Rare earth boride nanomaterial, preparation method and application thereof

Abstract

The application discloses monodisperse rare earth boride nanomaterials with a size less than 20 nm, a preparation method and application thereof, and the phase state of the rare earth boride nanomaterials is REB6 or REB4; the preparation method comprises the following steps: S1, weighing compound raw materials containing RE elements and compound raw materials containing B elements respectively; S2, adding an additive and grinding thoroughly; S3, then performing a reaction under the protection of an inert gas; S4, after the reaction is completed, adding excessive methanol, performing centrifugal separation after no bubbles are generated, and reserving a precipitate A; S5, adding dilute hydrochloric acid for soaking, performing centrifugal separation again, and reserving a precipitate B; S6, washing the precipitate B with deionized water, drying, and obtaining the rare earth boride nanomaterials. The application adopts a normal-pressure low-temperature preparation method, and pure-phase rare earth hexaboride nanocrystals can be obtained at normal pressure and a temperature as low as 270 DEG C, and any active metal element is not needed to be introduced in the preparation process.

Description

Technical Field

[0001] This invention relates to a rare earth boride nanomaterial, its preparation method and application, specifically a monodisperse rare earth boride nanomaterial with a diameter of less than 20 nm, belonging to the field of nanomaterial technology. Background Technology

[0002] Rare earth elements (REs) refer to 17 elements including scandium (Sc), yttrium (Y), and the lanthanides. Their unique electronic structures endow them with a wide range of optical, electrical, and magnetic properties. Rare earth borides (REB6 or REB4) are a special class of rare earth compounds that have attracted widespread attention due to their unique properties such as high melting point, high hardness, chemical stability, magnetism, efficient thermionic emission, and surface plasmon resonance. The excellent properties of rare earth borides stem from their unique crystal structure, which consists of rare earth metal atoms embedded in a stable boron octahedral network, with covalent, ionic, and metallic bonds coexisting within it. However, while this structure endows the materials with excellent properties such as high melting point and high hardness, it also greatly increases the difficulty of their preparation and control.

[0003] Patent CN113582190A discloses a multi-element rare earth boride nanopowder and its preparation method, including the following steps: S1, using La2O3, RE2O3, B2O3 and Ca as raw materials, mixing them evenly and pre-pressing them into blocks to obtain a blocky blank; S2, placing the blocky blank in S1 under vacuum or inert atmosphere protection conditions and heating it at a predetermined heating temperature of 800-1000℃ to prepare the multi-element rare earth boride reaction product; S3, subjecting the multi-element rare earth boride reaction product in S2 to acid washing, repeated washing with pure water until neutral, filtering, and vacuum drying to obtain the multi-element rare earth boride La 1-x RE x B6 nanoparticles, where 0 < X ​​< 1. The calcium thermal reduction process in this invention reduces La. 1-x RE x The increased formation probability of BO3 compounds improves the yield of rare earth hexaborides and simplifies the purification process in the magnesothermic reduction method for preparing rare earth hexaborides, thus improving production efficiency. However, the above method involves high reaction temperatures, high energy consumption, and demanding equipment requirements, making it unsuitable for industrial production. To date, no reports have been found regarding methods for preparing monodisperse rare earth boride nanomaterials with diameters less than 20 nm.

[0004] Traditional preparation methods typically require extremely high temperatures (exceeding 1500 °C) and high pressures, or the introduction of reactive elemental metals as reducing agents and to provide high temperatures. These processes are energy-intensive and highly dangerous, placing greater demands on the reaction apparatus and post-processing. Furthermore, the extremely high hardness of rare earth borides makes the material crushing process extremely difficult, and an effective method for preparing their nanomaterials has yet to be found. Therefore, the preparation of rare earth boride nanomaterials still faces significant challenges.

[0005] This application is submitted in response to the above-mentioned issues. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the primary objective of this invention is to provide a method for preparing rare earth boride nanomaterials.

[0007] A second objective of this invention is to provide rare earth boride nanomaterials prepared by the above method.

[0008] A third objective of this invention is to provide applications of the aforementioned rare earth boride nanomaterials.

[0009] To achieve the primary objective, this invention is implemented through the following technical solution: a method for preparing rare earth boride nanomaterials, wherein the rare earth boride nanomaterials are in the phase state REB6 or REB4, wherein RE is selected from one of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; the preparation method includes the following steps:

[0010] S1: Weigh out the compound raw material containing RE element and the compound raw material containing B element respectively, with a molar ratio of 1:4-12, to obtain a mixed raw material;

[0011] S2: Add additives to the mixed raw materials obtained in step S1, grind thoroughly to obtain mixture A, and then transfer mixture A to a three-necked flask or porcelain boat;

[0012] S3: The mixture A obtained in step S2 is reacted under inert gas protection, and heated using a heating jacket or tube furnace. The reaction temperature is controlled at 270-800 ℃ and the reaction time is 3-8 h to obtain mixture B.

[0013] S4: After the reaction is complete, add excess methanol to the mixture B obtained in step S3. After no more bubbles emerge, centrifuge and separate the precipitate A.

[0014] S5: Add dilute hydrochloric acid to precipitate A obtained in step S4 and soak for 12 hours. Centrifuge again to separate and retain precipitate B.

[0015] S6: Wash the precipitate B obtained in step S5 with deionized water and dry it to obtain rare earth boride nanomaterials.

[0016] Preferably, the compound raw material containing RE element in step S1 includes anhydrous rare earth halides, and the compound raw material containing B element is an alkali metal borohydride.

[0017] Preferably, the additive in step S2 is an alkali metal halide, and the molar ratio of the additive to the mixed raw materials is 1:1.

[0018] Preferably, the additive in step S2 is a mixture of LiI, LiCl and KI, with a molar ratio of LiI to KI of 20:80-80:20, and the amount of LiCl added is 1%-3% of the total amount of LiI and KI. The molar ratio of the additive to the mixed raw materials is 2:1 to 1:2.

[0019] The additive of the present invention uses iodide + chloride as a molten salt system instead of using only chloride, mainly for the following reasons:

[0020] (1) According to the theory of hard and soft acids and bases, strong acids and strong bases, and weak acids and weak bases combine more strongly. Iodide ions are soft bases and chloride ions are strong bases. Lithium, sodium and potassium are all alkali metals and are strong acid ions. Therefore, chloride ions combine more strongly with these alkali metal ions, resulting in a higher melting point. This requires a higher temperature to make the reaction system liquid, which hinders the reaction.

[0021] (2) In the reaction process, the raw material is rare earth chloride and the product is sodium chloride. If the molten salt system also contains a large amount of chloride ions, according to Le Chatelier's principle, it will hinder the forward reaction. Therefore, we choose a molten salt system containing iodide ions to promote the forward reaction.

[0022] Preferably, in step S3, the inert gas is nitrogen or argon, and the system pressure is one atmosphere.

[0023] Preferably, the concentration of dilute hydrochloric acid in step S5 is 0.6 mol / L.

[0024] Using the above technical solution, the calcined product is washed with methanol to remove the active metals in the product. During the synthesis process, sodium borohydride decomposes to generate elemental sodium. In the post-processing of the product, methanol is used to remove the metallic sodium produced in the reaction. If water or even hydrochloric acid is added directly for washing, the metallic sodium will react violently with it, resulting in combustion or even explosion. Washing with hydrochloric acid is used to remove oxide impurities in the product, including boron oxides and rare earth oxides. XRD analysis shows that the unwashed product has very poor crystallinity and exhibits obvious oxide characteristic diffraction peaks, which even affect the intensity of the product's own diffraction peaks.

[0025] Preferably, the centrifugation conditions in steps S4 and S5 are: 8000 rpm and 3-7 min.

[0026] Using the above technical solution, excess methanol is added in step S4 to remove the active metals generated in the reaction; in step S6, deionized water is used for washing to effectively remove soluble salts such as alkali metal halides. Adding molten salt can weaken the chemical bonds in the boron source precursor, thus allowing the synthesis of rare earth borides to proceed under mild conditions.

[0027] To achieve the second objective, the present invention is implemented through the following technical solution: a rare earth boride nanomaterial, which is in the phase of REB6 or REB4, is black or dark brown in color, and has a near-spherical or cubic morphology with a diameter of less than 20 nm, is a monodisperse rare earth boride nanomaterial.

[0028] Using the above technical solution, rare earth boride nanomaterials exhibit a monodisperse morphology under transmission electron microscopy.

[0029] Using the above technical solution, rare earth boride nanomaterials exhibit good dispersibility in various solvents, enabling them to be dispersed for extended periods without settling, including but not limited to chloroform, acetone, acetonitrile, N-N'-dimethylformamide, dimethyl sulfoxide, water, ethanol, and ethylene glycol.

[0030] Using the above technical solution, rare earth boride nanomaterials exhibit localized surface plasmon resonance characteristics and good light absorption properties in the ultraviolet-visible-near-infrared regions. Simultaneously, rare earth boride nanomaterials also possess excellent photothermal properties, antibacterial properties, and dye degradation properties.

[0031] The third objective of this invention is to apply rare earth boride nanomaterials in the fields of heat insulation coatings, photocatalysis, and solar water evaporation.

[0032] Preferably, the solar water evaporation includes seawater desalination, bacterial wastewater treatment, and high-salt dye wastewater treatment.

[0033] The beneficial effects of this invention are:

[0034] (1) The preparation conditions of the present invention are mild, do not require active metals or additional reducing atmosphere, only require atmospheric pressure, and the reaction temperature is much lower than that of traditional methods; it has good universality, is applicable to all rare earth elements, and the product size can be controlled.

[0035] (2) The rare earth boride nanomaterials of the present invention have local surface plasmon resonance properties, good light absorption properties in the ultraviolet-visible-near infrared region, and excellent photothermal properties, antibacterial properties and dye degradation properties, indicating that the material has the potential to be used as a photocatalyst and a light absorber in a solar water evaporation system.

[0036] (3) The preparation method provided by this invention has the advantages of being simple, efficient, low-energy, low-pollution, high-yield, safe and reliable, and the prepared materials have excellent properties. It can provide a reliable raw material supply for the application of rare earth functional materials related to optoelectronics, energy and environmental protection, and has certain practical significance.

[0037] (4) The present invention adopts a low-temperature preparation method under normal pressure, which can obtain pure phase rare earth hexaboride nanocrystals under normal pressure and at temperatures as low as 300 °C, and the preparation process does not require the introduction of any active metal element. Attached Figure Description

[0038] Figure 1 These are transmission electron microscope images of the samples in Example 1 of this invention;

[0039] Figure 2 This is the X-ray powder diffraction pattern of the sample in Example 1 of this invention;

[0040] Figure 3 This is the ultraviolet-visible-near-infrared absorption spectrum of the sample in Example 1 of this invention;

[0041] Figure 4 This is the X-ray powder diffraction pattern of the sample in Example 2 of this invention;

[0042] Figure 5 This is the X-ray powder diffraction pattern of the sample in Example 3 of this invention;

[0043] Figure 6 This is the X-ray powder diffraction pattern of the sample in Example 4 of this invention;

[0044] Figure 7 This is the X-ray powder diffraction pattern of the sample in Example 5 of this invention;

[0045] Figure 8 This is the X-ray powder diffraction pattern of the sample in Example 6 of this invention;

[0046] Figure 9 This is the X-ray powder diffraction pattern of the sample in Example 7 of this invention;

[0047] Figure 10 This is the X-ray powder diffraction pattern of the sample in Example 8 of this invention;

[0048] Figure 11 These are transmission electron microscope images of the samples in Example 9 of this invention;

[0049] Figure 12 This is the X-ray powder diffraction pattern of the sample in Example 9 of this invention;

[0050] Figure 13 These are transmission electron microscope images of the samples in Example 10 of this invention;

[0051] Figure 14 This is the X-ray powder diffraction pattern of the sample in Example 10 of this invention;

[0052] Figure 15 This is the photothermal conversion performance curve of the sample in Example 1 of this invention;

[0053] Figure 16 This is the solar evaporation performance curve of the sample in Example 1 of this invention;

[0054] Figure 17 This is the dye degradation performance curve of the sample in Example 1 of this invention;

[0055] Figure 18 These are photographs of the antibacterial properties of the samples in Example 1 of this invention;

[0056] Figure 19 This is the X-ray powder diffraction pattern of the sample in Comparative Example 6 of this invention;

[0057] Figure 20 These are transmission electron microscope images of the samples in Comparative Example 6 of this invention;

[0058] Figure 21 This is the X-ray powder diffraction pattern of the sample in Test Example 6 of this invention;

[0059] Figure 22 These are the differential scanning calorimetry (DSC) test results of the sample in Example 1 of this invention;

[0060] Figure 23 This is the X-ray powder diffraction pattern of the sample in Test Example 6 of this invention;

[0061] Figure 24 This is the absorption spectrum of the sample in Test Example 7 of this invention;

[0062] Figure 25 This is a comparison diagram of the photothermal properties of the samples in Test Example 7 of this invention;

[0063] Figure 26 This is a comparison diagram of the photothermal properties of the samples in Test Example 7 of this invention;

[0064] Figure 27 This is a comparison chart of the degradation performance of the samples in Test Example 7 of this invention;

[0065] Figure 28 This is a comparison chart of the antibacterial properties of the samples in Test Example 7 of this invention;

[0066] Figure 29This is a dispersion performance diagram of the sample in Test Example 8 of this invention;

[0067] Figure 30 This is a comparison chart of the dispersion performance of the samples in Experiment Example 8 of this invention. Detailed Implementation

[0068] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0069] Example 1: Preparation of rare earth boride nanomaterial LaB6

[0070] S1: Mix 1 mmol of anhydrous lanthanum chloride and 8 mmol of sodium borohydride to obtain a mixed raw material;

[0071] S2: Add 9 mmol of alkali metal halide (LiI to KI molar ratio of 6:4, and the amount of LiCl added is 1% of the total amount of LiI and KI) to the mixed raw materials, grind thoroughly, and obtain mixture A;

[0072] S3: Transfer mixture A to a three-necked flask and seal it. Under the protection of N2 at one atmosphere, heat it to 350 °C and react for 6 h to obtain mixture B;

[0073] S4: After cooling, add excess methanol to mixture B. After no more bubbles emerge, centrifuge at 8000 rpm for 5 min and retain precipitate A.

[0074] S5: Add dilute hydrochloric acid to precipitate A and soak for 12 hours, then centrifuge again to retain precipitate B;

[0075] S6: After washing precipitate B three times with deionized water and drying, rare earth boride LaB6 nanomaterials were obtained.

[0076] The morphology of the obtained products was analyzed using transmission electron microscopy, such as... Figure 1 As shown, the prepared material has a near-spherical morphology with a diameter of 3-4 nm. The phase and structure of the obtained product were characterized using X-ray powder diffraction, as shown... Figure 2 As shown, the X-ray powder diffraction peaks of the prepared material match the diffraction peaks corresponding to the LaB6 standard PDF card. These characterization results indicate the successful preparation of the rare-earth boride nanomaterial LaB6. The particle size was calculated to be 4.2 nm according to the Scherrer equation, which corresponds to the results obtained from transmission electron microscopy.

[0077] The optical properties of the above samples were tested using a UV-Vis-NIR spectrometer, such as... Figure 3As shown, the sample absorbs in the ultraviolet-visible-near-infrared regions, with strong absorption in the near-infrared region, indicating that it is a good light-absorbing material.

[0078] Example 2: Preparation of rare earth boride nanomaterial CeB6

[0079] S1: Mix 1 mmol of anhydrous cerium chloride and 8 mmol of sodium borohydride to obtain a mixed raw material;

[0080] S2-S6: Same as Example 1.

[0081] The obtained products were characterized by phase and structure using X-ray powder diffraction, such as... Figure 4 As shown, the X-ray powder diffraction peaks of the prepared material match the diffraction peaks corresponding to the CeB6 standard PDF card. These characterization results indicate the successful preparation of the rare-earth boride nanomaterial CeB6.

[0082] Example 3 Preparation of rare earth boride nanomaterial PrB6

[0083] S1: Mix 1 mmol of anhydrous praseodymium chloride and 8 mmol of potassium borohydride to obtain a mixed raw material;

[0084] S2-S6: Same as Example 1.

[0085] The obtained products were characterized by phase and structure using X-ray powder diffraction, such as... Figure 5 As shown, the X-ray powder diffraction peaks of the prepared material match the diffraction peaks corresponding to the PrB6 standard PDF card. These characterization results indicate the successful preparation of the rare-earth boride nanomaterial PrB6.

[0086] Example 4: Preparation of rare earth boride nanomaterial NdB6

[0087] S1: Mix 1 mmol of anhydrous neodymium chloride and 8 mmol of sodium borohydride to obtain a mixed raw material;

[0088] S2-S6: Same as Example 1.

[0089] The obtained products were characterized by phase and structure using X-ray powder diffraction, such as... Figure 6 As shown, the X-ray powder diffraction peaks of the prepared material match the diffraction peaks corresponding to the NdB6 standard PDF card. These characterization results indicate the successful preparation of the rare-earth boride nanomaterial NdB6.

[0090] Example 5: Preparation of rare earth boride nanomaterial EuB6

[0091] S1: Mix 1 mmol of anhydrous europium chloride and 8 mmol of lithium borohydride to obtain a mixed raw material;

[0092] S2-S6: Same as Example 1.

[0093] The obtained products were characterized by phase and structure using X-ray powder diffraction, such as... Figure 7 As shown, the X-ray powder diffraction peaks of the prepared material match the diffraction peaks corresponding to the EuB6 standard PDF card. These characterization results indicate the successful preparation of the rare-earth boride nanomaterial EuB6.

[0094] Example 6 Preparation of rare earth boride nanomaterial ErB6

[0095] S1: Mix 1 mmol of anhydrous erbium chloride and 8 mmol of sodium borohydride to obtain a mixed raw material;

[0096] S2: Same as Example 1;

[0097] S3: Transfer mixture A to a ceramic boat and place it in a tube furnace. Under the protection of N2 at one atmosphere, heat the mixture to 800°C and react for 6 hours to obtain mixture B.

[0098] S4-S6: Same as Example 1.

[0099] The obtained products were characterized by phase and structure using X-ray powder diffraction, such as... Figure 8 As shown, the X-ray powder diffraction peaks of the prepared material match the diffraction peaks corresponding to the ErB6 standard PDF card. These characterization results indicate the successful preparation of the rare-earth boride nanomaterial ErB6.

[0100] Example 7 Preparation of rare earth boride nanomaterial YbB6

[0101] S1: Mix 1 mmol of anhydrous ytterbium chloride and 8 mmol of sodium borohydride to obtain a mixed raw material;

[0102] S2-S6: Same as Example 6.

[0103] The obtained products were characterized by phase and structure using X-ray powder diffraction, such as... Figure 9 As shown, the X-ray powder diffraction peaks of the prepared material match the diffraction peaks corresponding to the YbB6 standard PDF card. These characterization results indicate the successful preparation of the rare-earth boride nanomaterial YbB6.

[0104] Example 8 Preparation of rare earth boride nanomaterial LuB4

[0105] S1: Mix 1 mmol of anhydrous lutetium chloride and 12 mmol of potassium borohydride to obtain a mixed raw material.

[0106] S2-S6: Same as Example 6.

[0107] The obtained products were characterized by phase and structure using X-ray powder diffraction, such as... Figure 10 As shown, the X-ray powder diffraction peaks of the prepared material match the diffraction peaks corresponding to the LuB4 standard PDF card. These characterization results indicate the successful preparation of the rare-earth boride nanomaterial LuB4.

[0108] Example 9 Preparation of rare earth boride nanomaterial LaB6

[0109] S1: Mix 1 mmol of anhydrous lanthanum chloride and 8 mmol of sodium borohydride to obtain a mixed raw material;

[0110] S2-S6: Same as Example 6.

[0111] The morphology of the obtained products was analyzed using transmission electron microscopy, such as... Figure 11 As shown, the prepared material has a cubic morphology with dimensions of 8-10 nm. The phase and structure of the obtained product were characterized using X-ray powder diffraction, as shown... Figure 12 As shown, the X-ray powder diffraction peaks of the prepared material match the diffraction peaks corresponding to the LaB6 standard PDF card. These characterization results indicate the successful preparation of the rare-earth boride nanomaterial LaB6. The particle size was calculated to be 8.2 nm according to the Scherrer equation, which corresponds to the results of transmission electron microscopy. These results demonstrate that this method has good controllability over the size of the product.

[0112] Example 10 Preparation of rare earth boride nanomaterial LaB6

[0113] S1: Mix 1 mmol of anhydrous lanthanum chloride and 8 mmol of sodium borohydride to obtain a mixed raw material;

[0114] S2: Same as Example 6;

[0115] S3: Transfer mixture A to a ceramic boat and place it in a tube furnace. Heat the mixture to 1000℃ under N2 protection at one atmosphere and react for 6 hours.

[0116] S4-S6: Same as Example 6.

[0117] The morphology of the obtained products was analyzed using transmission electron microscopy, such as... Figure 13 As shown, the prepared material has a cubic morphology with dimensions of 18-20 nm. The phase and structure of the obtained product were characterized using X-ray powder diffraction, as shown... Figure 14As shown, the X-ray powder diffraction peaks of the prepared material match the diffraction peaks corresponding to the LaB6 standard PDF card. These characterization results indicate the successful preparation of the rare-earth boride nanomaterial LaB6. The particle size was calculated to be 17.0 nm according to the Scherrer equation, which corresponds to the results obtained from transmission electron microscopy. These results demonstrate that this method offers good control over the size of the product.

[0118] Comparative Example 1

[0119] The difference from Example 1 is that the molar ratio of LiI to KI is 7:3.

[0120] Comparative Example 2

[0121] The difference from Example 1 is that the molar ratio of LiI to KI is 6:4.

[0122] Comparative Example 3

[0123] The difference from Example 1 is that the molar ratio of LiI to KI is 3:7.

[0124] Comparative Example 4

[0125] The difference from Example 1 is that the molar ratio of LiI to KI is 2:8.

[0126] Comparative Example 5

[0127] The difference from Example 1 is that the molar ratio of LiI to KI is 1:9.

[0128] Comparative Example 6

[0129] The difference from Example 1 is that no additives are added.

[0130] Comparative Example 7

[0131] The difference from Example 1 is that LiI is replaced with LiCl and KI is replaced with KCl.

[0132] Experimental Example 1

[0133] Test group: Samples obtained in Example 1;

[0134] Experimental method: The sample obtained in Example 1 was used as the photothermal material for the photothermal layer of a solar thermal interface evaporator. The test conditions were as follows: the loading of LaB6 nanomaterials was 1 mg / cm³. 2 The substrate of the solar thermal evaporator was 3*3*3 cm wooden sponge. The test environment was set as a constant temperature and humidity chamber at 25 ℃ and 45%, and the light source was a Solar-500Q xenon lamp solar simulator with a light intensity of 1 kW / m². 2 The illumination time is 300 s;

[0135] Test results: such as Figure 15 As shown, the loading of LaB6 nanomaterials is 1 mg / cm³. 2 After 60 seconds of illumination, the interface temperature of the wooden solar evaporator rose to 76.2 ℃, and the highest temperature stabilized at 80.5 ℃, demonstrating excellent photothermal conversion performance.

[0136] Experimental Example 2

[0137] Test group: Samples obtained in Example 1;

[0138] Experimental method: The loading amount of LaB6 nanomaterials was 1 mg / cm³. 2 The wooden solar evaporator was applied in the field of seawater desalination. The test conditions were as follows: the light source was a Solar-500Q xenon lamp solar simulator, and the light intensity was set to 1 kW / m². 2 The water source was a 3.5% NaCl salt solution with a simulated seawater concentration, and the evaporation time was 120 s;

[0139] Test results: such as Figure 16 As shown, the water evaporation rate increases with prolonged illumination time, reaching a maximum of 3.12 kg / m³. 2 / h 1 It is a sustainable clean freshwater production platform with a high water evaporation rate.

[0140] Experimental Example 3

[0141] Experimental group: Example 1;

[0142] Experimental Method: The sample obtained in Example 1 was used as a catalyst for the degradation of organic dyes. The test conditions were as follows: the concentration of LaB6 nanomaterials was 0.1 mg / mL, the concentration of methyl orange dye was 20 ppm, the volume of the dye degradation reaction solution was 100 mL, the reaction was carried out at room temperature, the reaction vessel was a self-made quartz tube, the light source was a Solar-500Q xenon lamp, and the light intensity was 1 kW / m². 2 The xenon lamp irradiation reaction lasted for 120 min;

[0143] Test results: such as Figure 17 As shown, under the catalytic condition of 0.1 mg / mL LaB6 nanoparticles, the degradation rate of methyl orange dye reached 98.2%, and LaB6 nanomaterials showed potential catalytic performance in degrading organic pollutants in wastewater under sunlight.

[0144] Test Example 4

[0145] Experimental group: Example 1;

[0146] Experimental Methods: The antibacterial properties of the samples obtained in Example 1 were tested. The antibacterial activity of different doses of LaB6 nanomaterials against Gram-negative bacteria *E. coli* was studied by plate coating experiments. The experimental conditions were as follows: the preserved *E. coli* strain was amplified before the experiment and stored at 4 °C for later use; the LaB6 nanomaterials were sterilized. Different amounts of nanomaterials were added to a bacterial suspension (4.0 × 10⁻⁶). 5 The concentrations of nanomaterials were 0 μg / mL (as a blank control group), 100 μg / mL, 200 μg / mL, and 300 μg / mL in test tubes containing CFU / mL and PBS, respectively. Co-culturing conditions were a constant temperature shaker at 37 °C and 160 rpm for 12 h to ensure sufficient contact between bacteria and nanomaterials. After 12 h of co-culturing, the bacterial suspension in the test tubes was diluted 10 μg / mL with sterile PBS. 4 Take 80 μL of the diluted solution and spread it evenly on an agar plate. After the bacterial culture has completely absorbed the solution, incubate the plate upside down in a biochemical incubator at 37 °C for 15 h. Then take a picture to record the results.

[0147] Test results: such as Figure 18 As shown, compared with the control group, the survival rate of E. coli decreased with the increase of sample nanoparticle dosage, reaching nearly 100% antibacterial performance at a concentration of 300 μg / ml. The results indicate that LaB6 nanomaterials exhibit significantly enhanced antibacterial activity.

[0148] Experimental Example 5

[0149] Experimental groups: Example 1, Comparative Examples 1-5;

[0150] Experimental Method: In the preparation process of rare earth boride nanomaterial LaB6 in Example 1, the proportion of alkali metal halide components added in step S2 was changed. Specifically, while keeping the amount of LiCl added constant, the molar ratio of LiI to KI was successively adjusted to 7:3, 6:4, 3:7, 2:8, and 1:9, while other preparation steps remained unchanged. Subsequently, XRD tests were performed on the products prepared according to different proportions.

[0151] Experimental Results: As shown in Figure 21, through this series of conditional experiments, it was found that when the molar ratio of LiI to KI was too high or too low, the XRD diffraction peak intensities of the obtained product were weak, indicating poor crystallinity. However, when the molar ratio of LiI to KI was around 6:4, the crystallinity of the product reached its optimal state. Based on this, a molar ratio of LiI to KI around 6:4 was determined to be the optimal ratio range for iodides.

[0152] Experimental Example 6

[0153] Experimental groups: Example 1, Comparative Example 6, Comparative Example 7;

[0154] like Figure 19 As shown, without additives, LaB6 cannot be obtained at 300°C. The LaB6 phase only begins to appear when the temperature is raised to 400-500°C, but its crystallinity remains very poor. Therefore, a suitable molten salt system can significantly reduce the phase formation temperature of the product. For example... Figure 2 As shown, the product obtained without molten salt exhibits extremely uneven size distribution and chaotic morphology. Therefore, a suitable molten salt system can improve product quality, resulting in products with regular morphology and uniform size.

[0155] The optimal product crystallinity was obtained when the LiI:KI ratio was around 6:4; other ratios resulted in lower product quality. Furthermore, introducing a trace amount of LiCl further lowered the melting point of the mixed molten salt and improved the controllability of the reaction. Therefore, the optimal ratio was LiI:KI = 6:4 (see details). Figure 21 Meanwhile, differential scanning calorimetry (DSC) results showed that, under optimal molten salt ratios, the mixed molten salt had the lowest melting point, around 280°C. This means that the reaction system can transition from a solid to a liquid state at temperatures as low as 280°C, and the faster mass transfer efficiency of the liquid phase reaction is more conducive to the effective progress of the reaction (e.g., Figure 22 ).

[0156] Under the same conditions, Comparative Example 7 replaced the additive with a chloride molten salt system, such as... Figure 23 As shown, high-crystallinity pure-phase LaB6 cannot be obtained in the chloride molten salt system, while the molten salt system in Example 1 can obtain high-quality pure-phase LaB6, illustrating the importance of additive selection in this invention.

[0157] Experimental Example 7

[0158] Test samples: the product obtained in Example 1 (diameter less than 20 nm) and bulk LaB6 (diameter greater than 100 nm);

[0159] like Figure 24 As shown, the rare earth boride nanocrystals prepared in Example 1 have a size of less than 20 nm and a uniform size distribution, allowing them to be well dispersed in solvents for processing and application. Furthermore, the nanoscale LaB6 exhibits localized surface plasmon resonance characteristics, showing significant absorption in the infrared region. In contrast, larger bulk LaB6 particles precipitate rapidly in solvents and exhibit weaker absorption in the infrared region.

[0160] like Figure 24 and Figure 25As shown, based on the unique localized surface plasmon resonance characteristics of rare-earth hexaborides, they can generate a thermal effect under photoexcitation, exhibiting photothermal properties. Compared with bulk LaB6 materials, the LaB6 nanocrystals prepared in Example 1 have stronger absorption of visible and near-infrared light, thus exhibiting superior photothermal properties. After 10 minutes of irradiation, the nanomaterials are nearly 20°C hotter than the bulk materials.

[0161] like Figure 26 and Figure 27 As shown, based on the unique localized surface plasmon resonance characteristics of rare-earth hexaborides, they can generate hot electrons under photoexcitation, which then react with water to produce free radicals, achieving dye degradation and antibacterial properties. Compared with bulk LaB6 materials, the LaB6 nanocrystals prepared in Example 1 exhibit superior degradation and antibacterial properties.

[0162] The rare-earth boride nanomaterials of this invention possess excellent dispersibility, photothermal properties, antibacterial properties, and dye degradation properties; they can be applied in the field of heat insulation coatings, as well as photocatalysis and solar water evaporation, including applications such as seawater desalination, treatment of bacterial wastewater, and treatment of high-salt dye wastewater. The atmospheric pressure low-temperature preparation method of this invention is simple, efficient, safe, and reliable, with good controllability and versatility, suitable for large-scale industrial production. The obtained samples exhibit excellent performance and can be used in catalysis, antibacterial applications, and seawater desalination.

[0163] Experimental Example 8

[0164] Test samples: the product obtained in Example 1 (diameter less than 20 nm) and bulk LaB6 (diameter greater than 100 nm).

[0165] The product obtained in Example 1 was dispersed at a concentration of 1 mg / mL in solvents such as chloroform, acetone, acetonitrile, N-N'-dimethylformamide, dimethyl sulfoxide, water, ethanol, and ethylene glycol, and allowed to stand for 30 min. Figure 29 As shown, the product obtained in Example 1 forms a homogeneous and stable dispersion in a solvent that is difficult to penetrate. The product obtained in Example 1 (diameter less than 20 nm) and bulk LaB6 (diameter greater than 100 nm) were both dispersed in water at a concentration of 1 mg / mL. Figure 30 As shown, after standing for 30 minutes, the dispersion of the product prepared in Example 1 showed no significant change, while the dispersion of bulk LaB6 completely settled. The above experimental results clearly demonstrate that the product prepared using this patented method has an ultra-small size. In the dispersion system, the interaction between product particles effectively counteracts gravity, thus exhibiting excellent dispersion performance in various solvents and successfully producing a uniform and stable dispersion. Compared to traditional bulk LaB6, this product possesses superior dispersibility and solution processability.

[0166] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0167] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing rare earth boride nanomaterials, characterized in that, The rare earth boride nanomaterial is in the phase state of REB6 or REB4, wherein RE is selected from one of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; its preparation method includes the following steps: S1: Weigh out the compound raw material containing RE element and the compound raw material containing B element respectively, with a molar ratio of 1:4-12, to obtain a mixed raw material; S2: Add additives to the mixed raw materials obtained in step S1, and grind them thoroughly to obtain mixture A; S3: The mixture A obtained in step S2 is reacted under an inert gas protection, the reaction temperature is controlled at 300-800℃ and the reaction time is 6h, to obtain mixture B; S4: After the reaction is complete, add excess methanol to the mixture B obtained in step S3. After no more bubbles emerge, centrifuge and separate the precipitate A. S5: Add dilute hydrochloric acid to precipitate A obtained in step S4 and soak for 12 hours. Centrifuge again to separate and retain precipitate B. S6: Wash the precipitate B obtained in step S5 with deionized water and dry it to obtain rare earth boride nanomaterials.

2. The method for preparing rare earth boride nanomaterials as described in claim 1, characterized in that, The compound raw materials containing RE elements in step S1 include anhydrous rare earth halides, and the compound raw materials containing B elements are alkali metal borohydrides.

3. The method for preparing rare earth boride nanomaterials as described in claim 1, characterized in that, The additive in step S2 is a mixture of LiI, LiCl and KI, with a molar ratio of LiI to KI of 20:80-80:20, and the amount of LiCl added is 1%-3% of the total amount of LiI and KI. The molar ratio of the additive to the mixed raw materials is 2:1 to 1:

2.

4. The method for preparing rare earth boride nanomaterials as described in claim 1, characterized in that, In step S3, the inert gas is nitrogen or argon, and the system pressure is one atmosphere.

5. The method for preparing rare earth boride nanomaterials as described in claim 1, characterized in that, The concentration of dilute hydrochloric acid in step S5 is 0.6 mol / L.

6. The method for preparing rare earth boride nanomaterials as described in claim 1, characterized in that, The centrifugation conditions in steps S4 and S5 are: 8000 rpm and 3-7 min.

7. The rare earth boride nanomaterial prepared by the method according to any one of claims 1-6, characterized in that, It is a monodisperse rare earth boride nanomaterial with a phase of REB6 or REB4, a color of black or dark brown, a morphology of nearly spherical or cubic, and a diameter of less than 20 nm.

8. The application of the rare earth boride nanomaterial as described in claim 7 in the fields of heat insulation coating, photocatalysis and solar water evaporation.

9. The application of a rare earth boride nanomaterial as described in claim 8, characterized in that, The solar-powered water evaporation includes seawater desalination, treatment of bacteria-containing wastewater, and treatment of high-salt dye wastewater.

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