A method and system for monitoring chloride ions in concrete

Abstract

The invention discloses a method and system for monitoring chloride ions in concrete, belonging to the technical field of concrete monitoring. The chloride ion monitoring system performs multi-point real-time monitoring on the chloride ion concentration inside the concrete through the linear relationship between the fluorescence wavelength change value and the chloride ion concentration. The chloride ion monitoring system comprises an excitation light source, a spectrometer, a filter, a fluorescent probe, and an optical splitter; the fluorescent probe is obtained by encapsulating cesium lead bromide with a porous polymer obtained by reacting octaallyl bromide-POSS with a diamine compound to obtain fluorescent nanoparticles, and click chemistry is performed under ultraviolet light reaction through double bonds in the outer layer of the fluorescent nanoparticles and double bonds on the surface after optical fiber cone modification and thiol, so as to obtain the fluorescent probe through photoplating.

Description

[0001] The invention belongs to the technical field of concrete monitoring, and in particular relates to a method and a system for monitoring the chloride ion concentration of concrete. Background Art

[0002] Concrete is one of the most widely used building materials in modern construction and infrastructure. It provides high strength and long-term durability, can withstand various loads and environmental conditions, and can be used in buildings, roads, bridges, dams, etc., supporting our cities, transportation networks and infrastructure. The impact of chloride ions on concrete is an important engineering issue, mainly involving the durability of concrete and steel corrosion. Therefore, it is necessary to conduct early real-time monitoring of chloride ions in concrete, obtain the chloride ion concentration at the steel bar position in time, detect steel bar corrosion problems early, and take necessary measures to reduce the safety of concrete structures caused by steel bar corrosion.

[0003] At present, the monitoring methods of chloride ion corrosion of concrete can be divided into destructive monitoring methods and non-destructive monitoring methods. The destructive monitoring method is based on the needs of structural monitoring. Samples are regularly drilled from different parts and depths of the concrete structure, and the concentration of chloride ions is determined by titration or modern testing technology. Then, the degree of chloride ion corrosion of the concrete structure is judged based on experience. The non-destructive monitoring method is based on various sensors, such as electrical sensors, ultrasonic sensors, infrared temperature sensors, and optical fiber sensors. The concentration of chloride ions in the concrete structure is monitored, and the degree of chloride ion corrosion is judged based on experience or numerical simulation after the collected data is obtained.

[0004] Optical fiber sensors are resistant to electromagnetic interference and small in size. They can be embedded in any part of concrete components for real-time, multi-point monitoring, making them an excellent choice for chloride ion monitoring. CN 118222278 discloses a method for preparing a fluorescent probe and an optical fiber sensing system for monitoring chloride ion concentration, which is used to monitor the chloride ion concentration in concrete pore fluid and fresh concrete, but can only perform single-point testing; CN219935680 discloses a multi-point simultaneous concrete chloride ion monitoring system; both use the change in fluorescence intensity after the chloride ion fluorescent film reacts with the chloride ions in the concrete to monitor the chloride ions. This method mainly has the following defects: 1) loss of fluorescence intensity during optical fiber transmission; 2) the effect of photobleaching on fluorescence intensity; 3) during multi-point testing, light of the same wavelength but different intensities will have light superposition and interference, which will affect the accuracy of the test. Summary of the invention

[0005] In order to overcome the above-mentioned deficiencies of the prior art, the present invention adopts a chloride ion sensitive membrane based on wavelength change as a fluorescent probe to monitor concrete. This method has high sensitivity and good accuracy and can perform multi-point real-time monitoring of the concentration of chloride ions in concrete.

[0006] The technical solution for achieving the purpose of the present invention is as follows: the chloride ion monitoring system performs multi-point real-time monitoring of the chloride ion concentration inside the concrete through the linear relationship between the fluorescence wavelength change value and the chloride ion concentration.

[0007] The chloride ion monitoring system comprises an excitation light source, a spectrometer, a filter, a fluorescent probe, and an optical splitter; the excitation light source is connected to the optical splitter, the optical splitter is connected to 1 to 32 fluorescent probes, and is responsible for splitting and exciting multiple fluorescent probes at the same time; the filter is installed inside the spectrometer, one end of the spectrometer is connected to a computer, and the other end of the spectrometer is connected to another optical splitter, the other optical splitter is responsible for collecting the maximum emission wavelengths of different wavelengths generated by the light emitted by the excitation light source after the 1 to 32 fluorescent probes react with chloride ions in concrete, and transmitting them to the inside of the spectrometer; the filter is responsible for filtering the excitation wavelength; the fluorescent probe comprises fluorescent nanoparticles and optical fiber cones; the fluorescent nanoparticles are obtained by the following steps:

[0008] S1. Octaveyl-POSS and 3-bromopropylene were dissolved in dichloromethane, and catalyst 1 and catalyst 2 were added. After stirring for 2 to 24 hours, the solvent was removed by rotary evaporation, and octaallyl bromide-POSS was obtained after purification by column chromatography using a mixture of dichloromethane and petroleum ether;

[0009] S2. Add 100-120eq octadecene, 9-10eq diamine compound, 1eq octaallyl bromide-POSS obtained in step S1, 0.6-0.8eq cesium carbonate, and 0.4-0.5eq lead stearate into the reactor, stir and heat to 115-125°C, cool the obtained product with cold water, disperse it in a mixture of ethyl acetate and n-hexane, centrifuge, and collect the bottom product to obtain fluorescent nanoparticles.

[0010] Preferably, in step S1, the molar ratio of octaethylene-POSS, 3-bromopropylene, catalyst 1, and catalyst 2 is (10-12):100:(1-1.2):(5-6).

[0011] Preferably, the catalyst 1 in step S1 is one or more of Grubbs first-generation catalyst, Grubbs second-generation catalyst, and Grubbs third-generation catalyst; the catalyst 2 is one or more of cuprous iodide, cuprous bromide, and cuprous chloride; and the diamine compound in step S2 is one or more of ethylenediamine, propylenediamine, and butanediamine hydrochloride.

[0012] More preferably, the catalyst 1 is a Grubbs second-generation catalyst; the catalyst 2 is cuprous chloride; and the diamine compound is preferably at least one of ethylenediamine and propylenediamine hydrochloride.

[0013] Preferably, the ratio of the dichloromethane to petroleum ether mixture in step S1 is (12:1) to (10:1); the ratio of the ethyl acetate to n-hexane mixture in step S2 is (4:1) to (3:1).

[0014] Preferably, the optical splitter is a planar optical waveguide splitter, and the splitting ratio is (1:4) to (1:32).

[0015] Preferably, the excitation light source, spectrometer, filter, fluorescent probe, and optical splitter are connected via a multimode optical fiber.

[0016] The fiber cone is used as a probe, one end of which is connected to an excitation light source to excite fluorescent nanoparticles; the other end is connected to a spectrometer to absorb emission wavelengths of different wavelengths. The fiber cone preparation method is as follows: 8 to 12 cm of the end portions of two multimode optical fibers are immersed in an acetone solution, and after 4 to 6 minutes, the protective layer is removed after softening, and then wiped and cleaned with anhydrous ethanol and dried with nitrogen. Then, two multimode optical fibers in the same direction and parallel to each other are placed in a fiber splicer and the default multimode optical fiber taper program of the machine is selected to make the fiber cone of the fused multimode optical fiber.

[0017] The preparation method of the fluorescent probe comprises the following steps:

[0018] 1) Surface modification of optical fiber cone: fix the optical fiber cone vertically downward on a three-dimensional moving stage, then insert it into a mixture of concentrated sulfuric acid and hydrogen peroxide, heat it to 60-80°C, soak it for 20-40 minutes, clean the surface mixture with anhydrous ethanol, soak it in 5%-10% dimethylvinylchlorosilane ethanol solution for 18-20 hours under nitrogen protection, clean it with deionized water and anhydrous ethanol three times respectively, and blow it dry with argon gas;

[0019] 2) Photoplating: 0.3-0.4 g of fluorescent nanoparticles obtained in step S2, 100-130 μL of dithiol, and 4-6 mg of benzoin dimethyl ether are dispersed in 0.6-0.7 mL of a mixed solvent of toluene and tetrahydrofuran, and added to a 1 mL four-way cuvette. One end of the optical fiber cone obtained in step 1) is inserted into a semiconductor laser with a wavelength of 350-400 nm and a power of 100-500 mW. The optical fiber cone is inserted into the cuvette through a three-dimensional moving stage, and the excitation light source is turned on. After reacting for 30-60 seconds, the light source is turned off, the composite optical fiber is taken out and cleaned with tetrahydrofuran for 3 times, ultrasonicated in anhydrous ethanol for 20-30 minutes, blown dry with argon gas, and a polyetheretherketone material is installed as a protective cover to obtain a fluorescent probe.

[0020] Preferably, the volume ratio of the mixed solution of concentrated sulfuric acid and hydrogen peroxide in step 1) is (7:3) to (8:2); the volume ratio of the mixed solvent of toluene and tetrahydrofuran in step 2) is (1:1) to (5:2), and the dithiol is one or more of 1,5-pentanedithiol, 1,6-hexanedithiol, and 1,7-heptanedithiol.

[0021] More preferably, the dithiol is 1,6-hexanedithiol.

[0022] Beneficial Effects

[0023] The present invention provides a method and system for monitoring chloride ions in concrete by changing the fluorescence wavelength. After the fluorescent probe of the present invention reacts with the chloride ions in the concrete, the bromine element in the fluorescent nanoparticles is replaced by the chloride ions, resulting in a blue shift in the fluorescence emission wavelength. The chloride ion concentration is monitored according to the wavelength difference of the fluorescence signal. Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) Through wavelength change monitoring, multi-point monitoring can be carried out simultaneously, and the mutual influence between different wavelengths is small; it is not affected by the fluctuation of light source intensity, and long-distance remote monitoring can be carried out, and the wavelength will not change due to the increase of light transmission distance; by measuring the fluorescence intensity ratio at two wavelengths, a certain degree of self-calibration is achieved; wavelength changes are not as easily affected by the photobleaching effect as intensity, which is conducive to long-term monitoring and repeated measurements.

[0025] 2) The cesium lead bromide fluorescent nanoparticles are prepared by using octaallyl bromide-POSS and diamine, which can improve the stability of the cesium lead bromide fluorescent nanoparticles. At the same time, chloride ions can freely pass through the porous structure of the POSS group to replace the bromine element in the nanoparticles.

[0026] 3) Through the reaction of the double bond structure introduced by the optical fiber surface and the nanoparticles with disulfide, the probe is prepared by photoplating, which connects to the optical fiber through a copolymer bond. Compared with the dip-coating method, it is more stable and effectively solves the interface problem between them. The structure of the prepared film is looser, the specific surface area is larger, and it has excellent sensing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of the chloride ion monitoring system of the present invention;

[0028] Figure 2 The synthetic route of the fluorescent nanoparticles of the present invention;

[0029] Figure 3 The modified structure of the optical fiber taper of the present invention;

[0030] Figure 4The normalized fluorescence spectrum of the fluorescent probe 1 of the present invention for measuring different chloride ion mass concentrations;

[0031] Figure 5 It is a fitting curve diagram of the relationship between the maximum emission wavelength change value calibrated during the chloride ion mass concentration monitoring process of the fluorescent probe 1 of the present invention and the chloride ion concentration. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0034] The raw materials and equipment used in the embodiments and comparative examples are described as follows:

[0035] Octavinyl-POSS: purchased from Jinan Shicheng Silicone Technology Co., Ltd.;

[0036] 3-Propylene bromide; Product No. A800668, Shanghai MacLean Biochemical Technology Co., Ltd.;

[0037] Grubbs second-generation catalyst: product number G789000, Anaiji Chemical;

[0038] Cuprous chloride: Product No. C798746, Shanghai MacLean Biochemical Technology Co., Ltd.;

[0039] Octadecene: Product No. O854515, Shanghai MacLean Biochemical Technology Co., Ltd.;

[0040] Ethylenediamine hydrochloride: Product No. QF4160, Hubei Qifei Pharmaceutical Chemicals;

[0041] Propylenediamine hydrochloride: Product No. N816493, Shanghai MacLean Biochemical Technology Co., Ltd.;

[0042] Cesium carbonate: Product No. C804638, Shanghai MacLean Biochemical Technology Co., Ltd.;

[0043] Lead stearate: Product No. L812512, Shanghai MacLean Biochemical Technology Co., Ltd.;

[0044] 1,6-Hexanedithiol: Product No. H811007, Shanghai MacLean Biochemical Technology Co., Ltd.;

[0045] Benzoin dimethyl ether: product number B802287, Shanghai MacLean Biochemical Technology Co., Ltd.;

[0046] Spectrometer: Ocean HDX compact high-performance fiber optic spectrometer, Ocean Insight;

[0047] Multimode fiber: product code PSC_SI_MM50 / 125 / 155PI, Jiangyin Yunxiang Optoelectronic Technology;

[0048] Excitation light source: 375nm, 500mw adjustable light power laser module, Shenzhen Infrared Laser Technology Co., Ltd.;

[0049] Splitter: MPM-2000 fiber optic multiplexer, Ocean Insight;

[0050] Filter: OF2-GG400 high-pass filter, Ocean Insight.

[0051] Preparation of Octallyl Bromide-POSS

[0052] In a nitrogen atmosphere, 1 mol of octavinyl-POSS and 10 mol of 3-bromopropylene were added to the reaction kettle, and then dichloromethane was added to dissolve it, and the mixture was stirred at 30°C for 5 min. 0.1 mol of Grubbs second-generation catalyst was added and stirred for 10 min. 0.5 mol of cuprous chloride was added and stirred for 18 to 24 h. The solvent was removed by rotary evaporation, and the mixture was purified by column chromatography using a mixture of dichloromethane and petroleum ether in a volume ratio of (12:1) to (10:1) to obtain octaallyl bromide-POSS.

[0053] Preparation of fluorescent nanoparticles 1

[0054] Under a nitrogen atmosphere, 100 mol of octadecene, 9 mol of propylenediamine hydrochloride, 1 mol of the obtained octaallyl bromide-POSS, 0.6 mol of cesium carbonate, and 0.4 mol of lead stearate were added to the reactor in sequence. After stirring for 2 minutes, the mixture was heated to 115°C in air. The obtained product was cooled with cold water, dispersed in a mixture of ethyl acetate and n-hexane in a volume ratio of 4:1, and centrifuged at 9000 rpm for 8 minutes. The bottom product was collected to obtain fluorescent nanoparticles 1.

[0055] Preparation of fluorescent nanoparticles 2

[0056] Under a nitrogen atmosphere, 120 mol of octadecene, 10 mol of propylenediamine hydrochloride, 1 mol of octaallyl bromide-POSS obtained in step 1, 0.8 mol of cesium carbonate, and 0.5 mol of lead stearate were added to the reactor in sequence. After stirring for 2 minutes, the mixture was heated to 125°C in air. The obtained product was cooled with cold water, dispersed in a mixture of ethyl acetate and n-hexane, and centrifuged at 10000 rpm for 10 minutes. The bottom product was collected to obtain fluorescent nanoparticles 2.

[0057] Preparation of fluorescent nanoparticles 3

[0058] The preparation method is different from that of the fluorescent nanoparticle 1 in that propylenediamine hydrochloride is replaced by ethylenediamine hydrochloride.

[0059] Preparation of fiber tapers

[0060] Immerse 10 cm of the end parts of the two multimode optical fibers in acetone solution for 5 minutes, remove the protective layer after it softens, wipe it with anhydrous ethanol and blow it dry with nitrogen, then put the two parallel multimode optical fibers into the optical fiber welding machine and select the machine's default multimode optical fiber taper program to make the fiber taper of the fused multimode optical fiber.

[0061] Preparation of fluorescent probe 1

[0062] The fiber cone was fixed vertically downward on a three-dimensional moving stage, and then inserted into a mixture of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 7:3, heated to 80°C, soaked for 30 minutes, and then cleaned with anhydrous ethanol. Under nitrogen protection, it was soaked in a 10% dimethylvinylchlorosilane ethanol solution for 20 hours, and then cleaned with deionized water and anhydrous ethanol for three times, respectively, and blown dry with argon gas.

[0063] The obtained 0.3 g fluorescent nanoparticles 1, 120 μL of 1,6-hexanedithiol, and 6 mg of benzoin dimethyl ether were dispersed in a mixed solvent of 0.7 ml toluene and tetrahydrofuran in a volume ratio of 7:3, and added to a 1 mL four-way cuvette. One end of the optical fiber cone obtained in step 1) was inserted into a semiconductor excitation light source with a wavelength of 375 nm and a power of 400 mW. The optical fiber cone was inserted into the cuvette through a three-dimensional moving stage, the excitation light source was turned on, and after reacting for 40 seconds, the light source was turned off. The composite optical fiber was taken out and cleaned with tetrahydrofuran for 3 times, ultrasonicated in anhydrous ethanol for 30 minutes, dried with argon gas, and installed with polyetheretherketone material as a protective cover to obtain a fluorescent probe.

[0064] Preparation of fluorescent probe 2

[0065] The preparation method is different from that of the fluorescent probe 1 in that the fluorescent nanoparticles 1 are replaced by fluorescent nanoparticles 2 .

[0066] Preparation of fluorescent probe 3

[0067] The preparation method is different from that of the fluorescent probe 1 in that the fluorescent nanoparticles 1 are replaced by fluorescent nanoparticles 3 .

[0068] Example 1

[0069] A chloride ion monitoring system for concrete comprises an excitation light source, a spectrometer, a filter, a fluorescent probe and an optical splitter. The excitation light source is connected to the optical splitter, which is a planar optical waveguide splitter with a splitting ratio of 1:16. The excitation light source, the spectrometer, the filter, the fluorescent probe and the optical splitter are connected via a multimode optical fiber. The optical splitter is connected to 16 fluorescent probes and is responsible for splitting and exciting multiple fluorescent probes at the same time. The filter is installed inside the spectrometer. One end of the spectrometer is connected to a computer, and the other end of the spectrometer is connected to another optical splitter. The other optical splitter is responsible for collecting the maximum emission wavelength of different wavelengths generated by the light emitted by the excitation light source after the 16 fluorescent probes react with chloride ions in concrete, and transmitting the maximum emission wavelength to the inside of the spectrometer. The filter is responsible for filtering the excitation wavelength. The fluorescent probe comprises fluorescent nanoparticles and optical fiber cones. Two identical optical splitters are connected to the laser light source and the spectrometer respectively through multimode optical fibers. A 400nm filter is inserted into the spectrometer to filter the excitation light source below 400nm. The multimode optical fibers at both ends of the obtained fluorescent probe 1 are respectively inserted into the No. 1 interface of the optical splitter connected to the laser light source and the No. 1 interface of the optical splitter connected to the spectrometer.

[0070] Example 2

[0071] Compared with Example 1, the difference is that the multimode optical fibers at both ends of the obtained fluorescent probe 2 are respectively inserted into the No. 2 interface of the optical splitter connected to the laser light source and the No. 2 interface of the optical splitter connected to the spectrometer.

[0072] Example 3

[0073] Compared with Example 1, the difference is that the multimode optical fibers at both ends of the obtained fluorescent probe 3 are respectively inserted into the No. 3 interface of the optical splitter connected to the laser light source and the No. 3 interface of the optical splitter connected to the spectrometer.

[0074] The fluorescent probes in Examples 1 to 3 were calibrated according to the standard equation of fluorescence wavelength change and chloride ion concentration. The present invention used sodium chloride solution as the standard solution for calibration, and prepared sodium chloride solutions with concentrations of 0%, 0.01%, 0.05%, 0.10%, 0.15% and 0.30%, measured the fluorescence emission wavelength, normalized it, recorded the values ​​of the maximum emission wavelength corresponding to different concentrations, and fitted the data. The data are shown in Table 1.

[0075] Table 1 Standard curves of different fluorescent probes

[0076] Example 1 <![CDATA[Δλ=259.39C (CI-) +2.68]]> <![CDATA[R 2 =0.99813]]> Example 2 <![CDATA[Δλ=213.15C (CI -)+5.97]]> <![CDATA[R 2 =0.99925]]> Example 3 <![CDATA[Δλ=241.52C (CI -)+7.21]]> <![CDATA[R 2 =0.99871]]>

[0077] Where Δλ=λ0-λ 测 , λ0 is the maximum emission wavelength when the chloride ion concentration is 0%, λ 测 It is the maximum emission wavelength measured during monitoring.

[0078] Example 4

[0079] The chloride ion concentration inside the concrete is monitored in real time at multiple points through the linear relationship between the fluorescence wavelength change value and the chloride ion concentration. The sensitivity of the fluorescent probe prepared by the present invention is 0.01%, and the chloride ion concentration can be accurately monitored within the range of 0.01% to 0.30%. For ordinary reinforced concrete structures, when the chloride ion concentration exceeds 0.05% by mass, there will be a high corrosion risk. The concentration of 0.05% is substituted into the equation to obtain Δλ, and λ0 is known, then the corresponding maximum emission wavelength can be obtained. When the monitored maximum emission wavelength is lower than this value, it means that the chloride ion concentration exceeds the standard. The chloride ion monitoring system of the present invention can pre-embed multiple fluorescent probes into the concrete structure, thereby realizing multi-point real-time monitoring.

[0080] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A chloride ion monitoring system for concrete, characterized in that: The chloride ion monitoring system comprises an excitation light source, a spectrometer, a filter, a fluorescent probe, and an optical splitter; the excitation light source is connected to the optical splitter, the optical splitter is connected to 1 to 32 fluorescent probes, and is responsible for splitting and exciting multiple fluorescent probes at the same time; the filter is installed inside the spectrometer, one end of the spectrometer is connected to a computer, and the other end of the spectrometer is connected to another optical splitter, the other optical splitter is responsible for collecting the maximum emission wavelengths of different wavelengths generated by the light emitted by the excitation light source after the 1 to 32 fluorescent probes react with chloride ions in concrete, and transmitting them to the inside of the spectrometer; the filter is responsible for filtering the excitation wavelength; the fluorescent probe comprises fluorescent nanoparticles and optical fiber cones; The fluorescent nanoparticles are obtained by the following steps: S1. Octaveyl-POSS and 3-bromopropylene were dissolved in dichloromethane, and catalyst 1 and catalyst 2 were added. After stirring for 2 to 24 hours, the solvent was removed by rotary evaporation, and octaallyl bromide-POSS was obtained after purification by column chromatography using a mixture of dichloromethane and petroleum ether; S2. Add 100-120eq octadecene, 9-10eq diamine compound, 1eq octaallyl bromide-POSS obtained in step S1, 0.6-0.8eq cesium carbonate, 0.4-0.5eq lead stearate to the reactor, stir and heat to 115-125°C, cool the product with cold water, disperse it in a mixture of ethyl acetate and n-hexane, centrifuge, and collect the bottom product to obtain fluorescent nanoparticles; The catalyst 1 in step S1 is one or more of Grubbs first-generation catalyst, Grubbs second-generation catalyst, and Grubbs third-generation catalyst; the catalyst 2 is one or more of cuprous iodide, cuprous bromide, and cuprous chloride; the diamine compound in step S2 is one or more of ethylenediamine, propylenediamine, and butanediamine hydrochloride.

2. The chloride ion monitoring system according to claim 1, characterized in that: In step S1, the molar ratio of octaethylene-POSS, 3-bromopropylene, catalyst 1, and catalyst 2 is (10-12):100:(1-1.2):(5-6).

3. The chloride ion monitoring system according to claim 1, characterized in that: The volume ratio of the dichloromethane and petroleum ether mixed liquid in step S1 is (12:1) to (10:1); the volume ratio of the ethyl acetate and n-hexane mixed liquid in step S2 is (4:1) to (3:1).

4. The chloride ion monitoring system according to claim 1, characterized in that: The optical splitter is a planar optical waveguide splitter with a splitting ratio of (1:4) to (1:32); the excitation light source, spectrometer, filter, fluorescent probe and optical splitter are connected via a multimode optical fiber.

5. The chloride ion monitoring system according to claim 1, characterized in that: The optical fiber taper is obtained by the following steps: immersing 8 to 12 cm of the end portions of two multimode optical fibers in an acetone solution for 4 to 6 minutes, removing the protective layer after it softens, wiping and cleaning with anhydrous ethanol and drying with nitrogen, and then placing two multimode optical fibers in parallel in the same direction into an optical fiber welding machine and selecting the machine's default multimode optical fiber taper program to produce the optical fiber taper of the fused multimode optical fiber.

6. The chloride ion monitoring system according to claim 1, characterized in that: The preparation method of the fluorescent probe comprises the following steps: 1) Surface modification of optical fiber cone: fix the optical fiber cone vertically downward on a three-dimensional moving stage, then insert it into a mixture of concentrated sulfuric acid and hydrogen peroxide, heat it to 60-80°C, soak it for 20-40 minutes, clean the surface mixture with anhydrous ethanol, soak it in 5%-10% dimethylvinylchlorosilane ethanol solution for 18-20 hours under nitrogen protection, clean it with deionized water and anhydrous ethanol three times respectively, and blow it dry with argon gas; 2) Photoplating: 0.3-0.4 g of fluorescent nanoparticles obtained in step S2, 100-130 μL of dithiol, and 4-6 mg of benzoin dimethyl ether are dispersed in 0.6-0.7 mL of a mixed solvent of toluene and tetrahydrofuran, and added to a 1 mL four-way cuvette. One end of the optical fiber cone obtained in step 1) is inserted into an excitation light source with a wavelength of 350-400 nm and a power of 100-500 mW. The optical fiber cone is inserted into the cuvette through a three-dimensional moving stage, the excitation light source is turned on, and after reacting for 30-60 seconds, the light source is turned off. The composite optical fiber is taken out and cleaned with tetrahydrofuran for 3 times, ultrasonicated in anhydrous ethanol for 20-30 minutes, blown dry with argon gas, and a polyetheretherketone material is installed as a protective cover to obtain a fluorescent probe.

7. The chloride ion monitoring system according to claim 6, characterized in that: The volume ratio of the mixed solution of concentrated sulfuric acid and hydrogen peroxide in step 1) is (7:3) to (8:2); the volume ratio of the mixed solvent of toluene and tetrahydrofuran in step 2) is (1:1) to (5:2), and the dithiol is one or more of 1,5-pentanedithiol, 1,6-hexanedithiol, and 1,7-heptanedithiol.

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