Periodic Au / Ag cascade nanoflower array structure and preparation method thereof

Abstract

The application belongs to the technical field of Raman spectrum, and discloses a periodic Au / Ag cascade nanoflower array structure and a preparation method thereof. The preparation method comprises the following steps: S1, preparing a PS ball template, and performing reactive ion etching on the PS ball template; S2, preparing a silver-ammonia solution, adding the silver-ammonia solution and the PS ball template prepared in the step S1 into a beaker, adding a glucose solution, reacting at room temperature, removing the reaction solution after the reaction is completed, washing and drying the product with deionized water, and obtaining a silver nanoparticle-wrapped flower-shaped PS ball array; and S3, taking the silver nanoparticle-wrapped flower-shaped PS ball array as a sacrifice template, soaking the silver nanoparticle-wrapped flower-shaped PS ball array in an Au + solution to react, and obtaining the periodic Au / Ag cascade nanoflower array structure. The method realizes low-cost large-area preparation, and the obtained nanoflower array structure has a strong SERS enhancement effect.

Description

Technical Field

[0001] This invention belongs to the field of Raman spectroscopy technology, specifically relating to a periodic Au / Ag cascaded nanoflower array structure and its preparation method. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) is an ultrasensitive detection technique that utilizes the nanoscale roughness of metallic surfaces, based on the Raman scattering effect, to achieve rapid identification and ultrasensitive detection of analyte molecules. Compared to traditional analytical methods, SERS offers advantages such as high sensitivity, high resolution, and real-time detection. The sensitivity and detection limit of SERS can even reach the single-molecule level. Improvements in SERS performance rely on "hot spot" regions on the surface of noble metal nanostructures, including nano-tippies, nanopores, and nano-gap structures. SERS provides a rapid and efficient detection method for fields such as biomedicine, food safety, and environmental monitoring. With the development and application of SERS, various fields are placing higher demands on detection sensitivity and stability; therefore, developing an efficient, stable, and low-cost SERS detection technology is particularly important. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a periodic Au / Ag cascaded nanoflower array structure and its preparation method, which can realize the controllable preparation of large-area periodic noble metal nanoflower arrays.

[0004] The technical solution adopted in this invention is as follows:

[0005] A method for preparing a periodic Au / Ag cascaded nanoflower array structure includes the following steps:

[0006] S1. Prepare a PS sphere template and perform reactive ion etching on the PS sphere template;

[0007] S2. Prepare silver ammonia solution. Add the silver ammonia solution and the PS ball template prepared in step S1 into a beaker, add glucose solution, react at room temperature, remove the reaction solution after the reaction is completed, and obtain the product. Wash the product with deionized water and dry it to obtain a flower-shaped PS ball array wrapped with silver nanoparticles.

[0008] S3. Using the flower-shaped PS sphere array coated with silver nanoparticles as a sacrificial template, immerse the flower-shaped PS sphere array coated with silver nanoparticles in Au. + The reaction in solution yielded a periodic Au / Ag cascaded nanoflower array structure.

[0009] Furthermore, in step S1, the preparation of the PS sphere template includes the following steps:

[0010] S11. Mix the PS sphere suspension with ethanol to obtain a PS sphere solution;

[0011] S12. Pour deionized water into a clean petri dish and add a few drops of 20mM sodium dodecyl sulfate to the surface of the water to enhance the surface tension of the water.

[0012] S13. The PS sphere solution is slowly dripped onto the water surface after step S12 along a hydrophilic glass slide. Under the combined action of electrostatic force and surface tension, the PS spheres form a dense PS sphere film on the liquid surface.

[0013] S14. The PS sphere membrane is separated from the water surface using a hydrophilic silicon wafer, and the deionized water is allowed to dry naturally to form a tightly packed PS sphere template.

[0014] Furthermore, in the PS sphere solution, the volume ratio of PS sphere suspension to ethanol is 2:3.

[0015] Furthermore, the method for preparing the hydrophilic silicon wafer is as follows: irradiating a clean silicon wafer surface with ultraviolet light.

[0016] Furthermore, in step S1, the conditions for reactive ion etching are: gas is N2, etching power is 90W, and time is 6min.

[0017] Furthermore, in step S1, after reactive ion etching of the PS sphere template, it is immersed in a 1 wt% stannous chloride solution for 5-10 seconds, then rinsed with deionized water and dried. The purpose of this step is to allow tin ions to be adsorbed on the surface of the PS spheres, so that a small amount of silver can be reduced and adsorbed on the surface of the PS spheres during the silver mirror reaction, allowing the silver particles generated by the silver mirror reaction to grow better on the surface of the PS spheres.

[0018] Furthermore, in step S2, the silver ammonia solution is prepared by adding a 20 mmol / L AgNO3 solution to a clean beaker, and then gradually adding a 1 mol / L ammonia solution until the precipitate disappears and the mixed solution becomes clear and transparent, thus forming a silver ammonia solution.

[0019] Furthermore, the volume ratio of the AgNO3 solution to the ammonia solution is 10:0.7.

[0020] Furthermore, in step S2, the ratio of silver ammonia solution, PS ball template, and glucose solution is 10.7 mL: 0.418 g: 2 mL, and the reaction time is 100-800 s.

[0021] Furthermore, in step S2, the reaction time is 600 s.

[0022] Furthermore, in step S3, Au + The solution was prepared by adding NaBr to a chloroauric acid solution and shaking to dissolve it. Then, ascorbic acid solution was continuously added dropwise while shaking until the solution became clear and transparent. This yielded a colorless Au solution. + Solution.

[0023] Furthermore, the molar concentration of the chloroauric acid solution was 1 mM, the molar concentration of the ascorbic acid solution was 0.1 M, and the volume ratio of the chloroauric acid solution, NaBr, and ascorbic acid solution was 12 ml: 40 mg: 121 μl.

[0024] Furthermore, Au + The concentration of the solution is 0.99 mM.

[0025] Furthermore, in step S3, the reaction time is 1-5 minutes.

[0026] Furthermore, in step S3, the reaction time is 2 minutes.

[0027] The present invention also provides a periodic Au / Ag cascaded nanoflower array structure prepared by the above preparation method.

[0028] Furthermore, the aforementioned periodic Au / Ag cascaded nanoflower array structure can be applied to trace detection.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) This invention employs a combination of template method and chemical synthesis method to prepare periodic Au / Ag cascaded nanoflower array structures. First, a densely arranged PS microsphere array is self-assembled on the surface of ultrapure water using liquid surface self-assembly. This array is then retrieved and placed on the desired substrate to prepare a periodically densely arranged PS sphere array template. This template method is low in cost, simple in preparation, and highly reproducible.

[0031] (2) This invention utilizes chemical synthesis, leveraging its advantage of generating highly active sites, to synthesize highly active metal nanostructures on PS microsphere templates. Based on this, an in-situ substitution method is used to synthesize Au / Ag nanocomposite structures. Utilizing the cascade coupling enhancement effect of the composite structure, a large-area periodic cascaded metal nanoflower-like structure is prepared, exhibiting advantages such as uniformity, stability, and reproducibility, and possessing a strong SERS enhancement effect. Attached Figure Description

[0032] Figure 1 A template for uniformly arranged PS spheres;

[0033] Figure 2SEM images of the silver mirror reaction at different times in Example 2 of the present invention: (a) 100s, (b) 200s, (c) 300s, (d) 400s, (e) 500s, (f) 600s, (g) 700s, (h) 800s (scale bar is 200nm).

[0034] Figure 3 The signal intensities of the samples corresponding to different times of the silver mirror reaction in Example 2 of the present invention are: (a) 100s, (b) 200s, (c) 300s, (d) 400s, (e) 500s, (f) 600s, (g) 700s, (h) 800s.

[0035] Figure 4 In Embodiment 3 of the present invention, in Au + SEM images of the substitution reaction in solution at different times; (a) 1 minute, (b) 2 minutes, (c) 5 minutes (scale bar is 200 nm); the image with the black border in the upper right corner is the SEM image after increasing the magnification of the current image (scale bar is 50 nm);

[0036] Figure 5 The signal intensities of the samples at different times during the substitution reaction in Example 3 of this invention are: (a) 1 minute, (b) 2 minutes, and (c) 5 minutes.

[0037] Figure 6 The following is a graph showing the test results of Ag-600 / Au-2 provided in Example 3 of the present invention, wherein (a) is the SERS spectrum of the CV solution collected at 30 random sites on the Ag-600 / Au-2 substrate; (b) is the SERS spectrum of the solution collected at 1162 cm⁻¹. -1 (c) Statistical analysis of Raman intensity of characteristic peaks at CV; (d) Concentration-dependent SERS spectrum of CV on Ag-600 / Au-2 substrate; -1 Quantitative relationship between SERS intensity and the corresponding logarithm of concentration. Detailed Implementation

[0038] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the invention as detailed in the claims.

[0039] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials are all commercially available products.

[0040] PS sphere suspension: Purchased from Nantong Feiyu Biotechnology Co., Ltd. Product information: 300nm PS spheres dispersed in deionized water at a ratio of 2.5% (w / v). Ingredients: Sodium dodecyl sulfate (SDS), anhydrous ethanol, acetone (C3H6O), silver nitrate (AgNO3), ammonia solution (NH3·H2O), glucose (C6H... 12 O6), tin chloride dihydrate (SnCl2·2H2O), chloroauric acid (HAuCl4·4H2O), sodium bromide (NaBr), ascorbic acid (AA), crystal violet (C 24 H 28 C l N3 was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0041] Example 1: Preparation of PS sphere template

[0042] 1. Immerse the cut silicon wafer (5mm*5mm) in deionized water, acetone, ethanol and deionized water in sequence for ultrasonic cleaning for 5 minutes, and then dry with N2.

[0043] 2. Irradiate the silicon wafer obtained in step 1 with an ultraviolet surface irradiation device for 20 minutes to ensure that its surface is hydrophilic.

[0044] 3. Mix the PS sphere suspension and ethanol in a 2:3 ratio, and then mix them evenly by ultrasonication to obtain a PS sphere solution.

[0045] 4. Pour deionized water into a clean petri dish, and add 35 μl of 20 mM sodium dodecyl sulfate (SDS) to the water surface to enhance its surface tension. Take a clean glass slide, and after hydrophilic treatment, place it on the edge of the petri dish. Slowly drop the PS spheroid solution onto the water surface along the slide. Under the combined action of electrostatic force and surface tension, the PS spheroids form a dense PS spherical film on the liquid surface.

[0046] 5. Place the silicon wafer obtained from the hydrophilic treatment in step 2 under the PS sphere membrane, gently lift it up to separate the PS sphere membrane from the water surface, and wait for the deionized water to dry naturally to form a tightly packed PS sphere template.

[0047] 6. Perform reactive ion etching (RIE) on the PS ball template obtained in step 5 to obtain an etched PS ball template. The gas used for RIE is N2, the etching power is 90W, and the time is 6 minutes. The purpose of RIE is to create gaps between the PS balls for silver particle growth and to fix the PS balls on the silicon wafer so that the template will not fall off due to subsequent operations.

[0048] Example 2: Silver Mirror Reaction

[0049] 1. Pre-treatment was performed on the etched PS ball templates (10 pieces) prepared in Example 1. The treatment method is as follows: the beaker and the PS ball template were immersed in a 1% stannous chloride solution for 5-10 seconds, then rinsed with deionized water and dried for further use.

[0050] 2. Add 10 ml of 20 mmol / L AgNO3 solution to a clean beaker, and then gradually add 0.7 ml of 1 mol / L ammonia solution until the precipitate disappears and the mixed solution becomes clear and transparent, forming a silver ammonia solution.

[0051] 3. Add 10.7 ml of silver ammonia solution and 0.418 g of the etched PS sphere template obtained in step 1 to a beaker, add 2 ml of 0.985 mol / L glucose solution, and proceed with the reaction at room temperature. After the reaction time is reached, remove the reaction solution, rinse with deionized water, and dry to obtain a flower-like PS sphere array coated with silver nanoparticles.

[0052] SEM images of the silver mirror reaction from 100s to 800s are shown below. Figure 2 As shown. Samples reacting at different times were labeled Ag-100, Ag-200, ..., Ag-800, respectively. According to... Figure 2 It can be observed that, due to the in-situ growth mechanism of silver particles, as the reaction time progresses, the silver particles gradually increase in size, the gaps between particles gradually decrease, and the PS sphere template still maintains its original array structure, presenting a silver nanoflower shape based on the PS sphere template.

[0053] Using samples after silver mirror reaction (samples after silver mirror reaction at 8 different times) as substrates, and crystal violet (CV) as the probe molecule, SERS detection was performed on substrates at different reaction times. The results are as follows: Figure 3 As shown, the characteristic peak is at 162 cm⁻¹. -1 As the silver mirror reaction time progresses, the signal intensity of the substrate gradually increases. When the reaction reaches a certain point, around 500 seconds, the signal enhancement tends to level off. The signal intensity reaches its maximum at 600 seconds, and then gradually decreases.

[0054] Example 3: Using Ag-600 (sample obtained with a silver mirror reaction time of 600 s) as a sacrificial template, Ag-Au composite nanoarray structures were obtained through in-situ substitution reduction.

[0055] 1. Add 40 mg of NaBr to 12 ml of 1 mM chloroauric acid solution and shake to dissolve. Then, continuously add 121 μl of 0.1 M ascorbic acid (AA) solution dropwise while shaking until the solution becomes clear and transparent. This prepares colorless Au. + Solution.

[0056] 2. Soak Ag-600 in 12ml Au + Periodic nanostructures with different alloy morphologies were obtained by immersing the nanostructures in solution for different durations.

[0057] SEM images of samples after soaking for different times are shown below. Figure 4 As shown. Among them, Figure 4 (a) The soaking reaction time is 1 minute (denoted as Ag-600 / Au-1). Figure 4 (b) The soaking reaction time is 2 minutes (denoted as Ag-600 / Au-2). Figure 4 (c) The soaking reaction time is 5 minutes (denoted as Ag-600 / Au-5).

[0058] according to Figure 4 It can be observed that, using a flower-shaped PS sphere array encapsulated in silver nanoparticles as a sacrificial template, in Au + Immersion in the solution for different times yielded gold / silver nanoflower arrays with different alloy morphologies, increasing the surface roughness of the samples. With increasing reaction time, the growth morphology of the gold nanostructures depended on the morphology of the sacrificial template.

[0059] Au + The modified sample (periodic nanostructure) served as the SERS detection substrate. CV was used as the probe molecule to detect the sample, and the results are as follows: Figure 5 As shown in the figure. The results show that the sample signal strengthens with increasing soaking time, reaching a maximum at 2 minutes. When the time is extended to 5 minutes, the signal intensity decreases significantly.

[0060] Testing was performed on the Ag-600 / Au-2 substrate, with all probe molecules being CV and a concentration of 10. -5 M. The result is as follows Figure 5 As shown, Figure A shows the SERS spectra collected at 30 random points on an Ag-600 / Au-2 substrate, and Figure B shows the SERS spectra collected at 1162 cm⁻¹. -1 Statistical analysis of Raman intensities of characteristic CV peaks. Figure C shows the SERS spectra of different concentrations of CV molecules detected on an Ag-600 / Au-2 substrate. Figure D shows the SERS spectra at 1162 cm⁻¹. -1 Quantitative relationship between SERS intensity and the corresponding logarithm of concentration.

[0061] As the detection concentration decreases, the CV of the probe molecule at its characteristic peak of 1162 cm⁻¹... -1 The Raman intensity gradually decreased at the specified location, indicating that the substrate possesses good quantitative analytical capabilities; when the CV concentration was below 10... -9 Even at M, the characteristic peaks of CV molecules can still be detected, demonstrating high detection sensitivity.

Claims

1. A method for preparing a periodic Au / Ag cascaded nanoflower array structure, characterized in that, Includes the following steps: S1. Prepare a PS sphere template and perform reactive ion etching on the PS sphere template; S2. Prepare silver ammonia solution. Add the silver ammonia solution and the PS ball template prepared in step S1 into a beaker, add glucose solution, and react at room temperature. After the reaction is completed, the product is washed with deionized water and dried to obtain a flower-shaped PS ball array wrapped with silver nanoparticles. The ratio of silver ammonia solution, PS ball template, and glucose solution was 10.7 mL: 0.418 g: 2 mL, and the reaction time was 100-800 s. S3. Using the flower-shaped PS sphere array as a sacrificial template, immerse the flower-shaped PS sphere array in Au. + The reaction in solution for 1-5 minutes yielded a periodic Au / Ag cascaded nanoflower array structure. Au + The solution is prepared by adding NaBr to a chloroauric acid solution and shaking to dissolve it. Subsequently, ascorbic acid solution was added dropwise while shaking until the solution became clear and transparent, thus preparing a colorless Au solution. + Solution; The molar concentration of chloroauric acid solution was 1 mM, the molar concentration of ascorbic acid solution was 0.1 M, and the volume ratio of chloroauric acid solution, NaBr and ascorbic acid solution was 12 ml: 40 mg: 121 μl.

2. The preparation method according to claim 1, characterized in that, In step S1, the preparation of the PS sphere template includes the following steps: S11. Mix the PS sphere suspension with ethanol to obtain a PS sphere solution; S12. Pour deionized water into a clean petri dish and add a few drops of 20mM sodium dodecyl sulfate to the surface of the water to enhance the surface tension of the water. S13. The PS sphere solution is slowly dripped onto the water surface after step S12 along a hydrophilic glass slide. Under the combined action of electrostatic force and surface tension, the PS spheres form a dense PS sphere film on the liquid surface. S14. The PS sphere membrane is separated from the water surface using a hydrophilic silicon wafer, and the deionized water is allowed to dry naturally to form a tightly packed PS sphere template.

3. The preparation method according to claim 2, characterized in that, In the PS sphere solution, the volume ratio of PS sphere suspension to ethanol is 2:

3.

4. The preparation method according to claim 2, characterized in that, The method for preparing the hydrophilic silicon wafer is as follows: irradiating the clean surface of the silicon wafer with ultraviolet light.

5. The preparation method according to claim 1, characterized in that, In step S1, the conditions for reactive ion etching are: gas is N2, etching power is 90 W, and time is 6 min.

6. The preparation method according to claim 1, characterized in that, In step S1, after reactive ion etching of the PS ball template, it is immersed in a 1wt% stannous chloride solution for 5-10 seconds, then rinsed with deionized water and dried.

7. The preparation method according to claim 1, characterized in that, In step S2, the silver ammonia solution is prepared as follows: 20 mmol / L AgNO3 solution is added to a clean beaker, and then 1 mol / L ammonia solution is gradually added dropwise until the precipitate disappears and the mixed solution becomes clear and transparent, thus forming a silver ammonia solution; the volume ratio of the AgNO3 solution to the ammonia solution is 10:0.

7.

8. The periodic Au / Ag cascaded nanoflower array structure prepared by the preparation method according to any one of claims 1-7.

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