CN110790220A - Surface-enhanced Raman scattering substrate, preparation method thereof and in-situ rapid detection method - Google Patents

Abstract

The invention discloses a surface-enhanced Raman scattering substrate, a preparation method thereof, and an in-situ rapid detection method. The preparation method comprises adding a solvent to a gold nanoparticle solution, and the solvent is immiscible with the gold nanoparticle solution and floats on the gold nanoparticle solution. Above the nanoparticle solution, a layering phenomenon with a liquid-liquid interface is formed; the alcohol solution is injected into the gold nanoparticle solution, and the gold nanoparticles are transferred to the liquid-liquid interface to form a self-assembled film of gold nanoparticles through self-assembly ; Transfer the gold nanometer self-assembled film to a transparent substrate to obtain a surface-enhanced Raman scattering substrate. Through the above methods, a dense and ordered arrangement of gold nanoparticles can be formed by self-assembly at the liquid-liquid interface, and the self-assembled film of gold nanoparticles can be transferred to a surface-enhanced Raman scattering substrate formed on a transparent substrate, which can be used for liquid Rapid in situ real-time detection of illegal additive molecules (such as malachite green, rhodamine B, etc.) in the phase system, with high detection sensitivity and good reproducibility.

Description

Surface-enhanced Raman scattering substrate, preparation method and in-situ rapid detection method

technical field

The invention relates to the technical field of detection, in particular to a surface-enhanced Raman scattering substrate, a preparation method thereof, and an in-situ rapid detection method.

Background technique

Illegal additives mostly refer to illegal additives in food. Generally speaking, it does not belong to the traditionally considered food raw materials, does not belong to the new resource food approved for use, does not belong to the dual use of medicine and food announced by the health department or is used as a general food management substance, and is not listed in the food additives of various countries. Substances permitted by other laws and regulations are illegal additives; such as Sudan Red, Alkaline Orange, etc. Liquid-phase systems mostly refer to liquid-phase environments such as beverages, drinking water, aquaculture water, and rivers and lakes. Existing detection methods for illegal additives in liquid systems include high performance liquid chromatography, high performance liquid chromatography-tandem mass spectrometry, gas chromatography-tandem mass spectrometry, solid phase extraction-high performance liquid chromatography, ultraviolet spectrophotometry, ELISA, etc. Although the traditional detection method has high detection accuracy and good repeatability, it is not suitable for on-site detection due to the complicated pretreatment process, long instrument analysis time and high detection cost. Therefore, it is crucial to develop a simple, fast, and efficient method for the in situ detection of illegal additives in liquid-phase systems.

Surface-Enhanced Raman Scattering (SERS) effect means that when a suitable frequency laser irradiates the surface of noble metal nanoparticles, the plasmon resonance on the surface of noble metal nanoparticles will be excited, resulting in the enhancement of electromagnetic field. In the enhanced electromagnetic field, its Raman scattering signal will be enhanced by a million times or even higher. It is a non-destructive, label-free, high-sensitivity, near-field effect analysis and detection method, which is widely used in biology, chemistry, environment and other fields. . As a molecular spectroscopic fingerprint identification method, compared with other traditional detection methods, SERS has the advantages of rapidity, simple operation, no need for sample preparation or simple sample preparation, etc. It is a high sensitivity, high temporal and spatial resolution, real-time Non-destructive testing technology.

Experimental and theoretical studies have shown that SERS technology can obtain high-sensitivity signals on low-concentration test substances, and the prerequisite for obtaining high-quality Raman signals is the enhanced performance of the SERS active substrate, which is determined by the material and morphology of the SERS substrate. the enhancement effect of the SERS substrate. The existing SERS substrate is usually prepared by preparing a gold nanoparticle solution, then dropping the gold nanoparticle solution on the substrate, and then drying to form gold nanoparticle aggregates on the substrate, so as to prepare the SERS substrate. In the above method, the gold nanoparticle aggregates are set by directly drawing the solution onto the substrate and then drying. The arrangement of the gold nanoparticles is chaotic and disorderly, so that the formed SERS substrate is used for the detection of the analyte. , the detection stability and signal reproducibility are poor. Therefore, it is particularly important to develop a SERS substrate with excellent performance for in-situ rapid detection of illegal additive molecules in the liquid phase.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the present invention proposes a surface-enhanced Raman scattering substrate, a preparation method thereof, and an in-situ rapid detection method, and the surface-enhanced Raman scattering substrate prepared by the preparation method can be used for the in-situ rapid detection of illegal additive molecules in a liquid system , with high sensitivity and good reproducibility.

The technical scheme adopted by the present invention is:

A first aspect of the present invention provides a method for preparing a surface-enhanced Raman scattering substrate, comprising the following steps:

S1. Preparation of gold nanoparticle self-assembled film: adding a solvent to the gold nanoparticle solution, standing for stratification; the solvent and the gold nanoparticle solution are immiscible, and float in the gold nanoparticle solution. Above; inject the alcohol solution into the gold nanoparticle solution, the gold nanoparticles in the gold nanoparticle solution are transferred to the interface between the gold nanoparticle solution and the solvent, and form gold through self-assembly Nanoparticle self-assembled films;

S2, disposing at least one layer of the gold nanoparticle self-assembled film on a transparent substrate to prepare a surface-enhanced Raman scattering substrate.

In step S1, the gold nanoparticle solution is usually an aqueous solution of gold nanoparticles; the particle size of the gold nanoparticles in the gold nanoparticle solution is generally 10-150 nm. The solvent is usually an oil phase solvent; according to some embodiments of the present invention, the solvent is an alkane-based organic solvent, and specifically, at least one of hexane and heptane can be used. When the solvent is added to the gold nanoparticle solution, an oil-water layer will appear, and the oil phase solvent floats on the top of the gold nanoparticle solution. By adding alcohol solution, the surface charge of the gold nanoparticle can be reduced, and the oil-water interface energy can be reduced. Gold nanoparticles can ascend and transfer to the oil-water interface, and form a self-assembled monolayer film of gold nanoparticles through self-assembly. Among them, the alcohol solution is usually an ethanol solution.

In step S1, the gold nanoparticle solution can be prepared by reacting a gold salt solution with a reducing agent. According to some embodiments of the present invention, the gold nanoparticle solution is prepared by a preparation method comprising the following steps:

a. Boil the reducing agent solution, add the gold salt solution, and then perform a heat reflux treatment to obtain a gold nanoparticle seed solution;

b. A gold salt solution is added to the gold nanoparticle seed solution, and heat treatment is performed to prepare a gold nanoparticle solution.

The gold nanoparticles in the gold nanoparticle solution prepared by the above method are uniform in size, and are used to prepare a surface-enhanced Raman scattering substrate, which can further improve its sensitivity, stability and reproducibility.

According to some embodiments of the present invention, in step a, the reducing agent solution is selected from citrate solution; in step a and/or step b, the gold salt solution is selected from chloroauric acid solution and sodium chloroauric acid solution at least one of them. The concentration of the reducing agent solution is generally 2-2.5 mM (ie, mmol/L); the concentration of the gold salt solution is generally 20-30 mM. In addition, in step a, the time of thermal reflow treatment is generally 10-20 min.

According to some embodiments of the present invention, step b specifically includes the following steps:

① Add gold salt solution to the gold nanoparticle seed solution, and then heat treatment;

② Repeat step ① at least once to obtain a gold nanoparticle solution;

Alternatively, it also includes: 3. adding a reducing agent solution to the gold nanoparticle solution obtained in step (2) to obtain a second round of gold nanoparticle seed solution; and then according to step (1) or steps (1) and (2), preparing gold nanoparticles with desired particle size. solution of gold nanoparticles. Through the above method or by further repeating step ③, the gold nanoparticle solution can be prepared according to the required particle size of the gold nanoparticle. In addition, with the increase of the number of rounds, the reducing agent and the gold salt solution are continuously added, so that the gold nanoparticles continue to grow, and the concentration of the gold nanoparticles solution is also increasing. Therefore, in order to make the gold nanoparticles synthesized in each round The concentrations are roughly the same, and appropriate amount of water can be added for dilution at the same time as the reducing agent solution is added later.

In the above step ①, the concentration of the gold salt solution is generally 20-30 mM, and the heat treatment time is generally 20-30 min; the concentration of the reducing agent solution in step ③ is generally 50-70 mM.

In step S1, the volume ratio of the gold nanoparticle solution, the alkane-based organic solvent and the ethanol solution may be 5:5:2.

According to some embodiments of the present invention, in step S2, the transparent substrate is a flexible transparent substrate. A flexible transparent substrate is used to prepare a surface-enhanced Raman scattering substrate. When it is further applied to illegal additive molecules, the wrapping shape of the surface-enhanced Raman scattering substrate can be flexibly changed according to the shape of the object to be detected, so that the gold nanoparticles on it can self-assemble. The film is fully contacted with the object to be detected for detection, thereby improving the detection flexibility and sensitivity.

The material of the transparent substrate may specifically be at least one of polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET). The flexible material is used and the substrate is light in weight. It is used to prepare a surface-enhanced Raman scattering substrate, and then used for the detection of illegal additive molecules in a liquid system. The surface-enhanced Raman scattering substrate can be self-assembled film containing gold nanoparticles on the substrate. The side of the substrate is facing down and is in contact with the surface of the solution to be tested for detection. Since the density of the substrate is smaller than that of the solution to be tested, the substrate can be suspended on the surface of the solution to be tested, enabling real-time in-situ detection without damage. The object to be detected or the object to be detected is extracted and then dropped on the substrate, which is easy to operate.

According to some embodiments of the present invention, in step S2, the LB technology (ie, the Langmuir-Blodgett transfer technology) is specifically used, and at least one layer of the gold nanoparticle self-assembled film is disposed on the transparent substrate. The number of layers of the gold nanoparticle self-assembled thin film may specifically be 2 layers, 3 layers, 4 layers, 5 layers, etc.; preferably 2 layers.

A second aspect of the present invention provides a surface-enhanced Raman scattering substrate, which is prepared by any of the methods for preparing a surface-enhanced Raman scattering substrate of the first aspect of the present invention.

A third aspect of the present invention provides an in-situ rapid detection method for illegal additive molecules in a liquid phase system, which specifically includes the following steps: attaching the surface-enhanced Raman scattering substrate of the second aspect of the present invention to a self-assembled film containing gold nanoparticles on a substrate One side of the test solution is in contact with the surface of the solution to be tested, and then the Raman spectrometer is used for detection. The illegal additive molecules include at least one of malachite green, rhodamine B, Sudan red, and alkaline orange; the liquid phase system specifically includes, but is not limited to, beverages, drinking water, aquaculture water, and river and lake water.

In the above detection method, the surface-enhanced Raman scattering substrate of the second aspect of the present invention is used, and the self-assembled film containing gold nanoparticles on the surface-enhanced Raman scattering substrate is turned down, and the surface of the solution to be tested is attached to the surface of the surface-enhanced Raman scattering substrate. It is easy to operate and can realize the in-situ rapid detection of illegal additive molecules in the liquid system, without destroying the object to be detected or extracting the object to be detected and then dropping it on the surface-enhanced Raman scattering substrate; and the detection sensitivity is high, Good stability and reproducibility.

The Raman spectrometer is used to detect the Raman scattering signal of the solution to be tested above. Specifically, the laser can be injected from the side of the surface-enhanced Raman scattering substrate away from the self-assembled film of gold nanoparticles, and the focusing depth can be adjusted to focus the laser on the gold nanoparticle. On the self-assembled film of nanoparticles, the in-situ SERS detection of illegal additive molecules in the liquid phase system was performed, and the SERS map was obtained, which could be qualitatively analyzed according to the characteristic peaks. Among them, the wavelength of the laser used in Raman spectrum detection is generally 532 nm, 633 nm or 785 nm, and the scanning range is 200-2000 cm ^-1 .

Generally speaking, the more layers of self-assembled films of gold nanoparticles on the surface-enhanced Raman scattering substrate, the better the enhancement effect of SERS signal. , if the number of layers of the gold nanoparticle self-assembled film is too large, the transmittance of laser and SERS signals will be reduced. Experience has found that the above detection method using a surface-enhanced Raman scattering substrate containing two layers of gold nanoparticles self-assembled film for detection can maximize the SERS signal while ensuring the transmittance.

The beneficial technical effects of the present invention are as follows: the present invention provides a surface-enhanced Raman scattering substrate, a preparation method thereof, and an in-situ rapid detection method. In the preparation method, a solvent is added to the gold nanoparticle solution, and the solution is left to stand for stratification; the solvent It is immiscible with the gold nanoparticle solution, and floats above the gold nanoparticle solution, forming a layering phenomenon with a liquid-liquid interface; and then injecting the alcohol solution into the gold nanoparticle solution, the gold nanoparticles in the gold nanoparticle solution The nanoparticles are transferred to the liquid-liquid interface, and then a dense gold nanoparticle self-assembled film is formed by self-assembly; and the gold nanoparticle self-assembled film is transferred to a transparent substrate to prepare a surface-enhanced Raman scattering substrate. From the above, a dense and ordered arrangement of gold nanoparticles can be formed by self-assembly at the liquid-liquid interface, and the self-assembled film of gold nanoparticles can be transferred to a surface-enhanced Raman scattering substrate formed on a transparent substrate, which can be used for illegal Detection of additive molecules (including malachite green, rhodamine B, Sudan red, basic orange, etc.), once illegal additive molecules enter the gap between gold nanoparticles on the gold nanoparticle self-assembled film (the width of this gap is usually less than 10nm, called "hot spot"), its Raman scattering signal (ie SERS signal) is strongly enhanced, and the sensitivity is high; and the dense and neat arrangement of gold nanoparticles on the self-assembled film of gold nanoparticles can make the detected SERS signal High uniformity, good stability and reproducibility. In addition, the self-assembled film containing gold nanoparticles on the surface-enhanced Raman scattering substrate can be placed in contact with the surface of the solution to be tested in an upside-down manner, so that the rapid prototyping of illegal additive molecules in the liquid system can be carried out. For real-time detection, it is not necessary to destroy the object to be detected or extract the object to be detected and then drop it on the surface-enhanced Raman scattering substrate for detection, and the operation is simple and convenient.

Instruction drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly describes the accompanying drawings that are used in the description of the embodiments.

Fig. 1 is the transmission electron microscope photograph of the gold nanoparticles of the gold nanoparticle solution prepared in step S2 in Example 1;

Fig. 2 is the scanning electron microscope photograph of the gold nanoparticle self-assembled film prepared in step S3 in Example 1;

Fig. 3 is the scanning electron microscope photograph of the gold nanoparticle aggregate prepared in step S3 in Comparative Example 1;

Fig. 4 is the SERS detection spectrum of different concentrations of malachite green molecules in lake water using the surface-enhanced Raman scattering substrate of Example 1;

5 is a spectrogram showing the reproducibility of SERS detection of 10 ^-6 M malachite green molecules in lake water using the surface-enhanced Raman scattering substrate of Example 1;

FIG. 6 is a spectrogram showing the reproducibility of SERS detection of 10 ^-6 M malachite green molecules in lake water using the surface-enhanced Raman scattering substrate of Comparative Example 1.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

A surface-enhanced Raman scattering substrate, the preparation method of which comprises the following steps:

S1. Boil 150 mL of a sodium citrate solution with a concentration of 2.2 mM, quickly add 1 mL of a 25 mM chloroauric acid solution, and heat under reflux for 10 min, then stop heating to obtain a gold nanoparticle seed solution;

S2, prepare a gold nanoparticle solution; specifically include:

① Add 1 mL of 25 mM chloroauric acid solution to the gold nanoparticle seed solution obtained in step S1, and heat for 30 min;

② Repeat step ① twice to complete the first round of growth of gold nanoparticles to obtain a gold nanoparticle solution containing gold nanoparticles with a particle size of 15-28 nm;

3. Take 55 mL of the gold nanoparticle solution obtained in the first round, add 53 mL of ultrapure water and 2 mL of sodium citrate solution with a concentration of 60 mM, and use this as the gold nanoparticle seed solution of the second round of growth;

4. Add 1 mL of chloroauric acid solution with a concentration of 25 mM to the gold nanoparticle seed solution obtained in step 3, and heat for 30 min;

⑤ Repeat step ④ twice to complete the growth of the second round of gold nanoparticles to obtain the second round of gold nanoparticles solution;

⑥ Take 55 mL of the second-round gold nanoparticle solution obtained in step ⑤, add 53 mL of ultrapure water and 2 mL of sodium citrate solution with a concentration of 60 mM, and use this as the gold nanoparticle seed solution for the third round of growth;

⑦Add 1 mL of 25mM chloroauric acid solution to the gold nanoparticle seed solution prepared in step ⑥, and heat for 30min;

⑧ Repeat step ⑦ twice to complete the third round of gold nanoparticle growth, and obtain the third round of gold nanoparticle solution.

S3, add 5mL of the gold nanoparticle solution obtained in step S2 into the serum bottle, and add 5mL of hexane to it, and after adding, the hexane is suspended above the gold nanoparticle solution to form a layering phenomenon with a liquid-liquid interface; Then 2 mL of ethanol solution was slowly injected into the gold nanoparticle solution, and then the gold nanoparticles in the gold nanoparticle solution were transferred to the liquid-liquid interface, and formed a self-assembled film of gold nanoparticles through self-assembly;

S4. Using LB technology, transfer the gold nanoparticle film self-assembled film obtained in step S3 to a flexible and transparent PDMS substrate to form a PDMS-supported gold nanoparticle self-assembled monolayer to obtain a surface-enhanced Raman scattering substrate.

Example 2

A surface-enhanced Raman scattering substrate, the preparation method of which comprises the following steps:

S1. Boil 150 mL of a sodium citrate solution with a concentration of 2 mM, quickly add 1 mL of a 20 mM chloroauric acid solution, and heat under reflux for 15 min, then stop heating to obtain a gold nanoparticle seed solution;

S2, prepare a gold nanoparticle solution; specifically include:

① Add 1 mL of 20 mM chloroauric acid solution to the gold nanoparticle seed solution obtained in step S1, and heat for 30 min;

② Repeat step ① twice to complete the first round of gold nanoparticle growth, and obtain the first round of gold nanoparticle solution;

③ Take 55 mL of the first-round gold nanoparticle solution obtained in step ②, add 53 mL of ultrapure water and 2 mL of sodium citrate solution with a concentration of 50 mM, and use this as the gold nanoparticle seed solution for the second round of growth;

4. Add 1 mL of chloroauric acid solution with a concentration of 25 mM to the gold nanoparticle seed solution obtained in step 3, and heat for 30 min;

⑤ Repeat step ④ twice to complete the growth of the second round of gold nanoparticles to obtain the second round of gold nanoparticles solution;

⑥ Take 60 mL of the second-round gold nanoparticle solution obtained in step ⑤, add 53 mL of ultrapure water and 2 mL of sodium citrate solution with a concentration of 60 mM, and use this as the gold nanoparticle seed solution for the third round of growth;

⑦Add 1 mL of 25mM chloroauric acid solution to the gold nanoparticle seed solution prepared in step ⑥, and heat for 30min;

⑧ Repeat step ⑦ twice to complete the third round of gold nanoparticle growth, and obtain the third round of gold nanoparticle solution.

S3, add 5mL of the gold nanoparticle solution obtained in step S2 into the serum bottle, and add 5mL of hexane to it, and after adding, the hexane is suspended above the gold nanoparticle solution to form a layering phenomenon with a liquid-liquid interface; Then 2 mL of ethanol solution was slowly injected into the gold nanoparticle solution, and then the gold nanoparticles in the gold nanoparticle solution were transferred to the liquid-liquid interface, and self-assembled to form a gold nanoparticle self-assembled film; 3 pieces of gold were prepared by the above method Nanoparticle self-assembled films;

S4. Using the LB technique, transfer the three gold nanoparticle self-assembled films obtained in step S3 to the same flexible and transparent PMMA substrate in turn to form a stacked arrangement to form a PMMA-supported gold nanoparticle self-assembled three-layer film, A surface-enhanced Raman scattering substrate is obtained.

Example 3

A surface-enhanced Raman scattering substrate, the preparation method of which comprises the following steps:

S1. Boil 150 mL of sodium citrate solution with a concentration of 2.5 mM, quickly add 1 mL of a solution of chloroauric acid with a concentration of 30 mM, and heat under reflux for 15 min, then stop heating to obtain a gold nanoparticle seed solution;

S2, prepare a gold nanoparticle solution; specifically include:

① Add 1 mL of chloroauric acid solution with a concentration of 30 mM to the gold nanoparticle seed solution obtained in step S1, and heat for 30 min;

② Repeat step ① twice to complete the first round of gold nanoparticle growth, and obtain the first round of gold nanoparticle solution;

③ Take 60 mL of the first-round gold nanoparticle solution obtained in step ②, add 53 mL of ultrapure water and 2 mL of sodium citrate solution with a concentration of 50 mM, and use this as the gold nanoparticle seed solution for the second round of growth;

4. Add 1 mL of chloroauric acid solution with a concentration of 30 mM to the gold nanoparticle seed solution obtained in step 3, and heat for 30 min;

⑤ Repeat step ④ twice to complete the second round of growth of gold nanoparticles to obtain a solution of gold nanoparticles;

S3, add 5mL of the gold nanoparticle solution obtained in step S2 into the serum bottle, and add 5mL of hexane to it, and after adding, the hexane is suspended above the gold nanoparticle solution to form a layering phenomenon with a liquid-liquid interface; Then 2 mL of ethanol solution was slowly injected into the gold nanoparticle solution, and then the gold nanoparticles in the gold nanoparticle solution were transferred to the liquid-liquid interface, and a self-assembled film of gold nanoparticles was formed by self-assembly; 2 pieces of gold were prepared by the above method. Nanoparticle self-assembled films;

S4. Using LB technology, transfer the two gold nanoparticle self-assembled films obtained in step S3 to a flexible and transparent PET substrate in turn, and stack them to form a PET-supported gold nanoparticle self-assembled two-layer film to obtain surface enhancement. Raman scattering substrate.

Comparative Example 1

A surface-enhanced Raman scattering substrate, the preparation method of which comprises the following steps:

S1. Boil 150 mL of a sodium citrate solution with a concentration of 2.2 mM, quickly add 1 mL of a 25 mM chloroauric acid solution, and heat under reflux for 10 min, then stop heating to obtain a gold nanoparticle seed solution;

S2, prepare a gold nanoparticle solution; specifically include:

① Add 1 mL of 25 mM chloroauric acid solution to the gold nanoparticle seed solution obtained in step S1, and heat for 30 min;

② Repeat step ① twice to complete the first round of growth of gold nanoparticles to obtain a gold nanoparticle solution containing gold nanoparticles with a particle size of 15-28 nm;

3. Take 55 mL of the gold nanoparticle solution obtained in the first round, add 53 mL of ultrapure water and 2 mL of sodium citrate solution with a concentration of 60 mM, and use this as the gold nanoparticle seed solution of the second round of growth;

4. Add 1 mL of chloroauric acid solution with a concentration of 25 mM to the gold nanoparticle seed solution obtained in step 3, and heat for 30 min;

⑤ Repeat step ④ twice to complete the growth of the second round of gold nanoparticles to obtain the second round of gold nanoparticles solution;

⑥ Take 55 mL of the second-round gold nanoparticle solution obtained in step ⑤, add 53 mL of ultrapure water and 2 mL of sodium citrate solution with a concentration of 60 mM, and use this as the gold nanoparticle seed solution for the third round of growth;

⑦Add 1 mL of 25mM chloroauric acid solution to the gold nanoparticle seed solution prepared in step ⑥, and heat for 30min;

⑧ Repeat step ⑦ twice to complete the third round of gold nanoparticle growth, and obtain the third round of gold nanoparticle solution.

S3, sucking the gold nanoparticle solution prepared in step S2 and dripping it onto a flexible and transparent PDMS substrate, and after the gold nanoparticle solution is dried, gold nanoparticle aggregates are formed on the PDMS substrate to obtain a surface-enhanced Raman scattering substrate.

A transmission electron microscope was used to observe the gold nanoparticles in the gold nanoparticle solution prepared in step S2 in the preparation method of the surface-enhanced Raman scattering substrate in Example 1, and the obtained results are shown in FIG. 1 . It can be seen from FIG. 1 that the gold nanoparticles in the gold nanoparticle solution prepared by step S2 in Example 1 are uniform in size.

In addition, scanning electron microscopy was used to detect the gold nanoparticle self-assembled film prepared in step S3 in Example 1 and the gold nanoparticle aggregate prepared in step S3 in Comparative Example 1. The results are shown in Figures 2 and 3. It can be seen from Figure 2 that the gold nanoparticles in the gold nanoparticles self-assembled film formed by self-assembly at the liquid-liquid interface in Example 1 are densely arranged and neatly ordered; The gold nanoparticle aggregates are set by drawing the solution and dropping it on the substrate and then drying, and the arrangement of the gold nanoparticles is disordered.

The surface-enhanced Raman scattering substrate of the above embodiment can be used for the detection of illegal additive molecules (malachite green, rhodamine B, Sudan red, basic orange, etc.), especially the detection of illegal additive molecules in a liquid phase system.

For example, the surface-enhanced Raman scattering substrate prepared in Example 1 can be used to detect different concentrations of malachite green molecules in lake water. Concretely configure the lake aqueous solution with malachite green molecular concentrations of 10 ^-6 M (ie mol/L), 10 ^-7 M and 10 ^-8 M respectively, and then detect by the following method: using the surface-enhanced Raman method in Example 1 Scattering substrate, the side of the surface-enhanced Raman scattering substrate containing the self-assembled film of gold nanoparticles is facing down, and it is in contact with the surface of the solution to be tested, and then the surface-enhanced Raman scattering substrate is separated from the self-assembled gold nanoparticles by laser light. One side of the assembled film is injected, and the focusing depth is adjusted to focus the laser on the self-assembled film of gold nanoparticles, and then the in-situ SERS detection of illegal additive molecules in the liquid system is performed. The test results are shown in Figure 4. It can be seen from Fig. 4 that the detection of malachite green molecules using the surface-enhanced Raman scattering substrate can reach a lower detection limit concentration of 10 ^-7 M, and the detection sensitivity is high. In addition, during the detection process, since the density of the substrate is lower than that of the solution to be tested, the substrate will float on the surface of the solution, but the self-assembled film of gold nanoparticles on the surface of the substrate is immersed in the solution. Once the molecules to be detected in the solution to be tested enter the gold nanoparticles The Raman scattering signal is significantly enhanced, so that real-time in-situ detection can be realized without destroying the object to be detected or extracting the object to be detected and then dripping it on the substrate, which is easy to operate.

In addition, the surface-enhanced Raman scattering substrates prepared in Example 1 and Comparative Example 1 were used to perform SERS detection on 10 ^-6 M malachite green molecules in lake water to investigate the stability of the detection of illegal additive molecules in the liquid phase. The results are shown in Figure 5 and Figure 6. Among them, the relative standard deviation of the SERS detection reproducibility of 10 ^-6 M malachite green molecules in lake water using the surface-enhanced Raman scattering substrate of Example 1 of the present invention is 3.2%. The relative standard deviation of SERS detection for 10 ^-6 M malachite green molecules in lake water was 40.8%. The results shown in Fig. 5 and Fig. 6 prove that the self-assembled film of gold nanoparticles formed by liquid-liquid interface self-assembly and LB transfer technology in Example 1 of the present invention is used as the SERS substrate. The gold nanoparticle aggregates formed by dropping on the substrate are SERS substrates, which have better spectral reproducibility and detection stability.

Although the present invention has been particularly shown and described in connection with preferred embodiments, it will be understood by those skilled in the art that the present invention may be modified in form and detail without departing from the spirit and scope of the invention as defined by the appended claims. Various changes are made within the protection scope of the present invention.

Claims (10)

1. a preparation method of a surface-enhanced Raman scattering substrate, is characterized in that, comprises the following steps: S1. Preparation of gold nanoparticle self-assembled film: adding a solvent to the gold nanoparticle solution, and standing for stratification; the solvent is immiscible with the gold nanoparticle solution, and floats above the gold nanoparticle solution; The alcohol solution is injected into the gold nanoparticle solution, the gold nanoparticles in the gold nanoparticle solution are transferred to the interface between the gold nanoparticle solution and the solvent, and gold nanoparticles are formed by self-assembly self-assembled films; S2, disposing at least one layer of the gold nanoparticle self-assembled film on a transparent substrate to prepare a surface-enhanced Raman scattering substrate. 2 . The method for preparing a surface-enhanced Raman scattering substrate according to claim 1 , wherein the solvent is an alkane organic solvent. 3 . 3. The method for preparing a surface-enhanced Raman scattering substrate according to claim 1, wherein in step S1, the gold nanoparticle solution is prepared by a preparation method comprising the following steps: a. Boil the reducing agent solution, add the gold salt solution, and then perform a heat reflux treatment to obtain a gold nanoparticle seed solution; b. A gold salt solution is added to the gold nanoparticle seed solution, and heat treatment is performed to prepare a gold nanoparticle solution. 4. The method for preparing a surface-enhanced Raman scattering substrate according to claim 3, wherein in step a, the reducing agent solution is selected from a citrate solution; in step a and/or step b, the reducing agent solution is The gold salt solution is selected from at least one of chloroauric acid solution and sodium chloroauric acid solution. 5. The method for preparing a surface-enhanced Raman scattering substrate according to claim 3, wherein step b specifically comprises the following steps: ① Add gold salt solution to the gold nanoparticle seed solution, and then heat treatment; ② Repeat step ① at least once to obtain a gold nanoparticle solution; Alternatively, it also includes: 3. adding a reducing agent solution to the gold nanoparticle solution obtained in step (2) to obtain a second round of gold nanoparticle seed solution; and then according to step (1) or steps (1) and (2), preparing gold nanoparticles with desired particle size. solution of gold nanoparticles. 6 . The method for preparing a surface-enhanced Raman scattering substrate according to claim 1 , wherein, in step S2 , the transparent substrate is a flexible transparent substrate; preferably, the material of the transparent substrate is selected from polydimethyl methacrylate. At least one of siloxane, polymethyl methacrylate, and polyethylene terephthalate. 7. The method for preparing a surface-enhanced Raman scattering substrate according to any one of claims 1 to 6, wherein in step S2, using LB technology, at least one layer of the gold nanoparticles is arranged on the transparent substrate Self-assembled films. 8 . The method for preparing a surface-enhanced Raman scattering substrate according to claim 7 , wherein in step S2 , the LB technique is specifically adopted, and two layers of the gold nanoparticle self-assembled film are arranged on the transparent substrate. 9 . 9 . A surface-enhanced Raman scattering substrate, characterized in that, it is prepared by the method for preparing a surface-enhanced Raman scattering substrate according to any one of claims 1 to 8 . 10. A method for in-situ rapid detection of illegal additive molecules in a liquid phase system, characterized in that it comprises the following steps: attaching the surface-enhanced Raman scattering substrate according to claim 9 to one side of the self-assembled film containing gold nanoparticles It is in close contact with the surface of the solution to be tested, and is then detected by a Raman spectrometer.

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