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An unexpected restructuring of combustion soot aggregates by subnanometer coatings of polycyclic aromatic hydrocarbons
Author(s) -
Chen Chao,
Fan Xiaolong,
Shaltout Tasneem,
Qiu Chong,
Ma Yan,
Goldman Andrew,
Khalizov Alexei F.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl070877
Subject(s) - soot , triphenylene , phenanthrene , pyrene , fluoranthene , anthracene , combustion , perylene , methylcyclohexane , chemical engineering , polycyclic aromatic hydrocarbon , materials science , hydrocarbon , aerosol , photochemistry , chemistry , organic chemistry , toluene , molecule , engineering
We investigated the effect of thin polycyclic aromatic hydrocarbon (PAH) coatings on the structure of soot aggregates. Soot aerosol from an inverted diffusion burner was size classified, thermally denuded, coated with six different PAHs, and then characterized using scanning electron microscopy, light scattering, and mass‐mobility measurements. Contrary to our expectation, significant restructuring was observed in the presence of subnanometer layers of pyrene, fluoranthene, and phenanthrene. These PAHs remained in subcooled liquid state in thin films, whereby the liquid layer acted as a lubricant, reducing the force required to initiate the restructuring. Thin layers of PAH of higher melting temperatures (perylene, anthracene, and triphenylene) presumably remained solid because these chemicals induced lesser structural changes. Our results suggest that some of the intrinsic PAH generated during incomplete combustion may induce significant restructuring of soot aggregates, even when present in small quantities, altering the properties and atmospheric impacts of combustion aerosols.