A liquid-core optical fiber coupling and signal enhancement device for Raman spectroscopy detection of micro (trace) samples

Abstract

The present invention provides a liquid-core optical fiber (LCOF) coupling and signal enhancement device for Raman spectroscopy detection of micro (trace) samples. The device includes an LCOF, a sealed joint, an excitation optical coupling coaxial adjustment platform, and a liquid injection and cleaning system. The LCOF is used to accommodate the solution to be measured as a sample cell to increase the Raman scattering path; the sealed joint is used to seal the LCOF port to prevent the solution to be measured from leaking; the excitation optical coupling coaxial adjustment platform is used to fix and adjust the position of the coupling head to improve the coupling efficiency of the excitation light and the LCOF; the liquid injection and cleaning system is used to inject liquid and clean the LCOF to realize the reuse of the LCOF. The device is easy to operate, has strong compatibility, is easy to be coupled with common macroscopic, microscopic, portable and other Raman spectrometers on the market, effectively improves the signal-to-noise ratio of Raman spectra, realizes high-sensitivity detection of low-concentration trace liquids, and promotes the practical application of Raman detection technology in on-site detection of clinical body fluids, biomarkers, drugs, food, drugs, chemicals, environment, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of analysis and measurement control in the field of instrumentation technology, and relates to liquid core optical fiber (LCOF) and Raman spectroscopy detection technology, in particular to an LCOF coupling and signal enhancement device for micro (trace) liquid Raman spectroscopy detection. Background Art

[0002] All along, molecular spectroscopy technology has always been one of the most important technical means for people to study the structure of substances, and Raman spectroscopy technology is an important part of molecular spectroscopy technology, which is widely used in various fields. Raman spectroscopy can provide rapid, simple, repeatable and non-destructive qualitative and quantitative analysis. Compared with infrared spectroscopy, Raman spectroscopy requires less sample volume and is not affected by water, and has unique advantages in the detection and analysis of biological tissues. Although the advantages of Raman spectroscopy technology are extremely prominent, its weak signal characteristic results in a low detection sensitivity for liquid samples, a high requirement for the concentration of the liquid to be measured, and it is difficult to detect low-concentration liquid samples.

[0003] LCOF is an optical transmission element with a new structure, which has the characteristics of large core diameter, large numerical aperture, wide spectral range, high transmission efficiency, long service life, etc. Compared with traditional quartz optical fibers, it uses a high refractive index liquid to replace the conventional quartz glass fiber bundle as the core, so that the excitation light undergoes total internal reflection at the liquid waveguide interface, so that the excitation light energy can propagate along the fiber axis and obtain a longer light-matter interaction length.

[0004] At present, Raman spectrometers have made great progress in miniaturization and portability, but the problem of limited detection sensitivity needs to be solved urgently, especially in the detection of low-concentration or micro (trace) solutions. Using LCOF as a sample cell can effectively increase the Raman scattering path, thereby enhancing the Raman signal and signal-to-noise ratio, and can achieve a 10 3 -fold enhancement of the Raman spectrum intensity [1], but the problem of low efficiency of manual operation when it is coupled with the excitation light greatly limits its practical application. Therefore, it is of great significance to develop an LCOF coupling and signal enhancement device suitable for efficient coupling with common Raman spectrometers on the market. Summary of the Invention

[0005] Object of the Invention: The main object of the present invention is to solve the problem that most Raman spectrometers on the market cannot perform high-sensitivity detection on low-concentration or micro (trace) liquid samples. By developing an LCOF signal enhancement device suitable for coupling with Raman spectrometers, the signal-to-noise ratio of Raman spectra is improved, and the practical application of Raman spectroscopy detection technology in on-site detection of clinical body fluids, biomarkers, drugs, foods, drugs, chemical drugs, environments, etc. is promoted.

[0006] Technical solution: An LCOF signal enhancement device for Raman spectroscopy detection of micro (trace) samples and suitable for coupling most Raman spectrometers on the market. The device includes: LCOF, a sealed joint, an excitation optical coupling coaxial adjustment platform, and a liquid injection and cleaning system.

[0007] [1]Shuqin G, Baokun H, Zuowei L. Application of liquid-core optical fiber in the measurements of Fourier transform Raman spectra[J]. Chemical physics letters, 2004, 392(1-3): 123-126.

[0008] 1. The LCOF is used to hold the solution to be measured as a sample cell. It needs to be made of a low refractive index material to ensure that the refractive index of the optical fiber is always lower than that of the solution to be measured, so that the excitation light can undergo total internal reflection at the junction of the solution to be measured and the inner surface of the optical fiber, thereby increasing the Raman scattering path.

[0009] 2. The sealed joint is used to seal the LCOF port to prevent evaporation and leakage of the solution to be measured, and it is required to have high light transmittance to efficiently converge the excitation light to the LCOF port.

[0010] 3. The excitation optical coupling coaxial adjustment platform includes bases of different length specifications, a Raman probe holder, and an XYZ displacement adjustment frame. Different specifications or numbers of components can be freely selected and adapted according to the type and model of the Raman spectrometer. For example, for a probe-type Raman spectrometer, the Raman probe holder can fix Raman probes of different sizes for coupling; by removing the Raman probe holder and selecting a short-distance base, it can be applicable to macro or portable Raman spectrometers without a probe; if the base is further placed vertically, it can meet the detection requirements of a micro Raman spectrometer. The XYZ displacement adjustment frame is used to fix and finely adjust the position of the sealed joint to align the excitation light focus with the light window part of the sealed joint, improving the coupling efficiency of the excitation light and the LCOF.

[0011] 4. The liquid injection and cleaning system has three functions. One is to inject the solution to be measured into the LCOF; the second is to inject a detergent into the LCOF to clean the inside of the optical fiber; the third is to drain the internal solution of the LCOF and air-dry it, so that the LCOF can be reused.

[0012] Furthermore, the material type of the LCOF can have multiple choices according to different solutions to be measured, including hollow optical fibers or capillaries made of materials such as Teflon and quartz, meeting the detection requirements of most solutions; the length L of the LCOF needs to follow the equation: L = 1 / α, where α is the attenuation coefficient of the optical fiber for the excitation light [1].

[0013] Further, the sealing joint is made of quartz glass and is in an "L" shape. One end is used to introduce LCOF, and the other end is used for liquid injection or drainage.

[0014] Further, the Raman probe holder of the excitation optical coupler coaxial adjustment platform and the XYZ displacement adjustment frame form a coaxial system using a cage-type bracket; the Raman probe holder consists of two self-centering holders, which can meet the requirements of different-sized probes being centered in the holders; the center of the XYZ displacement adjustment frame is provided with a thread, and the sealing joint can be fixed through a thread adapter and the XYZ-direction displacement adjustment with a stroke of ±1.5 mm can be performed.

[0015] Further, the liquid injection and cleaning system uses a micro-flow peristaltic pump and is equipped with a small-inner-diameter hose. One end is placed in the solution or detergent to be measured to suck liquid, and the other end is connected to the sealing joint for liquid injection; after washing, the liquid suction end of the hose is connected to a small air filter, and the peristaltic pump is started for air drying.

[0016] The beneficial effects of the present invention include:

[0017] The present invention designs an LCOF coupling and signal enhancement device for Raman spectroscopy detection of micro (trace) samples. The device can efficiently couple the excitation light into the LCOF through the excitation optical coupler coaxial adjustment platform, and utilize the principle of total internal reflection to significantly enhance the Raman scattering of micro (trace) solutions, improving the liquid detection sensitivity;

[0018] During use, the micro-flow peristaltic pump can quickly and stably complete the liquid injection process inside the LCOF, avoiding the generation of air bubbles inside the optical fiber that hinder the optical path transmission; and the present invention can realize the reusable of the LCOF by cleaning and air drying the LCOF.

[0019] [1]Shuqin G, Baokun H, Zuowei L. Application of liquid-core optical fiber in the measurements of Fourier transform Raman spectra[J]. Chemical physics letters, 2004, 392(1-3): 123-126. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of an LCOF coupling and signal enhancement device provided by the present invention, which is universal and can be used for micro (trace) liquid detection by various Raman spectrometers;

[0021] Figure 2It is a schematic structural diagram of the base of the excitation optical coupler coaxial adjustment platform provided by the present invention;

[0022] Figure 3 It is a schematic structural diagram of the Raman probe self-centering holder of the excitation optical coupler coaxial adjustment platform provided by the present invention;

[0023] Figure 4 It is a schematic structural diagram of the XYZ displacement adjustment frame of the excitation optical coupler coaxial adjustment platform provided by the present invention;

[0024] Figure 5 It is a schematic structural diagram of the sealed joint. Specific embodiments

[0025] To clarify the purpose, technical solutions and beneficial effects of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0026] As Figure 1 shown, the present invention provides a general-purpose LCOF coupling and signal enhancement device that can be used for micro (trace) liquid detection in a variety of Raman spectrometers, including an LCOF, a sealed joint, an excitation optical coupler coaxial adjustment platform, and a liquid injection and cleaning system.

[0027] The LCOF 106 is used to accommodate the solution to be measured and increase the Raman scattering path. The type of cladding material can have various selections according to different solutions to be measured, including hollow optical fibers or capillary tubes made of materials such as Teflon and quartz, which can meet the detection requirements of most solutions. Since the excitation light and Raman light will gradually attenuate with the increase of the LCOF length, only when an appropriate fiber length is intercepted can the optimal Raman scattering intensity be obtained. The intercepted length L needs to follow the following equation: L = 1 / α, where α is the attenuation coefficient of the optical fiber for the excitation light.

[0028] The sealed joint is divided into a coupling head 105 and a liquid injection head 107, both of which are made of quartz glass into the same "L"-shaped hollow structure, as Figure 5As shown: the quartz housing 501 has high light transmittance, which not only reduces the loss of excitation light and signal light during coupling, but also facilitates observation of the liquid column during liquid injection; the diameter of the optical fiber guide hole 503 is the same as the outer diameter of the LCOF and is used to fix and align the LCOF; the liquid guide hole 502 is used to connect the hose 108 for liquid injection in the liquid injection head and is used for exhaust and liquid discharge in the coupling head. At the same time, some solution is retained during detection to maintain the stability of the liquid inside the LCOF; the sealing ring 504 is made of sealing material and further seals the optical fiber guide hole 503 to prevent leakage of the test solution.

[0029] The excitation light coupling coaxial adjustment platform is as follows Figure 1 As shown, it consists of a base 102, a self-centering clamp 103 and an XYZ displacement adjustment frame 104:

[0030] The base 102 has a variety of length specifications (3-10cm), and the structure is as follows Figure 2 As shown, the fixed mounting block 201 is an integrated structure, with five apertures, one large and four small, on each of the left and right frame plates. The large aperture serves as a channel for the placement of the Raman probe 101 and LCOF 106, while the four small apertures are used to mount four coaxial system mounting (sliding) rods 202-205 to form a coaxial adjustment platform. By varying the component specifications or quantity of the excitation light coupling coaxial adjustment platform, the present invention can be adapted for horizontal detection applications in a variety of Raman spectrometers, including macro, portable, and probe-type Raman spectrometers. By placing the excitation light coupling coaxial adjustment platform vertically and adding a sealing cap to the drainage end of the sealing joint, the vertical detection requirements of microscopic Raman spectrometers can be further met.

[0031] The self-centering clamp 103 is as follows Figure 3 As shown, the main shell 301 has small holes 304 at the four corners for connecting with the base 102 to form a coaxial system, and the front and rear positions can be adjusted by sliding; the three clamping claws 303 can be opened synchronously by moving the internal movable ring 302, and the items can be automatically fixed in the center position by releasing them after the items are placed.

[0032] The XYZ displacement adjustment frame 104 is used to fix the coupling head 105 and adjust the port position of the LCOF 106 to ensure efficient coupling with the excitation light. The structure is as follows: Figure 4 As shown, the main housing 401 has small holes 402 at the four corners for connecting to the base 102 to form a coaxial system, and the front-back position can be adjusted by sliding. The movable sleeve 406 has internal threads and can be fixed to the coupling head 105 via a threaded adapter. The X-axis knob 403 is used to adjust the horizontal position of the movable sleeve 406; the Y-axis knob 404 is used to adjust the vertical position of the movable sleeve 406; and the Z-axis knob 405 is used to adjust the front-back position of the movable sleeve 406.

[0033] The liquid injection and cleaning system is as follows Figure 1 As shown in the figure, it consists of a hose 108, a peristaltic pump 109, a container 110, and an air filter 111: The hose 108 is made of silica gel, with one end connected to the liquid guiding hole of the liquid injection head 107 and the other end connected to the container 110. Through the peristaltic pump 109, the test solution or cleaning solvent in the container 110 can be quickly and smoothly injected into the LCOF 106. After the detection is completed and the LCOF 106 is cleaned with the cleaning solvent, the end of the hose can be connected to the air filter 111, and the inside of the LCOF 106 can be air-dried by the peristaltic pump 109 using the filtered air, realizing the reusable of the LCOF 106.

[0034] An LCOF coupling and signal enhancement device for Raman spectroscopy detection of micro (trace) samples designed by the above solution has the advantages of simple operation and strong compatibility. It is easy to couple with common mainstream Raman spectrometers such as macroscopic, microscopic, and portable ones on the market, effectively improving the signal-to-noise ratio of Raman spectroscopy, realizing high-sensitivity detection of low-concentration or micro (trace) liquids, and promoting the practical application of Raman detection technology in on-site detection of clinical body fluids, biomarkers, drugs, foods, drugs, chemical drugs, the environment, etc.

[0035] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A liquid-core fiber coupling and signal enhancement device for Raman spectroscopy detection of micro and trace samples, characterized in that: The device includes a liquid core optical fiber (LCOF), a sealed joint, an excitation light coupling coaxial adjustment platform, and a liquid injection and cleaning system: The LCOF is used to hold the solution to be tested as a sample pool and needs to be made of a low-refractive-index Teflon material with a refractive index between 1.29 and 1.

35. This ensures that the refractive index of the fiber material is always lower than that of the solution to be tested, allowing the excitation light to undergo total internal reflection at the interface between the solution to be tested and the inner surface of the fiber, thereby increasing the Raman scattering path. The sealing joint is used to seal the LCOF port to prevent evaporation and leakage of the solution to be tested, and is required to have high light transmittance so that the excitation light can be efficiently focused on the LCOF port; The excitation light coupling coaxial adjustment platform includes a base with different lengths of 3-10 cm, a Raman probe clamping frame, and an XYZ displacement adjustment frame. The Raman probe clamping frame consists of two self-centering clamps, each of which includes a main body shell, an internal movable ring, and a clamping claw. The clamping claws can be opened synchronously by toggling the internal movable ring, automatically fixing the Raman probe in the center position. The XYZ displacement adjustment frame is used to fix and fine-tune the position of the sealing joint, so that the excitation light focus is aligned with the optical window of the sealing joint, thereby improving the coupling efficiency of the excitation light and the LCOF. The liquid injection and cleaning system includes three functions: first, injecting the test solution into the LCOF; second, injecting detergent into the LCOF to clean the inside of the optical fiber; and third, draining the solution inside the LCOF and air-drying it to make the LCOF reusable.

2. The LCOF according to claim 1, wherein The LCOF mentioned above can have various Teflon material selections according to different solutions to be measured, including hollow optical fibers or capillaries made of PTFE, FEP, PFA, ETFE, and Teflon AF, meeting the detection requirements of most solutions; the effective excitation length L of the excitation light of the LCOF follows the equation: L = 1 / α, where α is the attenuation coefficient of the optical fiber for the excitation light. Considering the solution dosage and enhancement amplitude comprehensively, it is more appropriate to intercept the LCOF with a length of 0.5 - 1 m. TM The effective excitation length L of the excitation light of the LCOF follows the equation: L = 1 / α, where α is the attenuation coefficient of the optical fiber for the excitation light. Considering the solution dosage and enhancement amplitude comprehensively, it is more appropriate to intercept the LCOF with a length of 0.5 - 1 m.

3. The sealed joint according to claim 1, wherein, The sealing joint is made of quartz glass and has an "L"-shaped hollow structure, one end of which is used to introduce LCOF and the other end is used for liquid injection or drainage.

4. The excitation optical coupler coaxial adjustment platform according to claim 1, characterized in that, The Raman probe clamping frame and XYZ displacement adjustment frame of the excitation light coupling coaxial adjustment platform use a cage bracket to form a coaxial system; the Raman probe clamping frame can support automatic centering clamping of probes with a diameter of less than 1 inch; the XYZ displacement adjustment frame has a center thread, which can fix the sealed joint through a threaded adapter and perform displacement adjustment in the XYZ direction with a stroke of ±1.5mm.

5. The excitation optical coupler coaxial adjustment platform according to claim 1, wherein The excitation light coupling coaxial adjustment platform can be freely adapted to components of different specifications or quantities according to the type and model of the Raman spectrometer.

6. The liquid injection and cleaning system according to claim 1, wherein The liquid injection and cleaning system uses a micro-flow peristaltic pump and is equipped with a small inner diameter hose. One end is placed in the solution to be tested or detergent to absorb the liquid, and the other end is connected to a sealed joint for liquid injection. After washing, the liquid suction end of the hose is connected to a small air filter and the peristaltic pump is started for air drying.

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