Hollow PtAgS nanocrystalline material as well as preparation method and application thereof

Abstract

The invention provides a hollow PtAgS nanocrystalline material as well as a preparation method and application thereof, and belongs to the technical field of synthesis of nano materials. A simple two-step hydrothermal method is adopted, firstly, a gel precursor is synthesized to serve as a self-sacrifice template, then a platinum source, a silver source, a sulfur source and the template are subjected to a hydrothermal reaction together, and the hollow PtAgS nanocrystal is obtained. According to the preparation method disclosed by the invention, platinum and silver atoms are induced to diffuse outwards from a sulfur-containing core by utilizing twin crystal defects formed in the initial stage of reaction, so that a hollow structure is formed; the process is simple and efficient, the product is pure, the structure is uniform and controllable, and the prepared hollow PtAgS nanocrystal is a ternary alloy nanocrystal with a uniform hollow structure, has twin crystal defects, shows excellent soft magnetic properties including high saturation magnetization and low coercive force, is particularly suitable for high-frequency and low-loss magnetic devices, and has wide application prospects. Such as miniaturized electronic components and magnetic sensors, and has a wide industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial synthesis technology, specifically relating to a hollow PtAgS nanocrystalline material, its preparation method, and its application. Background Technology

[0002] Recent significant advancements in nanoscience and nanotechnology have demonstrated that the properties and performance enhancement of nanocrystals are closely related to their morphological characteristics. Precise control of the shape of nanocrystals can significantly optimize their application performance in catalysis, magnetism, photonics, electronic devices, sensing, and energy storage. Among numerous metallic materials, platinum (Pt), as a typical noble metal, exhibits unique physicochemical properties due to its face-centered cubic structure and ability to form various nanostructures, including zero-dimensional, one-dimensional, two-dimensional, and three-dimensional structures. Currently, various morphologies of platinum-based nanocrystals, such as nanowires, nanosheets, nanospheres, nanoribbons, and nanorods, have been successfully synthesized, achieving structure-controllable synthetic pathways. Hollow-structured nanomaterials, such as core-shell nanoparticles, possess advantages such as high specific surface area, abundant surface active sites, low density, and excellent permeability, showing broad application prospects in catalysis, biomedicine, energy conversion, and storage, and have become one of the current research hotspots.

[0003] Currently, methods for synthesizing hollow nanostructures mainly include template methods, Kirkendall effect, Ostwald ripening, substitution reactions, oxidative etching, and template-free synthesis. However, the synthesis of hollow nanocrystals in alloy systems still faces many challenges, such as cumbersome synthesis steps, unclear reaction mechanisms, low alloying degree, poor structural uniformity, and low yield. Especially for platinum-based alloy hollow structures, existing methods are typically time-consuming and complex, limiting their widespread application. Although studies have reported excellent electrocatalytic and magnetic properties of hollow nanoparticles such as PtNi, Fe-Pt, and Pt-Ag, a highly efficient, controllable synthesis strategy suitable for noble metal alloy systems is still lacking.

[0004] Therefore, developing a simple, economical synthesis method that can precisely control the morphology of hollow structures is of great significance for promoting the application of noble metal-based nanomaterials in catalysis and functional devices. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a hollow PtAgS nanocrystalline material, its preparation method, and its applications, to solve problems such as poor controllability of morphology and structure and insufficient magnetic properties of Pt-Ag-based materials. The nanocrystalline material of this invention is prepared by a two-step hydrothermal method, using twin defects to induce hollowing, resulting in a uniform hollow nanostructure. Its saturation magnetization (Ms) and remanent magnetization (Mr) are significantly higher than those of solid PtAgSCu nanocrystals, increasing by nearly an order of magnitude, exhibiting excellent soft magnetic properties. Furthermore, the preparation method of this invention employs a self-sacrificing template strategy, integrating template synthesis, shell deposition, and template removal into a continuous reaction. The process is simple, efficient, and produces high-purity products. Moreover, the uniformity and controllability of the structure can be achieved by adjusting the reaction parameters. This hollow PtAgS nanocrystalline material is particularly suitable for high-frequency, low-loss miniaturized electronic devices and magnetic sensors, and has broad industrial application prospects.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing hollow PtAgS nanocrystalline material includes the following steps: Step (1) Synthesis of gel precursor: Tris(hydroxymethyl)aminomethane, polyvinylpyrrolidone and formaldehyde solution are mixed to obtain a mixture; then the mixture is subjected to hydrothermal reaction and centrifuged to obtain gel precursor; Step (2) Synthesis of hollow PtAgS nanocrystals: Platinum diacetylacetonate, silver nitrate, sulfur powder and formamide solution are mixed to obtain a mixture; then the mixture is mixed with the gel precursor obtained in step (1) and a hydrothermal synthesis reaction is carried out to obtain the hollow PtAgS nanocrystals.

[0007] Preferably, in step (1), the ratio of tris(hydroxymethyl)aminomethane, polyvinylpyrrolidone and formaldehyde solution is 20~80:100~300:1~4.

[0008] Preferably, the heating temperature in step (1) is 150~220℃ and the time is 2~6h.

[0009] Preferably, in step (2), the ratio of the amount of platinum diacetylacetonate, silver nitrate, sulfur powder and formamide solution is 0.005~0.03:0.005~0.03:0.005~0.03:1~4.

[0010] Preferably, the ratio of the amount of the gel precursor to the amount of the mixture in step (2) is 1~4 mL: 1~4 mL.

[0011] Preferably, the temperature of the hydrothermal synthesis reaction in step (2) is 100~180℃ and the time is 5min~6h.

[0012] Preferably, after the hydrothermal synthesis reaction is completed, a centrifugal washing step is further included, wherein the number of centrifugal washing steps is 1 to 5, and the washing reagent is acetone solution.

[0013] The present invention also provides a hollow PtAgS nanocrystalline material, wherein the hollow PtAgS nanocrystalline material is a ternary alloy nanocrystalline material with a uniform hollow structure, and its composition is platinum, silver and sulfur.

[0014] Preferably, the hollow structure consists of an inner cavity and an outer shell, and the diameter of the cavity accounts for 60% to 80% of the overall size of the nanocrystal.

[0015] The present invention further provides the application of the hollow PtAgS nanocrystalline material in the preparation of magnetic devices, characterized in that the magnetic devices include high-frequency electronic devices or magnetic sensor devices; the hollow PtAgS nanocrystalline material exhibits soft magnetic properties, with high saturation magnetization and low coercivity.

[0016] The present invention has the following beneficial technical effects: (1) The preparation process of the present invention is simple and efficient, and the product has high purity: the traditional soft / hard template method is usually complicated and time-consuming, and the template is difficult to remove completely, which can easily lead to product contamination. The present invention adopts the self-sacrificing template method, which integrates the template synthesis, shell deposition and template removal processes into two consecutive reaction steps. The template decomposes in situ during the reaction process, without the need for an additional etching step, which not only simplifies the process flow, but also effectively ensures the integrity and chemical purity of the hollow shell structure. (2) The structure of this invention is uniform and controllable, with excellent reproducibility: By precisely controlling the composition of the precursor and the reaction parameters, a gel template with a regular structure and uniform size can be prepared, thereby guiding the generation of hollow PtAgS nanocrystals with consistent morphology. This method has good repeatability and scalability in terms of structure control, laying the foundation for the stable realization of material properties and practical applications; (3) This invention reveals for the first time the hollowing mechanism induced by twin defects. In the Pt-Ag-S ternary system, the twin defects formed in the early stage provide channels for atomic diffusion, driving the formation of hollow structures from the inside out. This mechanism provides a theoretical basis for the design of novel complex hollow nanomaterials; (4) The formation mechanism of this invention is novel and has strong theoretical guidance: This invention reveals the key role of twin defects in the formation of hollow structures and proposes a defect-induced mechanism based on the intrinsic regulation of crystal growth. This mechanism not only explains the formation process of hollow PtAgS nanocrystals, but also provides a new theoretical basis and synthetic route for the future design of anisotropic and complex hollow structures, and has strong scientific foresight and structural expansion potential.

[0017] (5) The material of the present invention has excellent performance and opens up new application fields: Hollow PtAgS nanocrystals exhibit excellent soft magnetic properties. The saturation magnetization and remanent magnetization are increased by nearly an order of magnitude compared with solid PtAgSCu nanocrystals. The characteristics of high magnetic responsiveness and low magnetic residue make it particularly suitable for high-frequency, low-loss miniaturized electronic devices and magnetic sensors. It solves the problem that the application of existing platinum-based hollow materials is limited to the catalytic field and opens up new application directions.

[0018] Examples and comparative examples show that the present invention successfully prepared hollow PtAgS nanocrystals through a specific two-step hydrothermal method under the combined effect of the Pt-Ag-S ternary system and twin defects. These nanocrystals have the characteristics of high saturation magnetization and low coercivity, making them particularly suitable for high-frequency, low-loss miniaturized electronic devices and magnetic sensors, providing a key material solution for improving device efficiency and sensitivity. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0020] Figure 1 : Schematic diagram of the hollow PtAgS nanocrystalline material of the present invention; Figure 2 Different reaction times in Examples 1-3 Figure 2 (a): 5 min, Figure 2 (b): 30 min, Figure 2 (c): TEM morphology image of PtAgS nanocrystals obtained under 3h) shows the evolution process from solid twins to hollow structure; Figure 3 In Comparative Example 1, Cu was introduced. 2+ TEM morphology image of the solid PtAgSCu nanocrystals obtained later; Figure 4 TEM morphology of PtAg nanosheets obtained in Comparative Example 2 without sulfur; Figure 5 TEM image of solid PtS nanocrystals obtained in Comparative Example 3; Figure 6 TEM morphology image of the solid AgS nanocrystals obtained in Comparative Example 4; Figure 7 Comparison of hysteresis (MH) curves of hollow PtAgS nanocrystals obtained in Example 3 and solid PtAgSCu nanocrystals obtained in Comparative Example 1. Detailed Implementation

[0021] This invention provides a method for preparing hollow PtAgS nanocrystalline materials, comprising the following steps: Step (1) Synthesis of gel precursor: Tris(hydroxymethyl)aminomethane, polyvinylpyrrolidone and formaldehyde solution (37 wt.%) were mixed to obtain a mixture; then the mixture was subjected to hydrothermal reaction and centrifuged to obtain the gel precursor; Step (2) Synthesis of hollow PtAgS nanocrystals: Platinum diacetylacetonate, silver nitrate, sulfur powder and formamide solution (AR, ≥99%) are mixed to obtain a mixture; then the mixture is mixed with the gel precursor obtained in step (1) and subjected to a hydrothermal synthesis reaction to obtain the hollow PtAgS nanocrystals.

[0022] In this invention, the preferred ratio of tris(hydroxymethyl)aminomethane, polyvinylpyrrolidone, and formaldehyde solution in step (1) is 20-80:100-300:1-4; more preferably, it is 50:200:2. Furthermore, the tris(hydroxymethyl)aminomethane and polyvinylpyrrolidone are used by mass, and the formaldehyde solution is used by volume. In one embodiment of this invention, the specific amounts of the tris(hydroxymethyl)aminomethane, polyvinylpyrrolidone, and formaldehyde solution are 50 mg, 200 mg, and 2 mL, respectively. This invention does not have special requirements regarding the source of the tris(hydroxymethyl)aminomethane, polyvinylpyrrolidone, and formaldehyde solution; commercially available products are sufficient.

[0023] The present invention does not have any special limitation on the mixing method of tris(hydroxymethyl)aminomethane, polyvinylpyrrolidone and formaldehyde solution in step (1), as long as tris(hydroxymethyl)aminomethane and polyvinylpyrrolidone can be dissolved in formaldehyde solution and mixed evenly.

[0024] After obtaining the mixture, the present invention preferably transfers the mixture in step (1) to a stainless steel high-pressure reactor for hydrothermal reaction. The temperature of the hydrothermal reaction is preferably 150~220℃ and the time is preferably 2~6h; more preferably, the temperature is 200℃ and the time is 3h.

[0025] After the hydrothermal reaction is completed, the reaction product is centrifuged. The centrifugation is preferably carried out in a centrifuge at a speed of 6000~10000 r / min, preferably 8000 r / min. The purpose of centrifugation in this invention is to separate the reaction product and obtain a gel product.

[0026] After obtaining the gel product, the present invention preferably uses acetone solution (AR, ≥99%) to repeatedly centrifuge and wash three times to obtain the gel precursor.

[0027] The preparation process of step (1) of this invention is simple and efficient, and the product has high purity. This advantage comes from the selection and synthesis of the self-sacrificing template in the synthesis step, which realizes the integration of the whole process of template synthesis → utilization → in-situ gentle removal. This directly solves the core pain points of traditional methods, such as step separation, template removal difficulty and easy residue, thus achieving simple and efficient process and high product purity.

[0028] In this invention, the preferred ratio of the amounts of platinum diacetylacetonate, silver nitrate, sulfur powder, and formamide solution in step (2) is 0.005~0.03:0.005~0.03:0.005~0.03:1~4, more preferably 0.01:0.01:0.01:2; furthermore, the amounts of platinum diacetylacetonate, silver nitrate, and sulfur powder are millimoles per liter, and the amount of formaldehyde solution is by volume; in one embodiment of this invention, the specific amounts of platinum diacetylacetonate, silver nitrate, sulfur powder, and formamide solution are 0.01 mM, 0.01 mM, 0.01 mM, and 2 mL, respectively. This invention does not have special requirements regarding the source of the platinum diacetylacetonate, silver nitrate, sulfur powder, and formamide solution; commercially available products are acceptable.

[0029] The present invention does not have any special limitation on the mixing method of diacetylacetonate platinum, silver nitrate, sulfur powder and formamide solution in step (2), as long as diacetylacetonate platinum, silver nitrate and sulfur powder can be dissolved in formaldehyde solution and mixed evenly.

[0030] After obtaining the mixture, the present invention preferably mixes the mixture in step (2) and the gel precursor obtained in step (1), and then transfers it to a stainless steel high-pressure reactor for hydrothermal synthesis reaction. The temperature of the hydrothermal synthesis reaction is preferably 100~180℃ and the time is preferably 5min~6h; more preferably, the temperature is 120~150℃ and the time is 3~6h, and the most preferably, the temperature is 130℃ and the time is 3h. The ratio of the amount of the mixture in step (2) to the amount of the gel precursor obtained in step (1) is preferably 1~4mL:1~4mL, and the optimal amount is 2mL:2mL. The present invention does not have any special limitation on the mixing method of the mixture in step (2) and the gel precursor obtained in step (1), as long as the two are mixed evenly.

[0031] After the hydrothermal synthesis reaction in step (2) is completed, the hydrothermal synthesis reaction product obtained is preferably centrifuged and washed. The number of centrifugation and washing is preferably 1 to 5 times, more preferably 3 times, and the washing reagent is preferably acetone solution (AR, ≥99%).

[0032] The present invention obtains PtAgS nanocrystalline materials with uniform and controllable structure and excellent reproducibility through the above two steps. This advantage comes from the uniform template provided in the first synthesis step and the fact that the reaction is carried out within the template in the second step. The combination of the two ensures that the morphology and size of the final product have high repeatability and controllability.

[0033] Meanwhile, the two-step hydrothermal method of this invention creates a unique reaction environment conducive to defect formation. It is through the careful design of these specific reaction parameters that the intrinsic growth mechanism of twin defect induction is successfully induced and utilized. This not only explains the formation of current materials, but more importantly, by adjusting these parameters, other types of crystal defects can be intentionally introduced, thereby providing a replicable experimental method and theoretical model for the development of nanomaterials with novel structures.

[0034] The present invention also provides a hollow PtAgS nanocrystalline material, wherein the hollow PtAgS nanocrystalline material is a ternary alloy nanocrystalline material with a uniform hollow structure, and its composition is platinum, silver and sulfur.

[0035] In this invention, the hollow structure is preferably composed of an inner cavity and an outer shell, and the diameter of the cavity is preferably 60% to 80% of the overall size of the nanocrystal.

[0036] The present invention further provides the application of the hollow PtAgS nanocrystalline material in the preparation of magnetic devices, wherein the magnetic devices preferably include high-frequency electronic devices or magnetic sensor devices; the hollow PtAgS nanocrystalline material exhibits soft magnetic properties, with high saturation magnetization and low coercivity.

[0037] To illustrate in detail the synthesis process and formation mechanism of hollow PtAgS nanocrystals, this invention investigated the second step of the hydrothermal reaction in the synthesis and preparation of hollow PtAgS nanocrystals. While keeping other experimental parameters constant, three groups of different hydrothermal reaction durations were selected to illustrate the formation process of the resulting PtAgS nanocrystals. The specific experimental process and results are as follows:

[0038] Example 1: A method for preparing hollow PtAgS nanocrystalline material includes the following steps: Step (1) Synthesis of gel precursor: Dissolve 50 mg of tris(hydroxymethyl)aminomethane and 200 mg of polyvinylpyrrolidone in 2 mL of formaldehyde solution and mix well to obtain a mixture; then transfer the mixture to a stainless steel high-pressure reactor and heat at 200 °C for 3 h. After the reaction is completed, use a centrifuge to separate the gel product and wash it repeatedly with acetone solution by centrifugation 3 times to obtain the gel precursor; Step (2) Synthesis of hollow PtAgS nanocrystalline material: 0.01 mM platinum diacetylacetonate, 0.01 mM silver nitrate and 0.01 mM sulfur powder were added to 2 mL of formamide solution and mixed evenly to obtain a mixture; then the mixture and the gel precursor obtained in step (1) were added to a stainless steel high-pressure reactor and mixed evenly. The mixture was heated at 130 °C for 5 min to carry out a hydrothermal synthesis reaction. After the reaction was completed, the product was repeatedly centrifuged and washed 3 times with acetone solution to obtain the hollow PtAgS nanocrystalline material.

[0039] Example 2 A method for preparing hollow PtAgS nanocrystalline material includes the following steps: Step (1) Synthesis of the gel precursor: The steps are exactly the same as in Example 1; Step (2) Synthesis of hollow PtAgS nanocrystalline material: 0.01 mM platinum diacetylacetonate, 0.01 mM silver nitrate and 0.01 mM sulfur powder were added to 2 mL of formamide solution and mixed evenly to obtain a mixture; then the mixture and the gel precursor obtained in step (1) were added to a stainless steel high-pressure reactor and mixed evenly. The mixture was heated at 130 °C for 30 min to carry out a hydrothermal synthesis reaction. After the reaction was completed, the product was repeatedly centrifuged and washed 3 times with acetone solution to obtain the hollow PtAgS nanocrystalline material.

[0040] Example 3 A method for preparing hollow PtAgS nanocrystalline material includes the following steps: Step (1) Synthesis of the gel precursor: The steps are exactly the same as in Example 1; Step (2) Synthesis of hollow PtAgS nanocrystalline material: 0.01 mM platinum diacetylacetonate, 0.01 mM silver nitrate and 0.01 mM sulfur powder were added to 2 mL of formamide solution and mixed evenly to obtain a mixture; then the mixture and the gel precursor obtained in step (1) were added to a stainless steel high-pressure reactor and mixed evenly. The mixture was heated at 130 °C for 3 h to carry out hydrothermal synthesis reaction. After the reaction was completed, the product was repeatedly centrifuged and washed 3 times with acetone solution to obtain the hollow PtAgS nanocrystalline material.

[0041] Figure 1This is a schematic diagram of the hollow PtAgS nanocrystalline material of the present invention. The formation mechanism of hollowing induced by twin defects is as follows: In the initial stage of the reaction, the large Pt / Ag lattice mismatch promotes the preferential formation of thermodynamically stable PtAgS spherical twin particles. The twin interface provides favorable nucleation sites for subsequent growth. At the same time, the particle growth is regulated by the mechanism of Pt and Ag atoms diffusing outward from the sulfur-containing core. As the reaction proceeds, the sulfidation process drives Pt and Ag atoms to diffuse outward along the twin defect channels, resulting in the gradual supersaturation of core vacancies. This "inside-out" diffusion mode causes the formation of cavities inside the particles, while the outer shell continues to grow epitaxially. As the reaction time increases, the internal strain continues to accumulate, and the number of atoms available for structural relaxation and surface deposition gradually decreases. The growth mechanism gradually shifts from thermodynamic dominance to kinetic dominance, thereby promoting the further evolution of the hollow structure and finally forming stable hollow PtAgS nanocrystalline materials.

[0042] Figure 2 Different reaction times in Examples 1-3 ( Figure 2 (a): 5 min, Figure 2 (b): 30 min, Figure 2 (c): TEM morphology image of PtAgS nanocrystals obtained under 3h) shows the evolution process from solid twins to hollow structure; in, Figure 2 (a) shows a TEM image of the nanoparticles obtained after the reaction in step (2) has proceeded for 5 minutes. Figure 2 (a) It can be seen that the nanoparticles are solid and have obvious twinning characteristics. This is because the twinning structure is a kind of planar defect, which is formed by two subgrains sharing the same lattice plane and growing together. The formation of such twinning nanoparticles can be attributed to the rapid reduction nucleation process of the precursor. This process is short and not conducive to the evolution of other structures. Therefore, the alloy products tend to form thermodynamically stable morphologies. like Figure 2 As shown in (b), when the reaction time is extended to 30 min, the particles begin to exhibit a hollow structure. This transformation process is nucleus sulfidation, because this process involves the diffusion of the PtAgS alloy core from the inside to the outside, thereby inducing the formation of a hollow structure, indicating that the growth mechanism has been transformed into kinetic control. like Figure 2 As shown in (c), when the reaction time is further extended to 3 hours, more core material continues to diffuse outward, and the internal cavity of the nanoparticles gradually expands. This diffusion mechanism from the inside out will continue to operate until the twinning defects are completely eliminated; that is... Figure 2(c) PtAgS nanocrystals form a stable hollow structure with a central pore diameter of about 60% to 80% of the original twin particle size. Twin defects are completely eliminated. This high hollowness is beneficial to increasing the specific surface area of ​​nanomaterials, enriching surface active sites and improving material permeability, thereby further increasing the performance of materials.

[0043] To further investigate the important role of twinned structure defects in the formation of hollow PtAgS nanocrystals, this invention adds the oxidant Cu in the second step of the nanocrystal preparation process. 2+ The twinning defects in the crystal nucleus were removed, and other experimental parameters remained the same as in Example 3. The specific experimental procedures and results are as follows: Comparative Example 1 A method for preparing hollow PtAgS nanocrystalline material includes the following steps: Step (1) Synthesis of the gel precursor: The steps are exactly the same as in Example 1; Step (2) Synthesis of hollow PtAgS nanocrystalline material: 0.01 mM platinum diacetylacetonate, 0.01 mM silver nitrate, 0.01 mM sulfur powder and 0.01 mM copper diacetylacetonate were added to 2 mL of formamide solution and mixed evenly to obtain a mixture; then the mixture and the gel precursor obtained in step (1) were added to a stainless steel high-pressure reactor and mixed evenly. The mixture was heated at 130 °C for 3 h to carry out hydrothermal synthesis reaction. After the reaction was completed, the product was repeatedly centrifuged and washed 3 times with acetone solution to obtain the hollow PtAgS nanocrystalline material.

[0044] Figure 3 To introduce Cu into Comparative Example 1 2+ TEM morphology images of the solid PtAgSCu nanocrystals obtained later; from Figure 3 As can be seen from the introduction of Cu 2+ After eliminating the twin structure in the crystal nucleus, the nanocrystals failed to form a hollow structure but instead formed a solid crystal structure. This result clearly shows that the twin structure is a necessary condition for the formation of hollow nanostructures. In the initial stage of the reaction, the rapid reduction process preferentially promotes the formation of thermodynamically more stable PtAgS spherical twin particles (mainly dodecahedral). The twin faces in the particles provide favorable sites for subsequent growth, and their growth process is regulated by the mechanism of Pt and Ag diffusion from the sulfur-containing core outward. As Pt and Ag atoms migrate outward through the twin structure, internal vacancy supersaturation occurs, thereby driving the formation of hollow PtAgS nanostructures. In contrast, by introducing the strong oxidizing etchant Cu... 2+ Eliminating twinning defects in PtAgS particles can effectively suppress the outward diffusion of Pt and Ag, thereby hindering the formation of hollow structures and ultimately forming solid PtAgSCu nanoparticles.

[0045] To further investigate the important roles of sulfidation and alloy combination in the formation of hollow PtAgS nanocrystals, this invention, in the second step of the nanocrystal preparation process, selected different combinations of elements, while keeping other experimental parameters the same as in Example 3. The specific experimental process and results are as follows: Comparative Example 2 A method for preparing PtAg nanocrystalline materials includes the following steps: Step (1) Synthesis of the gel precursor: The steps are exactly the same as in Example 1; Step (2) Synthesis of PtAg nanocrystalline material: 0.01 mM platinum diacetylacetonate and 0.01 mM silver nitrate were added to 2 mL of formamide solution and mixed evenly to obtain a mixture; then the mixture and the gel precursor obtained in step (1) were added to a stainless steel high-pressure reactor and mixed evenly. The mixture was heated at 130 °C for 3 h to carry out hydrothermal synthesis reaction. After the reaction was completed, the product was repeatedly centrifuged and washed 3 times with acetone solution to obtain the PtAg nanocrystalline material.

[0046] Comparative Example 3 A method for preparing PtS nanocrystalline material includes the following steps: Step (1) Synthesis of the gel precursor: The steps are exactly the same as in Example 1; Step (2) Synthesis of PtS nanocrystalline material: 0.01 mM platinum diacetylacetonate and 0.01 mM sulfur powder were added to 2 mL of formamide solution and mixed evenly to obtain a mixture; then the mixture and the gel precursor obtained in step (1) were added to a stainless steel high-pressure reactor and mixed evenly. The mixture was heated at 130 °C for 3 h to carry out hydrothermal synthesis reaction. After the reaction was completed, the product was repeatedly centrifuged and washed 3 times with acetone solution to obtain the PtS nanocrystalline material.

[0047] Comparative Example 4 A method for preparing AgS nanocrystalline material includes the following steps: Step (1) Synthesis of the gel precursor: The steps are exactly the same as in Example 1; Step (2) Synthesis of AgS nanocrystalline material: Add 0.01 mM silver nitrate and 0.01 mM sulfur powder to 2 mL formamide solution and mix evenly to obtain a mixture; then add the mixture and the gel precursor obtained in step (1) into a stainless steel high-pressure reactor and mix evenly. Heat at 130 °C for 3 h to carry out hydrothermal synthesis reaction. After the reaction is completed, the product is repeatedly centrifuged and washed 3 times with acetone solution to obtain the AgS nanocrystalline material.

[0048] Figure 4 The image shows the TEM morphology of the PtAg nanosheets obtained in Comparative Example 2 without sulfur; from Figure 4As can be seen, under sulfur-free conditions, the formed nanoparticles are thin-layer nanosheet structures, and their morphology is significantly different from that of the PtAgS system. Figure 5 The image shows the TEM morphology of the solid PtS nanocrystals obtained in Comparative Example 3. Figure 6 The image shows the TEM morphology of the solid AgS nanocrystals obtained in Comparative Example 4; it can be seen from the image that... Figure 5 PtS nanocrystals and Figure 6 The AgS nanocrystals in the study are all solid structures, further confirming the key role played by the twin structure and the specific combination of specific metals Pt and Ag in the formation of hollow nanocrystals. The two have a synergistic relationship and neither can be omitted.

[0049] Application Example 1 The hollow PtAgS nanocrystals prepared in Example 3 of the present invention and the solid PtAgSCu nanocrystals prepared in Comparative Example 1 were systematically characterized magnetically.

[0050] Figure 7 This is a comparison of the hysteresis (MH) curves of the hollow PtAgS nanocrystals obtained in Example 3 and the solid PtAgSCu nanocrystals obtained in Comparative Example 1. Figure 7 The comparison of hysteresis (MH) curves shows that hollow PtAgS nanocrystals exhibit superior soft magnetic properties. Calculations show that their saturation magnetization (Ms) and remanent magnetization (Mr) (Ms = 0.15 emu / g, 0.0159 emu / g) are significantly higher than those of solid PtAgSCu nanocrystals (Ms = 0.015 emu / g, 0.0020 emu / g), representing an increase of nearly an order of magnitude. This significant performance improvement is attributed to a unique sulfidation phase transition process: sulfidation successfully transforms the initially weakly magnetic PtAg precursor into a soft magnetic PtAgS phase with a high intrinsic magnetic moment. This phase transition is efficiently achieved in the hollow structure, thus endowing the material with excellent combined properties of high magnetic responsiveness and low magnetic remanence.

[0051] The aforementioned characteristics of high saturation magnetization and low coercivity make the hollow PtAgS nanocrystals of the present invention particularly suitable for high-frequency, low-loss miniaturized electronic devices and magnetic sensors, providing a key material solution for improving device efficiency and sensitivity.

[0052] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing hollow PtAgS nanocrystalline material, characterized in that, Includes the following steps: Step (1) Synthesis of gel precursor: Tris(hydroxymethyl)aminomethane, polyvinylpyrrolidone and formaldehyde solution are mixed to obtain a mixture; then the mixture is subjected to hydrothermal reaction and centrifuged to obtain gel precursor; Step (2) Synthesis of hollow PtAgS nanocrystals: Platinum diacetylacetonate, silver nitrate, sulfur powder and formamide solution are mixed to obtain a mixture; then the mixture is mixed with the gel precursor obtained in step (1) and a hydrothermal synthesis reaction is carried out to obtain the hollow PtAgS nanocrystals.

2. The method for preparing hollow PtAgS nanocrystalline material according to claim 1, characterized in that, In step (1), the ratio of tris(hydroxymethyl)aminomethane, polyvinylpyrrolidone and formaldehyde solution is 20~80:100~300:1~4.

3. The method for preparing hollow PtAgS nanocrystalline material according to claim 1, characterized in that, The heating temperature in step (1) is 150~220℃ and the time is 2~6h.

4. The method for preparing hollow PtAgS nanocrystalline material according to claim 1, characterized in that, In step (2), the ratio of the amount of platinum diacetylacetonate, silver nitrate, sulfur powder and formamide solution is 0.005~0.03:0.005~0.03:0.005~0.03:1~4.

5. The method for preparing hollow PtAgS nanocrystalline material according to claim 1, characterized in that, The ratio of the amount of the gel precursor to the amount of the mixture in step (2) is 1~4 mL: 1~4 mL.

6. The method for preparing hollow PtAgS nanocrystalline material according to claim 1, characterized in that, The temperature of the hydrothermal synthesis reaction in step (2) is 100~180℃ and the time is 5min~6h.

7. The method for preparing hollow PtAgS nanocrystalline material according to claim 1, characterized in that, After the hydrothermal synthesis reaction is completed, a centrifugal washing step is also included. The number of centrifugal washing steps is 1 to 5, and the washing reagent is acetone solution.

8. The hollow PtAgS nanocrystalline material prepared by the method according to any one of claims 1 to 7 is characterized in that, The hollow PtAgS nanocrystalline material is a ternary alloy nanocrystalline material with a uniform hollow structure, and its composition is platinum, silver and sulfur.

9. A hollow PtAgS nanocrystalline material according to claim 8, characterized in that, The hollow structure consists of an inner cavity and an outer shell, and the diameter of the cavity accounts for 60% to 80% of the overall size of the nanocrystal.

10. The application of the hollow PtAgS nanocrystalline material according to any one of claims 8 to 9 in the fabrication of magnetic devices, characterized in that, The magnetic devices include high-frequency electronic devices or magnetic sensors; the hollow PtAgS nanocrystalline material exhibits soft magnetic properties, with high saturation magnetization and low coercivity.

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