A method for preparing a surface-enhanced raman scattering detection substrate

Abstract

The application belongs to the technical field of Raman spectrum detection, and particularly relates to a preparation method of a surface enhanced Raman scattering detection substrate, comprising the following steps: cutting a paper substrate by using a laser to form aldehyde compounds obtained by pyrolysis of cellulose at the cutting position; dropping a precursor solution of silver ions on the paper substrate cut to reduce the silver ions to form silver nanoparticles by the aldehyde compounds at the cutting position; and performing sound wave treatment to cover the upper surface of the entire substrate with the reduced silver nanoparticles by using a sound flow effect to form the surface enhanced Raman scattering detection substrate. The preparation method does not need to add a reducing agent additionally, has low cost, simple steps, short preparation time, low raw material consumption, can be prepared on a large scale, solves the problem of poor uniformity of the SERS substrate, and is expected to realize large-scale commercial application.

Description

Technical Field

[0001] This invention belongs to the field of Raman spectroscopy detection technology, specifically relating to a method for preparing a surface-enhanced Raman scattering detection substrate. Background Technology

[0002] As a powerful analytical technique, surface-enhanced Raman scattering (SERS) has been widely used to identify specific chemical fingerprints of trace analytes, including cancer biomarkers, toxins, heavy metals, pesticide and antibiotic residues. SERS has many unique advantages, such as ease of operation, excellent selectivity and sensitivity, rapid signal response, and good biocompatibility.

[0003] The metallic materials used for SERS detection are crucial. The strong electromagnetic field between closely packed noble metal (usually gold or silver) nanostructures is the fundamental reason for SERS enhancement. The effects of different gold or silver morphologies have been extensively studied, including spheres, cubes, tetrahedrons, octahedrons, and so on. The substrates supporting the metallic materials are diverse, and they also play an important role in achieving detection performance. Silicon wafers, quartz glass, and various polymers are frequently used as substrates for SERS detection. In recent years, the SERS field has been booming. However, for this technology to be commercialized on a large scale, factors such as material cost, process complexity, and environmental impact must be considered. Among these, the cost of the materials used is the most important factor; in terms of the metallic materials used, gold is more expensive than silver. Regarding the detection substrates supporting the metallic materials, silicon wafers, quartz glass, and other substrates are also relatively expensive. In addition, the complexity of the process flow is also an important factor. To improve detection sensitivity, researchers have proposed various gold- and silver-containing composite structures. However, the preparation process of these composite structures is extremely complex, requiring multiple steps and typically taking several days and consuming a significant amount of manpower. These complex processes greatly hinder the commercial application of SERS. Furthermore, environmental impact is also a factor to consider. The complex synthesis process uses various chemicals, and the resulting waste liquids may harm the environment, making this method unsustainable. Therefore, to achieve large-scale application of SERS detection technology, there is an urgent need for a low-cost, time-saving, simple, and environmentally friendly method for preparing SERS detection substrates. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing a surface-enhanced Raman scattering (SERS) detection substrate. This method does not require the addition of an additional reducing agent, is low in cost, simple in steps, short in preparation time, consumes few raw materials, and can be prepared on a large scale. It also solves the problem of poor uniformity of SERS substrates and is expected to achieve large-scale commercial applications.

[0005] The present invention is specifically implemented through the following technical solution.

[0006] A method for preparing a surface-enhanced Raman scattering detection substrate includes the following steps:

[0007] Using laser cutting of paper substrate, aldehyde compounds obtained from cellulose pyrolysis are formed at the cut point;

[0008] A precursor solution of silver ions was dropped onto the cut paper substrate, and the silver ions were reduced by the aldehyde compound at the cut site to form silver nanoparticles.

[0009] Acoustic wave processing is performed, and the acoustic flow effect is used to make the reduced silver nanoparticles cover the entire upper surface of the substrate, forming a detection substrate for surface-enhanced Raman scattering.

[0010] In a preferred embodiment of the present invention, the main component of the paper substrate is cellulose.

[0011] In a preferred embodiment of the present invention, the type of laser is a gas laser, a solid-state laser, a semiconductor laser, a liquid laser, or a fiber laser.

[0012] In a preferred embodiment of the present invention, the laser is applied as a continuous laser or a pulsed laser.

[0013] In a preferred embodiment of the present invention, the laser wavelength is between 100nm and 1500nm.

[0014] In a preferred embodiment of the present invention, the precursor solution of silver ions includes silver nitrate solution, silver fluoride solution, silver chlorate solution, silver perchlorate solution, silver perbromate solution, and silver periodate solution.

[0015] In a preferred embodiment of the present invention, the concentration of silver ions in the silver ion precursor solution is 1 mM-1 M. The volume of the silver ion precursor solution added must exceed the absorption capacity of the paper substrate to form a droplet that completely covers the paper substrate.

[0016] In a preferred embodiment of the present invention, the device for generating sound waves includes a piezoelectric ceramic sheet, a buzzer, an ultrasonic transducer, an oscillator, and a loudspeaker. The sound wave processing time is 1-30 minutes.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] This invention discloses a method for preparing a SERS detection substrate. First, a paper substrate of the desired shape is cut using a laser. During the cutting process, due to the thermal effect of the laser, the cellulose in the paper substrate pyrolyzes to release aldehyde compounds. After adding a precursor solution containing silver ions, the pyrolyzed aldehyde compounds act as a reducing agent to reduce the silver ions, yielding elemental silver. Then, the acoustic flow effect of sound waves is used to coat the entire surface of the detection substrate with the reduced elemental silver, completing the preparation of the detection substrate. This preparation process has the following advantages:

[0019] In terms of materials, silver, which is cheaper than gold, was used, and the testing substrate was made of very low-cost paper.

[0020] In terms of process flow, the entire process requires only three steps, and chemical synthesis requires only one step.

[0021] Laser cutting combines the functions of shape cutting and reducing agent generation. During the preparation process, only a precursor solution containing silver ions needs to be added, without the need to add additional reducing agents, which minimizes the types of chemical reagents used and reduces the impact on the environment.

[0022] Therefore, the preparation method of the present invention does not require the addition of additional reducing agents, has low cost, simple steps, short preparation time, low raw material consumption, can be prepared on a large scale, and solves the problem of poor uniformity of SERS substrate, and is expected to achieve large-scale commercial application. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of laser cutting a paper substrate.

[0024] Figure 2 It is a physical image of the edge of a paper substrate obtained through mechanical cutting and laser cutting.

[0025] Figure 3 These are scanning electron microscope images of the edges of paper substrates obtained through mechanical cutting and laser cutting.

[0026] Figure 4 It is a Fourier transform infrared spectrum of the edge of a paper substrate obtained by mechanical cutting and laser cutting.

[0027] Figure 5 This is a schematic diagram of the acoustic flow inside a droplet caused by an acoustic device.

[0028] Figure 6 This is a physical image of the experimental setup at the initial moment.

[0029] Figure 7 This is a picture of the experimental setup five minutes after it was turned on.

[0030] Figure 8The image shows the paper substrate after being mechanically cut, laser-cut (without the sonic device turned on), and laser-cut (with the sonic device turned on) five minutes after silver nitrate solution was added.

[0031] Figure 9 This is a scanning electron microscope image of the SERS detection substrate obtained by laser cutting and activating the acoustic wave device.

[0032] Figure 10 The present invention provides Raman spectra of different concentrations of malachite green obtained from the SERS detection substrate.

[0033] Figure 11 The present invention provides Raman spectra of different concentrations of tetracycline obtained from the SERS detection substrate.

[0034] Figure 12 The present invention provides Raman spectra of different concentrations of thiabendazole obtained from the SERS detection substrate. Detailed Implementation

[0035] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0036] Unless otherwise specified, the experimental and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0037] This invention focuses on the fabrication of SERS substrates, where the strong electromagnetic field between closely packed noble metal (typically gold or silver) nanostructures is the fundamental reason for SERS enhancement. A variety of substrates can support the metal materials, and they play a crucial role in achieving detection performance. Silicon wafers, quartz glass, and various polymers are frequently used as substrates for SERS detection. However, for large-scale commercial application of this technology, factors such as material cost, process complexity, and environmental impact must be considered. Among these, material cost is the most important factor; gold is more expensive than silver. As for the substrates supporting the metal materials, silicon wafers and quartz glass are also relatively expensive. Furthermore, the complexity of the process flow is also a significant factor.

[0038] Therefore, this application provides a method for preparing a surface-enhanced Raman scattering detection substrate, using a paper substrate, which significantly reduces raw material costs compared to substrates such as silicon wafers and quartz glass. The method specifically includes the following steps:

[0039] Using laser cutting, an aldehyde compound obtained from the pyrolysis of cellulose is formed at the cut point on a paper substrate.

[0040] A precursor solution of silver ions is dropped onto the cut paper substrate. The silver ions are reduced by the aldehyde compound at the cut site to form silver nanoparticles. The volume of the silver ion precursor solution dropped must exceed the absorption capacity of the paper substrate to form a droplet that completely covers the paper substrate.

[0041] Acoustic wave processing is performed, and the acoustic flow effect is used to make the reduced silver nanoparticles cover the entire upper surface of the substrate, forming a detection substrate for surface-enhanced Raman scattering.

[0042] As can be seen, the method for preparing a surface-enhanced Raman scattering detection substrate according to this invention is simple. It involves laser-cutting a paper matrix, adding silver ions, and then utilizing acoustic flow to distribute nanoparticles onto the substrate surface. It is easy to implement and suitable for large-scale production.

[0043] In a preferred embodiment of the present invention, the laser type is a gas laser, solid-state laser, semiconductor laser, liquid laser, or fiber laser, and the laser mode of action is continuous laser or pulsed laser, with a laser wavelength between 100nm and 1500nm. Laser cutting combines the functions of shape cutting and reducing agent generation. During the preparation process, only a precursor solution containing silver ions needs to be added; no additional reducing agent is required, minimizing the types of chemical reagents used and reducing environmental impact.

[0044] In a preferred embodiment of the present invention, the silver ion precursor solution includes silver nitrate solution, silver fluoride solution, silver chlorate solution, silver perchlorate solution, silver perbromate solution, and silver periodate solution. The concentration of silver ions in the silver ion precursor solution is 1 mM-1 M. The volume of the silver ion precursor solution added must exceed the absorption capacity of the paper substrate to form a droplet that completely covers the paper substrate.

[0045] In a preferred embodiment of the present invention, the device for generating sound waves includes a piezoelectric ceramic sheet, a buzzer, an ultrasonic transducer, an oscillator, and a loudspeaker. The sound wave processing time is 1-30 minutes.

[0046] The invention will now be described in detail through the following embodiments.

[0047] Example 1

[0048] A method for preparing a surface-enhanced Raman scattering detection substrate includes the following steps:

[0049] A 0.5 mm thick tomographic paper is cut using a 450 nm semiconductor continuous laser. During the cutting process, the pyrolysis of cellulose produces brown tar at the cut point. This tar contains aldehyde compounds, such as... Figure 1 As shown.

[0050] A 100 mM silver nitrate solution containing silver ions is dropped onto a diced paper substrate. The volume of the silver nitrate solution added must exceed the absorbance of the paper substrate to form a droplet that completely covers the substrate. The silver ions are reduced by the aldehyde compounds at the dicing sites to form silver nanoparticles. Sound waves are then introduced, and the acoustic flow effect is used to spread the reduced silver nanoparticles across the entire upper surface of the substrate, forming a surface-enhanced Raman scattering (SERS) detection substrate.

[0051] The specific steps are as follows: Figure 6 As shown, a glass slide is used as the base. A piezoelectric ceramic sheet is attached to the left side of the glass slide. A circular paper substrate with a diameter of 3 mm and a thickness of 0.32 mm, obtained by laser cutting, is placed next to the piezoelectric ceramic sheet. 5 μL of 100 mM silver nitrate solution is dropped onto the paper substrate. A signal generator is then activated, providing a sinusoidal signal to the piezoelectric ceramic sheet, causing it to vibrate. The vibration is transmitted through the glass slide to the droplet, triggering an acoustic flow effect. This causes the silver nitrate solution to mix with the aldehyde groups obtained by laser cutting, reducing them to silver nanoparticles. The acoustic flow effect then causes the silver nanoparticles to be evenly distributed on the paper substrate. Two minutes after the signal generator is activated, the entire droplet is filled with silver nanoparticles, turning both the droplet and the paper substrate black (as shown). Figure 7 (As shown). Figure 5 The diagram shows the acoustic flow generated by the acoustic device. When a droplet is dropped onto a piece of paper, the vibration generated by the acoustic wave creates a vortex inside the droplet, which enhances the mixing of the substances and makes the product evenly distributed.

[0052] Example 2

[0053] A method for preparing a surface-enhanced Raman scattering detection substrate includes the following steps:

[0054] A 0.92 mm thick filter paper is cut using a semiconductor continuous laser with a wavelength of 1060 nm. During the cutting process, brown tar is produced at the cut point due to the pyrolysis effect of cellulose. The tar contains aldehyde compounds.

[0055] A 100 mM silver nitrate solution containing silver ions is dropped onto a diced paper substrate. The volume of the silver nitrate solution added must exceed the absorbance of the paper substrate to form a droplet that completely covers the substrate. The silver ions are reduced by the aldehyde compounds at the dicing sites to form silver nanoparticles. Sound waves are then introduced, and the acoustic flow effect is used to spread the reduced silver nanoparticles across the entire upper surface of the substrate, forming a surface-enhanced Raman scattering (SERS) detection substrate.

[0056] The specific steps are as follows: Using a glass slide as a base, a piezoelectric ceramic sheet is attached to the left side of the glass slide. Next to the piezoelectric ceramic sheet, a circular paper substrate with a diameter of 3mm and a thickness of 0.32mm (obtained by laser cutting) is placed. Five microliters of 100mM silver nitrate solution are dropped onto the paper substrate. At this point, a signal generator is activated, providing a sinusoidal signal to the piezoelectric ceramic sheet, causing it to vibrate. This vibration is transmitted through the glass slide to the droplet, triggering an acoustic flow effect. This causes the silver nitrate solution to mix with the aldehyde groups obtained from the laser cutting, reducing them to nano-silver particles. The acoustic flow effect then causes the nano-silver particles to be evenly distributed on the paper substrate. Two minutes after the signal generator is activated, the entire droplet is filled with nano-silver particles, turning both the droplet and the paper substrate black.

[0057] Example 3

[0058] A method for preparing a surface-enhanced Raman scattering detection substrate, compared with Example 1, involves adding silver nitrate droplets and turning on a signal generator for 5 minutes, including the following steps:

[0059] A semiconductor continuous laser with a wavelength of 450nm cuts 0.5mm thick tomographic paper. During the cutting process, brown tar is produced at the cutting point due to the pyrolysis effect of cellulose. The tar contains aldehyde compounds.

[0060] Silver nitrate droplets containing silver ions are dropped onto the cut paper substrate. The silver ions are reduced by the aldehyde compounds at the cut site to form silver nanoparticles. Sound waves are added, and the acoustic flow effect is used to make the reduced silver nanoparticles cover the entire upper surface of the substrate, forming a detection substrate for surface-enhanced Raman scattering (SERS).

[0061] The specific steps are as follows: Using a glass slide as a base, a piezoelectric ceramic sheet is attached to the left side of the glass slide. Next to the piezoelectric ceramic sheet, a circular paper substrate with a diameter of 3mm and a thickness of 0.32mm (obtained by laser cutting) is placed. Five microliters of 100mM silver nitrate solution are dropped onto the paper substrate. At this point, a signal generator is activated, providing a sinusoidal signal to the piezoelectric ceramic sheet, causing it to vibrate. This vibration is transmitted through the glass slide to the droplet, triggering an acoustic flow effect. This causes the silver nitrate solution to mix with the aldehyde groups obtained from the laser cutting, reducing them to nano-silver particles. The acoustic flow effect then causes the nano-silver particles to be evenly distributed on the paper substrate. Five minutes after the signal generator is activated, the entire droplet is filled with nano-silver particles, turning both the droplet and the paper substrate black.

[0062] Comparative Example 1

[0063] The paper base is mechanically cut to obtain a circular paper base with a diameter of 3 mm and a thickness of 0.32 mm.

[0064] Comparative Example 2

[0065] The paper substrate was mechanically cut to obtain a circular paper substrate with a diameter of 3 mm and a thickness of 0.32 mm, and 5 microliters of 100 mM silver nitrate solution were dropped into it and kept for 5 minutes.

[0066] Comparative Example 3

[0067] Laser cutting was used, but the acoustic device was not activated.

[0068] A semiconductor continuous laser with a wavelength of 450 nm was used to cut a 0.5 mm thick chromatographic paper to obtain a circular paper substrate with a diameter of 3 mm and a thickness of 0.32 mm. During the cutting process, brown tar containing aldehyde compounds was generated at the cutting point due to the pyrolysis effect of cellulose. 5 μL of silver nitrate solution with a concentration of 100 mM silver ions was dropped onto the paper substrate. The silver ions were reduced by the aldehyde compounds at the cutting point to form silver nanoparticles, which were maintained for 5 minutes.

[0069] The following analysis is performed on the above embodiments and comparative examples:

[0070] Figure 2 The difference between the edges of the paper substrate obtained by mechanical cutting (such as scissors) in Comparative Example 1 and laser cutting in Example 1 is shown. The edges obtained by mechanical cutting do not produce any compounds and retain the original composition of the paper substrate, while the edges obtained by laser cutting produce brown tar.

[0071] Figure 3 Scanning electron microscope images of the edges of paper substrates obtained by mechanical cutting in Comparative Example 1 and laser cutting in Example 1 are shown. The edges obtained by mechanical cutting retain the original cellulose composition, while those obtained by laser cutting cause the cellulose to be pyrolyzed into coke, resulting in a change in morphology.

[0072] Figure 4 Fourier transform infrared spectra of the edges of mechanical cutting in Comparative Example 1 and laser cutting in Example 1 are shown. The laser-cut edge has an additional aldehyde peak at 1620 cm⁻¹, which proves that the pyrolysis effect of laser cutting produces aldehydes at the edge.

[0073] Figure 8The images show the physical results of paper substrates prepared by mechanical cutting (Comparative Example 2), laser cutting (Comparative Example 3 without acoustic wave device), and laser cutting (Example 3 with acoustic wave device) after 5 minutes of silver nitrate droplet application. The mechanically cut paper did not produce aldehyde groups, so the silver nitrate was not reduced, and the paper retained its original color. Although aldehyde groups were produced at the edges of the laser-cut paper (without acoustic wave device), the reduced silver nanoparticles only appeared near the edges due to penetration without the aid of acoustic flow. With the aid of acoustic flow, the silver nitrate solution was fully reduced and uniformly covered the entire upper surface of the paper substrate, forming a high-quality SERS detection substrate. This demonstrates that the acoustic wave treatment step is necessary for the successful preparation of surface-enhanced Raman scattering (SERS) detection substrates, as the metal nanoparticles need to be uniformly distributed on the substrate surface, a fundamental requirement for SERS detection substrates.

[0074] Figure 9 The image shows a scanning electron microscope (SEM) image of the SERS detection substrate obtained in Example 1 of this invention. The nano-silver particles are uniformly covered on the paper substrate, which can be used as a high-quality SERS detection substrate.

[0075] To test the application performance of the surface-enhanced Raman scattering detection substrate prepared by this invention, the following application verifications were also conducted:

[0076] Application Example 1

[0077] With a concentration of 10 -4 10 -5 10 -6 A solution of malachite green M was dropped onto the SERS detection substrate prepared in this invention, and Raman spectroscopy was performed using a 785 nm laser. Figure 10 Raman spectra of malachite green at different concentrations obtained using the SERS detection substrate prepared according to this invention are shown. A good SERS signal for malachite green was obtained. This demonstrates that the substrate prepared according to this invention can be used for Raman spectroscopy detection of malachite green solutions with good results.

[0078] Application Example 2

[0079] With a concentration of 10 -4 10 -5 10 -6 A tetracycline solution of M was dropped onto the SERS detection substrate prepared in this invention, and Raman spectroscopy was performed using a 633 nm laser. Figure 11 Raman spectra of tetracycline at different concentrations were obtained using the SERS detection substrate prepared according to this invention. Good SERS signals for tetracycline were obtained. This demonstrates that the substrate prepared according to this invention can be used for tetracycline Raman spectroscopy detection with good results.

[0080] Application Example 3

[0081] With a concentration of 10 -4 10 -5 10 -6 A solution of thiabendazole (M) was dropped onto the SERS detection substrate prepared in this invention, and Raman spectroscopy was performed using a 785 nm laser. Figure 12 Raman spectra of different concentrations of thiabendazole were obtained using the SERS detection substrate prepared according to this invention. Good SERS signals for thiabendazole were obtained. This demonstrates that the substrate prepared according to this invention can be used for Raman spectroscopy detection of thiabendazole with good results.

[0082] The above verification results demonstrate that the substrate prepared using the method of this invention can be used for Raman spectroscopy detection, indicating that the method of this invention can successfully prepare SERS detection substrates with excellent performance. This invention uses paper substrates as raw materials, which reduces costs compared to traditional substrate materials, and the preparation method is simple, effective, and meets the requirements for large-scale applications, representing a significant advancement in the field of SERS detection substrates.

[0083] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. A method for preparing a surface-enhanced Raman scattering detection substrate, characterized in that, Includes the following steps: Using laser cutting of paper substrate, aldehyde compounds obtained from cellulose pyrolysis are formed at the cut point; A precursor solution of silver ions was dropped onto the cut paper substrate, and the silver ions were reduced by the aldehyde compound at the cut site to form silver nanoparticles. Acoustic wave processing is performed, and the acoustic flow effect is used to make the reduced silver nanoparticles cover the entire upper surface of the substrate, forming a detection substrate for surface-enhanced Raman scattering.

2. The preparation method according to claim 1, characterized in that, The main component of the paper substrate is cellulose.

3. The preparation method according to claim 1, characterized in that, Lasers can be classified as gas lasers, solid-state lasers, semiconductor lasers, liquid lasers, or fiber lasers.

4. The preparation method according to claim 1, characterized in that, The laser can be applied in the form of continuous laser or pulsed laser.

5. The preparation method according to claim 1, characterized in that, The laser wavelength is 100nm-1500nm.

6. The preparation method according to claim 1, characterized in that, The precursor solutions for silver ions are silver nitrate solution, silver fluoride solution, silver chlorate solution, silver perchlorate solution, silver perbromate solution, or silver periodate solution.

7. The preparation method according to claim 6, characterized in that, In the precursor solution of silver ions, the concentration of silver ions is 1 mM-1 M.

8. The preparation method according to claim 6, characterized in that, The precursor solution of silver ions is dropped into a volume exceeding the absorption capacity of the paper substrate to form a droplet that completely covers the paper substrate.

9. The preparation method according to claim 1, characterized in that, Devices that generate sound waves include piezoelectric ceramic plates, buzzers, ultrasonic transducers, oscillators, and loudspeakers.

10. The preparation method according to claim 1, characterized in that, The acoustic processing time is 1-30 minutes.

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