Flexible SERS (Surface Enhanced Raman Scattering) chip based on chemical pollutant in-situ detection and preparation method thereof

Abstract

The invention discloses a flexible SERS (Surface Enhanced Raman Scattering) chip based on in-situ detection of chemical pollutants and a preparation method of the flexible SERS chip. The flexible SERS chip comprises a copper net, the gold film is plated on the surface of the copper net; and the gold nanoparticles are arranged on the surface of the gold film. Cleaning the copper net by using oxygen plasma; the cleaned copper net is plated with a gold film through electron beam evaporation; the copper net plated with the gold film is put into an octyldithiol solution to be soaked and activated; taking out the copper mesh, washing with an ethanol solution, and naturally airing; putting the copper net into a colloidal gold particle solution, and soaking for reaction; and taking out the soaked copper wire mesh, and washing the copper wire mesh with ultrapure water to obtain the flexible SERS chip. The flexible SERS chip can be directly attached to the surface of an object to be detected, Raman signals of chemical pollutants such as pesticide residues can be effectively enhanced, Raman in-situ detection of the chemical pollutants such as the pesticide residues can be achieved by irradiating the back of the chip through laser, the detection time is short, and good sensitivity is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of in-situ detection of chemical reagents, and more specifically, relates to a flexible SERS chip based on in-situ detection of chemical pollutants and a preparation method thereof. Background Art

[0002] Traditionally, the detection of chemical pollutants such as pesticide residues is mainly carried out through chromatography and immunochromatography. The pretreatment process of chromatography is complicated, time-consuming, and difficult to achieve in-situ detection. Immunochromatography has the advantages of convenient and fast detection and no need for detection instruments, but the sensitivity of this method is low and quantitative analysis cannot be achieved. Therefore, it is very important to develop a detection method with high detection sensitivity, convenience and speed.

[0003] Surface Enhanced Raman Spectroscopy (SERS) can amplify the Raman signal of the analyte by more than a million times by preparing a specific nanostructure enhanced chip, achieving ultra-high sensitivity detection, and the detection time is short. It is widely used in the fields of biology and pesticides. At present, most commonly used SERS chips are prepared using hard materials such as silicon wafers and quartz as substrates, which are rigid chips. Rigid SERS chips can only drop the analyte on the surface of the chip for detection, lacking flexibility and having great limitations in practical applications. It is impossible to realize Raman in-situ detection of samples with uneven surfaces such as aquatic products, fruits and vegetables. Developing a flexible in-situ detection SERS chip is very necessary to realize Raman in-situ detection of samples with uneven surfaces such as aquatic products, fruits and vegetables. Summary of the invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these purposes and other advantages according to the present invention, a flexible SERS chip based on in-situ detection of chemical pollutants is provided, which is a "Cu mesh-Au-AuNP" composite structure, comprising:

[0006] Copper mesh;

[0007] A gold film, which is plated on the surface of the copper mesh;

[0008] Gold nanoparticles are arranged on the surface of the gold film.

[0009] Preferably, the copper mesh is formed by interlacing copper wires with a diameter of 100 μm, and the side length of the square holes of the copper mesh is 10 μm to 200 μm;

[0010] The thickness of the gold film is 30 to 50 nm;

[0011] The diameter of the gold nanoparticles is 30-100 nm.

[0012] A method for preparing a flexible SERS chip based on in-situ detection of chemical pollutants comprises the following steps:

[0013] S1. Clean the copper mesh using oxygen plasma;

[0014] S2, coating the cleaned copper mesh with a gold film by electron beam evaporation;

[0015] S3, immersing the copper mesh coated with the gold film in an octanedithiol solution diluted with ethanol for activation;

[0016] S4. Take out the copper mesh, wash it with ethanol solution, and let it air dry naturally;

[0017] S5, then put the copper mesh into the colloidal gold particle solution and soak it for a certain reaction time;

[0018] S6. Take out the soaked copper mesh and wash it with ultrapure water to obtain a flexible SERS chip.

[0019] Preferably, in said S1, the copper mesh is cleaned by oxygen plasma for 2 to 6 minutes.

[0020] Preferably, in said S2, the specific method of coating the cleaned copper mesh with a gold film by electron beam evaporation comprises:

[0021] S21, fixing the copper mesh by a clamp and placing it in the electron beam cavity of the electron beam evaporation coating apparatus;

[0022] S22, close the chamber, turn on the dry pump, control the vacuum to below 50Pa through the dry pump, and then turn on the molecular pump to control the vacuum to 1×10 -4 Below Pa;

[0023] S23. Turn on the power of the electron gun, turn on the high voltage permission, turn on the gun high voltage, rotate the knob on the control handle to make the current passing through the electron gun 0.6A, and preheat for 2 minutes;

[0024] S24, select a gold evaporation source, select a gold film system, turn on the beam of the electron gun, and start evaporation of the gold evaporation source. Set the beam to 220 mA, the high voltage to 9.98 kV, and the current to 1.22 A to perform film coating;

[0025] S25. When the film thickness reaches the required thickness, turn off the beam, turn off the high voltage, and take out the sample to obtain a copper mesh with a gold film on the surface.

[0026] Preferably, in said S3, the concentration of the octanedithiol solution diluted with ethanol is 20 mM, and the immersion activation time is 12 to 24 hours.

[0027] Preferably, in said S5, the copper mesh is immersed in the colloidal gold particle solution for a reaction time of 12 to 24 hours.

[0028] Preferably, in said S5, the method for preparing the colloidal gold particle solution comprises:

[0029] Add ultrapure water and chloroauric acid into a reaction container, heat and stir with a heating magnetic stirrer until boiling, and no vortex should be generated during the stirring process; after boiling, add trisodium citrate all at once, and heat and boil for another 5 minutes. During this period, the color of the solution changes from light yellow to gray-black, and finally to wine red, and then cool naturally to obtain a colloidal gold particle solution.

[0030] Preferably, the usage ratio of ultrapure water, chloroauric acid and trisodium citrate is 25 mL:1 mL:50 μL; the concentration of chloroauric acid is 1 wt %; and the concentration of sodium citrate is 20 wt %.

[0031] A Raman spectrum detection method of a flexible SERS chip based on in-situ detection of chemical pollutants comprises: attaching the flexible SERS chip to the surface of an object to be tested, with one side of the gold nanoparticles facing the surface of the object to be tested, and then using a 785nm laser of a Raman spectrometer to perform a Raman spectrum test on the back of the flexible SERS chip; using a Si sample to calibrate the Raman spectrometer wave number before measurement; using a 50× objective telephoto lens to collect Raman signals; the test integration time is 1s, the laser power is 10mW; the selected spectral range is 600cm -1 ~1680cm -1 .

[0032] The present invention includes at least the following beneficial effects: the traditional SERS chip needs to drip the solution to be tested onto the chip surface for detection, lacks flexibility, has great limitations in practical applications, and is difficult to achieve in-situ detection. The flexible SERS chip of the present invention is aimed at the actual application scenario of detecting chemical pollutants such as pesticide residues on uneven surfaces. The flexible SERS chip can be directly attached to the surface of the object to be tested to achieve effective enhancement of the Raman signal of chemical pollutants such as pesticide residues, and by irradiating the back of the chip with laser, Raman in-situ detection of chemical pollutants such as pesticide residues can be achieved, with a short detection time and good sensitivity.

[0033] The present invention plates a gold film on the surface of a copper mesh. The gold film has a connecting effect, so that gold nanoparticles can be coupled to the surface of the copper mesh through gold-sulfur bonds, playing the role of chemical bond connection; the gold film and the gold nanoparticles interact with each other, and the gaps between them produce stronger Raman enhancement "hotspot" areas, thereby improving detection sensitivity.

[0034] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a scanning electron microscope photo of the copper mesh of the flexible SERS chip in Example 1;

[0036] Figure 2 This is a photo of the distribution of gold nanoparticles on the gold film surface of the flexible SERS chip in Example 1;

[0037] Figure 3 This is a real photo of the flexible SERS chip prepared in Example 1;

[0038] Figure 4 The present invention is a flow chart of the preparation of a flexible SERS chip based on in-situ detection of chemical pollutants;

[0039] Figure 5 This is a Raman spectrum obtained by using the flexible SERS chip prepared in Example 1 to perform Raman testing on fish immersed in methylene blue solutions of different concentrations. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0041] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0042] Example 1

[0043] This embodiment provides a flexible SERS chip based on in-situ detection of chemical pollutants, which is a "Cu mesh-Au-AuNP" composite structure, including:

[0044] The copper mesh is formed by interlacing copper wires with a diameter of 100 μm, and the size of the square holes of the copper mesh is 200 μm×200 μm; the scanning electron microscope photo of the copper mesh is as shown in Figure 1 As shown;

[0045] A gold film is plated on the surface of the copper mesh, and the thickness of the gold film is 50 nm;

[0046] Gold nanoparticles are arranged on the surface of the gold film. The diameter of the gold nanoparticles is 40 nm. The distribution of the gold nanoparticles on the surface of the gold film is shown in the following figure. Figure 2 shown.

[0047] The actual picture of the flexible SERS chip based on in-situ detection of chemical pollutants in this embodiment is as follows: Figure 3 shown.

[0048] Example 2

[0049] For the flexible SERS chip based on in-situ detection of chemical pollutants in Example 1, Figure 4 As shown, this embodiment provides a method for preparing a flexible SERS chip based on in-situ detection of chemical pollutants, comprising the following steps:

[0050] S1. Clean the copper mesh with oxygen plasma for 2 min;

[0051] S2. The cleaned copper mesh is plated with a gold film by electron beam evaporation. The specific method includes:

[0052] S21, fixing the copper mesh by a clamp and placing it in the electron beam cavity of the electron beam evaporation coating apparatus;

[0053] S22, close the chamber, turn on the dry pump, control the vacuum to below 50Pa through the dry pump, and then turn on the molecular pump to control the vacuum to 1×10 -4 Below Pa;

[0054] S23. Turn on the power of the electron gun, turn on the high voltage permission, turn on the gun high voltage, rotate the knob on the control handle to make the current passing through the electron gun 0.6A, and preheat for 2 minutes;

[0055] S24, select a gold evaporation source, select a gold film system, turn on the beam of the electron gun, and start evaporation of the gold evaporation source. Set the beam to 220 mA, the high voltage to 9.98 kV, and the current to 1.22 A to perform film coating;

[0056] S25, when the film thickness reaches the required thickness, the beam is turned off, the high voltage is turned off, and the sample is taken out to obtain a copper mesh with a gold film on the surface;

[0057] S3, immerse the copper mesh coated with gold film in a 20 mM octanedithiol solution (diluted with ethanol) for activation for 12 h;

[0058] S4. Take out the copper mesh, wash it with ethanol solution, and let it air dry naturally;

[0059] S5, then put the copper mesh into the colloidal gold particle solution and soak it for reaction for 12 hours; wherein, the preparation method of the colloidal gold particle solution includes: adding 200mL ultrapure water and 8mL of 1% chloroauric acid into a 250mL conical flask, heating and stirring with a heating magnetic stirrer until boiling, and no vortex can be generated during the stirring process; after boiling, adding 480μL of 20% trisodium citrate solution at one time, and then heating and boiling for 5 minutes, during which the color of the solution changes from light yellow to gray-black, and finally to wine red, and then naturally cooling to obtain a colloidal gold particle solution

[0060] S6. Take out the soaked copper mesh and wash it with ultrapure water to obtain a flexible SERS chip.

[0061] Example 3

[0062] For the flexible SERS chip based on in-situ detection of chemical pollutants in Example 1, this embodiment provides a Raman spectroscopy detection method, including:

[0063] The commercially available fish were immersed in pure water, 1pg / mL, 10pg / mL, 100pg / mL and 1ng / mL methylene blue solutions for 30 minutes. After the fish were taken out, the flexible SERS chip was attached to the surface of the fish for Raman testing. The test conditions were as follows: the flexible SERS chip was attached to the surface of the fish with the side of the gold nanoparticles facing the fish. The back of the flexible SERS chip was tested using a 785nm laser of a Raman spectrometer. The Raman spectrometer was calibrated with a Si sample before measurement. A 50× objective telephoto lens was used to collect Raman signals. The test integration time was 1s and the laser power was 10mW. The selected spectral range was 600cm -1 ~1680cm -1 The test results show that the methylene blue detection sensitivity of the flexible SERS chip can reach 1pg / mL, and it has a good enhancement effect on the surface of fish. Figure 5 shown.

[0064] The number of devices and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the present invention will be obvious to those skilled in the art.

[0065] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A flexible SERS chip based on in-situ detection of chemical pollutants, characterized in that: It is a "Cu mesh-Au-AuNP" composite structure, including: Copper mesh; A gold film, which is plated on the surface of the copper mesh; Gold nanoparticles are arranged on the surface of the gold film.

2. The flexible SERS chip based on in-situ detection of chemical pollutants according to claim 1, characterized in that: The copper mesh is formed by interlacing copper wires with a diameter of 100 μm, and the side length of the square holes of the copper mesh is 10 μm to 200 μm; The thickness of the gold film is 30 to 50 nm; The diameter of the gold nanoparticles is 30-100 nm.

3. A method for preparing a flexible SERS chip based on in-situ detection of chemical pollutants as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Clean the copper mesh using oxygen plasma; S2, coating the cleaned copper mesh with a gold film by electron beam evaporation; S3, immersing the copper mesh coated with the gold film in an octanedithiol solution diluted with ethanol for activation; S4. Take out the copper mesh, wash it with ethanol solution, and let it air dry naturally; S5, then put the copper mesh into the colloidal gold particle solution and soak it for a certain period of time; S6. Take out the soaked copper mesh and wash it with ultrapure water to obtain a flexible SERS chip.

4. The method for preparing a flexible SERS chip based on in-situ detection of chemical pollutants according to claim 3, characterized in that: In S1, the copper mesh is cleaned with oxygen plasma for 2 to 6 minutes.

5. The method for preparing a flexible SERS chip based on in-situ detection of chemical pollutants according to claim 3, characterized in that: In S2, the specific method of coating the cleaned copper mesh with a gold film by electron beam evaporation includes: S21, fixing the copper mesh by a clamp and placing it in the electron beam cavity of the electron beam evaporation coating apparatus; S22, close the chamber, turn on the dry pump, control the vacuum to below 50Pa through the dry pump, and then turn on the molecular pump to control the vacuum to 1×10 -4 Below Pa; S23, turn on the electron gun power supply, turn on the high voltage permission, turn on the gun high voltage, rotate the knob on the control handle to make the current passing through the electron gun 0.6A, and preheat for 2 minutes; S24, select a gold evaporation source, select a gold film system, turn on the beam of the electron gun, and start evaporation of the gold evaporation source. Set the beam to 220 mA, the high voltage to 9.98 kV, and the current to 1.22 A to perform film coating; S25. When the film thickness reaches the required thickness, turn off the beam, turn off the high voltage, take out the sample, and obtain a copper mesh with a gold film plated on the surface.

6. The method for preparing a flexible SERS chip based on in-situ detection of chemical pollutants according to claim 3, characterized in that: In S3, the concentration of the octanedithiol solution diluted with ethanol is 20 mM, and the immersion activation time is 12 to 24 hours.

7. The method for preparing a flexible SERS chip based on in-situ detection of chemical pollutants according to claim 3, characterized in that: In S5, the copper mesh is immersed in the colloidal gold particle solution for a reaction time of 12 to 24 hours.

8. The method for preparing a flexible SERS chip based on in-situ detection of chemical pollutants according to claim 3, characterized in that: In S5, the method for preparing the colloidal gold particle solution comprises: Add ultrapure water and chloroauric acid into a reaction vessel, heat and stir with a heating magnetic stirrer until boiling, and no vortex should be generated during the stirring process; after boiling, add trisodium citrate solution all at once, and heat and boil for another 5 minutes. During this period, the color of the solution changes from light yellow to gray-black, and finally to wine red, and then cool naturally to obtain a colloidal gold particle solution.

9. The method for preparing a flexible SERS chip based on in-situ detection of chemical pollutants according to claim 8, characterized in that: The usage ratio of ultrapure water, chloroauric acid and trisodium citrate is 25mL:1mL:50μL; the mass fraction of the chloroauric acid is 1wt%; and the mass fraction of the sodium citrate solution is 20wt%.

10. A Raman spectrum detection method based on a flexible SERS chip for in-situ detection of chemical pollutants according to any one of claims 1 to 2, characterized in that: include: The flexible SERS chip was attached to the surface of the object to be tested, with one side of the gold nanoparticles facing the surface of the object to be tested. Then, the Raman spectrum of the back of the flexible SERS chip was tested using a 785nm laser of a Raman spectrometer. The Raman spectrometer was calibrated with a Si sample before measurement. A 50× objective telephoto lens was used to collect Raman signals. The test integration time was 1s, the laser power was 10mW, and the selected spectral range was 600cm -1 ~1680cm -1 .

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