Preparation method of silver nanosheet array structure
The preparation of silver nanosheet arrays through laser direct write lithography and SF6 etching technology solves the problems of poor structural controllability and complex preparation in traditional methods, and realizes an efficient and regular silver nanosheet array, which significantly improves SERS performance. The application of SERS technology provides new possibilities.
Patent Information
- Application Number
- CN202411332238.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-24
- Publication Date
- 2024-12-31
AI Technical Summary
The traditional silver nanosheet preparation method has problems such as poor structural controllability and complex preparation process, and it is difficult to achieve a regular and uniform silver nanosheet array on large-area substrates, which limits the improvement of surface-enhanced Raman scattering (SERS) performance.
The silver nanosheet array was prepared by laser direct writing lithography and SF6 etching technology. The silver nanosheets were generated by forming micropore arrays on the silicon wafer, depositing metal silver films, and induced treatment of reactive ion etching and 4-MBA solution. Regular silver nanosheet structure.
This method is simple and has high control, significantly improves the strength of the SERS signal, and provides a SERS substrate with high sensitivity and high stability, suitable for chemical sensing, biological detection and environmental monitoring.
Smart Images
Figure CN119220943A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of micro-nano structures and relates to a method for preparing a silver nanosheet array structure. Background Art
[0002] Surface enhanced Raman scattering (SERS) technology has gained widespread attention in recent years due to its outstanding performance in the field of ultrasensitive detection. The performance of SERS substrates depends largely on their surface plasmon resonance properties, which are usually provided by nanostructured materials. Silver, as a common SERS substrate material, is widely used to prepare SERS substrates due to its unique optical properties and high plasmon resonance frequency. In particular, silver nanosheet structures can significantly enhance Raman scattering signals due to their high surface area and surface localized plasmon resonance (LSPR) effect, showing excellent SERS performance.
[0003] Traditional methods for preparing silver nanosheets, including chemical reduction, electrochemical and template methods, can produce silver nanostructures with certain SERS performance, but these methods have some significant limitations. For example, the size and shape of the nanosheets in the chemical reduction method are difficult to control accurately, the arrangement and uniformity of the nanosheets in the electrochemical method are poor, and although the template method can provide certain structural controllability, its preparation process is complicated and it is not easy to prepare uniformly over a large area.
[0004] In recent years, researchers have further enhanced the SERS performance of silver nanosheets by introducing multi-level roughness and nanoscale concave-convex structures on the surface of silver nanostructures. These microstructures can provide more "hot spots" (i.e., local electric field enhancement areas) and significantly improve the intensity of SERS signals. However, how to achieve the preparation of structured and controllable silver nanosheets on large-area substrates remains a technical challenge.
[0005] How to effectively control the structure and surface characteristics of silver nanosheets has become a key issue in improving the performance of SERS substrates. Therefore, developing a new method for preparing silver nanosheets can further improve the SERS performance while maintaining structural regularity and ease of preparation, which has important scientific significance and practical application value. Summary of the invention
[0006] The purpose of the present invention is to develop a new method for preparing silver nanosheets, which can further improve the SERS performance while maintaining structural regularity and simplicity of preparation. The present invention prepares silver nanosheet surface enhanced Raman scattering (SERS) substrates based on laser direct writing lithography and SF6 etching technology.
[0007] A method for preparing a silver nanosheet array structure comprises the following steps:
[0008] A silicon wafer with a photoresist layer on its surface is obtained as a substrate;
[0009] According to the preset position, the photoresist layer is processed by a laser direct writing method to obtain a microwell array at the preset position on the substrate; the photoresist layer at the bottom of the microwells in the microwell array is completely removed to expose the substrate;
[0010] Depositing a metallic silver film on one side of the substrate having the microhole array;
[0011] The photoresist layer is stripped to obtain a silver column array at the location of the micropores on the substrate surface, wherein the silver columns have a diameter of 4 μm and a height of 600 nm;
[0012] The surface of the silver column array is etched with SF6 using a reactive ion etching (RIE) method; the silver column array after SF6 etching is induced to obtain silver nanosheets on the surface of the silver columns.
[0013] Preferably, the SF6 etching of the surface of the silver column array structure using a reactive ion etching (RIE) method specifically includes the following steps: etching power of 100 W, pressure of 20 Pa, gas flow rate of 50 sccm, and etching time of 30 to 90 s.
[0014] Preferably, the induction treatment specifically comprises the following steps: immersing the silver column array in a 4-MBA solution to induce the formation of nanosheets, the immersion time being 4 to 24 hours.
[0015] Preferably, the depositing of the metal silver film specifically comprises the following steps: firstly depositing a 5-nanometer-thick chromium layer and then depositing a 600-nanometer-thick silver layer by magnetron sputtering, and improving the bonding force between the silver layer and the substrate by the chromium layer.
[0016] Preferably, the deposition of 5 nanometers thick chromium specifically includes the following steps: controlling the sputtering pressure to 0.6 Pa, the sputtering power of Cr to 0.01 KW, and the sputtering time to 5 s.
[0017] Preferably, the deposition of a 600-nanometer-thick silver layer specifically includes the following steps: controlling the sputtering pressure to 0.6 Pa, the Ag sputtering power to 0.1 KW, and the sputtering time to 2 min.
[0018] Preferably, the composition of the photoresist layer is positive photoresist RZJ-390PG; the thickness of the photoresist layer is 1 micron; the de-gumming process specifically includes the following steps: using N-methylpyrrolidone to remove the photoresist.
[0019] Preferably, the diameter of the micropores in the micropore array is 4 microns.
[0020] The method prepares a regular silver nanocolumn array on a silicon wafer, and obtains a silver nanosheet structure by etching and solution immersion. This silver nanosheet structure can significantly improve the intensity of the SERS signal. Since SF6 reacts with Ag to form a large number of sulfur-silver bonds, and there are carboxyl bonds in 4-MBA molecules, both are key substances for the formation of silver nanosheets, in which silver ions are reduced to silver through a reduction reaction, thereby forming a silver nanosheet structure. The silver column array etched by SF6 can generate silver nanosheets by simply immersing it in a 4-mercaptobenzoic acid (4-MBA) solution, while the silver column array that has not been etched by SF6 shows no signs of growth under solution immersion.
[0021] The method of the present invention has simple steps and strong controllability, and can prepare a uniform and high-efficiency silver nanosheet SERS substrate on a large-area substrate. Compared with the traditional method, the silver nanosheet SERS substrate prepared by the present invention not only has higher structural regularity and better SERS performance, but also does not require illumination conditions during the preparation process, and has a wider range of applicability. The SERS substrate of the invention has broad application potential in the fields of chemical sensing, biological detection, environmental monitoring, etc.
[0022] The present invention solves the problems of poor structural controllability and complex process in the traditional silver nanosheet SERS substrate preparation method, provides a new type of SERS substrate material with high sensitivity and high stability, and provides new possibilities for the further development and application of SERS technology. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 It is a schematic diagram of the preparation process of the present invention.
[0024] Figure 2 SEM images of the evolution of silver pillar arrays under different conditions, where (a) is the silver pillar array without SF6 etching. (b) is the SEM of the silver pillars without SF6 etching after 4-MBA induction. (c) is the silver pillars etched by SF6. (d) is the SEM of the silver pillars etched by SF6 and induced by 4-MBA.
[0025] Figure 3 Figures 2-3 show the SEM images and SERS performance images of silver nanosheets at different etching times, where (a1) and (a2) are low-magnification and high-magnification SEM images of the silver nanosheets after etching for 30 seconds, respectively, corresponding to Example 2-2; (b1) and (b2) are low-magnification and high-magnification SEM images of the silver nanosheets after etching for 60 seconds, respectively, corresponding to Example 2-1; (c1) and (c2) are low-magnification and high-magnification SEM images of the silver nanosheets after etching for 90 seconds, respectively, corresponding to Example 2-3.
[0026] Comparing the three different embodiments, the SERS performance of the samples at different etching times will change over time, and the SERS performance of the sample in embodiment 2-1 is the best.
[0027] Figure 4 The SEM images of silver nanosheets and SERS performance images after etching for 60s at different immersion times. In the figure, (a) is immersion for 4 hours, corresponding to Example 3-1; (b) is immersion for 8 hours, corresponding to Example 3-2; (c) is immersion for 12 hours, corresponding to Example 3-3; (d) is immersion for 24 hours, corresponding to Example 3-4. 4, 8, 12 hours, the number and size of the silver nanosheets prepared in Example 3-1, Example 3-2, and Example 3-3 increase with the immersion time, and the SERS performance also increases accordingly, as shown in FIG. Figure 4 However, after more than 12 hours, that is, 24 hours, the number of silver nanosheets prepared in Example 3-4 did not increase significantly, and the SERS performance remained basically unchanged. Figure 4 (d) as shown. DETAILED DESCRIPTION
[0028] In order to further understand the present application, the method for preparing silver nanosheets provided in the present application is described in detail below in conjunction with examples, and the protection scope of the present application is not limited by the following examples.
[0029] The method for preparing silver nanosheets provided in the present application comprises the following steps:
[0030] The microwell array was obtained on the silicon wafer substrate by laser direct writing method.
[0031] The micro-hole array is subjected to a coating process to form a layer of Ag film, and the coated micro-hole array is subjected to a debonding process to obtain a columnar array structure.
[0032] The silver column array is etched and induced to obtain silver nanosheets. Since SF6 reacts with Ag to form a large number of sulfur-silver bonds, and there are carboxyl bonds in the 4-MBA molecule, both are key substances for the formation of silver nanosheets. The silver ions are reduced to silver through a reduction reaction, thus forming a silver nanosheet structure.
[0033] Example 1
[0034] The microwell array was obtained on the silicon wafer substrate by laser direct writing method.
[0035] The positive photoresist RZJ-390PG is spin-coated on the silicon wafer to form a photoresist layer with a thickness of about 1 micron. The photoresist is exposed by laser direct writing lithography technology, and the developer is used to develop to generate a hole array structure with a diameter of 4 microns.
[0036] The treated micropore array was subjected to coating treatment. During the coating process, single sputtering of Cr and Ag was used to ensure that the pressure in the chamber was 0.6 Pa during sputtering. The sputtering power of Cr was adjusted to 0.01 KW, and the sputtering time was 5 s. The sputtering power of Ag was adjusted to 0.1 KW, and the sputtering time was 2 min.
[0037] Magnetron sputtering was performed on the hole array to deposit a 5 nm thick chromium layer and a 600 nm thick silver layer in sequence. The photoresist was removed using N-methylpyrrolidone (NMP) to retain the silver column array.
[0038] The surface of the silver pillars was etched with SF6 using reactive ion etching (RIE) technology, and the silver pillar array was immersed in a 4-MBA solution to induce the formation of nanosheets.
[0039] Example 2 includes Example 2-1, Example 2-2 and Example 2-3
[0040] Example 2-1
[0041] The difference between this embodiment and embodiment 1 is that:
[0042] As described in Example 1, the silver column array is immersed in a 4-MBA solution to induce the formation of nanosheets, specifically comprising:
[0043] The silver column array was immersed in a 4-MBA solution with a concentration of 1 mM for 12 hours.
[0044] The SF6 etching of the silver column surface by using reactive ion etching (RIE) technology described in Example 1 specifically includes:
[0045] The surface of the silver column was etched by ion etching (RIE) technology, and the etching gas was SF6, the etching power was 100W, the pressure was 20Pa, the gas flow rate was 50sccm, and the etching time was 60s.
[0046] Example 2-2
[0047] The difference from Example 2-1 is that the etching time is 30 seconds, and the other preparation methods and conditions are the same as those of Example 2-1.
[0048] Example 2-3
[0049] The difference from Example 2-1 is that the etching time is 90 seconds, and other preparation methods and conditions are the same as those of Example 2-1.
[0050] Example 3 includes Example 3-1, Example 3-2, Example 3-3 and Example 3-4
[0051] Example 3-1
[0052] The difference between this embodiment and embodiment 1 is that:
[0053] The SF6 etching of the silver column surface by using reactive ion etching (RIE) technology described in Example 1 specifically includes:
[0054] The surface of the silver column was etched by ion etching (RIE) technology, and the etching gas was SF6, the etching power was 100W, the pressure was 20Pa, the gas flow rate was 50sccm, and the etching time was 60s.
[0055] As described in Example 1, the silver column array is immersed in a 4-MBA solution to induce the formation of nanosheets, specifically comprising:
[0056] The silver column array was immersed in a 4-MBA solution with a concentration of 1 mM for 4 hours.
[0057] Example 3-2
[0058] The difference from Example 3-1 is that the soaking time is 8 hours, and the other preparation methods and conditions are the same as those of Example 3-1.
[0059] Example 3-3
[0060] The difference from Example 3-1 is that the soaking time is 12 hours, and other preparation methods and conditions are the same as those of Example 3-1.
[0061] Embodiment 3-4
[0062] The difference from Example 3-1 is that the soaking time is 24 hours, and other preparation methods and conditions are the same as those of Example 3-1.
Claims
1. A method for preparing a silver nanosheet array structure, characterized in that: The following steps are involved: A silicon wafer with a photoresist layer on its surface is obtained as a substrate; According to the preset position, the photoresist layer is processed by a laser direct writing method to obtain a microhole array at the preset position on the substrate; The photoresist layer at the bottom of the microwells in the microwell array is completely removed to expose the substrate; Depositing a metallic silver film on one side of the substrate having the microhole array; The photoresist layer is stripped to obtain a silver column array at the location of the micropores on the substrate surface, wherein the silver columns have a diameter of 4 μm and a height of 600 nm; The surface of the silver column array is etched with SF6 using a reactive ion etching (RIE) method; the silver column array after SF6 etching is induced to obtain silver nanosheets on the surface of the silver columns.
2. The method for preparing the silver nanosheet array structure according to claim 1, characterized in that: The method of using reactive ion etching (RIE) to perform SF6 etching on the surface of the silver column array structure specifically comprises the following steps: The etching power is 100W, the pressure is 20Pa, the gas flow rate is 50sccm, and the etching time is 30 to 90s.
3. The preparation method and application of the silver nanosheet array structure according to claim 1, characterized in that: The induction treatment specifically includes the following steps: immersing the silver column array in a 4-MBA solution to induce the formation of nanosheets, and the immersion time is 4 to 24 hours.
4. The method for preparing the silver nanosheet array structure according to claim 1, characterized in that: The depositing of the metallic silver film specifically comprises the following steps: By magnetron sputtering, a 5-nanometer-thick chromium layer is first deposited and then a 600-nanometer-thick silver layer is deposited. The chromium layer improves the bonding strength between the silver layer and the substrate.
5. The method for preparing the silver nanosheet array structure according to claim 4, characterized in that: The deposition of 5 nanometer thick chromium specifically includes the following steps: controlling the sputtering pressure to 0.6 Pa, the sputtering power of Cr to 0.01 KW, and the sputtering time to 5 s.
6. The method for preparing the silver nanosheet array structure according to claim 4, characterized in that: The process of depositing a 600-nanometer-thick silver layer specifically includes the following steps: controlling the sputtering pressure to be 0.6 Pa, the Ag sputtering power to be 0.1 KW, and the sputtering time to be 2 minutes.
7. The method for preparing the silver nanosheet array structure according to claim 1, characterized in that: The composition of the photoresist layer is positive photoresist RZJ-390PG; the thickness of the photoresist layer is 1 micron; The degumming process specifically includes the following steps: using N-methylpyrrolidone to remove the photoresist.
8. The method for preparing the silver nanosheet array structure according to claim 1, characterized in that: The diameter of the micropores in the micropore array is 4 microns.