quality. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to address the shortcomings of existing zinc-based nanoparticles in antibacterial effects, as well as the problems of uncontrollable synthesis processes and poor product quality in the preparation methods, by providing a molybdenum-based ZIF-67 antibacterial nanoparticle, its preparation method, and its application.

[0007] The molybdenum-based ZIF-67 antibacterial nanoparticles prepared by the method of this invention improve upon the individual antibacterial capabilities of molybdenum metal and zinc-based MOFs, as well as their limitations due to low biocompatibility, and also enhance the antibacterial effect of ZIF-67 alone. The preparation method of this invention achieves efficient and controllable synthesis of molybdenum-based ZIF-67, yielding molybdenum-based ZIF-67 antibacterial nanoparticles with good crystallinity, uniform particle size, and significant antibacterial effect.

[0008] Technical solution: The purpose of the present invention is achieved through the following technical solution:

[0009] This invention provides a method for preparing molybdenum-based ZIF-67 antibacterial nanoparticles, comprising the following steps:

[0010] (1) Cobalt nitrate hexahydrate was dispersed in a solvent to obtain a cobalt nitrate hexahydrate dispersion;

[0011] (2) Disperse 2-methylimidazole in a solvent to obtain a 2-methylimidazole dispersion;

[0012] (3) Add polyvinylpyrrolidone to the 2-methylimidazole dispersion obtained in step (2), stir to dissolve, and obtain a 2-methylimidazole dispersion of polyvinylpyrrolidone;

[0013] (4) Disperse ammonium molybdate tetrahydrate in a solvent to obtain an ammonium molybdate tetrahydrate dispersion;

[0014] (5) At 40-65℃, the ammonium molybdate tetrahydrate dispersion obtained in step (4) is added to the cobalt nitrate hexahydrate dispersion obtained in step (1) to obtain an organic ligand solution containing molybdenum and cobalt.

[0015] (6) Add the organic ligand solution obtained in step (5) to the 2-methylimidazolium dispersion of polyvinylpyrrolidone obtained in step (3), let it stand at 0-5℃, add triethylamine, stir the reaction to obtain the initial reaction solution.

[0016] (7) The initial reaction solution obtained in step (6) is reacted under ultrasonic action to obtain Mo / ZIF-67 solution;

[0017] (8) The Mo / ZIF-67 solution obtained in step (7) is subjected to solid-liquid separation, the precipitate is washed, filtered, and dried to obtain the molybdenum-based ZIF-67 antibacterial nanoparticles, namely Mo / ZIF-67 nanoparticles.

[0018] Existing reactions for synthesizing ZIF-67 and other metal-based ZIF-67 typically require the use of organic solvents and ultra-high temperatures (e.g., conventional methods: high-temperature calcination derivatization temperature > 300℃, and hot solvent methods at 100–160℃). The reaction time usually ranges from several hours to several days. For example, the hot solvent method for synthesizing ZIF-67 may take 8–12 hours. The prepared nanoparticles have uneven morphology, are unstable, and consume a lot of energy, requiring sophisticated experimental equipment.

[0019] This invention employs an ultrasonically coordinated and controllable method to prepare Mo / ZIF-67, resulting in mild and simple reaction conditions, improved nanoparticle stability, and shorter synthesis time. The invention uses a mixture of polyvinylpyrrolidone and 2-methylimidazole dispersions, and a mixture of ammonium molybdate tetrahydrate and cobalt nitrate hexahydrate dispersions. After contacting the organometallic ligands and the 2-methylimidazole dispersion of polyvinylpyrrolidone, triethylamine is added, and the mixture is prepared under ice-water bath conditions. This process promotes nanoparticle crystal growth and allows for size control, resulting in better nanoparticle morphology and stability.

[0020] Preferably, in steps (1), (2) and (4), the solvent is water, ethanol or methanol.

[0021] More preferably, the solvent is water.

[0022] In some specific embodiments of the present invention, the effects of different molar ratios of 2-methylimidazole and cobalt nitrate hexahydrate on the synthesis of nanoparticles were investigated. Preferably, the molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 47:1-94:1.

[0023] Furthermore, the molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 59:1-82:1.

[0024] Furthermore, the molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 67:1.

[0025] Preferably, the molar ratio of ammonium molybdate tetrahydrate to cobalt nitrate hexahydrate is 1:130-1:180.

[0026] Furthermore, the molar ratio of ammonium molybdate tetrahydrate to cobalt nitrate hexahydrate is 1:152.

[0027] Preferably, in step (3), the stirring time is 15-30 min and the stirring rate is 550-750 rpm; the mass ratio of 2-methylimidazole to polyvinylpyrrolidone is 183-367:1.

[0028] Furthermore, the stirring time is 20 minutes and the stirring speed is 700 rpm.

[0029] Preferably, in step (5), the ammonium molybdate tetrahydrate dispersion is slowly added dropwise to the cobalt nitrate hexahydrate dispersion obtained in step (1), with a dropping rate of 2 to 3 drops / second; in step (6), the organic ligand solution is added dropwise to the polyvinylpyrrolidone 2-methylimidazole dispersion obtained in step (3), with a dropping rate of 2 to 3 drops / second.

[0030] Preferably, in step (6), the standing time is 10-30 min, the mass ratio of 2-methylimidazole to triethylamine is 15-80:1, the stirring rate is 500-750 rpm, and the stirring time is 5-8 min.

[0031] More preferably, the settling time is 30 min, the mass ratio of 2-methylimidazole to triethylamine is 25:1, the stirring rate is 600 rpm, and the stirring time is 6 min.

[0032] Preferably, in step (7), the reaction time under ultrasonic action is 10 min to 1 h, and the reaction temperature is 15 to 55 °C.

[0033] More preferably, the reaction time under ultrasonic action is 45 minutes, and the reaction temperature is 25°C.

[0034] Preferably, in step (8), the solid-liquid separation method is: centrifugation at a speed of 5000-9000 rpm, a temperature of 20-35℃, and a time of 3-8 min.

[0035] More preferably, centrifugation is performed at a speed of 8000 rpm, a temperature of 28°C, and a time of 3 min.

[0036] Preferably, in step (8), the washing solvent is one of water, methanol, or ethanol. More preferably, the washing solvent is ethanol.

[0037] Preferably, in step (8), the drying temperature is 60-80°C and the drying time is 10-15 hours.

[0038] More preferably, the drying temperature is 65°C and the drying time is 14 hours.

[0039] The obtained Mo / ZIF-67 nanoparticles were stored in a -20°C refrigerator away from light.

[0040] The present invention also provides molybdenum-based ZIF-67 antibacterial nanoparticles prepared by the above preparation method, wherein Mo is loaded onto ZIF-67 to form Mo / ZIF-67, and the resulting Mo / ZIF-67 has a stable structure and good dispersibility.

[0041] Preferably, the nanoparticles have a particle size of 240±10nm and an absolute value of Zeta potential >40mV.

[0042] This invention also provides the application of the above-mentioned molybdenum-based ZIF-67 antibacterial nanoparticles in the fight against Staphylococcus aureus.

[0043] Beneficial effects:

[0044] (1) In this invention, Mo is loaded onto ZIF-67 and molybdenum-based ZIF-67 nanoparticles (i.e., Mo / ZIF-67) are synthesized in a green manner using an ultrasonically coordinated and controllable method. The particle size of the Mo / ZIF-67 nanoparticles of this invention is maintained in the range of 240±10 nm, and the absolute value of the zeta potential of the nanoparticles is between 37 and 43 mV, exhibiting a stable particle size range and good stability.

[0045] (2) In this invention, polyvinylpyrrolidone (PVP) is dispersed in a 2-methylimidazole dispersion to induce the synthesis of Mo / ZIF-67. After adding the 2-methylimidazole dispersion of polyvinylpyrrolidone to the organometallic ligand solution, a certain amount of triethylamine is added to stabilize the molybdenum metal, regulate the pH and proton consumption, reduce by-products, and maximize the stability of Mo / ZIF-67 nanoparticles.

[0046] (3) This invention optimizes the reactant ratio, reaction conditions, and reagent addition, significantly improving the performance of nanoparticles, reducing reaction difficulty, energy consumption, and equipment requirements. The nanoparticles prepared using the method of this invention maintain a particle size of around 240 nm and an absolute Zeta value of over 40 mV, exhibiting extremely high stability.

[0047] (4) This invention successfully synthesized stable molybdenum-based ZIF-67, which expands the anti-Staphylococcus aureus potential of the zinc-based family of metal-organic frameworks. Molybdenum metal and ZIF-67 provide more effective materials and solutions for antibacterial purposes, and are expected to improve the antibacterial effect of simple zinc-based metal-organic frameworks and achieve a synergistic antibacterial mechanism. Attached Figure Description

[0048] Figure 1 The effects of different preparation methods on the particle size of Mo / ZIF-67 in Examples 1 and 2 of this invention are shown.

[0049] Figure 2 The effects of different preparation methods on the potential of Mo / ZIF-67 in Examples 1 and 2 of this invention are shown.

[0050] Figure 3 The effect of the molar ratio of 2-methylimidazolium and cobalt nitrate hexahydrate on the particle size and PDI of Mo / ZIF-67 in this invention;

[0051] Figure 4 This invention relates to the effect of the molar ratio of cobalt nitrate hexahydrate and ammonium molybdate tetrahydrate on the particle size and PDI of Mo / ZIF-67.

[0052] Figure 5 This invention illustrates the effect of different PVP feed amounts on the particle size and potential of ZIF-67.

[0053] Figure 6 This invention illustrates the effect of different PVP feed amounts on the particle size and potential of Mo / ZIF-67.

[0054] Figure 7 This invention relates to the effect of the mass ratio of 2-methylimidazole and triethylamine on the particle size and PDI of Mo / ZIF-67.

[0055] Figure 8 This invention illustrates the effect of different ultrasonic reaction times on the particle size and PDI of Mo / ZIF-67.

[0056] Figure 9 This invention illustrates the effect of different ultrasonic reaction temperatures on the particle size and PDI of Mo / ZIF-67.

[0057] Figure 10 Example 7 of this invention illustrates the effect of different concentrations of ZIF-67 on the survival rate of Staphylococcus aureus.

[0058] Figure 11 This illustrates the effect of different nanoparticles on the survival rate of Staphylococcus aureus in Example 7 of the present invention.

[0059] Figure 12 The image shows the anti-Staphylococcus aureus effect of 0.2 mg / ml Mo / ZIF-67 in Example 7 of this invention;

[0060] Figure 13 The image shows the anti-Staphylococcus aureus effect of 0.2 mg / mL ZIF-67 in Example 7 of this invention;

[0061] Figure 14 This is a diagram showing the anti-Staphylococcus aureus effect of the blank group in Example 7 of the present invention;

[0062] Figure 15 This is a diagram showing the anti-Staphylococcus aureus effect of the blank group in Example 8 of the present invention;

[0063] Figure 16 This is a graph showing the anti-Staphylococcus aureus effect of 1 mg / mL Mo / ZIF-67 in Example 8 of the present invention;

[0064] Figure 17 This is a graph showing the anti-Staphylococcus aureus effect of 500 ug / mL Mo / ZIF-67 in Example 8 of the present invention;

[0065] Figure 18 This is a graph showing the anti-Staphylococcus aureus effect of 250ug / mLMo / ZIF-67 in Example 8 of the present invention;

[0066] Figure 19 This is a graph showing the anti-Staphylococcus aureus effect of 100ug / mLMo / ZIF-67 in Example 8 of the present invention;

[0067] Figure 20 This is a graph showing the anti-Staphylococcus aureus effect of 50ug / mLMo / ZIF-67 in Example 8 of the present invention;

[0068] Figure 21 This illustrates the effect of different concentrations of Mo / ZIF-67 on the survival rate of Staphylococcus aureus in Example 8 of this invention.

[0069] Figure 22 X-ray diffraction patterns of Mo / ZIF-67 prepared in Example 1 and ZIF-67 nanomaterials prepared in Comparative Example 2 of this invention;

[0070] Figure 23 Thermogravimetric analysis (TGA) diagrams of Mo / ZIF-67 nanomaterials prepared in Example 1 and ZIF-67 nanomaterials prepared in Comparative Example 2 are shown.

[0071] Figure 24 Fourier transform infrared (FTIR) images of the Mo / ZIF-67 nanomaterials prepared in Example 1 and the ZIF-67 nanomaterials prepared in Comparative Example 2 of this invention. Detailed Implementation

[0072] The technical solution of the present invention is described in detail below through specific embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0073] Example 1: Preparation of Mo / ZIF-67 using the "Ultrasonic Coordinated and Controllable Method"

[0074] Solution A was prepared by dissolving 0.29 g of cobalt nitrate hexahydrate in 3 mL of deionized water. Solution B was prepared by dissolving 5.5 g of 2-methylimidazole in 20 mL of deionized water. Solution C was prepared by dissolving 8.1 mg of ammonium molybdate tetrahydrate in 1 mL of deionized water. Solution D was prepared by adding 20 mg of polyvinylpyrrolidone to solution B and stirring at 700 rpm for 20 min at room temperature. Solution E was prepared by slowly adding solution C dropwise to solution A at a rate of 2–3 drops / second under a 50°C water bath. Solution E was then slowly added to solution D at a rate of 3 drops / second. The mixture was then incubated at 0°C in an ice bath for 30 min. After adding 0.22 g of triethylamine, the mixture was stirred at 600 rpm for 6 min at room temperature to obtain solution F. Solution F was then sonicated at 25°C for 45 min to obtain the Mo / ZIF-67 solution.

[0075] After the reaction, the Mo / ZIF-67 solution was centrifuged at 8000 rpm for 3 minutes at 28°C. The supernatant was discarded, and the dark purple precipitate was collected. The precipitate was washed three times with 10 ml of analytical ethanol and then dried in a vacuum oven at 65°C for 14 hours to obtain a dark purple powder, which was the Mo / ZIF-67 nanoparticle, with a product mass of 2.38 g. The product was then stored at -20°C in the dark.

[0076] Comparative Example 1 uses a one-pot method to prepare Mo / ZIF-67

[0077] Solution A was prepared by dissolving 0.29 g of cobalt nitrate hexahydrate in 3 mL of deionized water. Solution B was prepared by dissolving 5.5 g of 2-methylimidazole in 20 mL of deionized water. Solution C was prepared by dissolving 8.1 mg of ammonium molybdate tetrahydrate in 1 mL of deionized water. Solution C was slowly added dropwise to solution A at room temperature at a rate of 2–3 drops / second to obtain solution D. Solution D was then slowly added dropwise to solution B at a rate of 2 drops / second. The mixture was stirred at 600 rpm for 2 hours at room temperature.

[0078] After the reaction was completed, the reactants were centrifuged at 8000 rpm for 3 minutes at 28°C. The supernatant was discarded, and the dark purple precipitate was collected. The precipitate was washed three times with 10 ml of analytical ethanol and then dried in a vacuum oven at 65°C for 14 hours to obtain a dark purple powder, which was Mo / ZIF-67 nanoparticles, with a product mass of 1.97 g. The product was then stored at -20°C in the dark.

[0079] The particle size distribution and zeta potential of the Mo / ZIF-67 nanoparticles prepared in Example 1 and Comparative Example 1 were determined using a Malvern particle size analyzer. The results are shown in the figure. Figure 1 , Figure 2 .

[0080] like Figure 1 As shown, compared with the Mo / ZIF-67 prepared by the "ultrasonic coordinated and controllable method", the Mo / ZIF-67 nanoparticles obtained by the "one-pot method" have significantly larger particle size and an aggregation index much greater than 0.3, and the particle size distribution in the dispersion system is not uniform; the Mo / ZIF-67 nanoparticles prepared by the "ultrasonic coordinated and controllable method" have a suitable particle size and are uniformly distributed in the solution system.

[0081] like Figure 2 As shown, compared to the Mo / ZIF-67 prepared by the "ultrasonic coordinated and controllable method", the absolute value of the Zeta potential of the Mo / ZIF-67 nanoparticles obtained by the "one-pot method" is 14.7mV, which is not large. The particles in the system tend to aggregate and become unstable. The absolute value of the Zeta potential of the Mo / ZIF-67 nanoparticles prepared by the "ultrasonic coordinated and controllable method" reaches more than 40mV, which has good stability.

[0082] Comparative Example 2: ZIF-67 was prepared using the "ultrasonic coordinated and controllable method".

[0083] Solution A was prepared by dissolving 0.29 g of cobalt nitrate hexahydrate in 3 ml of deionized water. Solution B was prepared by dissolving 5.5 g of 2-methylimidazole in 20 ml of deionized water. Solution C was prepared by adding 20 mg of polyvinylpyrrolidone to solution B and stirring at 700 rpm at room temperature for 20 min. Solution D was then slowly added dropwise to solution C to obtain solution D at a dropping rate of 2 drops / second. Solution D was then incubated in an ice bath at 0°C for 10 min, followed by the addition of 0.22 g of triethylamine and stirring at 450 rpm at room temperature for 4 min to obtain solution E. Solution E was then sonicated at 30°C for 30 min to obtain ZIF-67 solution.

[0084] After the reaction, the ZIF-67 solution was centrifuged at 8000 rpm for 3 minutes at 28°C. The supernatant was discarded, and the dark purple precipitate was collected. The precipitate was washed three times with 10 ml of analytical ethanol and then dried in a vacuum oven at 65°C for 14 hours to obtain a purple powder, which was the ZIF-67 nanoparticle, with a product mass of 2.04 g. The product was then stored at -20°C in the dark.

[0085] Example 2 investigated the effect of the molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate on the particle size and PDI of Mo / ZIF-67.

[0086] While maintaining a cobalt nitrate hexahydrate mass of 0.29 g, the molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate was adjusted to 47:1, 59:1, 70:1, 82:1, and 94:1, respectively. The remaining reaction conditions and preparation steps were the same as in Example 1, and Mo / ZIF-67 nanoparticles were obtained.

[0087] The particle size distribution was analyzed and determined using a Malvern particle size analyzer, such as... Figure 3 As shown, when the molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate is between 59:1 and 82:1, the prepared Mo / ZIF-67 has a suitable particle size of 240±10 nm, and the aggregation index comparison shows that the Mo / ZIF-67 in each group is uniformly dispersed in the system.

[0088] Example 3 investigated the effect of the molar ratio of cobalt nitrate hexahydrate to ammonium molybdate tetrahydrate on the particle size and PDI of Mo / ZIF-67.

[0089] While maintaining an ammonium molybdate tetrahydrate mass of 8.1 mg, the molar ratio of cobalt nitrate hexahydrate to ammonium molybdate tetrahydrate was adjusted to 130:1, 140:1, 150:1, 160:1, 170:1, and 180:1. The remaining reaction conditions and preparation steps were the same as in Example 1, and Mo / ZIF-67 nanoparticles were obtained.

[0090] The particle size distribution was analyzed and determined using a Malvern particle size analyzer, such as... Figure 4 As shown, when the molar ratio of cobalt nitrate hexahydrate to ammonium molybdate tetrahydrate is between 150:1 and 160:1, the prepared Mo / ZIF-67 has a suitable particle size of 240±10 nm. Furthermore, the comparison of aggregation index shows that when the molar ratio of cobalt nitrate hexahydrate to ammonium molybdate tetrahydrate is between 150:1 and 160:1, Mo / ZIF-67 is uniformly dispersed in the system.

[0091] Example 4 investigated the effect of different polyvinylpyrrolidone (PVP) feed amounts on ZIF-67 and Mo / ZIF-67 nanoparticles.

[0092] The effects of 2-methylimidazole and polyvinylpyrrolidone mass ratios of 183–367:1 on the particle size and PDI of ZIF-67 and Mo / ZIF-67 were investigated.

[0093] While maintaining a 2-methylimidazole mass of 5.5 g, the mass of polyvinylpyrrolidone was adjusted to 15 mg, 20 mg, 25 mg, and 30 mg (i.e., the mass ratio of 2-methylimidazole to polyvinylpyrrolidone was 367:1, 275:1, 220:1, and 183:1, respectively). The remaining reaction conditions and preparation steps were the same as those in Comparative Example 2, and ZIF-67 nanoparticles were obtained.

[0094] While maintaining a 2-methylimidazole mass of 5.5 g, the mass of polyvinylpyrrolidone was adjusted to 15 mg, 20 mg, 25 mg, and 30 mg, respectively. The remaining reaction conditions and preparation steps were the same as in Example 1, and Mo / ZIF-67 nanoparticles were obtained.

[0095] Using a Malvern particle size analyzer, while keeping the mass of 2-methylimidazole constant, ZIF-67 and Mo / ZIF-67 prepared from different masses of polyvinylpyrrolidone showed differences in particle size and potential. Figure 5 and Figure 6 As shown, in comparison, when the dosage of polyvinylpyrrolidone is 20 mg, the particle sizes of the prepared ZIF-67 and Mo / ZIF-67 are suitable, at 440±10 nm and 240±10 nm, respectively. The potentials of the prepared ZIF-67 and Mo / ZIF-67 are relatively high. The potential of ZIF-67 nanoparticles can reach 24±1 mV, which has a certain degree of stability, while the potential of Mo / ZIF-67 can reach 43±1 mV, which has good stability.

[0096] Example 5 investigated the effect of different triethylamine dosages on ZIF-67 and Mo / ZIF-67 nanoparticles.

[0097] While maintaining a 2-methylimidazole mass of 5.5 g, the amount of triethylamine added was adjusted to 0.069 g, 0.092 g, 0.137 g, 0.22 g, and 0.36 g (i.e., the mass ratio of 2-methylimidazole to triethylamine was 80:1, 60:1, 40:1, 25:1, and 15:1, respectively). The remaining reaction conditions and preparation steps were the same as in Example 1, and Mo / ZIF-67 nanoparticles were obtained.

[0098] The particle size distribution was analyzed and determined using a Malvern particle size analyzer, such as... Figure 7 As shown, the particle size of Mo / ZIF-67 prepared with different masses of triethylamine varies. Relatively speaking, when the amount of triethylamine is 0.22g, the particle size of the prepared Mo / ZIF-67 is suitable at 240±10nm. A PDI of less than 0.3 indicates good dispersibility.

[0099] Example 6 investigated the effects of different ultrasonic reaction times and reaction temperatures on Mo / ZIF-67 nanoparticles.

[0100] 1. The ultrasonic reaction time was adjusted to 10 min, 25 min, 35 min, 45 min and 60 min respectively. The other reaction conditions and preparation steps were the same as in Example 1 to obtain Mo / ZIF-67 nanoparticles.

[0101] The particle size distribution was analyzed and determined using a Malvern particle size analyzer, such as... Figure 8As shown, the particle size of Mo / ZIF-67 prepared by different ultrasonic reaction times varies. When the ultrasonic reaction is performed for 45 min, the particle size of the prepared Mo / ZIF-67 nanoparticles is suitable, ranging from 240 ± 10 nm. The PDI is less than 0.3, indicating good dispersibility and stability.

[0102] 2. The ultrasonic reaction temperatures were adjusted to 15℃, 25℃, 35℃, 45℃, and 55℃ respectively. The remaining reaction conditions and preparation steps were the same as in Example 1, and Mo / ZIF-67 nanoparticles were obtained.

[0103] The particle size distribution was analyzed and determined using a Malvern particle size analyzer, such as... Figure 9 As shown, the particle size of Mo / ZIF-67 prepared at different ultrasonic temperatures varies. Relatively speaking, when the ultrasonic reaction temperature is 25℃, the particle size of the prepared Mo / ZIF-67 is suitable at 240±10nm. A PDI of less than 0.3 indicates good dispersibility and stability.

[0104] Example 7 investigated the antibacterial effect of ZIF-67 prepared by ultrasonic coordination method against Staphylococcus aureus.

[0105] The effect of ZIF-67 prepared by the ultrasonic coordination method in Comparative Example 2 on the survival rate of Staphylococcus aureus was studied. ZIF-67 solutions with concentrations of 10 mg / ml, 5 mg / ml, 1.25 mg / ml, 0.5 mg / ml, 0.1 mg / ml, 0.05 mg / ml, and 0.025 mg / ml were prepared using ultrapure water, with sterile water serving as the control group. Diluted Staphylococcus aureus (S. aureus) in the logarithmic growth phase (two colonies were selected from the cultured colonies the night before the experiment, cultured in 6 ml of TSB (tryptone soy broth) for 1 h, and then diluted 20,000 times) and ZIF-67 solutions with concentrations of 10 mg / ml, 5 mg / ml, 1.25 mg / ml, 0.5 mg / ml, 0.1 mg / ml, 0.05 mg / ml, and 0.025 mg / ml were placed on a shaker (250 rpm, 37 °C) and incubated for 1 h. Both the bacterial culture and ZIF-67 solution were 200 μL. The co-incubated sample was diluted 2 × 10⁻⁶ times. 4 Take 100 μL of the sample and spread it evenly on a solid agar plate. After 24 hours, count the bacteria and calculate the bacterial survival rate compared with the blank control group.

[0106] Blank control group: The diluted bacterial suspension of Staphylococcus aureus in the aforementioned logarithmic growth phase was directly placed in a petri dish and cultured for 12 hours (TSB (tryptic soy peptone) liquid medium, 37°C, biochemical incubator), without the addition of any antibacterial materials.

[0107] like Figure 10As shown, the antibacterial effect reached 90.07% when the concentration was 10 mg / ml.

[0108] The effects of the various components of Mo / ZIF-67 prepared in Example 1 on the survival rate of Staphylococcus aureus under the same conditions were investigated. ZIF-67 solutions with concentrations of 0.2 mg / ml and Mo / ZIF-67 solutions with concentrations of 0.2 mg / ml were prepared using ultrapure water, with sterile water serving as a control group. The aforementioned logarithmic growth cycle diluted S. aureus bacterial suspension and the 0.2 mg / ml ZIF-67 and Mo / ZIF-67 solutions were placed in a shaker (250 rpm, 37°C) and incubated for 1 h. The volume of both the bacterial suspension and the sample solution was 200 μL. The incubated sample was diluted 2 × 10⁻⁶ times. 4 Take 100 μL of the sample and spread it evenly on a solid agar plate. After 24 hours, count the bacteria and compare it with the blank control group to calculate the bacterial survival rate.

[0109] like Figure 11 As shown, compared to the blank group, 0.2 mg / ml Mo / ZIF-67 showed an inhibitory effect of over 90% on S. aureus. (See the graph below.) Figure 12 The inhibitory effect of 0.2 mg / mL ZIF-67 solution on S. aureus was approximately 78%, as shown in the figure below. Figure 13 The blank group effect image is as follows: Figure 14 The antibacterial effects of Mo-loaded nanoparticles differed significantly before and after loading. Example 8 investigated the antibacterial effect of Mo / ZIF-67 prepared by ultrasonic coordination method against Staphylococcus aureus.

[0110] The effect of Mo / ZIF-67 prepared in Example 1 of this invention on the survival rate of Staphylococcus aureus was studied. Mo / ZIF-67 solutions with concentrations of 1 mg / mL, 500 μg / mL, 250 μg / mL, 100 μg / mL, and 50 μg / mL were prepared using ultrapure water, with sterile water serving as the control group. A diluted bacterial suspension of *S. aureus* in the logarithmic growth phase (two colonies were selected from the cultured colonies the night before the experiment, cultured in 6 mL of TSB (tryptophan) liquid medium for 1 h, and then diluted 20,000 times) and Mo / ZIF-67 solutions with concentrations of 1 mg / mL, 500 μg / mL, 250 μg / mL, 100 μg / mL, and 50 μg / mL were incubated together on a shaker (250 rpm, 37 °C) for 1 h. The volume of both the bacterial suspension and the Mo / ZIF-67 solution was 200 μL. The co-incubated sample was diluted 2 × 10⁻⁶ times. 4 Take 100 μL of the sample and spread it evenly on a solid agar plate. After 24 hours, count the bacteria and compare it with the blank control group to calculate the bacterial survival rate.

[0111] The antibacterial effect graph for the blank control group is shown in Figure 15. The antibacterial effect graphs for Mo / ZIF-67 solutions with concentrations of 1 mg / mL, 500 μg / mL, 250 μg / mL, 100 μg / mL, and 50 μg / mL are shown in Figure 15. Figure 16 , Figure 17 , Figure 18 , Figure 19 , Figure 20 .like Figure 21 As shown, the antibacterial effect reached 90.07% when the concentration was 100 ug / mL. With the increase of concentration, the antibacterial effect increased significantly to 97.69% when the concentration was 1 mg / mL.

[0112] Example 9: Structural characterization of Mo / ZIF-67 nanoparticles prepared by an ultrasonically coordinated and controllable method

[0113] Figure 22 The X-ray diffraction patterns are of the Mo / ZIF-67 nanomaterial prepared in Example 1 and the ZIF-67 nanomaterial prepared in Comparative Example 2.

[0114] (1) Comparison of diffraction peak positions (2θ) and characteristic peak shift analysis: ZIF-67: Typical diffraction peaks are mainly distributed at the following positions: approximately 7.3°, 10.4°, 12.8°, 16.5°, 19.9°, 23.1°, etc., corresponding to the standard diffraction peaks of ZIF-67. Mo / ZIF-67: Compared with ZIF-67, the positions of the main diffraction peaks are slightly shifted: the 7.3° peak shifts to approximately 7.1°, and the 10.4° peak shifts to 10.2°, indicating that the lattice parameters increase due to the introduction of molybdenum. Analysis of new or missing peaks: No obvious new peaks were observed in the XRD pattern of molybdenum-based ZIF-67, indicating that the introduction of molybdenum did not form a new phase and still maintains the framework structure of ZIF-67, with local structural adjustments. All main diffraction peaks correspond to the characteristic peaks of ZIF-67, and no characteristic peaks have disappeared, indicating that the framework structure has not been destroyed.

[0115] (2) Comparison of diffraction peak intensities and characteristics of intensity changes: Molybdenum-based ZIF-67: The intensity of some diffraction peaks differs from that of ZIF-67. For example, the intensity of the 2θ peak at approximately 19.9° is significantly enhanced in the molybdenum-based ZIF-67, while the intensity of the 23.1° peak is slightly reduced. Molybdenum has an atomic number (42) greater than that of cobalt (27), resulting in stronger scattering ability. If Mo replaces Co, the diffraction intensity of certain crystal planes is enhanced due to changes in electron cloud density. Intensity changes may also be related to crystal orientation, grain size, or defect concentration. Peak width changes: The diffraction peak width of molybdenum-based ZIF-67 is slightly increased compared to ZIF-67, especially the high-angle peaks. The increase in peak width may indicate a decrease in grain size or the presence of more defects in the lattice.

[0116] (3) Crystal structure and coordination environment analysis, framework structure retention: The diffraction peak distributions of the two are highly similar, indicating that the molybdenum-based ZIF-67 still maintains the zeolite-like imidazole framework structure of ZIF-67, and the introduction of Mo did not destroy the tetrahedral coordination network. The shifted peak positions and changes in intensity indicate that the structural adjustment mainly stems from the difference in ionic radii of the metal sites, rather than changes in the framework topology.

[0117] (4) Overall, the introduction of molybdenum did not disrupt the framework structure of ZIF-67, but because the atomic radius of Mo is larger than that of Co, it caused slight lattice expansion and a shift of the diffraction peaks to lower angles. The changes in diffraction peak intensity are related to the high scattering ability of Mo and lattice distortion. No new phase was formed, indicating that Mo-based ZIF-67 is a doped or substituted derivative. The increase in peak width suggests a decrease in grain size or an increase in defects, which may be related to the changes in crystallinity during the synthesis process caused by the introduction of Mo.

[0118] Figure 23 Thermogravimetric analysis (TGA) diagrams of Mo / ZIF-67 nanomaterials prepared in Example 1 and ZIF-67 nanomaterials prepared in Comparative Example 2 are shown.

[0119] As shown in the figure, it can be seen that:

[0120] (1) Low temperature zone (50-200℃): Adsorbed water desorption stage ZIF-67:

[0121] Starting from 50℃, the mass decreases slowly, dropping from 100% to approximately 86.8% at 200℃. The DTG curve shows a slight weight loss peak in the low-temperature region, corresponding to the removal of physically adsorbed water. For Mo / ZIF-67, the mass decreases from 100% to approximately 94.6% between 50-200℃, a smaller weight loss than ZIF-67. This is because the introduction of Mo reduces the hydrophilic sites in the material, or the presence of molybdenum oxide inhibits water adsorption.

[0122] Mid-temperature range (200-400℃): Framework decomposition stage. ZIF-67: The 200-400℃ range is the main decomposition range, with the mass decreasing from 86.8% to about 70%. The DTG curve shows a significant weight loss peak at 300-350℃, corresponding to the decomposition of the ZIF-67 organic ligand. Mo / ZIF-67: The mass decreases from 94.6% to about 80% at 200-400℃. The weight loss rate is more gradual than that of ZIF-67, with no obvious sharp weight loss peak, indicating that the introduction of Mo delays the thermal decomposition of the framework and increases the activation energy of ligand decomposition.

[0123] High-temperature zone (400-610℃): Residue stabilization stage. ZIF-67: At 400-610℃, the mass slowly decreases to about 58%. The DTG curve shows a decrease in the rate of weight loss, and the final residue is metal oxides such as CoO. Mo / ZIF-67: At 400-610℃, the mass decreases to about 56%, with a slightly lower residue than ZIF-67. This difference in residue mass is due to the partial volatilization of Mo oxides at high temperatures or the formation of low-melting-point solid solutions with CoO.

[0124] (2) Analysis of thermal stability differences: ZIF-67 begins to lose weight significantly at 100℃, while the weight loss rate of Mo / ZIF-67 only increases significantly after 150℃, indicating that Mo doping increases the initial decomposition temperature of the material by about 50℃, thus enhancing thermal stability. Decomposition rate and number of stages: The DTG curve of ZIF-67 shows a single main decomposition peak (300-350℃), corresponding to the one-time decomposition of the ligand; the mass curve of Mo / ZIF-67 is smoother with no obvious peak, possibly because Mo and Co form a mixed coordination environment, resulting in a more dispersed ligand decomposition process and a lower decomposition rate.

[0125] (3) Final residual mass: ZIF-67 has a residual mass of about 58% at 610℃, which corresponds to the theoretical residual amount of CoO; Mo / ZIF-67 has a residual mass of about 56%, because the residual composition is changed due to the partial decomposition or volatilization of MoO3 at high temperature or the formation of mixed oxides.

[0126] Figure 24 Fourier transform infrared spectra of Mo / ZIF-67 nanomaterials prepared in Example 1 and ZIF-67 nanomaterials prepared in Comparative Example 2.

[0127] (1) ZIF-67: at 3100-3000cm -1 The nearby absorption peaks indicate the presence of unsaturated CH bonds (such as in alkenes and aromatics). The absorption peaks in the 3000-2850 cm⁻¹ range indicate the presence of unsaturated CH bonds. -1 The nearby absorption peaks are associated with saturated CH bonds (such as in alkanes).

[0128] At 1700cm -1 The strong absorption peaks in the vicinity correspond to C=O double bonds (such as carbonyl groups). At 1600-1500 cm⁻¹... -1 The nearby absorption peaks may be related to the skeletal vibrations of the benzene ring.

[0129] (2) Ammonium molybdate tetrahydrate: 3600-3200 cm -1 The nearby absorption peaks may be related to the stretching vibrations of the OH groups in water molecules, since ammonium molybdate tetrahydrate contains water of crystallization. The absorption peaks are located at 1600-1500 cm⁻¹. -1 The nearby absorption peaks are related to ammonium ions (NH4). +The absorption peaks related to the deformation vibrations of molybdenum-oxygen (Mo-O) are observed in the 1000-400 cm⁻¹ range. -1 Interval.

[0130] (3) Mo / ZIF-67: 3100-3000cm -1 The nearby absorption peaks indicate the presence of unsaturated CH bonds (such as in alkenes and aromatics). The absorption peaks in the 3000-2850 cm⁻¹ range indicate the presence of unsaturated CH bonds. -1 The nearby absorption peaks are associated with saturated CH bonds (such as in alkanes).

[0131] At 1700cm -1 The strong absorption peaks in the vicinity correspond to C=O double bonds (such as carbonyl groups). At 1600-1500 cm⁻¹... -1 The nearby absorption peaks are related to the skeletal vibrations of the benzene ring.

[0132] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to it in form and detail without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A method for preparing molybdenum-based ZIF-67 antibacterial nanoparticles, characterized in that, Includes the following steps: (1) Cobalt nitrate hexahydrate was dispersed in a solvent to obtain a cobalt nitrate hexahydrate dispersion; (2) Disperse 2-methylimidazole in a solvent to obtain a 2-methylimidazole dispersion; (3) Add polyvinylpyrrolidone to the 2-methylimidazole dispersion obtained in step (2), stir to dissolve, and obtain a 2-methylimidazole dispersion of polyvinylpyrrolidone; (4) Disperse ammonium molybdate tetrahydrate in a solvent to obtain an ammonium molybdate tetrahydrate dispersion; (5) At 40-65℃, the ammonium molybdate tetrahydrate dispersion obtained in step (4) is added to the cobalt nitrate hexahydrate dispersion obtained in step (1) to obtain an organic ligand solution containing molybdenum and cobalt. (6) Add the organic ligand solution obtained in step (5) to the 2-methylimidazolium dispersion of polyvinylpyrrolidone obtained in step (3), let it stand at 0-5℃, add triethylamine, stir the reaction to obtain the initial reaction solution. (7) The initial reaction solution obtained in step (6) is reacted under ultrasonic action to obtain Mo / ZIF-67 solution; (8) The Mo / ZIF-67 solution obtained in step (7) is subjected to solid-liquid separation, the precipitate is washed, filtered, and dried to obtain the molybdenum-based ZIF-67 antibacterial nanoparticles, namely Mo / ZIF-67 nanoparticles.

2. The preparation method according to claim 1, characterized in that, In steps (1), (2) and (4), the solvent is water, ethanol or methanol.

3. The preparation method according to claim 1, characterized in that, The molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 47:1-94:

1.

4. The preparation method according to claim 1, characterized in that, The molar ratio of ammonium molybdate tetrahydrate to cobalt nitrate hexahydrate is 1:130-1:

180.

5. The preparation method according to claim 1, characterized in that, In step (3), the stirring time is 15-30 min and the stirring speed is 550-750 rpm; the mass ratio of 2-methylimidazole to polyvinylpyrrolidone is 183-367:

1.

6. The preparation method according to claim 1, characterized in that, In step (6), the settling time is 10-30 min, the mass ratio of 2-methylimidazole to triethylamine is 15-80:1, the stirring rate is 500-750 rpm, and the stirring time is 5-8 min.

7. The preparation method according to claim 1, characterized in that, In step (7), the reaction time under ultrasound is 10 min to 1 h, and the reaction temperature is 15 to 55 °C.

8. The preparation method according to claim 1, characterized in that, In step (8), the solid-liquid separation method is: centrifugation at a speed of 5000-9000 rpm, a temperature of 20-35℃, and a time of 3-8 min.

9. Molybdenum-based ZIF-67 antibacterial nanoparticles prepared by the preparation method according to any one of claims 1-8.

10. The application of the molybdenum-based ZIF-67 antibacterial nanoparticles according to claim 9 in the fight against Staphylococcus aureus.

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