Preparation method of amorphous TiO2 colloid

Abstract

The present invention belongs to the technical field of the preparation of inorganic functional materials, and particularly relates to a method for preparing amorphous TiO2 colloid. The TiO2 colloidal particles prepared by the present invention have a relatively high crosslinking degree and can be well dispersed in ethanol to form a transparent TiO2 colloid. This method first carries out a complexation reaction between tetrabutyl titanate and acetylacetone to synthesize a tetrabutyl titanate complex, and then ages the reaction solution system at room temperature. The water vapor molecules diffusing from the air react with the tetrabutyl titanate complex to undergo a hydrolysis reaction. The Ti-OH bonds formed by the hydrolysis reaction can easily form Ti-O-Ti bonds through a polycondensation reaction, thereby achieving the purpose of forming a high crosslinking degree; Then, ethanol and water are sequentially added to the system to cause phase separation of the TiO2 colloidal particles therein and precipitate them. Dispersing the separated precipitate in ethanol can obtain a transparent TiO2 colloid.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of inorganic functional materials, and particularly relates to a method for preparing amorphous TiO2 colloid. Background Art

[0002] Titanium dioxide (TiO2) has been applied not only to the research in the fields of self-cleaning, photocatalysis, antibacterial, etc. because of its stable physical and chemical properties, rich raw material sources and low preparation cost, but also has a wide range of applications as a pigment or filler in coatings, cosmetics, plastics, synthetic fibers, etc. The phases of titanium dioxide include amorphous, anatase, brookite and rutile. Under the irradiation of ultraviolet light, a series of free radicals generated by the TiO2 photocatalyst have strong oxidation activity and can oxidize organic pollutant molecules in water or air into small molecules such as H2O and CO2, thereby achieving the purpose of purifying the environment. Generally, it is considered that crystalline TiO2, especially anatase, has higher activity, while amorphous TiO2 basically does not show photocatalytic activity. Therefore, there have been relatively few research reports on amorphous TiO2. However, it is also the photocatalytic activity of TiO2 that causes the coating to embrittle and peel off especially under the condition of light irradiation. In addition, the free radicals generated by TiO2 in cosmetics will also pose a potential hazard to the skin. Thus, in such occasions, amorphous TiO2 is often used as an inert isolation layer to coat the particles of crystalline TiO2. There are various synthesis methods for TiO2. Among them, the sol-gel method has a relatively low synthesis temperature and is particularly suitable for the preparation of nano-powders and large-area thin film products. For example, sol-gel method can be used to prepare amorphous TiO2 nanoparticles in the shape of rice grains with a size of about 100-180 nm (CN102688753A). The sol-gel process can be divided into an organic route and an inorganic route according to the precursors used. The inorganic route using inorganic salts or oxides as precursors has a relatively low preparation cost but requires a large amount of acid and alkali, and a large number of inorganic salt ions generated by the acid and alkali in the system are difficult to be separated. The organic route using alkoxides as precursors generally forms a sol by hydrolysis and polycondensation reactions of alkoxides in an alcohol / water medium. This process route has a relatively low degree of polycondensation reaction, so the cross-linking degree of the colloidal particles is also relatively low, and residual organic groups often exist in the formed colloidal particles. The present invention provides a simple method for preparing amorphous TiO2 colloid based on the sol-gel organic process route. The TiO2 colloidal particles prepared by the present invention have a relatively high cross-linking degree and have good dispersibility in ethanol to form a transparent colloid. Summary of the Invention

[0003] The present invention provides a method for preparing amorphous TiO2 colloid. The prepared TiO2 colloidal particles have a relatively high crosslinking degree and are characterized by being able to be well dispersed in ethanol to form a transparent colloid. The TiO2 colloidal particles are soft and do not exhibit a fixed shape. The colloid formed after their dispersion in ethanol is particularly suitable for preparing a TiO2 thin film layer with a flat surface.

[0004] The technical solution of the present invention to achieve this goal is as follows: First, tetrabutyl titanate and acetylacetone are subjected to a complexation reaction to synthesize a tetrabutyl titanate complex. Then, the reaction solution system is aged at room temperature for 7 - 10 days. No water is added to the system. Water vapor molecules diffusing from the air react with the tetrabutyl titanate complex through a hydrolysis reaction. The water slowly entering the system is quickly consumed through the hydrolysis reaction, and there is no excess water in the system all the time. Therefore, the Ti - OH bonds formed by the hydrolysis reaction can easily form Ti - O - Ti bonds through a polycondensation reaction, thereby achieving the purpose of forming a high crosslinking degree and low residual organic groups. Then, ethanol and water are sequentially added to the system, and the TiO2 colloidal particles therein can be phase - separated and precipitated. The precipitate after separation and washing is dispersed in ethanol to obtain a transparent TiO2 colloid. In this specification, the water used in the laboratory refers to distilled water.

[0005] A method for preparing amorphous TiO2 colloid, comprising the following steps:

[0006] (1) Add tetrabutyl titanate and acetylacetone into a beaker, seal the cup mouth with plastic wrap, and stir magnetically for 30 min. A complex of tetrabutyl titanate is generated in the system through a reaction.

[0007] Among them, the volume ratio of tetrabutyl titanate to acetylacetone is 7.5:2 - 3

[0008] (2) Make some small holes in the plastic wrap to connect the air inside and outside the beaker. Age the tetrabutyl titanate complex system at room temperature for 7 - 10 days. During this period, the liquid viscosity slowly increases, but it remains transparent continuously.

[0009] Among them, the temperature of the room - temperature environment is: 25°C, and the humidity is: 65RH%.

[0010] Preferably: The aging time in step (2) is 10 days, which can increase the yield of amorphous TiO2 colloidal particles; if it exceeds 10 days, the tetrabutyl titanate complex system is prone to gelation.

[0011] (3) Under stirring conditions, add ethanol to the tetrabutyl titanate complex system. The system still presents a transparent state. Then add water, and the system immediately changes from transparent to white turbid, and white precipitate appears after standing.

[0012] Among them, the volume ratio of the tetrabutyl titanate complex system, ethanol and water is 3 - 3.5:6 - 12:8 - 14.

[0013] (4) Centrifuge and wash, and collect the white precipitate, namely TiO2 colloidal particles;

[0014] Further, the conditions for the centrifugal separation operation: the rotation speed is 3500 - 7000 revolutions per minute, and the time is 3 - 5 min; preferably: the rotation speed is 3500 revolutions per minute and the time is 3 min;

[0015] (5) Add a dispersion medium to the washed white precipitate to obtain an amorphous TiO2 colloid.

[0016] Preferably: the dispersion medium is ethanol, and the dosage relationship between TiO2 colloidal particles and ethanol is 30 - 70 mg:10 mL.

[0017] The preparation method of the present invention is simple. By using the water vapor molecules diffused from the air to react with the tetrabutyl titanate complex, the water slowly entering the system is quickly consumed through the hydrolysis reaction, and there is no excess water in the system all the time. Therefore, the Ti - OH bonds formed by the hydrolysis reaction can easily form Ti - O - Ti bonds through the polycondensation reaction, so as to achieve the purpose of forming a high cross - linking degree and low organic group residue. The prepared TiO2 colloidal particles have a relatively high cross - linking degree and have the characteristic of being able to be well dispersed in ethanol to form a transparent colloid. The TiO2 colloidal particles are soft and do not present a fixed shape. The colloid formed after their dispersion in ethanol is particularly suitable for preparing a TiO2 thin film layer with a flat surface. Description of the Drawings

[0018] Figure 1 It is a photograph of the turbid state of the tetrabutyl titanate complex system in Example 1 of the present invention after aging for 10 days, then successively adding ethanol and water, a photograph of the precipitate appearing after standing, and a photograph of the transparent TiO2 colloid formed after adding ethanol to the separated precipitate.

[0019] Figure 2 It is a photograph of the tetrabutyl titanate complex system in Comparative Example 1, which is successively added with ethanol and water first, and then aged for 10 days, and the system always maintains a transparent state.

[0020] Figure 3 It is a photograph of the turbid system formed by adding water to uncomplexed tetrabutyl titanate in Comparative Example 2 and a photograph of the turbid system formed by adding ethanol to the separated white precipitate.

[0021] Figure 4 It is the TEM image (a), SAED pattern (b), and HRTEM image (c) of the TiO2 colloidal particles prepared in Example 1 of the present invention.

[0022] Figure 5XRD patterns of the TiO2 colloidal particles prepared in Example 1 of the present invention and those after heat treatment at 550 °C.

[0023] Figure 6 FT-IR spectra of the TiO2 colloidal particles prepared in Example 1 of the present invention and the TiO2 precipitate prepared in Comparative Example 2. Embodiment

[0024] The present invention will be further illustrated by specific examples below.

[0025] Example 1

[0026] (1) Add 2.5 mL of tetrabutyl titanate and 0.67 mL of acetylacetone into a 50 mL beaker, seal the beaker mouth with plastic wrap, and stir magnetically for 30 min. A complex of tetrabutyl titanate is generated in the system.

[0027] (2) Make some small holes in the plastic wrap to connect the air inside and outside the beaker. Age the tetrabutyl titanate complex system at room temperature for 10 days. During this period, the liquid viscosity slowly increases, but it remains transparent.

[0028] (3) Under stirring conditions, add 10 mL of ethanol to the system. The system still remains transparent. Then add 10 mL of water. Immediately, the system changes from transparent to white and turbid, and precipitation appears after standing.

[0029] (4) Perform centrifugal separation on the white and turbid system, separate and remove the supernatant, and wash the white precipitate with 2 mL of water; collect the precipitate by centrifugation; the conditions of the centrifugal separation operation: rotation speed 3500 revolutions per minute, time 3 min; the mass of the precipitate is weighed as 45 mg.

[0030] (5) Add 10 mL of ethanol to the washed white precipitate to obtain amorphous TiO2 colloid. The colloidal solution is allowed to stand for 3 days, and no change in the colloidal state is observed.

[0031] Figure 1 The photos show the state of the system becoming turbid after sequentially adding ethanol and water in step 3 of this example and the state of precipitation in the system after standing, indicating that highly cross-linked TiO2 colloidal particles are generated in the system during the aging process, and these colloidal particles can form precipitates and be separated by adding ethanol and water. The separated precipitate can be well dispersed in ethanol to form a transparent TiO2 colloid.

[0032] Figure 4 Show the TEM image, SAED pattern, and HRTEM image of the TiO2 colloidal particles prepared in this example. The TiO2 colloidal particles form a thin layer with a uniform structure on the copper foil ( Figure 4((a)) indicates that the colloidal particles have a certain flexibility, no fixed shape, and good film-forming properties; under the irradiation of an electron beam, crystallization phenomena occur in a few local areas ( Figure 4 ((a, b, c)) indicates that the amorphous TiO2 colloidal particles with a high degree of cross-linking have good crystallization properties; most areas are in an amorphous phase state, indicating that the prepared TiO2 colloidal particles are amorphous.

[0033] Figure 5 The XRD patterns of the TiO2 colloidal particles prepared in this example and after heat treatment at 550 °C are shown. Before heat treatment, it is amorphous TiO2, and after heat treatment, it is transformed from amorphous to anatase TiO2.

[0034] Example 2

[0035] (1) Add 2.5 mL of tetrabutyl titanate and 1.0 mL of acetylacetone to a 50 mL beaker, seal the beaker mouth with plastic wrap, and stir magnetically for 30 min. A complex of tetrabutyl titanate is formed in the system;

[0036] (2) Pierce some small holes in the plastic wrap to make the air inside and outside the beaker communicate. Age the tetrabutyl titanate complex system at room temperature for 10 days. During this period, the liquid viscosity slowly increases, but it remains transparent;

[0037] (3) Under stirring conditions, add 10 mL of ethanol to the system. The system still remains transparent. Then add 10 mL of water, and the system immediately changes from transparent to white turbid. Precipitation appears after standing;

[0038] (4) Perform centrifugal separation on the white turbid system, separate and remove the supernatant, and wash the white precipitate with 2 mL of water; collect the precipitate by centrifugation; the conditions of the centrifugal separation operation: rotation speed 3500 revolutions per minute, time 5 min; the mass of the precipitate is weighed as 43 mg;

[0039] (5) Add 10 mL of ethanol to the washed white precipitate to obtain amorphous TiO2 colloid.

[0040] Example 3

[0041] (1) Add 2.5 mL of tetrabutyl titanate and 0.67 mL of acetylacetone to a 50 mL beaker, seal the beaker mouth with plastic wrap, and stir magnetically for 30 min. A complex of tetrabutyl titanate is formed in the system;

[0042] (2) Pierce some small holes in the plastic wrap to make the air inside and outside the beaker communicate. Age the tetrabutyl titanate complex system at room temperature for 7 days. During this period, the liquid viscosity slowly increases, but it remains transparent;

[0043] (3) Under stirring conditions, 10 mL of ethanol was added to the system, and the system remained transparent. Then, 10 mL of water was added, and the system immediately changed from transparent to white turbid. After standing, precipitation occurred;

[0044] (4) The white turbid system was subjected to centrifugation to separate and remove the supernatant liquid, and the white precipitate was washed with 2 mL of water; the precipitate was collected by centrifugation; the conditions for the centrifugation operation were: rotation speed 7000 revolutions per minute, time 3 min; the mass of the precipitate was weighed as 30 mg;

[0045] (5) 10 mL of ethanol was added to the washed white precipitate to obtain an amorphous TiO2 colloid.

[0046] Example 4

[0047] (1) 2.5 mL of tetrabutyl titanate and 1.0 mL of acetylacetone were added to a 50 mL beaker, the beaker mouth was sealed with plastic wrap, and magnetic stirring was carried out for 30 min. A complex of tetrabutyl titanate was generated in the system;

[0048] (2) A number of small holes were pricked in the plastic wrap to allow air communication inside and outside the beaker. The tetrabutyl titanate complex system was aged at room temperature for 4 days. During this period, the liquid viscosity slowly increased, but it remained transparent;

[0049] (3) Under stirring conditions, 10 mL of ethanol was added to the system, and the system remained transparent. Then, 10 mL of water was added, and the transparency of the system decreased, but no precipitation occurred after standing;

[0050] In this example, after sequentially adding ethanol and water in step 3, no precipitation occurred in the system, indicating that it is necessary to age for a long time to make precipitation occur in the system.

[0051] Example 5

[0052] (1) 2.5 mL of tetrabutyl titanate and 0.67 mL of acetylacetone were added to a 50 mL beaker, the beaker mouth was sealed with plastic wrap, and magnetic stirring was carried out for 30 min. A complex of tetrabutyl titanate was generated in the system;

[0053] (2) A number of small holes were pricked in the plastic wrap to allow air communication inside and outside the beaker. The tetrabutyl titanate complex system was aged at room temperature for 10 days. During this period, the liquid viscosity slowly increased, but it remained transparent;

[0054] (3) Under stirring conditions, 6 mL of ethanol was added to the system, and the system remained transparent. Then, 14 mL of water was added, and the system immediately changed from transparent to white turbid. After standing, precipitation occurred;

[0055] (4) Centrifuge the white turbid system to separate and remove the supernatant liquid, wash the white precipitate with 2 mL of water; centrifuge to collect the precipitate; conditions for the centrifuge separation operation: rotation speed 3500 revolutions per minute, time 5 min; the mass of the precipitate weighed is 64 mg;

[0056] (5) Add 10 mL of ethanol to the washed white precipitate to obtain amorphous TiO2 colloid.

[0057] Example 6

[0058] (1) Add 2.5 mL of tetrabutyl titanate and 0.67 mL of acetylacetone to a 50 mL beaker, seal the beaker mouth with plastic wrap, and magnetically stir for 30 min. A complex of tetrabutyl titanate is generated in the system;

[0059] (2) Pierce some small holes in the plastic wrap to allow air communication inside and outside the beaker. Age the tetrabutyl titanate complex system at room temperature for 10 days. During this period, the liquid viscosity slowly increases, but it remains in a transparent state;

[0060] (3) Under stirring conditions, add 12 mL of ethanol to the system. The system still remains transparent. Then add 8 mL of water. The system immediately turns from transparent to white turbid, and precipitation appears after standing;

[0061] (4) Centrifuge the white turbid system to separate and remove the supernatant liquid, wash the white precipitate with 2 mL of water; centrifuge to collect the precipitate; conditions for the centrifuge separation operation: rotation speed 7000 revolutions per minute, time 3 min; the mass of the precipitate weighed is 40 mg;

[0062] (5) Add 10 mL of ethanol to the washed white precipitate to obtain amorphous TiO2 colloid.

[0063] Comparative Example 1

[0064] (1) Add 2.5 mL of tetrabutyl titanate and 0.67 mL of acetylacetone to a 50 mL beaker, seal the beaker mouth with plastic wrap, and magnetically stir for 30 min. A complex of tetrabutyl titanate is generated in the system;

[0065] (2) Open the plastic wrap, add 10 mL of ethanol under stirring conditions, and then add 10 mL of water. The system still remains transparent;

[0066] (3) Seal the beaker mouth with plastic wrap again, pierce some small holes in the plastic wrap to allow air communication inside and outside the beaker. Age the mixed liquid system at room temperature for 10 days;

[0067] Compared with Example 1, the main differences are as follows: In Example 1, the tetrabutyl titanate complex system was aged at room temperature for 10 days first, and then ethanol and water were added successively; in Comparative Example 1, ethanol and water were added to the tetrabutyl titanate complex system successively first, and then it was aged at room temperature for 10 days.

[0068] Figure 2 The photograph of Figure 2 shows the change in the solution state of Comparative Example 1. The mixture remained clear and transparent throughout, without precipitation. This result indicates that the degree of hydrolysis and polycondensation reaction of the tetrabutyl titanate complex in Comparative Example 1 is relatively low, the crosslinking degree of the colloidal particles is very low, and it also illustrates the key role of Step 2 in Example 1.

[0069] Comparative Example 2

[0070] (1)Add 2.5 mL of tetrabutyl titanate to a 50 mL beaker;

[0071] (2)Add 10 mL of ethanol under stirring, and then add 10 mL of water. When water was added, the system immediately became white and turbid, and precipitation occurred after standing;

[0072] (3)Perform centrifugal separation on the white turbid system, separate and remove the supernatant, wash the white precipitate with 2 mL of water; centrifuge to collect the precipitate; Conditions for the centrifugal separation operation: rotation speed 3500 revolutions per minute, time 3 min; The mass of the precipitate was weighed as 410 mg;

[0073] (4)Add ethanol to the washed white precipitate, and a turbid system was obtained.

[0074] Compared with Example 1, the main differences are as follows: In Comparative Example 2, acetylacetone complexing agent was not used. Because the hydrolysis activity of tetrabutyl titanate is very high, hydrolysis and polycondensation reaction occurs immediately when it encounters water, forming white TiO2 precipitate.

[0075] Figure 3 The photograph of Figure 3 shows the state of the TiO2 precipitate prepared in Comparative Example 2 and the dispersion performance of the precipitate in ethanol. The turbid system formed after adding ethanol to the separated precipitate indicates that the TiO2 prepared in Comparative Example 2 cannot be dispersed in ethanol to form a sol. This result also shows that the crosslinking degree of the TiO2 prepared in Comparative Example 2 is relatively low and the agglomeration phenomenon is more serious.

[0076] Figure 6 Shows the comparison of the FT-IR spectra of the TiO2 prepared in Example 1 of the present invention and the TiO2 prepared in Comparative Example 2. The relatively broad absorption peak at a wavenumber of 3400 cm -1 is the stretching vibration peak of -OH, and 450 cm -1The absorption peak at [location] is the absorption peak of the Ti-O-Ti bond. Compared with the TiO2 prepared in Comparative Example 2, the relative intensity of the Ti-O-Ti bond absorption peak of the TiO2 prepared in Example 1 is higher, indicating that the TiO2 prepared in Example 1 of the present invention has a higher degree of crosslinking.

Claims

1. A preparation method of amorphous TiO2 colloid, characterized in that: It includes the following steps: (1) Mix tetrabutyl titanate and acetylacetone, seal it with plastic wrap, and stir magnetically to form a complex of tetrabutyl titanate; (2) Pierce small holes in the plastic wrap to allow water molecules in the air to react with the tetrabutyl titanate complex by hydrolysis, and age the tetrabutyl titanate complex system at room temperature for 7 - 10 days; (3) Under stirring conditions, add ethanol to the system, then add water to make it in a white turbid state, and white precipitate appears after standing; (4) Centrifuge and wash, collect the white precipitate, which is TiO2 colloidal particles; (5) Add a dispersion medium to the washed white precipitate to obtain amorphous TiO2 colloid.

2. The preparation method of the amorphous TiO2 colloid according to claim 1, characterized in that: In step (1), the volume ratio of tetrabutyl titanate to acetylacetone is 7.5:2 - 3.

3. The preparation method of the amorphous TiO2 colloid according to claim 1, characterized in that: In step (1), the stirring reaction time is 30 min.

4. The preparation method of the amorphous TiO2 colloid according to claim 1, characterized in that: In step (2), the temperature of the room temperature environment is: 25°C, and the humidity is: 65RH%.

5. The preparation method of the amorphous TiO2 colloid according to claim 1, characterized in that: In step (3), the volume ratio of the tetrabutyl titanate complex system, ethanol and water is 3 - 3.5:6 - 12:8 - 14.

6. The preparation method of the amorphous TiO2 colloid according to claim 1, characterized in that: In step (4), the centrifuge speed is 3500 - 7000 revolutions per minute, and the time is 3 - 5 min.

7. The preparation method of the amorphous TiO2 colloid according to claim 1, characterized in that: In step (5), the dispersion medium is ethanol, and the dosage relationship between TiO2 colloidal particles and ethanol is 30 - 70 mg:10 mL.

Images