SERS (Surface Enhanced Raman Scattering) substrate based on foamed nickel material as well as preparation method and application thereof

Abstract

The invention provides an SERS (Surface Enhanced Raman Scattering) substrate based on a foamed nickel material as well as a preparation method and application of the SERS substrate. According to the SERS substrate based on the foamed nickel material, silver nanoparticles are deposited on foamed nickel (Ni foam) through a pulse laser deposition technology, and an Ag NPs-Ni foam substrate material, namely the SERS substrate based on the foamed nickel material, is obtained. By comparing the influence of different deposition times on the SERS performance, the SERS performance of the material is optimal when the deposition time is 30 minutes, the limit of detection (LOD) is reduced to 10 <-14 > M, and the analysis enhancement factor is as high as 1.682 * 10 < 12 >. As practical application, the SERS substrate is successfully used for detecting brilliant blue, amaranth and allura red pigment in beverages, and the detection limit is lower than the national safety limit value. The result shows that the SERS substrate provided by the invention is an effective strategy and can be used as an analysis platform for detecting the pigment in the beverage.

Description

Technical Field

[0001] The invention belongs to the field of nano detection, and designs a SERS substrate based on nickel foam material and a preparation method and application thereof. Background Art

[0002] In this colorful world, colors add endless splendor and diversity to our lives. Similarly, for food, in addition to the tempting taste, a pleasing appearance is also crucial. Therefore, in the process of food production, merchants often add natural or synthetic pigments to stimulate consumers' appetite. However, most synthetic colorants contain azo (N=N) functional groups and aromatic ring structures. Excessive consumption may pose a potential risk to human health and may even cause cancer in severe cases.

[0003] Surface Enhanced Raman Spectroscopy (SERS), as a technology that can quickly identify the fingerprint of the object to be tested, plays an important role in many fields such as food safety and environmental testing. Compared with traditional detection technologies, SERS has many unique advantages, such as rapid on-site detection, avoiding cumbersome pretreatment steps, having sufficient sensitivity and specificity, and being able to accurately identify and quantitatively analyze various organic pollutants.

[0004] SERS requires a substrate material for detection, but existing SERS substrate materials generally have low SERS activity and high detection limits, so new technical means are needed to overcome this problem. Summary of the invention

[0005] Based on the problem that the existing SERS substrate materials generally have low SERS activity and high detection limit, the purpose of the present invention is to provide a SERS substrate based on nickel foam material and its preparation method and application. The SERS substrate based on nickel foam material provided by the present invention has a low detection limit and strong anti-interference ability, and has good detection ability and detection performance in the detection of brilliant blue, allura red and amaranth in beverages. The present invention also provides a preparation method of the SERS substrate based on nickel foam material, and characterizes and tests the substrate through a series of experiments such as SEM, TEM, XPS, XRD, Raman, etc., to verify that it has good detection ability for pigments in beverages.

[0006] Nickel foam (Ni foam), as a flexible material with a honeycomb, three-dimensional network structure, has the characteristics of high porosity and low density; in addition, it also has a certain degree of roughness and high specific surface area, and can contain more "hot spot" molecules in the three-dimensional focal volume, providing an effective way for the separation, analysis and detection of target objects. Therefore, the present invention provides a simple synthesis scheme, by using pulsed laser deposition technology, silver nanoparticles are deposited on the surface of nickel foam to prepare a substrate material with excellent SERS activity and low detection limit.

[0007] Based on the above background and invention purpose, this application provides the following technical solutions:

[0008] One of the technical solutions of the present invention provides a SERS substrate based on nickel foam material, wherein the SERS substrate has nickel foam as the main structure, and silver nanoparticles are deposited on the surface of the nickel foam;

[0009] Furthermore, the particle size of the silver nanoparticles in the SERS substrate is 10.0-19.1 nm, and the gap is 3-10 nm.

[0010] Furthermore, the thickness of the nickel foam material is 0.9-1.1 mm; the pore density of the nickel foam material is 110 ppi.

[0011] Furthermore, the SERS substrate can be named as Ag NPs@Ni foam according to the structure; the substrate has excellent SERS activity, low detection limit and good repeatability.

[0012] A second technical solution of the present invention provides a method for preparing the SERS substrate based on the nickel foam material, the method comprising the following steps:

[0013] S1. Clean and dry the nickel foam;

[0014] S2. Deposit silver on the surface of nickel foam by pulsed laser deposition technology: Pump the pressure in the reaction chamber to below 10 - 4 Pa; focusing the laser onto a rotating Ag metal target; the sputtered silver nanoparticles are evenly dispersed on the surface of nickel foam, and finally Ag NPs@Ni foam substrate material is obtained, which is a SERS substrate based on nickel foam material.

[0015] Furthermore, the cleaning in step S1 is: ultrasonically cleaning the nickel foam with acetone, alcohol and deionized water in sequence for 15 to 30 minutes; and the drying is: drying the cleaned nickel foam at 55 to 65° C. for 4 to 6 hours.

[0016] Furthermore, in step S2, the conditions for the deposition operation are: room temperature, inert gas environment; the inert gas environment is preferably an argon environment; and the deposition time is 20 to 35 minutes.

[0017] In some specific embodiments of the present invention, according to different deposition times, the obtained SERS substrate based on nickel foam material is further named as Ag NPs X@Ni foam, wherein X represents the deposition time (min).

[0018] Further, in step S2, the laser is generated by a Nd:YAG laser, the wavelength of the laser is 1064nm, the repetition rate is 10-15Hz, and the pulse width is 5-8ns;

[0019] Furthermore, in step S2, the distance between the metal target and the substrate is 3 cm.

[0020] A third technical solution of the present invention provides an application of the SERS substrate based on the nickel foam material, wherein the application refers to the use of the SERS substrate based on the nickel foam material for detecting the content of pigments.

[0021] In some specific embodiments of the present invention, Roman test molecule (probe molecule) rhodamine (R6G) is used to test the detection performance of the SERS substrate based on nickel foam material; the concentration range of the R6G solution is 10 -14 ~10 -6 mol / L; when deposited for 30 min, the peak in the Raman spectrum is the highest and the activity is the strongest. Therefore, Ag NPs 30@Nifoam is preferred as the substrate material in practical applications.

[0022] Further, in the application, the pigment is any one of food blue (brilliant blue), amaranth, and allura red;

[0023] In some embodiments of the present invention, it is proved that the detection limits of the SERS substrate based on nickel foam material for standard brilliant blue, allura red and amaranth red solutions are 10 -8 mol / L、10 -8 mol / L、10 -6 mol / L, the detection limit is lower than the national safety limit.

[0024] Furthermore, the specific method for detecting the content of the pigment comprises the following steps:

[0025] S1. Prepare a standard solution of the pigment contained in the solution to be tested or prepare a standard powder of the pigment to be tested;

[0026] S2. Take the above-mentioned standard solution / powder and the sample to be tested, place them on a SERS substrate based on nickel foam material, and perform SERS detection in a confocal micro-Raman spectrometer; obtain the Raman spectra of the standard and the sample to be tested, compare the difference in the absorption peak intensity between the two, and judge the content of the pigment in the sample to be tested.

[0027] In some specific embodiments of the present invention, the concentration of the standard solution in step S1 is set to 10 - 7 mol / L or directly using pigment solid powder for measurement. In some other embodiments, the concentration of the standard can be modified according to the type of pigment actually measured.

[0028] Furthermore, in step S2, the size of the SERS substrate is 2 mm×2 mm, the sampling amount of the standard solution and the test solution is 25 μL, and the sampling amount of the standard or sample solid powder is 50 mg.

[0029] Furthermore, if the standard or sample is in a solution state, it is necessary to wait for the solvent to evaporate under ambient conditions before performing SERS detection.

[0030] Furthermore, the parameters of the confocal Raman microscope in step S2 are set as follows: a 514.5 nm laser is used as the excitation source, the accumulation time is 10 s (50× objective lens); and the laser power is set to 1 mW to avoid sample heating and photodamage.

[0031] In some specific embodiments of the present application, commercially available Mirinda watermelon-flavored beverage, Fanta grape-flavored beverage and Gatorade blueberry-flavored beverage are used as samples to be tested; the Mirinda watermelon-flavored beverage contains amaranth pigment, the Fanta grape-flavored beverage contains allura red pigment, and the Gatorade blueberry-flavored beverage contains brilliant blue pigment; the SERS substrate based on nickel foam material has good detection capability for the samples to be tested.

[0032] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0033] (1) The present invention is easy to operate. The nickel foam used has porosity and roughness, which makes it easy for the probe molecule R6G (Raman test molecule) to pass through the pores and contact the hot spots on the substrate to achieve electromagnetic enhancement. The signal of R6G proves the excellent SERS activity of the SERS substrate. At the same time, the nickel foam can gather more molecules to be tested, thereby significantly enhancing the Raman intensity of the analyte.

[0034] (2) The SERS substrate provided in this application is capable of detecting brilliant blue, amaranth, and allura red pigments in beverages, and the detection limit is lower than the national safety limit, indicating that the substrate has good application prospects in practical systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Field emission electron microscopy images of Ni foam and Ag NPs@Ni foam with deposition time of 0, 20, 25, 30, and 35 min;

[0036] Figure 2 is the transmission electron microscopy image of Ag NPs;

[0037] Figure 3 The particle size distribution diagram of silver nanoparticles on the surface of Ag NPs@Ni foam substrate with deposition time of 20, 25, 30, and 35 min;

[0038] Figure 4 Comparison of SERS enhancement effects of Ag NPs 25@Ni foam, Ag NPs@Ni, and Ni foam on R6G;

[0039] Figure 5 Comparison of SERS enhancement effect of Ag NPs@Ni foam with different deposition times on R6G;

[0040] Figure 6 The detection limit test and linear fitting diagram of Ag NPs 30@Ni foam on R6G;

[0041] Figure 7 This is the repeatability test diagram of Ag NPs 30@Ni foam on R6G;

[0042] Figure 8 The detection limit test and linear fitting diagram of Ag NPs 30@Ni foam for brilliant blue pigment;

[0043] Fig. 9 The detection limit test and linear fitting diagram of Ag NPs 30@Ni foam for amaranth red pigment;

[0044] Fig.10 The detection limit test and linear fitting diagram of Ag NPs 30@Ni foam for allura red pigment;

[0045] Fig.11 The detection of Ag NPs 30@Ni foam on Gatorade blueberry flavored beverage;

[0046] Fig.12 The detection of Ag NPs 30@Ni foam on Mirinda watermelon-flavored beverage;

[0047] Fig.13 Detection of Ag NPs 30@Ni foam on Fanta grape flavored beverage. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with specific embodiments. It should be noted that the following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, several variations and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0049] All raw materials of the present invention are not particularly limited in their sources, and can be purchased on the market or prepared according to conventional methods known to those skilled in the art. Nickel foam was purchased from Kunshan Guangjiayuan New Materials Co., Ltd., nickel foil was purchased from Qingyuan Metal Materials Co., Ltd., food blue (brilliant blue), amaranth, and allura red were purchased from Sinopharm Chemical Reagent Shanghai Co., Ltd., and rhodamine (R6G) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0050] Example 1: A SERS substrate based on nickel foam material

[0051] The steps for preparing the SERS substrate based on nickel foam material in this embodiment are as follows:

[0052] S1. Ultrasonic cleaning of nickel foam was carried out with acetone, alcohol and deionized water for 15 minutes in sequence; and the cleaned nickel foam was dried at 60° C. for 4 hours;

[0053] S2. Pulse laser deposition technology to deposit silver on the surface of nickel foam sample: Before deposition, the pressure in the reaction chamber must be pumped down to less than 10 -4 Pa. Then the Nd:YAG laser (1064nm, repetition rate 10Hz, pulse width 8ns) is focused onto the rotating Ag metal target. The sputtered silver nanoparticles (Ag atoms) will be evenly dispersed on the surface of nickel foam (Ni foam). The deposition process is carried out at room temperature and in an argon environment, and the distance between the metal target and the substrate is 3cm. Finally, the Ag NPs@Ni foam substrate material is obtained.

[0054] The pulsed laser deposition technology described in step S2 is an operation well known to those skilled in the art, and the reaction system / device used can be built according to conventional methods in the art; the reaction system includes two parts: a vacuum system and a reaction chamber. The vacuum system includes: a mechanical pump (Beijing Beiyi Youcheng Vacuum Technology Co., Ltd., RVP-6) for achieving a low vacuum state; a turbomolecular pump (Beijing Zhongke Keyi Technology Development Co., Ltd., FD-11B) for achieving a high vacuum state; a molecular pump controller (Beijing Zhongke Keyi Technology Development Co., Ltd. FD-ⅡB); a resistance gauge (Chengdu Zhenghua Electronic Instrument Co., Ltd., ZJ-52T / KF25) and a cold gauge (Chengdu Zhenghua Electronic Instrument Co., Ltd., ZJ-14 / CF35) for detecting the vacuum degree of the reaction chamber; a composite vacuum gauge (Chengdu Zhenghua Electronic Instrument Co., Ltd., ZDF-V-LED) for reading the vacuum degree. Optical path system: The optical path system includes a laser (Spectra-physics), a spectroscope, a reflector (1064nm, R>99.5%) and a focusing lens (f=150mm). The laser is a Nd:YAG laser with a wavelength of 1064nm, a repetition rate of 10Hz and a pulse width of 8ns.

[0055] Since the present invention will subsequently optimize different deposition times (20 to 35 min), the obtained product is named Ag NPs X@Ni foam, where X is the deposition time; that is, if the deposition time is 20 min, it is named Ag NPs 20@Nifoam, and the same applies to the others.

[0056] Example 2: Physical and chemical properties of a SERS substrate based on nickel foam material

[0057] In this embodiment, scanning electron microscopy, transmission electron microscopy, and XPS are used to characterize the microstructure, lattice, and physical and chemical properties of the SERS substrate material to optimize the deposition time of the silver nanoparticles.

[0058] (1) Field emission scanning electron microscopy (FESEM).

[0059] Silver nanoparticles were grown on nickel foam by pulsed laser deposition in an argon environment. By changing the deposition time, substrate materials with different particle sizes and distributions were prepared. The field emission electron microscopy images are shown in Figure 2. Figure 1 shown.

[0060] Figure 1 a shows an electron microscope image of nickel foam Ni foam. It can be seen that the nickel foam presents a three-dimensional porous structure with a pore density of 110ppi, which provides a large surface area for the deposition of silver nanoparticles. Figure 1b~1f show the electron microscope images when the deposition time is 0, 20, 25, 30, and 35 minutes, respectively. As the deposition time increases, the size of the nanoparticles gradually increases. When the deposition time is 30 minutes, the interval between adjacent silver nanoparticles is about 10nm, and the particle size is summarized by Nano Measurer software as follows: Figure 3 As shown (Nano Measurer software can count, mark and count the particle sizes in the SEM image). The diameter distribution of the four types of silver nanoparticles has slight fluctuations, all of which conform to the typical GaussAmp curve.

[0061] (2) Transmission electron microscopy (TEM).

[0062] In this embodiment, the silver nanoparticles on the silver nanoparticles (Ag NPs 30@Ni foam) with a deposition time of 30 minutes are subjected to ultrasonic treatment and dispersion to detect the lattice structure thereof. The ultrasonic step is:

[0063] The Ag NPs@Ni foam substrate was immersed in ethanol and then placed in an ultrasonic cleaner for ultrasonic treatment. The ultrasonic frequency was set to 40 kHz and the duration was 1 hour to ensure that the silver nanoparticles were fully dispersed to obtain a uniform solution. After the ultrasonic treatment, the silver nanoparticles in the solution were detected by TEM.

[0064] TEM images ( Figure 2 ) shows that the silver nanoparticles with a deposition time of 30 minutes have a particle size of about 20 nm, which is consistent with the SEM and particle size distribution diagrams. Figure 2 In b), the 0.24 nm lattice fringe corresponds to the (111) crystal plane of Ag.

[0065] Example 3: Raman test of R6G using a SERS substrate based on nickel foam material

[0066] (1) This example first compares the effects of Ag NPs 25@Ni foam, Ag NPs@Ni, and Ni foam on the SERS enhancement of R6G. The specific steps are as follows:

[0067] S1. Sample preparation:

[0068] The preparation method of Ag NPs 25@Ni foam material is referred to Example 1.

[0069] The preparation process of Ag NPs@Ni material is similar to that of Ag NPs 25@Ni foam, except that the Ni foam material is replaced by Ni foil, and the deposition time is the same as 25 minutes. The specific preparation process is referred to Example 1.

[0070] Ni foam is untreated nickel foam material.

[0071] After the above materials are prepared, they are cut into 2mm×2mm sizes and set aside.

[0072] S2. Detection method:

[0073] First, a Raman test molecule R6G solution was prepared, the concentration of which was 10 -6 mol / L; 25μL R6G solution was placed on the SERS substrate, and after the solvent evaporated under ambient conditions, a confocal micro-Raman spectrometer was used for SERS detection, and finally the Raman spectrum of the R6G solution was obtained. The parameters of the confocal micro-Raman spectrometer were set as follows: a 514.5nm laser was used as the excitation source, and the accumulation time was 10s (50× objective lens). The laser power was set to 1mW to avoid sample heating and photodamage.

[0074] The results show that the Raman spectrum peak of Ag NPs 25@Ni foam is much higher than that of Ag NPs@Ni and Ni foam, and the SERS activity of Ag NPs 25@Ni foam is much higher than that of the other two ( Figure 4 ).

[0075] (2) This example further compares the effects of different deposition times (i.e., 20, 25, 30, and 35 min) on the SERS enhancement effect and activity. It is found that when the deposition time is 30 min, the peak in the Raman spectrum is the highest and the activity is the strongest, at 1645 cm -1 The Raman intensity at is close to 140000 ( Figure 5 ), and the analytical enhancement factor (AEF) was calculated as follows:

[0076]

[0077] Among them, I SERS and I o Respectively expressed at 1645cm -1 On the band, 10 -14 M R6G on Ag NPs30@NiO foam and 10 -4 Raman intensity of M R6G on Si substrate, C SERS and C o Indicates the corresponding concentration. The calculated AEF value is as high as 1.682×10 12 .

[0078] It can be seen that Ag NPs 30@Ni foam has the best SERS activity and enhancement effect, and AgNPs 30@Ni foam was used as the substrate material in subsequent tests.

[0079] Example 4: Detection limit and repeatability of a SERS substrate based on nickel foam material

[0080] In this example, R6G is used as a probe molecule to test the detection limit and repeatability of the substrate material.

[0081] The concentration gradient of the R6G molecule is set to: 10 -14 ~10 -6 mol / L.

[0082] Detection method: 25 μL of R6G solution with different concentration gradients was placed on the SERS substrate. After the solvent evaporated under ambient conditions, a confocal micro-Raman spectrometer was used for SERS detection, and finally the Raman spectrum of the R6G solution was obtained. The parameters of the confocal micro-Raman spectrometer were set as follows: a 514.5 nm laser was used as the excitation source, and the accumulation time was 10 s (50× objective lens). The laser power was set to 1 mW to avoid sample heating and photodamage.

[0083] like Figure 6 As shown, when the R6G concentration was as low as 10 -14 M, its characteristic peak can still be detected, and the linear fitting result R 2 =0.983, which also shows that the probe molecule concentration and SERS intensity have a good linear relationship.

[0084] The repeatability of the SERS substrate is another major indicator for testing its performance. Figure 7 The Raman spectra of 14 points randomly selected on the same substrate, with R6G concentration of 10 -6 M. Its relative standard deviation in, represents the sample average, S represents the sample standard deviation) is less than 10%, indicating that the Ag nanoparticles on the surface are evenly distributed and the substrate has good repeatability.

[0085] Example 5: Detection capability of a SERS substrate based on nickel foam material for brilliant blue, allura red, and amaranth

[0086] Based on the above results, we have reason to believe that the Ag NPs 30@Ni foam substrate has high SERS activity, low detection limit and good repeatability. To further explore its detection possibility, this example uses water as solvent to prepare concentration gradients of brilliant blue, allura red, and amaranth red solutions or pigment powders, and conducts Raman tests on the Ag NPs 30@Ni foam substrate.

[0087] The concentration gradients of brilliant blue and allure red solutions are: 10 -8 ~10 -4 mol / L; the concentration gradient of amaranth solution is 10 -6 ~10 -4 mol / L; in addition, the signal peaks of brilliant blue and amaranth powder are amplified 3 times, and the signal peak of allura red powder is amplified 5 times. The powder×3 in the figure means that the Raman signal directly measured by brilliant blue powder is used as the standard control. Since the signal is weak, the signal is amplified 3 times.

[0088] Detection method: 25 μL of brilliant blue, allura red, and amaranth solutions with different concentration gradients (measurement is performed after the solvent evaporates under ambient conditions) or 50 mg of pigment powder is placed on a SERS substrate, and a confocal micro-Raman spectrometer is used for SERS detection, and finally the Raman spectrum of the R6G solution is obtained. The parameters of the confocal micro-Raman spectrometer are set as follows: a 514.5 nm laser is used as the excitation source, and the accumulation time is 10 s (50× objective lens). The laser power is set to 1 mW to avoid sample heating and photodamage.

[0089] According to the "Chinese Food Additives Usage Standard" (GB 2760-2014), the maximum content of brilliant blue, allura red and amaranth in fruit juice drinks is 0.025g / kg, 0.04g / kg and 0.05g / kg respectively, which is converted into a corresponding concentration of 3.15×10 -5 mol / L、8.09×10 -5 mol / L and 8.27×10 -5 mol / L. Figure 8 (bright blue), Fig. 9 (Amaranth), Fig.10 It can be seen that the detection limits of Ag NPs 30@Ni foam substrate for standard brilliant blue, allura red and amaranth red solutions are 10 - 8 mol / L、10 -8 mol / L、10 -6 mol / L, and according to the linear fitting results, its R 2 They are 0.990(1615cm -1 )、0.999(1342cm -1 )、0.996(1342cm -1 ), with a good linear relationship. The results show that the detection ability of Ag NPs 30@Ni foam substrate for these three pigments meets the national detection safety standards.

[0090] Example 6: A SERS substrate based on nickel foam material is used to detect brilliant blue, allura red and amaranth in beverages

[0091] Example 5 has proved that the detection capability of the Ag NPs 30@Ni foam substrate provided in this application for standard brilliant blue, allura red, and amaranth solutions can meet the national detection safety standards. In order to further explore the application prospects of a SERS substrate based on nickel foam material provided in this application, the Ag NPs 30@Ni foam substrate was used to detect Mirinda watermelon-flavored beverage, Fanta grape-flavored beverage, and Gatorade blueberry-flavored beverage. It is known that Mirinda watermelon-flavored beverage contains amaranth pigment, Fanta grape-flavored beverage contains allura red pigment, and Gatorade blueberry-flavored beverage contains brilliant blue pigment.

[0092] Detection method: Take 25 μL of the sample to be tested (wait for the solvent to evaporate under ambient conditions before measuring, the following liquid samples must wait for evaporation), and use brilliant blue (brilliant blue powder × 3), allura red (10 -7 Allura red solution) and amaranth red powder standard as control group were placed on SERS substrates, and SERS detection was performed using a confocal micro-Raman spectrometer to finally obtain the Raman spectrum of the R6G solution. The parameters of the confocal micro-Raman spectrometer were set as follows: a 514.5nm laser was used as the excitation source, and the accumulation time was 10s (50× objective lens). The laser power was set to 1mW to avoid sample heating and photodamage.

[0093] Raman spectroscopy Fig.11 (Gatorade blueberry flavored drink, bright blue), Fig.12 (Minda watermelon flavored drink, amaranth), Fig.13 (Fanta grape-flavored beverage, Allura Red) is shown. Compared with the standard sample peaks, it is found that the characteristic Raman peaks of the three pigments can be detected by the substrate, which indicates that the Ag NPs 30@Ni foam substrate can perform highly sensitive and rapid detection of trace amounts of Brilliant Blue, Amaranth Red and Allura Red contained in these beverages with complex and diverse matrices.

[0094] In summary of the above embodiments, the present invention provides a SERS substrate based on nickel foam material, which has a simple preparation method, high SERS activity, low detection limit and good repeatability, and can be used to detect trace amounts of brilliant blue, amaranth and allura red in beverages, and has good application prospects.

[0095] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A SERS substrate based on nickel foam material, characterized in that: The SERS substrate has nickel foam as the main structure, and silver nanoparticles are deposited on the surface of the nickel foam; The particle size of the silver nanoparticles in the SERS substrate is 10.0 to 19.1 nm, and the gap is 3 to 10 nm; The thickness of the nickel foam material is 0.9-1.1 mm; the pore density of the nickel foam material is 110 ppi.

2. The method for preparing a SERS substrate based on nickel foam material according to claim 1, characterized in that: The preparation method comprises the following steps: S1. Clean and dry the nickel foam; S2. Deposit silver on the surface of nickel foam by pulsed laser deposition technology: Pump the pressure in the reaction chamber to below 10 -4 Pa; focusing the laser onto a rotating Ag metal target; the sputtered silver nanoparticles are evenly dispersed on the surface of nickel foam, and finally a SERS substrate based on nickel foam material is obtained.

3. The method for preparing a SERS substrate based on nickel foam material according to claim 2, characterized in that: The cleaning in step S1 is: ultrasonically cleaning the nickel foam with acetone, alcohol and deionized water in sequence for 15 to 30 minutes; the drying is: drying the cleaned nickel foam at 55 to 65° C. for 4 to 6 hours.

4. The method for preparing a SERS substrate based on nickel foam material according to claim 2, characterized in that: In step S2, the deposition operation conditions are: room temperature, inert gas environment; the deposition time is 20 to 35 minutes.

5. The method for preparing a SERS substrate based on nickel foam material according to claim 2, characterized in that: In step S2, the laser is generated by a Nd:YAG laser, the wavelength of the laser is 1064 nm, the repetition rate is 10-15 Hz, and the pulse width is 5-8 ns.

6. The method for preparing a SERS substrate based on nickel foam material according to claim 2, characterized in that: In step S2, the distance between the metal target and the substrate is 3 cm.

7. The use of a SERS substrate based on nickel foam material as claimed in claim 1, characterized in that: The SERS substrate based on nickel foam material is used to detect the content of pigment.

8. The use of a SERS substrate based on nickel foam material according to claim 7, characterized in that: The pigment is any one of brilliant blue, amaranth and allura red.

9. The use of a SERS substrate based on nickel foam material according to claim 7, characterized in that: The specific method for detecting the content of the pigment comprises the following steps: S1. Prepare a standard solution of the pigment contained in the solution to be tested or prepare a standard powder of the pigment to be tested; S2. Take the above-mentioned standard solution / powder and the sample to be tested, place them on a SERS substrate based on nickel foam material, and perform SERS detection in a confocal micro-Raman spectrometer; obtain the Raman spectra of the standard and the sample to be tested, compare the difference in the absorption peak intensity between the two, and judge the content of the pigment in the sample to be tested.

10. The use of a SERS substrate based on nickel foam material according to claim 9, characterized in that: The size of the SERS substrate in step S2 is 2mm×2mm, the sampling amount of the standard solution and the test solution is 25μL, and the sampling amount of the standard or sample solid powder is 50mg; if the standard or sample is in a solution state, it is necessary to wait for the solvent to evaporate under ambient conditions before performing SERS detection; the parameters of the confocal micro-Raman spectrometer are set as follows: a 514.5nm laser is used as the excitation source, and the accumulation time is 10s; the laser power is set to 1mW.

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