Nanorod Templates Research Articles

GaN Schottky Barrier Photodetectors

We report the fabrication of GaN photodetectors (PDs) prepared on nanorod template. Using the nanorods template, it was found that we can effectively suppress leakage current, ultraviolet-to-visible rejection ratio and photoconductive gain of the PDs. With -2 V applied bias, it was found that noise equivalent power (NEP) and normalized detectivity (D*) were 7.00 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> W and 2.26 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> cmHz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sup> W <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , respectively, for the PD prepared on nanorods template. With the same -2 V bias, it was found that NEP and D* were 3.56 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> W and 4.44 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cmHz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sup> W <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , respectively, for the PD prepared on a conventional sapphire substrate.

Functionalization of ZnO nanorods with γ-Fe 2O 3 nanoparticles: Layer-by-layer synthesis, optical and magnetic properties

Bifunctional magnetic–optical ZnO-γ-Fe 2O 3 hybrid nanomaterials have been synthesized via a layer-by-layer assembly technique on ZnO nanorod templates. X-ray diffraction, transmission electron microscope, field emission scanning electron microscope, high-resolution transmission electron microscope and X-ray photoelectron spectroscopy have been used to characterize the as-synthesized products. The photoluminescence spectra indicate that ZnO-γ-Fe 2O 3 hybrid nanomaterials exhibit enhanced UV emission and passivated defect emission. The magnetic property investigation reveals that ZnO-γ-Fe 2O 3 hybrid nanomaterials exhibit a superparamagnetic behavior.

GaN Metal–Semiconductor–Metal Photodetectors Prepared on Nanorod Template

The authors report the fabrication of GaN-based metal-semiconductor-metal photodetectors (PDs) on a conventional flat sapphire substrate and on a nanorod template. Compared with the PD prepared on the flat sapphire substrate, it was found that leakage current of the PD prepared on the nanorod template was significantly smaller due to the improved crystal quality. It was also found that we can reduce the photoconductive gain and enhance ultraviolet-to-visible rejection ratio by using the nanorod template.

Efficiency Improvement of GaN-Based Light-Emitting Diode Prepared on GaN Nanorod Template

We demonstrated the formation of GaN-based nanorod (NR) structure by using self-assemble Ni nanoislands as the etching mask. It was found that crystal quality of the GaN epilayer prepared on an NR GaN template was significantly better than that prepared with a conventional low-temperature GaN nucleation layer. With the NR GaN template, it was found that 20-mA light-emitting diode (LED) output power can be enhanced by 39.8%, as compared to the conventional LED.

A facile route to n-type TiO2-nanotube/p-type boron-doped-diamond heterojunction for highly efficient photocatalysts

Anatase TiO(2) nanotube (TiNT) arrays have been fabricated on a p-type boron-doped diamond substrate by a liquid phase deposition method using a ZnO nanorod template. The n-type TiNT/p-type diamond heterojunction structures which are realized show significantly enhanced photocatalytic activities with good recyclable behavior, with respect to the cases of sole TiNTs.

Controllable growth and magnetic properties of nickel nanoclusters electrodeposited on theZnO nanorod template

The ZnO nanorods were used as a template to fabricate nickel nanoclusters byelectrodeposition. The ZnO nanorod arrays act as a nano-semiconductor electrodefor depositing metallic and magnetic nickel nanoclusters. The growth sites ofNi nanoclusters could be controlled by adjusting the applied potential. Under−1.15 V the Ni nanoclusters could be grown on the tips of ZnO nanorods. On increasing thepotential to be more negative the ZnO nanorods were covered by Ni nanoclusters. Themagnetic properties of the electrodeposited Ni nanoclusters also evolved with the appliedpotentials.

Crystal quality improvement of a-plane GaN using epitaxial lateral overgrowth on nanorods

The crystal quality of a-plane GaN films was improved by using epitaxial lateral overgrowth on nano-rod GaN template. The scanning electron microscope images showed the fully coalesced regrowth process completed within only 2 μm thickness. The a-plane GaN films grown on nano-rod template showed superior surface quality and less surface pits. The on-axis and off-axis FWHMs of X-ray rocking curves decreased with the increase in the etching depth of the nano-rod template. TEM analysis revealed that the dislocation density was reduced to around 1.2×10 9 cm −2 by the nano-rod epitaxial lateral overgrowth. In addition, the photoluminescence intensity of the a-plane GaN was enhanced significantly. These results demonstrated the opportunity of achieving a-plane GaN films with high crystal quality via nano-rod epitaxial lateral overgrowth.

Polyaniline “Nanotube” Self‐Assembly: The Stage of Granular Agglomeration on Nanorod Templates

The identification and control of a critical stage of polyaniline "nanotube" self-assembly is presented, namely the granular agglomeration or growth onto nanorod templates. When the synthesis pH is held above 2.5, smooth insulating nanorods exhibiting hydrogen bonding and containing phenazine structures are produced, while below pH 2.5, small 15-30 nm granular polyaniline nanoparticles appear to agglomerate onto the available nanorod surface, apparently improving conductivity of the resulting structures by three orders of magnitude. This finding affects both fundamental theories of polyaniline nanostructure self-assembly and their practical applications.

PREPARATION OF ROD‐SHAPED POLYANILINE NANOCAPSULES WITH α‐Fe2O3 NANOROD AS TEMPLATE

The rod‐shaped polyaniline encapsulated α‐Fe2O3 (Fe2O3@PANI) were successfully prepared by the in‐situ chemical oxidative polymerization of aniline in presence of the p‐aminobenzoic acid modified α‐Fe2O3 nanorods (AA‐Fe2O3) as seeds. The Fe2O3@PANI nanoparticles were characterized with Fourier transform infrared spectrophotometry (FTIR), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) techniques. The rod‐shaped polyaniline nanocapsules were obtained after the α‐Fe2O3 nanorod templates were etched with hydrochloric acid. The effect of the ratios of the template and monomer on the morphologies of the rod‐shaped polyaniline nanocapsules was investigated.

Enhancement of random lasing based on the composite consisting of nanospheres embedded in nanorods template

A simple and general approach has been developed for the enhancement of random lasing based on the composite consisting of nanospheres and nanorods array. Due to the inherent nature of high refractive index, the selected nanorods act efficiently as scattering feedback centers, which can promote the formation of closed loop paths of the emission arising from nanospheres. To illustrate our working principle, the composite consisting of Tb(OH)(3)/SiO(2) nanospheres and ZnO nanorods was chosen as an example. Quite interestingly, it is found that the random lasing behavior can be easily achieved for the composite system, while it is absent in pure Tb(OH)(3)/SiO(2) nanospheres. The strategy demonstrated here should be very useful for the future development of coherent light emission sources and many other optoelectronic devices.

A Versatile Approach for the Synthesis of ZnO Nanorod-Based Hybrid Nanomaterials via Layer-by-Layer Assembly

A layer-by-layer (LBL) assembly approach has been developed to synthesize ZnO nanorod-based hybrid nanomaterials such as ZnO/CeO2, ZnO/CdS, and ZnO/Ag on ZnO nanorod templates at room temperature. The morphology, structure, and composition of the ZnO nanorod-based hybrid nanomaterials have been characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. It is indicated that a uniform coating layer consisting of homogeneous nanoparticles is deposited on the surface of ZnO nanorods due to the strong electrostatic attraction between metal ions and polyelectrolyte modified ZnO nanorods. The general approach presented here can be extended to the synthesize other one-dimensional (1D) nanostructure-based hybrid nanomaterials.

Gold Nanotubes with a Nanoporous Wall: Their Ultrathin Platinum Coating and Superior Electrocatalytic Activity toward Methanol Oxidation

This paper describes a new strategy for synthesizing hollow nanotubes (pore d > 100 nm) with nanoporous walls (pore d < 10 nm) as well as how the nanoporous hollow nanotubes exhibit better intrinsic electrocatalytic activity toward methanol oxidation compared with an analogous nanotube system with smooth walls. Compared with vertical arrays of a nanorod system, the nanotube system is better in terms of increasing the effective surface area because the inner and outer surfaces are both in contact with the reaction medium. Au nanotubes with smooth wall and nanoporous walls were synthesized using AAO and conducting polymer nanorod templates. The surface of Au nanotube walls could be electrochemically coated with ultrathin Pt layers without changing the nanoporous structure. The resulting nanotubes showed different “intrinsic” electrocatalytic activities toward methanol oxidations depending on the wall structure (smooth or nanoporous). We compared its catalytic activity with the commercially available carbon-...

Controlled growth of ZnO nanorod templates and TiO2 nanotube arrays by using porous TiO2 film as mask

Porous TiO2 thin films obtained from sol–gel self-organize approach were firstly used as masks to control the growth of ZnO nanorod arrays by aqueous solution method. The effect of TiO2 pore size on the density of ZnO nanorod arrays was investigated by atomic force microscopy and field emission scanning electron microscope. The results show that the density of ZnO nanorod arrays obviously decreases after using porous TiO2 masks, and increases with increasing the TiO2 pore size. Additionally, the existence of TiO2 mask can also effectively prolong the wet-chemical etching time of TiO2 nanotube arrays manufactured from ZnO nanorod templates assisted sol–gel method, to completely remove the ZnO nanorod templates and to avoid collapsing of TiO2 nanotube arrays from the substrates.

A Library of Single-Crystal Metal−Tin Nanorods: Using Diffusion as a Tool for Controlling the Morphology of Intermetallic Nanocrystals

We describe a unified and general template-based strategy for synthesizing a library of morphology-controllable M−Sn (M = Co, Ni, Cu, Ag, Au, Pt, Ru) intermetallic nanorods. The reaction of β-Sn nanorod templates with appropriate metal salt solutions under reducing conditions yields single-crystal intermetallic nanorods of CoSn3, Ni3Sn4, Cu6Sn5, Ag4Sn, AuSn, PtSn, and RuSn2. Temperature plays a key role in maintaining the morphology of the β-Sn nanorod templates in the final M−Sn products and also selectively generating spherical nanocrystals vs dense nanorods vs hollow nanorods, in some cases (e.g., CoSn3) within the same system. These observations are linked to the diffusion process, and accordingly, the melting points of the transition elements used in this study can help us understand and predict the morphologies that can be formed, as well as the lowest temperature at which a particular intermetallic compound can form using low-temperature solution routes.

TiO2 Nanotube Arrays by using ZnO Nanorod Template through Liquid Phase Deposition for Organic- Inorganic Hybrid Photovoltaic Cells

ABSTRACTTiO2 nanotube arrays had been selected as electron transport material incorporate with P3HT:PCBM blended polymer to fabricate the hybrid organic-inorganic solar cells. Well aligned TiO2 nanotube arrays has been synthesized though the liquid phase deposition by using ZnO nanorod arrays as templates. Three types of dyes (viz. NKX-2677, D149, N719) were adsorbed onto the surface of TiO2 nanotube arrays to increase the interfacial contacts between the organic polymer and inorganic metal oxide. Surface modification with NKX-2677 exhibited remarkable improvement of the cell efficiencies in terms of current density, open circuit voltage, and fill factor as compared with those of other dyes.

Fabrication of TiO 2 nanotubes by using electrodeposited ZnO nanorod template and their application to hybrid solar cells

Vertically aligned TiO 2 nanotubes have been fabricated on the indium-doped tin oxide (ITO) by a simple and versatile technique using the electrochemically deposited ZnO nanorods, oriented along the c-axis, as a template in the spin-on based sol–gel reaction of a Ti precursor. The diameter, length, and shape of TiO 2 nanotubes were controlled by changing the initial ZnO nanorod template and the spin conditions during sol–gel process of a Ti precursor. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, and X-ray diffraction (XRD) were used to confirm the successful formation of TiO 2 nanotubes and characterize their structure and morphology. Furthermore, as an application of the TiO 2 nanotubes, hybrid solar cells based on TiO 2 and poly[2-methoxy,5-(2′-ethyl-hexyloxy)1,4-phenylenevinylene] (MEH-PPV) were successfully fabricated.

The evolution of morphology of ordered porous TiO2 films fabricated from sol-gel method assisted ZnO nanorod template

Ordered porous TiO2 films, including TiO2 nanotube arrays, are fabricated by a sol-gel dip-coating approach via ZnO nanorod templates obtained from aqueous solution approach. The results indicate that the morphologies of ordered porous TiO2 films have been great affected by the sol-gel dip-coating cycle number. Open-ended TiO2 nanotube arrays can be obtained in optimum dip-coating cycle numbers. The TiO2 nanotubes with the inner diameter matching well with the diameters of ZnO nanorods, are well assembled and separate each other. When the cycle number is less than this optimum value, no intact porous TiO2 film can be obtained. As the cycle number is larger than this optimum value, an ordered porous TiO2 film with many throughout holes is formed. The evolutive mechanism of ordered porous TiO2 films is proposed.

Fabrication and characterization ofTiO2 nanotube arrays having nanopores in their walls by double-template-assistedsol–gel

We present herein a simple method named the double-template-assisted sol–gel method for preparingTiO2 nanotube arrays with nanopores on their walls. Poly(ethylene glycol) dissolved inTiO2 sol was used as a soft template to form nanopores on the walls ofTiO2 nanotube arrays, which were templated from ZnO nanorod hardtemplates by a dip-coating technique. The microstructure of nanoporousTiO2 nanotube arrays can change from end-opened to end-closed by increasing thedip-coating cycle number. In addition, the essential parameters of nanoporousTiO2 nanotube arrays are determined by the growth conditions of ZnO nanorod templates. Thispaper gives a simple and universal way to produce nanopores on the walls ofTiO2 nanotube arrays to increase the specific surface area.

Novel fabrication of silica nanotube by selective photoetching of CdS nanorod template

CdS/silica core–shell nanorod was prepared by silica coating over the CdS nanorod template of which the surface was initially capped by (3-mercaptopropyl)trimethoxysilane. The silica nanotube with both ends closed was fabricated from the core–shell nanorod by selective photoetching of the core CdS nanorod template with controlled photon energy in the oxygen-saturated aqueous solution including methyl viologen.

Molecular Sensing with Ultrafine Silver Crystals on Hexagonal Aluminum Nitride Nanorod Templates

A fully plasma-based technique of generating ultrafine (sub-10-nm) nanocrystalline silver particulates on wide band gap and chemically inert hexagonal aluminum nitride nanorod templates has been demonstrated. These specially prepared substrates are ready to use for molecular sensing by room-temperature surface-enhanced Raman scattering. An enhancement factor of 2 x 106 was observed for micromolar solutions of Rhodamine 6G.