A method for preparing a raman silent zone magnetic sers substrate

Abstract

The application discloses a preparation method of a Raman silent zone magnetic SERS substrate, and belongs to the technical field of surface enhanced Raman spectroscopy. The preparation method of the Raman silent zone magnetic SERS substrate comprises the following steps: firstly, a layer of gold nanoshell is wrapped on the surface of a ferroferric oxide particle to obtain Fe3O4@Au nanoparticles; then, a Raman beacon molecule 4-mercaptobenzonitrile is modified on the surface of the Fe3O4@Au; and further, a layer of silver nanoshell is wrapped on the surface of the Fe3O4@Au@4-mercaptobenzonitrile to obtain the Raman silent zone magnetic SERS substrate Fe3O4@Au@4-mercaptobenzonitrile@Ag. The Fe3O4@Au@4-mercaptobenzonitrile@Ag prepared by the method has uniform size and morphology, has a strong spectral peak at a Raman silent zone 2226 cm ‑1 ; and in combination with the local surface plasmon resonance property of the core-shell structure, the sensitivity of SERS detection can be effectively enhanced, and the Raman silent zone magnetic SERS substrate has a good practical application prospect in the field of rapid detection of food and the like.

Description

Technical Field

[0001] This invention relates to a method for preparing a magnetic SERS substrate in the Raman silent region, belonging to the field of surface-enhanced Raman spectroscopy technology. Background Technology

[0002] In recent years, surface-enhanced Raman spectroscopy (SERS), as an ultrasensitive detection technique, has been widely applied in rapid on-site detection fields such as food safety, environmental monitoring, and biomedicine due to its unique advantages such as speed, non-destructive nature, high sensitivity, and strong spectral fingerprint characteristics. However, in practical applications, complex matrices such as food can affect the stability of the SERS substrate. This necessitates that the prepared SERS substrate be sufficiently stable to avoid matrix interference. Furthermore, the consistency of the substrate's size and morphology can affect the reproducibility of experiments in practical applications.

[0003] In recent years, scholars in this field have been continuously dedicated to the research of various superior SERS substrates. Common SERS substrates include single-particle nanomaterials with different morphologies, core-shell nanomaterials, and nanoassemblies. Among them, magnetic nanoparticles are a commonly used high-quality SERS substrate, which can selectively separate and concentrate target substances from complex matrices in a short time through the magnetic separation effect of an external magnet. However, this type of SERS substrate still faces interference from complex matrices, affecting the sensitivity and accuracy of detection. Summary of the Invention

[0004] To address the shortcomings and deficiencies of existing technologies, the present invention aims to provide a method for preparing a Raman-silent region magnetic SERS substrate. This magnetic SERS substrate can selectively separate and concentrate target analytes from complex matrices in a short time through the magnetic separation action of an external magnet. At the same time, the spectral peaks in the Raman-silent region can effectively avoid interference from complex matrices such as food. Furthermore, combined with the localized surface plasmon resonance properties of the core-shell structure, it can effectively enhance the sensitivity of SERS detection, showing good practical application prospects in rapid detection fields such as food safety.

[0005] To achieve the above objectives, the following technical solution is adopted:

[0006] This invention provides a method for preparing a Raman silent region magnetic SERS substrate, the method comprising the following steps:

[0007] (1) Preparation of Fe3O4@Au

[0008] Fe3O4 was mixed with hydroxylamine hydrochloride and tetramethylammonium hydroxide, mechanically stirred and heated in a water bath, then chloroauric acid aqueous solution was added dropwise, followed by sodium citrate aqueous solution, and the reaction was continued with stirring. After the reaction, Fe3O4@Au nanoparticles were obtained.

[0009] (2) Preparation of Fe3O4@Au@4-MBN

[0010] 4-Mercaptobenzonitrile (4-MBN) was added to the Fe3O4@Au nanoparticles obtained in step (1), and the reaction was carried out at room temperature. After the reaction was completed, Fe3O4@Au@4-MBN modified with 4-MBN was obtained.

[0011] (3) Preparation of Fe3O4@Au@4-MBN@Ag

[0012] Add sodium citrate aqueous solution and ascorbic acid solution to Fe3O4@Au@4-MBN obtained in step (2), mix well, add silver nitrate solution under mechanical stirring, and incubate for 1 h to obtain Raman silent region magnetic SERS substrate, namely Fe3O4@Au@4-MBN@Ag.

[0013] In one embodiment of the present invention, the Fe3O4 in step (1) has a particle size of 20 nm and a concentration of 5 mg / mL.

[0014] In one embodiment of the present invention, the concentration of hydroxylamine hydrochloride in step (1) is 0.2 mol / L and the concentration of tetramethylammonium hydroxide is 0.01 mol / L.

[0015] In one embodiment of the present invention, the volume ratio of Fe3O4 to hydroxylamine hydrochloride and tetramethylammonium hydroxide in step (1) is 5:1.5:37.5.

[0016] In one embodiment of the present invention, the water bath heating temperature in step (1) is 70-75°C, and the entire reaction is carried out under constant temperature of 70-75°C and nitrogen protection.

[0017] In one embodiment of the present invention, the chloroauric acid aqueous solution in step (1) has a mass fraction of 0.1%.

[0018] In one embodiment of the present invention, the concentration of sodium citrate aqueous solution in step (1) is 15 mmol / L.

[0019] In one embodiment of the present invention, the reaction in step (2) is carried out under mechanical stirring conditions.

[0020] In one embodiment of the present invention, the concentration of sodium citrate aqueous solution in step (3) is 0.388 mmol / L, the concentration of ascorbic acid solution is 1 mmol / L, and the concentration of silver nitrate solution is 10 mmol / L.

[0021] In one embodiment of the present invention, the Fe3O4@Au@4-MBN@Ag is in the Raman quiescent region of 2226 cm⁻¹. -1 There is a strong spectral peak at this location.

[0022] The present invention also provides a Raman silent region magnetic SERS substrate Fe3O4@Au@4-MBN@Ag prepared by the method described above.

[0023] This invention also provides the application of the aforementioned Raman silent region magnetic SERS substrate Fe3O4@Au@4-MBN@Ag in the field of rapid food safety detection.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) This invention proposes a method for preparing a magnetic SERS substrate in the Raman silent region. The prepared Fe3O4@Au@4-MBN@Ag substrates have uniform size and morphology, and exhibit uniformity in size and morphology in the Raman silent region at 2226 cm⁻¹. -1 There are strong spectral peaks at this location;

[0026] (2) The magnetic SERS substrate prepared by the present invention can be rapidly separated by the strong magnetism of Fe3O4. At the same time, the spectral peaks in the Raman silent region can effectively avoid interference from complex matrices such as food. Combined with the local surface plasmon resonance properties of the core-shell structure, the sensitivity of SERS detection can be effectively enhanced. It has good practical application prospects in the field of rapid detection of food and other products. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the process for preparing Fe3O4@Au@4-MBN@Ag in Example 1 of the present invention;

[0028] Figure 2 This is a transmission electron microscope image of Fe3O4@Au@4-MBN@Ag prepared in Example 1 of this invention;

[0029] Figure 3 The Raman spectrum of Fe3O4@Au@4-MBN@Ag prepared in Example 1 of this invention. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0031] Unless otherwise specified, the reagents and materials used in the following examples are commercially available or can be prepared by known methods.

[0032] Fe3O4 was purchased from Oceananotech, beacon molecule 4-MBN was purchased from Beijing Bailingwei Technology Co., Ltd., and hydroxylamine hydrochloride, tetramethylammonium hydroxide, chloroauric acid, sodium citrate, ascorbic acid and silver nitrate were purchased from Sinopharm Group and Aladdin Company, respectively.

[0033] Example 1

[0034] A method for preparing a Raman silent region magnetic SERS substrate (Fe3O4@Au@4-MBN@Ag) includes the following steps:

[0035] (1) Preparation of Fe3O4@Au nanoparticles by coating a gold nanoshell onto the surface of iron oxide particles:

[0036] 5 mL of Fe3O4 with a particle size of 20 nm and a concentration of 5 mg / mL was sonicated for 10 min and mixed with 1.5 mL of 0.2 mol / L hydroxylamine hydrochloride and 37.5 mL of 0.01 mol / L tetramethylammonium hydroxide aqueous solution. The mixture was then mechanically stirred and heated in a water bath to 75 °C. The entire reaction was carried out under constant temperature of 75 °C and nitrogen protection. Then, 8.5 mL of 0.1% chloroauric acid aqueous solution was added dropwise, followed by 50 mL of 15 mmol / L sodium citrate aqueous solution. The reaction was stirred for another 2 h to obtain Fe3O4@Au nanoparticles.

[0037] (2) Preparation of Fe3O4@Au surface-modified Raman beacon molecules, i.e., Fe3O4@Au@4-MBN:

[0038] 4-Mercaptobenzonitrile (4-MBN) was added to the Fe3O4@Au nanoparticles obtained in step (1), and the reaction was mechanically stirred at room temperature for 3 h to obtain 4-MBN modified Fe3O4@Au@4-MBN;

[0039] (3) Preparation of Fe3O4@Au@4-MBN particles coated with a silver nanoshell, i.e., Fe3O4@Au@4-MBN@Ag:

[0040] Add 4 mL of 0.388 mmol / L sodium citrate aqueous solution and 1 mL of 1 mmol / L ascorbic acid solution to the Fe3O4@Au@4-MBN nanoparticles obtained in step (2), mix well, and add 2 mL of 10 mmol / L silver nitrate solution under mechanical stirring. Incubate for 1 h to obtain Fe3O4@Au@4-MBN@Ag.

[0041] Results analysis:

[0042] The performance of Fe3O4@Au@4-MBN@Ag prepared in Example 1 was analyzed. Figure 1 Fe3O4@Au@

[0043] A schematic diagram of the preparation process of 4-MBN@Ag.

[0044] Figure 2 Transmission electron microscopy (TEM) image of Fe3O4@Au@4-MBN@Ag, by Figure 2 The results show that the Fe3O4@Au@4-MBN@Ag has a size of about 23nm, and its size and morphology are uniform. It can be rapidly separated magnetically by adding an external magnet.

[0045] Figure 3 The image shows the Raman spectral data of Fe3O4@Au@4-MBN@Ag. Figure 3 The results show that the Fe3O4@Au@4-MBN@Ag prepared in this invention has strong SERS activity, and exhibits excellent performance in the Raman quiescent region at 2226 cm⁻¹. -1 It has a strong spectral peak, which can effectively enhance the sensitivity of SERS detection and avoid interference from complex matrices such as food.

[0046] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing a Raman silent region magnetic SERS substrate, characterized in that, The method includes the following steps: (1) Preparation of Fe3O4@Au Fe3O4 was mixed with hydroxylamine hydrochloride and tetramethylammonium hydroxide, mechanically stirred and heated in a water bath, then chloroauric acid aqueous solution was added dropwise, followed by sodium citrate aqueous solution, and the reaction was continued with stirring. After the reaction, Fe3O4@Au nanoparticles were obtained. (2) Preparation of Fe3O4@Au@4-MBN 4-Mercaptobenzonitrile (4-MBN) was added to the Fe3O4@Au nanoparticles obtained in step (1), and the reaction was carried out at room temperature. After the reaction was completed, Fe3O4@Au@4-MBN modified with 4-MBN was obtained. (3) Preparation of Fe3O4@Au@4-MBN@Ag Add sodium citrate aqueous solution and ascorbic acid solution to Fe3O4@Au@4-MBN obtained in step (2), mix well, add silver nitrate solution under mechanical stirring, and incubate for 1 h to obtain Raman silent region magnetic SERS substrate, namely Fe3O4@Au@4-MBN@Ag.

2. The preparation method according to claim 1, characterized in that, In step (1), the Fe3O4 has a particle size of 20 nm and a concentration of 5 mg / mL.

3. The preparation method according to claim 1, characterized in that, In step (1), the concentration of hydroxylamine hydrochloride is 0.2 mol / L and the concentration of tetramethylammonium hydroxide is 0.01 mol / L.

4. The preparation method according to claim 1, characterized in that, In step (1), the water bath heating temperature is 70-75℃, and the entire reaction is carried out under constant temperature of 70-75℃ and nitrogen protection.

5. The preparation method according to claim 1, characterized in that, In step (1), the chloroauric acid aqueous solution has a mass fraction of 0.1%.

6. The preparation method according to claim 1, characterized in that, The concentration of sodium citrate aqueous solution in step (1) is 15 mmol / L.

7. The preparation method according to claim 1, characterized in that, In step (3), the concentration of sodium citrate aqueous solution is 0.388 mmol / L, the concentration of ascorbic acid solution is 1 mmol / L, and the concentration of silver nitrate solution is 10 mmol / L.

8. The preparation method according to claim 1, characterized in that, The Fe3O4@Au@4-MBN@Ag is in the Raman silent region at 2226 cm⁻¹ -1 There is a strong spectral peak at this location.

9. The Raman silent region magnetic SERS substrate Fe3O4@Au@4-MBN@Ag prepared by the method according to any one of claims 1 to 8.

10. The application of the Raman silent region magnetic SERS substrate Fe3O4@Au@4-MBN@Ag as described in claim 9 in the field of rapid food safety detection.

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