Composite structure substrate for surface enhanced Raman scattering and preparation method thereof

Abstract

The invention relates to a composite structure substrate for surface enhanced Raman scattering and a preparation method thereof. The substrate comprises an Ag metal layer, a dielectric layer and precious metal nanoparticles, wherein the Ag metal layer is formed by an array of Ag nanorods; wherein the medium layer is coated on the Ag nanorod; wherein the noble metal nanoparticles are modified on the dielectric layer. The composite structure substrate for surface enhanced Raman scattering is good in stability, controllable in cost and high in detection sensitivity.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of composite structure substrate for surface enhanced Raman scattering and its preparation method, belong to surface enhanced Raman scattering detection field. BACKGROUND

[0002] Surface enhanced Raman scattering (SERS) technology is a powerful analytical tool, which is based on Raman scattering, i.e. the non-elastic scattering of photons when interacting with molecules. Raman scattering provides detailed information about the vibrations of molecules, which allows the identification and analysis of specific compounds in a sample. However, traditional Raman scattering signals are weak, limiting its application in trace analysis.

[0003] To solve this problem, surface enhanced Raman scattering (SERS) technology has emerged. SERS technology enhances Raman signals by using special substrates, allowing even trace amounts of organic pollutants to be detected. This substrate is usually composed of Ag or Au nanoparticles and is deposited on a suitable carrier such as a glass or silicon wafer. When light is shone on these nanoparticles, they scatter the light and produce a strong signal.

[0004] The advantage of SERS technology is its high sensitivity and fingerprint characteristics. Since the Raman scattering signal is closely related to the vibration mode of the molecule, SERS can distinguish between different types of organic pollutants. At the same time, the enhancement effect of the SERS substrate allows even trace levels of pollutants to be detected, thereby improving detection sensitivity.

[0005] In practical applications, SERS technology has been used in environmental monitoring, food safety, biomedical and other fields. For example, SERS technology can be used to detect organic pollutants in water to ensure water quality safety; it can also be used to detect additives and harmful substances in food to ensure food safety; in the biomedical field, SERS technology can be used to detect trace molecules in biological samples such as proteins, DNA, etc., providing strong support for disease diagnosis and research.

[0006] Currently, the application of SERS technology in trace organic pollutant detection is mostly the preparation of Ag or Au nanoparticles as SERS substrate. Among them, pure Ag nanostructure has excellent SERS performance, but due to the high chemical activity of nano-Ag, the surface is easy to be oxidized, sulfidized and contaminated by impurities, and the stability is poor, therefore, it is necessary to choose expensive and medium-performance Au nanostructure as SERS substrate, but this results in a significant increase in detection cost.

[0007] Therefore, there is an urgent need in the prior art to develop a SERS substrate with good stability, low manufacturing cost and high detection sensitivity. SUMMARY

[0008] Problem to be solved by the invention

[0009] In view of the above technical problems existing in the prior art, the present application provides a composite structure substrate for surface-enhanced Raman scattering and a preparation method thereof, the composite structure substrate for surface-enhanced Raman scattering of the present application is good in stability, controllable in cost and high in detection sensitivity, and meanwhile, the preparation method of the present application is good in controllability of the morphology of the composite structure substrate and good in repeatability.

[0010] Solution for solving the problem

[0011] The present application provides a composite structure substrate for surface-enhanced Raman scattering, which comprises:

[0012] an Ag metal layer, a dielectric layer and noble metal nanoparticles;

[0013] wherein the Ag metal layer is formed by an array of Ag nanorods;

[0014] wherein the dielectric layer is coated on the Ag nanorods;

[0015] wherein the noble metal nanoparticles are modified on the dielectric layer.

[0016] According to the substrate of the present application, the length of the Ag nanorods is 200-800 nm.

[0017] According to the substrate of the present application, the thickness of the dielectric layer is 0.6 nm-6 nm.

[0018] According to the substrate of the present application, the noble metal is Au.

[0019] According to the substrate of the present application, the dielectric layer is formed by at least one of Al2O3, TiO2, HfO2, ZnO, ZrO2, SnO2, Ta2O5, In2O3, MgO, ZnS, CdS, AlN, TaN, TiN and TiO2.

[0020] A preparation method of the substrate for surface-enhanced Raman scattering according to the present application comprises the following steps:

[0021] Step 1), preparing an array of Ag nanorods on a substrate by electron beam evaporation plating to obtain an Ag metal layer;

[0022] Step 2), coating the dielectric layer on the Ag nanorods by atomic layer deposition;

[0023] Step 3), modifying the noble metal nanoparticles on the dielectric layer by atomic layer deposition.

[0024] According to the preparation method, in the step 1), Ag with purity of 99.9% or above is used as the target material, and the vacuum degree is 5*10 -5 The incident angle of the electron beam is 80-88°, and the electron beam evaporation is performed to obtain the array of the inclined Ag nanorods.

[0025] According to the preparation method, in the step 2), the medium layer is formed by TiO2, and tetramethylammonium titanium and water are used as the precursors of TiO2, the tetramethylammonium titanium is pulsed for 80-120 ms, stays for 5-15 s, is flushed for 20-30 s, then the H2O is pulsed for 20-30 ms, stays for 5-15 s, is flushed for 20-30 s, one atomic layer deposition cycle is completed, and after 10-100 atomic layer deposition cycles, annealing is performed in an inert atmosphere, the annealing temperature is 400 DEG C, and the holding time is 1 hour, so that the medium layer is coated on the Ag nanorods, and N2 is used as the flushing and carrier gas.

[0026] According to the preparation method, in the step 3), the noble metal is Au, and trimethyl(trimethylphosphine) gold and tert-butyl hydrazine are used as the precursors of Au, the trimethyl(trimethylphosphine) gold is pulsed for 500-2000 ms, stays for 5-15 s, is flushed for 20-30 s, the tert-butyl hydrazine is pulsed for 100-200 ms, stays for 5-15 s, is flushed for 20-30 s, one atomic layer deposition cycle is completed, and after 30-100 atomic layer deposition cycles, the substrate for surface enhanced Raman scattering is obtained, and N2 is used as the flushing and carrier gas.

[0027] According to the preparation method, in the step 3), the temperature of atomic layer deposition is 120 DEG C-200 DEG C.

[0028] Effects of the invention

[0029] The composite structure substrate for surface enhanced Raman scattering of the application has the advantages of Ag and Au nanometer structures, is high in stability, and controllable in cost. The preparation method of the composite structure substrate adopts the physical growth method combining electron beam deposition and atomic layer deposition to prepare the composite structure substrate, the shape and size of each structure of the substrate can be accurately controlled, and the surface enhanced Raman scattering effect is optimized. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The flowchart of the preparation method of the substrate for surface enhanced Raman scattering.

[0031] Figure 2SEM images of the Ag nanorod array film substrate obtained in step 1) of Example 1, the TiO2@Ag nanorod array film composite structure substrate obtained in step 2) and the substrate-1 obtained in step 3).

[0032] Among them, (a) the substrate of the Ag nanorod array film obtained in step 1) of Example 1, (b) the substrate of the TiO2@Ag nanorod array film composite structure obtained in step 2), and (c) the substrate-1 obtained in step 3).

[0033] Figure 3 TEM test image of substrate-1 obtained in Example 1.

[0034] Figure 4 SEM test images of substrate-1, substrate-2, and substrate-3.

[0035] Among them, (a) 120℃; (b) 150℃; (c) 200℃.

[0036] Figure 5 Schematic diagram of the results of surface-enhanced Raman scattering (SERS) tests on substrate-1, substrate-pair 1, and substrate-pair 2. Detailed Implementation

[0037] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment illustrated herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0038] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0039] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0040] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0041] In this specification, reference to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc. means that a particular element described in connection with the embodiment is included in at least one embodiment described herein, and can or can not be present in other embodiments. In addition, it is to be understood that the described elements can be combined in any suitable manner in the various embodiments.

[0042] In this specification, a numerical range expressed using "numerical value A ~ numerical value B" means a range including the end point numerical values A, B.

[0043] Invention of the first aspect

[0044] The present application provides a composite structure substrate for surface enhanced Raman scattering, the substrate comprising:

[0045] an Ag metal layer, a dielectric layer and noble metal nanoparticles;

[0046] wherein the Ag metal layer is formed by an array of Ag nanorods;

[0047] wherein the dielectric layer is coated on the Ag nanorods;

[0048] wherein the noble metal nanoparticles are modified on the dielectric layer.

[0049] The composite structure substrate for surface enhanced Raman scattering of the present application has a metal plane-dielectric layer-metal nanoparticle (MIM) mirror film coupling structure, wherein the dielectric layer is an insulator / wide band gap semiconductor, and the coupling mechanism of the structure is the hybridization of localized surface plasmon resonance of metal nanoparticles and conductive surface plasmon in the mirror film. This coupling structure will cause a huge enhancement of electromagnetic field in the gap area between the metal nanoparticles and the mirror surface, forming a hot spot. Since the specific surface area of the rod structure of the Ag nanorod is much larger than that of the plane, by replacing the plane in the MIM structure with a nanorod structure, a composite structure composed of "infinite" nanomirror cavities can be constructed, greatly increasing the formation of hot spots, thereby ensuring that the composite structure substrate has high sensitivity and good time stability.

[0050] According to the substrate of the present application, the length of the Ag nanorod is 200-800 nm, preferably 400-800 nm, and more preferably 600-800 nm.

[0051] According to the substrate of the present application, the thickness of the dielectric layer is 0.6-6 nm, preferably 0.8-4 nm, and more preferably 1-2.5 nm.

[0052] According to the substrate of the present application, the noble metal is Au.

[0053] According to the substrate of the present application, the medium layer is formed by at least one of Al2O3, TiO2, HfO2, ZnO, ZrO2, SnO2, Ta2O5, In2O3, MgO, ZnS, CdS, AlN, TaN, TiN and TiO2, preferably the medium layer is formed by TiO2.

[0054] By utilizing the photocatalytic performance of TiO2, the composite structure substrate can be recycled after UV irradiation, and on the basis of retaining the original high sensitivity and rapid detection, the detection cost is greatly reduced, and the substrate has certain market competitiveness.

[0055] Invention of the second aspect

[0056] As shown in Figure 1 The present application further provides a preparation method of the substrate for surface enhanced Raman scattering according to the present application, comprising the following steps:

[0057] Step 1), preparing an array of Ag nanorods on a substrate by electron beam evaporation plating to obtain an Ag metal layer;

[0058] Step 2), coating the medium layer on the Ag nanorods by atomic layer deposition;

[0059] Step 3), modifying the noble metal nanoparticles on the medium layer by atomic layer deposition.

[0060] The type of the substrate is not particularly limited, for example, a silicon substrate or a glass substrate can be selected.

[0061] According to the preparation method of the present application, in the step 1), Ag with a purity of 99.9% or above is used as the target material, the vacuum degree is 5×10 -5 Pa, the incident angle of the electron beam is 80-88°, preferably 82-86°, and electron beam evaporation plating is performed to obtain an array of inclined Ag nanorods.

[0062] According to the preparation method, in the step 2), the medium layer is formed by TiO2, and the TiO2 precursor is selected as tetramethylammonium titanium and water, the tetramethylammonium titanium is pulsed for 80-120 ms, stays for 5-15 s, is flushed for 20-30 s, then the H2O is pulsed for 20-30 ms, stays for 5-15 s, is flushed for 20-30 s, to complete one atomic layer deposition cycle, and after 10-100 atomic layer deposition cycles, annealing is performed under an inert atmosphere, the annealing temperature is 400 DEG C, and the annealing time is 1 h, so that the medium layer is coated on the Ag nanorod, and N2 is used as the flushing and carrier gas.

[0063] Preferably, in the step 2), the medium layer is formed by TiO2, and the TiO2 precursor is selected as tetramethylammonium titanium and water, the tetramethylammonium titanium is pulsed for 100 ms, stays for 10 s, is flushed for 25 s, then the H2O is pulsed for 20 ms, stays for 5 s, is flushed for 30 s, to complete one atomic layer deposition cycle, and after 10-100 atomic layer deposition cycles, annealing is performed under an inert atmosphere, the annealing temperature is 400 DEG C, and the annealing time is 1 h, so that the medium layer is coated on the Ag nanorod, and N2 is used as the flushing and carrier gas.

[0064] According to the preparation method, in the step 3), the noble metal is Au, the Au precursor is selected as trimethyl(trimethylphosphine) gold and tert-butyl hydrazine, the trimethyl(trimethylphosphine) gold is pulsed for 500-2000 ms, stays for 5-15 s, is flushed for 20-30 s, the tert-butyl hydrazine is pulsed for 100-200 ms, stays for 5-15 s, is flushed for 20-30 s, to complete one atomic layer deposition cycle, and after 30-100 atomic layer deposition cycles, the substrate for surface enhanced Raman scattering is obtained, and N2 is used as the flushing and carrier gas.

[0065] Preferably, in the step 3), the noble metal is Au, the Au precursor is selected as trimethyl(trimethylphosphine) gold and tert-butyl hydrazine, the trimethyl(trimethylphosphine) gold is pulsed for 1000 ms, stays for 10 s, is flushed for 30 s, the tert-butyl hydrazine is pulsed for 200 ms, stays for 10 s, is flushed for 30 s, to complete one atomic layer deposition cycle, and after 30-100 atomic layer deposition cycles, the substrate for surface enhanced Raman scattering is obtained, and N2 is used as the flushing and carrier gas.

[0066] Embodiment

[0067] Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. The specific conditions not noted in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not noted by the manufacturer, which are all conventional products that can be obtained by purchase.

[0068] Example 1

[0069] Step 1):

[0070] The silicon substrate was sequentially cleaned with acetone, alcohol, and deionized water by ultrasonic cleaning and dried, and then the pretreated substrate was fixed on the sample stage of the electron beam evaporation coating machine; at room temperature, high-purity silver (purity 99.99%) was used as the target material, the chamber of the electron beam evaporation coating machine was pumped to a vacuum degree of 5×10 -5 Pa below; the incident angle of the electron beam was adjusted to 86 degrees, and the sample stage was stationary, and the Ag nanorod array film substrate with a length of 800 nm was grown on the base of the sample stage.

[0071] Step 2):

[0072] The atomic layer deposition technology (ALD) was used to coat TiO2 film on the Ag nanorod to obtain TiO2@Ag nanorod array film composite structure. Tetramethylammonium titanium (TDMAT) and water (H2O) were selected as the precursors of TiO2, which were alternately pumped into the reaction chamber, and N2 was used as the flushing and carrier gas.

[0073] The substrate of the Ag nanorod array film prepared in step 1 was placed in the middle of the atomic layer deposition reaction cavity. First, TDMAT pulse 100 ms, stop 10 s, reaction chamber flushing 25 s. Second, H2O pulse 20 ms, stop 5 s, reaction chamber flushing 30 s. This process is marked as one ALD cycle, and the TiO2 film thickness deposited by one ALD cycle is about 0.06 nm, and 40 cycles of coating are selected. Finally, the TiO2@Ag nanorod array film composite structure was annealed in an inert atmosphere using a tube furnace, the annealing temperature was 400℃, and the holding time was 1 hour.

[0074] Step 3):

[0075] The atomic layer deposition technology (ALD) was used to coat TiO2 film on the Ag nanorod to obtain TiO2@Ag nanorod array film composite structure. Tetramethylammonium titanium (TDMAT) and water (H2O) were selected as the precursors of TiO2, which were alternately pumped into the reaction chamber, and N2 was used as the flushing and carrier gas.

[0076] The TiO2@Ag nanorod array film composite substrate prepared in step 2 was placed in the middle of the atomic layer deposition (ALD) chamber. The ALD temperature was 150℃. First, a Me3Au(PMe3) pulse was applied for 1000ms, followed by a 10s pause, and then the reaction chamber was rinsed for 30s. Next, a tBuNHNH2 pulse was applied for 200ms, followed by a 10s pause, and then the reaction chamber was rinsed for 30s. This process was marked as one ALD cycle, and 50 cycles were performed to prepare the Au@TiO2@Ag nanorod array film composite substrate, denoted as substrate-1.

[0077] Example 2

[0078] The atomic layer deposition temperature in step 3) was set to 120°C, and the composite structure substrate of Au@TiO2@Ag nanorod array film was prepared in the same manner as in Example 1, denoted as substrate-2.

[0079] Example 3

[0080] The atomic layer deposition temperature in step 3) was set to 200℃, and the composite structure substrate of Au@TiO2@Ag nanorod array film was prepared in the same manner as in Example 1, and denoted as substrate-3.

[0081] Comparative Example 1

[0082] Without performing step 3), everything else is the same as in Example 1, resulting in substrate-pair 1.

[0083] Comparative Example 2

[0084] Steps 2) and 3) are omitted, and everything else is the same as in Example 1, resulting in substrate-pair 2.

[0085] SEM test

[0086] The surface morphology and microstructure of the samples were characterized using a ZEISS GeminiSEM 500 field emission scanning electron microscope. Before testing, the samples were cut into 1cm × 1cm pieces and lightly blew with nitrogen to remove surface dust. Testing was conducted in high vacuum mode, with an accelerating voltage set to 15 kV and a working distance of approximately 9 mm. Multiple regions of each sample were imaged to ensure the representativeness of the characterization results. The substrates of the Ag nanorod array film obtained in step 1) of Example 1, the TiO2@Ag nanorod array film composite structure obtained in step 2), and substrate-1 obtained in step 3) were tested, and the results are as follows: Figure 2 As shown.

[0087] Tests were performed on substrate-1, substrate-2, and substrate-3, and the results are as follows: Figure 4 As shown.

[0088] TEM test

[0089] The microstructure and crystal characteristics of the samples were characterized using a JEM-2100F field emission transmission electron microscope (FET). Before testing, the powder samples were ultrasonically dispersed in anhydrous ethanol and dropped onto the surface of a carbon film copper mesh, allowing them to air dry. TEM was performed at an accelerating voltage of 200 kV, acquiring high-resolution imaging (HRTEM) and selected area electron diffraction (SAED) data to analyze the lattice structure and phase composition of the material. The substrate-1 was tested, and the results are as follows: Figure 3 As shown.

[0090] Surface enhanced Raman scattering (SERS) test

[0091] The SERS substrate was immersed in the test solution for 30 min, then removed and allowed to air dry at room temperature. SERS measurements were performed using a HORIBA LabRAM HR Evolution Raman spectrometer with a 633 nm laser as the excitation source. The laser power was set to 15 mW, and the laser spot diameter was approximately 10 μm. Spectra were acquired at 10 different locations for each sample, and the average values ​​were used for subsequent analysis.

[0092] The substrate-1, substrate-pair 1, and substrate-pair 2 were used at a concentration of 5 × 10⁻⁶. -6 A solution of MB molecules in mol / L was subjected to surface-enhanced Raman scattering (SERS) testing, and the results are as follows: Figure 5 As shown in (a) of the diagram.

[0093] For a concentration of 5×10 -6 mol / L, 1×10 -6 mol / L, 5×10 -7 mol / L, 1×10 -7 A solution of MB molecules in mol / L was subjected to surface-enhanced Raman scattering (SERS) testing, and the results are as follows: Figure 5 As shown in (b) of the diagram.

[0094] Figure 5 (c) Comparison of SERS performance of Ag and Au@TiO2@Ag substrates before and after 2 weeks of storage, to highlight the time stability of Au@TiO2@Ag substrates.

[0095] After substrate-1 and substrate-pair 2 were placed for 2 weeks, surface-enhanced Raman scattering (SERS) tests were performed on 50 nm PS microspheres from substrate-1 and substrate-pair 2. The results are as follows. Figure 5 As shown in (d) in the figure.

[0096] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0097] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A composite structure substrate for surface enhanced Raman scattering, characterized by, The substrate comprises: an Ag metal layer, a dielectric layer and noble metal nanoparticles; wherein the Ag metal layer is formed by an array of Ag nanorods; wherein the dielectric layer is coated on the Ag nanorods; wherein the noble metal nanoparticles are modified on the dielectric layer.

2. The substrate of claim 1, wherein, The length of the Ag nanorods is 200-800 nm.

3. The substrate according to claim 1 or 2, wherein, The thickness of the dielectric layer is 0.6-6 nm.

4. The substrate according to claim 1 or 2, wherein, The noble metal is Au.

5. The substrate according to claim 1 or 2, wherein The dielectric layer is formed by at least one of Al2O3, TiO2, HfO2, ZnO, ZrO2, SnO2, Ta2O5, In2O3, MgO, ZnS, CdS, AlN, TaN, TiN and TiO2.

6. A method for the preparation of a substrate for surface enhanced Raman scattering according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: Step 1), preparing an array of Ag nanorods on a substrate by electron beam evaporation, to obtain an Ag metal layer; Step 2), coating the dielectric layer on the Ag nanorods by atomic layer deposition; Step 3), modifying the noble metal nanoparticles on the dielectric layer by atomic layer deposition.

7. The production method according to claim 6, wherein In the step 1), Ag with purity of 99.9% or above is used as the target material, and the vacuum degree is 5×10 -5 The electron beam evaporation is performed at an incident angle of 80-88° to obtain the array of the inclined Ag nanorods.

8. The production method according to claim 6 or 7, wherein In Step 2), the dielectric layer is formed by TiO2, using tetramethylammonium titanium and water as the precursors of TiO2, pulsing the tetramethylammonium titanium for 80-120 ms, staying for 5-15 s, flushing for 20-30 s, then pulsing H2O for 20-30 ms, staying for 5-15 s, flushing for 20-30 s, to complete one atomic layer deposition cycle, and performing 10-100 atomic layer deposition cycles as above, and then annealing in an inert atmosphere, at an annealing temperature of 400℃, for 1 hour, to coat the dielectric layer on the Ag nanorods, wherein N2 is used as the flushing and carrier gas.

9. The production method according to claim 6 or 7, wherein In Step 3), the noble metal is Au, using trimethyl(trimethylphosphine)gold and tert-butyl hydrazine as the precursors of Au, pulsing the trimethyl(trimethylphosphine)gold for 500-2000 ms, staying for 5-15 s, flushing for 20-30 s, pulsing the tert-butyl hydrazine for 100-200 ms, staying for 5-15 s, flushing for 20-30 s, to complete one atomic layer deposition cycle, and performing 30-100 atomic layer deposition cycles as above, to obtain the substrate for surface-enhanced Raman scattering, wherein N2 is used as the flushing and carrier gas.

10. The production method according to claim 6 or 7, wherein In Step 3), the temperature for atomic layer deposition is 120-200℃.

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