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High-Quality Graphene Ribbons Prepared from Graphene Oxide Hydrogels and Their Application for Strain Sensors Qiang Liu, Miao Zhang, Liang Huang, Yingru Li, Ji Chen, Chun Li, and Gaoquan Shi ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.5b05609 • Publication Date (Web): 20 Oct 2015 Downloaded from http://pubs.acs.org on October 21, 2015
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High-Quality Graphene Ribbons Prepared from Graphene Oxide Hydrogels and Their Application for Strain Sensors
Qiang Liu†, Miao Zhang†, Liang Huang, Yingru Li, Ji Chen, Chun Li and Gaoquan Shi* Country Collaborative Innovation Center for Nanomaterial Science and Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, People’s Republic of China †
These authors contributed equally to this work.
*
Corresponding author, E-mail:
[email protected] KEYWORDS: reduced graphene oxide, ribbon, dry spinning, hydrogel, strain sensor
ABSTRACT: Reduced graphene oxide (rGO) ribbons with arbitrary lengths were prepared by dry spinning of the hydrogels of graphene oxide (GO) formed via thermal annealing GO dispersions, and followed by chemical reduction. These rGO ribbons are flexible, having ultrahigh tensile strengths of 582 ± 17 MPa, ultrahigh fracture energies of 18.29 ± 2.47 MJ m−3, high conductivities of 662 ± 41 S cm−1 and an extremely large breakdown current density of about 11,500 A cm−2. Strain sensors based on the meshes of these ribbons showed sensitive recoverable responses to different tensile strains with excellent cycling stability, promising for the applications in wearable devices.
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Multifunctional materials with light weights, high electrical and mechanical properties are highly expected to satisfy the practical requirements for their applications in portable electronics,1 tissue engineering,2 and space materials,3 etc. Among them, synthetic fibers or ribbons with integrated excellent properties beyond mechanical strengths have attracted special attention.4 Inspired by carbon fibers and carbon nanotube yarns, graphene fibers have also been extensively studied.5, 6 However, unlike one-dimensional carbon nanotubes, graphene sheets possess atom-thick two-dimensional nanostructures with ultra-large aspect ratios;7 thus it is difficult to assemble individual graphene sheets into ordered macroscopic fibers or ribbons without sacrificing their excellent mechanical and electrical properties. Much effort has been devoted to the self-assembly of reduced GO (rGO) sheets into macroscopic architectures via solution processes8, 9 and several breakthroughs have been achieved. Typically, rGO fibers can be fabricated by wet spinning of GO dispersions in various coagulation baths followed by washing and chemical reduction10, 11 or hydrothermal reduction of GO dispersions sealed in glass microtubes.12 Nevertheless, the mechanical and electrical properties of pristine rGO fibers are still unsatisfactory (tensile strength < 400 MPa; conductivity < 320 S cm−1).13, 14 This is mainly due to that these fibers have low stacking densities as well as irregular-shaped cross-sections, resulting in unwanted stress concentrations under loading and large contact resistances between rGO sheets.14 Moreover, hydrothermal approach is energy consuming and cannot be scaled up to industrial levels. In the cases of wet spinning, mechanical or electrical properties of rGO fibers can be improved by using giant GO sheets as precursors,15, 16 optimizing the coagulation conditions,10, 11, 17 or introducing ionic15/covalent18, 19
cross linkers or conductive fillers.20 Unfortunately, none of the strategies can improve the mechanical
and electrical properties of rGO fibers simultaneously. For example, covalent or ionic crosslinking can 2 ACS Paragon Plus Environment
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enhance the mechanical properties, however, the introduction of foreign components leads to hinder the electron transfer between graphene sheets, thus reducing the electrical conductivity of rGO fibers.13 Silver (Ag) nanowires have been used to increase the electrical conductivity of rGO composite fibers up to 930 S cm−1 with a high current capacity of 7.1 × 103 A cm−2. However, the mechanical strength of Ag nanowire filled rGO fibers decreased dramatically to 360 MPa from 500 MPa for calcium ion (Ca2+) cross-linked rGO fibers caused by the weak interaction between the fillers and graphene matrix.20 Therefore, it is still a great challenge to fabricate ultrastrong, ultratough, and highly conductive pristine graphene fibers.
Ribbons are fibers with sheet-like cross-sections. However, pristine rGO ribbons have rarely been studied. One special case was the fabrication of GO and rGO wide ribbons (or films) with moderate mechanical properties (Tensile strength
