CN110763659A - Optical fiber SPR biosensor and preparation method thereof - Google Patents
Optical fiber SPR biosensor and preparation method thereof Download PDFInfo
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- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
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- G01N21/552—Attenuated total reflection
- G01N21/553—Attenuated total reflection and using surface plasmons
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- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
- G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
- G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
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- G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
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Abstract
The invention provides an optical fiber SPR biosensor and a preparation method thereof, wherein the biosensor adopts a sensing structure of a molybdenum disulfide-gold film interlayer based on a U-shaped optical fiber, the middle bending part of the U-shaped optical fiber is a sensing area, the surface of the optical fiber in the sensing area is coated with a molybdenum disulfide coating, the surface of the molybdenum disulfide coating is plated with a gold film layer, and the surface of the gold film is fixed with an antibody through dopamine. The SPR biosensor provided by the invention adopts an optical fiber-molybdenum disulfide-gold film sandwich structure, molybdenum disulfide has a larger band gap and higher light absorption efficiency, a stronger SPR effect can be excited, the surface electric field of the sensor is enhanced, the sensitivity of the sensor can be effectively improved, dopamine is used for fixing an antibody on the surface of the sensor, the measurement of high sensitivity and low detection limit of an antigen is realized, and the sensor has wider application in the aspect of biological detection.
Description
Technical Field
The invention relates to the technical field of biosensors, in particular to an optical fiber SPR biosensor and a preparation method thereof.
Background
In recent years, the application of Surface Plasmon Resonance (SPR) technology to various fields has raised research enthusiasm, such as food safety testing, environmental monitoring, medical diagnosis, bioengineering, etc. Particularly, the application of SPR in the bio-sensing technology has attracted much attention and research, and various high performance biosensors have been developed, among which the optical fiber biosensor has been favored because of its advantages of small volume, no label, high detection speed, etc. Surface Plasmon Resonance (SPR) biosensors are one of the optical sensors that is rapidly and comprehensively developed, but SPR biosensors use a metal having a negative dielectric constant as an excitation element, which increases the internal loss of the sensor, thereby affecting the sensitivity and detection limit of the sensor.
After the 21 st century, the material science enters a brand-new rapid development stage, a plurality of new materials are discovered and arouse great interest of people, and advanced and practical two-dimensional materials such as graphene, transition metal compounds (TMDCs), black phosphorus and the like are used for improving the performance of the biosensor so as to make up the limitation problems of low sensitivity and high detection limit in the SPR biosensor.
Disclosure of Invention
In order to solve the problems of low sensitivity and high detection limit of the conventional optical fiber SPR biosensor, the invention provides the optical fiber SPR biosensor and a preparation method thereof.
The invention provides an optical fiber SPR biosensor, which adopts a sensing structure of a molybdenum disulfide-gold film interlayer based on a U-shaped optical fiber, wherein the middle bending part of the U-shaped optical fiber is a sensing area, the surface of the optical fiber in the sensing area is coated with a molybdenum disulfide coating, the surface of the molybdenum disulfide coating is plated with a gold film layer, and the surface of the gold film is fixed with an antibody through dopamine.
Further, the molybdenum disulfide coating is coated on the surface of the optical fiber by an electrostatic self-assembly method.
Furthermore, the length of the sensor optical fiber is 30-40 cm, and the length of the sensing area is 20-30 mm.
Further, the thickness of the molybdenum disulfide coating is 0.65-13 nm.
Further, the thickness of the gold film layer is 40-55 nm.
Preferably, the total thickness of the molybdenum disulfide-gold film interlayer is 60 nm.
Further preferably, the molybdenum disulfide coating is 10nm, and the thickness of the gold film layer is 50 nm.
In another aspect, the present invention provides a method for preparing the optical fiber SPR biosensor, comprising the steps of:
(a) optical fiber pretreatment: taking a multimode optical fiber of 30-40 cm, taking down a coating layer of 20-30 mm in length in the middle of the optical fiber, removing impurities attached to the surface of the optical fiber in a sensing area to form the sensing area, bending the optical fiber to form a U shape, and heating the bent part by utilizing the outer flame of an alcohol lamp to fix the shape;
(b) preparing a molybdenum disulfide coating: soaking the bent part of the U-shaped optical fiber in a piranha solution for 0.5-1.5 hours, taking out the bent part of the U-shaped optical fiber, soaking the bent part of the U-shaped optical fiber in a PDDA aqueous solution of 10mg/ml-1g/ml for 0.5-1.5 hours, and then soaking the bent part of the U-shaped optical fiber in molybdenum disulfide nanosheet water or ethanol dispersion of 0.1 mg/ml-200 mg/ml for 3-12 hours; the method comprises the following steps of (1) taking a PDDA solution as a connecting medium between an optical fiber and molybdenum disulfide, enabling the PDDA to be positively charged and the molybdenum disulfide nanosheet to be negatively charged, and fixing the molybdenum disulfide on the surface of the optical fiber by an electrostatic adsorption method;
(c) and (3) deposition of a gold film layer: depositing a gold film by adopting a magnetron sputtering instrument, wherein the discharge time is 1.5-5 min, the current is 0-10 mA, and the thickness of the gold film is controlled by adjusting the discharge time and the current;
(d) and (3) fixing the antibody: immersing the bent part of the U-shaped optical fiber in 1 mg/ml-100 mg/ml dopamine solution for half an hour, carrying out polymerization reaction on dopamine in water to form polydopamine on the surface of a gold film in a sensing area, taking out the polydopamine, drying the polydopamine in a constant temperature box at 60 ℃ for half an hour, and then immersing the sensing area of the sensor in 0.01 mg/ml-1 mg/ml antibody solution for 12 hours; and poly-dopamine is used as a connecting medium for the gold film and the immobilized antibody, and the antibody is immobilized on the surface of the gold film.
The principle of the invention is as follows:
transition Metal Disulfides (TMDC), similar to graphene, belonging to two-dimensional nanomaterials, molybdenum disulfide and tungsten disulfide belonging to TMDC, molybdenum disulfide having a larger band gap and higher light absorption efficiency than graphene, and they also have a high specific surface area and good biocompatibility, which makes it possible to introduce transition metal dichalcogenides into SPR sensors, which can better improve the sensitivity of the sensors.
According to the molybdenum disulfide-gold film interlayer optical fiber SPR biosensor based on the U-shaped optical fiber, the gold film SPR sensor has high sensitivity, the molybdenum disulfide has a large band gap and high light absorption efficiency, and a surface electric field can be further enhanced to improve the sensitivity; the specific combination between the antibody and the antigen causes the shift of resonance wavelength, the measurement of high sensitivity of the antigen is realized according to the ratio of the concentration of the biological analyte to the shift of resonance wavelength, and the measurement of the lowest detection limit is realized by calculating the limit test efficiency index LOD, so that the sensor has better application in the field of biological detection.
The sensor with the molybdenum disulfide nanosheet coated between the gold film and the optical fiber has better sensitivity performance than the sensor with the molybdenum disulfide nanosheet coated on the surface of the gold film. In U-shaped fiber SPR sensing systems, part of the light energy generated by the disappearance of cladding modes is used to excite the SPR phenomenon, with the remaining loss being in the surrounding medium. When only the gold film exists on the surface of the optical fiber, the light energy absorbed by the gold film is not enough to support the strong SPRThe phenomenon is excited. When molybdenum disulfide nanosheets are added between the fiber and the gold film, MoS is due to the high light absorption rate (-5%) of molybdenum disulfide2The presence of (b) may effectively increase the absorption of light energy, thereby promoting a stronger excitation of the SPR phenomenon. Meanwhile, due to the single-layer MoS2The semiconductor is a direct band gap semiconductor, absorbed energy is used for electron transfer, and energy loss in the transfer process is small. More electrons are transferred from the molybdenum disulfide to the gold film, increasing the surface electric field strength of the sensor. Coating a layer of molybdenum disulfide on the surface of the gold film of the sensor only increases the utilization rate of the light energy absorbed by the sensor system. However, on the basis that the molybdenum disulfide coating exists between the gold film and the optical fiber, the utilization rate of absorbed light energy is improved, and the absorption rate of the light energy is improved.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the molybdenum disulfide-gold film interlayer optical fiber SPR biosensor based on the U-shaped optical fiber, the molybdenum disulfide-gold film interlayer structure is adopted, so that the sensor has higher sensitivity;
2. the functionalized sensor for detecting the human IgG by the dopamine immobilized antibody on the surface of the sensor has excellent biosensing characteristic, and can better reduce the detection limit; different kinds of antigens can be fixed by dopamine, so that detection of different antibodies is realized;
3. by adopting the interlayer mechanism, the molybdenum disulfide in the interlayer mechanism cannot fall off while the sensitivity is enhanced, so that the stability of the sensing structure is enhanced;
in conclusion, the invention solves the problems of lower sensitivity and higher detection limit of the existing optical fiber SPR biosensor, and provides a new solution for the detection of low-concentration biological analytes.
Drawings
FIG. 1 is a schematic structural diagram of a U-shaped fiber-based molybdenum disulfide-gold film sandwich optical fiber SPR biosensor in example 1 of the present invention;
FIG. 2 is a schematic structural diagram of a U-shaped fiber-based molybdenum disulfide-gold film sandwich optical fiber SPR biosensor system in example 1 of the present invention;
FIG. 3 is a schematic structural view of a U-shaped fiber-based gold-coated fiber SPR biosensor in example 1 of the present invention;
FIG. 4 is a schematic structural diagram of a fiber SPR biosensor based on a U-shaped optical fiber based on molybdenum disulfide film;
FIG. 5 is a transmission spectrum of a U-shaped fiber-based molybdenum disulfide-gold film sandwich fiber SPR biosensor in example 1 of the present invention in ethanol solutions with different refractive indexes;
FIG. 6 is a fitting curve of refractive index sensitivity of the U-shaped fiber-based molybdenum disulfide-gold film sandwich fiber SPR biosensor in example 1 of the present invention;
FIG. 7 shows the change of resonance wavelength with time in different igG solution concentrations for the U-shaped fiber-based molybdenum disulfide-gold film sandwich fiber SPR biosensor in example 1 of the present invention;
FIG. 8 shows the variation of the resonance wavelength shift of the U-shaped fiber-based molybdenum disulfide-gold film sandwich optical fiber SPR biosensor in example 1 of the present invention as a function of the concentration of igG solution;
FIG. 9 is a linear fitting curve of the resonance wavelength shift amount of the U-shaped fiber-based molybdenum disulfide-gold film sandwich optical fiber SPR biosensor in example 1 of the present invention in the range of igG concentration of 5-20 μ g/ml;
reference numerals:
1. a multimode optical fiber core; 2. a fiber cladding; 3. a molybdenum disulfide coating; 4. gold film; 5. antibody-goat anti-human immunoglobulin;
A. a molybdenum disulfide-gold film interlayer optical fiber SPR biosensor of a U-shaped optical fiber; B. a broadband light source; C. a spectrometer; D. a multimode fiber optic path; E. a computer; F. a beaker;
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. Any specific values in all examples shown and discussed herein are to be construed as exemplary only and not as limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
In the description of the present invention, it is to be understood that the orientation or positional relationship indicated by the directional terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc., are generally based on the orientation or positional relationship shown in the drawings, and are used for convenience of description and simplicity of description only, and in the absence of any contrary indication, these directional terms are not intended to indicate and imply that the device or element so referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore should not be considered as limiting the scope of the present invention: the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.
Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of the present invention should not be construed as being limited.
Example 1
In this embodiment, a U-shaped fiber-based molybdenum disulfide-gold membrane sandwich fiber SPR biosensor for detecting human immunoglobulin IgG is prepared, i.e., the antigen to be detected is human immunoglobulin IgG, and the antibody to be detected is goat anti-human immunoglobulin.
As shown in figure 1, the optical fiber SPR biosensor adopts a sensing structure of a molybdenum disulfide-gold film interlayer based on a U-shaped optical fiber, and comprises a U-shaped multimode optical fiber with the length of 30-40 cm, wherein the middle bending part of the U-shaped multimode optical fiber is a sensing area, the length of the sensing area is 20-30 mm, a molybdenum disulfide coating 3 is fixed on the surface of the optical fiber of the sensing area through electrostatic self-assembly, the thickness of the molybdenum disulfide coating is 0.65-13 nm, plating a gold film 4 on the surface fixed with the molybdenum disulfide coating, wherein the thickness of the gold film is 40-55 nm, the surface of the gold film is solidified with an antibody-goat anti-human immunoglobulin 5 film through dopamine, the antigen to be detected is human immunoglobulin, the antibody-goat anti-human immunoglobulin is combined with the antigen-human immunoglobulin 6 in the detection process, so that the antigen-human immunoglobulin fixed on the surface is fixed on the antibody-sheep anti-human immunoglobulin film.
The sensing system formed by the molybdenum disulfide-gold film interlayer optical fiber SPR biosensor based on the U-shaped optical fiber is shown in figure 2 and comprises an optical fiber SPR biosensor A, wherein the system takes a multimode optical fiber as a light path, namely the multimode optical fiber is taken as a light path D, the input end of the optical fiber SPR biosensor A is connected with a broadband light source B with a visible light waveband, the output end of the optical fiber SPR is connected with a broadband spectrometer C, the broadband spectrometer C is connected to a computer E through a data interface, the optical fiber SPR biosensor A is arranged in a container to be detected, the container to be detected is a beaker F in the embodiment, and the optical fiber SPR biosensor A is arranged in a solution to be detected.
The method for preparing the optical fiber SPR biosensor comprises the following steps:
(a) optical fiber pretreatment: taking a 35cm multimode optical fiber, taking down a coating layer 25mm long in the middle of the optical fiber, removing impurities attached to the surface of the optical fiber in a sensing area to form the sensing area, bending the optical fiber to form a U shape, heating the bent part by using the outer flame of an alcohol lamp to fix the shape, and checking the curvature radius of the U-shaped optical fiber by controlling the bending degree;
(b) preparing a molybdenum disulfide coating: soaking the bent part of the U-shaped optical fiber in a piranha solution (a mixed solution of concentrated sulfuric acid with the mass fraction of 95-98% and hydrogen peroxide with the mass fraction of 30% in a volume ratio of 7: 3) for 1 hour, taking out the U-shaped optical fiber, soaking the U-shaped optical fiber in a 100mg/ml PDDA aqueous solution for 1 hour, and then soaking the U-shaped optical fiber in a 0.1mg/ml molybdenum disulfide nanosheet absolute ethyl alcohol dispersion for 3 hours; the method comprises the following steps of (1) taking a PDDA solution as a connecting medium between an optical fiber and molybdenum disulfide, enabling the PDDA to be positively charged and the molybdenum disulfide nanosheet to be negatively charged, fixing the molybdenum disulfide on the surface of the optical fiber by an electrostatic adsorption method, and enabling the thickness of the molybdenum disulfide coating to be 10 nm;
(c) and (3) deposition of a gold film layer: depositing a gold film by adopting a magnetron sputtering instrument, and controlling the thickness of the gold film to be 50nm by adjusting the discharge time to be 3 minutes and the current to be 7 mA;
(d) and (3) fixing the antibody: immersing the bent part of the U-shaped optical fiber in 5mg/ml dopamine solution (solvent is 2% tris buffer solution) for half an hour, carrying out polymerization reaction on dopamine in water to form polydopamine on the surface of a gold film of a sensing area, taking out the polydopamine, drying the polydopamine in a constant temperature box at 60 ℃ for half an hour, and then immersing the sensing area of the sensor in 0.1mg/ml antibody solution for 12 hours; the polydopamine is used as a connecting medium for the gold film and the fixed antibody, and the antibody is fixed on the surface of the gold film;
(f) detection of antigens
The U-shaped optical fiber-molybdenum disulfide-gold film sandwich structure SPR biosensor is immersed in an IgG solution at the temperature of 25 ℃, resonance wavelength shift is caused according to specific binding between an antibody and an antigen, the antigen is detected, and meanwhile, the wavelength shift caused by specific adsorption between the actual antigen and the antibody is obtained according to the wavelength shift.
The refractive index sensing characteristics of the prepared SPR biosensor based on the U-shaped optical fiber-molybdenum disulfide-gold film sandwich structure, the prepared gold film optical fiber SPR biosensor based on the U-shaped optical fiber and the prepared gold film molybdenum disulfide optical fiber SPR biosensor based on the U-shaped optical fiber are tested as follows:
wherein, the gold film optical fiber SPR biosensor of the U-shaped optical fiber adopts a multimode optical fiber as shown in figure 3, and the surface of an outer cladding layer 2 of a fiber core 1 of the U-shaped multimode optical fiber is plated with a layer of gold film 4 with the thickness of 50 nm; the optical fiber SPR biosensor of U-shaped optical fiber-gold film-molybdenum disulfide adopts multimode optical fiber, and the surface of the outer cladding 2 of the fiber core 1 of the U-shaped multimode optical fiber is sequentially plated with a gold film 4 and a molybdenum disulfide coating 3 from inside to outside as shown in figure 4.
In order to research the invention, molybdenum disulfide coatings are sequentially fixed on the surface of the multimode optical fiber from inside to outsideAnd the refractive index sensing performance of the sensor after the gold-plated film, the sensor is connected into a sensing system with a multimode optical fiber as an optical path, a deuterium-halogen lamp with the wavelength range of 215nm to 2500nm is used as a light source at the input end, an ocean optical spectrometer is used for detecting a resonance spectrum, then the sensor is respectively immersed into an ethanol solution with the refractive index variation range of 1.3314-1.3623, the resonance spectrum is shown in figure 5, and the resonance wavelength shifts to the right along with the increase of the refractive index. The sensitivity of the sensor can be expressed as the shift of the resonance peak Δ λpChange deltan from refractive index of sample to be measuredaThe ratio of (a) to (b), namely:
through detection, the refractive index sensitivity of the gold film optical fiber SPR biosensor of the U-shaped optical fiber is 3887.6 nm/RIU; the refractive index sensitivity of the optical fiber SPR biosensor of U-shaped optical fiber-gold film-molybdenum disulfide is 4946.8 nm/RIU; the optical fiber SPR biosensor is based on a U-shaped optical fiber-molybdenum disulfide-gold film sandwich structure, the refractive index sensitivity fitting curve of the optical fiber SPR biosensor is shown in figure 6, and the refractive index sensitivity of the optical fiber SPR biosensor is 6184.4nm/RIU according to the slope of the fitting curve.
The optical fiber SPR biosensor is based on a U-shaped optical fiber-molybdenum disulfide-gold film sandwich structure, the change of resonance wavelength in IgG solution with different concentrations along with time is shown in figure 7, the change of resonance wavelength shift along with the concentration of the IgG solution is shown in figure 8, and a linear fitting curve of the resonance wavelength shift in the range of 5-20 mu g/ml of IgG concentration is shown in figure 9.
Obviously, the molybdenum disulfide-gold film sandwich optical fiber SPR biosensor based on the U-shaped optical fiber has higher sensitivity than a common sensor.
The invention mainly utilizes the molybdenum disulfide-gold film sandwich structure to enhance the surface electric field intensity so as to improve the detection sensitivity of the sensor. The method comprises the steps of fixing a molybdenum disulfide coating on the surface of the multimode optical fiber by an electrostatic self-assembly method, promoting absorption of light energy by utilizing molybdenum disulfide, enhancing a surface electric field to improve sensitivity, fixing an antibody by using dopamine to detect an antigen, enabling specific binding between the antibody and the antigen to cause resonance wavelength drift, realizing measurement of high sensitivity of the antigen according to the ratio of concentration of a biological analyte to movement of the resonance wavelength, and realizing measurement of the lowest detection limit by calculating a limit test performance index LOD.
The technical idea of the present invention is described in the above technical solutions, and the protection scope of the present invention is not limited thereto, and any changes and modifications made to the above technical solutions according to the technical essence of the present invention belong to the protection scope of the technical solutions of the present invention.
Claims (8)
1. The optical fiber SPR biosensor is characterized in that a sensing structure of a molybdenum disulfide-gold film interlayer based on a U-shaped optical fiber is adopted, the middle bending part of the U-shaped optical fiber is a sensing area, a molybdenum disulfide coating is coated on the surface of the sensing area optical fiber, a gold film layer is plated on the surface of the molybdenum disulfide coating, and an antibody is fixed on the surface of the gold film through dopamine.
2. The fiber SPR biosensor of claim 1, wherein said molybdenum disulfide coating is applied to the surface of said optical fiber by electrostatic self-assembly.
3. The optical fiber SPR biosensor of claim 1, wherein the length of said sensor optical fiber is 30-40 cm, and the length of said sensing area is 20-30 mm.
4. The optical fiber SPR biosensor of claim 1, wherein said molybdenum disulfide coating has a thickness of 0.65 to 13 nm.
5. The optical fiber SPR biosensor of claim 1, wherein the thickness of said gold film layer is 40-55 nm.
6. The fiber SPR biosensor of claim 1, wherein said molybdenum disulfide-gold film sandwich layer has a total thickness of 60 nm.
7. The fiber SPR biosensor of claim 1, wherein said molybdenum disulfide coating is 10nm and said gold film layer is 50nm thick.
8. The method of claim 1, wherein the method comprises the steps of:
(a) optical fiber pretreatment: taking a multimode optical fiber of 30-40 cm, taking down a coating layer of 20-30 mm in length in the middle of the optical fiber, removing impurities attached to the surface of the optical fiber in a sensing area to form the sensing area, bending the optical fiber to form a U shape, and heating the bent part by utilizing the outer flame of an alcohol lamp to fix the shape;
(b) preparing a molybdenum disulfide coating: soaking the bent part of the U-shaped optical fiber in a piranha solution for 0.5-1.5 hours, taking out the bent part of the U-shaped optical fiber, soaking the bent part of the U-shaped optical fiber in a PDDA aqueous solution of 10mg/ml-1g/ml for 0.5-1.5 hours, and then soaking the bent part of the U-shaped optical fiber in molybdenum disulfide nanosheet water or ethanol dispersion of 0.1 mg/ml-200 mg/ml for 3-12 hours; the method comprises the following steps of (1) taking a PDDA solution as a connecting medium between an optical fiber and molybdenum disulfide, enabling the PDDA to be positively charged and the molybdenum disulfide nanosheet to be negatively charged, and fixing the molybdenum disulfide on the surface of the optical fiber by an electrostatic adsorption method;
(c) and (3) deposition of a gold film layer: depositing a gold film by adopting a magnetron sputtering instrument, wherein the discharge time is 1.5-5 min, the current is 0-10 mA, and the thickness of the gold film is controlled by adjusting the discharge time and the current;
(d) and (3) fixing the antibody: immersing the bent part of the U-shaped optical fiber in 1 mg/ml-100 mg/ml dopamine solution for half an hour, carrying out polymerization reaction on dopamine in water to form polydopamine on the surface of a gold film in a sensing area, taking out the polydopamine, drying the polydopamine in a constant temperature box at 60 ℃ for half an hour, and then immersing the sensing area of the sensor in 0.01 mg/ml-1 mg/ml antibody solution for 12 hours; and poly-dopamine is used as a connecting medium for the gold film and the immobilized antibody, and the antibody is immobilized on the surface of the gold film.
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