title: Study on the surface energy of graphene by contact angle measurements.
abstract: Because of the atomic thinness of graphene, its integration into a device will always involve its interaction with at least one supporting substrate, making the surface energy of graphene critical to its real-life applications. In the current paper, the contact angle of graphene synthesized by chemical vapor deposition (CVD) was monitored temporally after synthesis using water, diiodomethane, ethylene glycol, and glycerol. The surface energy was then calculated based on the contact angle data by the Fowkes, Owens-Wendt (extended Fowkes), and Neumann models. The surface energy of fresh CVD graphene grown on a copper substrate (G/Cu) immediately after synthesis was determined to be 62.2 ± 3.1 mJ/m(2) (Fowkes), 53.0 ± 4.3 mJ/m(2) (Owens-Wendt) and 63.8 ± 2.0 mJ/m(2) (Neumann), which decreased to 45.6 ± 3.9, 37.5 ± 2.3, and 57.4 ± 2.1 mJ/m(2), respectively, after 24 h of air exposure. The ellipsometry characterization indicates that the surface energy of G/Cu is affected by airborne hydrocarbon contamination. G/Cu exhibits the highest surface energy immediately after synthesis, and the surface energy decreases after airborne contamination occurs. The root cause of intrinsically mild polarity of G/Cu surface is discussed.
authors.affiliation: Department of Chemical & Petroleum Engineering, Swanson School of Engineering, ‡Department of Chemistry, §Department of Physics and Astronomy, and ∥Department of Mechanical Engineering & Materials Science, Swanson School of Engineering, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kozbial
authors.forename: Zhiting
authors.initials: Z
authors.lastname: Li
authors.forename: Caitlyn
authors.initials: C
authors.lastname: Conaway
authors.forename: Rebecca
authors.initials: R
authors.lastname: McGinley
authors.forename: Shonali
authors.initials: S
authors.lastname: Dhingra
authors.forename: Vahid
authors.initials: V
authors.lastname: Vahdat
authors.forename: Feng
authors.initials: F
authors.lastname: Zhou
authors.forename: Brian
authors.initials: B
authors.lastname: D'Urso
authors.forename: Haitao
authors.initials: H
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Li