Multi-core infrared optical fiber sensing device and method for monitoring chemical reaction kinetics

Abstract

The invention provides a multi-core infrared optical fiber sensing device and method for chemical reaction kinetics monitoring. The multi-core infrared optical fiber sensing device comprises an infrared spectrometer with a light source, a first lens, an optical fiber embedded reaction device, a second lens and an MCT liquid nitrogen refrigeration detector which are sequentially and optically connected in the incident light propagation direction. The optical fiber embedded reaction device comprises an in-situ infrared reaction container for loading a solution to be detected and an infrared micro-nano optical fiber sensor with a plurality of fiber cores; wherein the infrared micro-nano optical fiber sensor completely penetrates through the in-situ infrared reaction container, and the infrared micro-nano optical fiber sensor is used for monitoring characteristic absorption spectrum signals of reactants and products in a solution to be detected in real time after receiving mid-infrared light emitted by the light source. The multi-core infrared optical fiber sensing device provided by the invention can synchronously obtain reaction kinetics of reactants and products through single monitoring, can be repeatedly used for standard solution calibration and multiple reaction monitoring, and can provide an efficient and low-cost scheme for real-time analysis of complex reactions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber evanescent wave sensing technology and in-situ analytical chemistry technology, and particularly relates to a multi-core infrared optical fiber sensing device and method for monitoring chemical reaction kinetics. BACKGROUND

[0002] The reaction kinetics of chemical synthesis is influenced by many factors such as catalyst activity, light, temperature, etc., and the dynamic change is complex. In order to meet the needs of exploring reaction mechanism, selecting reaction path and optimizing yield in industrial production, it is of great significance to develop an in-situ monitoring technology that can accurately reflect real-time data to track the reaction process for dynamic tracking and precise control of the reaction process.

[0003] However, the existing chemical synthesis reaction kinetics monitoring related technologies have the following problems: the traditional offline analysis method (such as high performance liquid chromatography, gas chromatography) cannot capture the transient change of components due to time lag, resulting in low accuracy of reaction kinetics research; although the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) can realize in-situ monitoring by reflecting the functional group vibration information in real time, it still faces the problems of complex sample pretreatment, easy damage of equipment and limited sensitivity; the fiber evanescent wave spectrum (FEWS) technology has the advantages of high sensitivity, no sample pretreatment and anti-electromagnetic interference, and can accurately detect low concentration components and be suitable for long-term continuous monitoring, but it still has the problems of standardization challenge, such as difficulty in establishing accurate quantitative relationship and spectral overlap interference in the presence of multiple components.

[0004] Therefore, there is an urgent need for a multi-core infrared optical fiber sensing device and method for monitoring chemical reaction kinetics to solve the above technical problems. SUMMARY

[0005] The purpose of the present application is to provide a multi-core infrared optical fiber sensing device and method for monitoring chemical reaction kinetics to solve the technical problems of low sensitivity and poor anti-interference of the existing chemical synthesis reaction kinetics monitoring related technologies.

[0006] The present application first proposes a multi-core infrared optical fiber sensing device for monitoring chemical reaction kinetics, which comprises an infrared spectrometer with a light source, a first lens, a fiber-embedded reaction device, a second lens and an MCT liquid nitrogen refrigeration detector connected in sequence along the propagation direction of incident light, the fiber-embedded reaction device comprises an in-situ infrared reaction container for loading the solution to be measured and an infrared micro-nano optical fiber sensor with multiple cores; The infrared micro-nano optical fiber sensor completely penetrates the in-situ infrared reaction container, and the infrared micro-nano optical fiber sensor is used to monitor the characteristic absorption spectrum signal of the reactants and products in the solution to be measured in real time after receiving the mid-infrared light emitted by the light source.

[0007] Preferably, the infrared micro-nano fiber sensor further comprises a cladding layer, the refractive index of the cladding layer is less than the refractive index of the core; the plurality of cores are embedded in the cladding layer and are arranged at equal intervals along the circumferential direction of the cladding layer.

[0008] Preferably, the material of the core and the cladding layer both comprises Ge-As-Se-Te chalcogenide glass.

[0009] Preferably, the part of the infrared micro-nano fiber sensor embedded in the in-situ infrared reaction container is provided with a tapering part, the non-tapering parts adjacent to the two ends of the tapering part are fixed to the through holes in the wall of the in-situ infrared reaction container respectively, and the main part of the tapering part corresponds to being suspended in the in-situ infrared reaction container and being in contact with the to-be-measured solution.

[0010] Preferably, the tapering part comprises a waist part and two sub-tapering parts connected to the two ends of the waist part; the diameter of the sub-tapering part decreases linearly along the direction close to the waist part, the diameter of the waist part is the same as the minimum diameter of the sub-tapering part; the length of the waist part is 15-25 mm, and the length of the sub-tapering part is 1-3 mm.

[0011] Preferably, the waist part comprises one fiber sub-part bent into a ring, and the bending radius of the fiber sub-part is 1-3 mm.

[0012] Preferably, the micro-nano fiber further comprises non-tapering parts at the two ends of the tapering part, in the cross section of the non-tapering part along the vertical diameter direction: the diameter of the cladding layer is 400-600 μm, the diameter of the core is 100-150 μm, and the distance between the core and the outer circle of the cladding layer is 20-40 μm; in the cross section of the waist part along the vertical diameter direction: the diameter of the cladding layer is 40-60 μm, the diameter of the core is 10-15 μm, and the distance between the core and the outer circle of the cladding layer is 1-4 μm.

[0013] Preferably, the infrared micro-nano fiber sensor is used for in-situ monitoring the absorbance change of the infrared characteristic absorption peak of the molecular functional group of the reactant and the product in the range of 4000-850 cm -1 The characteristic absorption peak of the reactant and the characteristic absorption peak of the product are in the range of 4000-850 cm -1 .

[0014] Preferably, the in-situ infrared reaction container is provided with an ultraviolet light source capable of emitting ultraviolet light, and the to-be-measured solution reacts under the irradiation of the ultraviolet light; the material of the in-situ infrared reaction container comprises any one of quartz glass, ceramic and polytetrafluoroethylene.

[0015] Correspondingly, the application further provides a method for monitoring chemical reaction kinetics by using the multi-core infrared fiber sensing device according to any one of the above, the method comprising: S10, adjust the position of the three-dimensional adjustment fiber embedded reaction device and the MCT liquid nitrogen refrigeration detector, so that the light focused by the first lens is fully coupled into the multiple cores of the infrared micro-nano optical fiber sensor; S20, use the infrared micro-nano optical fiber sensor to sequentially collect the characteristic evanescent wave absorption spectra of multiple groups of different standard concentrations of reactant solutions and multiple groups of different standard concentrations of product solutions, respectively, and calculate the quantitative relationship between the absorbance and the concentration of the reactants and the products according to the Lambert-Beer law, and finally obtain the sensitivity calibration fitting curve of the reactants and the products, respectively. S30, place the to-be-measured solution in the in-situ infrared reaction container and ensure that it fully immerses the infrared micro-nano optical fiber sensor, then turn on the ultraviolet light source of the in-situ infrared reaction container to make the to-be-measured solution undergo photocatalytic reaction, collect the infrared evanescent wave absorption spectrum data of the reaction system every pre-set time, and then intercept the reactant and the product in the characteristic absorption band to obtain their respective spectrum and absorbance change data; S40, according to the sensitivity calibration fitting curve of the reactant and the absorbance change of the reactant of different concentrations, the real-time concentration of the reactant in the reaction process is calculated, and according to the sensitivity calibration fitting curve of the product and the absorbance change of the product of different concentrations, the real-time concentration of the product in the reaction process is calculated, then the real-time concentration of the reactant and the product is fitted by the first-order kinetic equation, respectively, and finally the fitting curve of the concentration change of the reactant and the product with time in the photocatalytic reaction of the to-be-measured solution is obtained. The beneficial effects of the present application are: different from the prior art, the present application provides an infrared micro-nano optical fiber sensor and a multi-core infrared optical fiber sensing device for chemical reaction kinetics monitoring, the infrared micro-nano optical fiber sensor comprises a plurality of cores embedded in a cladding; wherein the infrared micro-nano optical fiber sensor comprises a tapered section and non-tapered sections located at both ends of the tapered section; the tapered section comprises a waist and a sub-tapered section connected to both ends of the waist, the diameter of the sub-tapered section decreases linearly along the direction close to the waist, and the diameter of the waist is the same as the minimum diameter of the tapered section; the waist comprises one loop of fiber sub-sections bent into a ring. The multi-core infrared optical fiber sensing device for chemical reaction kinetics monitoring provided by the present application designs a fiber-embedded reaction device containing an in-situ infrared reaction container and an infrared micro-nano optical fiber sensor, the infrared micro-nano optical fiber sensor is directly immersed in the solution to be measured without complex pretreatment, the tapered section is suspended in the solution in the in-situ infrared reaction container, and simple operation, portable device, non-damage equipment and long-time continuous monitoring are realized. At the same time, the multiple cores of the infrared micro-nano optical fiber sensor can make the infrared light transmit independently in each core and produce superimposed evanescent waves, combined with the enhanced evanescent field leakage of the tapered section, the detection sensitivity is significantly improved to accurately capture the signal of low-concentration components. In addition, the fiber-embedded reaction device is matched with an infrared spectrometer and an MCT liquid nitrogen cooling detector, the reaction kinetics of reactants and products can be synchronously obtained by single monitoring, the device can also be repeatedly used for standard solution calibration and multiple reaction monitoring, and the functionality is powerful. Ultimately, an efficient and low-cost solution is provided for real-time analysis of complex reactions, which is suitable for industrial continuous production online quality control and reaction mechanism research, and has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A multi-core infrared optical fiber sensing device for chemical reaction kinetics monitoring provided by an embodiment of the present application is shown in the figure; Figure 2 A partial physical diagram of a fiber-embedded reaction device in the multi-core infrared optical fiber sensing device for chemical reaction kinetics monitoring provided by an embodiment of the present application is shown in the figure; Figure 3 A two-dimensional axis measurement schematic diagram of an infrared micro-nano optical fiber sensor in the multi-core infrared optical fiber sensing device for chemical reaction kinetics monitoring provided by an embodiment of the present application is shown in the figure; Figure 4 An end face structure schematic diagram of the infrared micro-nano optical fiber sensor in the multi-core infrared optical fiber sensing device for chemical reaction kinetics monitoring provided by an embodiment of the present application is shown in the figure; Figure 5 An infrared evanescent wave absorption spectrum diagram of reactants with different concentrations in Example 1 of the present application is shown in the figure; Figure 6 An infrared evanescent wave absorption spectrum diagram of products with different concentrations in Example 1 of the present application is shown in the figure; Figure 7The fitting curve obtained by calibrating the sensitivity of the optical fiber embedded reaction device with a series of standard concentration solutions of reactants and products for the embodiment 1 of the present application; Figure 8 The infrared evanescent wave absorption spectrum diagram reflecting the change of absorbance with time during the whole reaction process for the reactants obtained in the embodiment 1 of the present application; Figure 9 The infrared evanescent wave absorption spectrum diagram reflecting the change of absorbance with time during the whole reaction process for the products obtained in the embodiment 1 of the present application; Figure 10 The fitting curve diagram of the concentration change of the reactants and products with time in the chemical reaction process according to the absorbance change of Figure 8 and Figure 9 for the embodiment 1 of the present application; Figure 11 The infrared evanescent wave absorption spectrum diagram reflecting the whole reaction process (4000~850 cm -1 ); In the description of the drawings: 100 - multi-core infrared optical fiber sensing device; 10 - infrared spectrometer; 20 - first lens; 30 - optical fiber embedded reaction device; 31 - infrared micro-nano optical fiber sensor; 301 - non-tapered part; 302 - tapered part; 3021 - waist part; 30211 - optical fiber subpart; 3022 - sub-tapered part; 311 - fiber core; 312 - cladding; 32 - in-situ infrared reaction container; 321 - ultraviolet light source; 40 - second lens; 50 - MCT liquid nitrogen refrigeration detector; 60 - computer. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0018] In view of the deficiencies of the prior art, the present application provides an in-situ infrared monitoring technology based on FEWS, which overcomes the defects of low sensitivity and poor anti-interference of the traditional method, and provides an efficient, low-cost and reliable solution for real-time analysis of complex chemical reactions, which is suitable for online quality control and reaction mechanism research in industrial continuous production process.

[0019] Specifically, based on the infrared fingerprint spectrum of the significant difference between the reactants and the target product, the applicant first calibrates the sensitivity of the sensor with a series of standard concentration reactant and product solution respectively, and establishes a linear fitting model based on the characteristic absorption information of two functional groups to the infrared evanescent wave, the quantitative relationship between the characteristic absorption peak area and the concentration based on the Lambert-Beer law; then the infrared evanescent wave spectrum data of the reaction system is collected in situ every preset time to monitor the reaction until the reaction is completed, and then the first infrared spectrum data is defined as the original spectrum, and the original spectrum is used as the reference difference spectrum analysis, the reaction process is dynamically tracked by the weakening of the infrared characteristic peak of the reactant and the enhancement of the infrared characteristic peak of the product, and finally the concentration change is quantitatively reflected.

[0020] Please refer to Figures 1 to 4 , Figure 1 The structural schematic diagram of the multi-core infrared optical fiber sensing device 100 for chemical reaction kinetics monitoring provided by the embodiment of the present application is shown in the figure. Figure 2 The local physical diagram of the optical fiber embedded reaction device 30 in the multi-core infrared optical fiber sensing device 100 for chemical reaction kinetics monitoring provided by the embodiment of the present application is shown in the figure. Figure 3 The two-dimensional axis measurement schematic diagram of the infrared micro-nano optical fiber sensor 31 in the multi-core infrared optical fiber sensing device 100 for chemical reaction kinetics monitoring provided by the embodiment of the present application is shown in the figure. Figure 4 The end face structure schematic diagram of the infrared micro-nano optical fiber sensor 31 in the multi-core infrared optical fiber sensing device 100 for chemical reaction kinetics monitoring provided by the embodiment of the present application is shown in the figure; wherein, the present application provides a multi-core infrared optical fiber sensing device 100 for chemical reaction kinetics monitoring, which comprises an infrared spectrometer 10 with a light source, a first lens 20, an optical fiber embedded reaction device 30, a second lens 40 and a MCT (Mercury Cadmium Telluride, Tellurium Cadmium Mercury) liquid nitrogen refrigeration detector 50 which are connected in sequence along the propagation direction of incident light. Wherein, the optical fiber embedded reaction device 30 comprises an in-situ infrared reaction container 32 for loading the solution to be measured and an infrared micro-nano optical fiber sensor 31 penetrating through the in-situ infrared reaction container 32; the infrared micro-nano optical fiber sensor 31 is used to monitor the characteristic absorption spectrum signal of the reactant and the product in the solution to be measured in real time after receiving the mid-infrared light emitted by the light source; Wherein, the multi-core infrared optical fiber sensing device 100 further comprises a computer 60, one end of the MCT liquid nitrogen refrigeration detector 50 is electrically connected with the infrared spectrometer 10, the other end of the MCT liquid nitrogen refrigeration detector 50 is electrically connected with the computer 60, and the computer 60 is also electrically connected with the infrared spectrometer 10.

[0021] Specifically, the infrared spectrometer 10 with a light source is responsible for outputting mid-infrared light and initially processing the electrical signal transmitted from the MCT detector; the first lens 20 collimates / focuses the infrared light of the infrared spectrometer 10 to reduce loss and efficiently transmit it into the infrared micro / nano fiber optic sensor 31 in the fiber-optic embedded reaction device 30; the fiber-optic embedded reaction device 30 loads the test solution through the in-situ infrared reaction container 32, allowing the infrared light transmitted by the infrared micro / nano fiber optic sensor 31 to interact with the reaction system, so that the light signal carries the characteristic absorption information of the reactants and products; the second lens 40 collimates / focuses the infrared light carrying the information, reduces loss and efficiently transmits it to the MCT detector; the MCT liquid nitrogen-cooled detector 50 converts the light signal into an electrical signal, while liquid nitrogen cooling reduces noise to improve sensitivity; the computer 60 receives the electrical signal and converts it into a spectral spectrum, calculates the concentrations of reactants and products, fits kinetic parameters, and also coordinates the operation of the infrared spectrometer 10 and the detector.

[0022] In this embodiment of the invention, the infrared micro-nano fiber optic sensor 31 includes a plurality of fiber cores 311; the portion of the infrared micro-nano fiber optic sensor 31 located in the in-situ infrared reaction container 32 has a tapered portion 302, the non-tapered portions 301 at both ends of the tapered portion 302 are respectively fixed to the through holes of the in-situ infrared reaction container 32, and the main body of the tapered portion 302 is correspondingly suspended in the in-situ infrared reaction container 32 and in contact with the solution to be tested.

[0023] Specifically, when mid-infrared light is fully coupled into the infrared micro / nano fiber optic sensor 31 within the fiber-embedded reaction device 30, the mid-infrared light readily satisfies the total internal reflection condition at the core-cladding interface of the infrared micro / nano fiber optic sensor 31. Due to the continuity of electromagnetic waves, the infrared light does not immediately stop upon total internal reflection, generating an evanescent wave at the contact surface between the infrared micro / nano fiber optic sensor 31 and the solution to be tested. This evanescent wave briefly leaks out of the reflecting plane and then returns to the infrared micro / nano fiber optic sensor 31. During this process, the solution to be tested selectively absorbs light within the incident light frequency region, and the light intensity at the characteristic absorption frequency position decreases, producing an effect similar to transmission absorption, thereby outputting an evanescent wave absorption spectrum carrying material information (molecular vibrational information).

[0024] To enhance the interaction between evanescent waves and matter, thereby improving the detection sensitivity of the infrared micro / nano fiber optic sensor 31, the penetration depth d of the evanescent field should be maximized. p d p The equation can be expressed by the following formula (1): (1); Where, λ i and θ i n1 and n2 are the wavelength and angle of incidence of the incident light, respectively, and the refractive indices of the infrared micro-nano fiber optic sensor 31 and the surrounding medium (i.e. the sample to be tested), respectively.

[0025] Specifically, the taper section 302 (diameter reduction area) of the infrared micro-nano fiber sensor 31 changes the propagation angle of the mid-infrared light in the fiber core. After the tapering, the incident angle θ i closer to the critical angle of total reflection, which reduces the denominator of formula (1) and directly leads to the increase of the penetration depth d p of the evanescent wave. At the same time, the taper section 302 is suspended in the solution to be measured, ensuring that the evanescent wave can directly and fully contact the solution (without the barrier of the container wall), further enhancing the interaction with the substance. The increase of d p means that the evanescent wave propagates further in the solution, interacts more fully with the reactant / product molecules, and the absorption of the characteristic frequency light is more significant.

[0026] Further, the infrared micro-nano fiber sensor 31 includes multiple fiber cores 311, each of which can independently transmit mid-infrared light and satisfy the total reflection condition, and each generates an independent evanescent wave. The multiple fiber cores 311 form a "multiple evanescent wave superposition" effect: even if the d p of a single fiber core 311 remains unchanged as determined by the formula parameters, the total energy and range of the superimposed evanescent field are significantly expanded, the contact probability with the molecules in the solution to be measured is greatly improved, and the characteristic absorption signal of low-concentration components can also be fully captured.

[0027] Therefore, the taper section 302 of the infrared micro-nano fiber sensor 31 enhances the evanescent wave interaction efficiency by increasing the penetration depth of a single evanescent wave; at the same time, multiple fiber cores 311 superimpose the total amount of evanescent wave leakage, both of which synergistically enhance the interaction between the evanescent wave and the measured substance, and ultimately greatly improve the detection sensitivity of the infrared micro-nano fiber sensor 31.

[0028] Please refer to Figure 2 , the in-situ infrared reaction container 32 is embedded with a ultraviolet light source 321 capable of emitting ultraviolet light, and the solution to be measured reacts under ultraviolet light irradiation; the selection of the material of the in-situ infrared reaction container 32 requires chemical stability and does not react with any organic matter in the reaction system; the material of the in-situ infrared reaction container 32 is preferably any one of quartz glass, ceramic and polytetrafluoroethylene.

[0029] Specifically, the in-situ infrared reaction container 32 is provided with a ultraviolet light source 321, which can provide the required ultraviolet light for the reaction in-situ and uniformly, without transferring the reaction system, avoiding the fluctuation of light intensity, temperature and other conditions, realizing the synchronization of "ultraviolet light catalytic reaction" and "in-situ monitoring of mid-infrared", ensuring the stability of the reaction and the accuracy of the kinetic data, and simplifying the operation and improving the experimental repeatability; while the selected quartz glass, ceramic or polytetrafluoroethylene material has no significant absorption in the key mid-infrared characteristic absorption band of the reaction, does not interfere with the spectral signal capture of the reactants and products, and has excellent chemical stability and corrosion resistance, which can be compatible with organic solvents in the reaction system, ensuring the purity of the reaction and the long-term durability of the device, both of which provide reliable protection for the accurate in-situ monitoring of chemical reaction kinetics.

[0030] Please refer to Figure 4 , the infrared micro-nano optical fiber sensor 31 further comprises a cladding 312, and the plurality of cores 311 are embedded in the cladding 312; the refractive index of the core 311 is greater than the refractive index of the cladding 312, and the plurality of cores 311 are arranged at equal intervals along the circumferential direction of the cladding 312; wherein the difference in refractive index between the cladding 312 and the refractive index in the infrared micro-nano optical fiber sensor 31 can meet the total reflection condition of mid-infrared light in the core 311, which limits the light in the core 311 for efficient transmission, and lays a foundation for generating strong evanescent waves in the subsequent taper section 302; at the same time, the cladding 312 can protect the core 311 from corrosion or physical damage of the to-be-measured solution, ensuring the stability of in-situ monitoring of the sensor. The plurality of cores 311 are arranged at equal intervals along the circumference of the cladding 312, which can independently transmit light and generate multiple sets of evanescent waves in each core 311, enhance the total amount of action with the to-be-measured solution through the superposition effect, and improve the detection sensitivity; on the other hand, the equal interval design makes the evanescent waves uniformly distributed in the taper section 302, covering a wider solution area, avoiding detection deviation caused by uneven signal strength in local area, ensuring the stability and repeatability of the spectral signal, and finally making the infrared micro-nano optical fiber sensor 31 more accurately capture the characteristic absorption information of the reactants and products while efficiently and stably transmitting the light signal, and strengthening the monitoring performance of the optical fiber embedded reaction device 30.

[0031] Please refer to Figure 3 and Figure 4, the infrared micro-nano optical fiber sensor 31 further comprises non-tapered sections 301 located at both ends of the taper section 302, and in the cross section of the non-tapered section 301 along the vertical diameter: the diameter of the cladding 312 is 400-600 μm, the diameter of the core 311 is 100-150 μm, and the shortest distance between the core 311 and the outer ring of the cladding 312 is 20-40 μm; the above design not only reduces the transmission loss of the mid-infrared light through the appropriate core diameter, but also provides sufficient mechanical strength through the cladding 312 diameter to stabilize and protect the core from damage, ensuring efficient and stable light introduction into the taper section 302; and the reasonable distance between the core and the cladding 312 isolates multiple cores 311, avoids light field crosstalk, allows the cladding 312 to fully constrain the light field to reduce leakage, and does not occupy too much container space to affect the reaction system; ultimately, the non-tapered section 301 becomes a high-efficiency light transmission channel, a stable structure support, and a signal anti-interference barrier, laying the foundation for the taper section 302 to accurately generate evanescent waves and capture molecular vibration information of the chemical reaction system, and helping the infrared micro-nano optical fiber sensor 31 to improve detection sensitivity and data repeatability.

[0032] In the embodiment of the present application, the material of the core 311 is Ge 10 As 30 Se 44 Te 16 , which can transmit mid-infrared light with a wave number of 4000-850 cm -1 ; the material of the cladding 312 is Ge 10 As 30 Se 46 Te 14 ; the above two are both chalcogenide glass systems, which have excellent light transmission and no significant absorption in the 3-15 μm mid-infrared waveband, can avoid interference with the characteristic infrared signals of reactants and products in the reaction system, and ensure detection accuracy; by adjusting the element content, the refractive index can be accurately controlled, and "core 311 refractive index > cladding 312 refractive index" can be easily realized, satisfying the total reflection transmission of mid-infrared light in the core and reducing light leakage loss, providing sufficient light energy for the taper section 302 to generate strong evanescent waves; and the thermal expansion coefficients and chemical compatibility of the two are highly matched, which can avoid interface peeling and cracking, improve the stability of the optical fiber structure, and at the same time, the chalcogenide glass is resistant to chemical corrosion and can resist the erosion of organic solvents in the reaction system, prolonging the service life of the device.

[0033] Please refer to Figure 3 , the taper section 302 includes a waist section 3021 and sub-taper sections 3022 connected to both ends of the waist section 3021, the diameter of the sub-taper section 3022 linearly decreases along the direction close to the waist section 3021, and the diameter of the waist section 3021 is the same as the minimum diameter of the sub-taper section 3022; wherein the waist section 3021 includes one optical fiber sub-section 30211 bent into a ring, and the bending radius of the optical fiber sub-section 30211 is 1-3 mm.

[0034] Specifically, the diameter of the sub-tapered portion 3022 decreases linearly in the direction close to the waist portion 3021, which can avoid the loss caused by the sudden change of the diameter when the light is transmitted from the non-pulled tapered portion 301 to the waist portion 3021, and ensure smooth transmission of the optical signal, while realizing gradual enhancement of the evanescent wave. The diameter of the waist portion 3021 is consistent with the minimum diameter of the sub-tapered portion 3022 (the thinnest region of the pulled tapered portion 302), and the evanescent wave intensity of the waist portion 3021 is more obvious than that of the non-pulled tapered portion 301. The waist portion 3021 is designed as a 1-turn annular optical fiber sub-portion 30211 with a bending radius of 1-3 mm, which further amplifies the evanescent wave leakage, makes the evanescent wave and the molecules interact more fully to improve the detection sensitivity, and balances the mechanical stability of the optical fiber (avoids bending and breaking) and the spatial adaptability (does not occupy too much container space). The overall design ultimately helps the stable transmission of the optical signal and the efficient action of the evanescent wave, and improves the detection performance and data stability of the infrared micro-nano optical fiber sensor 31.

[0035] Further, since the waist portion 3021 includes a 1-turn annular optical fiber sub-portion 30211, the incident angle θ of the infrared incident light entering the optical fiber sub-portion 30211 is reduced. i According to formula (1), the presence of the optical fiber sub-portion 30211 increases the penetration depth d of the evanescent field. p Thus, the detection sensitivity of the infrared micro-nano optical fiber sensor 31 is improved; at the same time, the presence of the annular optical fiber sub-portion 30211 also increases the propagation path of the infrared light in the waist portion 3021, which enhances the evanescent field leakage by increasing the number of total internal reflections of the infrared light, thereby improving the detection sensitivity of the infrared micro-nano optical fiber sensor 31.

[0036] Please refer to Figure 3 and Figure 4 In the cross section of the waist portion 3021 along the vertical diameter: the diameter of the cladding 312 is 40-60 μm, the diameter of the core 311 is 10-15 μm, and the shortest distance between the core 311 and the outer circle of the cladding 312 is 1-4 μm. Among them, the thin diameter design of the pulled tapered portion 302 (compared with the non-pulled tapered portion 301, which is greatly reduced) can significantly weaken the constraint of the optical field in the core, greatly enhance the evanescent wave intensity and the interaction efficiency with the to-be-measured solution to improve the detection sensitivity, while the core diameter retains enough light transmission cross section to avoid excessive light scattering loss; the distance of 1-4 μm can isolate multiple cores 311 to prevent light field crosstalk and avoid spectral distortion, and the cladding 312 is moderately thin, which can protect the core and not hinder the evanescent wave leakage; the overall thin diameter also does not occupy too much space of the container, and is suitable for the in-situ reaction environment (does not affect the solution volume, ultraviolet irradiation, etc.), which ultimately makes the waist portion 3021 become the core area of strong evanescent wave generation and stable light transmission, and strengthens the detection performance of the infrared micro-nano optical fiber sensor 31.

[0037] In the embodiment of the present application, the length of the waist part 3021 is 15-25 mm, and the length of the sub-cone part 3022 is 1-3 mm. The waist part 3021 is the core area of strong evanescent wave action, and the length can extend the light transmission path in the limited space of the in-situ infrared reaction container 32, so that the leaked evanescent field enters the solution to be measured more and acts more fully, the signal capture efficiency of low-concentration components is improved, and excessive light loss is avoided; the sub-cone part 3022 is the transition area between the non-pull-taper part 301 and the waist part 3021, and is used to realize smooth transition of infrared light and avoid light leakage loss in this area, so as to ensure stable input of light energy into the waist part 3021; the length matching of the two can also adapt to the container space, without affecting the solution amount, ultraviolet light irradiation and other reaction conditions, and finally help the infrared micro-nano optical fiber sensor 31 to capture signals efficiently and transmit light stably, and improve the detection performance and data reliability.

[0038] In the embodiment of the present application, the infrared micro-nano optical fiber sensor is used for in-situ monitoring of 4000-850 cm -1 The absorbance change of the reactant and product molecules in the range where the characteristic absorption peaks of the functional groups do not overlap; the above-mentioned two kinds of functional groups do not overlap (4000-2500 cm Figure 8 、 Figure 9 -1), which completely avoids signal interference of the two on the spectrum, and the consumption rate of the reactant and the generation rate of the product at different time points can be accurately quantitatively calculated through the absorbance change of the independent peak, so as to provide accurate concentration data basis for subsequent fitting of the first-order kinetic equation, acquisition of the reaction rate constant and other key parameters, simplify the spectrum analysis process, improve the real-time performance and data repeatability of in-situ monitoring, and ensure the reliability of the chemical reaction kinetics analysis result.

[0039] Correspondingly, the present application also provides a method for monitoring chemical reaction kinetics by using the above-mentioned multi-core infrared optical fiber sensing device 100, and the method comprises the following steps: S10, adjusting the optical path of the multi-core infrared optical fiber sensing device 100, three-dimensionally adjusting the positions of the fiber-embedded reaction device 30 and the MCT liquid nitrogen refrigeration detector 50, so that the light rays focused by the first lens are fully coupled into each core of the infrared micro-nano optical fiber sensor 31, and the highest signal strength at the output end is ensured; S20, using the infrared micro-nano optical fiber sensor to sequentially collect characteristic evanescent wave absorption spectra of multiple groups of reactant solutions with different standard concentrations, multiple groups of product solutions with different standard concentrations, and calculating and establishing a quantitative relationship between the absorbance and the concentration of the reactant and the product according to the Lambert-Beer law, so as to finally obtain a sensitivity calibration fitting curve corresponding to each of the reactant and the product. S30, placing the to-be-tested solution in the in-situ infrared reaction container and ensuring that the infrared micro-nano fiber sensor 31 is completely immersed, then turning on the ultraviolet light source of the in-situ infrared reaction container to cause the to-be-tested solution to undergo a photocatalytic reaction, and collecting infrared evanescent wave absorption spectrum data of the reaction system every preset time, and then intercepting the reactant and the product in a characteristic absorption band to obtain their respective spectrum and absorbance change data; S40, according to the sensitivity calibration fitting curve of the reactant and the absorbance change of the reactant with different concentrations, the real-time concentration of the reactant in the reaction process is calculated, and according to the sensitivity calibration fitting curve of the product and the absorbance change of the product with different concentrations, the real-time concentration of the product in the reaction process is calculated, then the real-time concentration of the reactant and the product is fitted respectively according to the first-order kinetic equation, and finally the fitting curve of the concentration of the reactant and the product in the photocatalytic reaction of the to-be-tested solution with time is obtained.

[0040] In the embodiment of the present application, the monitoring method of the above-mentioned in-situ tracking chemical reaction multi-core infrared fiber sensing device 100 includes the following steps: Step (1) preparation before detection: turn on the infrared spectrometer 10, place the fiber-embedded reaction device 30 in the test light path, adjust the position of the fiber-embedded reaction device 30 to make the infrared light fully couple into the six cores 311 in the infrared micro-nano fiber sensor 31, and the infrared outgoing light energy is received by the MCT liquid nitrogen cooled detector 50. Do not add liquid, scan to obtain the background of the infrared micro-nano fiber sensor 31.

[0041] Step (2) sensitivity calibration of the infrared micro-nano fiber sensor 31: the reactant and the product are respectively prepared into at least 5 groups of standard solutions with different concentrations, the evanescent wave absorption spectrum of the to-be-tested solution is collected by using the infrared spectrometer 10, the characteristic absorption peaks of the reactant and the product are selected respectively, the quantitative relationship between the characteristic absorbance and the concentration of the reactant and the product is established, and two linear relationship curves are fitted to obtain the sensitivity.

[0042] Step (3) in-situ infrared monitoring: mix a certain concentration of reactant solution with a certain amount of photocatalyst in the in-situ infrared reaction container 32 embedded with the infrared micro-nano fiber sensor 31, and promote the reaction under ultraviolet light. Collect infrared absorption spectrum every certain time to reflect the infrared spectrum change of the reactant and the product characteristic absorption band.

[0043] Step (4) reaction kinetics quantitative: by calculating the absorbance change of reactants and products in their characteristic absorption band, the real-time concentration of two substances in the reaction process is calculated according to the established sensitivity calibration curve of infrared micro-nano fiber sensor 31, and the fitting curve of the concentration of reactants and products changing with time in the chemical reaction process is obtained by fitting with the first order kinetic equation.

[0044] The technical solutions of the present application will be described in conjunction with specific embodiments.

[0045] Embodiment 1: Please refer to Figures 1 to 4 The embodiment 1 provides a multi-core infrared optical fiber sensing device 100 for chemical reaction kinetics monitoring, which comprises an infrared spectrometer 10 with a light source, a first lens 20, a fiber-embedded reaction device 30, a second lens 40 and an MCT liquid nitrogen refrigeration detector 50 which are connected in sequence along the direction of incident light propagation, the fiber-embedded reaction device 30 comprises an in-situ infrared reaction container 32 for loading the solution to be measured and an infrared micro-nano fiber sensor 31. The infrared micro-nano fiber sensor 31 penetrates the in-situ infrared reaction container 32, and the infrared micro-nano fiber sensor 31 is used to monitor the characteristic absorption spectrum signal of the reactants and products in the solution to be measured in real time after receiving the mid-infrared light emitted by the light source. The part of the infrared micro-nano fiber sensor 31 located in the in-situ infrared reaction container 32 has a taper part 302, and the non-taper parts 301 at both ends of the taper part 302 are fixed in the through holes of the in-situ infrared reaction container 32, and the main part of the taper part 302 is suspended in the in-situ infrared reaction container 32 and contacts with the solution to be measured.

[0046] Specifically, the multi-core infrared optical fiber sensing device 100 further comprises a computer 60, one end of the MCT liquid nitrogen refrigeration detector 50 is electrically connected with the infrared spectrometer 10, the other end of the MCT liquid nitrogen refrigeration detector 50 is electrically connected with the computer 60, and the computer 60 is also electrically connected with the infrared spectrometer 10.

[0047] Specifically, the light source of the infrared spectrometer 10 can emit 4000~850 cm -1 mid-infrared light; the first lens 20 and the second lens 40 are both made of ZnSe material; the infrared micro-nano fiber sensor 31 comprises six cores 311; the part of the infrared micro-nano fiber sensor 31 located in the in-situ infrared reaction container 32 has a taper part 302, and the non-taper parts 301 at both ends of the taper part 302 are fixed in the through holes of the in-situ infrared reaction container 32, and the taper part 302 embedded in the in-situ infrared reaction container 32 remains suspended as the main part and contacts with the solution to be measured.

[0048] Please refer to Figure 4, the infrared micro-nano fiber sensor 31 further comprises a cladding 312, and the six cores 311 are embedded in the cladding 312; the refractive index of the core 311 is greater than the refractive index of the cladding 312, and the plurality of cores 311 are arranged at equal intervals along the circumferential direction of the cladding 312; the material of the core 311 is Ge 10 As 30 Se 44 Te 16 chalcogenide glass, the material of the cladding 312 is Ge 10 As 30 Se 46 Te 14 chalcogenide glass.

[0049] Specifically, the infrared micro-nano fiber sensor 31 further comprises a non-tapered portion 301 located at both ends of the tapered portion 302, and in a cross section of the non-tapered portion 301 along the vertical diameter direction: the diameter D clad of the cladding 312 is 500 μm, the diameter D core of the core 311 is 120 μm, the shortest distance D t between the core 311 and the outer ring of the cladding 312 is 30 μm; the six cores 311 are externally tangent to a circle with the center of the cladding 312 as the center and a diameter D l of 200 μm; and the included angle between the core center of the adjacent two cores 311 and the center line of the cladding 312 is 60°.

[0050] Specifically, the tapered portion 302 comprises a waist portion 3021 and a sub-tapered portion 3022 connected to both ends of the waist portion 3021; the diameter of the sub-tapered portion 3022 decreases linearly along the direction close to the waist portion 3021, and the diameter of the waist portion 3021 is the same as the minimum diameter of the sub-tapered portion 3022; and in a cross section of the waist portion 3021 along the vertical diameter direction: the diameter D clad of the cladding 312 is 50 μm, the diameter D core of the core 311 is 12 μm, the shortest distance D t between the core 311 and the outer ring of the cladding 312 is 3 μm; the six cores 311 are externally tangent to a circle with the center of the cladding 312 as the center and a diameter D l of 20 μm; and the included angle between the core center of the adjacent two cores 311 and the center line of the cladding 312 is 60°. Wherein, the fiber is processed by the tapering to form the tapered portion 302, and due to the overall size being thin, the evanescent wave leakage is more obvious than the non-tapered portion 301, and after the waist portion 3021 is bent into a ring structure, the evanescent wave leakage is further increased, and the detection sensitivity of the infrared micro-nano fiber sensor 31 is improved.

[0051] Specifically, the waist 3021 includes 1 ring of optical fiber sub 30211, the bending radius of the optical fiber sub 30211 is 1 mm; the length of the waist 3021 (including the optical fiber sub 30211 bent into a ring) of the infrared micro-nano fiber sensor 31 after being pulled into a taper is 20 mm, and the length of the sub-tapered part 3022 is 2 mm. The in-situ infrared reaction container 32 is internally provided with a ultraviolet light source 321 capable of emitting ultraviolet light, and the to-be-measured solution undergoes a chemical reaction under the irradiation of ultraviolet light. The material of the in-situ infrared reaction container 32 is quartz glass.

[0052] In the in-situ tracking chemical reaction multi-core infrared optical fiber sensing device 100 provided in the embodiment 1, the preparation process of the infrared micro-nano fiber sensor 31 with a multi-core-cladding structure is as follows: First, Ge 10 As 30 Se 44 Te 16 glass with a refractive index of 3.13 is prepared as the material of the core 311, and Ge 10 As 30 Se 46 Te 14 glass with a refractive index of 3.12 is prepared as the material of the cladding 312. The two kinds of glass components have good compatibility in thermal properties and mechanical properties, and are suitable for preparing core-cladding structure optical fibers. Secondly, a section of Ge 10 As 30 Se 46 Te 14 glass rod is ultrasonically drilled to form a structured glass rod with six uniformly distributed and equal-sized air holes, and then the structured Ge 10 As 30 Se 44 Te 16 glass rod is drawn into an elongated shape to match the air holes of the structured Ge 10 As 30 Se 46 Te 14 glass rod; Thirdly, the elongated Ge 10 As 30 Se 44 Te 16 rod is inserted into the structured Ge 10 As 30 Se 46 Te 14The rod is then put into a drawing tower, and certain process parameters, such as drawing temperature and speed, are set to draw and lengthen the rod into a 500-μm-diameter optical fiber with six 120-μm-diameter cores distributed at equal intervals; Again, a section of the optical fiber is cut and is drawn into a tapering part 302 by a tapering platform, and a 20-mm-long waist 3021 of the tapering part 302 is wound around a heated ceramic rod with a radius of 1 mm to form a 1-mm-radius ring (optical fiber subpart 30211), which is the infrared micro-nano optical fiber sensor 31 in Embodiment 1. Finally, the original infrared reaction container 32 is symmetrically punched on the left and right sides, and the prepared infrared micro-nano optical fiber sensor 31 is inserted thereinto, and the left and right through holes are sealed and fixed with ultraviolet curing glue to obtain the fiber-embedded reaction device 30. The in-situ infrared monitoring method for the photocatalytic reaction is based on infrared evanescent wave spectroscopy. The fiber-embedded reaction device 30 is placed in the infrared sensing light path, and infrared data can be collected in real time for quantitative and qualitative analysis.

[0053] Embodiment 1 provides a low-cost and non-invasive in-situ infrared device and method based on optical fiber evanescent wave spectroscopy. The innovation lies in that the sensor with excellent sensitivity can track the reaction kinetics of the reaction liquid without pretreatment in real time. The multi-core infrared optical fiber sensing device 100 for monitoring the chemical reaction kinetics comprises an infrared spectrometer 10, a first lens 20, a second lens 40, a fiber-embedded reaction device 30, an MCT liquid nitrogen cooling detector 50, and a computer 60, as shown in the schematic diagram: Figure 1 As shown in the schematic diagram: a beam of infrared light emitted by an infrared light source (generally a carbon-silicon rod) is focused and coupled into the infrared micro-nano optical fiber sensor 31 in the fiber-embedded reaction device 30 through the first lens 20 made of ZnSe, and the emitted infrared light is again coupled into the MCT detector through the second lens 40 at the exit end of the infrared micro-nano optical fiber sensor 31 after multiple total reflections in the core; the in-situ infrared reaction container 32 is made of materials with stable chemical properties, such as quartz glass, ceramic, and polytetrafluoroethylene, which do not react with any organic substances in the reaction system to interfere with the in-situ infrared monitoring; the infrared micro-nano optical fiber sensor 31 is fixed by being embedded in the in-situ infrared reaction container 32, and the thinner tapering part 302 contacts the reaction liquid. The infrared light is first focused and coupled into the core for transmission, total internal reflection occurs at the core-cladding interface to generate evanescent waves that penetrate the cladding 312 to interact with the surrounding liquid to produce evanescent wave absorption. Due to the presence of the cladding 312, there is a clear evanescent field only in the tapering part 302. The consumption of reactants and the generation of products cause changes in the evanescent wave absorption of specific functional groups. The applicant collects infrared absorption spectra at intervals until the reaction is completed to obtain a series of spectral data reflecting the changes (displayed on the spectrum software of the computer).

[0054] The multi-core infrared optical fiber sensing device 100 for chemical reaction kinetics monitoring provided in Embodiment 1 is applied to in-situ infrared monitoring of the chemical reaction of an ethanol solution of C7H6O (benzaldehyde), and the in-situ infrared monitoring method using the optical fiber embedded reaction device 30 generally includes the following steps: tapering the optical fiber and bending the thinner tapered part 302 into a ring to obtain an infrared micro-nano fiber sensor 31, and embedding the infrared micro-nano fiber sensor 31 in the in-situ infrared reaction container 32 to obtain the optical fiber embedded reaction device 30; placing the whole infrared micro-nano fiber sensor 31 in the infrared sensing light path; and immersing the tapered part 302 of the infrared micro-nano fiber sensor 31 in the mixed reaction system to realize dynamic monitoring of the reaction process by observing the changes in the real-time infrared evanescent wave absorption spectrum, and the specific monitoring steps include: Step (1) light path adjustment: place the in-situ infrared reaction container 32 with the embedded infrared micro-nano fiber sensor 31 on the operation platform, so that the infrared micro-nano fiber sensor 31 is in the test light path, and precisely adjust the relative positions of the infrared micro-nano fiber sensor 31, the first lens 20, the second lens 40 and the MCT liquid nitrogen cooled detector using the three-dimensional displacement table, to ensure that the focused infrared light beam is fully coupled into the infrared micro-nano fiber sensor 31 in the optical fiber embedded reaction device 30 to obtain the highest signal strength at the output end, set the spectral parameters, the measurement wave number is 4000~850 cm -1 , the resolution is 4 cm -1 , and the scanning number is 32 times. After scanning the fiber background, the test can be started.

[0055] Step (2) sensitivity calibration: prepare at least 5 groups of standard concentration reactants and product solutions for fiber sensor sensitivity calibration, wherein the 5 groups of concentrations of the reactant C7H6O solution are 50 mmol / L, 150 mmol / L, 300 mmol / L, 400 mmol / L and 500 mmol / L, and the 5 groups of concentrations of the product C 11 H 16 O2 solution are 42.29 mmol / L, 126.87 mmol / L, 211.46 mmol / L, 338.34 mmol / L and 422.92 mmol / L, and the infrared fiber is used to collect the infrared evanescent wave absorption spectrum of the test liquid in sequence, as shown in Figure 5 and Figure 6 ; select the characteristic absorption peaks of the two substances as the research objects, calculate the quantitative relationship between the characteristic wave number absorption peak area (hereinafter referred to as absorbance) of the reactant and the product and the concentration according to the Lambert-Beer law, as shown in Figure 7 , and the tapered infrared micro-nano fiber sensor 31 is used to monitor the reactant benzaldehyde (C7H6O) and the product benzaldehyde diethyl acetal (C 11 H 16The detection sensitivity of C7H6O and C7H6O2 is 0.01644 a.u. / (mmol / L) and 0.0032 a.u. / (mmol / L) respectively.

[0056] Step (3) generates C7H6O from C7H6O 11 H 16 O2 in-situ infrared monitoring: a certain volume of 400 mmol / L C7H6O mixed solution is mixed with a certain amount of photocatalyst (TiO2) in a liquid reaction container to ensure that the optical fiber is immersed, and the reaction is started under ultraviolet light. The infrared absorption spectrum is tested at intervals. The change of absorbance of each characteristic wave number of reactants and products is shown in the following figure: Figures 8 to 9 The real-time concentration change of the two substances in the reaction process is calculated according to the sensitivity fitting curve of the infrared micro-nano fiber sensor 31 for the reactants and products respectively.

[0057] Step (4) reaction kinetics analysis: according to the change of absorbance of the reactant C7H6O and the product C7H6O2, the real-time concentration of the two substances is calculated by the absorbance-concentration quantitative model established in step (2), as shown in the following figure: 11 H 16 Figure 10 The in-situ infrared monitoring results clearly show the whole process of the concentration of the reactant C7H6O decreasing from 400 mmol / L to the reaction equilibrium point and the product C7H6O2 being generated; since the chemical reaction is a first-order kinetic reaction, i.e. the reaction rate is proportional to the real-time concentration of the reactant, the real-time concentration curve of the reactant and the product is fitted by selecting a first-order kinetic fitting equation, and the reaction kinetics is analyzed. The corresponding conversion rate and yield can also be obtained by calculation. 11 H 16

[0058] Specifically, steps (2) and (3) are two independent steps, and the same infrared micro-nano fiber sensor 31 is used for testing, and before each test, the fiber background signal needs to be scanned, that is, the operation of step (1) is repeated before steps (2) and (3), and the modulated signal values are consistent. The real-time concentration fitting formula (2) of the reactant and the product in step (4) is: ; The formula is used for quantitative analysis of reaction kinetics, wherein C represents the concentration of the reactant or the product monitored by the sensor in real time; t the parameter a represents the change of equilibrium concentration, wherein a <0 represents the consumption of the reactant, and vice versa a >0 represents the generation of the product; the parameter b represents the first-order reaction kinetics parameter; c ​​The initial concentration of the reactant or product in the solution corresponds to the initial concentration of the reactant or product in the solution, the initial concentration of the reactant is 400 mmol / L by default, and the initial concentration of the product is 0 by default.

[0059] Embodiment 2: See Figures 1 to 4 Embodiment 2 provides a multi-core infrared optical fiber sensing device 100 for monitoring the kinetics of chemical reactions and an in-situ infrared monitoring method, which has the same structure and specific parameters as Embodiment 1.

[0060] The specific steps of in-situ infrared monitoring of the reaction of the multi-core infrared optical fiber sensing device 100 for monitoring the kinetics of chemical reactions provided in Embodiment 2 on the ethanol solution of C7H5OCl (p-chlorobenzaldehyde) are similar to those of Embodiment 1, and the same catalyst is used for the reaction of Embodiment 1, and the infrared evanescent wave absorption spectrum also accurately reflects and analyzes the reaction kinetics of C7H5OCl to C 11 H 15 O2Cl (p-chlorobenzaldehyde diethyl acetal).

[0061] Embodiment 3: See Figures 1 to 4 Embodiment 3 provides a multi-core infrared optical fiber sensing device 100 for monitoring the kinetics of chemical reactions and an in-situ infrared monitoring method applied to photocatalytic reactions, which has the same structure and specific parameters as Embodiments 1 and 2.

[0062] The multi-core infrared optical fiber sensing device 100 for monitoring the kinetics of chemical reactions provided in Embodiment 3 monitors the reaction of the ethanol solution of C7H6O in Embodiment 1 using a composite photocatalyst (CsPbBr3 / TiO2 composite material) as catalyst. As in the in-situ infrared monitoring steps of Embodiment 1, the analysis of the reaction kinetics through the infrared evanescent wave absorption spectrum reflects that the composite photocatalyst makes the reaction rate faster than the photocatalyst (TiO2) in Embodiment 1.

[0063] Specifically, the fitting data of the reaction kinetics of Embodiments 1 to 3 is shown in Table 1: Table 1

[0064] As can be seen from Table 1, the in-situ infrared monitoring based on the evanescent wave spectrum of the optical fiber accurately reflects the kinetic characteristics of different photocatalytic reactions, i.e. the consumption of reactants is accompanied by the generation of respective products, and the reaction can proceed faster after replacing the original photocatalyst with a composite photocatalyst, which further reveals the reaction mechanism.

[0065] The application discloses a multi-core infrared optical fiber sensing device 100 based on an optical fiber evanescent wave effect and a monitoring method. The optical fiber sensing module: the infrared micro-nano optical fiber sensor 31 with the multi-core-cladding 312 structure is prepared by using different refractive indexes of the core 311 and the cladding 312, based on the principle that infrared light generates evanescent waves at the core-cladding interface, the prepared infrared micro-nano optical fiber sensor 31 realizes high-sensitivity detection of reactants and products and establishes linear models of absorbance-concentration of the two substances respectively. The in-situ spectrum detection module: the infrared micro-nano optical fiber sensor 31 of the module is not affected by ultraviolet light, has the characteristics of anti-electromagnetic interference and corrosion resistance, can be in contact with the reaction liquid for a long time, and the changes of the reactants and the products are reflected through a series of infrared evanescent wave absorption spectra. The kinetic analysis module: through time series difference spectrum analysis, the periodically collected real-time infrared spectrum of the reaction system is differentially operated with the initial spectrum of the reaction system, the absorbance attenuation trend of the reactants and the absorbance growth trend of the products (as shown in the drawing) are obtained, the absorbance-concentration quantitative model established according to the Lambert-Beer law is used to display the real-time concentration curves of the reactants and the products, and the curves are fitted and analyzed to obtain the reaction kinetics. Figures 8 to 9 The multi-core infrared optical fiber sensing device 100 and the method for monitoring chemical reaction kinetics provided by the application have the advantages of simple operation, portable device, no damage to equipment and long-time monitoring of the reaction process, and the reaction kinetics of the reactants and the products can be obtained simultaneously by monitoring a complete reaction once. The same device can be repeatedly used to complete the sensitivity calibration of standard reactants and products and in-situ infrared monitoring of multiple reaction kinetics (such as examples 1 to 3). The in-situ infrared monitoring function of the multi-core infrared optical fiber sensing device 100 is powerful, and as a new in-situ infrared monitoring technology, has a broad application prospect.

[0066] It should be noted that the above examples all belong to the same inventive concept, and the description of each example has its own emphasis.

[0067] The above embodiments only express the implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A multicore infrared optical fiber sensing device for chemical reaction kinetics monitoring, characterized by, The infrared spectrometer comprises, in sequence along the direction of incident light propagation, an infrared spectrometer with a light source, a first lens, a fiber-embedded reaction device, a second lens, and an MCT liquid nitrogen-cooled detector. The fiber-embedded reaction device comprises an in-situ infrared reaction container for loading a solution to be measured and an infrared micro-nano fiber sensor with a plurality of cores.

2. The multi-core infrared optical fiber sensing device for chemical reaction kinetics monitoring according to claim 1, wherein, The infrared micro-nano fiber sensor is used to monitor the characteristic absorption spectrum signals of reactants and products in the solution to be measured in real time after receiving the mid-infrared light emitted by the light source.

3. The multi-core infrared optical fiber sensing device for chemical reaction kinetics monitoring according to claim 2, wherein, The infrared micro-nano fiber sensor further comprises a cladding layer with a refractive index smaller than that of the core.

4. The multi-core infrared optical fiber sensing device for monitoring chemical reaction kinetics according to claim 2, wherein, The plurality of cores are embedded in the cladding layer and are arranged at equal intervals along the circumferential direction of the cladding layer.

5. The multi-core infrared optical fiber sensing device for chemical reaction kinetics monitoring according to claim 4, wherein, The materials of the core and the cladding layer both comprise Ge-As-Se-Te chalcogenide glass.

6. The multi-core infrared optical fiber sensing device for monitoring chemical reaction kinetics according to claim 4, wherein, The part of the infrared micro-nano fiber sensor embedded in the in-situ infrared reaction container is provided with a tapered section, the non-tapered sections adjacent to the two ends of the tapered section are respectively fixed to the through holes in the wall of the in-situ infrared reaction container, and the main body part of the tapered section is suspended in the in-situ infrared reaction container and is in contact with the solution to be measured.

7. The multi-core infrared optical fiber sensing device for monitoring chemical reaction kinetics according to claim 4, wherein, The tapered section comprises a waist section and two sub-tapered sections connected to the two ends of the waist section.

8. The multi-core infrared optical fiber sensing device for monitoring chemical reaction kinetics according to claim 1, wherein, The infrared micro-nano fiber sensor is used for in-situ monitoring absorbance changes of infrared characteristic absorption peaks of molecular functional groups of reactants and products in a range of 4000~850 cm -1 The characteristic absorption peaks of the reactants and the characteristic absorption peaks of the products are in a non-overlapping wave band in a range of 4000~850 cm -1 The characteristic absorption peaks of the reactants and the characteristic absorption peaks of the products are in a non-overlapping wave band in a range of 4000~850 cm 9. The multi-core infrared optical fiber sensing device for monitoring chemical reaction kinetics according to claim 1, wherein, The length of the waist section is 15-25 mm, and the length of the sub-tapered section is 1-3 mm.

10. A method for monitoring chemical reaction kinetics using the multi-core infrared optical fiber sensing device according to any one of claims 1 to 9, characterized in that, The waist section comprises one loop of fiber sub-sections with a bending radius of 1-3 mm. The micro-nano fiber further comprises non-tapered sections at the two ends of the tapered section. In the non-tapered sections along the vertical radial cross section, the diameter of the cladding layer is 400-600 μm, the diameter of the core is 100-150 μm, and the spacing between the core and the outer circle of the cladding layer is 20-40 μm. In the waist section along the vertical radial cross section, the diameter of the cladding layer is 40-60 μm, the diameter of the core is 10-15 μm, and the spacing between the core and the outer circle of the cladding layer is 1-4 μm. The in-situ infrared reaction container is built-in with a ultraviolet light source capable of emitting ultraviolet light, and the solution to be measured reacts under ultraviolet light irradiation. The material of the in-situ infrared reaction container comprises any one of quartz glass, ceramic, and polytetrafluoroethylene. The method comprises: S10, three-dimensionally adjusting the positions of the fiber-embedded reaction device and the MCT liquid nitrogen-cooled detector, so that the light focused by the first lens is fully coupled into the plurality of cores of the infrared micro-nano fiber sensor; S20, using the infrared micro-nano fiber sensor to sequentially collect a plurality of groups of characteristic evanescent wave absorption spectra of reactant solutions with different standard concentrations and a plurality of groups of characteristic evanescent wave absorption spectra of product solutions with different standard concentrations, and calculating and establishing the quantitative relationship between the absorbance and the concentration of the reactants and the products according to the Lambert-Beer law to finally obtain the sensitivity calibration fitting curves of the reactants and the products, respectively; S30, placing the to-be-tested solution in the in-situ infrared reaction container and ensuring complete immersion of the infrared micro-nano optical fiber sensor, then turning on the ultraviolet light source of the in-situ infrared reaction container to cause the to-be-tested solution to undergo a photocatalytic reaction, collecting infrared evanescent wave absorption spectrum data of the reaction system every preset time interval, and then respectively intercepting reactants and products in a characteristic absorption band to obtain their respective corresponding spectrum and absorbance change data; S40, calculating the real-time concentration of the reactant in the reaction process according to the sensitivity calibration fitting curve of the reactant and the absorbance change of the reactant with different concentrations, and calculating the real-time concentration of the product in the reaction process according to the sensitivity calibration fitting curve of the product and the absorbance change of the product with different concentrations, then respectively performing first-order kinetic equation fitting on the respective corresponding real-time concentrations of the reactant and the product, and finally obtaining the fitting curve of the concentration change of the reactant and the product with time in the photocatalytic reaction of the to-be-tested solution.

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