Gold nano array structure, preparation method thereof and application of gold nano array structure in SERS (Surface Enhanced Raman Scattering) trace detection

Abstract

The invention belongs to the technical field of Raman spectrum, and relates to a gold nano array structure, a preparation method thereof and application of the gold nano array structure in SERS (Surface Enhanced Raman Scattering) trace detection. The preparation method comprises the following steps: dropwise adding a PDMS curing liquid on the surface of a first gold nanoparticle film taking a PVP film as a substrate, heating until PDMS is cured, cooling to a second temperature, removing PVP, carrying out gold evaporation, then heating to a third temperature to form a gold nano array with consistent gap size, dropwise adding a PVP solution on the surface, and tearing off the PVP film after the PVP solution is cured into the PVP film, so as to obtain the gold nano array with the uniform gap size. And the PVP thin film with the gold nano array is obtained and attached to a non-metal substrate, PVP is removed, and the gold nano array structure is obtained. According to the preparation method, hot spot distribution of the gold nano array structure can be optimized, the uniformity of hot spots can be improved, gaps of the gold nano array structure can be precisely regulated and controlled by adjusting the third temperature, the enhancement effect of the nano structure can be optimized in different detection environments, and various practical application requirements are met.

Description

Technical Field

[0001] The invention belongs to the technical field of Raman spectroscopy and relates to a gold nanometer array structure, a preparation method thereof and an application thereof in SERS trace detection. Background Art

[0002] Metal nanomaterials have shown great application prospects in surface enhanced Raman scattering (SERS) technology due to their local electromagnetic field enhancement effect. SERS technology is an ultra-high sensitivity detection method based on the Raman scattering effect. It significantly enhances the local electromagnetic field of metal nanostructures, greatly enhances the Raman scattering signal of target molecules, and achieves high-sensitivity and high-resolution molecular detection. With its excellent sensitivity and selectivity, this technology has shown a wide range of application value in many fields such as environmental monitoring, biomedicine and food safety.

[0003] The key to improving SERS performance lies in the rational design and optimization of the areas (hot spots) where local electromagnetic fields are enhanced in metal nanostructures. These hot spots are usually located at the tips, holes or gaps of metal nanostructures, which can significantly enhance the local electromagnetic field strength, thereby improving the Raman scattering signal of molecules. Studies have shown that when the nanogap is reduced, the electromagnetic field enhancement effect of the hot spots is more significant, which not only helps to improve the sensitivity of the SERS substrate, but also puts higher requirements on the uniformity and repeatability of the detection. However, the distribution density and uniformity of hot spots are still the main bottlenecks restricting the further improvement of the performance of SERS substrates.

[0004] Therefore, studying how to optimize the hotspot distribution of metal nanostructures and achieve precise control is an important research direction to promote the further development of SERS technology. Summary of the invention

[0005] The purpose of the present invention is to at least partially solve the above technical problems, and to provide a gold nanoarray structure, a preparation method thereof and an application thereof in SERS trace detection.

[0006] The first aspect of the present invention provides a method for preparing a gold nanoarray structure, the method comprising the following steps: dripping a PDMS curing liquid on the surface of a first gold nanoparticle film with a PVP film as a substrate, heating to a first temperature, cooling to a second temperature after the PDMS is cured, removing the PVP, and obtaining a second gold nanoparticle film with a PDMS substrate and a reduced gap, wherein the gold nanoparticles of the second gold nanoparticle film are denser than those of the first gold nanoparticle film; performing gold evaporation on the surface of the second gold nanoparticle film, and then heating to a preset third temperature to form a gold nanoarray with a uniform gap size, dripping a PVP solution on the surface, and tearing off the PVP solution after the PVP solution is cured into a PVP film to obtain a PVP film with the gold nanoarray, and attaching the PVP film to a non-metallic substrate, removing the PVP, and obtaining a gold nanoarray structure; wherein the non-metallic substrate is a non-metallic substrate modified with a cross-linking agent, the third temperature is determined according to the target gap between the gold nanoparticles, and different third temperature values ​​result in different gap sizes.

[0007] Furthermore, in the above preparation method, the preparation method of the first gold nanoparticle film with the PVP film as the substrate is: preparing the first gold nanoparticle film on the template; adding PVP solution to the surface of the first gold nanoparticle film, and after the PVP solution is solidified into a PVP film, tearing the PVP film with the first gold nanoparticle film from the template.

[0008] Furthermore, in the above preparation method, the preparing the first gold nanoparticle film on the template specifically comprises: preparing the first gold nanoparticle film on a silicon wafer using a seed growth method.

[0009] Furthermore, in the above preparation method, the first temperature is 80-85°C.

[0010] Furthermore, in the above preparation method, the second temperature is 20-30°C.

[0011] Furthermore, in the above preparation method, the thickness of the gold evaporation is 28-32 nm.

[0012] Furthermore, in the above preparation method, the conditions for gold evaporation are: the evaporation rate is The vacuum degree is 6.6×10 -4 Pa-8×10 -4 Pa.

[0013] Furthermore, in the above preparation method, the third temperature is 60-80°C.

[0014] Furthermore, in the above preparation method, the cross-linking agent is a monothiol cross-linking agent.

[0015] Furthermore, in the above preparation method, the cross-linking agent is 3-mercaptopropyltrimethoxysilane.

[0016] Furthermore, in the above preparation method, the preparation method also includes: performing surface plasma treatment on the gold nanoarray structure.

[0017] Furthermore, in the above preparation method, the surface plasma treatment is specifically as follows: the first plasma treatment is performed under a pressure of 30Pa, the treatment power is 90W, and the treatment time is 180 seconds; the second plasma treatment is performed under a pressure of 50Pa, the treatment power is 90W, and the treatment time is 180 seconds.

[0018] The second aspect of the present invention provides a gold nanoarray structure prepared by the above preparation method.

[0019] The third aspect of the present invention provides an application of the above-mentioned gold nanoarray structure in SERS trace detection.

[0020] Compared with the prior art, the gold nanoarray structure, preparation method thereof and application thereof in SERS trace detection provided by the present invention have at least one of the following advantages:

[0021] 1. The present invention utilizes the thermal expansion property of PDMS material. First, a gap is formed in the gold nanoparticle film by adjusting the curing temperature of PDMS (which expands during the curing process) during the process of transferring the gold nanoparticle film to a polydimethylsiloxane (PDMS) substrate. Then, the temperature is lowered to a second temperature, and the gold nanoparticles are brought closer together by the contraction of PDMS, that is, the gold nanoparticles in the gold nanoparticle film are made denser. Then, the temperature is raised to a specific third temperature to form a gold nanoarray with uniform gap size and solidify it with PVP, which can not only optimize the hotspot distribution of the gold nanoarray structure, but also improve the uniformity of the hotspots.

[0022] 2. The technical solution provided by the present invention can accurately control the gap of the gold nanoarray structure by adjusting the third temperature, which helps to optimize the enhancement effect of the nanostructure in different detection environments and meet various practical application needs.

[0023] 3. Plasma treatment of the substrate further activates the surface of gold nanoparticles, enhances their adsorption capacity for target molecules, and improves the effect of surface enhanced Raman scattering. This surface activation treatment can optimize the performance of the substrate and improve the sensitivity of SERS detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of preferred embodiments in conjunction with the accompanying drawings, in which:

[0025] Figure 1 The preparation process of a gold nanoarray structure provided by an embodiment of the present invention is shown;

[0026] Figure 2 A scanning electron microscope (SEM) image of the gold nanoarray structure obtained in Example 2 is shown;

[0027] Figure 3 The Raman spectrum obtained in Test Example 1 is shown;

[0028] Figure 4 The Raman spectrum obtained in Test Example 2 is shown;

[0029] Figure 5 The Raman spectrum obtained in Test Example 3 is shown;

[0030] Figure 6 The Raman spectrum obtained in Test Example 4 (Figure a) and the statistical analysis diagram of the characteristic peak intensity of crystal violet 1160 cm-1 (Figure b) are shown. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further specifically described below by examples and in conjunction with the accompanying drawings. In the specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation of the present invention.

[0032] A typical embodiment of the present invention provides a method for preparing a gold nanoarray structure, the preparation method comprising the following steps: dripping PDMS curing liquid on the surface of a first gold nanoparticle film with a PVP film as a substrate, heating to a first temperature, and removing PVP under a second temperature condition after the PDMS is cured to obtain a second gold nanoparticle film with a PDMS substrate and a reduced gap, and compared with the first gold nanoparticle film, the gold nanoparticles of the second gold nanoparticle film are denser; performing gold evaporation on the surface of the second gold nanoparticle film, and then heating to a third temperature to form a gold nanoarray with uniform gaps, dripping PVP solution on the surface, and tearing off the PVP solution after it is cured into a PVP film to obtain a PVP film with the gold nanoarray, and sticking it to a non-metallic substrate, removing PVP, and obtaining a gold nanoarray structure, wherein the gold nanoarray structure has gaps of uniform size; wherein the non-metallic substrate is a non-metallic substrate modified with a cross-linking agent, and the third temperature is determined according to the target gap between the gold nanoparticles, and the gap sizes obtained with different third temperature values ​​are different.

[0033] In a preferred embodiment of the present invention, the method for preparing a first gold nanoparticle film with a PVP film as a substrate is: preparing a first gold nanoparticle film on a template; dripping a PVP solution on the surface of the first gold nanoparticle film, and after the PVP solution solidifies into a PVP film, tearing the PVP film with the first gold nanoparticle film off the template.

[0034] Since the gold nanoparticles on the first gold nanoparticle film directly prepared on the template are not dense enough and unevenly distributed, the embodiment of the present invention connects the gold nanoparticles together by gold evaporation, and then heats up to the third temperature to break the connection, and uses PVP to fix after pulling out the gaps of the same size, which solves the problem of uniform distribution of the hot spots of the gold nanoarray, and at the same time, the distribution of the hot spots is accurately regulated by the design of the third temperature. However, in the place where the gaps between the gold nanoparticles on the first gold nanoparticle film are large, gold evaporation will pass through the gaps and plate gold on the substrate, and it is impossible to connect each gold particle well. To solve this problem, the embodiment of the present invention drips PDMS curing liquid on the surface of the first gold nanoparticle film with PVP film as the substrate, heats to the first temperature, and after PDMS is cured, the curing temperature of PDMS (which will expand during the curing process) forms a gap in the gold nanoparticle film, and then drops to the second temperature, and the gold nanoparticles are made closer by the contraction of PDMS, that is, the gold nanoparticles in the gold nanoparticle film are made denser, and then gold evaporation is performed. At this time, gold evaporation can perfectly connect the gold nanoparticles together.

[0035] In a preferred embodiment of the present invention, a method for preparing a gold nanoarray structure is provided, wherein the preparation process is as follows: Figure 1 As shown, the method comprises the following steps: S100. preparing a first gold nanoparticle film on a template; S200. dripping a PVP solution on the surface of the first gold nanoparticle film, and after the PVP solution is solidified into a PVP film, tearing off the PVP film with the first gold nanoparticle film from the template to obtain a first gold nanoparticle film with the PVP film as a substrate; S300. dripping a PDMS curing solution on the surface of the first gold nanoparticle film, heating it to a first temperature, and after the PDMS is solidified, removing the PVP under a second temperature condition to obtain a first gold nanoparticle film with the PVP film as a substrate. MS and a second gold nanoparticle film with reduced gaps; S400. performing gold evaporation on the surface of the second gold nanoparticle film, then heating to a third temperature to form a gold nanoarray with uniform gaps, dripping a PVP solution on the surface, and tearing off the PVP film after the PVP solution solidifies into a PVP film to obtain a PVP film with the gold nanoarray; S500. attaching the gold nanoarray side of the PVP film with the gold nanoarray to a non-metallic substrate, removing the PVP, and obtaining a gold nanoarray structure; S600. performing surface plasma treatment on the gold nanoarray structure.

[0036] In the above preparation method, the design of the first temperature, the second temperature and the third temperature has a great influence on the hot spot distribution of the gold nanoarray structure. In some preferred embodiments of the present invention, the first temperature is designed to be 80-85°C, and the second temperature is designed to be 20-30°C, at which time the gold nanoparticles can be brought closer together, making the gold nanoparticles in the gold nanoparticle film more dense. The third temperature is used to precisely control the gap of the gold nanoarray structure, so that the gold nanoarray can adapt to different detection environments and have a better enhancement effect. The third temperature is preferably designed to be 60-80°C.

[0037] In some embodiments of the present invention, the non-metallic substrate is a non-metallic substrate modified with a monothiol crosslinking agent, such as a silicon wafer modified with 3-mercaptopropyltrimethoxysilane.

[0038] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all the raw materials used are commercially available.

[0039] Product Information

[0040] Sulfuric acid (H2SO4), hydrogen peroxide (H2O2), polyvinylpyrrolidone (PVP), polydimethylsiloxane (PDMS), 3-mercaptopropyltrimethoxysilane (3-MPTMS), anhydrous ethanol (C2H5OH), acetone (C3H6O), citric acid (C6H8O7), chloroauric acid (HAuCl4·4H2O), n-hexane (C6H14), and crystal violet (C24H28ClN3) were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0041] Example 1

[0042] Step 1: Prepare gold nanoparticles using the seed growth method.

[0043] (1) Preparation of gold seed solution

[0044] Add 150mL ultrapure water and 97.05mg citric acid into a 250mL conical flask and boil; add 0.5mL 2wt% chloroauric acid solution into the conical flask and continue boiling for 5 minutes, then turn off the heating and stirring, and wait for the solution to cool naturally to room temperature. Transfer to the refrigerator for storage, the color is transparent wine red.

[0045] (2) Preparation of gold nanosol

[0046] Take 50mL of gold seed solution, add it to 100mL of ultrapure water, add 1mL of 50mM citric acid solution, boil it, add 0.5mL of 2wt% chloroauric acid solution drop by drop under vigorous stirring, continue to stir vigorously for 10min after adding, and naturally cool to room temperature, then repeat the step of "add 1mL of 50mM citric acid solution, add 0.5mL of 2wt% chloroauric acid solution drop by drop under boiling and vigorous stirring, continue to stir vigorously for 10min after adding, and naturally cool to room temperature" three times until the gold nanoparticles grow to 50nm in size, and obtain gold nanosol. Store in a refrigerator and use it as an aqueous solution for gold film induction.

[0047] Step 2: Assemble a monolayer of gold nanoparticles on a silicon wafer by the “dropping funnel” method.

[0048] (1) Place a silicon wafer at the bottom of the funnel and close the funnel valve. Pour the prepared gold nanosol and n-hexane solution into the funnel at a volume ratio of 1:1, and observe a clear two-phase interface. Slowly add ethanol to the funnel. As the potential barrier of the two-phase interface decreases, the gold particles are captured at the interface and begin to form a gold nanoparticle film.

[0049] (2) Open the valve to slowly lower the liquid level until the film shrinks at the liquid-liquid interface to form a bright and dense gold film. After the n-hexane is completely volatilized, control the valve drip rate to 1.8 μL / s to slowly lower the gold nanoparticle film and drop it onto the silicon wafer. After it is naturally dried, a gold nanoparticle film (the first gold nanoparticle film) based on the silicon wafer is obtained.

[0050] Example 2

[0051] Step 1: PVP solution is dripped onto the gold nanoparticle film based on silicon wafer, and the mass ratio of PVP to deionized water in the solution is 1:100. After PVP is cured, the film is torn off the template. PDMS curing liquid is dripped onto one side of the structure, and the ratio of PDMS to curing agent in the curing liquid is 10:1. Then, the PDMS coating on the film is cured at 80°C. After curing, it is naturally cooled to room temperature, and then the PVP is washed with ethanol and deionized water to obtain a gold nanoparticle film with reduced gaps (a second gold nanoparticle film with PDMS as the substrate and reduced gaps).

[0052] Step 2: The second gold nanoparticle film with a reduced gap and gold evaporation was performed on the substrate of PDMS, and then the temperature was raised to 60°C, 70°C and 80°C respectively, and the PVP solution was dripped on the surface of the structure. After it was solidified, the PVP film with gold nanoparticles was torn off from the template, and then the side with the structure was attached to the silicon wafer modified with 3-mercaptopropyltrimethoxysilane (3-MPTMS). After the film and the silicon wafer were fully combined, the PVP film was washed with ethanol and deionized water to remove the PVP film, and then dried with nitrogen to obtain a gold nanoarray structure, which was marked as sample 1-3. The scanning electron microscope (SEM) image is shown in FIG. Figure 2 As shown, Figure 2 In the figure, (a) shows a gold nanoarray structure obtained by heating to 60°C (sample 1), (b) shows a gold nanoarray structure obtained by heating to 70°C (sample 2), and (c) shows a gold nanoarray structure obtained by heating to 80°C (sample 3).

[0053] The modification method of the silicon wafer is: washing with piranha solution (piranha solution is a mixture of 98wt% concentrated sulfuric acid and 30wt% hydrogen peroxide in a volume ratio of 7:3), rinsing with deionized water and drying with nitrogen, and finally soaking the silicon wafer in 1wt% 3-MPTMS ethanol solution for 24 hours. The evaporation rate is The vacuum degree is 8×10-4Pa and the evaporation thickness is 30nm.

[0054] Example 3

[0055] Samples 1, 2, and 3 prepared in Example 2 were subjected to two surface activation treatments using a plasma cleaning machine, respectively, with a treatment power of 90 W and a treatment time of 180 seconds. The pressure of the first surface activation treatment was 30 Pa, and the pressure of the second surface activation treatment was 50 Pa. The gold nanoarray structures obtained by the surface activation treatment were marked as sample 1' (sample 1 after activation treatment), 2' (sample 2 after activation treatment), and 3' (sample 3 after activation treatment).

[0056] Test Example 1

[0057] Sample 1'-3' was used as the SERS active substrate, and 2 μL of 10 -5 M concentration of crystal violet (CV) aqueous solution, after drying, the SERS active substrate is gently washed with deionized water to remove unadsorbed CV, and then the substrate is blown dry with nitrogen gas for Raman spectrum detection. The excitation wavelength of Raman spectrum is 785nm, and the integration time is 10s. The Raman spectra of samples 1'-3' are shown in Figure 3 The results show that the SERS signal intensity changes significantly with the change of transfer temperature, which proves that the gap between nanoparticle arrays can be effectively changed by adjusting the temperature.

[0058] Test Example 2

[0059] Sample 1 and sample 1' (gold nanoarray structure treated with plasma activation) were used as SERS active substrates, and 2 μL 10 -5 M concentration CV aqueous solution, after drying, gently wash the substrate with deionized water to remove unadsorbed CV, then blow dry the substrate with nitrogen gas and perform Raman spectroscopy detection. The excitation wavelength of Raman spectroscopy is 785nm and the integration time is 10s. Figure 4 The comparison results show that the SERS signal intensity is significantly improved after plasma treatment.

[0060] Test Example 3

[0061] Sample 1' (gold nanoarray structure transferred at 60°C after plasma treatment) was used as the SERS active substrate, and 2 μL of CV aqueous solution with different concentrations (concentrations were 10-5M, 10-6M, 10-7M, 10-8M, 10-9M, 10-10M, 10-11M) was added (write clearly which concentrations), and after drying, the substrate was gently washed with deionized water to remove the unadsorbed CV, and then the substrate was blown dry with nitrogen for Raman spectroscopy detection. The excitation wavelength of the Raman spectrum was 785nm, the integration time was 10s, and the Raman spectrum was as follows Figure 5 The structure can be detected at a minimum of 10 -11 M's CV.

[0062] Test Example 4

[0063] In order to further verify the repeatability and uniformity of the SERS signal, sample 1' (gold nanoarray structure transferred at 60°C after plasma treatment) was used as the SERS active substrate, and 2 μL of 10 -5 M concentration CV aqueous solution, after drying, gently wash the substrate with deionized water to remove unadsorbed CV, and then blow dry the substrate with nitrogen. 50 different positions were randomly selected on the same substrate for Raman spectrum detection. The excitation wavelength of Raman spectrum was 785nm, the integration time was 10s, and the Raman spectrum was as follows Figure 6 (a) and the intensity of the characteristic peak of crystal violet 1160cm-1 was selected for statistical analysis. Figure 6 As shown in (b), the relative standard deviation (RSD) is 4.69%. The RSD is less than 10%, indicating that the structure has good SERS signal stability and repeatability.

[0064] Compared with the prior art, the gold nanoarray structure, preparation method thereof and application thereof in SERS trace detection provided by the present invention have at least one of the following advantages:

[0065] 1. The present invention utilizes the thermal expansion property of PDMS material. First, a gap is formed in the gold nanoparticle film by adjusting the curing temperature of PDMS (which expands during the curing process) during the process of transferring the gold nanoparticle film to a polydimethylsiloxane (PDMS) substrate. Then, the temperature is lowered to a second temperature, and the gold nanoparticles are brought closer together by the contraction of PDMS, that is, the gold nanoparticles in the gold nanoparticle film are made denser. Then, the temperature is raised to a specific third temperature to form a gold nanoarray with uniform gap size and solidify it with PVP, which can not only optimize the hotspot distribution of the gold nanoarray structure, but also improve the uniformity of the hotspots.

[0066] 2. The technical solution provided by the present invention can accurately control the gap of the gold nanoarray structure by adjusting the third temperature, which helps to optimize the enhancement effect of the nanostructure in different detection environments and meet various practical application needs.

[0067] 3. Plasma treatment of the substrate further activates the surface of gold nanoparticles, enhances their adsorption capacity for target molecules, and improves the effect of surface enhanced Raman scattering. This surface activation treatment can optimize the performance of the substrate and improve the sensitivity of SERS detection.

[0068] Although some embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a gold nanoarray structure, characterized in that: The preparation method comprises the following steps: Add PDMS curing liquid to the surface of a first gold nanoparticle film with a PVP film as a substrate, heat it to a first temperature, cool it to a second temperature after the PDMS is cured, remove the PVP, and obtain a second gold nanoparticle film with a PDMS substrate and reduced gaps, wherein the gold nanoparticles of the second gold nanoparticle film are denser than those of the first gold nanoparticle film; Gold is evaporated on the surface of the second gold nanoparticle film, and then the temperature is raised to a preset third temperature to form a gold nanoarray with uniform gap sizes, a PVP solution is dripped on the surface, and after the PVP solution is solidified into a PVP film, it is torn off to obtain a PVP film with the gold nanoarray, and the PVP film is attached to a non-metallic substrate, and the PVP is removed to obtain a gold nanoarray structure; in, The third temperature is used to adjust the size of the gaps between the gold nanoparticles; The non-metal substrate is a non-metal substrate modified by a cross-linking agent.

2. The preparation method according to claim 1, characterized in that: The first temperature is 80-85°C.

3. The preparation method according to claim 1, characterized in that: The second temperature is 20-30°C.

4. The preparation method according to claim 1, characterized in that: The gold evaporation thickness is 28-32 nm.

5. The preparation method according to claim 1, characterized in that: The third temperature is 60-80°C.

6. The preparation method according to claim 1, characterized in that: The cross-linking agent is a monothiol cross-linking agent.

7. The preparation method according to claim 1, characterized in that: The preparation method further comprises: performing surface plasma treatment on the gold nanoarray structure.

8. The preparation method according to claim 1, characterized in that: The surface plasma treatment is specifically: The first plasma treatment was carried out under the condition of 30Pa pressure, 90W processing power and 180s processing time; The second plasma treatment was carried out under a pressure of 50 Pa, a processing power of 90 W, and a processing time of 180 seconds.

9. The gold nanoarray structure prepared according to any one of the preparation methods of claims 1-8.

10. Use of the gold nanoarray structure according to claim 9 in SERS trace detection.

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