CN105129724A - Manufacturing method of surface-enhanced Raman scattering (SERS) substrate - Google Patents

Abstract

The invention provides a preparation method of a surface-enhanced Raman scattering substrate. The preparation method includes: step A: obtaining a high molecular polymer film, the composition of which is a high molecular polymer material that can be etched by oxygen plasma; step B: performing oxygen plasma on the high molecular polymer film Bulk etching treatment to form a vertically upward array of nanorods; and step C: covering the surface of the nanorod array with a metal layer with surface-enhanced Raman scattering activity to form an upwardly-arranged metal nanorod array to complete the surface-enhanced Raman Preparation of scattering substrates. In the present invention, the size and gap of metal nanorods can be controlled at the nanoscale, so that the prepared SERS substrate has a larger specific surface area, which is beneficial to the adsorption of molecules to be tested, and is beneficial to the reduction of light reflectance and the reduction of metal nanorods. The mutual coupling of the electric fields between them enables the SERS substrate to achieve a greater improvement in the enhancement effect of Raman scattering.

Description

Preparation method of surface-enhanced Raman scattering substrate

technical field

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

Background technique

Surface-enhanced Raman scattering (SERS), as an analytical technique, has important application potential in chemical analysis and biological detection. The substrate with higher enhancement effect, lower detection limit and better consistency is the basis for its application.

At present, the widely recognized SERS enhancement mechanisms mainly include electromagnetic enhancement and chemical enhancement, and electromagnetic enhancement is the main reason. The effect of electromagnetic enhancement mainly depends on the surface plasmon oscillation of the metal, so the surface structure with rough structure and electric field coupling between metal particles is most suitable for SERS substrates.

Utilizing silicon and aluminum to prepare rough structures and using them as templates to realize the preparation of metal structures is a common preparation method at present (see references 1 and 2). For example, reference 2 discloses that aluminum with pits is used as a template to deposit a gold film, and then the aluminum template is removed and turned over to obtain a structurally ordered and controllable SERS substrate. These preparation methods have achieved good enhancement effects, but the preparation methods are relatively complex and time-consuming, and some methods have poor regulation of the local electric field intensity on the metal surface.

Using polymers to prepare SERS structures is a relatively novel preparation method. Due to the characteristics of strong plasticity and easy processing, organic polymers have attracted the attention of researchers. For example, reference 3 discloses a method of embossing a pattern of polymer material and evaporating metal to prepare a SERS substrate. Since these methods utilize polymers to prepare rough structures, the preparation process will be relatively simple and fast. Polymers that have been used to prepare SERS substrates include polymethyl methacrylate PMMA (reference 4), dimethylsiloxane PDMS (reference 5) and so on. However, the required imprint templates still need to undergo relatively complicated processing, and it is difficult to control the metal structures prepared by these methods at the nanoscale.

Plasma surface treatment is a more commonly used surface treatment technology. After plasma treatment, polymethylsiloxane (reference 6), polymethyl methacrylate (reference 7) and polystyrene (reference 8) Nanostructures will appear on the surface of other polymers. At present, plasma treatment of organic surfaces is mainly used to improve the hydrophobicity of organic surfaces and reduce light reflection and other characteristics. However, there are few reports on the use of plasma to treat polymers to obtain nanostructures and prepare nanofunctional materials. Reference 9 used plasma to treat an array of polystyrene beads and sputtered metal on its surface to obtain a SERS substrate. Although this patent utilizes plasma treatment, it only utilizes the etching on the side of the polystyrene pellets to adjust the distance between the pellets.

Reference 1: Patent CN200810100562;

Reference 2: Patent CN201310130493

Reference 3: Patent CN201310032239

Reference 4: Patent CN201310316980

Reference 5: Patent CN201210543908

Reference 6: Plasma Process. Polym. 2007, 4: 98-405; Nanotechnology 2006, 17: 3977-3983

Reference 7: PlasmaProcess.Polym.2007, 4:S878-S881

Reference 8: PS, Langmuir2008, 24:5044-5051

Reference 9: Patent CN201110115269

Contents of the invention

(1) Technical problems to be solved

In view of the above technical problems, the present invention provides a method for preparing a surface-enhanced Raman scattering substrate, so as to realize the adjustment of the size and spacing of metal nanorods.

(2) Technical solutions

The preparation method of the surface-enhanced Raman scattering substrate of the present invention comprises: step A: obtaining a high molecular polymer film, and the composition of the high molecular polymer film is a high molecular polymer material capable of oxygen plasma etching; step B: performing oxygen plasma etching on the polymer film to form a vertically upwardly aligned nanorod array; and step C: covering the surface of the nanorod array with a metal layer having surface-enhanced Raman scattering activity to form an upwardly aligned metal layer Nanorod arrays are prepared to complete the surface-enhanced Raman scattering substrate.

(3) Beneficial effects

It can be seen from the above technical scheme that in the preparation method of the surface-enhanced Raman scattering substrate of the present invention, since the size of the metal nanorods can be controlled at the nanometer scale, the prepared SERS substrate has a larger specific surface area, which is beneficial to the detection of molecules to be detected. of adsorption. In addition, the spacing of metal nanorod arrays can also be controlled at the nanometer scale, which is beneficial to the reduction of light reflectivity and the mutual coupling of the electric field between metal nanorods. Therefore, the SERS substrate prepared by this method can greatly improve the enhancement effect of Raman scattering.

Description of drawings

1A is a flowchart of a method for preparing a surface-enhanced Raman scattering substrate according to an embodiment of the present invention;

FIG. 1B and FIG. 1C are perspective views and cross-sectional views of the device after each step is performed using the preparation method shown in FIG. 1A;

Fig. 2 is the SEM photo of the longitudinal section of the silver nanorod array prepared by the preparation method shown in Fig. 1A;

Fig. 3 is the SEM photo of the surface of the silver nanorod array finally formed by different oxygen plasma etching treatment time in step B under the situation of adopting polyimide film;

Fig. 4 is the SEM photo of the finally formed silver nanorod array surface of different metal sputtering thicknesses in step C;

FIG. 5 is a SEM photo of the surface of the silver nanorod array finally formed in step B with different oxygen plasma etching treatment times in the case of using a polyvinylidene fluoride film.

Detailed ways

The invention can realize the adjustment of the metal nanorod gap by adjusting the oxygen plasma etching treatment time and the sputtering metal thickness; the adjustment of the metal nanorod diameter can be realized by changing the sputtering thickness.

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

In the first exemplary embodiment of the present invention, a method for preparing a surface-enhanced Raman scattering substrate is provided. FIG. 1A is a flowchart of a method for preparing a surface-enhanced Raman scattering substrate according to an embodiment of the present invention. As shown in Figure 1A, the preparation method of the surface-enhanced Raman scattering substrate in this embodiment includes:

Step A: making a high molecular polymer film on the substrate, as shown in (A) in Figure 1B and Figure 1C;

In this embodiment, a silicon wafer is used as the substrate, and a polyimide film is used as the polymer film. The preparation process of the polyimide film is as follows: first drop the polyimide solution on the silicon wafer with a clean surface, and use a spin coater to rotate at a rate of 1200r/min for one minute; then place the film at 80°C Dry for 2 hours under ambient conditions to form a polyimide film on the surface of the silicon wafer.

It should be clear to those skilled in the art that in addition to silicon substrates, hard substrates such as ceramic sheets, glass sheets, and organic glass plates can also be used, and in addition to polyimide (PI) films, polyvinylidene fluoride can also be used. Polymer films such as ethylene, polystyrene, polymethyl methacrylate, and polyethylene terephthalate. In addition to the above-mentioned spin-coating method, the method for preparing the polymer film may also be a film-drawing method. In addition, in addition to using polymer solutions to prepare films, finished membranes of polymers such as polyimide, polyvinylidene fluoride, polystyrene, polymethyl methacrylate, and polyethylene terephthalate can also be used. Used as a template material, in which case a substrate can be omitted.

Step B: performing oxygen plasma etching treatment on the polymer film to form a vertically upward array of nanorods, that is, the SERS substrate template, as shown in Figure 1B and (B) in Figure 1C;

In this embodiment, a silicon wafer with a polyimide film on the surface is placed in a reactive ion etching machine, and the surface of the polyimide film is etched using oxygen plasma treatment technology. It was carried out in an etching machine, the RF power frequency was 13.56MHz, the oxygen flow rate was 30mL/min, the reaction chamber pressure was 3Pa, the RF coupling power was 100W, and the processing time was 60s.

Wherein, the spacing between the nanorods in the nanorod array can be adjusted by changing the oxygen plasma etching treatment time. The nanorod arrays formed with different oxygen plasma etching treatment times will be presented in subsequent embodiments. In the nanorod array, the diameter of the nanorod is about 20-30nm, the cross-sectional shape is circular, and the distance between adjacent nanorods is less than 80nm.

Step C: sputtering a metal layer with SERS activity on the surface of the nanorod array of the SERS substrate template to form an upwardly arranged metal nanorod array, and complete the preparation of the surface-enhanced Raman scattering substrate, as shown in Figure 1B and Figure 1C ( C) as shown.

In this embodiment, the polyimide film after oxygen plasma treatment is used as a template, and silver is sputtered on its surface, wherein the sputtering power is 100W, the chamber atmosphere is argon, and the chamber pressure is 0.5Pa. The thickness is 20nm. The SEM image of the longitudinal section of the prepared silver nanorod array is shown in Fig. 2 .

Among them, the diameter of the metal nanorods can be adjusted by changing the thickness of the sputtered metal. Generally, the thickness of the sputtered metal is less than 90nm. After sputtering, the diameter of the metal nanorods is between 30nm and 80nm, and the gap between adjacent metal nanorods is between 5nm and 50nm. In addition to silver, metal materials with SERS activity such as gold and copper can also be used.

In the second embodiment of the present invention, another method for preparing a surface-enhanced Raman scattering substrate is also provided. The process of this embodiment is similar to that of the first embodiment, the difference lies in the time of the oxygen plasma etching treatment in step B.

FIG. 3 is a SEM photo of the surface of the silver nanorod array finally formed in step B with different oxygen plasma etching treatment times in the case of using a polyimide film. Among them, (a), (b), (c), (d) are scanning electron micrographs of silver nanorod arrays with oxygen plasma treatment time of 15s, 30s, 45s and 60s, respectively. It can be seen that the gap of the nanorod array can be adjusted by changing the oxygen plasma etching treatment time.

In the third exemplary embodiment of the present invention, another method for preparing a surface-enhanced Raman scattering substrate is provided. The process of this embodiment is similar to that of the first embodiment, the difference lies in the thickness of the sputtered metal in step C.

FIG. 4 is a SEM photo of the surface of the finally formed silver nanorod array with different metal sputtering thicknesses in step C. Wherein, the sputtering thicknesses of figures (a), (b), (c) and (d) are 30nm, 50nm, 70nm and 90nm respectively. It can be seen that the diameter of the metal nanorods can be adjusted by changing the thickness of the sputtered metal. It should be noted that the thickness of the metal attached to the sidewall of the nanorod is smaller than the thickness of the metal in the vertical direction, as shown in (C) in FIG. 1C .

In the fourth exemplary embodiment of the present invention, another method for preparing a surface-enhanced Raman scattering substrate is provided. The process of this embodiment is similar to that of the first embodiment, except that the polymer film in step A is a polyvinylidene fluoride film, and the oxygen plasma etching treatment in step B is changed.

FIG. 5 is a SEM photo of the surface of the silver nanorod array finally formed in step B with different oxygen plasma etching treatment times in the case of using a polyvinylidene fluoride film. Among them, (a), (b), (c), (d) are scanning electron micrographs of silver nanorod arrays with oxygen plasma treatment time of 15s, 30s, 45s and 60s, respectively. It can be seen that the gap of the nanorod array can be adjusted by changing the oxygen plasma treatment time.

So far, four embodiments of the present invention have been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the preparation method of the surface-enhanced Raman scattering substrate of the present invention.

It should be noted that, in the accompanying drawings or in the text of the specification, implementations that are not shown or described are forms known to those of ordinary skill in the art, and are not described in detail. In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and those of ordinary skill in the art can easily modify or replace them, for example:

(1) In step A, in addition to the film drawing method and the spin coating method, other methods can also be used to prepare the polymer film. Even if the spin coating method is used, the process parameters therein can also be adjusted as required, For example: dry the spin-coated polyimide film, the drying temperature is 50-250 ℃, and the holding time is ≥1h;

(2) In step B, the process parameters of the oxygen plasma etching treatment can be adjusted as needed, for example: the reaction chamber pressure is 3Pa, the RF coupling power is between 50W-200W, and the processing time t satisfies: 1s≤t≤60s ;

(3) In step C, the method of sputtering the metal film can be magnetron sputtering, pulsed laser deposition, electron beam evaporation and the like.

To sum up, the present invention utilizes oxygen plasma etching to treat the polymer surface and obtain metal nanorod arrays arranged vertically upward. The gap between the metal nanorods can be adjusted by changing the oxygen plasma treatment time and the thickness of the sputtered metal, and the diameter of the metal nanorods can be adjusted by changing the thickness of the metal sputtering. The adjusted metal nanorod gap and The diameter of metal nanorods can be controlled at the nanoscale. The method is relatively simple in technology and fast in processing, and has great application potential in the field of surface-enhanced Raman scattering technology.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A method for preparing a surface-enhanced Raman scattering substrate, comprising: Step A: obtaining a high molecular polymer film, the composition of which is a high molecular polymer material capable of oxygen plasma etching; Step B: performing oxygen plasma etching on the polymer film to form a vertically upward array of nanorods; and Step C: covering the surface of the nanorod array with a metal layer having surface-enhanced Raman scattering activity to form an upwardly aligned metal nanorod array, and completing the preparation of the surface-enhanced Raman scattering substrate. 2. The preparation method according to claim 1, characterized in that, in the step B, the distance between adjacent nanorods in the nanorod array is adjusted by changing the oxygen plasma etching treatment time. 3. The preparation method according to claim 2, wherein, in the nanorod array, the diameter of the nanorods is between 20nm and 30nm, and the cross-sectional shape is circular; the distance d1 between adjacent nanorods satisfies : 10nm≤d1≤80nm. 4. The preparation method according to claim 2, characterized in that, said step B comprises: putting the high molecular polymer film into a reactive ion etching machine, utilizing an oxygen plasma treatment method to treat the surface of the high molecular polymer film to etch; Wherein, the process parameters of the reactive ion etching are as follows: RF power frequency is 13.56MHz, oxygen flow rate is 30mL/min, reaction chamber pressure is 3Pa, RF coupling power is between 50W and 200W, and processing time t satisfies: 1s≤ t≤60s. 5. The preparation method according to claim 1, characterized in that, in the step C, the diameter of the metal nanorods is adjusted by changing the thickness of the covering metal layer. 6. The preparation method according to claim 5, wherein the thickness d of the metal layer satisfies: 10nm≤d≤90nm; In the metal nanorod array, the gap d2 between adjacent metal nanorods is between 5nm and 50nm. 7. The preparation method according to claim 1, characterized in that, in the step C, the metal having surface-enhanced Raman scattering activity is: gold, silver or copper; The surface of the nanorod array is covered with a metal layer having surface-enhanced Raman scattering activity by one of the following methods: magnetron sputtering, pulsed laser deposition and electron beam evaporation. 8. according to the preparation method described in any one in claim 1 to 7, it is characterized in that, the approach that obtains high molecular polymer film in described step A is: making a thin film of said high molecular polymer material on a rigid substrate; or A film of the high molecular polymer material is used as the high molecular polymer film. 9. The preparation method according to claim 8, wherein the polymer material is one of the following materials: polyimide, polyvinylidene fluoride, polystyrene, polymethacrylate esters and polyethylene terephthalate. 10. The preparation method according to claim 8, characterized in that, the high molecular polymer film is obtained by making a thin film of high molecular polymer material on a hard substrate; Wherein, the method of making the thin film of polymer material is spin coating method or film pulling method, and the hard substrate is one of the following substrates: silicon wafer, ceramic wafer, glass wafer and plexiglass plate.