CN101789297B - Magnetic silicon oxide sphere and synthesizing method thereof - Google Patents

Abstract

The invention discloses a magnetic silica sphere and a synthesis method thereof. The magnetic silica sphere has a three-layer core-shell structure, including silica spheres, magnetic nanoparticles, and silica shell layers from the inside out; the size of the magnetic silica sphere The control range is between 50nm and 5μm. The synthesis method is: acidify the prefabricated positively charged magnetic nanoparticles, and sequentially add distilled water with a volume ratio of 40:8:1, prefabricated silica sphere ethanol suspension, ammonia water and a sufficient amount of ethyl orthosilicate. Stir at room temperature, filter, collect and vacuum-dry the product to obtain magnetic silica spheres. After the technical solution of the present invention is applied and implemented, it is possible to achieve one-step synthesis of magnetic silica spheres, and has the advantages of good product size controllability and high yield; the outer layer of silicon oxide not only serves as a protective layer, but also can be synthesized through simple silane modification and functionalization. It can give magnetic silica spheres a wider range of functionality and is a magnetic multi-functional platform.

Description

Magnetic silica ball and its synthesis method

technical field

The invention relates to a nanometer material and a synthesis preparation method thereof, in particular to a magnetic silicon oxide ball widely used in the research of biological needs and a synthesis method thereof.

Background technique

With the rise of the field of nano-biomedicine research, magnetic nanoparticles have become a research hotspot in recent years, and are widely used in targeted drug delivery, cell separation, nuclear magnetic resonance imaging, and cancer magnetothermal therapy. Among these magnetic nanoparticles, _Fe3O4 nanoparticles have attracted _much attention. Conventional preparation methods include co-precipitation, microemulsion/reversed micelles, sonochemical, hydrothermal/solvothermal, and pyrolysis, etc. The aqueous co-precipitation method obtains Fe ₃ O ₄ nanoparticles with poor crystallization, and the production yield of the microemulsion method is low; the pyrolysis method is a preparation method developed in recent years. ₃ O ₄ nanoparticles, which can precisely control the size of nanoparticles and prepare high-quality magnetic nanoparticles. However, most of the application fields of nanoparticles require good hydrophilicity, and the surface modification of magnetic nanoparticles is a difficult task, thus limiting the application of magnetic nanoparticles. The researchers expect to directly obtain well-crystallized monodisperse magnetic nanoparticles.

In practical applications, because magnetic particles are easy to agglomerate and have disadvantages such as poor chemical and physical stability, it is often necessary to modify the surface with a transition layer for protection and improve its biocompatibility, such as silicon oxide, polystyrene, etc. , copolymers, and other macromolecular organic compounds. Among them, silicon oxide is an ideal modification and encapsulation material, and mature silane chemistry can achieve good functional modification of silicon oxide. To obtain magnetic silica spheres, conventionally used methods include aggregation and adsorption. The aggregation method is to wrap magnetic particles in the formed silicon oxide matrix while forming silicon oxide. Although the Stober process is widely used to prepare various core/shell nanostructures, it is not an easy task to obtain monodisperse magnetic silica spheres with controllable size and shape. The microemulsion method can obtain magnetic silica spheres with uniform size and shape distribution, but the yield is low, and a large amount of organic solvent is used, which is difficult to remove. In short, the aggregation method is not ideal in the controllability of the shape and size of the product, and the position of the magnetic particles in the matrix cannot be controlled. In contrast, the adsorption method uses ready-made colloidal spheres as templates, and magnetic nanoparticles are adsorbed and assembled on the surface of colloidal spheres through electrostatic assembly or coordination to form a core/shell structure, and the size of the product is controlled by the colloidal sphere template. In this process, it is often necessary to modify the surface of the colloidal sphere to have a good adsorption effect on the magnetic nanoparticles. Such as the electrostatic assembly mechanism of Layer-by-layer method, or the coordination mechanism of grafting -SH group or _-NH2 group after silane modification. In order to maintain the stability of the core/shell structure, a protective layer needs to be wrapped at the end. It can be seen that there are multi-step reactions in the synthesis of magnetic silica spheres by the existing adsorption methods, and so far there are few reports on the one-step synthesis of magnetic silica spheres.

Contents of the invention

In view of the defects of the above-mentioned existing synthesis methods, the purpose of the present invention is to provide a magnetic silica sphere and a synthesis method thereof, so as to better control the size of the final magnetic silica sphere, or better size distribution, simplify Preparation process, increase yield.

The technical scheme that realizes first object of the present invention is:

A magnetic silicon oxide ball, characterized in that: the magnetic silicon oxide ball has a three-layer core-shell structure, the innermost layer is a silicon oxide ball, and the middle is a positively charged magnetic nanoparticle, which is self-assembled on the surface of the silicon oxide ball through charge difference , the outermost layer is a silicon oxide shell, which completely covers the magnetic nanoparticles. The control range of the size of the magnetic silicon oxide ball is between 50 nm and 5 μm.

The second purpose of the present invention will be achieved through the following technical solutions:

The synthesis method of magnetic silicon oxide balls: it is characterized in that: the prefabricated positively charged magnetic nanoparticles are acidified, and the distilled water with a volume ratio of 40:8:1, the prefabricated silicon oxide ball ethanol suspension, ammonia water and sufficient A certain amount of tetraethyl orthosilicate was stirred at room temperature, and the product was filtered, collected and vacuum-dried to obtain magnetic silica balls.

Further, the aforementioned method for synthesizing magnetic silica spheres, wherein the positively charged magnetic nanoparticles are prepared by a polyol solvothermal method; the silica spheres are prepared by hydrolysis of ethyl orthosilicate in a mixed solution of ethanol and ammonia water get.

The invention provides a magnetic silicon oxide sphere with a three-layer core-shell structure and a synthesis method thereof, which can realize one-step synthesis of magnetic silicon oxide spheres, and has the advantages of good product size controllability and high yield; the outer layer of silicon oxide not only As a protective layer, through simple silane modification and functionalization, magnetic silica spheres can be endowed with a wider range of functionality, which is a magnetic multifunctional platform.

Description of drawings

Fig. 1 is the XRD pattern of magnetic nanoparticles prepared by Synthesis Method Example 1 of the present invention;

Fig. 2a is the TEM photo of the magnetic nanoparticles prepared in Example 1 of the synthesis method of the present invention;

Fig. 2b is the selected area electron diffraction photo of Fig. 2a;

Fig. 3 is the TEM photograph of the product of different stages of Synthetic Method Example 1 of the present invention, wherein:

Figures 3a and 3b are silicon oxide balls, Figures 3c to 3e are magnetic silicon oxide balls, and Figure 3f is the cavity structure formed after the magnetic silicon oxide balls are pickled;

Figure 4 is a schematic diagram of the characterization of the magnetic properties of the magnetic nanoparticles and magnetic silica balls prepared in Example 1 of the present invention, wherein: Figure 4a and Figure 4b are the hysteresis loops of the magnetic nanoparticles and magnetic silica balls respectively; 4c and Fig. 4d are photos of the product magnetic silica sphere solution before and after adding magnetism;

Figure 5a and Figure 5b are TEM photos of the magnetic silica spheres prepared in Example 2 of the synthesis method of the present invention;

Figure 5c and Figure 5d are TEM photos of the magnetic silica spheres prepared in Example 3 of the synthesis method of the present invention.

Detailed ways

The invention provides a method for synthesizing female silica spheres with a core-shell structure in one step. Firstly, magnetic ferric oxide nanoparticles with good dispersibility were grown and synthesized by polyol solvothermal method. Due to the coordination effect of diethanolamine introduced in the reaction on the magnetic particles, the surface of the magnetic particles was positively charged. It electrostatically assembles with the negatively charged silicon oxide balls on the surface and adsorbs on the surface of the silicon oxide balls. At the same time, the hydrolysis of tetraethyl orthosilicate forms silica and deposits on the surface of silica spheres adsorbed with magnetic nanoparticles, forming a stable multilayer core/shell structure. Since the method of the present invention is to directly assemble magnetic nanoparticles on the surface of silicon oxide in one step, the size of silicon oxide balls can be precisely controlled based on the mature Stober process, so it is more convenient to control the size of the final magnetic silicon oxide balls, or better size distribution, Its size control range is between 50nm and 5μm.

From the perspective of the implementation of the present invention: the chemical reagents used in its synthesis are ferric trichloride (FeCl ₃ ), iron sulfate (Fe ₂ (SO ₄ ) ₃ ), iron nitrate (Fe(NO ₃ ) ₃ ), sulfurous acid Iron (FeSO ₄ ), ferrous chloride (FeCl ₂ ), sodium hydroxide (NaOH), diethanolamine, ethylene glycol, tetraethyl orthosilicate (TEOS), ammonia water, hydrochloric acid (HCl), acetic acid, sulfuric acid , nitric acid, etc.

(1) Synthesis of magnetic nanoparticles

Dissolve FeCl ₃ (or Fe ₂ (SO ₄ ) ₃ , Fe(NO ₃ ) ₃ ) and FeCl ₂ (or FeSO ₄ ) in ethylene glycol to form a final Fe ⁺³ and Fe ⁺² concentration of 0.01 -0.1mol/ml solution, wherein the ratio of Fe ⁺³ to Fe ⁺² is 2:1; at the same time, NaOH is dissolved in another part of ethylene glycol to form a solution with a concentration of 0.16-1.6M. During the reaction, first inject 2-20mL diethanolamine into the rapidly stirred 50mL iron ion solution, a dark green solution is formed immediately, and then 10mL NaOH is added. Stir evenly and transfer to a PTFE-lined stainless steel reaction kettle with a volume of 100mL, and keep warm at 180-220°C for 5-20 hours. The product was filtered, washed several times with distilled water and absolute ethanol, and finally dispersed in water to form a 0.5 wt% nanoparticle suspension.

(2) Preparation of silica balls

Inject tetraethyl orthosilicate (TEOS) into the mixed solution of ammonia water and ethanol, wherein the ratio of ethanol to ammonia water is 5:1-10:1, the concentration of TEOS formed is 0.001-0.01wt%, and stir at room temperature for 10 hours . The product was separated by a centrifuge, washed several times with absolute ethanol, and finally dispersed in ethanol to form a 0.8 wt% silica colloidal suspension.

(3) Preparation of magnetic silica balls

First, add a few drops of hydrochloric acid (or acetic acid, nitric acid, sulfuric acid) solution (0.1M) dropwise into 1-5mL magnetic particle aqueous solution, and immediately form a brown transparent solution, then add distilled water, silicon oxide ethanol suspension, and ammonia water in sequence, and then The volume ratio is 40:8:1. Finally, 0.05-0.3 mL of TEOS was added, stirred at room temperature for 5 hours, collected by filtration, and finally dried under vacuum at 40-70° C. for 2-10 hours to obtain magnetic silica balls.

The invention provides a method for synthesizing magnetic silica spheres with a core-shell structure in one step:

First, using ethylene glycol as a solvent and diethanolamine as a complexing agent, high-quality magnetic iron oxide nanoparticles were prepared by solvothermal, the surface of which was positively charged, and the charge density could be significantly enhanced in acidic solution to obtain Ideally dispersed clear suspension.

Next, using silica colloidal spheres as a template, magnetic nanoparticles can be assembled on the surface of silica colloidal spheres through electrostatic assembly due to their own negative charge, forming a core-shell structure.

The above-mentioned synthesis method of magnetic silica spheres has the following advantages:

1. Although the stability of the electrostatic assembly structure is not ideal, through the hydrolysis of TEOS, a silicon oxide protective layer can be wrapped around it at the same time, and the silicon oxide layer can be easily functionalized by silane modification. The magnetic silicon oxide ball is a kind of Good magnetic multifunctional material platform;

Second, because silica gel balls are used as templates, the existing Stober process has been able to achieve precise control of the size and shape of silica balls, and it is easier to control the size and shape of the final product as a template. And by adjusting the thickness of the outer layer of silicon oxide, the size of the magnetic silicon oxide ball can be further adjusted;

3. Since the magnetic nanoparticles are assembled on the surface of the silica ball, they can carry more magnetic particles and obtain higher magnetic induction;

4. The experimental process route is simple and the operation is convenient, especially the process of synthesizing magnetic silicon oxide balls is carried out in one step. The whole process is carried out at room temperature without any protective atmosphere, the process is simple, no complicated experimental equipment is required, and the reaction is fast. It is an efficient, rapid and environment-friendly method for preparing high-quality magnetic silicon oxide spheres.

Below just with three embodiments of the present invention in conjunction with accompanying drawing, the substantive characteristics of the present invention and remarkable progress are described in further non-restrictive detail:

Example 1

First, 4 mmol of FeCl ₃ and 2 mmol of FeCl ₂ were dissolved in 50 ml of ethylene glycol; at the same time, 16 mmol of NaOH was dissolved in another 10 ml of ethylene glycol. During the reaction, 10 mL of diethanolamine was first injected into 50 mL of the rapidly stirred iron ion solution, and a dark green solution was formed immediately, and then 10 mL of NaOH was added. Stir evenly and transfer to a 100mL polytetrafluoroethylene-lined stainless steel reaction kettle, and keep warm at 200°C for 8 hours. The product was filtered, washed several times with distilled water and absolute ethanol, and finally dispersed in water to form a 0.5 wt% nanoparticle suspension.

Inject 3ml of TEOS into 250ml of a mixed solution of ammonia water and ethanol, wherein the ratio of ethanol to ammonia water is 8:1, and stir at room temperature for 10 hours. The product was separated by a centrifuge, washed several times with absolute ethanol, and finally dispersed in ethanol to form a 0.8 wt% silica colloidal suspension.

First add 0.1ml of hydrochloric acid solution (0.1M) dropwise to 3mL of magnetic particle aqueous solution to form a brown transparent solution immediately, then add distilled water, silicon oxide ethanol suspension, and ammonia water in sequence, and the volume ratio is 40:8:1. Finally, 0.12 ml of TEOS was added, stirred at room temperature for 5 hours, collected by filtration, and finally dried in vacuum at 60° C. for 5 hours to obtain magnetic silica balls.

As shown in FIG. 1 , it is the XRD spectrum of the magnetic nanoparticles prepared in Example 1, from which it can be seen that the diffraction peaks can be well matched with the standard spectrum of Fe ₃ O ₄ . As shown in Fig. 2a, it is a TEM photo of the nanoparticles prepared in Example 1, the nanoparticles have good dispersion, and the average size is about 8nm. The selected area electron diffraction photo (Fig. 2b) shows a clear diffraction ring, indicating that the product has good crystallinity.

As shown in Figure 3, it is a TEM photo of the product in different stages in Example 1, wherein Figure 3a and Figure 3b are silicon oxide spheres, from which it can be found that its average diameter is about 170nm; what Figure 3c shows is the prepared magnetic silicon oxide Ball, Figure 3d and Figure 3e are a single magnetic ball and its partial enlarged photos, respectively, the multi-layer core-shell structure is clearly visible, and the magnetic nanoparticles are wrapped between the core and shell of the silica ball, forming a product similar to the structure of an egg. By acid washing, the magnetic nanoparticles can be dissolved to form a cavity structure, as shown in Figure 3f. Figure 4 shows the magnetic characterization results of the product. The saturation magnetization of the magnetic nanoparticles and the magnetic silica spheres are 45.3emu/g and 6.35emu/g respectively. The optical photos show that the magnetic silica spheres have a strong response to external magnetic fields. .

Example 2

A silicon oxide sphere with a diameter of 110 nm was used as a core to prepare a magnetic silicon oxide sphere, and the others were the same as in Example 1. Figure 5a and Figure 5b are TEM pictures of the finally obtained magnetic silica balls.

Example 3

A silicon oxide sphere with a diameter of 250 nm was used as a core to prepare a magnetic silicon oxide sphere, and the others were the same as in Example 1. Figure 5c and Figure 5d are TEM pictures of the finally obtained magnetic silica balls.

It can be seen that the method of the present invention can realize the assembly of magnetic nanoparticles on the surface of silica spheres with different diameters, thereby preparing magnetic silica spheres with different sizes.

Claims (5)

1. Magnetic silica ball, characterized in that: the magnetic silica ball has a three-layer core-shell structure, the innermost layer is a silica ball, and the middle is a positively charged magnetic nanoparticle, which is self-assembled on the silica through charge difference On the surface of the ball, the outermost layer is a silicon oxide shell, which completely covers the magnetic nanoparticles. 2 . The magnetic silicon oxide ball according to claim 1 , wherein the size of the magnetic silicon oxide ball can be adjusted within a range of 50 nm to 5 μm. 3 . 3. The synthesis method of magnetic silica balls: it is characterized in that: the prefabricated positively charged magnetic nanoparticles are acidified in aqueous solution, and distilled water with a volume ratio of 40:8:1 and prefabricated silica balls are suspended in ethanol successively solution, ammonia water and a sufficient amount of tetraethyl orthosilicate were stirred at room temperature, and the product was filtered, collected and vacuum-dried to obtain magnetic silica balls. 4 . The method for synthesizing magnetic silica spheres according to claim 3 , wherein the positively charged magnetic nanoparticles are prepared by a polyol solvothermal method. 5 . The method for synthesizing magnetic silica balls according to claim 3 , characterized in that: the silica balls are prepared by hydrolysis of ethyl orthosilicate in a mixed solution of ethanol and ammonia water. 5 .

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