Surface-enhanced Raman gas multi-pass cell based on Herriott cavity

Abstract

The invention relates to a surface-enhanced Raman gas multi-pass cell based on a Herriott cavity, and belongs to the field of optics. Comprising an incident main frame and an emergent main frame which are symmetrically arranged at the two axial ends of a detection pipe, an incident hole and an air inlet hole are formed in the incident main frame, and an emergent hole and an air outlet hole are formed in the emergent main frame; the two main frames are respectively provided with a window piece, a window sheet and a reflector with holes, and the window pieces, the window sheets and the reflector with the holes are sealed with the main frames through sealing washers; and a supporting column connected with the incident main frame and the emergent main frame is arranged outside the detection pipe. Incident light enters the cavity of the detection tube through the incident hole, is reflected for multiple times between the two reflectors with holes, and then is emitted from the emergent hole. The effective action optical path of the incident light is increased through multiple reflections, the incident light interacts with the diaphragm with the nano-particles, surface plasma resonance occurs, a local electromagnetic field is enhanced, and the intensity of a Raman scattering signal is effectively enhanced through superposition of the actions of the incident light and the diaphragm.

Description

Technical Field

[0001] The invention belongs to the field of optics and relates to a surface enhanced Raman gas multi-pass cell based on a Herriott cavity. Background Art

[0002] Raman spectroscopy, as a highly sensitive and powerful analytical tool, has demonstrated its unique advantages in many scientific fields and industrial applications. This technology can not only achieve accurate measurement of homonuclear diatomic molecules and more complex molecular structures - this capability covers almost all molecular types except monatomic molecules, but also can use a single laser light source to stimulate Raman scattering of multiple gases and perform rapid detection of multiple gases at the same time, thereby simplifying the detection system and improving analysis efficiency.

[0003] The working principle of Raman spectroscopy is based on the inelastic scattering phenomenon between incident photons and molecules (or atoms) of substances. In this process, after the photons interact with molecules, their energy will change, generating scattered light with a specific frequency shift, namely Raman scattered light. This frequency shift is directly related to the vibration and rotation energy level structure inside the molecule, providing each molecule with a unique "spectral fingerprint", making Raman spectroscopy a powerful tool for identifying and analyzing different molecules.

[0004] However, despite the many advantages of Raman spectroscopy technology, its application in the field of gas sensing has long been constrained by a key limiting factor - the extremely low Raman scattering cross section of gas molecules. The small scattering cross section means that the effective area for the interaction between gas molecules and photons is very limited. In addition, during the interaction process, only a very small number of photons can be converted into Raman scattered photons, which further aggravates the weakness of the signal. Therefore, in practical applications, especially in scenarios that require high-sensitivity detection, how to effectively enhance the Raman scattering signal has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a surface enhanced Raman gas multi-pass cell based on the Herriott cavity, which enhances the Raman scattering signal of the detected gas by increasing the optical path and combining the surface Raman spectroscopy technology.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A surface enhanced Raman gas multi-pass cell based on a Herriott cavity comprises two oppositely arranged main frames, wherein the adjacent main frames are connected via a detection tube; window pieces are respectively embedded on two opposite surfaces of the main frames close to and away from the detection tube, and the oppositely arranged window pieces press a window sheet and a perforated reflector onto the main frames; a perforation is provided in the middle of the window piece for light to pass through the window sheet and the perforated reflector in sequence; a nano film layer is provided on one side of the window sheet close to the detection tube; and air holes are also provided on the main frame.

[0008] Optionally, one of the main frames is an incident main frame, the perforations on the incident main frame are incident holes, and the air holes are air inlet holes; the other main frame is an exit main frame, the perforations on the exit main frame are exit holes, and the air holes are air outlet holes.

[0009] Optionally, the incident main frame and the exit main frame are symmetrically arranged at both ends of the detection tube; the incident hole and the exit hole are symmetrically arranged, and the air inlet and the air outlet are symmetrically arranged.

[0010] Optionally, the window piece and the reflector with holes are sealed and connected to the perforations via sealing gaskets respectively.

[0011] Optionally, the nano film layer is composed of nanoparticles, and the shape of the nanoparticles includes a combination of one or more of a sphere, a cone, and a polyhedron.

[0012] Optionally, the nanoparticles include gold nanoparticles and / or silver nanoparticles.

[0013] Optionally, the detection tube is a hollow cylinder.

[0014] Optionally, a sealing gasket is provided between the detection tube and the main frame.

[0015] Optionally, adjacent main frames are connected via support columns, and the support columns are arranged on the outside of the detection tube.

[0016] Optionally, the reflector with holes is a concave high-reflection mirror with holes.

[0017] The beneficial effects of the present invention are:

[0018] The present invention adopts the method of increasing the optical path and combines the surface Raman spectroscopy technology to enhance the intensity of the Raman scattering signal. By installing concave high-reflection mirrors with holes at both ends of the detection tube in the axial direction, and the window parts with perforations are respectively arranged on the high-reflection mirrors with holes at both ends, the light entering through the incident hole is reflected multiple times by the high-reflection mirrors with holes at both ends in the detection tube, and then emitted through the emission hole to be received by the external light detection device; a window piece with nanoparticles attached is added to the side of the high-reflection mirror with holes away from the detection tube, and the optical property of nanoparticles that can strongly absorb and scatter light is utilized, so that the laser interacts with the nanoparticles when entering and emitting, greatly enhancing the local electromagnetic field, thereby enhancing the Raman scattering signal.

[0019] The overall device of the present invention has a simple structure, is easy to install and has a low manufacturing cost. The optical path and optical path length can be adjusted conveniently, and the Raman peaks of multiple gases can be detected simultaneously. Each component is sealed by a sealing gasket, and has good air tightness. The detection tube is a hollow cylindrical glass tube, which can withstand a gas sample with a pressure of 4Mpa, and the gas detection signal strength can be increased by increasing the gas pressure. In addition, the device can also replace the glass tube to achieve the optical path length adjustment of the multi-pass cell.

[0020] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0022] Figure 1 It is a schematic diagram of the structure of the gas multi-pass cell incident on one side of the main frame of the present invention;

[0023] Figure 2 It is a schematic diagram of the structure of one side of the main frame of the gas multi-pass cell outlet of the present invention;

[0024] Figure 3 It is a structural cross-sectional view of one side of the incident main frame of the gas multi-pass cell of the present invention;

[0025] Figure 4 This is a schematic diagram of the structure of nanoparticles attached to the window;

[0026] Figure 5 It is a schematic diagram of the light refraction path when gas detection is performed using the gas multi-pass cell of the present invention.

[0027] Reference numerals:

[0028] 1 main frame, 11 incident main frame, 12 exit main frame, 2 window member, 3 window plate, 4 reflector with hole, 5 nanometer film layer, 6 perforation, 61 incident hole, 62 exit hole, 7 air hole, 71 air inlet hole, 72 air outlet hole, 8 detection tube, 9 support column. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0030] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0031] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0032] See also Figure 1 to Figure 4, is a surface enhanced Raman gas multi-pass cell based on Herriott cavity, comprising two oppositely arranged main frames 1, adjacent main frames 1 are connected by a detection tube 8; window pieces 2 are respectively embedded on two opposite surfaces of the main frame 1 close to and far from the detection tube 8, and the oppositely arranged window pieces 2 press the window sheet 3 and the holed reflector 4 on the main frame 1; a perforation 6 is provided in the middle of the window piece 2 to facilitate light to pass through the window sheet 3 and the holed reflector 4 in sequence; and air holes 7 are also provided on the main frame 1. A nano film layer 5 is provided on one side of the window sheet 3 close to the detection tube 8. The nano film layer 5 is composed of nanoparticles, and the shape of the nanoparticles includes but is not limited to a combination of one or more of a sphere, a cone, and a polyhedron; the nanoparticles include gold nanoparticles and / or silver nanoparticles. In actual operation, the nanoparticles are evenly applied on the window sheet 3, and the nano film layer 5 is formed by drying it. The window piece 2 is fixed to the main frame 1 by a plurality of bolts.

[0033] One of the main frames 1 is the incident main frame 11, the perforation 6 on the incident main frame 11 is the incident hole 61, and the air hole 7 is the air inlet 71; the other main frame 1 is the exit main frame 12, the perforation 6 on the exit main frame 12 is the exit hole 62, and the air hole 7 is the air outlet 72. The incident main frame 11 and the exit main frame 12 are symmetrically arranged at both ends of the detection tube 8; the incident hole 61 and the exit hole 62 are symmetrically arranged, and the air inlet 71 and the air outlet 72 are symmetrically arranged. The incident main frame 11 and the exit main frame 12 are preferably made of aluminum alloy. The incident main frame 11 and the exit main frame 12 are also connected by a support column 9, and the support column 9 is arranged on the outside of the detection tube 8 to strengthen the relative position relationship between the incident main frame 11, the exit main frame 12, and the detection tube 8 to ensure the stability and accuracy of the detection. Internal threads are provided on the inner walls of the air inlet hole 71 and the air outlet hole 72 so as to screw the air inlet pipe or the air inlet device into and fix it in the air inlet hole 71 and the air outlet hole 72 .

[0034] The window plate 3 and the reflector with holes 4 are respectively sealed and connected to the incident hole 61 and the exit hole 62 through sealing gaskets. The detection tube 8 and the main frame 1 are sealed by setting a sealing gasket. The reflector with holes 4 is a Herrtiott concave high reflector with holes.

[0035] The detection tube 8 is a hollow cylindrical glass tube that can withstand a maximum gas pressure of 4Mpa. In the actual detection process, the detection tube 8 adapted to the gas to be detected can be replaced according to the actual gas pressure of the gas to be detected to meet more detection requirements and improve the applicability of the gas multi-pass cell of the present invention.

[0036] The gas to be tested is introduced from the air inlet 71 and then discharged from the air outlet 72; the light enters the inner cavity of the glass tube through the incident hole 61 and the window plate 3, and is emitted from the window plate 3 and the exit hole 62 after multiple reflections between the perforated reflectors 4 at both ends of the glass tube.

[0037] like Figure 5 FIG. 1 is a schematic diagram of the laser refraction path of the detection system when the gas multi-pass cell of the present invention is used for gas detection. Figure 5 F in the figure represents a narrowband filter, M1 and M2 represent plane reflectors with different setting angles, CM1 and CM2 represent concave reflectors with holes in the present invention, LPF represents a long-pass filter, and L1 represents a focusing lens. The laser emits a laser, which is reflected by the narrowband filter F, the plane reflectors M1 and M2 to the gas multi-pass cell of the present invention in sequence, and the laser reflected to the gas multi-pass cell is injected into the inner cavity of the detection tube 8 through the incident hole 61, the window plate 3, and the reflector with holes CM1, and then reflected multiple times between the reflectors with holes CM1 and CM2 in the inner cavity of the detection tube 8 and passes through the window plate 3 with nanoparticles attached, and then emitted from the reflector with holes CM2, the window plate 3, and the exit hole 62 on the exit main frame 12, and is received by the spectrometer for detection after passing through the long-pass filter LPF and the focusing lens L1 in sequence.

[0038] The Herriott cavity is a special optical resonator designed so that the laser beam can be reflected multiple times in the cavity. The cavity usually contains two or more mirrors, and the specific arrangement and curvature of these mirrors enable the laser beam to return along a specific path after each reflection, thus forming a stable oscillation mode in the cavity.

[0039] The laser beam injected into the inner cavity of the detection tube 8 interacts with the gas to be tested and generates Raman scattering, generating scattered light related to the vibration mode of the gas molecules. Multiple reflections greatly extend the path of the laser beam in the inner cavity of the detection tube 8, which effectively increases the effective action optical path, thereby making the interaction between the laser and the gas sample more sufficient, thereby increasing the number of Raman scattering events, and the intensity of the Raman scattering signal is also significantly enhanced. On the other hand, nanoparticles have the optical property of being able to strongly absorb and scatter light. When the laser interacts with the nanoparticles, surface plasmon resonance (SPR) occurs. The nanoparticles change the electromagnetic field distribution around the gas molecules, enhance the local electromagnetic field, and thus enhance the intensity of the Raman scattering signal. The SPR effect of the nanoparticles can also make the Raman scattered light more efficiently scattered and collected, thereby improving the detection sensitivity of the signal.

[0040] Usually, there are two methods for signal enhancement: increasing laser power and increasing the optical path. Using an optical multi-pass cell to increase the optical path is the most common method in surface enhanced Raman spectroscopy. There are many types of gas absorption cells, including traditional White cells and Herriott cells, among which Herriott cells are widely used due to their high stability.

[0041] Surface enhanced Raman spectroscopy (SERS) is an important optical detection method. It amplifies and enhances the Raman signal of the sample under test through the local field formed on the surface of the rough nano-metal structure. By analyzing the SERS spectrum peak and intensity, the internal structure information at the molecular level can be obtained. This detection method can realize the rapid detection of samples, and there is no need to label biological samples. Therefore, surface enhanced Raman spectroscopy is particularly suitable for biochemical analysis. At present, surface enhanced Raman spectroscopy is widely used in many fields such as food safety, biological sciences, drug analysis, and water body detection. The present invention combines the Herriott cavity with the surface enhanced Raman technology to enhance the intensity of the Raman scattering signal, and has broad application prospects.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A surface enhanced Raman gas multi-pass cell based on a Herriott cavity, characterized in that: The invention comprises two main frames (1) arranged opposite to each other, wherein the adjacent main frames (1) are connected via a detection tube (8); window components (2) are respectively embedded on two opposite surfaces of the main frames (1) close to and away from the detection tube (8); the window components (2) arranged opposite to each other press a window sheet (3) and a reflector with a hole (4) onto the main frames (1); a perforation (6) is provided in the middle of the window components (2) for facilitating light to pass through the window sheet (3) and the reflector with a hole (4) in sequence; a nano film layer (5) is provided on one side of the window sheet (3) close to the detection tube (8); and air holes (7) are also provided on the main frames (1).

2. The surface enhanced Raman gas multi-pass cell based on the Herriott cavity according to claim 1, characterized in that: One of the main frames (1) is an incident main frame (11), the perforations (6) on the incident main frame (11) are incident holes (61), and the air holes (7) are air inlet holes (71); the other main frame (1) is an exit main frame (12), the perforations (6) on the exit main frame (12) are exit holes (62), and the air holes (7) are air outlet holes (72).

3. The surface enhanced Raman gas multi-pass cell based on the Herriott cavity according to claim 2, characterized in that: The incident main frame (11) and the exit main frame (12) are symmetrically arranged at the two ends of the detection tube (8); the incident hole (61) and the exit hole (62) are symmetrically arranged; and the air inlet (71) and the air outlet (72) are symmetrically arranged.

4. The surface enhanced Raman gas multi-pass cell based on the Herriott cavity according to claim 1, characterized in that: The window piece (3) and the reflector with holes (4) are respectively sealed and connected to the perforation (6) via sealing gaskets.

5. The surface enhanced Raman gas multi-pass cell based on the Herriott cavity according to claim 1, characterized in that: The nano film layer (5) is composed of nanoparticles, and the shapes of the nanoparticles include a combination of one or more of a sphere, a cone, and a polyhedron.

6. The surface enhanced Raman gas multi-pass cell based on the Herriott cavity according to claim 5, characterized in that: The nanoparticles include gold nanoparticles and / or silver nanoparticles.

7. The surface enhanced Raman gas multi-pass cell based on the Herriott cavity according to claim 1, characterized in that: The detection tube (8) is a hollow cylinder.

8. The surface enhanced Raman gas multi-pass cell based on the Herriott cavity according to claim 1, characterized in that: A sealing gasket is provided between the detection tube (8) and the main frame (1).

9. The surface enhanced Raman gas multi-pass cell based on the Herriott cavity according to claim 1, characterized in that: Adjacent main frames (1) are also connected via support columns (9), and the support columns (9) are arranged outside the detection tubes (8).

10. The surface enhanced Raman gas multi-pass cell based on the Herriott cavity according to claim 1, characterized in that: The holed reflector (4) is a concave holed high-reflection mirror.

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