A method for preparing tin dioxide nanofilms

Abstract

This invention discloses a method for preparing tin dioxide nanofilms. The method uses micron-sized tin dioxide powder and potassium hydrofluoric acid as raw materials, and synthesizes tin dioxide nanofilms through a two-step process of high-temperature calcination and hydrolysis precipitation. The entire process utilizes simple and readily available raw materials, reducing raw material costs. The synthesized tin dioxide nanofilms exhibit varying densities, with small and uniformly distributed nanoparticles and minimal particle aggregation. The synthesis process is relatively simple, with extremely short reaction times and low reaction temperatures, avoiding complex chemical processes and simplifying the overall process.

Description

Technical Field

[0001] This invention belongs to the field of nano-multifunctional materials technology, specifically relating to a method for preparing tin dioxide (SnO2) nanofilms. Background Technology

[0002] Tin dioxide (SnO2) is a wide-bandgap semiconductor oxide. Due to its superior optical, electrical, and catalytic properties, it is widely used in luminescent materials, light-absorbing materials, catalysts, gas-sensitive materials, dilute magnetic semiconductor materials, and lithium-ion battery anodes. Tin dioxide dopants can be used in conductive materials, thin-film resistors, solar cells, optoelectronic devices, mirrors, sensitive materials, fluorescent materials, fluorescent lamps, and electrode materials. Nanoscale tin dioxide possesses unique small-size, quantum-size, and surface effects, exhibiting extremely high specific surface area and numerous oxygen defects and low oxygen coordination numbers, which are conducive to the generation of electron carriers, resulting in a relatively high carrier concentration. Therefore, tin dioxide shows broad application prospects in lithium-ion batteries, gas sensors, sensitized solar cells, catalysts, and ultraviolet detection.

[0003] In recent years, numerous scholars have focused on researching novel preparation methods for nano-tin dioxide, including hydrothermal methods, chemical vapor deposition, physical vapor deposition, sol-gel methods, electrospinning, carbothermal reduction, high-temperature self-propagating synthesis, pulsed laser deposition, and spray thermal bonding. Various methods have successfully prepared tin dioxide nanomaterials with different morphologies, such as nanospheres, nanorods, nanoribbons, nanosheets, nanoflora, hollow microspheres, nanofibers, nanotube arrays, and nanoporous structures.

[0004] The synthesis methods described above generally employ a variety of raw materials and reagents, including tin raw materials, precipitants, stabilizers, and solvents. Currently, the most widely used tin raw material is stannous chloride pentahydrate (SnCl4·5H2O), followed by stannous chloride dihydrate (SnCl2·2H2O), stannous chloride (SnCl4), stannous nitrate pentahydrate (Sn(NO3)4·5H2O), sodium stannate (Na2SnO3), potassium stannate (K2SnO3), tin oxide (SnO2), tetraethyltin (Sn(C2H5)), and monobutyltin trichloride, etc. Some inorganic or organic reagents are used as precipitants (such as urea, ammonia, potassium hydroxide, sodium hydroxide, etc.), while some organic reagents are used as solvents or co-surfactants (such as ethanol, hydrogen peroxide, cyclohexane, ethylene glycol, etc.). Therefore, the traditional process for synthesizing tin dioxide nanopowder uses a relatively limited variety of tin source materials, and there is a need to further develop new high-quality and inexpensive tin source materials. At the same time, the traditional process uses a variety of inorganic and organic reagents, some of which are rare and expensive, increasing the synthesis cost and making the synthesis process too complex. There is also an urgent need to simplify the synthesis process in order to reduce the synthesis cost. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing tin dioxide nanofilms. This method uses micron-sized tin dioxide powder and potassium fluoride as raw materials, and synthesizes tin dioxide nanofilms through a two-step process of high-temperature calcination and subsequent hydrolysis. The synthesized tin dioxide nanofilms have different densities, and the nanoparticles are small in size, uniformly distributed, and have less particle aggregation.

[0006] The above-mentioned objective of this invention can be achieved by the following technical solution: a method for preparing tin dioxide nanofilms, comprising the following steps:

[0007] (1) Using tin dioxide and potassium hydrofluoric acid powder as initial raw materials, place the two raw materials in a container and cover it. Heat the container and adjust the heating temperature to 300-400℃ for 0.3-1.0 hours to allow the solid powder to fully melt and react. After the reaction, cool the container and add dilute hydrofluoric acid solution. Heat the container again to boiling and stir continuously until the solid in the container is completely dissolved. Stop heating.

[0008] (2) Filter the solution in the container while it is still hot and collect the filtrate;

[0009] (3) Add deionized water to the filtrate from step (2) to obtain a dilute solution. Place the dilute solution in a hydrothermal reaction vessel, seal it, and heat the hydrothermal reaction vessel. Adjust the temperature inside the hydrothermal reaction vessel to 150-500℃. Adjust the pressure inside the hydrothermal reaction vessel to 10-100MPa by injecting inert gas into the hydrothermal reaction vessel. The reaction time is 8-48 hours. After the reaction, cool it rapidly to room temperature.

[0010] (4) Open the hydrothermal reaction vessel and obtain tin dioxide nanofilms through subsequent processing.

[0011] This invention uses micron-sized tin dioxide powder and potassium hydrofluoric acid as raw materials to synthesize tin dioxide nanofilms through a two-step method of high-temperature calcination and hydrolysis precipitation. The entire process uses only four inorganic reagents: tin dioxide, potassium hydrofluoric acid, hydrofluoric acid, and ethanol. The raw materials are simple and readily available, reducing raw material costs. The synthesized tin dioxide nanofilms have varying densities, and the nanoparticles are small in size, uniformly distributed, and have minimal particle aggregation. The synthesis process is relatively simple, with extremely short reaction times and low reaction temperatures, avoiding complex chemical processes and simplifying the overall process.

[0012] In the above method for preparing tin dioxide nanofilms:

[0013] More preferably, in step (1), tin dioxide and potassium fluoride powder are used as initial raw materials. The two raw materials are placed in a container and covered. The container is heated and the heating temperature is adjusted to 350°C. The heating time is 0.5 hours, so that the solid powder can fully melt and react.

[0014] Optionally, the mass ratio of tin dioxide and potassium hydrofluoric acid in step (1) is 1:2 to 3.

[0015] Optionally, the volume percentage of the dilute hydrofluoric acid solution in step (1) is 3-8%, more preferably 5%, and the amount added is 40-60%, more preferably 50%, of the total volume of the container.

[0016] Optionally, the container in step (1) is a crucible, the crucible is a hafnium alloy, or the crucible is a crucible lined with silver, gold or platinum.

[0017] Optionally, a Teflon stirring rod may be used for stirring in step (1).

[0018] Optionally, in step (2), an evaporating dish with a Teflon, silver, gold, or platinum liner is used to collect the filtrate.

[0019] Optionally, the filtering process can be repeated 3 to 5 times in step (2).

[0020] Optionally, the molar concentration of the dilute solution in step (3) is 0.01 to 0.05 mol / L.

[0021] Optionally, the inert gas in step (3) is argon or helium.

[0022] More preferably, the reaction temperature described in step (3) is 200–450 °C.

[0023] Optionally, the reaction time mentioned in step (3) includes the time required for heating.

[0024] Optionally, the rapid cooling described in step (3) is to rapidly cool the reactor using ice water or compressed air.

[0025] In one preferred embodiment of the present invention, in step (3), the dilute solution is directly added to the hydrothermal reaction vessel, and the volume of the dilute solution accounts for 30-70% of the total volume of the hydrothermal reaction vessel; the hydrothermal reaction vessel is a hydrothermal reactor, which is a sealed high-temperature and high-pressure reactor. The high-temperature and high-pressure reactor is connected to a high-precision ultra-high-pressure pressure gauge, a vent pipe and a shut-off valve. The high-temperature and high-pressure reactor has a metal shell, and the metal shell is provided with a strong acid and strong alkali resistant liner. The strong acid and strong alkali resistant liner is made of polytetrafluoroethylene, polyphenylene ester, or polyimide plastic, or the strong acid and strong alkali resistant liner is made of silver, gold or platinum inert metal, or the strong acid and strong alkali resistant liner is made of gold-palladium or silver-palladium alloy.

[0026] Optionally, the hydrothermal reaction vessel is a conventional commercially available hydrothermal reaction vessel, the sealed high-temperature and high-pressure reactor is a conventional commercially available sealed high-temperature and high-pressure reactor, and the metal in the metal shell is conventional stainless steel or Hastelloy.

[0027] When using this technical solution, optionally, in step (4), opening the hydrothermal reaction vessel and obtaining the tin dioxide nanofilm through subsequent processing includes: opening the hydrothermal reaction vessel, recovering the residual solution in the hydrothermal reaction vessel, washing the inner wall of the hydrothermal reaction vessel with deionized water, collecting the washing fluid to obtain the nanotin dioxide turbid liquid, centrifuging the obtained turbid liquid, taking the lower precipitate, washing and drying the lower precipitate to obtain the tin dioxide nanofilm.

[0028] When using this technical solution, optionally, the bottom of the hydrothermal reaction vessel in step (3) is provided with a sample collection sheet, which is a sample collection sheet made of plastic or inert metal; the step (4) of opening the hydrothermal reaction vessel and obtaining tin dioxide nanofilm through subsequent processing includes: opening the hydrothermal reaction vessel, recovering the residual solution in the hydrothermal reaction vessel, taking out the sample collection sheet, washing and drying it, and then obtaining tin dioxide nanofilm on the surface of the sample collection sheet.

[0029] Optionally, the plastic is polytetrafluoroethylene, polyphenylene oxide, or polyimide, etc.; the inert metal is silver, gold, or platinum, etc.

[0030] Optionally, the cleaning or washing process involves washing with deionized water and anhydrous ethanol 2 to 3 times in succession.

[0031] Alternatively, drying can be achieved by air drying or storage in a desiccator.

[0032] As another preferred technical solution of the present invention, in step (3), the dilute solution is first added to the precious metal vessel, and then the precious metal vessel is placed in the hydrothermal reaction vessel. The precious metal is silver, gold or platinum; or the precious metal is gold-palladium or silver-palladium alloy. The high-temperature and high-pressure reactor is connected to a high-precision ultra-high pressure gauge, a gas pipeline and a shut-off valve. The high-temperature and high-pressure reactor has a stainless steel or Hastelloy metal shell.

[0033] When using this technical solution, optionally, in step (4), opening the hydrothermal reaction vessel and obtaining tin dioxide nanofilms through subsequent processing includes: opening the hydrothermal reactor, taking out the precious metal vessel, recovering the residual solution in the precious metal vessel, washing the inner wall of the precious metal vessel with deionized water, collecting the washing fluid to obtain nanotin dioxide turbid liquid, centrifuging the obtained turbid liquid, taking the lower precipitate, washing and drying the lower precipitate to obtain tin dioxide nanofilms.

[0034] Optionally, the cleaning process involves washing with deionized water and anhydrous ethanol 2 to 3 times.

[0035] Alternatively, drying can be achieved by air drying or storage in a desiccator.

[0036] The core of the tin dioxide nanofilm preparation method of the present invention lies in the two-step method of high-temperature calcination and hydrolysis of tin dioxide and potassium fluoride to introduce fluorine and promote the formation of tetragonal tin dioxide. The presence of fluorine can promote the development of multiple crystal planes such as (101) and (211) of tin dioxide nanocrystals, and help the connection and growth of tin dioxide nanocrystals during hydrolysis, thereby improving the density of the tin dioxide film.

[0037] In the method for preparing tin dioxide nanofilms of the present invention, the core reagents used are common and inexpensive tin dioxide and potassium hydrofluoric acid, avoiding the complex process of using multiple raw materials such as tin source + precipitant ± surface agent ± solvent in traditional processes. Because in step (3) of the present invention, the type and crystal form of nanocrystals are controlled by temperature and pressure, and the degree of hydrolysis and the size of tin dioxide nanocrystals are controlled by reaction time.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The preparation method of the present invention uses common and inexpensive micron-sized tin dioxide powder and potassium fluoride as raw materials for the first time. Tetragonal tin dioxide nanocrystals are generated by a two-step method of high-temperature calcination and subsequent hydrolysis, and then grown into nanofilms. This realizes the preparation of tin dioxide nanofilms with simple common reagents and expands the synthesis process of tin dioxide nanocrystals.

[0040] (2) The preparation method of the present invention inherits the advantages of the traditional hydrothermal liquid phase synthesis process. The entire synthesis process only requires the use of four common and inexpensive reagent raw materials: tin dioxide, potassium hydrofluoric acid, hydrofluoric acid and ethanol. This avoids the need for the proportioning and weighing of various expensive precursors, precipitants, surface area enhancers and solvents, as well as the sequential process steps in the traditional process. Therefore, this method is simple, easy to operate and control, and has a low cost.

[0041] (3) The preparation method of the present invention uses common and inexpensive tin dioxide and potassium fluoride reagents to synthesize tin dioxide nanofilms of different densities in a two-step process. The nanofilms of different densities can be used for different purposes according to the gap size, such as molecular filter membranes, porous catalytic materials, battery materials and material protective layers, etc. Attached Figure Description

[0042] Figure 1 These are scanning electron microscope images (a, b) of the tin dioxide nanofilm prepared in Example 1 of the present invention at different magnifications, where (a) is magnified 80,000 times and (b) is magnified 50,000 times.

[0043] Figure 2 The images shown are scanning electron microscope (SEM) images of the tin dioxide nanofilm prepared in Example 2 of this invention at different magnifications (ad), where (a) is magnified 50,000 times, (b) is magnified 35,000 times, (c) is magnified 20,000 times, and (d) is magnified 20,000 times.

[0044] Figure 3 The images (a, b) are scanning electron microscope images (SEM) of the tin dioxide nanofilm prepared in Example 3 of the present invention at different magnifications, where (a) is magnified 20,000 times and (b) is magnified 35,000 times.

[0045] Figure 4 The images shown are scanning electron microscope (SEM) images of the tin dioxide nanofilm prepared in Example 4 of this invention at different magnifications (ad), where (a) is magnified 20,000 times, (b) is magnified 30,000 times, (c) is magnified 50,000 times, and (d) is magnified 50,000 times.

[0046] Figure 5 The images (a, b) are scanning electron microscope images (SEM) of the tin dioxide nanofilm prepared in Example 5 of the present invention at different magnifications, where (a) is magnified by 10,000 times and (b) is magnified by 40,000 times.

[0047] Figure 6 The images (a, b) are scanning electron microscope images (SEM) of the tin dioxide nanofilm prepared in Example 6 of this invention at different magnifications, where (a) is magnified 35,000 times and (b) is magnified 40,000 times.

[0048] Figure 7The images (a, b) are scanning electron microscope images (SEM) of the tin dioxide nanofilm prepared in Example 7 of the present invention at different magnifications, where (a) is magnified 35,000 times and (b) is magnified 20,000 times.

[0049] Figure 8 The images shown are scanning electron microscope (SEM) images of the tin dioxide nanofilm prepared in Example 8 of this invention at different magnifications (ad), where (a) is magnified 20,000 times, (b) is magnified 30,000 times, (c) is magnified 50,000 times, and (d) is magnified 60,000 times.

[0050] Figure 9 The images shown are scanning electron microscope (SEM) images of the tin dioxide nanofilm prepared in Example 9 of this invention at different magnifications (ad), where (a) is magnified 15,000 times, (b) is magnified 12,000 times, (c) is magnified 50,000 times, and (d) is magnified 22,000 times.

[0051] Figure 10 The images show a comparison of the laser Raman spectra of the tin dioxide nanofilms and standard tin dioxide crystals prepared in Examples 1-9 of this invention.

[0052] Figure 11 The figures shown are μ-XRD spectra of tin dioxide nanofilms prepared in the embodiments of the present invention. Since the tin dioxide nanofilms are deposited on gold sheets, gold spectral lines appear in the XRD background. The upper figure is the μ-XRD spectrum obtained under low temperature conditions in Example 1; the middle figure is the μ-XRD spectrum obtained under high temperature conditions in Example 3; and the lower figure is the μ-XRD spectrum obtained under high temperature conditions in Example 9. The vertical axis Intensity (Counts) is the count, and the horizontal axis Two-Theta (deg) is the diffraction angle. Detailed Implementation

[0053] The present invention will be further described below with reference to specific embodiments. The following embodiments are for illustrative purposes only and should not be construed as limiting the present invention. Unless otherwise specified, the raw materials used in the following embodiments are commercially available or conventionally obtained raw materials. Unless otherwise specified, the methods and equipment used in the following embodiments are methods and equipment conventionally used in the art. The hydrothermal reactor is a conventional hydrothermal reactor, mostly made of stainless steel or Hastelloy. Unless otherwise specified in the synthesis methods, all operations or equipment are conventional.

[0054] The present invention will be further described below with reference to the embodiments and accompanying drawings, but the scope of protection of the present invention, such as the reaction apparatus, reaction temperature, reaction time and volume of the reaction liquid, is not limited to the embodiments described.

[0055] Example 1

[0056] The method for preparing tin dioxide nanofilms provided in this embodiment includes the following steps:

[0057] (1) Place 2.00g of tin dioxide (SnO2, 99.99% purity, Aladdin, the same below, micron-sized powder crystal) and 6.00g of potassium hydrofluoric acid (KHF, 99% purity, Aladdin, the same below) powder into a silver crucible, cover it, place the platinum crucible on an electric furnace, set the furnace temperature to 350℃, heat for half an hour, and after slightly cooling, open the crucible lid and add 5% (volume percentage) hydrofluoric acid into the crucible until it reaches half the volume of the crucible. Continue to turn on the electric furnace and heat until boiling. Use a Teflon rod to stir continuously until the solid in the crucible is completely dissolved, and then stop heating.

[0058] (2) While the solution in the crucible is still hot, pour it onto filter paper for filtration. Use a silver evaporating dish to collect the filtrate. Repeat the filtration three times. Dilute the filtrate with 100 mL of deionized water to 0.01 mol / L to obtain the reaction solution. Put the prepared reaction solution into a 200 mL hydrothermal reactor. The hydrothermal reactor is a sealed high-temperature and high-pressure reactor. The high-temperature and high-pressure reactor is connected to a high-precision ultra-high-pressure pressure gauge, a gas pipe and a shut-off valve. The high-temperature and high-pressure reactor has a stainless steel metal shell with a polytetrafluoroethylene liner inside the metal shell. After tightening the reactor, inject argon gas into the reactor through the gas pipe to a pressure of 40 MPa. Close the shut-off valve to stop the gas injection. Heat the reactor through a heating furnace and set the reaction temperature to 200℃. After the temperature reaches 200℃, open the shut-off valve and continue to inject argon gas to a pressure of 60 MPa. Maintain the reaction time for 22.5 hours. After the reaction is completed, pour ice water over the reactor to quickly cool it down to room temperature.

[0059] (3) Open the reactor, recover the residual solution in the reactor, wash the inner wall of the reactor with deionized water, collect the washing fluid to obtain nano tin dioxide turbid liquid, put the obtained turbid liquid in a centrifuge for centrifugation, after centrifugation, take out the lower precipitate and rinse it with deionized water and anhydrous ethanol 2 to 3 times, and finally air dry the precipitate to obtain low density tin dioxide nano film.

[0060] Figure 1 Figures (a) and (b) show the morphology and particle size of the tin dioxide nanoparticles in the tin dioxide nanofilm at different magnifications. It can be seen that the nanoparticles are rice-grain shaped with a particle size of several nanometers to 100 nanometers.

[0061] Figure 10 Laser Raman spectroscopy revealed distinct Raman scattering peaks in the tin dioxide nanoparticles synthesized at 200℃, clearly indicating three Raman scattering peaks similar to those of standard single tin dioxide crystals, namely at 474 cm⁻¹. -1 634cm-1 and 775cm -1 This indicates that the synthesized rice-grain-like nanoparticles are basically tin dioxide.

[0062] Figure 11 μ-XRD analysis showed that the tin dioxide nanoparticles in the tin dioxide film synthesized at 200℃ were tetragonal, with only the (101) and (211) planes developed, and the other crystal planes not developed.

[0063] Example 2

[0064] The method for preparing tin dioxide nanofilms provided in this embodiment includes the following steps:

[0065] (1) Add 100 mL of deionized water to the filtrate prepared in step (1) of Example 1 to fully dissolve and prepare a dilute solution with a concentration of 0.01 mol / L. Put 5 mL of the prepared dilute solution into a 4.5 mm diameter gold tube and seal it. Then put the gold tube into the high temperature and high pressure reactor in Example 1. After tightening the reactor, inject argon gas into the reactor through the gas pipe to a pressure of 80 MPa. Close the shut-off valve to stop the gas injection. Heat the reactor through the heating furnace and set the reaction temperature to 250 °C. After the temperature rises to 250 °C, open the shut-off valve and continue to inject argon gas to a pressure of 100 MPa. Maintain the reaction time for 22.5 hours. After the reaction is completed, use ice water to pour on the reactor to quickly cool it down to room temperature.

[0066] (2) Open the reactor in step (1), take out the gold tube and break it open, recover the residual solution, wash the inner wall of the gold tube with deionized water, collect the washing fluid to obtain nano tin dioxide turbid liquid, put the obtained turbid liquid in a centrifuge for centrifugation, after centrifugation, take out the lower precipitate and rinse it with deionized water and anhydrous ethanol 2 to 3 times, and finally air dry the precipitate to obtain a high density tin dioxide nano film.

[0067] Figure 2 Figures (a)-(d) show the morphology and particle size of tin dioxide nanoparticles at different magnifications. It can be seen that the nanoparticles are rice-grain shaped and cone-shaped, with particle sizes ranging from a few nanometers to 100 nanometers. The tin dioxide nanocrystals are tightly connected to form a dense nanolayer film. Figure 2 Figure (c) shows a longitudinal cross-sectional image of the nanofilm, which is an array of nanoparticles composed of nanocrystals. The nanofilm has a uniform thickness of about 100 nanometers.

[0068] Figure 10 Laser Raman spectroscopy revealed distinct Raman scattering peaks in the tin dioxide nanoparticles synthesized at 250℃, clearly indicating three Raman scattering peaks similar to those of standard single tin dioxide crystals, namely at 474 cm⁻¹. -1634cm -1 and 775cm -1 This indicates that the synthesized nanoparticles are all tin dioxide.

[0069] Example 3

[0070] The method for preparing tin dioxide nanofilms provided in this embodiment includes the following steps:

[0071] (1) Add 100 mL of deionized water to the filtrate prepared in step (1) of Example 1 to fully dissolve and obtain a dilute solution with a concentration of 0.01 mol / L. Put the dilute solution into a hydrothermal reactor. Place a flat gold sheet at the bottom of the reactor. After tightening the reactor, inject argon gas into the reactor through the gas pipe to a pressure of 80 MPa. Close the shut-off valve to stop the gas injection. Heat the reactor through the heating furnace and set the reaction temperature to 450°C. After the temperature rises to 450°C, open the shut-off valve and continue to inject argon gas to a pressure of 100 MPa. Maintain the reaction time for 22.5 hours. After the reaction is completed, use ice water to pour over the reactor to quickly cool it down to room temperature.

[0072] (2) Open the reaction vessel in step (1), recover the residual solution in the vessel, take out the gold sheet in the vessel, wash it 2-3 times with deionized water and anhydrous ethanol, and after air drying, a layer of nano tin dioxide film can be seen on the surface of the gold sheet.

[0073] Figure 3 Figures (a) and (b) show scanning electron microscope images of tin dioxide nanoparticles in tin dioxide films at different magnifications. The images show that the nanoparticles are uniform, mainly in the shape of rice grains and cones, with a particle size of a few nanometers to about 100 nanometers. The tin dioxide nanocrystals are tightly connected to form a dense nanolayer film.

[0074] Figure 10 Laser Raman spectroscopy revealed distinct Raman scattering peaks in the tin dioxide nanoparticles synthesized at 450℃, clearly indicating three Raman scattering peaks similar to those of standard single tin dioxide crystals, namely at 474 cm⁻¹. -1 634cm -1 and 775cm -1 This indicates that the synthesized nanoparticles are all tin dioxide.

[0075] Figure 11 μ-XRD analysis showed that the tin dioxide nanoparticles in the tin dioxide film synthesized at 450℃ were tetragonal with euhedral crystal structure and multiple crystal faces such as (110), (101), (211), (220), (310), (320), (321), (222), and (312).

[0076] Example 4

[0077] The method for preparing tin dioxide nanofilms provided in this embodiment includes the following steps:

[0078] (1) Add 100 mL of deionized water to the filtrate prepared in step (1) of Example 1 to fully dissolve it and obtain a dilute solution with a concentration of 0.02 mol / L. Put the dilute solution into a 200 mL hydrothermal reactor. The hydrothermal reactor is a sealed high-temperature and high-pressure reactor. The high-temperature and high-pressure reactor is connected to a high-precision ultra-high pressure gauge, a gas pipe and a shut-off valve. The high-temperature and high-pressure reactor has a metal shell with a polytetrafluoroethylene liner inside the metal shell. After tightening the reactor, inject argon gas into the reactor through the gas pipe to a pressure of 80 MPa. Close the shut-off valve to stop the gas injection. Heat the reactor through a heating furnace and set the reaction temperature to 200°C. After the temperature rises to 200°C, open the shut-off valve and continue to inject argon gas to a pressure of 100 MPa. Maintain the reaction time for 37 hours. After the reaction is completed, use ice water to pour ice water over the reactor to quickly cool it down to room temperature.

[0079] (2) Open the reactor in step (1), recover the residual solution in the reactor, wash the inner wall of the reactor with deionized water, collect the washing fluid to obtain nano tin dioxide turbid liquid, put the obtained turbid liquid in a centrifuge for centrifugation, after centrifugation, take out the lower precipitate and rinse it with deionized water and anhydrous ethanol 2 to 3 times, and finally air dry the precipitate to obtain a high density tin dioxide nano film.

[0080] Figure 4 Figures (a)-(d) show the morphology and particle size of tin dioxide nanoparticles in tin dioxide nanofilms at different magnifications. It can be seen that the nanoparticles are rice-grain shaped and cone-shaped, with a particle size of several nanometers to 200 nanometers.

[0081] Figure 10 Laser Raman spectroscopy revealed distinct Raman scattering peaks in the tin dioxide nanofilm synthesized at 200℃, clearly indicating three Raman scattering peaks similar to those of standard single tin dioxide crystals, namely at 474 cm⁻¹. -1 634cm -1 and 775cm -1 This indicates that the synthesized rice-grain-shaped nanoparticles are basically tin dioxide.

[0082] Example 5

[0083] The method for preparing tin dioxide nanofilms provided in this embodiment includes the following steps:

[0084] (1) Add 100 mL of deionized water to the filtrate prepared in step (1) of Example 1 to fully dissolve and obtain a dilute solution with a concentration of 0.02 mol / L. Put the dilute solution into a hydrothermal reactor. Place a flat gold sheet at the bottom of the reactor. After tightening the reactor, inject argon gas into the reactor through the gas pipe to a pressure of 80 MPa. Close the shut-off valve to stop the gas injection. Heat the reactor through the heating furnace and set the reaction temperature to 300℃. After the temperature rises to 300℃, open the shut-off valve and continue to inject argon gas to a pressure of 100 MPa. Maintain the reaction time for 23 hours. After the reaction is completed, use ice water to pour over the reactor to quickly cool it down to room temperature.

[0085] (2) Open the reactor in step (1), recover the residual solution in the reactor, take out the gold sheet in the reactor in step (1), wash it with deionized water 2 to 3 times, and after air drying, a layer of nano tin dioxide film can be seen on the surface of the gold sheet.

[0086] Figure 5 Figures (a) and (b) show scanning electron microscope images of tin dioxide nanoparticles in tin dioxide films at different magnifications. The images show that the nanoparticles are uniform, mainly in the shape of irregular cones, with a particle size of tens of nanometers to about 300 nanometers. The tin dioxide nanoparticles are tightly connected to form a dense nanolayer film.

[0087] Figure 10 Laser Raman spectroscopy revealed distinct Raman scattering peaks in the tin dioxide nanoparticles synthesized at 300℃, clearly indicating three Raman scattering peaks similar to those of standard single tin dioxide crystals, namely at 474 cm⁻¹. -1 634cm -1 and 775cm -1 This indicates that the synthesized nanoparticles are all tin dioxide.

[0088] Example 6

[0089] The method for preparing tin dioxide nanofilms provided in this embodiment includes the following steps:

[0090] (1) Add 100 mL of deionized water to the filtrate prepared in step (1) of Example 1 to fully dissolve and obtain a dilute solution with a concentration of 0.05 mol / L. Put the dilute solution into a 200 mL hydrothermal reactor. The hydrothermal reactor is a sealed high-temperature and high-pressure reactor. The high-temperature and high-pressure reactor is connected to a high-precision ultra-high pressure gauge, a gas pipeline and a shut-off valve. The high-temperature and high-pressure reactor has a metal shell with a polytetrafluoroethylene liner inside the metal shell. After tightening the reactor, inject argon gas into the reactor through the gas pipeline to a pressure of 80 MPa. Close the shut-off valve to stop the gas injection. Heat the reactor through a heating furnace and set the reaction temperature to 200°C. After the temperature rises to 200°C, open the shut-off valve and continue to inject argon gas to a pressure of 100 MPa. Maintain the reaction time for 8 hours. After the reaction is completed, use ice water to pour over the reactor to quickly cool it down to room temperature.

[0091] (2) Open the reactor in step (1), recover the residual solution in the reactor, wash the inner wall of the reactor with deionized water, collect the washing fluid to obtain nano tin dioxide turbid liquid, put the obtained turbid liquid in a centrifuge for centrifugation, after centrifugation, take out the lower precipitate and rinse it with deionized water and anhydrous ethanol 2 to 3 times, and finally air dry the precipitate to obtain low density tin dioxide nano film.

[0092] Figure 6 Figures (a) and (b) show the morphology and particle size of tin dioxide nanoparticles in tin dioxide films at different magnifications. It can be seen that the nanoparticles are rice-grain shaped with a particle size of tens of nanometers to 200 nanometers.

[0093] Figure 10 Laser Raman spectroscopy revealed distinct Raman scattering peaks in the tin dioxide nanoparticles synthesized at 200℃, clearly indicating three Raman scattering peaks similar to those of standard single tin dioxide crystals, namely at 474 cm⁻¹. -1 634cm -1 and 775cm -1 This indicates that the synthesized rice-grain-like nanoparticles are basically tin dioxide.

[0094] Example 7

[0095] The method for preparing tin dioxide nanofilms provided in this embodiment includes the following steps:

[0096] (1) Add 100 mL of deionized water to the filtrate prepared in step (1) of Example 1 to fully dissolve and obtain a dilute solution with a concentration of 0.05 mol / L. Put 5 mL of the dilute solution into a 4.5 mm diameter gold tube and seal it. Then put the gold tube into a high-temperature and high-pressure reactor. The high-temperature and high-pressure reactor is connected to a high-precision ultra-high pressure gauge, a gas pipe and a shut-off valve. The high-temperature and high-pressure reactor has a metal shell. After tightening the reactor, inject argon gas into the reactor through the gas pipe to a pressure of 80 MPa. Close the shut-off valve to stop the gas injection. Heat the reactor through a heating furnace and set the reaction temperature to 200 °C. After the temperature rises to 200 °C, open the shut-off valve in step (1) and continue to inject argon gas to a pressure of 100 MPa. Maintain the reaction time for 48 hours. After the reaction is completed, use ice water to pour over the reactor in step (1) to quickly cool it down to room temperature.

[0097] (2) Open the reactor in step (1), take out the gold tube and break it open, recover the residual solution, wash the inner wall of the gold tube with deionized water, collect the washing fluid to obtain nano tin dioxide turbid liquid, put the obtained turbid liquid in a centrifuge for centrifugation, after centrifugation, take out the lower precipitate and rinse it with deionized water and anhydrous ethanol 2 to 3 times, and finally air dry the precipitate to obtain low density tin dioxide nano film.

[0098] Figure 7 Figures (a) and (b) show the morphology and particle size of tin dioxide nanoparticles in tin dioxide films at different magnifications. It can be seen that the nanoparticles are rice-grain shaped with a particle size of tens of nanometers to 500 nanometers.

[0099] Figure 10 Laser Raman spectroscopy revealed distinct Raman scattering peaks in the tin dioxide nanofilm synthesized at 200℃, clearly indicating three Raman scattering peaks similar to those of standard single tin dioxide crystals, namely at 474 cm⁻¹. -1 634cm -1 and 775cm -1 This indicates that the synthesized rice-grain-like nanoparticles are basically tin dioxide.

[0100] Example 8

[0101] The method for preparing tin dioxide nanofilms provided in this embodiment includes the following steps:

[0102] (1) Add 100 mL of deionized water to the filtrate prepared in step (1) of Example 1 to fully dissolve and obtain a dilute solution with a concentration of 0.05 mol / L. Put the dilute solution into a hydrothermal reactor. Place a flat gold sheet at the bottom of the reactor. After tightening the reactor, inject argon gas into the reactor through the gas pipe to a pressure of 80 MPa. Close the shut-off valve to stop the gas injection. Heat the reactor through the heating furnace and set the reaction temperature to 300℃. After the temperature rises to 300℃, open the shut-off valve and continue to inject argon gas to a pressure of 100 MPa. Maintain the reaction time for 14 hours. After the reaction is completed, use ice water to pour on the reactor to quickly cool it down to room temperature.

[0103] (2) Open the reactor in step (1), recover the residual solution in the reactor, take out the gold sheet in the reactor, wash it with deionized water 2 to 3 times, and after air drying, a layer of nano tin dioxide film can be seen on the surface of the gold sheet.

[0104] Figure 8 Figures (a) and (b) show scanning electron microscope images of tin dioxide nanoparticles in tin dioxide films at different magnifications. The images show that the nanoparticles are uniform, mainly in the shape of irregular cones, with a particle size of tens of nanometers to about 300 nanometers. The tin dioxide nanoparticles are tightly connected to form a dense nanolayer film.

[0105] Figure 10 Laser Raman spectroscopy revealed distinct Raman scattering peaks in the tin dioxide nanoparticles synthesized at 300℃, clearly indicating three Raman scattering peaks similar to those of standard single tin dioxide crystals, namely at 474 cm⁻¹. -1 634cm -1 and 775cm -1 This indicates that the synthesized nanoparticles are all tin dioxide.

[0106] Example 9

[0107] The method for preparing tin dioxide nanofilms provided in this embodiment includes the following steps:

[0108] (1) Add 100 mL of deionized water to the filtrate prepared in step (1) of Example 1 to fully dissolve and prepare a 0.05 mol / L reaction solution. Put the prepared reaction solution into a hydrothermal reactor. Place a flat gold sheet at the bottom of the reactor. After tightening the reactor, inject argon gas into the reactor through the gas pipe to a pressure of 80 MPa. Close the shut-off valve to stop the gas injection. Heat the reactor through the heating furnace and set the reaction temperature to 500℃. After the temperature rises to 500℃, open the shut-off valve and continue to inject argon gas to a pressure of 100 MPa. Maintain the reaction time for 24 hours. After the reaction is completed, use ice water to pour on the reactor to quickly cool it down to room temperature.

[0109] (2) Open the reactor in step (1), recover the residual solution in the reactor, take out the gold sheet in the reactor in step (1), wash it with deionized water 2 to 3 times, and after air drying, a layer of nano tin dioxide film can be seen on the surface of the gold sheet.

[0110] Figure 9 Figures (a) and (b) show scanning electron microscope images of tin dioxide nanofilms at different magnifications. The images show that the nanoparticles are of uneven size, mainly in the form of irregular cones and blocks, with a particle size of tens of nanometers to about 600 nanometers. The tin dioxide nanoparticles are tightly connected to form a dense nanofilm.

[0111] Figure 10 Laser Raman spectroscopy revealed distinct Raman scattering peaks in the tin dioxide nanoparticles synthesized at 500℃, clearly indicating three Raman scattering peaks similar to those of standard single tin dioxide crystals, namely at 474 cm⁻¹. -1 634cm -1 and 775cm -1 This indicates that the synthesized nanoparticles are all tin dioxide.

[0112] Figure 11 μ-XRD analysis showed that the tin dioxide nanoparticles in the tin dioxide nanofilm synthesized at 500℃ were tetragonal with euhedral crystal structure and multiple crystal faces such as (110), (101), (211), (220), (310), (320), (321), (222), and (312).

[0113] The above embodiments are only used to illustrate the present invention, and the scope of protection of the present invention is not limited to the above embodiments. Those skilled in the art can achieve the purpose of the present invention based on the above disclosure. Any improvements and modifications made based on the concept of the present invention fall within the scope of protection of the present invention, and the specific scope of protection is determined by the claims.

Claims

1. A method for preparing a tin dioxide nanofilm, characterized in that, The method comprises the following steps: (1) taking tin dioxide and potassium bifluoride powder as initial raw materials, placing the two raw materials in a container and covering, heating the container, adjusting the heating temperature to 300-400 DEG C, heating for 0.3-1.0 hours, so that the solid powder is fully molten and reacted, after reaction, cooling, adding dilute hydrofluoric acid solution to the container, heating the container to boiling again, and continuously stirring to make the solid in the container completely dissolved, and stopping heating; (2) filtering the solution in the container while hot, and collecting the filtrate; (3) adding deionized water to the filtrate of step (2) to prepare a dilute solution, placing the dilute solution in a hydrothermal reaction container, sealing the hydrothermal reaction container, heating the hydrothermal reaction container, adjusting the temperature in the hydrothermal reaction container to 150-500 DEG C, adjusting the pressure in the hydrothermal reaction container by injecting inert gas into the hydrothermal reaction container to 10-100 MPa, and reacting for 8-48 hours, and then rapidly cooling to room temperature; (4) opening the hydrothermal reaction container, and obtaining the tin dioxide nanofilm through subsequent treatment. The mass ratio of tin dioxide and potassium bifluoride in step (1) is 1:2-3; The molar concentration of the dilute solution in step (3) is 0.01-0.05 mol / L.

2. The method of claim 1, wherein the tin dioxide nanofilm is prepared by a process comprising: In step (1), the volume percentage of the dilute hydrofluoric acid solution is 3-8%, and the amount of addition is 40-60% of the total volume of the container; the container in step (1) is a crucible, the crucible is hafnium alloy, or the crucible is a crucible with silver, gold or platinum lining; the stirring in step (1) uses a Teflon stirring rod.

3. The method for preparing tin dioxide nanofilms according to claim 1, characterized in that, In step (2), the filtrate is collected by using an evaporating dish with Teflon, silver, gold or platinum lining.

4. The method for preparing tin dioxide nanofilms according to claim 1, characterized in that, The inert gas in step (3) is argon or helium.

5. The method for preparing tin dioxide nanofilms according to claim 1, characterized in that, In step (3), the dilute solution is directly added to the hydrothermal reaction container, and the volume of the dilute solution accounts for 30-70% of the total volume of the hydrothermal reaction container; the hydrothermal reaction container is a hydrothermal reaction kettle, the hydrothermal reaction kettle is a sealed high temperature and high pressure reaction kettle, the high temperature and high pressure reaction kettle is connected with a high precision ultrahigh pressure gauge, a ventilation pipeline and a stop valve, the high temperature and high pressure reaction kettle has a metal shell, the metal shell is provided with a strong acid and alkali resistant lining, the strong acid and alkali resistant lining is polytetrafluoroethylene, polyphenyl ester or polyimide plastic, or the strong acid and alkali resistant lining is silver, gold or platinum inert metal, or the strong acid and alkali resistant lining is gold palladium or silver palladium alloy.

6. The method for preparing tin dioxide nanofilms according to claim 5, characterized in that, In step (4), opening the hydrothermal reaction container and obtaining the tin dioxide nanofilm through subsequent treatment comprises: opening the hydrothermal reaction container, recovering the residual solution in the hydrothermal reaction container, washing the inner wall of the hydrothermal reaction container with deionized water, collecting the washing fluid to obtain a nanometer tin dioxide slurry, centrifuging the obtained slurry, taking the lower sediment, washing and drying the lower sediment to obtain the tin dioxide nanofilm; the residual solution mainly comprises potassium hexafluorostannate, hydrofluoric acid and potassium fluoride.

7. The method for preparing tin dioxide nanofilms according to claim 5, characterized in that, The bottom of the hydrothermal reaction container in step (3) is provided with a sample collection sheet, and the sample collection sheet is made of plastic or inert metal material; in step (4), the hydrothermal reaction container is opened, and the tin dioxide nanometer film is obtained through subsequent treatment, including: opening the hydrothermal reaction container, recovering the residual solution in the hydrothermal reaction container, taking out the sample collection sheet, and washing and drying to prepare the tin dioxide nanometer film on the surface of the sample collection sheet; the residual solution mainly includes potassium hexafluorostannate, hydrofluoric acid and potassium fluoride.

8. The method for preparing tin dioxide nanofilms according to claim 1, characterized in that, In step (3), the potassium hexafluorostannate solution is first added to the noble metal container, and then the noble metal container is placed in the hydrothermal reaction container, wherein the noble metal is silver, gold or platinum; or the noble metal is gold-palladium or silver-palladium alloy.

9. The method for preparing tin dioxide nanofilms according to claim 8, characterized in that, In step (4), the hydrothermal reaction container is opened, and the tin dioxide nanometer film is obtained through subsequent treatment, including: opening the hydrothermal reaction container, taking out the noble metal container, recovering the residual solution in the noble metal container, washing the inner wall of the noble metal container with deionized water, collecting the washing fluid to obtain a nanometer tin dioxide slurry, centrifuging the obtained slurry, taking the lower layer precipitate, and washing and drying the lower layer precipitate to obtain the tin dioxide nanometer film.

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