WO2018121146A1 - 一种提高激光探针中碳元素检测灵敏度的方法 - Google Patents

一种提高激光探针中碳元素检测灵敏度的方法 Download PDF

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WO2018121146A1
WO2018121146A1 PCT/CN2017/112766 CN2017112766W WO2018121146A1 WO 2018121146 A1 WO2018121146 A1 WO 2018121146A1 CN 2017112766 W CN2017112766 W CN 2017112766W WO 2018121146 A1 WO2018121146 A1 WO 2018121146A1
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cyano
laser
carbon
plasma
sample
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PCT/CN2017/112766
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French (fr)
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李祥友
李嘉铭
郭连波
曾晓雁
陆永枫
郝中骐
周冉
唐云
杨平
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华中科技大学
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Priority to US16/035,072 priority Critical patent/US10267741B2/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
    • G01N21/718—Laser microanalysis, i.e. with formation of sample plasma
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/10—Arrangements of light sources specially adapted for spectrometry or colorimetry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/64—Fluorescence; Phosphorescence
    • G01N21/6402—Atomic fluorescence; Laser induced fluorescence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/12—Circuits of general importance; Signal processing
    • G01N2201/124—Sensitivity

Definitions

  • the invention belongs to the field of laser plasma emission spectroscopy, and particularly relates to a method for improving the sensitivity of carbon element detection in a laser probe, which can enhance the spectral signal of carbon elements in the plasma and improve the detection sensitivity of the laser probe to carbon elements.
  • Laser probe also known as laser-induced breakdown spectroscopy (LIBS)
  • LIBS laser-induced breakdown spectroscopy
  • the basic principle is to use a pulsed laser beam to ablate the plasma on the surface of the sample to be tested, and collect and analyze the emission spectrum of the plasma to obtain the type and content information of the elements contained in the sample. Because laser probes have all-element detection, fast, real-time, online, and remote analysis, they have been widely concerned by researchers at home and abroad for many years.
  • N. Abdulmadjid et al. (Spectrochimica Acta Part B, 2015, 114: 1-6). This method is suitable for detecting carbon in the laboratory, requires re-inflation when changing samples, and can not achieve gas protection of the entire spectrum collection optical path in remote measurement, and has great limitations in industrial field detection applications; 2 Deriving the carbon content using a multi-element spectral correction algorithm. A multi-line internal standard algorithm as used by C.Y. Pan et al. (Applied Spectroscopy, 2016, 70(4): 702-708). This method uses multiple elements from the perspective of post-experiment data processing. The spectrum of the element compensates for the line of the disturbed carbon, but the method is limited by other elements in the sample and is only suitable for sample detection with consistent matrix.
  • the present invention provides a method for improving the sensitivity of carbon element detection in a laser probe, which uses a laser to ablate a sample, and carbon in the sample reacts with nitrogen in an ambient gas to form cyanide.
  • Base usually the cyano molecule has a weak emission spectrum, and the wavelength tunable laser is used to resonate and excite the electrons of the cyano molecule to emit a cyano characteristic fluorescent signal.
  • This method has high selection without affecting the spectrum of the matrix.
  • the cyano signal is enhanced, the interference generated by the matrix is overcome, the spectral signal of the carbon element in the plasma is enhanced, and the detection sensitivity of the laser probe to the carbon element is improved.
  • a method for improving sensitivity of detecting carbon elements in a laser probe which comprises the following steps:
  • the electrons of the cyano molecule in the plasma are excited to generate an energy level transition, thereby emitting a fluorescent signal, collecting a fluorescence spectrum emitted by the electrons in the cyano molecule at a transition level, and recording the fluorescence spectrum;
  • step S2 when adjusting the wavelength of the laser beam of the wavelength tunable laser, first select the target excitation electron in the cyano band, select the appropriate line as the excitation line according to the target excitation electron, and then wavelength The wavelength of the laser beam of the tunable laser is adjusted to be the same as the selected excitation line.
  • step S2 when the plasma is irradiated with the laser beam in step S2, nitrogen is blown to the plasma to increase the reaction efficiency of carbon atoms and nitrogen atoms.
  • step S4 based on the relationship between the spectral intensity of the cyano group and the carbon content in the sample, a carbon quantitative analysis model is established, and the carbon element in the sample to be tested is qualitatively or quantitatively analyzed.
  • the mechanism of action of the carbon element detecting method for improving the sensitivity of the laser probe of the present invention is:
  • the laser output laser beam ablate the surface of the sample to be tested, and the surface of the sample and the ambient gas near the surface of the sample rapidly heat up to become a plasma.
  • the carbon contained in the sample is atomized into carbon atoms into the plasma, and the nitrogen in the ambient gas is The atomization enters the plasma, and the carbon atom and the nitrogen atom combine to form a cyano molecule; the wavelength of the excited transition of the electron of the cyano molecule is adjusted by a wavelength tunable laser, the laser is output and the plasma is irradiated, and the laser is irradiated
  • the single photon energy is equal to the difference between the two energy levels in the cyano molecule, and the lower level electron will undergo stimulated transition absorption, transition At the highest level, the upper level electrons are unstable, spontaneous radiation transition occurs, and fluorescence is emitted.
  • the emission fluorescence spectrum of the cyano group is collected and recorded, and the sensitivity of the laser probe to carbon detection can be improved by using a
  • the method of the present invention replaces the carbon atom spectrum in a conventional laser probe by detecting the emission spectrum of a cyano molecule in a plasma, and characterizes the carbon content by detecting the spectral intensity of the cyano molecule, and the wavelength tunable laser beam is added.
  • Direct irradiation of the plasma selective excitation of only the cyano molecules in the plasma, almost does not affect other spectral lines of the plasma emission spectrum, can effectively reduce the interference of the matrix line, reduce the matrix effect, and high selectivity
  • the cyano signal is enhanced to improve the sensitivity of the laser probe to carbon.
  • the method of the invention utilizes the visible band cyano spectrum instead of the deep ultraviolet band carbon atom spectrum detection to compensate for the low efficiency of the optical acquisition system in the deep ultraviolet band and improve the carbon element detection sensitivity.
  • the optical path system does not require vacuum or inert gas protection by avoiding the use of carbon atoms in the deep ultraviolet band that are susceptible to air absorption and using cyano molecular lines in the visible range.
  • the method of the present invention can change the sample more quickly during the detection process, and can realize industrial online and remote analysis. Moreover, the method utilizes a wavelength tunable laser as a carbon element spectral enhancement tool, and has the same as the excitation source of the laser probe. Therefore, compared with the existing methods at home and abroad, the laser probe is retained in the atmospheric environment for remote detection and online. Analysis, solid-liquid gas state without distinction analysis and other advantages.
  • the wavelength tunable laser beam added by the method of the invention directly irradiates the plasma, and the optical path is less modified, and the advantages of the laser probe detection are not damaged, and the detection of carbon elements in the laboratory or industrial field can be realized.
  • Figure 1 is a schematic flow chart of the method of the present invention
  • Figure 2 is a cyano spectrum diagram of polyvinyl chloride in Example 1 of the method of the present invention.
  • Figure 3 is a cyano spectrum diagram of a soil sample contaminated with petroleum in Example 2 of the method of the present invention.
  • Figure 4 is a cyano spectrum diagram of pig iron in Example 3 of the method of the present invention.
  • Figure 5 is a graph showing the relationship between the cyanofluorescence spectral intensity and the carbon content plotted in Example 3 of the method of the present invention.
  • the invention provides a method for improving the sensitivity of detecting carbon elements in a laser probe, the principle of which is to replace the carbon atom of a conventional laser probe by using a cyano molecule emission spectrum formed by reacting carbon in a sample to be tested with nitrogen in an ambient gas.
  • the spectroscopy uses a wavelength tunable laser beam to irradiate the plasma to selectively excite the cyano molecule in the plasma to emit a characteristic fluorescence spectrum.
  • the method specifically includes the following steps:
  • the electrons of the cyano molecule in the plasma are excited to generate an energy level transition, thereby emitting a fluorescent signal, collecting a fluorescence spectrum emitted by the electrons in the cyano molecule at a transition level, and recording the fluorescence spectrum;
  • the carbon element in the sample to be tested is qualitatively or quantitatively analyzed, and a mathematical model is established to obtain a carbon element detection result.
  • step S2 when adjusting the wavelength of the laser beam of the wavelength tunable laser, the target excitation electron in the cyano band is first selected, and the appropriate spectrum is selected according to the target excitation electron.
  • the excitation line is then adjusted to the wavelength of the laser beam of the wavelength tunable laser to be the same as the selected excitation line.
  • step S2 when the plasma is irradiated with a laser beam in step S2, nitrogen is blown to the plasma to increase the reaction efficiency of carbon atoms and nitrogen atoms.
  • step S4 a carbon quantitative analysis model is established based on the relationship between the spectral intensity of the cyano group and the carbon content in the sample, and the carbon element in the sample to be tested is qualitatively or quantitatively determined. analysis.
  • the method of detecting carbon in polyvinyl chloride is taken as an example to describe the method in detail.
  • the sample was selected as polyvinyl chloride plastic with a carbon content of 38.7%.
  • the laser selected the Brunelant laser from France Quantel and the Vibrant wavelength tunable laser from OPOTEK, USA.
  • the spectrometer selected the SCT320 spectrometer from Princeton Instrument.
  • the tunable laser wavelength is adjusted to 388.3 nm.
  • a 421.6 nm spectrum of weaker cyano molecules can be observed without 388.3 nm laser irradiation.
  • 388.3 nm laser irradiation By adding 388.3 nm laser irradiation, a 421.6 nm spectrum of the cyano molecule with higher signal to noise ratio can be observed.
  • the method of the present invention can significantly enhance the spectrum of carbon elements in the laser probe with high selectivity, and improve the sensitivity of the laser probe for detecting carbon in polyvinyl chloride.
  • the method of detecting carbon in soil is taken as an example to describe the method in detail.
  • the sample was selected to be oil contaminated soil with a petroleum content of 10%.
  • the laser selected American Bigsky Ultra50 laser and American OPOTEK Vibrant wavelength tunable laser.
  • the spectrometer selected Princeton Instrument's SCT320 spectrometer.
  • the tunable laser wavelength is adjusted to 388.3 nm.
  • a 421.6 nm spectrum of weaker cyano molecules can be observed without 388.3 nm laser irradiation.
  • a 421.6 nm spectrum of the cyano molecule with higher signal to noise ratio can be observed.
  • the method of the invention can significantly enhance the carbon atoms in the laser probe with high selectivity.
  • the spectrum of the element enhances the sensitivity of the laser probe to detect oil contamination in the soil.
  • the method of detecting carbon in steel is taken as an example to describe the method in detail.
  • the sample was selected as a set of 7 pig iron national standard materials GSB03-2582-2010, with a carbon content of 2.46-4.12%.
  • the laser selected the Beijing Limburg Nimma400 laser and the US OPOTEK Vibrant wavelength tunable laser.
  • the spectrometer selected the SCT320 spectrometer from Princeton Instrument of the United States.
  • the tunable laser wavelength is adjusted to 421.6 nm.
  • the 388.3 nm spectrum of the cyano molecule could not be observed without 421.6 nm laser irradiation.
  • the 388.3nm spectrum of the cyano molecule with strong signal-to-noise ratio can be observed.
  • Nitrogen gas blowing on the plasma can increase the reaction efficiency of carbon atoms and nitrogen atoms, further enhance the 388.3 nm spectrum of the cyano molecule, and improve the detection sensitivity.
  • Fig. 5 by plotting the relationship between the cyanofluorescence spectral intensity and the carbon content, a carbon quantitative analysis model can be established.
  • the method of the invention can significantly enhance the spectrum of carbon elements in the laser probe with high selectivity, improve the sensitivity of the laser probe for detecting carbon in steel, and realize the qualitative and quantitative analysis of carbon in steel.

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Abstract

一种提高激光探针中碳元素检测灵敏度的方法，具体过程如下：采用激光器输出激光束烧蚀待测样品表面，样品表面和靠近样品表面的环境气体迅速升温变为等离子体，样品中所含的碳元素和环境气体中的氮气被原子化并结合为氰基分子；通过将波长可调谐激光器调节至氰基分子的电子发生受激跃迁所需波长，输出激光并辐照等离子体，氰基分子中的电子发生辐射跃迁，发射荧光，收集氰基的发射荧光光谱并记录，对碳元素进行定性或定量分析。本方法在几乎不影响基体光谱的情况下，高选择性地增强氰基信号，克服基体产生的干扰，增强等离子体中碳元素的光谱信号，提高激光探针对碳元素的检测灵敏度。

Description

一种提高激光探针中碳元素检测灵敏度的方法 [技术领域]
本发明属于激光等离子体发射光谱领域，具体涉及一种提高激光探针中碳元素检测灵敏度的方法，其能够增强等离子体中碳元素的光谱信号，提高激光探针对碳元素的检测灵敏度。
[背景技术]
激光探针，又叫激光诱导击穿光谱(laser-induced breakdown spectroscopy，简称LIBS)，是一种原子发射光谱分析技术。其基本原理是利用脉冲激光束在待测样品表面烧蚀出等离子体，通过收集并分析等离子体的发射光谱，获得样品中所含元素的种类和含量信息。由于激光探针具有全元素检测、快速、实时、在线、远程分析等特点，多年来持续受到国内外研究学者的广泛关注。
然而，由于碳原子的特殊结构，其在等离子体中的特征谱线很弱，容易受到基体光谱的干扰，并且主要集中在易受空气吸收的深紫外区域，对光学采集系统提出很高的要求。因此，激光探针检测碳元素的研究主要集中在含碳量较高的样品中，如煤炭、塑料、生物组织等。而对于低含量的碳元素，一直以来是激光探针的检测难点。目前，国内外利用激光探针检测微量碳元素的方法主要有以下两种：①在整个光路中充惰性气体等保护气体，减弱碳在深紫外区域光谱被空气的吸收，提高光谱采集效率。如S.N.Abdulmadjid等(SpectrochimicaActa Part B，2015，114：1-6)中所用的低压氦气环境。这种方法适合在实验室中检测碳，在更换样品的时候需要重新充气，并且在远程等测量中也无法实现整个光谱收集光路的气体保护，在工业现场检测应用方面有很大的局限性；②利用多元素光谱校正算法推导碳含量。如C.Y.Pan等(Applied Spectroscopy,2016,70(4)：702-708)所用的多谱线内标算法。这种方法从实验后期数据处理的角度，利用多个元 素的光谱补偿受干扰的碳的谱线，但是该方法受样品中别的元素限制，仅适用于基体一致的样品检测。
由于存在上述缺陷和不足，本领域亟需做出进一步的完善和改进，设计一种激光探针检测含碳量的方法，使其能够避免基体光谱对碳元素光谱的影响，提高激光探针对碳元素的检测灵敏度。
[发明内容]
针对现有技术的以上缺陷或改进需求，本发明提供了一种提高激光探针中碳元素检测灵敏度的方法，该方法采用激光烧蚀样品，样品中的碳与环境气体中的氮反应生成氰基，通常氰基分子发射光谱强度较弱，利用波长可调谐激光对氰基分子的电子进行共振激发，使其发射氰基特征荧光信号，该方法在几乎不影响基体光谱的情况下，高选择性地增强氰基信号，克服基体产生的干扰，增强等离子体中碳元素的光谱信号，提高激光探针对碳元素的检测灵敏度。
为实现上述目的，按照本发明的一个方面，提供了一种提高激光探针中碳元素检测灵敏度的方法，其特征在于，具体包括以下步骤：
S1.准备好待测样品，打开固定波长激光器输出激光束，采用激光束烧蚀待测样品表面，在激光束的作用下，待测样品表面和靠近待测样品表面的环境气体迅速升温变为等离子体，待测样品中所含的碳元素和环境气体中的氮气被原子化进入等离子体，等离子体中的碳原子和氮原子结合为氰基分子；
S2.准备一波长可调谐激光器，将该波长可调谐激光器调节至氰基分子的电子发生受激跃迁所需波长，波长可调谐激光器的激光束输出并辐照等离子体，对等离子体中的氰基分子的电子进行共振激发；
S3.对等离子体中的氰基分子的电子受激发产生能级跃迁，从而发射出荧光信号，收集氰基分子中的电子在跃迁能级时发射的荧光光谱，并记录该荧光光谱；
S4.根据步骤S3中采集的对等离子体中的氰基分子发射的荧光光谱，对待测样品中的碳元素进行定性或定量分析，得到碳元素的检测结果。
进一步优选地，步骤S2中，在调节波长可调谐激光器的激光束波长时，先选取氰基能带中的目标激发电子，根据该目标激发电子来选取合适的谱线为激发线，然后将波长可调谐激光器的激光束波长调节至与所选取的激发线相同。
通过检测等离子体中氰基分子的发射光谱来代替常规激光探针中的碳原子光谱，通过检测氰基分子光谱强度来表征碳元素含量，可避免使用易受空气吸收的深紫外波段的碳原子线，而使用可见光波段的氰基分子谱线，提高碳元素检测的灵敏度。而选择合适的目标激发电子和激发线，可以得到强度较高的氰基分子发射光谱，便于后续对碳元素的分析。
进一步优选地，在步骤S2中采用激光束对等离子体进行辐照时，对等离子体吹氮气以提高碳原子和氮原子的反应效率。
较多的比较试验表明，通过在辐照时吹入氮气，可有效地提高碳原子和氮原子的反应效率，提高氰基分子的生成率，从而，得到强度更高的氰基分子中电子的发射光谱。
进一步优选地，在步骤S4中，根据氰基光谱强度与样品中的碳含量成正比的关系，建立碳元素定量分析模型，对待测样品中的碳元素进行定性或定量分析。
本发明的提高激光探针灵敏度的碳元素检测方法的作用机理为：
采用激光器输出激光束烧蚀待测样品表面，样品表面和靠近样品表面的环境气体迅速升温变为等离子体，样品中所含的碳元素被原子化成碳原子进入等离子体，环境气体中的氮气被原子化进入等离子体，碳原子和氮原子结合为氰基分子；通过将波长可调谐激光器调节至氰基分子的电子发生受激跃迁所需波长，输出激光并辐照等离子体，当辐照激光的单光子能量等于氰基分子中的两能级之差，下能级电子将发生受激跃迁吸收，跃迁 至上能级，上能级电子不稳定，发生自发辐射跃迁，发射荧光。收集氰基的发射荧光光谱并记录，利用氰基光谱强度与样品中的碳含量成正比，进行定性或定量分析，能够提高激光探针对碳元素检测的灵敏度。
总体而言，通过本发明所构思的以上技术方案与现有技术相比，具备以下优点和有益效果。
(1)本发明的方法通过检测等离子体中氰基分子的发射光谱来代替常规激光探针中的碳原子光谱，通过检测氰基分子光谱强度来表征碳元素含量，加入的波长可调谐激光束直接辐照等离子体，仅对等离子体中的氰基分子进行选择性激发，几乎不影响等离子体发射光谱的其他谱线，可有效降低基体谱线的干扰，减小基体效应，同时高选择性地增强氰基信号，提高激光探针对碳元素的检测灵敏度。
(2)本发明方法利用可见波段的氰基光谱代替深紫外波段的碳原子光谱检测，弥补光学采集系统在深紫外波段采集效率低的不足，提高碳元素检测灵敏度。由于避免使用易受空气吸收的深紫外波段的碳原子线，而使用可见光波段的氰基分子谱线，光路系统无需真空或惰性气体保护。
(3)本发明的方法与真空或惰性气体保护方法相比，检测过程中可以更快更换样品，并且可以实现工业在线和远程分析。且该方法利用波长可调谐激光作为碳元素光谱增强工具，与激光探针的激发源有共同之处，因此与国内外已有方法相比，保留了激光探针在大气环境中远程探测、在线分析、固液气态无区别分析等优势。
(4)本发明的方法加入的波长可调谐激光束直接辐照等离子体，对光路改动较少，不破坏激光探针检测的优势，可以实现在实验室或工业现场对碳元素的检测。
[附图说明]
图1是本发明方法的流程示意图；
图2是本发明方法实施例1中聚氯乙烯中氰基光谱图；
图3是本发明方法实施例2中被石油污染的土壤样品中氰基光谱图；
图4是本发明方法实施例3中生铁中氰基光谱图；
图5是本发明方法实施例3中绘制的氰基荧光光谱强度和碳含量的关系图。
[具体实施方式]
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。此外，下面所描述的本发明各个实施方式中所涉及到的技术特征只要彼此之间未构成冲突就可以相互组合。
本发明提供的一种提高激光探针中碳元素检测灵敏度的方法，其原理是利用待测样品中的碳与环境气体中的氮反应生成的氰基分子发射光谱代替传统激光探针的碳原子光谱，再利用波长可调谐激光束辐照等离子体，选择性激发等离子体中的氰基分子，使其发出特征荧光光谱，该方法具体包括以下步骤：
S1.准备好待测样品，打开固定波长激光器输出激光束，采用激光束烧蚀待测样品表面，在激光束的作用下，待测样品表面和靠近待测样品表面的环境气体迅速升温变为等离子体，待测样品中所含的碳元素和环境气体中的氮气被原子化进入等离子体，等离子体中的碳原子和氮原子结合为氰基分子；
S2.准备一波长可调谐激光器，将该波长可调谐激光器调节至氰基分子的电子发生受激跃迁所需波长，波长可调谐激光器的激光束输出并辐照等离子体，对等离子体中的氰基分子的电子进行共振激发；
S3.对等离子体中的氰基分子的电子受激发产生能级跃迁，从而发射出荧光信号，收集氰基分子中的电子在跃迁能级时发射的荧光光谱，并记录该荧光光谱；
S4.根据步骤S3中采集的对等离子体中的氰基分子发射的荧光光谱，对待测样品中的碳元素进行定性或定量分析，建立数学模型，得到碳元素的检测结果。
在本发明的一个优选实施例中，步骤S2中，在调节波长可调谐激光器的激光束波长时，先选取氰基能带中的目标激发电子，根据该目标激发电子来选取合适的谱线为激发线，然后将波长可调谐激光器的激光束波长调节至与所选取的激发线相同。
在本发明的另一个优选实施例中，在步骤S2中采用激光束对等离子体进行辐照时，对等离子体吹氮气以提高碳原子和氮原子的反应效率。
在本发明的另一个优选实施例中，在步骤S4中，根据氰基光谱强度与样品中的碳含量成正比的关系，建立碳元素定量分析模型，对待测样品中的碳元素进行定性或定量分析。
为了更好地解释本发明，以下给出三个具体实施例：
实施例1
以检测聚氯乙烯中的碳为例，对该方法进行详细说明。
选取样品为聚氯乙烯塑料，碳含量38.7％。
激光器选择法国Quantel公司Brilliant型激光器和美国OPOTEK公司Vibrant波长可调谐激光器，光谱仪选择Princeton Instrument公司的SCT320型光谱仪。选取氰基A2Π能带中ν＝0振动能级电子为目标激发电子，氰基B2Σ-A2Π能带中的(0，0)388.3nm谱线为激发线，并将波长可调谐激光器波长调节至388.3nm处。
(1)打开Brilliant激光器输出激光，烧蚀聚氯乙烯样品表面，聚氯乙烯样品表面产生等离子体，聚氯乙烯中的碳和空气中的氮被原子化，进入等离子体，碳原子和氮原子结合为氰基分子；
(2)波长可调谐激光器输出388.3nm激光，共振激发氰基分子A2Π能带ν＝0能级电子，使其发生受激跃迁至B2Σ能带ν＝0能级；
(3)采集氰基分子B2Σ能带ν＝0能级电子自发辐射跃迁至A2Π能带ν＝1能级时发射的荧光信号并记录。
如图2所示，在没有388.3nm激光辐照的情况下，可以观察到较弱的氰基分子421.6nm光谱。加入388.3nm激光辐照，可以观察到信噪比更高的氰基分子421.6nm光谱。
综上所述，使用本发明方法可以显著地高选择性增强激光探针中碳元素的光谱，提高激光探针检测聚氯乙烯中碳元素的灵敏度。
实施例2
以检测土壤中的碳为例，对该方法进行详细说明。
选取样品为被石油污染的土壤，石油含量为10％。
激光器选择美国Bigsky公司Ultra50型激光器和美国OPOTEK公司Vibrant波长可调谐激光器，光谱仪选择Princeton Instrument公司的SCT320型光谱仪。选取氰基A2Π能带中ν＝0振动能级电子为目标激发电子，氰基B2Σ-A2Π能带中的(0，0)388.3nm谱线为激发线，并将波长可调谐激光器波长调节至388.3nm处。
(1)打开Ultra50激光器输出激光，烧蚀土壤样品表面，土壤样品表面产生等离子体，土壤中的碳和空气中的氮被原子化，进入等离子体，碳原子和氮原子结合为氰基分子；
(2)波长可调谐激光器输出388.3nm激光，共振激发氰基分子A2Π能带ν＝0能级电子，使其发生受激跃迁至B2Σ能带ν＝0能级；
(3)采集氰基分子B2Σ能带ν＝0能级电子自发辐射跃迁至A2Π能带ν＝1能级时发射的荧光信号并记录。
如图3所示，在没有388.3nm激光辐照的情况下，可以观察到较弱的氰基分子421.6nm光谱。加入388.3nm激光辐照，可以观察到信噪比更高的氰基分子421.6nm光谱。
综上所述，使用本发明方法可以显著地高选择性增强激光探针中碳元 素的光谱，提高激光探针检测土壤中石油污染的灵敏度。
实施例3
以检测钢铁中的碳为例，对该方法进行详细说明。
选取样品为一套共7个的生铁国家标准物质GSB03-2582-2010，碳含量2.46-4.12％。
激光器选择北京镭宝公司Nimma400型激光器和美国OPOTEK公司Vibrant波长可调谐激光器，光谱仪选择美国Princeton Instrument公司的SCT320型光谱仪。选取氰基A2Π能带中ν＝0振动能级电子为目标激发电子，氰基B2Σ-A2Π能带中的(0，1)421.6nm谱线为激发线，并将波长可调谐激光器波长调节至421.6nm处。
(1)打开Nimma400激光器输出激光，烧蚀生铁样品表面，生铁样品表面产生等离子体，生铁中的碳和空气/氮气的氮被原子化，进入等离子体，碳原子和氮原子结合为氰基分子；
(2)波长可调谐激光器输出421.6nm激光，共振激发氰基分子A2Π能带ν＝1能级电子，使其发生受激跃迁至B2Σ能带ν＝0能级；
(3)采集氰基分子B2Σ能带ν＝0能级电子自发辐射跃迁至A2Π能带ν＝0能级时发射的荧光信号并记录。
如图4所示，在没有421.6nm激光辐照的情况下，无法观察到氰基分子388.3nm光谱。加入421.6nm激光辐照，可以观察到信噪比较强的氰基分子388.3nm光谱。对等离子体吹氮气可以提高碳原子和氮原子的反应效率，进一步增强氰基分子388.3nm光谱，提高检测灵敏度。如图5所示，绘制氰基荧光光谱强度和碳含量的关系图，可以建立碳元素定量分析模型。
综上所述，使用本发明方法可以显著地高选择性增强激光探针中碳元素的光谱，提高激光探针检测钢铁中碳元素的灵敏度，并实现钢铁中的碳元素的定性和定量分析。
本领域的技术人员容易理解，以上所述仅为本发明的较佳实施例而 已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (4)

  1. 一种提高激光探针中碳元素检测灵敏度的方法，其特征在于，具体包括以下步骤：
    S1.准备好待测样品，打开固定波长激光器输出激光束，采用激光束烧蚀待测样品表面，在激光束的作用下，待测样品表面和靠近待测样品表面的环境气体迅速升温变为等离子体，待测样品中所含的碳元素和环境气体中的氮气被原子化进入等离子体，等离子体中的碳原子和氮原子结合为氰基分子；
    S2.准备一波长可调谐激光器，将该波长可调谐激光器调节至氰基分子的电子发生受激跃迁所需波长，波长可调谐激光器的激光束输出并辐照等离子体，对等离子体中的氰基分子的电子进行共振激发；
    S3.对等离子体中的氰基分子的电子受激发产生能级跃迁，从而发射出荧光信号，收集氰基分子中的电子在跃迁能级时发射的荧光光谱，并记录该荧光光谱；
    S4.根据步骤S3中采集的对等离子体中的氰基分子发射的荧光光谱，对待测样品中的碳元素进行定性或定量分析，得到碳元素的检测结果。
  2. 如权利要求1所述的方法，其特征在于，步骤S2中，在调节波长可调谐激光器的激光束波长时，先选取氰基能带中的目标激发电子，根据该目标激发电子来选取合适的谱线为激发线，然后将波长可调谐激光器的激光束波长调节至与所选取的激发线相同。
  3. 如权利要求1或2所述的方法，其特征在于，在步骤S2中采用激光束对等离子体进行辐照时，对等离子体吹氮气以提高碳原子和氮原子的反应效率。
  4. 如权利要求3所述的方法，其特征在于，在步骤S4中，根据氰基光谱强度与样品中的碳含量成正比的关系，建立碳元素定量分析模型，对待测样品中的碳元素进行定性或定量分析。
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CN103792215A (zh) * 2014-01-24 2014-05-14 国电科学技术研究院 一种快速测量钢铁中碳元素含量的方法
CN105067592A (zh) * 2015-07-07 2015-11-18 华中科技大学 一种抑制激光探针自吸收效应的方法
CN105486676A (zh) * 2015-12-25 2016-04-13 中国科学院合肥物质科学研究院 一种基于微波辅助的激光诱导击穿光谱装置
CN106770191A (zh) * 2016-12-29 2017-05-31 华中科技大学 一种提高激光探针中碳元素检测灵敏度的方法

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