Nanosheet Networks Research Articles

Research on the growth of ZnO nanowall by soft-solution route

Three types of two dimensional ZnO nanowall networks were grown uniformly on the surface of ITO glass substrate by two different kinds of soft solutions. Scanning electronic microscopy (SEM) confirmed the formation of nanowalls with three kinds of distinct morphologies, such as (1) interlaced nanowall stood perpendicularly on the substrate, (2) nanowall with triangle cross section with widths ~80–100nm, (3) high-density nanosheets network with about 30nm in thickness. X-ray diffraction (XRD) showed that all of the ZnO nanowall networks were well crystallized in a wurtzite structure and highly oriented direction parallel to [0001]. The growth mechanisms of the ZnO nanowall networks were discussed.

Microwave assisted rapid growth of Mg(OH)2 nanosheet networks for ethanol chemical sensor application

This paper reports a facile microwave-assisted synthesis of magnesium hydroxide (Mg(OH)2) nanosheet networks and their utilization for the fabrication of efficient ethanol chemical sensor. The synthesized nanosheets networks were characterized in terms of their morphological, structural and optical properties using various analysis techniques such as field emission scanning electron microscopy (FESEM), X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR) and UV–Vis spectroscopy. The detailed morphological and structural investigations reveal that the synthesized (Mg(OH)2) products are nanosheet networks, grown in high density, and possessing hexagonal crystal structure. The optical band gap of as-synthesized Mg(OH)2 nanosheet networks was examined by UV–Vis absorption spectrum, and found to be 5.76eV. The synthesized nanosheet networks were used as supporting matrices for the fabrication of I–V technique based efficient ethanol chemical sensor. The fabricated ethanol sensor based on nanosheet networks exhibits good sensitivity (∼3.991μAcm−2mM−1) and lower detection limit (5μM), with linearity (R=0.9925) in short response time (10.0s). This work demonstrate that the simply synthesized Mg(OH)2 nanosheet networks can effectively be used for the fabrication of efficient ethanol chemical sensors.

Preparation, characterization and room temperature photoluminescence properties of a zinc oxide nanosheet network grown on glass substrate by a facile chemical route

An ultralong and ultrathin zinc oxide nanosheet network grown on glass substrate is prepared using an organic CTAB (cetyltrimethylammonium bromide, CH 3(CH 2) 15N +(CH 3) 3Br −) and the simple chemical materials (Zn(AC) 2·2H 2O and NaOH) by hydrothermal method. The morphology and microstructure of ZnO nanosheet network have been characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–vis spectroscopy. The results revealed that the product grown on glass substrate was the ultralong and ultrathin zinc oxide nanosheet network and the crystalline hexagonal wurtzite ZnO crystal structure. The zinc oxide nanosheet network exhibits room temperature photoluminescence (RTPL) characteristics and three blue emissions located at 452, 459, and 469 nm, and a green emission located at about 494 nm were observed.

PbTe hierarchical nanostructures: solvothermal synthesis, growth mechanism and their electrical conductivities

PbTe micropeony consisting of nanosheet networks and PbTe hollow spheres composed of self-assembled nanocrystals have been synthesized by a simple solvothermal method in mixtures of water and ethanol at 180 °C with the help of glucose. By adjusting the experimental parameters, such as the amount of NaOH, volume ratio of ethanol to water, reaction time and concentration of glucose, the nucleation, growth, and self-assembly of the PbTe nanosheets could be readily tuned, resulting in different morphologies and nanostructures. Based on the electron microscopy observations, the formation mechanism of such hierarchical structures has been proposed as an Ostwald ripening process followed by anisotropic growth process. Nitrogen adsorption–desorption measurements and pore size distribution analysis revealed that both mesopores (2–50 nm) and macropores (>50 nm) existed in the products. Moreover, PbTe crystals with micropeony and hollow sphere morphology were measured to investigate the possible impact of morphology on the electrical conductivity.

Multilayered Nano-Architecture of Variable Sized Graphene Nanosheets for Enhanced Supercapacitor Electrode Performance

The diverse physical and chemical aspects of graphene nanosheets such as particle size surface area and edge chemistry were combined to fabricate a new supercapacitor electrode architecture consisting of a highly aligned network of large-sized nanosheets as a series of current collectors within a multilayer configuration of bulk electrode. Capillary driven self-assembly of monolayers of graphene nanosheets was employed to create a flexible, multilayer, free-standing film of highly hydrophobic nanosheets over large macroscopic areas. This nanoarchitecture exhibits a high-frequency capacitative response and a nearly rectangular cyclic voltammogram at 1000 mV/s scanning rate and possesses a rapid current response, small equivalent series resistance (ESR), and fast ionic diffusion for high-power electrical double-layer capacitor (EDLC) application.

Highly sensitive and ultra-fast responding gas sensors using self-assembled hierarchical SnO 2 spheres

The Sn 3O 4 hierarchical microspheres self-assembled from nanosheets were prepared by a hydrothermal reaction of aqueous solution containing SnCl 2·2H 2O, H 2C 2O 4, HCl, and N 2H 4·H 2O, which were successfully transformed into nano-porous SnO 2 hierarchical microspheres for gas sensor applications by heat treatment at 600 °C. The morphology of building blocks within the SnO 2 hierarchical spheres could be manipulated from 0-dimensional nanoparticles to 2-dimensional nanosheets by varying the amount of H 2C 2O 4 and N 2H 4·H 2O. The SnO 2 hierarchical spheres showed both the ultra-fast response (∼1 s) and high sensitivity to 50 ppm C 2H 5OH. The dramatic improvement in gas sensing characteristics was explained by the rapid diffusion of the target gas onto the entire sensing materials through the nano-porous network of nanosheets.

In Situ Growth of Self-Assembled and Single In2O3 Nanosheets on the Surface of Indium Grains

Self-assembled In2O3 nanosheet networks and flowerlike nanoarchitectures, as well as single In2O3 nanosheets, have been grown in situ on indium substrate by heating indium grains at 900−950 °C under the flow of O2 in the presence of a small quantity of P2O5. The as-synthesized In2O3 nanosheets were characterized by transmission electron microscopy, scanning electron microscopy, and Raman spectrum. It was found that the In2O3 nanosheets were single crystals with body-centered cubic structure and dimensions of about 0.5−3 μm. A possible mechanism for the In2O3 nanosheet growth was also proposed on the basis of the results of the present and previous works. This mechanism not only can explain all the experimental observations but also helps to clarify the growth mechanism of other nanostructures in the gas phase. A strong and narrow photoluminescent (PL) peak at 428 nm was observed from the nanosheets, which is attributed to radiative recombination between an electron on an oxygen vacancy and a hole on an indium−oxygen vacancy center in the In2O3 nanosheets.

Low-temperature growth and properties of flower-shaped [formula omitted]- Ni(OH) 2 and NiO structures composed of thin nanosheets networks

Flower-shaped β - Ni(OH) 2 structures composed of thin nanosheet networks have been synthesized via the simple aqueous solution route by using nickel chloride and ammonium hydroxide at 65 ∘C in 4 h. The general morphological observations revealed that the flowers are composed of thin nanosheets which were connected to each other in such a manner that they form network-like morphologies. Moreover, single-crystalline flower-shaped NiO structures composed of thin nanosheets were also obtained by thermal decomposition of flower-shaped β - Ni(OH) 2 structures. The shape of nanosheet networks in β - Ni(OH) 2 was sustained after thermal decomposition to NiO however, some broken nanosheets were also observed from the flower-shaped structures of NiO. The as-prepared products were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), high-resolution TEM (HRTEM), Fourier transform infrared spectroscopy (FTIR), and Thermogravimetric analysis (TGA).

Wet-Chemical Route to ZnO Nanowire-Layered Basic Zinc Acetate/ZnO Nanoparticle Composite Film

ZnO nanowire-layered basic zinc acetate (LBZA)/ZnO nanoparticle (NP) composite films with different NP occupying extents have been synthesized using a simple wet-chemical route, i.e., aligned ZnO nanowire (NW) array first formed by an aqueous chemical bath deposition (CBD) and then heterogeneous nucleation and growth of LBZA/ZnO NPs on the surface of ZnO NWs by another base-free CBD. The features of the composites from three-dimensional (3D) NW−nanosheet (NS) networks to dense NW−NP composite films and NW−NP composite films with flowerlike particles are able to be obtained easily by varying the NP growth period. X-ray diffraction (XRD) and cathodoluminescence (CL) analyses indicate that the LBZA fraction and defect concentration in the composite film are increased with the NP growth period in the base-free chemical bath solution. Shifts of the ZnO (002) diffraction peak and UV emission peak with the NP growth period are observed at the series of composite films. HRTEM analyses indicate that there is no epitaxial relationship between the ZnO NW and ZnO NPs, suggesting that heterogeneous nucleation of LBZA structure on the surface of the ZnO NWs is crucial for the formation of the NW−NP composite using the base-free route. Photovoltaic measurements of the ZnO NW−LBZA/ZnO NP composite dye-sensitized solar cells (DSSCs) show that the overall efficiency is affected by the LBZA fraction, defect concentration, and cracks within the NW−NP composite film.

A Facile Hydrothermal Route to Flower‐Like Cobalt Hydroxide and Oxide

AbstractFlower‐like cobalt hydroxide [β‐Co(OH)2] consisting of nanosheet networks has been synthesized by a hydrothermal method from Co(CH3COO)2·4H2O in mixtures of water and glycerol/ethylene glycol at 200 °C. The morphology and phase of the cobalt hydroxide can be controlled by adjusting the experimental parameters that include cobalt acetate concentration and the volume ratio of water to glycerol/ethylene glycol. The possible formation mechanism of flower‐like cobalt hydroxide is discussed on the basis of experimental results. Cobalt oxide (Co3O4) flowers have also been obtained by thermal decomposition of cobalt hydroxide flowers in air at 400 °C. The products were characterized by powder XRD, TEM, selected‐area electron diffraction (SAED), high resolution TEM (HRTEM), and field‐emission SEM (FESEM). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

ZnO nanosheet networks and hexagonal nanodiscs grown on silicon substrate: growthmechanism and structural and optical properties

Two-dimensional ZnO nanosheet networks composed of many thin anduniform hexagonal-shaped ZnO nanosheets and ZnO nanodiscs were preparedin a large scale on silicon substrate through thermal evaporation usingZnCl2 and O2 as source materials for Zn and oxygen, respectively, without the use of metal catalysts oradditives. Detailed structural studies indicated that the synthesized products aresingle crystalline with wurtzite hexagonal structure. Raman scattering of thesynthesized products confirmed that the as-grown structures have good crystalquality with a hexagonal wurtzite phase. Room temperature photoluminescencespectra showed a strong green band with a suppressed UV emission from the ZnOnanosheet networks, but on the other hand a dominant and strong near bandedge emission with a much suppressed deep level emission was observed in thenanodiscs. The growth mechanism of these structures is also discussed in detail.

Electrochemical fabrication of neuron-type networks based on crystalline oligopyrene nanosheets

Electrochemical polymerization of pyrene in boron trifluoride diethyl etherate (BFEE) produced oligopyrenes (pyrene oligomers) with repeat unit numbers of 2–15. The oligoyrenes grown at the working electrode are nanosheets with high crystallinity. As an array of microelectrodes or a semiconductive silicon wafer patterned with microelectrodes were used as the working electrode, a dendritic network of cyrstalline oligopyrene nanosheets was fabricated. The initially grown nanosheets on the microelectrodes act as nodes and the network with interconnects of the nanosheets grow from the nodes. The number and structure of the inconnectects can be controlled by the structure of the patterned electrode, the concentration of the monomer, the value of applied potential and the charge density used for electrochemical deposition. This is the first example of fabrication neuron-type network based on conductive organic nanosheets.

Effects of acrylonitrile content on PC/ABS alloy systems with a flame retardant : Choi, H.J., Park, S.H., Kim, J.K., Jun, J.I., Inha University, Inchon, South Korea in journal of applied polymer science, vol 75, issue 3, 2000

Core-shell nano-ring α-Fe2O3@Carbon (CSNR) composites with different carbon content (CSNR-5%C and CSNR-13%C) are synthesized using a hydrothermal method by controlling different amounts of glucose and α-Fe2O3 nano-rings with further annealing. The CSNR electrodes exhibit much improved specific capacity, cycling stability and rate capability compared with that of bare nano-ring α-Fe2O3 (BNR), which is attributed to the core-shell nano-ring structure of CSNR. The carbon shell in the inner and outer surface of CSNR composite can increase electron conductivity of the electrode and inhibit the volume change of α-Fe2O3 during discharge/charge processes, and the nano-ring structure of CSNR can buffer the volume change too. The CSNR-5%C electrode shows super high initial discharge/charge capacities of 1570/1220 mAh g−1 and retains 920/897 mAh g−1 after 200 cycles at 500 mA g−1 (0.5C). Even at 2000 mA g−1 (2C), the electrode delivers the initial capacities of 1400/900 mAh g−1, and still maintains 630/610 mAh g−1 after 200 cycles. The core-shell nano-rings opened during cycling and rebuilt a new flower-like structure consisting of α-Fe2O3@Carbon nano-sheets. The space among the nano-sheet networks can further buffer the volume expansion of α-Fe2O3 and facilitate the transportation of electrons and Li+ ions during the charge/discharge processes, which increases the capacity and rate capability of the electrode. It is the first time that the evolution of core-shell α-Fe2O3@Carbon changing to flower-like networks during lithiation/de-lithiation has been reported.