Vanadium nitride-based sensitized optical fiber SPR sensor

Abstract

This utility model relates to the field of biosensor technology and discloses a vanadium nitride-enhanced fiber optic SPR sensor. The vanadium nitride-enhanced fiber optic SPR sensor provided includes an optical fiber body with a sensing region formed on the optical fiber body. From the inside to the outside, a gold film layer, a vanadium nitride film layer, and a gold nanoparticle film layer are respectively attached to the surface of the sensing region. By introducing vanadium nanosheets, which have high conductivity, low loss, and high refractive index, a composite structure is formed with noble metal nanoparticles (Au NPs), constructing a "high refractive index medium enhancement-localized surface plasmon resonance synergy" system. This compensates for the energy loss of the metal film, enhances the interaction between the electromagnetic field and the target molecules, and further improves the sensitivity of the sensor.

Description

Technical Field

[0001] This utility model relates to the field of biosensor technology, and in particular to a fiber optic SPR sensor based on vanadium nitride sensitization. Background Technology

[0002] The structure of a fiber optic biosensor mainly consists of a light source, optical fiber, biosensitive element, and signal detection system. Among them, the biosensitive element is the key component of the sensor. Commonly used biosensitive elements include antigens, antibodies, enzymes, and nucleic acids. The analyte interacts selectively with a specific biosensitive element (i.e., specific binding of antigens, antibodies, or receptor ligands; complementary base pairing of nucleic acid molecules; specificity of enzymes to substrates, etc.), and the resulting biochemical information modulates the physical properties of the light transmitted in the optical fiber, such as light intensity, light amplitude, and phase. Therefore, this type of sensor has strong selectivity and high sensitivity, and can save the tedious work of separating and purifying the analyte during the analysis process. Compared with other biosensors, fiber optic biosensors combine the characteristics of fiber optic sensing, specifically: (1) Due to the good insulation and shielding effect of the optical fiber itself, it has strong anti-interference ability and is not affected by the surrounding electromagnetic field. (2) No reference electrode is required, the probe can be miniaturized, and it is easy to operate. (3) Remote measurement can be realized, and real-time, online, and dynamic detection can be performed. (4) Fast response speed and high sensitivity, and it is widely used in disease monitoring, drug development, and clinical diagnosis.

[0003] SPR-based biosensors have received increasing attention in the field of biosensing in recent years due to their high sensitivity, good biocompatibility, flexible orientation, stability, and strong anti-interference ability.

[0004] However, current fiber optic SPR biosensors still have some problems. They are limited in detecting ultra-low concentrations of analytes and weak intermolecular interactions, and have the disadvantage of low sensitivity. Therefore, it is still necessary to improve the sensitivity and quality factor of SPR sensors. Utility Model Content

[0005] The purpose of this invention is to provide a fiber optic SPR sensor based on vanadium nitride sensitization to solve the problem of low sensitivity mentioned in the background art.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a fiber optic SPR sensor based on vanadium nitride sensitization, comprising a fiber optic SPR sensor disposed on a fiber optic body, wherein a sensing region is formed on the surface of the fiber optic SPR sensor, and the two ends of the sensing region are respectively a first tapered fiber transition region and a second tapered fiber transition region, wherein the end of the first tapered fiber transition region away from the sensing region is connected to a first tapered fiber conventional region, and the end of the second tapered fiber transition region away from the sensing region is connected to a second tapered fiber conventional region, wherein a gold film layer is disposed on the sensing region, the gold film having a thickness of 45nm to 55nm, and a vanadium nitride film layer is attached to the gold film layer, the vanadium nitride film layer having a thickness of 25nm, the vanadium nitride film layer being disposed on the side of the gold film layer opposite to the fiber optic body, and a gold nanoparticle film layer is disposed on the vanadium nitride film layer, the gold nanoparticle film layer being formed by a composite of VN nanosheets and noble metal nanoparticles Au NPs, wherein the VN nanosheets, as a high refractive index dielectric layer, constitute a synergistic enhancement system with the noble metal nanoparticles.

[0007] Preferably, the gold nanoparticle film has a three-dimensional porous network structure with a porosity of 60%-70%, forming a through-type molecular diffusion channel.

[0008] Preferably, the three-dimensional porous network structure includes a gradient pore structure, with the pore size near the fiber optic SPR sensor side being 50-100 nm and the pore size on the surface side being 10-30 nm.

[0009] Preferably, the VN nanosheets and metal nanoparticles are composited in the form of a heterojunction, and a Schottky junction is formed at the final interface with a barrier height ≤0.2 eV, which promotes hot electron injection. The distance between N and AUNPS is 1-3 nm, maximizing the realization of plasma-exciton coupling.

[0010] Preferably, the carrier mobility of the VN nanosheets is 18000-22000 cm⁻¹. 2 / (V·s), conductivity >1x10 6 S / m is key to reducing SPR ohmic loss, plasmon lifetime >15fs to support efficient LSPR coupling, imaginary part of dielectric function <0.5, wavelength 632nm.

[0011] Preferably, the conductivity of the VN nanosheets is combined with the SPR optical signal of AuNPs to form a photoelectric dual-mode detection module.

[0012] Preferably, the lengths of the first tapered fiber transition region and the second tapered fiber transition region are both 0.4cm to 0.6cm, and the total length of the sensing area is 0.9cm to 1.1cm.

[0013] Preferably, the sensing area includes a fiber core and a cladding, wherein the fiber core has a diameter of 9 μm and the vertical thickness of the cladding is 0.9 μm to 1.1 μm.

[0014] Preferably, an optical fiber mounting platform is provided below the optical fiber SPR sensor, and a broadband light source and a broadband spectrometer are respectively connected to the two ends of the optical fiber SPR sensor.

[0015] The beneficial effects of this utility model are:

[0016] In this invention, VN nanosheets are introduced, which, due to their low-loss and high-refractive-index properties, form a composite structure with noble metal nanoparticles Au NPs to construct a "high-refractive-index medium enhancement-localized surface plasmon resonance synergy" system. This compensates for the energy loss of the metal film, enhances the interaction between the electromagnetic field and the target molecules, and further improves the sensitivity of the sensor. The high carrier mobility, high light absorption, and excellent optical properties of the VN nanosheets significantly improve the surface electric field intensity of the gold film, thereby enhancing the sensitivity of the sensor. Attached Figure Description

[0017] Figure 1 This is a structural diagram of the main structure of a fiber optic SPR sensor based on vanadium nitride sensitization proposed in this utility model.

[0018] Figure 2 This is a schematic diagram of the cross-sectional layered structure of a fiber optic SPR sensor based on vanadium nitride sensitization proposed in this utility model.

[0019] Figure 3 This is a schematic structural diagram of a connection system for a vanadium nitride-enhanced fiber optic SPR sensor proposed in this utility model.

[0020] Figure 4 The sensitivity linearity diagram of a fiber optic SPR sensor based on vanadium nitride enhancement proposed in this utility model is shown.

[0021] In the figure: 110, fiber optic SPR sensor; 111, conventional region of the first tapered fiber; 112, transition region of the first tapered fiber; 113, sensing area; 114, transition region of the second tapered fiber; 115, conventional region of the second tapered fiber; 120, gold film layer; 130, vanadium nitride film layer; 140, gold nanoparticle film layer; 200, broadband light source; 300, broadband spectrometer; 400, fiber optic mounting platform. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0023] Reference Figure 1-4 A vanadium nitride-enhanced fiber optic SPR sensor includes a fiber optic SPR sensor 110 disposed on a fiber optic body. The sensor 110 is characterized by a sensing region 113 formed on its surface. The two ends of the sensing region 113 are a first tapered fiber transition region 112 and a second tapered fiber transition region 114, respectively. The end of the first tapered fiber transition region 112 furthest from the sensing region 113 is connected to a first tapered fiber conventional region 111. The end of the second tapered fiber transition region 114 furthest from the sensing region 113 is connected to a first tapered fiber conventional region 111. One end of the sensing region 113 is connected to the conventional region 115 of the second tapered optical fiber. A gold film layer 120 is disposed on the sensing region 113, with a thickness of 45nm to 55nm. A vanadium nitride film layer 130 is attached to the gold film layer 120, with a thickness of 25nm. The vanadium nitride film layer 130 is disposed on the side of the gold film layer 120 away from the optical fiber body. A gold nanoparticle film layer 140 is disposed on the vanadium nitride film layer 130. The gold nanoparticle film layer 140 is formed by combining VN nanosheets and noble metal nanoparticles Au NPs. The VN nanosheets serve as a high refractive index medium layer and form a synergistic enhancement system with the noble metal nanoparticles.

[0024] By introducing VN nanosheets, which possess low-loss and high-refractive-index properties, and forming a composite structure with noble metal nanoparticles Au NPs, a "high-refractive-index medium enhancement-local surface plasmon resonance synergy" system is constructed. This system compensates for the energy loss of the metal film, enhances the interaction between the electromagnetic field and the target molecules, and further improves the sensitivity of the sensor.

[0025] Specifically, in this embodiment, the gold nanoparticle film 140 has a three-dimensional porous network structure with a porosity of 60%-70%, forming a through-type molecular diffusion channel. The three-dimensional porous network structure provides a three-dimensional diffusion path, which is conducive to improving the molecular diffusion rate, thereby increasing the number of target molecules adsorbed per unit time, thereby improving the rate of change of the resonance signal, thus shortening the response time and accelerating the transmission of target molecules to the sensing interface.

[0026] Specifically, in this embodiment, the three-dimensional porous network structure includes a gradient pore structure. The pore size near the fiber optic SPR sensor 110 is 50-100 nm, and the pore size on the surface side is 10-30 nm. The pores with a diameter of 50-100 nm near the fiber optic SPR sensor 110 help accelerate the diffusion of molecules into the sensing area, while the pores with a diameter of 10-30 nm on the surface can increase the specific surface area and improve the molecular adsorption efficiency. At the same time, this structure can balance the diffusion rate and the trapping capacity, reducing the problems of clogging or non-specific adsorption.

[0027] Specifically, in this embodiment, VN nanosheets and metal nanoparticles are combined in the form of a heterojunction, and a Schottky junction is formed at the final interface with a barrier height of ≤0.2 eV, which promotes hot electron injection. The distance between N and AUNPS is 1-3 nm, thereby maximizing the realization of plasma-exciton coupling.

[0028] Specifically, in this embodiment, the carrier mobility of the VN nanosheets is 18000-22000 cm⁻¹. 2 / (V·s), conductivity >1x10 6 S / m is key to reducing SPR ohmic loss; plasmon lifetime >15 fs to support efficient LSPR coupling; imaginary part of dielectric function <0.5; 632 nm wavelength, thereby reducing optical absorption loss.

[0029] Specifically, in this embodiment, the conductivity of VN nanosheets is combined with the SPR optical signal of AuNPs to form a photoelectric dual-mode detection module. Through a signal fusion processor, it is configured to perform weighted analysis of optical and electrical signals. The high conductivity of VN is used to monitor the change of interface charge in real time. By complementing the electrical signal and the SPR optical signal, the adsorption of target molecules and non-specific interference can be distinguished, thereby improving the detection specificity.

[0030] Specifically, in this embodiment, the lengths of the first tapered fiber transition region 112 and the second tapered fiber transition region 114 are both 0.4cm to 0.6cm, and the total length of the sensing region 113 is 0.9cm to 1.1cm.

[0031] Specifically, in this embodiment, the sensing area 113 includes a fiber core and a cladding. The diameter of the fiber core is 9 μm, and the vertical thickness of the cladding is 0.9 μm to 1.1 μm.

[0032] Specifically, in this embodiment, an optical fiber mounting platform 400 is provided below the optical fiber SPR sensor 110, and a broadband light source 200 and a broadband spectrometer 300 are respectively connected to both ends of the optical fiber SPR sensor 110. By integrating the optical fiber SPR sensor 110, the broadband light source 200, and the broadband spectrometer 300 into one system, photoelectric detection and system integration technology is formed, thereby realizing high-precision detection of changes in the refractive index of the external environment.

[0033] Specifically, the fabrication method of the aforementioned fiber optic SPR sensor includes the following steps:

[0034] (1) Fabrication of the tapered fiber body: The tapered fiber is drawn from single-mode fiber. The lengths of the first tapered fiber transition region 112 and the second tapered fiber transition region 114 are both 0.4 cm to 0.6 cm. The length of the tapered fiber sensing region 113 is 0.9 cm to 1.1 cm, and the core diameter is 9 μm. It is preferable that the length of the tapered fiber sensing region 113 is 1 cm, and it is preferable that the lengths of the first tapered fiber transition region 112 and the second tapered fiber transition region 114 are both 0.5 cm. The sensing region 113 of the tapered fiber is then polished to make the tapered fiber sensing region 113 a regular hexagonal structure with a core diameter of 9 μm and a cladding vertical thickness of 0.9 μm to 1.1 μm.

[0035] (2) Gold plating: The prepared sensing area 113 fiber optic sensor is placed in a vacuum ion beam sputtering instrument, and a gold film is deposited on the surface of the sensing area 113. Based on experience, the current of the vacuum ion beam sputtering instrument is 8mA, the time is 80 seconds, and the thickness of the gold film 120 is 50nm.

[0036] (3) Fixing the vanadium nitride film: Preparation work is required before coating the vanadium nitride nanosheet dispersion. First, dilute 50 ml of 4% glacial acetic acid solution with deionized water. Weigh 500 mg of chitosan powder and pour it into the glacial acetic acid solution, stirring continuously for 15 min until the chitosan is completely dissolved. Transfer 3 ml of chitosan solution to a small beaker, and add 3 ml of vanadium nitride nanosheet dispersion to the chitosan solution. Treat the mixture obtained by the above operation with ultrasound for 15 min to obtain a well-distributed gallium selenide nanosheet dispersion. The vanadium nitride dispersion obtained at this time has positive charge characteristics. PSS is a negatively charged anionic polymer that can combine with cationic polymers. Immerse the prepared gold film sensing area 3 in a 5 mg / ml PSS solution for 2 min. After completion, let it stand in the air for 10 min. This makes the surface of the sensing area 113 after sputtering the gold film negatively charged, which can better adsorb the positively charged vanadium nitride nanosheets and form a stable vanadium nitride nanofilm on the gold film. The sensor, treated with PSS solution, was fixed on a lift coating machine with a traction speed of 1500 μm / s and a traction length of 20 mm. A dispersion of vanadium nitride nanosheets with positive charge properties, treated with chitosan, was coated onto sensing region 3 for 20 / 30 / 40 / 50 / 60 cycles, respectively. The thickness of the vanadium nitride nanofilm increased with the number of cycles. After coating, the sensor was left to stand in air for 24 hours. The vanadium nitride film was then fixed onto the surface of the gold film.

[0037] (4) Immobilization of gold nanoparticle film: Before immobilizing gold nanoparticles, the sensor coated with vanadium nitride film was immersed in an ethanol solution of 2 mmol / L p-aminothiophenol for 24 hours, rinsed with distilled water, and dried. Then the sensor was immersed in a gold nanoparticle dispersion for 12 hours and dried. After drying, the gold nanoparticle film was fixed on the surface of the vanadium nitride layer.

[0038] Specifically, the refractive index test of the liquid: The fiber optic SPR sensor 110, based on the novel two-dimensional vanadium nitride nanosheets enhanced by this invention, was placed on the fiber optic mounting platform 400 and sequentially immersed in solutions with refractive indices of 1.33303, 1.34320, 1.35308, 1.36372, and 1.37340, obtaining transmission spectrum curves. Linear fitting of the above measurement results yields the sensor's sensitivity, which is improved compared to traditional fiber optic SPR sensors where the sensing area 113 only has a gold film.

[0039] The above are merely preferred embodiments of this utility model, but the scope of protection of this utility model is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this utility model, based on the technical solution and inventive concept of this utility model, should be included within the scope of protection of this utility model.

Claims

1. A vanadium nitride-enhanced fiber optic SPR sensor, comprising a fiber optic SPR sensor (110) disposed on a fiber optic body, characterized in that: The surface of the fiber optic SPR sensor (110) has a sensing area (113). The two ends of the sensing area (113) are a first tapered fiber transition region (112) and a second tapered fiber transition region (114), respectively. The end of the first tapered fiber transition region (112) away from the sensing area (113) is connected to a first tapered fiber conventional region (111), and the end of the second tapered fiber transition region (114) away from the sensing area (113) is connected to a second tapered fiber conventional region (115). A gold film layer (120) with a thickness of 45 nm to 55 nm is disposed on the sensing area (113). A vanadium nitride film layer (130) with a thickness of 25 nm is attached to the gold film layer (120). The vanadium nitride film layer (130) is disposed on the side of the gold film layer (120) away from the optical fiber body. A gold nanoparticle film layer (140) is disposed on the vanadium nitride film layer (130). The gold nanoparticle film layer (140) is formed by combining VN nanosheets and noble metal nanoparticles Au NPs. The VN nanosheets serve as a high refractive index medium layer and form a synergistic enhancement system with the noble metal nanoparticles.

2. The fiber optic SPR sensor based on vanadium nitride sensitization according to claim 1, characterized in that: The gold nanoparticle film (140) has a three-dimensional porous network structure with a porosity of 60%-70%, forming a through-type molecular diffusion channel.

3. The fiber optic SPR sensor based on vanadium nitride sensitization according to claim 2, characterized in that: The three-dimensional porous network structure includes a gradient pore structure, with the pore size near the fiber optic SPR sensor (110) being 50-100 nm and the pore size on the surface being 10-30 nm.

4. The fiber optic SPR sensor based on vanadium nitride sensitization according to claim 1, characterized in that: The VN nanosheets and metal nanoparticles are composited in the form of a heterojunction, and a Schottky junction is formed at the final interface with a barrier height of ≤0.2 eV and a spacing of 1-3 nm between N and AUNPS.

5. The fiber optic SPR sensor based on vanadium nitride sensitization according to claim 1, characterized in that: The carrier mobility of the VN nanosheets is 18000-22000 cm⁻¹. 2 / (V·s), conductivity >1x10 6 S / m, plasmon lifetime >15fs, imaginary part of dielectric function <0.5, wavelength 632nm.

6. The fiber optic SPR sensor based on vanadium nitride sensitization according to claim 1, characterized in that: The conductivity of the VN nanosheets, combined with the SPR optical signal of AuNPs, forms a photoelectric dual-mode detection module.

7. The fiber optic SPR sensor based on vanadium nitride sensitization according to claim 1, characterized in that: The lengths of the first tapered fiber transition region (112) and the second tapered fiber transition region (114) are both 0.4 cm to 0.6 cm, and the total length of the sensing region (113) is 0.9 cm to 1.1 cm.

8. The fiber optic SPR sensor based on vanadium nitride sensitization according to claim 1, characterized in that: The sensing area (113) includes a fiber core and a cladding, the fiber core having a diameter of 9 μm and the cladding having a vertical thickness of 0.9 μm to 1.1 μm.

9. A fiber optic SPR sensor based on vanadium nitride sensitization according to any one of claims 1-8, characterized in that: The fiber optic SPR sensor (110) is provided with a fiber optic mounting platform (400) below it, and a broadband light source (200) and a broadband spectrometer (300) are respectively connected to the two ends of the fiber optic SPR sensor (110).

Images