On the early stages of soot formation: Molecular structure elucidation by high-resolution atomic force microscopy

Commodo, Mario; Kaiser, Katharina; Falco, Gianluigi De; Schulz, Fabian; D’Anna, Andrea; Groß, Leo

doi:10.1016/j.combustflame.2019.03.042

Cited by 165 publications

(158 citation statements)

References 72 publications

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“…There are some notable differences in both flame system and sampling protocol between the present study and the Commodo et al. reference . The distributions revealed in our LDI‐MS experiments lie much closer to the highly‐condensed limit than the cata‐condensed line.…”

Section: Resultssupporting

confidence: 43%

“…Observed species that are below this peri‐condensed curve may represent structures with 5‐membered rings or ethynyl side chains added to peri‐condensed PAHs. In their high resolution AFM study of soot, Commodo et al . report both PAH with five‐membered rings as well many PAH with aliphatic branches, predominantly methyl groups, although they note the presence of sp 3 methylene groups in some of the penta rings.…”

Section: Resultsmentioning

confidence: 99%

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The Molecular Composition of Soot

et al. 2020

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Soot (sometimes referred to as black carbon) is produced when hydrocarbon fuels are burned. Our hypothesis is that polynuclear aromatic hydrocarbon (PAH) molecules are the dominant component of soot, with individual PAH molecules forming ordered stacks that agglomerate into primary particles (PP). Here we show that the PAH composition of soot can be exactly determined and spatially resolved by low‐fluence laser desorption ionization, coupled with high‐resolution mass spectrometry imaging. This analysis revealed that PAHs of 239–838 Da, containing few oxygenated species, comprise the soot observed in an ethylene diffusion flame. As informed by chemical graph theory (CGT), the vast majority of species observed in the sampled particulate matter may be described as benzenoids, consisting of only fused 6‐membered rings. Within that limit, there is clear evidence for the presence of radical PAH in the particulate samples. Further, for benzenoid structures the observed empirical formulae limit the observed isomers to those which are nearly circular with high aromatic conjugation lengths for a given aromatic ring count. These results stand in contrast to recent reports that suggest higher aliphatic composition of primary particles.

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Section: Resultssupporting

confidence: 43%

Section: Resultsmentioning

confidence: 99%

The Molecular Composition of Soot

et al. 2020

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“…Three primary pathways have been postulated for the soot nucleation and growth processes (Wang, 2011). The first one involves the growth of "two-dimensional" PAH into curved, fullerene-like structures (Homann, 1998), the second one involves the physical dimerisation of planar PAH and their coalescence into clusters of stacked PAH (Frenklach and Wang, 1991;Herdman and Miller, 2008;Schuetz and Frenklach, 2002) and the third one is a chemical pathway in which PAH react to form crosslinked three-dimensional structures (D'Anna et al, 2001;Violi et al, 2002Violi et al, , 2004Ciajolo et al, 2000;Commodo et al, 2015Commodo et al, , 2019. All the above mechanisms are believed to take part in the soot formation process, but their relative importance or feasibility at different conditions and temperatures is still unclear.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties of Soot Particles: The Impact of Crosslinked Polycyclic Aromatic Hydrocarbons

Pascazio

Martin

Botero

et al. 2019

Combustion Science and Technology

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“…A large variety of mechanisms are expected to contribute to the formation of PAHs in the combustion of fossil fuels (Richter & Howard 2000;Moriarty & Frenklach 2000;Parker et al 2014;Kaiser et al 2015;Yang et al 2017), some of which are applied to astrochemistry to explain the formation of interstellar aromatic molecules in the outflows of carbon-rich stars (e.g., Frenklach & Feigelson 1989;Cherchneff et al 1992). The sequences of chemical reactions involved not only produce clean hexagon containing aromatic molecules, but they have also been shown in the laboratory to result in pentagon containing species (Bouwman et al 2015;Johansson et al 2018;Commodo et al 2019;Schulz et al 2019;McCabe et al 2020). Pentagon inclusion is also invoked to explain the formation of fullerenes through erosion of large PAHs as this provides a way to bowl the planar PAH plane (Berné & Tielens 2012).…”

Section: Introductionmentioning

confidence: 99%

Gas-phase infrared spectroscopy of the rubicene cation (C₂₆H₁₄^•+)

Bouwman

Boersma

Bulak

et al. 2020

A&A

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Infrared bands at 3.3, 6.2, 7.6, 7.8, 8.6, and 11.2 μm have been attributed to polycyclic aromatic hydrocarbons (PAHs) and are observed toward a large number of galactic and extragalactic sources. Some interstellar PAHs possibly contain five-membered rings in their honeycomb carbon structure. The inclusion of such pentagon defects can occur during PAH formation, or as large PAHs are eroded by photo-dissociation to ultimately yield fullerenes. Pentagon formation is a process that is associated with the bowling of the PAH plane, that is, the ability to identify PAH pentagons in space holds the potential to directly link PAHs to cage and fullerene structures. It has been hypothesized that infrared (IR) activity around 1100 cm−1 may be a spectral marker for interstellar pentagons. We present an experimentally measured gas-phase IR absorption spectrum of the pentagon-containing rubicene cation (C26H14•+) to investigate if this band is present. The NASA Ames PAH IR Spectroscopic Database is scrutinized to see whether other rubicene-like species show IR activity in this wavelength range. We find that a specific molecular characteristic is responsible for this IR band. Namely, the vibrational motion attributed to this IR activity involves pentagon-containing harbors. An attempt to find this specific mode in Spitzer observations is undertaken and tentative detections around 9.3 μm are made toward the reflection nebula NGC 7023 and the H II-region IRAS 12063-6259. Simulated emission spectra are used to derive upper limits for the contributions of rubicene-like pentagonal PAH species to the IR band at 6.2 μm toward these sources.

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On the early stages of soot formation: Molecular structure elucidation by high-resolution atomic force microscopy

Cited by 165 publications

References 72 publications

The Molecular Composition of Soot

The Molecular Composition of Soot

Mechanical Properties of Soot Particles: The Impact of Crosslinked Polycyclic Aromatic Hydrocarbons

Gas-phase infrared spectroscopy of the rubicene cation (C₂₆H₁₄^•+)

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On the early stages of soot formation: Molecular structure elucidation by high-resolution atomic force microscopy

Cited by 165 publications

References 72 publications

The Molecular Composition of Soot

The Molecular Composition of Soot

Mechanical Properties of Soot Particles: The Impact of Crosslinked Polycyclic Aromatic Hydrocarbons

Gas-phase infrared spectroscopy of the rubicene cation (C26H14•+)

Contact Info

Product

Resources

About

Gas-phase infrared spectroscopy of the rubicene cation (C₂₆H₁₄^•+)