Disclosure of Invention
The present invention is directed to a method for preparing a surface-enhanced raman scattering substrate, so as to solve one or more of the above-mentioned problems. The substrate prepared by the method has the characteristic of uniform large-area structure; the sensitivity is high; the method has universality for molecules with different scales; has no-label detection capability.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention discloses a preparation method of a surface enhanced Raman scattering substrate, which comprises the following steps:
step 1, in SiO2Preparing a close-packed nano microsphere two-dimensional colloidal crystal layer on a/Si (001) substrate to obtain a two-dimensional colloidal crystal-SiO2a/Si (001) substrate sample;
step 2, the two-dimensional colloidal crystal-SiO obtained in the step 1 is used2The diameter of the nano-microspheres in the/Si (001) substrate sample is reduced to obtain the treated two-dimensional colloidal crystal-SiO2a/Si (001) substrate sample;
step 3, the processed two-dimensional colloidal crystal-SiO obtained in the step 2 is processed2Using the nano microspheres in the/Si (001) substrate sample as a mask, and depositing a metal film on one surface of the substrate sample, which is provided with the nano microspheres, to obtain a two-dimensional colloidal crystal-metal film-SiO2a/Si (001) substrate sample;
step 4, stripping the two-dimensional colloidal crystal-metal film-SiO obtained in step 32Obtaining a metal film-SiO by a nano microsphere two-dimensional colloidal crystal layer in a/Si (001) substrate sample2a/Si (001) substrate sample;
step 5, the metal film-SiO obtained in step 42The metal film in the/Si (001) substrate sample is used as a mask, and SiO is etched by a dry method2Layer of metal thin film mask-SiO2Mask layer-Si (001) substrate sample;
step 6, using the metal film mask-SiO obtained in step 52Mask layer-SiO in Si (001) substrate samples2Using the layer as a mask, and wet etching the Si (001) substrate to form an inverted pyramid structure to obtain a metal thin film mask-SiO2Mask layer-Si (001) substrate sample with inverted pyramid structure;
step 7, masking the metal thin film obtained in step 6 with SiO2Mask layer-Si (001) substrate sample with inverted pyramid Structure, SiO stripping2Layer and metal film, obtaining Si (001) substrate sample with inverted pyramid structure;
step 8, taking the Si (001) substrate sample with the inverted pyramid structure obtained in the step 7 as a Si template of the surface enhanced Raman scattering substrate; preparing a noble metal film on a Si (001) template to obtain a noble metal film-Si (001) template with a pyramid structure;
step 9, transferring the noble metal film obtained in the step 8 to a new Si substrate by using an adhesive; wherein, the pyramid structure is exposed to obtain a precious metal film-adhesive-Si substrate sample with the pyramid structure;
and step 10, transferring a layer of graphene on the surface of the noble metal pyramid structure to obtain graphene, the noble metal film with the pyramid structure, an adhesive and a Si substrate, and finishing the preparation.
The further improvement of the invention is that in the step 1, the method for preparing the two-dimensional colloidal crystal layer of the close-packed nanospheres comprises the following steps: spin coating, drop coating, dip coating, electrophoretic deposition, and gas-liquid interface self-assembly; wherein, the gas-liquid interface self-assembly method comprises a Langmuir-Blodgett membrane method;
when the two-dimensional colloid crystal layer of the close-packed nano microspheres is prepared, the monodisperse nano microspheres are used in a dispersion liquid form; the nano-microspheres are made of polymer; the diameter distribution range of the nano-microspheres is 50 nm-10 mu m.
The invention further improves the method that in the step 2, the two-dimensional colloidal crystal-SiO obtained in the step 12The step of reducing the diameter of the nanospheres in the/Si (001) substrate sample specifically comprises the following steps: and reducing the diameter of the nano microsphere by using a plasma etching method.
In step 2, the equipment adopted in the process of etching by using plasma comprises: an inductively coupled plasma etcher, a reactive ion etcher, or a plasma photoresist remover.
The further improvement of the invention is that in step 3, the step of depositing the metal film on the surface of the substrate sample provided with the nano-microspheres specifically comprises the following steps: growing a metal film by using an electron beam evaporation method; the metal material of the metal film is Cr, Ti, Ni, Fe, Cu, Au or Pt.
The further improvement of the invention is that in the step 4, the step of peeling off the nano microsphere two-dimensional colloidal crystal layer comprises the following steps: cleaning the two-dimensional colloidal crystal layer by using oxygen plasma, and ultrasonically dissolving the two-dimensional colloidal crystal layer in an organic solvent; wherein the organic solvent is acetone, chloroform, dichlorobenzene, dichloromethane, toluene or xylene.
The invention has the further improvement that the step 5 specifically comprises the following steps: etching SiO by using unidirectional reactive etching method2A layer; wherein the reactive gas used is CF4、CHF3、SF6、NF3、BCl3Or Cl2。
The invention is further improved in that the step 6 specifically comprises: carrying out wet etching on the Si (001) substrate by using a KOH solution to form an inverted pyramid structure; wherein, the concentration of the used KOH solution is 5 to 64 percent by mass; and stirring the reaction solution in the etching process.
In a further improvement of the present invention, in step 8, the method for preparing the noble metal thin film on the Si (001) template includes, but is not limited to: physical vapor deposition and chemical vapor deposition; the physical vapor deposition comprises magnetron sputtering and electron beam evaporation; the chemical vapor deposition comprises atomic layer deposition; the prepared noble metal is Au, Ag or Cu.
In a further improvement of the present invention, in step 10, the selected graphene is a single-layer graphene grown on copper by using a chemical vapor deposition method.
Compared with the prior art, the invention has the following beneficial effects:
the method can prepare the SERS substrate which has low cost, uniform wafer scale, nano structure and SERS signal, high sensitivity and universality and can be used for label-free testing.
In the method, a layer of graphene transferred on the surface of the pyramid plays an important role, and comprises the following steps: the Raman peak of the graphene can be used as the measurement of the near-field electromagnetic field intensity, so that the quantitative measurement of target molecules can be realized; as an environment-friendly material, is used as a support layer of biomolecules and improves the biocompatibility of the substrate; the integral enhancing capability of the SERS substrate is further improved; effectively slow down the oxidation speed of nano-particles and keep the long-term enhancement capability of the SERS substrate. The prepared large-area uniform, high-sensitivity and universal label-free detection surface-enhanced Raman scattering substrate not only can play an important role in biosensing and early disease detection, but also can be widely applied to the fields of chemical sensing, food safety detection and environmental monitoring.
The invention uses two methods of colloid photoetching and micro-nano processing to successfully realize the preparation of the pyramid-type SERS substrate; the prepared substrate realizes the uniformity of the nano pyramid structure in a large scale range, has high sensitivity, and can test objects with different scales, typically test molecules/particles with nano scale and micron scale. The invention uses a plurality of ways to prepare the two-dimensional colloid crystal with high coverage rate, and the cost for preparing the nano structure in large area is obviously reduced by using the colloid photoetching method subsequently. The invention uses a series of micro-nano processing methods to realize that each colloid microsphere is converted into each nano pyramid structure to be used as a characteristic structure of the surface enhanced Raman scattering substrate.
Detailed Description
In order to make the purpose, technical effect and technical solution of the embodiments of the present invention clearer, the following clearly and completely describes the technical solution of the embodiments of the present invention with reference to the drawings in the embodiments of the present invention; it is to be understood that the described embodiments are only some of the embodiments of the present invention. Other embodiments, which can be derived by one of ordinary skill in the art from the disclosed embodiments without inventive faculty, are intended to be within the scope of the invention.
Referring to fig. 1, a method for manufacturing a surface enhanced raman scattering substrate according to an embodiment of the present invention includes the following steps:
step 1, at 4 inches of SiO2Preparing two-dimensional colloidal crystal of close-packed monolayer nano microsphere on a/Si (001) substrate to obtain two-dimensional colloidal crystal-SiO2a/Si (001) substrate sample; SiO 22the/Si (001) substrate comprises a Si layer 4, and SiO provided on its surface2Layer 3.
Step 2, reducing the diameter of the nano microsphere 2 by using a plasma etching method to obtain an etched second microsphereVital colloid crystal-SiO2a/Si (001) substrate sample;
step 3, using the etched microspheres of the sample in the step 2 as a mask, and depositing a layer of metal film 5 on the substrate as a mask to obtain the etched two-dimensional colloidal crystal-metal film mask-SiO2a/Si (001) substrate sample;
step 4, stripping the microsphere two-dimensional colloidal crystal layer in the sample in the step 3 to obtain a metal film mask-SiO2a/Si (001) substrate sample;
step 5, using the metal film 5 in the sample of the step 4 as a mask, and adopting a dry etching method to etch SiO2Layer 3, obtaining a metal thin film mask-SiO2Mask layer-Si (001) substrate sample;
step 6, using SiO in the sample in step 52Using layer 3 as mask, wet etching Si (001) substrate to form inverted pyramid structure to obtain metal film mask-SiO2Mask layer-Si (001) substrate sample with inverted pyramid structure;
step 7, stripping SiO by using corrosive solution2Layer and metal film, get Si (001) substrate sample with inverted pyramid structure, as Si (001) template of the surface enhanced Raman scattering substrate;
step 8, sputtering a noble metal film 6 on the Si (001) template obtained in the step 7 to obtain a noble metal nano pyramid structure 7, and obtaining a noble metal film-Si (001) template with a pyramid structure;
and 9, transferring the noble metal film obtained in the step 8 to a new Si substrate 9 by using an adhesive 8 through a stripping method. Wherein the pyramid structure is exposed to obtain a precious metal film-adhesive-Si substrate sample with the pyramid structure;
and 10, transferring a layer of graphene 10 on the surface of the noble metal pyramid structure to obtain graphene, the noble metal film with the pyramid structure, an adhesive and a Si substrate.
Thus, the preparation of the surface enhanced Raman scattering substrate is completed; the prepared substrate is uniform in a large area, has high sensitivity, has universality for test objects with different scales, and has label-free detection capability.
The further improvement of the invention is that in the step 1, the thickness of the silicon oxide layer on the surface of the Si substrate is 10 nm-10 μm; the substrate surface is hydrophilically treated prior to use.
The further improvement of the present invention is that, in step 1, the monodisperse nanospheres used are in the form of dispersion, and the microsphere material is a polymer material, including but not limited to: polystyrene microspheres, polymethyl methacrylate microspheres, hydrogel microspheres. The diameter distribution of the microspheres is from 50nm to 10 mu m.
A further improvement of the present invention is that in step 1, the method for preparing monolayer two-dimensional colloidal crystals includes, but is not limited to: spin coating, drop coating, dip coating, electrophoretic deposition, and gas-liquid interface self-assembly. In particular, the gas-liquid interface self-assembly method includes a Langmuir-Blodgett film method. The Langmuir-Blodgett membrane method employs a Langmuir-Blodgett membrane analyzer 1.
The further improvement of the present invention is that in step 2, plasma is used for etching the nanospheres, and the equipment capable of performing the experiment includes but is not limited to: ICP etcher, RIE machine and plasma degumming machine.
In a further improvement of the present invention, in step 3, the growth of the metal thin film is performed using an electron beam evaporation method. Metals that can be grown as masks include, but are not limited to: cr, Ti, Ni, Fe, Cu, Au, Pt.
A further improvement of the present invention resides in a method of peeling off the two-dimensional colloidal crystal layer in step 4 by cleaning with oxygen plasma and dissolving in an organic solvent or ultrasonically. The equipment used for oxygen plasma cleaning includes, but is not limited to: ICP etcher, RIE machine and plasma degumming machine. Organic solvents that may be used include, but are not limited to: acetone, chloroform, dichlorobenzene, dichloromethane, toluene and xylene. Wherein the dissolution using the organic solvent is carried out in an ultrasonic state.
The invention is further improved in that in step 5, the SiO is etched by using a unidirectional reactive etching method2A layer; reactive gases used include, but are not limited to: CF (compact flash)4、CHF3、SF6、NF3、BCl3、Cl2。
In step 6, the Si (001) substrate is subjected to wet etching by using KOH solution to form an inverted pyramid structure. The concentration of the used KOH solution is 5 to 64 percent by mass; the etching temperature is 0-100 ℃; and stirring the reaction solution in the etching process.
The present invention is further improved in that, in step 7, the corrosive solution used uses hydrofluoric acid as the main etching solution, including but not limited to: hydrofluoric acid aqueous solution and buffer oxide etching solution.
A further development of the invention is that in step 8 the precious metals produced comprise: au, Ag, Cu; the preparation method includes but is not limited to: physical vapor deposition and chemical vapor deposition. Wherein physical vapor deposition includes, but is not limited to, magnetron sputtering, electron beam evaporation; chemical vapor deposition includes, but is not limited to, atomic layer deposition.
In a further improvement of the present invention, in step 9, the adhesive for peeling off the noble metal film with the pyramid structure includes, but is not limited to: organic adhesives such as epoxy, AB, tape; inorganic adhesives such as water glass.
In a further improvement of the present invention, in step 10, the selected graphene is a single-layer graphene grown on copper by using a chemical vapor deposition method.
The invention uses two methods of colloid photoetching and micro-nano processing to successfully realize the preparation of the pyramid-type SERS substrate. The prepared substrate realizes the uniformity of the pyramid structure and SERS signals in a large-scale range, has high sensitivity, and can test objects with different scales, typically nanoscale and microscale test molecules/particles. A layer of graphene transferred on the surface of the pyramid plays an important role, including: the Raman peak of the graphene can be used as the measurement of the near-field electromagnetic field intensity, so that the quantitative measurement of target molecules can be realized; as an environment-friendly material, is used as a support layer of biomolecules and improves the biocompatibility of the substrate; the integral enhancing capability of the SERS substrate is further improved; effectively slow down the oxidation speed of nano-particles and keep the long-term enhancement capability of the SERS substrate. The prepared large-area uniform, high-sensitivity and universal label-free detection surface-enhanced Raman scattering substrate can play an important role in biosensing and early disease detection, and can also be widely applied to the fields of chemical sensing, food safety detection and environmental monitoring. The invention uses a plurality of ways to prepare the two-dimensional colloid crystal with high coverage rate, and the cost for preparing the nano structure in large area is obviously reduced by using the colloid photoetching method subsequently. The invention uses a series of micro-nano processing methods to realize that each colloid microsphere is converted into each nano pyramid structure to be used as a characteristic structure of the surface enhanced Raman scattering substrate.
Example 1
The preparation method of the surface enhanced Raman scattering substrate provided by the embodiment of the invention comprises the following steps:
step 1, using Langmuir-Blodgett method at 50nm SiO2Preparing large-area two-dimensional colloidal crystal of close-packed single-layer 500nm Polystyrene (PS) microsphere on a/Si (001) substrate to obtain PS microsphere two-dimensional colloidal crystal-SiO2a/Si substrate sample; wherein the surface of the Si substrate is previously subjected to hydrophilic treatment.
Step 2, use of O2As reaction gas, the diameter of the PS microspheres is reduced to 250nm by using an ICP (inductively coupled plasma) etching method to obtain etched two-dimensional colloidal crystals-SiO (silicon dioxide) of the PS microspheres2the/Si substrate sample.
Step 3, using the etched PS microspheres of the sample in the step 2 as a mask, and depositing a layer of Cr on the substrate by using an electron beam evaporation method as a mask to obtain etched PS microsphere two-dimensional colloidal crystals-Cr mask-SiO2the/Si substrate sample.
And 4, stripping the microsphere two-dimensional colloidal crystal layer in the sample in the step 3: cleaning PS microspheres by using an oxygen ion degumming machine, and then ultrasonically cleaning a sample in acetone for 20 minutes to obtain Cr mask-SiO2the/Si substrate sample.
And 5, etching SiO by adopting ICP dry method by taking the Cr film in the sample in the step 4 as a mask2Layer of CHF3The gas acts as a reactive gas. Obtaining Cr mask-SiO2Mask layer-Si substrate sample.
Step 6, inSiO in step 5 sample2The layer is used as a mask and the Si (001) substrate is wet etched. Using KOH solution with the concentration of 40 percent by weight to carry out etching reaction at the temperature of 20 ℃, and continuously stirring the reaction solution in the process to form an inverted pyramid structure. Obtaining Cr mask-SiO2Mask layer-Si substrate sample with inverted pyramid structure.
Step 7, stripping SiO by using hydrofluoric acid aqueous solution2And laminating and a Cr mask layer to obtain a Si substrate sample with an inverted pyramid structure, wherein the Si substrate sample is used as a Si template of the surface-enhanced Raman scattering substrate.
Step 8, preparing an Au film on the Si template obtained in the step 7 by magnetron sputtering to obtain an Au film-Si template with a pyramid structure;
and 9, transferring the Au film obtained in the step 8 to a new Si substrate by using epoxy resin through a stripping and transferring method. The pyramid structure is exposed, and an Au film-epoxy resin-Si substrate sample with the pyramid structure is obtained;
and step 10, transferring a layer of copper graphene grown by CVD on the surface of the Au pyramid structure to obtain the graphene-Au film-epoxy resin-Si substrate with the pyramid structure. Thus, the preparation of the label-free detection surface enhanced Raman scattering substrate which is uniform in large area, high in sensitivity and universal is completed.
Please refer to fig. 2 to 4. In the method of the embodiment of the present invention, fig. 2 corresponds to the sample after step eight in fig. 1; FIG. 3 corresponds to the sample after step nine in FIG. 1; fig. 4 corresponds to the sample after step ten in fig. 1. In fig. 2, the gradual change of the structural color reflects that the nano pyramid structure is uniformly distributed on the 4-inch Si substrate; as can be seen from FIG. 3, the prepared pyramid structure has a regular shape and is arranged neatly and uniformly; as can be seen from fig. 4, graphene was successfully transferred to the pyramid surface.
Please refer to fig. 5 to 7. FIG. 5 shows Raman spectra of single-layer graphene on a flat Au film and an Au film with a pyramid structure, and considering that the signal area on the Au film with the pyramid structure is far smaller than that on the flat Au film, the enhancement factor of the pyramid structure to the graphene peak reaches 106And has high sensitivity. FIGS. 6 and 7 show the resultsThe prepared surface enhanced Raman scattering substrate has universality and label-free detection capability on test objects with different scales. Wherein FIG. 6 shows that the surface enhanced Raman scattering substrate has sensitive detection capability on nano-scale methylene blue, and the detection concentration is as low as 10-12M (mole/L). Fig. 7 shows the detection capability of the surface enhanced raman scattering substrate for lymphocytes at the micrometer scale.
Example 2
The preparation method of the surface enhanced Raman scattering substrate provided by the embodiment of the invention comprises the following steps:
step 1, spin coating method is used to form SiO film with 10nm2Preparing large-area two-dimensional colloidal crystal of close-packed monolayer polymethyl methacrylate (PMMA) microspheres on a/Si (001) substrate to obtain PMMA microsphere two-dimensional colloidal crystal-SiO2a/Si substrate sample; wherein the surface of the Si substrate is previously subjected to hydrophilic treatment.
Step 2, use of O2As reaction gas, reducing the diameter of the PS microspheres to 800nm by using a RIE etching method to obtain etched PMMA microspheres two-dimensional colloidal crystal-SiO2the/Si substrate sample.
Step 3, using the PMMA microspheres etched by the sample in the step 2 as a mask, and depositing a layer of Ni on the substrate by using an electron beam evaporation method as a mask to obtain etched PMMA microsphere two-dimensional colloidal crystals-Ni mask-SiO2the/Si substrate sample.
And 4, ultrasonically cleaning the sample in trichloromethane for 20 minutes, and stripping the PMMA microsphere two-dimensional colloidal crystal layer in the sample in the step 3. Obtaining Ni mask-SiO2the/Si substrate sample.
Step 5, taking the Ni film in the sample in the step 4 as a mask, and etching SiO by RIE dry method2Layer of CF4The gas acts as a reactive gas. Obtaining Ni mask-SiO2Mask layer-Si substrate sample.
Step 6, using SiO in the sample in step 52The layer is used as a mask and the Si (001) substrate is wet etched. Using 60 wt% KOH solution, carrying out etching reaction at 60 ℃, and continuously stirring the reaction solution in the process to form an inverted pyramid structure. Obtaining Ni mask-SiO2Mask layer-Si substrate sample with inverted pyramid structure.
Step 7, stripping SiO by using buffer oxide etching liquid2And laminating and a Cr mask layer to obtain a Si substrate sample with an inverted pyramid structure, wherein the Si substrate sample is used as a Si template of the surface-enhanced Raman scattering substrate.
Step 8, preparing a layer of Ag film on the Si template obtained in the step 7 by using electron beam evaporation to obtain an Ag film-Si template with a pyramid structure;
and 9, transferring the Ag film obtained in the step 8 to a new Si substrate by a stripping and transferring method by using an adhesive tape. Wherein the pyramid structure is exposed to obtain an Ag film-epoxy resin-Si substrate sample with the pyramid structure;
and step 10, transferring a layer of copper graphene grown by CVD on the surface of the Ag pyramid structure to obtain the graphene-Ag film with pyramid structure-epoxy resin-Si substrate. Thus, the preparation of the label-free detection surface enhanced Raman scattering substrate which is uniform in large area, high in sensitivity and universal is completed.
Example 3
The preparation method of the surface enhanced Raman scattering substrate provided by the embodiment of the invention comprises the following steps:
step 1, using Langmuir-Blodgett method at 10nm SiO2Preparing large-area two-dimensional colloidal crystal of close-packed single-layer 50nm Polystyrene (PS) microsphere on a/Si (001) substrate to obtain PS microsphere two-dimensional colloidal crystal-SiO2a/Si substrate sample; wherein the surface of the Si substrate is previously subjected to hydrophilic treatment.
Step 2, use of O2As reaction gas, the diameter of the PS microspheres is reduced to 25nm by using an ICP (inductively coupled plasma) etching method to obtain etched two-dimensional colloidal crystals-SiO (silicon dioxide) of the PS microspheres2the/Si substrate sample. Wherein, the adopted equipment is an inductively coupled plasma etching machine.
Step 3, using the etched PS microspheres of the sample in the step 2 as a mask, and depositing a layer of Ti on the substrate by using an electron beam evaporation method as a mask to obtain etched PS microsphere two-dimensional colloidal crystals-Ti mask-SiO2the/Si substrate sample.
Step 4, peeling off the sample of step 3The microsphere two-dimensional colloidal crystal layer in (1): cleaning the PS microspheres by using an oxygen ion degumming machine, and then ultrasonically cleaning the sample in dichlorobenzene for 20 minutes to obtain Ti mask-SiO2the/Si substrate sample.
And 5, etching SiO by adopting an ICP dry method by taking the Ti film in the sample in the step 4 as a mask2Layer, using BCl3The gas acts as a reactive gas. Obtaining Ti mask-SiO2Mask layer-Si substrate sample.
Step 6, using SiO in the sample in step 52The layer is used as a mask and the Si (001) substrate is wet etched. KOH solution with the concentration of 64 percent by weight is used for carrying out etching reaction at the temperature of 100 ℃, and the reaction solution is continuously stirred in the process to form an inverted pyramid structure. Obtaining Ti mask-SiO2Mask layer-Si substrate sample with inverted pyramid structure.
Step 7, stripping SiO by using hydrofluoric acid aqueous solution2And laminating and Ti mask layers to obtain a Si substrate sample with an inverted pyramid structure, wherein the Si substrate sample is used as a Si template of the surface enhanced Raman scattering substrate.
Step 8, preparing a layer of Cu film on the Si template obtained in the step 7 by magnetron sputtering to obtain a Cu film-Si template with a pyramid structure;
and 9, transferring the Cu film obtained in the step 8 to a new Si substrate by using epoxy resin through a stripping and transferring method. Exposing the pyramid structure to obtain a Cu film-epoxy resin-Si substrate sample with the pyramid structure;
and step 10, transferring a layer of copper graphene grown by CVD on the surface of the Au pyramid structure to obtain the graphene-Cu film with the pyramid structure-epoxy resin-Si substrate. Thus, the preparation of the label-free detection surface enhanced Raman scattering substrate which is uniform in large area, high in sensitivity and universal is completed.
Example 4
The preparation method of the surface enhanced Raman scattering substrate provided by the embodiment of the invention comprises the following steps:
step 1, using Langmuir-Blodgett method at 10 μm SiO2Two-dimensional colloidal crystal for preparing large-area close-packed monolayer 10-micron Polystyrene (PS) microspheres on/Si (001) substrateObtaining PS microsphere two-dimensional colloidal crystal-SiO2a/Si substrate sample; wherein the surface of the Si substrate is previously subjected to hydrophilic treatment.
Step 2, use of O2As reaction gas, the diameter of the PS microspheres is reduced to 5 μm by using an ICP (inductively coupled plasma) etching method to obtain etched two-dimensional colloidal crystals-SiO of the PS microspheres2the/Si substrate sample.
Step 3, using the etched PS microspheres of the sample in the step 2 as a mask, and depositing a layer of Cr on the substrate by using an electron beam evaporation method as a mask to obtain etched PS microsphere two-dimensional colloidal crystals-Cr mask-SiO2the/Si substrate sample.
And 4, stripping the microsphere two-dimensional colloidal crystal layer in the sample in the step 3: cleaning PS microspheres by using an oxygen ion degumming machine, and then ultrasonically cleaning a sample in acetone for 20 minutes to obtain Cr mask-SiO2the/Si substrate sample.
And 5, etching SiO by adopting ICP dry method by taking the Cr film in the sample in the step 4 as a mask2Layer of CHF3The gas acts as a reactive gas. Obtaining Cr mask-SiO2Mask layer-Si substrate sample.
Step 6, using SiO in the sample in step 52The layer is used as a mask and the Si (001) substrate is wet etched. Using KOH solution with the concentration of 5 percent by weight to carry out etching reaction at the temperature of 0 ℃, and continuously stirring the reaction solution in the process to form an inverted pyramid structure. Obtaining Cr mask-SiO2Mask layer-Si substrate sample with inverted pyramid structure.
Step 7, stripping SiO by using hydrofluoric acid aqueous solution2And laminating and a Cr mask layer to obtain a Si substrate sample with an inverted pyramid structure, wherein the Si substrate sample is used as a Si template of the surface-enhanced Raman scattering substrate.
Step 8, preparing an Au film on the Si template obtained in the step 7 by magnetron sputtering to obtain an Au film-Si template with a pyramid structure;
and 9, transferring the Au film obtained in the step 8 to a new Si substrate by using epoxy resin through a stripping and transferring method. The pyramid structure is exposed, and an Au film-epoxy resin-Si substrate sample with the pyramid structure is obtained;
and step 10, transferring a layer of copper graphene grown by CVD on the surface of the Au pyramid structure to obtain the graphene-Au film-epoxy resin-Si substrate with the pyramid structure. Thus, the preparation of the label-free detection surface enhanced Raman scattering substrate which is uniform in large area, high in sensitivity and universal is completed.
In summary, the invention discloses a preparation method of a surface enhanced raman scattering substrate, which mainly comprises the following steps: in SiO2Preparing a close-packed monolayer nano microsphere two-dimensional colloidal crystal layer on a/Si (001) substrate; reducing the diameter of the nano-microsphere by using a plasma etching method; depositing a layer of metal film on the surface of the sample; stripping the microsphere two-dimensional colloidal crystal layer; etching SiO by dry method2A layer; etching the Si (001) substrate by adopting a wet method to form an inverted pyramid structure; stripping SiO using an etching solution2Laminating and metal masking layers to obtain a Si template with an inverted pyramid structure; sputtering a noble metal film on the Si template; transferring the noble metal film onto a new substrate by using an adhesive, wherein the pyramid structure is exposed; and transferring a layer of graphene on the surface of the noble metal pyramid. The method uses two methods of colloid photoetching and micro-nano processing, and successfully realizes the preparation of the pyramid-type SERS substrate. The prepared substrate realizes the uniformity of the pyramid structure and SERS signals in a large-scale range, and has high sensitivity and universality. The substrate can play an important role in biosensing and early detection of diseases, and can be widely applied to the fields of chemical sensing, food safety detection and environmental monitoring.
Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the claims of the present application.