A preparation method of an AgNWs@LiG@PDMS sandwich structure flexible SERS substrate

Abstract

The application discloses a preparation method of an AgNWs@LiG@PDMS sandwich structure flexible SERS substrate, characterized by the following steps: a carbon dioxide laser is used to prepare laser-induced graphene (LiG), then the LiG is completely transferred to a PDMS flexible substrate through a polydimethylsiloxane (PDMS) transfer strategy, a LiG@PDMS double-layer structure is obtained, silver nanowires (AgNWs) are spin-coated on the surface of the double-layer structure, and finally, the AgNWs@LiG@PDMS sandwich structure flexible surface-enhanced Raman spectroscopy (SERS) substrate is prepared. The advantage of the AgNWs / LiG@PDMS sandwich structure flexible material as the SERS substrate material lies in that the PDMS provides a flexible substrate and has good tensile resistance, but the AgNWS is directly coated on the hydrophobic PDMS surface, and the Ag nanowires are prone to falling off, the LiG layer is beneficial to the deposition and stability of the AgNWS, and the good conductivity of the LiG is helpful to the SERS performance of the Ag nanowires.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of preparation of surface enhanced Raman scattering active substrate, in particular to a preparation of AgNWs@LiG@PDMS sandwich structure flexible SERS substrate. BACKGROUND

[0002] Surface enhanced Raman spectroscopy (SERS) is considered as one of the most promising and versatile analytical tools as it is a non-destructive, rapid and ultra-sensitive technique that allows real-time analysis and provides molecular information. In the past few decades, SERS has been widely applied in environmental monitoring, food safety and forensic science. According to the SERS enhancement mechanism, silver is considered as the best SERS material with strong signal response. In addition, the manufacture of suitable silver-based SERS substrates is a key factor to improve SERS performance. In most cases, silicon and glass sheets are chosen as solid carriers for various Ag nanostructures; however, their rigid and brittle properties can not be convenient for practical applications. In contrast, flexible SERS substrates are more advantageous for detecting contamination residues on surfaces, where residues can be directly collected by wiping irregular or rough surfaces with minimal or non-invasive. Most efforts have been focused on the development of flexible SERS substrates, including paper, glass fiber and cellulose, to adapt to various flexible, curved or non-planar surfaces. It is reported that in most cases, noble metal nanoparticles are decorated on the surface of flexible substrates. However, without a protective layer, nanoparticles are easily damaged by surface wiping; therefore, subsequent reuse is not possible.

[0003] Polydimethylsiloxane (PDMS) elastomers have also attracted great interest for flexible SERS sensor applications due to their chemical stability, non-toxicity, mechanical flexibility, bendability and hydrophobicity. In particular, the hydrophobicity of PDMS not only prevents the random diffusion of analyte solution to make it fully concentrated, but also can be recovered and reused by washing with alcohol and water. Generally, multifunctional SERS detection involves loading plasmonic metal nanoparticles on the surface of PDMS, providing local surface plasmon resonance and subsequent electromagnetic field enhancement. However, the "sticky" properties of PDMS alone are not enough to prevent modified metal nanoparticles from being damaged or peeled off. Therefore, it is necessary to manufacture a very stable special structure. SUMMARY

[0004] To solve the above technical effects, the present application prepares an AgNWs@LiG@PDMS sandwich structure flexible material, which adopts a PDMS flexible substrate with good tensile resistance; LiG is used to connect between the PDMS flexible substrate and AgNWS, which on the one hand facilitates the deposition and stability of AgNWS, and on the other hand the good conductivity of LiG helps to enhance the SERS performance of Ag nanowires.

[0005] To achieve the above technical purpose, the application adopts the following technical scheme, and the preparation flow chart is as shown in Figure 1 ,

[0006] A preparation method of an AgNWs@LiG@PDMS sandwich structure flexible SERS substrate, characterized in that it comprises the following steps:

[0007] (1) laser-induced preparation of laser-induced fluffy structure graphene (LiG) on a polyimide film (PI film) by using a carbon dioxide laser;

[0008] (2) transferring the LiG to a PDMS flexible substrate by a polydimethylsiloxane (PDMS) transfer strategy to obtain a LiG@PDMS double-layer structure;

[0009] (3) spin-coating silver nanowires (AgNWs) on the surface of the LiG, and the AgNWS is dried to obtain the AgNWs@LiG@PDMS sandwich structure flexible SERS substrate.

[0010] Further, in the step (1), the excitation power of the carbon dioxide laser is 6%-30%, the scanning frequency is 60-180 KHZ, and the scanning speed is 10-60 mm / s.

[0011] Further, in the step (1), the preparation of graphene on the PI film by the ultraviolet laser can prepare graphene materials of different shapes and sizes by using C4D software.

[0012] Further, in the step (2), the PDMS flexible substrate comprises PDMS and a fixing agent, and the PDMS and the curing agent are mixed in a ratio of 10:1 and then laid in a polytetrafluoroethylene container with a thickness of about 1-8 mm.

[0013] Further, the preparation method of the LiG@PDMS double-layer structure in step (2) is as follows: the LiG prepared in step (1) is pasted with the front face downward in the polytetrafluoroethylene container laid with the mixed colloid of PDMS and curing agent, and then transferred to a vacuum drying box for curing. After curing, the PI film is peeled off, and the flexible LIG@PDMS double-layer structure is left.

[0014] Further, the process parameters of the vacuum drying box are as follows: temperature 100-130℃, and curing heating time 1-3h.

[0015] Further, in step (3), the diameter of the AgNWs is 20-30 nm, and the length is 20-50 μm. The AgNWs suspension is an ethanol or acetone solution of AgNWs with a concentration of 0.2-3 mg / ml.

[0016] Further, the sample after step (3) spin coating is placed in a vacuum drying box, the drying temperature is 40-60 DEG C, and the drying time is 6-12 hours.

[0017] Further, the prepared AgNWs@LiG@PDMS composite material has a flexible PDMS as a bottom layer, LiG as an intermediate layer, and AgNWs as an uppermost layer.

[0018] Compared with the prior art, the application has the advantages that:

[0019] 1. The application obtains the sandwich structure flexible material of AgNWs@LiG@PDMS by taking PDMS as a flexible base, LiG as an intermediate layer, and AgNWs as a surface coating, and the AgNWs@LiG@PDMS flexible composite material with uniform AgNWs surface dispersion, good conductivity, good tensile resistance and effectively enhanced surface Raman effect can be obtained by adjusting experimental parameters.

[0020] 2. The reaction adopts carbon dioxide laser induction to prepare LiG, is simple to operate, stable in yield, and can obtain the LiG material with controllable morphology structure and is convenient for large-scale production.

[0021] 3. The AgNWs@LiG@PDMS flexible composite material prepared by the application takes LiG as an intermediate layer, which is convenient for Ag nanowire deposition and limits Ag nanowire in LiG, thereby enhancing the stability of the SERS substrate and further improving the SERS performance. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a scanning electron microscope picture of carbon dioxide laser-induced graphene according to Embodiment 1 of the application;

[0023] Figure 2 is a scanning electron microscope picture of AgNWs@LiG@PDMS obtained in Embodiment 1 of the application;

[0024] Figure 3 is a scanning electron microscope picture of AgNWs@LiG@PDMS obtained in Embodiment 2 of the application;

[0025] Figure 4 is a SERS characteristic spectrum of the AgNWs@LiG@PDMS flexible composite material obtained in Embodiment 2 of the application on a rhodamine B solution;

[0026] Figure 5 is a SERS characteristic spectrum of the AgNWs@LiG@PDMS flexible composite material obtained in Embodiment 2 of the application on a rhodamine B solution of 10 -9 M. DETAILED DESCRIPTION

[0027] For a further understanding of the application, reference will be made to the following examples combined with the accompanying drawings. The advantages and features of the present application will be more readily understood from a reading of the following examples and the accompanying drawings in which:

[0028] Example 1

[0029] The carbon dioxide laser parameters were set as follows: laser emission power was 10%, scanning frequency was 120 KHZ, scanning speed was 30 mm / s, scanning thickness of PI film was 100 μm, C4D was preset to be rectangular shape, and size was 1.5 cm*0.5 cm. Laser-induced graphene was prepared, and a scanning electron microscope image thereof is shown in FIG. 1. About 1 mL of a mixture containing PDMS and curing agent (PDMS:curing agent = 10:1 w / w) was dropped on the surface of LiG and spread on the surface of LiG. The sample was placed in a polytetrafluoroethylene container and put into a vacuum drying box. Bubble removal was repeated for about 6 times. Then, the sample was transferred to a high-temperature oven at 130°C for curing for 1 h. The PI film was torn off, and then LiG@PDMS flexible SERS substrate without PI film was left. AgNWS with a diameter of 25 nm and a length of 25 μm were dispersed in isopropyl acetone suspension to prepare a solution with a concentration of 3 mg / ml. 30 μL of the solution was spin-coated on the surface of LiG, and then dried in a vacuum drying box at 60°C for 6 h. Thus, a flexible surface SERS enhancement material with a sandwich structure of AgNWs@LiG@PDMS was prepared, and the surface morphology thereof is shown in FIG. 2. Figure 1 Figure 2

[0030] Example 2

[0031] The carbon dioxide laser parameters were set as follows: laser emission power was 10%, scanning frequency was 120 KHZ, scanning speed was 30 mm / s, scanning thickness of PI film was 100 μm, C4D was preset to be rectangular shape, and size was 1.5 cm*0.5 cm. Laser-induced graphene was prepared, and a scanning electron microscope image thereof is shown in FIG. 1. About 1 mL of a mixture containing PDMS and curing agent (PDMS:curing agent = 10:1 w / w) was dropped on the surface of LiG and spread on the surface of LiG. The sample was placed in a polytetrafluoroethylene container and put into a vacuum drying box. Bubble removal was repeated for about 6 times. Then, the sample was transferred to a high-temperature oven at 130°C for curing for 1 h. The PI film was torn off, and then LiG@PDMS flexible SERS substrate without PI film was left. AgNWS with a diameter of 25 nm and a length of 25 μm were dispersed in isopropyl acetone suspension to prepare a solution with a concentration of 3 mg / ml. 30 μL of the solution was spin-coated on the surface of LiG, and then dried in a vacuum drying box at 60°C for 6 h. Thus, a flexible surface SERS enhancement material with a sandwich structure of AgNWs@LiG@PDMS was prepared, and the surface morphology thereof is shown in FIG. 2. Figure 1 Figure 3 ​​​As shown, increasing the concentration of Ag nanowires to completely cover LIG can enhance SERS performance to some extent and improve the repeatability of SERS performance detection.

[0032] The prepared AgNWs@LiG@PDMS flexible composite material blocks were thoroughly immersed in 10... -3 M, 10 -4 M, 10 -5 M, 10 -6 M, 10 -7 M, 10 -8 M and 10 -9 M was placed in a Rhodamine B solution and allowed to air dry before SERS characterization. Figure 4 As shown, it is 10 -3 M, 10 -4 M, 10 -5 M, 10 -6 M, 10 -7 M, 10 -8 M and 10 -9 The SRES characterization spectra of Rhodamine B in M ​​confirmed that the prepared AgNWs@LiG@PDMS flexible composite material exhibits surface SERS enhancement. Figure 4 and Figure 5 As shown, the synthesized AgNWs@LiG@PDMS flexible composite material can detect 10 -9 The detection limit of Rhodamine B aqueous solution at concentration M is 10 times that reported in the literature. -8 M is an order of magnitude higher.

[0033] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing description, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing an AgNWs@LiG@PDMS sandwich structure flexible SERS substrate, characterized in that, It comprises the following steps: (1) using carbon dioxide laser to induce preparation of laser-induced loose structure graphene (LiG) on polyimide film (PI film); (2) transferring LiG to PDMS flexible substrate by polydimethylsiloxane (PDMS) transfer strategy to obtain LiG@PDMS double-layer structure; the PDMS flexible substrate comprises PDMS and fixing agent, the PDMS and curing agent are mixed in a ratio of 10:1, and the LiG prepared in step (1) is pasted with the front down in a polytetrafluoroethylene container paved with PDMS and curing agent mixed colloid; (3) spin coating silver nanowires (AgNWs) on the surface of LiG, and the AgNWS is dried to prepare AgNWs@LiG@PDMS sandwich structure flexible SERS substrate.

2. The preparation method according to claim 1, characterized in that, The excitation power of the carbon dioxide laser is 6%-30%, the scanning frequency is 60-180KHZ, and the scanning speed is 10-60mm / s.

3. The preparation method according to claim 2, characterized in that, In step (1), the graphene prepared by UV laser induced PI film is prepared by C4D software to prepare graphene materials with different shapes and sizes.

4. The preparation method according to claim 1, characterized in that, The thickness of the PDMS flexible substrate is 1-8mm.

5. The preparation method according to claim 4, characterized in that, In step (2), the LiG@PDMS double-layer structure is transferred to a vacuum drying oven for curing, and after curing, the PI film is peeled off, leaving a flexible LIG@PDMS double-layer structure.

6. The preparation method according to claim 5, characterized in that, The process parameters of the vacuum drying oven are: temperature 100-130℃, curing heating time 1-3h.

7. The preparation method according to claim 1, characterized in that, In step (3), the diameter of the AgNWs is 20-30nm, the length is 20-50μm, and the AgNWs suspension is formed by using AgNWs ethanol or acetone solution with a concentration of 0.2-3mg / ml.

8. The production method according to claim 7, wherein After spin coating in step (3), the sample is placed in a vacuum drying oven, the drying temperature is 40-60℃, and the drying time is 6-12 hours.

9. The method of claim 1, wherein the step of forming the first and second layers is performed by a method selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The prepared AgNWs@LiG@PDMS composite material, wherein the bottom layer is flexible PDMS, the middle layer is LiG, and the uppermost layer is AgNWs.

Images