WO2015135450A1

WO2015135450A1 - Mushroom array type surface enhanced raman spectrum active substrate and preparation method

Info

Publication number: WO2015135450A1
Application number: PCT/CN2015/073856
Authority: WO
Inventors: 周勇亮; 樊海涛; 杨防祖; 张大霄; 单洁洁; 任斌; 田中群
Original assignee: 厦门大学
Priority date: 2014-03-14
Filing date: 2015-03-09
Publication date: 2015-09-17
Also published as: CN103868909A; CN103868909B

Abstract

A mushroom array type surface enhanced Raman spectrum active substrate (8) and a preparation method. The active substrate is a gold or silver mushroom nano-structure array. The preparation method comprises: first imprinting an ordered nano through-hole structure (6) in a photoresist on the surface of a silicon or glass substrate with a gold film by using a nano-imprinting technique (5); and then depositing metal in the nano through-hole by means of electrochemical deposition (7) and making the metal overflow the hole to form the mushroom nano-structure array. The diameter of mushroom caps is 50-300 nm, and the distance between the caps is 0-50 nm. By means of 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 thereof

Technical field

The invention belongs to the technical field of Raman spectroscopy, and in particular relates to a method for preparing a surface-enhanced Raman-active substrate.

Background technique

Indian scientist C. V. Raman, 1928 The inelastic scattering phenomenon in which the frequency of the scattered light changes is observed by sunlight. This phenomenon is caused by the energy exchange between the incident photons and the medium molecules, which is related to electron clouds or chemical bonds in the molecules. Raman spectroscopy is a versatile non-destructive testing and molecular recognition technology. It provides fingerprint information on chemical and biomolecular structures. The discovery of the Raman phenomenon is of great significance to the scientific community, but the Raman signal is extremely weak. This inherently low sensitivity defect has restricted Raman spectroscopy in the field of trace detection and surface science, and wants to study Raman signals. Almost all use a certain enhancement effect. In the mid-1970s, The three research groups led by Fleischmann, VanDuyne, and Creighton observed and confirmed the surface-enhanced Raman phenomenon. That is, the Raman signal of the pyridine molecule on the surface of the rough silver electrode is about 106 times stronger than that in the solution. People adsorb or very close to a surface with a certain nanostructure due to species such as molecules. The phenomenon that the Raman signal intensity is significantly enhanced compared to its bulk molecules is called Surface Enhanced Raman Scattering (SERS). The discovery of the SERS effect effectively solved the low sensitivity problem of Raman spectroscopy in surface science and trace analysis. The development of nanotechnology has injected new vitality into the application of SERS technology, and the SERS signal of the sol nanoparticle system can be amplified to a hundred million times. Has become an important testing tool in single-molecule science (Shu MingNie et al. Science, 1997, 275, 1102–1106), but the stability and readability of the sol nanoparticle substrate are poor. Therefore, SRES with good stability, enhanced effect and repeatability is prepared. The substrate is the focus of current research. In recent years, people have begun to try to prepare ordered structures of SERS using nanoimprint technology. Substrate, which can realize batch, low-cost production of SERS substrate, and can well meet the requirements of stability and preparation repeatability of SERS substrate (Chinese patent CN 103091983 A). However, the enhancement activity of the Raman spectral signal is closely related to the spacing between the nanostructures (or particles) and exponentially decays as the spacing increases. That is, theoretically, the smaller the pitch of the nanostructures is, the higher the enhancement activity is, and the nanometer spacing is usually required to be below 10 nm, and due to the limitations of the technology itself (the penetration of the photoresist into the nanostructure, the elimination of the bubbles, when the mold is released) Structural retention, etc., nanoimprint technology cannot produce arrays of structures spaced below 50 nm. That is, the enhancement effect of the SERS substrate prepared by simply using the nanoimprint technique is not satisfactory.

Summary of the invention

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

The technical solution of the present invention is as follows:

A surface-enhanced Raman scattering active substrate characterized by: The flat base layer is provided with a mushroom-shaped nanostructured metal array, and the diameter of the mushroom cap portion is 50-300 nm, and the distance between the caps is 0-50 nm.

The flat base layer of the present invention may be one of a conductive glass or a glass, a silicon wafer or a quartz wafer on which a metal layer is evaporated. The metal layer may be one or more of gold, silver, and copper.

The metal of the metal nanostructure array of the present invention may 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 a surface of a flat substrate such as a glass, a silicon wafer or a quartz wafer on which a metal layer is vapor-deposited,

2) preparing an ordered nano-via structure on the photoresist by using nanoimprint technology and etching technology;

3) Electrode deposition is performed on the nano-via holes to deposit metal gold, silver or copper, and overflowing the pores to form a cap. Together with the columnar shape at the through hole, the whole shape is like a mushroom;

4) Removing the nanoimprinted photoresist to obtain a surface-enhanced Raman scattering substrate of an ordered mushroom-like nanostructured metal array.

Wherein: step (2) preferably comprises: using a nanoimprinting system, first adopting a hot imprinting technique, using a nickel template as a master, and replicating the surface nanostructure thereof onto the surface of the polydimethylsiloxane soft film by hot stamping Then, using a UV imprint technique, using a spin coater, spin-coating the nanoimprintant on the surface of the silicon wafer on which the gold film is evaporated;

The surface of the nanoimprinted adhesive is UV-imprinted by using a polydimethylsiloxane soft film as a master to obtain a nanopore structure; and the UV-imprinted residual adhesive layer is removed by using a plasma etching machine in the nanopore The bottom is exposed to metal.

Wherein, step (3) preferably comprises: the effective mass fraction of gold in the solution is 0.01-1%, the pH of the solution is 1-6, and the nanoimprint adhesive after ultraviolet imprinting is used as a template to block at 20-70 ° C. The layer is subjected to constant current or constant potential electrodeposition, and the deposition time is 300-1200 s;

The nanoimprinting rubber barrier layer is removed by using a microwave plasma stripping machine to finally obtain a surface-enhanced Raman scattering substrate of the ordered gold nanostructure;

After the mushroom array electrodeposition preparation is completed by a microwave plasma etching machine, the nanoimprinting rubber barrier layer is removed, and an ordered gold nano mushroom array is obtained.

Among them, the effective mass fraction of gold in the solution is more preferably from 0.01 to 0.5%, the solution PH is more preferably from 2 to 5, the temperature is more preferably from 40 to 50 ° C, and the deposition time is more preferably from 400 to 1,000 s.

At a constant current, the current density is 1-5 mA/cm ² , and more preferably 1-3 mA/cm ² .

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

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

1. The present invention prepares a nanostructured metal array having a mushroom cap portion having a diameter of 50-300 nm and a distance between the caps of 0-50 nm.

2. The preparation method of the invention combines the advantages of nanoimprinting capable of preparing nanostructure arrays on a large scale and at a low cost, and electrochemical deposition of controlled nanostructure size, thereby ensuring repeatability of the method and uniformity of the array, and large The amplitude reduces the spacing of the metal nano-intervals, thereby greatly improving the enhancement effect of the Raman scattering signal. The surface enhancement Raman spectrum of the prepared mushroom array substrate to 4-mercaptopyridine molecule was enhanced by 108.

DRAWINGS

The invention is further described below in conjunction with the drawings and embodiments.

1 is a schematic view showing a process flow for preparing a surface-enhanced Raman scattering active substrate;

2 and FIG. 3 are SEM photographs of the nanoimprinting rubber barrier layer after removing the ultraviolet embossed residual adhesive of Example 2.

4 and FIG. 5 are SEM photographs of the surface-enhanced Raman scattering active substrate prepared by using gold as an electrodeposited layer in Example 3;

6 is a surface-enhanced Raman scattering active substrate prepared by using Example 1 with 1 mM 4-mercaptopyridine as a molecule to be tested and gold as an electrodeposited layer. a spectrum obtained by testing a portable Raman spectrometer that excites light;

7 and FIG. 8 are SEM photographs of the surface-enhanced Raman scattering active substrate prepared by using gold as an electrodeposited layer in Example 5;

9 and 10 are SEM photographs of the surface-enhanced Raman scattering active substrate prepared by using gold as an electrodeposited layer in Example 6.

detailed description

Example 1

The surface-enhanced Raman scattering active substrate (8) of the present invention is prepared as shown in Figure 1:

The first step: coating the surface of the flat substrate such as glass, silicon wafer, quartz plate (4), etc. on which the metal layer (3) is evaporated on the surface, (2),

The second step: using the template (1) nano-imprint process (5) and etching technology to prepare ordered nano-via structure (6) on the photoresist;

The third step: deposition by electrochemical method (7) deposition of metal gold, silver or copper at the nano-via, and overflowing the pores to form a cap. Together with the columnar shape at the through hole, the whole shape is like a mushroom;

The fourth step: removing the nanoimprint photoresist to obtain a surface-enhanced Raman scattering substrate (8) of an ordered mushroom-shaped nanostructured metal array, which is provided with a mushroom-shaped nanostructure metal array on the flat base layer, and a mushroom cap The diameter of the part is 50-300 nm, and the distance between the caps is 0-50 nm.

Example 2

Using a electron beam evaporation technique, a gold film was deposited on the surface of a circular wafer having a diameter of two inches after standard cleaning, and the thickness thereof was 200 nm. Standard cleaning procedure: 1. Prepare a solution of H ₂ SO ₄ :H ₂ O ₂ = 1:4, place the silicon wafer on a quartz boat, and dip for 15 minutes. Wash with hot deionized water, then replace with cold deionized water for cleaning. 2. The silicon wafer was immersed in an HF solution (HF: H ₂ O = 1:1) for 30 seconds, and the ionized water was washed out for 15 minutes. 3. Boiling with a solution (NH ₄ OH:H ₂ O ₂ :H ₂ O=1:1:5): first heat the deionized water in the beaker to 85 ° C, and pour the corresponding proportion of NH ₄ OH and H ₂ O ₂ solution, boil for 15 minutes, remove and wash with hot deionized water, then rinse with cold deionized water. 4. The wafer was immersed in a diluted HF solution (HF: H ₂ O = 1:20) for 20 seconds, and deionized water was flushed for 15 minutes. 5. Boiling with solution (HCl: H ₂ O ₂ : H ₂ O = 1:1: 5): first heat the deionized water to 85 ° C, pour the corresponding ratio of HCl and H ₂ O ₂ solution, cook 15 In minutes, remove and wash with hot deionized water, then rinse with cold deionized water. 6. Dry the cleaned silicon wafer with nitrogen.

Using Temescal 2000 electron beam evaporation system, at a deposition rate of 0.2Å / s, a layer of 30nm thick chromium was deposited on the surface of the silicon wafer as a bonding layer; then a layer of evaporation on the surface of the chromium layer at a deposition rate of 0.5Å / s 200nm gold.

Example 3

An ordered nanoporous structure pattern is embossed on the surface of the gold film by a composite nanoimprint technique. The nanopore structure has a diameter of 200 nm and a period of 400 nm:

Use Obducat Eitre The 6-type nanoimprinting system first uses hot imprint technology to copy the surface nanostructures to polydimethylsiloxane by hot stamping with a two-inch nickel template with a nanopore diameter of 200 nm and a period of 400 nm as the master. Film surface; then using UV imprint technology, using G3P-8 type spin coater, TU2-170 nano-imprinted adhesive was spin-coated on the surface of the above-mentioned vapor-deposited 200nm gold film, and the thickness of nano-imprinted adhesive was controlled at 200nm. The surface of the nanoimprinted adhesive was UV-imprinted with a polydimethylsiloxane soft film as the master to obtain a nanopore structure with a diameter of 200 nm and a period of 400 nm. After removing the ultraviolet imprint by using an AMS200 plasma etching machine The layer of residual glue reveals gold at the bottom of the nanopore. The electron micrograph is shown in Figures 2 and 3. The effective area of the nanostructure is about 20 square centimeters.

Example 4

The gold is deposited by electrochemical method, and the deposition current is controlled by the galvanostatic method. Gold is deposited on the basis of Example 2, so that the electrodeposited gold grows out of the nanopore and has a shape like a mushroom, specifically:

A saturated sodium sulfite solution containing sodium gold sulfite is used as a plating additive with potassium dihydrogen phosphate (9% by mass) and sodium citrate (4% by mass). The effective mass fraction of gold in the solution is 0.2%, and the solution pH is 4.5. Under the condition of 45 °C, the current density is 2 mA/cm ² , and the nano-imprinted adhesive after UV imprinting is used as a template barrier layer, and CU760E is used for constant current electrodeposition, and the deposition time is 660 s.

The nano-imprinted rubber barrier is removed using an Alpha microwave plasma stripper to finally obtain a surface-enhanced Raman scattering substrate of ordered gold nanostructures;

Using Q240 Alpha microwave plasma etching machine, after the mushroom array electrodeposition preparation is completed, the nanoimprinting rubber barrier layer is removed, the power is 300W, the process pressure is 20Pa, and the time is 2min, and an ordered gold nano mushroom array is obtained.

The diameter of the mushroom cap portion prepared in this embodiment is about 50-300 nm, and the distance between the caps is about 0-50 nm. The "stalk" height is approximately 10-200 nanometers. The electron micrograph is shown in Figures 4 and 5. The effective area of the mushroom array is about 20 square centimeters.

Example 5

5 uL of a 1 mM aqueous solution of 4-mercaptopyridine was dropped on the surface of the surface-enhanced Raman scattering substrate prepared in Example 3, dried, washed with a large amount of ultrapure water, blown dry with nitrogen, and tested by a portable Raman spectrometer of 785 nm excitation light. The results are shown in Fig. 6. The surface-enhanced Raman spectrum enhancement factor of the 4-mercaptopyridine molecule prepared by the mushroom array substrate was 10 ⁸ .

Example 6

The gold was deposited by electrochemical method, and the deposition potential was controlled by the potentiostatic method, so that the gold deposited in Example 2 grew into a nanopore, and the shape was like a mushroom, specifically.

A saturated sodium sulfite solution containing sodium gold sulfite is used as a plating additive with potassium dihydrogen phosphate (9% by mass) and sodium citrate (4% by mass). The effective mass fraction of gold in the solution is 0.2%, and the solution pH is 4.5. At 45 ° C, constant potential -0.9 V electrodeposition, UV imprinted nanoimprint adhesive as a template barrier, using CHI760E for potentiostatic electrodeposition, deposition time of 400s.

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

Example 7

Basically the same as Embodiment 6, the difference is

Using 3g/L gold potassium cyanide solution as electroplating solution, sodium citrate with mass fraction of 1% as additive, the pH value of the solution is about 4.0, and the effective mass fraction of gold in the solution is 0.2%, at 55 °C, Constant current electrodeposition, current density of 3 mA / cm ² , UV imprinted nanoimprint adhesive as a template barrier, CHI760E for constant current electrodeposition, deposition time of 300s.

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

Example 8

Basically the same as Embodiment 6, the difference is

Using 1 mM aqueous solution of chloroauric acid as the plating solution, sodium perchlorate with 1.5% by mass as the additive, the effective mass fraction of gold in the solution is 0.02%, the pH of the solution is about 2, and the constant potential is 50 °C. Electrodeposition, deposition potential was 0.6V, UV imprinted nanoimprint adhesive as template barrier, CHI760E for constant potential electrodeposition, deposition time of 560s.

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

Example 9

Basically the same as Embodiment 6, the difference is

Using 1 mM aqueous solution of chloroauric acid as the plating solution, the pH 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, the current density is 1.6 mA/cm ² , The nanoimprinted adhesive after UV imprinting is a template barrier layer, and CU760E is used for constant current electrodeposition with a deposition time of 1000 s.

It is to be understood that the above-described embodiments are merely illustrative of the technical solutions of the present invention and are not to be construed as limiting. Modifications or equivalents of the technical solutions of the present invention are intended to be included within the scope of the appended claims.

Industrial applicability

The invention greatly improves the enhancement effect of the Raman scattering signal. The surface enhancement Raman spectrum of the prepared mushroom array substrate for the 4-mercaptopyridine molecule has an enhancement factor of 10 ⁸ .

Claims

A surface-enhanced Raman scattering active substrate characterized by: The flat base layer is provided with a mushroom-shaped nanostructured metal array, and the diameter of the mushroom cap portion is 50-300 nm, and the distance between the caps is 0-50 nm.
The surface-enhanced Raman scattering active substrate according to claim 1, wherein the flat base layer is one of a conductive glass or a glass, a silicon wafer or a quartz wafer on which a metal layer is evaporated.
The surface-enhanced Raman scattering active substrate according to claim 1, wherein the metal of the metal nanostructure array is one or more selected from the group consisting of gold, silver, and copper.
A method for preparing a surface-enhanced Raman scattering active substrate, comprising the steps of:

1) coating a photoresist on the surface of the flat substrate on which the metal layer is evaporated,

2) preparing an ordered nano-via structure on the photoresist by using nanoimprint technology and etching technology;

3) Electrolytic method is used to deposit metal gold, silver or copper at the nano-via, and overflow the pores to form a cap shape, together with a columnar shape at the through hole, and the whole shape is like a mushroom;

4) Removing the nanoimprinted photoresist to obtain a surface-enhanced Raman scattering substrate of an ordered mushroom-like nanostructured metal array.
The method for preparing a surface-enhanced Raman scattering active substrate according to claim 4, wherein the step (2) comprises: using a nanoimprinting system, first adopting a hot imprinting technique, and using a nickel template as a master. The surface nanostructures are copied onto the surface of the polydimethylsiloxane soft film by hot stamping; then the nanoimprint adhesive is spin-coated on the surface of the silicon wafer on which the gold film is evaporated by using a UV embossing technique;

The surface of the nanoimprinted adhesive is UV-imprinted by using a polydimethylsiloxane soft film as a master to obtain a nanopore structure; and the UV-imprinted residual adhesive layer is removed by using a plasma etching machine in the nanopore The bottom is exposed to metal.
The method for preparing a surface-enhanced Raman scattering active substrate according to claim 4, wherein the step (3) comprises: the effective mass fraction of gold in the solution for electrodeposition is 0.01-1%, and the solution PH 1-6, at 20-70 ° C, the UV imprinted nanoimprint adhesive as a template barrier layer for constant current or potentiostatic electrodeposition, deposition time of 300-1200s;

The nanoimprinting rubber barrier layer is removed by using a microwave plasma stripping machine to finally obtain a surface-enhanced Raman scattering substrate of the ordered gold nanostructure;

After the mushroom array electrodeposition preparation is completed by a microwave plasma etching machine, the nanoimprinting rubber barrier layer is removed, and an ordered gold nano mushroom array is obtained.
The method of producing a surface-enhanced Raman scattering active substrate according to claim 6, wherein the current density is 1-5 mA/cm 2 at a constant current.
A method of preparing a surface-enhanced Raman scattering active substrate according to claim 6, wherein the voltage of the constant potential is -2 V to 2 V.
The method for preparing a surface-enhanced Raman scattering active substrate according to claim 4, wherein the flat base layer is one of a conductive glass or a glass, a silicon wafer or a quartz wafer on which a metal layer is vapor-deposited.
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 of gold, silver and copper.