CN108640149A - Titanium dioxide nano hollow ball and preparation method thereof - Google Patents

Abstract

The invention discloses a preparation method of titanium dioxide nanometer hollow spheres. In the preparation method, tetraethyl orthosilicate is used as the silicon source, and the silica microspheres are prepared by the Stobe method, and then the titanium dioxide precursor is coated on the surface of the silica microspheres, and then the silica core is removed by strong alkali etching. Finally, hydrothermal treatment is carried out to prepare crystalline titanium dioxide nano hollow spheres with sheet-like branched structures on the surface. The invention also discloses a titanium dioxide nano hollow sphere prepared by the above preparation method. The method of the invention is simple in operation, good in repeatability, does not need high-temperature sintering, is suitable for large-scale production, avoids the agglomeration phenomenon of titanium dioxide powder, has little process pollution, high product yield, and low production cost; the purity of the titanium dioxide nano hollow spheres obtained is High, uniform particles, good crystallization, controllable crystal form, good dispersion, many flaky branches on the surface, large specific surface area, strong adsorption and capture capabilities for pollutants, and high photocatalytic efficiency.

Description

Titanium dioxide nano hollow sphere and preparation method thereof

technical field

The invention belongs to the field of nanometer materials, and relates to a preparation method of titanium dioxide nanometer hollow spheres and titanium dioxide nanometer hollow spheres prepared by the method.

Background technique

Due to its unique advantages in structure and photoelectrochemical properties, nanomaterials have become a research hotspot in the field of material science today. Nano-titanium dioxide has unique optical properties, high chemical stability, non-toxicity, low cost, high catalytic activity, and can completely contact with food and human body, so nano-titanium dioxide has potential development prospects in many fields. Especially in the field of photocatalysis, titanium dioxide semiconductor photocatalysts can be used to convert solar energy into electrical and chemical energy. Titanium dioxide semiconductor photocatalyst will generate photogenerated electrons and holes when it is illuminated. Photogenerated holes have strong oxidative properties and can photocatalytically degrade organic pollutants to achieve the purpose of antibacterial, antivirus and self-cleaning; while photogenerated electrons have strong Reduction, not only can be used in environmental photocatalysis, but also photocatalytic decomposition of water to produce hydrogen to prepare new energy. Therefore, titanium dioxide semiconductor photocatalysis technology has huge economic and environmental benefits in environmental governance.

However, due to the wide band gap (3.0-3.2eV) of titanium dioxide, its absorption range is mainly concentrated in the ultraviolet region, and the visible light accounting for 90% of sunlight cannot be utilized; in addition, the recombination rate of photogenerated electrons and holes Higher, lower photon utilization rate, resulting in low photocatalytic efficiency, which greatly limits its application range. In order to improve the photocatalytic activity of titanium dioxide, various methods have been used to modify and modify it, including ion doping, morphology control, noble metal loading, semiconductor recombination and other methods. Among them, morphology control has the advantages of simple operation, mild conditions, less process pollution, easy control, low cost, and high yield.

Titanium dioxide hollow nanospheres prepared by shape control are a kind of core-shell particles with a special structure whose inner core is air or other gases. Compared with other morphological materials, titanium dioxide nanospheres with hollow structure have the following advantages: larger specific surface area, lower density, special mechanical, optical, electrical and other physical properties and application value. Therefore, titanium dioxide hollow nanospheres can be used as coating materials, catalyst carriers, nanoreactors, and carriers for nanomaterials, biomacromolecules, and drug sustained release, and have broad application prospects in the fields of biology, medicine, and bioengineering.

However, the titanium dioxide nano hollow spheres prepared by the existing method generally have a smooth surface, the specific surface area is not large enough, the adsorption capacity is limited, and the photocatalytic performance is not high enough. In addition, in the existing method of preparing hollow titanium dioxide nanospheres, high-temperature sintering treatment is required, and the sintering process not only causes high production costs, pollutes the environment, and the product yield is not high, it is not suitable for large-scale production, and it is easy to cause powder Hard agglomeration occurs, the particles are uneven, the dispersion is poor, and the product quality is poor.

Contents of the invention

(1) Technical problems to be solved

In order to solve the above-mentioned problems in the prior art, the present invention provides a preparation method of titanium dioxide nano hollow spheres, the preparation method is simple to operate, does not require high-temperature sintering, is suitable for large-scale production, avoids the agglomeration of titanium dioxide powder, and has little process pollution , high product yield and low production cost.

The present invention provides titanium dioxide nano hollow spheres prepared by the method for preparing titanium dioxide nano hollow spheres. The titanium dioxide nano hollow spheres have high purity, uniform particles, good crystallization, good dispersibility, and many flaky branches on the surface, which can increase the ratio Increase the surface area, improve the adsorption capacity and capture capacity of pollutants, and enhance the photocatalytic efficiency.

(2) Technical solutions

In order to achieve the above object, the main technical solutions adopted in the present invention are as follows:

The invention provides a titanium dioxide nano hollow sphere. First, tetraethyl orthosilicate is used as a silicon source to prepare silicon dioxide microspheres by the Stobe method, and then a titanium dioxide precursor is coated on the surface of the silicon dioxide microspheres, and then a strong alkali The silicon dioxide inner core is removed by etching, and finally hydrothermal treatment is carried out to prepare crystalline titanium dioxide nano hollow spheres with sheet-like branched structures on the surface.

In a preferred embodiment, the silicon dioxide microspheres prepared by the Stobe method using tetraethyl orthosilicate as silicon source include:

Mix water, ethanol and ammonia water to prepare solvent liquid I;

Tetraethyl orthosilicate was added to the solvent solution I, stirred at room temperature for hydrolysis reaction, washed with ethanol, and dried to obtain silica microspheres.

In a preferred embodiment, in the process of preparing solvent liquid I, the volume ratio of water, ethanol and ammonia water is 5:35-40:1; And/or

During the process of preparing silica microspheres, slowly add 0.5-1.5 ml of tetraethyl orthosilicate into solvent liquid I; and/or

The drying temperature is 50-80°C.

In a preferred embodiment, the titanium dioxide precursor coated on the surface of silica microspheres includes:

Mix water and ethanol to prepare solvent solution II;

Add high-substituted hydroxypropyl cellulose into solvent liquid II, and after fully dissolving, add the prepared silica microspheres and fully dissolve to obtain solution A;

Mix tetrabutyl titanate and ethanol to prepare solution B;

Add solution B to solution A to obtain a mixed solution, then reflux the mixed solution, centrifuge, and finally wash with ethanol to prepare a core-shell nanocomposite of titanium dioxide precursor coated silica microspheres.

In a preferred embodiment, in the process of preparing solvent liquid II, the volume ratio of water and ethanol is 1:150-300; and/or

In the process of preparing solution A, the addition amount of high-substituted hydroxypropyl cellulose is 50-150 mg, and the addition amount of silica microspheres is 0.15-0.3 g; and/or

In the process of preparing solution B, the volume ratio of tetrabutyl titanate and ethanol is 1:3.5-5.5; and/or

In the process of preparing the core-shell nanocomposite of titanium dioxide precursor coated silica microspheres, 4-7ml of solution B is added dropwise to solution A within 10-20min to obtain a mixed solution, the mixed solution The reflux temperature is 70-95°C, and the reflux time is 80-150min.

In a preferred embodiment, the removal of the silicon dioxide inner core by strong alkali etching comprises:

Ultrasonic disperse the core-shell nanocomposite of titanium dioxide precursor coated silica microspheres in water, add a strong alkali solution, and stir at 30-70°C to form solution C;

The solution C was subjected to centrifugal separation and precipitation, and the precipitate was washed with ultrapure water and absolute ethanol until the solution was close to neutral, and then the precipitate was dried to obtain amorphous titanium dioxide precursor hollow nanospheres.

In a preferred embodiment, in the process of forming solution C, the strong alkali solution is sodium hydroxide and/or potassium hydroxide solution, the concentration of the strong alkali solution is 1-3mol/L, the strong alkali solution The volume of the alkali solution is 0.5-2ml, after adding the strong alkali solution, stir at 30-70°C for 6-12h; and/or

During the process of preparing the amorphous titanium dioxide precursor nano hollow spheres, the drying temperature is 50-80° C., and the drying time is 8-15 hours.

In a preferred embodiment, the hydrothermal treatment comprises:

Mix water and ethanol to prepare solution D;

Ultrasonically disperse amorphous titanium dioxide precursor nano hollow spheres in solution D, hydrothermally treat, centrifuge and precipitate, wash and dry the precipitate with ultrapure water and absolute ethanol, and obtain a sheet-like branched structure on the surface Crystalline titanium dioxide hollow nanospheres.

In a preferred embodiment, in the process of preparing solution D, the volume ratio of water and ethanol is 1-2.5:1; And/or

The temperature of the hydrothermal treatment is 100-250° C., the time of the hydrothermal treatment is 6-12 hours, the temperature of the drying is 50-80° C., and the drying time is 8-15 hours.

The present invention also provides a hollow titanium dioxide nanosphere prepared by the method for preparing hollow titanium dioxide nanosphere according to any one of the above embodiments.

(3) Beneficial effects

In the present invention, tetraethyl orthosilicate is used as the silicon source at first, and the silicon dioxide microspheres are prepared by the Stobe method, and then the titanium dioxide precursor is coated on the surface of the silicon dioxide microspheres, and then the silicon dioxide core is removed by strong alkali corrosion, and finally Hydrothermal treatment is carried out to prepare crystalline titanium dioxide nano hollow spheres with sheet-like branched structure on the surface. The preparation method of the titanium dioxide nano hollow spheres of the present invention is simple in operation, good in repeatability, does not need high-temperature sintering, is suitable for large-scale production, avoids agglomeration of titanium dioxide powder, has little process pollution, high product yield and low production cost. Titanium dioxide nano hollow spheres prepared by this method have high purity, uniform particles, good crystallization, controllable crystal form, good dispersion, and many flaky branches on the surface, which can increase the specific surface area, improve the adsorption capacity and capture capacity of pollutants, Enhanced photocatalytic efficiency.

Description of drawings

Fig. 1 is a schematic flow chart of the preparation method of hollow titanium dioxide nanospheres in Example 1 of the present invention.

Fig. 2 is the X-ray diffraction spectrum of hollow titanium dioxide nanospheres in Example 1 of the present invention;

Fig. 3 is the transmission electron microscope picture of titanium dioxide nano hollow sphere in the embodiment 1 of the present invention;

Fig. 4 is the absorption spectrum of titanium dioxide nano hollow spheres degrading Rhodamine B solution under ultraviolet light in Example 1 of the present invention;

Fig. 5 is a linear fitting curve diagram of degradation of rhodamine B solution by titanium dioxide nano hollow spheres and pure titanium dioxide spheres in Example 1 of the present invention.

Detailed ways

In order to better explain the present invention and facilitate understanding, the present invention will be described in detail below through specific embodiments.

This embodiment proposes a method for titanium dioxide nano hollow spheres. First, tetraethyl orthosilicate is used as the silicon source, and the silica microspheres are prepared by the Stobe method, and then the titanium dioxide precursor is coated on the surface of the silica microspheres, and then The silicon dioxide inner core is removed by strong alkali corrosion, and finally hydrothermal treatment is carried out to prepare crystalline titanium dioxide nano hollow spheres with sheet-like branched structures on the surface.

In this embodiment, using tetraethyl orthosilicate as the silicon source, the silica microspheres prepared by the Stobe method include the following steps:

Water, ethanol and ammonia water are mixed according to the ratio of 5:35-40:1 by volume to prepare solvent liquid I;

Slowly add 0.5-1.5ml of tetraethyl orthosilicate into the solvent solution I, stir at room temperature for 5-12h, carry out hydrolysis reaction, then wash with ethanol for several times, and dry at 50-80°C to obtain carbon dioxide Silica microspheres.

In this embodiment, coating the titanium dioxide precursor on the surface of the silica microspheres includes the following steps:

Mix water and ethanol according to the volume ratio of 1:150-300 to prepare solvent liquid II;

Add 50-150 mg of highly substituted hydroxypropyl cellulose dropwise into solvent solution II, and after fully dissolving, add 0.15-0.3 g of prepared silica microspheres, fully dissolve, and obtain a uniform mixed solution, which is recorded as Solution A;

Mix tetrabutyl titanate and ethanol at a volume ratio of 1:3.5-5.5 to prepare solution B;

Add 4-7ml of solution B dropwise to solution A within 10-20 minutes to obtain a mixed solution, then reflux the mixed solution at 70-95°C for 80-150 minutes, centrifuge, and finally wash with ethanol several times to obtain titanium dioxide Precursor-coated core-shell nanocomposites of silica microspheres.

In this embodiment, the use of strong alkali corrosion to remove the silicon dioxide core includes the following steps:

Ultrasonic disperse the core-shell nanocomposite of titanium dioxide precursor coated silica microspheres in 10-30ml of water, add 0.5-2ml of strong alkali solution with a concentration of 1-3mol/L, at 30-70℃ Stir for 6-12h to form solution C; wherein the strong base solution is sodium hydroxide solution and/or potassium hydroxide solution.

Centrifuge and precipitate solution C at 3000-4000rpm, wash the precipitate with ultrapure water and absolute ethanol until the solution is close to neutral, dry the precipitate at 50-80°C for 8-15h, and obtain Amorphous titanium dioxide precursor nano hollow spheres.

In this embodiment, in order to make the amorphous titanium dioxide precursor nano hollow spheres have semiconductor crystal properties, it is necessary to perform hydrothermal treatment on the amorphous titanium dioxide precursor nano hollow spheres. Wherein the hydrothermal treatment comprises the following steps:

Mix water and ethanol according to the volume ratio of 1-2.5:1 to prepare solution D;

Ultrasonically disperse the nano hollow sphere sample of amorphous titanium dioxide precursor in solution D, move it to the reaction kettle, heat it in water at 100-250°C for 6-12h, centrifuge and separate the precipitate, and use ultrapure water and absolute ethanol to carry out the precipitation washing and drying at 50-80° C. for 8-15 hours to prepare crystalline titanium dioxide nano hollow spheres with sheet-like branched structures on the surface.

The present invention also provides a titanium dioxide nano hollow sphere prepared by the above-mentioned preparation method of the titanium dioxide nano hollow sphere.

The present invention adopts the template method to generate titanium dioxide nano hollow spheres, that is, the Stobe method is used to manufacture silicon dioxide as a template in one step, and then the surface is covered with a titanium dioxide precursor coating, and then the silicon dioxide template is removed by strong alkali corrosion. Finally, hydrothermal treatment is carried out to obtain crystalline titanium dioxide nanometer hollow spheres.

Specifically, when making a silica template, tetraethyl orthosilicate is used as a silicon source, and ammonia water is used as a pH regulator and a catalyst for the reaction to slowly dissolve tetraethyl orthosilicate in a mixed solution of water and ethanol. Hydrolyzed to generate silica microspheres with uniform size and good dispersion.

When coating the titanium dioxide precursor, tetrabutyl titanate is used as the titanium source, and highly substituted hydroxypropyl cellulose is used as the dispersant and binder, which are attached to the surface of silica molecules to form a bimolecular layer, and then adsorbed The titanium dioxide precursor makes the titanium dioxide precursor evenly adhere to the surface of the silicon dioxide layer to form a uniform and complete coating layer of the titanium dioxide precursor.

When removing the silica inner core, use a high-concentration sodium hydroxide solution as an etchant, and the hydroxide ions in the strong base react with silica to form silicate and water, and then remove the silica inner core, and then pass through Wash with ultrapure water and absolute ethanol several times to remove excess sodium hydroxide and highly substituted hydroxypropyl cellulose.

Finally, the hydrothermal reaction is carried out in the mixed solution of water and ethanol. Since the precursor reacts at the molecular level under subcritical and supercritical hydrothermal conditions, the reactivity is improved, and the precursor is decomposed by heat to form oxides and transform into crystalline state, and then self-assembled to produce micro-nanostructures with different morphologies.

Adding ethanol to the hydrothermal solvent makes the reactants and products in the whole process evenly dispersed, increases the fluidity, and the probability of intermolecular collisions tends to be gentle, thereby inhibiting the violent hydrolysis reaction of the titanium dioxide precursor. Therefore, the nucleation rate and growth rate of the crystals are relatively slow, and the crystals tend to grow anisotropically, which provides favorable conditions for the formation of sheet-like structures, and then these particles derive sheet-like branches on the surface of titanium dioxide through self-assembly, resulting in a Sheet-like branched crystalline titanium dioxide nanohollow spheres.

The preparation method of the titanium dioxide nano hollow spheres of the present invention is simple in operation, good in repeatability, does not need high-temperature sintering, is suitable for large-scale production, avoids agglomeration of titanium dioxide powder, has little process pollution, high product yield and low production cost.

The titanium dioxide nano hollow spheres prepared by the method of the present invention have high purity, uniform particles, good crystallization, controllable crystal form, good dispersion, and many lamellar branches on the surface, which can increase the specific surface area, improve the adsorption capacity and capture of pollutants ability to enhance the photocatalytic efficiency.

The invention is further illustrated by the following examples.

Example 1

As shown in Figure 1, embodiment 1 proposes a kind of preparation method of titanium dioxide nano hollow sphere, specifically comprises the following steps:

_1. Preparation of SiO spheres

1.1. Mix water, ethanol and ammonia water according to the volume ratio of 5:37:1 to prepare solvent liquid I;

1.2. Slowly add 0.8ml tetraethyl orthosilicate into the above solvent solution I, stir at room temperature for 8 hours, carry out hydrolysis reaction, then wash with ethanol several times, and dry at 60°C to obtain dispersed SiO ₂ ball.

2. TiO ₂ precursor coating

2.1. Mix water and ethanol at a volume ratio of 1:80 to prepare solvent solution II;

2.2. Add 80 mg of highly substituted hydroxypropyl cellulose dropwise into the above solvent solution II. After fully dissolving, add 0.18g of _SiO2 spheres prepared in step 1, fully dissolve to obtain a uniform mixed solution, which is designated as solution A;

2.3. Mix tetrabutyl titanate and ethanol at a volume ratio of 1:4 to prepare solution B;

2.4. Add 6ml of solution B dropwise to solution A within 10 minutes to obtain a mixed solution, then reflux the above mixed solution at 75°C for 90 minutes, centrifuge, and finally wash with ethanol several times to obtain a titanium dioxide precursor coating Core-shell nanocomposites of silica microspheres.

3. Remove SiO ₂ nuclei

3.1. Ultrasonic disperse the core-shell nanocomposite of titanium dioxide precursor coated silica microspheres prepared above in 10ml of water, add 0.7ml of sodium hydroxide solution with a concentration of 1mol/L, and stir at 40°C for 8h to form a solution C;

3.2. Take out the solution C, centrifuge the precipitate at 3500rpm, wash the precipitate with ultrapure water and absolute ethanol until the solution is close to neutral, dry the precipitate at 60°C for 12 hours to obtain an amorphous state The titanium dioxide precursor nano hollow spheres, which are amorphous, need to undergo the hydrothermal crystallization in step 4 to make them have semiconductor crystal properties.

4. Hydrothermal crystallization

4.1. Mix water and ethanol according to the volume ratio of 1.5:1 to form solution D;

4.2. Ultrasonically disperse the nano hollow sphere sample of the amorphous titanium dioxide precursor in the solution D, move it to the reaction kettle, heat it in water at 120°C for 10 hours, centrifuge and separate the precipitate, and wash the precipitate with ultrapure water and absolute ethanol. Dry at 60°C for 12 hours to prepare hollow crystalline titanium dioxide nanospheres with sheet-like branched structures on the surface.

Fig. 2 is the X-ray diffraction pattern of titanium dioxide nano hollow spheres in embodiment 1, as can be seen from Fig. 2, X-ray diffraction pattern has only appeared the diffraction peak of the anatase crystal form of _TiO2 , does not have the diffraction of other crystal forms peak generation, indicating that Example 1 has prepared pure anatase crystal form TiO ₂ hollow spheres.

Fig. 3 is the transmission electron microscope figure of titanium dioxide nano hollow sphere in embodiment 1, as shown in Fig. 3, the _TiO2 hollow sphere prepared in embodiment 1 has a cavity diameter of 230-300nm, and a wall thickness of 45-65nm. A sheet-like branch structure is derived from the surface of the hollow sphere, and the thickness of the sheet is 3-5nm.

Example 2

Embodiment 2 proposes a kind of preparation method of titanium dioxide nanometer hollow sphere, specifically comprises the following steps:

_1. Preparation of SiO spheres

1.1. Mix water, ethanol and ammonia water according to the volume ratio of 5:38:1 to prepare solvent liquid I;

1.2. Slowly add 1.0ml tetraethyl orthosilicate into the above solvent solution I, stir at room temperature for 10 hours, carry out hydrolysis reaction, then wash with ethanol several times, and dry at 50°C to obtain dispersed SiO ₂ ball.

2. TiO ₂ precursor coating

2.1. Mix water and ethanol according to the volume ratio of 1:130 to prepare solvent liquid II;

2.2. Add 100 mg of highly substituted hydroxypropyl cellulose dropwise into the above solvent solution II. After fully dissolving, add 0.25g of _SiO2 spheres prepared in step 1, fully dissolve to obtain a uniform mixed solution, which is designated as solution A;

2.3. Mix tetrabutyl titanate and ethanol at a volume ratio of 1:4.8 to prepare solution B;

2.4. Add 5ml of solution B dropwise to solution A within 10 minutes to obtain a mixed solution, then reflux the above mixed solution at 85°C for 120 minutes, centrifuge, and finally wash with ethanol several times to obtain a titanium dioxide precursor coating Core-shell nanocomposites of silica microspheres.

3. Remove SiO ₂ nuclei

3.1. Ultrasonic disperse the above-prepared titanium dioxide precursor-coated silica microsphere core-shell nanocomposite in 30ml of water, add 1.8ml of sodium hydroxide solution with a concentration of 2.0mol/L, and stir at 50°C for 12h to form Solution C;

3.2. Take out solution C, centrifuge the precipitate at 3800rpm, wash the precipitate with ultrapure water and absolute ethanol until the solution is close to neutral, dry the precipitate at 65°C for 10 hours to obtain an amorphous state The titanium dioxide precursor nano hollow spheres, which are amorphous, need to undergo the hydrothermal crystallization in step 4 to make them have semiconductor crystal properties.

4. Hydrothermal crystallization

4.1. Mix water and ethanol according to the volume ratio of 2:1 to form solution D;

4.2. Ultrasonically disperse the nano hollow sphere sample of the amorphous titanium dioxide precursor in the solution D, move it to the reaction kettle, heat it in water at 150°C for 12 hours, centrifuge and separate the precipitate, and wash the precipitate with ultrapure water and absolute ethanol. Dry at 80°C for 8 hours to prepare hollow crystalline titanium dioxide nanospheres with sheet-like branched structures on the surface.

Example 3

Embodiment 3 proposes a kind of preparation method of titanium dioxide nanometer hollow sphere, specifically comprises the following steps:

_1. Preparation of SiO spheres

1.1. Mix water, ethanol and ammonia water according to the volume ratio of 5:35:1 to prepare solvent liquid I;

1.2. Slowly add 1.2ml tetraethyl orthosilicate to the above solvent solution I, stir at room temperature for 8 hours, carry out hydrolysis reaction, then wash with ethanol several times, and dry at 60°C to obtain dispersed SiO ₂ ball.

2. TiO ₂ precursor coating

2.1. Mix water and ethanol according to the volume ratio of 1:200 to prepare solvent solution II;

2.2. Add 80 mg of highly substituted hydroxypropyl cellulose dropwise into the above solvent solution II. After fully dissolving, add 0.2g of _SiO2 spheres prepared in step 1, fully dissolve to obtain a uniform mixed solution, which is designated as solution A;

2.3. Mix tetrabutyl titanate and ethanol at a volume ratio of 1:5 to prepare solution B;

2.4. Add 7ml of solution B dropwise to solution A within 15 minutes to obtain a mixed solution, then reflux the above mixed solution at 90°C for 90 minutes, centrifuge, and finally wash with ethanol several times to obtain a titanium dioxide precursor coating Core-shell nanocomposites of silica microspheres.

3. Remove SiO ₂ nuclei

3.1. Ultrasonic disperse the above-prepared titanium dioxide precursor-coated silica microsphere core-shell nanocomposite in 30ml of water, add 1.8ml of sodium hydroxide solution with a concentration of 2.6mol/L, and stir at 60°C for 12h to form Solution C;

3.2. Take out solution C, centrifuge the precipitate at 4000rpm, wash the precipitate with ultrapure water and absolute ethanol until the solution is close to neutral, dry the precipitate at 70°C for 15 hours to obtain an amorphous state The titanium dioxide precursor nano hollow spheres, which are amorphous, need to undergo the hydrothermal crystallization in step 4 to make them have semiconductor crystal properties.

4. Hydrothermal crystallization

4.1. Mix water and ethanol according to the volume ratio of 2.5:1 to form solution D;

4.2. Ultrasonically disperse the nano hollow sphere sample of the amorphous titanium dioxide precursor in the solution D, move it to the reaction kettle, heat it in water at 200°C for 6 hours, centrifuge and separate the precipitate, and wash the precipitate with ultrapure water and absolute ethanol. Dry at 70°C for 10 h to prepare crystalline titanium dioxide hollow nanospheres with sheet-like branched structures on the surface.

Example 4

Embodiment 4 proposes a kind of preparation method of titanium dioxide nanometer hollow sphere, specifically comprises the following steps:

_1. Preparation of SiO spheres

1.1. Mix water, ethanol and ammonia water according to the volume ratio of 5:40:1 to prepare solvent liquid I;

1.2. Slowly add 1.5ml tetraethyl orthosilicate to the above solvent solution I, stir at room temperature for 12 hours, carry out hydrolysis reaction, then wash with ethanol several times, and dry at 80°C to obtain dispersed SiO ₂ ball.

2. TiO ₂ precursor coating

2.1. Mix water and ethanol according to the volume ratio of 1:280 to prepare solvent solution II;

2.2. Add 140 mg of highly substituted hydroxypropyl cellulose dropwise into the above solvent solution II. After fully dissolving, add 0.3g of _SiO2 spheres prepared in step 1, fully dissolve to obtain a uniform mixed solution, which is designated as solution A;

2.3. Mix tetrabutyl titanate and ethanol at a volume ratio of 1:5.5 to prepare solution B;

2.4. Add 7ml of solution B dropwise to solution A within 20 minutes to obtain a mixed solution, then reflux the above mixed solution at 75°C for 150 minutes, centrifuge, and finally wash with ethanol several times to obtain a titanium dioxide precursor coating Core-shell nanocomposites of silica microspheres.

3. Remove SiO ₂ nuclei

3.1. Ultrasonic disperse the above-prepared titanium dioxide precursor-coated silica microsphere core-shell nanocomposite in 20ml of water, add 1.2ml of sodium hydroxide solution with a concentration of 1.5mol/L, and stir at 70°C for 6h to form Solution C;

3.2. Take out solution C, centrifuge the precipitate at 3000rpm, wash the precipitate with ultrapure water and absolute ethanol until the solution is close to neutral, dry the precipitate at 80°C for 8 hours to obtain an amorphous state The titanium dioxide precursor nano hollow spheres, which are amorphous, need to undergo the hydrothermal crystallization in step 4 to make them have the properties of semiconductor crystals.

4. Hydrothermal crystallization

4.1. Mix water and ethanol according to the volume ratio of 1:1 to form solution D;

4.2. Ultrasonically disperse the nano hollow sphere sample of the amorphous titanium dioxide precursor in the solution D, move it to the reaction kettle, heat it in water at 120°C for 12 hours, centrifuge and separate the precipitate, and wash the precipitate with ultrapure water and absolute ethanol. Dry at 65°C for 15 hours to prepare hollow crystalline titanium dioxide nanospheres with sheet-like branched structures on the surface.

Application example

Adopting ultraviolet light source is 300W ultraviolet lamp, and organic dye is the rhodamine B solution of 30mg/L, utilizes ultraviolet-visible spectrophotometer to detect the titanium dioxide nanometer hollow sphere of embodiment 1 as photocatalyst, in sampling sample under different time the content of rhodamine B Absorbance. According to the Lambie-Beer law, at the same wavelength, the intensity of the organic dye absorption peak is proportional to its concentration. The absorption spectrum of titanium dioxide nano hollow spheres degrading rhodamine B solution under ultraviolet light is shown in Figure 4, and the ultraviolet light irradiation time from top to bottom is 0min, 5min, 10min, 15min, 20min. As can be seen from Fig. 4, the absorption peak of rhodamine B in the visible region (wavelength is 500nm to 700nm) decreases with time, and the ultraviolet photodegradation rate of titanium dioxide nano hollow spheres of embodiment 1 can reach 100% in 20min, wherein , the calculation formula of the degradation rate is: (initial concentration C ₀ -concentration C _i at a certain moment)/C ₀ *100%.

As a comparison, the sol-gel method was used to prepare pure titanium dioxide spheres with similar diameters, and then the pure titanium dioxide spheres and the hollow titanium dioxide nanospheres prepared in Example 1 were tested for the performance of ultraviolet photocatalytic degradation of organic dyes. The linear fitting curve of rhodamine B solution is shown in Figure 5. The slope of the linear fitting curve in Figure 5 reflects the photocatalytic efficiency (reaction kinetic constant), that is, the larger the slope, the better the photocatalytic efficiency. It can be seen from Figure 5 that the slope (0.32339min ^-1 ) of the titanium dioxide hollow spheres prepared in Example 1 is much larger than that of the pure titanium dioxide spheres (0.0223min ^-1 ), so the catalytic degradation efficiency of the titanium dioxide hollow spheres under ultraviolet light Higher than titanium dioxide balls. The main reasons can be attributed to the following three aspects: 1. The empty shell structure greatly increases the specific surface area of the product and increases the reaction sites for degrading pollutants; 2. The main composition of the empty shell structure is the atoms on the surface (inner and outer surfaces ), when the hollow shell structure is excited by light, more electrons are excited to the valence band, and more holes will be generated on the surface; The entire surface of the hollow sphere is stretched, which improves its ability to adsorb and capture pollutants, thereby greatly enhancing the photocatalytic efficiency.

The technical principle of the present invention has been described above in conjunction with the specific embodiments. These descriptions are only for explaining the principles of the present invention, and cannot be construed as limiting the protection scope of the present invention in any way. Based on the explanations herein, those skilled in the art can think of other specific implementation modes of the present invention without creative efforts, and these modes will all fall within the protection scope of the present invention.

Claims (10)

1. a kind of preparation method of titanium dioxide nano hollow ball, it is characterised in that：First using tetraethyl orthosilicate as silicon source, adopt Silicon dioxide microsphere is obtained with Stobe legal systems, then in silicon dioxide microsphere surface cladding titanium dioxide predecessor, then uses highly basic Erosion removal silica kernel, finally carries out hydro-thermal process, and surface, which is made, has the crystalline titania of sheet branched structure Nano-hollow ball.

2. the preparation method of titanium dioxide nano hollow ball as described in claim 1, it is characterised in that：It is described with positive silicic acid four Ethyl ester is silicon source, and obtaining silicon dioxide microsphere using Stobe legal systems includes：

Water, ethyl alcohol and ammonium hydroxide are mixed, solvent liquid I is prepared；

Tetraethyl orthosilicate is added in solvent liquid I, reaction is hydrolyzed in stirring at room temperature, is cleaned using ethyl alcohol, dries, and is made Silicon dioxide microsphere.

3. the preparation method of titanium dioxide nano hollow ball as claimed in claim 2, it is characterised in that：Preparing solvent liquid I During, the volume ratio of water, ethyl alcohol and ammonium hydroxide is 5:35-40:1；And/or

During silicon dioxide microsphere is made, the tetraethyl orthosilicate of 0.5-1.5ml is slowly added in solvent liquid I；With/ Or

Drying temperature is 50-80 DEG C.

4. the preparation method of titanium dioxide nano hollow ball as claimed in claim 3, it is characterised in that：It is described in silica Microsphere surface cladding titanium dioxide predecessor includes：

Water and ethyl alcohol are mixed, solvent liquid II is prepared；

Hydroxypropylcelliloxe is added in solvent liquid II, fully after dissolving, the silicon dioxide microsphere prepared is added, fills Divide dissolving, obtained solution A；

Butyl titanate and ethyl alcohol are mixed, solution B is prepared；

Solution B is added in solution A, mixed liquor is obtained, later by mixed-liquor return, centrifuges, finally ethyl alcohol is used to clean, The core-shell nano complex of titanium dioxide predecessor coated silica microballoon is made.

5. the preparation method of titanium dioxide nano hollow ball as claimed in claim 4, it is characterised in that：Preparing solvent liquid II During, the volume ratio of water and ethyl alcohol is 1:150-300；And/or

During obtained solution A, the additive amount of Hydroxypropylcelliloxe is 50-150mg, and silicon dioxide microsphere adds Dosage is 0.15-0.3g；And/or

During preparing solution B, the volume ratio of butyl titanate and ethyl alcohol is 1:3.5-5.5；And/or

During the core-shell nano complex of titanium dioxide predecessor coated silica microballoon is made, by the molten of 4-7ml Liquid B is added drop-wise in 10-20min in solution A, obtains mixed liquor, and the reflux temperature of the mixed liquor is 70-95 DEG C, when reflux Between be 80-150min.

6. the preparation method of titanium dioxide nano hollow ball as claimed in claim 5, it is characterised in that：It is described rotten using highly basic Etching off includes except silica kernel：

By the core-shell nano complex ultrasonic disperse of titanium dioxide predecessor coated silica microballoon in water, it is molten that highly basic is added Liquid stirs at 30-70 DEG C, forms solution C；

Precipitation is centrifuged in solution C, sediment is washed using ultra-pure water and absolute ethyl alcohol, until solution is in Property, sediment is dried, amorphous titanium dioxide predecessor nano-hollow ball is made.

7. the preparation method of titanium dioxide nano hollow ball as claimed in claim 6, it is characterised in that：Forming solution C In the process, the strong base solution be sodium hydroxide and/or potassium hydroxide solution, a concentration of 1-3mol/L of the strong base solution, The volume of the strong base solution is 0.5-2ml, and 6-12h is stirred at 30-70 DEG C after strong base solution is added；And/or

During amorphous titanium dioxide predecessor nano-hollow ball is made, the temperature of the drying is 50-80 DEG C, is done The dry time is 8-15h.

8. the preparation method of titanium dioxide nano hollow ball as claimed in claims 6 or 7, it is characterised in that：At the hydro-thermal Reason includes：

Water and ethyl alcohol are mixed, solution D is prepared；

By amorphous titanium dioxide predecessor nano-hollow ball ultrasonic disperse in solution D, hydro-thermal process, it is heavy to centrifuge It forms sediment, sediment is washed using ultra-pure water and absolute ethyl alcohol, dry, surface, which is made, has the crystalline state two of sheet branched structure TiOx nano hollow ball.

9. the preparation method of titanium dioxide nano hollow ball as claimed in claim 8, it is characterised in that：Preparing solution D In the process, the volume ratio of water and ethyl alcohol is 1-2.5:1；And/or

The temperature of the hydro-thermal process is 100-250 DEG C, and the time of hydro-thermal process is 6-12h, and the temperature of the drying is 50-80 DEG C, the dry time is 8-15h.

10. dioxy made from a kind of preparation method using claim 1-9 any one of them titanium dioxide nano hollow balls Change titanium nano-hollow ball.