Three-dimensional SERS substrate based on ABS material and preparation and application thereof

Abstract

The invention discloses a preparation method of a three-dimensional SERS (Surface Enhanced Raman Scattering) substrate based on an ABS (Acrylonitrile Butadiene Styrene) material. The preparation method comprises the following steps: S1, forming a three-layer hierarchical structure by utilizing femtosecond laser; step S2, forming a single-layer 15 [mu] m PS microsphere array; step S3, forming a single-layer 600 nm PS (Poly Styrene) microsphere array; step S4, ICP etching is carried out; and S5, electron beam evaporation is conducted. According to the three-dimensional SERS substrate provided by the invention, a method in which femtosecond laser processing and ICP etching are mutually matched is adopted, the process is simple, the SERS substrate can be rapidly prepared in a large scale, meanwhile, the substrate has the advantages of being good in enhancement effect, high in repeatability, stable in property and the like, and a feasible method is provided for rapid and sensitive detection of trace substances.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano sensing technology. Specifically, the present invention relates to a three-dimensional SERS substrate based on ABS material and its preparation and application. Background Art

[0002] The Raman effect, also known as Raman scattering, was discovered by Indian physicist CV Raman in an experiment in 1928. When light radiates into a medium, it causes the charged particles in the medium to be forced to vibrate, and radiate to the surroundings to form scattering. If the photons of radiation energy collide inelastically with the electrons in the molecules, the frequency of the scattered light is different from the frequency of the incident light. This scattered light is called Raman scattering. However, the Raman scattering effect is very weak and its application is relatively limited. In 1977, Jeanmaire and Van Duyne, Albrecht and Creighton and others improved the experiment and found that by increasing the specific surface area of ​​the rough silver electrode by 10 times, the Raman scattering signal of the pyridine molecules adsorbed on the rough silver surface was enhanced by 6 orders of magnitude compared with the Raman scattering signal of the pyridine molecules in the solution phase. They called this enhancement effect the surface enhanced Raman scattering effect (SERS), and the corresponding spectrum was called the surface enhanced Raman spectrum.

[0003] Surface-Enhanced Raman Spectroscopy (SERS) is a powerful tool for identifying trace substances through vibrational fingerprints, with high sensitivity and excellent multiplex detection capabilities. It usually relies on the plasma coupling of metal nanoparticles to generate local hot spots with high electric field strength, especially when biochemical molecules are confined to SERS "hot spots", single molecule detection can be achieved.

[0004] In the prior art, most of the processing techniques in the SERS substrate manufacturing process are high in cost and demanding in processing conditions, and the SERS detection sensitivity is relatively insufficient.

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to solve the problems of high cost and harsh processing conditions of most processing techniques in the substrate production process, and to provide a femtosecond laser processing method, which is reasonably combined with inductively coupled plasma etching (ICP) technology to prepare a new SERS substrate with good enhancement effect, high repeatability and stable properties, which is used for high-sensitivity detection of trace targets.

[0007] To achieve the above purpose, the technical solution provided by the present invention is:

[0008] A three-dimensional SERS substrate based on ABS material, wherein the SERS substrate is an ABS bottom material 1 on which at least three levels of hierarchical structures 2 are arrayed, wherein adjacent interlayer regions 3 of the hierarchical structures 2 are arranged with single-layer PS beads 4, and PS microspheres 5 with gold films evaporated on the surfaces of the PS beads 4 are arranged on the upper portions of the PS beads 4.

[0009] The hierarchical structure 2 is a concentric rectangle or circle.

[0010] The present invention also provides a method for preparing a three-dimensional SERS substrate based on ABS material, comprising the following steps:

[0011] Step S1, selecting and preparing base materials;

[0012] Select ABS material for cleaning and drying;

[0013] Step S2, processing of hierarchical structure 2;

[0014] Placing the ABS material in step S1 on a femtosecond laser processing platform, setting processing parameters and processing patterns, and using femtosecond laser processing to form a hierarchical structure 2 of three or more layers;

[0015] Step S3, preparation of a single-layer PS ball 4;

[0016] In the interlayer region 3 adjacent to the hierarchical structure 2 on the ABS material processed in step S2, a single-layer array of PS beads 4 is formed;

[0017] Step S4, preparation of a single-layer PS microsphere 5;

[0018] A single layer of PS microspheres 5 array is formed on the upper part of the PS beads 4 processed in step S3;

[0019] Step S5, ICP etching;

[0020] The ABS material substrate obtained in step S4 is placed in an inductively coupled plasma etching machine, and ICP etching is performed using the chemical reaction and physical action of the plasma;

[0021] Step S6, surface evaporation;

[0022] The ABS material substrate obtained in step S5 is subjected to gold film deposition on the surface using an electron beam vacuum coating apparatus to complete the preparation.

[0023] Preferably,

[0024] In the step S1, the thickness of the ABS material is selected to be 280-320 μm, and the cleaning work is specifically as follows: the ABS material is ultrasonically cleaned in 98% alcohol for three times, each time for 20 minutes, for a total of 60 minutes; the ABS material is taken out and ultrasonically cleaned in deionized water for three times, each time for about 20 minutes, for a total of 60 minutes.

[0025] Preferably,

[0026] In step S2, the specific process of using femtosecond laser to process ABS material is as follows:

[0027] Use Pharos software to set the femtosecond laser light source to a repetition frequency of 10kHz, use the concentric rectangles or circles drawn in EzCad2 software, set the scanning speed to 5mm / s, and set a 0.005mm straight line to fill the adjacent layer height area. After the settings are completed, enter the execution processing command and repeat the array processing for the number of layer heights; ultrasonically treat the processed ABS material for about 15 minutes, then continue to wash it with deionized water and let it air dry naturally.

[0028] Preferably,

[0029] In the step S3, the forming of a single-layer PS ball array is specifically as follows:

[0030] The glass sheets used for laying the balls are first cleaned, then subjected to hydrophilic treatment, vacuumed using a plasma cleaning machine, and treated with oxygen plasma;

[0031] The PS beads were self-assembled and laid flat on a glass slide to form a single layer, and the mixing ratio of the PS beads to ethanol was 3:1;

[0032] Finally, the single layer of PS beads on the glass slide was transferred to the ABS, and the surfactant used was TX-100 diluted 4 times.

[0033] Preferably,

[0034] The mixing ratio of PS beads and ethanol used to form the monolayer PS microsphere array is 1:1, and the surfactant used is 20-fold diluted TX-100.

[0035] Preferably,

[0036] In the step S4, the mixing ratio of PS beads and ethanol used to form the monolayer PS microsphere array is 1:1, and the surfactant used is 20-fold diluted TX-100.

[0037] Preferably,

[0038] In the step S5, the ABS material is subjected to ICP etching, and the processed ABS material is placed in an inductively coupled plasma etching machine, the upper radio frequency is set to 100W, the lower radio frequency is set to 100W, and the process time is set to 60s;

[0039] In step S6, the gold film is evaporated by using an electron beam evaporation device to deposit a gold film with a thickness of 45 to 55 nm on the surface of the substrate at a gold evaporation rate of 0.04 to 0.05 nm·s -1 .

[0040] Preferably,

[0041] The method further comprises step S7 of performing SERS detection on the prepared substrate;

[0042] The detection step is: adding the prepared SERS substrate to -5 mol / L MGITC solution for 2-3 hours, take out and rinse, and then soak in 10 -6 ~10 -12 mol / L MGITC solution for 2-3 h; SERS measurements were performed on a Renishaw Invia Raman microscope system using a 633 nm HeNe laser, a charge-coupled device camera, and a spectral resolution of 1 cm -1 1800 grooves / mm grating; laser is focused onto the sample through a 20× microscope objective; the accumulation times, exposure time and laser power of each sample are 3 times, 3s and 10% respectively; background subtraction and smoothing are performed on the collected Raman spectra as the final SERS results.

[0043] The present invention also provides an application of a three-dimensional SERS substrate based on ABS material in trace detection.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The substrate preparation uses a method in which femtosecond laser processing and ICP etching cooperate with each other. The process is simple and can prepare SERS substrates quickly and in large quantities, which can further improve the processing efficiency of the substrate. At the same time, the selected substrate material is economical and applicable.

[0046] 2. The three-dimensional structure of ABS material is formed by femtosecond laser processing. The substrate has the advantages of good enhancement effect, high repeatability and stable properties. It can improve the sensitivity of SERS detection and perform sensitive detection of trace substances, providing a feasible method for achieving high-sensitivity SERS detection.

[0047] Terminology explanation:

[0048] ABS material - acrylonitrile butadiene styrene copolymer;

[0049] ICP etching - inductively coupled plasma etching technology;

[0050] PS microspheres——polystyrene microspheres;

[0051] MGITC solution – malachite green isothiocyanate solution;

[0052] TX diluent——TritonX-100. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a schematic diagram of the overall structure of a three-dimensional SERS substrate based on ABS material of the present invention;

[0054] Figure 2 for Figure 1 Schematic diagram of the middle level structure;

[0055] Figure 3 for Figure 2 Schematic diagram of PS balls;

[0056] Figure 4 The preparation flow chart of the three-dimensional SERS substrate of the present invention;

[0057] Figure 5 It is a structural diagram of the preparation process of the three-dimensional SERS substrate of the present invention;

[0058] Figure 6 To detect the uniformity and repeatability of three-dimensional SERS substrates;

[0059] Figure 7 This is the SERS spectrum of direct detection of MGITC concentration gradient. DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings.

[0061] Figure 1 is a schematic diagram of the overall structure of a three-dimensional SERS substrate based on ABS material of the present invention, Figure 2 for Figure 1 Schematic diagram of the middle level structure, Figure 3 for Figure 2 Schematic diagram of PS balls in Figure 1 , Figure 2 , Figure 3As shown in the figure, the three-dimensional SERS substrate based on ABS material of the present invention is that on the ABS bottom material 1, an array of at least three-level hierarchical structures 2 are arranged, and three layers are preferably arranged in this embodiment. In the adjacent interlayer regions 3 of the hierarchical structure 2, that is, between the first layer and the second layer, and between the second layer and the third layer, a single layer of PS beads 4 is arranged, and PS microspheres 5 with a gold film evaporated on the surface are arranged on the upper part of the PS beads 4.

[0062] The hierarchical structure 2 is a concentric rectangle or circle. The rectangle includes but is not limited to a square, a rhombus, etc. This embodiment uses concentric squares with side lengths of 60 μm, 260 μm and 460 μm.

[0063] Figure 1 The preparation flow chart of the three-dimensional SERS substrate based on ABS material of the present invention specifically includes the following steps:

[0064] Step S1, selecting ABS material with a thickness of 280-320 μm, and performing cleaning and drying operations;

[0065] The ABS material was ultrasonically cleaned in 98% alcohol for three times, each time for about 20 minutes, for a total of 60 minutes. Then the ABS material was taken out and ultrasonically cleaned in deionized water for three times, each time for about 20 minutes, for a total of 60 minutes.

[0066] Step S2, using a femtosecond laser to process the ABS material to form a three-layer hierarchical structure;

[0067] According to the femtosecond laser direct writing processing method, the femtosecond laser light source was set to a repetition frequency of 10 kHz using the Pharos software, and concentric squares with side lengths of 60 μm, 260 μm, and 460 μm were drawn using the EzCad2 software. The scanning speed was set to 5 mm / s, and a 0.005 mm straight line was set to fill the area outside the square. After the settings were completed, the execution processing command was entered, and the concentric square array processing was repeated three times.

[0068] Femtosecond laser processing of ABS materials is mainly divided into two parts. The first part is ionization, which involves photoionization and impact ionization mechanisms; the second part is phase change. After the ionization and electron heating in the first part, a large number of free electrons accumulate inside the material, so that the non-metallic material exhibits transient metallic properties, and the interaction between free electrons and the lattice can cause phase change. When the lattice temperature rises above the melting point of the material, melting becomes the main phase change mechanism of the material, and multiple processing can form a three-layer hierarchical structure. The processed ABS material is ultrasonically treated for about 15 minutes, then continued to be washed with deionized water and naturally air-dried.

[0069] Step S3, forming a single-layer PS ball array on the processed three-layer hierarchical structure. In this embodiment, a single-layer 15 μm PS ball array is formed. The specific steps are as follows:

[0070] First, prepare the slides before laying the balls and clean the glass slides used for laying the balls. Use a glass cutter to divide the slide into three equal parts, and put the divided slides into acetone for ultrasonic cleaning three times, about 20 minutes each time, for a total of 60 minutes. Then put the glass slides into 98% alcohol for ultrasonic cleaning three times, about 20 minutes each time, for a total of 60 minutes. Then take out the glass slides and put them into deionized water for ultrasonic cleaning three times, about 20 minutes each time, for a total of 60 minutes. Mix concentrated sulfuric acid and hydrogen peroxide in a ratio of 3:1 to prepare piranha solution, transfer the glass slides in deionized water to the piranha solution, soak and clean for 6 hours, and the strong oxidizing piranha solution can thoroughly clean the stains on the surface of the glass slides. Then take out the glass slides, wash them with deionized water, and wipe them dry.

[0071] The second step is to perform hydrophilic treatment on the glass sheet and the ABS processed by femtosecond laser. The glass sheet and the ABS material processed by femtosecond laser are placed in a plasma cleaning machine for plasma treatment. Put the glass sheet and ABS into the chamber, close the valve, evacuate for about 90 seconds, then adjust the knob to "HI", irradiate with ultraviolet light, and perform oxygen plasma treatment for about 180 seconds. Then release the air. This process should be done slowly to prevent the ABS from being blown away. Then take out the surface-modified glass sheet and ABS.

[0072] The third step is to self-assemble and lay out the 15μm PS beads on the glass slide into a single layer. Take 300μL of 15μm PS bead solution, put it into a centrifuge for 5 minutes, take out 180μL of supernatant, concentrate the PS bead solution 2.5 times, mix the PS beads and ethanol in a ratio of 3:1, add 40μL of ethanol to the PS bead solution, and prepare a PS bead ethanol mixed solution, and use a mixer to mix thoroughly. Then add deionized water to the surface of the surface-modified glass slide to make the water film thickness reach 2-3mm, and add the PS bead ethanol mixed solution drop by drop from the corners of the glass slide. Using the mutual solubility of water and ethanol, the water film will be forced back. Continue to slowly add the mixed solution, and the PS beads will float to the surface of the water film and self-assemble to form a single layer of PS beads. Add until the PS bead monolayer fills the entire glass slide. After the water film is stable, place a dust-free cloth on the diagonal of the glass slide where the mixed solution is added, absorb the excess water, and wait for it to dry naturally to obtain a single layer of PS beads.

[0073] Finally, transfer the single layer of PS beads on the glass slide to the ABS obtained in step 2. Pour a certain amount of deionized water into the beaker, slowly insert the glass slide with the single layer of PS beads into the water at a 45-degree angle, and the single layer of PS beads will leave the glass slide and float on the water. Add 4 times diluted TX-100 surfactant to the water to reduce the water tension, and the PS beads will float on the water surface in a tightly arranged manner. Then use tweezers to clamp the hydrophilic treated ABS, move it to the bottom of the PS bead monolayer film, and slowly pull the ABS out of the water at a 45-degree angle. In this way, a single layer of PS beads is laid on the surface of the ABS processed by the femtosecond laser. After waiting for natural air drying, the substrate of the single layer of 15μm PS microsphere array formed on the surface of the ABS processed by the femtosecond laser can be obtained.

[0074] Step S4, forming a single layer of PS microsphere array on a single layer of 15 μm PS microsphere array, in this embodiment, a single layer of 600 nm PS microspheres, the specific steps are:

[0075] First, carry out the preparation work before laying the balls and clean the glass pieces used for laying the balls.

[0076] The second step is to perform hydrophilic treatment on the glass sheet and ABS.

[0077] In the third step, the PS microspheres were self-assembled and laid flat on a glass slide to form a single layer. The mixing ratio of the 600 nm PS microspheres and ethanol used was 1:1.

[0078] Finally, the monolayer of 600 nm PS microspheres on the glass slide was transferred to the ABS obtained in step S3. The surfactant used was TX-100 diluted 20 times.

[0079] Step S5, performing ICP etching on the ABS material obtained above;

[0080] The ABS material obtained in step S4 is placed in an inductively coupled plasma etching machine, the upper radio frequency is set to 100W, the lower radio frequency is set to 100W, and the process time is set to 60s. The gas is ionized by a high-frequency electric field. Under the action of the high-frequency electric field, the gas molecules are ionized to form positive ions and electrons. The positive ions are accelerated under the action of the electric field and collide with the wall surface in the reaction chamber to generate secondary electrons to form plasma, and the chemical reaction and physical action of the plasma are used to etch the surface of the material. Chemical reaction refers to the chemical reaction between the plasma and the surface of the material to form a gas or compound, thereby etching the surface of the material. The physical action refers to the energy of the plasma directly acting on the surface of the material, peeling off the surface atoms or molecules, thereby etching the surface of the material. ICP etching can achieve high-precision, high-speed and low-damage etching, and it is easy to control the etching morphology, and a very smooth surface can be obtained.

[0081] Step S6, evaporating a gold film on the surface of the polymer material substrate;

[0082] In order to further improve the SERS signal, a gold film with a thickness of 45-55 nm is uniformly coated on the polymer array substrate obtained in step S5 using an electron beam evaporation coating process, and the evaporation rate is 0.04-0.05 nm·s -1 .

[0083] Step S7, performing SERS detection on the prepared substrate.

[0084] The obtained SERS substrates were added to 10 -5 mol / L MGITC solution for 2-3 hours, remove with tweezers and rinse with deionized water to remove excess probe, and place in a fume hood to air dry. SERS measurements were performed on a Renishaw Invia Raman microscope system. The Raman spectrometer uses a 633nm helium-neon laser, a charge-coupled device camera, and a spectral resolution of 1cm -1 The laser was focused onto the sample through a 20× microscope objective. The accumulation times, exposure time, and laser power of each sample were 3 times, 3s, and 10%, respectively. The background subtraction and smoothing were performed on the collected Raman spectra as the final SERS results.

[0085] The uniformity and reproducibility of SERS substrate signals are important parameters for measuring SERS performance. Figure 3 As shown in the figure, 20 average spectra collected on the same substrate are taken at 1614 cm -1 As a characteristic peak, its relative standard deviation is calculated to be 9.26%, indicating that the SERS substrate has good uniformity.

[0086] In order to verify the detection sensitivity of the SERS substrate, we selected MGITC as the Raman reporter molecule. The thiol group of the MGITC aqueous solution will combine with gold to form Au-S. The MGITC solutions with different concentrations were detected by direct detection. -6 ~10 -12 mol / L MGITC solution, and then perform SERS detection under the same conditions as above, such as Figure 4 As shown in the figure, it can be concluded that the SERS enhancement substrate we designed can reach 10 -11 mol·L -1 The detection limit of the substrate is good and the SERS enhanced detection line is excellent.

[0087] The SERS prepared by the above method can be used for trace detection.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A three-dimensional SERS substrate based on ABS material, characterized in that: The SERS substrate comprises an ABS bottom material (1) on which an array of at least three levels of hierarchical structures (2) are arranged, a single layer of PS beads (4) is arranged in adjacent interlayer regions (3) of the hierarchical structure (2), and PS microspheres (5) with a gold film evaporated on the surface are arranged on the upper part of the PS beads (4).

2. The three-dimensional SERS substrate based on ABS material according to claim 1, characterized in that: The hierarchical structure (2) is a concentric rectangle or circle.

3. A method for preparing a three-dimensional SERS substrate based on ABS material as claimed in claim 1, characterized in that: The following steps are involved: Step S1, selecting and preparing base materials; Select ABS material for cleaning and drying; Step S2, processing of the hierarchical structure (2); Placing the ABS material in step S1 on a femtosecond laser processing platform, setting processing parameters and processing patterns, and using femtosecond laser processing to form a hierarchical structure of three or more layers (2); Step S3, preparation of a single-layer PS ball (4); A single layer of PS beads (4) array is formed in the adjacent interlayer region (3) of the hierarchical structure (2) on the ABS material processed in step S2; Step S4, preparation of a single-layer PS microsphere (5); A single layer of PS microspheres (5) array is formed on the upper part of the PS beads (4) processed in step S3; Step S5, ICP etching; The ABS material substrate obtained in step S4 is placed in an inductively coupled plasma etching machine, and ICP etching is performed using the chemical reaction and physical action of the plasma; Step S6, surface evaporation; The ABS material substrate obtained in step S5 is subjected to gold film deposition on the surface using an electron beam vacuum coating apparatus to complete the preparation.

4. The method for preparing a three-dimensional SERS substrate based on ABS material according to claim 3, characterized in that: In the step S1, the thickness of the ABS material is selected to be 280-320 μm, and the cleaning work is specifically as follows: the ABS material is ultrasonically cleaned in 98% alcohol for three times, each time for 20 minutes, for a total of 60 minutes; the ABS material is taken out and ultrasonically cleaned in deionized water for three times, each time for about 20 minutes, for a total of 60 minutes.

5. The method for preparing a three-dimensional SERS substrate based on ABS material according to claim 3, characterized in that: In step S2, the specific process of using femtosecond laser to process ABS material is as follows: Use Pharos software to set the femtosecond laser light source to a repetition frequency of 10kHz, use the concentric rectangles or circles drawn in EzCad2 software, set the scanning speed to 5mm / s, and set a 0.005mm straight line to fill the adjacent layer height area. After the settings are completed, enter the execution processing command and repeat the array processing for the number of layer heights; ultrasonically treat the processed ABS material for about 15 minutes, then continue to wash it with deionized water and let it air dry naturally.

6. The method for preparing a three-dimensional SERS substrate based on ABS material according to claim 3, characterized in that: In the step S3, the specific process of forming a single-layer PS ball array is as follows: The glass sheets used for laying the balls are first cleaned, then subjected to hydrophilic treatment, vacuumed using a plasma cleaning machine, and treated with oxygen plasma; The PS beads were self-assembled and laid flat on a glass slide to form a single layer, and the mixing ratio of the PS beads to ethanol was 3:1; Finally, the single layer of PS beads on the glass slide was transferred to the ABS, and the surfactant used was TX-100 diluted 4 times.

7. The method for preparing a three-dimensional SERS substrate based on ABS material according to claim 3, characterized in that: In the step S4, the mixing ratio of PS beads and ethanol used to form the monolayer PS microsphere array is 1:1, and the surfactant used is 20-fold diluted TX-100.

8. The method for preparing a three-dimensional SERS substrate based on ABS material according to claim 3, characterized in that: In the step S5, the ABS material is subjected to ICP etching, and the processed ABS material is placed in an inductively coupled plasma etching machine, the upper radio frequency is set to 100W, the lower radio frequency is set to 100W, and the process time is set to 60s; In step S6, the gold film is evaporated by using an electron beam evaporation device to deposit a gold film with a thickness of 45 to 55 nm on the surface of the substrate at a gold evaporation rate of 0.04 to 0.05 nm·s -1 .

9. The method for preparing a three-dimensional SERS substrate based on ABS material according to claim 3, characterized in that: The method further comprises step S7 of performing SERS detection on the prepared substrate; The detection step is: adding the prepared SERS substrate to -5 mol / L MGITC solution for 2-3 hours, take out and rinse, and then soak in 10 -6 ~10 -12 mol / L MGITC solution for 2-3 h; SERS measurements were performed on a Renishaw Invia Raman microscope system using a 633 nm HeNe laser, a charge-coupled device camera, and a spectral resolution of 1 cm -1 1800 grooves / mm grating; laser is focused onto the sample through a 20× microscope objective; the accumulation times, exposure time and laser power of each sample are 3 times, 3s and 10% respectively; background subtraction and smoothing are performed on the collected Raman spectra as the final SERS results.

10. Use of the three-dimensional SERS substrate based on ABS material as claimed in any one of claims 1 to 9 in trace detection.

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