title: Graphene Oxide Papers Simultaneously Doped with Mg(2+) and Cl(-) for Exceptional Mechanical, Electrical, and Dielectric Properties.
abstract: This paper reports simultaneous modification of graphene oxide (GO) papers by functionalization with MgCl2. The Mg(2+) ions enhance both the interlayer cross-links and lateral bridging between the edges of adjacent GO sheets by forming Mg-O bonds. The improved load transfer between the GO sheets gives rise to a maximum of 200 and 400% increases in Young's modulus and tensile strength of GO papers. The intercalation of chlorine between the GO layers alters the properties of GO papers in two ways by forming ionic Cl(-) and covalent C-Cl bonds. The p-doping effect arising from Cl contributes to large enhancements in electrical conductivities of GO papers, with a remarkable 2500-fold surge in the through-thickness direction. The layered structure and the anisotropic electrical conductivities of reduced GO papers naturally create numerous nanocapacitors that lead to charge accumulation based on the Maxwell-Wagner (MW) polarization. The combined effect of much promoted dipolar polarizations due to Mg-O, C-Cl, and Cl(-) species results in an exceptionally high dielectric constant greater than 60 000 and a dielectric loss of 3 at 1 kHz by doping with 2 mM MgCl2. The excellent mechanical and electrical properties along with unique dielectric performance shown by the modified GO and rGO papers open new avenues for niche applications, such as electromagnetic interference shielding materials.
authors.affiliation: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Xiuyi
authors.initials: X
authors.lastname: Lin
authors.affiliation: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Xi
authors.initials: X
authors.lastname: Shen
authors.affiliation: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Xinying
authors.initials: X
authors.lastname: Sun
authors.affiliation: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Xu
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Jang-Kyo
authors.initials: JK
authors.lastname: Kim
keywords: Mg and Cl doping; dielectric constant; electrical conductivity; graphene oxide paper; mechanical properties