Crumpled Graphene Nanosheets Research Articles

Crumpled graphene epoxy nanocomposites modified with polydopamine for advanced semiconductor packaging applications

Graphene-based epoxy nanocomposites are effective TIMs due to the unique properties of graphene – extraordinarily high thermal conductivity and large specific surface area. However, graphene easily aggregates due to strong van der Waals interactions and has poor interfacial connections due to a smooth surface. In this work, a facile method fabricates highly crumpled graphene nanosheets. The crumpled architecture prevents graphene nanosheets from restacking and maintaining the high specific surface area. Polydopamine (PDA) is used to promote uniform dispersion of graphene through π−π bonds, reducing the thermal interface resistance. Additionally, it enhances the thermal transport between as a TIM as proved by experimentation and modeling. The resultant 2.5 wt% filler loading epoxy nanocomposites present a high through-plane thermal conductivity of 1.02 W/mK. They also have a low CTE, low viscosity, low moisture absorption, high electric resistivity, and high adhesion strength. These results provide insights into the design of graphene-based epoxy nanocomposites to meet TIMs requirements in high density 3D electronic packaging.

Anisotropic conductive, tough and stretchable heater based on nacre-like crumpled graphene composite

In this work, the nacre-like styrene-butadiene rubber/crumpled graphene nanosheets heater (NSGH) with integrated superior performance, including excellent anisotropic conductivity (safety), flexible stretchable Joule heating performance and comprehensive mechanical performance, is prepared on a large-scale by the blade-coating technique. The excellent flexible stretchable Joule heating performance, almost constant of the saturation temperature (163 °C) at the excitation of 8 V suffering 70% strain and 4000 times of bending, is originated from the selection of elastic styrene-butadiene rubber matrix and introduction of flexible conductive crumpled graphene nanosheets. The excellent comprehensive mechanical performance (increment of 215.7% on toughness and 531.85% on initial tensile modulus) and the ultrahigh anisotropic conductivity are attributed to the distinctive nacre-like structure. Moreover, the heating model of the NSGH is proposed and validated, that the heating performance can be tailored and forecasted.

Dry ice-mediated rational synthesis of edge-carboxylated crumpled graphene nanosheets for selective and prompt hydrolysis of cellulose and eucalyptus lignocellulose under ambient reaction conditions

Edge-carboxylated graphene (ECG) crumpled nanosheets with tuneable COOH content were synthesized by a facile one pot approach for selective hydrolysis of cellulose to glucose and eucalyptus to xylose and glucose under ambient conditions.

A self-adhesive graphene nanoscroll/nanosheet paper with confined Fe1−xS/Fe3O4 hetero-nanoparticles for high-performance anode material of flexible Li-ion batteries

Graphene based free-standing membrane/paper materials have been proved to be promising electrodes for flexible Lithium-ion batteries, whereas the rate capability is still unsatisfied unfortunately due to the typical layer-by-layer configuration of the graphene building blocks. Herein, a novel 3D porous architecture with a graphene nanoscroll (GNS)/nanosheet hybrid as the framework and ultrasmall Fe1−xS/Fe3O4 hetero-nanoparticles (NPs) as the primary active matter is developed by a facile and scalable route of cold quenching, freeze drying and the subsequent roll-in treatment. The crumpled graphene nanosheets and GNSs with high length/diameter ratio are found to intertwine together and construct a 3D network with multiscale pores. Meanwhile, the Fe1−xS/Fe3O4 NPs with a uniform dimension of <10 nm and homogeneous dispersion are firmly anchored on the graphene nanosheets or confined in the gallaries of the GNSs through their strong interface interaction. Benefiting from the unique and robust 3D hybridized design, the self-adhesive flexible electrode exhibits high reversible capacity (946 mAh g−1 at 0.1 A g−1) and excellent long-term stability up to 400 cycles with a low capacity loss rate of 0.047% per cycle. In addition, the prominently enhanced rate performance (capacity retention of 40.1% at 6 A g−1) compared with the traditional 2D structured graphene materials is also stressed.

Facile assembly of α-Fe2O3 nanorings@reduced graphene oxide composites with high lithium storage performance

In this study, α-Fe2O3 nanorings@reduced graphene oxide (α-Fe2O3@rGO) composites have been prepared through a facile hydrothermal self-assembly process. This strategy achieved the effective reduction of graphene oxide (GO) to graphene as well as the homogenous distribution of α-Fe2O3 nanorings on the surface of crumpled graphene nanosheets. The α-Fe2O3@rGO composites exhibit a much higher specific capacity of 781mAhg−1 after 100cycles at the current density of 100mAg−1 and good rate capability than the pure α-Fe2O3 nanorings (225mAhg−1), outperforming the most of reported Fe2O3/graphene electrode materials previously. The excellent electrochemical performance of α-Fe2O3@rGO benefits from the synergistic effect between α-Fe2O3 nanorings and graphene nanosheets. Moreover, the present work will be contributed to the future development of diverse graphene-based metal oxide materials for lithium-ion batteries applications.

Graphene nanoscroll/nanosheet aerogels with confined SnS2 nanosheets: simultaneous wrapping and bridging for high-performance lithium-ion battery anodes

In this paper, we report graphene nanoscrolls bridged by crumpled graphene nanosheets as an effective conductive framework for confining SnS2 nanosheets for lithium-ion battery (LIB) applications. The nanoscroll/nanosheet hybrid aerogels (GNAs) with confined SnS2 nanosheets are facilely prepared via fast quenching, freeze-drying and thermal annealing. During quenching, wrapping SnS2 nanosheets in the nanoscrolls and bridging the one-dimensional nanoscrolls by the two-dimensional nanosheets occur simultaneously, and the ratio of nanoscrolls/nanosheets can be controlled by simply adjusting quenching conditions. The optimized SnS2/GNA is highly porous with a large specific surface area of 127.1 m2 g−1 and multi-scale pore structure, which can effectively prevent SnS2 aggregation to provide abundant lithiation/delithiation sites, and buffer volumetric change and pulverization of SnS2 nanosheets. Moreover, the three-dimensional conductive network formed in the hybrid aerogels can remarkably improve its electrical conductivity while providing sufficient channels for the transportation of lithium ions and charges. As a result, the optimized SnS2/GNA nanocomposite exhibits enhanced electrochemical performance with a high initial reversible capacity (1514.8 mAh g−1 at 0.1 A g−1), excellent rate capacity (665.4 mAh g−1 at 5 A g−1) and good cyclic stability (1050 mA h g-1 at the 50th cycle). This may provide an efficient generic approach for encapsulation of transition metal dichalcogenide materials in conductive nano/micro confined spaces for fabrication of high-performance LIB anodes.

Green Synthesis of Reduced Graphene Oxide-Silver Nanoparticles Using Environmentally Friendly L-arginine for H2O2 Detection

The paper reports on the preparation of reduced graphene oxide/silver nanoparticles (rGO/AgNPs) nanocomposite through the reduction of graphene oxide (GO) and silver nitrate (AgNO3) using environmentally friendly L-arginine (Arg). The chemical composition of the resulting nanocomposite has been analyzed using transmission infrared (FTIR) spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results indicated that Arg was incorporated in the rGO matrix. The morphology of the rGO/Arg/AgNPs composite has been characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Ag NPs with an average diameter of 20 nm are homogeneously distributed on crumpled graphene nanosheets. The electrocatalytic activity of the rGO/Arg/AgNPs hybrid nanomaterial has been investigated for the nonenzymatic detection of hydrogen peroxide (H2O2) in PBS solution. The sensor displayed a detection limit of ≈50 μM over a wide linear range from 0.2 to 2.5 mM with a sensitivity of 1.34 mA mM−1 cm−2. In addition, the sensor also showed good selectivity for H2O2 detection and long-term stability.

Crumpled graphene paper for high power sodium battery anode

Graphene-based electrodes typically form a compact uniaxially oriented stacked structure during electrode preparation due to the highly anisotropic morphology. This leads to limited diffusion paths for the insertion of Li or Na when used as electrodes in rechargeable batteries. Here, we demonstrate that self-standing electrodes formed of randomly folded and/or crumpled graphene nanosheets can be obtained via a simple modified reduction process, and that the crumpled structure can significantly increase the power capability of graphene-based anodes of sodium-ion batteries. These electrodes can deliver a power density of approximately 20,000 W kg−1, which surpasses the Li storage capability of conventional graphene paper electrodes. Moreover, the specific capacity was stably maintained without a binder, conductive agent, or substrate for more than 500 charge/discharge cycles and 1000 cycles of repeated bending.

Hydrothermal deposition of manganese dioxide nanosheets on electrodeposited graphene covered nickel foam as a high-performance electrode for supercapacitors

In this paper, the graphene oxide nanosheets are simultaneously reduced and deposited on nickel foam (denoted as Ni-foam@GNS) by one step electrodeposition method. The interconnected crumpled graphene nanosheets grown on Ni foam serve as a three-dimensional (3D) conductive skeleton for hydrothermal deposition of MnO2 nanosheets by in-situ redox reaction. The MnO2 nanosheets anchored on the graphene covered nickel foam (denoted as Ni-foam@GNS@MnO2) show unique 3D porous interconnected networks. The samples are characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), N2 adsorption–desorption measurements and fourier transform infrared spectroscopy (FT-IR). The capacitive performances are researched by cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The results reveal that the Ni-foam@GNS@MnO2 electrode exhibits a high specific capacitance of 462 F g−1 at 0.5 A g−1 and excellent capacitance retention of 93.1% after 5000 cycles at 10 A g−1. Furthermore, the Ni-foam@GNS@MnO2 electrode delivers a high energy density of 26.1 Wh kg−1 even at a high power density of 3981 W kg−1. These results demonstrate that the Ni-foam@GNS@MnO2 composite offers great promise in large-scale energy storage device applications.

Effects of highly crumpled graphene nanosheets on the electrochemical performances of pseudocapacitor electrode materials

Highly crumpled graphene nanosheets (GS) with a BET surface area as high as 722.1 m2g−1 is prepared by a thermal exfoliation method. A systematical investigation is performed on the electrochemical performances of porous Ni2P/GS nanocomposite synthesized by the low temperature solid state reaction method. It is shown that Ni2P nanoparticles anchor on graphene sheets producing a porous structure and GS have beneficial effects on the electrochemical properties of Ni2P nanoparticles when investigated as pseudocapacitor materials. The novel Ni2P/GS composite electrode exhibits a superior specific capacitance of 1912 F g−1 and 888 F g−1 at current densities of 5 and 50mAcm−2, respectively. The specific capacitance decreases to 1473 F g−1 after 2500 cycles, suggesting its excellent cycling stability. It is confirmed that the GS with good electrical conductivity serve as a conducting network for fast electron transfer between the active materials and charge collector, as well as buffered spaces to accommodate the volume expansion/contraction during cycling, thus, leading to enhancement of the electrochemical properties of the Ni2P electrode.

PREPARATION OF THREE-DIMENSIONAL GRAPHENE NETWORKS FOR USE AS ANODE OF LITHIUM ION BATTERIES

The three-dimensional (3D) graphene networks have been prepared by annealing the mixture of graphene oxide and SiO 2 nanoparticles and then etching SiO 2. The obtained material was characterized by X-ray diffraction, scanning electron microscope and transmission electron microscopy, which revealed that 3D networks consisting of crumpled graphene nanosheets were preserved after the removal of SiO 2. When used as anode material of lithium ion batteries, the graphene networks showed a reversible capacity of 610.9 mAh/g at a current density of 50 mA/g after 50 cycles and excellent rate capability of 291.5 mAh/g at a current density of 5000 mA/g. The good electrochemical performance can be attributed to the network structure, which enables graphene to electrochemically absorb more lithium ions and significantly improve the electrical conductivity of electrode. The graphene networks have the potential applications in ultracapacitor and catalyst supports.

Excellent catalytic effects of highly crumpled graphenenanosheets on hydrogenation/dehydrogenation of magnesium hydride

Highly crumpled graphene nanosheets (GNS) with a BET surface area as high as 1159 m(2) g(-1) was fabricated by a thermal exfoliation method. A systematic investigation was performed on the hydrogen sorption properties of MgH(2)-5 wt% GNS nanocomposites acquired by ball-milling. It was found that the as-synthesized GNS exhibited a superior catalytic effect on hydrogenation/dehydrogenation of MgH(2). Differential Scanning Calorimetry (DSC) and isothermal hydrogenation/dehydrogenation measurements indicated that both hydrogen sorption capacity and dehydrogenation/hydrogenation kinetics of the composites improved with increasing milling time. The composites MgH(2)-GNS milled for 20 h can absorb 6.6 wt% H(2) within 1 min at 300 °C and 6.3 wt% within 40 min at 200 °C, even at 150 °C, it can also absorb 6.0 wt% H(2) within 180 min. It was also demonstrated that MgH(2)-GNS-20 h could release 6.1 wt% H(2) at 300 °C within 40 min. In addition, microstructure measurements based on XRD, SEM, TEM as well as Raman spectra revealed that the grain size of thus-prepared MgH(2)-GNS nanocomposites decreased with increasing milling time, moreover, the graphene layers were broken into smaller graphene nanosheets in a disordered and irregular manner during milling. It was confirmed that these smaller graphene nanosheets on the composite surface, providing more edge sites and hydrogen diffusion channels, prevented the nanograins from sintering and agglomerating, thus, leading to promotion of the hydrogenation/dehydrogenation kinetics of MgH(2).

Nanocomposites of hematite (α-Fe2O3) nanospindles with crumpled reduced graphene oxide nanosheets as high-performance anode material for lithium-ion batteries

Nanocomposites of Fe2O3 nanospindles with crumpled reduced graphene oxide (RGO) nanosheets were prepared using a facile solvothermal synthesis method. The RGO-Fe2O3 nanocomposite with about 24.4 wt% RGO demonstrated an excellent electrochemical performance as a promising anode material for lithium-ion batteries (LIBs), which achieved a high reversible capacity of 969 mA h g−1 after 100 cycles at a current density of 100 mA g−1 (0.1 C). Furthermore, it also exhibited a large capacity of 336 mA h g−1 after 100 cycles at the high rate of 5 C. The cycling performance and reversible capacities of the RGO-Fe2O3 composites were much better than those of bare Fe2O3 nanospindles and pure RGO nanosheets, as well as previously reported RGO-Fe2O3 nanocomposites. The enhanced performance towards lithium storage can be ascribed to the crumpled RGO nanosheets, which may act as efficient volume buffer and electron conductor in the composites. The strategy proposed here could be extended to produce other nanocomposites based on crumpled graphene nanosheets for various applications.

Crumpled Graphene Nanosheets as Highly Effective Barrier Property Enhancers

Near-trace concentrations (0.02 vol%) of crumpled graphene nanosheets suspended within a polystyrene matrix drastically inhibit the permeation of oxygen molecules through the resulting polymer-graphene nanocomposite. This decrease in permeability is a direct result of the low solubility of oxygen within the nanocomposite, which is considerably densified by the graphene. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.