Ag / pdms nanocolumn array sers substrate, preparation method and application

Abstract

The application belongs to the technical field of Raman spectrum detection, and discloses an Ag / PDMS nano pillar array SERS substrate, a preparation method and application. The nano pillar structure of AAO is copied by PDMS, a silver layer is evaporated on the top by using the grazing angle evaporation technology, and finally, the silver layer is broken to form the Ag / PDMS nano pillar array SERS substrate with small gaps by using the thermal expansion effect of PDMS. By adjusting the temperature, SERS substrates with different performances can be obtained. The SERS substrate provided by the application can be applied to a detection chip. The experimental results show that when the concentration of R6G is as low as 10 ‑9 M, the SERS substrate can still detect Raman signals, which indicates that the SERS substrate has the potential for trace detection.

Description

Technical Field

[0001] This invention belongs to the field of Raman spectroscopy detection technology, and particularly relates to an Ag / PDMS nanopillar array SERS substrate, its preparation method and application. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) technology has been widely applied in recent years in fields such as biosensing, energy storage and conversion, and cultural relic detection due to its advantages such as high sensitivity, low detection limit, and rapid operation. The development of SERS technology is inseparable from efficient and stable SERS substrates. Therefore, the preparation of SERS substrates with high sensitivity and good repeatability is both a hot topic and a challenge in the field of SERS technology. Among these, the gap size determines the sensitivity of the SERS substrate. Currently, most methods utilize template methods and photolithography to achieve the formation of the gap size; however, the former cannot achieve precise control of the gap size, while the latter is expensive. Summary of the Invention

[0003] In view of this, the present invention aims to provide an Ag / PDMS nanopillar array SERS substrate, its preparation method, and its application. The Ag / PDMS nanopillar array SERS substrate has the advantages of temperature control, large area, low cost, good uniformity, high detection sensitivity, simple and controllable preparation method, low cost, and wide application.

[0004] To address the above problems, the present invention provides the following technical solution:

[0005] A method for preparing an Ag / PDMS nanopillar array SERS substrate includes the following steps:

[0006] S1. Mix PDMS with curing agent, stir and hydrolyze thoroughly to remove internal air bubbles, then pour into the pores of V-shaped AAO template, dry to cure PDMS, remove AAO template, and obtain PDMS nanopillar array;

[0007] S2. An Ag layer is deposited on the top of the PDMS nanopillar array to obtain a tightly connected Ag / PDMS nanopillar array at the top;

[0008] S3. The tightly connected Ag / PDMS nanopillar array at the top is heated until the top Ag layer just breaks to form a small gap, thus obtaining an Ag / PDMS nanopillar array SERS substrate with a small gap in the top Ag layer.

[0009] Furthermore, in step S1, removing internal air bubbles specifically involves placing the device in a vacuum chamber to remove internal air bubbles.

[0010] Furthermore, in step S1, the AAO template has a lower pore diameter of 100 nm, an upper pore diameter of 450 nm, and a pore depth of 400 nm. The resulting PDMS nanopillar array has an upper diameter of 100 nm, a lower diameter of 450 nm, and a height of 400 nm. Adjacent nanopillars are independent of each other and exhibit large-area uniformity.

[0011] Furthermore, in step S1, the removal of the AAO template specifically involves: using a mixed solution of CuCl2, HCl, and H2O to remove the aluminum substrate of the AAO template, and then using a phosphoric acid solution to remove the aluminum oxide.

[0012] Further, in step S2, the deposition specifically involves: attaching the bottom of the PDMS nanopillar array to a metal plate and placing it 4 cm to the left and 1 cm above the evaporation source, with the evaporation rate controlled at... / S, is deposited using a vacuum thermal deposition evaporation method.

[0013] Furthermore, in step S2, the thickness of the Ag layer is 120 nm.

[0014] Furthermore, in step S3, the heating device is a heating platform with a temperature that can be precisely adjusted between room temperature and 400 degrees Celsius.

[0015] Furthermore, in step S3, the heating specifically involves placing the tightly connected Ag / PDMS nanopillar array on a heating stage and slowly raising the temperature until the Ag layer between the Ag / PDMS nanopillars just breaks to form a small gap, thereby obtaining an Ag / PDMS nanopillar array with a small gap.

[0016] Furthermore, in step S3, the heating specifically involves: slowly raising the temperature to 50°C and then stopping the heating.

[0017] The present invention also provides an Ag / PDMS nanopillar array SERS substrate prepared by the above preparation method.

[0018] The present invention also provides an application of the above-mentioned Ag / PDMS nanopillar array SERS substrate in the preparation of detection chips for detecting single molecules and / or biomolecules.

[0019] Furthermore, this invention provides an application of the above-mentioned Ag / PDMS nanopillar array SERS substrate in the fabrication of a detection chip for detecting R6G, wherein the detection limit is 10⁻⁶. -9 M.

[0020] Compared with existing technologies, the preparation method provided by this invention first uses PDMS to replicate the structure of AAO to form a nanopillar array, then uses grazing angle evaporation technology to deposit a layer of silver on the top of the nanopillars and connect the silver between the pillars, and finally uses heating to cause the PDMS to thermally expand, thereby causing the silver layer between the nanopillars to break and form a small gap, so that the SERS performance of the substrate is maximized. The preparation method provided by this invention can obtain SERS substrates with different properties by controlling the temperature. The preparation method is simple, controllable and easy to achieve large-area preparation. Experimental results show that the SERS substrate performance reaches its maximum at 50℃. We randomly selected 50 points on the sample surface for Raman signal testing and obtained an RSD value of 5.15%, indicating that the substrate has good uniformity. When the R6G concentration is as low as 10 -9 Even at M, Raman signals can still be detected, indicating that the substrate has the potential for trace detection. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram illustrating the fabrication process of the Ag / PDMS nanopillar array SERS substrate provided by the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of the Ag / PDMS nanopillar array SERS substrate provided by the present invention;

[0024] Figure 3 This is a scanning electron microscope (SEM) image of the PDMS nanopillar array obtained in step S2 of Example 1 of the present invention;

[0025] Figure 4 (a) is a scanning electron microscope (SEM) image of the tightly connected Ag / PDMS nanopillar array obtained in step S3 of Example 1 of the present invention;

[0026] Figure 4 (b) is a SEM image of the Ag / PDMS nanopillar array SERS substrate obtained at 75°C in Example 3;

[0027] Figure 5 This is a schematic diagram of the relative position of the sample to the evaporation source in step S3 of embodiment 1 of the present invention.

[0028] Figure 6The 10 N / A nanopillar array SERS substrate measured at different temperatures in Examples 1-6 of this invention is an example of this invention. -5 Raman spectra of Rhodamine 6G probe molecules at concentration M; wherein, (a) shows the Raman spectral measurement results obtained at different temperatures in Examples 1-6, and (b) shows the temperature on the horizontal axis and the highest peak of the Raman signal (621 cm⁻¹) on the vertical axis. -1 The plot shows the relationship between the Raman signal and temperature.

[0029] Figure 7 (a) shows the 10 ohms measured at 50 points on the Ag / PDMS nanopillar array SERS substrate obtained in Example 1 of this invention. -5 (a) is the Raman spectrum of Rhodamine 6G probe molecule at concentration M; (b) is the Raman spectrum at 621 cm⁻¹. -1 Raman intensity statistics of the R6G characteristic peak;

[0030] Figure 8 (a) Raman spectra of different concentrations of Rhodamine 6G probe molecules measured on the Ag / PDMS nanopillar array SERS substrate obtained in Example 1 of this invention; (b) 621 cm⁻¹ -1 Quantitative relationship between SERS intensity at characteristic peak and corresponding concentration. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention provides a method for preparing an Ag / PDMS nanopillar array SERS substrate, the process of which is illustrated in the schematic diagram below. Figure 1 As shown, it includes the following steps:

[0033] S1. Mix PDMS with the curing agent, stir thoroughly to hydrolyze, and place in a vacuum chamber to remove internal air bubbles. Pour the prepared PDMS into the holes of the V-shaped AAO template and place in a drying oven to allow the PDMS to fully cure; the preferred AAO template model is VS450-100-400 (lower pore diameter 100nm, upper pore diameter 450nm, pore depth 400nm).

[0034] S2. Take out the cured sample, use a mixed solution of CuCl2, HCl and H2O to remove the aluminum substrate of the AAO template, and then use phosphoric acid solution to remove the alumina to obtain the PDMS nanopillar array;

[0035] S3. An Ag / PDMS nanopillar array was obtained using a grazing angle evaporation technique. At a specific grazing angle, Ag was deposited on the top of the PDMS nanopillars, resulting in a tightly connected Ag / PDMS nanopillar array; the preferred evaporation rate was... / s;

[0036] S4. Place the prepared Ag / PDMS nanopillar array on a heating stage and slowly raise the temperature until the Ag layer between the Ag / PDMS nanopillars just breaks to form small gaps, thus obtaining an Ag / PDMS nanopillar array with small gaps. The structural schematic diagram is shown below. Figure 2 As shown.

[0037] Materials preparation: Cut AAO into 0.5cm x 0.5cm square AAO pieces; prepare PDMS, curing agent, and petri dishes.

[0038] Example 1

[0039] S1. Mix PDMS with the curing agent, stir thoroughly to hydrolyze, and place in a vacuum chamber to remove internal air bubbles. Pour the prepared PDMS into the holes of the V-shaped AAO template and place in a drying oven to allow the PDMS to fully cure.

[0040] S11. Place the small AAOs face up evenly in the petri dish;

[0041] S12. Slowly drip the mixed PDMS reagent (PDMS and curing agent in a 6:1 ratio) onto each small AAO using a dropper until it is submerged;

[0042] S13. Place the petri dish containing small AAOs into a drying oven at 60 degrees Celsius and dry for 4 hours.

[0043] S2. Remove the cured sample, remove the aluminum substrate of the AAO template using a mixed solution of CuCl2, HCl, and H2O, and then remove the alumina using a phosphoric acid solution to obtain a PDMS nanopillar array.

[0044] S21. Use a knife to remove the small AAO from the petri dish, scrape off the PDMS on the back of each template and stick tape on the PDMS on the front of each template to distinguish the front and back;

[0045] S22. Take 3.4g CuCl2, 75mL HCl and 100mL H2O to prepare an aluminum removal solution. Place the small AAO in the aluminum removal solution until the small AAO becomes transparent, then take it out and put it into ultrapure water.

[0046] S23. Prepare a 5% phosphoric acid solution. Transfer small AAO particles from ultrapure water to the phosphoric acid solution, heat in a 30°C water bath for 24 hours, then remove and dry to form a uniform and ordered PDMS nanopillar array. Its SEM image is shown below. Figure 3 .

[0047] S3. An Ag / PDMS nanopillar array was obtained using a grazing angle evaporation technique. At a 75-degree evaporation angle, Ag was deposited on the top of the PDMS nanopillars, resulting in a tightly connected Ag / PDMS nanopillar array.

[0048] S31. Open the vacuum chamber, attach the prepared sample to the metal plate, and place it 4cm to the left and 1cm above the vapor deposition source. The specific position is as follows: Figure 5 As shown;

[0049] S32. Close the vacuum chamber, turn on the mechanical pump, and open the pre-evacuation valve;

[0050] S33. After the vacuum level reaches 1 Pa, open the solenoid valve.

[0051] S34. After the rotation speed reaches 3000r, close the pre-extraction valve and open the slide gate valve;

[0052] S35. Wait for the vacuum level to reach 8×10⁻⁶. -4 Then, turn on the current and start the rotary evaporation, controlling the evaporation rate at 0.2A / s;

[0053] S36. After the Ag layer reaches a deposition thickness of 120 nm, turn off the evaporation according to the specified sequence and remove the sample, which is a tightly connected Ag / PDMS nanopillar array. If the Ag layer is not connected, a second evaporation is required until the Ag layer is connected. The SEM image is shown below. Figure 4 (a).

[0054] S4. Place the prepared Ag / PDMS nanopillar array on a heating stage and slowly raise the temperature to 50℃. The Ag layer between the Ag / PDMS nanopillars breaks to form small gaps, thus obtaining an Ag / PDMS nanopillar array with small gaps.

[0055] Example 2

[0056] The other steps are the same as in Example 1, except that the temperature in step S4 is changed to 25°C.

[0057] Example 3

[0058] The other steps are the same as in Example 1, except that the temperature in step S4 is changed to 75°C.

[0059] It should be noted that because PDMS is elastic, it expands when heated to 50 degrees Celsius. However, when the temperature returns to room temperature for testing, the PDMS will recover to a certain state due to its elasticity. Although the gaps still exist, they are not visible under an electron microscope. However, when heated to 75 degrees Celsius, the strain of PDMS exceeds the maximum value of its elastic modulus, thus losing its elasticity. Even when the temperature returns to room temperature, PDMS will not deform, which can be observed under an electron microscope. The SEM image of the Ag / PDMS nanopillar array morphology at 75 degrees Celsius is shown below. Figure 4 (b)

[0060] Example 4

[0061] The other steps are the same as in Example 1, except that the temperature in step S4 is changed to 100℃.

[0062] Example 5

[0063] The other steps are the same as in Example 1, except that the temperature in step S4 is changed to 125°C.

[0064] Example 6

[0065] The other steps are the same as in Example 1, except that the temperature in step S4 is changed to 150°C.

[0066] Test Example 1

[0067] 20 μl of 10 was added to each of the samples from Examples 1-6. -5 The R6G probe molecule of M was dried and then the Raman signal was measured using a Raman spectrometer with a laser wavelength of 785 nm and a power of 10 mW. The measurement results are as follows: Figure 6 As shown, (a) shows the Raman spectral measurement results obtained at different temperatures in Examples 1-6, and (b) shows the temperature on the horizontal axis and the highest peak of the Raman signal (621 cm⁻¹) on the vertical axis. -1 The plot shows the relationship between the Raman signal and temperature. Figure 6 This indicates that the sample strength at 50℃ is stronger than that at other temperatures, and the sample signal becomes weaker as the temperature exceeds 50℃.

[0068] Test Example 2

[0069] Add 20 μl of the sample from Example 1. -5 After drying, the R6G probe molecules were dissolved at a concentration of mg / ml and the Raman signal was measured using a 785 nm, 10 mW Raman spectrometer. The signals were measured at 50 different points on the sample, and plotted as shown below. Figure 7 The RSD plot shown reflects the homogeneity of the sample.

[0070] Test Example 3

[0071] 20 μl of rhodamine (R6G) probe molecules of different concentrations were dropped onto the surface of the sample obtained in Example 1. After drying, the Raman signal was measured using a Raman spectrometer with a laser wavelength of 785 nm and a power of 10 mW. The measurement results are as follows. Figure 8 As shown. Figure 8 This indicates that its lowest detection limit can detect 10. -9 M.

[0072] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an Ag / PDMS nanopillar array SERS substrate, characterized in that, The method comprises the following steps: S1. mixing PDMS with a curing agent, stirring sufficiently to hydrolyze, removing internal bubbles, and then pouring into the holes of a V-shaped AAO template, drying and curing, removing the AAO template, and obtaining a PDMS nanocolumn array; S2. depositing an Ag layer on the top end of the PDMS nanocolumn array by using a glancing angle evaporation technique to obtain a top closely connected Ag / PDMS nanocolumn array, wherein the thickness of the Ag layer is 120 nm; S3. heating the top closely connected Ag / PDMS nanocolumn array to make the top Ag layer just break to form small gaps, and obtaining an Ag / PDMS nanocolumn array SERS substrate with small gaps in the top Ag layer.

2. The production method according to claim 1, characterized by, The lower aperture of the AAO template is 100 nm, the upper aperture is 450 nm, and the hole depth is 400 nm.

3. The preparation method according to claim 1, characterized in that, In step S2, the deposition is specifically as follows: the bottom of the PDMS nanocolumn array is attached to a metal plate and placed at the left side of the evaporation source at 4 cm and 1 cm above, the evaporation rate is controlled at 0.2 Å / S, and vacuum thermal deposition is used for deposition.

4. The method of claim 1, wherein, In step S3, the heating is as follows: slowly heating to 50℃.

5. The Ag / PDMS nanocolumn array SERS substrate prepared by the preparation method according to any one of claims 1-4.

6. Application of the Ag / PDMS nanocolumn array SERS substrate of claim 5 in the preparation of a detection chip for detecting a single molecule level and / or a biomolecule level.

7. The use of the Ag / PDMS nanopillar array SERS substrate of claim 5 in the preparation of a detection chip for detecting R6G, wherein the detection limit of the detection is 10 -9 M.

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