A local surface plasmon resonance-based optical fiber sensor, a preparation method and an optical fiber sensing system

Abstract

The application discloses a kind of based on local surface plasmon resonance optical fiber sensor, preparation method and optical fiber sensing system, it is related to optical fiber sensing technical field.Based on the optical fiber sensor of local surface plasmon resonance includes: optical fiber base and the medium layer and metal nanoparticle layer sequentially arranged on the optical fiber base, medium layer can accurately adjust the position of the characteristic peak of optical fiber sensor, the local surface plasmon resonance effect of metal nanoparticle layer and the interference effect of Fabry-Perot cavity are coupled, a new characteristic peak is constructed in its spectrum, the sensitivity of the characteristic peak is higher, effectively solve the problem of low sensitivity of traditional gold nanoparticle local surface plasmon resonance effect optical fiber end surface sensor, improve the stability and reliability of optical fiber sensor, so that optical fiber sensor is suitable for the specificity detection of object to be detected in various different situations.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, and in particular to a fiber optic sensor based on localized surface plasmon resonance, its fabrication method, and a fiber optic sensing system. Background Technology

[0002] In recent years, sensors based on localized surface plasmon resonance (LSPR) have become an important optical analysis technique with wide applications in chemistry, biology, and the environment. When incident light shines on the surface of metal nanoparticles, the free electrons on the surface interact with photons, generating collective oscillations. These collective oscillations reach their maximum amplitude at a specific frequency called the "resonance frequency," thus producing the LSPR phenomenon. Under resonance conditions, the electric field near the nanoparticle surface is enhanced, and this enhanced electric field is confined to the vicinity of the nanoparticles, experiencing exponential decay within a certain nanometer range from the nanoparticle surface. This plasmon resonance phenomenon occurring at the nanoscale can be integrated with transducers to develop biochemical sensors applicable to a variety of fields.

[0003] In the field of sensors, fiber optic sensing technology has made great strides in sensor design, manufacturing process optimization, and system integration in recent years. Various fiber optic sensors based on different principles have been proposed, such as interferometric fiber optic sensors, scattering fiber optic sensors, total internal reflection fiber optic sensors, and surface plasmon resonance fiber optic sensors. Among them, fiber optic sensors based on nanostructure localized surface plasmon resonance (LSPR) are widely used in biochemical detection and integrated photonic devices because they combine the characteristics of traditional fiber optic sensors and plasmon resonance sensors.

[0004] Currently, common methods for obtaining LSPR-based fiber optic sensors include using metal nanoparticles to modify the end face or side face of the fiber, thereby directly obtaining the LSPR-based fiber optic sensor. However, fiber optic sensors prepared by this method have several drawbacks. First, the distribution of nanoparticles on the surface is uncontrollable, leading to poor device performance consistency. Second, due to the dissipation effect of the metal nanoparticles themselves and the mutual attraction between the electric dipoles of two metal nanoparticles, their LSPR characteristic peaks are usually very broad and the wavelength sensitivity is low, which reduces the stability and reliability of LSPR-based fiber optic sensors. Summary of the Invention

[0005] The purpose of this invention is to provide a fiber optic sensor based on localized surface plasmon resonance (LSPR), its fabrication method, and a fiber optic sensing system, thereby addressing the problems of low stability and reliability in current fiber optic sensors. The fiber optic sensor of this invention differs from current fiber optic sensors that modify the end faces or sides of the fiber with metal nanoparticles in that it incorporates several dielectric layers on the fiber substrate. The interference effect of the Fabry-Perot cavity in the dielectric layers couples with the localized surface plasmon resonance effect of the gold nanoparticles, constructing a new characteristic peak in the near-infrared region of the spectrum. This enables high-sensitivity sensing and allows for precise adjustment of the characteristic peak position of the fiber optic sensor.

[0006] In a first aspect, the present invention provides an optical fiber sensor based on localized surface plasmon resonance, the optical fiber sensor comprising: an optical fiber substrate, and a plurality of dielectric layers and a metal nanoparticle layer disposed on the optical fiber substrate; the dielectric layer comprising a single dielectric film or a group of multiple dielectric films with different refractive indices; the metal nanoparticle layer being located above, below, or between multiple dielectric layers; the dielectric layer being used to adjust the position of the characteristic peaks of the optical fiber sensor.

[0007] With the above technical solution, the fiber optic sensor provided in this application has a dielectric layer made of parylene (420 nm thick), which allows for precise adjustment of the position of the characteristic peak of the fiber optic sensor. The metal nanoparticle layer on the dielectric layer consists of uniformly dispersed gold nanoparticles with a diameter of 50 nm and an average spacing of 75 nm. The localized surface plasmon resonance effect of these nanoparticles couples with the interference effect of the Fabry-Perot cavity in the dielectric layer, constructing a new characteristic peak in the near-infrared region of the spectrum. The sensitivity of this characteristic peak can reach 400-800 nm / RIU, comparable to the sensitivity of fiber optic sensors obtained through top-down micro / nano fabrication processes. This effectively solves the problem of low sensitivity in traditional fiber optic end-face sensors based on the localized surface plasmon resonance effect of gold nanoparticles, improving the stability and reliability of the fiber optic sensor and making it suitable for specific detection of objects in various scenarios.

[0008] In one possible implementation, the dielectric layer is used to introduce reflected light, which interferes with the signal light, thereby increasing sensing sensitivity and adjusting the position of the characteristic peak of the fiber optic sensor.

[0009] In one possible implementation, the dielectric layer includes any one or more of the following: a polychloro-p-xylene material layer, a polydimethylsiloxane material layer, a polymethyl methacrylate material layer, a silicon oxide material layer, a silicon nitride material layer, an aluminum oxide material layer, a titanium oxide material layer, and a photoresist layer.

[0010] In one possible implementation, the metal nanoparticle layer comprises multiple metal nanoparticles, the shape of which includes any one of spherical, star-shaped, rod-shaped, spindle-shaped, or triangular.

[0011] In one possible implementation, the metal nanoparticles include any one of gold nanoparticles, silver nanoparticles, or copper nanoparticles.

[0012] Secondly, the present invention also provides a method for fabricating an optical fiber sensor based on localized surface plasmon resonance, the method comprising:

[0013] Provide an optical fiber substrate;

[0014] A single or multiple dielectric layers of a predetermined thickness are deposited on the surface of the optical fiber substrate;

[0015] A layer of metal nanoparticles is assembled on the surface of the dielectric layer to obtain an optical fiber sensor.

[0016] In one possible implementation, depositing a dielectric layer of a predetermined thickness on the surface of the second optical fiber segment includes:

[0017] The optical fiber substrate is cut and cleaned to obtain a first optical fiber segment of the target length;

[0018] The first optical fiber segment is treated with a silane coupling agent to obtain a treated second optical fiber segment.

[0019] A dielectric layer of a predetermined thickness is deposited on the surface of the second optical fiber segment.

[0020] In one possible implementation, assembling a layer of metal nanoparticles on the surface of the dielectric layer to obtain a fiber optic sensor includes:

[0021] By using block polymers as templates, metal nanoparticle layers are assembled on the surface of the dielectric layer through self-assembly to obtain an optical fiber sensor.

[0022] In one possible implementation, after using a block polymer as a template to assemble a layer of metal nanoparticles onto the surface of the dielectric layer via self-assembly to obtain an optical fiber sensor, the fabrication method further includes:

[0023] The sensing material is modified on the metal nanoparticle layer by means of covalent bonding, hydrogen bonding, coordination bonding or electrostatic bonding, for the specific detection of specific substances.

[0024] In one possible implementation, the step of using a block polymer as a template to assemble a layer of metal nanoparticles onto the surface of the dielectric layer via self-assembly to obtain an optical fiber sensor includes:

[0025] The dielectric layer is modified with a block polymer to form the block polymer on the dielectric layer, and the block polymer is uniformly distributed in a single layer on the surface of the dielectric layer.

[0026] Using the block polymer as a template, the metal nanoparticle layer is assembled on the surface of the dielectric layer by electrostatic adsorption to obtain an optical fiber sensor.

[0027] The beneficial effects of the fiber optic sensor fabrication method based on local surface plasmon resonance provided in the second aspect are the same as those of the fiber optic sensor based on local surface plasmon resonance described in the first aspect or any possible implementation of the first aspect, and will not be repeated here.

[0028] Thirdly, the present invention also provides an optical fiber sensing system based on local surface plasmon resonance, the system comprising an optical fiber sensor based on local surface plasmon resonance as described in any of the first aspects, as well as a coupler, a light source, a spectrometer, and electronic equipment.

[0029] The fiber optic sensor is connected to the coupler, the coupler is connected to the spectrometer and the light source respectively, and the electronic device is connected to the spectrometer.

[0030] During the detection of the sample to be tested, the fiber optic sensor is used to make contact with the sample to be tested; the coupler is used to couple the light emitted by the light source to the fiber optic sensor and transmit the light signal reflected from the metal nanoparticle layer of the fiber optic sensor to the spectrometer, the spectrometer is used to generate a detection electrical signal based on the reflected light signal and send the detection electrical signal to an electronic device; wherein, the fiber optic sensor includes a dielectric layer, the fiber optic sensor has a characteristic peak, and the position of the characteristic peak is determined according to the thickness of the dielectric layer.

[0031] The beneficial effects of the fiber optic sensing system based on local surface plasmon resonance provided in the third aspect are the same as those of the fiber optic sensor based on local surface plasmon resonance described in the first aspect or any possible implementation of the first aspect, and will not be repeated here. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 A schematic diagram of the structure of an optical fiber sensing system based on local surface plasmon resonance provided in an embodiment of this application is shown.

[0034] Figure 2 A schematic diagram of the structure of an optical fiber sensor based on local surface plasmon resonance provided in an embodiment of this application is shown;

[0035] Figure 3 A schematic flowchart of a method for fabricating an optical fiber sensor based on localized surface plasmon resonance, provided in an embodiment of this application, is shown.

[0036] Figure 4 This illustration shows a scenario of a poly(p-chloroxylene) thin film deposition process according to an embodiment of this application;

[0037] Figure 5 This illustration shows a scenario where a metal nanoparticle layer is assembled on the fiber end face of the third optical fiber segment, according to an embodiment of this application.

[0038] Figure 6 A schematic flowchart of another method for fabricating an optical fiber sensor based on localized surface plasmon resonance provided in an embodiment of this application is shown.

[0039] Figure 7 This illustration shows a scenario diagram of a method for fabricating an optical fiber sensor based on localized surface plasmon resonance, as provided in an embodiment of this application.

[0040] Figure 8 This illustration shows a schematic diagram of the spectral results based on the LSPR effect of gold nanoparticles and the LSPR effect of gold nanoparticles coupled with the Fabry-Perot cavity interference effect, provided by an embodiment of this application.

[0041] Figure 9 This illustration shows another schematic diagram of the spectral results based on the LSPR effect of gold nanoparticles and the LSPR effect of gold nanoparticles coupled with the Fabry-Perot cavity interference effect provided in the embodiments of this application. Attached image description:

[0043] 101-Fiber optic sensor; 102-Coupled; 103-Light source; 104-Spectrometer; 105-Electronic device; 1011-Fiber optic substrate; 1012-Dielectric layer; 1013-Metal nanoparticle layer; 401-First fiber segment; 402-Second fiber segment; 403-Third fiber segment; 404-Block polymer; 405-Fiber optic sensor; 406-Target fiber optic sensor. Detailed Implementation

[0044] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0045] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0046] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0047] Figure 1 This illustration shows a schematic diagram of a fiber optic sensing system based on localized surface plasmon resonance, as provided in an embodiment of this application. Figure 1 As shown, the fiber optic sensing system based on local surface plasmon resonance includes a fiber optic sensor 101 based on local surface plasmon resonance, a coupler 102, a light source 103, a spectrometer 104, and an electronic device 105.

[0048] The fiber optic sensor 101 is connected to the coupler 102, the coupler 102 is connected to the spectrometer 104 and the light source 103 respectively, and the electronic device 105 is connected to the spectrometer 104.

[0049] During the detection of the sample to be tested, the fiber optic sensor is used to make contact with the sample to be tested; the electronic device is used to send spectrometer control signals; the coupler is used to transmit the light emitted by the light source to the fiber end face of the fiber optic sensor, and is also used to control the spectrometer to receive the signal reflected back from the metal nanoparticle layer of the fiber optic sensor.

[0050] Specifically, the coupler is used to couple the light emitted by the light source to the fiber optic sensor and transmit the light signal reflected from the metal nanoparticle layer of the fiber optic sensor to the spectrometer. The spectrometer is used to generate a detection electrical signal based on the reflected light signal and send the detection electrical signal to an electronic device.

[0051] Optionally, the fiber optic sensor includes a dielectric layer and has a characteristic peak, the position of which is determined by the thickness of the dielectric layer. That is, the position of the characteristic peak of the fiber optic sensor can be precisely adjusted by controllably adjusting the thickness of the dielectric layer, thus making it suitable for various scenarios with different requirements for the position of the characteristic peak.

[0052] Optionally, in this application, the aforementioned electronic device may be a computer or other electronic terminal, and the embodiments of this application do not specifically limit it.

[0053] Optionally, during the detection of the sample to be tested, the structural end of the fiber optic sensor is immersed in the sample to be tested for contact detection.

[0054] Figure 2 This illustration shows a schematic diagram of a fiber optic sensor based on localized surface plasmon resonance, as provided in an embodiment of this application. Figure 2 As shown, the fiber optic sensor includes: an optical fiber substrate 1011, and a plurality of dielectric layers 1012 and a metal nanoparticle layer 1013 disposed on the optical fiber substrate 1011; the dielectric layer 1012 includes a single-layer dielectric film or a group of multiple dielectric films with different refractive indices; the metal nanoparticle layer 1013 is located above, below, or between multiple dielectric layers 1012; Figure 2 In this process, the metal nanoparticle layer 1013 is located on top of the dielectric layer 1012. The dielectric layer 1012 is used to introduce reflected light, which interferes with the signal light, thereby increasing the sensing sensitivity and adjusting the position of the characteristic peak of the fiber optic sensor.

[0055] Optional, see Figure 2 The optical fiber substrate 1011 includes a core 1011A and a cladding 1011B.

[0056] Optionally, the material of the dielectric layer 1012 may include any one or more of the following: parylene, polydimethylsiloxane (PDMS), polymethylmethacrylate (PMMA), silicon nitride (Si3N4), alumina (Al2O3), titanium dioxide (TiO2), and photoresist. The photoresist may be SU-8 photoresist, and the dielectric layer material may also be other insulating materials. This application embodiment does not specifically limit this, and adjustments can be made according to the actual application scenario.

[0057] Optionally, the metal nanoparticle layer 1013 includes multiple metal nanoparticles. The shape of the metal nanoparticles includes any one of spherical, star-shaped, rod-shaped, spindle-shaped, or triangular shapes, or other shapes, such as pentagrams. This application embodiment does not specifically limit this, and can be calibrated and adjusted according to the actual application scenario.

[0058] Optionally, the metal nanoparticles may include any one of gold nanoparticles, silver nanoparticles, or copper nanoparticles, or nanoparticles made of other precious metals. This application embodiment does not specifically limit this, and calibration adjustments can be made according to actual application scenarios.

[0059] Optionally, the optical fiber substrate can be a single-mode optical fiber substrate or a multimode optical fiber substrate. In this embodiment, the dielectric layer covers the optical fiber end face and / or optical fiber sidewall of the optical fiber substrate, and the metal nanoparticle layer can be fixed on the optical fiber end face and / or optical fiber sidewall by chemical modification.

[0060] In this application, the dielectric layer can be a single layer or multiple layers, and the embodiments of this application do not specifically limit this.

[0061] In this application, after growing a dielectric layer on the sidewall of the optical fiber core, a layer of metal nanoparticles is assembled on the surface of the dielectric layer on the sidewall, thereby realizing an optical fiber sidewall sensor based on the LSPR effect coupling interference effect of nanoparticles.

[0062] In summary, by adopting the above technical solution, the fiber optic sensor provided in this application has a dielectric layer, which is poly(p-chloro-xylene) with a thickness of 420 nm, allowing for precise adjustment of the position of the characteristic peak of the fiber optic sensor. The metal nanoparticle layer on the dielectric layer consists of uniformly dispersed gold nanoparticles with a diameter of 50 nm and an average spacing of 75 nm. The localized surface plasmon resonance effect of these nanoparticles couples with the interference effect of the Fabry-Perot cavity in the dielectric layer, constructing a new characteristic peak in the near-infrared region of the spectrum. The sensitivity of this characteristic peak can reach 400-800 nm / RIU, comparable to the sensitivity of fiber optic sensors obtained through top-down micro / nano fabrication processes. This effectively solves the problem of low sensitivity in traditional fiber optic end-face sensors based on the localized surface plasmon resonance effect of gold nanoparticles, improving the stability and reliability of the fiber optic sensor and making it suitable for specific detection of objects in various scenarios.

[0063] Figure 3 This paper illustrates a flowchart of a method for fabricating an optical fiber sensor based on localized surface plasmon resonance, as provided in an embodiment of this application. Figure 3 As shown, the method includes:

[0064] Step 201: Provide an optical fiber substrate.

[0065] Step 202: Deposit a single or multiple dielectric layer of a predetermined thickness on the surface of the optical fiber substrate.

[0066] Step 203: Assemble the metal nanoparticle layer on the surface of the dielectric layer to obtain the fiber optic sensor.

[0067] In summary, the method for fabricating an optical fiber sensor based on localized surface plasmon resonance provided in this application involves providing an optical fiber substrate; depositing a single or multiple dielectric layers of a predetermined thickness on the surface of the optical fiber substrate; and assembling a layer of metal nanoparticles on the surface of the dielectric layers to obtain the optical fiber sensor. By setting the thickness of the dielectric layer and the distribution of the metal nanoparticles, the position of the characteristic peaks of the optical fiber sensor can be precisely adjusted for detection in various scenarios.

[0068] Figure 6 The following is a schematic flowchart illustrating another method for fabricating an optical fiber sensor based on localized surface plasmon resonance provided in an embodiment of this application. Figure 6 As shown, the method includes:

[0069] Step 301: Provide an optical fiber substrate.

[0070] In this application, the optical fiber substrate can be a single-mode optical fiber substrate or a multimode optical fiber substrate. The embodiments of this application do not specifically limit this, and calibration adjustments can be made according to the actual application scenario.

[0071] In this application, the optical fiber substrate can be a multimode optical fiber with a core diameter of 50 micrometers and a cladding diameter of 105 micrometers.

[0072] Step 302: Cut and clean the optical fiber substrate to obtain a first optical fiber segment of the target length.

[0073] In this application, the optical fiber substrate can be cut into a first optical fiber segment of the target length. After cutting the optical fiber substrate, approximately 2.5 cm of the coating layer at both ends can be peeled off. The target length can be 15 cm or 16 cm. This application does not specifically limit this length and can be adjusted according to the actual application scenario.

[0074] In this application, the fiber substrate can be cut with a fiber optic cutter perpendicular to the incident light direction, so that the fiber end face of the fiber substrate can be used as a sensing area. The flat fiber end face after cutting can be ultrasonically cleaned with acetone, ethanol and deionized water for 10 minutes respectively, and then hydroxylated with oxygen ionizer.

[0075] Step 303: Modify the first optical fiber segment with a silane coupling agent to obtain a modified second optical fiber segment.

[0076] The fiber end face and sidewall are modified with a silane coupling agent to obtain a modified second fiber segment.

[0077] In this application, the first optical fiber segment is modified with a silane coupling agent to obtain a modified second optical fiber segment. The modified second optical fiber segment can have stronger adhesion to the dielectric layer.

[0078] Optionally, the silane coupling agent may include 3-aminopropyltriethoxysilane (APTES) with isopropanol and deionized water.

[0079] Specifically, 3-aminopropyltriethoxysilane (APTES) can be mixed with isopropanol and deionized water at a volume ratio of 1:100:100. After thorough stirring, the mixture is allowed to stand for 2 hours to allow the APTES to diffuse evenly in the solution. During modification, the end of the first optical fiber segment is immersed in the prepared solution and allowed to stand for 20 minutes. Subsequently, the first optical fiber segment is removed and rinsed with deionized water to remove excess silane molecules from the fiber surface, yielding the second optical fiber segment.

[0080] Step 304: Deposit a dielectric layer of a predetermined thickness on the surface of the second optical fiber segment.

[0081] In this application, the modified second optical fiber segment can be dried in an oven at 110°C and a dielectric layer can be grown within 24 hours.

[0082] In this application, the preset thickness is not specifically limited and can be calibrated and adjusted according to the actual application scenario.

[0083] In this application, the dielectric layer used can be a polychloroparaxylene (Parylene) film obtained by chemical vapor deposition, and the thickness of the film can be precisely controlled by the quality of the initial dimer. Figure 4 This illustration shows a scenario diagram of a poly(p-chlorophenyl)xylene thin film deposition process according to an embodiment of this application. Figure 4 As shown, the process mainly consists of three steps. First, powdered Parylene dimer x is evaporated in a vacuum at approximately 135°C. Then, the evaporated dimer y is pyrolyzed at 690°C to form free radical Parylene monomer z. Finally, the monomer z vapor enters a room temperature deposition chamber and polymerizes on the surfaces of all exposed optical fibers.

[0084] Low pressure can be used to provide a slow deposition rate, which can obtain a high-quality Parylene coating. Furthermore, because the deposited Parylene is highly conformal, a flat surface can be obtained on the fiber end face.

[0085] Specifically, a pressure of approximately 15 mTorr can be used to deposit Parylene films.

[0086] In this application, a Parylene dielectric layer can be grown on the surface of the optical fiber of the optical fiber sensor by chemical vapor deposition. Oxides such as titanium dioxide (TiO2) and aluminum oxide (Al2O3) can be grown by chemical vapor deposition or atomic layer deposition to serve as the dielectric layer. Alternatively, polymers such as SU-8 and PDMS can be spin-coated on the end face of the optical fiber to serve as the dielectric layer. This application does not specifically limit the specific methods used, and calibration adjustments can be made according to the actual application scenario.

[0087] Step 305: Modify the dielectric layer with a block polymer to form the block polymer on the dielectric layer, wherein the block polymer is uniformly distributed in a single layer on the surface of the dielectric layer.

[0088] Step 306: Using the block polymer as a template, the metal nanoparticle layer is assembled on the end face of the optical fiber by electrostatic adsorption to obtain the optical fiber sensor.

[0089] In this application, the metal nanoparticles may include any one of gold nanoparticles, silver nanoparticles, or copper nanoparticles, or nanoparticles made of other precious metals. This application does not specifically limit the specific types of nanoparticles, and adjustments can be made according to the actual application scenario.

[0090] Optionally, the block polymer may include polystyrene-poly4-vinylpyridine (PS-b-P4VP), or other block polymers such as polystyrene-b-polyacrylic acid (PS-b-PAA). Silane coupling agents such as 3-aminopropyltrimethoxysiloxane (APTMS) and 3-aminopropyltriethoxysilane (APTES) may also be used instead. This application does not specifically limit the specific application in this regard, and the markings may be adjusted according to the actual application scenario.

[0091] As both bottom-up chemical vapor deposition and nanoparticle self-assembly processes, they share the characteristic of being able to process multiple optical fibers simultaneously. Therefore, the fiber end-face sensor based on the LSPR effect of gold nanoparticles coupled with the Fabry-Perot cavity interference effect in this embodiment can be mass-produced at a very low cost.

[0092] For example, in the scenario where the metal nanoparticles are spherical gold nanoparticles, this embodiment uses a block polymer, polystyrene-poly4-vinylpyridine (PS-b-P4VP), as a template to fix the gold nanoparticles to the fiber end face through self-assembly. Figure 5 This illustration shows a scenario where a metal nanoparticle layer is assembled on the fiber end face of the third optical fiber segment, as provided in an embodiment of this application. Figure 5 As shown, the surface of the dielectric layer is first treated with oxygen plasma to enrich it with hydroxyl groups. Then, the end of the optical fiber is slowly immersed in a 0.05 mg / ml PS-b-P4VP aqueous solution. After standing for 15 min, the end of the optical fiber is slowly pulled out at the same speed (10 mm / min). Through this process, PS-b-P4VP is assembled on the surface of the dielectric layer in a non-covalent manner. The block copolymer PS-b-P4VP forms a monolayer and is uniformly distributed on the surface of the dielectric layer. The P4VP end is used to adsorb gold nanoparticles, and the PS end is used to prevent gold particle agglomeration. After the dielectric surface is dried, the PS-b-P4VP modified optical fiber is immersed in a 0.5 nM gold nanoparticle solution. Due to the Coulomb force, the gold nanoparticles in the solution will be fixed on the surface of the dielectric layer, thus obtaining a discrete and uniformly distributed gold nanoparticle above the dielectric layer.

[0093] The fiber optic sensor in this application has a sensitivity of 680 nm / RIU, which is comparable to fiber endface LSPR sensors obtained through top-down micro-nano fabrication processes. Compared to existing fiber endface sensors based on gold nanoparticle LSPR, its sensitivity is improved by an order of magnitude.

[0094] Step 307: Modify the metal nanoparticle layer with a sensing material through covalent bonds, hydrogen bonds, coordination bonds or electrostatic forces for the specific detection of specific substances.

[0095] Example, Figure 7 This illustration shows a scenario diagram of a method for fabricating an optical fiber sensor based on localized surface plasmon resonance, as provided in an embodiment of this application. Figure 7 As shown, the target length is 15 cm. The first optical fiber segment 401 of 15 cm is silanized to obtain the second optical fiber segment 402 with a silane monolayer. The second optical fiber segment 402 is treated with Parylene chemical vapor deposition to obtain the third optical fiber segment 403. The third optical fiber segment 403 is modified with a block polymer to form the block polymer 404 on the end face of the optical fiber. Using the block polymer 404 as a template, the metal nanoparticle layer 1013 is assembled on the end face of the optical fiber by electrostatic adsorption to obtain the optical fiber sensor 405. The excess block polymer of the optical fiber sensor 405 is removed by plasma etching to obtain the target optical fiber sensor 406.

[0096] In summary, the method for fabricating a fiber optic sensor based on localized surface plasmon resonance provided in this application involves providing a fiber optic substrate, cutting and cleaning the substrate to obtain a first fiber segment of a target length, modifying the first fiber segment with a silane coupling agent to obtain a modified second fiber segment, depositing a dielectric layer of a predetermined thickness on the second fiber segment, and using a block polymer as a template to achieve monodisperse self-assembly of metal nanoparticles to obtain the fiber optic sensor. By setting the dielectric layer thickness and the distribution of metal nanoparticles, the position of the characteristic peaks of the fiber optic sensor can be precisely adjusted for detection in various scenarios.

[0097] The fiber optic sensing system based on local surface plasmon resonance in this application, which uses a fiber optic end-face sensing system based on the LSPR effect of metal nanoparticles coupled with the Fabry-Perot cavity interference effect to perform biological sample detection operations, includes two main steps: experimental preparation and biological sample detection.

[0098] For example, in the scenario where the metal nanoparticles are gold nanoparticles, let's take the detection of immunoglobulin G (IgG) in urine as an example:

[0099] In the experimental preparation stage, the pre-prepared fiber optic sensor based on localized surface plasmon resonance was immersed in a 10 mM mercaptoundecanoic acid ethanol solution for 12 hours to form a carboxyl monolayer on the surface of gold nanoparticles. Subsequently, the fiber end face was rinsed with ethanol and phosphate buffer to remove unbound mercaptoundecanoic acid. The fiber end face of the sensor was then immersed in a mixture of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide for 15 minutes to activate the carboxyl groups. After activating the carboxyl groups, the fiber end face was then sequentially immersed in phosphate buffer containing 100 μg / ml IgG antibody and phosphate buffer containing 1 mg / ml bovine serum albumin for 1 hour. After modification, the fiber optic sensor was connected to a coupler and... Figure 1 The spectrometer and light source are connected as shown.

[0100] In biological sample (IgG) detection, the fiber optic sensor end face can be immersed in the test solution (urine), and the integration time and smoothing times of the spectrometer can be set on the electronic device. When antigen molecules in the test solution specifically bind to antibody molecules modified on the surface of gold nanoparticles, the refractive index of the environment surrounding the gold nanoparticles changes, thereby causing a shift in the position of the characteristic peaks in the spectrum. Figure 8 This diagram illustrates a spectroscopic result based on the LSPR effect of gold nanoparticles and the LSPR effect coupled with the Fabry-Perot cavity interference effect provided in an embodiment of this application. From... Figure 8 As can be seen from graph a, traditional fiber optic sensors based on the LSPR effect of gold nanoparticles exhibit only a characteristic peak at 550 nm in their spectrum. When the refractive index around the sensor changes (from 1.33 to 1.38), the intensity of this characteristic peak increases, but its position hardly shifts, indicating very low wavelength sensitivity. Figure 8 As can be seen in b, for the fiber optic sensor in this embodiment, in its spectral results, in addition to the characteristic peak of LSPR at 600 nm, a new characteristic peak (at 756 nm) appears in the spectrum due to the Fabry-Perot cavity interference effect caused by the presence of the Parylene dielectric layer. When the refractive index of the sensor end face environment increases, the position of the characteristic peak of gold nanoparticle LSPR in the spectrum remains basically unchanged, while the position of the characteristic peak of LSPR coupling interference moves from 756 nm to 791 nm, and the wavelength sensitivity reaches 680 nm / RIU.

[0101] In this application, different scenarios typically have different requirements for the position of spectral characteristic peaks. For example, for water and biological tissue structures, light with wavelengths in the near-infrared region (650nm-900nm) has lower absorption and scattering coefficients, and light in this region has better penetration ability into biological tissues. Therefore, the characteristic peaks of LSPR in the near-infrared region are more suitable for applications in the field of biochemical detection. However, for traditional fiber optic sensors based on spherical gold nanoparticles, changing the size of the gold nanoparticles has little effect on the position of the characteristic peaks; that is, it is difficult to move the LSPR characteristic peaks to the near-infrared region by changing the size of the gold nanoparticles. Figure 9 This illustration shows another schematic diagram of the spectral results based on the LSPR effect of gold nanoparticles and the LSPR effect of gold nanoparticles coupled with the Fabry-Perot cavity interference effect provided in the embodiments of this application. Figure 9 'a' represents the numerical simulation results when the diameter of the gold nanoparticles changes from 50 nm to 100 nm. Figure 9 As can be seen from Figure a, the characteristic peak of LSPR only shifted from 550 nm to 580 nm. For the fiber optic sensor based on the LSPR coupling interference effect of gold nanoparticles in this embodiment, since its characteristic peak is the result of the combined effect of LSPR and interference, the position of the characteristic peak can be adjusted by adjusting the thickness of the Parylene dielectric layer (dielectric layer). Figure 9 Figure b shows the numerical simulation results when the Parylene dielectric layer thickness varies from 340 nm to 420 nm. As can be seen from the figure, the characteristic peak of the LSPR coupling interference effect shifts from 650 nm to 760 nm. This result demonstrates the adjustability of the characteristic peak position of the fiber optic sensor in this embodiment, thus enabling it to be applied to different detection scenarios.

[0102] In summary, the fiber optic sensing system provided in this application embodiment only requires appropriate modification of the fixed metal nanoparticles to achieve highly sensitive and selective analysis and identification of different biomolecules or metal ions, and has the advantages of small equipment size, simple operation and low cost.

[0103] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0104] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely exemplary descriptions of the invention as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A method for fabricating an optical fiber sensor based on localized surface plasmon resonance, characterized in that, The method includes: Provide an optical fiber substrate; cut and clean the optical fiber substrate to obtain a first optical fiber segment of a target length; treat the first optical fiber segment with a silane coupling agent to obtain a treated second optical fiber segment; and deposit a single or multiple dielectric layer of a preset thickness on the surface of the second optical fiber segment. The dielectric layer is a poly(p-chloroxylene) material layer of the target thickness. The deposition method is as follows: First, powdered poly(p-chloroxylene) dimer is evaporated in a vacuum. Then, the evaporated dimer is decomposed into free radical poly(p-chloroxylene) monomers. Finally, the poly(p-chloroxylene) monomer vapor enters the room temperature deposition chamber and polymerizes on the surface of all exposed optical fibers. The dielectric layer is modified with a block polymer to form the block polymer on the dielectric layer. The block polymer is uniformly distributed in a monolayer on the surface of the dielectric layer. Using the block polymer as a template, a metal nanoparticle layer is assembled on the surface of the dielectric layer by electrostatic adsorption to obtain an optical fiber sensor. The optical fiber sensor has characteristic peaks, the positions of which are determined according to the thickness of the dielectric layer. The metal nanoparticle layer consists of multiple metal nanoparticles uniformly dispersed with a target diameter and target spacing. The metal nanoparticles are any one of gold nanoparticles, silver nanoparticles, or copper nanoparticles. The block polymer is polystyrene-poly4-vinylpyridine.

2. The method for fabricating an optical fiber sensor based on localized surface plasmon resonance according to claim 1, characterized in that, After assembling a layer of metal nanoparticles onto the surface of the dielectric layer using the block polymer as a template via electrostatic adsorption to obtain an optical fiber sensor, the fabrication method further includes: The sensing material is modified on the metal nanoparticle layer by means of covalent bonding, hydrogen bonding, coordination bonding or electrostatic bonding, for the specific detection of specific substances.

3. A fiber optic sensor based on localized surface plasmon resonance, prepared using the method described in claim 1 or 2, is characterized in that... The fiber optic sensor includes: a fiber optic substrate, and a single-layer or multi-layer dielectric layer and a metal nanoparticle layer disposed on the fiber optic substrate; the dielectric layer is a poly(p-chloroxylene) material layer of a target thickness, the dielectric layer is modified with a block polymer to form the block polymer on the dielectric layer, the single-layer block polymer is uniformly distributed on the surface of the dielectric layer, and the metal nanoparticle layer is assembled on the surface of the dielectric layer by electrostatic adsorption using the block polymer as a template to obtain the fiber optic sensor. The fiber optic sensor has characteristic peaks, the positions of which are determined according to the thickness of the dielectric layer. The metal nanoparticle layer is composed of multiple metal nanoparticles uniformly dispersed with a target diameter and target spacing, the metal nanoparticles being any one of gold nanoparticles, silver nanoparticles, or copper nanoparticles, and the block polymer being polystyrene-poly4-vinylpyridine.

4. The fiber optic sensor based on localized surface plasmon resonance according to claim 3, characterized in that, The shape of the metal nanoparticles includes any one of spherical, star-shaped, rod-shaped, spindle-shaped, or triangular.

5. A fiber optic sensing system based on localized surface plasmon resonance, characterized in that, The system includes the fiber optic sensor based on local surface plasmon resonance as described in claim 3 or 4, as well as a coupler, a light source, a spectrometer, and electronic equipment. The fiber optic sensor is connected to the coupler, the coupler is connected to the spectrometer and the light source respectively, and the electronic device is connected to the spectrometer. During the detection of the sample to be tested, the fiber optic sensor is used to make contact with the sample to be tested; the coupler is used to couple the light emitted by the light source to the fiber optic sensor and transmit the light signal reflected from the metal nanoparticle layer of the fiber optic sensor to the spectrometer, the spectrometer is used to generate a detection electrical signal based on the reflected light signal and send the detection electrical signal to an electronic device; wherein, the fiber optic sensor includes a dielectric layer, the fiber optic sensor has a characteristic peak, and the position of the characteristic peak is determined according to the thickness of the dielectric layer.

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