title: Controlled Gas Exfoliation of Boron Nitride into Few-Layered Nanosheets.
abstract: The controlled exfoliation of hexagonal boron nitride (h-BN) into single- or few-layered nanosheets remains a grand challenge and becomes the bottleneck to essential studies and applications of h-BN. Here, we present an efficient strategy for the scalable synthesis of few-layered h-BN nanosheets (BNNS) using a novel gas exfoliation of bulk h-BN in liquid N2 (L-N2 ). The essence of this strategy lies in the combination of a high temperature triggered expansion of bulk h-BN and the cryogenic L-N2 gasification to exfoliate the h-BN. The produced BNNS after ten cycles (BNNS-10) consisted primarily of fewer than five atomic layers with a high mass yield of 16-20 %. N2 sorption and desorption isotherms show that the BNNS-10 exhibited a much higher specific surface area of 278 m(2)  g(-1) than that of bulk BN (10 m(2)  g(-1) ). Through the investigation of the exfoliated intermediates combined with a theoretical calculation, we found that the huge temperature variation initiates the expansion and curling of the bulk h-BN. Subseqently, the L-N2 penetrates into the interlayers of h-BN along the curling edge, followed by an immediate drastic gasification of L-N2 , further peeling off h-BN. This novel gas exfoliation of high surface area BNNS not only opens up potential opportunities for wide applications, but also can be extended to produce other layered materials in high yields.
authors.affiliation: School of Chemistry and Chemical Engineering, Institute for Energy Research, Jiangsu University, Zhenjiang, 212013, China. zhuws@ujs.edu.cn.|Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA. zhuws@ujs.edu.cn.
authors.forename: Wenshuai
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
authors.affiliation: Center for nanophase materials sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.affiliation: School of Chemistry and Chemical Engineering, Institute for Energy Research, Jiangsu University, Zhenjiang, 212013, China.
authors.forename: Hongping
authors.initials: H
authors.lastname: Li
authors.affiliation: School of Chemistry and Chemical Engineering, Institute for Energy Research, Jiangsu University, Zhenjiang, 212013, China.
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Chao
authors.affiliation: Department of Chemistry, University of Tennessee, Knoxville, TN, 37996, USA.
authors.forename: Meijun
authors.initials: M
authors.lastname: Li
authors.affiliation: Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Mahurin
authors.affiliation: School of Chemistry and Chemical Engineering, Institute for Energy Research, Jiangsu University, Zhenjiang, 212013, China.
authors.forename: Huaming
authors.initials: H
authors.lastname: Li
authors.affiliation: Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA. zhuh@ornl.gov.
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA. dais@ornl.gov.|Department of Chemistry, University of Tennessee, Knoxville, TN, 37996, USA. dais@ornl.gov.
authors.forename: Sheng
authors.initials: S
authors.lastname: Dai
keywords: boron nitride; exfoliation; liquid nitrogen; nanosheets; thermal expansion