LIBS spectrum enhancement method and system based on micro-nano structure

Abstract

The invention discloses an LIBS spectrum enhancement method and system based on a micro-nano structure. The method comprises the following steps: S1, converging laser beams emitted by a laser onto a sample through an optical lens group; s2, adjusting processing parameters of the laser so as to form a preset processing light spot size on the surface of the sample; and S3, carrying out laser scanning processing on the sample, preparing a micro-nano structure on the surface of the sample, and forming a surface with a specific micro-nano structure so as to improve the LIBS spectral intensity. The invention provides an LIBS (Laser-induced Breakdown Spectroscopy) spectrum enhancement method and system based on a micro-nano structure, and the principle is that a surface with a specific micro-nano structure is prepared to enhance the spectrum signal intensity and the signal-to-noise ratio of laser-induced breakdown spectroscopy, so that the purposes of improving the detection stability and reducing the detection lower limit are achieved. The method has the significance of improving the sensitivity, accuracy and reliability of the LIBS technology, so that the method can be better applied to the fields of chemical analysis, material characterization and the like.

Description

Technical Field

[0001] The present invention belongs to the field of plasma emission spectrum detection, and in particular relates to a LIBS spectrum enhancement method and system based on micro-nano structures. Background Art

[0002] LIBS (Laser Induced Breakdown Spectroscopy) is a technique that uses ultrashort pulse lasers to focus on the surface of a sample to ablate the surface material to form a plasma, and then analyzes the plasma emission spectrum to determine the material composition and content of the sample. In practical applications, the intensity of the LIBS spectral signal is extremely important. Improving the LIBS spectral signal intensity can improve the stability of the test results and the detection limit. Currently, the common LIBS spectral signal enhancement methods include double-pulse or multi-pulse re-excitation, discharge pulses, laser ablation crater confinement, and self-pore confinement, all of which have their own advantages and disadvantages.

[0003] Micro-nano structure refers to microscopic structural features with sizes ranging from nanometers to micrometers. The principles of its enhancement of LIBS spectrum mainly include the following aspects: The effective laser excitation area increases: the micro-nano structure will increase the surface area of ​​the sample. When the laser ablates the sample surface to form plasma, the increased surface area can increase the spectral signal intensity.

[0004] Localized surface plasmon resonance effect: Surface micro-nanostructures can induce localized surface plasmon resonance effect, enhance the interaction between laser and sample, and increase the intensity of spectral signals.

[0005] The enhanced absorption of micro-nano structures reduces the surface laser breakdown threshold: Surface micro-nano structures can effectively reduce the laser breakdown threshold and produce better excitation effects under the same laser power.

[0006] The technical problems of applying LIBS spectral enhancement method based on micro-nano structure include: 1. Controllable preparation of surface micro-nano structures: The preparation process of micro-nano structures needs to have good reproducibility and stability to ensure that the analysis results between different samples are comparable. This involves the optimization and control of the preparation process to ensure that the performance of the micro-nano structures is stable and repeatable.

[0007] 2. Effective enhancement of plasma spectroscopy signal and signal-to-noise ratio: The design and preparation of micro-nano structures need to be able to effectively enhance LIBS signals to improve detection sensitivity and accuracy. This may involve optimizing the shape, size and material of the micro-nano structures to maximize the enhancement of plasma generation and signal emission during laser-induced breakdown. At the same time, it is necessary to consider how to effectively suppress background signals to improve the signal-to-noise ratio and analysis accuracy.

[0008] 3. Practicality and cost-effectiveness: The preparation methods of micro-nano structures need to consider their practicality and cost-effectiveness so that they can be widely promoted in practical applications. This may require combining existing preparation technologies and materials to find the best balance. Summary of the invention

[0009] In view of the above-mentioned deficiencies in the prior art, the present invention provides a LIBS spectrum enhancement method and system based on micro-nano structures to solve the technical problems existing in the above-mentioned LIBS spectrum enhancement method based on micro-nano structures.

[0010] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a LIBS spectrum enhancement method based on micro-nano structure, comprising the following steps: S1, focusing the laser beam emitted by the laser onto the sample through an optical lens group; S2, adjusting the processing parameters of the laser to form a preset processing spot and spot size on the sample surface; S3. Perform laser scanning processing on the sample to prepare micro-nano structures on the sample surface, forming a surface with specific micro-nano structures to improve the LIBS spectrum intensity.

[0011] Furthermore: in S2, the processing parameters of the laser include pulse width, frequency, wavelength, laser energy spot shape, spot size and scanning speed.

[0012] Further: In S3, the method for preparing on the sample surface includes large-spot laser scanning microstructure, linear-spot laser scanning microstructure, and focused small-spot laser micromachining, wherein the large-spot laser scanning microstructure and linear-spot laser scanning microstructure are used to produce non-periodic micro-nano structures, and the focused small-spot laser micromachining is used to produce periodic micro-nano structures with a period of 50nm-100um.

[0013] Further: in S3, the surface of the specific micro-nano structure includes micro-nano particles, micro-nano wires, micro-nano holes and micro-nano meshes.

[0014] Furthermore: in S3, the linear spot laser scanning microstructure is to focus the laser beam into a line to improve the microstructure preparation efficiency and improve the preparation uniformity.

[0015] The system of the LIBS spectrum enhancement method based on micro-nano structure includes a laser, an optical lens group and a moving platform, wherein the optical lens group includes a first reflector, a second reflector, a 1 / 2 wave plate, a polarization beam splitter, a third reflector and a plano-convex lens; The laser emits a laser beam which passes through a first reflector, a second reflector, a 1 / 2 wave plate, a polarization beam splitter, a third reflector and a plano-convex lens in sequence, and the plano-convex lens converges the laser beam onto a sample fixed on a moving platform.

[0016] The beneficial effects of the present invention are: (1) The present invention provides a LIBS spectrum enhancement method and system based on micro-nano structures. The principle is to prepare a surface with a specific micro-nano structure to reduce the laser excitation threshold, increase the effective surface area, and enhance the spectral signal intensity, signal-to-noise ratio and stability of the laser-induced breakdown spectroscopy, thereby achieving the purpose of improving detection stability and reducing the detection limit. The significance of this method is to improve the sensitivity, accuracy and reliability of LIBS technology, so as to better apply it to chemical analysis, material characterization and other fields.

[0017] (2) The present invention solves the technical problems existing in the application of LIBS spectrum enhancement methods based on micro-nano structures, and utilizes the surface plasmon resonance effect of micro-nano structures to enhance the radiation of plasma generated during laser induced breakdown. This enhancement effect can improve the intensity and stability of LIBS signals, thereby improving spectral resolution and detection sensitivity, achieving higher sensitivity, lower detection limit and more accurate elemental analysis, thereby playing an important role in the fields of material analysis and environmental monitoring.

[0018] (3) The advantages of the present invention are high repeatability, controllability, low cost and simple operation. The significance of this method is that it can enhance the interaction between laser and sample by using micro-nanostructures, increase the intensity of spectral signals, thereby improving the sensitivity of detection and reducing the detection limit. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of a LIBS spectrum enhancement method based on micro-nano structures of the present invention.

[0020] Figure 2 Schematic diagram of large spot laser scanning microstructure morphology Figure 3 Schematic diagram of periodic microstructure morphology Figure 4 Schematic diagram of the system structure of the micro-nanostructure-based LIBS spectrum enhancement method of the present invention.

[0021] Among them: 1. Laser; 2. First reflector; 3. Second reflector; 4. 1 / 2 wave plate; 5. Polarization beam splitter; 6. Third reflector; 7. Plano-convex lens; 8. Moving platform. DETAILED DESCRIPTION

[0022] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0023] Embodiment 1: like Figure 1 As shown, in one embodiment of the present invention, a LIBS spectrum enhancement method based on micro-nano structure includes the following steps: S1, focusing the laser beam emitted by laser 1 onto the sample through an optical lens group; S2, adjusting the processing parameters of the laser 1 so that a preset processing spot size is formed on the sample surface; S3. Perform laser scanning processing on the sample to prepare micro-nano structures on the sample surface, forming a surface with specific micro-nano structures to improve the LIBS spectrum intensity.

[0024] In S1, the sample is any material that can be used to prepare micro-nano structures, such as metal, soil and glass. In this embodiment, metallic copper is used.

[0025] In S2, the processing parameters of the laser 1 include pulse width, frequency, wavelength, laser energy, spot shape, spot size and scanning speed.

[0026] In this embodiment, the pulse width is a fixed parameter of the laser, and the pulse width of this embodiment is 9ns. The frequency ranges from 1Hz to 10000Hz, and 10Hz is taken in this embodiment. The wavelength of this embodiment is 355nm, and the laser energy ranges from 1mJ to 1000mJ, and 24mJ is taken in this embodiment. The spot shape is adjusted by changing the type of focusing lens, and the spot is a circular spot in this embodiment. The spot size is adjusted by changing the sample placement height, and the sample placement position in this embodiment is 2mm in front of the focus. The scanning speed ranges from 0.01mm / s to 0.1mm / s, and 0.02mm / s is taken in this embodiment.

[0027] In this embodiment, the processing parameters of the laser 1 are adjusted to match the characteristics of the micro-nano structure to achieve the best interaction effect between the laser and the sample.

[0028] In S3, the method for preparing on the sample surface includes large-spot laser scanning microstructure, linear-spot laser scanning microstructure and focused small-spot laser micromachining, wherein the large-spot laser scanning microstructure and linear-spot laser scanning microstructure are used to generate non-periodic micro-nano structures, and the focused small-spot laser micromachining is used to generate periodic micro-nano structures with a period of 50nm-100um.

[0029] In this embodiment, the principle of preparing a surface with a specific micro-nano structure by large-spot laser scanning microstructuring to improve the LIBS spectrum intensity is specifically as follows: 1) Lowering the laser breakdown threshold of the sample surface: By preparing micro-nano structures, the surface absorption rate of the micro-nano structures can be increased, thereby lowering the laser breakdown threshold and enhancing the intensity of the plasma spectrum signal at the same laser energy density.

[0030] 2) Increase the effective area of ​​laser-excited samples: The surface morphology of specific micro-nano structures can increase the interaction surface area between the laser and the sample, increase the absorption and conversion efficiency of laser energy, and thus improve the intensity of the spectral signal. Figure 2 As shown, in this embodiment, the area processed by laser scanning forms a specific micro-nano structure, which produces an increase in the effective area of ​​surface excitation, a localized surface plasmon resonance effect, and a surface breakdown threshold reduction effect, thereby enhancing the LIBS spectral signal intensity.

[0031] like Figure 4 As shown, in this embodiment, the system of the LIBS spectrum enhancement method based on micro-nano structure includes a laser 1, an optical lens group and a moving platform 12, wherein the optical lens group includes a first reflector 2, a second reflector 3, a 1 / 2 wave plate 4, a polarization beam splitter 5, a third reflector 6 and a plano-convex lens 7; The laser beam emitted by the laser 1 passes through the first reflector 2, the second reflector 3, the 1 / 2 wave plate 4, the polarization beam splitter 5, the third reflector 6 and the plano-convex lens 7 in sequence, and the plano-convex lens 7 converges the laser beam onto the sample fixed on the moving platform 8.

[0032] In this embodiment, the present invention uses laser to prepare micro-nano structures, and different micro-nano structures are prepared by adjusting laser parameters. This preparation method is not limited to laser, and micro-nano particles and microstructures composed of micron-level metal wires and metal meshes can also be prepared by electron beam scanning, chemical etching technology and high-temperature sintering to prepare micro-nano structures.

[0033] Embodiment 2: like Figure 1 As shown, in one embodiment of the present invention, a LIBS spectrum enhancement method based on micro-nano structure includes the following steps: S1, focusing the laser beam emitted by laser 1 onto the sample through an optical lens group; S2, adjusting the processing parameters of the laser 1 so that a preset processing spot size is formed on the sample surface; S3. Perform laser scanning processing on the sample to prepare micro-nano structures on the sample surface, forming a surface with specific micro-nano structures to improve the LIBS spectrum intensity.

[0034] In S1, the sample is any material that can be used to prepare micro-nano structures, such as metal, soil and glass. In this embodiment, metal aluminum is used.

[0035] In S2, the processing parameters of the laser 1 include pulse width, frequency, wavelength, laser energy, spot shape, spot size and scanning speed.

[0036] In this embodiment, the pulse width is a fixed parameter of the laser, and the pulse width of this embodiment is 8-10ns. The frequency ranges from 1Hz to 10000Hz, and 10Hz is taken in this embodiment. The wavelength of this embodiment is 355nm, and the laser energy ranges from 1 mJ to 1000 mJ, and 6mJ is taken in this embodiment. The spot shape is adjusted by changing the type of focusing lens, and the spot is a circular spot in this embodiment. The spot size is adjusted by changing the sample placement height. The sample placement position in this embodiment is the focus. The scanning speed ranges from 0.01mm / s to 0.2mm / s, and 0.2mm / s is taken in this embodiment.

[0037] In this embodiment, the processing parameters of the laser 1 are adjusted to match the characteristics of the micro-nano structure to achieve the best interaction effect between the laser and the sample.

[0038] In S3, the method for preparing on the sample surface includes large-spot laser scanning microstructure, linear-spot laser scanning microstructure and focused small-spot laser micromachining, wherein the large-spot laser scanning microstructure and linear-spot laser scanning microstructure are used to generate non-periodic micro-nano structures, and the focused small-spot laser micromachining is used to generate periodic micro-nano structures with a period of 50nm-100um.

[0039] In this embodiment, the principle of focusing a small spot to micro-process the surface of a micro-nano structure with a period of 80 um to improve the LIBS spectrum intensity is specifically as follows: 1) Lowering the laser breakdown threshold of the sample surface: By preparing micro-nano structures, the surface absorption rate of the micro-nano structures can be increased, thereby lowering the laser breakdown threshold and enhancing the intensity of the plasma spectrum signal at the same laser energy density.

[0040] 2) Increase the effective area of ​​laser-excited samples: The surface morphology of specific micro-nano structures can increase the interaction surface area between the laser and the sample, increase the absorption and conversion efficiency of laser energy, and thus improve the intensity of the spectral signal. Figure 3 As shown, in this embodiment, the area processed by laser scanning forms a periodic micro-nano structure, which produces an increase in the effective area of ​​surface excitation, a localized surface plasmon resonance effect, and a surface breakdown threshold reduction effect, thereby enhancing the LIBS spectral signal intensity.

[0041] like Figure 4 As shown, in this embodiment, the system of the LIBS spectrum enhancement method based on micro-nano structure includes a laser 1, an optical lens group and a moving platform 12, wherein the optical lens group includes a first reflector 2, a second reflector 3, a 1 / 2 wave plate 4, a polarization beam splitter 5, a third reflector 6 and a plano-convex lens 7; The laser beam emitted by the laser 1 passes through the first reflector 2, the second reflector 3, the 1 / 2 wave plate 4, the polarization beam splitter 5, the third reflector 6 and the plano-convex lens 7 in sequence, and the plano-convex lens 7 converges the laser beam onto the sample fixed on the moving platform 8.

[0042] In this embodiment, the present invention uses laser to prepare micro-nano structures, and different micro-nano structures are prepared by adjusting laser parameters. This preparation method is not limited to laser, and micro-nano particles and microstructures composed of micron-level metal wires and metal meshes can also be prepared by electron beam scanning, chemical etching technology and high-temperature sintering to prepare micro-nano structures.

[0043] The beneficial effects of the present invention are as follows: the present invention provides a LIBS spectrum enhancement method and system based on micro-nano structures, the principle of which is to reduce the laser excitation threshold, increase the effective surface area, and enhance the spectral signal intensity, signal-to-noise ratio and stability of the laser-induced breakdown spectroscopy by preparing a surface with a specific micro-nano structure, thereby achieving the purpose of improving detection stability and reducing the detection limit. The significance of this method is to improve the sensitivity, accuracy and reliability of LIBS technology, so as to better apply it to the fields of chemical analysis, material characterization, etc.

[0044] The present invention solves the technical problems existing in the application of LIBS spectrum enhancement methods based on micro-nano structures, utilizes the surface plasmon resonance effect of micro-nano structures, and enhances the radiation of plasma generated during laser induced breakdown. This enhancement effect can improve the intensity and stability of LIBS signals, thereby improving spectral resolution and detection sensitivity, achieving higher sensitivity, lower detection limit and more accurate elemental analysis, thereby playing an important role in the fields of material analysis and environmental monitoring.

[0045] Microstructured samples were prepared. In LIBS spectral analysis, there are two main uses: (1) for electrolytic enrichment of heavy metal elements in water, followed by laser excitation; (2) for component analysis of substances such as water, air, and soil that can directly contact the microstructure. Trace amounts of water, air, and soil are evenly distributed in the microstructure on the surface of the sample. When the laser excites the microstructure, the substances to be tested, such as water, air, and soil, are excited.

[0046] The advantages of the present invention are high repeatability, controllability, low cost and simple operation. The significance of this method is that the interaction between laser and sample can be enhanced by using micro-nano structures, the intensity of spectral signals can be increased, thereby improving the sensitivity of detection and reducing the detection limit.

[0047] In the description of the present invention, it is necessary to understand that the orientation or positional relationship indicated by the terms "center", "thickness", "upper", "lower", "horizontal", "top", "bottom", "inner", "outer", "radial", etc. is based on the orientation or positional relationship shown in the drawings, and 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 operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", and "third" are used only for descriptive purposes, and cannot be understood as indicating or implying the relative importance or the number of implicitly specified technical features. Therefore, the features defined by "first", "second", and "third" may explicitly or implicitly include one or more of the features.

Claims

1. A LIBS spectrum enhancement method based on micro-nano structure, characterized in that: The following steps are involved: S1, focusing the laser beam emitted by the laser (1) onto the sample through an optical lens group; S2, adjusting the processing parameters of the laser (1) so that a preset processing spot shape and spot size are formed on the surface of the sample; S3. Perform laser scanning processing on the sample to prepare micro-nano structures on the sample surface, forming a surface with specific micro-nano structures to improve the LIBS spectrum intensity.

2. The LIBS spectrum enhancement method based on micro-nano structure according to claim 1, characterized in that: In S2, the processing parameters of the laser (1) include pulse width, frequency, wavelength, laser energy spot shape, spot size and scanning speed.

3. The LIBS spectrum enhancement method based on micro-nano structure according to claim 2, characterized in that: In S3, the method for preparing on the sample surface includes large-spot laser scanning microstructure, linear-spot laser scanning microstructure and focused small-spot laser micromachining, wherein the large-spot laser scanning microstructure and linear-spot laser scanning microstructure are used to produce non-periodic micro-nano structures, and the focused small-spot laser micromachining is used to produce periodic micro-nano structures with a period of 50nm-100um.

4. The LIBS spectrum enhancement method based on micro-nano structure according to claim 1, characterized in that: In S3, the surface of the specific micro-nano structure includes micro-nano particles, micro-nano wires, micro-nano holes and micro-nano networks.

5. A system according to any one of claims 1 to 4, characterized in that: It comprises a laser (1), an optical lens group and a moving platform (12), wherein the optical lens group comprises a first reflector (2), a second reflector (3), a 1 / 2 wave plate (4), a polarization beam splitter (5), a third reflector (6) and a plano-convex lens or a plano-convex cylindrical mirror (7); The laser (1) emits a laser beam which passes through a first reflector (2), a second reflector (3), a half-wave plate (4), a polarization beam splitter (5), a third reflector (6) and a plano-convex lens (7) in sequence, and converges the laser beam onto a sample fixed on a moving platform (8) via the plano-convex lens (7).

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