Growth Mechanism Of Nanowires Research Articles

Synthesis of Millimeter-Long Tungsten Oxide Nanowires for Flexible Molecule Sensor

As one of the crucially important oxide 1D nanostructures, tungsten oxide (WO3) nanowire holds great promise for diverse applications range from the electrochromic to high performance of catalysis, sensors, photoelectric catalyst for water splitting, etc. However, although great efforts have been made to elongate the WO3 nanowire, the length of the as-grown nanowire is still limited at several tens of micrometers, which impedes its extensively applications in the flexible and wearable electronics. Here, we firstly realize the millimeter-level WO3 nanowire growth and demonstrate the feasibility of such ultra-long WO3 nanowire integrated with the flexible substrate for the molecule sensing application. It is found that the ultra-long WO3 nanowire constructed flexible sensor presents a superior sensing performance and mechanical robustness to the lung cancer biomarker molecules. The detail synthesis method, nanowire growth mechanism and performance of the flexible WO3 nanowire sensor will be presented at the meeting.

A brief review on the growth mechanism of CuO nanowires via thermal oxidation

Abstract

Optical and field emission performances of bamboo shoot-shaped GaN nanowires

Novel single-crystalline bamboo shoot-shaped gallium nitride (GaN) nanowires were prepared on silicon substrates using Ga2O3 and ammonia (NH3) by chemical vapor deposition (CVD) method. From the view morphology of bamboo shoot-shaped GaN nanowires, it can be seen that the average diameter of sample is 200 nm, and along the axial direction to the tip diameter decreases slowly. The growth mechanism of bamboo shoot-shaped GaN nanowires obeys the vapor-liquid-solid (VLS) mechanism. In addition, field emission tests indicate that the turn on field of bamboo shoot-shaped GaN nanowires is 7.5 V/μm (at the current density of 10 μA/cm2), with field enhancement factor of 646, which is sufficient meets the field emission device and vacuum microelectronic device. Moreover, the photoluminescence (PL) spectrum measurement shows that the main luminescence peak of bamboo shoot-shaped GaN nanowires is at 364 nm (3.41 eV), which indicate the bamboo shoot-shaped GaN nanowires can be used for preparation flexible optoelectronic devices.

Controlling the Growth of Single Nanowires in a Nanowire Forest for near-Infrared Photodetection

Controlling one-dimension nanowire growth at single nanowire level is vital for building up multifunctional nanowire-based devices and getting insights into nanowire growth mechanisms. In this lett...

A simple and efficient route to synthesize hafnium carbide nanowires by catalytic pyrolysis of a polymer precursor

One-dimensional hafnium carbide (HfC) nanowires were synthesized on carbon fiber by catalyst-assisted pyrolysis of organometallic polymer precursor. The effects of the pyrolysis temperature and the concentration of catalyst on the formation and morphologies of HfC nanowires were investigated, the growth mechanism was explained by thermodynamic calculation. The results show that the diameter of HfC nanowires increases with the pyrolysis temperature increasing; the yield of HfC nanowires was increased by increasing the concentrations of catalyst. The obtained nanowires were randomly oriented around the carbon fibers with the diameters of 50–200 nm and the length of several micrometers, and the product has perfect single crystalline structure. The growth mechanism of the as-prepared HfC nanowires can be explained by solid-liquid-solid (SLS) mechanism.

Wet-chemically etched silicon nanowire: Effect of etching parameters on the morphology and optical characterizations

A two-step metal-catalyzed electroless etching (MCEE) of silicon wafer in HF/AgNO3 and HF/H2O2 subsequently has been reported. Since the mechanism of nanowires (SiNWs) growth in MCEE route depends highly on etching process, we investigated the role of HF concentration and the etching time. The morphology and the optical absorption of the as-fabricated Si-based micro/nanostructured nanowires has been thoroughly investigated. It has been observed that the optical absorption characteristics were influenced by the etching time as well. An improvement by 10 of the absorption was obtained by increasing the etching time. Through finite-difference time-domain simulations it was observed that absorption, energy distribution, electric profile and generation get enhanced in presence of silicon SiNWs grown on bulk silicon. The experimental results reveal that the SiNWs produced by MCEE are very promising due to their potential application in photovoltaic devices.

Growth Texture and Mechanism of Zinc Nanowires Produced by Mechanical Elongation of Nanocontacts.

Two zinc nanotips were brought into contact and elongated inside a transmission electron microscope, thereby growing single-crystal nanowires. The growth dynamics was observed in situ via a lattice imaging method. The preferential crystal growth directions were identified as [10<mml:math display="block"><mml:msubsup><mml:mrow/><mml:mn>1</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math>0], [11<mml:math display="block"><mml:msubsup><mml:mrow/><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math>0], [10<mml:math display="block"><mml:msubsup><mml:mrow/><mml:mn>1</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math><mml:math display="block"><mml:msubsup><mml:mrow/><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math>], and [0001]. Of these, the nanowires grown along the [10<mml:math display="block"><mml:msubsup><mml:mrow/><mml:mn>1</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math>0] and [11<mml:math display="block"><mml:msubsup><mml:mrow/><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math>0] directions accounted for 75% of the total and were surrounded by low-energy side surfaces, i.e., {0001}, {10<mml:math display="block"><mml:msubsup><mml:mrow/><mml:mn>1</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math>1}, and {10<mml:math display="block"><mml:msubsup><mml:mrow/><mml:mn>1</mml:mn><mml:mo>-</mml:mo></mml:msubsup></mml:math>0}. On the basis of these features, models of the nanowire morphology were proposed. In either growth direction, the tensile force aligned parallel to the direction along which slip events corresponding to the predominant slip system were unlikely to occur. This led to a high tensile stress for extracting atoms from the growth region, i.e., the promotion of nanowire growth.

ZnO纳米线的快速生长机理及其场发射性能研究

ZnO纳米线的快速生长机理及其场发射性能研究

Direct Electrodeposition of Aluminum Nanowires from a Room Temperature Ionic Liquid: An Electrochemical 2D-3D-1D Process

Single-crystalline Al nanowires with diameters under 100 nm are successfully prepared by direct electrodeposition from a room temperature ionic liquid without using templates, additives or catalysts for the first time. We propose the three stages of nanowires growth mechanism including electrodeposition of the initial two dimensional nanofilm, subsequent electrochemical formation of three dimensional nano-nuclei and final one dimensional growth of nanowires. The electrodeposited Al nanowires can grow to lengths of up to 50 μm in 120 s with an average growth rate more than 0.4 μm/s, reaching a high aspect ratio over 1000. This study shows that the dimensions of nanowires are precisely controlled through the variation of electrode potential and are influenced by the electrodeposition temperature and time. The morphology of Al nanowires is very uniform and the nanowire diameters electrodeposited at −1.6 V/25°C within 60 s are in the range of 17 nm to 50 nm. It is found that diffusion strongly influences the growth process.

Thermal-induced formation of domain structures in CuO nanomaterials

The growth mechanisms of CuO nanowires (NWs) via thermal oxidation of copper remain controversial in spite of its extensive exploration. Herein, by effectively tuning the growth conditions, we show that the existence of oxygen-concentration-gradient is crucial to maintain the NW growth. Furthermore, based on the proposed growth mechanism, remarkable CuO nanomaterials, including two-dimensional nanosheets are successfully synthesized at higher temperature ($g700{\phantom{\rule{4pt}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$), at which temperature the growth of CuO nanostructures has been suppressed according to the former reports. Detailed structural investigation reveals that the thermal-induced fast ion diffusion may lead to the self-assembly of individual NWs and the nucleation of novel domain structures, such as the (114) twin structures with zigzag twin boundaries. The two-dimensional NSs with high surface area and novel domain structures may exhibit attractive physical properties, such as the high stiffness, which could be employed as building blocks for sophisticated nanodevices.

Growth of ZnO nanowires and their applications for CdS quantum dots sensitized solar cells

ZnO nanowires grown on ITO conductive glass substrates by chemical bath deposition (CBD) method were used as photoanodes to assemble the CdS quantum dots sensitized solar cells (QDSSCs). The growth mechanism of ZnO nanowires and the photovoltaic performance of CdS QDSSCs were investigated. The results show that the c-axis oriented seed layer and the growth process both contribute to the preferential alignment of ZnO nanowires along the [0001] direction. The average length and diameter of nanowires increase with increasing growth time, and the maximum aspect ratio is 20.56 at 9h. CdS quantum dots deposited on ZnO nanowires enhance the absorbance and extend the absorption range to the visible region. ZnO nanowires with higher aspect ratio effectively increase the energy conversion efficiency (η) of CdS QDSSCs, and the best η is 0.401% with an aspect ratio of 20.56. In such a solar cell, the short-circuit current density is significantly improved due to more electron-hole pairs and strong light trapping effect of ZnO nanowires.

Formation and possible growth mechanism of bismuth nanowires on various substrates

In this work, we report results of a study of bismuth nanowires growth on various substrates, including Fe, Ni, Co, W, Pt, Au thin films on oxidized Si, Si (111), oxidized Si (100), and fused quartz. The nanowires (NW) were prepared by RF diode sputtering of Bi onto a substrate heated to about 200 °C. The structure of the wires was studied by a scanning and transmission electron microscopy. The NWs are monocrystalline up to a length of several micrometers and possess a very thin (less than 2 nm) oxide layer. A major influence of the substrate type on the quantity and the length of the obtained nanowires is observed. Based on the above studies, we propose a possible mechanism of a bismuth nanowire growth.

Thermochemistry and growth mechanism of SiC nanowires

The chemical reaction thermodynamics and a novel two-stage growth mechanism of SiC nanowires synthesized by carbothermal reduction reactions were investigated based on the Si-C-O systems over a wide temperature range (1050 ≤ T ≤ 2000K). The carbothermal reduction reaction process involves the fast formation of gaseous SiO and CO crucial intermediates, and the further carbon reduction of SiO to SiC. The relationship between the free energy changes and temperature at different pressures was also discussed. Some fundamental data in the work can help to analyze the thermochemistry of the carbothermal reduction reaction in the Si-C-O system, which is beneficial to optimize the temperature, pressure and the input precursors for controlling the SiC nanowire growth.

Solid Conical Cap-closing Hollow Tube Growth by Axial Screw Dislocations

Exploration of the mechanisms for growth of the nanostructures is the key point to achieve nanomaterial syntheses with precisely controlled morphology and structure. Herein, we reported a new mechanism that realized the growth of solid conical cap-closing hollow tube by axial screw dislocations in the formation α-Al2O3 nanowires. A hollow tube was firstly grown by axial screw dislocations in the formation α-Al2O3 nanowires through vapor-phase synthesis. Afterwards, the hollow tube was closed up by generating a solid conical cap with axial screw dislocations based on the competition between the surface energy and the strain energy of screw dislocation controlled by the growth environment. The solid conical cap-closing hollow tube growth model based on the axial screw dislocations is expected to be a general growth mechanism for nanowires within low supersaturation. This study enriches the fundamental understanding with respective to the kinetics of nanostructured crystal growth and provides guidance to the precise structure control in nanosynthesis and manufacturing.

Controllable synthesis and growth mechanism of lead free bismuth sodium titanate nanowires

Abstract Highly uniform lead-free piezoelectric bismuth sodium titanate (Bi 0.5 Na 0.5 TiO 3 , BNT) nanowires were successfully synthesized via a hydrothermal method. Synthesized at a stirring speed range of 300–1000 rpm, the compositions and orientations of BNT nanowires were well controlled. The effects of stirring speeds on the formation of BNT nanoparticles and nanowires in the hydrothermal processes were systematically investigated. The BNT nanowires with a high aspect ratio were proven to be single crystals with [110] growth direction from high-resolution TEM analysis. The mechanism of growth of BNT nanowires out of nanoparticles in the hydrothermal processes was proposed.

Investigation on Properties of Collagen Nanowires Quasiepitaxially Grown on Mica Lattice Plane

Abstract Collagen fibrils and hydroxyapatite might recognize each other at the mesoscale by multiple cooperative interactions due to their intrinsically repetitive structured surfaces, and thus effectively directing the biomineralization, a biological process involving regulating the growth of bones, teeth and other organs. In this work, a simple technique was developed to prepare nanowire arrays of biological macromolecules by reversely using the biomineralization mechanism, with results similar to the ‘hot wall epitaxy’, a molecular beam deposition technique under vacuum. With this technique, we successfully cultured rat tail type I collagen monomers adsorbed on the mica (001) lattice plane into collagen nanowire arrays along one unique direction across the whole cleavage surface. Based on the characterization results of AFM, EBSD, and TEM, the quasiepitaxial growth mechanism of collagen nanowires was verified in detail. With low experimental requirements, this technique could precisely manipulate the collagen nanowire arrays despite its simple operations, which potentially provided a highly efficient method to manufacture hydrophilic cell culture vessels, produce biological probes with high specificities, and synthesize novel micro/nano optoelectronic materials.

Mechanisms involved in the hydrothermal growth of ultra-thin and high aspect ratio ZnO nanowires

Hydrothermal synthesis of ZnO nanowires (NWs) with tailored dimensions, notably high aspect ratios (AR) and small diameters, is a major concern for a wide range of applications and still represents a challenging and recurring issue. In this work, an additive-free and reproducible hydrothermal procedure has been developed to grow ultra-thin and high AR ZnO NWs on sol-gel deposited ZnO seed layers. Controlling the substrate temperature and using a low reagent concentration (1mM) has been found to be essential for obtaining such NWs. We show that the NW diameter remains constant at about 20–25nm with growth time contrary to the NW length that can be selectively increased leading to NWs with ARs up to 400. On the basis of investigated experimental conditions along with thermodynamic and kinetic considerations, a ZnO NW growth mechanism has been developed which involves the formation and growth of nuclei followed by NW growth when the nuclei reach a critical size of about 20–25nm. The low reagent concentration inhibits NW lateral growth leading to ultra-thin and high AR NWs. These NWs have been assembled into electrically conductive ZnO nanowire networks, which opens attractive perspectives toward the development of highly sensitive low-cost gas- or bio-sensors.

Synthesis of Ultralong, Monodispersed, and Surfactant-Free Gold Nanowire Catalysts: Growth Mechanism and Electrocatalytic Properties for Methanol Oxidation Reaction

The understanding of factors influencing the growth of nanowires is critical for the precise control of the nanowire morphologies and the design of active nanowire catalysts for fuel cell reactions. While the formation of gold nanoparticles followed by self-assembly into short strings of nanowires is known, little is understood in terms of the control of the morphologies and surface properties toward enhanced electrocatalytic properties. This report describes novel findings of an investigation of the growth mechanism of ultralong, highly monodispersed, and surface surfactant-free gold nanowires (Au NWs) synthesized by a galvanic replacement reaction of Te NWs as an initial template. By manipulating reaction time and Au precursor concentration, an aggregative growth mechanism in terms of 1D and 3D growth pathways for the NW length and diameter, respectively, is revealed to be operative in the template-directed Au NW formation process, shinning some fresh insight into the controllability of the nanowire mor...

Polarity and growth directions in Sn-seeded GaSb nanowires.

We here investigate the growth mechanism of Sn-seeded GaSb nanowires and demonstrate how the seed particle and its dynamics at the growth interface of the nanowire determine the polarity, as well as the formation of structural defects. We use aberration-corrected scanning transmission electron microscopy imaging methodologies to study the interrelationship between the structural properties, i.e. polarity, growth mechanism, and formation of inclined twin boundaries in pairs. Moreover, the optical properties of the Sn-seeded GaSb nanowires are examined. Their photoluminescence response is compared with one of their Au-seeded counterparts, suggesting the incorporation of Sn atoms from the seed particles into the nanowires.

Silver and Copper Microstructures: The Workfunction’s Effect

To understand the growth mechanism of Ag and Cu nanowires we have studied the effect of workfunction on the metal nanowire growth by XRD, SEM and Potentiostat. Under the same potential and overpotential, the metal with a smaller workfunction has a higher current density, i.e. current density for Ag is higher than of Cu nanowires. Likewise metals, the plane with smaller workfunction grows faster than with the larger workfunction, thus the preferential growth plane is (220) for both metals. We argued that the current arises from electrons tunneling from metal surface to hydrated metal and hydrogen ions. The metal with a smaller workfunction has a thinner barrier for tunneling, thus leading to a higher current density. It is found that deposition method have no such effect on the structure of deposited nanowires.