Understanding the laser-induced aerosol ablation of sub-micron liquid particles via size-resolved spectral and image analyses†,Journal of Analytical Atomic Spectrometry

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Understanding the laser-induced aerosol ablation of sub-micron liquid particles via size-resolved spectral and image analyses†
Journal of Analytical Atomic Spectrometry ( IF 3.1 ) Pub Date : 2019-10-17 , DOI: 10.1039/c9ja00278b
Muhammad Sher Afgan _{1,

2,

3,

4,

5} , Sahar Sheta _{1,

2,

3,

4,

5} , Zongyu Hou _{1,

2,

3,

4,

5} , Zheng Li _{1,

2,

3,

4,

5} , Zhe Wang _{1,

2,

3,

4,

5}

Affiliation

Laser-induced breakdown spectroscopy of aerosols is associated with large signal variability and lower sampling rates. In this study, aerosol ablation and signal variability associated with aerosol size were studied by size-resolved spectral and image analyses of submicron sized particles using a high-density stream of monodisperse liquid aerosols. The rise in the particle size from 0.16 μm to 0.96 μm for a similar aerosol mass concentration showed a size-dependent intensity increase. The initial increase in the analyte emission was due to the enhanced analyte concentration inside the plasma volume, whereas for larger aerosols, the stronger ablation of the larger liquid particles resulted in elevated emission intensity. The electron number density increased from 1.6 × 10¹⁷ cm⁻³ to 2.6 × 10¹⁷ cm⁻³ with an increase in the particle size; however, the temporal delay of number density was faster for the larger particles due to higher plasma–ambience interaction. The analyte signal variation reduced to 3%, calculated using ensemble averaging, for particles larger than 0.5 μm. Plasma image analysis showed that the signal variation stemmed from inhomogeneity in the initial breakdown process and grew with the increasing delay. The variation in the plasma image area increased from 8% to 16% for 0.16 μm particles and 12% to 28% for 0.96 μm particles at the respective delays of 0 and 3 μs. Thus, two different sources of signal variability were determined. For smaller particles, the major source of variation was the variable sample scarcity inside the plasma, whereas for larger particles, plasma variation contributed more to the analyte signal variability from the beginning.

中文翻译：

通过尺寸分辨光谱和图像分析了解激光诱导的亚微米液体颗粒气雾消融†

气溶胶的激光诱导击穿光谱法与较大的信号可变性和较低的采样率相关。在这项研究中，通过使用高密度单分散液态气溶胶流对亚微米级颗粒进行尺寸分辨光谱和图像分析，研究了与气溶胶尺寸相关的气溶胶消融和信号可变性。对于类似的气溶胶质量浓度，粒径从0.16μm升高到0.96μm，显示出强度依赖于尺寸的增加。分析物排放量的最初增加是由于血浆体积内分析物浓度的增加，而对于较大的气溶胶，较大液体颗粒的强力烧蚀导致排放强度的提高。电子数密度从1.6×10 ¹⁷ cm ^-3增加至2.6×10 ¹⁷ cm ^-3随着粒度的增加；然而，由于较高的等离子体-环境相互作用，较大粒子的数密度时间延迟更快。对于大于0.5μm的颗粒，使用集成平均法计算得出的分析物信号变化降低到3％。等离子体图像分析表明，信号的变化源于初始击穿过程中的不均匀性，并随着延迟的增加而增大。在分别延迟0和3 s的情况下，等离子体图像区域的变化从0.16μm颗粒从8％增加到16％，对于0.96μm颗粒从12％增加到28％。因此，确定了信号变化的两个不同来源。对于较小的颗粒，主要的变化来源是血浆内部的样品稀少，而对于较大的颗粒，

更新日期：2019-11-28

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