title: Edge and confinement effects allow in situ measurement of size and thickness of liquid-exfoliated nanosheets.
abstract: Two-dimensional nanomaterials such as MoS2 are of great interest both because of their novel physical properties and their applications potential. Liquid exfoliation, an important production method, is limited by our inability to quickly and easily measure nanosheet size, thickness or concentration. Here we demonstrate a method to simultaneously determine mean values of these properties from an optical extinction spectrum measured on a liquid dispersion of MoS2 nanosheets. The concentration measurement is based on the size-independence of the low-wavelength extinction coefficient, while the size and thickness measurements rely on the effect of edges and quantum confinement on the optical spectra. The resultant controllability of concentration, size and thickness facilitates the preparation of dispersions with pre-determined properties such as high monolayer-content, leading to first measurement of A-exciton MoS2 luminescence in liquid suspensions. These techniques are general and can be applied to a range of two-dimensional materials including WS2, MoSe2 and WSe2.
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Claudia
authors.initials: C
authors.lastname: Backes
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Ronan J
authors.initials: RJ
authors.lastname: Smith
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Niall
authors.initials: N
authors.lastname: McEvoy
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Nina C
authors.initials: NC
authors.lastname: Berner
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: David
authors.initials: D
authors.lastname: McCloskey
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland [3] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Hannah C
authors.initials: HC
authors.lastname: Nerl
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Arlene
authors.initials: A
authors.lastname: O'Neill
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: King
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Tom
authors.initials: T
authors.lastname: Higgins
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Damien
authors.initials: D
authors.lastname: Hanlon
authors.affiliation: Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Scheuschner
authors.affiliation: Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany.
authors.forename: Janina
authors.initials: J
authors.lastname: Maultzsch
authors.affiliation: Ernst Ruska Center for Microscopy and Spectroscopy with Electrons, Research Center Jülich, 52425 Jülich, Germany.
authors.forename: Lothar
authors.initials: L
authors.lastname: Houben
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Georg S
authors.initials: GS
authors.lastname: Duesberg
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: John F
authors.initials: JF
authors.lastname: Donegan
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland [3] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Valeria
authors.initials: V
authors.lastname: Nicolosi
authors.affiliation: 1] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland [2] School of Physics, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Jonathan N
authors.initials: JN
authors.lastname: Coleman