Silicon-based SERS (Surface Enhanced Raman Scattering) substrate material with high yield and preparation method thereof

Abstract

The invention relates to the field of nano material preparation and SERS (Surface Enhanced Raman Scattering) analysis, and particularly provides a preparation method of a high-yield silicon-based SERS substrate material. The method mainly comprises the following five steps of silicon wafer cleaning pretreatment, silicon wafer HF treatment, Ag nanoparticle deposition on the surface of the silicon wafer, Au-Ag nanoparticle deposition on the surface of the silicon wafer and silicon wafer aftertreatment. The silicon-based SERS substrate material prepared by the method shows high SERS activity (enhancement factor EFgt; 108) and good surface uniformity (RSDlt; 15%). In addition, the SERS substrate materials prepared in different batches keep high yield (95%). The method disclosed by the invention has the advantages of simple preparation process, low cost, short consumed time, high yield and the like, and is expected to be applied to the fields of commercial SERS substrate preparation and analysis thereof.

Description

Technical Field

[0001] The invention belongs to the field of nano material preparation and SERS analysis, and specifically relates to a silicon-based SERS substrate material with high Raman activity and high yield and a preparation method thereof. Background Art

[0002] Surface Enhanced Raman spectroscopy (SERS) has attracted extensive attention in the analytical field due to its ultra-high detection sensitivity, rapidity, low cost, and ability to obtain fingerprint information of molecules. The preparation of SERS substrate materials is the basis for obtaining SERS signals and is also the key to affecting SERS analytical performance.

[0003] In the past few decades, SERS active substrates have made significant progress in terms of substrate material composition, structure and preparation methods. In terms of material composition, it has expanded from simple Au / Ag nanoparticles to Au-Ag bimetallic nanoparticles. This material not only retains the excellent SERS activity of Ag nanoparticles, but also has the biocompatibility and excellent chemical stability of Au nanoparticles. In terms of particle structure, in addition to traditional spherical particles, various shapes such as nanorods, nanostars and various biomimetic materials have been continuously synthesized. In addition, the preparation method of SERS active substrates has also achieved a leap from preparing well-dispersed nanoparticle colloids to preparing highly ordered solid platform substrates using advanced nanoprocessing technology, including chemical reduction, nanoparticle assembly, nanolithography and nanoimprinting.

[0004] The inventors have previously reported several innovative silicon-based SERS substrate materials (Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2023, 301: 122941; A silicon-based SERS substrate material and its preparation method, patent number: 202311213662 [P]), which exhibit high Raman enhancement activity, excellent surface uniformity and good chemical stability. However, in the subsequent large-scale preparation process, the applicant found that the SERS substrate material obtained by the above method still needs to be improved in terms of batch consistency, and sometimes even quality problems occur; at the same time, the method reported in the CN 117418220 A method requires CuCl2 etching, and the operation is relatively complicated. Therefore, how to prepare a SERS substrate material that is easy to operate and has high Raman activity and high yield is still a key technical problem that needs to be solved in the SERS field. Summary of the invention

[0005] The purpose of the present invention is to make up for the deficiencies of the prior art and provide a new method for preparing a silicon-based SERS substrate material, which has the advantages of being simple, rapid and low-cost, and the obtained SERS substrate material has high SERS activity and high yield.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a silicon-based SERS substrate material with a high yield rate comprises the following steps:

[0008] (1) The silicon wafer is ultrasonically cleaned using acetone, ethanol and purified water in sequence;

[0009] (2) immersing the cleaned silicon wafer in an HF solution to remove surface oxides;

[0010] (3) placing the silicon wafer soaked in HF in a mixed solution of AgNO3 / HF to react, thereby obtaining Ag@Si with Ag nanoparticles coated on the surface;

[0011] (4) washing the Ag@Si in purified water and HF solution in turn;

[0012] (5) placing the Ag@Si obtained in step (5) in a HAuCl4 / HF mixed solution to react, thereby obtaining a SERS substrate material Au-Ag@Si;

[0013] (6) Au-Ag@Si was immersed in saturated NaCl solution, HF solution and purified water respectively to obtain the final product.

[0014] In the present invention, the silicon material in step (2) does not need to be treated with CuCl2, the operation is simpler, and the yield of the obtained product is significantly improved, while the SERS activity of the product is maintained without reduction.

[0015] There is no special requirement for the crystal form of the silicon wafer in step (1);

[0016] In step (1), the ultrasonic cleaning time of acetone, ethanol and purified water is 5 to 10 minutes respectively;

[0017] In step (2), the HF concentration is 5-10% (the original HF solution concentration is ≥40%, which is prepared by diluting with water, and the following are similar), and the soaking time is 0.5-2h;

[0018] In step (3), the concentration of AgNO3 is 6-10 mM, the concentration of HF is 5-10%, and the reaction time is 15-25 s;

[0019] In step (4), the immersion time of the purified water and HF solution is 1 to 5 minutes;

[0020] In step (4), the HF concentration is 5 to 10%;

[0021] In step (5), the HAuCl4 concentration is 1.25-3 mM, the HF concentration is 5-10%, the reaction temperature is 60-70°C, and the reaction time is 1-5 min;

[0022] In step (6), the concentration of HF solution is 1% to 3%, and the cleaning time of each step is not less than 5 minutes;

[0023] The SERS substrate material prepared in step (6) has strong SERS activity (enhancement factor EF>10 8 ), good surface uniformity (Raman probe molecular signal RSD <15%) and high yield rate (>95%);

[0024] The evaluation standard for the SERS substrate material prepared in step (6) to be a good product is that the enhancement factor EF must be greater than 10 8 , and the chip has no background interference peaks;

[0025] The method for calculating the yield rate of the SERS substrate material prepared in step (6) is to independently prepare no less than 10 batches, no less than 3 chips each time, and examine whether each chip is a good product;

[0026] The SERS performance of the SERS substrate material prepared in step (6) is studied under an excitation light source of 785 nm.

[0027] The SERS substrate material prepared in step (6) is prepared by a method for preparing the SERS substrate material, and the SERS performance of the prepared SERS substrate material is evaluated by rhodamine 6G (R6G).

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The present invention has the remarkable characteristics of simple preparation method and quick preparation time. Moreover, the prepared SERS substrate material not only shows higher Raman activity, but also significantly improves the yield rate of the product, successfully overcoming the problem that the yield rate of existing silicon-based SERS substrate materials is difficult to guarantee. In view of the excellent performance of the substrate material prepared by the method of the present invention, it shows broad prospects in the application field of commercial SERS substrate materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The results of SERS substrate material characterization are shown in Figure 3, where (a) and (b) are SEM morphology images, (c) is the distribution of Au, Ag and Si elements on the surface of the material, and (d) is the semi-quantitative analysis result of Au, Ag and Si elements.

[0031] Figure 2 Au-Ag@Si(I), Ag@Si(II) and pure silicon wafers were immersed in 10 -8 M R6G (Au-Ag@Si and Ag@Si) and 10 -2 M Raman spectrum of R6G (pure silicon wafer) solution after 2h;

[0032] Figure 3 For 10 -8 Raman spectra of MR6G adsorbed on the surface of Au-Ag@Si material at 20 random points (a) and its Raman spectrum at 1509 cm -1 RSD value of intensity at (b);

[0033] Figure 4 Calculation results of yield of different SERS substrate materials, where (a) is the method described in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2023, 301: 122941, (b) is the method described in Example 1 of CN117418220 A; (c) is the method described in Example 1 of the present invention;

[0034] Figure 5 The figure is a flow chart of the preparation of the SERS substrate material of the present invention. DETAILED DESCRIPTION

[0035] The specific implementation of the present invention is further described in detail below in conjunction with the drawings and specific embodiments.

[0036] The HF used in the following examples is obtained by diluting a commercially available HF solution, and the concentration of the original HF solution is ≥40%.

[0037] Example 1

[0038] (1) Take the crystal form <100> The silicon material was ultrasonically cleaned with acetone, ethanol and purified water for 5 minutes each.

[0039] (2) Soak the cleaned silicon wafer in 5% HF solution for 30 minutes;

[0040] (3) The HF-treated silicon wafer was placed in a mixed solution containing 7 mM AgNO3 and 5% HF, and gently shaken at room temperature for 20 seconds to obtain Ag@Si with Ag nanoparticles coated on the surface;

[0041] (4) After washing the Ag@Si with purified water, immerse it in 5% HF solution again for 1 min;

[0042] (5) placing Ag@Si in a mixed solution containing 2.5 mM HAuCl4 and 5% HF and reacting at 65°C for 3 min to obtain Au-Ag@Si with Au-Ag nanoparticles deposited on the surface;

[0043] (6) Soak Au-Ag@Si in saturated saline, 1% HF solution and purified water for 10 min in sequence, and then take it out to obtain the final SERS substrate material.

[0044] The performance of the obtained product was characterized as follows. The result characterization graph of the obtained SERS substrate material is shown in Figure 1 The obtained Au-Ag@Si and pure silicon wafers were immersed in 10 -8 M R6G (Au-Ag@Si) and 10 -2 The Raman spectrum of R6G (pure silicon wafer) solution after 2 hours is shown in Figure 2 The Raman spectra of R6G adsorbed on the surface of Au-Ag@Si material at 20 random points (a) and its Raman spectrum at 1509 cm -1 The RSD value of the intensity at (b) is shown in Figure 3 20 batches were prepared independently, with no less than 3 chips each time, and the yield rate of the prepared SERS chips was calculated and compared with the two reported methods. Figure 4 .Depend on Figure 4 It can be seen that under the premise of ensuring Raman activity, the yield rate of the preparation method of the present invention is significantly improved.

Claims

1. A method for preparing a silicon-based SERS substrate material with a high yield, characterized in that: The steps include: (1) The silicon wafer is ultrasonically cleaned using acetone, ethanol and purified water in sequence; (2) immersing the cleaned silicon wafer in an HF solution to remove surface oxides; (3) placing the silicon wafer soaked in HF in a mixed solution of AgNO3 / HF to react, thereby obtaining Ag@Si with Ag nanoparticles coated on the surface; (4) washing the Ag@Si in purified water and HF solution in turn; (5) placing the Ag@Si obtained in step (5) in a HAuCl4 / HF mixed solution to react, thereby obtaining a SERS substrate material Au-Ag@Si; (6) Au-Ag@Si was immersed in saturated NaCl solution, HF solution and purified water respectively to obtain the final product.

2. The method for preparing a silicon-based SERS substrate material according to claim 1, characterized in that: In step (1), the ultrasonic cleaning time of acetone, ethanol and purified water is 5 to 10 minutes.

3. The method for preparing a silicon-based SERS substrate material according to claim 1, characterized in that: In step (2), the HF concentration is 5-10%, and the soaking time is 0.5-2h.

4. The method for preparing a silicon-based SERS substrate material according to claim 1, characterized in that: In step (3), the concentration of AgNO3 is 6-10 mM, the concentration of HF is 5-10%, and the reaction time is 15-25 s.

5. The method for preparing a silicon-based SERS substrate material according to claim 1, characterized in that: In step (4), the soaking time of purified water and HF solution is 1 to 5 minutes.

6. The method for preparing a silicon-based SERS substrate material according to claim 1, characterized in that: The HF concentration in step (4) is 5-10%.

7. The method for preparing a silicon-based SERS substrate material according to claim 1, characterized in that: In step (5), the concentration of HAuCl4 is 1.25-3 mM, the concentration of HF is 5-10%, the reaction temperature is 60-70°C, and the reaction time is 1-5 min.

8. The method for preparing a silicon-based SERS substrate material according to claim 1, characterized in that: The concentration of the HF solution in step (6) is 1% to 3%, and the cleaning time for each step is not less than 5 minutes.

9. A silicon-based SERS substrate material obtained by the preparation method according to any one of claims 1 to 8.

10. The silicon-based SERS substrate material according to claim 9, characterized in that: The enhancement factor EF of the silicon-based SERS substrate material is > 10 8 , Raman probe molecule signal RSD<15%, yield>95%.

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