title: Gas Protection of Two-Dimensional Nanomaterials from High-Energy Impacts.
abstract: Two-dimensional (2D) materials can be produced using ball milling with the help of liquid surfactants or solid exfoliation agents, as ball milling of bulk precursor materials usually produces nanosized particles because of high-energy impacts. Post-milling treatment is thus needed to purify the nanosheets. We show here that nanosheets of graphene, BN, and MoS2can be produced by ball milling of their bulk crystals in the presence of ammonia or a hydrocarbon ethylene gas and the obtained nanosheets remain flat and maintain their single-crystalline structure with low defects density even after a long period of time; post-milling treatment is not needed. This study does not just demonstrate production of nanosheets using ball milling, but reveals surprising indestructible behaviour of 2D nanomaterials in ammonia or hydrocarbon gas under the high-energy impacts; in other milling atmospheres such as air, nitrogen or argon the same milling treatment produces nanosized particles. A systematic study reveals chemisorption of ammonia and hydrocarbon gases and chemical reactions occurring at defect sites, which heal the defects by saturating the dangling bonds. Density functional theory was used to understand the mechanism of mechanochemical reactions. Ball milling in ammonia or hydrocarbon is promising for mass-production of pure nanosheets.
authors.affiliation: Institute for Frontier Materials, Deakin University, Waurn Ponds, Victoria 3216, Australia.
authors.forename: Tan
authors.initials: T
authors.lastname: Xing
authors.affiliation: Institute for Frontier Materials, Deakin University, Waurn Ponds, Victoria 3216, Australia.
authors.forename: Srikanth
authors.initials: S
authors.lastname: Mateti
authors.affiliation: Institute for Frontier Materials, Deakin University, Waurn Ponds, Victoria 3216, Australia.
authors.forename: Lu Hua
authors.initials: LH
authors.lastname: Li
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, QLD 4001, Australia.
authors.forename: Fengxian
authors.initials: F
authors.lastname: Ma
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, QLD 4001, Australia.
authors.forename: Aijun
authors.initials: A
authors.lastname: Du
authors.affiliation: A. J. Drexel Nanomaterials Institute, and Materials Science and Engineering Department, Drexel University 3141 Chestnut Street, Philadelphia, PA 19104, USA.
authors.forename: Yury
authors.initials: Y
authors.lastname: Gogotsi
authors.affiliation: Institute for Frontier Materials, Deakin University, Waurn Ponds, Victoria 3216, Australia.
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen