A method for preparing monodisperse doped titanium dioxide with in-situ lattice strain

Abstract

This invention relates to a method for preparing monodisperse doped titanium dioxide with in-situ lattice strain, belonging to the field of nanomaterial dispersion preparation. The titanium dioxide prepared by this method possesses abundant oxygen vacancies and surface active sites. The method employs a secondary titanium source injection followed by a rapid solvothermal reaction with increasing temperature. Lattice strain is controlled by the difference in lattice contraction rates at the amorphous-crystalline interface, reducing the oxygen vacancy formation energy. Doping with low-valence metal ions further stabilizes the oxygen vacancy structure. Surface modifiers can regulate the particle surface properties to adapt to various solvent systems, facilitating the preparation of highly transparent composite functional materials.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial dispersion preparation technology; more specifically, it relates to a method for preparing monodisperse doped titanium dioxide with in-situ lattice strain. Background Technology

[0002] In recent years, titanium dioxide (TiO2) has been widely used in semiconductors, coatings, photovoltaics, pharmaceuticals, and displays due to its excellent and stable physicochemical properties, low cost, and non-toxicity. Its intrinsic surface properties and electronic structure have also been extensively studied. Oxygen vacancies, as a very common defect, play a crucial role in regulating the surface properties and electronic structure of titanium dioxide. Therefore, controlling the oxygen vacancy content in titanium dioxide is of great significance for its practical applications.

[0003] Oxygen vacancies can typically be obtained by calcining titanium dioxide under vacuum or reducing atmosphere conditions, and a large body of work has investigated blue / black titanium dioxide obtained by such methods. However, this usually leads to the consumption of organic groups on the surface of titanium dioxide particles and severe particle agglomeration, making it difficult to achieve high-quality monodisperse of titanium dioxide in solvents. If used as a filler in composite materials, it will severely affect the transparency and mechanical properties of the materials.

[0004] Constructing oxygen vacancies in situ during titanium dioxide preparation to avoid subsequent calcination will greatly enhance its potential and performance in future applications. Low-valence metal ion doping and anion doping are common methods for in-situ oxygen vacancy construction and have been widely studied and applied. However, their doping ratio is usually limited by lattice stability, thus restricting their ability to control oxygen vacancies. Reducing the oxygen vacancy formation energy through lattice strain, thereby efficiently modulating the oxygen vacancy content, is a novel and effective approach. During titanium dioxide preparation, based on the difference in lattice contraction between the amorphous and crystalline states, a secondary introduction of a homologous titanium source is used to in-situ control the lattice strain at the interface. This effectively controls the oxygen vacancy content while preserving the original surface structure and properties of titanium dioxide, which is beneficial for subsequent surface modification and the construction of high-transparency composite materials. Furthermore, using low-valence metal ions as dopants, based on charge balance, further reduces the oxygen vacancy formation energy and stabilizes the oxygen-rich vacancy structure. Therefore, designing and developing a simple preparation method for monodisperse doped titanium dioxide with in-situ lattice strain is of great significance. On the one hand, it provides a new synthetic approach for achieving titanium dioxide lattice strain, and on the other hand, it provides a material basis for the development of novel titanium dioxide composite materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing monodisperse doped titanium dioxide with in-situ lattice strain. The prepared nano-titanium dioxide simultaneously possesses monodispersity and abundant oxygen vacancies. By introducing a homogeneous titanium source a second time, the lattice strain at the interface is controlled in-situ based on the difference in lattice contraction rates between the amorphous and crystalline states. This effectively controls the oxygen vacancy content while preserving the original surface structure and properties of titanium dioxide. After surface modification, monodispersity of titanium dioxide is achieved, and a high-transparency composite functional material is constructed.

[0006] Based on this, the present invention mainly adopts the following technical solution: a method for preparing monodisperse doped titanium dioxide with in-situ lattice strain, which includes the following steps:

[0007] 1) Prepare and mature the precursor solution doped with nano-titanium dioxide, and carry out the first solvothermal reaction;

[0008] 2) After the first solvothermal reaction is completed, the reaction solution is cooled and a titanium source is added to it. Then the temperature is raised to carry out the second solvothermal reaction. The lattice strain is generated in situ by utilizing the difference in lattice shrinkage rate at the crystal-amorphous interface.

[0009] 3) The reaction product was subjected to multiple precipitation, centrifugation and washing processes, and the surface was modified using a surface modifier to obtain the monodisperse doped titanium dioxide with in-situ lattice strain.

[0010] The precursor solution mentioned in step 1) includes an organic solvent, water, a doped metal salt, a titanium source, and a hydrolysis inhibitor.

[0011] The organic solvent is selected from one or more of the following substances: methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, pentanol, hexanol, heptanol, octanol, dodecanol, ethylene glycol, propylene glycol, hexanediol, benzyl alcohol, and phenethyl alcohol.

[0012] The doped metal salt is selected from one or more of the following substances: lithium chloride, sodium chloride, potassium chloride, rubidium chloride, magnesium chloride, barium chloride, copper chloride, manganese chloride, ferric chloride, zinc chloride, tin chloride, aluminum chloride, lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, magnesium nitrate, barium nitrate, copper nitrate, manganese nitrate, ferric nitrate, zinc nitrate, tin nitrate, cerium nitrate, europium nitrate, aluminum nitrate, lanthanum nitrate, terbium nitrate, and samarium nitrate;

[0013] The titanium source is selected from one or more of the following substances: titanium tetrachloride, titanium oxysulfate, titanium acetylacetonate, tetraethyl titanate, tetrabutyl titanate, isopropyl titanate, titanic acid, and metatitanic acid.

[0014] The hydrolysis inhibitor is selected from one or more of the following substances: formic acid, acetic acid, propionic acid, butyric acid, lactic acid, citric acid, tartaric acid, salicylic acid, nitric acid, hydrochloric acid, and sulfuric acid.

[0015] In the precursor solution, the amount of doped metal salt added is 0.001-0.03 g / mL, the amount of titanium source added is 0.08-0.8 g / mL, and the amount of hydrolysis inhibitor added is 0.001-0.05 g / mL, relative to the organic solvent; the mass ratio of water to titanium source in the precursor solution is 0.02-0.7.

[0016] In step 1), the temperature of the first solvothermal reaction is 100-230℃, the pressure of the first solvothermal reaction is 0.01-5 MPa, and the time of the first solvothermal reaction is 0.5-72 h; preferably, the temperature of the first solvothermal reaction is 140-220℃, the pressure of the first solvothermal reaction is 0.1-3 MPa, and the time of the first solvothermal reaction is 1-48 h; more preferably, the temperature of the first solvothermal reaction is 160-200℃, the pressure of the first solvothermal reaction is 0.1-2 MPa, and the time of the first solvothermal reaction is 2-24 h.

[0017] The titanium source mentioned in step 2) is selected from one or more of the following substances: including titanium tetrachloride, titanium oxysulfate, titanium acetylacetonate, tetraethyl titanate, tetrabutyl titanate, isopropyl titanate, titanic acid, and metatitanic acid; preferably, the titanium source mentioned in step 2) is the same type of titanium source as in step 1).

[0018] Step 2) The molar ratio of the amount of titanium source added to the amount of titanium source in the precursor solution in Step 1) is 0.05-1.

[0019] Preferably, in step 2), an appropriate amount of water is added to the reaction solution at the same time as the titanium source is added, wherein the molar ratio of the added water to the added titanium source is 0.01-1; preferably, the molar ratio of the water to the added titanium source is 0.05-0.8; more preferably, the molar ratio of the water to the added titanium source is 0.1-0.6.

[0020] The second solvothermal reaction temperature is 200-400℃, the second solvothermal reaction pressure is 0.01-5 MPa, and the second solvothermal reaction time is 0.5-24 h; preferably, the second solvothermal reaction temperature is 220-350℃, the second solvothermal reaction pressure is 0.1-3 MPa, and the second solvothermal reaction time is 0.75-12 h; more preferably, the second solvothermal reaction temperature is 260-320℃, the second solvothermal reaction pressure is 0.1-2 MPa, and the second solvothermal reaction time is 1-6 h.

[0021] The second solvothermal reaction requires rapid heating and holding at the desired reaction temperature, with a heating rate of 20-100℃ / min; preferably, the heating rate is 25-80℃ / min; more preferably, the heating rate is 30-60℃ / min.

[0022] The surface modifier mentioned in step 3) includes one or more of titanate, phosphate ester, organic acid and silane coupling agent;

[0023] The titanate is selected from one or more of the following substances: isopropyl tris(dodecylbenzenesulfonyl) titanate, isopropyl triisostearate titanate, bis(acetylacetonyl) diisopropyl titanate, isopropyl tris(dioctylphosphoyloxy) titanate, isopropyl dioleoyloxy (dioctylphosphoyloxy) titanate, di(octylphenol polyoxyethylene ether) phosphate, and tetraisopropyl di(dioctylphosphite) titanate.

[0024] The phosphate ester is selected from one or more of the following substances: 4-hydroxybutyl phosphate dihydrogen ester, 2-ethylhexyl phosphate dihydrogen ester, 9-octadecene-1-ol phosphate ester, isooctyl phosphate ester, dodecyl phosphate ester, tetradecyl phosphate ester, lauryl polyoxyethylene ether phosphate ester, and tridecyl polyoxyethylene ether phosphate ester.

[0025] The organic acid is selected from one or more of the following substances: butyric acid, lactic acid, citric acid, tartaric acid, salicylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, oleic acid, linoleic acid, lauryl edodecanic acid, tetradecanoic acid, octadecanoic acid, and eicosanoic acid.

[0026] The silane coupling agent is selected from one or more of the following substances: vinyltrimethoxysilane, vinyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltrimethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, phenyltrimethoxysilane, γ-aminopropyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropyltriethoxysilane, methoxytriethylene glycol etherylpropyltrimethoxysilane, 11-mercaptoundecyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and diethylphosphorylethyltriethoxysilane.

[0027] In step 3), the centrifugation speed is 3000-8000 r / min; preferably, the centrifugation speed is 4000-7000 r / min; more preferably, the centrifugation speed is 5000-6000 r / min.

[0028] The washing solvent is selected from one or more of the following substances: ethanol, acetone, tetrahydrofuran, propylene glycol methyl ether acetate, toluene, and heptane.

[0029] Preferably, the surface modification process in step 3) is as follows: the washing product and the surface modifier are added to the reaction solvent to carry out the surface modification reaction.

[0030] The surface modification process is wherein the reaction temperature is 25-150℃ and the reaction time is 0.5-24h; preferably, the reaction temperature is 50-130℃ and the reaction time is 1-12h; more preferably, the reaction temperature is 80-120℃ and the reaction time is 2-8h.

[0031] The mass ratio of the surface modifier to the washing product is 0.05-1;

[0032] The reaction solvent is selected from one or more of the following substances: methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, pentanol, hexanol, heptanol, octanol, dodecanol, ethylene glycol, propylene glycol, hexanediol, benzyl alcohol, acetone, butanone, propylene glycol methyl ether acetate, tetrahydrofuran, dimethyl sulfoxide, dichloromethane, chloroform, ethyl acetate, butyl acetate, benzene, toluene, xylene, heptane, n-hexane, cyclohexane, and petroleum ether.

[0033] The doped titanium dioxide obtained by this invention can be monodispersed in a dispersion solvent, which may be selected from one or more of the following substances: methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, pentanol, hexanol, heptanol, octanol, dodecyl alcohol, ethylene glycol, propylene glycol, hexanediol, benzyl alcohol, acetone, butanone, propylene glycol methyl ether acetate, tetrahydrofuran, dimethyl sulfoxide, dichloromethane, chloroform, ethyl acetate, butyl acetate, benzene, toluene, xylene, heptane, n-hexane, cyclohexane, and petroleum ether.

[0034] The present invention also discloses a monodisperse doped titanium dioxide with in-situ lattice strain prepared by the above method, and the application of the doped titanium dioxide in transparent composite functional materials.

[0035] In one alternative application, doped titanium dioxide (prepared by the aforementioned method), methyl methacrylate, polyethylene glycol diacrylate, and diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide are thoroughly mixed in a dispersion solvent and then cured under ultraviolet light in a mold to form a transparent titanium dioxide / acrylate composite material, which is used as a transparent photochromic display material.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] 1) The doped titanium dioxide with in-situ lattice strain prepared by the method of this invention is a narrow-particle-size nano-titanium dioxide, which simultaneously possesses monodispersity and abundant oxygen vacancies. This titanium dioxide can achieve monodispersity in a variety of organic solvents. By controlling the reaction temperature and the ratio of water to titanium source, the particle size distribution can be controlled within the range of 5-100 nm. By increasing the reaction temperature and decreasing the ratio of water to titanium source, the particle size of the product can be reduced, and small-particle-size samples can be further reduced to 10-30 nm.

[0038] 2) By using a secondary titanium source, the lattice strain at the interface is controlled in situ by relying on the difference in lattice shrinkage rate between the amorphous and crystalline states. While controlling oxygen vacancies, the original surface structure and properties of titanium dioxide are preserved, avoiding the influence of calcination or other impurity layers on the surface. After surface modification, titanium dioxide is monodispersed and a high-transparency composite functional material is constructed. Surface modifiers can be selected according to different composite systems to ensure the monodispersity performance of titanium dioxide in the corresponding system. Attached Figure Description

[0039] Figure 1 A schematic diagram of the route and mechanism for preparing monodisperse doped titanium dioxide with in-situ lattice strain;

[0040] Figure 2 This is a photograph of the product dispersion from Example 2.

[0041] Figure 3 The images show transmission electron microscopy (TEM) images and geometric phase analysis diagrams of the particles in the dispersion of Example 2.

[0042] Figure 4 This is a particle size distribution diagram of the dispersion in Example 2;

[0043] Figure 5 The electron paramagnetic resonance spectra of the unmodified powders in Example 2 and Comparative Examples 1-3 are shown below.

[0044] Figure 6 This is a physical image of the composite film in Example 3. Detailed Implementation

[0045] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict. Figure 1 A roadmap for synthesizing monodisperse doped titanium dioxide with in-situ lattice strain is shown, illustrating how lattice strain is generated in situ at the crystal-amorphous interface due to the difference in lattice contraction rates between the two. Specific examples are given below:

[0046] Example 1

[0047] Dissolve 10 mL of isopropyl titanate and 0.15 g of potassium nitrate in 20 mL of ethanol and stir thoroughly until dissolved to form mixture A. Mix 0.8 mL of butyric acid, 0.75 mL of water and 10 mL of ethanol thoroughly to form mixture B. Add solution B dropwise to solution A under vigorous stirring and mix evenly. Transfer the above precursor solution to a hydrothermal reactor and react at 150 °C for 24 h.

[0048] After the reaction was complete and cooled, 4 mL of isopropyl titanate and 85 μL of water were added to the reaction solution under stirring. After mixing thoroughly, the solution was transferred to a hydrothermal reactor. The heating rate was set to 30 °C / min, the reaction temperature was 250 °C, and the reaction time was 2 h. The product was separated by centrifugation at 6000 rpm, washed with ethanol, and centrifuged three times. 0.5 g of wet solid was added to 10 mL of chloroform, and 0.1 g of dodecyltrimethoxysilane was added. The mixture was stirred at 80 °C for 4 h to form a homogeneous and transparent dispersion.

[0049] Example 2

[0050] Under stirring, 0.2 mL of acetic acid, 0.8 mL of water, 0.18 g of rubidium nitrate, and 6 mL of tetrabutyl titanate were dissolved in 25 mL of benzyl alcohol. After thorough mixing, the precursor solution was transferred to a hydrothermal reactor and reacted at 200 °C for 2 h.

[0051] After the reaction was completed and cooled, 1.2 mL of tetrabutyl titanate and 30 μL of water were added to the above reaction solution under stirring. After mixing evenly, the solution was transferred to a hydrothermal reactor. The heating rate was set to 30 °C / min, the reaction temperature was 300 °C, and the reaction time was 1 h. The product was separated by centrifugation at 6000 rpm, washed with propylene glycol methyl ether acetate, and centrifuged three times. 1.5 g of wet solid was added to 10 mL of propylene glycol methyl ether acetate, followed by 0.25 g of methoxytriethylene glycol ether propyltrimethoxysilane. The mixture was stirred at 130 °C for 50 min, and then 0.05 g of 3-(acryloyloxy)propyltrimethoxysilane was added. The mixture was stirred at 130 °C for another 10 min to form a homogeneous and transparent dispersion.

[0052] The above dispersion was backwashed and centrifuged three times using heptane as the antisolvent and ethyl acetate as the good solvent to remove impurities and excess surface modifier. The wet solid was placed under vacuum for 2 hours to obtain a dry powder. 1 g of the dry powder was dispersed in 10 mL of acetone to obtain a homogeneous and transparent dispersion. Figure 2 As shown.

[0053] The particles in the above dispersion were characterized by transmission electron microscopy (TEM), such as... Figure 3As shown, the particles are uniformly distributed, exhibiting monodisperse characteristics. High-resolution TEM characterization reveals a distinct amorphous structure layer on the particle surface, and geometric phase analysis indicates significant lattice tensile strain at the amorphous-crystalline interface. The particle size distribution of the product was further measured using a nanoparticle size analyzer. Figure 4 As shown, the average particle size in the dispersion is around 10 nm, and the particle size distribution range is narrow.

[0054] Example 3

[0055] 0.2 mL butyric acid, 0.8 mL water, 0.12 g barium chloride, and 6 mL tetrabutyl titanate were dissolved in 25 mL benzyl alcohol under stirring. After thorough mixing, the precursor solution was transferred to a hydrothermal reactor and reacted at 200 °C for 2 h.

[0056] After the reaction was completed and cooled, 0.6 mL of tetrabutyl titanate and 10 μL of water were added to the reaction solution under stirring. After mixing thoroughly, the solution was transferred to a hydrothermal reactor. The heating rate was set to 40 °C / min, the reaction temperature was 280 °C, and the reaction time was 2 h. The product was separated by centrifugation at 6000 rpm, washed with propylene glycol methyl ether acetate, and centrifuged three times. 1.5 g of wet solid was added to 10 mL of propylene glycol methyl ether acetate, and 0.25 g of methoxytriethylene glycol etherpropyltrimethoxysilane was added. The mixture was stirred at 130 °C for 60 min to form a homogeneous and transparent dispersion.

[0057] The above dispersion was backwashed and centrifuged three times, using heptane as the antisolvent and ethyl acetate as the good solvent, to remove impurities and excess surface modifier. The wet solid was placed under vacuum for 2 hours to obtain a dry powder. 1 g of the dry powder was dispersed in 10 mL of ethanol to obtain a homogeneous and transparent dispersion.

[0058] Example 4

[0059] Under stirring, 0.5 mL of lactic acid, 0.4 mL of water, 0.18 g of europium nitrate, and 4 mL of titanium tetrachloride were successively dissolved in 25 mL of octanol. After thorough mixing, the precursor solution was transferred to a hydrothermal reactor and reacted at 180 °C for 5 h.

[0060] After the reaction was complete and cooled, 0.5 mL of isopropyl titanate and 10 μL of water were added to the reaction solution under stirring. After mixing thoroughly, the solution was transferred to a hydrothermal reactor. The heating rate was set to 35 °C / min, the reaction temperature to 300 °C, and the reaction time to 1.5 h. The product was separated by centrifugation at 6000 rpm, washed with ethanol, and centrifuged three times. 1.5 g of wet solid was added to 10 mL of toluene, along with 0.25 g of isopropyl tris(dodecylbenzenesulfonyl) titanate. The mixture was stirred at 50 °C for 30 min to form a homogeneous and transparent dispersion. The dispersion was backwashed and centrifuged three times using acetone as the antisolvent and toluene as the good solvent to remove impurities and excess surface modifier. The wet solid was placed under vacuum for 2 h to obtain a dry powder. 1 g of the dry powder was dispersed in 10 mL of toluene to obtain a homogeneous and transparent dispersion.

[0061] Example 5

[0062] 0.2 g citric acid, 0.4 mL water, 0.1 g aluminum nitrate and 8 mL tetrabutyl titanate were dissolved in 30 mL n-butanol under stirring. After thorough mixing, the precursor solution was transferred to a hydrothermal reactor and reacted at 150 °C for 24 h.

[0063] After the reaction was complete and cooled, 2 mL of tetraethyl titanate was added to the reaction solution under stirring. After mixing thoroughly, the solution was transferred to a hydrothermal reactor. The heating rate was set to 30 °C / min, the reaction temperature was 280 °C, and the reaction time was 1 h. The product was separated by centrifugation at 6000 rpm, washed with ethanol, and centrifuged three times. 1.5 g of wet solid was added to 10 mL of toluene, along with 0.18 g of stearic acid. The mixture was stirred at 60 °C for 30 min to form a homogeneous and transparent dispersion.

[0064] The above dispersion was backwashed and centrifuged three times, using acetone as the antisolvent and toluene as the good solvent, to remove impurities and excess surface modifier. The wet solid was placed under vacuum for 2 hours to obtain a dry powder. 1 g of the dry powder was dispersed in 10 mL of toluene to obtain a homogeneous and transparent dispersion.

[0065] Example 6

[0066] 0.2 g nitric acid, 0.15 mL water, 0.2 g manganese nitrate and 8 mL isopropyl titanate were dissolved in 30 mL ethanol under stirring. After thorough mixing, the precursor solution was transferred to a hydrothermal reactor and reacted at 170 °C for 24 h.

[0067] After the reaction was complete and cooled, 2 mL of isopropyl titanate was added to the reaction solution under stirring. After mixing thoroughly, the solution was transferred to a hydrothermal reactor. The heating rate was set at 40 °C / min, the reaction temperature at 300 °C, and the reaction time at 0.5 h. The product was separated by centrifugation at 6000 rpm, washed with ethanol, and centrifuged three times. 1.5 g of wet solid was added to 10 mL of toluene, and 0.2 g of 9-octadecene-1-ol phosphate was added. The mixture was stirred at 100 °C for 30 min to form a homogeneous and transparent dispersion.

[0068] The above dispersion was backwashed and centrifuged three times, using acetone as the antisolvent and toluene as the good solvent, to remove impurities and excess surface modifier. The wet solid was placed under vacuum for 2 hours to obtain a dry powder. 1 g of the dry powder was dispersed in 10 mL of toluene to obtain a homogeneous and transparent dispersion.

[0069] Comparative Example 1

[0070] Under stirring, 0.2 mL of acetic acid, 0.8 mL of water, 0.18 g of rubidium nitrate, and 6 mL of tetrabutyl titanate were sequentially dissolved in 25 mL of benzyl alcohol solution. After thorough mixing, the precursor solution was transferred to a hydrothermal reactor and reacted at 200 °C for 2 h. After cooling, the temperature was increased to 300 °C at a rate of 30 °C / min, and the reaction was continued for 1 h. The product was separated by centrifugation at 6000 rpm, washed with ethanol, and centrifuged three times. The wet solid was then placed under vacuum for 2 h to obtain a dry powder.

[0071] Comparative Example 2

[0072] Under stirring, 0.2 mL of acetic acid, 0.8 mL of water, and 6 mL of tetrabutyl titanate were sequentially dissolved in 25 mL of benzyl alcohol solution. After thorough mixing, the precursor solution was transferred to a hydrothermal reactor. The reaction temperature was 200 °C, and the reaction time was 2 h. After the reaction was completed and cooled, 1.2 mL of tetrabutyl titanate and 30 μL of water were added to the reaction solution under stirring. After thorough mixing, the solution was transferred to a hydrothermal reactor. The heating rate was set to 30 °C / min, the reaction temperature was 300 °C, and the reaction time was 1 h. The product was separated by centrifugation at 6000 rpm, washed with ethanol, and centrifuged three times. The wet solid was placed under vacuum for 2 h to obtain a dry powder.

[0073] Comparative Example 3

[0074] Under stirring, 0.2 mL of acetic acid, 0.8 mL of water, and 6 mL of tetrabutyl titanate were sequentially dissolved in 25 mL of benzyl alcohol solution. After thorough mixing, the precursor solution was transferred to a hydrothermal reactor and reacted at 200 °C for 2 h. After cooling, the temperature was increased to 300 °C at a rate of 30 °C / min, and the reaction was continued for 1 h. The product was separated by centrifugation at 6000 rpm, washed with ethanol, and centrifuged three times. The wet solid was then placed under vacuum for 2 h to obtain a dry powder.

[0075] The oxygen vacancy status of the unmodified sample in Example 2 and the samples in Comparative Examples 1-3 was characterized using electron paramagnetic resonance (EPR) spectroscopy. Figure 5 As shown, compared with the samples in Comparative Examples 1-3, the sample in Example 2 under the synergistic effect of in-situ lattice strain and Rb doping has more oxygen vacancies. Compared with Example 2, Comparative Example 1, which only underwent doping treatment, and Comparative Example 2, which only underwent lattice strain treatment, showed reduced oxygen vacancy content. The sample in Comparative Example 3, which did not undergo lattice strain or doping, showed the least oxygen vacancy signal, indicating that both doping treatment and in-situ lattice strain have a promoting effect on the formation of oxygen vacancies.

[0076] Example 7

[0077] Take 5 mL of the dispersion from Example 2, and add 1.5 mL of methyl methacrylate, 2.5 mL of polyethylene glycol diacrylate, 0.2 mL of diethylene glycol, 0.4 g of pentatetrapentayl alcohol triacrylate, and 35 mg of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide. After mixing thoroughly, evaporate the solvent on a heating stage at 80°C, and then cure under ultraviolet light in a mold to obtain a transparent and uniform titanium dioxide / acrylate composite photochromic film. Figure 6 As shown, the film has high transparency and can change color under ultraviolet light to reduce transparency. With the help of a photomask, text or patterns can be customized to be displayed on the composite film.

[0078] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing monodisperse doped titanium dioxide with in-situ lattice strain, characterized in that, Includes the following steps: 1) Prepare a precursor solution containing a doped metal salt for the preparation of titanium dioxide, and carry out a first solvothermal reaction; the precursor solution includes an organic solvent, water, a doped metal salt, a titanium source, and a hydrolysis inhibitor; relative to the organic solvent, the amount of doped metal salt added is 0.001-0.03 g / mL, the amount of titanium source added is 0.08-0.8 g / mL, and the amount of hydrolysis inhibitor added is 0.001-0.05 g / mL; in the precursor solution, the mass ratio of water to titanium source is 0.02-0.7; the temperature of the first solvothermal reaction is 100-230℃, the pressure of the first solvothermal reaction is 0.01-5 MPa, and the time of the first solvothermal reaction is 0.5-72 h; 2) Add a titanium source to the reaction solution obtained in step 1) and carry out a second solvothermal reaction with rapid heating. Utilize the difference in lattice contraction rate at the crystal-amorphous interface to generate lattice strain in situ and reduce the oxygen vacancy formation energy. The molar ratio of the amount of titanium source added in step 2) to the amount of titanium source in the precursor solution in step 1) is 0.05-1. The second solvothermal reaction temperature is 200-400℃, the second solvothermal reaction pressure is 0.01-5 MPa, and the second solvothermal reaction time is 0.5-24 h; 3) The reaction product is centrifuged and washed, and its surface is modified with a surface modifier to obtain the monodisperse doped titanium dioxide with in-situ lattice strain.

2. The preparation method according to claim 1, characterized in that: In step 1) The organic solvent includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, pentanol, hexanol, heptanol, octanol, dodecanol, ethylene glycol, propylene glycol, hexanediol, benzyl alcohol, and phenethyl alcohol; The doped metal salt includes one or more of the following: lithium chloride, sodium chloride, potassium chloride, rubidium chloride, magnesium chloride, barium chloride, copper chloride, manganese chloride, ferric chloride, zinc chloride, tin chloride, aluminum chloride, lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, magnesium nitrate, barium nitrate, copper nitrate, manganese nitrate, ferric nitrate, zinc nitrate, tin nitrate, cerium nitrate, europium nitrate, aluminum nitrate, lanthanum nitrate, terbium nitrate, and samarium nitrate. The titanium source includes one or more of titanium tetrachloride, titanium oxysulfate, titanium acetylacetonate, tetraethyl titanate, tetrabutyl titanate, isopropyl titanate, titanic acid, and metatitanic acid. The hydrolysis inhibitors include one or more of formic acid, acetic acid, propionic acid, butyric acid, lactic acid, citric acid, tartaric acid, salicylic acid, nitric acid, hydrochloric acid, and sulfuric acid.

3. The preparation method according to claim 1, characterized in that: The titanium source mentioned in step 2) includes one or more of titanium tetrachloride, titanium oxysulfate, titanium acetylacetonate, tetraethyl titanate, tetrabutyl titanate, isopropyl titanate, titanic acid, and metatitanic acid. The second solvothermal reaction requires rapid heating and holding at the desired reaction temperature, with a heating rate of 20-100℃ / min.

4. The preparation method according to claim 1, characterized in that: In step 2), while adding the titanium source, an appropriate amount of water is also added to the reaction solution. The molar ratio of the added water to the titanium source added in step 2) is 0.01-1.

5. The preparation method according to claim 1, characterized in that: The surface modifiers mentioned in step 3) include one or more of titanate esters, phosphate esters, organic acids, and silane coupling agents; The titanate comprises one or more of the following: isopropyl tris(dodecylbenzenesulfonyl) titanate, triisostearate titanate isopropyl, bis(acetylacetonyl) diisopropyl titanate, isopropyl tris(dioctylphosphoyloxy) titanate, isopropyl dioleoyloxy (dioctylphosphoyloxy) titanate, di(octylphenol polyoxyethylene ether) phosphate, and tetraisopropyl di(dioctylphosphite) titanate. The phosphate esters include one or more of 4-hydroxybutyl phosphate, 2-ethylhexyl phosphate, 9-octadecene-1-ol phosphate, isooctyl phosphate, dodecyl phosphate, tetradecyl phosphate, lauryl polyoxyethylene ether phosphate, and tridecyl polyoxyethylene ether phosphate. The organic acids include one or more of butyric acid, lactic acid, citric acid, tartaric acid, salicylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, oleic acid, linoleic acid, lauryl edodecanic acid, tetradecanoic acid, octadecanoic acid, and eicosanoic acid; The silane coupling agent includes one or more of the following: vinyltrimethoxysilane, vinyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltrimethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, phenyltrimethoxysilane, γ-aminopropyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropyltriethoxysilane, methoxytriethylene glycol etherylpropyltrimethoxysilane, 11-mercaptoundecyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and diethylphosphorylethyltriethoxysilane.

6. The preparation method according to claim 1, characterized in that: The centrifugation speed mentioned in step 3) is 3000-8000 r / min; The washing solvent is one or more of ethanol, acetone, tetrahydrofuran, propylene glycol methyl ether acetate, toluene, and heptane.

7. The preparation method according to claim 1, characterized in that: In step 3), the surface modification process is as follows: the washing product and the surface modifier are added to the reaction solvent to carry out the surface modification reaction. The reaction temperature is 25-150℃ and the reaction time is 0.5-24h. The mass ratio of the surface modifier to the washing product is 0.05-1; The reaction solvent includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, pentanol, hexanol, heptanol, octanol, dodecanol, ethylene glycol, propylene glycol, hexanediol, benzyl alcohol, acetone, butanone, propylene glycol methyl ether acetate, tetrahydrofuran, dimethyl sulfoxide, dichloromethane, chloroform, ethyl acetate, butyl acetate, benzene, toluene, xylene, heptane, n-hexane, cyclohexane, and petroleum ether.

8. A monodisperse doped titanium dioxide with in-situ lattice strain prepared by the method of any one of claims 1-7.

9. The application of monodisperse doped titanium dioxide with in-situ lattice strain as described in claim 8 in the preparation of transparent composite functional materials.

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