CN107285325A - A kind of preparation method of the monodisperse silica nanosphere of novel green - Google Patents

Abstract

The invention provides a method for preparing novel green monodisperse silica nanospheres, comprising: preparing O/W type water/ethanol/dichloromethane surfactant-free microemulsion; Under the action of ultrasound and stirring, it is completely dissolved in the spherical "oil core" of the O/W surfactant-free microemulsion prepared in the first step, and then under the catalysis of ammonia water, tetraethyl orthosilicate realizes hydrolysis and polycondensation, and the reaction Centrifuge after completion. The solid component was washed several times with a polar solvent to obtain monodisperse SiO ₂ nanospheres, and the remaining liquid component was distilled to collect ethanol and dichloromethane. The method has the advantages of simple operation, low cost, environmental friendliness, reusable system and high efficiency. The prepared SiO ₂ nanospheres are uniform in size and have universal and large-scale production value. The steps are simple, the operation is convenient and the practicability is strong.

Description

A kind of preparation method of novel green monodisperse silica nanosphere

technical field

The invention belongs to the field of nanometer materials, in particular to a method for preparing novel green monodisperse silica nanospheres.

Background technique

Monodispersed SiO ₂ nanospheres have important application value in the fields of biomedicine, catalysis, functional materials, high-performance ceramics, coatings, etc. due to their large specific surface area, good dispersion, and good optical and mechanical properties. The method is one of the commonly used methods for preparing SiO ₂ nanospheres. This method has the advantages of simple operation and clean surface of the prepared silica nanospheres. This method only utilizes the interaction between solvents and does not contain a preparation template, so the controllability and repeatability of preparing silica nanospheres are poor, and it is difficult to obtain high-quality _SiO2 nanospheres. Another commonly used method for preparing _SiO2 nanospheres is the microemulsion method. The _SiO2 nanospheres prepared by this method have good monodispersity and adjustable size, but when building a microemulsion template, a large amount of surfactant and Co-surfactants, these two components are partially soluble in the water phase and oil phase in addition to entering the interface film of the microemulsion, which is not easy to recycle and cause pollution to the environment, and it is difficult to wash because of the surfactant loaded on the surface of the material These problems seriously restrict the application of the microemulsion method in the preparation of silica nanoparticles.

Contents of the invention

Aiming at the above problems, we proposed a method to prepare _SiO2 nanospheres using O/W type surfactant-free microemulsion as a template. Surfactant-free microemulsions are simple in composition, consisting only of water, oil, and "amphiphilic solvents." This new type of surfactant-free microemulsion system does not contain surfactants, but has similar microstructure and properties to microemulsions, and can overcome the shortcomings of containing a large amount of surfactants when preparing nanomaterials by microemulsions. Not only can the cost be significantly saved, but also the purity of the prepared nanometer material is higher.

In order to obtain monodisperse _SiO2 nanospheres with uniform shape and uniform particle size, this application carried out the preparation of _SiO2 nanospheres in different surfactant-free microemulsion systems. The formation law of SiO ₂ nanospheres in the surfactant-free microemulsion system was systematically studied. After a large number of experimental screenings, it was found that: the O/W type ethanol/dichloromethane/water surfactant-free microemulsion system was used as a template to prepare The silica nanospheres have the advantages of uniform shape and uniform particle size. And in this system, ethanol is used as a "dual solvent" and dichloromethane is used as an oil phase. These two solvents are not only low in cost, but also because of their low boiling points, they can be removed by simple distillation after the _SiO2 nanospheres are prepared. It can be recycled to achieve the purpose of recycling.

In order to achieve the above object, the present invention adopts the following technical solutions:

A method for preparing novel green monodisperse silica nanospheres, comprising:

Preparation of O/W type water/ethanol/dichloromethane surfactant-free microemulsion;

Under the action of ultrasound or stirring, tetraethyl orthosilicate (TEOS) is completely dissolved in the spherical "oil core" of the prepared O/W type surfactant-free microemulsion, and then under the catalysis of ammonia water, orthosilicic acid Ethyl ester is hydrolyzed and polycondensed. After the reaction is completed, the solid components are collected by centrifugation, washed three times with a polar solvent to obtain _SiO2 nanospheres, and the liquid components are distilled to collect ethanol and dichloromethane components.

Preferably, in the surfactant-free microemulsion, the mass fraction of fixed dichloromethane in the system is 20%, and the mass ratio of water to ethanol is 4-9.5:6-0.5 respectively.

Preferably, the volume ratio of ethyl orthosilicate to ammonia water (25%wt) is 1.3:3.

Preferably, the specific step of dissolving tetraethyl orthosilicate in the above-mentioned non-surfactant microemulsion is: slowly adding quantitative tetraethyl orthosilicate (TEOS) to the non-surfactant microemulsion under stirring. In the microemulsion, ultrasonic or mechanical stirring is performed for a certain period of time.

Preferably, the ammonia water is slowly added to the O/W surfactant-free microemulsion system in which tetraethyl orthosilicate is dissolved in an ice-water bath and under stirring conditions.

Preferably, the conditions for the hydrolysis and polycondensation are: standing and reacting in a water bath at 25-35° C. for 1-24 hours.

Preferably, the specific steps of separation are as follows: centrifuge the system after the reaction to collect solid components, wash with polar solvent three times, distill the liquid components, and collect ethanol and dichloromethane components.

Preferably, the polar solvent is ethanol, methanol, or water.

The present invention also provides monodisperse silica nanospheres prepared by any one of the above-mentioned methods.

Preferably, the particle size of the silica nanospheres is 275-785 mm.

The present invention also provides the application of any one of the above-mentioned monodisperse silica nanospheres in the preparation of biomedical materials, catalytic materials, functional materials, high-performance ceramics or coatings.

"Green" in the present invention refers to: a green synthesis method.

Beneficial effects of the present invention

(1) Compared with the traditional W/O type microemulsion method to prepare _SiO2 nanospheres, the present invention utilizes O/W type surfactant-free microemulsion as a template to prepare _SiO2 nanospheres, which significantly reduces the amount of oil phase , saving costs. Using O/W type water/ethanol/dichloromethane surfactant-free microemulsion as a template to prepare _SiO2 nanospheres, the method is simple to operate, low in cost, environmentally friendly, reusable in system, high in efficiency, and the prepared silica The nanosphere has a uniform shape and a uniform particle size, and has universal applicability and large-scale production value.

(2) The silicon dioxide nanospheres prepared by the present invention have good appearance, uniform size, wide adjustable range of particle diameter, clean surface and simple follow-up treatment. The surfactant-free microemulsion system has simple components, can be recycled, and does not contain surfactants, which can save a lot of cost.

(3) The preparation method of the present invention is simple, high in preparation efficiency, strong in practicability, and easy to popularize.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application, and do not constitute improper limitations to the present application.

Fig. 1 is the TEM figure of the silicon dioxide nanosphere obtained by changing the mass ratio of water and ethanol when the dichloromethane content is constant;

Fig. 2 is when water-alcohol ratio is 0.5:9.5, the EDS figure of the silica nanosphere of preparation;

3 is a TEM image of the silica nanospheres prepared in Comparative Example 1.

detailed description

It should be pointed out that the following detailed description is exemplary and intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

A kind of method that utilizes surfactant-free microemulsion to prepare silica nanosphere as template, comprises the steps:

(1) Preparation of O/W type surfactant-free microemulsion template: under stirring conditions, mix appropriate amount of water, ethanol and methylene chloride, and keep stirring for a certain period of time after mixing.

(2) Slowly add quantitative tetraethyl orthosilicate (TEOS) into the O/W type surfactant-free microemulsion system prepared in step (1) under stirring, and keep stirring for a certain period of time to make orthosilicic acid Ethyl esters are completely soluble in the O/W surfactant-free microemulsion "oil core".

(3) Slowly add quantitative ammonia water (25%wt) to the system obtained in step (2) under stirring conditions in an ice-water bath, continue stirring in an ice-water bath for a few minutes after the addition is complete, and then transfer to a 25°C water bath to stand for reaction 1 -24 hours.

(4) After the reaction is completed, centrifugation is carried out to obtain a white solid, which is washed 3 times with water, and the remaining liquid is distilled to recover ethanol and dichloromethane.

The principle of the present invention is: firstly utilize water, ethanol and dichloromethane to prepare O/W surfactant-free microemulsion template, then add reactant orthosilicate ethyl ester in the system, make orthosilicate Ethyl esters are completely soluble in the "oil core" of the O/W surfactant-free microemulsion system. Slowly add ammonia solution under ice-water bath conditions to ensure that the ammonia solution is dissolved in the water phase, and move the reaction device into a 25°C water bath to start the reaction.

The reaction process of the silica nanospheres prepared by this method is as follows:

hydrolysis:

Polycondensation:

When tetraethyl orthosilicate (TEOS) is added into the O/W surface-free microemulsion, it completely enters the "oil core" of the O/W type surfactant-free microemulsion, due to the interfacial film of the O/W droplet Composed of a large number of ethanol molecules and water molecules, water molecules can enter the "oil core" to undergo hydrolysis and condensation reactions with TEOS, from monohydroxysilicate monomers to polyhydroxysilicates until the formation of crystal nuclei. Finally, in the "oil core" of the O/W surfactant-free microemulsion system, spherical silica nanoparticles are formed.

Example 1:

(1) Mix 4 g of secondary ultrapure water with 76 g of ethanol, add 20 g of dichloromethane under stirring conditions, and continue stirring for 10 min after the addition is complete.

(2) Slowly add 1.3ml tetraethyl orthosilicate into the O/W type surfactant-free microemulsion system obtained in step (1) under stirring. After the addition is completed, sonicate for 10 minutes and stir for 20 minutes.

(3) Move the O/W type surfactant-free microemulsion system containing tetraethyl orthosilicate obtained in step (2) into an ice-water bath, and slowly add 3ml of ammonia water (25wt%) into it under stirring conditions, and continue stirring for 10min Afterwards, the reaction device was moved into a water bath at 25° C. for 6 hours of static reaction.

(4) After the reaction was finished, a white solid was obtained by centrifugation, and the white solid was washed 3 times to obtain SiO ₂ nanospheres. The remaining liquid components were distilled to collect ethanol and dichloromethane components. The SiO ₂ nanospheres were redispersed in ethanol, the TEM is shown in Figure (1)d, and the EDS image is shown in Figure (2).

Example 2:

(1) Mix 4 g of secondary ultrapure water with 36 g of ethanol, add 10 g of dichloromethane under stirring conditions, and continue stirring for 10 min after the addition is complete.

(2) Slowly add 1.3ml tetraethyl orthosilicate into the O/W type surfactant-free microemulsion system obtained in step (1) under stirring. After the addition is completed, sonicate for 10 minutes and stir for 20 minutes.

(3) Move the O/W type surfactant-free microemulsion system containing tetraethyl orthosilicate obtained in step (2) into an ice-water bath, and slowly add 3ml of ammonia water (25wt%) into it under stirring conditions, and continue stirring for 10min Afterwards, the reaction device was moved into a water bath at 25° C. for 6 hours of static reaction.

(4) After the reaction was finished, a white solid was obtained by centrifugation, and the white solid was washed 3 times to obtain SiO ₂ nanospheres. The remaining liquid components were distilled to collect ethanol and dichloromethane components. The _SiO2 nanospheres were redispersed in ethanol, and its TEM is shown in Fig. (1)c.

Example 3:

(1) Mix 4 g of secondary ultrapure water with 16 g of ethanol, add 5 g of dichloromethane under stirring conditions, and continue stirring for 10 min after the addition is complete.

(2) Slowly add 1.3ml tetraethyl orthosilicate into the O/W type surfactant-free microemulsion system obtained in step (1) under stirring. After the addition is completed, sonicate for 10 minutes and stir for 20 minutes.

(3) Move the O/W type surfactant-free microemulsion system containing tetraethyl orthosilicate obtained in step (2) into an ice-water bath, and slowly add 3ml of ammonia water (25wt%) into it under stirring conditions, and continue stirring for 10min Afterwards, the reaction device was moved into a water bath at 25° C. for 6 hours of static reaction.

(4) After the reaction was finished, a white solid was obtained by centrifugation, and the white solid was washed 3 times to obtain SiO ₂ nanospheres. The remaining liquid components were distilled to collect ethanol and dichloromethane components. The _SiO2 nanospheres were redispersed in ethanol, and the TEM is shown in Fig. (1)b.

Example 4:

(1) Mix 4 g of secondary ultrapure water with 16 g of ethanol, add 5 g of dichloromethane under stirring conditions, and continue stirring for 10 min after the addition is complete.

(2) Slowly add 1.3ml tetraethyl orthosilicate into the O/W type surfactant-free microemulsion system obtained in step (1) under stirring. After the addition is completed, sonicate for 10 minutes and stir for 20 minutes.

(3) Move the O/W type surfactant-free microemulsion system containing tetraethyl orthosilicate obtained in step (2) into an ice-water bath, and slowly add 3ml of ammonia water (25wt%) into it under stirring conditions, and continue stirring for 10min Afterwards, the reaction device was moved into a water bath at 25° C. for 6 hours of static reaction.

(4) After the reaction was finished, a white solid was obtained by centrifugation, and the white solid was washed 3 times to obtain SiO ₂ nanospheres. The remaining liquid components were distilled to collect ethanol and dichloromethane components. The _SiO2 nanospheres were redispersed in ethanol, and the TEM is shown in Figure (1)a.

Table 1. Particle sizes of silica nanospheres obtained under different water-alcohol ratios (R _w/e )

Comparative example 1:

(1) Mix 5 g of secondary ultrapure water with 45 g of ethanol.

(2) Slowly add 1.3ml tetraethyl orthosilicate into the mixed system of ethanol and water under stirring, and keep stirring for 20 minutes.

(3) Under stirring conditions, slowly add 2.0ml of ammonia water (25wt﹪) into the mixed system of ethanol and water containing ethyl orthosilicate obtained in step (2), continue stirring for 30min, and then move the reaction device into a 25°C water bath Place the reaction for 12h.

(4) After the reaction, the white solid was collected by centrifugation, washed three times with ethanol and once with water to obtain silica nanoparticles. The silica nanoparticles were redispersed in ethanol, as shown in TEM (3).

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, there may be various modifications and changes in the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims (10)

1. A preparation method of novel green monodisperse silica nanospheres, characterized in that it comprises: Preparation of O/W type water/ethanol/dichloromethane surfactant-free microemulsion; Dissolve tetraethyl orthosilicate TEOS in the spherical "oil core" of the above-mentioned O/W type surfactant-free microemulsion, and in the presence of ammonia water, tetraethyl orthosilicate is hydrolyzed and polycondensed, separated and washed to obtain single Disperse _SiO2 nanospheres. 2. The method according to claim 1, characterized in that, in the surfactant-free microemulsion, the fixed methylene chloride mass fraction is 20%, and the mass ratio of water to ethanol is 6-9.5:4-0.5. 3. The method according to claim 1, characterized in that, the volume ratio of the tetraethyl orthosilicate to the ammonia water 25%wt is 1.3:3. 4. method as claimed in claim 1, is characterized in that, described tetraethyl orthosilicate is dissolved in the concrete step of above-mentioned non-surfactant microemulsion as: quantitative tetraethyl orthosilicate TEOS, in Slowly add into the O/W surfactant-free microemulsion system under stirring, after the addition is completed, sonicate for 8-10 minutes, and stir for 8-10 minutes. 5. the method for claim 1, is characterized in that, described ammoniacal liquor slowly joins in the O/W type non-surfactant microemulsion system that is dissolved with ethyl silicate under ice-water bath, stirring condition. 6. The method according to claim 1, characterized in that, the conditions for the hydrolysis and polycondensation are: standing reaction in a water bath at 25-35°C for 1-24h. 7. The method according to claim 1, characterized in that, the specific steps of said separation are: centrifuging the system after the completion of the reaction, washing the solid component with a polar solvent for 3 times and distilling to obtain silica nanospheres , the remaining liquid components are distilled to collect ethanol, and dichloromethane is recycled. 8. The monodisperse silica nanosphere prepared by the method described in any one of claims 1-7. 9. The monodisperse silica nanosphere according to claim 8, characterized in that the particle diameter of the silica nanosphere is 275-785 mm. 10. The application of the monodisperse silica nanospheres described in any one of claim 8 or 9 in the preparation of biomedical materials, catalytic materials, functional materials, high-performance ceramics or coatings.