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Height and Phase Mode Images of Soot Using AFM

机译：使用AFM的烟灰的高度和相位模式图像

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Recent experiments have challenged the traditional idea the soot particles are fully carbonized. New Evidence has shown that nascent soot is composed of an aromatic core and a shell dominated by aliphatics. This observation is seen to be consistent among a large range of experimental tools, from particle mass spectrometry and micro-FTIR characterization. Various microscopy analyses were also utilized to probe the structure of nascent soot. Particle imaging by transmission electron microscopy has provided detailed information on the internal structure of soot. However due to the fact that these images are inherently two-dimensional and the opportunity for damage from the electron beam, this technique is necessary but not sufficient for full characterization of soot properties. Atomic force microscopy (AFM) is being used increasingly because this instrument is less invasive to the sample and is able to obtain a three-dimensional image. AFM observations show half-dome structures when soot is deposited via thermophoretic sampling onto a mica substrate. Although this evidence is consistent with core-shell model of nascent soot, further investigation has shown that even fully spherical particles would appear as half-domes due to AFM tip effect. In order to de-convolve the tip effect from the true image, a careful characterization of tip/sample interactions is conducted in this work. We use hard spheres, e.g., titania nanoparticles, to quantify the tip effect. After correcting this effect, it will be shown that the actual degree to which particles spread on the substrate is smaller than previously thought, but nascent soot does spread notably upon impact. Phase mode imaging will also be introduced in this work. This is a technique using AFM that is able to show differences in physical properties in a given sample. Further evidence of the two-phase core/shell structure of the soot particle will be shown using this technique.
机译：最近的实验挑战了传统的想法烟灰颗粒是完全碳化的。新的证据表明，新鲜的烟灰由芳香核心和由aliphatics主导的壳体组成。该观察结果在粒子质谱和微FTIR表征中，该观察结果在大量的实验工具中是一致的。还用于探测新生烟灰的结构的各种显微镜分析。透射电子显微镜的颗粒成像提供了有关烟灰内部结构的详细信息。然而，由于这些图像本质上是二维的并且机会损坏电子束，这种技术是必要的，但不足以充分表征烟灰属性。原子力显微镜（AFM）越来越多地使用，因为该仪器对样品的侵入性较少并且能够获得三维图像。 AFM观察显示半圆顶结构当烟灰沉积到云母衬底上时。虽然这种证据与新生烟灰的核心壳模型一致，但进一步的研究表明，即使是完全球形颗粒也会显示为由于AFM尖端效应而成为半圆形。为了使尖端效应从真实图像中旋转，在这项工作中进行仔细表征尖端/样品相互作用。我们使用硬球，例如二氧化钛纳米粒子来量化尖端效果。在纠正这种效果之后，将表明，粒子在基板上铺展的实际程度小于先前认为，但是肌肉烟灰会在冲击时显着扩散。在这项工作中也将引入相位模式成像。这是一种使用AFM能够在给定样本中显示物理性质的差异的技术。使用该技术将显示烟灰颗粒的两相核心/壳结构的进一步证据。

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