CN107879348B - A kind of preparation method of monodisperse silica nanosphere - Google Patents

Abstract

The invention provides a method for preparing monodisperse silica nanospheres, comprising: preparing O/W type water/ethanol/dichloromethane surfactant-free microemulsion; Under the action of stirring, it is completely dissolved in the prepared spherical "oil core" of the O/W type surfactant-free microemulsion, and then under the catalysis of ammonia water, the ethyl orthosilicate is hydrolyzed and polycondensed, and centrifugation is carried out after the reaction is completed. 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, reusability of the system and high efficiency. The prepared _SiO2 nanospheres are uniform in scale and have universality 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 monodisperse silica nanospheres

technical field

The invention belongs to the field of nanomaterials, and in particular relates to a preparation method of a novel green monodisperse silica nanosphere.

Background technique

Monodisperse _SiO2 nanospheres have important application value in biomedicine, catalysis, functional materials, high-performance ceramics, coatings and other fields due to their large specific surface area, good dispersibility, and good optical and mechanical properties. The method is one of the commonly used methods for preparing _SiO2 nanospheres at present, and this method has the advantages of simple operation and clean surface of the prepared silica nanospheres. However, this method only utilizes the interaction between solvents and does not prepare templates, so the controllability and repeatability of the preparation of silica nanospheres are poor, and it is difficult to obtain high-quality _SiO2 nanospheres. Another common method for preparing _SiO2 nanospheres is the microemulsion method. The _SiO2 nanospheres prepared by this method have good monodispersity and adjustable size, but when constructing microemulsion templates, a large amount of surfactant and Co-surfactant, the two components not only enter the interface film of the microemulsion, but also partially dissolve in the water phase and the oil phase, which are not easy to be recycled and cause pollution to the environment, and the surfactant loaded on the surface of the material is difficult to wash These problems seriously restrict the popularization and application of microemulsion method in the preparation of silica nanomaterials.

SUMMARY OF THE INVENTION

In response to the above problems, we propose a method to prepare _SiO2 nanospheres using O/W type surfactant-free microemulsion as a template. Surfactant-free microemulsions have simple components, consisting only of water, oil and an "amphiphilic solvent". This new type of surfactant-free microemulsion system does not contain surfactants, but has similar microstructure and properties as microemulsions, which can overcome the disadvantages of using a large amount of surfactants in the preparation of nanomaterials by microemulsion method. Not only can the cost be significantly saved, but also the prepared nanomaterials have higher purity.

In order to obtain monodisperse _SiO2 nanospheres with uniform morphology and particle size, the present application carried out the preparation of _SiO2 nanospheres in various surfactant-free microemulsion systems. The forming law of SiO ₂ nanospheres in the surfactant-free microemulsion system was systematically studied. After a large number of experiments, 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 morphology 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 cost, but also because of their low boiling points, can be prepared by a simple distillation method after the preparation of SiO _nanospheres . 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 preparation method of a novel green monodisperse silica nanosphere, comprising:

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

Ethyl orthosilicate (TEOS) was completely dissolved in the spherical "oil core" of the prepared O/W surfactant-free microemulsion under ultrasonic or stirring conditions, and then orthosilicic acid was catalyzed by ammonia water. The ethyl ester is hydrolyzed and polycondensed. After the reaction is completed, the solid components are collected by centrifugation, washed with a polar solvent for several times to obtain SiO _nanospheres , the liquid components are distilled, and the ethanol and dichloromethane components are collected.

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 the ethyl orthosilicate to ammonia water (25%wt) is 1.3:3.

Preferably, the specific step of dissolving ethyl orthosilicate in the above-mentioned surfactant-free microemulsion is as follows: slowly adding quantitative ethyl orthosilicate (TEOS) to the surfactant-free microemulsion under stirring In the microemulsion, ultrasonic or mechanical stirring is carried out for a certain period of time.

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

Preferably, the conditions for the hydrolysis and polycondensation are as follows: the reaction is allowed to stand for more than 18 hours in a water bath at 25-30°C.

Preferably, the specific steps of the separation are: centrifuging the components after the reaction is completed, collecting the solid components, washing with a polar solvent for several times, distilling the liquid components, collecting ethanol and dichloromethane components point.

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

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

Preferably, the particle size of the silica nanospheres is 170-785 mm.

The present invention also provides the application of any 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.

The beneficial effects of the present invention

(1) Compared with the traditional W/O type microemulsion method to prepare SiO ₂ nanospheres, the present invention uses the O/W type surfactant-free microemulsion as a template to prepare SiO ₂ nanospheres, which significantly reduces the amount of oil phase, Cost savings. Using O/W type water/ethanol/dichloromethane surfactant-free microemulsion as template to prepare _SiO2 nanospheres, the method is simple to operate, low cost, environmentally friendly, reusable system, high efficiency, the prepared silica The nanospheres are uniform in appearance and particle size, and have universality and large-scale production value.

(2) The silica nanospheres prepared by the present invention have good shape, uniform size, large adjustable range of particle size, clean surface and simple subsequent treatment. The surfactant-free microemulsion system has simple components, can be recycled, does not use surfactants, and can save a lot of costs.

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

Description of drawings

The accompanying drawings, which form a part of this specification, are included to provide further explanation of the application. The exemplary embodiments and descriptions of the present application are used to explain the present application, and do not constitute an improper limitation of the present application.

Fig. 1 is the TEM image of the silica nanosphere obtained by changing the mass ratio of water and ethanol when the methylene chloride content is constant;

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

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

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the application. Unless otherwise defined, 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 method for preparing silica nanospheres using surfactant-free microemulsion as a template, comprising the following steps:

(1) Preparation of O/W type surfactant-free microemulsion template: under stirring conditions, mix an appropriate amount of water, ethanol and dichloromethane uniformly, and continue to stir for a certain period of time after mixing.

(2) Slowly add quantitative ethyl orthosilicate (TEOS) into the O/W type surfactant-free microemulsion system prepared in step (1) under stirring, and continue to stir for a certain period of time to make orthosilicic acid The ethyl ester is completely soluble in the O/W surfactant-free microemulsion "oil core".

(3) under the stirring condition of ice-water bath, slowly add quantitative ammonia water (25%wt) into the system obtained in step (2), continue stirring in ice-water bath for several minutes after the addition, then move into 25°C water bath and leave standstill for reaction 18 hours or more.

(4) centrifugal separation is carried out after completion of the reaction, the obtained white solid is washed 3 times with water, the remaining liquid is distilled, and ethanol and dichloromethane are recovered.

The principle of the invention is as follows: firstly use water, ethanol and dichloromethane to prepare an O/W surfactant-free microemulsion template, then add the reactant ethyl orthosilicate into the system, and make orthosilicic acid by ultrasonic or mechanical stirring Ethyl esters are completely soluble in the "oil core" of the O/W surfactant-free microemulsion system. The ammonia aqueous solution was slowly added under ice-water bath conditions to ensure that the ammonia water was dissolved in the water phase, and the reaction apparatus was moved 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) was added to the O/W surface-free microemulsion, it completely entered the "oil core" of the O/W surfactant-free microemulsion, due to the interfacial film of the O/W droplets. It is composed of a large number of ethanol molecules and water molecules, and the 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 cores. Finally, spherical silica nanoparticles are formed in the "oil core" of the O/W surfactant-free microemulsion system.

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) 1.3 ml of ethyl orthosilicate was slowly added to the O/W surfactant-free microemulsion system obtained in step (1) under stirring, followed by sonicating for 10 minutes and stirring for 20 minutes after the addition was completed.

(3) The O/W type surfactant-free microemulsion system containing ethyl orthosilicate obtained in step (2) was moved into an ice-water bath, and under stirring conditions, 3ml ammonia water (25wt﹪) was slowly added therein, and stirring was continued for 10min Then, the reaction apparatus was moved into a 25°C water bath and allowed to react for 24h.

(4) After the reaction, a white solid was obtained by centrifugation, and the white solid was washed three times to obtain SiO ₂ nanospheres. The remaining liquid fractions were distilled, and the ethanol and dichloromethane fractions were collected. The _SiO2 nanospheres were redispersed in ethanol, and the TEM image was shown in Fig. (1)d, and the EDS image was shown in Fig. (2).

Example 2:

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

(2) 1.3 ml of ethyl orthosilicate was slowly added to the O/W surfactant-free microemulsion system obtained in step (1) under stirring, followed by sonicating for 10 minutes and stirring for 20 minutes after the addition was completed.

(3) The O/W type surfactant-free microemulsion system containing ethyl orthosilicate obtained in step (2) was moved into an ice-water bath, and under stirring conditions, 3ml ammonia water (25wt﹪) was slowly added therein, and stirring was continued for 10min Then, the reaction apparatus was moved into a 25°C water bath and allowed to react for 24h.

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

Example 3:

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

(2) 1.3 ml of ethyl orthosilicate was slowly added to the O/W surfactant-free microemulsion system obtained in step (1) under stirring, followed by sonicating for 10 minutes and stirring for 20 minutes after the addition was completed.

(3) The O/W type surfactant-free microemulsion system containing ethyl orthosilicate obtained in step (2) was moved into an ice-water bath, and under stirring conditions, 3ml ammonia water (25wt﹪) was slowly added therein, and stirring was continued for 10min Then, the reaction apparatus was moved into a 25°C water bath and allowed to react for 24h.

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

Example 4:

(1) Mix 4 g of secondary ultrapure water with 9.3 g of ethanol, add 3.3 g of dichloromethane under stirring conditions, and continue stirring for 10 min after the addition is complete.

(2) 1.3 ml of ethyl orthosilicate was slowly added to the O/W surfactant-free microemulsion system obtained in step (1) under stirring, followed by sonicating for 10 minutes and stirring for 20 minutes after the addition was completed.

(3) The O/W type surfactant-free microemulsion system containing ethyl orthosilicate obtained in step (2) was moved into an ice-water bath, and under stirring conditions, 3ml ammonia water (25wt﹪) was slowly added therein, and stirring was continued for 10min Then, the reaction apparatus was moved into a 25°C water bath and allowed to react for 24h.

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

Table 1. Particle size of silica nanospheres obtained under different water-alcohol ratio (R _w/e ) conditions

Comparative Example 1:

(1) Mix 4 g of secondary ultrapure water with 36 g of ethanol.

(2) 1.3 ml of ethyl orthosilicate was slowly added to the mixed system of ethanol and water under stirring, and the stirring was continued for 20 min.

(3) under stirring condition, slowly add 3.0ml ammonia water (25wt%) into the mixed system of ethanol and water containing ethyl orthosilicate obtained in step (2), and move the reaction device into a 25°C water bath after continuous stirring for 30min The reaction was allowed to stand for 24h.

(4) After the reaction is completed, centrifugation is performed to collect white solids, which are washed three times with ethanol and once with water to obtain silica nanoparticles. The silica nanoparticles were redispersed in ethanol, and the TEM was shown in Figure (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, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims (6)

1. a preparation method of monodisperse silica nanosphere, is characterized in that, comprises: Preparation of O/W type water/ethanol/dichloromethane surfactant-free microemulsion; Ethyl orthosilicate TEOS is dissolved in the spherical "oil core" of the above-mentioned O/W type surfactant-free microemulsion. Disperse _SiO2 nanospheres; In the surfactant-free microemulsion, the mass fraction of fixed dichloromethane is 20%, and the mass ratio of water to ethanol is 4-9.5:6-0.5. 2. method as claimed in claim 1 is characterized in that, the volume ratio of described ethyl orthosilicate and ammoniacal liquor 25%wt is 1.3:3. 3. method as claimed in claim 1 is characterized in that, the concrete step that described ethyl orthosilicate is dissolved in above-mentioned surfactant-free microemulsion is: by quantitative tetraethyl orthosilicate TEOS, in Slowly add it into the O/W surfactant-free microemulsion system under stirring, and after the addition is completed, ultrasonically sonicate for 8-10 minutes in sequence, and stir for 8-10 minutes. 4. method as claimed in claim 1 is characterized in that, described ammoniacal liquor is slowly added in the O/W type surfactant-free microemulsion system that is dissolved with ethyl orthosilicate under ice-water bath, stirring condition. 5. The method of claim 1, wherein the hydrolysis and polycondensation conditions are as follows: the reaction is allowed to stand for more than 18 hours in a water bath at 25-35°C. 6. method as claimed in claim 1, is characterized in that, the concrete step of described separation is: the system after reaction is carried out centrifugation, solid component is washed 3 times with polar solvent, obtains silicon dioxide nanospheres , the remaining liquid components are distilled to collect ethanol, and the dichloromethane is recycled.