A discharge-annealed MXene-based optical fiber water microplastic sensor

Abstract

The application provides a discharge annealing type MXene-based optical fiber water body microplastic sensor, and the discharge annealing type MXene-based optical fiber microplastic sensor is sequentially composed of a broadband light source, a micro optical fiber structure and a spectrometer, the micro optical fiber structure is sequentially connected by a first single-mode optical fiber, a first multi-mode optical fiber, a D-shaped few-mode optical fiber, a second multi-mode optical fiber and a second single-mode optical fiber, and the micro optical fiber structure is a Mach-Zehnder type optical fiber interference structure. A layer of uniform MXene nanosheet particles is adsorbed on the surface of the D-shaped few-mode optical fiber through light adsorption, and is subjected to discharge annealing through a fusion splicer, so that the material properties are improved, and a nanosheet film capable of specifically adsorbing microplastic particles is formed.

Description

Technical Field

[0001] This invention belongs to the field of spectral measurement technology, and more specifically, relates to an optical fiber water microplastic sensor based on discharge-annealed MXene. Background Technology

[0002] Plastics are widely used in daily life and are mainly composed of various organic compounds such as polyethylene (PE), polypropylene (PP), and polystyrene (PS). However, due to their non-degradability, they remain in the environment for a long time. Plastic fragments or microplastics (<5mm) remaining in the environment will further break down into even smaller particles, even reaching the nanoscale, through physical and chemical weathering, making them difficult to observe with the naked eye and ordinary microscopes. Compared to ordinary plastic fragments, the smaller the microplastic pollutants, the larger their surface area, and the greater the harm they cause to the environment and organisms. Numerous facts prove that microplastic particles are ubiquitous, from the air we breathe to the food we eat, from the blood of newborn babies to the feces of adults. These microplastic particles continuously enter natural water bodies and eventually accumulate in the marine environment due to human activities and atmospheric changes. The accumulation of microplastics in the marine environment can cause coral death, biotoxin accumulation, damage to marine fisheries, and ultimately affect normal human life and development.

[0003] Therefore, microplastic particulate pollution in the environment is receiving increasing attention, especially the detection of microplastic pollution in water bodies. Currently, the main methods for detecting microplastic particulate matter in aquatic environments include microscopic imaging-manual counting, Mie scattering, and Fourier transform infrared spectroscopy. These methods require complex sample pretreatment before monitoring, necessitate large-scale equipment, and are not only inefficient, but also lack the required accuracy in some cases. They cannot meet the current needs for building large-scale marine sensor networks and achieving long-term, unmanned, real-time, in-situ monitoring at sea. Summary of the Invention

[0004] This invention aims to solve the aforementioned problems in the detection, composition, and in-situ monitoring methods of microplastic pollutants in water bodies. To this end, an optical fiber water microplastic sensor based on discharge-annealed MXene is proposed.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A fiber optic water microplastic sensor based on discharge-annealed MXene, wherein the fiber optic sensor consists of a spectrometer, a microfiber structure and a broadband light source connected in sequence;

[0007] In a further optimization of this technical solution, the micro-fiber structure is composed of a first single-mode fiber, a first multimode fiber, a D-type few-mode fiber, a second multimode fiber, and a second single-mode fiber connected in sequence. The micro-fiber structure is a Mach-Zehnder type fiber interference structure.

[0008] This technical solution is further optimized, wherein the D-type few-mode optical fiber is polished by a grinding wheel.

[0009] This technical solution is further optimized by providing MXene nanosheet particles on the cross-section of the D-type few-mode fiber.

[0010] This technical solution is further optimized, and the types of MXene include, but are not limited to, Ti3C2, Ti3AlC2, and Ti2C series few-layer nanosheet particles.

[0011] This technical solution is further optimized by uniformly bonding the MXene nanosheet particles to the surface of a D-type few-mode optical fiber using photodeposition.

[0012] This technical solution is further optimized in that the MXene nanosheet particles are annealed by discharge through a welding machine, and the annealing charge is much smaller than the welding charge.

[0013] A fiber optic water microplastic sensing method based on discharge-annealed MXene, the sensing method being based on the fiber optic water microplastic sensor based on discharge-annealed MXene as described above, comprising the following steps:

[0014] The micro-fiber structure is inserted into the water body to be measured. A broadband light source emits signal light, which enters the first multimode fiber through the first single-mode fiber. Due to mode field mismatch, multiple higher-order modes are excited. Subsequently, the higher-order modes enter the core of the D-type few-mode fiber and the liquid microcavity, respectively. The modes in the microcavity are affected by the external environment. After inter-film interference occurs between the modes in the core of the second multimode fiber and the D-type few-mode fiber, the concentration of the analyte is quantitatively demodulated by the spectrometer.

[0015] The above technical solution has the following advantages, unlike existing technologies:

[0016] 1. This invention utilizes D-type few-mode optical fiber to construct an ultra-high sensitivity optical fiber sensor and applies it to the sensing and monitoring of microplastics in water bodies. Unlike traditional microscopic observation and counting and other spectral monitoring methods, this technology has small size, low energy consumption, and can carry out long-term in-situ unmanned monitoring of natural water bodies.

[0017] 2. This invention utilizes a commercial fusion splicer to anneal and enhance the sensitivity of MXene material on the surface of a fiber optic sensor through electrode discharge. This enables efficient and specific sensing and detection of microplastic particles, improving sensor sensitivity while eliminating interference from other water particles. These nanoparticles are environmentally friendly and pollution-free. Attached Figure Description

[0018] Figure 1 A simplified structural diagram of a fiber optic water microplastic sensor based on discharge-annealed MXene;

[0019] Figure 2 A schematic diagram of the microfiber structure of a fiber-optic water microplastic sensor based on discharge-annealed MXene;

[0020] Figure 3 This is a schematic diagram of the MXene discharge annealing enhancement process for an optical fiber water microplastic sensor based on discharge annealed MXene.

[0021] Figure 4 This is a schematic diagram of the specific adsorption process of an optical fiber water microplastic sensor based on discharge-annealed MXene. Detailed Implementation

[0022] To explain in detail the technical content, structural features, objectives, and effects of the technical solution, the following description is provided in conjunction with specific embodiments and accompanying drawings.

[0023] The fiber optic water microplastic sensor based on discharge-annealed MXene mainly consists of a broadband light source (1), a micro-fiber structure (2), and a spectrometer (3 sets). Utilizing the Mach-Zehnder interferometry principle, the micro-fiber system can detect changes in the external environment with high sensitivity. Simultaneously, the surface of the D-shaped fiber in the micro-fiber structure is modified with functional materials, enabling it to specifically and efficiently adsorb microplastics, improving the interaction between light and matter, and achieving in-situ sensing and detection of the concentration and type of microplastics in water.

[0024] The micro-fiber structure 2 is a Mach-Zehnder type fiber interference structure, consisting of a first single-mode fiber 21, a first multimode fiber 22, a D-type few-mode fiber 23, a second multimode fiber 24, and a second single-mode fiber 25, sequentially welded together, with the D-type few-mode fiber 23 featuring staggered fusion splicing. The D-type few-mode fiber 23 in the micro-fiber structure 2 is polished with a grinding wheel, retaining a diameter of 62.5 μm after polishing, i.e., half its original diameter. The multimode fiber, the D-type few-mode fiber, and the multimode fiber are all 500 μm in length. The refractive index sensing sensitivity of this sensor is greater than 10000 nm / RIU.

[0025] The annealed MXene nanosheets assembled on the surface of the micro-fiber structure 2 serve as a specific recognition film. The MXene nanosheets are a few-layer structure, self-assembled on the surface of the micro-fiber structure 2 via photodeposition. The annealed MXene nanosheet film is formed by electrostatic discharge processing of the MXene nanosheets using a fusion splicer, with the discharge charge being much smaller than the fusion charge. The annealed MXene nanosheet film can directionally adsorb microplastic particles in water through strong electrostatic adsorption, but it does not adsorb sand and biological particles of the same microplastic size through electrostatic repulsion.

[0026] like Figure 1 The diagram shows a simplified structure of a fiber-optic water microplastic sensor based on discharge-annealed MXene. The functionalized sensor is placed in the water body to be tested for the detection of microplastics. Light emitted from a broadband light source 1 in the 1250-1640 nm wavelength range enters the micro-fiber structure 2, which uses the Mach-Zehnder interferometry principle to sense the external environment. Because the surface of the micro-fiber structure 2 is modified with annealed MXene nanosheets that specifically adsorb microplastics, the interaction between light and microplastic particles is enhanced, allowing the concentration of microplastics in the environment to be demodulated in the spectrometer 3.

[0027] like Figure 2 As shown, in the fiber optic sensing system, light from the broadband light source 1 enters the micro-fiber structure 2 through the first single-mode fiber 21. The introduction of the first multimode fiber 22 causes mode field mismatch, exciting multiple higher-order modes. Some modes enter the core of the D-type few-mode fiber 23 (solid line in the figure), and some enter the microcavity composed of the D-type few-mode fiber 23 (dashed line in the figure). The modes in the microcavity are affected by external factors and interfere with the modes in the core of the D-type few-mode fiber 23 in the second multimode fiber 24. Finally, the light is output through the second single-mode fiber 25, and the output light intensity can be expressed as:

[0028]

[0029] Where I1(λ) and I2(λ) represent the light intensity of the microcavity intra-mode and the D-type few-mode fiber mode, respectively, λ is the light wavelength, and Δn eff Let L represent the effective refractive index difference between the two modes, and L be the total length of the D-type few-mode fiber 23. Therefore, the wavelength λ of the m-th interference valley is... m It can be represented as:

[0030] λ m =2Δn eff L / (2m+1) (2)

[0031] To achieve specific recognition of microplastics by the sensor, a specific recognition film needs to be constructed on the surface of the micro-fiber structure. For example... Figure 3As shown, a uniform MXene few-phase layer nanosheet particle film 32 was first deposited on the surface of a D-type few-mode optical fiber 23 using photodeposition. After the film stabilized, the micro-fiber structure 2 was placed in a fusion splicer, and the MXene few-phase layer nanosheet particles were annealed by rapid electrode discharge 31 to form an annealed MXene nanosheet particle film 33, which increased the specific recognition ability and adsorption binding sites of the film.

[0032] like Figure 4 As shown, annealed MXene nanosheets are positively charged in the aquatic environment, while microplastics 41 are negatively charged, thus exhibiting strong adsorption. Common aquatic particles such as sand and biological particles 42 do not exhibit these characteristics and therefore do not adsorb onto them, thus achieving specificity for microplastics in the aquatic environment. Annealed MXene nanosheets are environmentally friendly and highly stable in water.

[0033] A fiber optic water microplastic sensing method based on discharge-annealed MXene, the sensing method comprising:

[0034] The microfiber structure 2 of the fiber optic interferometry system is inserted into the water body being measured. A broadband light source 1 emits signal light, which enters the microfiber structure through the first single-mode fiber 21. The first multimode fiber 22 excites multiple higher-order modes; some modes enter the core of the D-type few-mode fiber 23, and some enter the microcavity. The modes in the microcavity are affected by external factors and interfere with the modes in the core of the D-type few-mode fiber 23 in the second multimode fiber 24. Parameters from the external environment can be demodulated using a spectrometer 3. Electrode discharge annealed nanosheets from the functional material adsorption system are incorporated into the microcavity of the microfiber structure. This allows for the specific adsorption of microplastic particles and the elimination of interference from other water particles, enhancing the interaction between light and microplastics and achieving efficient directional sensing and detection of microplastics in the water.

[0035] Fiber optic sensors utilize the high sensitivity of evanescent fields to detect changes in the external environment, enabling indexed measurements. Novel functional material processing methods achieve specific and efficient adsorption of microplastics, enhancing the effect of evanescent fields and enabling in-situ sensing and detection of the concentration and type of microplastics in water.

[0036] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising..." or "including..." does not exclude the presence of additional elements in the process, method, article, or terminal device that includes said element. Additionally, in this document, "greater than," "less than," "exceeding," etc., are understood to exclude the stated number; "above," "below," "within," etc., are understood to include the stated number.

[0037] Although the above embodiments have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the above descriptions are merely embodiments of the present invention and do not limit the scope of patent protection of the present invention. Any equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A fiber optic water microplastic sensor based on discharge-annealed MXene, characterized in that, The fiber optic water microplastic sensor consists of a spectrometer, a microfiber structure, and a broadband light source connected in sequence. The microfiber structure is composed of a first single-mode fiber, a first multimode fiber, a D-type few-mode fiber, a second multimode fiber, and a second single-mode fiber connected in sequence. The microfiber structure is a Mach-Zehnder type fiber interference structure. MXene nanosheets are disposed on the cross-section of the D-type few-mode fiber. The MXene types include Ti3C2, Ti3AlC2, or Ti2C series few-layer nanosheets. The MXene nanosheets are uniformly bonded to the surface of the D-type few-mode fiber by photodeposition. The MXene nanosheets are annealed by a fusion splicer discharge process, with the annealing charge being less than the fusion charge. After annealing, the MXene nanosheet film layer adsorbs microplastic particles in the water through strong electrostatic adsorption.

2. The fiber optic water microplastic sensor based on discharge-annealed MXene according to claim 1, characterized in that, The D-type few-mode optical fiber is produced by polishing with a grinding wheel.

3. A detection method using a fiber optic water microplastic sensor based on discharge-annealed MXene as described in any one of claims 1-2, characterized in that, The detection method is as follows: The micro-fiber structure is inserted into the water body to be measured. A broadband light source emits signal light, which enters the first multimode fiber through the first single-mode fiber. Due to mode field mismatch, multiple higher-order modes are excited. Subsequently, the higher-order modes enter the core of the D-type few-mode fiber and the liquid microcavity, respectively. The modes in the liquid microcavity are affected by the external environment. After inter-film interference occurs between the modes in the core of the second multimode fiber and the D-type few-mode fiber, the concentration of the analyte is quantitatively demodulated by the spectrometer.

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