CN-117805021-B - SERS substrate based on dual enhancement of graphite carbon material

CN117805021BCN 117805021 BCN117805021 BCN 117805021BCN-117805021-B

Abstract

The invention discloses a SERS substrate based on dual reinforcement of a graphite carbon material, which comprises the steps of S1, preparing a polymer array, S2, preparing a substrate array by a polymer rapid method, S3, performing femtosecond laser ablation on a PDMS substrate, S4, performing electron beam evaporation, preparing a pyramid array structure by using a processing method of combining femtosecond laser with chemical wet etching, efficiently obtaining an inverted pyramid template with uniform structure and high specific surface area, preparing the PDMS substrate by a polymer forming method, performing laser-induced modification on the surface of the PDMS polymer by using femtosecond laser pulse processing, generating a stacked GCs structure on the surface of the material, and the like, so that the substrate has the advantages of good enhancement effect, stable property, multiple 'hot spots', and the like, and overcomes the limitation of the traditional substrate.

Inventors

GAO RONGKE
GUAN ZIHAO
JIN HAO
LU YANG
YU LIANDONG

Assignees

中国石油大学(华东)

Dates

Publication Date: 20260512
Application Date: 20231228

Claims (5)

1. The SERS substrate based on the dual reinforcement of the graphite carbon material is characterized by comprising the following preparation steps of: Step S1, preparing a polymer array; etching and preparing an inverted pyramid array structure on the pretreated silicon wafer by a chemical wet method; The specific process for preparing the inverted pyramid array structure by chemical wet etching comprises the following steps: step S11, preparing a potassium hydroxide solution of 6mol.L -1 , taking 10.5ml of the potassium hydroxide solution, adding 1ml of isopropyl alcohol and 1ml of deionized water, and fully mixing the etching solution by using magnetic stirring to obtain an etching agent; Step S12, placing the processed silicon wafer and the etchant into a constant-temperature magnetic stirrer with the rotation speed of 300rpm at 60 ℃ for anisotropic wet etching for 120min; Step S13, using the silicon dioxide film which is not removed by femtosecond laser processing as a mask to prevent chemical wet etching by utilizing the difference of etching speeds of silicon dioxide and silicon, removing the regional anisotropic etching of the silicon dioxide film, and performing chemical wet etching along the crystal phase of monocrystalline silicon by an etchant so as to obtain a pyramid pit array template, namely a silicon template with an inverted pyramid array structure; s2, preparing a substrate array by a polymer rapid method; Utilizing the silicon template prepared in the step S1, and adopting a polymer rapid method to prepare a PDMS substrate array; In the step S2, the step of preparing the substrate array by using the polymer rapid method includes: Step S21, mixing PDMS and a curing agent according to the proportion of 10:1; step S22, stirring for 2 min; Step S23, placing the mixture in a vacuum pump to remove bubbles; Step S24, slowly pouring the PDMS mixed solution into a silicon template, and transferring the template into a 70 ℃ oven for heating for 2 hours; s25, cutting the PDMS after curing, placing the segmented PDMS substrate array into ethanol, and placing the ethanol into an ultrasonic cleaner for cleaning for 10min; step S26, obtaining a PDMS substrate array; S3, femtosecond laser ablating the PDMS substrate; the method adopts a femtosecond laser direct writing processing method, namely, the PDMS substrate is directly ablated by the femtosecond laser, and the specific process is as follows: s31, setting a femtosecond laser source to be 2.5kHz in repetition frequency, setting output wavelength to be 1030nm and setting the interval of a line scanning structure to be 0.03mm by utilizing Pharos software, so that a surface structure can be completely processed; s32, irradiating femtosecond laser on the surface of PDMS at a laser scanning speed of 10-30 mm/S by regulating and controlling laser energy of 27-42 mw to cause heat accumulation on the surface, thereby inducing a thermal effect and changing material properties; step S33, the femtosecond laser damages the PDMS surface to generate a surface roughness structure; step S34, completing the preparation of the SERS substrate based on the dual reinforcement of the graphitic carbon material.
2. The dual enhanced SERS substrate based on graphitic carbon material according to claim 1, further comprising step S4, electron beam evaporation; in order to further improve the SERS signal, a film coating process of electron beam evaporation is used, and a layer of gold film with the thickness of 50nm is uniformly coated on the PDMS array substrate processed in the step S3.
3. The SERS substrate based on dual reinforcement of graphite carbon materials according to claim 1, wherein the pretreated silicon wafer is a processed material surface of a femtosecond laser direct-writing processing platform, the processed material is an S silicon wafer with a crystal phase <100> of 300nmSiO 2 films, and SiO 2 films on the silicon wafer surface are selectively removed; And carrying out ultrasonic treatment on the processed silicon wafer for 15min, and then continuously washing with deionized water and naturally air-drying.
4. The dual enhanced SERS substrate of claim 1, wherein in step S3, the optimal parameters are controlled by controlling the laser power and the scanning speed to be 20mw, 10mm/S, or 30mw, 10mm/S, or 40mm/S, or 20mm/S, or 40mm/S, or 30mm/S under five processing conditions.
5. The SERS substrate based on dual reinforcement of graphitic carbon material according to claim 1 wherein the graphitic carbon characterization method of the SERS substrate based on dual reinforcement of graphitic carbon material comprises: The SERS substrate prepared under different processing conditions is placed on a Raney Raman test sample table, the laser power is set to be 1%, the exposure time and the cumulative frequency are respectively 3s and 2 times, the obtained data are subjected to background subtraction and smoothing treatment on all Raman spectrums through a wire5.5 software, and then a final SERS result is obtained, unique peaks corresponding to ID/IG of graphite carbon are observed at 1350 and 1580cm -1 in all the obtained Raman spectrums and are used for indicating the formation of graphite carbon, ID represents amorphous carbon, IG represents graphitized carbon, the ratio of ID/IG is related to graphitization degree, and the smaller the ratio of ID/IG is, the higher the graphitization degree of the material is indicated.

Description

SERS substrate based on dual enhancement of graphite carbon material Technical Field The invention belongs to the field of femtosecond laser processing and micro-nano sensing, and particularly relates to a three-dimensional SERS substrate with chemical enhancement and physical enhancement for high-sensitivity SERS detection. Background Surface Enhanced Raman Scattering (SERS) is a high-sensitivity and high-resolution molecular recognition technology, and has very important application value in various fields. The ideal detection substrate would have a high enhancement factor, long-term stability and excellent reproducibility. SERS is mainly characterized by two enhancement mechanisms, physical Enhancement (EM) and chemical enhancement (CM), which have a tremendous impact on raman signal intensity. The physical enhancement mechanism depends on the optical excitation of surface plasmon resonance in "hot spots" of nanostructures on SERS substrates, and its chemical enhancement mechanism results from the electronic coupling between the absorbed molecules and the surface structure. To date, a great deal of research has been conducted around these two mechanisms, and many methods for fabricating nanostructures have been developed, including "top-down" processing methods using electron beams, focused ion beams, nanoimprint techniques, etc. that etch on the surface of materials with external high energy beams, and "bottom-up" processing methods using self-assembled hydrothermal methods, template methods, chemical deposition, etc. that self-grow, react in a varying manner, etc. Although each micro-nano manufacturing technology has various characteristics, most processes require multiple complex processing steps to construct uniform nano structures, and have the defects of high processing cost, harsh processing conditions and the like. Therefore, there is an urgent need to develop a novel SERS substrate with good enhancement effect, high repeatability and stable properties for highly sensitive detection of trace target. The present invention has been made keeping in mind the above problems occurring in the prior art. Disclosure of Invention In order to prepare a novel SERS substrate with good enhancement effect, high repeatability and stable property, the invention utilizes a femtosecond laser processing method with the advantages of high processing precision, high flexibility, wide material applicability, no need of vacuum environment and the like, reasonably combines a chemical wet etching technology to prepare a pyramid array structure template with high repeatability and high specific surface area, prepares a PDMS substrate array by using a polymer rapid prototyping method, and utilizes femtosecond laser to carry out surface roughening and modification treatment on the PDMS array to obtain the three-dimensional SERS substrate structure with chemical enhancement and physical enhancement. In order to achieve the above purpose, the technical scheme provided by the invention is as follows: A SERS substrate based on dual reinforcement of graphitic carbon material, the SERS substrate comprising the steps of: Step S1, preparing a polymer array; etching and preparing an inverted pyramid array structure on the pretreated silicon wafer by a chemical wet method; s2, preparing a substrate array by a polymer rapid method; Utilizing the silicon template prepared in the step S1, and adopting a polymer rapid method to prepare a PDMS substrate array; And S3, femtosecond laser ablating the PDMS substrate. The method adopts a femtosecond laser direct writing processing method, namely, the PDMS substrate is directly ablated by the femtosecond laser, and the specific process is as follows: s31, setting a femtosecond laser source to be 2.5kHz in repetition frequency, setting output wavelength to be 1030nm and setting the interval of a line scanning structure to be 0.03mm by utilizing Pharos software, so that a surface structure can be completely processed; s32, irradiating femtosecond laser on the surface of PDMS at a laser scanning speed of 10-30 mm/S by regulating and controlling laser energy of 27-42 mw to cause heat accumulation on the surface, thereby inducing a thermal effect and changing material properties; step S33, the femtosecond laser damages the PDMS surface to generate a surface roughness structure; step S34, completing the preparation of the SERS substrate based on the dual reinforcement of the graphitic carbon material. And the femtosecond laser irradiates Polydimethylsiloxane (PDMS) to form a graphite carbon crystal (GCs) and silicon carbide composite structure, and in the femtosecond laser processing process, the femtosecond laser has a heat accumulation effect on the surface of a material, and the polymer is decomposed into small hydrocarbon molecules through heat treatment. With sufficient thermal energy, small hydrocarbon molecules can be pyrolyzed to form GCs, which continues to grow if the heat is sufficient, de