CN-118222278-B - Preparation method of fluorescent probe and optical fiber sensing system for monitoring chloride ion concentration

CN118222278BCN 118222278 BCN118222278 BCN 118222278BCN-118222278-B

Abstract

The invention belongs to the technical field of nondestructive monitoring of chloride ion concentration in concrete, and relates to a preparation method of a fluorescent probe and an optical fiber sensing system for monitoring the chloride ion concentration. The fluorescent probe takes a quartz bare fiber as a carrier, one end of the quartz bare fiber is coated with a sol-gel film which wraps chloride ion sensitive fluorescent nano particles after surface modification, the other end of the quartz bare fiber is connected to a bifurcated optical fiber through a fluorescent probe connector, the bifurcated optical fiber is divided into two paths at the other end after being connected with the fluorescent probe, one path is connected with a fluorescent spectrometer and then connected to a computer, and the other path is connected with a light source. Light emitted by the light source is converged into the fluorescent probe through the Y-shaped bifurcated optical fiber, when fluorescent nanoparticles at the coated end of the fluorescent probe are in contact with chloride ions to generate fluorescence quenching, the degree of the fluorescence quenching can be received by the optical fiber spectrometer through the bifurcated optical fiber, the fluorescence intensity is recorded, the chloride ion concentration is obtained through the Stokes-Volmer equation, and the chloride ion concentration monitoring is realized.

Inventors

FAN LIANG
MA ZHENTING
SUN CONGTAO
LIAO XIUFEN
ZHAO XIA
HOU BAORONG

Assignees

中国科学院海洋研究所
广西科学院

Dates

Publication Date: 20260512
Application Date: 20240319

Claims (7)

1. A method for preparing a fluorescent probe, comprising: (1) Treating the two ends of the Dan Yingluo fiber to expose the quartz fiber cores at the two ends of the Dan Yingluo fiber; (2) Carrying out surface modification on a quartz fiber core at one end of the quartz bare fiber so as to carry out hydroxylation on the surface of the fiber core at the corresponding end; (3) Preparing a sol-gel casting solution doped with fluorescent nanoparticles, wherein the sol-gel casting solution doped with fluorescent nanoparticles is prepared from tetraethoxysilane, ethanol, HCl, siO2 fluorescent nanoparticles and water; the specific method comprises the following steps: Mixing ethyl orthosilicate, ethanol, HCl, siO2 fluorescent nano particles and water according to the volume ratio of ethyl orthosilicate to ethanol to H2O to SiO2 fluorescent nano particles = (20-30): (32-48): (0.064-0.096): (8-12): (0.0015-0.0021), continuously stirring on a magnetic stirrer for 16-32H to prepare a sol-gel solution, and storing in a dark place for 1-2 days to obtain a sol-gel casting film solution doped with fluorescent nano particles after the sol-gel casting film solution becomes a semi-gel state; (4) Coating one end of the quartz fiber core after modification in the step (2) by adopting a lifting coating method so as to coat a chloride ion sensitive film on one end of the modified quartz fiber core, and preparing and obtaining a fluorescent probe sensitive to chloride ions; The coating process specifically comprises the following steps: coating by a lifting coating method, and performing 50 coating operations in each coating period, wherein parameters of each coating operation are set to be lifting speed 2083 mu m/s, descending speed 2083 mu m/s, dipping time 10 s and interval time 10 s; and after each coating period is finished, drying the substrate in a baking oven at 40-60 ℃ for 20-30min, and then carrying out the next period, wherein the whole coating process comprises 6 coating periods, and after the whole coating process is finished, preparing and obtaining the fluorescent probe sensitive to chloride ions.
2. The method for preparing the fluorescent probe according to claim 1, wherein the synthesis method of the SiO2 fluorescent nanoparticle is as follows: Mixing H2O, cyclohexane, tritionX-100 and n-hexanol according to the volume ratio of H2O to cyclohexane to TritionX-100 to n-hexanol= (9-11) to (3.8-4.6) to (0.9-1.1) to obtain microemulsion, adding aqueous solution of chloride ion sensitive fluorescent dye and aqueous solution of chitosan into the microemulsion to obtain mixed solution, regulating the pH value of the mixed solution to be neutral, adding tetraethoxysilane and ammonia water, continuously stirring on a magnetic stirrer for 24-36H to form emulsion, centrifugally washing, and drying to obtain SiO2 fluorescent nanoparticles; Wherein the concentration of the chloride ion-sensitive fluorescent dye in the adopted aqueous solution of the chloride ion-sensitive fluorescent dye is 0.005-0.015mol/L, and the concentration of chitosan in the adopted aqueous solution of chitosan is 0.25-0.75g/L; The volume ratio of the microemulsion to the aqueous solution of the chloride ion sensitive fluorescent dye to the aqueous solution of the chitosan is (14.6-17.8) (4.5-5.5) (9-11) when the mixed solution is prepared, and the volume ratio of the mixed solution to the ethyl orthosilicate to the ammonia water is (28.1-34.3) (5.4-6.6) (3.6-4.4) when the emulsion is prepared.
3. The method for preparing the fluorescent probe according to claim 1, wherein the step (1) comprises the steps of placing both ends of a bare quartz fiber into concentrated sulfuric acid for acid etching to remove a skin layer and a sheath layer, exposing quartz fiber cores at both ends of the bare quartz fiber, and washing the surfaces of the quartz fiber cores with deionized water; After acid etching, the exposed length of the quartz fiber core at one end of the quartz bare fiber is 1-2cm, the exposed length of the quartz fiber core at the other end is 4-6cm, and one end of the quartz fiber core with the exposed length of 1-2cm is subjected to surface modification in the step (2).
4. The method of claim 1, wherein the step (2) comprises: Immersing the quartz fiber core with one exposed end of the quartz bare fiber into isopropanol solution of potassium hydroxide, then rinsing with a large amount of distilled water, and drying with compressed nitrogen; immersing the dried quartz fiber core in Piranha solution, removing surface organic matters and hydroxylating the surface of the fiber core, rinsing in distilled water, drying and finishing the surface modification.
5. The fluorescent optical fiber sensing system for monitoring the concentration of chloride ions in concrete is characterized by comprising a light source, an optical fiber spectrometer, a Y-shaped bifurcated optical fiber, a fluorescent probe sensitive to the chloride ions and a fluorescent probe connector, wherein the fluorescent probe sensitive to the chloride ions is the fluorescent probe obtained by any one of claims 1-4; The Y-shaped bifurcated optical fiber comprises a first shunt and a second shunt and a combining end, wherein the first shunt and the second shunt are respectively connected with the light source and the optical fiber spectrometer; one end of the fluorescent probe is a film plating end for detecting chloride ions, and the other end of the fluorescent probe is a combining end of the Y-shaped bifurcated optical fiber, wherein the fluorescent probe connector is connected to the combining end of the Y-shaped bifurcated optical fiber; When the coated end of the fluorescent probe is contacted with chloride ions, the chloride ion sensitive fluorescent nano particles in the sol-gel film are subjected to fluorescence quenching, the degree of fluorescence quenching is converged and presented on a spectrometer through Y-shaped bifurcated optical fibers, and the chloride ion concentration is obtained through a Stokes-Volmer equation, so that the real-time monitoring of the chloride ion concentration in concrete is realized; the fluorescent probe connector is used for connecting the Y-shaped optical fiber combining end with a fluorescent probe and comprises a fluorescent probe fixing unit and a cylindrical connecting unit; The fluorescent probe fixing unit is used for fixing the fluorescent probe; The cylindrical connecting unit is used for connecting the fluorescent probe and the combining end of the Y-shaped bifurcated optical fiber, and a first plano-convex lens, a second plano-convex lens and a third plano-convex lens are arranged in the cylindrical connecting unit.
6. The fluorescent optical fiber sensing system for monitoring chloride ion concentration in concrete of claim 5, wherein the first plano-convex lens is arranged near one end of the fluorescent probe, and the plane of the first plano-convex lens faces the direction of the fluorescent probe; by controlling the positions of the three plano-convex lenses, light from the second light source enters the second plano-convex lens through the first optical path of the Y-shaped bifurcated optical fiber and then enters the first plano-convex lens, and the light from the first plano-convex lens is converged to the third plano-convex lens.
7. The fluorescent fiber optic sensing system for monitoring chloride ion concentration in concrete of claim 6, wherein the fluorescent fiber optic sensing system is used for monitoring chloride ion concentration in concrete interstitial fluid as well as fresh concrete.

Description

Preparation method of fluorescent probe and optical fiber sensing system for monitoring chloride ion concentration Technical Field The invention belongs to the technical field of nondestructive monitoring of chloride ion concentration in concrete, and relates to a preparation method of a fluorescent probe and an optical fiber sensing system for monitoring the chloride ion concentration. Background Reinforced concrete is a composite material for improving the mechanical properties of concrete by adding materials such as steel bars into the concrete, and is one of the most widely used building and structural materials in the world due to easy pouring, excellent mechanical properties and wide raw material sources. However, as far as application is concerned, the structure of reinforced concrete often has a premature cracking phenomenon in the service process, and one of the main reasons is the influence of chloride ions. Chloride ions gradually permeate into the concrete protective layer to reach the surface of the steel bar, when the concentration of the chloride ions reaches a certain threshold value, the passivation film on the surface of the steel bar can be damaged to cause corrosion of the steel bar, then an expansive corrosion product can be generated to cause cracking of the concrete, the bearing capacity of the reinforced concrete structure is finally reduced, and the life cycle of the concrete structure is shortened and the maintenance cost is increased. Therefore, the chloride ions in the concrete need to be monitored in real time in early stage, the chloride ion concentration at the position of the steel bar is obtained in time, the corrosion problem of the steel bar is found early, and the safety problem of the concrete structure caused by the corrosion of the steel bar is reduced by taking necessary measures. The method for testing the chloride ion concentration in the concrete at the present stage mainly comprises lossy monitoring and lossless monitoring, wherein the lossy monitoring aims at drilling and sampling the concrete by a physical method, and then the chloride ion concentration is obtained by a traditional laboratory chemical concentration titration monitoring method. The nondestructive monitoring can not damage the whole concrete structure, the chloride ion concentration in the concrete is usually obtained by external non-contact measurement or an embedded sensor in the concrete, and the continuous monitoring of the chloride ion concentration can be realized. The optical fiber sensor has the characteristics of electromagnetic interference resistance and small volume, and can be embedded into any part of a concrete member for real-time and multi-point monitoring, thereby becoming an excellent choice for chloride ion monitoring. The optical fiber sensor for monitoring chloride ions comprises a long-period grating type optical fiber sensor, a fluorescent type optical fiber sensor and the like. Where long period grating fiber optic sensors operate based on sensitivity to ambient refractive index, chloride ion is not the only factor in ambient refractive index change. Therefore, the long-period grating type optical fiber sensor has poor ion specificity on chloride ion monitoring and can be interfered by other ions in concrete, so that the measured chloride ion concentration is deviated. In addition, the long-period grating fiber sensor is sensitive to temperature and external force, and the temperature and external force change can also cause the drift of the central wavelength of the transmission spectrum, so that in actual chloride ion monitoring, additional work is required for improving the specificity and compensating the temperature and external force, and the monitoring error is increased. The fluorescent optical fiber sensor is based on the fluorescence quenching principle, the concentration of chloride ions can be rapidly and accurately monitored by selecting a specific chloride ion fluorescent indicator and fixing the fluorescent indicator on the surface of an optical fiber, however, the measurement principle of the fluorescent optical fiber sensor determines that the assembly and manufacturing cost of the fluorescent optical fiber sensor are high, the sensitivity of the fluorescent optical fiber sensor can be influenced by the selection of materials and the parameters of the optical fiber, and in many fluorescent optical fiber sensors embedded in concrete at the present stage, the connection mode of a fluorescent probe and a sensing system cannot be well applied to actual measurement, for example, the conventional fluorescent probe is used for fixing a fluorescent dye on the end face of the optical fiber after tabletting and then packaging and then connecting the fluorescent dye to the sensing system. In the method, the fluorescent dye is physically pressed into pieces and then fixed on the end face of the optical fiber in a splicing mode, but the pressed pieces are not firmly fi