Nanofiber Membrane-Based Surface-Enhanced Raman Sensor and Its Preparation Method and Application

Abstract

The present invention discloses a nanofiber membrane-based surface-enhanced Raman sensor, its preparation method and application. The nanofiber membrane-based surface-enhanced Raman sensor includes: a nanofiber membrane-based film, which is prepared by electrospinning; and nano-metal particles loaded with detection probes, which are uniformly deposited on the surface of the nanofiber membrane-based film by electrospray. The nanofiber membrane-based surface-enhanced Raman sensor can achieve rapid, accurate and highly sensitive detection of nitrite in food by direct contact or simple extraction.

Description

Technical Field

[0001] The present invention relates to the technical field of surface-enhanced Raman detection, and particularly to a nanofiber membrane-based surface-enhanced Raman sensor, a preparation method thereof, and an application thereof. Background Art

[0002] Surface Enhanced Raman Scattering (SERS) is an efficient vibrational spectroscopy technique for molecular structure characterization and chemical sensing. When the molecule to be detected is adsorbed onto the surface of nano metal particles, its Raman signal is amplified to a great extent, so that the Raman spectral information can be detected traceably and accurately. Since it is not sensitive to the interference of the detection environment and can cooperate with portable instruments to provide highly sensitive, timely, accurate, and non-destructive detection information, it has great application potential in the detection of toxic and harmful molecules. As a fast detection means with high sensitivity, high selectivity, and non-destructiveness, SERS analysis technology has been widely applied to the fields of biology, chemistry, environment, food, etc.

[0003] The preparation method of traditional membrane-based SERS sensors is to use the prepared membrane as a substrate and combine nano metal particles and detection probes through a plating method, mainly including: ion sputtering method, gas-phase deposition method, electrostatic adsorption method, membrane penetration method, and in-situ synthesis method. However, the above methods all have certain limitations. For example, the shape of nano metal particles cannot be controlled, and the aggregation and uneven distribution of nano metal particles limit the enhancement of Raman signals. Therefore, finding a method to prepare a more efficient, highly sensitive, fast, and accurate SERS sensor has become a popular research field.

[0004] Electrospinning technology is a technology that drives an electrospinning precursor solution to eject from a needle through an electric field force, then the solvent volatilizes in the air, and finally a nanofiber membrane is collected. It has the characteristics of simplicity, high efficiency, good repeatability, and low cost. The nanofiber membrane prepared by electrospinning technology has the characteristics of high porosity and high specific surface area.

[0005] Nitrite can improve and maintain the color of meat and inhibit the growth and reproduction of microorganisms and their spores. Therefore, it is often added to various meat products as a preservative and color fixative. However, nitrite can convert human hemoglobin into methemoglobin, making the blood lose its oxygen-carrying function, and can be converted into highly carcinogenic and teratogenic nitrosamines during the digestion and metabolism of the human body. When a person ingests 0.2 g to 0.5 g of nitrite, poisoning will occur, and more than 3 g will be fatal. Therefore, it is of great significance to develop a technology that can quickly detect nitrite in food.

[0006] According to literature reports, 4-aminothiophenol (4-ATP) and nitrite will undergo a surface plasmon-assisted oxidation reaction under light irradiation to generate 4,4'-dimercaptoazobenzene (DMAB), resulting in the appearance of three new Raman peaks (abbreviated as b -1 peaks) at 1141, 1392, and 1437 cm 2 of its Raman spectrum. The relative intensity of the peaks is proportional to the concentration of nitrite within a certain range. In addition, this reaction has good specificity for nitrite. Therefore, based on this characteristic, a SERS sensor with the functions of rapid, quantitative, and specific detection of nitrite can be developed. Summary of the Invention

[0007] The present invention provides a nanofiber membrane-based surface-enhanced Raman sensor, which can achieve rapid, accurate, and highly sensitive detection of nitrite in food by direct contact or simple extraction.

[0008] The technical solution of the present invention is as follows:

[0009] A nanofiber membrane-based surface-enhanced Raman sensor, comprising:

[0010] A nanofiber membrane-based membrane, prepared by electrospinning;

[0011] Nanometal particles loaded with detection probes, uniformly deposited on the surface of the nanofiber membrane-based membrane by electrospraying.

[0012] The present invention prepares a nanofiber membrane-based membrane by electrospinning technology. Then, nanometal particles loaded with the detection probe 4-ATP are uniformly deposited on the surface of the membrane by electrospraying technology to assemble into a SERS sensor.

[0013] The nanofiber-based membrane prepared by electrospinning has characteristics such as high porosity and high specific surface area, and can load a large amount of nanometal particles on its surface. Electrospraying technology is a technology that drives the electrospray precursor solution to be ejected from the needle through the electric field force, and the solvent volatilizes in the air, and finally nanometer particles are collected. Through electrospraying technology, the synthesized nanometal particles with various shapes can be uniformly and controllably sprayed onto the surface of the prepared nanofiber-based membrane to assemble a nanofiber membrane-based surface-enhanced Raman sensor.

[0014] The nanofibers of the nanofiber membrane-based membrane have a diameter of 200 nm to 1000 nm.

[0015] The material of the nanofiber membrane-based membrane is a natural polymer with low Raman effect.

[0016] Preferably, the material of the nanofiber membrane-based membrane is natural protein and / or polysaccharide.

[0017] Further preferably, the material of the nanofiber membrane base membrane is at least one of wheat protein, zein, gelatin, dextran, and chitosan.

[0018] Preferably, the nano metal particles are circular, sea urchin-shaped, cubic, or cauliflower-shaped gold, silver, or their composites.

[0019] Furthermore, the diameter of the nano metal particles is 20 nm to 300 nm.

[0020] Preferably, the amount of nano metal particles loaded on each square meter of the nanofiber base membrane is not less than 4 mmol.

[0021] The detection probe is 4-aminothiophenol (4-ATP).

[0022] Preferably, the amount of detection probe loaded on each square meter of the nanofiber base membrane is not less than 0.01 mmol.

[0023] The present invention also provides a preparation method of the nanofiber membrane-based surface-enhanced Raman sensor, including the following steps:

[0024] (1) Dissolve natural protein and / or polysaccharide in a solvent, add a plasticizer, and obtain an electrospinning preparation solution after complete dissolution;

[0025] (2) Perform electrospinning on the electrospinning preparation solution to obtain a nanofiber base membrane;

[0026] (3) Add nano metal particles, detection probes, and a dispersant to a dispersion medium, and obtain an electrospray preparation solution after homogenization;

[0027] (4) Spray the electrospray preparation solution onto the surface of the nanofiber base membrane through electrostatic spraying to obtain the nanofiber membrane-based surface-enhanced Raman sensor.

[0028] Preferably, in step (1), the solvent is an aqueous acetic acid solution, and the volume ratio of acetic acid to water is 3 - 5:1; the plasticizer is glycerol, and the addition amount of the plasticizer is 0.02 - 0.05 g / ml.

[0029] Preferably, in step (2), the parameters of electrospinning are: voltage is 15 kV to 30 kV, feeding speed is 0.4 mL / h to 1 mL / h, and receiving distance is 8 cm to 15 cm; furthermore, the ambient temperature is 20°C to 40°C, and the relative humidity is 20% to 40%.

[0030] Preferably, in step (3), the dispersion medium is an aqueous glucose solution with a mass fraction of 20%; the dispersant is Tween 80.

[0031] Preferably, in step (4), the parameters of the electrostatic spraying are as follows: the voltage is 25 kV to 30 kV, the feeding speed is 0.2 mL / h to 0.4 mL / h, and the receiving distance is 15 cm to 25 cm; further, the ambient temperature is 40 °C to 50 °C, and the relative humidity is 20% to 40%.

[0032] The present invention also provides an application of the nanofiber membrane-based surface-enhanced Raman sensor in detecting nitrite in food, including:

[0033] (1) Prepare a group of nitrite solutions with gradient concentrations, and use the nanofiber membrane-based surface-enhanced Raman sensor to perform Raman measurements on the nitrite solutions with different concentrations to obtain Raman spectra of the nitrite solutions with different concentrations;

[0034] (2) Take the intensity ratio of the Raman spectrum b 2 at the peak of 1141 cm -1 to the basic peak of 1078 cm -1 as the ordinate, and take the logarithm of the molar concentration of the nitrite solution as the abscissa to plot a standard curve;

[0035] (3) Use the nanofiber membrane-based surface-enhanced Raman sensor to perform Raman measurements on the food to be tested, and substitute the intensity ratio of the Raman spectrum b 2 at the peak of 1141 cm -1 to the basic peak of 1078 cm -1 into the standard curve to calculate the concentration of nitrite in the food to be tested.

[0036] Preferably, in step (1), the molar concentration of the nitrite solution is 0.1 - 1000 μmol / L.

[0037] Preferably, in step (2), the standard curve is: y = 0.03139x + 0.2649, R 2 = 0.998; where y is the intensity ratio of the Raman spectrum b 2 at the peak of 1141 cm -1 to the basic peak of 1078 cm -1 and x is the logarithm of the nitrite molar concentration.

[0038] In step (1), using the nanofiber membrane-based surface-enhanced Raman sensor to perform Raman measurements on the nitrite solutions with different concentrations includes: fixing the nanofiber membrane-based surface-enhanced Raman sensor on a glass slide, dropping the solution to be measured on the nanofiber membrane-based surface-enhanced Raman sensor, naturally drying it, and performing single-point Raman measurement using a Raman microscope system.

[0039] When performing single-point Raman measurement, a 785 nm He-Ne laser with a power of 10 mW is used as the SERS excitation light source.

[0040] In step (3), the nanofiber membrane-based surface-enhanced Raman sensor is used to perform Raman measurement on the food to be tested, including:

[0041] For the food to be tested with a high water content, the nanofiber membrane-based surface-enhanced Raman sensor is directly wiped on the surface of the food to be tested, taken away after 10 s, and after natural drying, single-point Raman measurement is performed;

[0042] For the food to be tested with a low water content, it is ground and water is added. After the nitrite component in the food to be tested is evenly dissolved and filtered, the filtrate is dropped on the nanofiber membrane-based surface-enhanced Raman sensor, and after natural drying, single-point Raman measurement is performed.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] The electrospray technology for preparing the SERS sensor provided by the present invention can load nano metal particles of different shapes, and at the same time can reduce the aggregation of nano metal particles, thereby enhancing the Raman signal to a greater extent, and has obvious advantages compared with the traditional ion sputtering method and electrostatic adsorption method. On the one hand, the electrospray process is completely controllable, so the thickness of the nano metal particles can be controlled to prevent their excessive aggregation from affecting the SERS enhancement effect. On the other hand, according to the literature report, nano metal particles of different shapes have different degrees of enhancement of the Raman signal. Traditional methods such as in-situ synthesis method and ion sputtering method cannot control the shape of nano metal particles. Therefore, through the electrospray technology, the synthesized and shape-controllable nano metal particles can be loaded, avoiding this disadvantage.

[0045] The method for detecting nitrite in food by a membrane-based SERS sensor provided by the present invention requires fewer pretreatment steps compared with the colorimetric method in the national food safety standard GB5009.33-2010, has a larger qualitative detection limit and quantitative detection range, and can be used for the detection of nitrite in food more quickly, accurately and specifically. Description of the Drawings

[0046] Figure 1 It is a scanning electron microscope image of the nanofiber membrane substrate (electrospun film) prepared in Example 1 of the present invention.

[0047] Figure 2 It is a transmission electron microscope image of the silver nano particles (Ag NPs) synthesized in Example 1.

[0048] Figure 3Scanning electron microscope image of the nanofiber membrane-based SERS sensor loaded with 4-ATP / nano silver particles prepared in Example 1 of the present invention.

[0049] Figure 4 Elemental scan of the nanofiber membrane-based SERS sensor loaded with 4-ATP / nano silver particles prepared in Example 1 of the present invention.

[0050] Figure 5 X-ray diffraction patterns of the nanofiber membrane-based SERS sensor (Ag NPs coated electrospun film) and the cast film-based SERS sensor (Ag NPs coated castedfilm) loaded with 4-ATP / nano silver particles in Example 1 of the present invention and Comparative Example 1.

[0051] Figure 6 Raman spectra of the nanofiber membrane-based SERS sensor and the cast film-based SERS sensor loaded with 4-ATP / nano silver particles prepared in Example 1 of the present invention and Comparative Example 1.

[0052] Figure 7 Raman spectra of the SERS sensor loaded with 4-ATP / nano silver particles prepared in the examples of the present invention for the detection of 8 common ions.

[0053] Figure 8 Raman spectra of the SERS sensor loaded with 4-ATP / nano silver particles prepared in the examples of the present invention for the detection of 5 common food additives and mixed solutions.

[0054] Figure 9 SERS detection results of the nanofiber membrane-based SERS sensor loaded with 4-ATP / nano silver particles prepared in the examples of the present invention for different concentrations of sodium nitrite.

[0055] Figure 10 Standard curve of the relative SERS intensity at the b2 peak (1141 cm-1) and nitrite concentration of the nanofiber membrane-based SERS sensor loaded with 4-ATP / nano silver particles prepared in the examples of the present invention.

[0056] Figure 11 Results of direct wipe SERS detection (DW-SERS), dissolution extraction SERS detection (CE-SERS), dissolution extraction filtration SERS detection (FE-SERS) of the nanofiber membrane-based SERS sensor loaded with 4-ATP / nano silver particles prepared in this example for chicken ham, luncheon meat, beef bacon, pork ham, and Korean kimchi, and the detection results of the colorimetric method (CM) in GB 5009.33-2010.

[0057] Figure 12 Scanning electron microscope image of the casted film-based SERS sensor prepared in the comparative example of the present invention.

[0058] Figure 13 Elemental scanning image of the casted film-based SERS sensor loaded with 4-ATP / nano silver particles prepared in the comparative example of the present invention. Detailed implementation manners

[0059] Example 1

[0060] A preparation method of a film-based SERS sensor assembled by electrospray technology, comprising the following steps:

[0061] Step 1: Prepare an electrospinning precursor solution. Dissolve 1.5 g of wheat protein and 1.5 g of zein in 8 mL of acetic acid and 2 mL of water, and then add 0.3 g of glycerol as a plasticizer. Stir the resulting solution with a magnetic stirrer until completely dissolved.

[0062] Step 2: Use an electrospinning machine to prepare the electrospinning precursor solution obtained in Step 1 into a nanofiber membrane (electrospun film). The condition parameters of electrospinning are a voltage of 25 kV, a feeding speed of 1 mL / h, a receiving distance of 15 cm, an environmental temperature of 25 °C, and a relative humidity of 30%.

[0063] The scanning electron microscope image of the prepared nanofiber membrane substrate is as shown in Figure 1 shown.

[0064] Step 3: Stir 200 mL of a glycerol-water mixture (the volume ratio of glycerol is 20%) in a 500 mL screw-capped conical flask with a magnetic stirrer and heat it to 90 °C. After the temperature stabilizes, add 36 mg of silver nitrate thereto, and then add 16 mL of a 3% sodium citrate solution by mass. After reacting for 1 hour, add 8 mg of silver nitrate and 4 mL of a 3% sodium citrate solution by mass again. This step is repeated every 10 minutes for a total of three times. Cool the obtained silver nano colloid to room temperature and store it in a refrigerator at 4 °C.

[0065] The transmission electron microscope image of the synthesized silver nano particles is as shown in Figure 2 shown.

[0066] Step 4: The silver nanocolloid obtained in Step 3 was centrifuged at 17,000 N of centrifugal force and 4 °C for 10 minutes using a refrigerated high-speed centrifuge, and the supernatant was aspirated to obtain monodisperse silver nanoparticles. The obtained monodisperse silver nanoparticles were added to a dextran solution with a mass fraction of 20%, and then 500 μl of 4-ATP (0.1 M) solution and 0.2 g of Tween 80 were added. The obtained mixed solution was homogenized at a speed of 12,000 revolutions per minute for 10 minutes using a homogenizer to obtain the electrospray preparation solution.

[0067] Step 5: Using an electrospinning machine, the prepared electrospray preparation solution was electrospray loaded. The nanofiber membrane prepared in Step 2 was placed on the receiver to receive the monodisperse silver nanoparticles ejected by the electrospray, and assembled into a SERS sensor. The electrospray parameters were: voltage 30 kV, flow rate 0.2 mL / h, and the distance between the needle and the receiver was 40 cm. The electrospray was carried out in an environment of 50 °C and a relative humidity of 20%. What was prepared was the nanofiber membrane-based SERS sensor loaded with 4-ATP / silver nanoparticles.

[0068] The scanning electron microscope image of the nanofiber membrane-based SERS sensor loaded with 4-ATP / silver nanoparticles prepared is as Figure 3 shown, and its corresponding elemental scanning image is as Figure 4 shown.

[0069] The X-ray diffraction pattern of the nanofiber membrane-based SERS sensor loaded with 4-ATP / silver nanoparticles prepared is as Figure 5 shown.

[0070] The Raman spectrum of the nanofiber membrane-based SERS sensor loaded with 4-ATP / silver nanoparticles prepared is as Figure 6 shown.

[0071] Application Example 1

[0072] A method for verifying the selectivity of a nanofiber membrane-based SERS sensor loaded with 4-ATP / silver nanoparticles for nitrite includes the following steps:

[0073] Step 1: Raman spectrum measurement method. The membrane-based SERS sensor prepared in Example 1 was cut into a 2 cm × 2 cm square and fixed on a clean glass slide. The solution to be measured was dropped on the membrane and dried naturally. Using a Raman microscope system, a 785 nm He-Ne laser with a power of 10 mW was used as the SERS excitation light source for single-point Raman measurement.

[0074] Step 2: Examine the recognition ability of the prepared nanofiber membrane-based SERS sensor loaded with 4-ATP / silver nanoparticles for common salt ions. Prepare a sodium nitrite (NO2 - ) Sodium sulfite (SO 3 2- ) Sodium bromide (Br - ) Sodium dihydrogen phosphate (H 2 PO 4 2- ) Sodium carbonate (CO 3 2- ) Sodium chloride (Cl - ) Sodium bicarbonate (HCO 3 - ) Sodium nitrate solution (NO 3 2- ), and detect their Raman spectra according to the method provided in Step 1.

[0075] Step 3: Examine the recognition ability of the prepared nanofiber membrane-based SERS sensor loaded with 4-ATP / nanoparticle silver for common food additives. Prepare sodium nitrite (Nitrite), sodium benzoate, potassium sorbate, D-sodium erythorbate, monosodium glutamate, and their mixed solution with sodium nitrite at a concentration of 0.1 M, and detect their Raman spectra according to the method provided in Step 1.

[0076] The Raman spectra of the prepared nanofiber membrane-based SERS sensor loaded with 4-ATP / nanoparticle silver for the detection of 8 common ions are as Figure 7 shown.

[0077] The detection results of the prepared nanofiber membrane-based SERS sensor loaded with 4-ATP / nanoparticle silver for 5 common food additives and the mixed solution are as Figure 8 shown.

[0078] Application Example 2

[0079] A method for detecting nitrite in food using a membrane-based SERS sensor, comprising the following steps:

[0080] Step 1: Prepare a sodium nitrite solution with a concentration of 1 mol / L as the base solution, and dilute it into sodium nitrite solutions with concentrations of 800, 600, 400, 200, 100, 80, 60, 40, 20, 10, 8, 6, 4, 2, 1, 0.1 μmol / L. Use the prepared SERS sensor for Raman measurement to obtain the Raman spectra of the SERS sensor at different sodium nitrite concentrations. Select the b 2 peak at 1141 cm -1The intensity ratio at this position to the base peak at 1078 cm -1 is used as the ordinate, and the logarithm of the sodium nitrite concentration is used as the abscissa to plot the standard curve.

[0081] Step 2: Select 20 g of chicken ham sausage, luncheon meat, beef bacon, pork ham, and Korean kimchi. Conduct surface-enhanced Raman scattering (SERS) detection after direct wiping (DW-SERS), SERS detection after dissolution and extraction (CE-SERS), and SERS detection after dissolution, extraction, and filtration (FE-SERS) respectively, and calculate the nitrite content according to the standard curve obtained in Step 1.

[0082] The detection effect of the nanofiber membrane-based SERS sensor loaded with 4-ATP / nanosilver particles prepared in this example for nitrites with different concentrations is as Figure 9 shown, and its linear relationship is as Figure 10 shown.

[0083] The three detection results of the nanofiber membrane-based SERS sensor loaded with 4-ATP / nanosilver particles prepared in this example for beef bacon, pork ham, chicken ham sausage, luncheon meat, and Korean kimchi, as well as the detection results of the colorimetric method (CM) in the national standard GB5009.33-2010 are as Figure 11 shown.

[0084] Comparative Example 1

[0085] A method for preparing a membrane-based SERS sensor substrate by the casting film technique, including the following steps:

[0086] Step 1: Dissolve 1.5 g of wheat protein and 1.5 g of zein in 8 mL of acetic acid and 2 mL of water, and then add 0.3 g of glycerol as a plasticizer. Stir the resulting solution with a magnetic stirrer until completely dissolved.

[0087] Step 2: Press the solution obtained in Step 1 into a uniform film using a casting film preparation device, and naturally dry it into a film (casted film) at ambient temperature.

[0088] Step 3: According to the method of assembling the membrane-based SERS sensor by the electrospray technique in the example, load the nanosilver loaded with 4-ATP onto the wheat / zein casting film prepared in Step 1 by the electrospray technique. The resulting product is the casting film-based SERS sensor loaded with 4-ATP / nanosilver particles.

[0089] The SEM image of the casting film-based SERS sensor loaded with 4-ATP / nanosilver particles prepared in this comparative example is as Figure 12 shown, and its corresponding elemental scanning image is as Figure 13 shown.

[0090] Experimental Results and Analysis

[0091] Figure 5 This is the X-ray diffraction pattern of the nanofiber membrane-based SERS sensor and the cast film-based SERS sensor loaded with 4-ATP / nanoscale silver particles in Example 1 of the present invention and Comparative Example 1. It can be found that after electrospray loading, the XRD peaks of nanoscale silver particles appear in both the cast film and the nanofiber membrane, indicating that the nanoscale silver particles have been successfully loaded onto the membrane by electrospray.

[0092] Figure 6 This is the Raman spectrum of the nanofiber membrane-based SERS sensor and the cast film-based SERS sensor loaded with 4-ATP / nanoscale silver particles prepared in Example 1 of the present invention and Comparative Example 1. It can be found that the Raman signals of both the nanofiber membrane and the cast film are significantly enhanced. After calculation, the enhancement factors of the nanofiber membrane-based SERS sensor and the cast film-based SERS sensor are 2.6357×10 8 and 2.6316×10 5 , indicating that the amplification effect of the nanofiber membrane on Raman signals is much higher than that of the cast film.

[0093] Figure 7 This is the Raman spectrum of the SERS sensor loaded with 4-ATP / nanoscale silver particles prepared in Example 1 for the detection of 8 common ions. It can be found that the SERS sensor only shows a b 2 peak in the presence of sodium nitrite, indicating that the SERS sensor has a good specific recognition function for nitrite.

[0094] Figure 8 This is the Raman spectrum of the nanofiber membrane-based SERS sensor loaded with 4-ATP / nanoscale silver particles prepared in Example 1 for the detection of 5 common food additives and their mixed solutions with sodium nitrite. It can be found that the SERS sensor shows a strong b 2 peak for the sodium nitrite solution and its mixed solutions, indicating that it still has good selectivity for sodium nitrite in a complex environment.

[0095] Figure 9 This is the SERS detection result of the nanofiber membrane-based SERS sensor loaded with 4-ATP / nanoscale silver particles in the examples of the present invention for different concentrations of sodium nitrite. After calculation, its detection limit (LOD) is 2.216×10 -14 M. It can be found that a b 2 peak appears after adding sodium nitrite, and the intensity of the b 2 peak is positively correlated with the concentration of sodium nitrite to a certain extent.

[0096] Figure 10This is b in the embodiment of the present invention 2 Standard curve of the relative SERS intensity of the peak and the nitrite concentration. It can be found that there is a good linear relationship in the range of 10 -1 M to 10 4 M, indicating that the sensor can quantitatively detect sodium nitrite within this range.

[0097] Figure 11 Detection results of five kinds of foods using the SERS sensor prepared in Example 1. It can be found that for high-moisture-content foods such as bacon and ham, the direct wiping or dissolution and dissolution filtration methods have the same accuracy as the GB 5009.33-2010 colorimetric method in the national standard. For low-moisture-content foods such as chicken ham sausage and luncheon meat, the dissolution filtration method can also obtain the same accuracy as the GB 5009.33-2010 colorimetric method. This proves the reliability of the SERS sensor in the detection of food nitrite.

[0098] The above embodiments have detailed the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements, equivalent replacements, etc. made within the principle scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A nanofiber membrane-based surface-enhanced Raman sensor, characterized in that, it includes: A nanofiber membrane-based film, prepared by electrospinning; Nanometal particles loaded with detection probes, uniformly deposited on the surface of the nanofiber membrane-based film by electrospray; the detection probe is 4-aminothiophenol.

2. The nanofiber membrane-based surface-enhanced Raman sensor according to claim 1, characterized in that, the nanofibers of the nanofiber membrane-based film have a diameter of 200 nm to 1000 nm.

3. The nanofiber membrane-based surface-enhanced Raman sensor according to claim 1, characterized in that, the material of the nanofiber membrane-based film is natural protein and / or polysaccharide.

4. The nanofiber membrane-based surface-enhanced Raman sensor according to claim 1, characterized in that, the nanometal particles are circular, sea urchin-shaped, cubic, cauliflower-shaped gold, silver or gold-silver composites.

5. A method for preparing a nanofiber membrane-based surface-enhanced Raman sensor according to any one of claims 1-4, comprising the following steps: (1) Dissolve natural protein and / or polysaccharide in a solvent, add a plasticizer, and obtain an electrospinning preparation solution after complete dissolution; (2) Perform electrospinning on the electrospinning preparation solution to obtain a nanofiber-based film; (3) Add nanometal particles, detection probes, and a dispersant to a dispersion medium, and obtain an electrospray preparation solution after homogenization; (4) Spray the electrospray preparation solution onto the surface of the nanofiber-based film by electrospray to obtain the nanofiber membrane-based surface-enhanced Raman sensor.

6. The preparation method according to claim 5, characterized in that, in step (2), the parameters of electrospinning are: the voltage is 15 kV to 30 kV, the feeding speed is 0.4 mL / h to 1 mL / h, and the receiving distance is 8 cm to 15 cm.

7. The preparation method according to claim 5, characterized in that, in step (4), the parameters of electrospray are: the voltage is 25 kV to 30 kV, the feeding speed is 0.2 mL / h to 0.4 mL / h, and the receiving distance is 15 cm to 25 cm.

8. An application of a nanofiber membrane-based surface-enhanced Raman sensor according to any one of claims 1-4 in detecting nitrite in food, characterized in that, it includes: (1) Prepare a group of nitrite solutions with a gradient distribution of concentrations, and use the nanofiber membrane-based surface-enhanced Raman sensor to perform Raman measurements on each concentration of nitrite solution to obtain the Raman spectra of different concentrations of nitrite solutions; (2)Using Raman spectrum b 2 Peak at 1141 cm -1 The intensity ratio at this position to the base peak at 1078 cm -1 is used as the ordinate, and the logarithm of the molar concentration of the nitrite solution is used as the abscissa to plot a standard curve; (3) Use the nanofiber membrane-based surface-enhanced Raman sensor to perform Raman measurement on the food to be tested, and obtain Raman spectrum b 2 Peak at 1141 cm -1 The intensity ratio at this position and the basic peak at 1078 cm -1 is substituted into the standard curve described above to calculate the concentration of nitrite in the food to be tested.

9. The application according to claim 8, characterized in that, In step (2), the standard curve is: y = 0.03139x + 0.2649, R 2 = 0.998; where y is the intensity ratio of the Raman spectrum b 2 peak at 1141 cm -1 to the base peak at 1078 cm -1 and x is the logarithm of the nitrite molar concentration.

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