Ag-Au cascade nanoarray SERS substrate, preparation method and application
By constructing Ag-Au cascaded nanoarray SERS substrate on porous anodized aluminum template, the problems of uniformity and low-cost preparation of high-active SERS substrates in the prior art are solved, and SERS detection with high sensitivity and stability are achieved, especially There are significant advantages in realizing extremely small nanogaps.
Patent Information
- Application Number
- CN202211193272.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-09-28
- Publication Date
- 2025-01-10
- Estimated Expiration
- 2042-09-28
AI Technical Summary
The prior art is difficult to meet the uniform hot spot structure distribution and low-cost preparation requirements of highly active SERS substrates at the same time, especially in the realization of extremely small nano gaps (such as below 10 nm), resulting in limited SERS activity enhancement ability.
Polycarbonate nanocolumn arrays were obtained by nanoimprinting using porous anodized aluminum template, silver and copper films were deposited to form hollow Ag nanoarrays, and gold nanoparticles were modified through electrochemical deposition technology to construct an Ag-Au cascaded nanoarray SERS substrate .
The high-active SERS substrate is uniformly constructed at a low cost and large area, which improves the stability and reliability of detection. The measured relative standard deviation of the crystal violet SERS signal is less than 10%, meeting the actual detection needs.
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Figure CN115575377B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of plasmon nanomaterial preparation, and relates to an Ag-Au cascade nanoarray SERS substrate, a preparation method and an application thereof. Background Art
[0002] In recent years, surface-enhanced Raman scattering (SERS) technology has attracted great attention in the fields of surface and interface analysis, chemical reaction monitoring, and biomedical sensing due to its high-sensitivity single-molecule recognition advantage. This technology is mainly based on the local electromagnetic field enhancement characteristics of noble metal plasmon hotspot structures (such as nano-scale gaps, holes, high-curvature nanotips, etc.), so that the Raman signal of molecules adsorbed on the surface of SERS hotspot structures can be super-amplified by at least a million times, achieving highly sensitive detection of molecules.
[0003] Research shows that the key to improving SERS detection performance lies in constructing a highly sensitive and reliable active substrate, which depends especially on the hotspot distribution state and structural morphology on the substrate surface. For example, a hotspot structure with uniform distribution and high surface density can provide a more uniform local electromagnetic field, which can ensure the signal uniformity and repeatability of SERS detection; and the structural morphology of the hotspot directly affects the enhancement characteristics of the local electromagnetic field. For example, a cascade nanostructure system with a multi-scale complex configuration (such as the gold nanostars and their polymers, sea urchin-shaped silver nanohemispheres, etc.) can utilize the step-by-step coupling and convergence of electromagnetic field energy in the multi-scale structure to maximize the localization and field enhancement of the field hotspot at a specific spatial position, and the molecular adsorption sites are more, thereby achieving the effect of effectively improving the SERS activity. Research shows that the SERS enhancement factor of this cascade nanostructure is usually 2 to 3 orders of magnitude higher than that of nanoparticles with a single configuration.
[0004] However, the current development of highly active multi-scale nanostructured SERS substrates often finds it difficult to simultaneously meet the uniform distribution requirements of hotspot structures. Therefore, how to construct uniformly distributed hotspot structures with high SERS activity has become a key difficulty in practical applications in this technical field. Currently, the commonly used focused plasma etching, electron beam etching, photolithography and other technologies can achieve uniform periodic preparation of nanoarray structures, but they are not universal due to their complex processes and high costs. At the same time, due to the existence of optical diffraction limits, it is difficult to achieve the preparation of extremely small nanogaps (such as less than 10nm). Therefore, their SERS activity enhancement capabilities are limited, and there is an urgent need to seek more economical and reliable methods for preparing highly active SERS substrates. Summary of the invention
[0005] In view of this, the object of the present invention is to provide a Ag-Au cascade nanoarray SERS substrate, a preparation method and an application thereof, which can realize large-area uniform construction of a multi-scale cascade nanostructure SERS substrate at low cost.
[0006] The technical solution adopted by the present invention is as follows:
[0007] A method for preparing a Ag-Au cascade nanoarray SERS substrate comprises the following steps:
[0008] S1. Polycarbonate nanorod arrays were obtained by nanoimprinting on a porous anodized aluminum template.
[0009] S2. A silver film is deposited on the top of the PC nanocolumns in the polycarbonate nanocolumn array; a thick copper film is then deposited on the surface of the silver film to obtain an Ag / Cu film, and the Ag / Cu film is removed to obtain a hollow Ag nanoarray;
[0010] S3. The surface of the hollow Ag nanoarray is modified with gold nanoparticles by electrochemical deposition technology to obtain an Ag-Au cascade nanoarray SERS substrate.
[0011] Furthermore, the porous anodized aluminum template has a hexagonally arranged through-hole structure.
[0012] Furthermore, in the hexagonally arranged through-hole structure, the hole spacing is 450 nm, the hole diameter is 300 nm, and the hole depth is 900 nm.
[0013] Furthermore, the porous anodized aluminum template is cleaned by: cleaning with acetone, ethanol and ultrapure water in an ultrasonic bath for 30 seconds respectively, then rinsing with ultrapure water for multiple times and drying under a nitrogen flow for later use.
[0014] Furthermore, the method of obtaining the PC nanocolumn array by nanoimprinting specifically comprises the following steps:
[0015] S11. Place PC particles on a glass slide and heat to 300°C. When the PC particles melt, continue heating for 10 minutes until the bubbles inside the PC are discharged.
[0016] S12. Place the porous anodized aluminum template with holes on the PC obtained in step S11 and press to ensure that the PC is completely infiltrated to the bottom of the holes of the porous anodized aluminum template. Heat for 5 minutes and then stop, cool naturally to room temperature, and remove the aluminum substrate and oxide layer of the porous anodized aluminum template in turn to obtain a polycarbonate nanocolumn array.
[0017] Furthermore, the deposition in step S2 is performed by a grazing angle thermal evaporation coating method.
[0018] Furthermore, the thickness of the silver film is 40 nm.
[0019] Furthermore, the thickness of the thick copper film is 0.1-0.5 mm.
[0020] Furthermore, the conditions of the electrochemical deposition are: the electroplating solution is prepared by mixing 3mM HAuCl4 and 0.2M HF solution; the electrochemical workstation uses a Cr / Ag hill array as a working electrode, a platinum electrode as a counter electrode, and Ag / AgCl2 as a reference electrode; and the electroplating time ranges from 200s to 800s.
[0021] Furthermore, the electrodeposition time is 600 s.
[0022] The present invention also provides an Ag-Au cascade nanoarray SERS substrate prepared by the above preparation method.
[0023] The present invention also provides application of the Ag-Au cascade nanoarray SERS substrate in detecting small molecules.
[0024] Furthermore, the small molecule is a CV small molecule.
[0025] Compared with the prior art, the present invention is based on template replication technology, and prepares Ag-Au cascade nanoarray SERS substrate by combining physical deposition and electrochemical deposition, which has the following technical effects:
[0026] (1) The preparation process is highly controllable and can be used to prepare nanoarray structures of various configurations with uniform morphology on a large scale, thus ensuring the stability and reliability of SERS detection. It has important application value in the field of plasmon nanomaterial preparation;
[0027] (2) The Ag-Au cascade nanoarray SERS substrate provided by the present invention effectively improves the SERS detection uniformity of the cascade nanostructure, and the measured crystal violet SERS signal has a relative standard deviation value of less than 10%, which can meet the actual detection requirements. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 The flow chart for the preparation of Ag-Au cascade nanoarray SERS substrate;
[0029] Figure 2 Schematic diagram of the porous anodized aluminum template structure;
[0030] Figure 3 It is a hexagonal schematic diagram;
[0031] Figure 4 This is a schematic diagram of the grazing angle deposition method;
[0032] Figure 5 This is a scanning electron microscope image of the Ag nanohollow array;
[0033] Figure 6 Ag-Au cascade nanoarray structures obtained with different electrodeposition times: (a) 200s; (b) 400s; (c) 600s; (d) 800s (the scale bars are all 200nm);
[0034] Figure 7 Based on a concentration of 10 -4 SERS spectra of M CV on different substrates;
[0035] Figure 8 (a) SERS spectra of the CV solution obtained at 50 randomly selected points based on the Ag-Au cascade nanoarray structure obtained by electrodeposition for 600 s;
[0036] Figure 8 (b) is 1160cm -1 The Raman intensity statistics of the CV characteristic peak;
[0037] Fig. 9 CV concentration-dependent SERS spectrum of the Ag-Au cascade nanoarray structure obtained based on electrodeposition for 600 s. DETAILED DESCRIPTION
[0038] The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the contents described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.
[0039] like Figure 1 As shown, the present invention provides a method for preparing a Ag-Au cascade nanoarray SERS substrate, and the specific implementation process is as follows:
[0040] (1) Using porous anodic aluminum oxide (AAO) as an initial template, a polycarbonate (PC) nanocolumn array is obtained by nanoimprinting; the porous anodic aluminum oxide template preferably has a hexagonally arranged straight through hole structure, such as Figure 2-3 As shown, the pore spacing of the porous anodized aluminum template is 450 nm, the pore diameter is 300 nm, and the pore depth is 900 nm.
[0041] Before use, the porous anodic aluminum oxide (AAO) template needs to be cleaned with acetone, ethanol and ultrapure water in an ultrasonic bath for 30 seconds respectively, then rinsed with ultrapure water several times and dried under a nitrogen flow for use.
[0042] The preparation process of PC nanocolumns is as follows: take a glass slide and place it on the heating table, place the PC particles on the glass slide, and heat it to 300°C; when the PC melts, continue heating for 10 minutes until the bubbles inside the PC are discharged. Buckle the side of the AAO template with holes on the PC and press it with another glass slide to ensure that the PC is completely infiltrated to the bottom of the AAO holes. Stop heating after five minutes, wait for the PC to cool naturally to room temperature, and use a mixture of 3.4g CuCl2, 75ml HCl and 100ml H2O to remove the aluminum substrate of the AAO template. Then, in a warm water bath at 35°C, use a phosphoric acid solution with a mass concentration of 5wt% to remove the remaining AAO template oxide layer, and finally obtain a PC nanocolumn array.
[0043] (2) depositing a silver (Ag) thin film on the top of the PC nanocolumn by grazing angle thermal evaporation coating, wherein the thickness of the silver (Ag) thin film is preferably 40 nm; then depositing a thick copper (Cu) film on the surface of the thin Ag film by grazing angle thermal evaporation coating, wherein the thickness of the thick copper (Cu) film is preferably 0.1 to 0.5 mm, more preferably 0.5 mm; removing the Ag / Cu film by using the thick copper film to obtain a hollow Ag nanoarray; wherein the grazing angle thermal evaporation coating method is as follows: Figure 4 As shown, the vertical distance between the Ag evaporation source and the template is 1 cm, the vertical distance between the evaporation source and the center of the template is 4 cm, and the vacuum degree is 8×10 -4 pa, evaporation rate is about
[0044] (3) Using electrochemical deposition technology, gold nanoparticles (AuNPs) were modified on the surface of the hollow Ag nanoarray to obtain the Ag-Au cascade nanoarray SERS substrate;
[0045] The conditions for the electroplating are as follows: the electroplating solution is prepared by mixing 3 mM HAuCl4 and 0.2 M HF solution; the electrochemical workstation uses a Cr / Ag hill array as a working electrode, a platinum electrode as a counter electrode, and Ag / AgCl2 as a reference electrode; the electroplating time ranges from 200 s to 800 s, and in the present invention, 600 s of electroplating is the optimal time condition.
[0046] Example 1 Preparation of Hollow Ag Nanoarrays
[0047] Step 1, take a glass slide and place it on the heating table, place the PC particles on the glass slide, and heat to 300°C; when the PC melts, continue heating for 10 minutes until the bubbles inside the PC are discharged. Buckle the side of the AAO template with holes on the PC and press it with another glass slide to ensure that the PC is completely infiltrated to the bottom of the AAO holes. Stop heating after five minutes, wait for the PC to cool naturally to room temperature, and use a mixture of 3.4g CuCl2, 75ml HCl and 100ml H2O to remove the aluminum substrate of the AAO template. Then, in a warm water bath at 35°C, use a phosphoric acid solution with a mass concentration of 5wt% to remove the remaining AAO template oxide layer, and finally obtain a polycarbonate (PC) nanocolumn array;
[0048] Step 2, depositing a 40 nm thick Ag film on the top of the PC nanorods by grazing angle thermal evaporation coating;
[0049] Step 3: Deposit a 0.5 mm thick continuous copper (Cu) film on the surface of the thin Ag film by thermal evaporation coating, remove the Ag / Cu film, and obtain a hollow Ag nanoarray. The scanning electron microscope image is as follows: Figure 5 shown.
[0050] Example 2
[0051] Through electrochemical deposition technology, a mixed solution of 3mM HAuCl4 and 0.2M HF was used as the electroplating solution, the electrochemical workstation used a Cr / Ag hill array as the working electrode, a platinum electrode as the counter electrode, and Ag / AgCl2 as the reference electrode. The electrodeposition time was controlled to be 200s, and gold nanoparticles (Au nanoparticles, AuNPs) were modified on the surface of the hollow Ag nanoarray prepared in Example 1 to obtain an Ag-Au cascade nanoarray SERS substrate.
[0052] Example 3
[0053] Through electrochemical deposition technology, a mixed solution of 3mM HAuCl4 and 0.2M HF was used as the electroplating solution, the electrochemical workstation used a Cr / Ag hill array as the working electrode, a platinum electrode as the counter electrode, and Ag / AgCl2 as the reference electrode. The electrodeposition time was controlled to be 400s, and the surface of the hollow Ag nanoarray prepared in Example 1 was modified with gold nanoparticles (Au nanoparticles, AuNPs) to obtain an Ag-Au cascade nanoarray SERS substrate.
[0054] Example 4
[0055] Through electrochemical deposition technology, a mixed solution of 3mM HAuCl4 and 0.2M HF was used as the electroplating solution, the electrochemical workstation used a Cr / Ag hill array as the working electrode, a platinum electrode as the counter electrode, and Ag / AgCl2 as the reference electrode. The electrodeposition time was controlled to be 600s, and gold nanoparticles (Au nanoparticles, AuNPs) were modified on the surface of the hollow Ag nanoarray prepared in Example 1 to obtain an Ag-Au cascade nanoarray SERS substrate.
[0056] Example 5
[0057] Through electrochemical deposition technology, a mixed solution of 3mM HAuCl4 and 0.2M HF was used as the electroplating solution, the electrochemical workstation used a Cr / Ag hill array as the working electrode, a platinum electrode as the counter electrode, and Ag / AgCl2 as the reference electrode. The electrodeposition time was controlled to be 800s, and gold nanoparticles (Au nanoparticles, AuNPs) were modified on the surface of the hollow Ag nanoarray prepared in Example 1 to obtain an Ag-Au cascade nanoarray SERS substrate.
[0058] Test Example 1: Scanning Electron Microscope
[0059] The Ag-Au cascade nanoarray SERS substrates obtained in Examples 2 to 5 were characterized by electron scanning microscopy. Figure 6 As shown. Among them, the electrodeposition time of Figures (a) to (d) is 200s, 400s, 600s, and 800s, respectively. It can be clearly seen that when the deposition time is 200s, the amount of charge accumulated on the hollow Ag nanoarray is small, and no obvious Au nanoparticles are formed. When the electrodeposition time increases to 400s, the accumulated charge on the hollow Ag nanoarray increases, and obvious Au nanoparticles are formed at the edge of the hollow structure. When the deposition time is 600s, the Au nanoparticles grow further and form many nanoscale gaps. Until the deposition time reaches 800s, the Au nanoparticles begin to agglomerate and the nanoscale gaps begin to disappear.
[0060] Test Example 2: Comparison of SERS detection effects of Ag-Au cascade nanoarrays with different morphologies
[0061] With a concentration of 10 -4 The crystal violet of M was used as the detection molecule, and the SERS performance of the Ag-Au cascade nanoarray obtained in Examples 2 to 5 was analyzed. Figure 7As shown. Among them, the detection substrate used in curve a is the Ag nano hollow array structure, and curves b to e are the Ag-Au cascade nano array structures after electroplating for 200s, 400s, 600s, and 800s, respectively. By comparing these five spectra, it can be seen that the modified Ag-Au cascade nano array structure has a more sensitive SERS performance. In addition, the Ag-Au cascade nano array substrate with an electroplating time of 600s has a stronger SERS activity. Combined with Figure 6 From the SEM results in , it can be seen that after electrodeposition, many nanoparticles are produced on the edges of the Ag nano-hollows, which together with the gaps in the original Ag nano-hollow arrays lead to smaller gaps. The local electromagnetic field enhancement generated by these smaller gaps is the main source of SERS enhancement.
[0062] Test Example 3: Application Analysis of Crystal Violet Detection Uniformity
[0063] The Ag-Au cascade nanoarray structure with an electrodeposition time of 600 s was selected as the SERS substrate, and the concentration of 10 -4 The uniformity of the substrate SERS signal was detected by CV solution of M. Figure 8 As shown. 50 different detection sites were randomly selected and a set of SERS spectra were obtained. Figure 8 (a) shows that the substrate has good SERS uniformity. The characteristic peak shape and relative intensity of CV molecules are similar, without interference from hybrid peaks. The main vibration mode is 725cm -1 (γ(CH)) and 800cm -1 (γ(CH)), 905cm -1 (radial vibration of aromatic ring skeleton), 1160cm -1 (δ(CH)) and 1280cm -1 (ν(CC)) etc. We -1 The relative standard deviation (RSD) of the intensity at Figure 8 (b), the RSD value obtained was 6.65%, showing good consistency.
[0064] Test Example 4: Application Analysis of Trace Detection of Crystal Violet
[0065] We prepared several CV molecular solutions with different concentrations and used the Ag-Au cascade nanoarray structure with an electrodeposition time of 600 s as the substrate to detect the concentration-dependent SERS spectra of CV to further explore the sensitivity of the substrate to the concentration of the probe molecule. The results are as follows Fig. 9As shown in Figure 2. From this set of spectra, it can be seen that the Raman characteristic peaks of CV molecules at different concentrations are consistent and have a high signal-to-noise ratio. As the concentration of the target molecule decreases, its relative peak intensity also gradually decreases. It is worth noting that when the concentration is as low as 10 -9 M, the main characteristic peaks of CV molecules can still be clearly detected, indicating that the prepared composite structure has good application prospects in trace detection.
Claims
1. A method for preparing a Ag-Au cascade nanoarray SERS substrate, characterized in that: The following steps are involved: S1. Polycarbonate nanorod arrays were obtained by nanoimprinting on a porous anodized aluminum template. S2. A 40 nm thick silver film is deposited on the top of the polycarbonate nanocolumns in the polycarbonate nanocolumn array by grazing angle thermal evaporation coating; and then a 0.1 to 0.5 mm thick copper film is deposited on the surface of the silver film by grazing angle thermal evaporation coating to obtain an Ag / Cu film, and the Ag / Cu film is removed to obtain a hollow Ag nanoarray; S3. The surface of the hollow Ag nanoarray is modified with gold nanoparticles by electrochemical deposition technology to obtain an Ag-Au cascade nanoarray SERS substrate.
2. The preparation method according to claim 1, characterized in that: The porous anodized aluminum template has a hexagonally arranged straight through hole structure.
3. The preparation method according to claim 2, characterized in that: In the hexagonally arranged through-hole structure, the hole spacing is 450 nm, the hole diameter is 300 nm, and the hole depth is 900 nm.
4. The preparation method according to claim 1, characterized in that: The porous anodic aluminum oxide template is cleaned by using acetone, ethanol and ultrapure water in an ultrasonic bath for 30 seconds respectively, then rinsed with ultrapure water for multiple times and dried under a nitrogen flow for later use.
5. The preparation method according to claim 1, characterized in that: The method of obtaining a polycarbonate nanocolumn array by nanoimprinting specifically comprises the following steps: S11. Place PC particles on a glass slide and heat to 300°C. When the PC particles melt, continue heating for 10 minutes until the bubbles inside the PC are discharged. S12. Place the porous anodized aluminum template with holes on the PC obtained in step S11 and press to ensure that the PC is completely infiltrated to the bottom of the holes of the porous anodized aluminum template. Heat for 5 minutes and then stop, cool naturally to room temperature, and remove the aluminum substrate and oxide layer of the porous anodized aluminum template in turn to obtain a polycarbonate nanocolumn array.
6. The Ag-Au cascade nanoarray SERS substrate prepared by the preparation method according to any one of claims 1 to 5.
7. Use of the Ag-Au cascade nanoarray SERS substrate according to claim 6 in detecting small molecules.