Preparation of water-soluble salt nanomaterials by anti-solvent crystallization method

Abstract

A preparation method of a water-soluble salt@PEI composite nanomaterial, the method comprising the following steps: adding a water-soluble salt to water and dissolving it, then adding an appropriate amount of alcohol to obtain a transparent mixed salt solution; dissolving polyethyleneimine (PEI) in methanol (or ethanol, propanol) to obtain a PEI alcohol solution; transferring and dropping the mixed salt solution into the PEI alcohol solution, and obtaining a transparent or slightly blue solution after dropping; heating the transparent or slightly blue solution to room temperature to obtain a blue or white water-soluble salt@PEI dispersion, and then centrifuging to obtain a water-soluble salt@PEI nanocomposite material. The prepared nanocomposite material has controllable particle size, high stability, good dispersibility, and is not easy to agglomerate.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterials, and particularly relates to a method for preparing water-soluble salt@PEI composite nanomaterials. Background Art

[0002] The design and fabrication of colloidal nanoparticles with hollow interiors have generated great interest in various applications such as encapsulation and drug delivery. The formation of the hollow interior typically relies on the use of templates (hard or soft), which are characterized by well-defined shapes and uniform, controllable sizes. Generally, it is necessary to remove the template under simple and mild conditions in order to retain the hollow structure while minimizing production costs. To this end, water-soluble templates are preferred because they can be easily and rapidly removed by simply dispersing the sample in water.

[0003] The simplest method may be based on the slow evaporation of an aqueous solution of salt, and various additives can be added to control the morphology of the resulting crystals. However, the crystals obtained using this method inevitably have large particle sizes, typically in the micrometer range. To reduce the particle size to the nanometer range, techniques such as spray drying, vapor shock cooling, and rapid evaporation of water from aerosols are employed. However, the typical characteristic of these products is a wide particle size distribution. And such evaporation methods are highly energy-consuming. If the separation of salt from water can be accomplished without evaporating water, a significant amount of energy can be saved.

[0004] Another method is the anti-solvent crystallization method. In the anti-solvent method, the salt to be crystallized is obtained by adding an anti-solvent to a solvent containing the salt, and vice versa. The crystallization of the salt is thereby induced. Then, if necessary, the resulting salt can be separated from the reaction mixture by centrifugation or filtration. The main drawback of the traditional anti-solvent method is that: due to the geometry of the container and the rate and location of addition of the anti-solvent, the particle size of the resulting product can vary over a wide range. For example, when scaling up the method proportionally, or when changing the process settings, different products can be obtained due to changes in process conditions. Especially for methods on an industrial scale, the anti-solvent method is problematic due to a lack of reproducibility and robustness.

[0005] A method often used in anti-solvent crystallization is the so-called quasi-emulsion solvent (QESD) diffusion method. In the QESD method, solvent droplets containing dissolved crystalline substances are generated in the anti-solvent. Generally, the droplets are generated by a high-shear method, which is a well-known technique in the field of mixing. Once these droplets are formed, the anti-solvent diffuses into these droplets, resulting in the precipitation of crystals, that is, the solvent and the anti-solvent need to diffuse out of and into the droplets respectively. The formed crystals are dispersed in a mixture of the anti-solvent and the solvent (diffused out from the original droplets). If necessary, an emulsifier (or a mixture of emulsifiers) can be added to the anti-solvent and / or the solvent to help stabilize the droplets. However, the key to this method lies in forming droplets where the anti-solvent is the continuous phase. The droplet size is controlled by the physical interaction between the solvent and the anti-solvent, such as surface tension. However, since emulsification and anti-solvent crystallization occur simultaneously in the QESD method, it is difficult to control the particle size distribution of the crystallized compounds.

[0006] Therefore, in order to obtain salts at the nanoscale, an improved anti-solvent method is needed that can control the particle size distribution and particle size. In practical applications, nanomaterials are prone to agglomeration, resulting in poor dispersibility. Therefore, it is often necessary to coat with surfactants to prevent agglomeration and improve dispersibility.

[0007] Polyethyleneimine (PEI) is a polymer containing amines and has the highest cation density among existing materials. It exists in the form of polycations in water, can neutralize and adsorb all anionic substances, and can also chelate heavy metal ions. It has high adhesion and high adsorption, can form hydrogen bonds with hydroxyl groups, ionic bonds with carboxyl groups, and can also form covalent bonds with carbonyl groups. At the same time, due to its structure with polar groups (amines) and hydrophobic groups (vinyl groups), it can be used as a surfactant to prevent the growth of nanoparticles and can be dissolved in water for removal.

[0008] Therefore, using PEI as a surfactant for water-soluble salt nanotemplates has potential advantages. Summary of the Invention

[0009] The object of the present invention is to provide a simple method for preparing water-soluble salt@PEI composite nanomaterials with controllable particle size, narrow particle size, and good dispersibility.

[0010] To solve the above technical problems, the present invention provides a preparation method of first low-temperature emulsification and then heating-induced anti-solvent crystallization, including the following steps:

[0011] Step 1: Dissolve the water-soluble salt in water, and then add an appropriate amount of methanol (or ethanol, propanol, ethylene glycol, or a mixed solution of ethylene glycol and one of the monohydric alcohols) according to a water / alcohol ratio of 3:1 to 3:5 to obtain a transparent mixed salt solution to lower the melting point, and then place it at a temperature of 10°C to -50°C;

[0012] Step 2: Dissolve polyethyleneimine (PEI) in methanol (or ethanol, propanol) to obtain a PEI alcohol solution, and place it in a constant temperature environment of -50°C to -90°C with continuous vigorous stirring.

[0013] Step 3: Transfer the mixed salt solution prepared in Step 1 to a syringe, and then slowly drip it into the PEI alcohol solution prepared in Step 2 according to the volume ratio of water / PEI alcohol solution in the mixed salt solution of 1:100 to 10:100. During the dripping process, the PEI alcohol solution is always kept under constant temperature and vigorous stirring at -50°C to -90°C. After dripping, a transparent or slightly blue solution is obtained. If there are solidified particles, continue to stir at -50°C to -90°C until completely melted and dissolved.

[0014] Step 4: Keep stirring the transparent or slightly blue solution obtained in Step 3 at -50°C to -90°C for 10 - 100 min (preferably 20 min), and then place it in a room temperature environment and continue to stir until it naturally warms up to room temperature to obtain a blue or white water-soluble salt@PEI dispersion. Subsequently, centrifuge it to obtain the water-soluble salt@PEI nanocomposite.

[0015] Preferably, in Step 2, the molecular weight of PEI is greater than or equal to 10000, and the concentration of PEI in the PEI alcohol solution is 0.5 g / L to 20 g / L.

[0016] Preferably, in Step 4, the centrifugation rate is greater than or equal to 10000 r / min, and the centrifugation time is 10 min to 60 min.

[0017] The present invention also includes a water-soluble salt@PEI nanocomposite prepared by using any of the above preparation methods.

[0018] The present invention also includes the application of the water-soluble salt@PEI nanocomposite as a water-soluble template for hollow structure materials.

[0019] The beneficial effects of the present invention are as follows:

[0020] The present invention first drops a water-alcohol mixed solution of a water-soluble salt into alcohol at a low temperature to obtain a transparent or slightly blue (with a small amount of crystallization) microemulsion. Then, during the heating process, inverse solvent crystallization starts to occur when the temperature is higher than a certain temperature. Since water (the solvent) is evenly dispersed in alcohol (the inverse solvent), a large amount of salt crystals are formed instantaneously, with a narrow particle size distribution, and the particle size can be controlled by controlling the concentration of the salt and the concentration of PEI (the surfactant).

[0021] The preparation method of the present invention is simple, suitable for industrial production. The prepared water-soluble salt@PEI nanocomposite has controllable particle size, narrow particle size distribution, good dispersibility, is not easy to agglomerate, and can be used for the application of a water-soluble template for hollow structure materials. Description of the Drawings

[0022] To make the content of the present invention easier to be clearly understood, the following further describes the present invention in detail according to specific embodiments of the present invention and in combination with the accompanying drawings, where

[0023] Figure 1 Figure 1 is a scanning electron microscope image of the Li2SO4@PEI nanocomposite prepared in Example 1;

[0024] Figure 2 Figure 2 is a scanning electron microscope image of the Na2SO4@PEI nanocomposite prepared in Example 2;

[0025] Figure 3 Figure 3 is a scanning electron microscope image of the Na2SO4@PEI nanocomposite prepared in Example 2;

[0026] Figure 4 Figure 4 is a scanning electron microscope image of the NaHCO3@PEI nanocomposite prepared in Example 3;

[0027] Figure 5 Figure 5 is a scanning electron microscope image of the NaHCO3@PEI nanocomposite prepared in Example 3. Detailed Description of the Embodiments

[0028] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in combination with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0029] Example 1

[0030] A preparation method of a water-soluble salt@PEI nanocomposite, comprising the following steps:

[0031] Step 1: Add the water-soluble salt to water and dissolve it, then add an appropriate amount of methanol (or ethanol, propanol, ethylene glycol, or a mixed solution of ethylene glycol and one of the monohydric alcohols) according to a water / alcohol ratio of 3 ml:1 ml to 3 ml:5 ml to obtain a transparent mixed salt solution, thereby reducing the melting point, and then place it at a temperature of 10°C to -50°C;

[0032] Step 2: Dissolve polyethyleneimine (PEI) in methanol (or ethanol, propanol) to obtain a PEI alcohol solution, and place it at a constant temperature of -50°C to -90°C with continuous vigorous stirring;

[0033] Step 3: Transfer the mixed salt solution prepared in Step 1 into a syringe, and then slowly drop it into the PEI alcohol solution prepared in Step 2 at a volume ratio of water / PEI alcohol solution in the mixed salt solution of 1 ml:100 ml to 10 ml:100 ml. During the dropping process, the PEI alcohol solution is constantly stirred vigorously at a constant temperature of -50°C to -90°C. After dropping, a transparent or slightly blue solution is obtained. If there are solidified particles, continue to stir at -50°C to -90°C until completely melted and dissolved;

[0034] Step 4: Keep stirring the transparent or slightly blue solution in Step 3 at -50°C to -90°C for 20 min, and then place it in a room temperature environment and continue to stir until it naturally warms up to room temperature to obtain a blue or white water-soluble salt@PEI dispersion. Subsequently, centrifuge it to obtain the water-soluble salt@PEI nanocomposite.

[0035] Specifically, in Step 1, the water-soluble salt is Li2SO4, the mass ratio of Li2SO4 to water is 1:14, the added alcohol is a mixed alcohol with a ratio of ethylene glycol / ethanol of 2 ml:1 ml, and the mixed alcohol is added at a water / mixed alcohol ratio of 1 ml:1 ml.

[0036] Further, the Li2SO4 mixed solution in Step 1 is placed at 0°C.

[0037] Preferably, in Step 2, PEI is dissolved in ethanol, the molecular weight of PEI is 10,000, the concentration of the PEI ethanol solution is 10 g / L, and the PEI ethanol solution is placed at a constant temperature of -90°C and stirred.

[0038] Further, in Step 3, it is slowly dropped at a volume ratio of water / PEI ethanol solution in the Li2SO4 mixed solution of 3 ml:100 ml. During the dropping process, the PEI ethanol solution is constantly stirred vigorously at a constant temperature of -90°C.

[0039] Further, in Step 4, keep stirring the transparent or slightly blue solution in Step 3 at -90°C for 20 min. The centrifugation rate is 10,000 r / min, and the centrifugation time is 20 min.

[0040] Characterization test: The scanning electron microscope image of the Li2SO4@PEI nanocomposite prepared in Example 1 is as Figure 1 shown. From Figure 1It can be seen that the particle size of Li2SO4@PEI nanoparticles is about 40 nm, and the particle size distribution is narrow. Due to the relatively dense aggregation caused by centrifugation, there is no spontaneous adsorption and agglomeration between the particles, which can be confirmed by the blue color of the mixed solution before centrifugation (Rayleigh scattering phenomenon) and the Tyndall effect generated by laser irradiation. In addition, there is less precipitation after the mixed solution before centrifugation is left standing for a long time, and the Li2SO4@PEI nanoparticles obtained by centrifugation can be easily dispersed by ultrasonic dispersion, proving that the Li2SO4@PEI nanoparticles have excellent dispersibility.

[0041] Example 2

[0042] A preparation method of a water-soluble salt@PEI nanocomposite, comprising the following steps:

[0043] Step 1: Dissolve the water-soluble salt in water, and then add an appropriate amount of methanol (or ethanol, propanol, ethylene glycol, or a mixed solution of ethylene glycol and one of the monohydric alcohols) according to a water / alcohol ratio of 3 ml:1 ml to 3 ml:5 ml to obtain a transparent mixed salt solution, thereby reducing the melting point, and then place it at a temperature of 10°C to -50°C;

[0044] Step 2: Dissolve polyethyleneimine (PEI) in methanol (or ethanol, propanol) to obtain a PEI alcohol solution, and place it at a constant temperature of -50°C to -90°C with continuous vigorous stirring;

[0045] Step 3: Transfer the mixed salt solution prepared in Step 1 to a syringe, and then slowly add it dropwise to the PEI alcohol solution prepared in Step 2 according to a volume ratio of water in the mixed salt solution to the PEI alcohol solution of 1 ml:100 ml to 10 ml:100 ml. During the dropping process, the PEI alcohol solution is always kept at a constant temperature of -50°C to -90°C with vigorous stirring. After dropping, a transparent or slightly blue solution is obtained. If there are solidified particles, continue to stir at -50°C to -90°C until completely melted and dissolved;

[0046] Step 4: Keep the transparent or slightly blue solution in Step 3 stirring at -50°C to -90°C for 20 min, and then place it in a room temperature environment and continue to stir until it naturally warms up to room temperature to obtain a blue or white water-soluble salt@PEI dispersion, and then centrifuge to obtain the water-soluble salt@PEI nanocomposite.

[0047] Specifically, in Step 1, the water-soluble salt is Na2SO4, the mass ratio of Na2SO4 to water is 1:21, the added alcohol is ethylene glycol, and ethylene glycol is added according to a water / ethylene glycol ratio of 3 ml:4 ml.

[0048] Further, the Na2SO4 mixed solution in Step 1 is placed at 0°C.

[0049] Preferably, in the second step, PEI is dissolved in ethanol. The molecular weight of PEI is 10,000, the concentration of the PEI ethanol solution is 5 g / L, and the PEI ethanol solution is placed in a constant temperature stirrer at -90°C.

[0050] Further, in the third step, the Na2SO4 mixed solution is slowly added dropwise according to the volume ratio of water / PEI ethanol solution of 3 ml:100 ml. During the dropping process, the PEI ethanol solution is always kept under violent stirring at a constant temperature of -90°C.

[0051] Further, in the fourth step, the transparent or slightly blue solution in the third step is kept under stirring at -90°C for 20 min. The centrifugation rate is 10,000 r / min and the centrifugation time is 20 min.

[0052] Characterization test: The scanning electron microscope images of the Na2SO4@PEI nanocomposite prepared in Example 2 are as shown in Figure 2 and Figure 3 As can be seen from Figure 2 and Figure 3 the diameter of the Na2SO4@PEI nanoparticles is about 50 nm - 100 nm, and the length is 100 nm - 200 nm, and the particle size distribution is relatively narrow; due to relatively dense aggregation caused by centrifugation, but there is no spontaneous adsorption and agglomeration between the particles, which can be confirmed by the blue color (Rayleigh scattering phenomenon) of the mixed solution before centrifugation and the Tyndall effect generated by laser irradiation. In addition, there is less precipitation after the mixed solution before centrifugation is left standing for a long time, and the Na2SO4@PEI nanoparticles obtained by centrifugation can be easily dispersed by ultrasonic dispersion, proving that the Na2SO4@PEI nanoparticles have excellent dispersibility.

[0053] Example 3

[0054] A preparation method of a water-soluble salt@PEI nanocomposite, comprising the following steps:

[0055] Step 1, adding a water-soluble salt to water to dissolve it, and then adding an appropriate amount of methanol (or ethanol, propanol, ethylene glycol, or a mixed solution of ethylene glycol and one of the monohydric alcohols) according to the water / alcohol ratio of 3 ml:1 ml - 3 ml:5 ml to obtain a transparent mixed salt solution, thereby reducing the melting point, and then placing it at a temperature of 10°C to -50°C;

[0056] Step 2, dissolving polyethyleneimine (PEI) in methanol (or ethanol, propanol) to obtain a PEI alcohol solution, and placing it under constant and violent stirring at a constant temperature of -50°C to -90°C;

[0057] Step 3: Transfer the mixed salt solution prepared in Step 1 into a syringe, and then slowly drop it into the PEI alcohol solution prepared in Step 2 according to the volume ratio of water / PEI alcohol solution in the mixed salt solution of 1 ml:100 ml to 10 ml:100 ml. During the dropping process, the PEI alcohol solution is constantly stirred vigorously at a constant temperature of -50°C to -90°C. After dropping, a transparent or slightly blue solution is obtained. If there are solidified particles, continue to stir at -50°C to -90°C until completely melted and dissolved;

[0058] Step 4: Keep stirring the transparent or slightly blue solution in Step 3 at -50°C to -90°C for 20 min, and then place it in a room temperature environment and continue to stir until it naturally warms up to room temperature to obtain a blue or white water-soluble salt@PEI dispersion. Subsequently, centrifuge it to obtain the water-soluble salt@PEI nanocomposite.

[0059] Specifically, in Step 1, the water-soluble salt is NaHCO3, the mass ratio of NaHCO3 to water is 1:18, the added alcohol is ethylene glycol, and ethylene glycol is added according to the water / ethylene glycol ratio of 3 ml:4 ml.

[0060] Further, the NaHCO3 mixed solution in Step 1 is placed at 0°C.

[0061] Preferably, in Step 2, PEI is dissolved in ethanol, the molecular weight of PEI is 10,000, the concentration of the PEI ethanol solution is 5 g / L, and the PEI ethanol solution is placed at -90°C and stirred constantly at a constant temperature.

[0062] Further, in Step 3, it is slowly dropped according to the volume ratio of water / PEI ethanol solution in the NaHCO3 mixed solution of 3 ml:100 ml. During the dropping process, the PEI ethanol solution is constantly stirred vigorously at a constant temperature of -90°C.

[0063] Further, in Step 4, keep stirring the transparent or slightly blue solution in Step 3 at -90°C for 20 min. The centrifugation rate is 10,000 r / min and the centrifugation time is 20 min.

[0064] Characterization test: The scanning electron microscope images of the NaHCO3@PEI nanocomposite prepared in Example 3 are as shown in Figure 4 and Figure 5 shown. From Figure 4 and Figure 5It can be seen that the diameter of the NaHCO3@PEI nanoparticles is less than 100 nm and the particle size distribution is narrow. Due to centrifugation, there is relatively dense aggregation, but there is no spontaneous adsorption and agglomeration between the particles, which can be confirmed by the blue color of the mixed solution before centrifugation (Rayleigh scattering phenomenon) and the Tyndall effect generated by laser irradiation. In addition, there is less precipitation after the mixed solution before centrifugation is left standing for a long time, and the NaHCO3@PEI nanoparticles obtained by centrifugation can be easily dispersed by ultrasonic dispersion, proving that the NaHCO3@PEI nanoparticles have excellent dispersibility.

[0065] Obviously, the above embodiments are only examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. Preparation method of a water-soluble salt@PEI nanocomposite, characterized in that, it includes the following steps: Step 1: Add the water-soluble salt to water for dissolution, then add an appropriate amount of alcohol according to a water / alcohol ratio of 3:1 to 3:5 to obtain a transparent mixed salt solution, and place it at a temperature of 10°C to -50°C; Step 2: Dissolve polyethyleneimine (PEI) in alcohol to obtain a PEI alcohol solution, and keep it at a constant temperature of -50°C to -90°C with stirring; Step 3: According to a volume ratio of water in the mixed salt solution to the PEI alcohol solution of 1:100 to 10:100, drop the mixed salt solution into the PEI alcohol solution prepared in Step 2. During the dropping process, the PEI alcohol solution always maintains a constant temperature of -50°C to -90°C with stirring. After dropping, a transparent or slightly blue solution is obtained; Step 4: Keep the transparent or slightly blue solution in Step 3 at -50°C to -90°C and stir for 10 - 100 min, then raise the temperature to room temperature to obtain a blue or white water-soluble salt@PEI dispersion, and then centrifuge to obtain the water-soluble salt@PEI nanocomposite; In Step 2, the molecular weight of PEI is greater than or equal to 10,000, and the concentration of PEI in the PEI alcohol solution is 0.5 g / L to 20 g / L; In Step 4, the centrifugation rate is greater than or equal to 10,000 r / min, and the centrifugation time is 10 min to 60 min.

2. A water-soluble salt@PEI nanocomposite, characterized in that, it is the water-soluble salt@PEI nanocomposite prepared by using the preparation method of Claim 1 above.

3. The water-soluble salt@PEI nanocomposite according to Claim 2, characterized in that, its application as a water-soluble template for a hollow structure material.

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