Multiple metal ion concentration optical fiber sensor, preparation method and sensing device thereof

Abstract

The present invention discloses a multiple metal ion concentration optical fiber sensor. By forming a detection surface corresponding to the sensing core on the outer wall of the optical fiber substrate, the metal film and heavy metal imprinted nanomaterial on each detection surface jointly form a sensing area. In the transmission spectrum, different metal coatings can excite different plasma resonance wavelengths. The specific metal ions in the solution will change the effective refractive index of the sensing layer, so that the information of the specific metal ions in the corresponding multiple sensing areas can be obtained through the change of the sensor output spectrum wavelength. The multiple metal ion concentration sensor of the present invention has a compact structure and only requires one optical fiber structure to realize the synchronous measurement of multiple metal ion concentrations. It also has the characteristics of strong specificity, high stability, and anti-electromagnetic interference. The present invention also proposes a method for preparing a multiple metal ion concentration optical fiber sensor and an optical fiber sensing device.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal ion concentration detection, and in particular to a multiple metal ion concentration optical fiber sensor, a preparation method thereof and a sensing device. Background Art

[0002] In recent years, fiber optic surface plasmon resonance (SPR) sensors based on surface plasmon resonance technology have broad application prospects in the fields of biological and chemical detection due to their high sensitivity, oxidation resistance, and strong versatility. Heavy metal ion concentration detection is one of the important application areas of fiber optic SPR sensors. This method usually adds a layer of functional film on the surface of the sensor metal film layer through chemical growth, physical deposition or adsorption. These functionalized film layers can react chemically with the heavy metal ions in the liquid to be tested or bind to complementary binding sites, thereby changing the dielectric constant or effective refractive index of the sensing film layer, thereby causing the SPR resonance wavelength to drift. The refractive index change information is obtained by analyzing the drift of the resonance wavelength, and then the type, concentration, content and other information of the heavy metal ions in the liquid to be tested are analyzed.

[0003] At present, SPR-based fiber optic sensors for single heavy metal ion detection are relatively common. However, in aquatic environments, there is often a need for multi-parameter heavy metal ion sensing. Therefore, the research on SPR-based fiber optic sensors for multiple heavy metal ions has received widespread attention and research. For example, researchers connected two SPR sensing areas in series on the sensing device and received the sensing spectra of the two sensing areas on the spectrometer, but this method is not easy to eliminate the interference between the first resonance spectrum and the second SPR sensing area. Therefore, in order to solve this problem, the researchers divided the excitation light source into two beams and connected the two SPR sensing areas in parallel. This method can avoid the interference between the first resonance spectrum and the second SPR sensing area, but the structure of the sensor is not compact. Summary of the invention

[0004] In order to solve the technical problems existing in the background technology, the present invention proposes a multiple metal ion concentration optical fiber sensor, a preparation method thereof and a sensing device.

[0005] The present invention provides a multiple metal ion concentration optical fiber sensor, comprising: an optical fiber substrate;

[0006] The outer wall of the optical fiber substrate has multiple detection surfaces, and the detection surfaces are provided with metal films and heavy metal imprinted nanomaterials coated on the metal films. The metal film and heavy metal imprinted nanomaterials on each detection surface together form a sensing area; the interior of the optical fiber substrate has a compensation fiber core and multiple sensing fiber cores, each sensing fiber core is arranged corresponding to a detection surface, and the outer wall of the sensing fiber core is in contact with the metal film on the corresponding detection surface.

[0007] Preferably, the compensation fiber core is located in the middle of the optical fiber matrix, and the plurality of sensing fiber cores are evenly distributed around the compensation fiber core.

[0008] Preferably, the plurality of detection surfaces are evenly distributed along the circumference around the compensation fiber core.

[0009] Preferably, the compensating fiber core has a grating therein.

[0010] Preferably, the detection surface is a plane extending parallel to the compensation fiber core.

[0011] Preferably, the metal film is one of a copper film, a silver film and a gold film.

[0012] In the present invention, the proposed multiple metal ion concentration optical fiber sensor forms a detection surface corresponding to the sensing core on the outer wall of the optical fiber substrate, and the metal film and heavy metal imprinted nanomaterial on each detection surface jointly form a sensing area. In the transmission spectrum, different metal coatings can excite different plasma resonance wavelengths, and the specific metal ions in the solution will change the effective refractive index of the sensing layer, so that the information of the specific metal ions in the corresponding multiple sensing areas can be obtained through the change of the sensor output spectrum wavelength. The multiple metal ion concentration sensor of the present invention has a compact structure and can realize the synchronous measurement of multiple metal ion concentrations with only one optical fiber structure, and has the characteristics of strong specificity, high stability, and anti-electromagnetic interference.

[0013] The present invention also provides a method for preparing the above-mentioned multiple metal ion concentration optical fiber sensor, comprising the following steps:

[0014] S1, etching the cladding of a multi-core optical fiber by femtosecond laser, forming a plurality of detection surfaces extending along the outer walls of a plurality of sensing cores on the surface of the multi-core optical fiber;

[0015] S2, directly writing the grating in the compensation core of the multi-core optical fiber by femtosecond laser;

[0016] S3, sputtering to form metal films on multiple detection surfaces of S1;

[0017] S4. Coating heavy metal imprinted nanomaterials on the surface of each metal film in S3.

[0018] In the present invention, the method for preparing the multiple metal ion concentration optical fiber sensor is simple in steps, and the prepared optical fiber sensor has a simple structure.

[0019] The present invention also provides a multiple metal ion concentration optical fiber sensing device, comprising the multiple metal ion concentration optical fiber sensor mentioned above.

[0020] Preferably, it also includes a laser and a spectrometer, the laser is used to emit laser light to the compensation fiber core and the sensing fiber core, and the spectrometer is used to acquire laser signals passing through the compensation fiber core and the sensing fiber core.

[0021] In the present invention, the proposed multiple metal ion concentration optical fiber sensing device has a technical effect similar to that of the above-mentioned optical fiber sensor, so it is not described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic structural diagram of an implementation of a multiple metal ion concentration optical fiber sensor proposed by the present invention.

[0023] Figure 2 This is a schematic structural diagram of an implementation of a multiple metal ion concentration optical fiber sensing device proposed by the present invention.

[0024] Figure 3 This is a schematic diagram of the optical path of an implementation of a multiple metal ion concentration optical fiber sensor proposed by the present invention. DETAILED DESCRIPTION

[0025] like Figures 1 to 3 As shown, Figure 1 This is a schematic structural diagram of an embodiment of a multiple metal ion concentration optical fiber sensor proposed by the present invention. Figure 2 This is a schematic structural diagram of an embodiment of a multiple metal ion concentration optical fiber sensing device proposed by the present invention. Figure 3 This is a schematic diagram of the optical path of an implementation of a multiple metal ion concentration optical fiber sensor proposed by the present invention.

[0026] Reference Figure 1 , a multiple metal ion concentration optical fiber sensor proposed by the present invention comprises: an optical fiber substrate 1;

[0027] The outer wall of the optical fiber matrix 1 has multiple detection surfaces, and the detection surfaces are provided with metal films 2 and heavy metal imprinted nanomaterials 5 coated on the metal films 2. The metal film 2 and heavy metal imprinted nanomaterials 5 on each detection surface together form a sensing area; the optical fiber matrix 1 has a compensation fiber core 3 and multiple sensing fiber cores 4 inside, and each sensing fiber core 4 is arranged corresponding to a detection surface, and the outer wall of the sensing fiber core 4 is in contact with the metal film 2 on the corresponding detection surface.

[0028] To explain the working mode of the optical fiber sensor of this embodiment in detail, refer to Figure 2 This embodiment also provides a multiple metal ion concentration optical fiber sensing device, including the multiple metal ion concentration optical fiber sensor described above. Specifically, it also includes a laser 20 and a spectrometer 30, the laser 20 is used to emit laser light to the compensation fiber core 3 and the sensing fiber core 4, and the spectrometer 30 is used to obtain laser signals passing through the compensation fiber core 3 and the sensing fiber core 4.

[0029] In the specific working process of the multiple metal ion concentration optical fiber sensor device of this embodiment, the optical fiber sensor is placed in the liquid to be tested, so that the sensing area on the surface of the optical fiber substrate is exposed to the working environment to be tested, and the laser emitted by the laser is coupled to the optical fiber and transmitted in multiple fiber cores. When the optical fiber sensor is immersed in the solution to be tested, the metal ions in the solution will bind to the complementary binding sites in the metal ion imprinted nanomaterial layer of the corresponding sensing area, thereby changing the effective refractive index of the sensing area. Therefore, different metal coatings excite different plasma resonance wavelengths that selectively drift, and the information of specific metal ions can be obtained by monitoring the three wavelength information of the transmission spectrum.

[0030] The optical fiber sensor of this embodiment is based on the surface plasma generated at the interface between metal and dielectric to monitor heavy metal ions in liquid. When the light propagating in the optical fiber core is totally reflected at the interface between the optical fiber and the metal, an exponentially decaying evanescent field is generated. The wave vector of the evanescent wave can be expressed as:

[0031]

[0032] Where ε0 is the dielectric constant of the fiber cladding, θ is the angle of the incident light, and ω is the frequency of the incident light. According to the Maxwell equations of the plasma non-radiative transient electromagnetic field corresponding to the boundary conditions, the wave vector of the surface plasma wave is

[0033]

[0034] Where ε1 is the dielectric constant of the metal film and ε2 is the dielectric constant of the surrounding medium on the metal film. When the real part of the surface plasmon wave vector matches the evanescent wave vector, that is, k x = real part (k sp), plasma resonance occurs and propagates lossily along the fiber cladding-metal interface. The resonance wavelength of the plasma resonance changes with the change of the refractive index around the metal layer. The optical fiber sensor of this embodiment coats a metal film on the potential field, and then coats a nanomaterial film layer that is sensitive to metal ions around the exposed metal layer. Due to the adsorption of metal ions by the nanomaterial film layer, the change in the refractive index of the nanomaterial film layer will cause a change in the resonance wavelength. By detecting the characteristics of the resonance wavelength, the concentration of metal ions can be detected. Therefore, the concentration of metal ions can be detected by detecting the changes in the optical path in the optical fiber through the spectrometer.

[0035] When detecting multiple heavy metal ion concentrations at the same time, the metal film coatings of multiple different sensing areas respectively excite different plasma resonance wavelengths, and the transmitted light is finally coupled to the spectrometer through the core of the four-core optical fiber. In order to facilitate understanding of the process of exciting the plasma resonance wavelength, the sensing area coated with a gold film coating is taken as an example. The sensing area coated with a gold film is close to the sensing fiber core. When the light propagating in the fiber core is totally reflected at the interface between the fiber and the metal, an exponentially decaying evanescent field is generated, so the gold film is excited to produce a plasma resonance wavelength. Similarly, the sensing areas near the other multiple sensing fiber cores are respectively excited to produce different plasma resonance wavelengths. In addition, the compensation fiber core is used for signal compensation. The optical paths of multiple fiber cores are independent and do not interfere with each other. When the sensor is immersed in the solution to be tested, the corresponding metal ion imprinted nanomaterial layer adsorbs specific metal ions in the solution, thereby changing the effective refractive index of the sensing layer. Therefore, the corresponding plasma resonance spectrum drifts. By using the linear function of the multiple wavelengths in the spectrum and the corresponding heavy metal ion concentrations to achieve demodulation, the information of specific metal ions can be obtained.

[0036] In this embodiment, the proposed multiple metal ion concentration optical fiber sensor and sensing device form a detection surface corresponding to the sensing core on the outer wall of the optical fiber substrate, and the metal film and heavy metal imprinted nanomaterial on each detection surface jointly form a sensing area. In the transmission spectrum, different metal coatings can excite different plasma resonance wavelengths, and the specific metal ions in the solution will change the effective refractive index of the sensing layer, so that the information of the specific metal ions in the corresponding multiple sensing areas can be obtained through the change of the sensor output spectrum wavelength. The multiple metal ion concentration sensor of the present invention has a compact structure and can realize the synchronous measurement of multiple metal ion concentrations with only one optical fiber structure. It also has the characteristics of strong specificity, high stability, and anti-electromagnetic interference.

[0037] In a specific embodiment of the optical fiber sensor, the compensation core 3 is located in the middle of the optical fiber matrix 1, and a plurality of sensing cores 4 are evenly distributed around the compensation core 3. Accordingly, a plurality of detection surfaces are evenly distributed along the circumference around the compensation core 3. The detection surface can be designed as a plane extending parallel to the compensation core 3.

[0038] In a specific implementation of the compensation core, a grating is provided in the compensation core 3 for temperature compensation of the optical signal to solve the problem of temperature crosstalk.

[0039] In the specific selection of the metal film, the metal film 2 is one of a copper film, a silver film and a gold film. Accordingly, the imprinted nanomaterial is selected according to the detection requirements. 2+ , Cu 2+ 、Cd 3+ etc. imprinted nanomaterials.

[0040] In other specific implementations, this embodiment further provides a method for preparing the above-mentioned multiple metal ion concentration optical fiber sensor, comprising the following steps:

[0041] S1, etching the cladding of the multi-core optical fiber by femtosecond laser, forming a plurality of detection surfaces extending along the outer walls of the plurality of sensing cores 4 on the surface of the multi-core optical fiber;

[0042] S2, directly writing a grating in the compensation core 3 of the multi-core optical fiber by using a femtosecond laser;

[0043] S3, sputtering to form metal films 2 on the multiple detection surfaces of S1;

[0044] S4. Coating the heavy metal imprinted nanomaterial on the surface of each metal film 2 in S3.

[0045] Taking the three-parameter heavy metal ion concentration detection as an example, the multiple metal ion concentration optical fiber sensor, its preparation method and sensing device of this embodiment are described in detail below.

[0046] This embodiment proposes a multiple metal ion concentration optical fiber sensor for simultaneous detection of three-parameter heavy metal ion concentrations, comprising: a four-core optical fiber, wherein the middle core of the four-core optical fiber is used as a compensation core, and the three offset cores are used as sensing cores respectively. The outer wall of the four-core optical fiber has three detection surfaces, respectively having copper, silver and gold films and Pb 2+ , Cu 2+ 、Cd 3+ Imprinted nanomaterials.

[0047] The preparation method of the multiple metal ion concentration optical fiber sensor of this embodiment comprises the following steps:

[0048] S1. First, place the four-core optical fiber on the optical fiber fixture of the three-dimensional operating platform, and adjust the optical fiber fixture so that the focus of the femtosecond laser beam is 0 cm away from the highest point of the outer surface of the cladding of the four-core optical fiber.

[0049] S2. Under the preset scanning speed, scanning direction, scanning time and laser power, three planes with a length of 360 μm and a width of 120 μm are formed on the outer surface of the cladding of the four-core optical fiber, wherein the three planes are 0 cm away from the cladding surface of the nearest core.

[0050] S3. Focus the femtosecond laser on the middle core of the four-core optical fiber to directly write the grating.

[0051] S4. Then, appropriate sputtering conditions are set to use an ion sputtering apparatus to plate copper, silver and gold films on three planes of the surface of the cladding of the four-core optical fiber.

[0052] S5. Finally, Pb is coated on the surface of copper film, silver film and gold film respectively. 2+ , Cu 2+ 、Cd 3+ The imprinted nanomaterials are used to obtain a structure that is an optical fiber sensor for simultaneous sensing of three-parameter heavy metal ion concentrations. 2+ , Cu 2+ 、Cd 3+ The imprinted nanomaterials should be completely exposed to the environment, which is more conducive to causing the optical fiber sensor to sense specific heavy metal ions.

[0053] Reference Figure 1 The present invention proposes an optical fiber sensor that can be used for simultaneous sensing of three-parameter heavy metal ion concentrations. The three views are respectively a top view, a side view and a front view, wherein the front view is a longitudinal cross-sectional view of a four-core optical fiber. The core diameter of the optical fiber sensor is 10 μm, and the surface of its cladding has three planes with a length of 360 μm and a width of 120 μm as detection surfaces. Each detection surface is coated with a copper film, a silver film and a gold film, and the surfaces of the copper film, the silver film and the gold film are coated with Pb 2 + , Cu 2+ 、Cd 3+ Imprinted nanomaterials. The three detection surfaces are symmetrically distributed, and the shortest distance between the three side fiber cores and the nearest sensing area is 0 mm, which is conducive to increasing the potential field and facilitating the excitation of SPR.

[0054] Reference Figure 2When a fiber optic sensor that can be used for simultaneous sensing of three-parameter heavy metal ion concentrations is used for specific detection of heavy metal ions in this embodiment, the fiber optic sensor is exposed to the working environment to be tested. A white light source with a wavelength range of 200-1000nm is used as an excitation light source, and the white light source is coupled to the core of a four-core optical fiber through a customized four-core coupling head, so that the light is only transmitted inside the four cores. The white light source is transmitted to the sensor through the core of the four-core optical fiber. The copper film, silver film, and gold film coatings in the sensing area respectively excite different plasma resonance wavelengths, and finally the transmitted light is coupled to the spectrometer through the core of the four-core optical fiber. The transmission spectrum signal of the optical fiber sensor is received by the spectrometer, and the three wavelengths of the three peaks in the spectrum are respectively compared with Pb 2+ , Cu 2+ 、Cd 3+ The linear function of heavy metal ion concentration enables specific metal ion concentration demodulation.

[0055] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A multiple metal ion concentration optical fiber sensor, characterized in that: include: Optical fiber substrate (1); The outer wall of the optical fiber substrate (1) has a plurality of detection surfaces, the detection surfaces have a metal film (2) and a heavy metal imprinted nanomaterial coated on the metal film (2), and the metal film (2) and the heavy metal imprinted nanomaterial (5) on each detection surface together form a sensing area; the optical fiber substrate (1) has a compensation fiber core (3) and a plurality of sensing fiber cores (4) inside, each sensing fiber core (4) is arranged corresponding to a detection surface, and the outer wall of the sensing fiber core (4) is in contact with the metal film (2) on the corresponding detection surface; The multiple detection surfaces are arranged along the circumference of the optical fiber substrate (1); The detection surface is a plane extending parallel to the compensation fiber core (3).

2. The multiple metal ion concentration optical fiber sensor according to claim 1, characterized in that: The compensation fiber core (3) is located in the middle of the optical fiber matrix (1), and a plurality of sensing fiber cores (4) are evenly distributed around the compensation fiber core (3).

3. The multiple metal ion concentration optical fiber sensor according to claim 1, characterized in that: The compensation fiber core (3) has a grating inside.

4. The multiple metal ion concentration optical fiber sensor according to claim 1, characterized in that: The metal film (2) is one of a copper film, a silver film and a gold film.

5. A method for preparing a multiple metal ion concentration optical fiber sensor according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, etching the cladding of the multi-core optical fiber by femtosecond laser, thereby forming a plurality of detection surfaces extending along the outer walls of the plurality of sensing cores (4) on the surface of the multi-core optical fiber; S2, directly writing a grating in the compensation core (3) of the multi-core optical fiber by using a femtosecond laser; S3, sputtering to form metal films (2) on the multiple detection surfaces of S1; S4. Coating the heavy metal imprinted nanomaterial (5) on the surface of each metal film (2) in S3.

6. A multiple metal ion concentration optical fiber sensing device, characterized in that: It comprises the multiple metal ion concentration optical fiber sensor according to any one of claims 1-4.

7. The multiple metal ion concentration optical fiber sensor device according to claim 6, characterized in that: It also includes a laser (20) and a spectrometer (30), wherein the laser (20) is used to emit laser light to the compensation fiber core (3) and the sensing fiber core (4), and the spectrometer (30) is used to obtain laser signals passing through the compensation fiber core (3) and the sensing fiber core (4).

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