Polyelectrolyte multilayer film modified surface enhanced Raman scattering substrate and application thereof

Abstract

The invention discloses a polyelectrolyte multilayer film modified surface enhanced Raman scattering substrate which is used for screening and analyzing antibiotics with different electrical properties and is used for enhancing signal detection. The polyelectrolyte multilayer film modified surface enhanced Raman scattering substrate comprises a nanorod deposited surface enhanced Raman scattering substrate and a polyelectrolyte layer-by-layer deposited film. Wherein the nanorod substrate is of a pure silver structure, the polyelectrolyte film is obtained by depositing polycations and polyanions layer by layer, and the film obtained by depositing the polyelectrolyte is formed by alternately depositing the polycation electrolyte and the polyanion electrolyte layer by layer. Wherein the film obtained through deposition is of a double-layer structure composed of at least one polycation layer and a polyanion layer.

Description

Technical Field

[0001] The present invention relates to the technical field of drug screening and detection, and in particular to a surface enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film, and a preparation method and application thereof. Background Art

[0002] Surface-enhanced Raman Scattering (SERS) is a Raman scattering technology based on the surface plasmon resonance enhancement effect, which is achieved through metal sol particles (such as gold, silver, copper) or metal surfaces with rough structures. The SERS phenomenon refers to when the analyte is adsorbed on these metal surfaces, the electromagnetic field on the metal surface or near the surface in the excitation region enhances the Raman scattering signal of the adsorbed molecules, making it have a significant enhancement effect compared to ordinary Raman scattering. SERS has the advantages of high sensitivity, selectivity, rapid detection and non-destructiveness, making it a characterization technology widely used in analytical chemistry, biomedicine and environmental monitoring. Due to its high sensitivity at the nanoscale and single-molecule level detection capabilities, SERS has become one of the important tools in the field of trace analysis, providing a powerful means for the structural characterization and quantitative analysis of various molecules.

[0003] The commonly used Raman detection method is to directly contact a substrate made of precious metal materials such as gold, silver or copper with the object to be tested for detection. However, in this detection method, when multiple substances exist in the solution of the object to be tested at the same time, the obtained Raman spectrum is the result of the superposition of multiple substances. Since a simple SERS substrate cannot separate and screen coexisting substances, it makes it difficult to identify the peak positions, thus hindering the application of traditional SERS substrates in the detection field.

[0004] In order to solve the above problems, it is known that there are technologies for functionalizing SERS substrates to achieve selective binding of different substances, such as the introduction of specific functional groups, biomolecule modification, nanoparticle modification and molecular imprinting. Although these technologies have achieved partial selective adsorption of target molecules, they have also limited stable mass production in practical applications to a certain extent due to the shortcomings of complex processes, difficulty in removing templates and high costs. Therefore, there is an urgent need for a SERS substrate modification technology that can both separate and detect target substances and have good Raman enhancement effects.

[0005] Polyelectrolytes are polymers with ionizable groups on their repeating units. They have good ionic conductivity and can be used in various electrochemical processes. Polyelectrolytes are divided into polycationic electrolytes, polyanionic electrolytes and polyampholytes. Polyelectrolyte multilayers can be obtained by layer-by-layer deposition (LBL) of polycationic electrolytes and polyanionic electrolytes. The adsorption process in LBL assembly is based on the electrostatic attraction of oppositely charged ions on the molecular structure of polyelectrolytes. By alternately immersing the solid substrate in polycationic electrolyte solutions and polyanionic electrolyte solutions, polyelectrolyte multilayers with controllable thickness can be grown. During the immersion process, the polyelectrolyte will be adsorbed on the surface of the substrate, and repeated immersion can construct a polyelectrolyte multilayer electrostatic cross-linked membrane.

[0006] Electrostatic interaction is the main driving force for the deposition of polyelectrolyte multilayers. The substrate with a negatively charged surface is immersed in a polycation electrolyte solution. At this time, due to the charge attraction, the polycation will bind to the negative charge, thereby reversing the charge on the substrate surface and making it positively charged. The deposited substrate needs to be impregnated to remove weakly bound polycation molecules to prevent them from reacting with oppositely charged polyanions and preventing them from depositing in the next adsorption step. The process is repeated until the desired number of layers is obtained, and rinsing is performed after each single deposition step. Through this LBL technique, the growth of multilayers with controllable thickness can be achieved. Parameters such as the deposition rate, roughness, thickness and porosity of the film depend on different experimental conditions (such as pH, temperature, polyelectrolyte concentration and ionic strength of the medium). By changing the experimental conditions, different polyelectrolyte multilayers can be prepared.

[0007] The polyelectrolyte multilayer membrane based on LBL technology can adsorb different substances through charge selection. Substances with different charges are adsorbed and combined with polycations and polyanions due to electrostatic effects, making it possible to deposit other substances on the polyelectrolyte multilayer membrane.

[0008] Therefore, the present invention develops a surface enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film, which is used to screen and analyze antibiotics with different electrical properties through charge attraction to enhance signal detection. Summary of the invention

[0009] In order to achieve the above object, the present invention provides a surface enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film, which includes a surface enhanced Raman scattering substrate obtained by depositing nanorods on a substrate and a thin film obtained by depositing a polyelectrolyte on the substrate, wherein the nanorods are a pure silver structure, the polyelectrolyte is a polycation electrolyte and a polyanion electrolyte, and the thin film obtained by depositing the polyelectrolyte is formed by alternately depositing the polycation electrolyte and the polyanion electrolyte layer by layer, wherein the deposited thin film consists of a double layer of at least one polycation layer and one polyanion layer, and preferably has 1 to 4 double layers obtained by depositing the polycation layer and the polyanion layer layer by layer.

[0010] Another embodiment of the present invention is a method for preparing a surface-enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film according to the present invention as follows:

[0011] Step 1: Prepare the surface enhanced Raman scattering substrate: Place the substrate on the sample stage of an electron beam evaporation coating machine at room temperature, where the chamber of the evaporation coating machine reaches 5×10 -5 Pa~2×10 -4 Under a high vacuum state of 1000 nm, metallic silver is used as a target material, and the evaporation coating machine is used to irradiate an electron beam with an incident angle of 85 to 90 degrees to deposit metallic silver on the substrate to form an array of silver nanorods, thereby preparing a surface enhanced Raman scattering substrate with an array of attached silver nanorods;

[0012] Step 2, preparation of a polyelectrolyte multilayer film: the surface enhanced Raman scattering substrate prepared in step 1 is first immersed in a polycation electrolyte solution for 20 to 45 minutes, immersed in deionized water for 5 to 10 minutes, and dried; then immersed in a polyanion electrolyte solution for 20 to 45 minutes, immersed in deionized water for 5 to 10 minutes, and dried, and the above steps are repeated to obtain a polyelectrolyte multilayer film;

[0013] The material of the substrate in step 1 is selected from single crystal silicon, quartz sheet or optical glass sheet.

[0014] The nanorod array in step 1 is obtained by oblique or vertical deposition, the length of the nanorods is 200 to 800 nm, and the diameter of the nanorods is 30 to 80 nm. At this time, the nanorod array is well separated and has strong uniformity, and the formed substrate has excellent Raman enhancement effect.

[0015] The deposition rate of metallic silver in step 1 is

[0016] The polyelectrolyte described in step 2 includes a polycation electrolyte and a polyanion electrolyte, wherein the polycation electrolyte is selected from one of poly(diallyldimethylammonium chloride) (PDADMAC), poly(acrylamide-co-diallyldimethylammonium chloride) (PDADMAC / AM), poly(allylamine hydrochloride) (PAH), poly(ethyleneimine) (PEI), poly(acrylamide) (PAMAM), poly(dimethyldiallylammonium) (PDDA) and poly(diallylmethylamine hydrochloride) (PDAMAHC), preferably poly(allylamine hydrochloride) (PAH).

[0017] The polyanion electrolyte in step 2 is selected from one of poly(styrene sulfonate) (PSS), poly(acrylic acid) (PAA), poly(vinyl alcohol) (PVA) and poly(sodium vinyl sulfonate) (PVS), preferably poly(styrene sulfonate) (PSS).

[0018] The concentrations of the polycation electrolyte and the polyanion electrolyte used in step 2 are both 0.1 g / L to 1 g / L, preferably 0.3 g / L to 0.8 g / L; the pH of the electrolyte solution is 3 to 11, preferably 5 to 10.

[0019] The polyelectrolyte multilayer film described in step 2, wherein the polycation electrolyte and polyanion electrolyte solutions may contain other salts for changing their film-forming states, and the other salts may be potassium nitrate (KNO3) or sodium nitrate (NaNO3), and the concentration thereof is 0 to 1 mol / L.

[0020] The polyelectrolyte multilayer membrane described in step 2 comprises at least one double layer formed by a polycation layer and a polyanion layer, preferably 1 to 4 double-layer structures, preferably 2 to 4 double-layer structures, obtained by depositing the polycation layer and the polyanion layer layer by layer.

[0021] One solution is the application of the surface enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film of the present invention in drug detection:

[0022] Different drugs are detected by electrostatic adsorption: the surface-enhanced Raman scattering substrate modified with the polyelectrolyte multilayer film obtained by the above preparation method is immersed in drug solutions of different concentrations and dried; wherein the drug concentration is 1fmol / L~1mmol / L; the immersion time is 20~45 minutes; the surface-enhanced Raman scattering substrate modified with the polyelectrolyte multilayer film adsorbed with drugs is placed in a Raman spectrometer, and a laser with a wavelength of 785nm is selected to perform drug detection.

[0023] The drug used at this time is an antibiotic selected from tetracycline (TCY), ciprofloxacin (CIP), penicillin (PSU), daptomycin (DAP), gentamicin (GEN) or amoxicillin (AMX).

[0024] Effects of the invention:

[0025] The present invention provides a surface enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film. Compared with the prior art, the advantages of the substrate are: enhanced selective adsorption of target molecules, better biocompatibility, and controllability of the SERS enhancement factor through the design of different film deposition. In addition, the present invention provides a preparation method of a surface enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film. The preparation method is simple to operate, cost-effective, environmentally friendly, and can be mass-produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The Raman spectrum of ciprofloxacin detected by the surface enhanced Raman scattering substrate modified with the polyelectrolyte monolayer film of Comparative Example 1.

[0027] Figure 2 The Raman spectrum of ciprofloxacin detected by the surface enhanced Raman scattering substrate modified with the polyelectrolyte multilayer film of Example 4. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with specific examples. Unless otherwise specified in the following examples, the methods used are conventional methods, and the reagents used can be obtained from commercial sources.

[0029] Preparation of Surface Enhanced Raman Scattering Substrates Modified with Polyelectrolyte Multilayers

[0030] Example 1

[0031] Step 1: Preparation of surface enhanced Raman scattering substrate

[0032] A single-sided polished single crystal silicon wafer was placed as a substrate on the sample stage of an electron beam evaporation coating machine. The chamber of the evaporation coating machine was pumped down to 1×10 -4 Pa high vacuum state; using metallic silver as the target material, the silver rod is grown by the inclined growth method; adjusting the incident angle of the electron beam to 87 degrees, and controlling the evaporation rate of metallic silver to Metallic silver is deposited on the substrate, and the prepared surface enhanced Raman scattering substrate has an array of attached silver nanorods, the length of the nanorods is 600nm, and the diameter of the nanorods is 50nm.

[0033] Step 2: Preparation of polyelectrolyte multilayer modified surface enhanced Raman scattering substrate

[0034] Prepare 1g / L polycation electrolyte and polyanion electrolyte solution respectively, measure the pH of the solution respectively, the pH of the prepared polycation electrolyte solution is 4.74, and the pH of the polyanion electrolyte solution is 5.56. First, the surface enhanced Raman scattering substrate is immersed in the polycation solution for 20 minutes, immersed in deionized water for 5 minutes, and dried; then immersed in the polyanion solution for 20 minutes, immersed in deionized water for 5 minutes, and dried, repeat the above operation four times to obtain a polyelectrolyte four-layer membrane.

[0035] The surface enhanced Raman scattering substrate modified with the polyelectrolyte multilayer film of the present invention obtained above detects drugs through electrostatic adsorption

[0036] The surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film was immersed in 1mmol / L tetracycline solution for 30 minutes and dried; then the surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film adsorbed with tetracycline was placed in a Raman spectrometer, and a laser with a wavelength of 785nm was selected to perform Raman spectrum detection of tetracycline to obtain a spectrum. At this time, the Raman signal of tetracycline on the surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film was located at 520cm -1 、792cm -1 、996cm -1 、1058cm -1 、1274cm -1 、1324cm -1 and 1584cm -1 At the wavelength, compared with the spectral data of the prior art, the signal is stronger and the characteristic peak is more obvious, indicating that the surface enhanced Raman scattering substrate modified with the polyelectrolyte multilayer film of the present invention improves the selective adsorption of tetracycline and realizes the detection of antibiotics with different electrical properties.

[0037] Comparative Example 1

[0038] Step 1: Preparation of surface enhanced Raman scattering substrate

[0039] The optical glass was placed on the sample stage of the electron beam evaporation coating machine as the substrate, and the chamber of the evaporation coating machine was pumped down to 2×10 -4 Pa high vacuum state; using metallic silver as the target material, the silver rod is grown by the inclined growth method; adjusting the incident angle of the electron beam to 85 degrees, and controlling the evaporation rate of metallic silver to Metallic silver is deposited on the substrate, and the prepared surface enhanced Raman scattering substrate has an array of attached silver nanorods, the length of the nanorods is 400nm, and the diameter of the nanorods is 60nm.

[0040] Step 2: Preparation of polyelectrolyte monolayer modified surface enhanced Raman scattering substrate

[0041] A 1 g / L polycation solution was prepared, and the pH of the solution was adjusted to 8. The surface enhanced Raman scattering substrate was immersed in the polycation solution for 30 minutes, immersed in deionized water for 10 minutes, and dried to obtain a polyelectrolyte monolayer film.

[0042] The following is the drug detected by electrostatic adsorption on the surface enhanced Raman scattering substrate modified with the polyelectrolyte monolayer film of the above comparative example

[0043] The surface enhanced Raman scattering substrate modified with a polyelectrolyte monolayer was immersed in a 1 μmol / L ciprofloxacin solution for 30 minutes and then dried. The surface enhanced Raman scattering substrate modified with a polyelectrolyte monolayer adsorbed with ciprofloxacin was then placed in a Raman spectrometer, and a laser with a wavelength of 785 nm was used to detect the Raman spectrum of ciprofloxacin, and a spectrum diagram (such as Figure 1 At this time, the Raman signal of ciprofloxacin on the surface enhanced Raman scattering substrate modified with the polyelectrolyte monolayer is located at 624 cm -1 、659cm -1 、738cm -1 、863cm -1 、1175cm -1 、1255cm -1 、1356cm -1 、1485cm -1 and 1620cm -1 Wavelength.

[0044] Example 2

[0045] Step 1: Make a surface enhanced Raman scattering substrate

[0046] The single crystal silicon substrate was placed on the sample stage of the electron beam evaporation coating machine. The chamber of the evaporation coating machine was pumped down to 5×10 -5 Pa high vacuum state; using metallic silver as the target material, the silver rod is grown by the inclined growth method; adjusting the incident angle of the electron beam to 86 degrees, and controlling the evaporation rate of metallic silver to Metallic silver is deposited on the substrate, and the prepared surface enhanced Raman scattering substrate has an array of attached silver nanorods, the length of the nanorods is 700nm, and the diameter of the nanorods is 45nm.

[0047] Step 2: Preparation of polyelectrolyte multilayer modified surface enhanced Raman scattering substrate

[0048] Prepare 0.5g / L polycation electrolyte and polyanion electrolyte solution, add 1mmol / L KNO3, measure the pH of the solution, the pH of the polycation solution is 5.07, the pH of the polyanion solution is 5.88. First, the surface enhanced Raman scattering substrate is immersed in the polycation solution for 45 minutes, immersed in deionized water for 10 minutes, and dried; then immersed in the polyanion solution for 45 minutes, immersed in deionized water for 10 minutes, and dried to obtain a polyelectrolyte double-layer membrane.

[0049] The following is a drug detected by electrostatic adsorption using the polyelectrolyte multilayer film modified surface enhanced Raman scattering substrate of the present invention obtained in Example 2.

[0050] The surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film was immersed in 1 nmol / L gentamicin solution for 45 minutes and dried; then the surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film adsorbed with gentamicin was placed in a Raman spectrometer, and a laser with a wavelength of 785nm was selected to perform Raman spectrum detection of gentamicin to obtain a spectrum. At this time, the Raman signal of gentamicin on the surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film was located at 346cm -1 、445cm -1 、574cm -1 、790cm -1 and 1019cm -1 At this wavelength, compared with the spectral data of the prior art, the signal is stronger and the characteristic peak is more obvious, indicating that the surface enhanced Raman scattering substrate modified with the polyelectrolyte multilayer film of the present invention improves the selective adsorption of gentamicin and realizes the detection of antibiotics with different electrical properties.

[0051] Example 3

[0052] Step 1: Preparation of surface enhanced Raman scattering substrate

[0053] A single-side polished silicon wafer was placed as a substrate on the sample stage of an electron beam evaporation coating machine. The chamber of the evaporation coating machine was pumped down to 8×10 -5 Pa high vacuum state; using metallic silver as the target material, the silver rod is grown by the inclined growth method; adjusting the incident angle of the electron beam to 88 degrees, and controlling the evaporation rate of metallic silver to Metallic silver is deposited on the substrate, and the prepared surface enhanced Raman scattering substrate has an array of attached silver nanorods, the length of the nanorods is 300nm, and the diameter of the nanorods is 70nm.

[0054] Step 2: Preparation of polyelectrolyte multilayer modified surface enhanced Raman scattering substrate

[0055] Prepare 0.8g / L polycation and polyanion solution, add 0.1mmol / L NaNO3, measure the pH of the solution, the pH of the polycation solution is 5.13, the pH of the polyanion solution is 6.88. First, soak the surface enhanced Raman scattering substrate in the polycation solution for 30 minutes, soak it in deionized water for 10 minutes, and dry it; then soak it in the polyanion solution for 30 minutes, soak it in deionized water for 10 minutes, and dry it. Repeat the above operation to obtain a polyelectrolyte four-layer membrane.

[0056] The following is a drug detected by electrostatic adsorption using the polyelectrolyte multilayer film modified surface enhanced Raman scattering substrate of the present invention obtained in Example 3.

[0057] The surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film was immersed in 10nmol / L amoxicillin solution for 40 minutes and dried; then the surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film adsorbed with amoxicillin was placed in a Raman spectrometer, and a laser with a wavelength of 785nm was selected to perform Raman spectrum detection of amoxicillin to obtain a spectrum. At this time, the Raman signal of amoxicillin on the surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film was located at 613cm -1 、663cm -1 、732cm -1 、825cm -1 、1044cm -1 、1240cm -1 、1355cm -1 、1461cm -1 and 1667cm -1 At the wavelength, compared with the spectral data of the prior art, the signal is stronger and the characteristic peak is more obvious, indicating that the surface enhanced Raman scattering substrate modified with the polyelectrolyte multilayer film of the present invention improves the selective adsorption of amoxicillin and realizes the detection of antibiotics with different electrical properties.

[0058] Example 4

[0059] Step 1: Preparation of surface enhanced Raman scattering substrate

[0060] The optical glass was placed as a substrate on the sample stage of the electron beam evaporation coating machine. The chamber of the evaporation coating machine was pumped down to 1×10 -4 Pa high vacuum state; using metallic silver as the target material, the silver rod is grown by the inclined growth method; adjusting the incident angle of the electron beam to 89 degrees, and controlling the evaporation rate of metallic silver to Metallic silver is deposited on the substrate, and the prepared surface enhanced Raman scattering substrate has an array of attached silver nanorods, the length of the nanorods is 500nm, and the diameter of the nanorods is 65nm.

[0061] Step 2: Preparation of polyelectrolyte multilayer modified surface enhanced Raman scattering substrate

[0062] Prepare 1g / L polycation and polyanion solution, measure the pH of the solution, the pH of the prepared polycation solution is 5.05, and the pH of the polyanion solution is 6.14. First, the surface enhanced Raman scattering substrate is immersed in the polycation solution for 30 minutes, immersed in deionized water for 5 minutes, and dried; then immersed in the polyanion solution for 30 minutes, immersed in deionized water for 5 minutes, and dried, and the above operation is repeated to obtain a polyelectrolyte double-layer membrane.

[0063] The following is the drug detected by electrostatic adsorption using the polyelectrolyte multilayer film modified surface enhanced Raman scattering substrate of the present invention obtained in Example 4

[0064] The surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film was immersed in 1 μmol / L ciprofloxacin solution for 30 minutes and dried; the surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film adsorbed with ciprofloxacin was then placed in a Raman spectrometer, and a laser with a wavelength of 785 nm was used to detect the Raman spectrum of ciprofloxacin, and a spectrum diagram (such as Figure 2 At this time, the Raman signal of ciprofloxacin on the surface enhanced Raman scattering substrate modified with polyelectrolyte multilayer film is located at 624cm -1 、659cm -1 、738cm -1 、863cm -1 、1175cm -1 、1255cm -1 、1356cm -1 、1485cm -1 and 1620cm -1 Wavelength.

[0065] Compared with the spectral data of the single-layer film modification of Comparative Example 1, it can be clearly seen that the Raman spectral signal of Example 4 is stronger and the characteristic peak is more obvious, which shows that the surface enhanced Raman scattering substrate modified with the polyelectrolyte multilayer film of the present invention improves the selective adsorption of ciprofloxacin and realizes the detection of antibiotics with different electrical properties.

[0066] In addition, the surface-enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film of the present invention has significant advantages over the prior art. Compared with the ciprofloxacin signal detected by a blank substrate, the surface-enhanced Raman scattering substrate modified with a polyelectrolyte single-layer film and a multilayer film can obtain ciprofloxacin Raman information with more characteristic peaks and stronger signals. Among them, the surface-enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film has a larger enhancement factor than that obtained by modifying with a single-layer film, which means that the product of the present invention has higher detection sensitivity and accuracy, and can effectively analyze target substances in complex samples, such as chemical and biological samples. Therefore, the surface-enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film of the present invention not only improves the sensitivity and reliability of detection, but also provides an efficient and accurate analysis tool for being widely used in chemical analysis, biomedicine, environmental monitoring and other fields.

[0067] In addition, the surface-enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film of the present invention can not only realize the screening and analysis of antibiotics with different electrical properties, but also significantly enhance the sensitivity and accuracy of signal detection. Through the surface enhancement effect, the intensity of the Raman scattering signal is improved, so that the presence and concentration of antibiotics can be quickly and reliably detected even at low concentrations. In addition, the multilayer film structure provides an ideal adsorption and reaction environment for antibiotic molecules, further improving the specificity and selectivity of detection. Therefore, this substrate not only has a wide range of application prospects in the field of drug screening, but also provides important technical support for the research of biosensors and the medical field.

Claims

1. A surface-enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film, characterized in that: The invention comprises a surface enhanced Raman scattering substrate obtained by depositing nanorods on a substrate and a film obtained by depositing polyelectrolytes on the substrate, wherein the nanorods are of a pure silver structure, the polyelectrolyte is a polycation electrolyte and a polyanion electrolyte, and the film obtained by depositing the polyelectrolyte is formed by alternately depositing the polycation electrolyte and the polyanion electrolyte layer by layer, wherein the deposited film has a double-layer structure consisting of at least one polycation layer and a polyanion layer.

2. The surface enhanced Raman scattering substrate according to claim 1, wherein: The substrate is selected from one of single crystal silicon, quartz sheet or optical glass sheet.

3. The surface enhanced Raman scattering substrate according to claim 1, wherein: The nanorod array is deposited obliquely or vertically, the length of the nanorod is 200-800 nm, the diameter of the nanorod is 30-80 nm, and the deposition rate of the metal silver is 4. The surface enhanced Raman scattering substrate according to claim 1, wherein: The polycation electrolyte is selected from one of poly(diallyldimethylammonium chloride), poly(acrylamide-co-diallyldimethylammonium chloride), poly(allylamine hydrochloride) (PAH), poly(ethyleneimine), poly(acrylamide), poly(dimethyldiallylammonium) and poly(diallylmethylamine hydrochloride); the polyanion electrolyte is selected from one of poly(styrene sulfonate), poly(acrylic acid), poly(vinyl alcohol) and poly(sodium vinyl sulfonate).

5. A method for preparing a surface-enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film according to claims 1 to 4, comprising the following steps: Step 1: Prepare the surface enhanced Raman scattering substrate: Place the substrate on the sample stage of an electron beam evaporation coating machine at room temperature, where the chamber of the evaporation coating machine reaches 5×10 -5 Pa~2×10 -4 Under a high vacuum state of 1000 nm, metallic silver is used as a target material, and the evaporation coating machine is used to irradiate an electron beam with an incident angle of 85 to 90 degrees to deposit metallic silver on the substrate to form an array of silver nanorods, thereby preparing a surface enhanced Raman scattering substrate with an array of attached silver nanorods; Step 2, preparation of polyelectrolyte multilayer film: the surface enhanced Raman scattering substrate prepared in step 1 is first immersed in a polycation electrolyte solution for 20 to 45 minutes, immersed in deionized water for 5 to 10 minutes, and dried; then immersed in a polyanion electrolyte solution for 20 to 45 minutes, immersed in deionized water for 5 to 10 minutes, and dried, and the above steps are repeated to obtain a polyelectrolyte multilayer film. 6 . The preparation method according to claim 5 , wherein the concentrations of the polycation electrolyte and the polyanion electrolyte are both 0.1 g / L to 1 g / L, and the pH of the solution is 3 to 11. 7 . The polyelectrolyte multilayer film according to claim 1 , wherein the polycation electrolyte solution and the polyanion electrolyte solution further comprise other salts, and the other salts are potassium nitrate or sodium nitrate, and the concentration is 0 to 1 mol / L.

8. The preparation method according to claim 1, wherein the polyelectrolyte multilayer film has 1 to 4 double-layer structures.

9. Application of a surface enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film in drug detection, the drug detection steps comprising: The surface enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film is immersed in drug solutions of different concentrations and dried; wherein the drug concentration is 1fmol / L to 1mmol / L; the immersion time is 20 to 45 minutes; the surface enhanced Raman scattering substrate modified with a polyelectrolyte multilayer film adsorbed with drugs is placed in a Raman spectrometer, and a laser with a wavelength of 785nm is selected to perform drug detection.

10. The use according to claim 9, wherein the drug is an antibiotic, which is tetracycline, ciprofloxacin, penicillin, daptomycin, gentamicin or amoxicillin.

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