Highly dispersible doped tin dioxide nanocrystals in any water-to-alcohol ratio and their preparation method

Abstract

This invention discloses a method for preparing doped tin dioxide nanocrystals that can be highly dispersed in any water-to-alcohol ratio. The preparation method includes the following steps: (1) adding trimethylamine oxide to an aqueous solution containing tin halide to produce a white precipitate and stirring; (2) subjecting the mixture obtained in step (1) to a hydrothermal reaction at 120–200°C for 3–24 h, separating the solid and liquid phases after the reaction, and dispersing the solid phase in pure water, pure alcohol, or a water-to-alcohol mixture with any water-to-alcohol ratio to obtain a halogen-doped tin dioxide dispersion; (3) adding an organic base stabilizer to the halogen-doped tin dioxide dispersion and mixing to obtain halogen-doped tin dioxide nanocrystals that are highly dispersed in pure water, pure alcohol, or a water-to-alcohol mixture with any water-to-alcohol ratio. The preparation method of this invention is simple and inexpensive, broadens the application field of tin dioxide, and has important application value.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials technology, specifically to a doped tin dioxide nanocrystal that can be highly dispersed in any water-to-alcohol ratio and its preparation method. Background Technology

[0002] Tin dioxide (SnO2), as a stable wide-bandgap semiconductor with a bandgap of approximately 3.6 eV, exhibits excellent performance in optoelectronic fields. By doping tin dioxide with elements such as fluorine (F), aluminum (Al), antimony (Sb), indium (In), and titanium (Ti), its electrical, optical, and chemical properties can be significantly improved. Doping elements can modulate the band structure of tin dioxide, increase carrier concentration, and reduce crystal defect density, thereby effectively enhancing the material's conductivity, transparency, and stability. This broadens the application prospects of tin dioxide in electronic and optoelectronic devices, leading to its widespread use in gas sensors, photocatalysis, transparent conductive films (TCOs), perovskite solar cells (PSCs), and organic light-emitting diode (OLED) devices.

[0003] Compared to other doping elements, doping fluorine (F) into tin dioxide (SnO2) offers significant performance and economic advantages, leading to its widespread application in transparent conductive films, optoelectronic devices, and sensors. Currently, tin tetrachloride pentahydrate (SnCl4·5H2O) and stannous chloride (SnCl2) are commonly used as tin sources, with hydrogen fluoride (HF) and ammonium fluoride (NH4F) added as fluorine sources. However, these materials often contain impurities such as chloride ions, which can reduce the purity of the final product, affecting its performance and stability. In contrast, stannous fluoride serves as both a tin and fluorine source, avoiding the introduction of impurities like chloride and ensuring the high purity of SnO2, making it suitable for applications requiring high material purity. Existing literature (Yu C, Jimmy CY, Wang F, et al. Growth of single-crystalline SnO2 nanocubes via ahydrothermal route[J]. CrystEngComm, 2010, 12(2): 341-343.) reports a method for preparing SnO2 nanocubes via a hydrothermal method using (NH4)2S2O8 as an oxidant, NaOH as a pH adjuster, and stannous fluoride (SnF2) as a tin source. In this method, (NH4)2S2O8, as an acidic salt, readily releases protons, accelerating the hydrolysis of SnF2. Simultaneously, (NH4)2S2O8 acts as an oxidant, causing soluble Sn(II) to oxidize. By adding NaOH to adjust the pH of the solution and change the solubility of Sn(II), SnO2 nanocubes with a size of 100-200 nm are prepared. However, due to the strong corrosiveness and irritant properties of (NH4)2S2O8, as well as its combustion-supporting nature, there are safety hazards during the experiment. Furthermore, its strong oxidizing agent makes the reaction process difficult to control. In addition, the prepared SnO2 nanomaterials have a size of 100-200 nm, and the particle size cannot be precisely controlled.

[0004] Tin dioxide nanocrystals with a size less than 10 nm can be called quantum dots. Due to their size being close to or smaller than the Bohr radius of electrons or holes, the quantum confinement effect gives them unique physical and chemical properties. The movement of electrons and holes in quantum dots is confined to three-dimensional space, leading to energy level discretization and an increased band gap, allowing for precise tuning of light absorption and emission wavelengths by adjusting the size. Furthermore, the energy level structure of quantum dots resembles the discrete energy levels of atoms or molecules, significantly enhancing their optical properties. However, due to the extremely small size and high surface energy of tin dioxide nanocrystals, quantum dots tend to aggregate in solutions or solid matrices, leading to a decline in their optical and electronic properties. Therefore, ensuring a stable dispersion system for tin dioxide nanocrystals in applications is a prerequisite for achieving their superior performance.

[0005] Currently, the dispersion systems for tin dioxide (SnO2) nanocrystals mainly include pure aqueous phases and pure alcohol solvents. In practical applications, the use of pure aqueous phases and pure alcohol solvents is limited by the solvent volume. Pure aqueous phases face the problem of low catalytic reaction rates, and fluctuations in pH and ionic strength can lead to decreased stability of the nanocrystals, resulting in precipitation or phase separation. Pure alcohol solvents, in some applications, present challenges such as insufficient solubility, reduced catalytic selectivity, and a mismatch between their physicochemical properties (e.g., polarity) and the requirements of optoelectronic applications. In contrast, water-alcohol mixed solvents can effectively adjust the polarity of the reaction medium, improve the rate and selectivity of the catalytic reaction, promote the exposure of active sites on the catalyst, and enhance catalytic efficiency. Furthermore, by optimizing the ratio of water to alcohol, the physicochemical properties of the mixed solvent (e.g., boiling point, viscosity, and solvent strength) can be flexibly adjusted to meet the specific needs of different experiments and applications. Therefore, water-alcohol mixed solvents provide a more flexible and efficient environment for the application of tin dioxide nanocrystals, significantly improving their performance in optoelectronics, catalysis, and sensors. Summary of the Invention

[0006] This invention provides a method for preparing doped tin dioxide nanocrystals that can be highly dispersed in any water-to-alcohol ratio. The method is an in-situ halogen-doped tin dioxide nanocrystal preparation method, where the size of the halogen-doped tin dioxide nanocrystals can be controlled by adjusting the hydrothermal reaction temperature and reaction time. This invention uses tin halides such as SnF2 as both a tin source and a halogen source (e.g., fluorine source), resulting in high purity in-situ doped SnO2 (e.g., element F). The use of trimethylamine oxide as an oxidant provides mild oxidizing properties, effectively controlling the oxidation rate of the reaction. The addition of an organic base stabilizer ensures that the halogen-doped tin dioxide nanocrystals form a stable dispersion in any water-to-alcohol ratio.

[0007] [1] A method for preparing doped tin dioxide nanocrystals that can be highly dispersed in any water-to-alcohol ratio, comprising the following steps:

[0008] (1) Trimethylamine oxide was added to an aqueous solution containing stannous halides, resulting in a white precipitate, and the mixture was stirred.

[0009] (2) The mixture obtained in step (1) is subjected to hydrothermal reaction at 120-200℃ (e.g., 120℃, 150℃, 180℃, 200℃, etc.) for 3-24h (e.g., 6h, 12h, 24h, etc.). After the reaction is completed, the solid and liquid phases are separated, and the solid phase is dispersed in pure water, pure alcohol or a water-alcohol mixture with any water-alcohol ratio to obtain a halogen in-situ doped tin dioxide dispersion.

[0010] (3) Add an organic base stabilizer to the halogen in-situ doped tin dioxide dispersion and mix well to obtain halogen in-situ doped tin dioxide nanocrystals that are highly dispersed in pure water, pure alcohol or a water-alcohol mixed solvent with any water-alcohol ratio.

[0011] In step (1), the stannous halide may include at least one of stannous fluoride, stannous chloride, stannous bromide, and stannous iodide.

[0012] In step (1), the concentration of the stannous halide in the aqueous solution containing the stannous halide can be 7 to 50 g / L.

[0013] In step (1), the molar ratio of the stannous halide and the trimethylamine oxide can be 1:1 to 3.5, and more preferably 1:2.5 to 3.5.

[0014] In step (2), the alcohol may include at least one of methanol, ethanol, ethylene glycol, propanol (including any type and quantity of isomers such as n-propanol and isopropanol), and butanol (including any type and quantity of isomers).

[0015] In some embodiments, the water-alcohol mixed solvent with any water-to-alcohol ratio described in this invention can refer to a solvent obtained by mixing water and alcohol in any conceivable proportion. Of course, the solvent obtained by mixing water and alcohol in any proportion may also contain any amount and type of other components that do not affect the high dispersibility of halogen-doped tin dioxide nanocrystals.

[0016] In step (2), the concentration of halogen-doped tin dioxide in the halogen-doped tin dioxide dispersion can be 1 to 75 mg / mL, for example, 3 mg / mL, 4 mg / mL, 5 mg / mL, 10 mg / mL, etc.

[0017] In step (3), the organic base stabilizer can be added in liquid form (including solution). Further, the volume ratio of the added organic base stabilizer liquid (including organic base stabilizer solution) to the halogen in-situ doped tin dioxide dispersion can be 1:5 to 500. The organic base stabilizer liquid (including organic base stabilizer solution) can be a commercially available product.

[0018] In step (3), the organic base stabilizer may include at least one of tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, ethylenediamine, triethylamine, ethanolamine, and propylamine.

[0019] [2] A halogen-doped tin dioxide nanocrystal that can be highly dispersed in any water-to-alcohol ratio, wherein the halogen-doped tin dioxide nanocrystal that can be highly dispersed in any water-to-alcohol ratio can be prepared by the preparation method described in [1].

[0020] In some embodiments, the halogen-doped tin dioxide nanocrystals, which can be highly dispersed in any water-to-alcohol ratio, are spherical with an average size of 5–14 nm.

[0021] In some embodiments, the arbitrary water-to-alcohol ratio mentioned in this invention can refer to any situation where there is no water (i.e., pure alcohol), no alcohol (i.e., pure water), or water and alcohol in any ratio (e.g., water-to-alcohol volume ratio (1:0.2) to (0.2:1), etc., specifically, water-to-alcohol volume ratios of 1:0.25, 1:0.5, 1:0.6, 1:1, 0.5:1, 0.25:1, 0.2:1, etc.).

[0022] Compared with the prior art, the beneficial effects of this invention are as follows:

[0023] This invention utilizes tin halides such as SnF2 as both a tin source and a halogen source (e.g., fluorine source), and trimethylamine oxide as an oxidant, to successfully synthesize high-purity, in-situ doped halogen (e.g., fluorine) tin dioxide (SnO2) nanocrystals with controllable size via a one-step hydrothermal method. By adding a small amount of organic base stabilizer, halogen-doped tin dioxide nanocrystals of different concentrations that can be dispersed in any water-to-alcohol ratio were obtained. The steric hindrance effect of the organic base stabilizer and the adsorption of hydroxyl groups on the halogen-doped tin dioxide nanocrystals effectively solved the dispersion problem in solvents with various water-to-alcohol ratios. The halogen-doped tin dioxide nanocrystals prepared by this invention exhibit transparency, clarity, and good stability in pure water, pure alcohol, and water-to-alcohol mixtures with any water-to-alcohol ratio.

[0024] The in-situ doped halogenated tin dioxide nanocrystals prepared by this invention have adjustable size and obvious quantum confinement effect. Moreover, the preparation method is simple and low-cost, which broadens the application field of tin dioxide and has important application value. Attached Figure Description

[0025] Figure 1 The X-ray diffraction patterns are those of the in-situ doped tin dioxide nanocrystals prepared in Examples 1-3 of this invention.

[0026] Figure 2 The Fourier transform infrared spectrum is shown for the F-doped tin dioxide nanocrystals prepared in Example 1 of this invention.

[0027] Figure 3 The images show digital photographs of the following: F in-situ doped tin dioxide nanocrystal dispersions prepared using the F in-situ doped tin dioxide nanocrystals obtained in step (1) of Example 1 of the present invention, without the addition of an organic base stabilizer (top image), and F in-situ doped tin dioxide nanocrystal dispersions with adjustable monodisperse size after the addition of an organic base stabilizer (addition concentration of 5 μL / mL dispersion) (bottom image).

[0028] Figure 4These are transmission electron microscope images of in-situ doped tin dioxide nanocrystals with adjustable monodisperse size in a water-alcohol mixed solvent, obtained in Examples 1-4 of this invention.

[0029] Figure 5 The particle size distribution diagrams are shown for the in-situ doped tin dioxide nanocrystals with adjustable monodisperse size obtained in a water-alcohol mixed solvent as described in Examples 1-4 of this invention.

[0030] Figure 6 The transmission electron microscopy (TEM) energy spectrum of the in-situ doped tin dioxide nanocrystals with tunable monodisperse size prepared in a water-alcohol mixed solvent as described in Example 1 of this invention.

[0031] Figure 7 The ultraviolet-visible-near-infrared absorption spectra and optical band gap diagrams of monodisperse in-situ doped tin dioxide nanocrystals in aqueous and alcoholic solutions prepared using the in-situ doped tin dioxide nanocrystals obtained in step (1) of Example 1 of the present invention are obtained. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0033] Example 1

[0034] Step (1): Weigh 0.235g of stannous fluoride and add it to 30mL of deionized water. Stir for 5min to prepare a uniform stannous fluoride solution. While stirring, slowly add 0.39g of trimethylamine oxide to the uniform stannous fluoride solution to produce a white precipitate. After stirring for 15min, add the mixture to a 50mL high-pressure reactor lined with polytetrafluoroethylene to carry out a hydrothermal reaction. The hydrothermal reaction conditions are: 180℃, 6h. After centrifugation, washing and drying of the reaction product with deionized water, agglomerated F in-situ doped tin dioxide nanocrystals are obtained.

[0035] Step (2): Dissolve the F-doped tin dioxide nanocrystals prepared in step (1) in a mixture of water and ethanol at a volume ratio of 1:0.25 to obtain a tin dioxide-water-alcohol mixture dispersion with a F-doped tin dioxide concentration of 4 mg / mL. Add tetrabutylammonium hydroxide solution to the dispersion at a concentration of 3 μL / mL and shake until homogeneous to obtain the F-doped tin dioxide nanocrystal-water-alcohol mixture dispersion.

[0036] Example 2

[0037] Step (1): The only difference from Step (1) of Example 1 is that the hydrothermal reaction conditions are changed to 200℃, 6h, and the rest are the same.

[0038] Step (2): Dissolve the F-doped tin dioxide nanocrystals prepared in step (1) in a mixture of water and ethanol with a volume ratio of 1:0.5 to obtain a tin dioxide-water-alcohol mixture dispersion with a F-doped tin dioxide concentration of 3 mg / mL. Add tetraethylammonium hydroxide solution to the dispersion at a concentration of 2 μL / mL and shake until homogeneous to obtain the F-doped tin dioxide nanocrystal-water-alcohol mixture dispersion.

[0039] Example 3

[0040] Step (1): The only difference from Step (1) of Example 1 is that the hydrothermal reaction conditions are changed to 200°C and 12h, and the rest are the same.

[0041] Step (2): Dissolve the F-doped tin dioxide nanocrystals prepared in step (1) in a mixture of water and methanol in a volume ratio of 1:0.6 to obtain a tin dioxide-water-alcohol mixture dispersion with a F-doped tin dioxide concentration of 10 mg / mL. Add tetrapropylammonium hydroxide solution to the dispersion at a concentration of 4 μL / mL and shake until homogeneous to obtain the F-doped tin dioxide nanocrystal-water-alcohol mixture dispersion.

[0042] Example 4

[0043] Step (1): The only difference from Step (1) of Example 1 is that the hydrothermal reaction conditions are changed to 200°C and 24h, and the rest are the same.

[0044] Step (2): Dissolve the F-doped tin dioxide nanocrystals prepared in step (1) in a mixture of water and ethanol in a volume ratio of 1:1 to obtain a tin dioxide-water-alcohol mixture dispersion with a F-doped tin dioxide concentration of 5 mg / mL. Add tetrapropylammonium hydroxide solution to the dispersion at a concentration of 2 μL / mL and shake until homogeneous to obtain the F-doped tin dioxide nanocrystal-water-alcohol mixture dispersion.

[0045] Example 5

[0046] Step (1): The only difference from Step (1) of Example 1 is that the amount of trimethylamine added is changed to 0.35g, and the hydrothermal reaction conditions are changed to 150℃, 12h, and the rest are the same.

[0047] Step (2): Dissolve the F-doped tin dioxide nanocrystals prepared in step (1) in a mixture of water and methanol with a volume ratio of 0.5:1 to obtain a tin dioxide-water-alcohol mixture dispersion with a F-doped tin dioxide concentration of 4 mg / mL. Add ethanolamine to the dispersion at a concentration of 3 μL / mL and shake until homogeneous to obtain the F-doped tin dioxide nanocrystal-water-alcohol mixture dispersion.

[0048] Example 6

[0049] Step (1): The only difference from Step (1) of Example 1 is that the hydrothermal reaction conditions are changed to 120°C and 6h, and the rest are the same.

[0050] Step (2): Dissolve the F-doped tin dioxide nanocrystals prepared in step (1) in a mixture of water and isopropanol with a volume ratio of 0.2:1 to obtain a tin dioxide-water-alcohol mixture dispersion with a F-doped tin dioxide concentration of 5 mg / mL. Add tetrabutylammonium hydroxide solution to the dispersion at a volume of 7 μL / mL and shake until homogeneous to obtain the F-doped tin dioxide nanocrystal-water-alcohol mixture dispersion.

[0051] Sample analysis:

[0052] Figure 1 The X-ray diffraction (XRD) patterns of the in-situ fluorine-doped tin dioxide nanocrystals prepared in Examples 1-3 of this invention are shown. As can be seen from the figures, the high intensity of the diffraction peaks indicates good crystallinity of the samples. Simultaneously, the large width of the diffraction peaks indicates extremely small crystal size. The half-width at half-maximum (FWHM) of the diffraction peaks was measured and calculated using the Scherrer formula (D = Kλ / βcosθ), where K is 0.89, λ is 0.15406, and β is the FWHM of the (110), (101), and (211) crystal planes. The average grain size of the sample in Example 1 was found to be 6.33 nm, and the average grain size of the sample in Example 3 was 6.62 nm. Further analysis revealed that the three main diffraction peaks in the three embodiments shown in the figure were all shifted to the right by 0.1° to 0.2° relative to the pure tetragonal tin dioxide crystal structure (PDF#71-0652), and the lattice constant was smaller. This indicates that heteroatoms (F) with smaller radii than the host atom (O) were in situ incorporated into the tin dioxide nanocrystals prepared with SnF2 as the tin source.

[0053] Figure 2 This is the Fourier transform infrared spectrum of the in-situ fluorine-doped tin dioxide nanocrystals prepared in Example 1 of this invention. Example 1 was obtained at 545 cm⁻¹. -1 The nearby absorption peak is due to the O-Sn-O angle vibration, 1640 cm⁻¹. -1The absorption peak is due to the deformation vibration of adsorbed water molecules, at 3400 cm⁻¹. -1 The absorption peak is due to the stretching vibration of the OH group.

[0054] Figure 3 To prepare dispersions of tin dioxide nanocrystals without organic base stabilizers in different water-to-alcohol volume ratios using the in-situ doped tin dioxide nanocrystals obtained in step (1) of Example 1 of this invention (… Figure 3 The image above shows a doped tin dioxide nanocrystal dispersion with adjustable monodisperse size after the addition of an organic base stabilizer. Figure 3 The image below shows a digital photograph taken under natural light. It can be seen that when the F-doped tin dioxide nanocrystals obtained in step (1) of Example 1 are dispersed at a concentration of 5 mg / mL in different water-to-alcohol volume ratios, the F-doped tin dioxide nanocrystal dispersion without the addition of an organic base stabilizer appears turbid and milky white under natural light, indicating that SnO2 exhibits agglomeration in different water-to-alcohol ratios. When the F-doped tin dioxide nanocrystals obtained in step (1) of Example 1 are dispersed at a concentration of 5 mg / mL in a water-to-alcohol mixed solvent, and the volume ratio of water to alcohol in the mixed solvent changes from 1:0 to 0:1, and tetrabutylammonium hydroxide is added at an addition concentration of 5 μL / mL of the dispersion, the resulting dispersion exhibits a transparent and stable appearance under natural light. This indicates that the SnO2 nanocrystals of the present invention can achieve sufficient and uniform dispersion in different water-to-alcohol ratios, forming a stable transparent colloidal solution.

[0055] Figure 4 These are transmission electron microscope (TEM) images of fluorine-doped tin dioxide nanocrystals with adjustable monodisperse size in a water-alcohol mixed solvent, prepared in Examples 1-4 of this invention. It can be seen that the fluorine-doped tin dioxide nanocrystals are regularly spherical. The addition of the organic base stabilizer ensures that the fluorine-doped tin dioxide nanocrystals are in a monodisperse state, thus achieving good dispersibility. Meanwhile, the clearly visible lattice fringes in the samples further demonstrate their high crystallinity. Measurement results show that the interplanar spacings of the tin dioxide nanocrystals on the (110) crystal plane are 0.341 nm, 0.338 nm, 0.334 nm, and 0.340 nm, respectively, indicating that the in-situ fluorine-doped tin dioxide nanocrystals have a highly ordered structure and good crystal quality.

[0056] Figure 5The figures show the particle size distribution of the Fiber-doped tin dioxide nanocrystals with adjustable monodisperse size in a water-alcohol mixed solvent obtained in Examples 1-4 of this invention. It can be seen that the particle size distribution of the Fiber-doped tin dioxide nanocrystals prepared in Examples 1-4 is a single-peak distribution with a narrow distribution width, indicating relatively uniform grain size. The average particle sizes of the Fiber-doped tin dioxide nanocrystals prepared in Examples 1-4 are 5.76 nm, 6.62 nm, 8.60 nm, and 13.23 nm, respectively. It can be seen that by using trimethylamine oxide as the oxidant and adjusting the temperature and reaction time of the hydrothermal reaction, the particle size of the nanocrystals can be effectively controlled within a relatively fine range.

[0057] Figure 6 This is a transmission electron microscopy (TEM) energy dispersive spectrum (EDS) image of tin dioxide nanocrystals in situ doped with fluorine (F) and dispersed in a water-alcohol mixed solvent, prepared in Example 1 of this invention. The TEM image shows tin (Sn), oxygen (O), and fluorine (F), indicating that fluorine was in situ doped into the tin dioxide nanocrystals prepared using tin fluoride as the tin source.

[0058] Figure 7 This study examines the UV-Vis-NIR absorption spectra and optical band gaps of monodisperse nano-tin dioxide quantum dots prepared from aqueous and ethanol solutions using the F-doped tin dioxide nanocrystals obtained in step (1) of Example 1 of this invention. The absorbance exhibits a significant absorption peak in the 300–400 nm wavelength range, gradually decreasing in the 400–800 nm range, while maintaining a certain level of absorption across the entire wavelength range. The optical band gap value is calculated using the formula αhv. 2 =A(hv-E) g The calculation is performed, where α is the absorption coefficient, hv is the photon energy, and E... g The intrinsic semiconductor band gap of SnO2 is 0 to 3.6 eV. Due to the doping of fluorine, the quantum confinement effect and the increase in carrier concentration, the optical band gap of SnO2 obtained in step (1) of Example 1 increases to 4.05 eV in aqueous solution and to 4.02 eV in ethanol solution.

[0059] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing doped tin dioxide nanocrystals that can be highly dispersed in any water-to-alcohol ratio, characterized in that, Including the following steps: (1) Trimethylamine oxide is added to an aqueous solution containing stannous halides, a white precipitate is produced, and the mixture is stirred; the stannous halides include at least one of stannous fluoride, stannous chloride, stannous bromide, and stannous iodide; (2) The mixture obtained in step (1) is subjected to hydrothermal reaction at 120~200℃ for 3~24 h. After the reaction is completed, the solid and liquid phases are separated, and the solid phase is dispersed in pure water, pure alcohol or water-alcohol mixed solvent with any water-alcohol ratio to obtain halogen in-situ doped tin dioxide dispersion. (3) Add an organic base stabilizer to the halogen in-situ doped tin dioxide dispersion and mix well to obtain halogen in-situ doped tin dioxide nanocrystals that are highly dispersed in pure water, pure alcohol, or a water-alcohol mixed solvent with any water-to-alcohol ratio; the organic base stabilizer is added in liquid form, and the volume ratio of the added organic base stabilizer liquid to the halogen in-situ doped tin dioxide dispersion is 1:5~500; the organic base stabilizer includes at least one of tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, ethylenediamine, triethylamine, ethanolamine, and propylamine.

2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of the stannous halide in the aqueous solution containing the stannous halide is 7~50 g / L.

3. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of the stannous halide and the trimethylamine oxide is 1:1 to 3.

5.

4. The preparation method according to claim 3, characterized in that, In step (1), the molar ratio of the stannous halide to the trimethylamine oxide is 1:2.5~3.

5.

5. The preparation method according to claim 1, characterized in that, In step (2), the alcohol includes at least one of methanol, ethanol, ethylene glycol, propanol, and butanol.

6. The preparation method according to claim 1, characterized in that, In step (2), the concentration of halogen-doped tin dioxide in the halogen-doped tin dioxide dispersion is 1~75 mg / mL.

7. A halogen-doped tin dioxide nanocrystal that can be highly dispersed in any water-to-alcohol ratio, characterized in that, The halogen-doped tin dioxide nanocrystals that can be highly dispersed in any water-to-alcohol ratio are prepared by the preparation method described in any one of claims 1 to 6.

8. The halogen-doped tin dioxide nanocrystals that can be highly dispersed in any water-to-alcohol ratio according to claim 7, characterized in that, The halogen-doped tin dioxide nanocrystals, which can be highly dispersed in any water-to-alcohol ratio, are spherical with an average size of 5-14 nm.

Images