Graphene has aroused intensive interest because of its unique structure, superior properties, and various promising applications. Graphene nanostructures with significant disorder and defects have been considered to be poor materials because disorder and defects lower their electrical conductivity. In this paper, we report that highly disordered graphene nanosheets can find promising applications in high-capacity Li ion batteries because of their exceptionally high reversible capacities (794−1054 mA h/g) and good cyclic stability. To understand the Li storage mechanism of graphene nanosheets, we have prepared graphene nanosheets with structural parameters tunable via different reduction methods including hydrazine reduction, low-temperature pyrolysis, and electron beam irradiation. The effects of these parameters on Li storage properties were investigated systematically. A key structural parameter, Raman intensity ratio of D bands to G bands, has been identified to evaluate the reversible capacity. The greatly enhanced capacity in disordered graphene nanosheets is suggested to be mainly ascribed to additional reversible storage sites such as edges and other defects.
Given the intensive application of nanoscale zinc oxide (ZnO) materials in our life, growing concerns have arisen about its unintentional health and environmental impacts. In this study, the neurotoxicity of different sized ZnO nanoparticles in mouse neural stem cells (NSCs) was investigated. A cell viability assay indicated that ZnO nanoparticles manifested dose-dependent, but no size-dependent toxic effects on NSCs. Apoptotic cells were observed and analyzed by confocal microscopy, transmission electron microscopy examination, and flow cytometry. All the results support the viewpoint that the ZnO nanoparticle toxicity comes from the dissolved Zn(2+) in the culture medium or inside cells. Our results highlight the need for caution during the use and disposal of ZnO manufactured nanomaterials to prevent the unintended environmental and health impacts.
In this study we demonstrate a facile templated chemical vapor deposition (CVD) method to produce CNT-encapsulated Sn nanoparticles with ∼100% particle encapsulation and high filling uniformity. The encapsulated Sn particles were formed either as Sn or Sn@carbon core−shell particles with good control of size and morphology. The complete and uniform encapsulation of small, electrochemically active Sn particles within a CNT matrix with large free volume accommodated the volume excursion problem in repetitive lithium insertion and extraction reactions very well, showing good resilience in maintaining electrical connective and mechanical integrity. Consequently the completely filled Sn@CNT nanocomposite showed excellent reversible lithium ion storage properties.
In this paper, a leaf-like porous CuO-graphene nanostructure is synthesized by a hydrothermal method.The as-prepared composite is characterized using XRD, Raman, SEM, TEM and nitrogen adsorptiondesorption. The growth mechanism is discussed by monitoring the early growth stages. It is shown that the CuO nanoleaves are formed through oriented attachment of tiny Cu(OH) 2 nanowires.Electrochemical characterization demonstrates that the leaf-like CuO-graphene are capable of delivering specific capacitances of 331.9 and 305 F g À1 at current densities of 0.6 and 2 A g À1 , respectively. A capacity retention of 95.1% can be maintained after 1000 continuous charge-discharge cycles, which may be attributed to the improvement of electrical contact by graphene and mechanical stability by the layer-by-layer structure. The method provides a facile and straightforward approach to synthesize CuO nanosheets on graphene and may be readily extended to the preparation of other classes of hybrids based on graphene sheets for technological applications. Recently, graphene nanosheets (GNS) based on transition metal oxides 2,3,22 have been studied and are expected to show improved capacitance owing their enhanced electronic conductivity, due to graphene materials possessing rapid electron transfer, high mechanical strength, high elasticity, and
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