CN103868909A - Mushroom array type surface enhanced Raman spectrum active substrate and preparation method thereof - Google Patents

Abstract

The invention discloses a mushroom array type surface enhanced Raman spectrum active substrate and a preparation method of the mushroom array type surface enhanced Raman spectrum active substrate. The active substrate is a gold or silver mushroom nano-structure array. The preparation method comprises the following steps: impressing a through hole in a photoresist on the surface of a silicon or glass substrate with a gold film by using a nano-impressing technology; then performing electro-deposition to form the mushroom nano-structure array. The mushroom nano-structure array is mainly characterized in that the diameters of mushroom cap parts are 50-300nm; the distance between the caps is 0-50nm. According to the substrate, the enhancement effect of a Raman scattering signal can be greatly improved.

Description

Mushroom-shaped array surface-enhanced Raman spectroscopy active substrate and preparation method

technical field

The invention belongs to the technical field of Raman spectrum detection, and in particular relates to a preparation method of a surface-enhanced Raman active substrate with simple process method, large scale, low cost and high performance.

Background technique

In 1928, Indian scientist CVRaman used sunlight to observe the inelastic scattering phenomenon in which the frequency of scattered light changes. This phenomenon is caused by the energy exchange between the incident photon and the medium molecule, which is related to the electron cloud or chemical bond in the molecule. Raman spectroscopy is a widely used non-destructive testing and molecular identification technology, which can provide fingerprint information of chemical and biological molecular structures. The discovery of the Raman phenomenon is of great significance to the scientific community, but the Raman signal is extremely weak. This inherent low sensitivity has restricted the application of Raman spectroscopy in the fields of trace detection and surface science. I want to study the Raman signal Almost all use some enhancement effect. In the mid-1970s, three research groups led by Fleischmann, VanDuyne, and Creighton respectively observed and confirmed the surface-enhanced Raman phenomenon, that is, the Raman signal of pyridine molecules on the surface of rough silver electrodes was enhanced by about 10 ⁶ compared with that in solution. times. The phenomenon that the Raman signal intensity of molecules and other species is adsorbed or very close to the surface with a certain nanostructure is significantly enhanced compared with its bulk molecules is called surface enhanced Raman scattering (Surface enhanced Raman Scattering, SERS) effect. The discovery of the SERS effect effectively solved the problem of low sensitivity of Raman spectroscopy in surface science and trace analysis. The development of nanotechnology has injected new vitality into the application of SERS technology. The SERS signal of the sol-nanoparticle system can be amplified to one million billion times, and has become an important detection tool in single-molecule science (Shu MingNie et al.Science, 1997, 275, 1102–1106), but the stability and reproducibility of the preparation of sol-nanoparticle substrates are poor. Therefore, the preparation of SRES substrates with good stability, good enhancement effect and repeatability is the focus of current research. In recent years, people have begun to try to use nanoimprinting technology to prepare SERS substrates with ordered structures, which can achieve mass and low-cost production of SERS substrates, and can well meet the requirements of SERS substrates for stability and preparation repeatability ( Chinese patent CN103091983A). However, the enhanced activity of the Raman spectrum signal is closely related to the spacing between nanostructures (or particles), and decays exponentially with the increase of the spacing. That is, theoretically, the smaller the spacing of the nanostructures, the higher the enhanced activity. Usually, the spacing of the nanostructures is required to be below 10 nanometers. Structure retention, etc.), nanoimprint technology cannot prepare structure arrays with intervals below 50 nanometers. That is, the enhancement effect of the SERS substrate prepared solely by nanoimprinting technology is not ideal.

Contents of the invention

The object of the present invention is to overcome the shortcoming of above-mentioned method, provide a kind of surface-enhanced Raman scattering active substrate of mushroom-like metal nanostructure array and preparation method thereof,

Technical scheme of the present invention is as follows:

A surface-enhanced Raman scattering active substrate is characterized in that: it is provided with a mushroom-shaped nanostructure metal array on a flat base layer, and the diameter of the mushroom cap part is 50-300 nanometers, and the distance between the caps is 0-300 nanometers. 50 nm.

The leveling base layer of the present invention may be one of conductive glass or glass, silicon wafer, and quartz wafer on which a metal layer is vapor-deposited on the surface. The metal layer can be one or more of gold, silver and copper.

The metal of the metal nanostructure array in the present invention can be one or more of gold, silver and copper.

Another technical solution of the present invention is:

A method for preparing a surface-enhanced Raman scattering active substrate, comprising the steps of:

1) Coating photoresist on the surface of flat substrates such as glass, silicon wafers, and quartz wafers with a metal layer evaporated on the surface,

2) Using nanoimprinting technology and etching technology to prepare an ordered nano-via structure on the photoresist;

3) Electrochemical deposition is used to deposit metal gold, silver or copper at the nano-through hole, and make it overflow out of the hole to form a mushroom cap. Together with the column shape at the through hole, the overall shape is like a mushroom;

4) Remove the nanoimprint photoresist to obtain the surface-enhanced Raman scattering substrate of the ordered mushroom-like nanostructured metal array.

Among them: step (2) preferably includes: using a nanoimprint system, first adopting hot embossing technology, using a nickel template as a master, and replicating its surface nanostructure to the surface of the polydimethylsiloxane soft film by hot embossing ; Then, using UV imprinting technology, using a spin coater, the nano-imprinting glue is spin-coated on the silicon wafer surface of the evaporated gold film;

Use the polydimethylsiloxane soft film as the master plate to imprint the surface of the nanoimprint adhesive with UV light to obtain the nanopore structure; then use a plasma etching machine to remove the residual glue layer after the UV imprint, and the nanopore The bottom is bare metal.

Among them, step (3) preferably includes: the effective mass fraction of gold in the solution is 0.01-1%, the pH of the solution is 1-6, and under the condition of 20-70°C, the UV-imprinted nano-imprint glue is used as a template to block The layer is subjected to constant current or constant potential electrodeposition, and the deposition time is 300-1200s;

Use a microwave plasma remover to remove the barrier layer of the nanoimprint adhesive, and finally obtain a surface-enhanced Raman scattering substrate with an ordered gold nanostructure;

Using a microwave plasma etching machine, after the electrodeposition of the mushroom array is prepared, the barrier layer of the nano-imprinting glue is removed to obtain an ordered gold nano-mushroom array.

Among them, the effective mass fraction of gold in the solution is more preferably 0.01-0.5%, the pH of the solution is more preferably 2-5, the temperature is more preferably 40-50°C, and the deposition time is more preferably 400-1000s.

At constant current, the current density is 1-5mA/cm2, more preferably 1-3mA/cm2.

The voltage of the constant potential is -2V-2V, more preferably -0.9V-0.6V.

Compared with the prior art, the present invention has the following advantages:

1. The present invention prepares a nanostructured metal array with a diameter of mushroom caps of 50-300 nanometers and a distance between caps of 0-50 nanometers.

2. The preparation method of the present invention combines the advantages of nanoimprinting for large-scale and low-cost preparation of nanostructure arrays and electrochemical deposition for controlling the size of nanostructures, which not only ensures the repeatability of the method and the uniformity of the array, but also has a large The amplitude narrows the pitch of the metal nanometer space, thereby greatly improving the enhancement effect of the Raman scattering signal. The enhancement factor of the prepared mushroom array substrate to the surface-enhanced Raman spectrum of 4-mercaptopyridine molecule is 108.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a schematic diagram of the preparation process of a surface-enhanced Raman scattering active substrate;

Fig. 2 and Fig. 3 are the SEM photos of the nano-imprint adhesive barrier layer after removing the ultraviolet imprint residual adhesive in Example 2;

Fig. 4 and Fig. 5 are the SEM photos of the surface-enhanced Raman scattering active substrate prepared by using gold as the electrodeposited layer in embodiment 3;

Fig. 6 is embodiment 4 using 1mM 4-mercaptopyridine as the molecule to be tested, using gold as the electrodeposition layer to prepare a surface-enhanced Raman scattering active substrate, and testing the spectrum obtained by a portable Raman spectrometer with 785nm excitation light;

Fig. 7 and Fig. 8 are the SEM photos of the surface-enhanced Raman scattering active substrate prepared by using gold as the electrodeposition layer in embodiment 5;

9 and 10 are SEM photos of the surface-enhanced Raman scattering active substrate prepared in Example 6 with gold as the electrodeposited layer.

Detailed ways

Example 1

A gold film with a thickness of 200nm was deposited on the surface of a circular silicon wafer with a diameter of two inches after standard cleaning by using electron beam evaporation technology. Standard cleaning steps: 1. Prepare a solution of H ₂ SO ₄ : H ₂ O ₂ =1:4, put the silicon wafer in a quartz boat and soak for 15 minutes. Rinse with hot deionized water and then with cold deionized water. 2. Soak the wafer in HF solution (HF: H ₂ O = 1:1) for 30 seconds, take it out and rinse with deionized water for 15 minutes. 3. Use solution (NH ₄ OH: H ₂ O ₂ : H ₂ O=1:1:5) to boil and clean: first heat the deionized water in the beaker to 85°C, pour in the corresponding proportion of NH ₄ OH and H ₂ O ₂ solution, boil for 15 minutes, take out and wash with hot deionized water, and then wash with cold deionized water. 4. Soak the wafer in diluted HF solution (HF: H ₂ O = 1:20) for 20 seconds, and rinse with hot deionized water for 15 minutes. 5. Use the solution (HCl: H ₂ O ₂ : H ₂ O = 1: 1: 5) to boil and clean: first heat the deionized water to 85°C, pour in the corresponding proportion of HCl and H ₂ O ₂ solution, boil for 15 Minutes, take it out and wash it with hot deionized water, and then replace it with cold deionized water. 6. Dry the cleaned silicon wafer with nitrogen gas.

的沉积速率，在硅片表面蒸镀一层30nm厚的铬作为粘结层；然后以

的沉积速率，在铬层表面蒸镀一层200nm金。Temescal2000 electron beam evaporation system was used to

A deposition rate of 30nm thick chromium is evaporated on the surface of the silicon wafer as a bonding layer; and then

A deposition rate of 200nm gold was evaporated on the surface of the chromium layer.

Example 2

The composite nanoimprint technology is used to imprint an ordered nanopore structure pattern on the surface of the gold film. The diameter of the nanopore structure is 200nm, and its period is 400nm:

Using the Obducat Eitre6 nanoimprinting system, first use thermal imprinting technology, using a two-inch nickel template with a nanopore diameter of 200nm and a period of 400nm as a master, and copy its surface nanostructure to polydimethylsiloxane by thermal embossing The surface of the alkane soft film; then use the UV imprinting technology, use the G3P-8 spin coater, spin-coat the TU2-170 nano-imprinting glue on the surface of the silicon wafer with a 200nm gold film, and control the thickness of the nano-imprinting glue at 200nm , using polydimethylsiloxane soft film as the master plate to UV imprint on the surface of the nanoimprint adhesive, that is, to obtain a nanopore structure with a diameter of 200nm and a period of 400nm; and then use the AMS200 plasma etching machine to remove the UV imprint After the residual adhesive layer, the gold is exposed at the bottom of the nanopore. The electron micrographs are shown in Fig. 2 and Fig. 3, and the effective area of the nanostructure is about 20 square centimeters.

Example 3

Utilize the electrochemical method to deposit gold, use the constant current method, control the deposition electric quantity, deposit gold on the basis of embodiment 2, make the gold of electrodeposition grow nanopore, shape is like mushroom, specifically:

Using saturated sodium sulfite solution of sodium gold sulfite, potassium dihydrogen phosphate (9% mass fraction) and sodium citrate (4% mass fraction) as electroplating additives, the effective mass fraction of gold in the solution is 0.2%, and the pH of the solution is 4.5 , under the condition of 45°C, the current density is 2mA/cm2, and the nano-imprint glue after ultraviolet imprinting is used as the template barrier layer, and CHI760E is used for constant current electrodeposition, and the deposition time is 660s.

Use the Alpha microwave plasma degumming machine to remove the barrier layer of the nanoimprint adhesive, and finally obtain a surface-enhanced Raman scattering substrate with an ordered gold nanostructure;

Using a Q240Alpha microwave plasma etching machine, after the electrodeposition of the mushroom array is completed, the barrier layer of the nano-imprinting glue is removed, the power is 300W, the process pressure is 20Pa, and the time is 2min, and the ordered gold nano-mushroom array is obtained.

The diameter of the cap part of the mushroom prepared in this embodiment is about 50-300 nanometers, and the distance between the caps is about 0-50 nanometers. The "stipe" is about 10-200 nm in height. The electron micrographs are shown in Figure 4 and Figure 5, and the effective area of the mushroom array is about 20 square centimeters.

Example 4

Take 5uL of 1mM 4-mercaptopyridine aqueous solution and drop it on the surface of the surface-enhanced Raman scattering substrate prepared in Example 3, wash it with a large amount of ultrapure water after drying, blow dry with nitrogen, and test it with a portable Raman spectrometer with 785nm excitation light. The results are shown in FIG. 6 , and the enhancement factor of the prepared mushroom array substrate to the surface-enhanced Raman spectrum of 4-mercaptopyridine molecules is 108.

Example 5

Electrochemical methods are used to deposit gold, and the constant potential method is used to control the deposition electricity, so that the gold deposited in Example 2 grows nanopores, which are shaped like mushrooms, specifically.

Using saturated sodium sulfite solution of sodium gold sulfite, potassium dihydrogen phosphate (9% mass fraction) and sodium citrate (4% mass fraction) as electroplating additives, the effective mass fraction of gold in the solution is 0.2%, and the pH of the solution is 4.5 , under the condition of 45 ℃, constant potential -0.9V electrodeposition, using the nanoimprint glue after UV imprinting as the template barrier layer, using CHI760E for constant potential electrodeposition, the deposition time is 400s.

The diameter of the cap part of the mushroom prepared in this embodiment is about 50-300 nanometers, and the distance between the caps is about 0-50 nanometers. The "stipe" is about 10-200 nm in height. The electron micrographs are shown in Figures 7 and 8, and the effective area of the mushroom array is about 20 square centimeters.

Example 6

Basically the same as Example 5, the difference is

A gold potassium cyanide solution of 3g/L is used as the electroplating solution, and sodium citrate with a mass fraction of 1% is used as an additive. The pH value of the solution is about 4.0, and the effective mass fraction of gold in the solution is 0.2%. Under the condition of 55°C, Constant current electrodeposition, the current density is 3mA/cm2, using the nano-imprint glue after UV imprinting as the template barrier layer, using CHI760E for constant current electrodeposition, the deposition time is 300s.

The diameter of the cap part of the mushroom prepared in this embodiment is about 50-300 nanometers, and the distance between the caps is 0-50 nanometers. The "stipe" is about 10-200 nm in height. Its electron micrograph is shown in Figure 9 and Figure 10.

Example 7

Basically the same as Example 5, the difference is

Use 1mM chloroauric acid aqueous solution as the electroplating solution, use sodium perchlorate with a mass fraction of 1.5% as an additive, the effective mass fraction of gold in the solution is 0.02%, and the pH value of the solution is about 2. At 50°C, the constant potential For electrodeposition, the deposition potential is 0.6V, and the nano-imprint glue after ultraviolet imprinting is used as the template barrier layer. CHI760E is used for constant-potential electrodeposition, and the deposition time is 560s.

The diameter of the cap part of the mushroom prepared in this embodiment is about 50-300 nanometers, and the distance between the caps is 0-50 nanometers. The "stipe" is about 10-200 nm in height.

Example 8

Basically the same as Example 5, the difference is

1mM chloroauric acid aqueous solution is used as the electroplating solution, the pH value of the solution is about 2, and the effective mass fraction of gold in the solution is 0.02%. Under the condition of 50°C, constant current electrodeposition is carried out, and the current density is 1.6mA/cm2. The imprinted nanoimprint glue is used as a template barrier layer, and CHI760E is used for constant current electrodeposition, and the deposition time is 1000s.

The diameter of the cap part of the mushroom prepared in this embodiment is about 50-300 nanometers, and the distance between the caps is 0-50 nanometers. The "stipe" is about 10-200 nm in height.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit them. The present invention has been described in detail with reference to the embodiments, which should be understood by those skilled in the art. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the claims of the present invention.

Claims (10)

1. a surface-enhanced Raman scattering active substrate, is characterized in that: it is provided with mushroom-shaped nanostructure metal array on the flat base layer, and the diameter of mushroom cap part is 50-300 nanometers, and the distance between caps is 0-50 nanometers. 2. The surface-enhanced Raman scattering active substrate according to claim 1, characterized in that: the flat base layer is one of conductive glass or glass, silicon wafer, and quartz wafer with a metal layer evaporated on the surface. 3. The surface-enhanced Raman scattering active substrate according to claim 1, wherein the metal of the metal nanostructure array is one or more than two of gold, silver and copper. 4. A method for preparing a surface-enhanced Raman scattering active substrate, comprising the steps of: 1) Coating photoresist on the surface of a flat substrate with a metal layer evaporated on the surface, 2) Using nanoimprinting technology and etching technology to prepare an ordered nano-via structure on the photoresist; 3) Electrochemical methods are used to deposit metal gold, silver or copper at the nano-hole, and make it overflow out of the hole to form a cap shape, together with the columnar shape of the through-hole, the overall shape is like a mushroom; 4) Remove the nanoimprint photoresist to obtain the surface-enhanced Raman scattering substrate of the ordered mushroom-like nanostructured metal array. 5. A method for preparing a surface-enhanced Raman scattering active substrate as claimed in claim 4, characterized in that: step (2) includes: using a nanoimprint system, first adopting hot embossing technology, using a nickel template as the mother Plate, its surface nanostructure is copied to the surface of polydimethylsiloxane soft film by hot embossing; then, using UV imprinting technology, using a spin coater, the nano-imprinting glue is spin-coated on the silicon wafer with evaporated gold film surface; Use the polydimethylsiloxane soft film as the master plate to imprint the surface of the nanoimprint adhesive with UV light to obtain the nanopore structure; then use a plasma etching machine to remove the residual glue layer after the UV imprint, and the nanopore The bottom is bare metal. 6. A method for preparing a surface-enhanced Raman scattering active substrate as claimed in claim 4, characterized in that: step (3) comprises: the effective mass fraction of gold in the solution for electrodeposition is 0.01-1%, The pH of the solution is 1-6, and under the condition of 20-70°C, the nano-imprint glue after UV imprinting is used as the template barrier layer for constant current or constant potential electrodeposition, and the deposition time is 300-1200s; Use a microwave plasma remover to remove the barrier layer of the nanoimprint adhesive, and finally obtain a surface-enhanced Raman scattering substrate with an ordered gold nanostructure; Using a microwave plasma etching machine, after the electrodeposition of the mushroom array is prepared, the barrier layer of the nano-imprinting glue is removed to obtain an ordered gold nano-mushroom array. 7. The method for preparing a surface-enhanced Raman scattering active substrate according to claim 6, wherein the current density is 1-5mA/cm2 at constant current. 8. The method for preparing a surface-enhanced Raman scattering active substrate according to claim 6, wherein the voltage of the constant potential is -2V-2V. 9. by the preparation method of the described surface-enhanced Raman scattering active substrate of claim 4, it is characterized in that: described flat base layer is one of conductive glass or the glass, silicon chip, quartz chip that the surface is vapor-deposited with metal layer kind. 10. The method for preparing a surface-enhanced Raman scattering active substrate according to claim 4, wherein the metal of the metal nanostructure array is one or more than two of gold, silver and copper.

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