A method for preparing a gold-silver hybrid hollow nanoring SERS substrate

Abstract

This invention discloses a method for preparing a gold-silver hybrid hollow nanoring SERS substrate, belonging to the field of functional material synthesis technology. Using trisodium citrate as an encapsulating agent, silver nanoparticles are synthesized via a seed synthesis method. After cooling, the nanoparticles are collected by centrifugation and then etched with HAuCl4 under reducing conditions to obtain a hollow nanoring structure. The resulting Ag-Au nanorings exhibit the strong LSPR and high SERS activity of silver nanoparticles, while also possessing the high stability and versatility of gold nanoparticles. By adjusting the ratio of HAuCl4 to AgNO3, Ag-Au nanorings with LSPRs of 531 nm, 628 nm, and 770 nm can be prepared, achieving a strong EM effect. This invention overcomes the drawbacks of easy oxidation of silver nanosubstrates and low sensitivity of gold nanosubstrates, while possessing the advantage of high stability.

Description

Technical Field

[0001] This invention belongs to the field of functional material synthesis technology, specifically relating to a method for preparing a gold-silver hybrid hollow nanoring SERS substrate. Background Technology

[0002] Due to their excellent optical properties and ease of fabrication, most plasma studies to date have been based on Ag (Ag) and Au nanostructures. These two elements each have their own advantages and disadvantages. Au's low interband transition energy (2.3 eV) leads to energy loss during this transition, while Ag's larger band gap (3.7 eV) does not allow for such interband transitions, thus implying more efficient utilization of incident light energy to generate hot electrons. Although Ag exhibits lower interband transition losses in the visible and near-infrared (NIR) range, Au nanostructures are more resistant to oxidative degradation. At the same size, Ag nanostructures show shorter local surface plasmon resonance (LSPR) wavelengths and stronger near-field enhancement than Au nanostructures.

[0003] Compared to single-metal nanoparticles, bimetallic nanoparticles possess unique physical and chemical properties, attracting widespread attention. In particular, Au-Ag bimetallic nanoparticles (NPs), due to their inherent composition-tunable plasmonic properties derived from the synergistic effect of Au and Ag, have significant potential applications in surface-enhanced Raman spectroscopy (SERS) and catalytic systems.

[0004] It has been recognized that these inherent properties largely depend on the ratio and composition of these bimetallic NPs; therefore, their controllable synthesis is crucial for discovering their properties and realizing practical applications. To this end, a simple method was developed to construct Ag, Au, and AgCl hybrid aggregated nanostructures. The resulting hybrid Ag-Au nanorings exhibit strong LSPR absorption, and their wavelengths can be tuned to the three most commonly used laser wavelengths (532, 633, and 785 nm) by changing the HAuCl4:AgNO3 ratio. Therefore, the obtained hybrid Ag-Au nanorings are advantageous for achieving strong electromagnetic enhancement (EM) effects under commonly used lasers. The obtained hybrid Ag-Au nanorings possess the Fermi level of AuNPs and Au / Ag alloys, as well as the valence band (VB) and conduction band (CB) of AgCl. The rich energy level structure allows the obtained hybrid Ag-Au nanorings to provide more CT opportunities for more molecules, thereby achieving a strong chemical enhancement (CM) effect. Therefore, the hybrid Ag-Au nanorings obtained exhibit excellent SERS activity for many molecules. Furthermore, the unique chemical composition of the obtained hybrid Ag-Au nanoring substrates contributes to their good long-term stability in terms of SERS activity. This provides a high-performance SERS substrate and, more importantly, valuable experience for coordinating EM and CM in constructing highly active SERS substrates. Summary of the Invention

[0005] To address the shortcomings of existing SERS substrates, the present invention aims to construct highly active SERS substrates by coordinating EM and CM effects. This invention provides a method for preparing a gold-silver hybrid hollow nanoring SERS substrate. This method is simple, convenient, and highly stable; the obtained Ag-Au hybrid hollow nanorings exhibit strong EM and CM effects simultaneously, resulting in excellent performance in SERS detection applications.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a gold-silver hybrid hollow nanoring SERS substrate involves using trisodium citrate as an encapsulating agent to synthesize silver nanoparticles via a seed synthesis method. Under reducing conditions, the ratio of HAuCl4 to AgNO3 is adjusted to etch the silver nanoparticles with HAuCl4 to obtain gold-silver hybrid hollow nanoring solutions with different LSPR absorption wavelengths. The prepared gold-silver hybrid hollow nanoring solutions are then dropped onto a silicon wafer to obtain the gold-silver hybrid hollow nanoring SERS substrate material.

[0008] A method for preparing a gold-silver hybrid hollow nanoring SERS substrate includes the following steps:

[0009] 1) Add ascorbic acid solution to boiling deionized water;

[0010] 2) Add Ag seed growth solution to step 1) and react for 10 min while keeping it boiling;

[0011] 3) Centrifuge the solution obtained in step 2) and collect the precipitate to obtain a silver nanoparticle solution;

[0012] 4) Disperse the silver nanoparticle solution obtained in step 3) in deionized water and add glucose solution as a reducing agent;

[0013] 5) Add HAuCl4 solution to the solution from step 4);

[0014] 6) React the solution from step 5) in an oil bath at 140 °C for 10 min;

[0015] 7) Centrifuge the solution obtained in step 6) and collect the lower precipitate, which is the solution of gold-silver hybrid hollow nanorings;

[0016] 8) Drop the gold-silver hybrid hollow nanoring solution obtained in step 7) onto the silicon wafer to obtain the gold-silver hybrid hollow nanoring SERS substrate;

[0017] 9) After drying the silicon wafer from step 8), add the detection solution.

[0018] Step 1) above specifically involves adding 1000 µL of freshly prepared 0.1 mol / L ascorbic acid solution to 160 mL of boiling deionized water.

[0019] In step 2) above, the Ag seed growth solution consists of 5 mL of deionized water, 1.47 g of trisodium citrate and 1 mL of 0.1 mol / L AgNO3 solution.

[0020] In step 4) above, the volume ratio of the silver nanoparticle solution to deionized water is 3:200.

[0021] In step 4) above, the concentration of the reducing agent glucose solution is 0.1 mol / L; the volume ratio of the silver nanoparticle solution to the reducing agent glucose solution is 1:1.

[0022] In step 5) above, add a 0.05 mol / L HAuCl4 solution with the molar ratio of AgNO3 used in the preparation of HAuCl4 and silver nanoparticle solution being 1-1.5:30.

[0023] A gold-silver hybrid hollow nanoring SERS substrate material prepared by the above method.

[0024] Application of the aforementioned gold-silver hybrid hollow nanoring SERS substrate material in SERS detection.

[0025] The significant advantages of this invention are:

[0026] 1. The method of this invention can prepare Ag-Au nanorings with three absorption wavelengths (LSPR) of 531 nm, 628 nm, and 770 nm by adjusting the ratio of HAuCl4 to AgNO3. These LSPR wavelengths match the wavelengths of three lasers (532 nm, 633 nm, and 785 nm), enabling a strong EM effect. Simultaneously, the hybrid Ag-Au nanorings possess a rich energy level structure, including the Fermi level of Ag-Au alloys and the AuNPs, CB, and VB levels of AgCl. This provides more opportunities for molecular CT (transient electrochemical reaction) in the hybrid Ag-Au nanorings, resulting in a strong CM (transient electrochemical reaction) effect. Therefore, the obtained gold-silver hybrid hollow nanorings exhibit ultra-high SERS sensitivity for many molecules.

[0027] 2. The silver nanoparticles synthesized in this invention have a size distribution in the range of 15 to 50 nm and a large number of surface charges, enabling them to be stably dispersed in aqueous solution. The resulting gold-silver hybrid hollow nanorings are uniform in size and morphology, exhibit high stability, and their unique chemical composition enables them to demonstrate good long-term stability in SERS activity.

[0028] 3. The gold-silver hybrid hollow nanorings prepared by this invention can overcome the disadvantages of easy oxidation of silver nanosubstrates and low sensitivity of gold nanosubstrates, and have the advantage of high stability. Furthermore, by combining abundant SERS "hot spots" and abundant energy level structures, it provides valuable experience for coordinating EM and CM to construct highly active SERS substrates.

[0029] 4. The SERS substrate with abundant energy levels of gold and silver hybrid hollow nanorings prepared in this invention has high SERS activity and is universally applicable to most Raman reporter molecules, showing good prospects for practical detection applications.

[0030] 5. The method for preparing the energy-level-rich gold-silver hybrid hollow nanoring SERS substrate adopted in this invention is simple to operate and has high reproducibility. Attached Figure Description

[0031] Figure 1 Transmission electron microscopy (TEM) images of the prepared silver nanoparticles and gold-silver hybrid hollow nanorings with absorption at three different LSPR wavelengths. a) Silver citrate nanoparticles; b) TEM image of the prepared gold-silver hybrid hollow nanorings with LSPR absorption at 531 nm; c) TEM image of the prepared gold-silver hybrid hollow nanorings with LSPR absorption at 628 nm; d) TEM image of the prepared gold-silver hybrid hollow nanorings with LSPR absorption at 770 nm.

[0032] Figure 2 The image shows the UV absorption spectra of silver nanoparticles and gold-silver hybrid hollow nanorings with different LSPR absorption wavelengths.

[0033] Figure 3 Color images of silver nanoparticles and gold-silver hybrid hollow nanoring solutions with absorption at three LSPR wavelengths. a) Color image of the prepared silver citrate nanoparticle solution; b) Color image of the prepared gold-silver hybrid hollow nanoring solution with LSPR absorption at 531 nm; c) Color image of the prepared gold-silver hybrid hollow nanoring solution with LSPR absorption at 628 nm; d) Color image of the prepared gold-silver hybrid hollow nanoring solution with LSPR absorption at 770 nm.

[0034] Figure 4 Three LSPR wavelength absorption wavelengths of gold-silver hybrid hollow nanorings for 10 -9 SERS spectrum of mol / L 4-cyanothiophenol detection solution.

[0035] Figure 5 A schematic diagram of the energy levels of gold-silver hybrid hollow nanorings and the CM effect mechanism of 4-cyanothiophenol under three laser conditions. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] Example 1

[0038] A method for preparing a gold-silver hybrid hollow nanoring SERS substrate includes the following steps:

[0039] 1) Take 1000 µL of freshly prepared 0.1 mol / L ascorbic acid solution and add it to 160 mL of boiling deionized water;

[0040] 2) Add Ag seed growth solution prepared by 5 mL of deionized water, 1.47 g of trisodium citrate and 1 mL of 0.1 mol / L AgNO3 solution to step 1), and keep the mixture boiling for 10 min.

[0041] 3) After cooling the solution obtained in step 2), centrifuge at 12000 rpm, collect the precipitate, and obtain 1 mL of Ag nanoparticle solution;

[0042] 4) Disperse 300 µL of the Ag nanoparticle solution obtained in step 3) in 20 mL of deionized water, and add 300 µL of 0.1 mol / L glucose solution;

[0043] 5) Add 20 µL of 0.05 mol / L HAuCl4 solution to the solution from step 4);

[0044] 6) The solution from step 5) was stirred at 840 rpm in an oil bath at 140 ℃ for 10 min. The color of the solution changed from bright yellow to brown and finally to pink.

[0045] 7) After cooling the solution obtained in step 6), centrifuge at 12000 rpm for 10 min and collect the lower precipitate, which is the solution of gold-silver hybrid hollow nanorings with LSPR absorption of 531 nm.

[0046] 8) Take 20 µL of the gold-silver hybrid hollow nanoring solution obtained in step 7) and drop it onto a silicon wafer; the silicon wafer is 5 × 5 mm. 2 The silicon wafers of the specified size were ultrasonically cleaned with acetone, anhydrous ethanol and deionized water, then the surface was cleaned with concentrated sulfuric acid and hydrogen peroxide solution, and finally the surface was modified with hexadecyl ammonium bromide solution.

[0047] 9) After drying the silicon wafer from step 8), add 20 µL of 10 -9 mol / L 4-cyanothiophenol detection solution.

[0048] Example 2

[0049] A method for preparing a gold-silver hybrid hollow nanoring SERS substrate includes the following steps:

[0050] 1) Take 1000 µL of freshly prepared 0.1 mol / L ascorbic acid solution and add it to deionized water, then heat to boiling;

[0051] 2) Add Ag seed growth solution prepared by 5 mL of deionized water, 1.47 g of trisodium citrate and 1 mL of 0.1 mol / L AgNO3 solution to step 1), and keep the mixture boiling for 10 min.

[0052] 3) After cooling the solution obtained in step 2), centrifuge at 12000 rpm, collect the precipitate, and obtain 1 mL of Ag nanoparticle solution;

[0053] 4) Disperse 300 µL of Ag nanoparticle solution obtained in step 3) in 20 mL of deionized water, and add 300 µL of 0.1 mol / L glucose solution;

[0054] 5) Add 25 µL of 0.05 mol / L HAuCl4 solution to the solution from step 4);

[0055] 6) The solution from step 5) was stirred at 840 rpm in an oil bath at 140 ℃ for 10 min. The color of the solution changed from bright yellow to brown and finally to royal blue.

[0056] 7) After cooling the solution obtained in step 6), centrifuge at 12000 rpm for 10 min and collect the lower precipitate, which is the solution of gold-silver hybrid hollow nanorings with LSPR absorption of 628 nm.

[0057] 8) Take 20 µL of the gold-silver hybrid hollow nanoring solution obtained in step 7) and drop it onto a silicon wafer; the silicon wafer is 5 × 5 mm. 2 The silicon wafers of the specified size were ultrasonically cleaned with acetone, anhydrous ethanol and deionized water, then the surface was cleaned with concentrated sulfuric acid and hydrogen peroxide solution, and finally the surface was modified with hexadecyl ammonium bromide solution.

[0058] 9) After drying the silicon wafer from step 8), add 20 µL of 10 -9 mol / L 4-cyanothiophenol detection solution.

[0059] Example 3

[0060] A method for preparing a gold-silver hybrid hollow nanoring SERS substrate includes the following steps:

[0061] 1) Take 1000 µL of freshly prepared 0.1 mol / L ascorbic acid solution and add it to deionized water, then heat to boiling;

[0062] 2) Add Ag seed growth solution prepared by 5 mL of deionized water, 1.47 g of trisodium citrate and 1 mL of 0.1 mol / L AgNO3 solution to step 1), and keep the mixture boiling for 10 min.

[0063] 3) After cooling the solution obtained in step 2), centrifuge at 12000 rpm, collect the precipitate, and obtain 1 mL of Ag nanoparticle solution;

[0064] 4) Disperse the 300 µL Ag nanoparticle solution obtained in step 3) in 20 mL of deionized water, and add 300 µL of 0.1 mol / L glucose solution;

[0065] 5) Add 30 µL of 0.05 mol / L HAuCl4 solution to the solution in step 4);

[0066] 6) The solution from step 5) was stirred at 840 rpm in an oil bath at 140 ℃ for 10 min. The color of the solution changed from bright yellow to brown and finally to grayish purple.

[0067] 7) Centrifuge the solution obtained in step 6) at 12000 rpm for 10 min and collect the lower precipitate, which is the solution of gold-silver hybrid hollow nanorings with LSPR absorption of 770 nm.

[0068] 8) Take 20 µL of the gold-silver hybrid hollow nanoring solution obtained in step 7) and drop it onto a silicon wafer; the silicon wafer is 5 × 5 mm. 2 The silicon wafers of the specified size were ultrasonically cleaned with acetone, anhydrous ethanol and deionized water, then the surface was cleaned with concentrated sulfuric acid and hydrogen peroxide solution, and finally the surface was modified with hexadecyl ammonium bromide solution.

[0069] 9) After drying the silicon wafer from step 8), add 20 µL of 10 -9 mol / L 4-cyanothiophenol detection solution.

[0070] Figure 1 Transmission electron microscopy (TEM) images of the prepared silver nanoparticles and gold-silver hybrid hollow nanorings with absorption at three LSPR wavelengths are shown. The images show that as the amount of HAuCl4 increases, the hollow structure of the prepared gold-silver hybrid nanorings gradually forms, and the nanorings gradually aggregate.

[0071] Figure 2 The images show the UV absorption spectra of silver citrate nanoparticles and gold-silver hybrid hollow nanorings with different LSPR absorption wavelengths. Figure 2 This indicates that as the amount of HAuCl4 added increased from 20 µL to 30 µL, the LSPR absorption peak gradually red-shifted, with the absorption center shifting from 403 nm to 531, 628, and 770 nm.

[0072] Figure 3 Color images of silver nanoparticles and gold-silver hybrid hollow nanoring solutions absorbing at three LSPR wavelengths. Figure 3 This indicates that as the amount of HAuCl4 added increased from 20 µL to 30 µL, the color of the solution gradually transitioned from pale yellow to brownish-yellow, then to pink, blue, and finally to a purple hue.

[0073] Figure 4 Three LSPR wavelength absorption wavelengths of gold-silver hybrid hollow nanorings for 10 -9 SERS spectrum of mol / L 4-cyanothiophenol detection solution. Figure 4 The results show that the gold-silver hybrid hollow nanoring SERS substrate prepared by this invention exhibits a strong SERS enhancement effect on 4-cyanothiophenol under three commonly used lasers.

[0074] Figure 5 A schematic diagram of the energy levels of gold-silver hybrid hollow nanorings and the CM effect mechanism of 4-cyanothiophenol under three lasers. Figure 5The results show that under three lasers at 532 nm, 633 nm, and 785 nm, the gold-silver hybrid hollow nanorings exhibit an energy level electron migration pathway that matches that of 4-cyanothiophenol.

[0075] Examples 1, 2, and 3 demonstrate the preparation of silver-hybrid hollow nanoring SERS active substrates through a series of measures, achieving a combination of EM and CM effects. Compared with conventional measurement methods, these methods exhibit both high detection sensitivity and high universality.

[0076] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a gold-silver hybrid hollow nanoring SERS substrate, characterized in that: Using trisodium citrate as a coating agent, silver nanoparticles were synthesized via a seed synthesis method. Under reducing conditions, the ratio of HAuCl4 to AgNO3 was adjusted to etch the silver nanoparticles with HAuCl4 to obtain gold-silver hybrid hollow nanoring solutions with different LSPR absorption wavelengths. The prepared gold-silver hybrid hollow nanoring solutions were then dropped onto a silicon wafer to obtain a gold-silver hybrid hollow nanoring SERS substrate material. The method for preparing the gold-silver hybrid hollow nanoring SERS substrate includes the following steps: 1) Add ascorbic acid solution to boiling deionized water; 2) Add Ag seed growth solution to step 1) and react for 10 minutes while keeping it boiling; 3) Centrifuge the solution obtained in step 2) and collect the precipitate to obtain a silver nanoparticle solution; 4) Disperse the silver nanoparticle solution obtained in step 3) in deionized water and add glucose solution as a reducing agent; 5) Add HAuCl4 solution to the solution from step 4); 6) React the solution from step 5) in an oil bath for a certain period of time; 7) Centrifuge the solution obtained in step 6) and collect the lower precipitate, which is the solution of gold-silver hybrid hollow nanorings; 8) Drop the gold-silver hybrid hollow nanoring solution obtained in step 7) onto the silicon wafer to obtain the gold-silver hybrid hollow nanoring SERS substrate; 9) After drying the silicon wafer from step 8), add the detection solution.

2. The method for preparing the gold-silver hybrid hollow nanoring SERS substrate according to claim 1, characterized in that: Step 1) specifically involves adding 1000µL of freshly prepared 0.1mol / L ascorbic acid solution to 160mL of boiling deionized water.

3. The method for preparing the gold-silver hybrid hollow nanoring SERS substrate according to claim 1, characterized in that: The Ag seed growth solution described in step 2) consists of 5 mL of deionized water, 1.47 g of trisodium citrate and 1 mL of 0.1 mol / L AgNO3 solution.

4. The method for preparing the gold-silver hybrid hollow nanoring SERS substrate according to claim 1, characterized in that: In step 4), the volume ratio of the silver nanoparticle solution to deionized water is 3:

200.

5. The method for preparing the gold-silver hybrid hollow nanoring SERS substrate according to claim 1, characterized in that: In step 4), the concentration of the reducing agent glucose solution is 0.1 mol / L; the volume ratio of the silver nanoparticle solution to the reducing agent glucose solution is 1:

1.

6. The method for preparing the gold-silver hybrid hollow nanoring SERS substrate according to claim 1, characterized in that: In step 5), add 0.05 mol / L HAuCl4 solution according to the molar ratio of AgNO3 used in the preparation of HAuCl4 and silver nanoparticle solution of 1-1.5:

30.

7. The method for preparing the gold-silver hybrid hollow nanoring SERS substrate according to claim 1, characterized in that: The solution described in step 5) in step 6) is reacted in an oil bath at 140°C for 10 min.

8. The gold-silver hybrid hollow nanoring SERS substrate material prepared by the method described in claim 1.

9. The application of the gold-silver hybrid hollow nanoring SERS substrate material as described in claim 8 in SERS detection.

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