Preparation method and application of an A-B-A nano trimer array

Abstract

The present invention discloses a preparation method and application of an A-B-A nano-trimer array. The method is as follows: an A-A dimer nano-array is prepared by depositing material A on a double-pass nano-pore array template through an angled oblique deposition method; the pore size of the template is regulated by depositing material on the surface of the above-mentioned template through physical vapor deposition, so that material B can be deposited inside or near the gaps between the A-A dimers; finally, material B is deposited inside or around the gaps between the A-A dimers, and the template is removed to obtain an A-B-A trimer nano-array. In the present invention, material A provides plasmon "hot spots", and B is a material for specifically adsorbing target molecules. By precisely constructing, B nanoparticles are deposited between A-A nanoparticles, ensuring that the target molecules are adsorbed at the "hot spots", and solving the problem of uneven distribution of "hot spots" in surface-enhanced Raman scattering. The present invention can be used as a spectral sensing chip for fields such as single-molecule detection and catalytic research.

Description

Technical Field

[0001] The present invention relates to a method for three-dimensional micro-nano processing and its applications, and particularly to a preparation method and applications for constructing an A-B-A nano-trimer array. Background Art

[0002] Noble metal material systems with nanostructures exhibit unique optical properties. Especially under the action of an external optical field, the cooperative oscillation of electrons inside metal nanoparticles can excite surface plasmon resonance on their surfaces, thereby enhancing the local electromagnetic field on the metal surface and obtaining a series of linear and nonlinear optical effects. Therefore, surface-enhanced Raman spectroscopy (SERS) based on the surface plasmon characteristics of noble metal nanostructure systems has been widely applied to research in many fields. As an important modern spectroscopic technique, Raman spectroscopy can reflect the vibrational and rotational energy information of molecular bond energies and has advantages such as "label-free" and "fingerprint". It is widely used in fields such as biosensing, chemical detection and analysis, single-molecule detection, and catalytic reaction research. However, in the actual engineering application process, obtaining a nanostructured substrate with a uniform "hot spot" is a necessary means to obtain a Raman spectrum with high sensitivity and signal-to-noise ratio, which has also become a research field that many researchers are concerned about.

[0003] In order to obtain a uniform hot spot distribution, researchers use a bottom-up assembly method to obtain uniform hot spots. However, this method will introduce new chemical functional groups such as surfactants to interfere with the signal of the substance to be measured, which limits the recognition of analytes by SERS spectra. Although top-down lithography and ion beam etching techniques can prepare nanostructures with uniform hot spots and can avoid the interference of substances such as surfactants, they require the use of high-precision experimental equipment such as lithography machines or ion beam etching sets. Therefore, the requirements for experimental conditions are quite high, especially in the preparation of nanostructured substrates with large-area dimensions, there are certain technical difficulties. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to provide a preparation method for an A-B-A nano-trimer array that can solve the problem of non-uniform distribution of "hot spots" in surface-enhanced Raman scattering;

[0005] The second object of the present invention is to provide an application of the A-B-A nano-trimer array prepared by the above method.

[0006] Technical Solution: The preparation method for the A-B-A nano-trimer array described in the present invention includes the following steps:

[0007] (1) Prepare a double-pass nanopore array template;

[0008] (2) Deposit material A on the double-pass nanopore array template by angled inclined deposition method to obtain an A-A dimer nanoarray;

[0009] (3) Deposit a metal material on the surface of the double-pass nanopore array template in step (2) by physical vapor deposition to regulate the pore size of the double-pass nanopore array, so that material B can be deposited inside or around the gap of the A-A dimer;

[0010] (4) Deposit material B inside or around the gap of the A-A dimer in step (3). After completion, remove the double-pass nanopore array template to obtain an A-B-A trimer nanoarray.

[0011] Among them, in step (1), the method for preparing the double-pass nanopore array template is as follows: First, prepare a single-channel nanopore array template, then expand the single-channel nanopore array template, spin-coat an organic polymer on the surface, remove the aluminum back substrate, and etch the alumina on the back of the nanopore array and regulate the pore depth channel of the nanopore array by the hot melt adhesive protection method. Finally, transfer it to a substrate to obtain a double-pass nanopore array template. Preferably, the double-pass nanopore array template is a double-pass AAO nanopore array template.

[0012] Furthermore, the method for preparing the single-pass nanopore array template is a two-step anodic oxidation electrochemical process; the specific process is: After cleaning the high-purity aluminum sheet, it is prepared by electrochemical polishing, first anodic oxidation, membrane removal, and second anodic oxidation in sequence; preferably, the voltages applied in the two anodic oxidations are 30-50V, the oxidation time is 2-14h, the pore diameter is 20-40nm, the pore spacing is 70-150nm, and the depth of the pore channel is 100-500nm.

[0013] Furthermore, it is preferably to use phosphoric acid for pore expansion; the pore expansion time is 5-40min; the temperature of phosphoric acid is preferably 30°C, and the mass fraction is 5%.

[0014] Furthermore, it is preferably to use the hot melt adhesive protection method to spin-coat PMMA to protect the pore channels, so that the pore channels are filled with protective organic substances. Preferably, the spin-coating parameters are 300r / min - 2000r / min, the concentration of PMMA is 1% - 12%, and a PMMA / single-pass nanopore array is obtained; heat-cure the PMMA / single-pass nanopore array, the heating temperature is 80-200°C, and the time is 5-50min, which can cure PMMA to form a protection for the nanopores.

[0015] Furthermore, float the PMMA / single-pass nanopore array in an alkaline solution to remove the aluminum oxide on the back aluminum substrate of the single-pass nanopore array, and then rinse it thoroughly with a large amount of deionized water; then float it in a salt solution to remove the back aluminum substrate; during the reaction process, continuously remove the adhered Cu particles and bubbles. Preferably, the alkaline solution is sodium hydroxide solution with a concentration of 5%; preferably, the salt solution is copper chloride with a concentration of 5-200 g / L.

[0016] Furthermore, float the PMMA / single-pass nanopore array with the aluminum substrate removed on the surface of the mixed solution to etch the aluminum oxide on the back of the nanopore array template for 5-40 minutes. By changing the etching time, the pore depth of the double-pass nanopore array template can be regulated; the longer the etching time, the smaller the pore depth of the double-pass nanopore array film. Finally, transfer the obtained double-pass nanopore array template to a solution to soak and remove the PMMA, and then transfer it to a silicon wafer or quartz to obtain an ultra-thin double-pass nanopore array template with the target pore depth. Preferably, the mixed solution is 5-100 g / L copper chloride and 5%-15% phosphoric acid; the temperature is preferably 30°C. Preferably, the pore depth is 150-300 nm. The soaking solution is acetone; the soaking time is 10-60 minutes, and then transfer it to the substrate of a silicon wafer or quartz wafer, so as to obtain an ultra-thin double-channel AAO nano-template, which can ensure that material A can be smoothly deposited on the substrate during the subsequent angle tilting process.

[0017] Among them, in step (2), select a double-pass nanopore array template sample with an appropriate pore depth and place it in the chamber of an electron beam coating machine. Place the target material A, and after the vacuum is pumped to below 7×10 -4 Pa, turn on the electron beam to start depositing the target material A. The method of depositing with an angled tilt is as follows: for the double-pass nanopore array template, deposit the target material A for the first time at an angled tilt of α, then rotate the substrate of the double-pass nanopore array template by 180°, and deposit for the second time at an angled tilt of β to obtain an A-A dimer nanoarray. Preferably, the angled tilt α is 5°-30°, and the deposition thickness is 5-50 nm; the angled tilt β is 4°-28°, and the deposition thickness is 5-60 nm, so that the particle gap and size of the A-A dimer can be adjusted. The selected material A is one of Ag, Au, and Cu, which can provide plasmons in the visible light range. If the angled tilt during the deposition process is greater than the preset parameter, it will cause material A to deposit on the AAO pore wall and it is difficult to form an A-A dimer. If the deposition angle is too small, it will cause adhesion between A-A, affecting the subsequent deposition of material B.

[0018] Among them, the pore depth of the A-A dimer nanoarray is 150 - 300 nm by the inclined deposition method, ensuring that material A can be smoothly deposited on the substrate during the subsequent angle inclination process. If the pore depth of the double-pass nanohole array is greater than 300 nm, it will cause difficulty in depositing the material on the substrate surface during the subsequent angle deposition process, and the corresponding dimer array cannot be obtained. If the template pore depth is less than 150 nm, the template is prone to breakage when transferred to the surface of a silicon wafer or quartz wafer, making it difficult to operate.

[0019] Among them, in step (3), the physical vapor deposition method can only deposit the material on the surface of the double-pass nanohole array template, rather than on the A-A dimer. Preferably, the physical vapor deposition method is magnetron sputtering; the specific process is as follows: Place the sample obtained in step (2) in the magnetron sputtering coating chamber. After pumping to a vacuum of 4×10 -4 Pa, turn on the magnetron sputtering instrument, set the argon gas flow rate to 4 - 12 sccm, keep the power at 40 - 90 W, and maintain the vacuum at 9.49×10 -1 Pa - 9.67×10 -1 Pa, start the deposition of the metal target, and control the coating time within 5 - 200 s; preferably, the deposited metal is one of Ag, Cu, Cr, Ge, which can ensure the regulation of the pore diameter of the double-pass nanohole array. During this sputtering process, factors such as vacuum degree, power, and gas flow rate will affect the coating quality. Therefore, it is necessary to select within the above reasonable parameter range for coating. Especially the magnetron sputtering time. If the time is too short, the diameter of the subsequent B material nanoparticles will be too large to cover the surface of the A-A dimer. If the time is too long, the diameter of the B material nanoparticles will be too small, affecting the adsorption of the B material to the molecule to be measured in the subsequent spectral test.

[0020] Among them, in step (4), preferably, the A-B-A trimer nanoarray is prepared by electron beam deposition; the deposition is vertical deposition; the specific process is as follows: Place the sample obtained in step (3) on the substrate. After pumping to a vacuum of 5×10 -4 Pa - 7×10 - 4 Pa, turn on the electron beam, start the deposition of the B material target, take out the sample after the deposition is completed, and remove the double-pass nanohole array template to obtain the A-B-A trimer nanoarray. Preferably, use tape to tear off the double-pass nanohole array template to achieve the removal effect; preferably, the thickness of the deposited B material is 2 - 50 nm; the B material is at least one of Au, Pt, Cu, Ag, Pd, SiO x 、TiO x 、Al2O3、WO x 、MgF2、TiN; among them, SiO x is preferably SiO2, SiO; TiO xPreferably TiO or TiO₂. Among them, material B can achieve specific adsorption of target molecules, ensuring the adsorption of molecules to be detected in the "hot spot" area. In this process, material B can be selected according to the nature of the functional groups of the molecules to be detected. If the deposition thickness of material B is too small, the diameter of B nanoparticles will be too small, affecting the subsequent adsorption of molecules to be detected. If the deposition thickness is too large, the diameter of B particles will become larger, covering the surface of A-A dimers.

[0021] Application of the A-B-A nano-trimer array prepared by the above method in Raman spectroscopy detection.

[0022] Among them, the A material is a metal nanoparticle with surface-enhanced Raman scattering effect or fluorescence enhancement effect; the B material is a material that specifically adsorbs molecules to be detected.

[0023] Among them, the A-B-A trimer nano-array sample is immersed in molecules to be detected with different concentrations, the immersion time is controlled to be 1-6 h, after immersion, it is taken out, rinsed and dried, and the signals of molecules to be detected with different concentrations are collected by a confocal Raman spectroscopy instrument.

[0024] Principle of the invention: In the study of surface-enhanced Raman scattering, since the "hot spot" area only accounts for 0.2-1% of the entire surface of the plasmonic material, this uneven distribution of "hot spots" will lead to a decrease in the probability of molecules falling into the "hot spot" area during the adsorption process, thereby reducing the detection sensitivity and detection efficiency. To solve the problem of uneven distribution of hot spots in SERS, the present invention proposes a method for preparing a trimer A-B-A nano-array. The A material is a plasmonic metal nanoparticle that can enhance the SERS signal, which is used to provide "hot spots", and the B material is a target material with specific adsorption ability for molecules. Through precise construction, the present invention precisely deposits B particles between two A particles. Due to the specific adsorption of the B material to the probe molecules, it is ensured that the molecules to be detected can be stably adsorbed in the "hot spot" area, improving the detection efficiency and sensitivity of the molecules. The trimer nanostructure array prepared by the present invention has the advantages of a large area and will not cause interference from other factors such as surfactants. Its ultra-high detection sensitivity can be used as an SERS, fluorescence and other spectral sensing detection chip.

[0025] Advantages: Compared with the prior art, the present invention has achieved the following remarkable effects: (1) In this nanostructure, material A provides "hot spots" to enhance the Raman signal of molecules, and material B can specifically adsorb the molecule to be detected and make it stably adsorbed in the "hot spot" region, solving the problem of uneven distribution of "hot spots" in SERS, thereby improving the detection sensitivity of the molecule to be detected; (2) Based on this template, a large-area regularly arranged trimer A-B-A metal nanostructure array is prepared, and the structure of this array has good uniformity and high repeatability; (3) The metal materials of A and B can be replaced according to experimental requirements, and can be used in the fields of optoelectronic device preparation, catalytic energy reaction research, etc. (4) Compared with photolithography and ion beam etching methods, the preparation process of the method of the present invention is simple, the production cost is low, and the repeatability and stability are high; (5) It can be used as a spectral sensing chip for food, environmental analyte detection, single molecule detection, molecular catalytic reaction, medical diagnosis, biosensing, food detection and other fields. Description of the Drawings

[0026] Figure 1 is the preparation process of the A-B-A trimer metal nanostructure array;

[0027] Figure 2 are SEM images of the upper surface of AAO after two-angle deposition in Examples 1, 2, and 3;

[0028] Figure 3 are SEM images of the metal nanoarrays of Ag-Ag dimers in Examples 1, 2, and 3;

[0029] Figure 4 are SEM images of the surface of the AAO film after the samples in Examples 1, 2, and 3 after angle deposition are further subjected to magnetron sputtering;

[0030] Figure 5 are SEM images, TEM images and elemental mapping images of the Ag-Au-Ag trimer metal nanoarray obtained by tearing off the AAO template with tape after vertically depositing the Au material in Examples 1, 2, and 3;

[0031] Figure 6 are SERS spectra of the metal nanoarrays of Ag-Ag dimers in Example 1 and the metal nanoarrays of Ag-Au-Ag trimers adsorbed with equal volume and the same concentration of 4-mercaptobenzoic acid molecules on the surface;

[0032] Figure 7 is the SERS spectrum of single-molecule-level rhodamine 6G on the surface of the Ag-Au-Ag trimer metal nanoarray in Example 2;

[0033] Figure 8It is the SERS spectrogram of the metal nanoarray of the Ag-Au-Ag trimer in Example 3 in the application of detecting organic volatile gases.

[0034] Figure 9 It is the SEM image of the Al2O3@Au-Au-Al2O3@Au trimer metal nanoarray in Example 4;

[0035] Figure 10 It is the SERS spectrogram of different concentrations of crystal violet molecules on the surface of the Al2O3@Au-Au-Al2O3@Au trimer array in Example 4;

[0036] Figure 11 It is Ag-TiO X -Ag trimer metal nanoarray's SEM image, TEM image and elemental mapping image. Detailed implementation manners

[0037] The present invention will be further described in detail below.

[0038] Example 1

[0039] A preparation method of an Ag-Au-Ag trimer nanoarray, the preparation process is shown in Figure 1 and the comparison of the sensitivity with the Ag-Ag dimer nanoarray in SERS detection, specifically includes the following steps:

[0040] (1) Immerse the 99.999% high-purity aluminum sheet in acetone, alcohol and deionized water in sequence, ultrasonically clean for 5 min, and then dry with nitrogen. Then, the cleaned aluminum sheet is successively processed by electrochemical polishing, first anodic oxidation, film removal and second anodic oxidation to obtain a single-channel AAO template with a pore depth of 300 nm, a pore diameter of 30 nm and a pore spacing of 100 nm; wherein, the parameters of electrochemical polishing are: the volume ratio of perchloric acid to absolute ethanol is 1:4, the DC voltage is 15 V, and the time is 5 min; the parameters of the first anodic oxidation are: 0.3 M oxalic acid solution, the temperature is kept at 0 °C, the DC voltage is 40 V, and the oxidation time is 12 h; the parameters of film removal are: a mixed solution of phosphoric acid with a volume ratio of 1:1, a mass fraction of 6% and chromic acid with a mass fraction of 1.8%, the temperature is kept at 75 °C, and the time is 2 h. The parameters of the second anodic oxidation are: 0.3 M oxalic acid solution, the temperature is kept at 0 °C, the DC voltage is 40 V, and the oxidation time is 12 h;

[0041] (2) I. Immerse the single-pass AAO template in step (1) above in a phosphoric acid solution at 30 °C with a mass fraction of 5% for pore widening for 27 min, then rinse with a large amount of deionized water and dry. II. Spin-coat PMMA with a mass fraction of 5%. Spin-coat is carried out with the parameters of 300 r / min for the first step for 300 s and 1200 r / min for the second step for 60 s respectively. III. Place the spin-coated PMMA / AAO on a hot plate and heat for 10 min. IV. Float the PMMA / AAO in a sodium hydroxide solution with a mass fraction of 5% to remove the aluminum oxide on the back of the AAO, then rinse thoroughly with a large amount of deionized water and float it in a copper chloride solution of 127 g / L to remove the aluminum on the back;

[0042] (3) Transfer the PMMA / AAO film with the aluminum back removed to the liquid surface of a mixed solution of 20 g / L copper chloride and 5% phosphoric acid at 30 °C to remove the AAO on the back to form a double-channel AAO film for 35 min. Finally, transfer the PMMA / AAO to an acetone solution and soak for 40 min to remove the PMMA, and then transfer it to a clean quartz surface to obtain an ultra-thin double-channel AAO template with a pore depth of about 240 nm;

[0043] (4) Place the ultra-thin double-channel AAO template sample with a pore depth of about 240 nm in the electron beam coating machine chamber, place the Ag target, and after the vacuum is pumped to below 7×10 -4 Pa, turn on the electron beam to start depositing the Ag target material. The tilt angle of the first deposition is controlled at 8.5°, and the deposition thickness is 27 nm. The tilt angle of the second deposition is controlled at 7.5°, and the deposition thickness is 33 nm. The SEM image of the upper surface of the AAO after two-angle depositions is as shown in Figure 2 It can be seen that after two-angle depositions, it is obvious to see the formation of, for example, Ag-Ag dimer nanoarrays at the bottom of the AAO. At the same time, the pore diameter on the upper surface of the AAO nano-template is about 75 nm. A dimer Ag-Ag nanoarray structure is obtained, as shown in Figure 3 It can be seen from the figure that by strictly controlling the deposition angle, a dimer Ag-Ag nanoarray structure can be successfully prepared;

[0044] (5) Use magnetron sputtering to regulate the pore diameter of the ultra-thin double-channel AAO template with a pore depth of about 240 nm: Place the Ag-Ag dimer sample in the magnetron sputtering coating chamber, and after pumping the vacuum to about 4×10 -4 Pa, turn on the magnetron sputtering instrument, set the argon gas flow rate to 8 sccm, keep the power at 60 W, adjust the shutter valve to maintain the vacuum at about 9.49×10 -1 Pa, and then start depositing the Ag target material. The coating time is controlled at 160 s. As compared with Figure 2After comparison, it was found that the pore size of the AAO film significantly decreased after magnetron sputtering deposition, and the pore size was about 35 nm, as Figure 4 shown;

[0045] (6) Preparation of Ag-Au-Ag trimeric nanoarrays: Place the sample after magnetron sputtering in the electron beam coating chamber, place the Au target, and wait until the vacuum is pumped to below 7×10 -4 Pa. Then turn on the electron beam to start the deposition of the Au target material vertically, and control the thickness of the deposited Au material to be 20 nm. After the deposition of the Au material is completed, select 3M semi-transparent magic tape to tear off the AAO film to obtain Ag-Au-Ag trimeric metal nanoarrays, as Figure 5 shown. Among them, the left figure is the SEM image, and the right figure is the elemental mapping image; it can be seen from Figure 5 that this process can deposit Au in the gap between Ag-Ag dimers, and successfully realize the preparation of Ag-Au-Ag trimeric metal nanoarrays.

[0046] (7) Immerse the obtained Ag-Au-Ag trimers and Ag-Ag dimer metal nanoarrays separately in 5 mL of 4-mercaptobenzoic acid (4-MBA) solution with a concentration of 10 -5 M for 4 h. After taking them out, wash them with alcohol and dry them with nitrogen. Then use a confocal Raman spectrometer to collect the SERS signals on the surfaces of the two different arrays. The laser wavelength is selected as 633 nm, the power is 0.5 mW, the grating is selected as 600 g / mm, and the integration time is 10 s. The experimental results show that due to the high affinity of the Au material in the Ag-Au-Ag trimeric metal nanoarrays for thiol molecules, the probability of the analyte molecules adsorbing on the "hot spots" increases, thus improving the SERS signals of the molecules, as Figure 6 shown. It can be clearly seen from the figure that compared with the Ag-Ag dimer array, the Ag-Au-Ag trimeric metal nanoarrays can significantly improve the SERS signals of 4-MBA.

[0047] Example 2

[0048] A preparation method of Ag-Au-Ag trimeric nanoarrays, the preparation process is shown in Figure 1 , and its application in single molecule detection, specifically including the following steps:

[0049] (1) Immerse 99.999% high-purity aluminum sheets successively in acetone, alcohol, and deionized water, ultrasonically clean for 5 min, and then dry with nitrogen. Then, subject the cleaned aluminum sheets to electrochemical polishing, first anodic oxidation, film removal, and second anodic oxidation to obtain a single-channel AAO template with a pore depth of 300 nm, a pore diameter of 30 nm, and a pore spacing of 100 nm. Among them, the parameters of electrochemical polishing are: the volume ratio of perchloric acid to absolute ethanol is 1:4, the DC voltage is 15 V, and the time is 5 min. The parameters of the first anodic oxidation are: 0.3 M oxalic acid solution, the temperature is maintained at 0 °C, the DC voltage is 40 V, and the oxidation time is 12 h. The parameters of film removal are: a mixed solution of phosphoric acid with a volume ratio of 1:1, a mass fraction of 6%, and chromic acid with a mass fraction of 1.8%, the temperature is maintained at 75 °C, and the time is 2 h. The parameters of the second anodic oxidation are: 0.3 M oxalic acid solution, the temperature is maintained at 0 °C, the DC voltage is 40 V, and the oxidation time is 12 h;

[0050] (2) I. Immerse the single-channel AAO template in (1) above in a 5% phosphoric acid solution at 30 °C for pore expansion for 27 min, then rinse with a large amount of deionized water and dry. II. Spin-coat PMMA with a mass fraction of 5%. Spin-coat is carried out with the parameters of the first step being 300 r / min for 300 s and the second step being 1200 r / min for 60 s respectively. III. Place the spin-coated PMMA / AAO on a hot plate and heat for 10 min. IV. Float the PMMA / AAO in a 5% sodium hydroxide solution to remove the aluminum oxide on the back of the AAO, then rinse thoroughly with a large amount of deionized water and float it in a 127 g / L copper chloride solution to remove the aluminum on the back;

[0051] (3) Transfer the PMMA / AAO film with the aluminum back removed to the liquid surface of a mixed solution of 20 g / L copper chloride and 5% phosphoric acid at 30 °C to remove the AAO on the back and form a double-channel AAO film for 35 min. Finally, transfer the PMMA / AAO to an acetone solution and soak for 40 min to remove the PMMA, and then transfer it to a clean quartz surface to obtain an ultra-thin double-channel AAO template with a pore depth of about 240 nm;

[0052] (4) Place the ultra-thin double-channel AAO template sample with a pore depth of about 240 nm in the chamber of an electron beam coating machine, place the Ag target, and after the vacuum is pumped to below 7×10 -4 Pa, turn on the electron beam to start depositing the Ag target material. The tilt angle of the first deposition is controlled at 8.5°, and the deposition thickness is 27 nm. The tilt angle of the second deposition is controlled at 7.5°, and the deposition thickness is 33 nm. The SEM image of the upper surface of the AAO after two-angle depositions is as Figure 2As shown, it can be seen that after two-angle depositions, an Ag-Ag dimer nanoarray can be clearly seen formed at the bottom of the AAO. Meanwhile, the pore diameter on the upper surface of the AAO nano-template is approximately 75 nm. The dimer Ag-Ag nanoarray structure is obtained, as Figure 3 shown. It can be seen from the figure that by strictly controlling the deposition angle, the dimer Ag-Ag nanoarray structure can be successfully prepared;

[0053] (5) Regulating the pore diameter of an ultra-thin double-channel AAO template with a pore depth of about 240 nm by magnetron sputtering: Place the Ag-Ag dimer sample in the magnetron sputtering coating chamber. After pumping to a vacuum of about 4×10 -4 Pa, turn on the magnetron sputtering instrument. Set the argon gas flow rate to 8 sccm, keep the power at 60 W, and adjust the shutter valve to maintain the vacuum at around 9.49×10 -1 Pa. Then start depositing the Ag target material, and control the coating time to 160 s. After comparison with Figure 2 it is found that the pore diameter of the AAO film significantly decreases after magnetron sputtering deposition, and the pore diameter is approximately 35 nm, as Figure 4 shown;

[0054] (6) Preparation of the Ag-Au-Ag trimer nanoarray: Place the sample after magnetron sputtering in the electron beam coating chamber, place the Au target material, and after pumping the vacuum below 7×10 -4 Pa, turn on the electron beam to start vertical deposition of the Au material, and control the thickness of the deposited Au material to 20 nm. After the deposition of the Au material is completed, use 3M semi-transparent magic tape to tear off the AAO film to obtain the Ag-Au-Ag trimer metal nanoarray, as Figure 5 shown. It can be seen from the figure that after the above operations, the Au material can perfectly fall in the middle of the Ag-Ag dimer nano-gap. This process can deposit Au in the Ag-Ag dimer gap, and successfully realize the preparation of the Ag-Au-Ag trimer metal nanoarray.

[0055] (7) Immerse the obtained Ag-Au-Ag trimer metal nanoarray in 1 mL of rhodamine 6G solution with a concentration of 10 -13 M (single-molecule level) for 4 h. After taking it out, wash it with alcohol and dry it with nitrogen. Then use a confocal Raman spectrometer to collect the SERS signal of rhodamine 6G on its surface. Select a laser wavelength of 532 nm, a power of 0.5 mW, a grating of 600 g / mm, and an integration time of 10 s. The experimental results show that this array can detect the SERS signal at the single-molecule level of rhodamine 6G, and the Raman spectrum is as Figure 7 shown. It can be seen from the figure that the rhodamine 6G molecule is at 612 cm -1The full width at half maximum of the Raman peak at [location] is relatively narrow, which conforms to the spectral phenomenon of single-molecule detection. Considering its ultra-low concentration, it can be considered that this detection approaches the single-molecule level.

[0056] Example 3

[0057] A preparation method of an Ag-Au-Ag trimer nanoarray. The preparation process is shown in Figure 1 , and its application in the detection of organic volatile gas VOC, which specifically includes the following steps:

[0058] (1) Immerse a 99.999% high-purity aluminum sheet in acetone, alcohol, and deionized water in sequence, ultrasonically clean for 5 min, and then dry with nitrogen. Then, the cleaned aluminum sheet is successively treated by electrochemical polishing, first anodic oxidation, film removal, and second anodic oxidation to obtain a single-channel AAO template with a pore depth of 300 nm, a pore diameter of 30 nm, and a pore spacing of 100 nm. Among them, the parameters of electrochemical polishing are: the volume ratio of perchloric acid to absolute ethanol is 1:4, the DC voltage is 15 V, and the time is 5 min; the parameters of the first anodic oxidation are: 0.3 M oxalic acid solution, the temperature is maintained at 0 °C, the DC voltage is 40 V, and the oxidation time is 12 h; the parameters of film removal are: a mixed solution of phosphoric acid with a volume ratio of 1:1, a mass fraction of 6%, and chromic acid with a mass fraction of 1.8%, the temperature is maintained at 75 °C, and the time is 2 h. The parameters of the second anodic oxidation are: 0.3 M oxalic acid solution, the temperature is maintained at 0 °C, the DC voltage is 40 V, and the oxidation time is 12 h;

[0059] (2) I. Immerse the single-channel AAO template in (1) above in a 5% phosphoric acid solution at 30 °C for pore expansion for 27 min, then rinse with a large amount of deionized water and dry. II. Spin-coat PMMA with a mass fraction of 5%. Spin-coating is carried out with the parameters of the first step being 300 r / min for 300 s and the second step being 1200 r / min for 60 s respectively. III. Place the spin-coated PMMA / AAO on a hot plate and heat for 10 min. IV. Float the PMMA / AAO in a 5% sodium hydroxide solution to remove the aluminum oxide on the back of the AAO, then rinse with a large amount of deionized water and float it in a 127 g / L copper chloride solution to remove the aluminum on the back;

[0060] (3) Transfer the PMMA / AAO film with the aluminum back removed to the liquid surface of a mixed solution of 20 g / L copper chloride and 5% phosphoric acid at 30 °C to remove the AAO on the back to form a double-channel AAO film for 35 min. Finally, transfer the PMMA / AAO to an acetone solution and soak for 40 min to remove the PMMA, and then transfer it to a clean quartz surface to obtain an ultra-thin double-channel AAO template with a pore depth of about 240 nm;

[0061] (4) Place the ultra-thin double-channel AAO template sample with a hole depth of about 240 nm in the electron beam coating machine chamber, place the Ag target, and after the vacuum is pumped to below 7×10 -4 Pa, turn on the electron beam to start depositing the Ag target material. The tilt angle of the first deposition is controlled at 8.5°, and the deposition thickness is 27 nm. The tilt angle of the second deposition is controlled at 7.5°, and the deposition thickness is 33 nm. The SEM image of the upper surface of the AAO after two-angle depositions is shown in Figure 2 . It can be seen that after two-angle depositions, it is obvious to see the formation of, for example, Ag-Ag dimer nanoarrays at the bottom of the AAO. At the same time, the pore diameter on the upper surface of the AAO nano-template is about 75 nm. The dimer Ag-Ag nanoarray structure is obtained, as shown in Figure 3 . It can be seen from the figure that by strictly controlling the deposition angle, the dimer Ag-Ag nanoarray structure can be successfully prepared;

[0062] (5) Use magnetron sputtering to regulate the pore diameter of the ultra-thin double-channel AAO template with a hole depth of about 240 nm: Place the Ag-Ag dimer sample in the magnetron sputtering coating chamber. After the vacuum is pumped to about 4×10 -4 Pa, turn on the magnetron sputtering instrument. Set the argon gas flow rate to 8 sccm, keep the power at 60 W, and adjust the shutter valve to maintain the vacuum at around 9.49×10 -1 Pa. Then start depositing the Ag target material, and control the coating time at 160 s. After comparison with Figure 2 , it is found that the pore diameter of the AAO film decreases significantly after magnetron sputtering deposition, and the pore diameter is about 35 nm, as shown in Figure 4 ;

[0063] (6) Preparation of Ag-Au-Ag trimer nanoarrays: Place the sample after magnetron sputtering in the electron beam coating chamber, place the Au target, and after the vacuum is pumped to below 7×10 -4 Pa, turn on the electron beam to start vertical deposition of the Au target material, and control the thickness of the deposited Au material to 20 nm. After the deposition of the Au material is completed, select 3M semi-transparent magic tape to tear off the AAO film to obtain the Ag-Au-Ag trimer metal nanoarray, as shown in Figure 5 . It can be seen from the figure that after the above steps of operation, the Au material can perfectly fall in the middle of the Ag-Ag dimer nano-gap. This process can deposit Au in the Ag-Ag dimer gap and successfully realize the preparation of the Ag-Au-Ag trimer metal nanoarray;

[0064] (7) Immerse the obtained Ag-Au-Ag trimer metal nanoarray in 5 mL of a solution with a concentration of 10 -7The substrate was immersed in a 4-aminothiophenol solution of M for 4 h, taken out, washed with alcohol, and dried with nitrogen. Then, the substrate was placed in a closed environment of 10 -4 M benzaldehyde for 30 min to adsorb benzaldehyde VOC gas molecules. Finally, a confocal Raman spectrometer was used to collect the SERS signals of benzaldehyde VOC gas molecules on its surface. The laser wavelength was selected as 633 nm, the power was 0.5 mW, the grating was 600 g / mm, and the integration time was 10 s. Its Raman spectrum is as Figure 8 shown. It can be seen that compared with the 4-aminothiophenol control group, a C=N Raman peak vibration mode appears near 1623 cm -1 after the array adsorbs benzaldehyde VOC gas, indicating that the substrate can detect benzaldehyde gas and has certain application potential in VOC gas detection.

[0065] Example 4

[0066] A preparation method of an Al2O3@Au-Au-Al2O3@Au trimer nanoarray and its application in SERS detection specifically include the following steps:

[0067] (1) The 99.999% high-purity aluminum sheet was successively immersed in acetone, alcohol, and deionized water and ultrasonically cleaned for 5 min and then dried with nitrogen. Then, the cleaned aluminum sheet was successively treated by electrochemical polishing, first anodization, film removal, and second anodization to obtain a single-channel AAO template with a pore depth of 300 nm, a pore diameter of 30 nm, and a pore spacing of 100 nm. Among them, the parameters of electrochemical polishing were: the volume ratio of perchloric acid to absolute ethanol was 1:4, the DC voltage was 15 V, and the time was 5 min; the parameters of the first anodization were: 0.3 M oxalic acid solution, the temperature was kept at 0 °C, the DC voltage was 40 V, and the oxidation time was 12 h; the parameters of film removal were: a mixed solution of phosphoric acid with a volume ratio of 1:1, a mass fraction of 6%, and chromic acid with a mass fraction of 1.8%, the temperature was kept at 75 °C, and the time was 2 h. The parameters of the second anodization were: 0.3 M oxalic acid solution, the temperature was kept at 0 °C, the DC voltage was 40 V, and the oxidation time was 12 h;

[0068] (2) I. Immerse the single-pass AAO template in step (1) in a phosphoric acid solution at 30 °C with a mass fraction of 5% for 27 min for pore widening, then rinse with a large amount of deionized water and dry. II. Spin-coat PMMA with a mass fraction of 5%. Spin-coat is carried out with the parameters of 300 r / min for 300 s in the first step and 1200 r / min for 60 s in the second step respectively. III. Place the spin-coated PMMA / AAO on a hot plate and heat for 10 min. IV. Float the PMMA / AAO in a sodium hydroxide solution with a mass fraction of 5% to remove the aluminum oxide on the back of the AAO, then rinse thoroughly with a large amount of deionized water and float it in a copper chloride solution of 127 g / L to remove the aluminum on the back;

[0069] (3) Transfer the PMMA / AAO film with the aluminum back removed to the liquid surface of a mixed solution of 20 g / L copper chloride and 5% phosphoric acid at 30 °C to remove the AAO on the back to form a double-channel AAO film for 35 min. Finally, transfer the PMMA / AAO to an acetone solution and soak for 40 min to remove the PMMA, and then transfer it to a clean quartz surface to obtain an ultra-thin double-channel AAO template with a pore depth of about 240 nm;

[0070] (4) Place the ultra-thin double-channel AAO template sample with a pore depth of about 240 nm in the chamber of an electron beam coating machine, place the Au target, and after the vacuum is pumped to below 7×10 -4 Pa, turn on the electron beam to start depositing the Au target material. The tilt angle of the first deposition is controlled at 8.5°, and the deposition thickness is 27 nm. The tilt angle of the second deposition is controlled at 7.5°, and the deposition thickness is 33 nm. The dimer Au-Au nanoarray structure is obtained by depositing at two angles;

[0071] (5) Place the dimer Au-Au nanoarray in an atomic layer deposition instrument. After the vacuum is pumped to about 10 Pa, introduce 20 sccm of nitrogen gas, set the temperature to 200 °C, turn on the water source and aluminum source, and start depositing. The deposition parameters are set to 12 cycles to coat about 1 nm of Al2O3 on the surface of the Au-Au dimer to obtain an Al2O3@Au-Al2O3@Au dimer array sample;

[0072] (6) Use magnetron sputtering to regulate the diameter of the ultra-thin double-channel AAO template with a pore depth of about 240 nm: Place the Al2O3@Au-Al2O3@Au dimer sample in the magnetron sputtering coating chamber. After the vacuum is pumped to about 4×10 -4 Pa, turn on the magnetron sputtering instrument, set the argon gas flow rate to 8 sccm, keep the power at 60 W, and adjust the shutter valve to maintain the vacuum at 9.49×10 -1After reaching around 1 Pa, the deposition of the Ag target material begins, and the coating time is controlled at 150 s. After magnetron sputtering deposition, the pore size of the AAO film decreases significantly;

[0073] (7) Preparation of Al2O3@Au - Au - Al2O3@Au trimeric nanoarrays: Place the sample after magnetron sputtering in the electron beam coating chamber, place the Au target material, and wait until the vacuum is pumped down to below 7×10 -4 Pa. Then turn on the electron beam to start the vertical deposition of the Au target material, and control the thickness of the deposited Au material to be 20 nm. After the deposition of the Au material is completed, select 3M semi - transparent magic tape to tear off the AAO film to obtain the Al2O3@Au - Au - Al2O3@Au trimeric metal nanoarrays. As Figure 9 shown, it can be seen from the figure that through the operations of the above steps, this process can deposit Au in the gap of the Al2O3@Au - Al2O3@Au dimer, and successfully prepare the Al2O3@Au - Au - Al2O3@Au trimeric metal nanoarrays.

[0074] (8) Immerse the obtained Al2O3@Au - Au - Al2O3@Au trimeric metal nanoarrays in 5 mL of crystal violet solutions with different concentrations for 4 h. After taking them out, wash them with alcohol and dry them with nitrogen. Finally, use a confocal Raman spectrometer to collect the SERS signal of crystal violet on its surface. The laser wavelength is selected as 532 nm, the power is 0.5 mW, the grating is 600 g / mm, and the integration time is 10 s. Its Raman spectrum is as Figure 10 shown. It can be seen from the figure that the Al2O3@Au - Au - Al2O3@Au trimeric metal nanoarrays can detect crystal violet solutions with a concentration of 10 -12 M, showing excellent detection sensitivity.

[0075] Example 5

[0076] A preparation method of Ag - TiO X - Ag trimeric nanoarrays, specifically including the following steps:

[0077] (1) The 99.999% high-purity aluminum sheets were successively immersed in acetone, alcohol, and deionized water for ultrasonic cleaning for 5 min and then dried with nitrogen. Then, the cleaned aluminum sheets were successively treated by electrochemical polishing, first anodization, film removal, and second anodization to obtain a single-channel AAO template with a pore depth of 300 nm, a pore diameter of 30 nm, and a pore spacing of 100 nm. Among them, the parameters of electrochemical polishing were: the volume ratio of perchloric acid to absolute ethanol was 1:4, the DC voltage was 15 V, and the time was 5 min; the parameters of the first anodization were: 0.3 M oxalic acid solution, the temperature was kept at 0 °C, the DC voltage was 40 V, and the oxidation time was 12 h; the parameters of film removal were: a mixed solution of phosphoric acid with a volume ratio of 1:1, a mass fraction of 6%, and chromic acid with a mass fraction of 1.8%, the temperature was kept at 75 °C, and the time was 2 h. The parameters of the second anodization were: 0.3 M oxalic acid solution, the temperature was kept at 0 °C, the DC voltage was 40 V, and the oxidation time was 12 h;

[0078] (2) I. The single-channel AAO template in the above step (1) was immersed in a phosphoric acid solution with a mass fraction of 5% at 30 °C for pore expansion for 27 min, and then rinsed with a large amount of deionized water and dried. II. PMMA with a mass fraction of 5% was spin-coated. Spin-coating was carried out with the parameters of the first step being 300 r / min for 300 s and the second step being 1200 r / min for 60 s respectively. III. The spin-coated PMMA / AAO was placed on a hot plate and heated for 10 min. IV. PMMA / AAO was floated in a sodium hydroxide solution with a mass fraction of 5% to remove the aluminum oxide on the back of AAO, rinsed thoroughly with a large amount of deionized water, and then floated in a copper chloride solution of 127 g / L to remove the aluminum on the back;

[0079] (3) The PMMA / AAO film with the aluminum back removed was transferred to the liquid surface of a mixed solution of 20 g / L copper chloride and 5% phosphoric acid at 30 °C to remove the AAO on the back and form a double-channel AAO film for 35 min. Finally, the PMMA / AAO was transferred to an acetone solution and soaked for 40 min to remove PMMA, and then transferred to a clean quartz surface to obtain an ultra-thin double-channel AAO template with a pore depth of about 240 nm;

[0080] (4) The ultra-thin double-channel AAO template sample with a pore depth of about 240 nm was placed in the chamber of an electron beam coating machine, and the Ag target was placed. After the vacuum was pumped to below 7×10 -4 Pa, the electron beam was turned on to start depositing the Ag target material. The tilt angle of the first deposition was controlled at 7°, and the deposition thickness was 27 nm. The tilt angle of the second deposition was controlled at 6°, and the deposition thickness was 33 nm. After two-angle depositions, a dimer Ag-Ag nanoarray structure was obtained;

[0081] (6) Magnetron sputtering was used to control the diameter of the ultra-thin dual-channel AAO template with a pore depth of about 240 nm: the Ag-Ag dimer sample was placed in the magnetron sputtering coating chamber and vacuumed to 4*10 -4 Pa, turn on the magnetic sputtering instrument, set the argon flow rate to 8sccm, keep the power at 60W, and adjust the gate valve to maintain the vacuum at 9.49*10 -1 After the temperature is close to Pa, the Ag target deposition begins, and the coating time is controlled at 150s. The pore size of the AAO film is significantly reduced after magnetron sputtering deposition;

[0082] (7) Ag-TiO X -Preparation of Ag trimer nanoarrays: Place the magnetron sputtered samples in the electron beam coating chamber, place the TiOx target, and wait until the vacuum is 7*10 -4 Pa, open the electron beam to start the vertical deposition of the target material of TiOx material, and the thickness of the deposited TiOx material is controlled to be 20nm. After the deposition is completed, use 3M translucent magic tape to tear off the AAO film to obtain Ag-TiO X -Ag trimer metal nanoarrays, such as Figure 11 As shown, the left picture is SEM, the right picture is TEM, and the scale bar in the TEM picture is 25 nm. Figure 11 It can be seen that after the above steps, the process can convert TiO X It was deposited near the Ag-Ag dimer structure and came into contact with Ag, thus successfully preparing Ag-TiO X -Ag trimer metal nanoarray. This material structure is of great significance for the study of charge transfer in Raman scattering and heterogeneous catalysis.

Claims

1. A method for preparing an A-B-A nano trimer array, characterized in that, It includes the following steps: (1) Prepare a double-pass nanopore array template; (2) Deposit material A on the double-pass nanopore array template by the angled inclined deposition method to obtain an A-A dimer nanoarray; the material A is metal nanoparticles with Raman enhancement effect or fluorescence enhancement effect; (3) Deposit a metal material on the surface of the double-pass nanopore array template in step (2) by physical vapor deposition to regulate the pore size of the double-pass nanopore array, so that material B can be deposited inside or around the gap of the A-A dimer; the physical vapor deposition method can only deposit the material mainly on the surface of the double-pass nanopore array template, and less or no deposition near the A-A dimer; the physical vapor deposition method is magnetron sputtering; the parameters of the magnetron sputtering are: the carrier gas flow rate is 4-12 sccm, the power is 40-90 W, and at a vacuum value of 9.49*10 -1 -9.67*10 -1 Pa, start depositing the metal target, and the coating time is 50-200 s; (4) Deposit material B into or around the gaps of the A-A dimers in step (3), and after completion, remove the double-pass nanopore array template to obtain an A-B-A trimer nanoarray; the material B is at least one of Au, Pt, Cu, Ag, Pd, SiO x , TiO x , Al2O3, WO x , MgF2, TiN.

2. The preparation method of the A-B-A nano trimer array according to claim 1, characterized in that, In step (2), the pore depth of the A-A dimer nanoarray is 100 - 500 nm by the inclined deposition method.

3. The preparation method of the A-B-A nano-trimer array according to claim 1, wherein In step (4), the thickness of the deposited material B is 2 - 50 nm.

4. The method for preparing the A-B-A nano-trimer array according to claim 1, wherein In step (2), the angled inclined deposition method is as follows: for the double-pass nanopore array template, the first deposition of the target material A is carried out at an inclined angle α of 5° - 30°, and the deposition thickness is 5 - 50 nm; then the substrate of the double-pass nanopore array template is horizontally rotated 180°, and the second deposition of the target material A is carried out at an inclined angle β of 4° - 28°, and the deposition thickness is 5 - 60 nm; the selection of the deposition angle is determined according to the thickness and pore diameter of the nano template.

5. Application of the A-B-A nano-trimer array prepared by the method according to claim 1 in Raman spectroscopy detection.

6. Use of the A-B-A nano-trimer array according to claim 5 in Raman spectroscopy detection, characterized in that, The material A is metal nanoparticles with Raman enhancement effect or fluorescence enhancement effect; the material B is a material that specifically adsorbs the molecule to be detected.

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