A surface-enhanced raman scattering substrate, a preparation method and application thereof

Abstract

The application relates to a surface enhanced Raman scattering (SERS) substrate, a preparation method and application thereof, and belongs to the technical field of Raman spectrum detection. The substrate comprises, from bottom to top, a substrate layer, a distributed Bragg reflector, a chalcogen phase change material functional layer and a nanoscale metal structure layer. The distributed Bragg reflector is composed of a periodic structure stack of medium materials with different refractive indexes. The distributed Bragg reflector is coupled with the nanoscale metal structure layer to excite a Tamm state. The chalcogen phase change material functional layer can realize reversible regulation of amorphous state and crystalline state under external light excitation, changes the Tamm state resonance wavelength to regulate the SERS enhancement effect. The application realizes high-sensitivity detection through double enhancement of the Tamm state and localized surface plasmon resonance, has the characteristics of non-volatility, reconfigurability, high reproducibility and design flexibility, is convenient to operate, stable in performance, and is suitable for fields of chemical biological sensing, laboratory chip systems and optical encryption.

Description

Technical Field

[0001] This invention belongs to the field of Raman spectroscopy detection technology, and relates to a surface-enhanced Raman scattering substrate, its preparation method and its application, especially to a surface-enhanced Raman scattering substrate with non-volatility, high sensitivity and reconfigurability, its preparation method and its application. Background Technology

[0002] Raman spectroscopy is an analytical technique based on molecular vibrational spectroscopy. It can achieve qualitative and quantitative identification of substances through characteristic spectra and is widely used in fields such as biological detection and environmental monitoring. However, its inherent drawbacks, such as a small Raman scattering cross section and weak Raman signal intensity, are quite prominent.

[0003] To address the problem of weak Raman detection signals, scholars both domestically and internationally have conducted extensive research and proposed several solutions using surface-enhanced Raman scattering (SERS) technology. For example, the silicon nanorod array SERS substrate proposed in Chinese invention patent (CN121090498A) enriches the target molecules with superhydrophobic structures, significantly improving the Raman signal sensitivity. The conductive fiber-based SERS probe developed in Chinese invention patent (CN120971392A) achieves high-magnification and stable detection of the target substance's Raman signal by constructing a high-density "hot spot" active layer.

[0004] While existing solutions can provide high enhancement factors, surface-enhanced Raman scattering (SERS) substrates lack tunability, leading to the following problems in practical detection: 1) Their performance is heavily dependent on the gaps and shape of the nanostructure, making the enhancement effect uncontrollable; 2) When performing real-time detection of various extremely low concentrations of biomolecules, the test sensitivity is difficult to guarantee. To achieve high-sensitivity detection of multiple biomolecules, it is usually necessary to prepare multiple SERS substrates with different periodic structures. This not only increases the testing time and economic cost but also limits the convenience of practical applications.

[0005] To address the issues of low sensitivity, high time and economic costs, and poor convenience caused by insufficient tunability of surface-enhanced Raman scattering (SERS) substrates, in 2023, Jinghua Teng's team at the Agency for Science, Technology and Research (A*STAR) in Singapore (Sreekanth KV, Perumal J, Dinish US, et al. Tunable Tamm plasmon cavity as a scalable biosensing platform for surface enhanced resonance Raman spectroscopy[J]. Nature Communications, 2023, 14(1): 7085.) developed a tunable SERS substrate using chalcogenide phase change materials, achieving single-molecule-level sensitivity in SERS detection. However, the proposed tunable SERS substrate can only be unidirectionally controlled by heating and cannot be cyclically and reversibly controlled, thus limiting its widespread application in practical scenarios.

[0006] Therefore, developing surface-enhanced Raman scattering substrates that combine non-volatility, high sensitivity, and reconfigurability is of great significance for promoting the application of Raman detection technology in multi-scenario and multi-target molecular detection. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing surface-enhanced Raman scattering (SERS) substrates and provide a SERS substrate, its preparation method, and its applications. Specifically, it is a non-volatile, highly sensitive, and reconfigurable SERS substrate based on chalcogenide phase change materials. This invention utilizes external light-triggered excitation, enabling the SERS substrate to achieve non-volatility and reconfigurable tuning, thus exhibiting outstanding advantages of portability and high sensitivity in SERS detection applications.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A surface-enhanced Raman scattering substrate, wherein the structure of the surface-enhanced Raman scattering substrate comprises, from bottom to top: a substrate layer, a distributed Bragg mirror, a chalcogenide phase change material functional layer, and a nanoscale metal structure layer.

[0010] The distributed Bragg reflector is composed of periodic structures stacked from dielectric materials with different refractive indices. Each periodic structure includes a high-refractive-index dielectric material layer and a low-refractive-index dielectric material layer, with the high-refractive-index dielectric material layer located at the bottom. The chalcogenide phase change material functional layer is located between the distributed Bragg reflector and the nanoscale metal structure layer, i.e., within the Tamm state electric field enhancement region. The chalcogenide phase change material in the functional layer can be reversibly tuned between an amorphous and crystalline state under external light excitation. During the reversible tuning process, the dielectric constants of the chalcogenide phase change material in the two phase states differ significantly, causing a change in the resonance wavelength of the Tamm state. This leads to a state where the wavelength is approximately consistent with the wavelength of the Raman spectroscopy-excited laser, thereby achieving control over the surface-enhanced Raman scattering enhancement effect.

[0011] The nanoscale metal structure layer serves both as an essential component for exciting the Tamm state and as a surface-enhanced Raman scattering active surface that carries the molecule to be tested.

[0012] The reconfigurability of the surface-enhanced Raman scattering substrate properties is non-volatile, meaning that after the external light excitation is removed, the lattice state of the chalcogenide phase change material can be maintained, and the properties of the surface-enhanced Raman scattering substrate do not change. If the properties of the surface-enhanced Raman scattering substrate are to be changed, external light excitation is required to change its state.

[0013] The substrate material is selected from common substrate materials such as silicon wafers, quartz, and polymers.

[0014] The distributed Bragg reflector has 5 to 20 periodic structures. The high-refractive-index dielectric material layer is made of materials such as GaN, Al2O3, ZnS, and ZrO2, with a thickness between 50 nm and 200 nm. The low-refractive-index dielectric material layer is made of materials such as SiO2, Si3N4, MgF2, and CaF2, with a thickness between 50 nm and 200 nm.

[0015] The thickness of the chalcogenide phase change material functional layer is between 5 nm and 200 nm, and the material of the chalcogenide phase change material functional layer is selected from GeSbTe, GeTe, etc. GaSb , , One of the following chalcogenide phase change materials: AgInSbTe, InSb, InSbTe, InSe, or SbTe.

[0016] The noble metal thin film material of the nanoscale metal structure layer is selected from gold, silver, or platinum, with a thickness between 2 nm and 50 nm. To achieve light transmission, the deposition thickness of the nanoscale metal structure layer must be strictly controlled below the maximum light-transmitting thickness of the metal.

[0017] A method for preparing a surface-enhanced Raman scattering substrate includes the following steps:

[0018] The first step is to clean the substrate and fabricate a distributed Bragg mirror;

[0019] Step 1.1: Clean the substrate layer in an ultrasonic cleaner for 10 to 15 minutes in sequence with acetone, isopropanol and deionized water.

[0020] Step 1.2: Under room temperature conditions, a distributed Bragg mirror is formed by alternately depositing high-refractive-index dielectric material layers and low-refractive-index dielectric material layers on the substrate layer using one of the following processes: thermal evaporation, electron beam evaporation, or magnetron sputtering.

[0021] Furthermore, the deposition parameters are: room temperature, high vacuum chamber, and gas pressure at... the following.

[0022] The second step is to prepare the functional layer of the chalcogenide phase change material.

[0023] At room temperature, a chalcogenide phase change material is deposited on a distributed Bragg mirror using one of the following processes: thermal evaporation, electron beam evaporation, or magnetron sputtering, as a functional layer of the chalcogenide phase change material.

[0024] Furthermore, the deposition parameters are: room temperature, high vacuum chamber, and gas pressure at... the following;

[0025] The third step is to deposit a nanoscale metal structure layer;

[0026] On the surface of the functional layer of a chalcogenide phase change material, a thin film of noble metal is deposited as a nanoscale metal structure layer by means of one of the following processes: thermal evaporation, electron beam evaporation, or magnetron sputtering.

[0027] Furthermore, the deposition parameters are: room temperature, high vacuum chamber, and gas pressure at... the following.

[0028] The fourth step involves modulating the surface-enhanced Raman scattering substrate, as detailed below:

[0029] For surface-enhanced Raman scattering substrates where the functional layer of chalcogenide phase change materials is in an amorphous state, low-energy light pulse excitation is used to precisely control the temperature of the functional layer of the chalcogenide phase change material above the crystallization temperature and below the melting point temperature of the chalcogenide phase change material in order to induce crystallization.

[0030] Furthermore, the parameters of the low-energy optical pulse are: the laser wavelength range is within 400~1500nm, the pulse width is between picoseconds and nanoseconds, and the pulse energy is between the energy required for crystallization and the energy required for melting of the chalcogen phase change material used.

[0031] For surface-enhanced Raman scattering substrates where the functional layer of chalcogenide phase change materials is in a crystalline state, high-energy light pulse excitation is used to cause the material to melt instantaneously (above the melting point temperature of chalcogenide phase change materials) and then quench it, thereby achieving amorphization.

[0032] Furthermore, the parameters of the high-energy optical pulse are: the laser wavelength range is within 400~1500nm, the pulse width is between picoseconds and nanoseconds, and the pulse energy is greater than or equal to the energy required to melt the chalcogen phase change material used.

[0033] An application of a surface-enhanced Raman scattering substrate, with its core characteristics of non-volatility, high sensitivity and reconfigurability, can be used for trace substance detection, biomolecular sensing or encryption and anti-counterfeiting, providing innovative detection and solutions for multiple key fields such as analytical chemistry, biomedicine, materials science and information security.

[0034] The beneficial effects of this invention are as follows:

[0035] 1) Reconfigurability and non-volatility: By changing the lattice state of chalcogenide phase change materials through optical excitation, it is possible to "write", "erase" and "rewrite" the enhancement performance of surface-enhanced Raman scattering substrates. Moreover, no energy is required to maintain the state after the change, realizing the non-volatile reconfigurability of the function, and providing feasible technical means for multi-band detection, multi-molecule high-sensitivity detection, etc.

[0036] 2) High sensitivity: The Tamm state can generate a stronger and more uniform electric field enhancement than the traditional local surface plasmon resonance. Combined with the local surface plasmon resonance effect of the nanoscale metal structure itself, dual enhancement can be achieved, resulting in extremely high detection sensitivity.

[0037] 3) High reproducibility: Based on precise thin film deposition technology, the structure has good uniformity and the distribution of "hot spots" can be controlled, which ensures the high reproducibility of Raman signals and is beneficial for quantitative analysis;

[0038] 4) Flexible design: By adjusting the thickness of the inner film, the material, and the thickness of the functional layer of the chalcogenide phase change material in the distributed Bragg reflector, the Tamm resonance peak can be flexibly designed within the required wavelength range to adapt to different excitation wavelengths and analytes. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of a surface-enhanced Raman scattering substrate.

[0040] Figure 2 The reflection spectrum of this surface-enhanced Raman scattering substrate when the chalcogenide phase change material is in the amorphous state.

[0041] Figure 3 The reflection spectrum of the surface-enhanced Raman scattering substrate after the chalcogenide phase change material is transformed into a crystalline state.

[0042] Figure 4 The Raman spectrum of the reconfigurable surface-enhanced Raman scattering substrate for biomolecule detection is shown in the example. Figure 4 (a) in the image shows the Raman spectrum measured on an amorphous surface-enhanced Raman scattering substrate. Figure 4 (b) in the figure is the crystalline Raman spectrum measured on the surface-enhanced Raman scattering substrate under crystalline conditions.

[0043] In the figure: 1. Substrate layer; 2. High refractive index dielectric material layer of distributed Bragg reflector; 3. Low refractive index dielectric material layer of distributed Bragg reflector; 4. Chalcogenide phase change material functional layer; 5. Nanoscale metal structure layer. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] This embodiment provides a method for preparing a surface-enhanced Raman scattering substrate, including the following steps:

[0046] Step 1: Cleaning of substrate layer 1 and fabrication of distributed Bragg mirrors;

[0047] Using a 500 μm thick silicon wafer as substrate layer 1, the substrate was ultrasonically cleaned for 12 minutes sequentially with acetone, isopropanol, and deionized water. Subsequently, at room temperature, zinc sulfide (ZnS, a high refractive index dielectric material layer, 53 nm thick) and silicon dioxide (…) were alternately deposited on substrate layer 1 using magnetron sputtering. A low-refractive-index dielectric material layer (85nm thick) thin film with a radio frequency power of 100W is formed. Each high-refractive-index dielectric material layer 2 and each low-refractive-index dielectric material layer 3 form a periodic structure. The high-refractive-index dielectric material layer is below the low-refractive-index dielectric material layer. The periodic structure is repeated for 5 times to form a distributed Bragg reflector.

[0048] The second step is to prepare the functional layer 4 of the chalcogenide phase change material;

[0049] On the fabricated distributed Bragg reflector, radio frequency magnetron sputtering was used at 20°C and cavity pressure. Under the condition of 30W power, using a diameter of 50.8mm and a purity of 99.9% Alloy target material, in an argon atmosphere The deposition rate, in A 10nm thick layer was deposited on the stacked layer. Thin film, serving as a functional layer 4 of a chalcogenide phase change material.

[0050] The third step is to deposit a nanoscale metal structure layer 5;

[0051] In the functional layer 4 of the chalcogenide phase change material (in this embodiment, it is...) A 15 nm thick silver (Ag) film was deposited on the functional layer by DC sputtering as a nanoscale metal structure layer 5.

[0052] The surface-enhanced Raman scattering substrate prepared in this embodiment using the above method is as follows: Figure 1 As shown, its structure, from bottom to top, includes: a substrate layer 1, a distributed Bragg mirror, a chalcogenide phase change material functional layer 4, and a nanoscale metal structure layer 5. The specific thicknesses are: , , One layer of ZnS and one layer As a cycle, the cycle number is 5. , .

[0053] Verification of the surface-enhanced Raman scattering substrate in this embodiment:

[0054] First, verification of the sensitivity of the surface-enhanced Raman scattering substrate: using Fourier transform infrared spectroscopy, the sensitivity of the functional layer 4 of the chalcogenide phase change material was measured. The reflection spectra of the substrate in both amorphous (AM) and crystalline (CR) states are shown in the test results. Figure 2 , Figure 3 As shown, the results indicate that The material phase transition caused a redshift of about 50 nm in the reflection valley (resonance wavelength) (from 530 nm to 580 nm), indicating that the optical response of this structure is highly sensitive to the phase transition of chalcogenide phase transition materials.

[0055] Second, verification of the reconfigurability of the surface-enhanced Raman scattering substrate: First, the substrate was thermally annealed (543K, 2 minutes) to... A redshift of the reflection valley was observed during the transition from the AM state to the CR state (crystallization). Subsequently, rapid heating and quenching were performed using nanosecond laser pulses (1064 nm, 150 mW) to quench the chalcogenide phase change material in its functional layer 4. Upon recovery from the CR state to the AM state, a blue shift occurs in the corresponding reflection valley. Furthermore, five reversible phase transition cycles were performed on the same device, and the resonance wavelength was recorded after each cycle. The results show that the line shape and peak position of the reflection spectrum remain consistent before and after the cycles, demonstrating that this surface-enhanced Raman scattering substrate possesses good reconfigurability and cyclic stability.

[0056] Third, the Raman enhancement effect of surface-enhanced Raman scattering substrates under different lattice states: crystalline and amorphous chalcogenide phase change material-based surface-enhanced Raman scattering substrates were immersed in... The R6G probe molecules were fully adsorbed in anhydrous ethanol solution at a concentration of mol / L. After removal, the residual solution on the surface was gently blown off with a nitrogen gun, and the sample was allowed to air dry naturally at room temperature in the dark. A 532 nm laser was used as the excitation source, and Raman spectra were acquired under low-power conditions (to avoid laser-induced substrate phase transition or R6G photobleaching). After subtracting the background signal, the Raman enhancement factor was calculated based on the intensity of the R6G characteristic peak. Figure 4 As shown in (a) in the figure, when In the amorphous state, the resonance position of the surface-enhanced Raman scattering substrate matches the Raman excitation wavelength, thus enhancing the R6G Raman signal; for example... Figure 4 As shown in (b) in the figure, when In its crystalline state, the resonant position of the surface-enhanced Raman scattering substrate does not match the Raman excitation wavelength, resulting in weak Raman signal enhancement of R6G. Experimental results show that by adjusting... The lattice state allows for reconfigurable control of the surface-enhanced Raman scattering effect.

[0057] An application of a surface-enhanced Raman scattering substrate for the detection of trace biomolecules.

[0058] In summary, this embodiment successfully combines chalcogenide phase change materials with tam-state structures to create a novel reconfigurable surface-enhanced Raman scattering substrate with excellent performance, which has broad application prospects in fields such as chemical and biological sensing, laboratory chip systems, and optical encryption.

[0059] The above embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A surface enhanced Raman scattering substrate, characterized by, The structure of the surface-enhanced Raman scattering substrate comprises, from bottom to top, a substrate layer, a distributed Bragg reflector, a chalcogen phase-change material functional layer, and a nanoscale metal structure layer. The distributed Bragg reflector is composed of a periodic structure stack of different refractive index dielectric materials, and one periodic structure comprises a high refractive index dielectric material layer and a low refractive index dielectric material layer, wherein the high refractive index dielectric material layer is located below; the chalcogen phase-change material functional layer is located between the distributed Bragg reflector and the nanoscale metal structure layer and is in an electric field enhancement region of a Tamm state; the thickness of the chalcogenide phase-change material functional layer is between 5 nm and 200 nm, the material of the chalcogenide phase-change material functional layer is selected from one of GeSbTe, GeTe, , GaSb, , , , AgInSbTe, InSb, InSbTe, InSe or SbTe chalcogenide phase-change material; The thickness of the noble metal film of the nanoscale metal structure layer is between 2 nm and 50 nm, and in order to achieve light transmission, the deposition thickness of the nanoscale metal structure layer is controlled to be below the maximum light transmission thickness of the noble metal; the nanoscale metal structure layer serves as a necessary component for exciting a Tamm state and also as a surface-enhanced Raman scattering active surface for loading a molecule to be detected; The chalcogen phase-change material of the chalcogen phase-change material functional layer can realize reversible regulation between amorphous and crystalline states under external light excitation, and there is a difference in the dielectric constant of the chalcogen phase-change material in the two states during the reversible regulation, which can cause a change in the resonance wavelength of the Tamm state, so that the wavelength reaches a state of approximate consistency with the wavelength of a Raman spectrum excitation laser, and the regulation of the surface-enhanced Raman scattering enhancement effect is realized; The reconfigurability of the performance of the surface-enhanced Raman scattering substrate is nonvolatile, that is, after the external light excitation is removed, the lattice state of the chalcogen phase-change material remains unchanged, and the performance of the surface-enhanced Raman scattering substrate does not change; if the performance of the surface-enhanced Raman scattering substrate is to be changed, the state of the substrate needs to be changed again by applying external light excitation.

2. The surface enhanced Raman scattering substrate according to claim 1, wherein The substrate layer material is selected from a silicon wafer, quartz, or a polymer.

3. The surface enhanced Raman scattering substrate of claim 1, wherein, The number of periodic structures in the distributed Bragg reflector is 5 to 20, the material of the high refractive index dielectric material layer is selected from GaN, Al2O3, ZnS, or ZrO2, and the thickness is between 50 nm and 200 nm; the material of the low refractive index dielectric material layer is selected from SiO2, Si3N4, MgF2, or CaF2, and the thickness is between 50 nm and 200 nm.

4. The surface enhanced Raman scattering substrate of claim 1, wherein, The noble metal film material of the nanoscale metal structure layer is selected from gold, silver, or platinum.

5. A method of producing a surface-enhanced Raman scattering substrate as claimed in any one of claims 1 to 4, characterized in that, The method comprises the following steps: First step, cleaning the substrate layer and preparing the distributed Bragg reflector; Step 1.1, sequentially using acetone, isopropyl alcohol, and deionized water to clean the substrate layer in an ultrasonic cleaning machine; Step 1.2, under room temperature conditions, using one of the following processes: thermal evaporation, electron beam evaporation, or magnetron sputtering, to alternately deposit a high refractive index dielectric material layer and a low refractive index dielectric material layer on the substrate layer to form the distributed Bragg reflector; Second step, preparing the chalcogen phase-change material functional layer; Under room temperature conditions, using one of the following processes: thermal evaporation, electron beam evaporation, or magnetron sputtering, to deposit a chalcogen phase-change material on the distributed Bragg reflector as the chalcogen phase-change material functional layer; Third step, depositing the nanoscale metal structure layer; On the surface of the chalcogen phase-change material functional layer, using one of the following processes: thermal evaporation, electron beam evaporation, or magnetron sputtering, to deposit a noble metal film as the nanoscale metal structure layer; Fourthly, the surface-enhanced Raman scattering substrate is regulated, specifically as follows: For the surface-enhanced Raman scattering substrate with the chalcogen phase change material functional layer in an amorphous state, low-energy light pulses are used for excitation, so that the temperature of the chalcogen phase change material functional layer is accurately controlled above the crystallization temperature and below the melting point temperature of the chalcogen phase change material, and crystallization is induced; For the surface-enhanced Raman scattering substrate with the chalcogen phase change material functional layer in a crystalline state, high-energy light pulses are used for excitation, so that the material is instantaneously melted and quenched to realize amorphization.

6. The method of preparing a surface-enhanced Raman scattering substrate according to claim 5, wherein In the preparation method: In step 1.2, the deposition parameters are: room temperature, high vacuum chamber, gas pressure in the range of below. In the second step, the parameters of the deposition are: room temperature, high vacuum chamber, pressure in the range of below. In the third step, the parameters of the deposition are: room temperature, high vacuum chamber, pressure in the range of below. In the fourth step, the parameters of the low-energy light pulses are as follows: the laser wavelength is in the range of 400-1500 nm, the pulse width is between picoseconds and nanoseconds, and the pulse energy is between the energy required for crystallization and the energy required for melting of the chalcogen phase change material functional layer used; In the fourth step, the parameters of the high-energy light pulses are as follows: the laser wavelength is in the range of 400-1500 nm, the pulse width is between picoseconds and nanoseconds, and the pulse energy is greater than or equal to the energy required for melting of the chalcogen phase change material functional layer used.

7. Use of a surface-enhanced Raman scattering substrate according to any one of claims 1 to 6, characterized in that, It is applied to trace substance detection, biological molecule sensing or encryption anti-counterfeiting.

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