title: Production of Highly Monolayer Enriched Dispersions of Liquid-Exfoliated Nanosheets by Liquid Cascade Centrifugation.
abstract: While liquid exfoliation is a powerful technique to produce defect-free nanosheets in large quantities, its usefulness is limited by broad nanosheet thickness distributions and low monolayer contents. Here we demonstrate liquid processing techniques, based on iterative centrifugation cascades, which can be designed to achieve either highly efficient nanosheet size-selection and/or monolayer enrichment. The resultant size-selected dispersions were used to establish quantitative metrics to determine monolayer volume fraction, as well as mean nanosheet size and thickness, from standard spectroscopic measurements. Such metrics allowed us to design and optimize centrifugation cascades to enrich liquid exfoliated WS2 dispersions up to monolayer contents of 75%. Monolayer-rich dispersions show relatively bright photoluminescence with narrow line widths (<35 meV) indicating the high quality of the nanosheets. The enriched dispersions display extinction spectra with distinct features, which also allow the direct estimation of monolayer contents.
authors.affiliation: CRANN & AMBER Research Centers, Trinity College Dublin , Dublin 2, Ireland.|School of Physics, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Claudia
authors.initials: C
authors.lastname: Backes
authors.affiliation: CRANN & AMBER Research Centers, Trinity College Dublin , Dublin 2, Ireland.|School of Physics, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Beata M
authors.initials: BM
authors.lastname: Szydłowska
authors.affiliation: CRANN & AMBER Research Centers, Trinity College Dublin , Dublin 2, Ireland.|School of Physics, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Andrew
authors.initials: A
authors.lastname: Harvey
authors.affiliation: Institute for Molecules and Materials, Radboud University of Nijmegen , Heijendaalseweg 135, 6525AJ Nijmegen, The Netherlands.
authors.forename: Shengjun
authors.initials: S
authors.lastname: Yuan
authors.affiliation: Department for Complex Matter, Jozef Stefan Institute , Jamova 39, 1000 Ljubljana, Slovenia.|Jozef Stefan International Postgraduate School , Jamova 39, 1000 Ljubljana, Slovenia.
authors.forename: Victor
authors.initials: V
authors.lastname: Vega-Mayoral
authors.affiliation: CRANN & AMBER Research Centers, Trinity College Dublin , Dublin 2, Ireland.|School of Physics, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Ben R
authors.initials: BR
authors.lastname: Davies
authors.affiliation: Department of Applied Physics, Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, NL-9747AG Groningen, The Netherlands.
authors.forename: Pei-Liang
authors.initials: PL
authors.lastname: Zhao
authors.affiliation: CRANN & AMBER Research Centers, Trinity College Dublin , Dublin 2, Ireland.|School of Physics, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Damien
authors.initials: D
authors.lastname: Hanlon
authors.affiliation: School of Mathematics and Physics and School of Chemistry and Chemical Engineering, Queen's University Belfast , Belfast, BT95AL, United Kingdom.
authors.forename: Elton J G
authors.initials: EJ
authors.lastname: Santos
authors.affiliation: Institute for Molecules and Materials, Radboud University of Nijmegen , Heijendaalseweg 135, 6525AJ Nijmegen, The Netherlands.
authors.forename: Mikhail I
authors.initials: MI
authors.lastname: Katsnelson
authors.affiliation: CRANN & AMBER Research Centers, Trinity College Dublin , Dublin 2, Ireland.|School of Physics, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Werner J
authors.initials: WJ
authors.lastname: Blau
authors.affiliation: Department for Complex Matter, Jozef Stefan Institute , Jamova 39, 1000 Ljubljana, Slovenia.|Jozef Stefan International Postgraduate School , Jamova 39, 1000 Ljubljana, Slovenia.
authors.forename: Christoph
authors.initials: C
authors.lastname: Gadermaier
authors.affiliation: CRANN & AMBER Research Centers, Trinity College Dublin , Dublin 2, Ireland.|School of Physics, Trinity College Dublin , Dublin 2, Ireland.
authors.forename: Jonathan N
authors.initials: JN
authors.lastname: Coleman
keywords: exfoliation; luminescence; monolayer; size-selection; tungsten disulfide