title: Inside and Outside: X-ray Absorption Spectroscopy Mapping of Chemical Domains in Graphene Oxide.
abstract: The oxidative chemistry of graphite has been investigated for over 150 years and has attracted renewed interest given the importance of exfoliated graphene oxide as a precursor to chemically derived graphene. However, the bond connectivities, steric orientations, and spatial distribution of functional groups remain to be unequivocally determined for this highly inhomogeneous nonstoichiometric material. Here, we demonstrate the application of principal component analysis to scanning transmission X-ray microscopy data for the construction of detailed real space chemical maps of graphene oxide. These chemical maps indicate very distinct functionalization motifs at the edges and interiors and, in conjunction with angle-resolved near-edge X-ray absorption fine structure spectroscopy, enable determination of the spatial location and orientations of functional groups. Chemical imaging of graphene oxide provides experimental validation of the modified Lerf-Klinowski structural model. Specifically, we note increased contributions from carboxylic acid moieties at edge sites with epoxide and hydroxyl species dominant within the interior domains.
authors.affiliation: Department of Chemistry, University at Buffalo, The State University of New York , Buffalo, New York 14260-3000, United States.
authors.forename: Luis R
authors.initials: LR
authors.lastname: De Jesus
authors.affiliation: Department of Chemistry, University at Buffalo, The State University of New York , Buffalo, New York 14260-3000, United States.
authors.forename: Robert V
authors.initials: RV
authors.lastname: Dennis
authors.affiliation: Department of Chemistry, University at Buffalo, The State University of New York , Buffalo, New York 14260-3000, United States.
authors.forename: Sean W
authors.initials: SW
authors.lastname: Depner
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Cherno
authors.initials: C
authors.lastname: Jaye
authors.affiliation: Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Fischer
authors.affiliation: Department of Chemistry, University at Buffalo, The State University of New York , Buffalo, New York 14260-3000, United States.
authors.forename: Sarbajit
authors.initials: S
authors.lastname: Banerjee
keywords: NEXAFS; STXM; X-ray absorption; graphene; graphene oxide; nanoscale imaging