Method and device for constructing in-situ absorption spectrum by using flow cell to explore femtosecond laser-induced ultrafast reaction mechanism

Abstract

The invention relates to the technical field of chemical reaction kinetics and characterization, in particular to a method and a device for constructing an in-situ absorption spectrum by using a flow cell to explore a femtosecond laser-induced ultrafast reaction mechanism. The method comprises the following steps: S1, adding metal salt into deionized water or absolute ethyl alcohol, and uniformly mixing to obtain a precursor solution; s2, building a flow cell system; s3, constructing a femtosecond laser pumping-probe system; and S4, collecting and analyzing the in-situ spectrum. Real-time monitoring of ultrafast response from femtosecond to nanosecond scale is realized, and dynamic mechanisms of electron-photon interaction, chemical bond fracture or material damage are disclosed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical reaction kinetics and characterization technology, and particularly relates to a method and device for exploring femtosecond laser-induced ultrafast reaction mechanism by using a flow cell to construct in-situ absorption spectrum. BACKGROUND

[0002] Femtosecond laser can induce ultrafast reactions under non-thermal equilibrium conditions in the time scale of picoseconds to nanoseconds due to its ultra-short pulse and high energy density, and is widely used in the fields of nanomaterial synthesis, chemical reactions and material processing. These reactions involve complex dynamic processes such as electron-photon interaction, ion reduction, chemical bond rupture or material damage. Traditional transient absorption spectroscopy technology can monitor spectral changes in real time through pump-probe method, but its design relies on multiple signal accumulation to improve signal-to-noise ratio, is only suitable for reversible reactions, and cannot capture irreversible reactive processes or damage processes. In addition, the traditional method is generally detected in a static liquid system, the sample is exposed unevenly, the spectral data has poor repeatability, it is difficult to reflect the real dynamics under continuous reaction conditions, and the static environment cannot maintain stable measurement for a long time, the signal noise is high, which limits the analysis of complex reaction mechanism. SUMMARY

[0003] In view of the above analysis, the embodiments of the present application aim to provide a method and device for exploring femtosecond laser-induced ultrafast reaction mechanism by using a flow cell to construct in-situ absorption spectrum, so as to solve one of the problems that the traditional detection method has poor universality and poor consistency and stability in non-static environment.

[0004] In one aspect, the embodiments of the present application provide a method for exploring femtosecond laser-induced ultrafast reaction mechanism by using a flow cell to construct in-situ absorption spectrum, comprising: S1: adding a metal salt into deionized water or anhydrous ethanol, uniformly mixing to obtain a precursor solution; S2: building a flow cell system; S3: constructing a femtosecond laser pump-probe system; S4: collecting and analyzing in-situ spectrum; The flow cell system comprises a transparent quartz cuvette for femtosecond laser transmission and spectral collection, a peristaltic pump for controlling the continuous flow of the precursor solution, a solution storage tank and a magnetic stirrer. The femtosecond laser pump-probe system comprises a femtosecond laser, a beam splitter for splitting the femtosecond laser into pump light and probe light, a plano-convex lens for focusing the light beam, a mirror and an optical delay line. The beam splitter splits the femtosecond laser into pump light and probe light, the pump light is focused into a linear light field by the plano-convex lens, irradiates the flow cell cuvette to induce ultrafast reaction, the probe light is time-controlled by the optical delay line, and the transient absorption spectrum is collected by the fiber-coupled spectrometer.

[0005] Furthermore, in S1, the metal salt is selected from one or more of HAuCl4, FeCl3, and CuCl2; preferably, the metal salt is HAuCl4.

[0006] Furthermore, the concentration of the metal salt in deionized water or anhydrous ethanol is 0.01-0.1 mol / L.

[0007] Furthermore, in S2, the optical path width of the transparent quartz cuvette is 1 mm; the peristaltic pump flow rate is 0.1-10 mL / min.

[0008] Furthermore, in S3, an ultrafast reaction is induced by irradiating the flow cell cuvette with pump light, the ultrafast reaction including a metal ion reduction reaction; The delay range of the optical delay line is 0-2 ns.

[0009] Furthermore, in S4, transient absorption spectra are recorded in real time under different peristaltic pump flow rates and femtosecond laser energy densities; by fitting the spectral signals, the ultrafast dynamic changes of irreversible reactions or damage processes are analyzed.

[0010] Furthermore, the femtosecond laser processing parameters are: laser repetition rate of 1 kHz, and femtosecond laser energy density adjusted to 0.1-10 J / cm² via an optical parametric amplifier. 2 Wavelength 320nm-800nm.

[0011] On one hand, embodiments of the present invention provide a device for exploring the mechanism of femtosecond laser-induced ultrafast reactions by constructing in-situ absorption spectroscopy using a flow cell, comprising: Femtosecond laser pump-probe system, flow cell system, spectrometer for acquiring final spectral data, and precursor solution to be detected; The femtosecond laser pump-probe system includes: a femtosecond laser, a beam splitter for splitting the femtosecond laser beam, a plano-convex lens for focusing the beam, a mirror, and an optical delay line; the beam splitter splits the femtosecond laser beam into pump light and probe light, the pump light is focused into a linear light field by the plano-convex lens to irradiate a flow cell cuvette to induce an ultrafast reaction, and the probe light has its timing controlled by the optical delay line and its transient absorption spectrum is collected by a fiber-coupled spectrometer; The flow cell system includes: a transparent quartz cuvette, a peristaltic pump, a solution storage tank, and a magnetic stirrer, used to achieve continuous flow and uniform mixing of the solution; The precursor solution is obtained by adding a metal salt to deionized water or anhydrous ethanol and mixing them evenly.

[0012] Furthermore, the metal salt is selected from one or more of HAuCl4, FeCl3, and CuCl2; preferably, the metal salt is HAuCl4. The concentration of the metal salt in deionized water or anhydrous ethanol is 0.01-0.1 mol / L.

[0013] Furthermore, the optical path width of the transparent quartz cuvette is 1 mm; the flow rate of the peristaltic pump is 0.1-10 mL / min; The delay range of the optical delay line is 0-2 ns.

[0014] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. This invention utilizes an in-situ absorption spectroscopy method combining a flow cell with a femtosecond laser-pumped probe system to overcome the reversibility limitations of traditional TA; by continuously updating reactants through the flow cell, it supports high signal-to-noise ratio spectral acquisition for a single reaction, and is suitable for irreversible reactive and damaging processes; it enables real-time monitoring of ultrafast reactions at the femtosecond to nanosecond scale, revealing the dynamic mechanisms of electron-photon interactions, chemical bond breaking, or material damage.

[0015] 2. This invention provides a universal method applicable to irreversible reactions, such as metal ion reduction, and supports mechanism studies under continuous reaction conditions.

[0016] 3. This invention supports single-response spectral acquisition by continuously updating reactants through a flow cell, overcoming the limitations of traditional TA which requires signal accumulation and is limited by reversible reactions. It is suitable for irreversible and damaging processes. The flow cell ensures sample consistency, overcoming the defects of uneven sample exposure in static systems. The spectral data has high repeatability and signal-to-noise ratio. Furthermore, the flow cell supports long-term stable spectral acquisition, making it suitable for mechanism studies under continuous reaction conditions.

[0017] 4. This invention captures the reaction dynamics on the picosecond to nanosecond scale using a pump-probe system, revealing the mechanism of irreversible reactions induced by femtosecond lasers. Attached Figure Description

[0018] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0019] Figure 1 This is a schematic diagram of the device used in this invention to construct in-situ absorption spectroscopy in a flow cell to explore the mechanism of femtosecond laser-induced ultrafast reactions; Figure 2 This is a schematic diagram illustrating the process and principle of the in-situ absorption spectroscopy method constructed using a flow cell for single signal detection according to the present invention. Figure 3This is a schematic diagram of the method for detecting different substances by controlling different flow rate control devices according to the present invention; Figure 4 for Figure 3 Schematic diagram of in-situ transient absorption spectra of 0.01 M HAuCl4 solution at different flow rates; Figure 5 This is a schematic diagram comparing the repeatability of traditional transient absorption spectra with in-situ transient absorption spectra. Figure 6 This is a schematic diagram showing the test results for different test solutions.

[0020] Figure label: 1-Femtosecond laser; 2-Optical parametric amplifier; 3-Spectrometer; 4-Peristaltic pump; 5-Beam splitter; 6-Reflector; 7-White light crystal; 8-Planto-convex lens I; 9-Planto-convex lens II; 10-Planto-convex lens III; 11-Filter; 12-Initial light source; 13-Laser optical path; 14-Detector optical path; 15-Displacement stage; 16-Transparent quartz cuvette. Detailed Implementation

[0021] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0022] Femtosecond lasers, due to their ultrashort pulses and high energy density, can induce ultrafast reactions under non-thermal equilibrium conditions within picosecond to nanosecond timescales. They are widely used in fields such as nanomaterial synthesis (e.g., metal nanoparticles), chemical reactions (e.g., molecular decomposition), and material processing (e.g., ablation, pyrolysis). These reactions involve complex dynamic processes such as electron-photon interactions, ion reduction, chemical bond breaking, or material damage. Traditional transient absorption spectroscopy (TA) techniques can monitor spectral changes in real time using a pump-probe method, but their design relies on multiple signal accumulations to improve the signal-to-noise ratio, and the experimental preconditions require reversible reactions (e.g., photoexcited state dynamics), which limits their application. Reversibility limitations: Traditional TA requires multiple signal accumulations and is only applicable to reversible reactions (such as photophysical processes). It cannot capture irreversible reactive processes (such as metal ion reduction and molecular decomposition) or damaging processes (such as material ablation). Static environment limitations: In static liquid phase systems, sample exposure is uneven, spectral data repeatability is poor, and it is difficult to reflect the true dynamics under continuous reaction conditions. Insufficient long-term stability: Static environments cannot maintain stable measurements for a long time, signal noise is high, and it limits the analysis of complex reaction mechanisms.

[0023] For offline characterization methods (such as TEM and XPS), in-situ real-time testing is not possible.

[0024] To address the above problems, this invention provides a method for exploring the mechanism of femtosecond laser-induced ultrafast reactions by constructing in-situ absorption spectroscopy using a flow cell, comprising: S1: Add the metal salt to deionized water or anhydrous ethanol and mix evenly to obtain a precursor solution; S2: Construct a flow cell system; S3: Constructing a femtosecond laser pump-probe system; S4: Acquire and analyze in-situ spectra; The flow cell system includes: a transparent quartz cuvette for femtosecond laser transmission and spectral acquisition, a peristaltic pump for controlling the continuous flow of the precursor solution, a solution storage tank, and a magnetic stirrer. The femtosecond laser pump-probe system includes: a femtosecond laser, a beam splitter for splitting the femtosecond laser beam, a plano-convex lens for focusing the beam, a mirror, and an optical delay line. The beam splitter splits the femtosecond laser beam into pump light and probe light. The pump light is focused into a linear light field by the plano-convex lens to irradiate a flow cell cuvette and induce an ultrafast reaction. The probe light has its timing controlled by the optical delay line and its transient absorption spectrum is collected by a fiber-coupled spectrometer.

[0025] In one possible implementation, in S1, the metal salt is selected from one or more of HAuCl4, FeCl3, and CuCl2; preferably, the metal salt is HAuCl4.

[0026] The concentration of each metal salt in deionized water or anhydrous ethanol is 0.01-0.1 mol / L.

[0027] Among them, the precursor solution is stirred by a magnetic stirrer to ensure that the precursor is evenly distributed in the solvent. The solution form of the sample ensures that the reactants are evenly dispersed and supports the monitoring of irreversible reactions.

[0028] In one possible implementation, in S2, the optical path width of the transparent quartz cuvette is 1 mm.

[0029] The peristaltic pump has a flow rate of 0.1-10 mL / min to control the continuous flow of the solution, ensuring that the reaction zone is always a fresh sample, thus overcoming the limitation of traditional TA which requires multiple accumulations.

[0030] During the detection process, a magnetic stirrer was used to continuously stir the precursor solution to ensure uniform mixing and enhance the repeatability of spectral data.

[0031] The solution storage tank is used to store the precursor solution.

[0032] In one possible implementation, in S3, an ultrafast reaction is induced by irradiating a flow cell cuvette with pump light; the ultrafast reaction includes a metal ion reduction reaction.

[0033] The delay range of the optical delay line is 0-2 ns.

[0034] Furthermore, the femtosecond laser pump-probe system also includes: an optical parametric amplifier and a filter; the plano-convex lens includes convex lens I, plano-convex lens II, and plano-convex lens III; wherein, plano-convex lens I is used to focus the white light in the probe optical path onto the sample; plano-convex lens II is used to focus the ultraviolet light in the laser optical path onto the sample; and plano-convex lens III is used to refocus the white light passing through the sample for subsequent signal acquisition.

[0035] In one possible implementation, in S4, transient absorption spectra are recorded in real time under different peristaltic pump flow rates and femtosecond laser energy densities; by fitting the spectral signals, the ultrafast dynamic changes of irreversible reactions or damage processes are analyzed.

[0036] The peristaltic pump has a flow rate of 0.1-10 mL / min, and the femtosecond laser energy density is 0.1-10 J / cm³. 2 ; The femtosecond laser processing parameters are as follows: laser repetition rate of 1 kHz, and femtosecond laser energy density controlled to 0.1-10 J / cm² via an optical parametric amplifier. 2 Wavelength 320nm-800nm.

[0037] The fitted spectral signals include the surface plasmon resonance peaks of metal nanoparticles and the characteristic absorption peaks of molecular decomposition products.

[0038] On the one hand, this invention provides a device for exploring the mechanism of femtosecond laser-induced ultrafast reactions by constructing in-situ absorption spectroscopy using a flow cell. Includes: a femtosecond laser pump-probe system, a flow cell system, a spectrometer for acquiring the final spectral data, and the precursor solution to be detected; The femtosecond laser pump-probe system includes: a femtosecond laser, a beam splitter for splitting the femtosecond laser beam, a plano-convex lens for focusing the beam, a mirror, and an optical delay line; the beam splitter splits the femtosecond laser beam into pump light and probe light, the pump light is focused into a linear light field by the plano-convex lens to irradiate a flow cell cuvette to induce an ultrafast reaction, and the probe light has its timing controlled by the optical delay line and its transient absorption spectrum is collected by a fiber-coupled spectrometer; The flow cell system includes: a transparent quartz cuvette, a peristaltic pump, a solution storage tank, and a magnetic stirrer, used to achieve continuous flow and uniform mixing of the solution; The precursor solution is obtained by adding a metal salt to deionized or anhydrous ethanol and mixing them uniformly.

[0039] In one possible implementation, the metal salt is selected from one or more of HAuCl4, FeCl3, and CuCl2; preferably, the metal salt is HAuCl4.

[0040] The concentration of each metal salt in deionized water or anhydrous ethanol is 0.01-0.1 mol / L.

[0041] In one possible implementation, the optical path width of the transparent quartz cuvette is 1 mm; the flow rate of the peristaltic pump is 0.1-10 mL / min; The delay range of the optical delay line is 0-2 ns.

[0042] Furthermore, the femtosecond laser pump-probe system also includes: an optical parametric amplifier and a filter; the plano-convex lens includes convex lens I, plano-convex lens II, and plano-convex lens III; wherein, plano-convex lens I is used to focus the white light in the probe optical path onto the sample; plano-convex lens II is used to focus the ultraviolet light in the laser optical path onto the sample; and plano-convex lens III is used to refocus the white light passing through the sample for subsequent signal acquisition.

[0043] The femtosecond laser processing parameters are as follows: laser repetition rate of 1 kHz, and femtosecond laser energy density controlled to 0.1-10 J / cm² via an optical parametric amplifier. 2 Wavelength 320nm-800nm.

[0044] During testing, the precursor solution was continuously stirred using a magnetic stirrer, the peristaltic pump flow rate was 0.1-10 mL / min, and the femtosecond laser energy density was 0.1-10 J / cm³. 2 The ultrafast reaction is induced by irradiating the flow cell cuvette with pump light, and the timing of the probe light is controlled by an optical delay line. The transient absorption spectrum is collected by a fiber-coupled spectrometer, realizing the acquisition and analysis of in-situ spectra in a non-static environment.

[0045] Compared with existing technologies, this invention utilizes an in-situ absorption spectroscopy method combining a flow cell with a femtosecond laser pump-probe system to overcome the reversibility limitations of traditional TA; by continuously updating reactants through the flow cell, it supports high signal-to-noise ratio spectral acquisition for a single reaction, making it suitable for irreversible and damaging processes; it enables real-time monitoring of ultrafast reactions at the femtosecond to nanosecond scale, revealing the dynamic mechanisms of electron-photon interactions, chemical bond breaking, or material damage.

[0046] This invention provides a universal method applicable to irreversible reactions, such as metal ion reduction, and supports mechanism studies under continuous reaction conditions.

[0047] This invention supports single-response spectral acquisition by continuously updating reactants in a flow cell, overcoming the limitations of traditional TA (transferase exchange) which requires signal accumulation and is limited by reversible reactions. It is suitable for irreversible and damaging processes. The flow cell ensures sample consistency, overcoming the defects of uneven sample exposure in static systems. The spectral data has high repeatability and signal-to-noise ratio. Furthermore, the flow cell supports long-term stable spectral acquisition, making it suitable for mechanism studies under continuous reaction conditions.

[0048] This invention captures reaction dynamics on the picosecond to nanosecond scale using a pump-probe system, revealing the mechanism of irreversible reactions induced by femtosecond lasers.

[0049] This invention utilizes an in-situ absorption spectroscopy method combining a flow cell with a femtosecond laser-pumped probe system to achieve high signal-to-noise ratio spectral acquisition for a single reaction, revealing in real time the dynamic mechanism of femtosecond laser-induced irreversible reactions and damage processes.

[0050] Example 1 A device for exploring the mechanism of femtosecond laser-induced ultrafast reactions by constructing in-situ absorption spectroscopy using a flow cell, such as... Figure 1 As shown, the device includes: a femtosecond laser pump-probe system, a flow cell system, a spectrometer for acquiring the final spectral data, and a precursor solution to be detected; The femtosecond laser pump-probe system includes: a femtosecond laser capable of continuously outputting femtosecond pulse width infrared laser, a beam splitter for splitting the femtosecond laser beam, a plano-convex lens, a reflector, and an optical delay line; the beam splitter splits the femtosecond laser beam into pump light and probe light, the pump light is focused into a linear light field by a cylindrical lens to irradiate a flow cell cuvette to induce an ultrafast reaction, and the probe light has its timing controlled by an optical delay line and transient absorption spectra are collected by a fiber-coupled spectrometer; The femtosecond laser is Coherent.

[0051] The delay range of the optical delay line is 0-2 ns.

[0052] The femtosecond laser processing parameters are as follows: laser repetition rate of 1 kHz, and femtosecond laser energy density controlled to 0.1-10 J / cm² via an optical parametric amplifier. 2 Wavelength 320nm-800nm.

[0053] Among them, the laser emitted by the laser can be split into two beams by a beam splitter, which are used for excitation and detection of the sample respectively.

[0054] The reflector is used to change the direction of the laser to adjust the optical path.

[0055] Among them, such as Figure 1As shown, this invention demonstrates the integration of a femtosecond laser pump-probe system with a flow cell, the pump light-induced ultrafast reaction, the probe light collecting transient spectra through a delay line, and the peristaltic pump ensuring continuous solution flow to support the monitoring of irreversible processes. The femtosecond laser pump-probe system further includes an optical parametric amplifier capable of adjusting various laser parameters. In this invention, this device converts the infrared laser output from the laser into an ultraviolet laser for sample excitation. White light crystals can convert single-wavelength femtosecond lasers into broadband white light, which can then be used as detection light for subsequent detection. Plano-convex lenses are used to focus the light beam, including convex lens I, plano-convex lens II, and plano-convex lens III; among them, plano-convex lens I 8 is used to focus the white light in the probe light path onto the sample; plano-convex lens II 9 is used to focus the ultraviolet light in the laser light path onto the sample; plano-convex lens III 10 is used to refocus the white light passing through the sample for subsequent signal acquisition. A filter is used to filter out the excitation light in the white light passing through the sample, which interferes with subsequent signal acquisition.

[0056] Among them, the laser parameters of the initial light source 12 are controlled by the laser and are infrared light.

[0057] The laser parameters of the laser optical path 13 are controlled by the optical parametric amplifier 2 and can be adjusted to any suitable wavelength, such as ultraviolet light for excitation.

[0058] Among them, the laser parameters of the detection optical path 14 are controlled by the white light crystal 7 and are fixed continuous wavelength white light.

[0059] The flow cell system includes: a transparent quartz cuvette, a peristaltic pump, a solution storage tank, and a magnetic stirrer, used to achieve continuous flow and uniform mixing of the solution; The optical path width of the transparent quartz cuvette is 1 mm; the flow rate of the peristaltic pump is 0.1-10 mL / min.

[0060] The precursor solution is obtained by adding a metal salt to deionized or anhydrous ethanol and mixing them evenly.

[0061] The metal salt is selected from one or more of HAuCl4, FeCl3, and CuCl2.

[0062] The concentration of each metal salt in deionized water or anhydrous ethanol is 0.01-0.1 mol / L.

[0063] Furthermore, the device for exploring the mechanism of femtosecond laser-induced ultrafast response by constructing in-situ absorption spectroscopy using a flow cell also includes a displacement stage 15 to adjust the optical path of the probe light, thereby regulating the optical path difference between the excitation light and the probe light.

[0064] Example 2 A method for exploring the mechanism of femtosecond laser-induced ultrafast reactions by constructing in-situ absorption spectroscopy using a flow cell includes: S1: Preparation of the reaction precursor solution; HAuCl4 was dissolved in anhydrous ethanol to prepare a concentration of 0.01 mol / L, which was then used as the sample to be tested.

[0065] S2: Construct a flow cell system; The flow cell system includes: A transparent quartz cuvette (1 mm optical path width) is used for laser transmission and spectral acquisition.

[0066] A peristaltic pump (flow rate 0.1-10 mL / min) controls the continuous flow of solution, ensuring that the reaction zone is always a fresh sample, overcoming the limitation of traditional TA requiring multiple accumulations.

[0067] A magnetic stirrer ensures uniform mixing of the solution and enhances the repeatability of spectral data.

[0068] S3: Constructing a femtosecond laser pump-probe system; A femtosecond laser is used, and the laser beam is split into pump light and probe light by a beam splitter.

[0069] In this process, the pump light is focused into a linear light field by a plano-convex lens, which illuminates the flow cell cuvette to induce ultrafast reactions, such as the reduction of metal ions. The probe light is time-controlled by an optical delay line (delay range 0-2 ns), and transient absorption spectra are collected by a fiber-coupled spectrometer (Princeton Instruments).

[0070] The femtosecond laser processing parameters are as follows: laser repetition rate of 1 kHz, and femtosecond laser energy density of 10 J / cm² controlled by an optical parametric amplifier. 2 , wavelength 320nm.

[0071] S4: Acquire and analyze in-situ spectra; Transient absorption spectra were recorded in real time at a flow rate of 1 ml per minute and a laser energy density of 1 joule per square centimeter.

[0072] By fitting spectral signals (such as the surface plasmon resonance peak at 550 nm of gold nanoparticles and the characteristic absorption peaks of molecular decomposition products), the ultrafast dynamic changes of irreversible reactions or damage processes can be analyzed.

[0073] In this process, data is collected at a certain time delay point each time the spectrum is acquired. By recording all the data within the time range of 0-2ns, the evolution of the spectrum over time is obtained.

[0074] Example 3: Study on the process and principle of single-segment signal detection using in-situ absorption spectroscopy method constructed with flow cell like Figure 2 The diagram shows the flow chart and principle of a single signal detection using the in-situ absorption spectroscopy method constructed with a flow cell. ①-⑥ in the diagram illustrate the detection process, as detailed below: ①: Initial state of the sample A homogeneous precursor solution is stably pumped into a cuvette using a peristaltic pump, maintaining continuous excitation light irradiation and keeping the flow rate and irradiation area stable. Within the irradiated area, the solution will exhibit the distribution shown in the diagram. The solution near the inlet experiences fewer laser irradiations. The entire irradiated area can be approximated based on the number of irradiations, categorized as 0 irradiations, 1 irradiation, 2 irradiations, up to n irradiations, where n is the upper limit of the total number of laser irradiations. Liquid reaching this limit will be transported out of the irradiated area. n can be calculated by dividing the spot diameter by the liquid flow rate. For example, in this experiment, the spot size is estimated to be 10 micrometers, and with the peristaltic pump parameters set to a flow rate of 6 cm / min, the maximum number of irradiations n = 10.

[0075] ②: Sample activation The acquisition of a single signal in in-situ absorption spectroscopy begins when the excitation light irradiates the sample, denoted as time zero. When the excitation light irradiates the sample, a nonlinear absorption process occurs, and the material is ionized due to the photoelectric effect, generating high-density electrons. The acquisition process of a single signal in in-situ absorption spectroscopy is completed within a nanosecond timescale, and the corresponding solution flow is less than 1 nm. Therefore, it is assumed that the solution does not undergo macroscopic movement during the in-situ absorption spectroscopy process, and the sample is in a static state for signal acquisition.

[0076] ③: The occurrence of ultrafast chemical reactions Because the electrons generated by laser irradiation are highly reactive, they react with ions in the solution on a very short timescale. In the example system, electrons can reduce metal ions in the solvent to form individual metal atoms.

[0077] ④: Sample detection By adjusting the displacement delay stage, any time point can be set within the time range of 0-2ns, and the sample can be irradiated by probe light to collect the transient absorption spectrum of the sample. This allows us to analyze the ultrafast species evolution process of the sample.

[0078] ⑤: The long-term reaction of the sample Two ns after laser irradiation, the sample detection process is complete. The sample will then continue to undergo subsequent reactions on a relatively long timescale, such as atomic clustering and nanoparticle growth, resulting in macroscopically observable nanoparticle morphologies. Since the detection is complete, the changes and movement of solutions ⑤ and ⑥ no longer affect the detection signal. ⑥: Movement of the solution Based on the repetition frequency of the detection laser being 1 kHz, a complete detection cycle can be calculated every 1 millisecond. During this time, the flow of the solution is no longer negligible. A region of the solution that was originally irradiated once becomes irradiated twice after laser irradiation, and flows to the corresponding twice-irradiated region after 1 millisecond. Subsequent regions follow the same pattern, and the sample state returns to state ①, ensuring sample consistency during each detection.

[0079] Example 4: Controlling different flow rates with different flow rate control devices to detect different substances like Figure 3 The diagram shows a method for detecting different substances by controlling different flow rate control devices. Since the repetition frequency of the laser is 1 kilohertz and the time interval between two detections is 1 millisecond, the number of times the solution is irradiated by the laser in the system can be calculated by controlling the flow rate of the solution pumped into the peristaltic pump.

[0080] Figures ①-③ show the results detected under different flow rates. Specifically, ① when the sample flow rate is relatively fast (5 mL / min), the sample is irradiated by the laser less frequently, with n being only 0-1 times, thus allowing signal acquisition from the precursor solution. ② when the sample flow rate is moderate (0.5 mL / min), the sample is irradiated a moderate number of times, with n being 12 times. At this point, the sample is in the early stages of nanoparticle formation, and the detection signal is contributed by the reduced metal atoms and clusters. ③ when the sample flow rate is slow (0.005 mL / min), the sample is fully irradiated, with n being 1250 times, forming stable nanoparticles. At this point, the detection signal is contributed by the synthesized nanoparticles.

[0081] like Figure 4 As shown in the figure, AC represents the in-situ transient absorption spectra of 0.01 M HAuCl4 solution at different flow rates. Among them, (A) 5 ml / min: the in-situ transient absorption spectrum of the intermediate species after 1 pulse irradiation, which is similar to the standard HAuCl4 solution; (B) 0.5 ml / min: the in-situ transient absorption spectrum of the intermediate species after 12 pulse irradiations; (C) 0.005 ml / min: the in-situ transient absorption spectrum of the solution after thousands of pulse irradiations, which is similar to the gold nanoparticle dispersion.

[0082] pass Figure 3The methods and Figure 4 The results demonstrate that the system can detect information at different stages after laser irradiation of nanoparticles by changing the flow rate.

[0083] Example 5: Comparison of repeatability between conventional transient absorption spectra and in-situ transient absorption spectra like Figure 5 The diagram shows a comparison of the repeatability of conventional transient absorption spectroscopy and in-situ transient absorption spectroscopy. In (AB), conventional transient absorption spectroscopy measurements performed during continuous sampling of the HAuCl4 solution in the reaction exhibit spectral characteristics that change due to the constantly evolving reaction kinetics. This variation complicates data interpretation and affects the repeatability of the results.

[0084] (C) A comparison of the signal intensities at 550 nm (corresponding to plasmon resonance on the gold surface) between two consecutive conventional transient absorption spectral scans showed a significant difference.

[0085] Five consecutive in-situ transient absorption spectroscopic measurements of HAuCl4 solution in the same reaction by (DH) showed high repeatability.

[0086] (I) The plasmonic resonance signal intensity at 550 nm on the gold surface was analyzed for all five in-situ transient absorption spectral scans, confirming the consistency of the spectral acquisition.

[0087] These results confirm the feasibility of using in-situ transient absorption spectroscopy for reliable and continuous monitoring of reaction systems. Furthermore, the signal-to-noise ratio can be improved by increasing the number of scans for signal averaging.

[0088] The traditional transient absorption spectroscopy test conditions are as follows: S1: Preparation of the reaction precursor solution; Chloroauric acid was dissolved in anhydrous ethanol to prepare a concentration of 0.01 mol / L, which was then used as the test sample.

[0089] S2: Traditional transient absorption liquid sample system; Place the prepared solution into a fixed-volume transparent quartz cuvette (optical path width 1 mm).

[0090] S3: Constructing a femtosecond laser pump-probe system; A femtosecond laser is used, and the laser beam is split into pump light and probe light by a beam splitter.

[0091] In this process, the pump light is focused into a linear light field by a cylindrical lens, which illuminates the flow cell cuvette to induce ultrafast reactions (such as metal ion reduction, molecular decomposition, or material damage). The probe light is time-controlled by an optical delay line (delay range 0-2 ns), and transient absorption spectra are collected by a fiber-coupled spectrometer (Princeton Instruments).

[0092] S4: Acquire and analyze in-situ spectra; By controlling the delay stage, the absorption spectra of materials under different time delays can be collected. By summarizing all data in the 0-2 nanosecond time range, the transient absorption spectra can be collected in real time.

[0093] By fitting spectral signals (such as the surface plasmon resonance peak at 550 nm of gold nanoparticles and the characteristic absorption peaks of molecular decomposition products), the ultrafast dynamic changes of irreversible reactions or damage processes can be analyzed.

[0094] For the same sample, continuous testing was conducted to obtain two sets of data as shown in Figures A and B.

[0095] Figure Five The AC results showed that due to the long-term laser irradiation during the test, the precursor solution chloroauric acid was continuously reduced to gold nanoparticles. This means that the test object was constantly changing during the test, so the collected signal was not repeatable and the collected data was meaningless. Traditional transient absorption spectroscopy systems do not have the ability to collect reactive processes.

[0096] The in-situ transient absorption spectroscopy test conditions are shown in Example 2. For the same sample, a continuous test method was adopted to obtain five sets of data in Figure DH.

[0097] Figure Five The DI results show that, due to the continuous and stable pumping of fresh solution during laser irradiation, the state of the tested area remained almost consistent. Therefore, the tested sample exhibited almost consistent signal results in multiple tests. This demonstrates the superior ability of the in-situ transient absorption spectroscopy testing system in this invention to specifically test reactive processes compared to traditional transient absorption spectroscopy testing systems.

[0098] In-situ transient absorption spectroscopy revealed a surface plasmon resonance peak at 550 nm, indicating an irreversible nucleation process of gold nanoparticles. Fitting results showed that the reaction rate was affected by the flow rate, validating the flow cell's support for the irreversible reaction.

[0099] The results of the second test in traditional transient absorption spectroscopy differ significantly from those of the first test. This is mainly because an irreversible reaction occurs in the sample during the test, causing the test results to change continuously over time and thus rendering the results meaningless. The experimental results show that the test results remain unchanged under multiple consecutive tests, demonstrating the feasibility of the method.

[0100] Example 6: Testing on different samples According to the experimental method in Example 2, deionized water, gold nanoparticle dispersion, and chloroauric acid solution were tested, and the results are as follows. Figure 6 As shown, at the horizontal axis position of 400, from top to bottom, the blue line represents chloroauric acid solution, the red line represents gold nanoparticle dispersion, and the black line represents deionized water.

[0101] Specifically, deionized water, 0.01 mol / L gold nanoparticle dispersion, and 0.01 mol / L chloroauric acid solution were used as test samples, and the tests were conducted according to the steps described above. The data at the 5th picosecond of the test signal was then displayed.

[0102] Deionized water exhibits a broad-spectrum positive signal in the long wavelength range (approximately 600 nanometers), corresponding to the signal of solvated electrons.

[0103] A chloroauric acid solution exhibits a broad-spectrum signal at a low wavelength (approximately 400 nm).

[0104] The gold nanoparticle dispersion exhibits a positive signal at approximately 500 nm and a negative signal at approximately 550 nm, which are attributed to photoinduced absorption (PIA) and ground-state bleaching (GSB) of the Au nanoparticles, respectively.

[0105] The experimental results above are consistent with the expected transient absorption signals of the three substances, indicating that the system data is reliable and can be used to conduct experiments on different samples.

[0106] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for exploring the mechanism of femtosecond laser-induced ultrafast reactions by constructing in-situ absorption spectroscopy using a flow cell, characterized in that, include: S1: Add the metal salt to deionized water or anhydrous ethanol and mix evenly to obtain a precursor solution; S2: Construct a flow cell system; S3: Constructing a femtosecond laser pump-probe system; S4: Acquire and analyze in-situ spectra; The flow cell system includes: a transparent quartz cuvette for femtosecond laser transmission and spectral acquisition, a peristaltic pump for controlling the continuous flow of the precursor solution, a solution storage tank, and a magnetic stirrer. The femtosecond laser pump-probe system includes: a femtosecond laser, a beam splitter for splitting the femtosecond laser beam, a plano-convex lens for focusing the beam, a mirror, and an optical delay line. The beam splitter splits the femtosecond laser beam into pump light and probe light. The pump light is focused into a linear light field by the plano-convex lens to irradiate a flow cell cuvette and induce an ultrafast reaction. The probe light has its timing controlled by the optical delay line and its transient absorption spectrum is collected by a fiber-coupled spectrometer.

2. The method according to claim 1, characterized in that, In step S1, the metal salt is selected from one or more of HAuCl4, FeCl3, and CuCl2; preferably, the metal salt is HAuCl4.

3. The method according to claim 1 or 2, characterized in that, The concentration of the metal salt in deionized water or anhydrous ethanol is 0.01-0.1 mol / L.

4. The method according to any one of claims 1-3, characterized in that, In S2, the optical path width of the transparent quartz cuvette is 1 mm; the flow rate of the peristaltic pump is 0.1-10 mL / min.

5. The method according to any one of claims 1-4, characterized in that, In S3, an ultrafast reaction is induced by irradiating the flow cell cuvette with pump light. The ultrafast reaction includes a metal ion reduction reaction. The delay range of the optical delay line is 0-2 ns.

6. The method according to any one of claims 1-5, characterized in that, In S4, transient absorption spectra are recorded in real time under different peristaltic pump flow rates and femtosecond laser energy densities; by fitting the spectral signals, the ultrafast dynamic changes of irreversible reactions or damage processes are analyzed.

7. The method according to any one of claims 1-6, characterized in that, The femtosecond laser processing parameters are: laser repetition rate of 1 kHz, and femtosecond laser energy density adjusted to 0.1-10 J / cm² via an optical parametric amplifier. 2 Wavelength 320nm-800nm.

8. A device for exploring the mechanism of femtosecond laser-induced ultrafast reactions by constructing in-situ absorption spectroscopy using a flow cell, characterized in that, include: Femtosecond laser pump-probe system, flow cell system, spectrometer for acquiring final spectral data, and precursor solution to be detected; The femtosecond laser pump-probe system includes: a femtosecond laser, a beam splitter for splitting the femtosecond laser beam, a plano-convex lens for focusing the beam, a mirror, and an optical delay line; the beam splitter splits the femtosecond laser beam into pump light and probe light, the pump light is focused into a linear light field by the plano-convex lens to irradiate a flow cell cuvette to induce an ultrafast reaction, and the probe light has its timing controlled by the optical delay line and its transient absorption spectrum is collected by a fiber-coupled spectrometer; The flow cell system includes: a transparent quartz cuvette, a peristaltic pump, a solution storage tank, and a magnetic stirrer, used to achieve continuous flow and uniform mixing of the solution; The precursor solution is obtained by adding a metal salt to deionized water or anhydrous ethanol and mixing them evenly.

9. The apparatus according to claim 8, characterized in that, The metal salt is selected from one or more of HAuCl4, FeCl3, and CuCl2; preferably, the metal salt is HAuCl4. The concentration of the metal salt in deionized water or anhydrous ethanol is 0.01-0.1 mol / L.

10. The apparatus according to claim 8 or 9, characterized in that, The optical path width of the transparent quartz cuvette is 1 mm; the flow rate of the peristaltic pump is 0.1-10 mL / min; The delay range of the optical delay line is 0-2 ns.

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