Growth Mechanism Of Nanorods Research Articles

Large-Scale Synthesis of ZnO Nanorods Bundles by Microwave Heating Method: Growth Mechanism and Possibility of Controllable Growth of Nanoneedle

This paper has presented a novel method for the synthesis of regular and reproductive ZnO nanostructures by microwave heating. Unlike the previous studies, it has focused on ZnO nanostructures grown on the Si wafer used as a cover rather than on the precursor top and the results show that ZnO nanostructures with different shapes depending on the amount of mixture and the position in the Si wafer grow on the regular and reproductive basis. In the center of the Si wafer, short and coarse ZnO nanorods have grown, and on the outer edges, the structure of bundles consisting of ZnO nanorods with much longer lengths and smaller diameters has been synthesized. Morphology of ZnO nanorods was characterized by using scanning electron microscope and the nanorods grown on the outer edges had a mean diameter of 200[Formula: see text]nm and were up to [Formula: see text]m long. In order to elucidate the growth mechanism of nanorods, we have carried out SEM, energy dispersive spectrometer (EDS) and XRD characterization, which shows that ZnO nanorods have grown according to VLS mechanism. A controllable growth method of ZnO nanoneedle is suggested.

Nickel selenide nanorod arrays as an electrode material for lithium-ion batteries and supercapacitors

The growing need for renewable energy and environmental concern has prompted extensive study into energy storage devices, especially batteries and supercapacitors and their electrode materials. Nano array structures are among the most promising electrode structures for improving the electrochemical performance of energy storage devices. In this work, nanorod arrays of nickel selenide grown on nickel foam were synthesized via a simple one-step binder-free hydrothermal method. The change in morphology and electrochemical performance were studied due to altering reaction time. The nanorod growth mechanism and its electrochemical behavior were investigated. The optimum reaction time was 18 h giving nanorod arrays of NixSey with unique electrochemical performance when inspected as an active electrode material for both lithium-ion battery (LIB) and a supercapacitor (SC). For LIB, the as-prepared electrode gave an initial discharge capacity of 632.8 mAh g−1 with a good rate capability and coulombic efficiency. Meanwhile, as an SC electrode, it delivered a capacity of 426.5 C g−1 at 1 A g−1 in a three-electrode apparatus. The hybrid supercapacitor demonstrates 24.67 Wh kg−1 specific energy at 1020.83 W kg−1 specific power with remarkable cycle stability of 92.3 % after 9000 cycles. These results prove that nanorod arrays of NixSey are a promising electrode material for energy-storage applications.

Random Oriented ZnO Nanorods Fabricated through Anodization of Zinc in KHCO3 Electrolyte

Randomly oriented zinc oxide (ZnO) nanorods with an average width of 150 nm were fabricated through anodic oxidation of zinc foil in aqueous KHCO3 electrolyte. Under the optimization of anodic parameters randomly and well oriented nanorods were obtained with randomly oriented nanowires beneath the structures. The growth mechanism of nanorods by optimization of anodization parameters and optical properties were studied in detail through scanning electron microscopy, X-ray powder diffraction, and UV-visible spectrometry The results obtained show that the prime factor affecting the morphology of nanorods is the applied voltage during anodization, while other anodic factors such as anodization time and concentration of electrolyte play a minor part in tuning the morphology. The optical spectrum shows the blue shift in the bandgap indicating applications in UV- visible sunlight electrode materials and photoanodes for water splitting purposes and electrodes in supercapacitors. The specific capacitance of 93.75 F g−1 at a scan rate of 100 mVs obtained using a three electrochemical cell display better performance in charge storing devices and will act as a potential candidate for electrodes used in supercapacitors.

Formation of Gold Nanorods by Seeded Growth: Mechanisms and Modeling

Seeded growth is one of the most successful and well-studied methods of making nanorods of face-centered cubic (FCC) metals such as Ag, Au, Pt, etc. In this method separately prepared tiny metal seeds (typically smaller than 10 nm) are added to a growth solution containing metal precursor, a weak reducing agent such as ascorbic acid, and a capping agent. The mechanisms that lead to specific shape selection and growth of nanoparticles, in this method, are poorly understood. We propose a mechanism of nanorod growth based on the physical phenomenon of twinning and develop a population balance based model. Briefly, on mixing with growth solution, the seeds start growing isotropically, during which some of the seeds undergo twinning and transform their growth habit to form nanorod nuclei. The nanorod nuclei grow along one dimension to form nanorods, and a mixture of nanorods and nanospheres is obtained after a short aging time (typically < 3 h). The simulations capture the salient features of one-dimensional g...

Three-dimensional Monte Carlo simulation of nanorod self-organization in REBa2Cu3Oy thin films grown by vapor phase epitaxy

Some metal-complex oxides (MCOs) self-organize within REBa2Cu3Oy (REBCO: RE = rare earth) superconducting thin films grown by vapor phase epitaxy. To clarify the self-organization mechanism, we developed a three-dimensional Monte Carlo (3D-MC) simulation code using a simple model and simulated nanorod growth under various growth conditions. As a result, the self-organization of nanorods was reproduced by 3D-MC simulations and we clarified the nanorod growth mechanism as follows. The growth mode of MCO particles was 3D island growth due to the instability of the interface of the MCO and the substrate. On the other hand, that of REBCO particles was 2D island growth. There were diverse nanostructures, which were strongly affected by substrate temperature (Ts) and deposition rate (vdep). We constructed a contour plot of the nanorod number density and a phase diagram of the nanostructures depending on Ts and vdep.

Concerted Growth and Ordering of Cobalt Nanorod Arrays as Revealed by Tandem in Situ SAXS-XAS Studies.

The molecular and ensemble dynamics for the growth of hierarchical supercrystals of cobalt nanorods have been studied by in situ tandem X-ray absorption spectroscopy-small-angle X-ray scattering (XAS-SAXS). The supercrystals were obtained by reducing a Co(II) precursor under H2 in the presence of a long-chain amine and a long-chain carboxylic acid. Complementary time-dependent ex situ TEM studies were also performed. The experimental data provide critical insights into the nanorod growth mechanism and unequivocal evidence for a concerted growth-organization process. Nanorod formation involves cobalt nucleation, a fast atom-by-atom anisotropic growth, and a slower oriented attachment process that continues well after cobalt reduction is complete. Smectic-like ordering of the nanorods appears very early in the process, as soon as nanoparticle elongation appears, and nanorod growth takes place inside organized superlattices, which can be regarded as mesocrystals.

Bottom-up processing and low temperature transport properties of polycrystalline SnSe

A hydrothermal approach was employed to efficiently synthesize SnSe nanorods. The nanorods were consolidated into polycrystalline SnSe by spark plasma sintering for low temperature electrical and thermal properties characterization. The low temperature transport properties indicate semiconducting behavior with a typical dielectric temperature dependence of the thermal conductivity. The transport properties are discussed in light of the recent interest in this material for thermoelectric applications. The nanorod growth mechanism is also discussed in detail.

Anionic polymerization in Co and Fe doped ZnO: Nanorods, magnetism and photoactivity

The growth mechanism of Zn1−xCoxO (ZC) and Zn1−xFexO (ZF) nanorods, and resulting magnetic and optical properties have been studied. The ZC and ZF nanorods were prepared by sol–gel synthesis route. X-ray diffraction results in polycrystalline phase with wurtzite structure of ZC and ZF nanorods. The transmission electron microscopy images show the formation of nanorods. The growth mechanism of nanorods is explained on the basis of agglomeration of Zn2+ with OH− ions which is react with poly vinyl alcohol involve anionic polymerization of oriented growth. Magnetic measurement of ZC and ZF nanorods exhibit superferromagnetic behavior and the large value of saturation magnetization observed at room temperature. The magnetization below room temperature measurement confirms the origin of observed magnetism. Raman and photoluminescence spectra show good photoactivity. The observed Raman active modes show wurtzite structure belongs to C6v symmetry group. Photoluminescence measurements of ZC and ZF nanorods exhibit ultraviolet peaks at 413.90 nm (∼3 eV) due to free exciton emission and at 546.31 nm (∼2.27 eV) due to transition from deep donor states which arises from oxygen vacancy.

Processing temperature dependent morphological and optical properties of ZnO nanorods

Zinc Oxide (ZnO) nanorods were synthesized by thermal decomposition of zinc acetate dihydrate at various processing temperatures. The morphology of samples, examined using transmission electron microscopy and field emission scanning electron microscopy, revealed large variations in length and diameter of nanorods. As temperature was increased from 300°C to 450°C, ZnO nanocrystal morphology changed from wire-like to rod-like. This morphology change is a result of competition between nucleation and growth rate in the vapor–solid growth mechanism of nanorods. Photoluminescence spectrum of the nanorods showed both band edge emission as well as native defect related visible emission. Relative intensity of UV and visible emission indicated crystal quality of the nanorods, the ratio increased upto 400°C and deteriorated at higher processing temperature. It is argued that process induced defects dominate at processing temperatures ≤400°C, whereas equilibrium concentration of native defects is high at temperatures >400°C.

Effect of Potassium Ions on the Formation of Crystalline Manganese Oxide Nanorods via Acidic Reduction of Potassium Permanganate

Uniformly grown manganese oxides nanorods are synthesized via a simple and rapid process through an acidic reduction of potassium permanganate followed by heat treatment. The as-produced manganese oxides nanorods are characterized with X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy, and transmission electron microscopy. The crystallinity of the nanostructure is found to have a dominant Mn2O3 phase. The compositional and microstructural analyses reveal that the potassium concentration within the as-prepared material has a profound effect on the morphological conversion of manganese oxide nanoparticles to nanorods. Potassium ions are believed to act as a template for the formation of nanorods and the conversion efficiency increases with the increasing content of potassium. Also the morphology of products is found to depend strongly on the annealing time. The mechanism of nanorod growth with respect to different potassium contents and annealing times is discussed.

Effect of CVD Synthesis Parameters on the Growth of Catalyst-Free ZnO NRs

The main development of ZnO nanorods (NRs) is focused on the gold catalyst and heteroepitaxial approach.However, the presence of Au may generate undesired deep level traps in the ZnO bandgap, which could be very harmful to the performance of transistors. The objective of this study is to synthesize ZnO NRs via homoepitaxial growth without using foreign catalyst by Chemical Vapour Deposition (CVD) technique. The growth of catalyst-free ZnO NWs at different CVD synthesis parameters such as amount of Zn powder, substrate location and synthesis duration on the catalyst-free ZnO NRs were studied systematically. The effect of these parameters on the size and areal density of ZnO NRs provided a better understanding on the growth mechanism of NRs via the Vapour-Solid (VS) mechanism.

Kinetics and mechanism of hydrothermally prepared copper oxide nanorod catalyzed decomposition of ammonium nitrate

One of the key aspects in the development of materials science is the synthesis of particles with specific size and morphology for catalytic applications. Nowadays, nanostructured materials with specific morphology are gaining great importance in the field of catalysis. Thin, one-dimensional, monodispersed CuO nanorods with a significantly higher aspect ratio of 5, were successfully prepared by the hydrothermal method with subsequent ultrasonication. The formation of pure monoclinic CuO nanorods was confirmed by powder XRD and SAED. The CuO nanorod growth mechanism is investigated by using TEM and further characterized by FTIR, UV–visible spectroscopy and thermogravimetry. The catalytic decomposition of ammonium nitrate, an environmental friendly rocket propellant oxidizer, over the synthesized CuO nanorods was investigated. The thermal kinetic constants for the catalytic and noncatalytic decomposition of ammonium nitrate samples were computed by using model free (differential and non-linear integral) and model fitting approaches. The catalytic influence was evident even with 1% catalyst concentration. The model fitting method suggested contracting cylinder mechanism as the effective mechanism for all the investigated samples. Apparently, the CuO nanorods provide Lewis acid and/or active metal sites, facilitating the removal of ammonium nitrate decomposition inhibition species such as NH3 and thereby enhance the rate of decomposition.

Growth of InN nanorods prepared by plasma-assisted molecular beam epitaxy with varying Cr thicknesses

This study investigates how the thickness of Cr deposited on the Si substrate after the nitridation process influences the AIN buffer layer and the InN nanorods. Atomic force microscopy results reveal that different thicknesses of Cr form varying sizes of CrN nanoislands. The results of scanning electron microscopy and X-ray diffraction show that a Cr deposition thickness of 10nm results in CrN nanoislands after the nitridation process, improving the quality and density of InN nanorods. A Cr layer that was too thick led to polycrystalline InN growth. The results of transmission electron microscopy indicate a baseball bat-like InN nanorod growth mechanism.

Non-catalytic and substrate-free method to titania-doped W18O49 nanorods: growth, characterizations, and electro-optical properties

In the present study, titania-doped (Ti-doped) W18O49 nanorods have been prepared using a modified plasma arc gas condensation technique. Characterizations by field-emission gun scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy and high-resolution X-ray photoelectron spectroscopy indicate that the as-prepared nanorods with a single-crystalline monoclinic W18O49 phase are of 20–100 nm in diameter and several micrometers in length. The Raman peaks of the Ti-doped W18O49 nanorods show a red-shift Raman peaks, and an additional green-emission peak at 497 nm is observed in the photoluminescence (PL) spectrum compared to pure W18O49 nanorods. Field-emission (FE) measurements reveal that the turn-on (Eto) and threshold (Ethr) voltages of the Ti-doped W18O49 nanorods are 2.2 and 3.4 V/μm, respectively. A vapor–solid process that does not involve the use of catalyst is proposed for the nanorod growth mechanism. Experimental results show that the additional defects resulting from titania doping are responsible for the enhancement of the optical and FE properties of the pure W18O49 nanorods.

Facile synthesis of Nb2O5 nanorod array films and their electrochemical properties

Nb2O5 nanorod array films were synthesized by a facile hydrothermal process using niobium metal foil and NH4F as precursors. The Nb2O5 nanorods stand on the niobium metal foil substrate and are less than 100nm in diameter and about 1μm in length. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) characterizations indicate that these nanorods have orthorhombic structure and grew longitudinally along 〈001〉 direction. The nanorod growth mechanism was discussed. Thermal annealing at a temperature below 500°C did not change the microstructure of nanorods but improve the crystallinity. The Nb2O5 nanorod array films have been tested as cathode material for lithium battery, which showed a good specific capacity up to 380mAhg−1 even after 50 charge/discharge cycles.

Hydrothermal in-situ growth of Tris(8-hydroxyquinolate) aluminum nanorods thin films

Tris(8-hydroxyquinolate) aluminum(Alq 3) thin films assembled with large-scaled nanorods have been fabricated on Al substrates through hydrothermal in-situ growth method assisted by the surfactant of sodium dodecylbenzenesulfonate. The obtained Alq 3 thin film is composed of uniformly sized (500–800nm × 4–10 μm) nanorods with regular hexagonal cross section, which are assembled to form dense nanorod arrays perpendicularly to the Al substrate. X-ray diffraction revealed that the prepared Alq 3 nanorods were the α-phase. Photoluminescence spectra showed that the Alq 3 nanorods thin film possessed a spectral blue-shift (10 nm) compared with the Alq 3 solution. The hydrothermal growth mechanism of nanorods was studied, which implied that the hydrothermal in-situ growth process on the metal substrate played an important role in the formation of the Alq 3 nanorods thin film. This simple hydrothermal method provides a convenient fabrication approach for nanocrystalline functional organic/metal interface.

Fabrication and Evaluation of ZnO Nanorods by Liquid-Phase Deposition

The ZnO nanorod growth mechanism during liquid-phase deposition (LPD) has been investigated, with results considered in the context of phase stabilization, LPD chemical processes, and Gibbs free energy and entropy. Zinc oxide (ZnO) possesses unique optical and electronic properties, and obtaining ZnO species with high specific surface area is important in ZnO applications. Highly c-axis-oriented ZnO films are expected to be utilized in future optical and electrical devices. ZnO nanorods were synthesized using an aqueous solution deposition technique on a glass substrate with a free-standing ZnO nanoparticle layer. ZnO nanorod growth was easily controlled on the nanoscale by adjustment of the immersion time (15-210 min). X-ray diffraction, field-emission scanning electron microscopy (FE-SEM), and film thickness measurements were used to characterize the crystalline phase, orientation, morphology, microstructure, and growth mechanism of the ZnO nanorods. FE-SEM images were analyzed by image processing software, which revealed details of the of ZnO nanorod growth mechanism.

Growth mechanism of nanorods in REBa 2Cu 3O y films (RE: rare-earth element)

Critical current density under magnetic fields has been improved by the introduction of artificial pinning centers. Nanorods in REBa 2Cu 3O y films are significantly effective as c-axis-correlated pinning centers. However, nanorods sometimes tilt from the c-axis direction of superconducting films. To understand the mechanism of nanorod tilting, ErBa 2Cu 3O y films containing Ba(Nb 0.5Er 0.5)O 3 (BNO) nanorods were deposited on a SrTiO 3 single crystal with a vicinal surface. Microstructures of the nanorods were examined by transmission electron microscopy (TEM). As a result, it was found that BNO nanorods grew diagonally from steps of the substrate surface in cross-sectional TEM images. The mechanism of the diagonal growth of nanorods can be explained by the segregation coefficient.

Synthesis and ultraviolet emission of aligned ZnO rod-on-rod nanostructures

Aligned ZnO rod-on-rod nanostructures were synthesized on silicon substrate via a simple thermal evaporation process at low temperature without catalysts. Pictures taken with the use of the scanning electron microscope demonstrate that the well-ordered ZnO rod-on-rod nanostructures grow on the Si substrate, and the single nanostructure consists of two parts. Transmission electron microscopy image and the selected area electron diffraction pattern indicate that the single-crystal nanorod grows along [0001] direction. The X-ray diffraction pattern proves that the samples have good crystal quality. The detailed nanorod growth mechanism is proposed and discussed. The room-temperature photoluminescence (PL) spectrum shows the dominant ultraviolet emission, which indicates their potential application in ultraviolet optoelectronic devices. The temperature-dependent PL spectra reveal that the strong ultraviolet emission should originate from the longitudinal optical phonon replicas of free exciton.

The study of low temperature hydrothermal growth of ZnO nanorods on stents and its applications of cell adhesion and viability

The hydrothermal growths of the ZnO nanorods with the densities ranging from 157 to 73 nanorods/μm 2 were achieved by diluting the ZnO seed solution. However, the ZnO seed nanocrystals started to agglomerate for the seed solution diluted below 1% of the original nano-crystalline solutions and resulted in the formation of clustered nanorods. With the assistance of a surfactant, Triton X-100, the nanorod density can be further reduced to 4 nanorods/μm 2. The diameters of the nanorods depended on the concentration of the seed solution and agitation speed of the nanorod growth solution. More diluted seed solution used and less agitation of the growth solution, the larger diameter of the nanorods was obtained. This indicated that the nanorod growth mechanism was controlled by the diffusion of reactants. With sufficient agitation of the growth solution, the nanorod can be uniformly grown with subjects on any arbitrary geometry. We have demonstrated ZnO nanorods growth on both inside and outside of biliary stents as well as on nitinol wires used as metal stents. The effect of nanorod density on the NIH 3T3 and HUVEC cells growth was also investigated in this study and the results suggested nanorod-coating to be a suitable method for controlling cell adhesion and viability on implantable devices.