A method for preparing a SERS substrate of a zirconium-based MOF-808 / AuNPs

Abstract

The application provides a preparation method of a SERS substrate of a zirconium-based MOF-808 / AuNPs. The method comprises three steps: in the first step, an AuNPs solution is prepared by using deionized water, chloroauric acid and sodium citrate to perform an oil bath reaction to obtain the AuNPs solution; in the second step, MOF-808 is prepared by mixing zirconium chlorohydrate, 1,3,5-benzene tricarboxylic acid, N,N-dimethylformamide and formic acid, and then performing a hydrothermal reaction on the mixed solution, centrifuging and vacuum drying to obtain activated MOF-808-Zr powder; in the third step, the activated MOF-808-Zr powder is dissolved in anhydrous ethanol, and then fully stirred and mixed with AuNPs solutions of different amounts to form a zirconium-based MOF-808 / AuNPs solution; and in the fourth step, the zirconium-based MOF-808 / AuNPs solution is poured into sample boxes containing silicon substrates, and the silicon substrates are immersed, and after drying, a SERS substrate of the zirconium-based MOF-808 / AuNPs is obtained. The method has the advantages of simple preparation process, low cost, good uniformity of the prepared substrate, good signal repeatability, high sensitivity, good structural stability and the like.

Description

TECHNICAL FIELD

[0001] The application relates to a SERS substrate preparation method and belongs to the technical field of SERS. BACKGROUND

[0002] Surface-enhanced Raman scattering (SERS) is a highly sensitive spectroscopic technique that can increase the Raman signal of molecules by several orders of magnitude, has extremely high sensitivity and specificity, can provide molecular structure information, can detect and analyze biological molecules at the single-molecule level, and has advantages such as rapid detection, and is applied to many fields such as biomedical and chemical molecule detection, chemical industry, disease diagnosis, environmental monitoring, explosive detection, trace material analysis, and agricultural food safety.

[0003] A large number of studies have proved that the mechanism of SERS enhancement mainly includes electromagnetic enhancement (EM) and chemical enhancement (CM). The EM mechanism mainly depends on the local surface plasmon resonance (LSPR) of noble metals, and the CM mechanism mainly depends on the charge transfer between the target molecules and the substrate. Based on the SERS enhancement mechanism, an effective way to improve the SERS sensitivity is to design a substrate to produce appropriate physical nanostructures to promote the molecular-metal interaction. The commonly used substrates at present include noble metals (Au, Ag and Cu), oxide-noble metal composites, etc., among which the "hot spots" near the traditional noble metal material plasmonic nanostructure can detect Raman spectrum, and the enhancement factor can be as high as 10^14 times. However, there are still some deficiencies such as poor adsorption capacity and poor signal repeatability.

[0004] In recent years, metal-organic framework (MOF) composites have been widely concerned due to their strong adsorption capacity and good Raman enhancement effect. MOF is a kind of crystalline porous material self-assembled by metal ions and organic ligands into a periodic network structure. The SERS substrate prepared by integrating MOF with noble metal particles (such as Au and Ag) not only has the excellent adsorption and enrichment capacity of MOF, but also has the local surface plasmon resonance characteristics of noble metal nanoparticles, thereby greatly improving the sensitivity of SERS detection. For example, Liu Yaqing et al. invented a patent with the patent number 201710486565.9 and the patent name MOF-noble metal composite SERS substrate and its preparation method. The patent mainly loads the CTAB-modified positively charged noble metal nanoparticles on the surface of MOF material through electrostatic interaction in an alcohol solution to form a MOF-noble metal nanoparticle composite SERS substrate, and the MOF material is MIL-101(Fe), MIL-101(Cr) or MIL-100(Fe). The noble metal nanoparticles are loaded on the surface of MOF through electrostatic interaction, which can realize the accurate control of the morphology, size and density of the metal nanoparticles on the surface of MOF, prepare a large number of Raman active sites, and further effectively improve the SERS performance of the composite substrate while maintaining the high porosity, large specific surface area and excellent adsorption capacity of the MOF material. However, most of the MOF materials commonly used for SERS substrate reported at present have the disadvantages of slow adsorption efficiency, poor structural stability, large drug consumption and low signal repeatability. MOF-808 has the characteristics of high pore volume, high porosity, high and fast adsorption performance and structural stability.

[0005] MOF-808 is a Zr-MOF formed by connecting six nuclear [Zr6(μ3-O)4(μ3-OH)4] nodes with 6 1,3,5-benzenetricarboxylic acid ligands, and a monobasic carboxylate as a charge balancing ion. The low node connection number and the moderate size of the connected pore of MOF-808 are beneficial to its application in the adsorption, enrichment, purification and catalytic degradation of toxic and harmful substances. The adsorption efficiency has always been the main limitation of traditional metal sol matrix, and the surface of MOF-808 has accessible active sites, so it has great rapid adsorption capacity. In recent years, Zr-MOF has been widely recognized due to its cost-effectiveness, large specific surface area and excellent thermal stability and chemical stability. SUMMARY

[0006] The application provides a preparation method of a zirconium-based MOF-808 / AuNPs SERS substrate, which has the advantages of simple preparation process, low cost, large specific surface area, high and fast adsorption capacity, low detection limit and high sensitivity.

[0007] The application comprises the following steps:

[0008] Step one: AuNPs solution preparation: firstly, 0.1 g of sodium citrate was completely dissolved in 9.9 ml of deionized water to obtain a 1% sodium citrate aqueous solution; secondly, 0.1 g of chloroauric acid was completely dissolved in 9.9 ml of deionized water to obtain a 1% chloroauric acid solution; 99 ml of deionized water and 1 ml of 1% chloroauric acid solution were measured and added to a three-necked flask, and the oil bath was heated and stirred until the solution boiled, and then the temperature was maintained while boiling, 1.4 ml of 1% sodium citrate aqueous solution was quickly added, the solution color gradually changed to wine red, and then heating was continued for 15 minutes, the oil bath was turned off, and the solution was naturally cooled to room temperature to obtain the AuNPs solution;

[0009] Step two: activated MOF-808-Zr powder preparation: zirconium oxychloride octahydrate and 1,3,5-benzenetricarboxylic acid were dissolved in a mixed solution of N,N-dimethylformamide and formic acid in a volume ratio of 1:1, poured into a screw bottle, ultrasonically mixed, then placed on a magnetic stirrer with a stirring speed of 600 rpm for 10 minutes, then added to a hydrothermal reactor and reacted at 100℃ for 24 hours, cooled to room temperature, centrifuged at a speed of 8000 rpm for 10 minutes, and the resulting product was washed with N,N-dimethylformamide and anhydrous ethanol at a speed of 8000 rpm for 10 minutes each time, then dried in a vacuum oven at 60℃ and 0.09 MPa for 12 hours to obtain the activated MOF-808-Zr powder;

[0010] Step three: 10 mg of the activated MOF-808-Zr powder in step two was suspended in 10 ml of anhydrous ethanol and ultrasonically dissolved to obtain a zirconium-based MOF-808 solution;

[0011] Step four: the zirconium-based MOF-808 solution in step three and the AuNPs solution in step one were poured into a screw bottle and stirred for 2 hours to form a zirconium-based MOF-808 / AuNPs solution, then the zirconium-based MOF-808 / AuNPs solution was poured into a sample box containing a silicon substrate and immersed in the silicon substrate, and then the sample box was placed in a vacuum drying oven at a temperature of 60℃ for 1 hour to obtain a zirconium-based MOF-808 / AuNPs SERS substrate;

[0012] The molar ratio of zirconium oxychloride octahydrate and 1,3,5-benzenetricarboxylic acid is 3:1, and the volume ratio of the zirconium-based MOF-808 solution to the AuNPs solution is 1:1 to 1:5.

[0013] The volume ratio of the N, N-dimethylformamide and formic acid solution in the step two is 1:1, and the volume of the N, N-dimethylformamide and anhydrous ethanol used for washing is 30ml.

[0014] The present application has the following advantages:

[0015] The present application enhances the intensity of the Raman signal of the prepared SERS substrate by modifying the introduction of AuNPs, and has the characteristics of good structural stability, without changing the crystal structure of MOF-808, and high signal repeatability.

[0016] The AuNPs of the prepared SERS substrate are uniformly distributed on the surface of MOF-808, the particle size is uniform, the surface roughness of MOF-808 is relatively high, and the uniformity of the prepared SERS substrate is good.

[0017] The prepared SERS substrate has large free volume in the pore channel of MOF-808 material, high pore volume and porosity, and high adsorption efficiency and strong adsorption capacity. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a schematic diagram of the SERS substrate in the embodiment of the present application;

[0019] Figure 2 It is a SEM diagram of the gold nanoparticle powder on the surface of the SERS substrate in the embodiment of the present application (scale 100nm);

[0020] Figure 3 It is an XRD diagram of the gold nanoparticle powder on the surface of the SERS substrate in the embodiment of the present application;

[0021] Figure 4 It is a Raman spectrum diagram of the SERS substrate in the embodiment of the present application labeled with different concentrations of R6G;

[0022] Figure 5 It is a Raman spectrum diagram of the SERS substrate in the embodiment of the present application labeled with different concentrations of R6G; -6 mol / L, and the Raman test results of the SERS substrate prepared by the zirconium-based MOF-808 solution and the AuNPs solution with different volume ratios are compared;

[0023] Figure 6 It is a Raman spectrum diagram of the SERS substrate in the embodiment of the present application with different adsorption times of R6G with a concentration of 10 -6 mol / L;

[0024] Figure 7 It is an adsorption rate diagram of the SERS substrate in the embodiment of the present application with different adsorption times of R6G with a concentration of 10 -6 mol / L. DETAILED DESCRIPTION

[0025] A preparation method of a SERS substrate of zirconium-based MOF-808 / AuNPs, comprising the following steps:

[0026] Step one: AuNPs solution preparation: firstly, 0.1 g of sodium citrate is completely dissolved in 9.9 ml of deionized water to obtain a sodium citrate aqueous solution with a mass concentration of 1%; secondly, 0.1 g of chloroauric acid is completely dissolved in 9.9 ml of deionized water to obtain a chloroauric acid solution with a mass concentration of 1%; 99 ml of deionized water and 1 ml of the chloroauric acid solution with a mass concentration of 1% are measured and added to a three-necked flask, oil bath heating and stirring are performed until the solution boils, then the temperature at the boiling point is maintained, 1.4 ml of the sodium citrate aqueous solution with a mass concentration of 1% is rapidly added, the solution color gradually changes to wine red, then heating is continued for 15 minutes, the oil bath is turned off, and the solution is naturally cooled to room temperature to obtain an AuNPs solution;

[0027] Step two: activated MOF-808-Zr powder preparation: zirconium oxychloride octahydrate and 1,3,5-benzenetricarboxylic acid with a molar ratio of 3:1 are dissolved in a mixed solution of 15 ml of N,N-dimethylformamide and 15 ml of formic acid, then the solution is poured into a screw bottle and ultrasonically mixed, and then the solution is placed on a magnetic stirrer and stirred at a speed of 600 rpm for 10 minutes, then the solution is added to a hydrothermal reaction kettle and hydrothermally reacted at 100℃ for 24 hours, then the solution is cooled to room temperature, centrifuged at a speed of 8000 rpm for 10 minutes, and then the obtained product is sequentially washed with 30 ml of N,N-dimethylformamide and 30 ml of anhydrous ethanol at a speed of 8000 rpm for 10 minutes each time, and then dried in a vacuum oven at 60℃ and 0.09 MPa for 12 hours to obtain activated MOF-808-Zr powder;

[0028] Step three: 10 mg of the activated MOF-808-Zr powder in step two is suspended in 10 ml of anhydrous ethanol, and ultrasonically dissolved to obtain a zirconium-based MOF-808 solution;

[0029] Step four: the zirconium-based MOF-808 solution in step three and the AuNPs solution in step one are mixed in a screw bottle in a volume ratio of 1:1 to 1:5, stirred for 2 hours, and then a zirconium-based MOF-808 / AuNPs solution is formed, then the zirconium-based MOF-808 / AuNPs solution is poured into a sample box containing a silicon substrate, and the silicon substrate is immersed, then the sample box is placed in a vacuum drying oven and dried at a temperature of 60℃ for 1 hour to obtain a SERS substrate of zirconium-based MOF-808 / AuNPs. EMBODIMENT

[0030] The application will be specifically explained in combination with specific examples as follows:

[0031] Example 1: Preparation scheme when the volume ratio of zirconium-based MOF-808 solution to AuNPs solution is 1:1

[0032] Step one: AuNPs solution preparation: firstly, 0.1 g of sodium citrate is completely dissolved in 9.9 ml of deionized water to obtain a 1% sodium citrate aqueous solution; secondly, 0.1 g of chloroauric acid is completely dissolved in 9.9 ml of deionized water to obtain a 1% chloroauric acid solution; 99 ml of deionized water and 1 ml of 1% chloroauric acid solution are measured and added to a three-necked flask, oil bath heating and stirring are performed until the solution boils, then the temperature is kept while boiling, 1.4 ml of 1% sodium citrate aqueous solution is rapidly added, the solution color gradually changes to wine red, then heating is continued for 15 minutes, the oil bath is turned off, and the solution is naturally cooled to room temperature to obtain the AuNPs solution;

[0033] Step two: activated MOF-808-Zr powder preparation: zirconium oxychloride (0.485 g) and 1,3,5-benzenetricarboxylic acid (0.105 g) with a molar ratio of 3:1 are dissolved in a mixed solution of 15 ml of N,N-dimethylformamide and 15 ml of formic acid, then ultrasonic mixing is performed, and the mixture is placed on a magnetic stirrer for stirring at a speed of 600 rpm for 10 minutes, then it is added to a hydrothermal reaction kettle for hydrothermal reaction at 100℃ for 24 hours, after cooling to room temperature, centrifugation is performed at a speed of 8000 rpm for 10 minutes, the obtained product is sequentially washed with 30 ml of N,N-dimethylformamide and 30 ml of anhydrous ethanol at a speed of 8000 rpm for 10 minutes each time, and then it is dried in a 60℃, 0.09 MPa vacuum oven for 12 hours to obtain the activated MOF-808-Zr powder;

[0034] Step three: 10 mg of the activated MOF-808-Zr powder in step two is suspended in 10 ml of anhydrous ethanol, and ultrasonic mixing is performed to obtain a zirconium-based MOF-808 solution;

[0035] Step four: the zirconium-based MOF-808 solution in step three and the AuNPs solution in step one with a volume ratio of 1:1 are poured into a screw-necked bottle, and stirring is performed for 2 hours to form a zirconium-based MOF-808 / AuNPs solution, then the zirconium-based MOF-808 / AuNPs solution is poured into a sample box containing a silicon substrate, and the silicon substrate is immersed, and then the sample box is placed in a vacuum drying oven for drying at a temperature of 60℃ for 1 hour to obtain a zirconium-based MOF-808 / AuNPs SERS substrate;

[0036] Step five: 10-10 10 -6 mol / L, 5 concentrations of solution, titration in the fourth step of the SERS substrate of zirconium-based MOF-808 / AuNPs, after drying in a vacuum drying oven at 60℃ for 30 minutes, it can be taken out for R6G labeled Raman test, test conditions: confocal Raman spectrometer, 633nm laser excitation for 10 seconds, ND filter is set to 25%, scanning spectral range 550~1800 cm -1 .

[0037] Example 2: Preparation scheme when the volume ratio of zirconium-based MOF-808 solution to AuNPs solution is 1:2

[0038] Step one: AuNPs solution preparation: first, weigh 0.1g of sodium citrate and completely dissolve it in 9.9ml of deionized water to obtain a 1% sodium citrate aqueous solution; second, weigh 0.1g of chloroauric acid and completely dissolve it in 9.9ml of deionized water to obtain a 1% chloroauric acid solution; take 99ml of deionized water and 1ml of 1% chloroauric acid solution into a three-necked flask, heat and stir in an oil bath until the solution boils, then maintain the boiling temperature, quickly add 1.4ml of 1% sodium citrate aqueous solution, continue to heat for 15 minutes after the solution color gradually changes to wine red, turn off the oil bath, and naturally cool to room temperature to obtain the AuNPs solution;

[0039] Step two: preparation of activated MOF-808-Zr powder: dissolve 0.485g of zirconium oxychloride octahydrate and 0.105g of 1,3,5-benzenetricarboxylic acid in a molar ratio of 3:1 in a mixed solution of 15ml of N,N-dimethylformamide and 15ml of formic acid, pour into a screw bottle and mix thoroughly under ultrasonic, then stir on a magnetic stirrer at a speed of 600rpm for 10 minutes, then add to a hydrothermal reaction kettle and react at 100℃ for 24 hours, cool to room temperature, centrifuge at a speed of 8000rpm for 10 minutes, wash the obtained product with 30ml of N,N-dimethylformamide and 30ml of anhydrous ethanol at a speed of 8000rpm for 3 times each, centrifuge for 10 minutes each time, then dry in a vacuum oven at 60℃ and 0.09MPa for 12 hours to obtain activated MOF-808-Zr powder;

[0040] Step three: take 10mg of activated MOF-808-Zr powder in step two and suspend it in 10ml of anhydrous ethanol, ultrasonically dissolve to obtain a zirconium-based MOF-808 solution;

[0041] Step four: take the zirconium-based MOF-808 solution in step three and the AuNPs solution in step one in a screw bottle in a volume ratio of 1:2, stir thoroughly for 2 hours, form a zirconium-based MOF-808 / AuNPs solution, then pour the zirconium-based MOF-808 / AuNPs solution into the sample box containing the silicon substrate, immerse the silicon substrate, and then place the sample box in a vacuum drying oven and dry at a temperature of 60°C for 1 hour to obtain a zirconium-based MOF-808 / AuNPs SERS substrate;

[0042] Step five: take R6G powder to prepare 10 -10 ~10 -6 mol / L solutions of five concentrations, titrate the zirconium-based MOF-808 / AuNPs SERS substrate obtained in step four, dry at 60°C in a vacuum drying oven for 30 minutes, and then take out for R6G labeled Raman test. The test conditions are: confocal Raman spectrometer, 633 nm laser excitation for 10 seconds, ND filter setting is 25%, and the scanning spectral range is 550-1800 cm -1 .

[0043] Example 3: Preparation scheme when the volume ratio of zirconium-based MOF-808 solution to AuNPs solution is 1:3

[0044] Step one: AuNPs solution preparation: first, weigh 0.1 g of sodium citrate and completely dissolve it in 9.9 ml of deionized water to obtain a 1% sodium citrate aqueous solution; second, weigh 0.1 g of chloroauric acid and completely dissolve it in 9.9 ml of deionized water to obtain a 1% chloroauric acid solution; take 99 ml of deionized water and 1 ml of 1% chloroauric acid solution and add them to a three-necked flask, heat and stir in an oil bath until the solution boils, then maintain the boiling temperature, quickly add 1.4 ml of 1% sodium citrate aqueous solution, continue to heat for 15 minutes after the solution color gradually changes to wine red, turn off the oil bath, and naturally cool to room temperature to obtain an AuNPs solution;

[0045] Step two: Preparation of activated MOF-808-Zr powder: Dissolve zirconium oxychloride octahydrate (0.485 g) and 1,3,5-benzenetricarboxylic acid (0.105 g) in a molar ratio of 3:1 in a mixed solution of 15 ml of N, N-dimethylformamide and 15 ml of formic acid, pour into a screw bottle, ultrasonic mixing, then put on a magnetic stirrer with a stirring speed of 600 rpm for 10 minutes, then add to the hydrothermal reactor, hydrothermal reaction at 100℃ for 24 hours, cool to room temperature, centrifuge at 8000 rpm for 10 minutes, wash the obtained product with 30 ml of N, N-dimethylformamide and 30 ml of anhydrous ethanol at 8000 rpm for 10 minutes each time, and then dry in a vacuum oven at 60℃ and 0.09 MPa for 12 hours to obtain activated MOF-808-Zr powder;

[0046] Step three: Take 10 mg of activated MOF-808-Zr powder in step two and suspend it in 10 ml of anhydrous ethanol, ultrasonic dissolve to obtain a zirconium-based MOF-808 solution;

[0047] Step four: Take the zirconium-based MOF-808 solution in step three and the AuNPs solution in step one in a volume ratio of 1:3, pour into a screw bottle, stir for 2 hours to form a zirconium-based MOF-808 / AuNPs solution, then pour the zirconium-based MOF-808 / AuNPs solution into a sample box containing a silicon substrate, immerse the silicon substrate, and then place the sample box in a vacuum drying oven at a temperature of 60℃ for 1 hour to obtain a zirconium-based MOF-808 / AuNPs SERS substrate;

[0048] Step five: Take R6G powder to prepare 10 -10 ~10 -6 mol / L solution of 5 kinds of concentrations, titrate on the zirconium-based MOF-808 / AuNPs SERS substrate obtained in step four, dry in a vacuum drying oven at 60℃ for 30 minutes, then take out for R6G labeled Raman test, test conditions: confocal Raman spectrometer, 633 nm laser excitation for 10 seconds, ND filter setting is 25%, scanning spectral range is 550~1800 cm -1 .

[0049] Example 4: Preparation scheme when the volume ratio of zirconium-based MOF-808 solution to AuNPs solution is 1:4

[0050] Step one: AuNPs solution preparation: firstly, 0.1 g of sodium citrate was completely dissolved in 9.9 ml of deionized water to obtain a 1% sodium citrate aqueous solution; secondly, 0.1 g of chloroauric acid was completely dissolved in 9.9 ml of deionized water to obtain a 1% chloroauric acid solution; 99 ml of deionized water and 1 ml of 1% chloroauric acid solution were measured and added to a three-necked flask, and the oil bath was heated and stirred until the solution boiled, and then the temperature was maintained while boiling, 1.4 ml of 1% sodium citrate aqueous solution was quickly added, the solution color gradually changed to wine red, and then heating was continued for 15 minutes, the oil bath was turned off, and the solution was naturally cooled to room temperature to obtain the AuNPs solution;

[0051] Step two: activated MOF-808-Zr powder preparation: zirconium oxychloride (0.485 g) and 1,3,5-benzenetricarboxylic acid (0.105 g) with a molar ratio of 3:1 were dissolved in a mixed solution of 15 ml of N,N-dimethylformamide and 15 ml of formic acid, and then ultrasonically mixed and poured into a screw bottle, and then placed on a magnetic stirrer with a stirring speed of 600 rpm for 10 minutes, and then added to a hydrothermal reactor for hydrothermal reaction at 100°C for 24 hours. After cooling to room temperature, centrifugation was performed at a speed of 8000 rpm for 10 minutes, and the obtained product was sequentially washed with 30 ml of N,N-dimethylformamide and 30 ml of anhydrous ethanol at a speed of 8000 rpm for 10 minutes each time, and then dried in a vacuum oven at 60°C and 0.09 MPa for 12 hours to obtain the activated MOF-808-Zr powder;

[0052] Step three: 10 mg of the activated MOF-808-Zr powder in step two was suspended in 10 ml of anhydrous ethanol, and ultrasonically dissolved to obtain a zirconium-based MOF-808 solution;

[0053] Step four: the zirconium-based MOF-808 solution in step three and the AuNPs solution in step one were mixed in a screw bottle at a volume ratio of 1:4, and stirred for 2 hours to form a zirconium-based MOF-808 / AuNPs solution, and then the zirconium-based MOF-808 / AuNPs solution was poured into a sample box containing a silicon substrate, and the silicon substrate was immersed, and then the sample box was placed in a vacuum drying oven at a temperature of 60°C for 1 hour to obtain a zirconium-based MOF-808 / AuNPs SERS substrate;

[0054] Step five: 10 -10 ~10 -6mol / L, 0.1 mol / L, 0.01 mol / L and 0.001 mol / L, respectively. The SERS substrate of zirconium-based MOF-808 / AuNPs obtained in step four was titrated with the above five kinds of concentration solutions. After drying in a vacuum drying oven at 60°C for 30 minutes, the SERS substrate was taken out for R6G labeled Raman test. The test conditions were as follows: confocal Raman spectrometer, 633 nm laser excitation for 10 seconds, ND filter setting at 25%, scanning spectral range 550~1800 cm -1 .

[0055] Example 5: Preparation scheme when the volume ratio of zirconium-based MOF-808 solution to AuNPs solution is 1:5

[0056] Step one: AuNPs solution preparation: first, 0.1 g of sodium citrate was completely dissolved in 9.9 ml of deionized water to obtain a 1% sodium citrate aqueous solution; second, 0.1 g of chloroauric acid was completely dissolved in 9.9 ml of deionized water to obtain a 1% chloroauric acid solution; 99 ml of deionized water and 1 ml of 1% chloroauric acid solution were measured and added to a three-necked flask, and the solution was heated and stirred in an oil bath until it boiled. Then, the temperature was maintained while boiling, and 1.4 ml of 1% sodium citrate aqueous solution was quickly added. After the solution color gradually changed to wine red, it was continuously heated for 15 minutes. The oil bath was turned off, and the solution was naturally cooled to room temperature to obtain the AuNPs solution;

[0057] Step two: activated MOF-808-Zr powder preparation: zirconium oxychloride (0.485 g) and 1,3,5-benzenetricarboxylic acid (0.105 g) with a molar ratio of 3:1 were dissolved in a mixed solution of 15 ml of N,N-dimethylformamide and 15 ml of formic acid, and then poured into a screw bottle and ultrasonically mixed. After that, it was placed on a magnetic stirrer and stirred at a speed of 600 rpm for 10 minutes. Then, it was added to a hydrothermal reaction kettle and hydrothermally reacted at 100°C for 24 hours. After cooling to room temperature, it was centrifuged at a speed of 8000 rpm for 10 minutes. The obtained product was washed with 30 ml of N,N-dimethylformamide and 30 ml of anhydrous ethanol at a speed of 8000 rpm for 10 minutes each time. Then, it was dried in a vacuum oven at 60°C and 0.09 MPa for 12 hours to obtain the activated MOF-808-Zr powder;

[0058] Step three: 10 mg of the activated MOF-808-Zr powder in step two was suspended in 10 ml of anhydrous ethanol and ultrasonically dissolved to obtain a zirconium-based MOF-808 solution;

[0059] Step four: take the zirconium-based MOF-808 solution in step three and the AuNPs solution in step one in a screw bottle in a volume ratio of 1:5, stir thoroughly for 2 hours, form a zirconium-based MOF-808 / AuNPs solution, then pour the zirconium-based MOF-808 / AuNPs solution into the sample box containing the silicon substrate, immerse the silicon substrate, and then place the sample box in a vacuum drying oven at a temperature of 60°C for 1 hour to obtain a zirconium-based MOF-808 / AuNPs SERS substrate;

[0060] Step five: take R6G powder to prepare 10 -10 ~10 -6 mol / L solutions of five concentrations, titrate on the zirconium-based MOF-808 / AuNPs SERS substrate obtained in step four, dry at 60°C in a vacuum drying oven for 30 minutes, then take out for R6G labeled Raman test, test conditions: confocal Raman spectrometer, 633nm laser excitation for 10 seconds, ND filter set to 25%, scanning spectral range 550~1800 cm -1 .

[0061] Example 6: Exploration of the adsorption of the zirconium-based MOF-808 / AuNPs SERS substrate to probe molecules

[0062] Step one: preparation of AuNPs solution: first, weigh 0.1g of sodium citrate and completely dissolve it in 9.9ml of deionized water to obtain a 1% sodium citrate aqueous solution; second, weigh 0.1g of chloroauric acid and completely dissolve it in 9.9ml of deionized water to obtain a 1% chloroauric acid solution; take 99ml of deionized water and 1ml of 1% chloroauric acid solution into a three-necked flask, heat and stir in an oil bath until the solution boils, then maintain the boiling temperature, quickly add 1.4ml of 1% sodium citrate aqueous solution, continue to heat for 15 minutes after the solution color gradually changes to wine red, turn off the oil bath, and naturally cool to room temperature to obtain the AuNPs solution;

[0063] Step two: activated MOF-808-Zr powder preparation: dissolve zirconium oxychloride (0.485g) and 1,3,5-benzenetricarboxylic acid (0.105g) in a molar ratio of 3:1 in a mixed solution of 15ml N,N-dimethylformamide and 15ml formic acid, pour into a screw bottle, ultrasonic mixing, then put on a magnetic stirrer with a speed of 600rpm for 10 minutes, then add to the hydrothermal reactor, hydrothermal reaction at 100℃ for 24 hours, cool to room temperature, centrifuge at 8000rpm for 10 minutes, wash the obtained product with 30ml of N,N-dimethylformamide and 30ml of anhydrous ethanol at 8000rpm for 10 minutes each time, then dry in a vacuum oven at 60℃ and 0.09MPa for 12 hours to obtain activated MOF-808-Zr powder;

[0064] Step three: take 10mg of activated MOF-808-Zr powder in step two and suspend it in 10ml of anhydrous ethanol, ultrasonic dissolve to obtain a zirconium-based MOF-808 solution;

[0065] Step four: take the zirconium-based MOF-808 solution in step three and the AuNPs solution in step one in a volume ratio of 1:4, pour into a screw bottle, stir for 2 hours to form a zirconium-based MOF-808 / AuNPs solution, then pour the zirconium-based MOF-808 / AuNPs solution into a sample box containing a silicon substrate, immerse the silicon substrate, then put the sample box into a vacuum drying oven and dry at 60℃ for 1 hour to obtain a zirconium-based MOF-808 / AuNPs SERS substrate;

[0066] Step five: immerse the zirconium-based MOF-808 / AuNPs SERS substrate in step four in a solution of R6G with a concentration of 10 -6 mol / L for 5 minutes, 10 minutes, 15 minutes, 20 minutes and 30 minutes respectively. Then dry the immersed zirconium-based MOF-808 / AuNPs SERS substrate in a vacuum drying oven at 60℃ for 30 minutes, then take it out for R6G labeled Raman test. The test conditions are: confocal Raman spectrometer, 633nm laser excitation for 10 seconds, ND filter setting is 25%, scanning spectral range is 550~1800 cm -1

[0067] Figure 1 The schematic diagram of the zirconium-based MOF-808 / AuNPs SERS substrate in the embodiment of the application.

[0068] Figure 2SEM image of gold nanoparticles powder on the surface of SERS substrate in the embodiment of the present application (scale 100 nm). It can be seen that the gold nanoparticles prepared in the present application are spherical, uniform in size, and uniformly distributed.

[0069] Figure 3 In the XRD pattern of the prepared gold nanoparticles, the diffraction peak angles are 2θ = 38.1°, 44.4°, 64.6° and 77.5°, respectively, corresponding to the crystal faces Au (111), Au (200), Au (220) and Au (311), which is consistent with the standard card No. JCPDS No. 04-0784, and it is confirmed by the XRD pattern that the prepared material is gold nanoparticles.

[0070] Figure 4 Raman spectrum of R6G labeled by SERS substrate of different concentrations in the embodiment of the present application. The SERS substrate of zirconium-based MOF-808 / AuNPs has R6G labeled Raman test spectrum characteristic peak wave number of 613 cm -1 , 774 cm -1 , 1360 cm -1 , 1510 cm -1 These Raman spectrum characteristic peak wave numbers completely correspond to the R6G vibration mode, and belong to the R6G Raman spectrum characteristic peak. It can be seen that when the concentration is lower than 10 -10 mol / L, the characteristic peak wave numbers 613 cm -1 and 1360 cm -1 still have strong Raman spectrum signals, which shows that the detection limit of the prepared SERS substrate of zirconium-based MOF-808 / AuNPs for R6G can be 10 -10 M concentration, and the sensitivity is high.

[0071] Figure 5 Raman test results of the SERS substrate prepared by different volume ratios of zirconium-based MOF-808 solution and AuNPs solution under the condition that the concentration of R6G is 10 -6 mol / L in the embodiment. It shows that by changing the proportion of the amount of AuNPs incorporated, the Raman intensity of the SERS substrate can be further optimized and improved. When the volume ratio of zirconium-based MOF-808 solution and AuNPs solution is 1:4, a higher SERS enhancement effect can be obtained.

[0072] Figure 6 , Figure 7 Raman test results of the SERS substrate of zirconium-based MOF-808 / AuNPs for the concentration of 10 -6R6G Raman intensity results at different adsorption times with 0.01 mol / L R6G. It shows that R6G reaches a rapid adsorption equilibrium within 10 minutes, which can be attributed to the rapid enrichment ability of the SERS substrate of zirconium-based MOF-808 / AuNPs on the target analyte, including hydrogen bonding, π-π interaction and electrostatic interaction.613 cm -1 and 1360 cm -1 Raman intensity of R6G at 613 cm-1, 772 cm-1, 1189 cm-1and 1360 cm-1shows that the amount of R6G adsorbed on the substrate gradually increases with the increase of immersion time, resulting in the gradual increase of Raman signal and stability. It can be seen that R6G can reach adsorption and desorption equilibrium within 30 minutes, indicating that the adsorption of the SERS substrate of zirconium-based MOF-808 / AuNPs is good and the adsorption rate is high.

Claims

1. A method for preparing a SERS substrate of Zr-based MOF-808 / AuNPs, the method comprising the following steps: Step 1: Preparation of AuNPs solution: firstly, 0.1 g of sodium citrate is completely dissolved in 9.9 ml of deionized water to obtain a 1% sodium citrate aqueous solution; secondly, 0.1 g of chloroauric acid is completely dissolved in 9.9 ml of deionized water to obtain a 1% chloroauric acid solution; 99 ml of deionized water and 1 ml of the 1% chloroauric acid solution are measured and added to a three-necked flask, and the solution is heated and stirred in an oil bath until it boils, and then the temperature is maintained while boiling, 1.4 ml of the 1% sodium citrate aqueous solution is quickly added, the solution color gradually changes to wine red, and then heating is continued for 15 minutes, the oil bath is turned off, and the solution is naturally cooled to room temperature to obtain the AuNPs solution; Step 2: Preparation of activated MOF-808-Zr powder: zirconium oxychloride octahydrate and 1,3,5-benzenetricarboxylic acid are dissolved in a mixed solution of N,N-dimethylformamide and formic acid in a volume ratio of 1:1, and then poured into a screw bottle and ultrasonically mixed, and then placed on a magnetic stirrer and stirred at a speed of 600 rpm for 10 minutes, and then added to a hydrothermal reaction kettle and reacted at 100℃ for 24 hours, and then cooled to room temperature, centrifuged at a speed of 8000 rpm for 10 minutes, and then washed with N,N-dimethylformamide and anhydrous ethanol at a speed of 8000 rpm for 10 minutes each time, and then dried in a vacuum oven at 60℃ and 0.09 MPa for 12 hours to obtain the activated MOF-808-Zr powder; Step 3: 10 mg of the activated MOF-808-Zr powder in step 2 is suspended in 10 ml of anhydrous ethanol and ultrasonically dissolved to obtain a Zr-based MOF-808 solution; Step 4: The Zr-based MOF-808 solution in step 3 and the AuNPs solution in step 1 are poured into a screw bottle and stirred for 2 hours to form a Zr-based MOF-808 / AuNPs solution, and then the Zr-based MOF-808 / AuNPs solution is poured into a sample box containing a silicon substrate and the silicon substrate is immersed, and then the sample box is placed in a vacuum drying oven and dried at 60℃ for 1 hour to obtain the SERS substrate of Zr-based MOF-808 / AuNPs. The molar ratio of zirconium oxychloride octahydrate and 1,3,5-benzenetricarboxylic acid is 3:1, and the volume ratio of the Zr-based MOF-808 solution to the AuNPs solution is 1:1 to 1:

5.

2. A method for preparing a SERS substrate of Zr-based MOF-808 / AuNPs according to claim 1, characterized in that: The volume of the 1:1 N,N-dimethylformamide and formic acid solution in step 2 is 15 ml, and the volume of the N,N-dimethylformamide and anhydrous ethanol used for washing is 30 ml.

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