A method for preparing a silver nanoparticle aggregate SERS substrate
By forming a droplet-like two-phase interface between an aqueous solution of silver nanoparticles and a toluene solution, and then treating it with ethanol and polymethyl methacrylate, a SERS substrate of silver nanoparticle aggregates was prepared, which solved the problem of hydrophobic substrate limitation and achieved high-sensitivity Raman detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CAPITAL NORMAL UNIVERSITY
- Filing Date
- 2022-11-24
- Publication Date
- 2026-05-26
AI Technical Summary
In the prior art, the preparation of hydrophobic substrates limits the convenient preparation of SERS substrates for silver nanoparticle aggregates and the improvement of Raman detection sensitivity, making it impossible to achieve higher Raman enhancement performance.
A droplet-like two-phase interface was formed by using an aqueous solution of silver nanoparticles and a toluene solution. A monolayer film of silver nanoparticles was prepared by using an ethanol solution and then treated with a polymethyl methacrylate toluene solution to form a SERS substrate of silver nanoparticle aggregates, thus avoiding the use of a hydrophobic substrate.
The preparation of silver nanoparticle aggregates without hydrophobic substrates was achieved, with good enhancement effect. The lowest concentration for detecting crystal violet molecules was 10-15 mol/L, and the SERS signal intensity and concentration conformed to the Hill equation, thus improving the detection sensitivity.
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Figure CN115855912B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of Raman spectroscopy detection technology, and in particular to a method for preparing a silver nanoparticle aggregate SERS substrate. Background Technology
[0002] Surface-enhanced Raman scattering (SERS) identifies specific molecules through Raman spectroscopy, known as molecular fingerprinting, making it a highly efficient and sensitive analytical tool with wide applications in analytical chemistry, materials science, and environmental science. Metal nanostructures containing nanoscale gaps, due to their ability to excite enhanced electromagnetic fields through localized surface plasmon resonance (LSPR), have been studied for ultrasensitive detection, even at the single-molecule level. In particular, when molecules are located within nanoscale gaps, the detection sensitivity can be improved by several orders of magnitude compared to inherent weak spontaneous Raman scattering.
[0003] Thanks to the highly reproducible and cost-effective synthesis of colloids, silver nanoparticles with plasmon resonance (SERS) properties have attracted significant attention in the field of Raman detection. In particular, the assembly of plasmon nanostructures with high density and uniformly distributed hot spots from silver nanoparticles (AgNPs) has become crucial for achieving high-sensitivity and reproducible Raman detection. Therefore, extensive research has been conducted in recent years on the preparation of AgNP-based SERS substrates. For example, interfacial self-assembly at the liquid-liquid interface can prepare AgNP monolayer films with uniform hot spot distribution, ensuring SERS enhancement without requiring stringent experimental conditions. However, SERS substrates prepared using this method cannot provide higher Raman enhancement performance due to the hot spot distribution being limited to two dimensions.
[0004] In 2016, Yang Shikuan et al. prepared silver nanoparticle aggregates by dropping a solution of silver nanoparticles onto a hydrophobic substrate and utilizing the evaporation and shrinkage process of the solution. They used this aggregate as a SERS substrate to achieve ultra-trace Raman detection of dye molecules such as Rhodamine 6G. However, their study required the additional preparation of the hydrophobic substrate, and the hydrophobicity of the substrate had a certain impact on Raman detection, making it difficult to prepare silver nanoparticle aggregates conveniently.
[0005] Therefore, there is an urgent need in the field to provide a method for preparing silver nanoparticle aggregates without a hydrophobic substrate. Summary of the Invention
[0006] The purpose of this invention is to provide a method for preparing a silver nanoparticle aggregate SERS substrate, so as to overcome or at least mitigate at least one of the above-mentioned defects of the prior art.
[0007] To achieve the above objectives, the present invention provides a method for preparing a silver nanoparticle aggregate SERS substrate, comprising:
[0008] Step 1: Prepare an aqueous solution of silver nanoparticles;
[0009] Step 2: Add the prepared silver nanoparticle aqueous solution to the toluene solution according to the volume ratio, let the sample stand, and obtain a droplet-like two-phase interface between the silver nanoparticle aqueous solution and the toluene solution; wherein the volume ratio of the silver nanoparticle aqueous solution to the toluene solution is in the range of 1-5:20.
[0010] Step 3: Inject the ethanol solution into the droplet-like interface between the silver nanoparticle aqueous solution and the toluene solution, let the sample stand, and a silver nanoparticle monolayer film is prepared at the droplet-like interface between the silver nanoparticle aqueous solution and the toluene solution.
[0011] Step 4: Prepare a toluene solution of polymethyl methacrylate; wherein the mass ratio of polymethyl methacrylate to toluene solution is 1:500-3000.
[0012] Step 5: Add the prepared polymethyl methacrylate toluene solution to the outside of the droplet-like two-phase interface between the silver nanoparticle aqueous solution and the toluene solution prepared in Step 3, and react to obtain the silver nanoparticle aggregate SERS substrate.
[0013] Step 1 includes: preparing an aqueous solution of silver nanoparticles using a seed synthesis method.
[0014] Step 2 includes: 50 μl of silver nanoparticle aqueous solution and 1 ml of toluene solution.
[0015] In step 3, the volume of ethanol solution added is 20 μl, and the injection rate is 20 μl / min.
[0016] In step 4, the mass ratio of polymethyl methacrylate to toluene solution is 1:1000.
[0017] Step 5 includes: controlling the reaction time within 0.5h-24h to obtain a self-assembled silver nanoparticle aggregate SERS substrate.
[0018] The reaction time is 2 hours.
[0019] The present invention has the following advantages due to the adoption of the above technical solutions:
[0020] This invention provides a method for preparing a SERS substrate of silver nanoparticle aggregates. The silver nanoparticle aggregates prepared in this way can be achieved without a hydrophobic substrate, and exhibit good enhancement effects. The lowest detectable concentration for crystal violet molecules is 10. -15 Mol / L, the SERS signal intensity and concentration follow the Hill equation relationship. Attached Figure Description
[0021] Figure 1 This is a schematic flowchart of the method for preparing the silver nanoparticle aggregate SERS substrate provided by the present invention.
[0022] Figure 2 Transmission electron microscope image of an aqueous solution of silver nanoparticles provided by the present invention.
[0023] Figure 3 An optical photograph of the interface between an aqueous solution of silver nanoparticles and toluene droplets provided by this invention.
[0024] Figure 4 The image provided by this invention is a scanning electron microscope image of a silver nanoparticle array prepared at the droplet-like interface between an aqueous solution of silver nanoparticles and a toluene solution.
[0025] Figure 5 This is a scanning electron microscope image of the silver nanoparticle aggregates prepared in Example 1 of the present invention.
[0026] Figure 6 This is a scanning electron microscope image of the silver nanoparticle aggregates prepared in Example 2 of the present invention.
[0027] Figure 7 This is a scanning electron microscope image of the silver nanoparticle aggregates prepared in Example 3 of the present invention.
[0028] Figure 8 The results of CV detection of silver nanoparticle aggregates prepared in Examples 1-3 of this invention are shown.
[0029] Figure 9 The image shows the Raman spectra of silver nanoparticle aggregates prepared in Example 3 of this invention against crystal violet solutions of different concentrations.
[0030] Figure 10 The graph shows the relationship between the signal intensity of crystal violet on silver nanoparticle aggregates and the logarithm of concentration according to the Hill equation. Detailed Implementation
[0031] In the accompanying drawings, the same or similar reference numerals are used to denote the same or similar elements or elements having the same or similar functions. The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0032] In the description of this invention, the terms "center," "longitudinal," "lateral," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.
[0033] Where there is no conflict, the technical features of the various embodiments and implementations of the present invention can be combined with each other, and are not limited to the embodiments or implementations in which the technical feature is located.
[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that the technical solution and design principle of the present invention will be described in detail below with reference to only one optimized technical solution, but the protection scope of the present invention is not limited thereto.
[0035] The following terms are used in this document, and their meanings are explained below for ease of understanding. Those skilled in the art should understand that the following terms may have other names, but without departing from their meanings, any other names should be considered consistent with the terms listed herein.
[0036] This invention provides a method for preparing a silver nanoparticle aggregate SERS substrate, such as... Figure 1 As shown, the method includes:
[0037] Step 1: Prepare an aqueous solution of silver nanoparticles.
[0038] The preferred diameter of the silver nanoparticles is 60 nm, and an aqueous solution of silver nanoparticles can be prepared using a seed synthesis method.
[0039] For example, the specific preparation process of silver nanoparticle aqueous solution is as follows: heat silver nitrate solution to boiling point in the dark, maintain boiling point for 10 minutes, quickly add sodium citrate solution and stir rapidly, maintain boiling point for 1 hour, and finally cool to room temperature to obtain silver nanoparticle aqueous solution, which is then stored in the dark at low temperature for subsequent operations.
[0040] Step 2: Add the prepared silver nanoparticle aqueous solution to the toluene solution according to the volume ratio, and let it stand to obtain a droplet-like two-phase interface between the silver nanoparticle aqueous solution and the toluene solution; wherein the volume ratio of the silver nanoparticle aqueous solution to the toluene solution is in the range of 1-5:20.
[0041] In this step, a certain amount of silver nanoparticle aqueous solution is added to a test tube containing a certain amount of toluene solution using a pipette. The volume ratio of the silver nanoparticle aqueous solution to the toluene solution is 1-5:20, i.e., 1:20 to 5:20. Due to the high density of the silver nanoparticle aqueous solution, after standing, a droplet-like two-phase interface of silver nanoparticle aqueous solution / toluene solution is eventually obtained at the bottom of the test tube.
[0042] Step 3: Inject the ethanol solution into the droplet-like interface between the silver nanoparticle aqueous solution and the toluene solution, and let it stand for a preset time to prepare a silver nanoparticle monolayer at the droplet-like interface between the silver nanoparticle aqueous solution and the toluene solution.
[0043] In this step, ethanol solution (20 μl) can be manually injected into the silver nanoparticle solution at the bottom of the test tube using a microsyringe at a rate of 20 μl / min. After standing for a period of time, the silver nanoparticle array assembles at the interface between the silver nanoparticle aqueous solution and toluene droplets, exhibiting a certain metallic luster. This time can be adjusted flexibly according to actual needs; for example, it can be stopped when no new metallic luster is produced.
[0044] Step 4: Prepare a toluene solution of polymethyl methacrylate; wherein the mass ratio of polymethyl methacrylate to toluene solution is 1:500-3000.
[0045] Step 5: Add the prepared polymethyl methacrylate toluene solution to the outside of the droplet-like two-phase interface between the silver nanoparticle aqueous solution and the toluene solution prepared in Step 3, and react to obtain the silver nanoparticle aggregate SERS substrate.
[0046] Polymethyl methacrylate (PMMA) was dissolved in a toluene solution to generate a transparent solution. This transparent solution was then added to the outside of the droplet-like two-phase interface between the silver nanoparticle aqueous solution and the toluene solution, which contains a silver nanoparticle monolayer film, i.e., into the toluene solution. After standing for 0.5–24 hours, the surface of the silver nanoparticle aggregates was washed repeatedly with a large amount of toluene solution to completely remove any toluene residue, thus obtaining the silver nanoparticle aggregates.
[0047] To more clearly illustrate the preparation method of the silver nanoparticle aggregate SERS substrate provided by this invention, detailed descriptions are provided below through specific embodiments. It should be understood that the specific parameters in these embodiments are preferred results, but not the only results. Without departing from the technical concept of this invention, those skilled in the art can adjust the parameters in the following examples to obtain other embodiments, all of which should fall within the protection scope of this invention.
[0048] Example 1:
[0049] Preparation of silver nanoparticles: Weigh 90 mg of silver nitrate solid using a balance, dissolve it in 500 ml of ultrapure water, and then heat it in the dark until it boils, maintaining this temperature for 10 minutes. Immediately add 10 ml of 1% sodium citrate solution, and continue heating for another hour. Then cool to room temperature, collect the nanoparticles, and store them in the dark at a low temperature. Figure 2 The image shows a transmission scanning electron microscope image of silver nanoparticles with a diameter of 60 nm.
[0050] Preparation of a droplet-like two-phase interface between silver nanoparticle aqueous solution and toluene: 1 ml of toluene solution was added to a 2 ml plastic test tube using a pipette. Then, 50 μl of silver nanoparticle aqueous solution was slowly added to the bottom of the toluene solution using a pipette. Due to the different polarities of the two solutions and the higher density of the silver nanoparticle solution, a droplet-like two-phase interface between the silver nanoparticle aqueous solution and toluene appeared at the bottom of the test tube. Figure 3 An optical photograph shows the interface between silver nanoparticles in aqueous solution and toluene droplets.
[0051] Preparation of silver nanoparticle arrays at the interface of silver nanoparticle aqueous solution / toluene droplets: A certain amount of ethanol solution was drawn up using a microsyringe, and the needle of the microsyringe was slowly placed inside the interface of silver nanoparticle aqueous solution / toluene. The injection rate was set to 20 μl / min, and the injection was stopped after one minute, with the total amount of ethanol injected controlled to be 20 μl. After the ethanol injection was completed, due to the change in the charge environment in the silver nanoparticle solution, the silver nanoparticles underwent close self-assembly at the interface of silver nanoparticle aqueous solution / toluene, forming a silver nanoparticle array with a metallic luster. Figure 4 A scanning electron microscope image of a silver nanoparticle array formed at the droplet-like two-phase interface of an aqueous / toluene solution of silver nanoparticles is shown.
[0052] Preparation process of silver nanoparticle aggregates: 86.6 mg of polymethyl methacrylate (PMMA) was weighed using a balance and then dissolved in 10 ml of toluene solution. After complete dissolution, a colorless and transparent solution was formed. 1 ml of the PMMA / toluene solution was added to the outer interface between the silver nanoparticle aqueous solution and the toluene using a pipette. After standing for 0.5 hours, due to the hygroscopic nature of PMMA, the water content in the silver nanoparticle solution gradually decreased, and the droplet volume gradually decreased, causing the silver nanoparticle array to shrink and form silver nanoparticle aggregates. The silver nanoparticle aggregates were then aspirated with a pipette and soaked in pure toluene solution for 30 min, repeated three times to remove the PMMA from the surface of the aggregates. This washing process completed the preparation of the silver nanoparticle aggregates. Figure 5 A scanning electron microscope image of silver nanoparticle aggregates is shown.
[0053] Example 2:
[0054] In Example 2, except for the addition of a toluene solution of polymethyl methacrylate and a standing time of 1 hour during the preparation of silver nanoparticle aggregates, the other process steps and parameters are the same as in Example 1, and will not be repeated here. Figure 6 The image shows a scanning electron microscope image of the silver nanoparticle aggregates prepared in Example 2.
[0055] Example 3:
[0056] In Example 3, except for the addition of a toluene solution of polymethyl methacrylate and a standing time of 2 hours during the preparation of silver nanoparticle aggregates, the other process steps and parameters are the same as in Example 1. Figure 7 The image shows a scanning electron microscope image of the silver nanoparticle aggregates prepared in Example 3.
[0057] Effect characteristics:
[0058] Figure 8 The results of CV (crystal violet) detection by silver nanoparticle aggregates in Examples 1-3 are shown, where the horizontal axis represents Raman shift, the vertical axis represents intensity, and au indicates that the intensity value is relative. Figure 8 and Figure 5-7 By combining and comparing the results, it can be seen that the silver nanoparticle aggregates prepared in Examples 1-3 of the present invention all have good detection results. However, the silver nanoparticle aggregates prepared in Example 3 have a larger shape and density, and the interparticle spacing is closer, which helps to improve the Raman detection effect. Figure 8 Raman spectroscopy results also support this conclusion, namely that the silver nanoparticle aggregates prepared in Example 3 have a better reinforcing effect.
[0059] Characterization of the effectiveness of silver nanoparticle aggregates as a SERS substrate for Raman spectroscopy detection:
[0060] This section uses the silver nanoparticle aggregates prepared in Example 3 as the SERS substrate. The silver nanoparticle aggregates were placed in CV solutions of different concentrations and allowed to stand for 12 hours. They were then aspirated and placed on a clean silicon wafer, allowed to dry naturally, and then subjected to Raman testing. The Raman signal intensity of CV on the SERS substrate is shown below. Figure 9 As shown in the Raman plot, this SERS substrate exhibits good enhancement performance, capable of enhancing substrates down to 10⁻⁶. -15 The M(Mol / L)CV detection showed strong Raman peaks and good recognition. A plot of the probe molecule concentration versus Raman enhancement intensity revealed a Hill equation relationship between the logarithm of the concentration and the Raman enhancement intensity. Figure 10 As shown, the horizontal axis represents CV concentration, the vertical axis represents signal intensity, and the correlation coefficient is as high as 0.99.
[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a silver nanoparticle aggregate SERS substrate, characterized in that, include: Step 1: Prepare an aqueous solution of silver nanoparticles; Step 2: Add the prepared silver nanoparticle aqueous solution to the toluene solution according to the volume ratio, and let it stand to obtain a droplet-like two-phase interface between the silver nanoparticle aqueous solution and the toluene solution; wherein the volume ratio of the silver nanoparticle aqueous solution to the toluene solution is in the range of 1-5:
20. Step 3: Inject the ethanol solution into the droplet-like interface between the silver nanoparticle aqueous solution and the toluene solution, and let it stand for a preset time to prepare a silver nanoparticle monolayer at the droplet-like interface between the silver nanoparticle aqueous solution and the toluene solution. Step 4: Prepare a toluene solution of polymethyl methacrylate; wherein the mass ratio of polymethyl methacrylate to toluene solution is 1:500-3000. Step 5: Add the prepared polymethyl methacrylate toluene solution to the outside of the droplet-like two-phase interface between the silver nanoparticle aqueous solution and the toluene solution prepared in Step 3, and react to obtain the silver nanoparticle aggregate SERS substrate.
2. The preparation method according to claim 1, characterized in that, Step 1 includes: preparing an aqueous solution of silver nanoparticles using a seed synthesis method.
3. The preparation method according to claim 1, characterized in that, Step 2 includes: 50 μl of silver nanoparticle aqueous solution and 1 ml of toluene solution.
4. The preparation method according to claim 3, characterized in that, In step 3, the volume of ethanol solution added is 20 μl, and the injection rate is 20 μl / min.
5. The preparation method according to claim 1, characterized in that, In step 4, the mass ratio of polymethyl methacrylate to toluene solution is 1:1000.
6. The preparation method according to claim 1, characterized in that, Step 5 includes: controlling the reaction time within 0.5h-24h to obtain a self-assembled silver nanoparticle aggregate SERS substrate.
7. The preparation method according to claim 6, characterized in that, The reaction time is 2 hours.