Surface enhanced Raman scattering substrate and preparation method thereof

Abstract

The invention relates to the technical field of surface-enhanced Raman scattering chips, in particular to a surface-enhanced Raman scattering substrate and a preparation method thereof. According to the surface-enhanced Raman scattering substrate provided by the invention, the sensitivity and high uniformity of surface-enhanced Raman scattering are synergistically improved through the antenna effect of the nanorod unit structure and gold-zinc oxide heterojunction charge transfer. Specifically, the antenna effect of the nano-column unit structure can form strong local plasmon resonance in gaps of the nano-column unit structure, and three-dimensional hot spot distribution can be constructed in the structural gaps between the nano-columns and the gold-zinc oxide heterojunction nano-columns and the structural gaps between the gold-zinc oxide heterojunction nano-columns. Meanwhile, an effective charge transfer channel is constructed by the high electron mobility of zinc oxide, and the Raman signal intensity is remarkably enhanced through the synergistic effect of zinc oxide and zinc oxide.

Description

Technical Field

[0001] This invention relates to the field of surface-enhanced Raman scattering chip technology, and more specifically to a surface-enhanced Raman scattering substrate and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Surface-enhanced Raman scattering (SERS) refers to the phenomenon where irradiation of the surface of noble metal nanoparticles with a laser of a suitable frequency excites plasmon resonance on the nanoparticle surface, resulting in an enhanced electromagnetic field. When the analyte molecule is placed in this enhanced electromagnetic field, its Raman scattering signal is amplified by millions of times or even higher. It is a non-destructive, label-free, highly sensitive, and near-field analytical detection method widely used in biology, chemistry, and environmental fields. As a molecular spectroscopic fingerprint identification method, SERS offers advantages over other traditional detection methods, including speed, ease of operation, and minimal or no sample pretreatment. It is a highly sensitive, high spatiotemporal resolution, real-time, and non-destructive detection technique.

[0004] However, SERS technology still faces many challenges in practical applications, among which the reproducibility, stability, and fabrication cost of the substrate are key factors restricting its widespread adoption. Although various substrates have been developed to enhance the enhancement factor, achieve quantitative detection, extend substrate lifetime, and allow the study of surface-enhanced Raman scattering in different environments, it remains difficult to obtain a surface-enhanced Raman scattering substrate that simultaneously possesses low cost, high stability, high sensitivity, and good reproducibility. Summary of the Invention

[0005] To overcome the above problems, the present invention provides a surface-enhanced Raman scattering substrate and its preparation method.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a surface-enhanced Raman scattering substrate, comprising a substrate, wherein an array structure composed of nanopillar unit structures is disposed on one side surface of the substrate; the nanopillar unit structure comprises nanopillars and gold caps on the top of the nanopillars; and gold-zinc oxide heterojunction nanopillars are disposed between adjacent nanopillar unit structures.

[0007] In one or more embodiments, the substrate is silicon.

[0008] In one or more embodiments, the diameter of the nanopillars is 280-350 nm; the height of the nanopillars is 300-400 nm; and the spacing between adjacent nanopillars is 450-600 nm.

[0009] In one or more embodiments, the diameter of the gold cap is 180~200 nm.

[0010] In one or more embodiments, the nanopillars are, from the gold cap downwards, a polystyrene layer, a zinc oxide layer, and silicon; Preferably, the thickness of the zinc oxide layer is 30~50 nm.

[0011] In one or more embodiments, the gold-zinc oxide heterojunction nanopillars are formed from gold nanoparticles and zinc oxide.

[0012] Preferably, the thickness of the zinc oxide layer is 30~50 nm.

[0013] In one or more embodiments, the gold-zinc oxide heterojunction nanopillars have a diameter of 30-60 nm and a height of 130-160 nm.

[0014] A second aspect of the present invention provides a method for preparing the surface-enhanced Raman scattering substrate described in the first aspect, comprising the following steps: (1) Deposit a zinc oxide thin film on one side of the substrate; (2) A monolayer polystyrene microsphere array was prepared on the surface of a zinc oxide film by a gas-liquid interface self-assembly method; (3) Deposit a gold film on the surface of a monolayer polystyrene microsphere array to obtain an intermediate for surface-enhanced Raman scattering substrate; (4) The intermediate of the surface-enhanced Raman scattering substrate is annealed in situ and then subjected to reactive ion etching to obtain the surface-enhanced Raman scattering substrate.

[0015] In one or more embodiments, in step (1), a zinc oxide thin film is deposited on one side surface of the substrate using a magnetron sputtering method.

[0016] In one or more embodiments, step (2), the method for preparing a monolayer polystyrene microsphere array on the surface of a zinc oxide film using a gas-liquid interface self-assembly method, includes: Polystyrene microspheres and anhydrous ethanol were uniformly mixed to obtain a polystyrene microsphere dispersion. The polystyrene microsphere dispersion was dropped onto a hydrophilic glass slide to ensure uniform distribution. The hydrophilic glass slide was then slowly and tilted into water with a stable surface, causing the polystyrene microspheres to form a densely packed monolayer array on the water surface. The monolayer array of polystyrene microspheres floating on the water surface was then slowly lifted using a zinc oxide film substrate, and dried after absorbing water to obtain the final product.

[0017] In one or more embodiments, in step (2), the diameter of the polystyrene microspheres is 450~600 nm, preferably 500 nm.

[0018] In one or more embodiments, in step (3), the method for depositing a gold film on the surface of a monolayer polystyrene microsphere array is magnetron sputtering.

[0019] In one or more embodiments, in step (3), the thickness of the gold film is 30~50 nm.

[0020] In one or more embodiments, in step (4), the in-situ annealing temperature is 700~900 ℃, preferably 800 ℃; the in-situ annealing time is 1.5~3 h, preferably 2 h.

[0021] During in-situ annealing, the gold film deposited on top of the polystyrene microspheres shrinks to form a gold cap, while the gold film deposited on the zinc oxide film surface shrinks to form gold nanoparticles. These gold nanoparticles then surround the polystyrene microspheres.

[0022] In one or more embodiments, the reactive ion etching method in step (4) is as follows: The etching gas is SF6, the gas flow rate is 60~80 sccm, the power is 180~220W, and the etching time is 100~140s.

[0023] After reactive ion etching, all the zinc oxide layer that was not covered was etched.

[0024] The beneficial effects of this invention are as follows: (1) The surface-enhanced Raman scattering substrate provided by this invention improves the sensitivity and high uniformity of SERS through the antenna effect of the nanopillar unit structure and the synergistic effect of charge transfer in the gold-zinc oxide heterojunction. Specifically, the antenna effect of the nanopillar unit structure can form strong local plasmon resonances in the gaps between the nanopillar unit structures. The gaps between the nanopillars and the gold-zinc oxide heterojunction nanopillars, as well as the gaps between the gold-zinc oxide heterojunction nanopillars, create a three-dimensional hotspot distribution. At the same time, the high electron mobility of zinc oxide creates an effective charge transfer channel. The synergistic effect of these two factors significantly enhances the Raman signal intensity.

[0025] (2) The present invention provides a method for preparing surface-enhanced Raman scattering substrates through a continuous process of zinc oxide thin film deposition, self-assembly to prepare a monolayer polystyrene microsphere array, gold film deposition, in-situ annealing and reactive ion etching. This method has low preparation cost, short production cycle, and large sample quantity, and can realize rapid batch preparation of samples.

[0026] (3) This invention can control the structural morphology of the surface-enhanced Raman scattering substrate by adjusting the size of the polystyrene microspheres, the magnetron sputtering time and power, the annealing time, and the reactive ion etching time. This includes the thickness of the gold cap in the nanopillar unit structure, the diameter and height of the nanopillars, and the diameter and height of the gold-zinc oxide heterojunction nanopillars. Compared with random growth (such as sol-gel method) or template exfoliation process, it has significant advantages in repeatability and uniformity.

[0027] (4) In this invention, zinc oxide has excellent chemical stability with resistance to acid and alkali and high temperature. The gold cap at the top of the nanopillar and the gold nanoparticles at the top of the gold-zinc oxide heterojunction nanopillar also have strong corrosion resistance. Therefore, the overall structure has strong stability, can be reused, and can maintain high detection sensitivity for a long time.

[0028] (5) The present invention uses small-sized single-crystal silicon as a substrate, which can be integrated into fiber optic sensor heads, chips, microcontrollers and wearable devices as small molecule detection sensor modules. It has a wide range of applications and low application threshold. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 In Figures a and b, both are SEM images of surface-enhanced Raman scattering substrates. Figure 2 This is a schematic diagram of a surface-enhanced Raman scattering substrate, where 1-substrate, 2-nanopillar, 3-gold cap, and 4-gold-zinc oxide heterojunction nanopillar; Figure 3 The results are Raman spectroscopy measurements of the surface-enhanced Raman scattering substrate. Detailed Implementation

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0034] Example 1 Fabrication of surface-enhanced Raman scattering substrates: (1) Cut out a single crystal silicon substrate with a size of about 4 mm × 4 mm, and then clean the silicon substrate with ultrasonic waves in anhydrous ethanol and ultrapure water respectively, and dry it at 60 ℃ to obtain the pretreated silicon substrate. (2) A zinc oxide thin film was deposited on one side of the pretreated silicon substrate by magnetron sputtering: a VNANO VJC-500 RF magnetron sputtering coating instrument was used with a power of 35 W, a gas flow rate of 15 sccm, a pressure of 1.5 Pa, a coating time of 15 min, and a zinc oxide thin film thickness of 35 nm.

[0035] (3) The glass slide was ultrasonically cleaned with anhydrous ethanol and deionized water for 10 min in sequence, then dried at 60 °C. The glass slide was then placed in a plasma cleaner for cleaning to obtain a hydrophilic glass slide. Polystyrene microsphere colloid and anhydrous ethanol were mixed at a mass ratio of 1:1.5 and ultrasonically mixed for 8 min to ensure thorough mixing. After standing, a polystyrene microsphere dispersion was obtained. A layer of ultrapure water film was coated on the surface of the hydrophilic glass slide and then cleaned with a 15-gauge plasma cleaner. A μL pipette is used to slowly add the polystyrene microsphere dispersion to one end of a hydrophilic glass slide, allowing the polystyrene microspheres to diffuse freely on the ultrapure water film. Once a uniform and dense polystyrene microsphere film is formed, the ultrapure water under the monolayer polystyrene microsphere film is removed with filter paper. Under the combined action of capillary force and electrostatic repulsion, the polystyrene microsphere dispersion is evenly distributed on the hydrophilic glass slide. The hydrophilic glass slide is then slowly slid into the stable ultrapure water at a 45° angle to the horizontal, causing the polystyrene microspheres to form a densely packed monolayer polystyrene microsphere array on the water surface. The monolayer polystyrene microsphere array floating on the water surface is then slowly lifted using a deposited zinc oxide thin film substrate, and dried after absorbing water to obtain the final product.

[0036] (4) A gold film was deposited on the surface of a monolayer polystyrene microsphere array by magnetron sputtering to obtain an intermediate for surface-enhanced Raman scattering substrate. The specific process was as follows: a magnetron sputtering coating instrument was used, the vacuum degree was controlled at 45-55 mTorr, the coating time was set to 80 s, and the current was controlled at about 30 mA after glow appeared in the cavity. A dense and regular gold film with a thickness of 40 nm was sputtered on the surface of the monolayer polystyrene microsphere array.

[0037] (5) The intermediate of the surface-enhanced Raman scattering substrate was annealed in a tubular furnace at 800 °C for 2 h. During the in-situ annealing process, the gold film deposited on the top of the polystyrene microspheres will shrink to form a gold cap, and the gold film deposited on the surface of the zinc oxide film will shrink to form gold nanoparticles; the gold nanoparticles and zinc oxide form gold-zinc oxide heterojunction nanopillars, which will surround the polystyrene microspheres.

[0038] (6) Reactive ion etching of the intermediate of the annealed surface-enhanced Raman scattering substrate: the gas is set to SF6, the gas flow rate is 70 sccm, the power is 200 W, and the etching time is 120 s. The surface-enhanced Raman scattering substrate is obtained after reactive ion etching.

[0039] Reactive ion etching can etch polystyrene microspheres into columnar structures.

[0040] The SEM image of the surface-enhanced Raman scattering substrate obtained in this embodiment is shown below. Figure 1 and 2 As shown, from Figure 2 As can be seen, the surface-enhanced Raman scattering substrate includes a substrate 1, and an array structure composed of nanopillar unit structures is disposed on one side surface of the substrate 1; the nanopillar unit structure includes nanopillar 2 and a gold cap 3 on the top of the nanopillar 2; and gold-zinc oxide heterojunction nanopillar 4 is disposed between adjacent nanopillar unit structures.

[0041] Among them, the nanopillar 2 consists of a polystyrene layer, a zinc oxide layer and silicon from the gold cap downwards; the gold-zinc oxide heterojunction nanopillar 4 is formed by gold nanoparticles and zinc oxide.

[0042] The diameter of nanopillar 2 is 300 nm; the height of nanopillar 2 is 350 nm; the diameter of the gold cap 3 is 190 nm, and the thickness of the zinc oxide layer is 35 nm; The gold-zinc oxide heterojunction nanopillar 4 has a diameter of 40 nm and a height of 150 nm.

[0043] Comparative Example 1 Compared to the structure in Example 1, no zinc oxide layer is provided.

[0044] Example 2 Raman spectroscopy detection of surface-enhanced Raman scattering substrates: SERS was measured using a micro-area Raman spectrometer with an excitation wavelength of 532 nm. Surface-enhanced Raman scattering substrates with and without zinc oxide layers were subjected to SERS measurements at 10 nm. -6 The sample was immersed in mol / L 4-aminothiophene (4-ATP) solution for 1 h. The effective power of the laser source used for Raman detection was 2 mW, and the detection integration time was 10 s. The detection results are as follows: Figure 3As shown, at 1074cm -1 1135 cm -1 1383 cm -1 1425 cm -1 1569 cm -1 The SERS substrate containing zinc oxide showed a clear Raman peak, and compared with the SERS substrate without zinc oxide, the Raman peak intensity was increased by 5-6 times, and the detection effect was significantly enhanced.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A surface-enhanced Raman scattering substrate, characterized in that, The substrate includes an array structure composed of nanopillar unit structures on one side surface of the substrate; the nanopillar unit structure includes nanopillars and gold caps on the top of the nanopillars; gold-zinc oxide heterojunction nanopillars are disposed between adjacent nanopillar unit structures.

2. The surface-enhanced Raman scattering substrate as described in claim 1, characterized in that, The substrate is silicon.

3. The surface-enhanced Raman scattering substrate as described in claim 1, characterized in that, The diameter of the nanopillars is 280~350 nm; the height of the nanopillars is 300~400 nm; and the spacing between adjacent nanopillars is 450~600 nm. Alternatively, the diameter of the gold cap is 180~200 nm; Alternatively, the nanopillars, from the gold cap downwards, consist of a polystyrene layer, a zinc oxide layer, and silicon; preferably, the thickness of the zinc oxide layer is 30~50 nm.

4. The surface-enhanced Raman scattering substrate as described in claim 1, characterized in that, The gold-zinc oxide heterostructure nanopillars are formed by gold nanoparticles and zinc oxide; preferably, the thickness of the zinc oxide layer is 30~50 nm. Alternatively, the diameter of the gold-zinc oxide heterostructure nanopillars is 30~60 nm and the height is 130~160 nm.

5. The method for preparing the surface-enhanced Raman scattering substrate according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Deposit a zinc oxide thin film on one side of the substrate; (2) A monolayer polystyrene microsphere array was prepared on the surface of a zinc oxide film by a gas-liquid interface self-assembly method; (3) Deposit a gold film on the surface of a monolayer polystyrene microsphere array to obtain an intermediate for surface-enhanced Raman scattering substrate; (4) The intermediate of the surface-enhanced Raman scattering substrate is annealed in situ and then subjected to reactive ion etching to obtain the surface-enhanced Raman scattering substrate.

6. The preparation method according to claim 5, characterized in that, In step (1), a zinc oxide thin film is deposited on one side surface of the substrate using magnetron sputtering.

7. The preparation method according to claim 5, characterized in that, In step (2), the method for preparing a monolayer polystyrene microsphere array on the surface of a zinc oxide film using a gas-liquid interface self-assembly method includes: Polystyrene microspheres and anhydrous ethanol were uniformly mixed to obtain a polystyrene microsphere dispersion. The polystyrene microsphere dispersion was dropped onto a hydrophilic glass slide to ensure uniform distribution. The hydrophilic glass slide was then slowly and tilted into water with a stable surface, causing the polystyrene microspheres to form a densely packed monolayer array on the water surface. The monolayer array of polystyrene microspheres floating on the water surface was then slowly lifted using a zinc oxide film substrate, and dried after absorbing water to obtain the final product.

8. The preparation method according to claim 5, characterized in that, In step (2), the diameter of the polystyrene microspheres is 450~600 nm, preferably 500 nm.

9. The preparation method according to claim 5, characterized in that, In step (3), the method for depositing a gold film on the surface of a monolayer polystyrene microsphere array is magnetron sputtering; Alternatively, in step (3), the thickness of the gold film is 30~50 nm.

10. The preparation method according to claim 5, characterized in that, In step (4), the in-situ annealing temperature is 700~900℃, preferably 800℃; the in-situ annealing time is 1.5~3 h, preferably 2 h; Alternatively, in step (4), the reactive ion etching method is as follows: The etching gas is SF6, the gas flow rate is 60~80 sccm, the power is 180~220W, and the etching time is 100~140 s.

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