Silver substrate and preparation method and application thereof

Abstract

The invention provides a silver substrate and a preparation method and application thereof.The preparation method comprises the steps that firstly, dispersed silver seeds are introduced to the surface of an aluminum-foil paper substrate through the reaction of silver nitrate and excessive alkali, and in-situ nucleation sites are provided for follow-up silver growth; and then, through in-situ reduction reaction of hydroquinone and silver nitrate, silver controllably grows on the basis of the silver seeds to form a structure rich in hot spots. Conventional raw materials such as aluminum foil, silver nitrate, alkali and hydroquinone are adopted in the whole process, complex equipment is not needed, and therefore the process is simple and low in cost; meanwhile, a step-by-step regulation and control mechanism ensures that a large number of'hot spots' formed by nano-structure gaps and tips are formed on the surface of the silver substrate, and the key structure can obviously enhance Raman signals, so that the high-sensitivity detection requirement is met. In conclusion, the method has the advantages of preparation convenience, cost and high performance of the product, a practical substrate which is easy to popularize and high in adaptability is provided for the field of surface enhanced Raman spectrum detection, and the method has remarkable application value.

Description

Technical Field

[0001] This invention relates to the field of surface-enhanced Raman spectroscopy, and more particularly to a silver substrate, its preparation method, and its application. Background Technology

[0002] Surface-enhanced Raman spectroscopy (SERS) is a non-destructive, rapid, and highly sensitive (single-molecule detection) in-situ analytical technique. Its fingerprint spectral region provides rich information on molecular composition and conformation, and it has wide applications in biomedicine, chemical analysis, food safety, environmental monitoring, and in-situ research. Single-molecule detection by SERS is achieved when the molecule is confined to a localized area of ​​the substrate (called a "hot spot"). High-hot-spot SERS substrates hold considerable promise for future applications.

[0003] However, existing SERS substrates made of different materials still have many shortcomings: liquid sol-based SERS substrates have poor stability and low detection sensitivity; noble metal substrates prepared by plasma sputtering can achieve rapid detection, but suffer from high loss rates. Furthermore, existing research has confirmed that noble metal substrates with abundant "hot spot" structures possess excellent SERS enhancement effects.

[0004] Therefore, developing a SERS substrate that is easy to operate, low in cost, has a low loss rate, and is rich in "hot spots" has important application value and broad prospects. Summary of the Invention

[0005] The purpose of this invention is to provide a silver substrate, its preparation method, and its application, in order to solve the technical problems of existing SERS substrates, such as complex preparation, high cost, high loss rate, and low detection sensitivity.

[0006] To address the aforementioned technical problems, this invention first provides a method for preparing a silver substrate, comprising the following steps: S10, the aluminum foil paper substrate is immersed in the first reaction solution and shaken. After rinsing, dispersed silver seeds are formed on the surface of the aluminum foil paper substrate. S20, an aluminum foil paper substrate with silver seeds is immersed in a growth solution for in-situ growth, so as to form a silver substrate rich in hot spots on the surface of the aluminum foil paper substrate. In step S10: the first reaction solution includes a first silver nitrate solution and an excess alkaline solution; in step S20: the growth solution includes a hydroquinone solution and a second silver nitrate solution.

[0007] Preferably, in step S10, the molar ratio of the first silver nitrate solution to the alkaline solution is 1:(8~12).

[0008] Preferably, in step S20: the hydroquinone solution and the second silver nitrate solution have the same concentration and the same volume.

[0009] Preferably, the concentration of the second silver nitrate solution is 10 to 20 times that of the first silver nitrate solution.

[0010] Preferably, after step S20 is completed, the method further includes: cutting the silver substrate to obtain a first silver electrode and a second silver electrode that are spaced apart from each other, wherein the area of ​​the first silver electrode is larger than the area of ​​the second silver electrode.

[0011] Preferably, the gap between the first silver electrode and the second silver electrode is greater than 0 and ≤2mm.

[0012] Preferably, when the width of the first silver electrode is the same as the width of the second silver electrode, the ratio of the length of the first silver electrode to the length of the second silver electrode is (1~8):1.

[0013] Accordingly, the present invention also provides a silver substrate prepared by any of the above methods.

[0014] Accordingly, the present invention also provides an application of the above-mentioned silver substrate in the field of surface-enhanced Raman spectroscopy detection.

[0015] Preferably, surface-enhanced Raman spectroscopy combined with electrohydrodynamics is used to detect p-methoxythiophenol.

[0016] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention provides a silver substrate, its preparation method, and its applications. The preparation method of the silver substrate is completed through a simple two-step process of "silver seed pre-formation—in-situ growth": First, in step S10, dispersed silver seeds are introduced onto the surface of an aluminum foil substrate using the reaction of silver nitrate with excess alkali, providing in-situ nucleation sites for subsequent silver growth; subsequently, in step S20, the in-situ reduction reaction of hydroquinone with silver nitrate allows silver to grow controllably on the silver seed, forming a structure rich in hot spots. Since the entire process uses conventional raw materials such as aluminum foil, silver nitrate, alkali, and hydroquinone, no complex equipment is required, making the process simple and cost-effective. Simultaneously, the step-by-step control mechanism ensures the formation of numerous "hot spots" on the silver substrate surface, composed of nanostructure gaps and tips—this key structure significantly enhances the Raman signal, meeting the requirements for high-sensitivity detection. In summary, this method combines ease of preparation, cost advantages, and high-performance products, providing an easily promoted and highly adaptable practical substrate for surface-enhanced Raman spectroscopy detection, possessing significant application value. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for preparing a silver substrate according to an embodiment of the present invention; Figure 2This is a schematic diagram of the preparation process of the silver substrate provided in Embodiment 1 of the present invention; Figure 3 This is a SEM image of the silver substrate provided in Embodiment 1 of the present invention; Figure 4 This is a test diagram of the signal detection of p-methoxythiophenol incubated on a silver substrate, provided in Example 1 of the present invention. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] To address the technical problems of existing SERS substrates, such as complex fabrication, high cost, high loss rate, and low detection sensitivity, this invention provides a silver substrate (solid-state SERS substrate), its fabrication method, and its applications. This substrate, combined with electrohydrodynamic (EHD) technology, can further amplify the SERS signal.

[0020] To achieve the above technical objectives, this application adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a silver substrate.

[0021] Please see Figure 1 , Figure 1 This is a flowchart illustrating a method for preparing a silver substrate according to an embodiment of the present invention; wherein, the preparation method specifically includes: S10, the aluminum foil paper substrate is immersed in the first reaction solution and shaken. After rinsing, dispersed silver seeds are formed on the surface of the aluminum foil paper substrate.

[0022] Specifically, step S10 also includes: First, the first silver nitrate solution and an excess alkaline solution are mixed to obtain the first reaction solution. Second, the aluminum foil substrate is immersed in the first reaction solution and shaken. After rinsing, dispersed silver seeds are formed on the surface of the aluminum foil substrate (the silver ions in the first silver nitrate solution participate in the redox process and Ag is reduced to Ag).

[0023] Specifically, a first reaction solution is prepared by mixing a first silver nitrate solution with an excess alkaline solution (such as sodium hydroxide solution or potassium hydroxide solution). The excess alkaline properties are used to regulate the form of silver ions (such as converting them into stable silver-based intermediates rather than directly forming large silver precipitates), providing a controllable precursor system for the subsequent formation of dispersed silver seeds. Subsequently, an aluminum foil substrate is immersed in the first reaction solution and shaken. The aluminum foil, by virtue of its reducing properties, can reduce the silver-based intermediates (silver oxide or silanate ions) in the solution to elemental silver. The shaking operation can promote sufficient contact between the aluminum foil surface and the first reaction solution, avoiding uneven local reactions, and can also reduce the tendency of elemental silver to agglomerate. Finally, a uniformly distributed dispersed silver seed is obtained by rinsing. This step not only provides precise nucleation sites for the subsequent in-situ growth of the silver substrate, ensuring the orderly growth of silver nanostructures along the silver seeds, but also lays a key foundation for the formation of "hot spots" in the final product (dependent on the gaps and tips of the silver nanostructures) by controlling the dispersion of the silver seeds. At the same time, the selection of aluminum foil substrate and the use of conventional chemical reagents also ensure the simplicity and low cost of the process.

[0024] In step S10: the molar ratio of the first silver nitrate solution to the alkaline solution is 1:(8~12); this ratio ensures that the alkaline is in sufficient excess to completely convert the silver ions into stable silver-based intermediates (such as [Ag(OH)2)). - This process avoids the agglomeration of silver seeds caused by the direct reduction of unreacted silver ions. At the same time, reasonable control of the excess amount of alkali can maintain the alkalinity of the system within an appropriate range, which not only avoids the corrosion of the aluminum foil substrate by excessive alkali concentration, but also ensures the efficient reduction of the silver-based intermediate by the aluminum foil. Ultimately, this lays a controllable chemical foundation for the formation of uniformly dispersed silver seeds in subsequent steps, and is a key process guarantee for improving the structural uniformity and performance stability of the silver substrate.

[0025] S20, an aluminum foil paper substrate with silver seeds is immersed in a growth solution for in-situ growth, so as to form a silver substrate rich in hot spots on the surface of the aluminum foil paper substrate. During the immersion of the aluminum foil substrate in the growth solution, it is slowly shaken to ensure that the concentration of Ag ions in the growth solution is uniformly reduced on the aluminum foil substrate, avoiding excessively high local concentrations.

[0026] Specifically, step S20 also includes: First, hydroquinone solution (HQ) and silver nitrate solution are mixed to obtain growth solution; hydroquinone, as a reducing agent, can undergo redox reaction with silver nitrate, providing the material basis for silver growth.

[0027] Secondly, the aluminum foil substrate containing silver seeds from step S10 is immersed in a growth solution for in-situ growth to form a silver substrate rich in hot spots on the surface of the aluminum foil substrate. The silver seeds act as in-situ nucleation sites, guiding the controlled deposition of silver ions on its surface and avoiding structural disorder caused by random growth of silver particles. This in-situ growth mechanism allows silver to form numerous "hot spots" on the substrate surface, composed of nanostructure gaps and tips. Because the silver seeds are uniformly dispersed, the distance between particles during growth is easily controlled at the nanometer level, thus forming a dense and stable hot spot structure (Hot spots refer to tiny regions with significantly enhanced electromagnetic field intensity on or near the surface of noble metal nanostructures).

[0028] Specifically, this process requires no complex equipment and can be completed through solution reaction, making it simple and low-cost. Furthermore, this step ensures efficient growth of the silver substrate and endows it with the key property of being rich in hot spots through in-situ nucleation and controlled growth, providing core support for the high sensitivity of subsequent surface-enhanced Raman spectroscopy detection. It combines the dual advantages of convenient preparation and high-performance products.

[0029] In step S20: the hydroquinone solution and the second silver nitrate solution have the same concentration and volume. This design ensures that hydroquinone, as a reducing agent, reacts fully with the silver ions in the silver nitrate in a stoichiometric ratio. This avoids incomplete silver ion reduction due to insufficient reducing agent (resulting in raw material waste or residual impurities), and also prevents side reactions caused by excessive reducing agent (such as excessive reduction leading to silver particle agglomeration). This creates a stable and controllable silver ion reduction environment in the growth solution, providing a precise guarantee for the uniform in-situ growth of silver seeds on the aluminum foil substrate and the final formation of a silver substrate rich in hot spots. At the same time, it simplifies the control of process parameters and improves the stability and repeatability of the preparation process.

[0030] Specifically, the concentration of the second silver nitrate solution is 10 to 20 times that of the first silver nitrate solution. The low concentration of the first silver nitrate solution ensures that the silver seeds are dispersed and do not agglomerate, while the high concentration of the second silver nitrate solution provides sufficient silver ions for the in-situ growth of the silver substrate. This supports the growth of silver from nano-silver seeds into a substrate with a complex structure, and also promotes the formation of more branches and tips by accelerating the deposition rate, thereby increasing the number of "hot spots". At the same time, the high concentration of silver ions can stabilize the redox reaction kinetics, buffer local concentration fluctuations, and ensure the uniformity of silver substrate growth and performance consistency. This is a key design for improving the SERS activity and preparation stability of the silver substrate.

[0031] Specifically, after step S20 is completed, the process further includes: cutting the silver substrate to obtain a first silver electrode and a second silver electrode that are spaced apart from each other, wherein the area of ​​the first silver electrode is larger than the area of ​​the second silver electrode; wherein the first silver electrode and the second silver electrode can be assembled into a hydrodynamic asymmetric substrate.

[0032] Furthermore, the asymmetric current generated by the asymmetric electrode can precisely act on the analyte molecules, improving the specificity of target molecule recognition and enhancing detection targeting; on the other hand, it effectively removes non-specific adsorption interference, improving the signal-to-noise ratio. This design combines the substrate structural characteristics with the detection mechanism, further enhancing the practical performance of silver substrates in analytical detection.

[0033] Furthermore, the gap between the first silver electrode and the second silver electrode is greater than 0 and ≤2mm, preferably 1mm; wherein, a gap greater than 0 can avoid short circuits to form an effective electric field and asymmetric current body force, while ≤2mm (preferably 1mm) can ensure that the force is accurately applied to the molecule to be tested, which not only improves the specific recognition efficiency and reduces interference to enhance the reliability of detection, but also takes into account the operability of actual processing. It is a key parameter design to enhance the practical performance of silver substrate analysis and detection.

[0034] Furthermore, when the width of the first silver electrode is the same as the width of the second silver electrode, the ratio of the length of the first silver electrode to the length of the second silver electrode is (1~8):1, preferably 4:1. This design aims to construct effective electrophysiological asymmetry through the length difference: this ratio range ensures that the asymmetric electrophysiological force acts precisely on the molecule to be tested, thereby improving the specific recognition efficiency of the target molecule and reducing non-specific adsorption interference to optimize the signal-to-noise ratio. Accordingly, the present invention also provides a silver substrate prepared by the silver substrate preparation method of any of the above claims.

[0035] Accordingly, the present invention also provides an application of the above-mentioned silver substrate in the field of surface-enhanced Raman spectroscopy detection.

[0036] Specifically, surface-enhanced Raman spectroscopy combined with electrohydrodynamics was used to detect p-methoxythiophenol. Electrohydrodynamics (EHD) involves applying alternating current to a pair of asymmetric microelectrodes, inducing two unevenly charged double layers and corresponding fluid forces on their surfaces. The intensity of the fluid forces can be changed by adjusting the frequency and amplitude of the alternating current, thereby driving the liquid to move in the nanoscale range.

[0037] The technical solution of the present invention will now be further described with reference to specific embodiments.

[0038] Example 1: Please refer to the following: Figure 2 This embodiment 1 first provides a silver substrate and its preparation method, the preparation method including the following steps: Step 1: Mix 0.5 mM silver nitrate solution and 100 mM sodium hydroxide solution at a molar ratio of 1:10. Immerse the aluminum foil substrate in the mixture and place it on a shaker to shake (during the shaking process, the mixed solution turns into a pale yellow colloidal state). After shaking vigorously for 3 minutes, remove the substrate and rinse the surface with ultrapure water to obtain an aluminum foil substrate with silver (at this time, the surface of the aluminum foil substrate is pale yellow).

[0039] Step two, place the aluminum foil substrate in a round dish. The growth solution is a mixture of 2 mL of 5 mM hydroquinone and silver nitrate in equal volumes and concentrations. Then, shake and incubate the aluminum foil substrate in the growth solution for 10 min. After the surface color of the aluminum foil substrate changes from yellow to dark purple and finally to a beige silver film, let it stand for another 2 min, remove it and dry it for later use to obtain the above silver substrate.

[0040] Please see Figure 3 , Figure 3 This is a SEM (Scanning Electron Microscope) image of a silver substrate provided in Embodiment 1 of the present invention; by Figure 3 It can be directly observed that the silver substrate surface has a dense morphology with abundant nanoscale structures, such as nanoparticles, nanodendritices, nanosheets, or irregular protrusions. There are a large number of nanoscale gaps (1-10 nm) and tips between these structures, which confirms that the silver substrate is rich in hot spots and provides a structural basis for the high signal enhancement effect of surface-enhanced Raman spectroscopy (SERS). At the same time, the above images show that the silver substrate is uniformly distributed on the aluminum foil paper substrate surface without obvious agglomeration or defects, which further illustrates the stability of the preparation process and verifies that the two-step preparation process can effectively obtain a high-performance silver substrate with uniform structure.

[0041] The silver substrate preparation method provided in Example 1 of this invention is convenient to operate, has few steps and low cost, and can be used to prepare asymmetric metal electrodes for SERS detection, with the potential for large-scale, mass production in one go.

[0042] The silver substrate prepared in Example 1 of this invention was used to detect p-methoxythiophenol molecules. The specific steps included: adding 20 μL of 1 μM p-methoxythiophenol dropwise onto a dry silver substrate for 1 hour, washing it clean, and then performing Raman signal detection. The test results are as follows: Figure 4 As shown.

[0043] Figure 4 A distinct Raman characteristic peak (1080 cm⁻¹) was observed. -1 The peak for the stretching vibration of the CS bond is 1100~1200 cm⁻¹. -1 The peak represents the stretching vibration of the CO bond in the methoxy group, 1500–1600 cm⁻¹. -1The peaks (representing the benzene ring skeleton vibration) indicate that the silver substrate successfully captured and detected the p-methoxybenzylthiophenol molecule, demonstrating that the silver substrate of Example 1 possesses the ability to detect this molecule. Furthermore, the aforementioned characteristic peaks all exhibit a certain intensity, indicating that the silver substrate effectively enhances the Raman signal of this molecule, enabling sensitive detection and showcasing the high sensitivity of the silver substrate for detection. Additionally, the peak positions correspond to the characteristic vibrational modes of the p-methoxybenzylthiophenol molecule, with no distracting peaks, indicating that during the detection process, the silver substrate, combined with relevant mechanisms (such as the asymmetric current-assisted detection mentioned earlier), effectively achieves the specific recognition of the test molecule (p-methoxybenzylthiophenol) and removes background noise caused by non-specific adsorption, ensuring the specificity and accuracy of the detection results.

[0044] Furthermore, the silver substrate prepared in Example 1 can be assembled into an electrohydrodynamic asymmetric substrate to further amplify the Raman signal: the silver substrate is cut into two pieces of equal width and length ratio of 1:4, and assembled into electrodes, connected to an AC power supply to form a circuit, which can be used for analysis and detection.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows: First, the silver substrate preparation steps of the present invention are simpler and less expensive, as it can be directly reduced and regrown on aluminum foil.

[0046] Second, the silver substrate of the present invention is rich in "hot spot" regions, which can greatly improve the detection sensitivity.

[0047] Third, the silver substrate of the present invention has the potential to be assembled into an asymmetric electrode. The asymmetric current generated by the asymmetric electrode can improve the specific recognition efficiency while removing non-specific adsorption.

[0048] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0049] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a silver substrate, characterized in that, Includes the following steps: S10, the aluminum foil paper substrate is immersed in the first reaction solution and shaken. After rinsing, dispersed silver seeds are formed on the surface of the aluminum foil paper substrate. S20, the aluminum foil paper substrate having the silver seed is immersed in the growth solution for in-situ growth, so as to form the silver substrate rich in hot spots on the surface of the aluminum foil paper substrate; In step S10: the first reaction solution includes a first silver nitrate solution and an excess alkaline solution; in step S20: the growth solution includes a hydroquinone solution and a second silver nitrate solution.

2. The method for preparing a silver substrate according to claim 1, characterized in that, In step S10: the molar ratio of the first silver nitrate solution to the alkaline solution is 1:(8~12).

3. The method for preparing a silver substrate according to claim 1, characterized in that, In step S20: the hydroquinone solution and the second silver nitrate solution have the same concentration and the same volume.

4. The method for preparing a silver substrate according to claim 1, characterized in that, The concentration of the second silver nitrate solution is 10 to 20 times that of the first silver nitrate solution.

5. The method for preparing a silver substrate according to claim 1, characterized in that, After step S20 is completed, the method further includes: cutting the silver substrate to obtain a first silver electrode and a second silver electrode that are spaced apart from each other, wherein the area of ​​the first silver electrode is larger than the area of ​​the second silver electrode.

6. The method for preparing a silver substrate according to claim 5, characterized in that, The gap between the first silver electrode and the second silver electrode is greater than 0 and ≤2mm.

7. The method for preparing a silver substrate according to claim 5, characterized in that, When the width of the first silver electrode is the same as the width of the second silver electrode, the ratio of the length of the first silver electrode to the length of the second silver electrode is (1~8):

1.

8. A silver substrate, characterized in that, It is prepared by the method for preparing a silver substrate as described in any one of claims 1 to 7.

9. An application of the silver substrate as described in claim 8 in the field of surface-enhanced Raman spectroscopy detection.

10. The application according to claim 9, characterized in that, Surface-enhanced Raman spectroscopy combined with electrohydrodynamic techniques was used to detect p-methoxythiophenol.

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