A Eu 3+ Hierarchical ZnO nanostructures and their preparation methods

Abstract

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Description

Technical Field

[0001] This invention belongs to the technical field of LED phosphor and nanomaterial preparation, and specifically relates to a simple method for preparing Eu. 3+ A novel approach to hierarchical ZnO nanostructures. Background Technology

[0002] ZnO is an important semiconductor material with significant applications in electronics, optoelectronics, optics, and sensors. Its unique photoelectric properties, chemical stability, and biocompatibility make it a hot topic for research and application. By carefully introducing luminescent centers such as transition metal ions or rare earth metal ions, the emission characteristics of ZnO semiconductors can be precisely controlled, thereby optimizing for specific wavelength emission bands. This breakthrough adjustment is of great significance for realizing a wide range of applications, including multicolor emission in light-emitting devices, demonstrating broad research value and application potential. Among the many rare earth ions, Eu... 3+ Eu3+ has attracted widespread attention due to its strong red emission characteristics in the 610-620 nm range. However, doping Eu3+ into ZnO remains a significant challenge due to the large differences in ionic radius and charge.

[0003] Several synthetic methods, such as chemical bath deposition, hydrothermal synthesis, electrodeposition, combustion, and co-precipitation, have been reported to control particle size in the nanoscale range, and red-luminescent Eu has been developed. 3+ Doped ZnO nanomaterials exhibit unique nanostructures such as nanowires, nanoflowers, nanorods, nanopillars, nanoribbons, and elliptical shapes. The aforementioned deposition methods require prolonged heating, metal catalysts, and substrates, significantly increasing preparation costs. Furthermore, chemical methods for preparing Eu... 3+ Doping ZnO nanomaterials requires a long time, has low yield, and cannot effectively avoid the introduction of impurity elements. In addition, the synthesis of complex three-dimensional (3D) ZnO nanostructures, especially three-dimensional nanostructures composed of one-dimensional nanostructures, has attracted widespread attention.

[0004] Therefore, there is an urgent need to find a simple, low-cost process suitable for industrial production, capable of producing high-purity, high-yield, uniformly sized, controllably doped, monochromatic, and high-luminescence-intensity Eu. 3+ A novel method for producing ZnO-doped nanostructures. To address the aforementioned issues, this patented technology focuses on preparing Eu using a plasma arc method. 3+ Hierarchical nanostructures of doped ZnO. Summary of the Invention

[0005] The purpose of this invention is to provide a Eu 3+ The doped ZnO hierarchical nanostructure and its preparation method solve the problems in the preparation of Eu in existing technologies. 3+The present invention addresses the technical problems of low purity and high cost in doped ZnO hierarchical nanostructures. The preferred technical solutions among the various technical solutions provided by this invention offer numerous technical advantages, which are detailed below.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a Eu 3+ A hierarchical ZnO nanostructure is described, comprising nanoparticles and multiple nanoneedles radiating outwards from the nanoparticles. The overall diameter of the hierarchical nanostructure is 300–500 nm, and the length of the nanoneedles is 100–300 nm, with a diameter of 10–20 nm. This hierarchical structure exhibits strong red light emission and photocatalytic properties.

[0007] The present invention also provides an Eu 3+ A method for preparing ZnO-doped hierarchical nanostructures includes the following steps: mixing Zn powder and Eu2O3 powder in a certain proportion and pressing them into a mixed powder block; placing the block in a graphite pot and then placing it into the copper pot anode in the reaction chamber of a DC arc discharge device; placing a tungsten rod cathode perpendicularly to the copper pot anode; filling the reaction chamber with air and circulating cooling water through the copper pot; operating the discharge reaction; and collecting the grayish-yellow fluffy powder as Eu2O3 on the condensation wall. 3+ Hierarchical nanostructures of doped ZnO.

[0008] Furthermore, in the method, the molar ratio of Zn powder to Eu2O3 powder is 100:1 to 2.

[0009] Furthermore, the air pressure inside the reactor is 20–40 kPa.

[0010] Furthermore, in the method, the reaction voltage is 20-30V, the current is 60-80A, and the reaction time is 10-30 seconds.

[0011] Compared to existing technologies, the preferred embodiment of this invention provides Eu 3+ The preparation method for doped ZnO hierarchical nanostructures is simple, easy to operate, highly efficient, energy-saving, and environmentally friendly, producing no harmful gases during the process. Eu nanostructures prepared using this method... 3+ The uniform and high-purity hierarchical nanostructure of doped ZnO exhibits strong red light and photocatalytic properties, providing endless possibilities for micro-nano devices and optoelectronic devices. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. However, the scope of protection claimed by the present invention is not limited to the scope described in the embodiments.

[0013] Figure 1This is a schematic diagram of the reaction apparatus used in the method of the present invention;

[0014] Figure 2 Eu prepared in Example 1 of this invention 3+ SEM images of hierarchical nanostructures of doped ZnO;

[0015] Figure 3 Eu prepared in Example 1 of this invention 3+ SEM images of hierarchical nanostructures of doped ZnO;

[0016] Figure 4 Eu prepared in Example 1 of this invention 3+ XRD patterns of hierarchical ZnO nanostructures;

[0017] Figure 5 Eu prepared in Example 1 of this invention 3+ EDS energy dispersive spectroscopy of hierarchical ZnO nanostructures;

[0018] Figure 6 Eu prepared in Example 1 of this invention 3+ Excitation spectrum of a hierarchical ZnO nanostructure (emission at 611 nm);

[0019] Figure 7 Eu prepared in Example 1 of this invention 3+ Emission spectrum of a hierarchical ZnO nanostructure (excited at 467 nm);

[0020] Figure 8 Eu prepared in Example 1 of this invention 3+ UV-Vis absorption spectra of time-varying photocatalytic degradation of methyl orange using ZnO-doped hierarchical nanostructures

[0021] Figure 9 Eu prepared in Example 2 of this invention 3+ SEM images of hierarchical nanostructures of doped ZnO;

[0022] Figure 10 Eu prepared in Example 2 of this invention 3+ SEM images of hierarchical nanostructures of doped ZnO;

[0023] Figure 11 This is a SEM image of the undoped ZnO nanowires prepared in Example 3 of this invention;

[0024] Figure 12 This is the emission spectrum (at 325 nm excitation) of the undoped ZnO nanowires prepared in Example 3 of this invention;

[0025] Figure 13This is the UV-Vis absorption spectrum of the photocatalytic degradation of methyl orange by undoped ZnO nanowires prepared in Example 3 of this invention, as a function of time.

[0026] Figure 1 In the middle: 1. Reaction chamber; 2. Condensing wall; 3. Tungsten cathode; 4. Reaction raw materials; 5. Graphite crucible anode; 6. Copper base (including water inlet and water outlet); 7. Gas inlet; 8. Gas outlet; 9. Condensing wall water inlet; 10. Condensing wall water outlet. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] Figure 1 This is a schematic diagram of the DC arc system used in the method of the present invention.

[0029] like Figure 1 As shown, the reaction chamber 1 contains a condenser wall 2, a tungsten cathode 3, and a graphite crucible anode 5. The graphite crucible anode 5, facing the tungsten cathode 3, is filled with reaction material 4 (a uniform mixture of Zn powder and Eu2O3 powder, pressed using a tablet press). Both the graphite crucible anode 5 and the tungsten cathode 3 are connected to a DC power supply. To ensure rapid nanowire growth, circulating cooling water is introduced into both the graphite crucible anode 5 and the condenser wall 2. A cooling water inlet and outlet are located below the graphite crucible anode 5. Figure 1 The cooling water inlet 6 (which includes an inlet and an outlet) is located in the condenser wall 2, and the two ends of the condenser wall 2 are respectively provided with a condenser wall inlet 9 and a condenser wall outlet 10. After the reaction is completed, the product is collected on the condenser wall, and the collected product is Eu. 3+ Hierarchical nanostructures of doped ZnO.

[0030] The reaction chamber 1 is equipped with a condenser wall 2. Cooling water (which can be recycled) needs to be circulated through the graphite crucible anode 5 and the condenser wall 2 to reduce the temperature at the graphite crucible anode 5 and the condenser wall 2, so as to generate a large temperature gradient in the reaction chamber, which is conducive to the rapid growth of ZnO hierarchical nanostructures.

[0031] Example 1

[0032] This embodiment prepared Eu 3+ The material preparation process for the doped ZnO hierarchical nanostructure is as follows:

[0033] Metallic Zn powder and Eu2O3 powder were thoroughly mixed at a molar ratio of 100:1 and pressed into cylindrical ingots 4 with a height of 1-2 cm in a tableting mold. The ingots 4 were then placed in a graphite crucible 5 within the reaction chamber of a DC arc discharge device, with a tungsten cathode 3 fixed a certain distance above the reactant 4, ensuring that the tip of the tungsten cathode 3 did not contact the reactant 4. The reaction chamber 1 was evacuated and then filled with 20 kPa air as the reaction gas. A circulating water system was activated, and cooling water was introduced through the condenser wall 2 and the copper base 6. By adjusting the height of the copper base 6, the graphite crucible 5 was brought into contact with the tungsten cathode 3, causing an arc to ignite and discharge. During the discharge process, the voltage was maintained at 30V, the current at 60A, and the reaction time at 10s. A large amount of yellow, fluffy powder, representing Eu, was collected on the condenser wall. 3+ Hierarchical nanostructures of doped ZnO.

[0034] Figure 2 For Eu 3+ The overall SEM image of the ZnO hierarchical nanostructure shows that the entire sample is a nano-hierarchical structure, with each hierarchical nanounit having an overall diameter of 300-400 nm. Figure 3 The magnified SEM image of the sample shows that the individual hierarchical nanostructure consists of nanorods or nanoparticles in the middle, with multiple nanoneedles radiating outwards from the nanorods or nanoparticles. The nanoneedles are 100-200 nm in length and 10-20 nm in diameter.

[0035] Figure 4 The XRD pattern shows that the diffraction peaks correspond to the ZnO wurtzite structure, indicating that the sample has high purity and no impurities. Figure 5 The image shows the EDS spectrum of the sample. The atomic ratio of Zn, O, and Eu is 54.7:43.9:1.4, indicating that the ZnO hierarchical nanostructure contains Eu ions.

[0036] Figure 6 For Eu 3+ Excitation line spectrum of the ZnO hierarchical nanostructure under 611 nm emission peak detection. The 380 nm excitation peak in this spectrum is the excitation band of ZnO itself, and the absorption peaks at 394 nm, 404 nm, 467 nm, and 533 nm correspond to Eu. 3+ of 7 F0- 5 L6, 7 F0- 5 D3, 7 F0- 5 D2 and 7 F0- 5 D1 transition. Figure 7 For the Eu 3+ The photoluminescence (PL) spectrum of the ZnO-doped nanomaterial under 467 nm excitation. It can be seen that the Eu... 3+The doped ZnO luminescent material emits red light at 610 nm when excited at 467 nm. This sharp emission peak is due to Eu. 3+ of 5 D0- 7 The peaks at 592, 650, and 707 nm correspond to the F2 transition. Other peaks at these locations correspond to Eu, respectively. 3+ leap 5 D0- 7 F1, 5 D0- 7 F3 and 5 D0- 7 F4. From the hierarchical nanostructures of ZnO with Eu 3+ The characteristic emission peak also proves that Eu 3+ It is doped into the ZnO lattice.

[0037] The ultraviolet-visible absorption spectrum of a dye can directly reflect Eu 3+ Photocatalytic activity of ZnO hierarchical nanostructure. Weigh 50 mg of Eu... 3+ A hierarchical ZnO-doped nanostructure was added to 50 mL of a 15 mg / L methyl orange aqueous solution. The photoresponse of methyl orange to Eu under visible light irradiation was simulated. 3+ The photocatalytic performance of the ZnO-doped hierarchical nanostructure was studied, and the results are as follows: Figure 8 As shown, the mass concentration of the methyl orange solution gradually decreased with increasing illumination time. When the photocatalytic degradation time was 25 min, the methyl orange in the solution was basically completely degraded by photocatalysis. This indicates that the prepared Eu... 3+ The hierarchical ZnO-doped nanostructures exhibit good photocatalytic activity for methyl orange.

[0038] Example 2

[0039] This embodiment prepared Eu 3+ The material preparation process for the doped ZnO hierarchical nanostructure is as follows:

[0040] Metallic Zn powder and Eu2O3 powder were thoroughly mixed at a molar ratio of 100:2 and pressed into cylindrical ingots 4 with a height of 1-2 cm in a tableting mold. The ingots 4 were then placed in a graphite crucible 5 within the reaction chamber of a DC arc discharge device, with a tungsten cathode 3 fixed at a certain distance above the reactant 4, ensuring that the tip of the tungsten cathode 3 did not contact the reactant 4. The reaction chamber 1 was evacuated and then filled with 40 kPa air as the reaction gas. A circulating water system was activated, and cooling water was introduced through the condenser wall 2 and the copper base 6. By adjusting the height of the copper base 6, the graphite crucible 5 was brought into contact with the tungsten cathode 3, causing an arc to ignite and discharge. During the discharge process, the voltage was maintained at 20V, the current at 80A, and the reaction time at approximately 30 seconds. A large amount of yellow, fluffy powder collected on the condenser wall was identified as a hierarchical nanostructure of Eu3+-doped ZnO.

[0041] Figure 9 The image shows the overall SEM image of the prepared sample, which reveals that its morphology is a uniformly sized hierarchical nanostructure, with each hierarchical nanounit having a diameter of 400-500 nm. Figure 10 The magnified SEM image of the sample shows that each nanounit has a nanoparticle in the middle, and multiple nanoneedles grow on the nanoparticle. The nanoneedles are 200-300 nm in length and 10-20 nm in diameter.

[0042] Example 3

[0043] In this embodiment, undoped ZnO nanowires were prepared. The material preparation process is as follows:

[0044] Metallic Zn powder is pressed into cylindrical ingots 4, 1-2 cm high, using a tableting mold. The ingots 4 are then placed in a graphite crucible 5 within the reaction chamber of a DC arc discharge device. A tungsten cathode 3 is fixed at a certain distance above the reactant material 4, ensuring the tip of the cathode 3 does not contact the reactant material 4. The reaction chamber 1 is evacuated and then filled with 20 kPa air as the reaction gas. A circulating water system is activated, and cooling water is introduced through the condenser wall 2 and the copper base 6. By adjusting the height of the copper base 6, the graphite crucible 5 contacts the tungsten cathode 3, momentarily creating an arc for discharge. During the discharge, the voltage is maintained at 10-12 V, the current at 70 A, and the reaction time is approximately 30 seconds. ZnO wire is collected in the anode graphite crucible.

[0045] Figure 11 The image shows an SEM image of undoped ZnO nanowires, which are approximately 1-5 μm long and 80-120 nm in diameter. Figure 12The image shows the PL spectrum of ZnO nanowires under 325 nm excitation. There is a strong emission peak at 384 nm, corresponding to the band gap of ZnO. There is a relatively broad green emission peak at 506 nm, which is attributed to the radial recombination of photogenerated holes and single-ionized oxygen vacancy electrons, as well as the combined effects of oxygen gaps and various defects. Figure 13 The UV-Vis absorption spectrum shows the time-dependent photocatalytic degradation of ZnO nanowires. As the irradiation time increases, the mass concentration of the methyl orange solution gradually decreases. When the photocatalytic degradation time is 60 min, the methyl orange in the solution has not yet been completely photocatalytically degraded. This indicates that the Eu in Example 1... 3+ The photocatalytic activity of doped ZnO hierarchical nanostructures is significantly improved compared to undoped ZnO nanowires.

[0046] The above examples demonstrate that Eu 3+ Doping is key to the fabrication of hierarchical ZnO nanostructures. The large ionic radius of Eu3+ ions incorporated into ZnO generates numerous zinc vacancy defects. These defects facilitate the secondary nucleation of nanoneedles, leading to the formation of multi-ZnO hierarchical nanostructures. 3+ Doping into ZnO not only alters the luminescence properties of ZnO, but also changes the nanomorphology of the prepared ZnO. The new hierarchical nanostructure has a higher specific surface area, which significantly enhances the photocatalytic performance.

[0047] The above description is merely a specific embodiment of the present invention, used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the invention without departing from the scope of the technical solution of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A Eu 3+ The doped ZnO hierarchical nanostructure is characterized by, The hierarchical nanostructure consists of nanoparticles and multiple nanoneedles radiating outward from the nanoparticles. The overall diameter of the hierarchical nanostructure is 300-500 nm, and the length of the nanoneedles is 100-300 nm, with a diameter of 10-20 nm. The preparation method of the hierarchical nanostructure includes the following steps: mixing Zn powder and Eu2O3 powder in a certain proportion and pressing them into a mixed powder block; placing the block in a graphite pot and then placing it in the copper pot anode of the reaction chamber of a DC arc discharge device; placing the tungsten rod cathode perpendicularly to the copper pot anode; filling the reaction chamber with air and circulating cooling water through the copper pot; operating the discharge reaction; and collecting the grayish-yellow fluffy powder, Eu2O3, on the condensation wall. 3+ Hierarchical nanostructures of doped ZnO.

2. A Eu 3+ The method for preparing doped ZnO hierarchical nanostructures is characterized by, The hierarchical nanostructure consists of nanoparticles and multiple nanoneedles radiating outward from the nanoparticles. The preparation method includes the following steps: mixing Zn powder and Eu2O3 powder in a specific ratio and pressing them into a mixed powder block; placing the block in a graphite pot, which is then placed in the copper pot anode within the reaction chamber of a DC arc discharge device; placing the tungsten rod cathode perpendicularly to the copper pot anode; filling the reaction chamber with air and circulating cooling water through the copper pot; operating the discharge reaction; and collecting the grayish-yellow fluffy powder (Eu2O3) on the condensation wall. 3+ Hierarchical nanostructures of doped ZnO.

3. The Eu according to claim 2 3+ The method for preparing doped ZnO hierarchical nanostructures is characterized by, In the method described, the molar ratio of Zn powder to Eu2O3 powder is 100:1~2.

4. The Eu according to claim 2 3+ The method for preparing doped ZnO hierarchical nanostructures is characterized by, The air pressure in the reaction chamber is 20~40 kPa.

5. The Eu according to claim 2 3+ The method for preparing doped ZnO hierarchical nanostructures is characterized by, The reaction voltage in the method is 20~30 V, the current is 60~80 A, and the reaction time is 10~30 seconds.

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