Growth Of Rods Research Articles

Forming extremely smooth ZnO thin film on silicon substrates for growth of large and well-aligned ZnO rods with the hydrothermal method

Sol–gel zinc oxide (ZnO) thin films generally have non-uniform stripes. After annealing at high temperatures, these thin films are rough and granular. When ZnO rods are grown on such rough and non-uniform surface with the hydrothermal method, collimation, crystalline structure, and defect density are very poor. Here we explore a method to solve this problem. The ZnO thin film is first coated with an Au layer to prohibit the vertical extension of crystallization during the annealing period. As a result, the surface morphology of ZnO thin film is very flat and uniform after annealing. Afterwards, the ZnO rods are grown on the flat and uniform thin film, which gives rise to ZnO rods with very good collimation and crystalline structure. The extremely flat ZnO thin film even enables the fabrication of patterned ZnO rod arrays with regular shapes through lithography.

Thermochemical analysis on the growth of NiAl2O4rods

We have succeeded in growing cubic submicron-sized NiAl2O4 rods on sapphire substrates by means of heating a mixture of NiO and graphite powders. At 1600 °C, NiAl2O4 rods terminated by SiOx-containing nanoparticles were grown on the sapphire substrates. In contrast, NiO rods grew randomly at 1500 °C. We elucidated the growth steps of cubic NiAl2O4 submicron-sized rods on the basis of a thermochemical approach, revealing the critical role of liquid silica that blocks the continuous loss of Ni to the vapor phase for the successful growth of NiAl2O4 rods.

In-Situ Electron Microscope Observations of Electrochemical Li Deposition/Dissolution with a LiPON Electrolyte

This paper studies the effect of current density on electrochemical Li deposition/dissolution at glassy solid electrolyte (LiPON) interfaces with a thin-film Cu current collector by in-situ scanning electron microscopy (SEM). The Li nucleation rate and the saturation density of Li nuclei increase with increasing current density. When the current density is smaller than 300 µA cm−2, Li islands continue to separately grow under a Cu film to the critical sizes to produce small cracks in the Cu film resulting in isolated Li rod growth from the cracks. On the other hand, a current density of 1.0 mA cm−2 provokes the nucleation of Li islands at a number of sites. They rapidly coalesce under a Cu film in all lateral directions before cracking the Cu film, whereby Li growth is prevented.

Crystal growth of Gd2PdSi3 intermetallic compound

Gd2PdSi3 single crystals were grown by a vertical floating zone method with radiation heating at a zone traveling rate of 3 mm/h. The compound exhibited congruent melting behavior at a liquidus temperature of about 1700 °C. The slightly Pd-depleted composition of the crystal, with respect to the nominal Gd2PdSi3 stoichiometry, led to gradual accumulation of Pd in the traveling zone and to a decreasing operating temperature during the growth process. Thin platelet-like precipitates of a GdSi phase were detected in the stoichiometric feed rod growth crystal matrix which can be reduced by annealing treatment. Feed rod composition shift crystal growth was proved to be a better way of getting high quality of Gd2PdSi3 single crystal.

Growth of ZnO rods on FTO electrodes by spray pyrolysis

ZnO layers comprizing rods were deposited by chemical spray pyrolysis (CSP) method at 520 °C on different FTO (SnO2:F)/glass substrates using zinc chloride aqueous solutions. Substrates were purchased from different manufactures and differ by morphology, grain size and roughness of FTO electrode. FTO/glass substrates and ZnO layers grown on them were characterised with the help of XRD, AFM, high resolution SEM, EDX methods. The relationship between nanorod formation and substrate properties was studied. It was found that substrate roughness and grain size influence the ZnO rods formation. Deposition of rods (d=300 nm, L=1.4 μm) was successful on the FTO layers with grain sizes around 30–50 nm and roughness below 10 nm, whereas large-grained FTO (grain size > 130 nm) resulted in thick, low-aspect ratio crystals with diameter around 400 nm and length of about 400 nm.

Influence of the gas phase composition on the properties of bimetallic Ag/Cu nanomaterials obtained via chemical vapor deposition

The carboxylate compounds [Ag(μ-O2CC2F5)]n and [Cu{CH2C(H)SiMe3}(μ-O2CC2F5)]m were used as precursors in chemical vapor deposition (CVD) for the preparation of bimetallic Ag/Cu nanomaterials. The composition and thermal stability of the copper and silver species transported in the gas phase were studied using mass spectrometry (EI-MS) and variable-temperature IR spectroscopy. The bimetallic [AgCu(O2CC2F5)2] carboxylate, which influences the properties of the resulting materials, was formed in the gas phase. The growth of rods and large copper grains on the silver surface was observed. Analyzing the morphology using scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicated that the nAg/nCu molar ratio determined the composition of the gas phase, which affected the structure, grain size, and packing density of the Ag/Cu materials.

Incorporation of silver-loaded ZnO rods into electrospun nylon-6 spider-web-like nanofibrous mat using hydrothermal process

Silver-doped zinc oxide rods were incorporated in a nylon-6 electrospun mat by a facile hydrothermal process. The rods exhibited excellent characteristics as a durable filter media with good antibacterial properties. ZnO nano-seeds blended with a nylon-6 solution were typically able to form ZnO-NPs-embedded spider-web-like nanonets during electrospinning. The simultaneous crystal growth of Ag NPs and ZnO rods from their precursor solutions on the surface of as-fabricated electrospun ZnO/nylon-6 fibers was carried out via a hydrothermal process. FE-SEM, TEM, UV–visible spectra, and photoluminescence spectra not only confirmed the formation of ZnO-nano-seeds-loaded electrospun nylon-6 composite fibers but also showed that ZnO rods doped with Ag NPs (approximately 50nm in size) were grown on the surface of the nylon-6 composite fibers during hydrothermal treatment. The antibacterial properties of different mats were tested against Escherichia coli. The as-synthesized Ag-NP-loaded nanocomposite revealed better antibacterial properties than those of composite mat without Ag NPs. The excellent stability of Ag-loaded ZnO rods (caused by ZnO nano-seeds) on the surface of electrospun fibers provides a new dimension in the fabrication of inorganic/organic nanocomposite.

A Phenomenological Model for the Adaptative Biomechanical Response of Growing Tree

Modelling the shape evolution of growing trees requires to account for the interaction between growth and adaptative biomechanical response to its environment. Trees develop growth strategies to ensure light and nutrient capture as stability. These strategies are linked with the branching process and shape evolution of the exisiting branches or stem. Unlike growth of bones and soft tissues where the change in volume originates from the insertion of new particles within the continuum, growth in trees is modeled by the addition of new material points on an existing deformed structure. Most of the existing models adopt an incremental approach and propose the equilibrium of the growing structure to be reached at each time after growth has occured, thus separating growth and mechanical effects. Guil lon et al. [1, 2] have origninally proposed a new formalism to model the time-space continuous growth of rod with applications to tree-like struc tures. The purpose of this work is to advance some thermodynamically consistent constitutive relations describing the biomechanical response of the continuously radially growing section. In particular, we introduce an internal variable which aims at accounting for the adaptative structure of the (growing) woody stem section. We present an existence analysis for both the constitutive relation problem and the quasi-static evolution problem.

Growth of Zinc Oxide Rods in Different Heating Medium

In this investigation, it was successfully shown that variation of heating media for infused substrates in precursor solution, affects the growth density and size of nanostructured ZnO rods. ZnO rods were prepared by precipitation on a template of cleaned p-type silicon wafer, sputter-coated with a thin layer of gold, infused in prepared precursor solution. The precursor solution consists of 0.01M zinc nitrate hexahydrate (Zn(NO3)2.6H2O) added with equal concentration of stabilizer hexamethylenetetramine, C6H12N4 (HMTA). The set-up was heated in water-bath or dry-oven at a constant low temperature of 80°C. Structural images of the prepared ZnO rods were captured using scanning electron microscope (SEM), its structural phase orientation was characterized by x-ray diffraction (XRD) and its optical property was analyzed from photoluminescence (PL) emission spectra.

Solution growth of spherulitic rod and platelet calcium phosphate assemblies through polymer-assisted mesoscopic transformations

Solution growth of apatite its precursors in the presence of urea commercial gelatin is found to lead, under appropriate conditions, to a rich spectrum of morphologies, among them high aspect ratio needles in uniform sturdy spherulitic assemblies resulting from a herein documented morphological ‘Chrysalis Transformation’; the latter transformation involves the growth of parallel arrays of high aspect ratio needles within micron-scale tablets the formation of a radial needle arrangement upon disruption of tablet wrapping. A different level of gelatin leads to the formation of sturdy platelet-based spherulites through another morphological transformation. We also probe the role of four simple synthetic water-soluble polymers; we find that three of them (poly(vinyl alcohol), polyvinylpyrrolidone and polyacrylamide)) also affect substantially the assembly habits of apatite; the effect is similar to that of gelatin but the attained control is less perfect/complete. The case of poly(vinyl alcohol) provides, through variation of the degree of hydrolysis, insights as regards the chain architecture features that might favor morphological transformations. Morphological transformations of particle assemblies documented herein constitute novel ways of generating dense quasi-isotropic reinforcements with high aspect ratio ceramic particles; it becomes possible to tailor calcium phosphate phases at the structural level of crystal assembly.

Ag nanostructures with various shapes created through degradation of rods

We developed a facile method (a polyol synthesis) to prepare uniform silver nanostructures with various morphologies using ethylene glycol (EG) reduction of silver nitrate at 120 °C in the presence of poly(vinyl pyrrolidone) (PVP) and NaCl. Ag rods were fabricated by simply aging the freshly prepared AgNO3 solution with PVP, EG, and NaCl under ambient atmosphere without changing other parameters. The formation and degradation of the rods were systematically investigated. The result indicates that twinned-crystal seeds play an important role for the growth of anisotropic Ag rods. The NaCl concentration in solutions affected the formation of the rod. The rod was degraded subsequently via an etching process of O2/Cl¯ (NaCl), resulting in the formation of Ag nanostructures with various shapes. Twinned Ag seeds in solutions were etched by increasing the concentration of NaCl, yielding uniform Ag cubes. Regular Ag cubes were fabricated under optimal preparation conditions. Ag cubes with various sizes (150–600 nm) were created by adjusting PVP concentrations in solutions.

Selective Growth of GaN Rods on the Apex of GaN Pyramids by Metal Organic Vapor Phase Epitaxy

We report on the growth and characterization of GaN rods selectively grown on the apex of hexagonal GaN pyramids. SiO2 near the apex of the hexagonal GaN pyramids was removed by an optimized photolithography process and subsequently subjected to Au deposition and selective growth of GaN rods by metal organic vapor phase epitaxy (MOVPE). It was observed that there were preferred GaN rods orientations toward <1100> directions. The GaN rods had triangular cross section enclosed with (1122), (1122), and (0001) side facets. A particular feature was that each rod has sharp edge at its very end. We found that the GaN rods could be formed not by vapor–liquid–solid (VLS) process but Ga–Au intermediate state. This work opens up new growth methods for position and density controlled III–nitride nano- and micro-structures which have potential use in high functional devices, such as field emitters and gas sensors.

Electrodeposition of a novel CdTe array on Ni foils and photoelectrochemical performance

A novel perpendicularly aligned CdTe array with cauliflower-like morphology was fabricated on a Ni substrate using a simple electrochemical synthesis method. The samples were characterized by XRD, EDX and FESEM, and the results demonstrate that a high-purity, uniform cauliflower-like CdTe array was obtained. Rod lengths can reach to 3.0 μm, with nanoparticles stacking along the rod growth direction, keeping the diameter at 1.5 μm. A schematic diagram of the possible growth process and evolution from CdTe seed nuclei to the cauliflower-like CdTe array was proposed. The device based on the aligned array-on-Ni configuration demonstrates excellent photoelectrical properties, which is ascribed to the large absorption coefficient of the material and also suggests good electronic structure quality of the cauliflower-like rods. The technique described is applicable to fabricate highly aligned cauliflower-like semiconductor arrays on other conductive substrates.

Dependence of N-polar GaN rod morphology on growth parameters during selective area growth by MOVPE

Selective area growth of GaN rods by metalorganic vapor phase epitaxy has attracted great interest due to its novel applications in optoelectronic and photonics. In this work, we will present the dependence of GaN rod morphology on various growth parameters i.e. growth temperature, H2/N2 carrier gas concentration, V/III ratio, total carrier gas flow and reactor pressure. It is found that higher growth temperature helps to increase the aspect ratio of the rods, but reduces the height homogeneity. Furthermore, H2/N2 carrier gas concentration is found to be a critical factor to obtain vertical rod growth. Pure nitrogen carrier gas leads to irregular growth of GaN structure, while an increase of hydrogen carrier gas results in vertical GaN rod growth. Higher hydrogen carrier gas concentration also reduces the diameter and enhances the aspect of the GaN rods. Besides, increase of V/III ratio causes reduction of the aspect ratio of N-polar GaN rods, which could be explained by the relatively lower growth rate on (000-1) N-polar top surface when supplying more ammonia. In addition, an increase of the total carrier gas flow leads to a decrease in the diameter and the average volume of GaN rods. These phenomena are tentatively explained by the change of partial pressure of the source materials and boundary layer thickness in the reactor. Finally, it is shown that the average volume of the N-polar GaN rods keeps a similar value for a reactor pressure PR of 66 and 125mbar, while an incomplete filling of the pattern opening is observed with PR of 250mbar. Room temperature photoluminescence spectrum of the rods is also briefly discussed.

The Protease Degrading Sperm Histones Post-Fertilization in Sea Urchin Eggs Is a Nuclear Cathepsin L That Is Further Required for Embryo Development

Proteolysis of sperm histones in the sea urchin male pronucleus is the consequence of the activation at fertilization of a maternal cysteine protease. We previously showed that this protein is required for male chromatin remodelling and for cell-cycle progression in the newly formed embryos. This enzyme is present in the nucleus of unfertilized eggs and is rapidly recruited to the male pronucleus after insemination. Interestingly, this cysteine-protease remains co-localized with chromatin during S phase of the first cell cycle, migrates to the mitotic spindle in M-phase and is re-located to the nuclei of daughter cells after cytokinesis. Here we identified the protease encoding cDNA and found a high sequence identity to cathepsin proteases of various organisms. A phylogenetical analysis clearly demonstrates that this sperm histone protease (SpHp) belongs to the cathepsin L sub-type. After an initial phase of ubiquitous expression throughout cleavage stages, SpHp gene transcripts become restricted to endomesodermic territories during the blastula stage. The transcripts are localized in the invaginating endoderm during gastrulation and a gut specific pattern continues through the prism and early pluteus stages. In addition, a concomitant expression of SpHp transcripts is detected in cells of the skeletogenic lineage and in accordance a pharmacological disruption of SpHp activity prevents growth of skeletal rods. These results further document the role of this nuclear cathepsin L during development.

Precursor and Oxygen Dependence of the Unidirectional, Seeded Growth of CdSe Nanorods

It was recently shown that, by controlling the O(2) concentration, the seeded-growth of CdSe nanocrystals (NC) can be manipulated to proceed either unidirectionally (from the (0001) facet) or three-dimensionally. In this contribution, we investigate two new Se precursors (i.e. SeO(2) and NaHSe) and compare them with Se obtained from etching of smaller NC seeds. Under anaerobic conditions, both precursors led to successful 3-dimensional (3D) NC growth. At high O(2) concentrations, the seeded growth of rods was enhanced by the NaHSe precursor, while impeded by the use of SeO(2). Mechanistic studies showed that the reduction of SeO(2) to Se(2-) produces an excessive amount of O(2). This leads to rod fragmentation due to etching as well as the production of deep traps that quench their luminescence. These new precursors, along with a heightened understanding of oxygen's role, expand the synthetic repertoire of the redox-assisted, seeded-growth of CdSe and better position this low temperature (125 °C) methodology towards realizing advanced NC heterostructures.

Morphoelastic rods. Part I: A single growing elastic rod

A theory for the dynamics and statics of growing elastic rods is presented. First, a single growing rod is considered and the formalism of three-dimensional multiplicative decomposition of morphoelasticity is used to describe the bulk growth of Kirchhoff elastic rods. Possible constitutive laws for growth are discussed and analysed. Second, a rod constrained or glued to a rigid substrate is considered, with the mismatch between the attachment site and the growing rod inducing stress. This stress can eventually lead to instability, bifurcation, and buckling.

Melioidosis: an unusual cause of recurrent buttock abscesses

An 18-year-old woman presented to Mahosot Hospital, Vientiane with a 3-year history of widespread abscess formation and significant scarring of her left buttock. The patient was a rice farmer from Saravan Province. The lesion had initially started as a small painless pustule, without preceding trauma or injection. It had grown in size, and had been treated with incision and drainage and a week’s course of ampicillin. However, the lesion persisted, and further abscesses developed despite subsequent (self-initiated) ampicillin therapy and treatment from a traditional Lao healer. The patient remained systemically well throughout with no fever or other symptoms. On physical examination, areas of atrophic scarring, induration, and discharging sinuses were seen on the patient’s left buttock (Fig. 1). The remainder of the buttock area was clear, and the rest of the clinical examination was unremarkable. Figure 1 Cutaneous melioid affecting the buttock. Blood tests revealed that the patient had microcytic anaemia, with haemoglobin 8.2 g/L (normal range 11.5–16.5 g/L) and mean corpuscular volume 50 fL (80–96 fL). Glucose and creatinine were within normal ranges, and screening for thalassaemia gave negative results. There was no growth from two sets of blood cultures. A pus culture yielded a pure growth of an oxidase-positive Gram-negative rod with a metallic sheen on blood agar, which was confirmed as Burkholderia pseudomallei by a biochemical test kit (API20NE; bioMerieux, Marcy L’Etoile, France). A chest radiograph was normal, but abdominal ultrasonography identified splenic microabscesses (Fig. 2). A fistulogram of the left buttock demonstrated no connection with underlying deep structures (Fig. 3). Ultrasonography of the buttock revealed a collection of pus within the soft tissue, 80 × 10 mm in size, which was drained percutaneously. Figure 2 Ultrasound scan of splenic microabcesses. Figure 3 Fistulogram of buttock lesion. A diagnosis of melioidosis was made, and the patient was treated with intravenous ceftazidime (2 g three times daily) for 3 weeks because of the delay in abscess drainage, evidence of splenic involvement and persistently culture-positive pus samples. The patient was discharged on a combination of oral cotrimoxazole (240/1200 mg twice daily) and doxycycline (200 mg once daily) for a further 16 weeks. At 3 months, there was marked improvement, with only one small sinus present without significant pus discharge. A swab of the site was culture-negative. Melioidosis is the clinical manifestation of infection with B. pseudomallei, a ubiquitous saprophytic environmental bacterium that resides in the water and soil of predominantly tropical climates, most notably south-east Asia and northern Australia.1 The area from where the patient originated, Saravan Province, is know to have a high prevalence of B. pseudomallei in the soil. Typically, infection occurs when working closely with soil, such as in paddy fields. Direct inoculation through breaks in the skin barrier and inhalation are recognized modes of transmission. Systemic disease, with or without dissemination, is typical, but localized cutaneous and soft-tissue disease is well described, and accounts for around 12–24% of clinical presentations of melioidosis.2 Skin presentations include subcutaneous abscesses, pustules, wound infections, cellulitis, and granulomatous lesions. Mortality ranges from 20% to 50% in Australia and Thailand, respectively.3 Although melioidosis is almost exclusively a disease of tropical climates, sporadic imported cases do occur among both immigrants and adventure tourists.4 This case was particularly interesting because of the extensive nature of the disease and long history, resulting in significant scarring that is unlikely to improve with treatment.

Annealing Effect on the Surface Morphology and Photoluminescence Properties of ZnO Hexagonal Rods by Immersion Method

ZnO hexagonal rod structure were prepared by immersion method deposited onto Si (Si/ZnO) and gold-seeded Si substrate (ZnO/Au/Si). The annealing temperatures were varied from 400, 500 and 600 °C. The effect of annealing temperature on the surface morphology and photoluminescence characteristics was investigated. The samples were characterized by Field Emission Scanning Electron Microscope (FESEM) to study their morphology and structural properties while the optical properties were characterized at room temperature using Photoluminescence Spectroscopy. The shape of ZnO showed growth of rods with hexagonal shape. As the annealing temperature increased, the morphology study indicates that diameter size of ZnO decreased while the crystallinity increases. The structures has high surface area, is a potential metal oxide nanostructures to be develop for optoelectronic devices and chemical sensors.

Vertically Oriented Iron Oxide Films Produced by Hydrothermal Process: Effect of Thermal Treatment on the Physical Chemical Properties

Our study describes the influence of the thermal treatment on the fundamental properties of the vertical oriented iron oxide nanorods synthesized under hydrothermal condition onto a conductor substrate. X-ray diffraction and X-ray absorption near edge structure spectra were used to investigate the phase evolution from iron oxyhydroxide (β-FeOOH) to pure hematite phase. The formation of nanorods distributed along of substrate was observed by top-view SEM images and the rod growth preferentially oriented at the highly conductive (001) basal plane of hematite, perpendicular to the substrate. Light absorption capacity increases with the temperature of treatment and the electronic transitions (direct and indirect electronic transition) were estimated from this result. From the electrochemical measurement, the hematite/electrolyte interface was evaluated. These findings demonstrated that the temperature plays an important role on the hematite (structural, morphological, and catalytic) properties and that many influences must work in great harmony in order to produce a promising hematite photoanode.