In this work, iron oxalate (FeC 2 O 4 ·2H 2 O) with different morphologies was synthesized through a simple solution-based direct precipitation process. Three samples with distinct morphologies, i.e., microrods with a parallelogram-like cross-section, nanorods, and multi-layered nanosheets, could be obtained in a selective manner. We found that the shapes of the iron oxalate could be controlled just through simply altering the solvents used. The one-dimensional (1D) characteristic of the infinite linear chains and the selective interaction between solvents and various crystallographic planes of FeC 2 O 4 ·2H 2 O played an important role in the formation of FeC 2 O 4 ·2H 2 O with different morphologies. Phase-pure hematite (α-Fe 2 O 3 ) had be obtained by annealing these as-prepared FeC 2 O 4 ·2H 2 O precursors without significant alterations in morphology….
Posts Tagged ‘formation’
Controlled synthesis of mesoporous hematite nanostructures and their application as electrochemical capacitor electrodes
Posted in Nanotechnology 
Tags: formation, important-role, iron-oxalate, linear-chains, Selective, shapes, simply-altering, solvents, the-formation, Work 
Comments OffSynthesis of SnS 2 nanoparticles by a surfactant-mediated hydrothermal method and their characterization
SnS 2 nanoparticles have been synthesized using a mild hydrothermal method in the presence of the surfactant sodium dodecyl sulfate (SDS) at 180 °C for 12 h. Physical investigations were carried out to study their structure, size, morphology and optical properties. The x-ray diffraction (XRD) pattern of the as-prepared sample is indexed to the hexagonal phase of SnS 2 and the particle size is 100 nm, which is further confirmed by transmission electron microscopy (TEM). The UV-visible spectrum shows that the absorption edge is blue shifted, and the band gap of the prepared SnS 2 nanoparticles has been evaluated with UV-visible spectroscopy to be 3.54 eV, which is larger than the bulk SnS 2 (~2.44 eV). The anionic surfactant SDS plays a key role in the formation of the 3D sphere like SnS 2 nanostructures. A probable reaction for the formation of nanocrystalline SnS 2 nanoparticles is proposed.
Posted in Nanotechnology Tags: Confirmed, formation, particle, particle-size, presence, spectrum-shows, surfactant, the-formation, the-hexagonal, the-surfactant Comments OffFlow-dependent directional growth of carbon nanotube forests by chemical vapor deposition
We demonstrated that the structural formation of vertically aligned carbon nanotube (CNT) forests is primarily affected by the geometry-related gas flow, leading to the change of growth directions during the chemical vapor deposition (CVD) process. By varying the growing time, flow rate, and direction of the carrier gas, the structures and the formation mechanisms of the vertically aligned CNT forests were carefully investigated. The growth directions of CNTs are found to be highly dependent on the nonlinear local gas flows induced by microchannels. The angle of growth significantly changes with increasing gas flows perpendicular to the microchannel, while the parallel gas flow shows almost no effect. A computational fluid dynamics (CFD) model was employed to explain the flow-dependent growth of CNT forests, revealing that the variation of the local pressure induced by microchannels is an important parameter determining the directionality of the CNT growth. We expect that the pre…
Posted in Nanotechnology Tags: carbon-nanotube, chemical-vapor, directionality, flows-induced, formation, geometry, increasing-gas, Structural, Structures, the-structures, variation Comments OffControlling spatial density and size of nanocrystals by two-step atomic layer deposition
Two-step atomic layer deposition (ALD) is proposed in order to control both the spatial density and size of nanocrystals (NCs) via modulation of the nucleation rate during deposition. In this process, two different deposition conditions are sequentially used: a high nucleation rate condition for the formation of high density NCs and a low nucleation rate condition with a slow growth rate for the subsequent growth of pre-formed NCs. To control the nucleation rate of Ru during ALD, pulsing time and carrier flow rate of the Ru precursor are varied. By controlling those factors, both the film growth rate and a nucleation rate of Ru are decreased considerably. Two-step ALD of Ru NCs using the surface-saturated condition followed by the reduced condition allows for variation of the spatial density from 7.9 × 10 11 to 3.2 × 10 12 cm − 2 and variation of the average diameter from 1.9 to 3.3 nm.
Posted in Nanotechnology Tags: both-the-film, formation, high-nucleation, low-nucleation, nucleation-rate, rate-condition, reduced, spatial, subsequent, Surface, the-nucleation, the-subsequent, via-modulation Comments OffFacile one-pot synthesis of near-infrared luminescent gold nanoparticles for sensing copper (II)
Novel near-infrared luminescent gold nanoparticles (NIRL-AuNPs) were synthesized by a simple, rapid and one-pot procedure. The driving force for the formation of these NIRL-AuNPs was attributed to the heat-assisted reduction of a gold(I)–thiol complex. These gold nanoparticles were characterized by TEM, DLS, FT-IR and XPS. Luminescence studies indicated that these NIRL-AuNPs exhibited strong emission with peak maximum at 810 nm, microsecond-range photoluminescence lifetime, large Stokes shifts (> 400 nm) and stabilities towards photobleaching and chemical oxidation. The sensing application for Cu 2 + ions of these NIRL-AuNPs was demonstrated. These as-synthesized gold nanoparticles will provide a new NIRL nanomaterial for in vitro and in vivo applications.
Posted in Nanotechnology Tags: dls, driving-force, formation, gold-nanoparticles, Heat, maximum-at-810, nirl, peak-maximum, stokes, tem, will-provide, xps Comments OffElectron-beam-induced deposition and post-treatment processes to locally generate clean titanium oxide nanostructures on Si(100)
We have investigated the lithographic generation of TiO x nanostructures on Si(100) via electron-beam-induced deposition (EBID) of titanium tetraisopropoxide (TTIP) in ultra-high vacuum (UHV) by scanning electron microscopy (SEM) and local Auger electron spectroscopy (AES). In addition, the fabricated nanostructures were also characterized ex situ via atomic force microscopy (AFM) under ambient conditions. In EBID, a highly focused electron beam is used to locally decompose precursor molecules and thereby to generate a deposit. A drawback of this nanofabrication technique is the unintended deposition of material in the vicinity of the impact position of the primary electron beam due to so-called proximity effects. Herein, we present a post-treatment procedure to deplete the unintended deposits by moderate sputtering after the deposition process. Moreover, we were able to observe the formation of pure titanium oxide nanocrystals (
Posted in Nanotechnology Tags: atomic-force, Deposition, electron-beam, formation, highly-focused, Impact, primary, the-fabricated, the-primary, the-unintended, under-ambient Comments OffStructural and optical properties of InGaN/GaN nanowire heterostructures grown by PA-MBE
The structural and optical properties of InGaN/GaN nanowire heterostructures grown by plasma-assisted molecular beam epitaxy have been studied using a combination of transmission electron microscopy, electron tomography and photoluminescence spectroscopy. It is found that, depending on In content, the strain relaxation of InGaN may be elastic or plastic. Elastic relaxation results in a pronounced radial In content gradient. Plastic relaxation is associated with the formation of misfit dislocations at the InGaN/GaN interface or with cracks in the InGaN nanowire section. In all cases, a GaN shell was formed around the InGaN core, which is assigned to differences in In and Ga diffusion mean free paths.
Posted in Nanotechnology Tags: all-cases, around-the-ingan, been-studied, diffusion-mean, formation, ingan, molecular-beam, strain, the-formation, the-strain Comments OffNanostructuring discotic molecules on ITO support
Patterning of organic compounds on a nanometer length scale is of great interest for solar applications: defined control over the donor–acceptor interface will allow design of an optimized nano-morphology promoting exciton separation and reducing charge recombination. Herein we present an imprinting technique using anodized alumina oxide (AAO) hard templates as stamps. We show an exact pattern transfer of the AAO structures into a solution processable hexa- peri -hexabenzocoronene (HBC), a discotic small molecule with acrylate moieties which is polymerized in situ . Film fabrication is realized for a variety of nanowire dimensions on square centimeter areas. The fabrication directly on conductive glass support and control over the formation of a dense barrier layer render this approach appealing for the fabrication of fully organic nanostructured photovoltaic devices.
Posted in Nanotechnology Tags: Approach, defined-control, donor, exact-pattern, formation, fully-organic, great-interest, over-the-donor, reducing-charge, the-formation, using-anodized Comments OffPhotoluminescent silicon quantum dots in core/shell configuration: synthesis by low temperature and spontaneous plasma processing
Quantum confinement in zero-dimensional silicon nanocrystals (nC) in the quantum dot (QD) configuration has triggered a tremendous interest in nanostructured device technology. However, the formation of Si-QDs eventually proceeds through multi-step routes and involves high temperature processing that impedes preferred device configuration. The present work demonstrates the formation of nC-Si QDs of controlled size, density and distribution through one-step and spontaneous plasma processing, at a low substrate temperature (300 °C) compatible for device fabrication. Direct growth of nC-Si/SiO x core/shell quantum dots embedded in the a-Si matrix, 6.4–3.7 nm in diameter and with number density in the range ~ 6 × 10 9 –1 × 10 11 cm − 2 has been accomplished, following a novel route where He dilution to SiH 4 in RF plasma CVD has been found instrumental. On gradual reduction in the size of QDs, splitting of the energy bands wide…
Posted in Nanotechnology Tags: controlled-size, dots-embedded, formation, low-substrate, novel-route, Quantum, shell-quantum, the-quantum Comments OffA structural investigation of highly ordered catalyst- and mask-free GaN nanorods
GaN nanorods were grown on r -plane sapphire substrates by a two-step approach. Nucleation sites for the nanorods were provided by the formation of AlN islands during nitridation in a metal organic vapor phase system. These islands are a -plane oriented as expected for nitride growth on r -plane sapphire. The nanorods themselves were grown by plasma assisted molecular beam epitaxy. The nanorods show an inclination towards the surface normal of 28.3° and are highly ordered. Studies with high resolution x-ray diffraction polar plots reveal the epitaxial relationship between the substrate and nanorods as a c -direction growth on inclined m -plane facets of the nitridated islands. The determined lattice constants show nanorods which are strain free. The growth direction of the nanorods has been confirmed in a transmission electron microscope by convergent beam electron diffraction patterns to be in the N-polar ##IMG## {[000bar {1}]}
Posted in Nanotechnology Tags: convergent-beam, epitaxial, formation, islands-during, molecular-beam, nanorods, nanorods-were, nanorods-which, nitridated, nitride-growth, plasma-assisted, substrate, surface-normal, the-nanorods, the-nitridated Comments Off