Nanosheet Networks Research Articles

High areal capacity Li ion battery anode based on thick mesoporous Co3O4 nanosheet networks

An advanced electrode for high areal capacity Li ion battery anode has been designed by growing ultra thick mesoporous Co3O4 nanosheet networks on Ni foam. This noval architecture consists of mesoporous Co3O4 nanosheets, which are interconnected with each other to form macropores. Benefiting from the favorable macro/meso-porous structures as well as the large mass loading of the synthesized Co3O4 on three dimensional foam, this unique electrode exhibits an areal capacity as high as 4.39mAhcm−2 and excellent rate capability and cycling stability.

Three-dimensional ultrathin Sn/polypyrrole nanosheet network as high performance lithium-ion battery anode

A schematic depiction of the detailed structure of 3D Sn/PPy nanosheet network as a lithium ion battery anode material.

Studies on TiO2/Reduced Graphene Oxide Composites as Cathode Materials for Magnesium-Ion Battery

The aim of this work is to introduce a high performance cathode for magnesium-ion batteries. TiO2/reduced graphene oxide (rGO) composites were mixed in ball mill. The samples are charac- terized using XRD and SEM. The spex-milled composites exhibit better electrochemical perfor- mance with higher reversible capacity and excellent cyclability. The excellent electrochemical performance of TiO2/rGO composites is due to their unique structures, which intimately combine the conductive graphene nanosheets network with TiO2 nanoparticles and possess the characteristic parallel channels running along the [010] orientation, which allow easy Mg2+ transport. It was found that layered TiO2 and rGO nanosheets in the composite interlace with each other to form novel sandwich-structured microspheres, which exhibit preferable electrochemical performance in rechargeable Mg batteries.

Carbon Nanosheet Frameworks Derived from Peat Moss as High Performance Sodium Ion Battery Anodes

We demonstrate that peat moss, a wild plant that covers 3% of the earth's surface, serves as an ideal precursor to create sodium ion battery (NIB) anodes with some of the most attractive electrochemical properties ever reported for carbonaceous materials. By inheriting the unique cellular structure of peat moss leaves, the resultant materials are composed of three-dimensional macroporous interconnected networks of carbon nanosheets (as thin as 60 nm). The peat moss tissue is highly cross-linked, being rich in lignin and hemicellulose, suppressing the nucleation of equilibrium graphite even at 1100 °C. Rather, the carbons form highly ordered pseudographitic arrays with substantially larger intergraphene spacing (0.388 nm) than graphite (c/2 = 0.3354 nm). XRD analysis demonstrates that this allows for significant Na intercalation to occur even below 0.2 V vs Na/Na(+). By also incorporating a mild (300 °C) air activation step, we introduce hierarchical micro- and mesoporosity that tremendously improves the high rate performance through facile electrolyte access and further reduced Na ion diffusion distances. The optimized structures (carbonization at 1100 °C + activation) result in a stable cycling capacity of 298 mAh g(-1) (after 10 cycles, 50 mA g(-1)), with ∼150 mAh g(-1) of charge accumulating between 0.1 and 0.001 V with negligible voltage hysteresis in that region, nearly 100% cycling Coulombic efficiency, and superb cycling retention and high rate capacity (255 mAh g(-1) at the 210th cycle, stable capacity of 203 mAh g(-1) at 500 mA g(-1)).

Hierarchical Sulfur‐Based Cathode Materials with Long Cycle Life for Rechargeable Lithium Batteries

Composite materials of porous pyrolyzed polyacrylonitrile-sulfur@graphene nanosheet (pPAN-S@GNS) are fabricated through a bottom-up strategy. Microspherical particles are formed by spray drying of a mixed aqueous colloid of PAN nanoparticles and graphene nanosheets, followed by a simple heat treatment with elemental sulfur. The pPAN-S primary nanoparticles are wrapped homogeneously and loosely within a three-dimensional network of graphene nanosheets (GNS). The hierarchical pPAN-S@GNS composite shows a high reversible capacity of 1449.3 mAh g(-1) sulfur or 681.2 mAh g(-1) composite in the second cycle; after 300 cycles at a 0.2 C charge/discharge rate the capacity retention is 88.8 % of its initial reversible value. Additionally, the coulombic efficiency (CE) during cycling is near 100 %, apart from in the first cycle, in which CE is 81.1 %. A remarkable capacity of near 700 mAh g(-1) sulfur is obtained, even at a high discharge rate of 10 C. The superior performance of pPAN-S@GNS is ascribed to the spherical secondary GNS structure that creates an electronically conductive 3D framework and also reinforces structural stability.

Vertically Oriented Graphene Bridging Active‐Layer/Current‐Collector Interface for Ultrahigh Rate Supercapacitors

Dense networks of graphene nanosheets standing vertically on a current collector can work as numerous electrically conductive bridges to facilitate charge transport and mitigate the constriction/spreading resistance at the interface between the active material and the current collector. The vertically oriented graphene-bridged supercapacitors present excellent rate and power capabilities.

Growth of In-Doped ZnO Hollow Spheres Composed of Nanosheets Networks and Nanocones: Structural and Optical Properties

This work reports the facile growth and characterizations of In-doped ZnO hollow spheres composed of nanosheets networks and nanocones. The In-doped ZnO hollow spheres composed of nanosheets networks and nanocones were grown on Si (100) substrate by simple and non-catalytic thermal evaporation process using metallic zinc and indium powders in the presence of oxygen. The prepared materials were examined in terms of their morphological, compositional, structural and optical properties. The detailed morphological studies revealed that the synthesized products are hollow spheres composed of nanosheet networks and nanocones and grown in high-density. The observed structural properties exhibited well-crystallinity and wurtzite hexagonal phase for the grown materials. The room-temperature photoluminescence (PL) spectrum showed a broad band in the visible region with a suppressed UV emission and hence due the enhancement in the green emission, the prepared materials exhibits a great interest in the area of ZnO phosphors, such as field emissive display technology, etc.

Facile fabrication of MWCNT-doped NiCoAl-layered double hydroxide nanosheets with enhanced electrochemical performances

Ternary-component NiCoAl-layered double hydroxide nanosheets (NiCoAl-LDH) and multiwall carbon nanotube (MWCNT) nanohybrids (NiCoAl-LDH–MWCNT) have been successfully fabricated by a facile yet simple urea precipitation method. The MWCNTs are well incorporated into the network of NiCoAl-LDH nanosheets to form homogeneous nanohybrid materials. The electrochemical performances of nanohybrids as pseudocapacitor electrode materials were measured and investigated by cyclic voltammetry (CV) and galvanostatic charge and discharge techniques. It was found that the electrochemical performances of NiCoAl-LDH nanosheets are enhanced by the incorporation of MWCNTs into the sheet-shaped NiCoAl-LDH network. The specific capacitance of NiCoAl-LDH–MWCNT nanohybrids reaches 1035 F g−1 at a current density of 1 A g−1, and keeps a value of 597 F g−1 with a 57.7% capacitance retention rate even at a current density of 10 A g−1, which increases by 33.3% in comparison to that of the pristine NiCoAl-LDH nanosheets.

Shell-adjustable hollow ‘soft’ silica spheres as a support for gold nanoparticles

Hollow silica spheres composed of a ‘soft’ nanosheet network exhibit a large surface area and pore volume and are used here as a support for gold nanoparticles. The nanosheet morphology changes upon binding of gold nanoparticles and facilitates their fixation in the shell. The gold nanoparticles remain well dispersed in the shell even after heat treatment at 500 °C. It is also possible to control easily the loading ratio of gold in the flake-shell sphere by varying the quantity of chloroauric acid added during the preparation. The stably confined but accessible gold nanoparticles in the flake-shell sphere show high performance for the catalytic reduction of nitrophenols with high conversion and good reusability. This new composite structure could also be useful for various other catalytic processes.

Mesoporous NiO nanosheet networks as high performance anodes for Li ion batteries

Mesoporous NiO nanosheet networks with a thickness of more than 5 μm were fabricated on Ni foam for application as an electrode in Li ion batteries. Benefiting from the favorable macro/meso-porous structures as well as the great loading of the synthesized NiO, the electrode exhibits high capacity and excellent rate capability.

Facile approach to synthesize CuO/reduced graphene oxide nanocomposite as anode materials for lithium-ion battery

An efficient synthesis is used for the first time to prepare CuO/reduced graphene oxide nanocomposite anode materials for lithium ion batteries. Initially, copper oxide (CuO) nanoparticles are synthesized via a simple, facile and inexpensive microwave-assisted method within short reaction times (<20 min) and subsequent heat treatment at 500 °C for 5 h. The obtained pure CuO nanoparticles are mixed with 10 wt% of graphene nanosheets by the use of spex mill for 1 min. By short-time spex-milling, a unique CuO/reduced graphene oxide nanocomposite is obtained with a microstructure of multi-scale CuO nanoparticles homogeneously dispersed in a graphene matrix. The synthesized samples are characterized using X-ray diffraction and field-emission transmission electron microscopy studies. The spex-milled nanocomposite anode exhibits better electrochemical performance with higher reversible capacity and excellent cyclability in comparison with pure CuO nanoparticles. The initial discharge capacity of the pure CuO nanoparticles and their nanocomposite are 785.2 mAh g−1 and 1043.3 mAh g−1 with reversible capacity retention of 392.1 mAh g−1 and 516.4 mAh g−1 after 45 cycles respectively. The excellent electrochemical performance of CuO/reduced graphene oxide nanocomposite can be attributed to their unique structures, which intimately combine the conductive graphene nanosheets network with uniformly dispersed CuO nanoparticles.

Morphology-Controlled Fabrication of CuO Architectures

CuO nanorod arrays, networks of nanosheets and pistachio nuts consisting nanorods were prepared via a multi-step synthesis method starting from copper oxalate precursor. CuO nanorod arrays were prepared by solid state thermal calcination of Cu(OH)2 nanorod arrays through the reaction of copper oxalate precursor with NaOH at 40°C. CuO networks of nanosheets were obtained by treatment at 60°C for 90min, and CuO pistachio nuts consisting nanorods were obtained at 80°C for 20min. The products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM).The influences of temperature and reaction time on the synthesis of CuO were investigated. The formation mechanism of CuO nanostructures was discussed.

ZnO nanosheet network formation by ZnTe oxidation in humid argon atmosphere annealing

The process of ZnTe film oxidation by humid argon annealing at different temperatures was analyzed. Grazing incidence x‐ray diffraction results indicate that the annealing mainly induces ZnO formation. However, the presence of a small amount of TeO2 was suggested by the simulation of Rutherford backscattering spectra. These spectra provided also information about the thickness and morphology of the annealed samples. It was concluded that the oxidation process is simultaneous with ZnTe sublimation; this leads to the degradation of the film surface and induces a net loss of material. The surface of the ZnO converted samples resulted in a network of nanosheets.

Deterministic control of structural and optical properties of plasma-grown vertical graphene nanosheet networks via nitrogen gas variation

The effect of nitrogen on the growth of vertically oriented graphene nanosheets on catalyst-free silicon and glass substrates in a plasma-assisted process is studied. Different concentrations of nitrogen were found to act as versatile control knobs that could be used to tailor the length, number density and structural properties of the nanosheets. Nanosheets with different structural characteristics exhibit markedly different optical properties. The nanosheet samples were treated with a bovine serum albumin protein solution to investigate the effects of this variation on the optical properties for biosensing through confocal micro-Raman spectroscopy and UV-Vis spectrophotometry.

In situ synthesis of TiO2–graphene nanosheets composites as anode materials for high-power lithium ion batteries

Abstract TiO2–graphene nanosheets (GNS) composites are prepared via an in situ chemical synthesis method, which enables a homogenous dispersion of TiO2 nanoparticles on the graphene nanosheets. The obtained TiO2–GNS composites are anatase-GNS, while TiO2 is nanosized rutile without the incorporation of GNS. The resulting TiO2–GNS composites are employed as anode materials for lithium-ion batteries, showing a high initial reversible capacity of 306 mAh g−1 as well as a good cycling stability. The TiO2–GNS composites can deliver 60 mAh g−1 at a current rate as high as 5 A g−1 and demonstrate negligible fade even after 400 cycles. The superior electrochemical performances of the TiO2–GNS composites can be attributed to their unique structures, which intimately combine the conductive graphene nanosheets network with uniformly dispersed TiO2 nanoparticles. The TiO2–GNS composites could be promising candidate materials for high-power, low-cost, and environmentally friendly anodes for lithium ion batteries.

Flower-like Bi2Se3 nanostructures: Synthesis and their application for the direct electrochemistry of hemoglobin and H2O2 detection

In this paper, flower-like Bi2Se3 nanostructures consisting of intercrossed nanosheets networks have been synthesized via a facile hydrothermal technique and applied to the protein electrochemistry for the first time. The prepared Bi2Se3 nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The direct electrochemistry of hemoglobin (Hb) has been achieved by immobilizing Hb on the prepared Bi2Se3 nanostructures and Nafion (Nf) modified glassy carbon electrode. Bi2Se3 nanostructures show significant promotion to the direct electron-transfer of Hb. The immobilized Hb retained its biological activity well and shows high catalytic activity to the reduction of hydrogen peroxide (H2O2). Under the optimal experimental conditions, the catalytic currents are linear to the concentrations of H2O2 in the range of 2.0×10−6 to 1.0×10−4M. The corresponding detection limits are 6.3×10−7M. The prepared flower-like Bi2Se3 nanostructures provide an alternative matrix for protein immobilization and biosensor preparation.

Co3O4/Ni(OH)2 composite mesoporous nanosheet networks as a promising electrode for supercapacitor applications

Co3O4/Ni(OH)2 composite mesoporous nanosheet networks (NNs) grown on conductive substrates were synthesized by heat treatment of Co(OH)2/Ni(OH)2 NNs that were synthesized on Ti substrates by a facile electrochemical deposition route. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and micro-Raman spectroscopy. The above products were directly functionalized as supercapacitor electrodes without using any ancillary materials such as carbon black or binder. Co3O4/Ni(OH)2 composite mesoporous NNs achieved a high specific capacitance (Csp) of 1144 F g−1 at 5 mV s−1 and long-term cyclability. The electrochemical measurements showed Co3O4/Ni(OH)2 composite mesoporous NNs exhibited much better electrochemical performances than single Co3O4 or Ni(OH)2. The binary redox couples of Ni2+/Ni3+ and Co2+/Co3+, nanosheet networks with porous structures, the mesoporous structure within nanosheets, the interconnections among nanosheets, together with the excellent electrical contact with the current collector (substrate) are responsible for the improved electrochemical performances of Co3O4/Ni(OH)2 composite mesoporous NNs. With the ease of large scale fabrication and superior electrochemical characteristics, Co3O4/Ni(OH)2 composite mesoporous NNs grown on Ti substrates will be good candidates for supercapacitor applications.

Layer-by-layer assembled MoO2–graphene thin film as a high-capacity and binder-free anode for lithium-ion batteries

Thin films of MoO(2) nanoparticles and graphene sheets are created by layer-by-layer (LBL) assembly as binder-free anodes for lithium-ion batteries. Both anionic polyoxometalate clusters and graphene oxide nanosheets with oxygen functional groups on both basal planes and edges are assembled into LBL films with the aid of a cationic polyelectrolyte. After a subsequent thermal treatment in an Ar-H(2) atmosphere, hybrid MoO(2)-graphene films with three-dimensionally interconnected nanopores are formed, which comprise ultrafine MoO(2) nanoparticles homogeneously embedded in the porous network of graphene nanosheets. When used as an anode for lithium-ion batteries, the MoO(2)-graphene thin-film electrode shows superior electrochemical performance with high specific capacity and excellent cyclability. A high specific capacity of 675.9 mA h g(-1) after 100 discharge-charge cycles is achieved, indicating a promising anode candidate for lithium-storage applications.

Silica-based gene reverse transfection: an upright nanosheet network for promoted DNA delivery to cells

A method for substrate-mediated reverse gene transfection was developed using a silica film composed of an upright-sheet network. The silica film with a dense upright-sheet network shows approximately double higher transgene expression efficiency than that of solution-based transfection.

Fabrication of Nanosheet/Nestlike Nanoarray Hierarchical TiO&lt;sub&gt;2&lt;/sub&gt; Film for Dye-Sensitized Solar Cell

A hierarchical configuration of TiO2 nanoarray film, comprising a nestlike TiO2 nanoarray layer integrated with a nanosheet network overlayer, was constructed. The hierarchical TiO2 film was obtained by the post-hydrothermal treatment with NaOH solution on hydrothermally synthesized TiO2-derived nanostructured arrays grown on fluorine-doped tin oxide substrate (FTO). The TiO2 films were characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy, and absorbance spectroscopy. FE-SEM shows that the hierarchical TiO2 film with a thickness of 1.5 mu m is composed of a nanosheet overlayer (similar to 0.2 mu m height) and the nestlike nanoarray layer (similar to 1.3 mu m height). XRD patterns display that the TiO2 films have pure anatase phase structure. UV-Vis spectra reveal enhanced light scattering and dye adsorption ability of the hierarchical TiO2 film. For the dye-sensitized solar cell (DSSC) based on the nanosheet/nestlike nanoarray hierarchical TiO2 film, a short-circuit current (J(sc)) of 7.79 mA.cm(-2), open-circuit voltage (V-oc) of 0.80 V, fill factor (FF) of 0.40, and photoelectric conversion efficiency (eta) of 2.48% are achieved. Within the dye-sensitized solar cell, the photoelectric conversion efficiency of the hierarchical TiO2 film was nearly ten times higher than that of nanostructured array film.