Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation.
Two-dimensional transition metal dichalcogenides have emerged as leading successors to graphene due to their diverse properties, which depend sensitively on sample thickness. Although solution-based exfoliation methods hold promise for scalable production of these materials, existing techniques introduce irreversible structural defects and/or lack sufficient control over the sample thickness. In contrast, previous work on carbon nanotubes and graphene has shown that isopycnic density gradient ultracentrifugation can produce structurally and electronically monodisperse nanomaterial populations. However, this approach cannot be directly applied to transition metal dichalcogenides due to their high intrinsic buoyant densities when encapsulated with ionic small molecule surfactants. Here, we overcome this limitation and thus demonstrate thickness sorting of pristine molybdenum disulfide (MoS2) by employing a block copolymer dispersant composed of a central hydrophobic unit flanked by hydrophilic chains that effectively reduces the overall buoyant density in aqueous solution. The resulting solution-processed monolayer MoS2 samples exhibit strong photoluminescence without further chemical treatment.
Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.
Joohoon
J
Kang
Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.
Jung-Woo T
JW
Seo
Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas 78249, USA.
Diego
D
Alducin
Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas 78249, USA.
Arturo
A
Ponce
Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas 78249, USA.
Miguel Jose
MJ
Yacaman
1] Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA [2] Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA [3] Department of Medicine, Northwestern University, Evanston, Illinois 60208, USA.
Mark C
MC
Hersam
D002499:Centrifugation, Density Gradient / Q000379:methods*; D018011:Chalcogens / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry* / Q000302:isolation & purification; D008982:Molybdenum / Q000737:chemistry* / Q000302:isolation & purification; D049329:Nanostructures / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D012996:Solutions / Q000737:chemistry
D018011:Chalcogens; D004220:Disulfides; D011108:Polymers; D012996:Solutions; D008982:Molybdenum; C082964:molybdenum disulfide