Bimetal optical fiber SPR (Surface Plasmon Resonance) sensor based on silver core-gold shell nanoparticles

Abstract

The application discloses a bimetallic optical fiber SPR sensor based on silver core-gold shell nanoparticles, comprising: an optical fiber, the outer surface of which is provided with a sensing area; and the metal functional layer is arranged on the sensing area, the metal functional layer comprises dispersedly stacked silver nanoparticles, and the outer surfaces of the silver nanoparticles are coated with gold films. The metal functional layer of the sensor is composed of the metal nanoparticles, and compared with a traditional metal film SPR sensor, the specific surface area and porosity of metal are remarkably improved, and the detection sensitivity of the SPR sensor can be improved; silver nanoparticles are adopted as a main metal material, SPR sensing is greatly promoted, the silver nanoparticles are coated with a gold film to form isolated bimetal nanoparticles, the chemical stability of the silver nanoparticles is improved, the sensor is endowed with common characteristics of gold and silver, and the detection performance is remarkably improved.

Description

Technical Field

[0001] The present application belongs to the technical field of SPR sensors, and in particular relates to a bimetallic optical fiber SPR sensor based on silver core and gold shell nanoparticles. Background Art

[0002] Surface plasmon resonance (SPR) is a physical optical phenomenon caused by the resonance between the evanescent wave and the metal surface plasma wave. Metal electrons absorb the incident light energy, resulting in a significant reduction in the reflected light energy, which is reflected in the SPR spectrum as a resonant wavelength or resonant angle. Changes in the surrounding medium of the metal film will cause changes in the refractive index, resulting in changes in the surface plasmon propagation constant. That is, when molecules bind or dissociate on the sensor surface, it will cause a shift in the resonant wavelength or resonant angle. The concentration of the target can be obtained based on the shift value. It is constructed as a sensor analysis tool that does not require labeling and can monitor and analyze chemical or biological molecular interactions in real time online, and realizes the characterization, analytical sensing and quantitative detection of low molecular weight substances such as antigens, antibodies, and proteins.

[0003] Conventional SPR sensors use a single metal film structure. The single metal film has a small specific surface area, which affects the detection sensitivity of the sensor. Its detection ability is limited when applied to low molecular weight biomolecules and biomolecules with concentrations at the ng / mL level, which restricts the application of SPR sensors. Summary of the invention

[0004] The purpose of the present application is to provide a bimetallic optical fiber SPR sensor based on silver core-gold shell nanoparticles to solve the technical problems that the SPR sensors in the prior art have low detection sensitivity and limited detection ability for low molecular weight biomolecules and biomolecules with a concentration of ng / mL, which restricts the application of SPR sensors.

[0005] In order to achieve the above-mentioned object, the first aspect of the present application provides a bimetallic optical fiber SPR sensor based on silver core gold shell nanoparticles, comprising:

[0006] An optical fiber having a sensing area arranged on its outer surface;

[0007] The metal functional layer is arranged on the sensing area, and the metal functional layer includes dispersed and stacked silver nanoparticles, and the outer surface of the silver nanoparticles is coated with a gold film.

[0008] In one or more embodiments, a graphene oxide layer is further included, and the graphene oxide layer is coated on the outer surface of at least a portion of the metal functional layer.

[0009] In one or more embodiments, the number of graphene oxide layers in the graphene oxide layer is 1 to 3 layers.

[0010] In one or more embodiments, the particle size of the silver nanoparticles is 50 to 60 nm.

[0011] In one or more embodiments, the thickness of the gold film is 1-3 nm.

[0012] In order to achieve the above-mentioned object, the second aspect of the present application provides a method for preparing a bimetallic optical fiber SPR sensor based on silver core gold shell nanoparticles, comprising:

[0013] In situ growth of silver nanoparticles on the outer surface of the sensing region of the optical fiber;

[0014] A layer of gold film is grown on the surface of the silver nanoparticles to obtain a metal functional layer located in the sensing area.

[0015] In one or more embodiments, the step of in-situ growing silver nanoparticles on the outer surface of the sensing region of the optical fiber comprises:

[0016] immersing the sensing area in a dopamine solution to form a polydopamine layer in the sensing area;

[0017] The optical fiber is immersed in a silver nanoparticle dispersion and placed in a constant temperature water bath without light, so that the silver nanoparticles can fully adhere to the sensing area.

[0018] In one or more embodiments, in the step of maintaining a constant temperature water bath in the absence of light, the temperature of the constant temperature water bath is 35 to 40° C. and the duration is 5 to 7 hours.

[0019] In one or more embodiments, the step of growing a layer of gold film on the surface of the silver nanoparticles comprises:

[0020] Immersing the optical fiber in the first mixed solution and subjecting it to ultrasonic treatment;

[0021] Adding the second mixed solution to the first mixed solution and heating in a water bath;

[0022] wherein the first mixed solution comprises polyvinyl pyrrolidone, L-ascorbic acid, NaOH and Na2SO3, and the second mixed solution comprises chloroauric acid, NaOH and Na2SO3;

[0023] The water bath heating temperature is 60-70°C and the heating time is 0.8-1.2h;

[0024] In one or more embodiments, the mass fraction of polyvinyl pyrrolidone in the first mixed solution is 4.5-5.5%, the molar concentration of L-ascorbic acid is 4-5 mM, the molar concentration of NaOH is 15-20 mM, and the molar concentration of Na2SO3 is 3.5-4 mM;

[0025] The mass fraction of chloroauric acid in the second mixed solution is 0.1-0.2%, the molar concentration of NaOH is 10-20 mM, and the molar concentration of Na2SO3 is 8-10 mM.

[0026] In one or more embodiments, the step of growing a layer of gold film on the surface of the silver nanoparticles further comprises:

[0027] Take out the optical fiber heated in the water bath and immerse it in the gold plating solution, stirring and shaking;

[0028] The gold plating solution comprises chloroauric acid and hydroxylamine hydrochloride, the mass fraction of chloroauric acid in the gold plating solution is 0.05-0.15%, and the molar concentration of hydroxylamine hydrochloride is 0.3-0.5 mM.

[0029] In one or more embodiments, after the step of growing a layer of gold film on the surface of the silver nanoparticles, the step further includes:

[0030] covalently modifying a graphene oxide layer in at least a portion of the metal functional layer;

[0031] The step of covalently modifying the graphene oxide layer in at least a portion of the metal functional layer comprises:

[0032] The sensing area is immersed in a dopamine solution and oscillated at a constant temperature;

[0033] Immersing the optical fiber in a graphene oxide dispersion to covalently modify the graphene oxide to the surface of the metal functional layer through dopamine;

[0034] The constant temperature oscillation is performed at a temperature of 35 to 40° C. and a time of 0.5 to 1 h.

[0035] Different from the prior art, the beneficial effects of this application are:

[0036] The metal functional layer of the bimetallic optical fiber SPR sensor of the present application is composed of metal nanoparticles, which significantly improves the specific surface area and porosity of the metal compared to the traditional metal film SPR sensor, and helps to improve the detection sensitivity of the SPR sensor;

[0037] The metal functional layer of the bimetallic optical fiber SPR sensor of the present application uses silver nanoparticles as the main metal material. Compared with gold, silver is more sensitive to changes in the thickness and refractive index of the sensor. The good optical properties of silver nanoparticles will greatly promote SPR sensing, and the silver-modified sensor has a narrower peak, half-peak width and higher SPR activity. However, silver has poor chemical stability and is easily oxidized, and cannot be stably stored in the air for a long time. By using a gold film to coat the silver nanoparticles, isolated bimetallic nanoparticles can be formed, which not only improves the chemical stability of the silver nanoparticles, but also gives the sensor the common characteristics of gold and silver, significantly improving the detection performance;

[0038] The metal functional layer of the bimetallic optical fiber SPR sensor of the present application is also coated with a graphene oxide layer. When the graphene oxide contacts the bimetal, charge transfer from the graphene to the metal occurs under the irradiation of incident light, which enhances the oscillation of resonant electrons on the gold / silver surface, which not only enhances the interaction between light and matter and improves absorption, but also enhances the sensitivity and stability of the plasma resonance system on the surface.

[0039] The preparation method of the present application uses dopamine to adhere silver nanoparticles, and grows a gold film on the surface of the silver nanoparticles by wet chemical method and sulfite complexation. The silver nanoparticles are evenly wrapped with the gold film, and the gold films are interconnected to form a uniform and dense film structure, which helps to improve the detection sensitivity of the sensor;

[0040] The detection sensitivity of the bimetallic optical fiber SPR sensor of the present application is as high as 5170.7 nm / RIU. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 This is a schematic structural diagram of an embodiment of a bimetallic optical fiber SPR sensor based on silver core and gold shell nanoparticles of the present application;

[0043] Figure 2 The invention relates to a method for preparing a bimetallic optical fiber SPR sensor based on silver core and gold shell nanoparticles;

[0044] Figure 3 yes Figure 2 A schematic flow chart of an implementation method corresponding to S100;

[0045] Figure 4 yes Figure 2 A schematic diagram of a flow chart of an implementation method corresponding to S200;

[0046] Figure 5 yes Figure 2 A schematic flow chart of an implementation method corresponding to S300;

[0047] Figure 6 It is a transmission electron microscope and EDX element mapping analysis diagram of the bimetallic optical fiber SPR sensor of Example 1 of the present application;

[0048] Figure 7 is a scanning electron microscope analysis diagram of the bimetallic optical fiber SPR sensor of Example 1 of the present application;

[0049] Figure 8 This is a polarizing microscope analysis diagram of the bimetallic optical fiber SPR sensor of Example 1 of the present application;

[0050] Fig. 9 is the FTIR characteristic spectrum of the bimetallic optical fiber SPR sensor of Example 1 of the present application;

[0051] Fig.10 This is a curve showing the change in wavelength shift as the refractive index changes in Effect Example 2 of the present application. DETAILED DESCRIPTION

[0052] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0053] Conventional single metal film SPR sensors have low detection sensitivity and limited detection capabilities for low molecular weight biomolecules and biomolecules at concentrations of ng / mL.

[0054] In order to solve the above problems, the applicant has developed a new type of bimetallic optical fiber SPR sensor, which significantly improves the specific surface area and porosity of the metal layer, and gives the sensor the common characteristics of bimetallic, greatly improving the sensitivity of the SPR sensor, so that the SPR sensor can be applied to the detection of low molecular weight biomolecules and low concentration biomolecules, such as the detection of antibiotics.

[0055] Specifically, see Figure 1 , Figure 1 It is a structural schematic diagram of an embodiment of a bimetallic optical fiber SPR sensor based on silver core and gold shell nanoparticles of the present application.

[0056] like Figure 1 As shown, the SPR sensor includes an optical fiber 100 , on which a preset sensing area 101 is arranged.

[0057] In one embodiment, the optical fiber 100 may be specifically a quartz optical fiber 100; in other embodiments, the optical fiber 100 may also be any optical fiber 100 applicable to an SPR sensor, and the effect of this embodiment can be achieved.

[0058] In one embodiment, the length of the sensing area 101 may be 1 to 2 cm, which may be adjusted based on actual needs.

[0059] A metal functional layer 200 is arranged on the sensing region 101 of the optical fiber 100 . The metal functional layer 200 includes dispersed and stacked silver nanoparticles, and the outer surface of the silver nanoparticles is coated with a gold film.

[0060] In one embodiment, the particle size of the silver nanoparticles may be 20 to 40 nm.

[0061] In one embodiment, the thickness of the gold film may be 1-3 nm.

[0062] Based on the SPR sensor of each embodiment described above, on one hand, the metal functional layer 200 is composed of metal nanoparticles, which significantly improves the specific surface area and porosity of the metal compared to the traditional metal film SPR sensor, and helps to improve the detection sensitivity of the SPR sensor;

[0063] On the other hand, silver nanoparticles are used as the main metal material. Compared with gold, silver is more sensitive to changes in the thickness and refractive index of the sensor. The good optical properties of silver nanoparticles will greatly promote SPR sensing, and the silver-modified sensor has a narrower peak, half-peak width and higher SPR activity. However, silver has poor chemical stability and is easily oxidized, and cannot be stored stably in the air for a long time. By coating silver nanoparticles with gold film, isolated bimetallic nanoparticles can be formed, which not only improves the chemical stability of silver nanoparticles, but also gives the sensor the common characteristics of gold and silver, significantly improving the detection performance.

[0064] In order to further improve the detection sensitivity of SPR sensors, Figure 1 As shown, the metal functional layer 200 is further coated with a graphene oxide layer 300. Specifically, the graphene oxide layer 300 may be coated on a partial area of ​​the metal functional layer 200, or may be coated on the entire area thereof.

[0065] When graphene oxide comes into contact with a bimetal, charge transfer from graphene to metal occurs under the irradiation of incident light, which enhances the oscillation of resonant electrons on the gold / silver surface. This not only enhances the interaction between light and matter and improves absorption, but also enhances the sensitivity and stability of the plasma resonance system on the surface.

[0066] In one embodiment, the number of graphene oxide layers in the graphene oxide layer 300 may be 1 to 3 layers.

[0067] In one embodiment, a cladding 400 structure is arranged outside the optical fiber 100. When the incident light is transmitted along the optical fiber 100 to the metal functional layer 200, the reflected light wave vector and the surface plasmon wave vector resonate to cause a surface plasmon resonance phenomenon.

[0068] The present application also provides a method for preparing the bimetallic optical fiber SPR sensor of each of the above embodiments, please refer to Figure 2 , Figure 2 The invention discloses a preparation method of a bimetallic optical fiber SPR sensor based on silver core and gold shell nanoparticles.

[0069] like Figure 2 As shown, the preparation method comprises:

[0070] S100, in-situ growing silver nanoparticles on the outer surface of the sensing region of the optical fiber.

[0071] In one embodiment, the silver nanoparticles can be fixed to the sensing area by dopamine adsorption. Figure 3 , Figure 3 yes Figure 2 A flow chart of an implementation method corresponding to S100 in FIG.

[0072] like Figure 3 As shown, the method for in situ growth of silver nanoparticles includes:

[0073] S101 , immersing the sensing area in a dopamine solution to form a polydopamine layer in the sensing area.

[0074] S102, immersing the optical fiber in a silver nanoparticle dispersion and placing it in a constant temperature water bath without light, so that the silver nanoparticles can fully adhere to the sensing area.

[0075] In one embodiment, the temperature of the constant temperature water bath may be 35-40° C., and the time may be 5-7 hours.

[0076] In one embodiment, the silver nanoparticle dispersion can be synthesized by the citrate thermal reduction silver nitrate method; in other embodiments, the silver nanoparticle dispersion can also be prepared by other methods, all of which can achieve the effect of this embodiment.

[0077] Based on the above method, the silver nanoparticles can be fully adsorbed and fixed in the sensing area. Of course, in other embodiments, the silver nanoparticles can also be grown in situ in the sensing area by other methods, and the silver nanoparticles can be dispersed and fixed in the sensing area, and the effect of this embodiment can be achieved.

[0078] S200, growing a layer of gold film on the surface of the silver nanoparticles to obtain a metal functional layer located in the sensing area.

[0079] After fixing the silver nanoparticles in the sensing area, a gold film can be grown on the surface of the silver nanoparticles to obtain a nanoparticle structure of a silver core and a gold shell.

[0080] In one embodiment, a gold film can be grown on the surface of silver nanoparticles by wet chemical method and sulfite complexation. Figure 4 , Figure 4 yes Figure 2 A schematic flow chart of an implementation method corresponding to S200.

[0081] like Figure 4 As shown, the method of growing a gold film on the surface of silver nanoparticles includes:

[0082] S201, immersing the optical fiber in the first mixed solution and performing ultrasonic treatment.

[0083] The first mixed solution includes polyvinyl pyrrolidone (PVP), L-ascorbic acid, NaOH and Na2SO3.

[0084] PVP as a protective agent can maintain the stability of silver nanoparticles; L-ascorbic acid and Na2SO3 as reducing agents have an antioxidant effect and can prevent the silver nanoparticles from being oxidized.

[0085] Through the ultrasonic treatment in the first mixed solution, the silver nanoparticles can be cleaned and activated, while the stability of the silver nanoparticles is ensured and oxidation is avoided.

[0086] In one embodiment, the ultrasonic treatment time may be 8 to 12 minutes.

[0087] S202, adding the second mixed solution to the first mixed solution, and heating in a water bath.

[0088] Wherein, the second mixed solution includes chloroauric acid, NaOH and Na2SO3.

[0089] It can be understood that chloroauric acid provides gold ions as a source of gold ions, and Na2SO3 as a reducing agent can reduce gold ions to obtain gold atoms. During the water bath heating process, gold atoms can be deposited on the surface of silver nanoparticles to form an ultra-thin gold film.

[0090] In one embodiment, the water bath heating temperature may be 60-70° C., and the heating time may be 0.8-1.2 h.

[0091] S203, taking out the optical fiber and immersing it in the gold plating solution, stirring and shaking.

[0092] Wherein, the gold plating solution includes chloroauric acid and hydroxylamine hydrochloride.

[0093] In S202, the surface of the silver nanoparticles is coated with a gold film by heating in a water bath. In order to further improve the gold film coating effect, the gold films on the surfaces of different silver nanoparticles can be connected to form a more compact film structure, thereby helping to improve the detection performance of the sensor; in this embodiment, the optical fiber is further immersed in a gold plating solution and stirred and oscillated. Hydroxylamine hydrochloride as a reducing agent can reduce gold ions to gold atoms. The oscillation process can promote the deposition of gold atoms in the solution, making the gold film more uniform and dense.

[0094] S300, covalently modifying the graphene oxide layer in at least a portion of the metal functional layer.

[0095] In the above S100 to S200, a metal functional layer covering the sensing area is prepared. In order to further improve the detection sensitivity of the sensor, this embodiment further includes the step of arranging a graphene oxide layer on the outer surface of the metal functional layer.

[0096] In one embodiment, the graphene oxide layer can be covalently modified on the gold film surface by dopamine adhesion. Figure 5 , Figure 5 yes Figure 2 A flow chart of an implementation method corresponding to S300 in FIG.

[0097] like Figure 5 As shown, the method for covalently modifying a graphene oxide layer on a metal functional layer comprises:

[0098] S301, immerse the sensing area in the dopamine solution and oscillate at a constant temperature.

[0099] First, the sensing area is immersed in a dopamine solution to form a polydopamine layer on the surface of the metal functional layer. The purpose of constant temperature oscillation is to form a dopamine layer everywhere on the gold film surface of the silver nanoparticles.

[0100] S302, immersing the optical fiber in a graphene oxide dispersion to covalently modify the graphene oxide to the surface of the metal functional layer through dopamine.

[0101] After the metal functional layer is immersed in the graphene oxide dispersion, the graphene oxide is covalently modified to the gold film surface under the adhesion effect of dopamine.

[0102] It should be noted that graphene oxide is a two-dimensional sheet structure, which can cover at least part of the metal functional layer after being covalently modified to the surface of the gold film. In this embodiment, after graphene oxide is covalently modified to the surface of the metal functional layer by dopamine, a graphene oxide layer with 1 to 3 layers can be formed.

[0103] The effects of the technical solution of the present application are further elaborated in detail below in conjunction with specific embodiments.

[0104] Embodiment 1:

[0105] A bimetallic optical fiber SPR sensor based on silver core and gold shell nanoparticles is prepared by the following steps:

[0106] Step 1: Cut a 10 cm quartz optical fiber, take a 1.5 cm length as the sensing area and immerse it in concentrated sulfuric acid and hydrofluoric acid to remove the optical fiber cladding, immerse the cladding-removed optical fiber in piranha etching solution to obtain a bare optical fiber core, immerse the core in dopamine solution, and then immerse the optical fiber in a silver nanoparticle solution synthesized by the citrate thermal reduction silver nitrate method, and react in a dark constant temperature water bath at 37°C for 6 hours to allow the silver nanoparticles to fully adhere to the surface of the sensing area.

[0107] Step 2: 5 mL of 5% polyvinyl pyrrolidone solution, 50 μL of 0.5 M L-ascorbic acid, 0.2 mL of 0.5 M NaOH and 0.2 mL of 0.1 M Na2SO3 solution were mixed, the optical fiber obtained in step 1 was immersed in the mixed solution, ultrasonically treated for 10 min, and then gold growth solution (a mixed solution of 50 μL of 10% HAuCl4 solution, 0.2 mL of 0.24 M NaOH solution and 3 mL of 0.01 M Na2SO3 solution) was added to the mixed solution, and heated in a 65°C water bath for 1 h to deposit an ultrathin gold film on the surface of the silver nanoparticles;

[0108] Step 3: Immerse the optical fiber obtained in step 2 in a gold plating solution (0.1% chloroauric acid and 0.4 mM hydroxylamine hydrochloride) and oscillate at a speed of 100 r / min for 8 min;

[0109] Step 4: Immerse the sensing area of ​​the optical fiber obtained in step 3 in a 2 mg / mL dopamine solution, oscillate at a constant temperature at 37°C for 40 minutes, and then immerse it in 2 mg / mL graphene oxide. Covalently modify the graphene oxide to the sensing area through dopamine adhesion to obtain a bimetallic optical fiber SPR sensor.

[0110] Effect Example 1: Characterization Analysis

[0111] The bimetallic optical fiber SPR sensor prepared in Example 1 was subjected to transmission electron microscopy analysis and EDX element mapping analysis, and the results were obtained. Figure 6 . Figure 6It is a transmission electron microscope and EDX element mapping analysis diagram of the bimetallic optical fiber SPR sensor of Example 1 of the present application, wherein a is a TEM image of the metal functional layer of Example 1, b is an HRTEM image of silver nanoparticles coated with a gold film, c is an HRTEM image of silver nanoparticles not coated with a gold film, d is an EDX element mapping spectrum of silver of the optical fiber obtained in step one, e is an EDX element mapping spectrum of gold of the optical fiber obtained in step two, and f is an EDX element mapping spectrum of gold-silver superposition of the optical fiber obtained in step two.

[0112] like Figure 6 As shown in a, b, and c, the silver nanoparticles coated with gold film prepared in Example 1 are uniform in size, with a particle size of about 50 to 60 nm, a clear texture, and no adverse phenomena such as agglomeration.

[0113] like Figure 6 As shown in d, e, and f, after the first gold plating in step 2 in Example 1, the distribution of gold and silver basically overlap and are similar in size, indicating that gold film-coated silver nanoparticles are prepared.

[0114] Furthermore, the sensing area of ​​Example 1 was analyzed by scanning electron microscopy, and the Figure 7 , Figure 7 1 is a scanning electron microscope analysis diagram of the bimetallic optical fiber SPR sensor of Example 1 of the present application, wherein a is the SEM diagram of the optical fiber sensing area obtained in step 2, and b is the SEM diagram of the optical fiber sensing area obtained in step 3.

[0115] like Figure 7 As shown in a, after the first deposition of gold in step 2, the surface of the silver nanoparticles is covered with a gold film, but the gold films on the surfaces of the silver nanoparticles are not connected to form a dense film structure; Figure 7 As shown in b, after the secondary gold deposition in step three, the gold film in the sensing area forms a more uniform and dense film structure, which helps to improve the detection effect of the sensor.

[0116] Furthermore, the bimetallic optical fiber SPR sensor of Example 1 was characterized and analyzed by polarizing microscope, and the Figure 8 , Figure 8 This is a polarizing microscope analysis diagram of the dual-metal optical fiber SPR sensor of Example 1 of the present application.

[0117] like Figure 8 As shown, graphene oxide is coated on the surface of the sensing area to form a uniform and smooth graphene oxide layer structure.

[0118] The sensing area of ​​the bimetallic optical fiber SPR sensor of Example 1 was analyzed by Fourier transform infrared spectroscopy to obtain Fig. 9 , Fig. 9This is the FTIR characteristic spectrum of the bimetallic optical fiber SPR sensor of Example 1 of the present application.

[0119] like Fig. 9 As shown, the FTIR characteristic spectrum of the sensing area is consistent with the characteristics of graphene oxide. It can be seen that the present application successfully encapsulates the graphene oxide layer outside the sensing area.

[0120] Effect Example 2: Sensor Performance Analysis

[0121] Preparing sucrose solutions of different concentrations to obtain sucrose solutions of different refractive indices;

[0122] The bimetallic optical fiber SPR sensor prepared in Example 1 was immersed in sucrose solutions with different refractive indices to obtain SPR reflection spectra, and then a curve of wavelength shift versus refractive index was obtained, such as: Fig.10 , Fig.10 This is a curve showing the change in wavelength shift as the refractive index changes in Effect Example 2 of the present application.

[0123] like Fig.10 As shown, the sensor of Example 1 has excellent sensitivity, and the detection sensitivity is as high as 5170.7 nm / RIU.

[0124] It is obvious to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

[0125] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A bimetallic optical fiber SPR sensor based on silver core gold shell nanoparticles, characterized in that: include: An optical fiber having a sensing area arranged on its outer surface; The metal functional layer is arranged on the sensing area, and the metal functional layer includes dispersed and stacked silver nanoparticles, and the outer surface of the silver nanoparticles is coated with a gold film.

2. The bimetallic optical fiber SPR sensor according to claim 1, characterized in that: It also includes a graphene oxide layer, which is coated on the outer surface of at least a portion of the metal functional layer.

3. The bimetallic optical fiber SPR sensor according to claim 2, characterized in that: The number of graphene oxide layers in the graphene oxide layer is 1 to 3.

4. The bimetallic optical fiber SPR sensor according to claim 1, characterized in that: The particle size of the silver nanoparticles is 50 to 60 nm; and / or, The thickness of the gold film is 1-3 nm.

5. A method for preparing a bimetallic optical fiber SPR sensor based on silver core gold shell nanoparticles, characterized in that: include: In situ growth of silver nanoparticles on the outer surface of the sensing region of the optical fiber; A layer of gold film is grown on the surface of the silver nanoparticles to obtain a metal functional layer located in the sensing area.

6. The preparation method according to claim 5, characterized in that: The step of in-situ growing silver nanoparticles on the outer surface of the sensing region of the optical fiber comprises: immersing the sensing area in a dopamine solution to form a polydopamine layer in the sensing area; Immersing the optical fiber in a silver nanoparticle dispersion and placing it in a constant temperature water bath without light, so that the silver nanoparticles can fully adhere to the sensing area; Wherein, in the step of keeping a constant temperature water bath in the absence of light, the temperature of the constant temperature water bath is 35-40° C. and the time is 5-7 hours.

7. The preparation method according to claim 5, characterized in that: The step of growing a layer of gold film on the surface of the silver nanoparticles comprises: Immersing the optical fiber in the first mixed solution and subjecting it to ultrasonic treatment; Adding the second mixed solution to the first mixed solution and heating in a water bath; wherein the first mixed solution comprises polyvinyl pyrrolidone, L-ascorbic acid, NaOH and Na2SO3, and the second mixed solution comprises chloroauric acid, NaOH and Na2SO3; The water bath heating temperature is 60-70°C and the heating time is 0.8-1.2h.

8. The preparation method according to claim 7, characterized in that: The mass fraction of polyvinyl pyrrolidone in the first mixed solution is 4.5-5.5%, the molar concentration of L-ascorbic acid is 4-5 mM, the molar concentration of NaOH is 15-20 mM, and the molar concentration of Na2SO3 is 3.5-4 mM; The mass fraction of chloroauric acid in the second mixed solution is 0.1-0.2%, the molar concentration of NaOH is 10-20 mM, and the molar concentration of Na2SO3 is 8-10 mM.

9. The preparation method according to claim 7, characterized in that: The step of growing a layer of gold film on the surface of the silver nanoparticles also includes: Take out the optical fiber heated in the water bath and immerse it in the gold plating solution, stirring and shaking; The gold plating solution comprises chloroauric acid and hydroxylamine hydrochloride, the mass fraction of chloroauric acid in the gold plating solution is 0.05-0.15%, and the molar concentration of hydroxylamine hydrochloride is 0.3-0.5 mM.

10. The preparation method according to claim 5, characterized in that: After the step of growing a layer of gold film on the surface of the silver nanoparticles, the step further includes: covalently modifying a graphene oxide layer in at least a portion of the metal functional layer; The step of covalently modifying the graphene oxide layer in at least a portion of the metal functional layer comprises: The sensing area is immersed in a dopamine solution and oscillated at a constant temperature; Immersing the optical fiber in a graphene oxide dispersion to covalently modify the graphene oxide to the surface of the metal functional layer through dopamine; The constant temperature oscillation is performed at a temperature of 35 to 40° C. and a time of 0.5 to 1 h.

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