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Two-dimensional (2D) atomic layers such as graphene, and metal chalcogenides have recently attracted tremendous attention due to their unique properties and potential applications. Unfortunately, in most cases, the free-standing nanosheets easily re-stack due to their van der Waals forces, and lose the advantages of their separated atomic layer state. Here, a bottom-up approach is developed to build three-dimensional (3D) architectures by 2D nanosheets such as MoS2 and graphene oxide nanosheets as building blocks, the thin nature of which can be well retained. After simply chemical reduction, the resulting 3D MoS2-graphene architectures possess high surface area, porous structure, thin walls and high electrical conductivity. Such unique features are favorable for the rapid diffusions of both lithium ions and electrons during lithium storage. As a consequence, MoS2-graphene electrodes exhibit high reversible capacity of ≈1200 mAh g−1, with very good cycling performance. Moreover, such a simple and low-cost assembly protocol can provide a new pathway for the large-scale production of various functional 3D architectures for energy storage and conversions. [ABSTRACT FROM AUTHOR]

Graphene and hexagonal boron nitride (h-BN) have similar crystal structures with a lattice constant difference of only 2%. However, graphene is a zero-bandgap semiconductor with remarkably high carrier mobility at room temperature, whereas an atomically thin layer of h-BN is a dielectric with a wide bandgap of ?5.9 eV. Accordingly, if precise two-dimensional domains of graphene and h-BN can be seamlessly stitched together, hybrid atomic layers with interesting electronic applications could be created. Here, we show that planar graphene/h-BN heterostructures can be formed by growing graphene in lithographically patterned h-BN atomic layers. Our approach can create periodic arrangements of domains with size ranging from tens of nanometres to millimetres. The resulting graphene/h-BN atomic layers can be peeled off the growth substrate and transferred to various platforms including flexible substrates. We also show that the technique can be used to fabricate two-dimensional devices, such as a split closed-loop resonator that works as a bandpass filter. [ABSTRACT FROM AUTHOR]

Abstract: Copper oxide hollow nanoparticles/graphene-nanosheet composites are prepared using the Kirkendall-effect approach. The composites exhibit a durable lifetime cycle at high rates. The reversible capacity of the material attains 640mAhg−1 at 50mAg−1 and the capacity retention is ca. 96% when the current density is increased 10 times. At 1Ag−1 (ca. 1.7C), the reversible capacity reaches 485mAhg−1 and remains at 281mAhg−1 after 500cycles, indicating that the capacity fading is less than 0.4mAhg−1 per cycle. This excellent electrochemical performance can be attributed to the hollow interior of CuO nanoparticles as well as synergistic effect between CuO and graphene. [Copyright &y& Elsevier]

State-of-the-art ultra-sensitive blood glucose-monitoring biosensors, based on glucose oxidase (GOx) covalently linked to a single layer graphene (SLG), will be a valuable next generation diagnostic tool for personal glycemic level management. We report here our observations of sensor matrix structure obtained using a multi-physics approach towards analysis of small-angle neutron scattering (SANS) on graphene-based biosensor functionalized with GOx under different pH conditions for various hierarchical GOx assemblies within SLG. We developed a methodology to separately extract the average shape of GOx molecules within the hierarchical assemblies. The modeling is able to resolve differences in the average GOx dimer structure and shows that treatment under different pH conditions lead to differences within the GOx at the dimer contact region with SLG. The coupling of different analysis methods and modeling approaches we developed in this study provides a universal approach to obtain detailed structural quantifications, for establishing robust structure-property relationships. This is an essential step to obtain an insight into the structure and function of the GOx-SLG interface for optimizing sensor performance. [ABSTRACT FROM AUTHOR]

A low-cost carbon/sulfur material has been prepared using interconnected porous carbon nanorods (PCNRs) as the framework, and self-assembled graphene sheets (GS) as the coating layer. This GS@PCNRs/S sulfur cathode exhibits excellent rate capability and cycle stability. It delivers a maximum discharge capacity of 549.9 mAh g −1 at 1 C and keeps superior cyclability over 500 cycles with an average capacity fading rate of only 0.083% per cycle. The improved electrochemical performance is primarily attributed to the wrapped, internally porous architecture of GS@PCNRs/S, which not only can offer an excellent transport of lithium ions and electrons within the electrodes, but also can inhibit polysulfide diffusion by the external chemical and physical barrier of graphene sheets. [ABSTRACT FROM AUTHOR]

The SnO 2 /carbon nanotubes encapsulated in graphene sheets (CSGN) composites are synthesized via a sonochemical method which is straightforward, low-cost and operable under ambient conditions. The open spaces formed by carbon nanotubes and graphene offering the accommodation of volume change and the access of an easy electrolyte-wetting, and the improved electrical conductivity by the presence of graphene and carbon nanotubes, lead to the superior cycling performance. As a result, the CSGN with SnO 2 content of 61.4 wt% exhibits a reversible specific capacity of 842.9 mAh g −1 at the first cycle and retains 793.8 mAh g −1 after 50 cycles at a current density of 125 mA g −1 , indicating a high capacity retention rate of 94%. The cycling performance is attributed to the unique structure of CSGN and enhanced electrical conductivity, which may make much sense to the structure designing of other electrode materials for lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: A graphene coating mesoporous carbon/sulfur (RGO@CMK-3/S) composite, which is characteristic of a hybrid structure by incorporating the merits of CMK-3 matrix and graphene (RGO) skin, is synthesized by a facile and scalable route. The CMK-3/S composite is synthesized via a simple melt-diffusion strategy, and then a thin RGO skin is absorbed on the CMK-3/S composite surface in aqueous solution. When evaluating the electrochemical properties of as-prepared RGO wrapped nanostructures as cathode materials in lithium–sulfur batteries, it exhibits much improved cyclical stability and high rate performance. The RGO@CMK-3/S composite with 53.14 wt.% sulfur presents a reversible discharge capacity of about 734 mA h g− 1 after 100 cycles at 0.5 C. The improved performance is attributed to the unique structure of RGO@CMK-3/S composite. CMK-3 with extensively mesopores can offer buffering space for the volume change of sulfur and efficient diffusion channel for lithium ions during the charge/discharge process. Meanwhile, the conductive RGO coating skin physically and chemically prevents the dissolution of polysulfides from the cathode, both of which contribute to the reduced capacity fade and improved electrochemical properties. [Copyright &y& Elsevier]

Although lithium ion batteries havegained commercial success owingto their high energy density, they lack suitable electrodes capableof rapid charging and discharging to enable a high power density criticalfor broad applications. Here, we demonstrate a simple bottom-up approachtoward single crystalline vanadium oxide (VO2) ribbonswith graphene layers. The unique structure of VO2-grapheneribbons thus provides the right combination of electrode propertiesand could enable the design of high-power lithium ion batteries. Asa consequence, a high reversible capacity and ultrafast charging anddischarging capability is achieved with these ribbons as cathodesfor lithium storage. A full charge or discharge is capable in 20 s.More remarkably, the resulting electrodes retain more than 90% ofthe initial capacity after cycling more than 1000 times at an ultrahighrate of 190C, providing the best reported rate performance for cathodesin lithium ion batteries to date. [ABSTRACT FROM AUTHOR]

Abstract: The structure and electronic properties of graphene nanosheet (GNS) render it a promising conducting agent in a lithium-ion battery. A graphite electrode loaded with GNS exhibits superior electrochemical properties including higher rate performance, increased specific capacity and better cycle performance compared with that obtained by adding the traditional conducting agent–acetylene black. The high-quality sp2 carbon lattice, quasi-two-dimensional crystal structure and high aspect ratio of GNS provide the basis for a continuous conducting network to counter the decrease in electrode conductivity with increasing number of cycles, and guarantee efficient and fast electronic transport throughout the anode. Effects of GNS loading content on the electrochemical properties of graphite electrode are investigated and results indicate that the amount of conductive additives needed is decreased by using GNS. The kinetics and mechanism of lithium-storage for a GNS-loaded electrode are explored using a series of electrochemical testing techniques. [Copyright &y& Elsevier]