Dimensional Nanostructures Research Articles

Novel Multi-Dimensional Nanocarbons and Their Applications in Electrochemical Energy Storage

In order to realize next generation energy storage devices with high efficiency, large energy/power density, and long life cycle, novel carbon-based nanomaterials are needed as electrodes. In here, we present interesting multidimensional carbon nanostructures which could find potential applications in electrodes for energy storage devices. We synthesized carbon nanoplatelets (CNPs) by simple thermal treatment of expandable graphites. By using carbon nanoplatelets (CNPs), multi- dimensional (1D+2D) carbon nanostructures (CNP-CNTs) were synthesized by use of metal catalysts and CVD process. Basic cyclic voltammetry study on the CNPs and CNP-CNTs reveals that CNP-CNTs possessed enhanced mass specific capacitances compared to those of CNPs. We will also present recent progress on our multi-dimensional carbons including WGO-CNTs and silica coated CNP-CNTs. Our multi-dimensional carbon nanostructures showed excellent electrochemical properties probably due to large surface area and unique geometry. These results suggest that the multi-dimensional carbon nanostructures could be promising in the applications for electrodes of next generation energy storage devices.

Thermo-electric figure of merit of quasi-two-dimensional Bi2Te3 nano-structures

Quasi-two dimensional nano-structures are characterized by radical changes in electron and phonon properties. Electron behavior in Q-2D nano-structures is modified by the presence of multiple sub-bands. For well widths smaller than 50 Å simplified model calculations based on the assumption of electrons occupying the lowest sub-band appears to be quite reasonable. For larger width others, parabolic sub-bands need to be considered. The present paper investigates the thermoelectric figure-of-merit of bismuth telluride which is five layered (Te-Bi-Te-Bi-Te) crystal with hexagonal symmetry with six equivalent valleys, in the range 40–300 Å and observe that for 100 Å well width three sub-band model and for 200 Å well width six sub-band model are good approximation at room temperature. Further it is observed that optimum carrier density for 200 Å well width is and maximum of ZT shifts towards lower concentration; and discusses the acceptability of single band approximation.

Seed layer effect on different properties and UV detection capability of hydrothermally grown ZnO nanorods over SiO2/p-Si substrate

Hydrothermally grown one dimensional ZnO nanostructures are among the most widely used semiconductor materials to build high-efficiency electronic devices for various applications. Few researchers have addressed the growth mechanism and effect of ZnO seed layer on different properties of ZnO nanorods grown by hydrothermal method, instead, no one has synthesized ZnO nanorod over SiO2/p-Si substrate. The aim of this study is to study the effect of ZnO seed layer and the growth mechanism of ZnO nanorods over SiO2/p-Si substrate. To achieve the goal, we have synthesized ZnO nanorods over different thickness ZnO seed layers by using the hydrothermal method on SiO2/p-Si substrate. The effects of c-plane area ratio were identified for the growth rate of c-plane, reaction rate constant and stagnant layer thickness also calculated by using a modified rate growth equation. We have identified maximum seed layer thickness for the growth of vertical ZnO nanorod. A step dislocation in the ZnO nanorods grown on 150and200nm thick seed layers was observed, the magnitude of Burges vector was calculated for this disorder. The seed layer and ZnO nanorods were characterized by AFM, XPS, UV-visible, XRD (X-ray diffraction, and SEM(scanning electron microscope). To justify the application of the grown ZnO nanorods Ti/Au was deposited over ZnO nanorods grown over all seed layers for the fabrication of photoconductor type UV detector.

Investigation of electron device based low dimensional nano structures

ABSTRACTNanowire is an important low dimensional semiconductor nano-material which can be used in field effect transistors, photovoltaic cells, field emission nanodevices, and chemical and gas sensors. In this paper, CuO nanowires are synthesized by heating copper substrates in air, and the CuO nanowire is assembled on two opposite microelectrodes to fabricate a single CuO nanowire nanodevice by dielectrophoresis (DEP). In experiment, suitable parameters are chosen, such as concentration of the CuO nanowire solution, applied voltage and frequency on the microelectrodes, time of DEP duration, to assemble a single CuO nanowire on the microelectrode. Using this single nanowire nanodevice, this paper measured FET effect and photoconductivity of the single CuO nanowire. The results show that the single CuO nanowire nanodevice can work as a FET and it also has novel sensitivity to light intensity.

Triple Ni-Co-Mo metal sulfides with one-dimensional and hierarchical nanostructures towards highly efficient hydrogen evolution reaction

Designing multi-transition metal-based sulfides holds promising in alkaline water electrolysis, whereas selecting proper candidates and facile building strategy remain challengeable. Herein, based on previous theory of combining 3d-transition metal (NiCo) with non-3d-transition metal (Mo) to lower hydrogen-adsorption energy barriers, we develop an indirect access to NiCoMo sulfides supported by nickel foam (CoMoO-S/NF) with one dimensional (1 D) and hierarchical nanostructures. In the first step, the metal oxides as precursor frameworks are designed as one-dimensional (1 D) nanostructures comprising interwoven nanosheets. The unique structure not only provides the large surface areas for exposing abundant active sites, but also improves the contact between catalyst/interface and facilitates the mass or charge transportation. Besides, the ternary metals are supposed to generate synergistic effect to boost hydrogen evolution reaction (HER) properties of CoMoO-S/NF via sulfurization in the second step. Furthermore, CoMoO-S/NF demonstrates high electrocatalytic performances with structural stability in long-term HER process. Therefore, the two-step building of ternary transition metal sulfides may be provide applications for various transition metal materials with unique architecture and high efficiency in alkaline HER.

Additive assisted hydrothermal synthesis, characterization and optical properties of one dimensional DyPO4:Ce3+ nanostructures

One dimensional nanostructures of cerium doped dysprosium phosphate (DyPO4:Ce3+) were synthesized via hydrothermal route in the presence of different surfactants [sodium dodecyl sulfate (SDS), dodecyl sulfosuccinate (DSS), polyvinyl pyrollidone (PVP)] and solvent [ethylene glycol and water]. The prepared nanostructures were characterized by Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV-VIS-NIR absorption spectrophotometer and photoluminescence (PL) studies. The PXRD and FTIR results indicate purity, good crystallinity and effective doping of Ce3+ in nanostructures. SEM and TEM micrographs display nanorods, nanowires and nanobundles like morphology of DyPO4:Ce3+. Energy-dispersive X-ray spectra (EDS) of DyPO4:Ce3+nanostructures confirm the presence of dopant. UV-VIS-NIR absorption spectra of prepared compounds are used to calculate band gap and explore their optical properties. Luminescent properties of DyPO4:Ce3+ was studied by using PL emission spectra. The effect of additives and solvents on the uniformity, morphology and optical properties of the nanostructures were studied in detail.

Few layer graphene wrapped mixed phase TiO2 nanofiber as a potential electrode material for high performance supercapacitor applications

A combination of favorable composition and optimized anatase/rutile mixed-phase TiO2 (MPTNF)/Hydrogen exfoliated graphene (HEG) composite nanofibers (MPTNF/HEG) and anatase/rutile mixed-phase TiO2/reduced graphene oxide (rGO) composite nanofibers (MPTNF/rGO) have been reported to enhance the electrochemical properties for supercapacitor applications. These composite nanofibers have been synthesized by an efficient route of electrospinning together with the help of easy chemical methods. Both the composites exhibit good charge storage capability with enhanced pseudocapacitance and electric double-layer capacitance (EDLC) as confirmed by cyclic voltammetry studies. MPTNF/HEG composite showed maximum specific capacitance of 210.5 F/g at the current density of 1 A/g, which was mainly due to its availability of the more active sites for ions adsorption on a few layers of graphene wrapped TiO2 nanofiber surface. The synergistic effect of anatase/rutile mixed phase with one dimensional nanostructure and the electronic interaction between TiO2 and few layer graphene provided the subsequent improvement of ion adsorption capacity. Also exhibit excellent electrochemical performance to improve the capacitive properties of TiO2 electrode materials which is required for the development of flexible electrodes in energy storage devices and open up new opportunities for high performance supercapacitors.

Tunnel injection transistor laser for optical interconnects

Transistor laser (TL) is already an established potential candidate for high speed optical interconnects and present day optical communication networks. This paper investigates theoretically the possibility of having lower base threshold current density and enhanced modulation bandwidth by inserting a tunnel injection structure in a TL having multiple quantum wells (MQW) in the base of the heterojunction bipolar transistor. Transfer of injected charge carriers from bulk to low dimensional nano-structure is assumed to occur via virtual energy states, which contributes to the terminal current. Small signal modulation response is obtained by solving the Statz–De Mars laser rate equations. The optimum threshold base current, confinement of carrier, light power outputs etc. are estimated for three QWs positioned at distances of 39, 59, and 79 nm from the emitter-base junction across the base. Incorporation of tunneling structure substantially lowers the base threshold current and increases the modulation bandwidth as compared to usual MQW transistor laser structure. The changes are more prominent with increasing tunneling probability.

Cured polysiloxane-boron nitride composite as novel precursor for SiBCN nanostructures

SiBCN nanostructures were produced by the pyrolysis silicone polymers reinforced using boron nitride (BN) and cured by hydrosilylation route. The base polymers used were low molecular weight vinyl terminated poly(dimethyl-co-diphenyl) siloxane (V-PMPS) and trimethylsilyl terminated poly(dimethyl-co-diphenyl-co-methyl hydrogen) siloxane (TMS-PMPHS). The composite was processed by compounding V-PMPS with BN filler followed by curing with TMS-PMPHS through platinum catalyzed hydrosilylation route. Pyrolysis of the reinforced polymer was carried out at different temperatures and the products were analysed by FTIR, Raman spectroscopy, FESEM and EDAX. It is found that one dimensional ceramic nanostructures were produced at a pyrolysis temperature of 1500 °C.

Construction of 0, 1, 2 and 3 dimensional SnO2 nanostructures decorated by NiO nanopetals: Structures, growth and gas-sensing properties

Different morphologies of SnO2 nanostructures, such as zero-dimensional (0D) nanoparticles (np), one-dimensional (1D) nanowires (nw), two-dimensional (2D) nanosheets (ns), and three-dimensional (3D) nanoflowers (nf) were synthesized by a user friendly and facile method just changing the kind of surfactant as morphology-director and structure-growth agent. NiO nanopetals (npe) were also synthesized by a direct precipitation method. Nanostructured SnO2-NiO hybrids with these four morphologies of SnO2 were also synthesized by a precipitation method. The structures, morphologies, and the surface area of the samples were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and surface area analyzer (using BET method), respectively. The surface area of the synthesized SnO2 nanostructures in the forms of particle, wire, sheet and flower were 45, 94, 11 and 33 m2 g−1, respectively. Gas sensing properties of these hybrid nanomaterials and the non-hybrid SnO2 were studied against ammonia gas. The hybrids showed much better performance, which could be related to the role of nickel oxide as a p-type semiconductor in these hybrids. Furthermore, the comparison between the sensitivities of these four hybrids indicated that SnO2 nw-NiO hybrid had the highest sensitivity and the shortest response time, most probably because of its highest surface area and porous structure. This wire-petal hetero-junction also showed good selectivity towards NH3 in presence of other gases including CO, NO, SO2, BTEX and ethanol.

Epoxy composites with functionalized molybdenum disulfide nanoplatelet additives.

As a typical layered inorganic analogue of graphene, molybdenum disulfide (MoS2) has gained intensive attention and become a research hotspot due to its unique two dimensional nanostructure and excellent properties. The enhancement in the thermal and mechanical properties of polymer/inorganic nanosheet composites depends strongly on their interfacial interaction. In this study, we exfoliated bulk MoS2 into nanosheets which were subsequently functionalized using 3-mercaptopropyltriethoxysilane. The functionalized MoS2 (f-MoS2) were dispersed in epoxy polymers at loading fractions of up to 1% by weight via ultrasonication and three roll mills. We characterized the tensile, fracture and adhesive properties of the composite and show that f-MoS2 nanoplatelets are highly effective at enhancing the mechanical properties of the epoxy at very low nanofiller loading fractions (0.1–0.7% by weight). Our results show the potential of functionalized 2D sheets of transition metal dichalcogenides as reinforcing additives in polymeric composites. The results indicate that the glass transition temperature increases significantly for the lower weight fraction composites, from 135 °C for the baseline (unfilled) epoxy to 146 °C at 0.7% f-MoS2 loading. The apparent shear strength at 120 °C increases significantly for the lower weight fraction composites, from 13.8 MPa for the baseline (unfilled) epoxy to 24.9 MPa at 0.7% f-MoS2 loading.

Gas sensing properties of 3D mesoporous nanostructured ZnO thin films

We successfully deposited a three dimensional (3D) mesoporous ZnO nanostructure on a glass substrate by using a hydrothermal method, and tested the material for its gas sensing performance.

One dimensional hierarchical nanostructures composed of CdS nanosheets/nanoparticles and Ag nanowires with promoted photocatalytic performance

One dimensional Ag@CdS core–shell hierarchical nanostructures with excellent photocatalytic performance have been fabricated via a simple wet-chemistry approach at low temperature.

Coupling effects in 3D plasmonic structures templated by Morpho butterfly wings.

This paper presents the study of the coupling effects of three dimensional (3D) plasmonic nanostructures templated by Morpho butterfly wings. Different from the random deposition of metallic nanoparticles (NPs) or conformal coating of metallic layers on butterfly wings reported previously, the 3D plasmonic nanostructures studied in this work consist of gold (Au) nanostrips quasi-periodically arranged in 3D, which allows us to investigate the plasmonic coupling effects. Through refractive index (RI) matching, the plasmonic coupling can be differentiated from the optical contribution of butterfly wings. By tuning the deposition thickness of Au from 30 to 90 nm, the plasmonic coupling effects between the 3D Au nanostrips are gradually enhanced. In particular, the near-field coupling results in two resonant modes and enhances the surface-enhanced Raman scattering (SERS) signals.

Titania Nanobelts as a Scattering Layer with Cu2ZnSnS4 as a Counter Electrode for DSSC with Improved Efficiency

Various nanostructures of Titania (TiO2) play a significant role in the performance of dye sensitized solar cells (DSSCs) and affect the overall light harvesting efficiency of the cells. In this article we present the one dimensional nanostructure of TiO2(nanobelts) can increase the light scattering effect, light harvesting effect and electron transport in the DSSC to improve its performance. Pure anatase TiO2 nanobelts were synthesized by a hydrothermal method using commercial material (P25) and characterized by XRD and SEM. Cu2ZnSnS4 (CZTS) nanoparticles have been prepared by thermal decomposition method used as counter electrode material instead of platinum. DSSC have been fabricated by using a new type of double layered photoanode, which was prepared and optimized by using TiO2 nanoparticles as the main layer and TiO2 nanobelts as the over-layer (scattering layer). The photoelectric conversion efficiency (PCE) of the prepared cells was measured by solar simulator under 1 sun illumination (100 mW/cm2, AM 1.5). The DSSCs with CZTS nanoparticles based counter electrodes without scattering layer relatively low PCE of 5.76 %. However, the PCE was clearly improved with scattering layer and a maximum PCE of 7.85% was achieved.

Impedance Of 3D Nanostructured MEAs: Influence of Coating and Cell Cultivation

Impedance Of 3D Nanostructured MEAs: Influence of Coating and Cell Cultivation

Mg-doped Li1.2Mn0.54Ni0.13Co0.13O2 nano flakes with improved electrochemical performance for lithium-ion battery application

Mg-doped Li1.2-xMgxMn0.54Ni0.13Co0.13O2 cathode materials were prepared by a molten salt method. Our results showed that the introduction of NaCl is rather important and will provide a fusion environment, which not only leads to an evenly distribution of the transition metals within the cathode materials but is also helpful for the formation of a unique two dimensional (2D) nano structures. Mg doping results in a structural variation of the cathode materials, leading to a continuous increase of the capacity at the first dozen cycles. Although Mg doping can significantly improve the rate capability, the cycling stability, and the capacity retention of the cathode materials, a large Mg doping amount (>6%) will cause the formation of impurity phases, which in turn reduce the electrochemical performance of the materials. Electrochemical impedance spectroscopy (EIS) measurement showed that the charge transfer resistance was reduced significantly due to Mg doping, and 4% Mg-doped sample exhibits promising lithium diffusion kinetics and rate capability.

Self-organized ZnMgO nanocolumns with ZnO/ZnMgO quantum wells on c-plane Al2O3 substrates by MBE: Growth conditions and properties

One dimensional zinc oxide nanostructures have great potential for applications in the fields of optoelectronic and sensor devices. In this paper, we present the synthesis of ZnO/ZnMgO heterostructures on c- plane Al2O3 by plasma-assisted molecular beam epitaxy and investigation of their structural and optical properties. We demonstrate that it is possible to grow a good quality nanocolumns on c- plane Al2O3 substrate without employing a catalyst such as Au or Ag. We have also studied a shift between polar- and nonpolar- ZnO/ZnMgO quantum wells. The non-polar a- plane ZnO/ZnMgO nanocolumns were achieved on r- plane sapphire substrate, while the on polar c-plane substrate was used to obtain a polar c-orientation of the nanostructures.

Nickel Nanowire@Porous NiCo2O4 Nanorods Arrays Grown on Nickel Foam as Efficient Pseudocapacitor Electrode

A three dimensional hierarchical nanostructure composed of nickel nanowires and porous NiCo2O4 nanorods arrays on the surface of nickel foam is successfully fabricated by a facile route. In this structure, the nickel nanowires are used as core materials to support high-pseudocapacitance NiCo2O4 nanorods and construct the well-defined NiCo2O4 nanorods shell/nickel nanowires core hierarchical structure on nickel foam. Benefiting from the participation of nickel nanowires, the nickel nanowire@NiCo2O4/Ni foam electrode shows a high areal specific capacitance (7.4 F cm-2 at 5 mA cm-2), excellent rate capability (88.04% retained at 100 mA cm-2) and good cycling stability (74.08% retained after 1500 cycles). The superior electrochemical properties made it promising as electrode for supercapacitors.

Fabrication of porous ZnCo2O4 nanoribbon arrays on nickel foam for high-performance supercapacitors and lithium-ion batteries

In order to meet the growing need for energy, much effort has been devoted to develop the powerful electrodes for electrical energy storage devices. Herein, we offer a facile and effective strategy to synthesize a versatile binder-free electrode for both supercapacitors and lithium-ion batteries, which are regarded as two major electrical energy storage devices. Using a one-step hydrothermal strategy followed by calcination treatment, the porous ZnCo2O4 nanoribbon arrays are successfully synthesized on nickel foam. With the favorable composition and three dimensional porous nanostructure, this advanced electrode demonstrates excellent cycling stability and rate capability. Moreover, a high specific capacitance of 1957.7 F g−1 (3 mA cm−2) is obtained for supercapacitors and a large reversible capacity of 1422 mA h g−1 is retained after 80 cycles at 200 mA g−1 for lithium-ion batteries. Our results suggest that the versatile ZnCo2O4 nanoribbon arrays/nickel foam electrode possesses great electrochemical performance and shows promising potential for large-scale application.