Preparation method of silicon oxide coated praseodymium doped lanthanum fluoride yolk-shell structure nanospheres

Abstract

The present application relates to a kind of preparation method of silicon oxide package praseodymium lanthanum fluoride yolk-shell structure nanosphere, belong to nanometer material preparation technical field.The present application includes three steps:(1) preparation of electrospray solution;(2) using single-axis electrospray ionization technology to prepare PVP / [La (NO3) 3+Pr (NO3) 3+TEOS] Composite nanosphere;(3) preparation of LaF3:Pr 3+ @SiO2 Yolk-shell structure nanosphere, using ammonium hydrogen fluoride as fluorination reagent, activated carbon particle is auxiliary reducing agent, using double crucible fluorination technology, composite nanosphere is heated fluorination treatment in air, obtain LaF3:Pr 3+ @SiO2 Yolk-shell structure nanosphere, average diameter is 794.08±4.89 nm.The preparation method of the present application is simple and easy to operate, and can be mass-produced, and the nanometer material with this special structure has broad application prospect.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation research, specifically to a method for preparing silicon oxide-doped praseodymium lanthanum fluoride yolk-shell structured nanospheres. Background Technology

[0002] The preparation, structure, properties, and applications of egg yolk-shell structured nanospheres have attracted significant attention and have become a frontier and hot topic in materials science, condensed matter physics, and chemistry. Egg yolk-shell structured nanospheres are artificially synthesized nanospheres where the yolk is contained within a shell, with a certain gap between the yolk and the shell. Typically, the yolk and shell are composed of different materials. These unique morphologies and structures, unlike ordinary hollow spheres and nanospheres, possess unique optical, electrical, and magnetic properties and applications, thus drawing considerable interest.

[0003] Lanthanum trifluoride (LaF3) is widely used as a raw material for the preparation of metallic lanthanum, as a non-ferrous metal additive, in solid electrolytes, gas sensors, humidity sensors, rare-earth ion luminescent substrates, lubricants, rare-earth laser crystals, fluoride glasses, optical fibers, and rare-earth infrared glasses. Silicon dioxide (SiO2) has a wide range of applications, primarily in the manufacture of glass, water glass, ceramics, enamel, refractory materials, aerogel felt, ferrosilicon, molding sand, elemental silicon, and cement. Rare earth praseodymium (Pr) 3+ The ion possesses multiple 4f energy levels, and in different matrices, it predominantly emits blue-green or red light. Only by using a suitable matrix can the emission intensity ratio of blue-green and red light be controlled, thereby achieving white light emission. If praseodymium-doped lanthanum trifluoride (LaF3:Pr) exhibits white light emission... 3+ The nanospheres, acting as egg yolks, are coated with silica (SiO2) as a shell, with gaps between them. This allows for the formation of silica-coated lanthanum trifluoride-doped egg yolk-shell structured nanospheres, labeled LaF3:Pr 3 + @SiO2 yolk-shell structured nanospheres, the material preceding @ is the core layer LaF3:Pr 3+ The substance following the @ symbol is a shell of SiO2, meaning that the @ symbol indicates that the following substance, SiO2, encapsulates the preceding substance, LaF3:Pr. 3+ Due to its unique zero-dimensional nanostructure, this material has broad application prospects. Currently, no white light emitting LaF3:Pr has been observed. 3+ Related reports on SiO2 egg yolk-shell structured nanospheres.

[0004] Electrospray ionization technology is an effective method for preparing nanoparticles. This method involves ejecting a charged polymer electrospray solution into a mist through a nozzle under electrostatic attraction in an electrostatic field. The mist is then projected onto a receiving screen, where the solvent evaporates at room temperature to obtain nanospheres or particles. If the polymer electrospray solution contains metal nitrates or acetates, the resulting inorganic-organic composite nanospheres can be heat-treated to remove the polymer template agent and decompose the metal nitrates or acetates, yielding inorganic oxide nanospheres. Therefore, this uniaxial electrospray ionization technology can prepare various polymer and inorganic oxide nanospheres. By improving the nozzle structure and electrospray device, using a two-layer coaxial nozzle and two polymer electrospray solutions, and by adjusting the electrospray parameters, core-shell structured nanospheres can be prepared using this two-layer coaxial electrospray ionization technology. Further, a three-layer coaxial nozzle and three polymer electrospray solutions were used. By adjusting the electrospray parameters, this three-layer coaxial electrospray ionization technique can prepare three-layer concentric nanospheres. The middle layer can then be removed by solvent etching, solvent extraction, or high-temperature calcination to obtain yolk-shell structured nanospheres. However, this method is complex, requires controlling many parameters, and the product morphology is difficult to control. This invention combines a simple uniaxial electrospray ionization technique with a dual-crucible fluorination technique, which conveniently and successfully prepares novel white light-emitting LaF3:Pr nanospheres directly. 3+ @SiO2 yolk-shell structured nanospheres avoid the complex three-layer coaxial electrospray ionization process, and no related reports have been found to date.

[0005] When preparing nanomaterials using electro-injection ionization technology, the nozzle structure, the type of raw material, the molecular weight of the polymer template agent, the composition of the electro-injection solution, the electro-injection process parameters, the heat treatment process, and the environmental atmosphere during heat treatment all have a significant impact on the morphology, structure, size, and composition of the final product. This invention first employs uniaxial electro-injection ionization technology to prepare praseodymium oxide (Pr6O). 11 After dissolving in nitric acid and evaporating, praseodymium nitrate (Pr(NO3)3·6H2O) is obtained. La(NO3)3·6H2O and solvent are then added. N,N Dimethylformamide (DMF) was used to obtain a solution. Polyvinylpyrrolidone (PVP), a polymeric template agent, was dissolved in dichloromethane (CH2Cl2) to obtain another solution. The two solutions were mixed, and tetraethyl orthosilicate (TEOS) was added to obtain an electrospraying solution. Controlling the viscosity of the electrospraying solution was crucial. Under optimal experimental conditions, PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres were prepared by electrospraying. Ammonium hydrogen fluoride (NH4HF2) was used as the fluorinating agent, and activated carbon particles were used as the auxiliary reducing agent. The nanospheres were then subjected to heating fluorination in air to directly obtain novel white light-emitting LaF3:Pr... 3+@SiO2 egg yolk-shell structured nanospheres. Summary of the Invention

[0006] In the background technology, nanospheres were prepared using uniaxial electrospray ionization, core-shell structured nanospheres were prepared using two-layer coaxial electrospray ionization, and yolk-shell structured nanospheres were prepared using three-layer coaxial electrospray ionization. The methods, raw materials, template agents, and solvents used differ from those of this invention. To provide a simple and convenient preparation technique for yolk-shell structured nanospheres in the fields of zero-dimensional nanomaterials and rare-earth luminescence, we combined uniaxial electrospray ionization with a double-crucible fluorination technique, and invented a white-light emitting LaF3:Pr 3+ A novel method for preparing SiO2 egg yolk-shell structured nanospheres.

[0007] This invention is achieved as follows: First, an electrospray solution with a certain viscosity is prepared. Then, uniaxial electrospray ionization technology is used for electrospraying. Under optimal experimental conditions, PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres are prepared. Using ammonium hydrogen fluoride (NH4HF2) as the fluorinating agent and activated carbon particles as the auxiliary reducing agent, fluorination is performed in air by heating, directly yielding novel white light-emitting LaF3:Pr... 3+ @SiO2 egg yolk-shell structured nanospheres. The steps are as follows:

[0008] (1) Preparation of electro-spray solution

[0009] The lanthanum source used was lanthanum nitrate hexahydrate La(NO3)3·6H2O, and the praseodymium source was Pr6O. 11 The silicon source used is tetraethyl orthosilicate (TEOS), and the polymeric template agent is polyvinylpyrrolidone (PVP) with a molecular weight of 58,000. N,N Using dimethylformamide (DMF) and dichloromethane (CH2Cl2) as solvents, weigh out 0.0047 g of Pr6O 11 Dissolved in 8 mL of concentrated nitric acid, excess nitric acid was evaporated at 120 °C to obtain Pr(NO3)3·6H2O. After cooling to room temperature, 1.1879 g of La(NO3)3·6H2O and 5.5000 g of DMF were added and stirred thoroughly for 30 minutes to obtain solution 1. 0.8000 g of PVP was dissolved in 4.4000 g of CH2Cl2 and stirred for 30 minutes to obtain solution 2. Solution 1 and solution 2 were mixed, and 0.5000 g of TEOS was added. After magnetic stirring for 10 hours, an electrospray solution was obtained.

[0010] (2) Preparation of PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres

[0011] Using uniaxial electro-injection ionization technology, the electro-injection solution was injected into a 10 mL syringe with a No. 7 stainless steel syringe needle. A copper wire was inserted into the electro-injection solution and connected to the positive terminal of a high-voltage DC power supply. The stainless steel syringe needle was at a 30º angle to the horizontal plane. An aluminum foil at a 60º angle to the horizontal plane was used as a receiving device and grounded. The needle was kept perpendicular to the aluminum foil and 13 cm away. Another copper wire was used to connect the aluminum foil to the zero potential terminal of the high-voltage DC power supply. The electro-injection voltage was 15 kV, the indoor temperature was 20-25 °C, and the relative humidity was 20%-50%. Electro-injection was performed, and as the solvent evaporated, PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres were obtained on the aluminum foil.

[0012] (3) Preparation of LaF3:Pr 3+ @SiO2 egg yolk-shell structured nanospheres

[0013] Using NH4HF2 as the fluorine source and activated carbon particles as the auxiliary reducing agent, a double-crucible fluorination technique was employed. 0.1 g of PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres were placed in a 10 mL crucible, and 0.5 g of NH4HF2 was placed at the bottom of a 30 mL crucible. 10 g of activated carbon particles were then placed on top. The 10 mL crucible was then placed in the middle of the 30 mL crucible. After covering the 30 mL crucible, both crucibles were placed in a high-temperature furnace. The temperature was increased to 700 °C at a rate of 2 °C / min and held for 4 h. The temperature was then decreased to 200 °C at a rate of 2 °C / min, and finally allowed to cool naturally to room temperature with the furnace to obtain LaF3:Pr 3+ @SiO2 egg yolk-shell structured nanospheres, with an average diameter of 794.08±4.89 nm, egg yolk spheres LaF3:Pr 3+ The average diameter is 416.36 ± 2.89 nm.

[0014] The LaF3:Pr mentioned in the above process 3+ The SiO2 yolk-shell structured nanospheres exhibit good crystallinity and emit white fluorescence under blue light excitation at a wavelength of 442 nm. The average diameter of the yolk-shell structured nanospheres is 794.08 ± 4.89 nm. The yolk-shell nanospheres are made of LaF3:Pr 3+ The average diameter is 416.36±2.89 nm, achieving the purpose of the invention. Attached Figure Description

[0015] Figure 1 This is a SEM image of PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres;

[0016] Figure 2 This is a histogram of the diameter distribution of PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres;

[0017] Figure 3 It is LaF3:Pr 3+ XRD pattern of SiO2 egg yolk-shell structured nanospheres;

[0018] Figure 4 It is LaF3:Pr 3+ SEM image of SiO2 egg yolk-shell structured nanospheres, which also serves as an appendix to the abstract;

[0019] Figure 5 It is LaF3:Pr 3+ Histogram of diameter distribution of SiO2 egg yolk-shell structured nanospheres;

[0020] Figure 6 It is LaF3:Pr 3+ Histogram of diameter distribution of yolk spheres in SiO2 yolk-shell structured nanospheres;

[0021] Figure 7 It is LaF3:Pr 3+ Excitation spectrum of SiO2 egg yolk-shell structured nanospheres;

[0022] Figure 8 It is LaF3:Pr 3+ Emission spectrum of SiO2 egg yolk-shell structured nanospheres;

[0023] Figure 9 It is LaF3:Pr 3+ CIE color coordinate diagram of SiO2 egg yolk-shell structured nanospheres. Detailed Implementation

[0024] The praseodymium oxide Pr6O selected in this invention 11 The purity of La(NO3)3·6H2O is 99.99%, and the molecular weight of polyvinylpyrrolidone (PVP) is 58000. N,N Dimethylformamide (DMF), dichloromethane (CH2Cl2), activated carbon granules, tetraethyl orthosilicate, ammonium hydrogen fluoride (NH4HF2), and nitric acid (HNO3) were all commercially available analytical grade products; the glassware, crucibles, and equipment used were commonly used laboratory instruments and equipment.

[0025] Example: Weigh 0.0047 g Pr6O 11Pr(NO3)3·6H2O was obtained by dissolving Pr(NO3)3 in 8 mL of concentrated nitric acid and evaporating the excess nitric acid at 120 °C. After cooling to room temperature, 1.1879 g of La(NO3)3·6H2O and 5.5000 g of DMF were added and stirred thoroughly for 30 minutes to obtain solution 1. 0.8000 g of PVP was dissolved in 4.4000 g of CH2Cl2 and stirred for 30 minutes to obtain solution 2. Solutions 1 and 2 were mixed, and 0.5000 g of TEOS was added. After magnetic stirring for 10 hours, an electro-injected solution was obtained. Using uniaxial electro-injection ionization technology, the electro-injected solution was injected into a 10 mL syringe with a No. 7 stainless steel syringe needle. A copper wire was inserted into the electro-injected solution and connected to the positive terminal of a high-voltage DC power supply. The stainless steel syringe needle was at a 30° angle to the horizontal plane. An aluminum foil at a 60° angle to the horizontal plane was used as a receiving device and grounded. The needle was kept perpendicular to the aluminum foil at a distance of 13°. cm, connect the aluminum foil to the zero potential terminal of the high-voltage DC power supply using another copper wire. The electrospray voltage is 15 kV, the indoor temperature is 20-25 °C, and the relative humidity is 20%-50%. Electrospraying is performed, and as the solvent evaporates, PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres can be obtained on the aluminum foil. Using NH4HF2 as the fluorine source and activated carbon particles as the auxiliary reducing agent, a double crucible fluorination technique is adopted. 0.1 g of PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres are placed in a 10 mL crucible, and 0.5 g of NH4HF2 is placed at the bottom of a 30 mL crucible. 10 g of activated carbon particles are then placed on top. The 10 mL crucible is then placed in the middle of the 30 mL crucible. After covering the large crucible, both crucibles are placed in a high-temperature furnace and heated to 700 °C at a heating rate of 2 °C / min. The furnace was heated to 200 °C and held at that temperature for 4 hours, then cooled to 200 °C at a rate of 2 °C / min, and then allowed to cool naturally to room temperature to obtain LaF3:Pr. 3+ @SiO2 egg yolk-shell structured nanospheres. The described PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres exhibit good spherical morphology, see... Figure 1 As shown, the PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres exhibit a uniform diameter distribution. The Shapiro-Wilk method was used to verify the normality of the diameter distribution; at a 95% confidence level, the diameter distribution is normally distributed, with an average diameter of 1017.82 ± 0.66 nm. Figure 2 As shown; LaF3:Pr 3+The SiO2 yolk-shell structured nanospheres exhibit good crystallinity. The d-values ​​and relative intensities of their diffraction peaks are consistent with those listed in the LaF3 PDF standard card (70-0001), indicating a hexagonal crystal system. This suggests that the crystalline material LaF3:Pr... 3+ Belonging to the hexagonal crystal system, the amount of amorphous SiO2 was very small and no diffraction peaks were detected. Figure 3 As shown; LaF3:Pr 3 + The SiO2 yolk-shell structured nanospheres exhibit a distinct yolk-shell structure, with clear gaps between the yolk and shell. Figure 4 As shown; LaF3:Pr 3+ The SiO2 yolk-shell structured nanospheres exhibit a uniform diameter distribution. The Shapiro-Wilk method was used to verify the normal distribution of the diameters; at a 95% confidence level, the diameter distribution is considered to be normally distributed, with an average diameter of 794.08 ± 4.89 nm. (See attached image.) Figure 5 As shown; LaF3:Pr 3+ The diameter distribution of the yolk-shell structured nanospheres in the SiO2 nanospheres is uniform. The Shapiro-Wilk method was used to verify the normal distribution of the diameters. At a 95% confidence level, the diameter distribution is normally distributed, with an average diameter of 416.36 ± 2.89 nm. (See attached image.) Figure 6 As shown; using 486 nm as the monitoring wavelength, LaF3:Pr 3+ The SiO2 yolk-shell structured nanospheres exhibit a weak, broad excitation peak at 377 nm and a narrow, strong excitation peak at 442 nm. (See...) Figure 7 As shown; using 442nm as the excitation wavelength, LaF3:Pr 3+ The SiO2 yolk-shell structured nanospheres exhibit emission peaks at 486 nm, 537 nm, and 601 nm, which correspond to Pr 3+ of 3 P0→ 3 H4 3 P0→ 3 H5 3 P0→ 3 The H6 level transition, with the emission peak at 610 nm originating from Pr 3 + Ionic 1 D2→ 3 The H4 level transition, with emission peaks at 468 nm, 521 nm, and 580 nm, originates from Pr, respectively. 3+ Ionic 3 P1 to 3 H4 3 H5 and 3 The energy level transition of H6, see Figure 8 As shown; under blue light excitation at a wavelength of 442 nm, LaF3:Pr 3+ The SiO2 yolk-shell structured nanospheres emitted white fluorescence, with color coordinates x and y of 0.3329 and 0.3367, respectively. (See attached image.) Figure 9 As shown.

[0026] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method for preparing a silicon oxide coated Pr-doped LaF3 yolk-shell structure nanosphere, characterized in that, This invention combines uniaxial electro-injection ionization technology with dual-crucible fluorination technology, using polyvinylpyrrolidone (PVP) as a polymeric template agent. N,N Using dimethylformamide (DMF) and dichloromethane (CH2Cl2) as solvents, ammonium hydrogen fluoride (NH4HF2) as the fluorinating agent, and activated carbon particles as an auxiliary reducing agent, the prepared product is LaF3:Pr. 3+ The steps for making SiO2 yolk-shell structured nanospheres are as follows: (1) Preparation of electro-spray solution The lanthanum source used was lanthanum nitrate hexahydrate La(NO3)3·6H2O, and the praseodymium source was Pr6O. 11 The silicon source used is tetraethyl orthosilicate (TEOS), and the polymeric template agent is polyvinylpyrrolidone (PVP). N,N Using dimethylformamide (DMF) and dichloromethane (CH2Cl2) as solvents, weigh out 0.0047 g of Pr6O 11 Dissolved in 8 mL of concentrated nitric acid, excess nitric acid was evaporated at 120 °C to obtain Pr(NO3)3·6H2O. After cooling to room temperature, 1.1879 g of La(NO3)3·6H2O and 5.5000 g of DMF were added and stirred thoroughly for 30 minutes to obtain solution 1. 0.8000 g of PVP was dissolved in 4.4000 g of CH2Cl2 and stirred for 30 minutes to obtain solution 2. Solution 1 and solution 2 were mixed, and 0.5000 g of TEOS was added. After magnetic stirring for 10 hours, an electrospray solution was obtained. (2) Preparation of PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres Using uniaxial electro-injection ionization technology, the electro-injection solution was injected into a 10 mL syringe with a No. 7 stainless steel syringe needle. A copper wire was inserted into the electro-injection solution and connected to the positive terminal of a high-voltage DC power supply. The stainless steel syringe needle was at a 30º angle to the horizontal plane. An aluminum foil at a 60º angle to the horizontal plane was used as a receiving device and grounded. The needle was kept perpendicular to the aluminum foil and 13 cm away. Another copper wire was used to connect the aluminum foil to the zero potential terminal of the high-voltage DC power supply. The electro-injection voltage was 15 kV, the indoor temperature was 20-25 °C, and the relative humidity was 20%-50%. Electro-injection was performed, and as the solvent evaporated, PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres were obtained on the aluminum foil. (3) Preparation of LaF3:Pr 3+ @SiO2 yolk-shell nanospheres Using NH4HF2 as the fluorine source and activated carbon particles as the auxiliary reducing agent, a double-crucible fluorination technique was employed. 0.1 g of PVP / [La(NO3)3+Pr(NO3)3+TEOS] composite nanospheres were placed in a 10 mL crucible, and 0.5 g of NH4HF2 was placed at the bottom of a 30 mL crucible. 10 g of activated carbon particles were then placed on top. The 10 mL crucible was then placed in the middle of the 30 mL crucible. After covering the 30 mL crucible, both crucibles were placed in a high-temperature furnace. The temperature was increased to 700 °C at a rate of 2 °C / min and held for 4 h. The temperature was then decreased to 200 °C at a rate of 2 °C / min, and finally allowed to cool naturally to room temperature with the furnace to obtain LaF3:Pr 3+ The SiO2 yolk-shell structured nanospheres exhibit good crystallinity, belonging to the hexagonal crystal system, with an average diameter of 794.08±4.89 nm. The yolk-shell nanospheres are made of LaF3:Pr. 3+ The average diameter is 416.36±2.89 nm, and it emits white fluorescence when excited by blue light at a wavelength of 442 nm.

2. The method for preparing the silicon oxide coated Pr-doped LaF3 yolk-shell structure nanospheres according to claim 1, characterized in that, The polymeric template agent is polyvinylpyrrolidone with a molecular weight of Mr=58000.

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