title: Formation of Two-Dimensional Micelles on Graphene: Multi-Scale Theoretical and Experimental Study.
abstract: Graphene and related two-dimensional (2D) materials possess outstanding electronic and mechanical properties, chemical stability, and high surface area. However, to realize graphene's potential for a range of applications in materials science and nanotechnology there is a need to understand and control the interaction of graphene with tailored high-performance surfactants designed to facilitate the preparation, manipulation, and functionalization of new graphene systems. Here we report a combined experimental and theoretical study of the surface structure and dynamics on graphene of pyrene-oligoethylene glycol (OEG) -based surfactants, which have previously been shown to disperse carbon nanotubes in water. Molecular self-assembly of the surfactants on graphitic surfaces is experimentally monitored and optimized using a graphene coated quartz crystal microbalance in ambient and vacuum environments. Real-space nanoscale resolution nanomechanical and topographical mapping of submonolayer surfactant coverage, using ultrasonic and atomic force microscopies both in ambient and ultrahigh vacuum, reveals complex, multilength-scale self-assembled structures. Molecular dynamics simulations show that at the nanoscale these structures, on atomically flat graphitic surfaces, are dependent upon the surfactant OEG chain length and are predicted to display a previously unseen class of 2D self-arranged "starfish" micelles (2DSMs). While three-dimensional micelles are well-known for their widespread uses ranging from microreactors to drug-delivery vehicles, these 2DSMs possess the highly desirable and tunable characteristics of high surface affinity coupled with unimpeded mobility, opening up strategies for processing and functionalizing 2D materials.
authors.affiliation: Department of Physics, Lancaster University , Lancaster LA1 4YB, U.K.|Materials Science Institute, Lancaster University , Lancaster LA1 4YW, U.K.
authors.forename: Benjamin J
authors.identifier: 0000-0001-8676-6469
authors.initials: BJ
authors.lastname: Robinson
authors.affiliation: Department of Physics, Lancaster University , Lancaster LA1 4YB, U.K.
authors.forename: Steven W D
authors.initials: SW
authors.lastname: Bailey
authors.affiliation: Department of Chemistry, Durham University , Durham DH1 3LE, U.K.
authors.forename: Luke J
authors.initials: LJ
authors.lastname: O'Driscoll
authors.affiliation: Department of Physics, Lancaster University , Lancaster LA1 4YB, U.K.|Department of Physics of Complex Systems, Eötvös University , Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary.
authors.forename: David
authors.initials: D
authors.lastname: Visontai
authors.affiliation: Department of Chemistry, Durham University , Durham DH1 3LE, U.K.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Welsh
authors.affiliation: Department of Physics, Lancaster University , Lancaster LA1 4YB, U.K.
authors.forename: Albertus B
authors.initials: AB
authors.lastname: Mostert
authors.affiliation: Department of Physics, Lancaster University , Lancaster LA1 4YB, U.K.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Mazzocco
authors.affiliation: CEA , LETI 17 rue des Martyrs, 38054 Grenoble, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Rabot
authors.affiliation: Department of Physics, Lancaster University , Lancaster LA1 4YB, U.K.|Materials Science Institute, Lancaster University , Lancaster LA1 4YW, U.K.|School of Physics and Astronomy, University of Nottingham , Nottingham NG7 2RD, U.K.
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Jarvis
authors.affiliation: Department of Physics, Lancaster University , Lancaster LA1 4YB, U.K.
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Kolosov
authors.affiliation: Department of Chemistry, Durham University , Durham DH1 3LE, U.K.
authors.forename: Martin R
authors.identifier: 0000-0003-2097-7823
authors.initials: MR
authors.lastname: Bryce
authors.affiliation: Department of Physics, Lancaster University , Lancaster LA1 4YB, U.K.
authors.forename: Colin
authors.identifier: 0000-0003-2332-9610
authors.initials: C
authors.lastname: Lambert
keywords: 2D micelles; graphene; molecular dynamics; scanning probe microscopy; surfactants