High-sensitivity SLR optical fiber sensor and preparation method and application thereof

Abstract

The invention belongs to the technical field of sensors, and particularly relates to a high-sensitivity SLR optical fiber sensor, a preparation method thereof and application of the high-sensitivity SLR optical fiber sensor to specific detection of biomolecules. A single layer of hexagonal non-close-packed nanogold ball array is distributed on the end face of an optical fiber adapter in SLR optical fiber sensing; the SLR optical fiber sensor is formed by loading a nanogold ball array on the end face of an optical fiber adapter through a transfer printing technology, an SLR mode capable of being effectively excited under the nearly vertical incidence white light illumination condition is adopted, and detection is conducted through a simple coaxial reflection light path and a convenient direct dropwise adding sample injection method. By using the SLR optical fiber sensor, a displacement signal of a surface lattice resonance spectrum peak is detected through a detection system, qualitative or quantitative analysis of target molecules can be realized, and in a NaCl solution refractive index test, the sensitivity of the sensor reaches 323 nm / RIU; after SH-T16 modification, the sensor can realize specific detection of a target molecule A16 in a concentration range of 10 to 100 nM.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a high-sensitivity SLR fiber optic sensor, its preparation method, and its application in the specific detection of biomolecules. Background Technology

[0002] Surface plasmon resonance (SPR) sensing technology, with its mechanism of exciting plasmon resonance on the surface of noble metal films through evanescent waves, can achieve highly sensitive detection of molecular interactions and is widely regarded as the "gold standard" in the field of sensing. However, SPR technology is extremely sensitive to the excitation angle, requiring complex prism coupling optical paths and precise angle / wavelength scanning components. This results in a large system structure, high cost, and complex operation, limiting its practical application in portable and rapid on-site detection.

[0003] In contrast, noble metal nanoparticles (such as gold nanoparticles) have attracted much attention in recent years due to their localized surface plasmon resonance (LSPR) properties, which allow for simpler transmission or absorption optical paths for optical sensing. LSPR is excited when the incident light matches the oscillation frequency of the free electrons in the nanoparticles, producing characteristic spectral peaks. The shift of these peaks can respond to changes in the refractive index of the surrounding medium. However, LSPR sensors based on single or disordered nanoparticles typically have large resonance peak widths and low quality factors (Q values), resulting in limited refractive index sensitivity.

[0004] To simultaneously overcome the challenges of complex SPR systems and insufficient sensitivity of LSPR systems, surface lattice resonance (SLR) has emerged as a significant advantage. When noble metal nanostructures (such as gold nanospheres) are arranged in a subwavelength periodic order, the LSPR modes of individual nanoparticles can form collective oscillations through far-field diffraction coupling, i.e., the SLR effect. This resonance mode possesses an extremely high quality factor and extremely narrow linewidth, and is highly sensitive to changes in the ambient refractive index, theoretically enabling sensing sensitivity far superior to that of traditional LSPR. Crucially, SLR can be excited under perpendicular or near-perpendicular incident conditions, greatly simplifying the optical path structure and providing a new approach for developing compact, easy-to-operate optical sensing systems, particularly for integration with fiber optic platforms.

[0005] Therefore, developing a fabrication method that can effectively integrate high-performance SLR structures with fiber optic sensing platforms is of great significance for the development of high-sensitivity, portable biochemical sensors. Summary of the Invention

[0006] In view of this, one of the objectives of the present invention is to provide a highly sensitive SLR fiber optic sensor that can achieve highly sensitive measurement of changes in the refractive index of the environment and changes in the refractive index (surface refractive index) caused by surface bonding by detecting the movement of the SLR peak position.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a high-sensitivity SLR fiber optic sensor, wherein a single-layer hexagonal non-close-packed gold nanosphere array is distributed on the end face of the fiber optic adapter, the center distance between adjacent gold nanospheres is 480-520 nm, and the diameter of the gold nanospheres is 190-210 nm.

[0008] A second objective of this invention is to provide a method for fabricating the aforementioned high-sensitivity SLR fiber optic sensor, comprising the following steps: S1. A hexagonal non-close-packed gold nanosphere array is prepared on a single-crystal silicon wafer. An acetone solution with a mass fraction of 10-30% polymethyl methacrylate (PMMA) is spin-coated onto the gold nanosphere array and the single-crystal silicon wafer. The spin-coating speed is 3000-10000 rpm and the spin-coating time is 10-60 s. The acetone is allowed to evaporate and coat the gold nanosphere array with a PMMA film. S2. The nano-gold ball array coated with PMMA film is placed in an oven at 180-200 ℃ and heated for 1-5 hours, and then immersed in 1 M KOH solution at 30-50 ℃ for 3-10 hours. The PMMA film coated with nano-gold ball array is peeled off from the flat substrate and is called PMMA-Au composite film. S3. Clean and dry the end face of the fiber optic adapter, lay the PMMA-Au composite film flat on the end face of the fiber optic adapter, and then place it in an oven at 180-200 ℃ for 2-5 hours. Then use acetone to dissolve and remove PMMA to obtain a high-sensitivity SLR fiber optic sensor loaded with a nano-gold ball array on the fiber optic adapter.

[0009] Preferably, in step S1, the mass fraction of PMMA in the acetone solution of PMMA is 10-30%, the spin coating speed is 3000-10000 rpm, and the spin coating time is 10-60 s.

[0010] Preferably, the method for dissolving and removing PMMA in step S3 is as follows: the fiber optic adapter with the PMMA-Au composite film fixed is immersed in acetone solution for 10-18 hours to dissolve and remove PMMA.

[0011] Preferably, the method for fabricating a hexagonal non-close-packed gold nanosphere array on a single-crystal silicon wafer is as follows: S11. A monolayer PS microsphere array was prepared on a hydrophilic single-crystal silicon wafer by gas-liquid interface self-assembly as a template. The diameter of the PS microspheres was 200-2000 nm. S12. A gold film is sputtered and deposited on the above-mentioned monolayer PS microsphere array; S13. The monolayer PS microsphere array with deposited gold film is calcined at high temperature to remove the PS microsphere template, and a hexagonal non-close-packed gold nanosphere array is prepared on a single crystal silicon wafer.

[0012] The third objective of this invention is to provide an application of the high-sensitivity SLR fiber optic sensor described in claim 1 in the specific detection of biomolecules.

[0013] Further improvements can be made to the application of the aforementioned high-sensitivity SLR fiber optic sensor for the specific detection of biomolecules: Preferably, the steps include: S21. Sensor functionalization: A DNA probe solution with thiol-modified ends is reacted with a nano-gold ball array at the sensor end, so that the DNA probe is fixed to the surface of the gold ball through Au-S bonds, and the functionalized sensor is obtained. S22. Specific binding: The test solution containing the target molecule is brought into contact with the functionalized sensor, so that the target molecule specifically binds to the immobilized DNA probe, thereby enriching it on the sensor surface. S23. Signal detection: The shift signal of the surface lattice resonance spectral peak is detected by a detection system to achieve qualitative or quantitative analysis of the target molecule; wherein the shift of the spectral peak is caused by the local refractive index change caused by the binding of the target molecule.

[0014] Preferably, the detection system described in step S23 includes: a Y-shaped optical fiber, the common end of which is connected to an SLR optical fiber sensor, and the two branches are respectively connected to a light source and a spectrometer; the light emitted by the light source is transmitted through the Y-shaped optical fiber to the SLR optical fiber sensor for reflection, and the reflected light is transmitted through the optical fiber to the spectrometer; the SLR peak position information is obtained by reading and analyzing the reflected spectral signal collected by the spectrometer through a computer connected to the spectrometer.

[0015] Preferably, the Y-type optical fiber is a FIB-M-600-NIR optical fiber manufactured by Shanghai Fuxiang Optics Co., Ltd.; the spectrometer is a PG2000-Pro fiber optic spectrometer manufactured by Shanghai Fuxiang Optics Co., Ltd., with a wavelength range of 200-1100 nm; and the light source is an HL2000 halogen light source manufactured by Shanghai Fuxiang Optics Co., Ltd.

[0016] Preferably, when the high-sensitivity SLR fiber optic sensor is used for bulk refractive index detection, the sensor directly contacts the solution to be tested; before changing the solution to be tested, the sensor is rinsed with deionized water multiple times, and the concentration of the solution to be tested is detected sequentially from low to high. Multiple tests are performed to obtain the linear relationship between the SLR peak shift and the refractive index of the solution to be tested.

[0017] Preferably, the DNA probe solution is a buffer solution containing 1-50 μM thiol-modified DNA probe, and the buffer solution consists of: 20-100 mM Tris-HCl, 0.4-0.7 M NaCl, and 1-10 mM MgCl₂. The pH value is 8.0.

[0018] Preferably, the test solution is a buffer solution containing 1-200 nM target DNA, and the buffer solution consists of: 20-100 mM Tris-HCl, 0.3-0.6 M NaCl, and 1-10 mM MgCl₂. The pH value is 7.4.

[0019] Preferably, in step S21, the reaction is carried out at room temperature for 10-30 hours to achieve the contact reaction; in step S22, the reaction is carried out at room temperature for 5-10 hours to achieve the specific binding.

[0020] The advantages of this invention compared to the prior art are as follows: (1) The present invention provides an SLR fiber optic sensor in which a single-layer hexagonal non-close-packed gold nanosphere array is distributed on the end face of the fiber optic adapter. Combined with a reflective optical path design, an integrated SLR fiber optic sensor is constructed, aiming to achieve high sensitivity, convenient operation and system stability at the same time.

[0021] Optical response characteristics: The array of gold nanospheres loaded on the end face of the optical fiber can excite a strong SLR mode. Compared with the traditional LSPR, SLR has a higher quality factor and a narrower resonant linewidth, exhibiting sharper and more sensitive reflection spectrum characteristic peaks. This characteristic is the physical basis for the high-sensitivity detection of this sensor.

[0022] Simplified optical system architecture: The SLR mode upon which this invention relies can be effectively excited under near-perpendicular white light illumination conditions. Therefore, a coaxial reflection mode design is adopted (incident and reflected light follow the same path), and the light source is directly integrated into the system (typically a broadband white light source). This design eliminates the complex optical system required for SPR sensing, thereby improving the fault tolerance, ease of operation, and practicality of the entire sensing system.

[0023] Integrated SLR fiber optic sensor: The nano-gold sphere array is integrated onto the fiber end face through transfer technology. This method not only ensures the mechanical stability of the sensor, but more importantly, it achieves seamless coupling between the sensing area and the fiber transmission path, laying the foundation for building a compact and portable sensing system.

[0024] Convenient detection operation process: Thanks to the coaxial reflective optical path and integrated design, this sensor can be directly immersed in the liquid to be tested or a small amount of sample can be picked up and placed on its functional end face for detection. The detection process is simple and fast.

[0025] Bulk refractive index sensitivity detection: In the refractive index detection experiment using a standard NaCl solution, the SLR fiber optic sensor achieved a sensitivity of 323 nm / RIU. This fully demonstrates its excellent ability to detect changes in the overall refractive index of the surrounding medium.

[0026] Specific biomolecular recognition: This sensing platform exhibits excellent biocompatibility and functionalization potential. Thiol-modified DNA probe molecules (such as SH-T16) can be immobilized on the surface of gold spheres through stable Au-S bond chemical self-assembly, enabling specific detection of specific target molecules (such as the complementary DNA sequence A16).

[0027] (2) This invention provides a method for fabricating an SLR fiber optic sensor, which uses transfer technology to precisely construct a gold nanosphere array on the end face of an optical fiber. The outstanding advantage of this method is that it avoids the structural damage caused by directly calcining the gold nanosphere array on the optical fiber adapter at high temperature.

[0028] (3) This invention provides an application of an SLR fiber optic sensor in the specific detection of biomolecules. By connecting the SLR fiber optic sensor to a detection system, the SLR reflectance spectral signal of the analyte is detected, utilizing the characteristic of SLR peak shift caused by changes in the refractive index of the environmental medium. Using this SLR fiber optic sensor, the shift signal of the surface lattice resonance spectral peak can be detected by the detection system, enabling qualitative or quantitative analysis of the target molecule. In the refractive index test of NaCl solution, the sensitivity of this sensor reaches 323 nm / RIU. After modification with SH-T16, this sensor can achieve specific detection of the target molecule A16 in the concentration range of 10-100 nM. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the process flow for fabricating the SLR fiber optic sensor in an embodiment of the present invention.

[0031] Figure 2The image shows the surface morphology of the PS microsphere template in the preparation example of the present invention; (a) is a scanning electron microscope image of the PS microsphere template, (b) is a scanning electron microscope image of the silicon-based gold nanosphere array, and (c) is a white light interference image of the gold nanosphere array after it has been transferred to the end face of the optical fiber.

[0032] Figure 3 This is a schematic diagram of the SLR fiber optic sensing system device in embodiments 4 and 5 of the present invention.

[0033] Figure 4 The following are the sensitivity test results of the fiber optic sensor to the refractive index of NaCl solution in Example 4 of the present invention: (a) is the SLR reflection spectrum under different refractive indices, and (b) is the relationship curve between SLR peak shift and refractive index.

[0034] Figure 5 This is a flowchart of the DNA-specific detection experiment in Example 5 of the present invention.

[0035] Figure 6 The DNA test results in Example 5 of this invention are as follows: (a) is the reflectance spectrum of 20 nM A16 target molecule at different reaction times; (b) is the curve of SLR peak shift (Δλ) as a function of A16 concentration. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0037] Preparation Example This preparation example provides a method for fabricating a hexagonal non-close-packed gold nanosphere array on a single-crystal silicon wafer. The specific steps are as follows: 1) Take <100> A 4-inch monocrystalline silicon wafer with a crystal orientation is cleaned sequentially with ethanol and water, dried, and then subjected to oxygen plasma cleaning to obtain a monocrystalline silicon wafer with a hydrophilic surface. 2) Prepare a PS microsphere dispersion with a concentration of 2.5 wt% and a diameter of 500 nm. Mix the PS microsphere dispersion with ethanol and acetone in a volume ratio of 2:1:1 and sonicate for 5 min to obtain the PS microsphere solution. 3) First, add 8 mL of deionized water to the hydrophilic surface of the monocrystalline silicon wafer, then add PS microsphere solution along the edge of the monocrystalline silicon wafer. The PS microspheres self-assemble. Then, add 10 μL of 0.1 mol / L sodium dodecyl sulfate (SDS) solution along the edge of the monocrystalline silicon wafer. The SDS solution makes the PS microspheres closely arranged with each other, forming a monolayer PS microsphere array on the monocrystalline silicon wafer. 4) Add 50 μL of 0.1 mol / L SDS solution to a water tank containing water, and immerse the monocrystalline silicon wafer with a monolayer PS microsphere array into it. The monolayer PS microsphere array floats on the water surface. 5) The 4 cm section after oxygen plasma cleaning 2 Small silicon wafers were immersed in water, and a monolayer PS microsphere array was transferred onto the hydrophilic surface of the silicon wafers, thus fabricating a PS microsphere film on the silicon substrate. The scanning electron microscope image is shown below. Figure 2 As shown in (a); 6) The PS microsphere film on the silicon substrate was placed in the Quorum Q150RS Plus magnetron sputtering instrument and sputtered with a current of 20 mA for 200 s to obtain a gold film with a thickness of 50 nm on the surface of the PS microspheres. 7) The PS microsphere film with gold sputtered on the silicon substrate was placed in a calcination furnace and calcined at 1050 °C for 3 hours, thus obtaining a monolayer hexagonal non-close-packed gold nanosphere array on a single-crystal silicon wafer. Its scanning electron microscope image is shown below. Figure 2 As shown in (b).

[0038] Example 1 This embodiment provides a method for fabricating a high-sensitivity SLR fiber optic sensor, the specific steps of which are as follows: S1. Take the hexagonal non-close-packed gold nanosphere array prepared on the single crystal silicon wafer in the preparation example, and spin-coat the gold nanosphere array and the single crystal silicon wafer on it with an acetone solution of PMMA (PMMA mass concentration of 17%). The spin-coating speed is 6000 rpm and the spin-coating time is 20 s. After the acetone evaporates, a layer of PMMA film is coated on the gold nanosphere array. S2. The array of gold nanospheres coated with PMMA film was heated in an oven at 190 °C for 2 hours, and then immersed in 1 M KOH solution at 40 °C for 8 hours. The PMMA film coated with gold nanospheres was peeled off from the planar substrate and was called PMMA-Au composite film. S3. Clean and dry the end face of the fiber optic adapter. The fiber optic adapter is an SMA905 female-FC male fiber optic adapter manufactured by Shenzhen Xinrui Optoelectronic Technology Co., Ltd., with a working wavelength range of UV-VIS and a core diameter of 600 μm. A PMMA-Au composite film is laid flat on the end face of the fiber optic adapter, heated in an oven at 190 ℃ for 4 hours, and then immersed in acetone for 12 hours to dissolve and remove the PMMA. A nano-gold ball array is loaded onto the fiber optic adapter to obtain a high-sensitivity SLR fiber optic sensor. Its white light interferogram is shown below. Figure 2 As shown in (c).

[0039] Example 2 This embodiment provides a method for fabricating a high-sensitivity SLR fiber optic sensor, the specific steps of which are as follows: S1. Take the hexagonal non-close-packed gold nanosphere array prepared on the single crystal silicon wafer in the preparation example, and spin-coat the gold nanosphere array and the single crystal silicon wafer on it with an acetone solution of PMMA (PMMA mass concentration of 10%). The spin-coating speed is 3000 rpm and the spin-coating time is 60 s. After the acetone evaporates, a layer of PMMA film is coated on the gold nanosphere array. S2. The array of gold nanospheres coated with PMMA film was heated in an oven at 200 ℃ for 1 hour, and then immersed in 1 M KOH solution at 30 ℃ for 10 hours. The PMMA film coated with gold nanospheres was peeled off from the planar substrate and was called PMMA-Au composite film. S3. Clean and dry the end face of the fiber optic adapter. The fiber optic adapter is an SMA905 female-FC male fiber optic adapter manufactured by Shenzhen Xinrui Optoelectronic Technology Co., Ltd., with a working wavelength range of UV-VIS and a core diameter of 600 μm. Lay a PMMA-Au composite film flat on the end face of the fiber optic adapter, heat it in an oven at 180 ℃ for 5 hours, and then immerse it in acetone for 18 hours to dissolve and remove PMMA. Load a nano-gold ball array onto the fiber optic adapter to obtain a high-sensitivity SLR fiber optic sensor.

[0040] Example 3 This embodiment provides a method for fabricating a high-sensitivity SLR fiber optic sensor, the specific steps of which are as follows: S1. Take the hexagonal non-close-packed gold nanosphere array prepared on the single crystal silicon wafer in the preparation example, and spin-coat the gold nanosphere array and the single crystal silicon wafer on it with an acetone solution of PMMA (PMMA mass concentration of 30%). The spin-coating speed is 10000 rpm and the spin-coating time is 10 s. After the acetone evaporates, a layer of PMMA film is coated on the gold nanosphere array. S2. The array of gold nanospheres coated with PMMA film was heated in an oven at 180 ℃ for 5 hours, and then immersed in 1 M KOH solution at 50 ℃ for 3 hours. The PMMA film coated with gold nanospheres was peeled off from the planar substrate and was called PMMA-Au composite film. S3. Clean and dry the end face of the fiber optic adapter. The fiber optic adapter is an SMA905 female-FC male fiber optic adapter manufactured by Shenzhen Xinrui Optoelectronic Technology Co., Ltd., with a working wavelength range of UV-VIS and a core diameter of 600 μm. Lay a PMMA-Au composite film flat on the end face of the fiber optic adapter, heat it in an oven at 200 ℃ for 2 hours, and then immerse it in acetone for 10 hours to dissolve and remove PMMA. Load a nano-gold ball array onto the fiber optic adapter to obtain a high-sensitivity SLR fiber optic sensor.

[0041] Performance testing: (1) The instruments required for testing mainly include: HL2000 halogen light source produced by Shanghai Fuxiang Optics Co., Ltd., which provides a stable and continuous white light source; PG2000-Pro fiber optic spectrometer produced by Shanghai Fuxiang Optics Co., Ltd., with a wavelength range of 200-1100 nm, which decomposes light into spectral components and measures their intensity distribution; FIB-M-600-NIR Y-type fiber produced by Shanghai Fuxiang Optics Co., Ltd., which is used as a fiber optic assembly with a single detection end and two branches (used for incident light and reflected light transmission respectively); computer used as the data processing and analysis center of the spectrometer; SLR fiber optic sensor as the core sensing element, which is a fiber optic adapter prepared according to the method of this invention with a nano-gold ball array loaded on the fiber end face.

[0042] (2) The test operation steps are as follows: 1) Connecting the equipment: Connect the spectrometer to the computer and connect it to the light source and fiber optic sensor via a Y-type optical fiber; 2) Sample preparation: Select appropriate samples and sample preparation methods according to experimental requirements; 3) Adjust parameters: Adjust the parameters of the light source and spectrometer, such as the brightness of the light source and the integration time of the spectrometer; 4) Sample testing: Place the prepared sample in the sample cell and immerse the SLR fiber optic sensor in the sample to be tested (or directly apply a small amount of sample to the end face of the sensor). 5) Data Acquisition: Start the light source and spectrometer to acquire reflectance spectral data; 6) Data analysis: Analyze spectral data on a computer, determine the SLR peak position, and calculate the shift.

[0043] Example 4 The SLR fiber optic sensor obtained in Example 1 was used for bulk refractive index sensitivity testing. The specific steps are as follows: Connect the fiber optic sensor to... Figure 3 In the test system shown, the sensor is placed in NaCl solutions with different refractive indices. Before changing the test solution, the sensor is rinsed three times with deionized water. The concentration of the test solution is measured sequentially from low to high, and the reflectance spectrum is obtained. Figure 4 As shown in (a), the SLR peak position gradually redshifts with increasing refractive index, and the two show a linear relationship. The curve of refractive index versus peak position change is shown in Figure 1. Figure 4 As shown in (b), the sensitivity of the sensor is 323 nm / RIU.

[0044] Using the same method, the SLR fiber sensors obtained in Examples 2 and 3 were used for bulk refractive index sensitivity testing, and the sensitivities of the sensors were found to be 338 nm / RIU and 302 nm / RIU, respectively.

[0045] Example 5 The SLR fiber optic sensor obtained in Example 1 was used for bulk refractive index sensitivity testing. The specific steps are as follows: Connect the fiber optic sensor to... Figure 3 In the test system shown, refer to Figure 5 The experiment was conducted according to the following procedure: Step 1: Immerse the SLR fiber optic sensor in deionized water to measure the initial position of the SLR peak.

[0046] Step 2: Immerse the SLR fiber optic sensor in 10 μM SH-T16 solution of 50 mM Tris-HCl (pH 8.0), 0.5 M NaCl, and 5 mM MgCl2. In a buffer solution, under suitable conditions, SH-T16 is incubated for 18-24 hours to allow it to self-assemble and fix onto the surface of the gold ball array via Au-S bonds.

[0047] Step 3: After the sensor is modified, rinse the sensor three times with the above buffer solution to remove unbound SH-T16, and then immerse it in deionized water to measure the position of the SLR peak at this time.

[0048] Step 4: Immerse the modified sensor in 1 nM A16 solution of 50 mM Tris-HCl (pH 7.4), 0.3 M NaCl, and 5 mM MgCl2. In the buffer solution, the target molecule A16 is enriched on the sensor surface through base pairing.

[0049] Step 5: After base pairing, rinse the sensor three times with the above buffer solution to remove unbound A16. Then immerse the SLR fiber sensor in deionized water to measure the position of the SLR peak at this time.

[0050] Step 6: Repeat steps 4 and 5, and detect different concentrations of A16 from low to high, and record the position of the SLR peak.

[0051] Figure 6 (a) shows the changes in the reflectance spectrum (red shift of peak position) of the sensor in 20 nM A16 solution at different reaction times. Figure 6 (b) shows the trend of SLR peak shift (Δλ) with increasing A16 concentration. The results show that Δλ increases with increasing A16 concentration; when the A16 concentration reaches 200 nM, the SLR peak shift no longer increases significantly because the pairing of probe T16 and target A16 reaches saturation.

[0052] While the best example of the invention is shown above, it is not intended to limit the invention. The refractive index of the environment can be resolved by changing the substrate, the material of the metal metasurface, the period, and the structural dimensions; similar sensing applications can be achieved by changing the types of biomolecules.

[0053] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A high-sensitivity SLR fiber optic sensor, characterized in that, The fiber optic sensor has a single-layer hexagonal non-close-packed gold nanosphere array distributed on the end face of the fiber optic adapter. The center distance between adjacent gold nanospheres is 480-520 nm, and the diameter of the gold nanospheres is 190-210 nm.

2. A method for fabricating a high-sensitivity SLR fiber optic sensor as described in claim 1, characterized in that, Includes the following steps: S1. A hexagonal non-close-packed gold nanosphere array is prepared on a single-crystal silicon wafer. An acetone solution with a mass fraction of 10-30% polymethyl methacrylate (PMMA) is spin-coated onto the gold nanosphere array and the single-crystal silicon wafer. The spin-coating speed is 3000-10000 rpm and the spin-coating time is 10-60 s. The acetone is allowed to evaporate and coat the gold nanosphere array with a PMMA film. S2. The nano-gold ball array coated with PMMA film is placed in an oven at 180-200 ℃ and heated for 1-5 hours, and then immersed in 1 M KOH solution at 30-50 ℃ for 3-10 hours. The PMMA film coated with nano-gold ball array is peeled off from the flat substrate and is called PMMA-Au composite film. S3. Clean and dry the end face of the fiber optic adapter, lay the PMMA-Au composite film flat on the end face of the fiber optic adapter, and then place it in an oven at 180-200 ℃ for 2-5 hours. Then use acetone to dissolve and remove PMMA to obtain a high-sensitivity SLR fiber optic sensor loaded with a nano-gold ball array on the fiber optic adapter.

3. An application of the high-sensitivity SLR fiber optic sensor of claim 1 in the specific detection of biomolecules.

4. The application of the high-sensitivity SLR fiber optic sensor according to claim 3 in the specific detection of biomolecules, characterized in that, Includes the following steps: S21. Sensor functionalization: A DNA probe solution with thiol-modified ends is reacted with a nano-gold ball array at the sensor end, so that the DNA probe is fixed to the surface of the gold ball through Au-S bonds, and the functionalized sensor is obtained. S22. Specific binding: The test solution containing the target molecule is brought into contact with the functionalized sensor, so that the target molecule specifically binds to the immobilized DNA probe, thereby enriching it on the sensor surface. S23. Signal detection: The shift signal of the surface lattice resonance spectral peak is detected by a detection system to achieve qualitative or quantitative analysis of the target molecule; wherein the shift of the spectral peak is caused by the local refractive index change caused by the binding of the target molecule.

5. The application of the high-sensitivity SLR fiber optic sensor according to claim 4 in the specific detection of biomolecules, characterized in that, The detection system described in step S23 includes: a Y-shaped optical fiber, the common end of which is connected to an SLR optical fiber sensor, and the two branches are respectively connected to a light source and a spectrometer; the light emitted by the light source is transmitted through the Y-shaped optical fiber to the SLR optical fiber sensor for reflection, and the reflected light is transmitted through the optical fiber to the spectrometer; the SLR peak position information is obtained by reading and analyzing the reflected spectral signal collected by the spectrometer through a computer connected to the spectrometer.

6. The application of the high-sensitivity SLR fiber optic sensor according to claim 5 in the specific detection of biomolecules, characterized in that, The Y-type optical fiber is a FIB-M-600-NIR optical fiber manufactured by Shanghai Fuxiang Optics Co., Ltd.; the spectrometer is a PG2000-Pro fiber optic spectrometer manufactured by Shanghai Fuxiang Optics Co., Ltd., with a wavelength range of 200-1100 nm; and the light source is an HL2000 halogen light source manufactured by Shanghai Fuxiang Optics Co., Ltd.

7. The application of the high-sensitivity SLR fiber optic sensor according to claim 4 in the specific detection of biomolecules, characterized in that, When this high-sensitivity SLR fiber optic sensor is used for bulk refractive index detection, the sensor directly contacts the test solution. Before changing the test solution, the sensor is rinsed multiple times with deionized water. The concentration of the test solution is detected sequentially from low to high. Multiple detections yield a linear relationship between the SLR peak shift and the refractive index of the test solution.

8. The application of the high-sensitivity SLR fiber optic sensor according to claim 4 in the specific detection of biomolecules, characterized in that, The DNA probe solution is a buffer solution containing 1-50 μM thiol-modified DNA probes. The buffer solution consists of: 20-100 mM Tris-HCl, 0.4-0.7 M NaCl, and 1-10 mM MgCl₂. The pH value is 8.

0.

9. The application of the high-sensitivity SLR fiber optic sensor according to claim 4 or 8 in the specific detection of biomolecules, characterized in that, The test solution is a buffer solution containing 1-200 nM target DNA. The buffer solution consists of: 20-100 mM Tris-HCl, 0.3-0.6 M NaCl, and 1-10 mM MgCl₂. The pH value is 7.

4.

10. The application of the high-sensitivity SLR fiber optic sensor according to claim 4 in the specific detection of biomolecules, characterized in that, In step S21, the reaction is carried out at room temperature for 10-30 hours to achieve the contact reaction; in step S22, the reaction is carried out at room temperature for 5-10 hours to achieve the specific binding.

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