A sers substrate and its preparation method and application

Abstract

The application relates to a SERS substrate, a preparation method and application. The SERS substrate comprises two layers of a bottom layer and a surface layer, the bottom layer is a glass sheet substrate, and the surface layer is a composite silver nanowire-gold nanorod layer; the silver nanowire-gold nanorod layer is based on a silver nanowire network structure, and gold nanorods are attached to the silver nanowire network structure. The substrate can realize quantitative and qualitative detection of three common environmental pollutants, rhodamine 6g, crystal violet and thiram, and the detection lower limits are 10 ‑12 M, 10 ‑10 M, 10 ‑10 M. The substrate has a low detection lower limit and high sensitivity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of detection, and particularly relates to a SERS substrate, a preparation method thereof and application thereof in detection of environmental pollutants. BACKGROUND

[0002] With the progress of science and technology and the development of society, environmental pollution has attracted more and more attention. Among numerous environmental pollutants, organic dyes and pesticides exist widely in soil, rivers and even food, and have a great impact on human health and production and life. Moreover, these pollutants are difficult to degrade, and have a significant cumulative effect along the biological chain. At present, detection of these substances mainly includes capillary electrophoresis, gas chromatography-mass spectrometry, fluorescence spectroscopy and the like. Although these methods have high sensitivity, they have long sample pretreatment time, complicated operation and are mainly carried out under laboratory conditions. Therefore, it is of important practical significance to establish a rapid, real-time and simple detection and analysis technology for alleviating the increasingly severe environmental situation.

[0003] As a new detection method, surface enhanced Raman scattering (SERS) technology has the advantages of high sensitivity, rich chemical fingerprint information, simple operation and in-situ detection. The detection mechanism of SERS is that when light is incident, the Raman scattering signal of an adsorbed molecule is greatly enhanced due to the electromagnetic field enhancement of the nano-structure surface in some specially prepared nano-substrate or sol. When there is a gap of several nanometers or less in the metal particles or array structure, the gap can strongly couple with the incident light, excite localized surface plasmon resonance (LSPR) or surface plasmon polaritons (SPP), and bind energy therein to form a very strong electromagnetic field enhancement region (also known as "hot spot"). The enhancement effect of the SERS substrate depends on these "hot spot" regions on the structure surface. The greater the density and intensity of the "hot spot", the more obvious the enhancement effect of the SERS substrate. At present, various nano materials can be used to prepare SERS substrates.

[0004] Currently, there are some reports on the preparation of SERS substrates by silver nanowires and gold nanoparticles. In the CN107037029A, a method for detecting drugs in human body fluid based on gold nanorod SERS substrate, a gold nanorod sol with different length-diameter ratios and SERS activity is synthesized, and only the LSPR effect of gold nanorods is used to generate electromagnetic field enhancement region to realize the detection of drugs in human body fluid, and the number and intensity of hot spots are limited. In the CN109946285A, gold nanospheres are adsorbed onto silver nanowires by electrostatic adsorption to prepare a SERS substrate with uniform and dense arrangement of gold-silver nanowires. However, one of the nanomaterials in this patent is nanospheres, and the "gap" formed by the combination of nanospheres and nanowires is limited, and the spacing between nanomaterial particles is the main factor affecting the formation of hot spots, so the combination of gold nanospheres and silver nanowires has limited improvement on the hot spots of the SERS substrate. SUMMARY

[0005] In view of the deficiencies of the prior art mentioned in the background, the present application provides a SERS substrate, a preparation method and application thereof, and expects to obtain a SERS substrate with a three-dimensional network structure, which can improve the coupling effect with incident light, excite multiple "hot spot" regions between nanomaterials, increase the probability of target molecules entering "hot spots", and thus improve the detection effect of the substrate.

[0006] The first aspect of the present application provides a SERS substrate comprising two layers of a bottom layer and a surface layer, wherein the bottom layer is a glass sheet substrate, and the surface layer is a composite silver nanowire-gold nanorod layer; the silver nanowire-gold nanorod layer is based on a silver nanowire network structure, and gold nanorods are attached to the silver nanowire network structure.

[0007] The length of the silver nanowires is 15-25 μm, and the diameter is 10-30 nm; the diameter of the gold nanorods is 10-30 nm, and the length is 50-80 nm.

[0008] The silver nanowires and gold nanorods are attached to the bottom layer by means of stepwise dropwise addition.

[0009] The second aspect of the present application further provides a preparation method of a SERS substrate, comprising the following steps:

[0010] (1) preparing a silver nanowire sol;

[0011] (2) preparing a gold nanorod sol;

[0012] (3) sequentially dropping the silver nanowire sol and the gold nanorod sol onto a glass sheet to prepare a composite silver nanowire-gold nanorod SERS substrate.

[0013] The process of preparing the composite silver nanowire-gold nanorod SERS substrate in step (3) comprises the following steps:

[0014] (31) drop silver nanowire sol on the glass sheet, put into the oven to heat to obtain the glass sheet with silver nanowire;

[0015] (32) put the glass sheet with silver nanowire obtained in step (31) on the hot plate, drop gold nanorod sol on the glass sheet with silver nanowire.

[0016] The drop amount of gold nanorod sol per unit area on the glass sheet with silver nanowire in step (32) is 40-70 μl / cm 2 ; the concentration of gold nanorod sol is 1-3 mg / ml; the heating temperature of the hot plate is 30-80 ℃, and heating is performed until volatilization is complete.

[0017] The drop amount of silver nanowire sol per unit area on the glass sheet in step (31) is 15-85 μl / cm 2 ; the concentration of silver nanowire sol is 0.3-2 mg / ml; the heating temperature of the oven is 40-70 ℃, and heating is performed until volatilization is complete.

[0018] Further, the glass sheet in step (31) needs to be pretreated; the pretreatment step is: washing the glass sheet with a piranha solution, then washing with acetone, ethanol and deionized water respectively, and finally drying with nitrogen to obtain a clean glass sheet. The piranha solution is a mixed solution of concentrated sulfuric acid and 30% hydrogen peroxide with a volume ratio of 2:3-10:3.

[0019] The process for preparing silver nanowire sol in step (1) includes the following steps:

[0020] (11) dissolving polyvinylpyrrolidone PVP in ethanol to form a clear solution by stirring;

[0021] (12) adding silver nitrate AgNO3 to the clear solution of step (11), sealing the reaction, centrifuging and washing to obtain an ethanol mixture of silver nanowires.

[0022] In step (11), the polyvinylpyrrolidone, abbreviated as PVP, has a weight average molecular weight M W of 55 000;

[0023] In step (12), the weight ratio of silver nitrate AgNO3 to PVP in step (11) is 1:15-1:20; the reaction container in step (12) is an autoclave, the sealing reaction temperature is 140-170 ℃, the reaction time is 4-8 h, the centrifugation speed is 3000-6000 r / min, and the centrifugation time is 3-7 min.

[0024] The preparation of gold nanorod sol in step (2) includes the following steps:

[0025] (21) : preparing a seed solution containing HAuCl4, CTAB and NaBH4, the molar ratio of HAuCl4, CTAB and NaBH4 in the seed solution being 1:380-400:2-3;

[0026] (22) : preparing a growth solution containing HAuCl4, AgNO3, CTAB and ascorbic acid, the molar ratio of HAuCl4, AgNO3, CTAB and ascorbic acid in the growth solution being 5:1-2:900-1100:7-12;

[0027] (23) : adding the seed solution prepared in step (21) into the growth solution in step (22), mixing, standing, centrifuging to obtain a gold nanorod sol.

[0028] Further, in step (22), the HAuCl4, AgNO3 and CTAB are mixed first, then the pH of the solution is adjusted to 1-2, and then the ascorbic acid is added.

[0029] In step (23), the standing time is 8-12 h; the centrifuging speed is 4000-7000 r / min, and the time is 8-12 min.

[0030] The third aspect of the present application provides an application of the SERS substrate in detection of environmental pollutants, preferably for SERS detection of Rhodamine 6G, crystal violet and thiram. The present application uses a Raman spectrometer for SERS detection, and can quantitatively and qualitatively analyze the environmental pollutants. First, Rhodamine 6G, crystal violet and thiram are detected at different concentrations, and the lowest detection concentrations are 10 -12 M, 10 -10 M and 10 -10 M respectively. Since the Raman characteristic peaks of different molecules are different, the type of molecule can be determined simply and quickly according to the position of the Raman peak, and qualitative detection is realized. In addition, since the intensity of the Raman characteristic peak of the molecule has a certain quantitative relationship with the concentration of the molecule, on the basis of knowing the intensity of the characteristic peak, combined with appropriate mathematical formula fitting, the functional relationship between the concentration of the target molecule and the intensity of the characteristic peak can be obtained, so that quantitative detection is realized.

[0031] Compared with the prior art, the composite silver nanowire-gold nanorod SERS substrate, the preparation method and the application thereof have the following advantages:

[0032] (1) The SERS substrate can combine gold nanorods with silver nanowires. Compared with the combination of gold nanospheres and silver nanowires, the combination of gold nanorods and silver nanowires can form more gaps when the gold nanorods contact the silver nanowires, trigger more plasmonic effects with the three-dimensional network structure of the silver nanowires, bring a larger area of electromagnetic field enhancement region, improve the coupling effect with incident light, excite multiple "hot spot" regions between gold nanorods, between silver nanowires and between gold nanorods and silver nanowires, and increase the probability of target molecules entering the enhanced region, thereby increasing the detection effect of the substrate.

[0033] (2) In the conventional preparation method, gold and silver nanomaterials are mixed and then added dropwise, which has a problem that in the mixing process, "agglomeration" phenomenon is prone to occur due to the charges of the two. This will lead to uneven mixing. Because reducing agents and surfactants are added during the synthesis of gold and silver nanomaterials, the surface of the synthesized particles will have charges. If the charges of the two mixed particles are not suitable, "agglomeration" phenomenon occurs, and the only way to avoid this phenomenon is to re-synthesize the particles and adjust the types and amounts of charges. The preparation method of the composite silver nanowire-gold nanorod SERS substrate of the application adopts the steps of adding silver nanowires and gold nanorods dropwise in stages, which avoids the occurrence of "agglomeration" phenomenon.

[0034] (3) The substrate can realize quantitative and qualitative detection of three common environmental pollutants, rhodamine 6g, crystal violet and thiram, and the detection lower limit is 10 -12 M, 10 -10 M and 10 -10 M respectively. The substrate has low detection lower limit and high sensitivity. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a schematic diagram of a silver nanowire-gold nanorod SERS substrate;

[0036] Figure 1 In the figure, 1 is a glass substrate, 2 is a silver nanowire, and 3 is a gold nanorod.

[0037] Figure 2A and Figure 2B is a scanning electron microscope image of the silver nanowire-gold nanorod SERS substrate prepared in Example 1;

[0038] Figure 3 is a Raman signal diagram of rhodamine 6g with different concentrations on the SERS substrate prepared in Example 1;

[0039] Figure 4 is a graph of the relationship between the concentration of rhodamine 6g and the Raman signal intensity;

[0040] Figure 5 Raman signal intensity of different concentrations of crystal violet on the SERS substrate prepared in Example 2;

[0041] Figure 6 Raman signal intensity of different concentrations of crystal violet on the SERS substrate prepared in Example 2;

[0042] Figure 7 Raman signal intensity of different concentrations of thiram on the SERS substrate prepared in Example 1;

[0043] Figure 8 Raman signal intensity of different concentrations of thiram on the SERS substrate prepared in Example 1;

[0044] Figure 9 Raman signal intensity of different concentrations of thiram on the SERS substrate prepared in Example 1; -6 Raman signal intensity of different concentrations of thiram on the SERS substrate prepared in Example 1;

[0045] 1 is the Raman signal intensity on the silver nanowire-gold nanorod substrate prepared in Example 1; 2 is the Raman signal intensity on the silver nanowire-gold nanosphere substrate prepared in Comparative Example 1; 3 is the Raman signal intensity on the gold nanorod substrate prepared in Comparative Example 2. DETAILED DESCRIPTION

[0046] The technical solutions of the present application are further described below by examples, but these examples cannot limit the protection scope of the present application. In the following examples and comparative examples, the scanning electron microscope is a high-resolution scanning electron microscope with a model number of JCM-7000, the electron beam high voltage is 5KV, and the focal length is 9.8mm. The Raman signal is tested by a Horiba Xplus microconfocal Raman spectrometer. During the test, a 633nm laser is used for irradiation.

[0047] Example 1

[0048] 1, Synthesis of silver nanowires: first, 0.3g of polyvinylpyrrolidone (PVP, M W =55 000) was added to 35mL of ethanol, and after stirring for 30 minutes, a clear solution was formed. Then 0.017g of AgNO3 was added, and after stirring vigorously for 10 minutes, the mixture was transferred to a hydrothermal kettle (volume of 50mL) and sealed at 165℃ for 6 hours. After the reaction, centrifugation was carried out at 4000rpm for 5 minutes, repeated three times, and the unreacted raw materials were washed away to obtain an ethanol sol of silver nanowires with a diameter of 20nm and a length of 20μm.

[0049] 2. Synthesis of gold nanorods: First, mix HAuCl4 solution (0.01 M, 0.25 mL) and CTAB solution (0.1 M, 9.75 mL) in a 15 mL plastic tube, then add NaBH4 solution (0.01 M, 0.6 mL) into the mixture as seed solution; then, mix HAuCl4 (0.01 M, 2.0 mL), AgNO3 (0.01 M, 0.4 mL) and CTAB (0.1 M, 40 mL), then add HCl (1.0 M, 0.8 mL) to adjust the pH value of the solution to 1.5, and add ascorbic acid (0.1 M, 0.32 mL). Finally, add the prepared seed solution (0.096 mL) into the mixture, mix gently for 10 s, and stand for 12 h. Centrifuge at 5000 rpm for 10 min to obtain an aqueous solution of gold nanorods with a diameter of 15 nm and a length of 60 nm.

[0050] 3. Clean the glass sheet with piranha solution (a mixed solution of concentrated sulfuric acid and 30% hydrogen peroxide with a volume ratio of 7:3), then clean it with acetone, ethanol and deionized water respectively, and finally dry it with nitrogen to obtain a clean glass sheet.

[0051] Place the treated glass sheet in an oven at 50°C, and drop 15 μl of 1.0 mg / ml silver nanowire sol on the glass sheet at a unit area drop amount of 60 μl / cm 2 ; obtain a three-dimensional silver nanowire network structure by solution evaporation self-assembly. The network structure can well become the substrate for the next step of gold nanorods, and plays an important role in the entire composite SERS substrate.

[0052] 4. Place the glass sheet with silver nanowires in step 3 on a hot plate at 50°C, and drop gold nanorod sol on the glass sheet with silver nanowires at a unit area drop amount of 60 μl / cm 2 ; the concentration of the gold nanorod sol is 2.4 mg / ml. Heat until the liquid is completely volatilized to obtain a silver nanowire-gold nanorod composite structure SERS substrate. The scanning electron microscope images are shown in Figure 2A and Figure 2B . Figure 1 Schematic diagram of silver nanowire-gold nanorod SERS substrate.

[0053] 5. Detection of environmental pollutants:

[0054] Use the silver nanowire-gold nanorod composite structure as the SERS substrate to detect organic dye rhodamine 6G. First, place the substrate in a 2 ml centrifuge tube, and add different concentrations (10 -8 , 10 -9 , 10 -10 , 10 -11 , 10-12 M) in an ethanol solution of 6g of rhodamine, soaked for 4 hours, removed, and the remaining solution on the substrate carefully absorbed with filter paper. Then, it was placed in ethanol and gently shaken. After removal, the excess ethanol was absorbed with filter paper. This was repeated three times to remove molecules that failed to adsorb on the substrate surface. Afterwards, the Raman signal was measured using a Horiba Xplus microconfocal Raman spectrometer, using a laser wavelength of 633nm, a power of 10mW, a filter transmittance of 1%, an integration time of 20s, and two integration times. Figure 3 As shown. Figure 3 It can be seen that the characteristic peaks of rhodamine 6g molecule are mainly 611, 774, 1183, 1312, 1361, 1509, and 1651 cm -1 From the intensity of the characteristic peak, it can be seen that as the concentration gradually decreases, the intensity of the characteristic peak also gradually decreases. The SERS substrate can achieve - 12 Qualitative detection of rhodamine 6g molecules at a concentration of 1.5 M.

[0055] In order to achieve the quantitative detection of rhodamine 6g molecules, according to Figure 3 The data in 1361cm is selected -1 The intensity of the characteristic peak at is the ordinate, and the logarithm of the concentration is the abscissa. Figure 4 .from Figure 4 It can be seen that the intensity of the characteristic peak and the logarithm of the concentration show a good linear function relationship, I = 13928.2 + 1164.5 * log [C], with a correlation coefficient R = 0.9952. Based on this straight line, the peak at 1361 cm -1 After measuring the intensity of the characteristic peak, the concentration of the solution can be calculated, thereby achieving quantitative detection of rhodamine 6g molecules.

[0056] Example 2

[0057] The preparation steps were the same as steps 1 to 4 of Example 1, except that in step 1, the length of the silver nanowires was 23 μm and the diameter was 25 nm; in step 2, the length of the gold nanorods was 70 nm and the diameter was 22 nm; and in step 3, the amount of the silver nanowire sol added per unit area on the glass sheet was 40 μl / cm 2 The concentration of the silver nanowire sol was 1.3 mg / ml; the temperature of the hot plate in step 4 was 60°C, the concentration of the gold nanorod sol was 2 mg / ml, and the amount of the gold nanorod sol added per unit area on the glass sheet with silver nanowires was 50 μl / cm 2 .

[0058] The silver nanowire-gold nanorod composite structure is used as a SERS substrate to detect organic dye crystal violet. First, the substrate is placed in a 2 ml centrifuge tube, and different concentrations (10 -6 , 10 -7 , 10 -8 , 10 -9 , 10 -10 M) of crystal violet ethanol solution are added to the substrate, which is soaked for 4 hours, and then the residual solution on the substrate is carefully absorbed with filter paper. After that, the substrate is placed in ethanol and gently shaken, and then the excess ethanol is absorbed with filter paper after being taken out. The process is repeated three times to remove the molecules that are not adsorbed on the surface of the substrate. Then, the Horiba Xplus micro-confocal Raman spectrometer is used for testing, with a wavelength of 633 nm, a power of 10 mW, a filter transmittance of 1%, an integration time of 20 s, and an integration number of 2 times. The Raman signal is shown in Figure 5 . As shown in Figure 5 , the characteristic peaks of the crystal violet molecule are mainly 732, 762, 807, 921, 1175, 1297, 1374, 1599, 1620 cm -1 . The intensity of the characteristic peaks can show that as the concentration gradually decreases, the intensity of the characteristic peaks also gradually decreases, and the SERS substrate can realize qualitative detection of the crystal violet molecule at a concentration of 10 -10 M.

[0059] In order to realize quantitative detection of the crystal violet molecule, according to the data in Figure 5 , the intensity of the characteristic peak at 1175 cm -1 is selected as the vertical coordinate, and the logarithm of the concentration is selected as the horizontal coordinate, to obtain Figure 6 . As shown in Figure 6 , the intensity of the characteristic peak and the logarithm of the concentration show a good linear function, I = 23463.2 + 2336.9*log[C], and the correlation coefficient R = 0.9910. Based on this straight line, after the intensity of the characteristic peak at 1175 cm -1 is measured, the concentration of the solution can be calculated, thereby realizing quantitative detection of the crystal violet molecule.

[0060] Example 3

[0061] The silver nanowire-gold nanorod composite structure prepared in Example 1 is used as a SERS substrate to detect pesticide thiram. First, the substrate is placed in a 2 ml centrifuge tube, and different concentrations (10 -6 , 10 -7 , 10 -8 , 10 -9 , 10 -10M) in an ethanol solution of thiram, soak for 4 hours, take it out, carefully absorb the residual solution on the substrate with filter paper, then put it into ethanol and shake it gently, take it out and absorb the excess ethanol with filter paper, repeat three times to remove the molecules that failed to adsorb on the surface of the substrate. Afterwards, the Horiba Xplus microconfocal Raman spectrometer was used for testing, using a laser with a wavelength of 633nm, a power of 10mW, a filter transmittance of 1%, an integration time of 20s, and 2 integration times. The Raman signal is as follows Figure 7 As shown. Figure 7 It can be seen that the characteristic peaks of the Fumei bimolecule are mainly 565, 933, 1151, 1387, and 1519 cm -1 From the intensity of the characteristic peak, it can be seen that as the concentration gradually decreases, the intensity of the characteristic peak also gradually decreases. The SERS substrate can achieve -10 Qualitative detection of thirami molecules at a concentration of M.

[0062] In order to achieve the quantitative detection of Furam molecules, according to Figure 7 The data in 1387cm is selected -1 The intensity of the characteristic peak at is the ordinate, and the logarithm of the concentration is the abscissa. Figure 8 .from Figure 8 As can be seen, the intensity of this characteristic peak and the logarithm of the concentration exhibit a good linear relationship: I = 19931.0 + 1973.3 * log[C], with a correlation coefficient R = 0.9995. Based on this straight line, by measuring the intensity of the characteristic peak at 1387 cm⁻¹, the concentration of the solution can be calculated, thus enabling quantitative detection of thiram molecules.

[0063] Example 4

[0064] The preparation steps were the same as steps 1 to 4 of Example 1, except that in step 1, the length of the silver nanowires was 17 μm and the diameter was 16 nm; in step 2, the length of the gold nanorods was 50 nm and the diameter was 23 nm; and in step 3, the amount of the silver nanowire sol added per unit area on the glass sheet was 30 μl / cm 2 , the concentration of the silver nanowire sol is 0.8 mg / ml; the temperature of the hot plate in step 4 is 40° C., and the concentration of the gold nanorod sol is 2 mg / ml.

[0065] The detection of environmental pollutants rhodamine, crystal violet, and thiram is the same as in Examples 1 to 3, and the test results are similar. Figures 3-9 .

[0066] Example 5

[0067] The preparation steps were the same as steps 1 to 4 of Example 1, except that in step 1, the length of the silver nanowires was 25 μm and the diameter was 15 nm; in step 2, the length of the gold nanorods was 50 nm and the diameter was 25 nm; and in step 3, the amount of the silver nanowire sol added per unit area on the glass sheet was 30 μl / cm 2 , the concentration of the silver nanowire sol is 0.8 mg / ml; the temperature of the hot plate in step 4 is 40° C., and the concentration of the gold nanorod sol is 2 mg / ml.

[0068] The detection of environmental pollutants rhodamine, crystal violet, and thiram is the same as in Examples 1 to 4, and the test results are similar. Figures 3-9 .

[0069] Comparative Example 1

[0070] The preparation steps are the same as those in Example 1, except that the gold nanorods in step 4 are replaced with gold nanospheres to obtain a silver nanowire-gold nanosphere substrate.

[0071] Gold nanospheres were prepared by adding 240 μl of a 0.2 mol / L chloroauric acid solution to 150 ml of water and heating to boiling while stirring at 850 rpm. Then, 2 ml of a 0.04 mol / L sodium citrate solution was quickly added and the reaction continued for 30 minutes. After cooling to room temperature, the mixture was centrifuged three times at 3000 rpm for 10 minutes to remove unreacted reactants, yielding a gold nanosphere sol. The gold nanospheres had a particle size of 20 nm.

[0072] Determination 10 -6 The Raman signal of Rhodamine 6g is as follows: Figure 9 As shown in 2. Figure 9 1 is 10 of Example 1 -6 The Raman signal of Rhodamine 6g of Example 1 can be seen from the figure at 1509cm -1 The intensity at 1509 cm-1 is 11540. The rhodamine 6g molecule of Comparative Example 1 has an intensity at 1509 cm-1. -1 The intensity at is 8715.

[0073] The Raman signal intensity of the substrate tested in Comparative Example 1 was 24.5% lower than that of the substrate tested in Example 1. This shows that replacing gold nanospheres with gold nanorods can effectively increase the number and intensity of hot spots in the substrate, thereby improving the detection capability of the substrate.

[0074] Comparative Example 2

[0075] The preparation steps are the same as those in Example 1, except that there are no silver nanowires and the SERS substrate only has gold nanorods; -6 The Raman signal of Rhodamine 6g is as follows:Figure 9 The intensity of Rhodamine 6G molecule at 1509 cm"1is 2993, which is about 1 / 4 of the intensity of the substrate of Example 1. This shows that in the composite substrate of gold nanorods and silver nanowires, the three-dimensional network structure of silver nanowires can effectively enhance the coupling effect of light and substrate, increase the number and intensity of hot spots, and thus effectively improve the detection ability of the substrate. -1 The intensity of Rhodamine 6G molecule at 1509 cm"1is 2993, which is about 1 / 4 of the intensity of the substrate of Example 1. This shows that in the composite substrate of gold nanorods and silver nanowires, the three-dimensional network structure of silver nanowires can effectively enhance the coupling effect of light and substrate, increase the number and intensity of hot spots, and thus effectively improve the detection ability of the substrate.

Claims

1. A SERS substrate, characterized in that: The bottom layer is a glass substrate, and the surface layer is a composite silver nanowire-gold nanorod layer. The silver nanowire-gold nanorod layer is based on a silver nanowire network structure, and the gold nanorods are attached to the silver nanowire network structure. The SERS substrate is a three-dimensional silver nanowire network structure; The length of the silver nanowire is 15-25 μm and the diameter is 10-30 nm; the diameter of the gold nanorod is 10-30 nm and the length is 50-80 nm.

2. The SERS substrate according to claim 1, wherein Silver nanowires and gold nanorods were attached to the substrate by a step-by-step drop-wise addition method.

3. A method for preparing the SERS substrate according to any one of claims 1 to 2, characterized in that: The steps include: (1) Preparation of silver nanowire sol; (2) Preparation of gold nanorod sol; (3) Silver nanowire sol and gold nanorod sol were sequentially added onto a glass slide to prepare a composite silver nanowire-gold nanorod SERS substrate.

4. The method for preparing a SERS substrate according to claim 3, wherein: The process of preparing the composite silver nanowire-gold nanorod SERS substrate in step (3) includes the following steps: (31) Add silver nanowire sol dropwise onto a glass sheet, place it in an oven and heat it to obtain a glass sheet with silver nanowires; (32) Place the glass sheet with silver nanowires obtained in step (31) on a hot plate, and drop the gold nanorod sol onto the glass sheet with silver nanowires.

5. The method for preparing a SERS substrate according to claim 4, wherein: In step (32), the amount of gold nanorod sol added per unit area on the glass sheet with silver nanowires is 40-70 μl / cm 2 ; The concentration of gold nanorod sol is 1~3mg / ml.

6. The method for preparing a SERS substrate according to claim 4, wherein: In step (32), the heating temperature of the hot plate is 30-80°C, and the heating is performed until all the volatilization is completed.

7. The method for preparing a SERS substrate according to claim 4, wherein: In step (31), the amount of silver nanowire sol added per unit area on the glass sheet is 15~85μl / cm 2 ; The concentration of silver nanowire sol is 0.3~2mg / ml.

8. The method for preparing a SERS substrate according to claim 4, wherein: The glass sheet in step (31) is pretreated; the pretreatment steps are: cleaning the glass sheet with piranha washing solution, then cleaning with acetone, ethanol and deionized water respectively, and finally drying with nitrogen to obtain a clean glass sheet.

9. The method for preparing a SERS substrate according to claim 3, wherein: The preparation of the gold nanorod sol in step (2) comprises the following steps: (21): Prepare a seed solution containing HAuCl4, hexadecyltrimethylammonium bromide (CTAB), and NaBH4. The molar ratio of HAuCl4, CTAB, and NaBH4 in the seed solution is 1:380~400:2~3; (22): preparing a growth solution containing HAuCl4, AgNO3, CTAB and ascorbic acid, wherein the molar ratio of HAuCl4, AgNO3, CTAB and ascorbic acid is 5:1~2:900~1100:7~12; (23): The seed solution prepared in step (21) is added to the growth solution in step (22), mixed, allowed to stand, and centrifuged to obtain a gold nanorod sol.

10. Use of the SERS substrate according to any one of claims 1 to 2 or the SERS substrate prepared by the preparation method according to any one of claims 3 to 9 in the detection of environmental pollutants.

11. The use according to claim 10, characterized in that The SERS substrate is used for SERS detection of rhodamine 6g, crystal violet and thiram.

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