Hollow silver-platinum nano-alloy particles, and preparation method and application thereof

Abstract

This invention discloses hollow silver-platinum nanoalloy particles, their preparation method, and applications. The silver-platinum nanoalloy particles have a particle size of 30-60 nm, an overall hollow structure, and a porous surface distribution of silver and platinum fused together. The preparation method includes: using epigallocatechin gallate as the sole reducing agent and stabilizer, reducing silver nitrate in ethylene glycol to prepare monodisperse silver nanoparticles; then, at 60-80°C, slowly adding chloroplatinic acid solution in batches to the silver nanoparticle solution to carry out an in-situ exchange reaction; after the reaction, washing and separation yields the final product. This invention provides a green, simple, mild, and highly controllable preparation method. The prepared silver-platinum nanoalloy particles simultaneously possess excellent nanozyme catalytic activity and high-sensitivity surface-enhanced Raman scattering performance, achieving integrated synergistic catalytic and detection functions. It has broad application prospects in food safety testing, environmental monitoring, and biosensing.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to hollow silver-platinum nanoalloy particles, their preparation method, and applications. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) spectroscopy, as a highly sensitive molecular vibrational spectroscopy analysis technique, has shown broad application prospects in fields such as chemical analysis, biosensing, environmental monitoring, and food safety due to its ability to provide rich molecular fingerprint information, fast response speed, and non-destructive testing capabilities. The core of SERS lies in the development of high-performance substrate materials. Ideal substrate materials should possess extremely strong electromagnetic field enhancement capabilities, good stability, and effective adsorption capacity for the analyte molecules.

[0003] Noble metal nanomaterials, especially gold, silver, and platinum, have become a hot topic in surface-enhanced Raman scattering (SERS) substrate research due to their unique localized surface plasmon resonance (SPR) properties. Among them, silver nanoparticles are considered one of the most effective SERS enhancement materials, exhibiting a strong localized SPR effect in the visible light region, generating extremely high electromagnetic field enhancement, and achieving detection sensitivity down to the single-molecule level. However, silver nanoparticles have poor chemical stability and are easily oxidized or sulfided in air, causing their SERS signal to decay over time, limiting their long-term use in practical detection. Furthermore, silver itself has low catalytic activity, making it impossible to directly achieve efficient detection of many target analytes requiring catalytic transformation.

[0004] Platinum nanoparticles are excellent catalysts for many important chemical reactions, such as oxygen reduction, methanol oxidation, and catalytic hydrogenation, exhibiting high catalytic activity and good chemical stability. However, platinum's localized surface plasmon resonance effect is very weak, resulting in an extremely low enhancement factor when used as a surface-enhanced Raman scattering substrate, making it difficult to meet the requirements for high-sensitivity Raman detection. Therefore, single-component noble metal nanomaterials cannot simultaneously satisfy the dual requirements of catalysis and high-sensitivity detection.

[0005] To address this issue, researchers have attempted to construct bimetallic composite nanostructures to integrate the functional advantages of different metals. Common strategies include preparing core-shell structures, such as silver@platinum or platinum@silver nanoparticles. However, these structures have inherent drawbacks: when platinum is used as the shell to coat the silver core, the dense platinum shell severely shields the electromagnetic field of the silver core, leading to a significant weakening of the surface-enhanced Raman scattering signal; conversely, if silver is used as the shell to coat the platinum core, the catalytically active sites of platinum are covered, resulting in a significant decrease in catalytic performance. Furthermore, core-shell structures may become unstable in the catalytic reaction environment due to atomic migration, alloying, or shell damage, affecting their long-term performance. Another strategy is to composite separately prepared silver and platinum nanoparticles through physical mixing or chemical coupling. However, this method usually struggles to achieve close contact and electronic coupling between the two metals at the nanoscale, and the performance is often merely a simple superposition of the two materials, sometimes even resulting in poor performance due to increased interfacial impedance. Moreover, the uniformity of the product and the reproducibility of the preparation are difficult to control.

[0006] Alloying silver and platinum is considered a more promising solution. Mixing the two metals at the atomic level is expected to optimize platinum's catalytic performance by modulating its electronic structure through the introduction of silver, while simultaneously improving silver's chemical stability through platinum alloying. It may also generate localized surface plasmon resonance properties between pure silver and pure platinum, achieving a coexistence of catalytic activity and surface-enhanced Raman scattering effects. However, silver and platinum are thermodynamically immiscible, and their significant differences in crystal structure, atomic radius, and surface energy tend to lead to phase separation rather than the formation of a homogeneous alloy. Traditional co-reduction methods readily yield non-alloyed mixtures or core-shell structures, making it difficult to obtain atomically uniformly dispersed silver-platinum alloy nanoparticles. Existing successful methods for preparing silver-platinum alloys often require high temperature and pressure, complex organic solvent systems, special templates, or lengthy steps, which are unfavorable for large-scale, low-cost, and environmentally friendly production, thus limiting their practical application.

[0007] Therefore, developing a silver-platinum nanoalloy particle with a simple and environmentally friendly preparation process, uniform size, controllable composition, and excellent catalytic performance and significant surface-enhanced Raman scattering enhancement effect is of great practical significance for promoting the application of bifunctional nanomaterials in the field of integrated catalysis and detection. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides hollow silver-platinum nanoalloy particles, their preparation method, and applications. Through a green and controllable preparation method, silver-platinum hollow alloy particles with both excellent catalytic activity and high-sensitivity surface-enhanced Raman scattering performance are obtained, achieving integrated synergy of catalytic and detection functions.

[0009] This invention is achieved through the following technical solution:

[0010] A hollow silver-platinum nano-alloy particle, wherein the particle size is 30~60 nm, the whole is hollow, and the surface is a porous distribution of silver and platinum fused together.

[0011] Preferably, the silver and platinum are atomically and uniformly fused on the particle surface.

[0012] The preparation method of the above-mentioned hollow silver-platinum nanoalloy particles includes the following steps:

[0013] Step 1) Add epigallocatechin gallate to ethylene glycol, remove oxygen with nitrogen, heat to 140~160℃, add silver nitrate in ethylene glycol solution and react for 50~70 min. After washing and separation, monodisperse silver nanoparticles are obtained.

[0014] Step 2) Disperse the silver nanoparticles obtained in Step 1) in a solvent, adjust the temperature to 60~80℃, and slowly add chloroplatinic acid aqueous solution in batches under stirring. After each batch is added, wait for a period of time before adding the next batch. After the reaction is completed, wash and separate to obtain the hollow silver-platinum nano-alloy particles.

[0015] Preferably, in step 1), epigallocatechin gallate is used as the sole reducing agent and stabilizer, and its ratio to ethylene glycol is 100~200 mg: 40 mL; the concentration of the ethylene glycol solution of silver nitrate is 0.01~0.04 mol / L.

[0016] Preferably, the concentration of the chloroplatinic acid aqueous solution in step 2) is 1.5 × 10⁻⁶. -4 ~2.5×10 -4 mol / L.

[0017] Preferably, the slow addition method in step 2) is as follows: inject at a rate of 0.4~0.6 mL / min, add 18~22 mL per batch, and add between batches of 8~12 min.

[0018] Preferably, in step 2), the balance between the catalytic performance and the surface-enhanced Raman scattering performance of the obtained hollow silver-platinum nano-alloy particles is controlled by adjusting the total amount of chloroplatinic acid aqueous solution added.

[0019] The above-mentioned hollow silver-platinum nanoalloy particles are used as bifunctional nanomaterials that simultaneously possess catalytic and surface-enhanced Raman scattering functions.

[0020] Preferably, the hollow silver-platinum nano-alloy particles are used for catalytic oxidation of leuco crystal violet and for surface-enhanced Raman scattering detection of it.

[0021] Preferably, the detection limit of the leuco crystal violet reaches 1×10⁻⁶. -9 mol / L.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) The silver-platinum nanoalloy particles prepared by this invention have a unique hollow structure with a uniform particle size distribution in the range of 30~60 nm and a porous distribution of silver and platinum fusion on the surface. This structural feature not only provides a larger specific surface area, creating more active sites for catalytic reactions and molecular adsorption, but also the hollow structure itself can serve as an additional electromagnetic field enhancement hotspot, which is beneficial to improving the sensitivity of surface-enhanced Raman scattering detection.

[0024] (2) This invention is the first to use epigallocatechin gallate (EGCG) as the sole reducing agent and stabilizer, achieving the green synthesis of silver nanoparticles. This reducing agent, derived from green tea extract, has the advantages of being environmentally friendly and highly biocompatible, avoiding the environmental pollution problems that may arise from traditional chemical reducing agents. Simultaneously, the silver nanoparticles prepared under the action of this reducing agent exhibit uniform particle size and good dispersibility, providing a high-quality template for subsequent alloying reactions and ensuring the uniformity and stability of the final product.

[0025] (3) This invention successfully achieved the uniform fusion of silver and platinum at the nanoscale through an in-situ substitution reaction and a strategy of slowly adding chloroplatinic acid (H2PtCl6) in batches. This atomic-level fusion results in a uniform distribution of silver and platinum on the particle surface, preserving the strong surface-enhanced Raman scattering activity of silver while endowing the particles with catalytic function. The two work synergistically on the same particle surface. By changing the amount of chloroplatinic acid added, the ratio of silver to platinum in the particles can be flexibly controlled, thereby achieving precise adjustment of catalytic activity and surface-enhanced Raman scattering enhancement, and achieving optimal analytical results under different usage environments.

[0026] (4) The silver-platinum nanoalloy particles prepared in this invention possess both excellent nanoenzyme catalytic performance and surface-enhanced Raman scattering (SERS) enhancement performance. In terms of catalytic function, its colorimetric reaction with tetramethylbenzidine (TMB) exhibits peroxidase-like catalytic activity; in terms of SERS performance, the enhancement factor for thiophene can reach 4.1 × 10⁻⁶ under 532 nm laser excitation. 6 Order of magnitude. The synergistic integration of these two functions makes the particles stand out in the detection of leuco crystal violet (LCV) for fish medication. First, they act as a catalyst to oxidize Raman-inactive leuco crystal violet into crystal violet with a strong Raman signal. Then, surface-enhanced Raman scattering (SERS) enhances the sensitivity of the generated crystal violet, achieving a detection limit as low as 1 × 10⁻⁶. -9 mol / L, and at 1.0×10 -9~1.0×10 -6 It exhibits good linearity within the mol / L concentration range.

[0027] (5) The preparation method of this invention is simple and easy to implement, with mild reaction conditions, requiring no high temperature, high pressure, or special equipment, making it suitable for laboratory-scale preparation and industrial-scale production. The entire preparation process uses aqueous phase and ethanol as solvents, avoiding the use of toxic organic solvents, which is in line with the development concept of green chemistry. The prepared silver-platinum nanoalloy particles, as bifunctional nanomaterials with both catalytic and surface-enhanced Raman scattering functions, have broad application prospects in food safety detection, environmental monitoring, catalytic mechanism research, and biosensing. Attached Figure Description

[0028] Figure 1 The following are transmission electron microscopy (TEM) images and elemental analysis images of the nanoparticles in Examples 1 and 2: a) TEM image of silver nanoparticles; b) TEM image of hollow silver-platinum alloy nanoparticles; c) High-resolution TEM image of hollow silver-platinum alloy nanoparticles; d) EDX spectrum of hollow silver-platinum alloy nanoparticles; e) Dark-field image of a single hollow silver-platinum alloy nanoparticle; f) Elemental imaging of silver in hollow silver-platinum alloy nanoparticles; g) Elemental imaging of platinum in hollow silver-platinum alloy nanoparticles.

[0029] Figure 2 Transmission electron microscopy (TEM) images of hollow silver-platinum alloy nanoparticles prepared with different amounts of chloroplatinic acid added in Example 2: a = 40 mL; b = 60 mL; c = 80 mL; d = 100 mL; e = 140 mL; f = 160 mL added at once.

[0030] Figure 3 The UV-Vis spectra of the TMB products catalyzed by hollow silver-platinum alloy nanoparticles prepared with different amounts of chloroplatinic acid in Example 4 are shown.

[0031] Figure 4 The image shows the SERS diagram of hollow silver-platinum alloy nanoparticles prepared with silver nanoparticles and different amounts of chloroplatinic acid in Example 5 for the catalytic detection of leuco crystal violet.

[0032] Figure 5 Example 6 illustrates the application of hollow silver-platinum alloy particles in the catalytic detection of leuco crystal violet: a) SERS diagrams of different concentrations of LCV detected by hollow silver-platinum alloy nanoparticles; b) Standard curve. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0034] Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art, and the experimental methods without specific conditions are all conventional methods in the art.

[0035] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0036] A method for preparing hollow silver-platinum nano-alloy particles, the specific steps of which are as follows:

[0037] (1) Add 40 mL of ethylene glycol and 150 mg of epigallocatechin gallate (EGCG) to a 250 mL three-necked flask equipped with a magnetic stirrer. Deoxygenate under nitrogen for 15 min and heat to 150 °C in an oil bath. Quickly inject 6 mL of a 0.01–0.04 mol / L AgNO3 ethylene glycol mixture and allow the reaction to continue for 60 min. During the reaction, the solution color will gradually change from colorless to yellow, orange, and finally to an opaque gray-green, indicating that silver nanoparticles have been formed. After the reaction is complete, immediately transfer the flask to an ice-water bath and cool it rapidly to room temperature to terminate the reaction. Then add an equal volume of acetone, mix well, and centrifuge at 8000 rpm for 15 min. Discard the supernatant, redisperse the precipitate with an appropriate amount of acetone / ethanol mixture, and centrifuge again. Repeat this washing process 2–3 times to thoroughly remove residual PVP and ethylene glycol. Finally, disperse the purified silver nanoparticles in 20 mL of ultrapure water to obtain a silver colloidal stock solution.

[0038] (2) Adjust the reaction temperature to 70℃ and continue stirring. Use a syringe pump to inject 2.0 × 10⁻⁶ mol / L very slowly in batches (0.5 mL / min). -440–160 mL of mol / L chloroplatinic acid (H₂PtCl₆) solution was added. Each batch was injected over a duration of 40 min, corresponding to a 20 mL addition volume per batch. After each batch was injected, a 10-min interval was observed before the next batch was added. This method allows the product to be prepared and stored stably for a long period using a novel green tea extract polyphenol-epigallocatechin gallate (EGCG) as a single reducing and protecting agent, thereby improving the enhancement effect when used as a surface-enhanced Raman spectroscopy substrate. The amount of chloroplatinic acid added was determined by real-time UV spectrophotometry. With the addition of platinum salt, the solution color gradually changed from grayish-yellow to brown, dark brown, and finally grayish-black. This is a typical characteristic of the change and even disappearance of the surface plasmon resonance peak caused by Pt deposition on the Ag surface. After all additions were completed, the reaction was continued at 70°C for 1 h with stirring to ensure complete displacement reaction and maturation. The cooled sol was transferred to centrifuge tubes, centrifuged at 8000 rpm for 10 min, and the supernatant was carefully removed. The precipitate was redispersed with ultrapure water or ethanol by gentle sonication (power <100W, sonication for 5-10 s, 10 s interval, repeated several times), and then centrifuged again. This washing process was repeated 2-3 times.

[0039] (3) The final product can be dispersed in the desired solvent (water or ethanol), and the concentration can be adjusted as needed. The Ag-Pt nano-alloy particle sol obtained at this time can be stored stably for a short period of time (several days) in a refrigerator at 4°C.

[0040] The prepared Ag-Pt nanoalloy particles have a particle size range of 30~60 nm and are hollow in structure. Their surface exhibits a porous distribution of atomic-level silver and platinum fusion. The platinum in the material can play a catalytic role in nanoenzymes, and the silver nanoparticles have extremely strong SERS performance.

[0041] Example 1: Preparation of silver nanoparticles with different particle sizes

[0042] 1. Experimental Procedure

[0043] 40 mL of ethylene glycol and 150 mg of epigallocatechin gallate were added to four 250 mL three-necked flasks equipped with magnetic stirrers, respectively. Nitrogen gas was bubbled through the flasks for 15 min to remove oxygen. The reaction system was heated to 150 °C in an oil bath, and then 6 mL of silver nitrate ethylene glycol solutions with concentrations of 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, and 0.04 mol / L were rapidly injected, respectively. The reaction was continued for 60 min under nitrogen protection. During the reaction, the solution color gradually changed from colorless to yellow, then orange, and finally to an opaque grayish-green, indicating the formation of silver nanoparticles. After the reaction was completed, the flasks were immediately transferred to an ice-water bath and rapidly cooled to room temperature to terminate the reaction. An equal volume of acetone was then added, and the mixture was centrifuged at 8000 rpm for 15 min. The supernatant was discarded, and the precipitate was redispersed with an acetone / ethanol mixture and centrifuged again. This washing process was repeated three times to completely remove residual ethylene glycol. Finally, the purified silver nanoparticles were dispersed in 20 mL of ultrapure water to obtain a silver colloidal stock solution.

[0044] 2. Experimental Results

[0045] Transmission electron microscopy characterization revealed that the average particle sizes of silver nanoparticles obtained from four concentrations of silver nitrate ethylene glycol solutions were 32 nm, 46 nm, 51 nm, and 58 nm, respectively, with uniform particle size distribution (46 nm, ...). Figure 1 (a) shows good dispersion.

[0046] Example 2: Effect of different amounts of chloroplatinic acid added on the morphology and properties of alloy particles

[0047] 1. Experimental Procedure

[0048] A method for preparing hollow silver-platinum nano-alloy particles, the specific steps of which are as follows:

[0049] (1) Silver nanoparticles with an average particle size of 51 nm were prepared as reaction templates according to the method shown in Example 1.

[0050] (2) Adjust the temperature of the reaction system to 70℃, and under continuous stirring, add 2.0×10⁻⁶ ppm of the above silver nanoparticles in batches at a rate of 0.5 mL / min using a syringe pump. -4A 100 mol / L chloroplatinic acid solution was used. Five different total amounts of chloroplatinic acid were added: 40 mL, 60 mL, 80 mL, 100 mL, 120 mL, and 140 mL. The addition method was to add 20 mL of solution in each batch (injection time 40 min), with a 10 min interval between each batch. A control group was also set up, using a single continuous addition method, with 160 mL of the same concentration of chloroplatinic acid solution continuously injected at a rate of 0.5 mL / min without any interval. After all the solution was added, the reaction was continued to be stirred at 70℃ for 1 h to ensure the displacement reaction was complete and to allow for maturation. During the reaction, the solution color was observed to gradually change from grayish-yellow to brown, dark brown, and finally grayish-black. After the reaction, the sol was transferred to centrifuge tubes and centrifuged at 8000 rpm for 10 min. The supernatant was removed, and the precipitate was redispersed with ultrapure water by gentle sonication and centrifuged again. This washing process was repeated 3 times. The final product was dispersed in ultrapure water for later use, yielding the hollow silver-platinum nano-alloy particles.

[0051] 2. Experimental Results

[0052] The results of transmission electron microscopy observation are as follows Figure 1 , 2 As shown. Figure 1 In section b, the hollow structure at the center of the particle and the porous structure on the particle surface can be clearly observed, indicating that its particle size ranges from 30 to 50 nm, and individual alloy particles are as follows: Figure 1 As shown in c. (As shown in the image) Figure 2 As shown, the hollow structure of the particles gradually becomes clearer with increasing chloroplatinic acid content. When the amount of chloroplatinic acid added is 40-80 mL, the particles maintain a complete spherical hollow structure. Figure 2 When the amount added is 100 mL, the hollow structure is more obvious and the surface porous features are more abundant. Figure 2 (d); When the amount added is 140 mL, the hollow structure of some particles begins to break down ( Figure 2 (e); however, the spherical hollow nanostructure of the particles obtained by adding 160 mL continuously at once was completely destroyed. Figure 2 (f). Energy-dispersive X-ray spectroscopy analysis ( Figure 1 The results (dg) confirmed that the obtained particles contained both silver and platinum, and elemental imaging showed that silver and platinum were uniformly fused and distributed on the particle surface.

[0053] Example 3: Effect of Chloroplatinic Acid Addition Method on Alloy Particle Properties

[0054] 1. Experimental Procedure

[0055] Two portions of silver nanoparticles with an average particle size of 51 nm prepared in Example 1 were used for comparative experiments using different methods of adding chloroplatinic acid. The first portion was added in batches using the batch addition method described in Example 2, with 80 mL of 2.0 × 10⁻⁶ chloroplatinic acid added at a rate of 0.5 mL / min. -4 20 mL of mol / L chloroplatinic acid solution was added in batches, with a 10-minute interval between each batch. The second batch was added continuously at a rate of 0.5 mL / min, totaling 80 mL of the same concentration of chloroplatinic acid solution, without any interval between batches. Other reaction conditions were the same as in Example 2.

[0056] The catalytic performance of the two silver-platinum alloy particles was tested: 10 mg / mL of tetramethylbenzidine anhydrous ethanol mother liquor was diluted with 0.05 M acetate buffer to prepare a tetramethylbenzidine solution with a final concentration of 0.3 mg / mL, and the pH was adjusted to 5.2. 20 mg of alloy particles were added to each, and the mixture was shaken to mix thoroughly. Hydrogen peroxide solution was then added to bring the final concentration to 0.005%. The mixture was incubated at 37°C for 20 min, and the UV-Vis absorption spectrum of the reaction solution at 652 nm was measured.

[0057] 2. Experimental Results

[0058] The results showed that the absorbance of the catalytic product of the alloy particles obtained by batch addition was about three times that of the particles obtained by one-time continuous addition, indicating that the batch slow addition method significantly improved the catalytic activity of the alloy particles.

[0059] Example 4: Testing of the catalytic performance of nanoenzymes from hollow silver-platinum alloy particles

[0060] 1. Experimental Procedure

[0061] Six groups of silver-platinum alloy particles prepared with different amounts of chloroplatinic acid in Example 2 were used for catalytic performance testing. The testing method was as follows: 10 mg / mL of tetramethylbenzidine anhydrous ethanol mother liquor was diluted with 0.05 M acetate buffer to prepare a tetramethylbenzidine solution with a final concentration of 0.2–0.4 mg / mL, and the pH was adjusted to 5.0–5.5. 20 mg of the alloy particles obtained in each example were added and mixed thoroughly by shaking. Hydrogen peroxide solution was then added to bring the final concentration to 0.005%, and the mixture was incubated at 37°C for 20 min. The UV-Vis absorption spectra of each reaction solution in the range of 500–800 nm were measured.

[0062] 2. Experimental Results

[0063] The results showed that the amount of chloroplatinic acid added had a significant impact on the catalytic performance of the silver-platinum alloy particles. For example... Figure 3As shown, with the addition of chloroplatinic acid increasing from 40 mL to 120 mL, the absorbance of the catalytic product at 652 nm gradually increased; it reached a peak at 120 mL; and when the amount was further increased to 140 mL, the absorbance value tended to stabilize and no longer increased significantly. This indicates that when the amount of chloroplatinic acid reaches a certain value, most of the silver nanoparticles are consumed, and the catalytic ability no longer increases significantly.

[0064] Example 5: Surface-enhanced Raman scattering performance test of hollow silver-platinum alloy particles

[0065] 1. Experimental Procedure

[0066] Three groups of silver-platinum alloy particles were prepared by adjusting different amounts of chloroplatinic acid (20, 80, and 160 mL) according to the method in Example 2. Surface-enhanced Raman scattering (SERS) performance tests were performed on each particle, with the silver nanoparticles (46 nm) prepared in Example 1 used as a control. Using thiophenol as a probe molecule, each alloy particle was subjected to 10 mL of chloroplatinic acid. -6 A mol / L thiophenol solution was mixed, dropped onto the surface of a silicon wafer, and allowed to dry naturally. The wafer was then tested using a confocal micro Raman spectrometer with an excitation wavelength of 532 nm, a laser power of 0.5 mW, and an integration time of 10 s.

[0067] 2. Experimental Results

[0068] Test results show that with increasing chloroplatinic acid content, the surface-enhanced Raman scattering (SERS) enhancement ability of the alloy particles initially increases and then decreases. This is because the silver on the surface of the silver nanoparticles is continuously consumed during the substitution reaction, leading to a weakening of the localized surface plasmon resonance effect and a decrease in the enhancement ability. Therefore, a balance should be struck between catalytic performance and SERS performance to achieve optimal detection performance of silver-platinum nanoparticles. Figure 4 As shown, the enhancement effect was strongest when chloroplatinic acid was added at a volume of 80 mL, and the enhancement factor for thiophenol reached 4.1 × 10⁻⁶. 6 The enhancement ability decreased significantly when the amount of chloroplatinic acid added was 160 mL. Combined with the catalytic performance test results of Example 4, the alloy particles obtained when the amount of chloroplatinic acid added was 80 mL achieved the best balance between catalytic performance and surface-enhanced Raman scattering performance.

[0069] Example 6: Hollow silver-platinum alloy particles used for the catalytic detection of leuco crystal violet.

[0070] 1. Experimental Procedure

[0071] The silver-platinum alloy particles prepared in Example 2 with 80 mL of chloroplatinic acid were used for the catalytic detection of leuco crystal violet. First, 1.0 mL of 0.10 M acetate-sodium acetate buffer solution was prepared, and different volumes of 1.0 mM leuco crystal violet (LCV) stock solution and 0.25 mL of 1.0 M hydrogen peroxide solution were added. Water was then added to bring the total volume to 4.0 mL, resulting in a series of leuco crystal violet reaction solutions with different concentrations (20, 50, 100, 200, 500 nmol / L and 1.0, 2.0, 5.0, 10.0, 20.0 μmol / L). The silver-platinum alloy particles obtained in Example 2 were fixed onto the surface of a glass slide by electrostatic adsorption and placed in the reaction solutions. The slides were reacted in a constant temperature and humidity chamber at 40 °C for 0.5 h. After the reaction, the glass slide surface was rinsed with ultrapure water and dried before Raman spectroscopy analysis.

[0072] 2. Experimental Results

[0073] Raman spectroscopy test results as follows Figure 5 As shown in Figure a, within the concentration range of 20 nmol / L to 20.0 μmol / L, the characteristic Raman peak of crystal violet (approximately 1175 cm⁻¹) is... -1 1370 cm -1 and 1620 cm -1 The intensity of the characteristic peak (at a specific location) increases with increasing concentration of leuco crystal violet. Quantitative analysis was performed on the characteristic peak intensity and leuco crystal violet concentration, expressed as lg[LCV] (ratio of 10⁻⁶ to 10⁻⁶). -9 A standard curve was plotted with the concentration of Raman ions (mol / L) as the baseline on the x-axis and the intensity of the Raman characteristic peak on the y-axis, as shown below. Figure 5 As shown in b. The results show that at 1.0 × 10 -9 mol / L to 1.0×10 -6 Within the concentration range of 1.0 nmol / L to 1000 nmol / L, the Raman intensity exhibits a good linear relationship with the logarithm of the leuco crystal violet concentration. The linear regression equation is y = 2699.64x - 1191.37, with a correlation coefficient r = 0.9942, indicating excellent quantitative detection capability within this concentration range. When the concentration exceeds 1.0 μmol / L, the Raman signal intensity continues to increase with increasing concentration, but the growth trend gradually slows down, showing response saturation characteristics in the high concentration range. Based on a signal-to-noise ratio (S / N) of 3, the detection limit of this invention for leuco crystal violet can reach 1.0 × 10⁻⁶. -9 mol / L, corresponding to 1.0 nmol / L.

[0074] The experimental results of this embodiment demonstrate that the hollow silver-platinum alloy particles prepared in this invention successfully achieve a synergistic integration of catalytic and surface-enhanced Raman scattering (SERS) functions. The particles first act as nanoenzymes, oxidizing leuco crystal violet (which lacks Raman activity) into crystal violet with a strong Raman signal. Subsequently, the particles utilize their own SERS enhancement capability to perform highly sensitive detection of the generated crystal violet. This integrated catalysis-detection design enables the indirect, highly sensitive detection of leuco crystal violet, a substance difficult to detect directly using Raman scattering, through catalytic conversion. Furthermore, the detection signal exhibits a good linear relationship with the analyte concentration within the range of 1.0 nmol / L to 1000 nmol / L, providing a reliable technical means for the quantitative detection of trace prohibited additives in actual samples.

[0075] Example 7: Determination of the recovery rate of leuco crystal violet in actual fish meat samples

[0076] This embodiment aims to verify the accuracy and reliability of the hollow silver-platinum nano-alloy particles prepared by the present invention in the detection of actual samples, and to evaluate its quantitative analysis capability for leuco crystal violet in fish meat through a spiked recovery experiment.

[0077] 1. Sample pretreatment and extraction

[0078] Accurately weigh 4-6 g of commercially available crucian carp muscle tissue sample, chop and homogenize it thoroughly, then transfer it to a 50 mL polypropylene centrifuge tube. Add 10 mL of formic acid / methanol solution (volume ratio 0.01:100) to the centrifuge tube and extract by ultrasonic stirring for 30 min. After extraction, centrifuge the sample at 10000 rpm for 10 min at 4℃ and collect the supernatant for later use.

[0079] 2. Solid-phase extraction purification

[0080] To reduce matrix interference in animal tissues, the extract was purified using an MCX solid-phase extraction column (Waters, Japan). The MCX column was pre-activated with 3 mL of methanol and 3 mL of water, and the supernatant was then slowly passed through the MCX column at a flow rate of 1 mL / min. Impurities were eluted sequentially with 3 mL of water and 3 mL of methanol, and the target analyte was eluted with 3 mL of ammonia-methanol solution (5% ammonia by volume). The eluent was collected and concentrated to near dryness under a nitrogen stream in a 50°C water bath. The residue was reconstituted with 1.0 mL of phosphate buffer solution and diluted to 100.0 mL with ultrapure water to obtain a blank sample stock solution. Surface-enhanced Raman spectroscopy confirmed that no leuco crystal violet was detected in this stock solution.

[0081] 3. Preparation of spiked samples

[0082] Take several 1.0 mL aliquots of the above blank sample stock solution and add different volumes of leuco crystal violet standard solution to each aliquot to prepare spiked samples with concentrations of 50.0, 100.0, 500.0, and 1000.0 nmol / L. Simultaneously, use unspiked blank sample stock solution as a control. Prepare four samples (n=4) for each spiked concentration.

[0083] 4. Surface-enhanced Raman scattering detection

[0084] Hollow silver-platinum alloy particles prepared in Example 2 with 80 mL of chloroplatinic acid were electrostatically fixed onto a glass slide. Each spiked sample was mixed with 0.25 mL of 1.0 mol / L hydrogen peroxide solution, and the pH was adjusted to a suitable range (approximately 5.0–5.5). The glass slides carrying the alloy particles were then immersed in the reaction solution and reacted in a 40°C constant temperature and humidity chamber for 0.5 h. After the reaction, the slides were removed, rinsed with ultrapure water, and dried. Confocal microRaman spectroscopy was used for testing. The excitation wavelength was 532 nm, the laser power was 0.5 mW, and the integration time was 10 s. Crystal violet was recorded at approximately 1175 cm⁻¹. -1 The characteristic peak intensity at the specified location was substituted into the standard curve equation (y = 2699.64x - 1191.37) established in Example 6 to calculate the measured concentration of leuco crystal violet in each spiked sample.

[0085] 5. Experimental Results and Analysis

[0086] The spiked recovery rate and relative standard deviation were calculated based on the measured concentration and the theoretical spiking concentration, and the results are shown in Table 1 below.

[0087] Table 1. Results of spiked recovery of leuco crystal violet in crucian carp samples (n=4)

[0088]

[0089] As shown in Table 1, the average recoveries of the four spiked concentration levels ranged from 97.9% to 109.2%, with relative standard deviations of 4.9% to 10.4%, indicating that the method has good accuracy and precision and can meet the quantitative analysis requirements of trace leuco crystal violet in actual samples.

[0090] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. The scope of protection of the present invention is determined by the scope claimed in the claims. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A hollow silver-platinum nano-alloy particle, characterized in that, The silver-platinum nano-alloy particles have a particle size of 30~60nm, are hollow in structure, and have a porous distribution of silver and platinum on their surface.

2. The hollow silver-platinum nano-alloy particles according to claim 1, characterized in that, The silver and platinum are atomically and uniformly fused on the particle surface.

3. A method for preparing hollow silver-platinum nanoalloy particles as described in claim 1 or 2, characterized in that, Includes the following steps: Step 1) Add epigallocatechin gallate to ethylene glycol, remove oxygen with nitrogen, heat to 140~160℃, add silver nitrate in ethylene glycol solution and react for 50~70 min. After washing and separation, monodisperse silver nanoparticles are obtained. Step 2) Disperse the silver nanoparticles obtained in Step 1) in a solvent, adjust the temperature to 60~80℃, and slowly add chloroplatinic acid aqueous solution in batches under stirring. After each batch is added, wait for a period of time before adding the next batch. After the reaction is completed, wash and separate to obtain the hollow silver-platinum nano-alloy particles.

4. The preparation method according to claim 3, characterized in that, Step 1) The epigallocatechin gallate is used as the sole reducing agent and stabilizer, and its ratio with ethylene glycol is 100~200 mg: 40 mL; the concentration of the ethylene glycol solution of silver nitrate is 0.01~0.04 mol / L.

5. The preparation method according to claim 3, characterized in that, Step 2) The concentration of the chloroplatinic acid aqueous solution is 1.5 × 10⁻⁶. -4 ~2.5×10 -4 mol / L.

6. The preparation method according to claim 3, characterized in that, Step 2) The method of slowly adding in batches is as follows: inject at a rate of 0.4~0.6 mL / min, add 18~22 mL in each batch, and the batch interval is 8~12 min.

7. The preparation method according to claim 3, characterized in that, In step 2), the balance between the catalytic performance and the surface-enhanced Raman scattering performance of the obtained hollow silver-platinum nano-alloy particles is controlled by adjusting the total amount of chloroplatinic acid aqueous solution added.

8. The application of the hollow silver-platinum nanoalloy particles as described in claim 1 or 2 as a bifunctional nanomaterial possessing both catalytic and surface-enhanced Raman scattering functions.

9. The application according to claim 8, characterized in that, The hollow silver-platinum nano-alloy particles are used to catalyze the oxidation of leuco crystal violet and to perform surface-enhanced Raman scattering detection on it.

10. The application according to claim 9, characterized in that, The detection limit of the leuco crystal violet is 1×10⁻⁶. -9 mol / L.

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