title: High yield exfoliation of two-dimensional chalcogenides using sodium naphthalenide.
abstract: Transition-metal dichalcogenides like molybdenum disulphide have attracted great interest as two-dimensional materials beyond graphene due to their unique electronic and optical properties. Solution-phase processes can be a viable method for producing printable single-layer chalcogenides. Molybdenum disulphide can be exfoliated into monolayer flakes using organolithium reduction chemistry; unfortunately, the method is hampered by low yield, submicron flake size and long lithiation time. Here we report a high-yield exfoliation process using lithium, potassium and sodium naphthalenide where an intermediate ternary Li(x)MX(n) crystalline phase (X=selenium, sulphur, and so on) is produced. Using a two-step expansion and intercalation method, we produce high-quality single-layer molybdenum disulphide sheets with unprecedentedly large flake size, that is up to 400 μm(2). Single-layer dichalcogenide inks prepared by this method may be directly inkjet-printed on a wide range of substrates.
authors.affiliation: Department of Chemistry and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Jian
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Department of Chemistry and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Han
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Dong
authors.affiliation: Department of Chemistry and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Yanpeng
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Chemistry and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Chang Tai
authors.initials: CT
authors.lastname: Nai
authors.affiliation: Interdisciplinary School of Green Energy and Low Dimensional Carbon Materials Center, UNIST Central Research Facilities (UCRF), Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-805, Korea.
authors.forename: Hyeon Suk
authors.initials: HS
authors.lastname: Shin
authors.affiliation: Interdisciplinary School of Green Energy and Low Dimensional Carbon Materials Center, UNIST Central Research Facilities (UCRF), Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-805, Korea.
authors.forename: Hu Young
authors.initials: HY
authors.lastname: Jeong
authors.affiliation: Department of Chemistry and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.affiliation: Department of Chemistry and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Kian Ping
authors.initials: KP
authors.lastname: Loh