Molecular orientation of asphaltenes and PAH model compounds in langmuir-blodgett films using sum frequency generation spectroscopy

Research output: Contribution to journalArticle


  • A. Ballard Andrews
  • Arthur McClelland
  • Oona Korkeila
  • Alexander Demidov
  • Amber Krummel
  • Oliver C. Mullins
  • Zhan Chen

Research units

  • Schlumberger
  • Northeastern University
  • Aalto University
  • Harvard University
  • Colorado State University
  • University of Michigan, Ann Arbor


Asphaltenes are an important class of compounds in crude oil whose surface activity is important for establishing reservoir rock wettability which impacts reservoir drainage.While many phenomenological interfacial studies with crude oils and asphaltenes have been reported, there is very little known about themolecular level interactions between asphaltenes and mineral surfaces. In this study, we analyze Langmuir-Blodgett films of asphaltenes and related model compounds with sum frequency generation (SFG) vibrational spectroscopy. In SFG, the polarization of the input (vis, IR) and output (SFG) beams can be varied, which allows the orientation of different functional groups at the interface to be determined. SFG clearly indicates that asphaltene polycyclic aromatic hydrocarbons (PAHs) are highly oriented in the plane of the interface and that the peripheral alkanes are transverse to the interface. In contrast, model compounds with oxygen functionality have PAHs oriented transverse to the interface. Computational quantumchemistry is used to support corresponding band assignments, enabling robust determination of functional group orientations.


Original languageEnglish
Pages (from-to)6049-6058
Number of pages10
Issue number10
Publication statusPublished - 1 Jun 2011
MoE publication typeA1 Journal article-refereed

ID: 12976919