The ability to bias chemical reaction pathways is a fundamental goal for chemists and material scientists to produce innovative materials. Recently, two-dimensional materials have emerged as potential platforms for exploring novel mechanically activated chemical reactions. Here we report a mechanochemical phenomenon in graphene oxide membranes, covalent epoxide-to-ether functional group transformations that deviate from epoxide ring-opening reactions, discovered through nanomechanical experiments and density functional-based tight binding calculations. These mechanochemical transformations in a two-dimensional system are directionally dependent, and confer pronounced plasticity and damage tolerance to graphene oxide monolayers. Additional experiments on chemically modified graphene oxide membranes, with ring-opened epoxide groups, verify this unique deformation mechanism. These studies establish graphene oxide as a two-dimensional building block with highly tuneable mechanical properties for the design of high-performance nanocomposites, and stimulate the discovery of new bond-selective chemical transformations in two-dimensional materials.
#1Changhong Cao(U of T: University of Toronto)H-Index: 11
#2Matthew Daly(U of T: University of Toronto)H-Index: 11
Last. Tobin Filleter(U of T: University of Toronto)H-Index: 30
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Abstract In this study, the strength of monolayer graphene oxide membranes was experimentally characterized. The monolayer GO membranes were found to have a high carbon-to-oxygen ratio (∼4:1) and an average strength of 17.3 N/m (24.7 GPa). This measured strength is orders of magnitude higher than previously reported values for graphene oxide paper and is approximately 50% of the 2D intrinsic strength of pristine graphene. In order to corroborate strength measurements, experimental values were co...
The hydration of graphene oxide (GO) membranes is the key to understand their remarkable selectivity in permeation of water molecules and humidity-dependent gas separation. We investigated the hydration of single GO layers as a function of humidity using scanning force microscopy, and we determined the single interlayer distance from the step height of a single GO layer on top of one or two GO layers. This interlayer distance grows gradually by approximately 1 A upon a relative humidity (RH) inc...
One of the main concerns in nanotechnology is the utilization of nanomaterials in macroscopic applications without losing their extreme properties. In an effort to bridge the gap between the nano- and macroscales, we propose a clever fabrication method, the inverted floating method (IFM), for preparing freestanding chemical-vapor-deposited (CVD) graphene membranes. These freestanding membranes were then successfully suspended over a gap a half-millimeter in diameter. To understand the working pr...
#1Lizhao Liu(DUT: Dalian University of Technology)H-Index: 12
#2Junfeng Zhang(DUT: Dalian University of Technology)H-Index: 17
Last. Feng Liu(UofU: University of Utah)H-Index: 134
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The mechanical properties, including the Young's modulus and intrinsic strength, of graphene oxides are investigated by first-principles computations. Structural models of both ordered and amorphous graphene oxides are considered and compared. For the ordered graphene oxides, the Young's modulus is found to vary from 380 to 470 GPa as the coverage of oxygen groups changes, respectively. The corresponding variations in the Young's modulus of the amorphous graphene oxides with comparable coverage ...
Based on the experimental observations, amorphous structural models of graphene oxides (GOs) were constructed and investigated by first-principles computations. Geometric structures, thermodynamic stabilities, and electron density of states of these amorphous GO models were examined and compared with the previously proposed ordered GO structures. The thermodynamically most favorable amorphous GO models always contain some locally ordered structures in the short range, due to a compromise of the ...
Last. Rodney S. Ruoff(University of Texas at Austin)H-Index: 165
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Reproducible dry and wet transfer techniques were developed to improve the transfer of large-area monolayer graphene grown on copper foils by chemical vapor deposition (CVD). The techniques reported here allow transfer onto three different classes of substrates: substrates covered with shallow depressions, perforated substrates, and flat substrates. A novel dry transfer technique was used to make graphene-sealed microchambers without trapping liquid inside. The dry transfer technique utilizes a ...
Last. Rodney S. Ruoff(University of Texas at Austin)H-Index: 165
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Mechanical properties of ultrathin membranes consisting of one layer, two overlapped layers, and three overlapped layers of graphene oxide platelets were investigated by atomic force microscopy (AFM) imaging in contact mode. In order to evaluate both the elastic modulus and prestress of thin membranes, the AFM measurement was combined with the finite element method (FEM) in a new approach for evaluating the mechanics of ultrathin membranes. Monolayer graphene oxide was found to have a lower effe...
Lu Wang,1,2 Y. Y. Sun,2,*,† Kyuho Lee,2 D. West,2 Z. F. Chen,3 J. J. Zhao,1,*,‡ and S. B. Zhang2,*,§ 1Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, China 2Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA 3Department of Chemistry, Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00931, USA Rece...
An improved method for the preparation of graphene oxide (GO) is described. Currently, Hummers’ method (KMnO4, NaNO3, H2SO4) is the most common method used for preparing graphene oxide. We have found that excluding the NaNO3, increasing the amount of KMnO4, and performing the reaction in a 9:1 mixture of H2SO4/H3PO4 improves the efficiency of the oxidation process. This improved method provides a greater amount of hydrophilic oxidized graphene material as compared to Hummers’ method or Hummers’ ...
Abstract null null Combining experimental and computational studies of nanocomposite interfaces is highly needed to gain insight into their performance. However, there are very few literature reports, combining well-controlled atomic force microscopy experiments with molecular dynamic simulations, which explore the role of polymer chemistry and assembly on interface adhesion and shear strength. In this work, we investigate graphene oxide (GO)-polymer interfaces prevalent in nanocomposites based ...
Abstract null null Under cyclic loading, while graphene can suffer from catastrophic brittle fatigue failure, graphene oxide (GO) can be engineered to improve fatigue response and possibly ductile failure. Herein, we study the fatigue response of atomically thin GO using atomistic simulations complemented by atomic force microscopy-based experiments. Analysis of the damage and failure mechanisms demonstrated a notable role of functionalization degree and ratio on the fatigue resistance of GO. In...
#5Wei Chen(CAS: Chinese Academy of Sciences)H-Index: 154
Abstract Nanomaterials (NMs) as lung-targeted drug delivery vehicles have attracted great attentions. Recent studies indicated that elastic or deformable property of NMs could play a vital role in biomedical applications. Herein, polyvinylpyrrolidone (PVP) functionalized graphene oxide (GO-PVP) via a facile one-pot method and PEGylated GO (GO-PEG) nanosheets (NSs) were synthesized at room temperature. By using rare earth elemental labeling method, we quantitatively revealed that GO-PVP NSs were ...
#1Fan Guo(Nanjing University of Science and Technology)H-Index: 11
#2Yue Wang(Nanjing University of Science and Technology)H-Index: 26
Last. Chao Gao(Ha Tai: Xiamen University)H-Index: 70
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Processing 2D sheets into desired structures with high precision is of great importance for fabrication and application of their assemblies. Solution processing of 2D sheets from dilute dispersions is a commonly used method but offers limited control over feature size precision owing to the extreme volume shrinkage. Plastic processing from the solid state is therefore a preferable approach to achieve high precision. However, plastic processing is intrinsically hampered by strong interlayer inter...
#2Xue Gao(Luoyang Institute of Science and Technology)
Last. Jianbin Luo(THU: Tsinghua University)H-Index: 55
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Abstract Graphene oxide (GO) is a promising solid lubricant used as a protective coating to reduce friction, while a detailed atomic understanding about its tribological behavior is required. In this study, ReaxFF reactive molecular dynamics simulations are used to explore the friction and wear mechanisms of GO. At low load, the structure of GO can be tailored via the tribochemical induced conversion from graphene oxide to graphene (GO-to-Gr), achieving low friction during the sliding process. T...
Summary Two-dimensional (2D) covalent organic frameworks (COFs) are promising polymeric crystalline nanomaterials with broad applications. However, the understanding of their mechanical properties and fracture mechanisms remains elusive. Here, we report a quantitative in situ tensile study of ultrathin COFTAPB-DHTA films. The fracture strength was measured to be 0.75 ± 0.34 GPa, and the tensile modulus was measured to be 10.38 ± 3.42 GPa, with a nominal density of 0.393 g/cc, thus having specifi...
Abstract The high stiffness and damping properties of flax fibres promote the integration of biocomposites in structural applications. However, the strength of flax/epoxy composites is still limited compared to glass/epoxy composites. Graphene oxide (GO) has proved to be a promising building block for nanocomposites due to its high toughness, stiffness and tunable interfacial interactions with polymers. This study aims to understand the potential of GO-based surface treatment of flax fibres to m...
#1Che Zhang(UOW: University of Wollongong)H-Index: 8
#2Cheng Lu(UOW: University of Wollongong)H-Index: 32
Last. Rui Wang(UOW: University of Wollongong)H-Index: 5
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Abstract The three-dimensional (3D) graphene-based materials have raised significant interest due to excellent catalytic performance and unique electronic properties, while the preparation of uniform and stable 3D graphene structures remains a challenge. In this paper, using molecular dynamics simulations, we found that the nanotwinned copper (nt-Cu) matrix with small twin spacing can induce the wave-shaped wrinkling and sawtooth-shaped buckling graphene structures under uniaxial compression. Th...
#1Bowen Zheng(University of California, Berkeley)H-Index: 7
#2Grace X. Gu(University of California, Berkeley)H-Index: 18
Graphene oxides have exhibited alluring potential for state-of-the-art applications such as biomedical devices and functional nanocomposites. The types and concentrations of oxygen-containing funct...
Graphene oxide (GO) can be defined as a single monolayer of graphite with oxygen-containing functionalities such as epoxides, alcohols, and carboxylic acids. It is an interesting alternative to graphene for many applications due to its exceptional properties and feasibility of functionalization. In this study, electrochemically exfoliated graphene oxides (EGOs) with different amounts of surface groups, hence level of oxidation, were prepared by an electrochemical two-stage approach using graphit...
