title: Direct exfoliation and dispersion of two-dimensional materials in pure water via temperature control.
abstract: The high-volume synthesis of two-dimensional (2D) materials in the form of platelets is desirable for various applications. While water is considered an ideal dispersion medium, due to its abundance and low cost, the hydrophobicity of platelet surfaces has prohibited its widespread use. Here we exfoliate 2D materials directly in pure water without using any chemicals or surfactants. In order to exfoliate and disperse the materials in water, we elevate the temperature of the sonication bath, and introduce energy via the dissipation of sonic waves. Storage stability greater than one month is achieved through the maintenance of high temperatures, and through atomic and molecular level simulations, we further discover that good solubility in water is maintained due to the presence of platelet surface charges as a result of edge functionalization or intrinsic polarity. Finally, we demonstrate inkjet printing on hard and flexible substrates as a potential application of water-dispersed 2D materials.
authors.affiliation: Mechanical Test &Analysis Section, Korea Electric Power Corporation Nuclear Fuel, Daedeok-daero 989 beon-gil, Youseong-gu, Daejeon 305-353, Korea.
authors.forename: Jinseon
authors.initials: J
authors.lastname: Kim
authors.affiliation: School of Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Korea.
authors.forename: Sanghyuk
authors.initials: S
authors.lastname: Kwon
authors.affiliation: Department of Mechanical Engineering, The Ohio State University, 281 W. Lane Ave. Columbus, Ohio 43210, USA.
authors.forename: Dae-Hyun
authors.initials: DH
authors.lastname: Cho
authors.affiliation: SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Korea.
authors.forename: Byunggil
authors.initials: B
authors.lastname: Kang
authors.affiliation: SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Korea.
authors.forename: Hyukjoon
authors.initials: H
authors.lastname: Kwon
authors.affiliation: SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Korea.
authors.forename: Youngchan
authors.initials: Y
authors.lastname: Kim
authors.affiliation: School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea.
authors.forename: Sung O
authors.initials: SO
authors.lastname: Park
authors.affiliation: School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea.
authors.forename: Gwan Yeong
authors.initials: GY
authors.lastname: Jung
authors.affiliation: School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea.
authors.forename: Eunhye
authors.initials: E
authors.lastname: Shin
authors.affiliation: Department of Physics, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746,Korea.
authors.forename: Wan-Gu
authors.initials: WG
authors.lastname: Kim
authors.affiliation: School of Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Korea.
authors.forename: Hyungdong
authors.initials: H
authors.lastname: Lee
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea.
authors.forename: Gyeong Hee
authors.initials: GH
authors.lastname: Ryu
authors.affiliation: New Material Team, Future Device R&D Department, LG Electronics Advanced Research Institute, 38 Baumoe-ro, Seocho-gu, Seoul 137-724, Korea.
authors.forename: Minseok
authors.initials: M
authors.lastname: Choi
authors.affiliation: New Material Team, Future Device R&D Department, LG Electronics Advanced Research Institute, 38 Baumoe-ro, Seocho-gu, Seoul 137-724, Korea.
authors.forename: Tae Hyeong
authors.initials: TH
authors.lastname: Kim
authors.affiliation: Department of Chemistry and Chemical Engineering, Inha University, Incheon 402-751, Korea.
authors.forename: Junghoon
authors.initials: J
authors.lastname: Oh
authors.affiliation: Department of Chemistry and Chemical Engineering, Inha University, Incheon 402-751, Korea.
authors.forename: Sungjin
authors.initials: S
authors.lastname: Park
authors.affiliation: School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea.
authors.forename: Sang Kyu
authors.identifier: http://orcid.org/0000-0002-0332-1534
authors.initials: SK
authors.lastname: Kwak
authors.affiliation: Department of Physics, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746,Korea.
authors.forename: Suk Wang
authors.initials: SW
authors.lastname: Yoon
authors.affiliation: School of Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Korea.
authors.forename: Doyoung
authors.initials: D
authors.lastname: Byun
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea.
authors.forename: Zonghoon
authors.identifier: http://orcid.org/0000-0003-3246-4072
authors.initials: Z
authors.lastname: Lee
authors.affiliation: School of Mechanical Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Korea.|SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Korea.
authors.forename: Changgu
authors.initials: C
authors.lastname: Lee