Gold and silver nanostar composite material and preparation method and application thereof
By preparing gold@silver nanostar composite materials and utilizing the blue shift of the SPR peak to detect Ag+ concentration, the problems of accuracy and economy in Ag+ detection in existing technologies have been solved, and highly sensitive Ag+ detection results have been achieved.
Patent Information
- Application Number
- CN202510826013.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-19
- Publication Date
- 2025-10-31
AI Technical Summary
Existing Ag+ detection methods struggle to balance accuracy and cost-effectiveness in complex environments and lack highly sensitive detection technologies.
Gold@silver nanostar composites were prepared by growing silver shells of different thicknesses on the surface of the gold nanostars. The concentration of Ag+ in the water was detected by the blue shift of the SPR peak, and the results were obtained by combining colorimetry and UV-Vis spectrophotometry.
It achieves highly sensitive, rapid, and economical Ag+ detection with a detection limit of 39.8 pM, making it suitable for Ag+ detection in complex environments. It also has the advantages of good stability and easy surface modification.
Smart Images
Figure CN120861832A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of nanomaterials technology, and particularly relates to a gold@silver nanostar composite material, its preparation method, and its application. Background Technology
[0002] In the wave of rapid global industrialization, heavy metal pollution has become a serious global environmental problem. These pollutants possess inherent characteristics of being non-biodegradable and thermally stable; even when released into the environment in trace amounts, they can easily accumulate through bioaccumulation, reaching toxicity thresholds that threaten ecosystem security. Silver ions (Ag) + As a typical heavy metal pollutant, Ag has a significantly increased risk of environmental leakage due to its widespread use in many important fields such as electronics manufacturing, pharmaceutical preparations, imaging technology, and antibacterial materials. + The detection of Ag in the environment is of great and far-reaching significance, mainly reflected in environmental protection, human health, industrial applications, and scientific research. + Detecting Ag concentrations allows us to understand its potential impact on ecosystems, enabling us to take targeted environmental protection measures. Therefore, developing rapid and highly sensitive Ag detection methods is crucial. + Detection technology is crucial for safeguarding human health and the safety of the ecological environment.
[0003] In existing technologies, Ag detection + Methods include fluorescence methods, surface-enhanced Raman scattering (SERS), electrochemical methods, and colorimetric methods. Given Ag... + Given the complexity of detection scenarios and the need for ease of operation, while also considering the economics and practicality of detection methods, colorimetric biosensors are undoubtedly one of the most promising detection methods. This biosensing strategy fully leverages the intuitive and portable advantages of colorimetry, thereby achieving both accuracy and cost-effectiveness in complex environments. + Testing. Summary of the Invention
[0004] To address the aforementioned background issues, this invention provides a gold@silver nanostar composite material, its preparation method, and its applications. The gold@silver nanostar composite material provided by this invention grows silver shells of varying thicknesses on the surface of gold nanostar materials, thereby obtaining a core-shell structure. The SPR peak of this composite material exhibits a blue shift with increasing silver shell thickness. Therefore, the gold nanostar material can be utilized in conjunction with Ag in water. + The degree of blue shift of the SPR peak of the reacted material was used to detect Ag in the water. + Concentration. This invention is for detecting Ag in the environment. + It provides new ideas and methods.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] On one hand, the present invention provides a method for preparing a gold@silver nanostar composite material, comprising the following steps:
[0007] (1) Gold nanoparticles (AuNPs) were prepared by reacting chloroauric acid and trisodium citrate in an aqueous solution under reflux.
[0008] (2) After reacting gold nanoparticles, chloroauric acid, and N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer (HEPES) in an aqueous solution, hydroxylamine hydrochloride was added to continue the reaction to prepare gold nanostar materials (AuNSs);
[0009] (3) After reacting the reducing agent and gold nanostar material in HEPES buffer, a silver source is added to continue the reaction to obtain the gold@silver nanostar composite material.
[0010] In a preferred embodiment, in step (1), the heating reflux reaction time is 10 to 20 minutes.
[0011] Preferably, in step (1), the molar ratio of chloroauric acid and trisodium citrate is (1-100):(300-500).
[0012] In some specific embodiments, step (1) is specifically performed as follows: the chloroauric acid solution is heated under stirring and refluxed; trisodium citrate solution is added, and the heating is continued for 10-20 minutes before stopping the heating and cooling; wherein the molar ratio of chloroauric acid to trisodium citrate is (1-100):(300-500); the concentration of the chloroauric acid solution can be 1-5 mmol / L; and the concentration of the trisodium citrate solution can be 20-50 mmol / L.
[0013] In a preferred embodiment, in step (2), the molar ratio of N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt, chloroauric acid, and hydroxylamine hydrochloride is (1-100):(1-5):(1-5).
[0014] Preferably, in step (2), the molar ratio of the gold nanoparticles to hydroxylamine hydrochloride is (1-5):(50-100).
[0015] Preferably, in step (2), the reaction time is 1 to 5 minutes; the reaction time is 10 to 20 minutes.
[0016] Preferably, step (2) further includes a post-processing step of centrifuging and concentrating the solution obtained from the reaction and dispersing it in N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer (HEPES).
[0017] In some specific embodiments, step (2) is specifically performed as follows: gold nanoparticles and N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer (HEPES) are dispersed in water; chloroauric acid solution is added and the reaction is stirred for 1-5 min; then hydroxylamine hydrochloride solution is added and the reaction is continued for 10-20 min; wherein, the molar ratio of N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt, chloroauric acid, and hydroxylamine hydrochloride is (1-100):(1-5):(1-5); the molar ratio of gold nanoparticles to hydroxylamine hydrochloride is (1-5):(50-100); the concentration of N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer can be 10-50 mmol / L; the concentration of chloroauric acid solution can be 1-5 mmol / L; and the concentration of hydroxylamine hydrochloride solution can be 20-50 mmol / L.
[0018] In a preferred embodiment, in step (3), the silver source is a soluble silver salt; and the reducing agent is ascorbic acid.
[0019] Preferably, in step (3), the molar ratio of ascorbic acid to Ag in the silver source is (1-5):(1-5), and more preferably 10:1-10.
[0020] Preferably, in step (3), the molar ratio of the gold nanostar material to Ag in the silver source is 1 to 11,450,000:1.
[0021] Preferably, in step (3), the reaction time is 1 to 5 minutes; the reaction time is 3 to 7 minutes.
[0022] In some specific embodiments, step (3) is specifically performed as follows: under stirring conditions, the reducing agent solution is added to the N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer solution of gold nanoparticles, and the reaction is carried out for 1 to 5 minutes; the silver source solution is added, and the reaction is continued for 3 to 7 minutes; wherein, the molar ratio of the reducing agent to Ag in the silver source is (1 to 5):(1 to 5), more preferably 10:1 to 10; the molar ratio of the gold nanostar material to Ag in the silver source is 1 to 11450000:1; the concentration of the reducing agent solution can be 1 to 10 mmol / L; the concentration of the silver source solution can be 1 nmol / L to 10 mmol / L.
[0023] In the technical solution of the present invention, in step (3), changing the amount of silver source can change the thickness of the silver shell.
[0024] In another aspect, the present invention provides a gold@silver nanostar composite material obtained by the above preparation method.
[0025] On another front, the present invention provides the application of the above preparation method in detecting the concentration of silver ions in water.
[0026] In the technical solution of this invention, a reducing agent reduces Ag of different concentrations. + In a solution, silver shells of varying thicknesses are deposited on the surface of AuNSs to form Au@Ag NSs. The different thicknesses of the silver shells result in varying degrees of blue shift in the plasmon resonance (SPR) peaks of Au@Ag NSs compared to AuNSs. With the increase in Ag... + With increasing concentration, the blue shift Δλ of the SPR peak of Au@Ag NSs gradually increases. Δλ can be correlated with Ag... + Concentration correlation curves were constructed; then, the gold nanostar material was correlated with Ag in the water sample. + The gold@silver nanostar composite material test sample was prepared using the same reaction as in step (3). By comparing the Δλ of the prepared test sample with the correlation curve constructed above, the Ag content in the water to be tested can be obtained. + Concentration, therefore this invention can achieve Ag + Highly sensitive colorimetric analysis.
[0027] Compared with the prior art, the beneficial effects of the present invention are:
[0028] (1) The gold@silver nanostar composite material provided by the present invention has pure gold as the core and silver as the shell; the composite material has excellent surface plasmon resonance (SPR) performance and color development performance, which can meet the needs of colorimetric sensing; the composite material has the SPR peak shift due to the different thickness of the silver shell coating on the surface; in addition, the composite material has the advantages of good stability and easy surface modification.
[0029] (2) The gold@silver nanostar composite material provided by the present invention has a simple process and mild conditions;
[0030] (3) The gold@silver nanostar composite material and its preparation method provided by the present invention can detect the concentration of silver ions in water by colorimetric method and ultraviolet-visible spectrophotometry. It has high detection sensitivity, is convenient and fast, has a wide linear range and is less affected by external interference. Attached Figure Description
[0031] Figure 1 Transmission electron microscope (TEM) images of AuNSs and Au@Ag NSs prepared in Example 1 of this invention: (A) AuNSs, (B) Au@0.1mM Ag NSs, (C) Au@1mM Ag NSs, (D) Au@10mM Ag NSs; (E), (F), (G), and (H) are magnified views of (A), (B), (C), and (D), respectively.
[0032] Figure 2Characterization images of Au@10mM Ag NSs prepared in Example 1 of this invention: (A) Transmission electron microscopy image, (B) High-angle annular dark field image, (C) and (D) Ag and Au elemental distribution maps, respectively, (E) Composite image of Ag and Au elemental distribution maps, (F) EDS line scan analysis image;
[0033] Figure 3 X-ray diffraction patterns (A) of AuNSs and Au@10mM AgNSs prepared in Example 1 of the present invention, and a partially enlarged view (B) of the X-ray diffraction patterns with 2θ between 60° and 80°.
[0034] Figure 4 The visible spectrum of the Au@Ag NSs composite material measured in Example 1 of this invention;
[0035] Figure 5 This is a graph showing the functional relationship between the Ag concentration (45 pM ~ 2.3 μM) in the Au@Ag NSs dispersion and Δλ in Example 1 of the present invention.
[0036] Figure 6 This is a graph showing the functional relationship between the Ag concentration (2.3 μM to 0.45 mM) in the Au@Ag NSs dispersion and Δλ in Example 1 of the present invention.
[0037] Figure 7 This is a graph showing the functional relationship between the Ag concentration and Δλ in the Au@Ag NSs dispersion of Example 1 of the present invention;
[0038] Figure 8 The visible spectrum of the Au@M NSs composite material prepared in Comparative Example 1 of this invention is shown. Detailed Implementation
[0039] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. 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.
[0040] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.
[0041] Example 1:
[0042] This embodiment synthesizes a gold@silver nanostar composite material, and the preparation process is as follows:
[0043] (1) Synthesis of gold nanomaterials (AuNPs):
[0044] 100 mL of 1 mM chloroauric acid solution was added to a 250 mL round-bottom flask and heated under reflux with continuous stirring. 10 mL of 38.8 mM trisodium citrate solution was added, and the solution was observed to gradually turn dark red. Heating was continued under reflux for 15 min, then heating was stopped and the mixture was cooled for 15 min with stirring. The resulting AuNPs dispersion (0.91 mM) was stored in a refrigerator at 4 °C.
[0045] (2) Synthesis of gold nanostar materials (AuNSs):
[0046] Add 750 μL of AuNPs dispersion obtained in step (1), 100 mM 18.75 mL of N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer (HEPES), and 38.5 mL of water to a 100 mL beaker in sequence; under continuous stirring, add 1 mM 22.5 mL of chloroauric acid solution dropwise; after reacting for 2 min, add 40 mM 750 μL of hydroxylamine hydrochloride solution to the mixed solution, and stop the reaction after stirring for 15 min; centrifuge the resulting solution at 4500 rpm for 12 min, concentrate it to half of the initial volume, and redisperse it in 40.625 mL of 12 mM HEPES solution to obtain AuNSs dispersion (AuNSs concentration is 0.571 mM), and store it in a refrigerator at 4 °C;
[0047] (3) Synthesis of gold@silver nanostar composite material (Au@Ag NSs):
[0048] Add 3 mL of HEPES buffer-dispersed AuNSs to a pre-washed 5 mL glass bottle; then, under continuous stirring, add 10 mM 150 μL of ascorbic acid solution, mix well and react for 2 min; slowly add 10 mM 150 μL of AgNO3 solution, continue stirring for 5 min and then stop the reaction; after the reaction is complete, centrifuge the resulting solution at 4500 rpm for 3 min to obtain core-shell structured Au@Ag NSs, disperse it in 3.3 mL of 12 mM HEPES buffer to obtain Au@Ag NSs dispersion, and store it in a refrigerator at 4 °C.
[0049] In step (3) of this embodiment, gold@silver nanostar composite materials were also prepared using AgNO3 solutions of other concentrations, with concentrations ranging from 1 nM to 5 mM.
[0050] Figure 1The figures show transmission electron microscopy (TEM) images of the AuNSs and Au@Ag NSs prepared in this embodiment. A, B, C, and D are TEM images of the AuNSs obtained in step (2), the gold@silver nanostar composite material prepared with 0.1 mM AgNO3 solution (Au@0.1 mM Ag NSs), the gold@silver nanostar composite material prepared with 1 mM AgNO3 solution (Au@1 mM Ag NSs), and the gold@silver nanostar composite material prepared with 10 mM AgNO3 solution (Au@10 mM Ag NSs), respectively. E, F, G, and H are magnified views corresponding to A, B, C, and D. As can be seen from the figures, with the increase of AgNO3 solution concentration, the silver shell layer of the gold@silver nanostar composite material gradually thickens, and the tip of the AuNSs is gradually covered by silver, eventually forming a spherical core-shell structure of Au@Ag NSs (D and H). At an AgNO3 concentration of 0.1 mM, the silver shell formed was relatively thin due to the low AgNO3 concentration, and the branches (B and F) of the gold nanostars could still be observed. In contrast, when the AgNO3 concentration was increased to 1 mM, Au@1 mM Ag NSs formed a thicker silver shell, with the tips of the Au NSs almost completely covered by the silver shell. When the added AgNO3 concentration was further increased to 10 mM, Au@10 mM Ag NSs completely transformed into a near-spherical core-shell structure.
[0051] Figure 2 Characterization images of Au@10mM Ag NSs prepared in this embodiment: (A) Transmission electron microscopy image; (B) High-angle annular dark-field image; (C) and (D) are the distribution maps of Ag and Au elements at corresponding positions obtained by elemental mapping analysis, respectively. It can be seen from the figures that Ag and Au elements coexist in the composite material; (E) is a composite image of the distribution maps of Ag and Au elements. It can be seen from the figures that the distribution profile of Ag element is larger than that of Au element, proving that the composite material is a core-shell structured gold-silver nanoalloy; (F) is an EDS line scan analysis image, which further verifies that the composite material has a core-shell structure of gold core and silver shell.
[0052] Figure 3X-ray diffraction (XRD) patterns of AuNSs and Au@10mM AgNSs are shown. The diffraction peaks of AuNSs at 2θ = 38.13°, 44.40°, 64.67°, 77.75°, and 81.69° correspond to the (111), (200), (220), (311), and (222) crystal planes of gold, respectively, consistent with the reported face-centered cubic structure of Au. Since the positions of the characteristic peaks in the standard diffraction cards of Ag (JCPDS No. 04-0783) are slightly smaller than those in the standard diffraction cards of Au (JCPDS No. 04-0784), the diffraction peaks of Au@10mM AgNSs show a slight shift towards lower angles compared to AuNSs (e.g., ...). Figure 2 (As shown in B). This result confirms the successful introduction of silver and provides strong structural characterization evidence for the successful preparation of gold-silver bimetallic nanomaterials.
[0053] In this embodiment, 1 mL of the Au@Ag NSs dispersion from step (3) was mixed with 1 mL of ultrapure water and transferred to a quartz cuvette. A UV-Vis spectrophotometer was used to perform a spectral scan in the wavelength range of 400–800 nm. The resulting visible spectrum is shown in the figure. Figure 4 (In the figure, a is the visible absorption spectrum of AuNSs, and b to k are the 10... -6 10 -5 10 -4 10 -3 10 -2 5×10 -2 10 -1 The visible absorption spectra of Au@Ag NSs composites prepared from 1, 5, and 10 mM AgNO3 solutions (corresponding to Ag concentrations in the Au@Ag NSs dispersions ranging from 45 pM to 0.45 mM) are shown in the figures. It can be seen that as the AgNO3 solution concentration gradually increases, the SPR peak of Au@Ag NSs exhibits a blue shift compared to AuNSs (λ). max The blue shift (from 645.5 nm to 496.5 nm) indicates a clear correlation between the degree of blue shift (Δλ) of the SPR peak and the Ag concentration. Furthermore, when the Ag concentration in the Au@AgNSs dispersion reaches 2.3 μM (5 × 10⁻⁶ nm), the blue shift also increases. -2 After preparing the dispersion from mM AgNO3 solution, λ max The value shows a rapid blue shift trend. Figure 4 This phenomenon can also be clearly observed in the color contrast of the inner illustrations. This phenomenon can be attributed to: higher Ag... +Under certain concentration conditions, the dendritic tips of the inner AuNSs layer are completely covered by the silver shell, leading to a significant increase in nanoparticle size and silver dominance in the overall SPR peak of the material. This results in a sharp increase in the Δλ value, which is also confirmed by transmission electron microscopy. Therefore, there are two linear relationships between Δλ and Ag concentration. Figure 7 Within the final concentration range of 45 pM to 2.3 μM, the regression equation for the linear relationship between Δλ and the logarithm of Ag concentration is: y = 0.58lgx + 3.54(R). 2 =0.997)( Figure 5 Within the final concentration range of 2.3 μM to 0.45 mM, the regression equation for the linear relationship between Δλ and the logarithm of Ag concentration is: y = 62.87lgx - 20.16 (R²). 2 =0.996)( Figure 6 Finally, the detection limit (LOD) was calculated to be 39.8 pM.
[0054] Comparative Example 1:
[0055] This invention further employs other metals (M) to replace Ag in the preparation of Au@M NSs composite materials. The preparation method is the same as in Example 1, and the metal source solution used is 10 mM Fe. 3+ Cu 2+ Zn 2+ and Co 2+ The nitrate solution was used. The composite materials prepared above were spectrally scanned in the wavelength range of 400–800 nm using a UV-Vis spectrophotometer. The blue shift Δλ of the SPR peak in the visible spectrum relative to AuNSs for composite materials synthesized from different metals was monitored. The results are as follows: Figure 8 As shown, after growing a silver shell on the surface, the solution color of Au@Ag NSs changed from blue to orange compared to the blank control group (AuNSs), with Δλ = 149.2 nm. Therefore, no significant change in Δλ was observed in composites prepared with other metals.
[0056] Application Example 1:
[0057] This invention uses the Au@Ag NSs composite material prepared in Example 1 to detect Ag in water. + The specific process is as follows:
[0058] (1) Weigh 1.6988 mg and 0.16988 mg of silver nitrate solid, and dissolve them in 10 mL of lake water to prepare solutions with silver nitrate concentrations of 1 mmol / L and 0.1 mmol / L to simulate the test sample;
[0059] (2) Take 3 mL of AuNSs dispersion from step (2) of Example 1, add 150 μL of 10 mM L-AA solution under continuous stirring, mix well and react for 2 min; then slowly add 150 μL of the two test samples respectively, continue stirring for 5 min and stop the reaction; after the reaction is completed, centrifuge the resulting solution at 4500 rpm for 3 min to obtain Au@Ag NSs, disperse it in 3.3 mL of 12 mM HEPES buffer to obtain Au@Ag NSs dispersion; add an equal volume of water to the dispersion, and then use a UV-Vis spectrophotometer to perform a spectral scan in the wavelength range of 400-800 nm and record the corresponding absorption spectrum; then, calculate Δλ based on the SPR peak;
[0060] (3) Using the regression equation constructed in Example 1, the concentration of Ag in the Au@Ag NSs dispersion obtained in step (2) is calculated based on the Δλ measured in step (2). The calculation results are shown in Table 2.
[0061] The present invention also detects Ag in the above-mentioned simulated test samples by inductively coupled plasma mass spectrometry (ICP-MS). + The concentration was detected as follows: 150 μL of simulated test sample was taken, and 3150 μL of water was added (Ag... + After the final concentrations (4.50 μM and 45.0 μM) were mixed thoroughly, ICP-MS was performed, and the results are shown in Table 1.
[0062] Due to the improved signal-to-noise ratio, the proposed biosensor is well-suited for detecting Ag in real samples. + Quantitative analysis was performed. Despite the presence of multiple contaminants in the lake water sample, the high recovery rate and low relative standard deviation indicate that the biosensor is suitable for detecting real-world samples (see Table 2). More importantly, the results obtained by this biosensor are in excellent agreement with the data obtained by inductively coupled plasma mass spectrometry (ICP-MS), which is expected of relevant biosensors, demonstrating that this biosensor can detect Ag in real-world water samples. + Concentration potential.
[0063] Table 1. ICP-MS Detection Results
[0064]
[0065] In Table 1, recovery rate = (concentration) ICP-MS -concentration 湖水 ) / actual concentration * 100%, where, concentration 湖水 =0.
[0066] Table 2. Colorimetric test results
[0067]
[0068] In Table 2, the Ag concentration is the concentration of Ag in the Au@Ag NSs dispersion; recovery rate = (concentration) / (concentration) 回归方程 -concentration 湖水 ) / actual concentration * 100%, where, concentration 湖水 =0.
[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a gold@silver nanostar composite material, characterized in that, Includes the following steps: (1) Gold nanoparticles were prepared by heating and refluxing chloroauric acid and trisodium citrate in an aqueous solution; (2) After reacting gold nanoparticles, chloroauric acid, and N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer in an aqueous solution, hydroxylamine hydrochloride was added to continue the reaction to prepare gold nanostar materials; (3) After reacting the reducing agent and gold nanostar material in N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer, a silver source is added to continue the reaction to obtain the gold@silver nanostar composite material.
2. The preparation method according to claim 1, characterized in that, In step (1), the heating and reflux reaction time is 10-20 min; Preferably, in step (1), the molar ratio of chloroauric acid and trisodium citrate is (1-100):(300-500).
3. The preparation method according to claim 1, characterized in that, The specific operation of step (1) is as follows: heating the chloroauric acid solution under stirring and reflux; adding trisodium citrate solution, continuing to stir and heat under reflux for 10-20 minutes, then stopping the heating and stirring to cool.
4. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt, chloroauric acid, and hydroxylamine hydrochloride is (1-100):(1-5):(1-5); Preferably, in step (2), the molar ratio of the gold nanoparticles to hydroxylamine hydrochloride is (1-5):(50-100); Preferably, in step (2), the reaction time is 1 to 5 minutes; the reaction time is 10 to 20 minutes.
5. The preparation method according to claim 1, characterized in that, Step (2) also includes a post-processing step of centrifuging and concentrating the solution obtained from the reaction and dispersing it in N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer.
6. The preparation method according to claim 1, characterized in that, The specific operation of step (2) is as follows: gold nanoparticles and N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer are dispersed in water; chloroauric acid solution is added and the reaction is stirred for 1 to 5 minutes; then hydroxylamine hydrochloride solution is added and the reaction is continued for 10 to 20 minutes.
7. The preparation method according to claim 1, characterized in that, In step (3), the silver source is a soluble silver salt; the reducing agent is ascorbic acid; Preferably, in step (3), the molar ratio of ascorbic acid to Ag in the silver source is (1-5):(1-5), and more preferably 10:1-10; Preferably, in step (3), the molar ratio of the gold nanostar material to Ag in the silver source is 1 to 1,145,000:1; Preferably, in step (3), the reaction time is 1 to 5 minutes; the reaction time is 3 to 7 minutes.
8. The preparation method according to claim 7, characterized in that, The specific operation of step (3) is as follows: under stirring conditions, the reducing agent solution is added to the N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) sodium salt buffer of gold nanoparticles, and the reaction is carried out for 1 to 5 minutes; then the silver source solution is added, and the reaction is continued for 3 to 7 minutes.
9. The gold@silver nanostar composite material obtained by any of the preparation methods described in claims 1-8.
10. The application of the preparation method according to any one of claims 1-8 in detecting the concentration of silver ions in water.