Silver nano@ZIF-8@gold nano SERS composite substrate, and preparation method and application thereof

Abstract

The application belongs to the technical field of surface enhanced Raman scattering spectrum, and particularly discloses a silver nanometer@ZIF-8@gold nanometer composite substrate and a preparation method and application thereof. The silver nanometer@ZIF-8@gold nanometer composite material provided by the application takes the silver nanometer ball with a particle size of 100-400 nm as a core, the silver ball is wrapped with a ZIF-8 film with a thickness of 1-10 nm, and the gold nanometer ball with a particle size of 30-50 nm is attached to the outer layer of the silver core ZIF-8 shell. The excellent material ZIF-8 in the MOF is combined with the two kinds of noble metal materials of gold and silver, and the noble metals form a multiple enhancement effect. Meanwhile, the design of taking the silver nanometer ball as the core, the ZIF-8 as the shell and the gold nanometer ball being uniformly attached to the surface of the core-shell avoids the plugging problem of the noble metal nanometer ball to the MOF material to a certain extent, improves the adsorption performance of the substrate and increases the number of the substrate surface "Raman hot spots", and greatly improves the detection sensitivity of the substrate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of surface enhanced Raman scattering spectrum, and particularly relates to a silver nano-ZIF-8-gold nano composite substrate and a preparation method and application thereof. BACKGROUND

[0002] Surface enhanced Raman scattering spectrum (SERS) technology is a technology for improving the intensity of Raman spectrum by using the enhanced electric field of a noble metal to adsorb a to-be-detected molecule. The SERS enhancement mechanism generally recognized by the academic circle mainly includes electromagnetic field enhancement mechanism and charge transfer enhancement mechanism. The electromagnetic field enhancement mechanism considers that the nano structure on the surface of the SERS substrate will be excited by laser irradiation to produce local surface plasmon, so that the Raman signal of the to-be-detected molecule is greatly enhanced. The charge transfer enhancement mechanism considers that the mutual electron transfer between the metal substrate and the to-be-detected molecule adsorbed on the surface thereof produces a resonance Raman scattering phenomenon, thereby enhancing the Raman signal of the to-be-detected molecule.

[0003] The traditional SERS substrate mainly uses noble metal materials such as gold and silver. However, pure noble metal nanoparticles cannot well adsorb the to-be-detected molecule, and therefore other materials are needed to help the noble metal nanoparticles to enrich the to-be-detected molecule so as to enhance the Raman signal intensity. Metal organic framework material (MOF) is a new type of porous material formed by coordination between metal ions or metal clusters and organic ligands. The zeolitic imidazolate framework material (ZIF-8) is a metal organic framework material self-assembled by zinc ions and 2-methyl imidazole ligands, which has the characteristics of large specific surface area, high porosity, convenient synthesis and controllable size, can effectively enrich and adsorb benzene ring-containing substances in the environment, and has excellent stability. Therefore, the combination of ZIF-8 and noble metal nanoparticles can obtain a relatively ideal SERS substrate.

[0004] The composite substrate composed of MOF and noble metal material can effectively capture and adsorb the to-be-detected molecule on the surface of the substrate to improve the Raman signal intensity. However, many researchers only combine MOF with a single noble metal material, and the SERS enhancement effect of the single noble metal is limited, and the detection effect of trace substances is not good. In addition, in the composite substrate composed of MOF and noble metal material, the noble metal nanoparticles are often simply attached to the surface of the MOF material, and the MOF and the noble metal nanoparticles are prone to agglomeration, which greatly reduces the dispersibility. At the same time, the noble metal nanoparticles attached to the surface of the MOF will cause the blockage of part of the pores on the surface of the MOF, affecting the adsorption of the substrate. SUMMARY

[0005] In order to solve the above-mentioned deficiencies in the prior art, the application provides a silver nano@ZIF-8@gold nano SERS composite substrate and a preparation method and application thereof. The application combines the excellent material ZIF-8 in MOF with two kinds of noble metal materials, gold and silver, and the noble metals form a multiple enhancement effect with each other. Meanwhile, the application adopts the design of taking silver balls as cores, ZIF-8 as shells and gold balls uniformly attached to the surface of the cores and shells, combines the prepared silver nano@ZIF-8 sol and gold nano sol, and makes the gold nano particles uniformly attached to the silver balls, thereby avoiding the above-mentioned problem of partial blockage of the pores on the surface of MOF to a certain extent, and realizing high overlap of the adsorption points and the Raman hot spots to greatly enhance the Raman signal intensity.

[0006] In order to achieve the above-mentioned purpose, the application realizes the above-mentioned purpose by the following technical scheme:

[0007] The silver nano@ZIF-8@gold nano SERS composite substrate comprises a silver nano@ZIF-8@gold nano material and can further comprise a substrate such as a silicon wafer. The structure of the silver nano@ZIF-8@gold nano material is as follows: a silver nano ball with a particle size of 100-400 nm is taken as a core, a ZIF-8 film with a thickness of 1-10 nm is wrapped outside the silver core, and a gold nano ball with a particle size of 30-50 nm is attached to the outer layer of the silver core ZIF-8 shell; wherein the pore size of the ZIF-8 material surface is less than 1 nm, which is much smaller than the particle size of the gold nano ball.

[0008] Preferably, the thickness of the ZIF-8 film wrapped outside the silver ball is 1-5 nm; more preferably, the thickness is 2 nm.

[0009] The application further provides a preparation method of the silver nano@ZIF-8@gold nano material, which comprises the following steps:

[0010] (1) silver nitrate solution, polyvinylpyrrolidone solution and deionized water are added into a container respectively, and the mixed solution is subjected to magnetic stirring and fully mixed;

[0011] (2) a reducing amount of ascorbic acid solution is quickly added into the container in (1), and stirring is continued, and the color of the mixed solution changes from colorless to light yellow, dark green and finally brown black; the mixed solution is subjected to centrifugal washing with deionized water and ethanol respectively, and the final centrifugal product is ultrasonically dispersed in methanol to obtain a silver nano sol;

[0012] (3) zinc nitrate hexahydrate and methyl imidazole are weighed and added into methanol, and after fully stirring and mixing, a ZIF-8 preparation liquid is obtained;

[0013] (4) adding the silver nanosol described in (2) into the ZIF-8 preparation liquid described in (3), after magnetic stirring at room temperature, the mixed liquid is left to stand for a period of time, then centrifugal washing is performed using methanol, and finally the centrifugal product is ultrasonically dispersed in methanol to obtain a silver nanometer@ZIF-8 sol;

[0014] (5) adding chloroauric acid solution and cetyltrimethylammonium bromide solution into a container respectively, after fully stirring and mixing, sodium borohydride solution is quickly added, after quick stirring and standing for a period of time, dilution is performed to obtain a gold seed solution;

[0015] (6) adding chloroauric acid solution and cetyltrimethylammonium bromide solution into a container respectively, after fully stirring and mixing, ascorbic acid solution, deionized water and the gold seed solution described in (5) are added, after mixing, the mixed liquid is left to stand for a period of time, centrifugal washing is performed using deionized water, and finally the centrifugal product is ultrasonically dispersed in methanol to obtain a gold nanosol;

[0016] (7) after mixing the silver nanometer@ZIF-8 sol described in (4) with the gold nanosol described in (6), after vigorous stirring and standing for a period of time, centrifugal washing is performed using methanol, and finally the centrifugal product is ultrasonically dispersed in methanol to obtain a silver nanometer@ZIF-8@gold nanosol;

[0017] (8) drying the silver nanometer@ZIF-8@gold nanosol described in (7) under vacuum to obtain a silver nanometer@ZIF-8@gold nanometer material.

[0018] Preferably, in step (1), the concentration of the silver nitrate solution is 0.1 mol / L; the mass fraction of the polyvinylpyrrolidone solution is 1%; the volume ratio of the silver nitrate solution, the polyvinylpyrrolidone solution and the deionized water is 1:1:48.

[0019] Preferably, in step (1), the magnetic stirring conditions are: the stirring speed is 500-1200 rpm, and the stirring time is 8-15 min.

[0020] Preferably, in step (2), the molar concentration ratio of the silver nitrate solution and the ascorbic acid solution is 1:1, and the volume ratio is 1:1.

[0021] Preferably, in step (2), the concentration of the obtained silver nanosol is 0.01 mol / L.

[0022] Preferably, in step (3), the amount ratio of the zinc nitrate hexahydrate, the methyl imidazole and the methanol is 0.67 mmol:0.67 mmol:80 mL.

[0023] Preferably, in step (3), the magnetic stirring conditions are: the stirring speed is 500-1200 rpm, and the stirring time is 8-15 min.

[0024] Preferably, in step (4), the molar ratio of silver element to zinc element in the mixed solution is 0.05:0.67.

[0025] Preferably, in step (4), the magnetic stirring condition is that the rotating speed is 500-1200 rpm and the stirring time is 8-15 min.

[0026] Preferably, in step (4), the standing time is 8-15 h, preferably 12 h.

[0027] Preferably, in step (4), the concentration of the obtained silver nano@ZIF-8 sol is 0.01 mol / L.

[0028] Preferably, in step (5), the molar concentration ratio of chloroauric acid solution, cetyltrimethylammonium bromide solution and sodium borohydride solution is 0.01:0.1:0.01; the volume ratio of chloroauric acid solution, cetyltrimethylammonium bromide solution and sodium borohydride solution is 0.25:7.5:0.25; and the dilution ratio is 1:10.

[0029] Preferably, in step (5), the standing time is 1-2 h.

[0030] Preferably, in step (6), the molar concentration ratio of chloroauric acid solution, cetyltrimethylammonium bromide solution and ascorbic acid solution is 0.01:0.1:0.1; the volume ratio of chloroauric acid solution, cetyltrimethylammonium bromide solution, ascorbic acid solution, deionized water and gold seed solution is 0.8:6.4:3.8:32:(1-4) x 10 -2 ; preferably, the volume ratio of chloroauric acid solution, cetyltrimethylammonium bromide solution, ascorbic acid solution, deionized water and gold seed solution is 0.8:6.4:3.8:32:3 x 10 -2 .

[0031] Preferably, in step (6), the standing time is 4-5 h.

[0032] Preferably, in step (6), the concentration of the obtained gold nano sol is 0.001 mol / L.

[0033] Preferably, in step (7), the molar ratio of silver element to gold element in the mixed solution is 10:(1-3); more preferably, the molar ratio of silver element to gold element in the mixed solution is 10:(1-2); most preferably, the molar ratio of silver element to gold element in the mixed solution is 10:2.

[0034] Preferably, in step (7), the standing time is 1-2 h.

[0035] Preferably, the vacuum drying conditions in step (8) are as follows: the drying temperature is 50 DEG C, and the drying time is 4-5h.

[0036] Meanwhile, the application also claims the silver nano@ZIF-8@gold nano SERS composite substrate prepared by the above method.

[0037] Meanwhile, the application also claims the application of the above silver nano@ZIF-8@gold nano SERS composite substrate and the silver nano@ZIF-8@gold nano SERS composite substrate prepared by the above method as a SERS substrate, specifically as a SERS substrate in pesticide detection, more specifically as a SERS substrate in benzene ring pesticide detection.

[0038] Compared with the prior art, the application has the following advantages and beneficial effects:

[0039] (1) The silver nano@ZIF-8@gold nano SERS composite substrate prepared by the application contains two kinds of precious metal materials, gold and silver, and the multiple enhancement effect between the double precious metal nanoparticles of gold and silver greatly improves the sensitivity of the substrate.

[0040] (2) The silver nano@ZIF-8@gold nano SERS composite substrate prepared by the application uses ZIF-8 material to capture and enrich the measured substances on the surface of the substrate, greatly enhancing the adsorption performance of the substrate.

[0041] (3) The silver nano@ZIF-8@gold nano SERS composite substrate prepared by the application takes silver balls as the core, ZIF-8 as the shell, and gold balls are uniformly attached to the surface of the core-shell. Through special structural design, the multiple enhancement effect between the double precious metal nanoparticles is generated, and the gold nanoparticles attached to the surface are ensured not to weaken the adsorption performance of the substrate.

[0042] (4) The application finds that the addition amount of gold seed solution, the volume ratio of silver nano@ZIF-8 sol and gold nano sol have an influence on the Raman enhancement effect of the prepared silver nano@ZIF-8@gold nano SERS material, and the optimal process parameters are obtained. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 SEM images of silver nano sol (Ag), silver nano@ZIF-8 sol (Ag@ZIF-8) and silver nano@ZIF-8@gold nano sol (Ag@ZIF-8@Au) materials in Example 1 of the application;

[0044] Figure 2 SEM image of silver nano@ZIF-8@gold nano material formed by adding 10 μL of gold seed solution in Example 3 of the application;

[0045] Figure 3 SEM image of silver nanometer@ZIF-8@gold nanometer material formed by adding 20 μL gold seed solution in the embodiment 4 of the present application;

[0046] Figure 4 SEM image of silver nanometer@ZIF-8@gold nanometer material formed by adding 40 μL gold seed solution in the embodiment 5 of the present application;

[0047] Figure 5 SEM image of silver nanometer@ZIF-8@gold nanometer material formed by adding 40 μL gold seed solution in the embodiment 5 of the present application;

[0048] Figure 6 SEM image of silver nanometer@ZIF-8@gold nanometer material formed by adding 40 μL gold seed solution in the embodiment 5 of the present application;

[0049] Figure 7 Raman spectrum of 4-aminothiophenol (4-ATP) probe molecule measured by silver nanometer@ZIF-8@gold nanometer material formed by adding different amounts of gold seed solution in the embodiments 1-5 of the present application.

[0050] Figure 8 Linear graph of the strongest characteristic peak of 4-aminothiophenol (4-ATP) probe molecule measured by silver nanometer@ZIF-8@gold nanometer material formed by adding different amounts of gold seed solution in the embodiments 1-5 of the present application.

[0051] Figure 9 Raman spectrum of 4-aminothiophenol (4-ATP) probe molecule measured by silver nanometer@ZIF-8@gold nanometer material formed by adding different amounts of gold seed solution in the embodiments 1-5 of the present application.

[0052] Figure 10 Columnar graph of the strongest characteristic peak of 4-aminothiophenol (4-ATP) probe molecule measured by silver nanometer@ZIF-8@gold nanometer material formed by adding different amounts of gold seed solution in the embodiments 1-5 of the present application.

[0053] Figure 11 Comparison graph (B) of the strongest characteristic peak intensity of 4-ATP probe molecule Raman detection spectrum (A) of three types of materials of silver nanometer, silver nanometer@ZIF-8 and silver nanometer@ZIF-8@gold nanometer;

[0054] Figure 12 SERS Raman spectrum of sensitivity of silver nanometer@ZIF-8@gold nanometer material prepared in the embodiment 1 of the present application for detecting different concentrations of 4-ATP probe molecule.

[0055] Figure 13 The linear fitting graph of the Raman shift peak intensity of the probe molecule 4-ATP at 1082 cm-1 for detecting different concentrations of the silver nanometer@ZIF-8@gold nanometer material prepared in embodiment 1 of the present application. -1

[0056] Figure 14 The columnar graph of the Raman shift intensity of the probe molecule at 1082 cm-1 for detecting the time stability of the silver nanometer@ZIF-8@gold nanometer material prepared in embodiment 1 of the present application. -1

[0057] Figure 15 The SERS Raman spectrum for detecting the uniformity of the silver nanometer@ZIF-8@gold nanometer material prepared in embodiment 1 of the present application: A is a single SERS Raman detection spectrum, B is the change graph of the peak intensity of the probe molecule 4-ATP at 1082 cm-1 and 1581 cm-1. -1 -1

[0058] Figure 16 The BET adsorption and desorption isotherm test graph (A) and the pore size distribution curve graph (B) of the ZIF-8 and the silver nanometer@ZIF-8@gold nanometer material prepared in embodiment 1 of the present application.

[0059] Figure 17 The SERS enhancement effect graph of the simulation result of the silver nanometer@ZIF-8@gold nanometer material simulation experiment in which the silver sphere and the silver sphere and the distance between the two is 1 nm by FDTD solutions software.

[0060] Figure 18 The SERS enhancement effect graph of the simulation result of the silver nanometer@ZIF-8@gold nanometer material simulation experiment in which the silver is the core and the gold is the shell and the distance between the two is 1 nm by FDTD solutions software.

[0061] Figure 19 The SERS enhancement effect graph of the simulation result of the silver nanometer@ZIF-8@gold nanometer material simulation experiment in which the silver is the core and the gold is the shell and the distance between the two is 2 nm by FDTD solutions software.

[0062] Figure 20 The SERS enhancement effect graph of the simulation result of the silver nanometer@ZIF-8@gold nanometer material simulation experiment in which the silver is the core and the gold is the shell and the distance between the two is 3 nm by FDTD solutions software.

[0063] Figure 21 ​​​​The SERS enhancement effect diagram of the simulation result of the silver nano@ZIF-8@gold nano material simulation experiment in which silver is used as a core, gold is used as a shell, and the distance between the two is 5 nm.

[0064] Figure 22 The SERS enhancement effect diagram of the simulation result of the silver nano@ZIF-8@gold nano material simulation experiment in which silver is used as a core, gold is used as a shell, and the distance between the two is 8 nm.

[0065] Figure 23 The SERS enhancement effect diagram of the simulation result of the silver nano@ZIF-8@gold nano material simulation experiment in which silver is used as a core, gold is used as a shell, and the distance between the two is 10 nm.

[0066] Figure 24 The SERS enhancement effect line chart of the simulation result of the silver nano@ZIF-8@gold nano material simulation experiment in which the distance between silver and silver ball and the distance between silver and gold is different.

[0067] Figure 25 The SERS enhancement effect diagram of the simulation result of the silver nano@ZIF-8@gold nano material simulation experiment in which two silver nano@ZIF-8@gold nano composite materials are used.

[0068] Figure 26 The SERS enhancement effect diagram of the simulation result of the silver nano@ZIF-8@gold nano material simulation experiment in which three silver nano@ZIF-8@gold nano composite materials are used.

[0069] Figure 27 The SERS enhancement effect diagram of the simulation result of the silver nano@ZIF-8@gold nano material simulation experiment in which multiple silver nano@ZIF-8@gold nano composite materials are used.

[0070] Figure 28 The SERS Raman spectrum of the silver nano@ZIF-8@gold nano material obtained in example 1 is used to test benzene ring pesticides of different concentrations in example 9. DETAILED DESCRIPTION

[0071] In order to make the invention purpose, technical scheme and invention advantage of the present application more clear, the present application will be further explained in detail in combination with examples and drawings.

[0072] The chemical reagents used in the present application are purchased through commercial channels unless otherwise specified. Among them, the methanol, ascorbic acid, sodium borohydride, chloroauric acid, zinc nitrate hexahydrate, methyl imidazole, cetyltrimethylammonium bromide, silver nitrate (AgNO3, purity 99.9%), PVP (polyvinylpyrrolidone), 4-aminothiophenol (4-ATP, purity ≥98%) used in each example of the present application are all analytical grade reagents without further purification, and the water used is deionized water.

[0073] Example 1

[0074] A preparation method of a silver nano@ZIF-8@gold nano material, comprising the following steps:

[0075] (1) 1 ml of 0.1 mol / L silver nitrate solution, 1 ml of 1 wt% polyvinylpyrrolidone solution and 48 ml of deionized water were added to a container, respectively, and the mixed solution was magnetically stirred at a speed of 800 rpm for 10 min, and fully mixed;

[0076] (2) 1 ml of 0.1 mol / L ascorbic acid solution was quickly added to the container in (1), and the magnetic stirring was continued for 10 min. The color of the mixed solution changed from colorless to light yellow, dark green, and finally to brown black. The mixed solution was centrifuged with deionized water and anhydrous ethanol, respectively, under the following conditions: the speed was 4000 rpm, and the centrifugation time was 10 min; the final centrifugation product was ultrasonically dispersed in 10 ml of methanol to obtain 10 ml of 0.01 mol / L silver nano sol;

[0077] (3) 0.67 mmol of zinc nitrate hexahydrate and 0.67 mmol of methyl imidazole were weighed and added to 80 ml of methanol, and the mixed solution was magnetically stirred at a speed of 800 rpm for 10 min, and fully mixed to obtain a ZIF-8 preparation solution;

[0078] (4) 5 ml of the 0.01 mol / L silver nano sol in (2) was added to 80 ml of the ZIF-8 preparation solution in (3). The mixed solution was magnetically stirred at a speed of 800 rpm for 3 h at room temperature, and then stood for 12 h. Then, the mixed solution was centrifuged with methanol, and the final centrifugation product was ultrasonically dispersed in 5 ml of methanol to obtain a silver nano@ZIF-8 sol;

[0079] (5) 0.25 mL of 0.01 mol / L chloroauric acid solution and 7.5 ml of 0.1 mol / L cetyltrimethylammonium bromide solution were added to a container, respectively, and fully stirred and mixed. Then, 0.25 ml of 0.01 mol / L sodium borohydride solution was quickly added, and after quick stirring, it was stood for 1 h. After dilution by 10 times, 80 ml of 3.125 x 10 -5mol / L gold seed solution;

[0080] (6) 0.8 mL of 0.01 mol / L chloroauric acid solution and 6.4 mL of 0.1 mol / L cetyltrimethylammonium bromide solution were added into the container respectively and stirred thoroughly. Then 3.8 mL of 0.1 mol / L ascorbic acid solution, 32 mL of deionized water and 30 μL of the gold seed solution in (5) were added and stirred thoroughly. After standing for 4 h, the mixture was centrifuged and washed with deionized water. The final centrifuged product was dispersed in 8 mL of methanol by ultrasonic treatment to obtain 8 mL of 10 -3 mol / L gold nanosol;

[0081] (7) 2 mL of the gold nanosol in (6) was added into 1 mL of the silver nanosol@ZIF-8 in (4). After stirring at a speed of 1200 rpm for 5 min and standing for 1 h, the mixture was centrifuged and washed with methanol. The final centrifuged product was dispersed in 8 mL of methanol by ultrasonic treatment to obtain silver nanosol@ZIF-8@gold nanosol, which was stored at -4 °C for standby use.

[0082] (8) The silver nanosol@ZIF-8@gold nanosol in (7) was dried at 50 °C under vacuum for 4 h to obtain silver nanosol@ZIF-8@gold nanosol material.

[0083] The SEM images of the silver nanosol, silver nanosol@ZIF-8 and silver nanosol@ZIF-8@gold nanosol dried by vacuum drying in Example 1 are shown in Figure 1

[0084] Examples 2-5

[0085] Except that the amount of gold seed solution added in step (6) was different, the other process conditions and preparation processes of Examples 2-5 were the same as those of Example 1. The amount of gold seed solution added in Examples 2-5 was 0 μL, 10 μL, 20 μL and 40 μL respectively. The SEM images of the materials obtained in Examples 3, 4 and 5 are shown in Figure 2 Figure 3 Figure 4

[0086] Examples 6-7

[0087] Except that the ratio of silver nanosol@ZIF-8 to gold nanosol in step (7) was different, the other process conditions and preparation processes of Examples 6-7 were the same as those of Example 1. The amount of silver nanosol@ZIF-8 in Examples 6-7 was 1 mL, and the volume ratio of silver nanosol@ZIF-8 to gold nanosol was 1:1 and 1:3 respectively. The SEM images of the materials obtained in Examples 6 and 7 are shown in Figure 5 Figure 6 ​​​​​​

[0088] From Figures 1-4 It can be seen from

[0089] From Figure 1 , 5 , 6, it can be seen that the density of the gold nanoshell in the silver nanometer@ZIF-8@gold nanometer material obtained by adding different proportions of gold nanometer sol and silver nanometer@ZIF-8 is different.

[0090] Example 8: Material characterization analysis

[0091] 1、SERS analysis

[0092] (1) Use a portable Raman instrument, 10 -6 mol / L of 4-aminothiophenol (4-ATP) as a probe molecule to test and analyze the enhancement effect of the silver nanometer@ZIF-8@gold nanometer sol prepared in Examples 1-7 and the silver nanometer sol and silver nanometer@ZIF-8 sol prepared in Example 1, the test method is as follows:

[0093] ①Drop 0.5ml of silver nanometer@ZIF-8@gold nanometer sol on a dry and clean silicon wafer, and dry it in a vacuum oven at 50°C for 4h, then use it as a substrate;

[0094] ②Drop 0.5ml of 10 -6 mol / L of 4-aminothiophenol (4-ATP) probe molecule solution on the substrate, make sure it is fully immersed, and stand at room temperature for 15min;

[0095] ③Put the substrate after standing into a vacuum drying oven and dry it at 60°C for 2h.

[0096] ④Test the Raman spectrum of the dried sample.

[0097] The test results are shown in Figures 7-11 .

[0098] Figure 7 The SERS enhancement effect test results of the silver nanometer@ZIF-8@gold nanometer material prepared in Examples 1-5 are Figure 8 The 1082cm -1 Raman shift characteristic peak line type of 4-ATP probe molecule, combined with the analysis, it can be seen that when the amount of gold seed added is 30μL, the enhancement effect is best.

[0099] Figure 9 The SERS enhancement effect test results of the silver nanometer@ZIF-8@gold nanometer material prepared in Examples 1, 6, and 7 are Figure 10 The 1082cm-1 The Raman shift characteristic peak histogram, combined with the fact that the best enhancement effect is achieved when the ratio of silver nanometer @ ZIF-8 to gold nanometer sol is 1:2.

[0100] Among the three materials of silver nanometer, silver nanometer @ ZIF-8 and silver nanometer @ ZIF-8 @ gold nanometer, the silver nanometer @ ZIF-8 @ gold nanometer has the best Raman enhancement effect, and the test results are shown in Figure 11 .

[0101] (3) Using a portable Raman instrument, the sensitivity of the silver nanometer @ ZIF-8 @ gold nanometer material prepared in Example 1 was tested for Raman enhancement effect using different concentrations of 4-ATP probe solution.

[0102] The test results are shown in Figure 12 Compared with the blank group CK (pure water sample of the same volume), the lowest concentration of detection can reach 10 -9 mol / L, and a standard curve is established using the target substance 1082 cm -1 -1 peak as shown in Figure 13 , and the fitting R 2 is 0.9661, indicating that the concentration of the target substance in the concentration range of 10 -4 - 10 -9 mol / L has a good linear relationship with the SERS strongest detection enhancement peak value. It is proved that the detection of the composite material has high sensitivity.

[0103] (4) Using a portable Raman instrument, the time stability of the silver nanometer @ ZIF-8 @ gold nanometer material prepared in Example 1 was tested for Raman enhancement effect using 10 -6 mol / L of 4-ATP probe solution, and the test was performed every 7 days.

[0104] The test results are shown in Figure 14 , and the enhancement effect lasts for 6 weeks and still has good enhancement effect. And the relative standard deviation RSD=3.127% is calculated, which proves that the composite material has strong stability.

[0105] (5) Using a portable Raman instrument, the uniformity of the silver nanometer @ ZIF-8 @ gold nanometer material prepared in Example 1 was tested for Raman enhancement effect using 10 -6 mol / L of 4-ATP probe solution, i.e. multiple data were detected for the same batch of substrates.

[0106] The test results are shown in Figure 15 , where Figure 15 A is the Raman detection spectrum, Figure 15 B is the 4-ATP probe molecule at the displacement 1082 cm -1 , 1581 cm -1The peak intensity analysis change chart of two places, the relative standard deviation RSD of two places is less than 10%, which proves that the composite material has good signal repeatability.

[0107] 2、BET analysis

[0108] The adsorption isotherm and pore size distribution of ZIF-8 and silver nano@ZIF-8@gold nano prepared by the method of example 1 were tested by BET adsorption method. The test results are shown in Figure 16 , such as Figure 16 A In the adsorption isotherm test, although the adsorption performance of silver nano@ZIF-8@gold nano composite material is lower than that of ZIF-8 (804.2m 2 / g), but in most cases, the specific surface area still reaches 401.9m 2 / g, which has strong adsorption capacity. At the same time, as Figure 16 B The detection results of pore size distribution show that in the preparation process of silver nano@ZIF-8@gold nano composite material, the pore diameter of ZIF-8 surface is not damaged, and the pore size of silver nano@ZIF-8@gold nano composite material still mainly remains at 0.9325nm, which is basically consistent with that of ZIF-8 material (0.9308). At the same time, the pore size of the material surface is much smaller than the diameter of the gold nano balls (30-50nm) used in this scheme, which also ensures that there will be no situation of gold nano balls entering the ZIF-8 surface hole to cause hole blockage, and ensures the adsorption performance of ZIF-8 material to the measured substance.

[0109] 3、FDTD simulation analysis

[0110] The silver nano@ZIF-8@gold nano material was simulated by FDTD solutions software to explore the SERS enhancement effect of gold, silver material and the distance between core and shell. The particle size of silver ball used in the simulation experiment is 210nm, and the particle size of gold ball is 44nm. Figure 17 is the enhancement effect diagram of silver ball and silver ball with a distance of 1nm between them; Figures 18-23 is the enhancement effect diagram of silver ball as core and gold ball as shell with a distance of 1nm, 2nm, 3nm, 5nm, 8nm and 10nm between them respectively; Figure 24 is the SERS enhancement effect line chart of silver ball and silver ball, silver ball and gold ball with different distances between them; Figures 25-27 are respectively the enhancement effect simulation diagrams of two, three and multiple "silver nano@ZIF-8@gold nano materials" (silver ball as core and gold ball as shell, and the distance between silver ball and gold ball is 2nm); combined Figures 17-27, it is proved that the enhancement effect of the material Ag@ZIF-8@Au prepared in Example 1 is significantly higher than that of pure silver nanoparticles, and the silver nano@ZIF-8@gold nano material with silver as the core, gold as the shell and the distance of 2nm has the best enhancement effect.

[0111] Example 9

[0112] This embodiment provides a silver nano@ZIF-8@gold nano material prepared in Example 1 for SERS detection of benzene ring pesticides.

[0113] In this embodiment, the specific detection method is:

[0114] ①Dissolve the target pesticide with ultrapure water and set the gradient as follows: 10 -3 , 10 -4 , 10 -5 , 10 -6 , 10 -7 , 10 -8 , 10 -9 mol / L;

[0115] ②Drop 0.5ml of silver nano@ZIF-8@gold nano sol on a dry and clean silicon wafer, and dry it in a vacuum drying oven at 50℃ for 4h, then use it as a substrate;

[0116] ③Drop 0.5ml of benzene ring pesticide solution with different concentrations on the substrate, make sure that the substrate is fully immersed, and stand for 15min at room temperature;

[0117] ④Put the substrate after standing into a vacuum drying oven, and dry it at 60℃ for 2h;

[0118] ⑤Test the dried sample by Raman spectroscopy.

[0119] The average Raman spectrum of the detected benzene ring pesticide solution with different concentration gradients is shown in Figure 28 .

[0120] The above description describes the preferred embodiments of the present application, which should not be regarded as a limitation on the scope of protection of the claims of the present application. Any modification, equivalent replacement and improvement without departing from the principles and ideas of the present application should be regarded as within the scope of protection of the claims of the present application.

Claims

1. A silver nano@ZIF-8@gold nano SERS composite substrate, characterized in that, The silver nano@ZIF-8@gold nano material comprises a silver nano sphere with a particle size of 100-400 nm as a core, a ZIF-8 film with a thickness of 1-10 nm wrapped outside the silver nano sphere, and gold nano spheres with a particle size of 30-50 nm attached to the outer layer of the ZIF-8 shell of the silver nano sphere; and the ZIF-8 material has a surface pore size of less than 1 nm. 2.The silver nano@ZIF-8@gold nano SERS composite substrate according to claim 1, characterized in that, The thickness of the ZIF-8 film wrapped outside the silver nano sphere is 1-5 nm. 3.The silver nano@ZIF-8@gold nano SERS composite substrate of claim 2, characterized in that, The thickness of the ZIF-8 film wrapped outside the silver nano sphere is 2 nm.

4. The method for preparing silver nano@ZIF-8@gold nano SERS composite substrate according to any one of claims 1-3, characterized in that, The method comprises the following steps: (1) adding silver nitrate solution, polyvinylpyrrolidone solution and deionized water into a container respectively, and magnetically stirring the mixed solution to fully mix; (2) quickly adding a reducing amount of ascorbic acid solution into the container in (1), and continuing to stir, so that the color of the mixed solution changes from colorless to light yellow, dark green, and finally to brown black; centrifugally washing the mixed solution with deionized water and ethanol respectively, and ultrasonically dispersing the final centrifugal product in methanol to obtain a silver nano sol; (3) weighing zinc nitrate hexahydrate and methyl imidazole, and adding them into methanol, fully stirring and mixing to obtain a ZIF-8 preparation liquid; (4) adding the silver nano sol in (2) into the ZIF-8 preparation liquid in (3), magnetically stirring the mixed solution at room temperature, and then standing for a period of time, and then centrifugally washing the mixed solution with methanol, and ultrasonically dispersing the final centrifugal product in methanol to obtain a silver nano@ZIF-8 sol; (5) adding chloroauric acid solution and cetyltrimethylammonium bromide solution into a container respectively, fully stirring and mixing, quickly adding sodium borohydride solution, standing for a period of time after quick stirring, and diluting to obtain a gold seed solution; (6) adding chloroauric acid solution and cetyltrimethylammonium bromide solution into a container respectively, fully stirring and mixing, adding ascorbic acid solution, deionized water and the gold seed solution in (5), standing for a period of time after mixing, and centrifugally washing the mixed solution with deionized water, and ultrasonically dispersing the final centrifugal product in methanol to obtain a gold nano sol; (7) mixing the silver nano@ZIF-8 sol in (4) and the gold nano sol in (6), stirring vigorously, standing for a period of time, centrifugally washing the mixed solution with methanol, and ultrasonically dispersing the final centrifugal product in methanol to obtain a silver nano@ZIF-8@gold nano sol; (8) dropping the silver nano@ZIF-8@gold nano sol in (7) on a silicon wafer, and vacuum drying to obtain the silver nano@ZIF-8@gold nano SERS composite substrate.

5. The preparation method according to claim 4, characterized in that, In the step (5), the molar concentration ratio of the chloroauric acid solution, the cetyltrimethylammonium bromide solution and the sodium borohydride solution is 0.01:0.1:0.01; the volume ratio of the chloroauric acid solution, the cetyltrimethylammonium bromide solution and the sodium borohydride solution is 0.25:7.5:0.25; and the dilution multiple is 1:

10. And in the step (6), the molar concentration ratio of the chloroauric acid solution, the cetyltrimethylammonium bromide solution and the ascorbic acid solution is 0.01:0.1:0.1; the volume ratio of the chloroauric acid solution, the cetyltrimethylammonium bromide solution, the ascorbic acid solution, the deionized water and the gold seed solution is 0.8:6.4:3.8:32:(1~4)×10 -2 .

6. The production method according to claim 5, wherein The volume ratio of the chloroauric acid solution, the cetyltrimethylammonium bromide solution, the ascorbic acid solution, the deionized water and the gold seed solution in the step (6) is 0.8:6.4:3.8:32:3x10 -2 .

7. The preparation method according to claim 5, characterized in that, In the step (7), the molar ratio of silver element to gold element in the mixed solution is 10:(1-3).

8. The preparation method according to claim 7, characterized in that, The molar ratio of silver element to gold element in the mixed solution is 10:(1-2).

9. The production method according to claim 8, characterized by, The molar ratio of silver element to gold element in the mixed solution is 10:

2.

10. The method of claim 5, wherein, In the step (3), the ratio of the amount of zinc nitrate hexahydrate, methyl imidazole and methanol is 0.67 mmol:0.67 mmol:80 mL; and In the step (4), the molar ratio of silver element to zinc element in the mixed solution is 0.05:0.

67.

11. The method of claim 5, wherein, The concentration of silver nitrate solution in the step (1) is 0.1 mol / L.

12. The silver nano@ZIF-8@gold nano SERS composite substrate as claimed in any one of claims 1-3 and the silver nano@ZIF-8@gold nano SERS composite substrate prepared by the method as claimed in any one of claims 4-11 is applied as a SERS substrate.

13. The silver nano@ZIF-8@gold nano SERS composite substrate as claimed in any one of claims 1-3 and the silver nano@ZIF-8@gold nano SERS composite substrate prepared by the method as claimed in any one of claims 4-11 is applied as a SERS substrate in pesticide detection.

14. The silver nano@ZIF-8@gold nano SERS composite substrate as claimed in any one of claims 1-3 and the silver nano@ZIF-8@gold nano SERS composite substrate prepared by the method as claimed in any one of claims 4-11 is applied as a SERS substrate in benzene ring pesticide detection.

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