Controlled synthesis of titanium nanochains using a template

Nanochains have unique properties due to their organized structures. We synthesized nanochains of titanium using crown ether as a template exploiting a simple sliding technique. The nanochains of Ti were formed with an average diameter of the sphere nodes around 80 nm separated by organic molecules with a space of 1–5 nm. The method developed here is the simplest reported to date. This process can be used for making nanostructures of different metallic materials. Trapping titanium ion particles is important to reduce the risk of the same material in the biomedical applications. The metallic nanochains are potentially applicable for making electronic and optical devices.     

不同间距的钴纳米粒子一维链的制备及磁性能研究

在室温条件下用简单、易操作的方法磁诱导自组装制备出钴纳米粒子一维链状结构,研究了工艺条件对钴链中粒子的大小以及间距的影响.重点分析了两种不同粒径及间距的钴纳米粒子链状结构的磁性与温度的变化关系,发现钴纳米粒子链状结构在室温时呈超顺磁性,而在10K时呈弱铁磁性.提出了间距长（约10nm左右）的纳米链更趋近于单个纳米粒子的...     

Morphological transition of ZnO nanostructures influenced by magnesium doping

Wurtzite zinc oxide (ZnO) nanochains have been synthesized through high-pressure pulsed laser deposition. The chain-like ZnO nanostructures were obtained from magnesium (Mg) doped ZnO targets, whereas vertically aligned nanorods were obtained from primitive ZnO targets. The Mg doping has influenced the morphological transition of ZnO nanostructures from nanorods to nanochains. The field emission scanning electron microscope images revealed the growth of beaded ZnO nanochains. The ZnO nanochains of different diameters 40 and 120 nm were obtained. The corresponding micro-Raman spectra showed strong E_2H mode of ZnO, which confirmed the good crystallinity of the nanochains. In addition to near band edge emission at 3.28 eV, ZnO nanochains show broad deep level emission at 2.42 eV than that of ZnO nanorods.     

Bimetallic Au–Ag nanochains as SERS substrates

Au–Ag bimetallic nanochains were prepared using pulsed laser ablation in liquid medium. Synthesis was performed by ablating silver target in a gold colloidal suspension. The plasmon characteristics of the nanostructures are found to be sensitive to ablation duration. AFM and TEM images indicate that almost all nanoparticles, both Au and Ag in the suspension participate in the growth process. An attempt was also made to realize plasmon hybridization by reducing the volume of the suspension by simple evaporation. The nanochains were tested for application as SERS substrates by using crystal violet as probe molecules.     

Synthesis and characterization of GaP nanochains with a twin-modulated quasi-periodic structure

GaP nanochains have been synthesized by hydrogen-assisted thermal evaporation, and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and Raman spectroscopy. GaP nanochains possess a (111) twin crystal plane-modulated quasi-periodic structure, that gives a strong green photoluminescence at 618 nm. While the Raman spectrum of the nanochains is similar to that of the GaP crystal, the intensity of the longitudinal optical (LO) peak is stronger than that of the transverse optical (TO) peak, which is supposedly related to the nanochain microstructures.     

Structural, optical and photoelectrochemical characterization of CdS nanowire synthesized by chemical bath deposition and wet chemical etching

Nanocrystalline thin films of CdS have been grown onto flexible plastic and titanium substrates by a simple and environmentally benign chemical bath deposition (CBD) method at room temperature. The films consist of clusters of CdS nanoparticles. The clusters of CdS nanoparticles in the films were successfully converted into nanowire (NW) networks using chemical etching process. The possible mechanism of the etching phenomenon is discussed. These films were examined for their structural, surface morphological and optical properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-vis spectrophotometry techniques, respectively. Photoelectrochemical (PEC) investigations were carried out using cell configuration as n-CdS/(1 M NaOH + 1 M Na₂S + 1 M S)/C. The film of nanowires was found to be hexagonal in structure with the preferential orientation along the (0 0 2) plane. The nanowires have widths in the range of 50-150 nm and have lengths of the order of a few micrometers. Optical studies reveal that the CdS nanowires have value of band gap 2.48 eV, whereas it is 2.58 eV for nanoparticles of CdS. Finally, we report on the ideality of junction improvement of PEC cells when CdS nanoparticles photoelectrode converted into nanowires photoelectrode.     

CuO Nanosheets Synthesized by Hydrothermal Process

CuO nanosheets are synthesized by oxidation of commercial Cu substrates through the hydrothermal process at 150℃. The as-synthesized nanosheets are characterized by powder x-ray diffraction, transmission electron microscopy, selected area electron diffraction and x-ray photoelectron spectroscopy. For comparison, Cu substrates are also oxidized without NaOH added in precursor solution. The results show that the morphology of CuO could be controlled by NaOH, which demonstrates that NaOH can serve as a cosolvent and modifier in the reaction system. The possible mechanism of the growth of CuO nanosheets is also discussed.     

Synthesis of [100] Wurtzite InN Nanowires and [011] Zinc-Blende InN Nanorods

One-dimensional wurtzite InN nanowires and zincblende InN nanorods are prepared by chemical vapour deposition （CVD） method on natural cleavage plane （110） of GaAs. The growth direction of InN nanowires is [100], with wurtzite structure. The stable crystal structure of InN is wurtzite （w-InN）, zincblende structure （z-InN） is only reported for 2D InN crystals before. However, in this work, the zincblende InN nanorods [011] are synthesized and characterized. The SEM and TEM images show that every nanorod shapes a conical tip, which can be explained by the anisotropy of growth process and the theory of Ehrlich Schwoebel barrier.     

Self-assembled gold nanochains hybrid based on insulin fibrils

We reported a facile method for preparing self-assembly gold nanochains by using insulin fibrils as biotemplate in aqueous environment. The gold nanochains hybrid nanostructures, which are insulin fibrils coated by gold nanoparticles, can be fabricated by simply reducing the salt precursors using DMAB. By increasing the molar ratio between salt precursors and insulin, denser hybrid nanochains can be obtained, meanwhile the mean diameter of gold nanoparticles is changing from 8 to 10 nm and then to 12 nm. The fabricated gold nanochains hybrid had helix structure, which was confirmed by circular dichroism spectra. The hybrid nanostructures were also investigated by transmission electron microscope, atomic force microscope, Fourier transform infrared spectra, and UV–Visible spectroscopy. As the wire-like structure become denser, the suspensions show color-changing, corresponding to the surface plasmon resonance red shift, which is attributed to the increasing mean size of nanoparticles. Based on the characterizations, a hypothetic mechanism was suggested to describe the formation processing of hybrid gold nanochains.     

Preparation of nanofibers consisting of MnO/Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> by using the electrospinning technique: the nanofibers have two band-gap energies

In the present study, nanofibers consisting of manganese monoxide (MnO), which is hard to prepare because of the chemical activity of the manganese metal, and the popular Mn₃O₄ have been synthesized via the electrospinning technique. The nanofibers were obtained by electrospinning of an aqueous sol–gel consisting of manganese acetate tetra-hydrate and poly(vinyl alcohol). The obtained nanofiber mats were dried in vacuum at 80°C for 24 h and then calcined in argon atmosphere at 900°C for 5 h. According to X-ray diffraction results, the obtained nanofibers contain 65% MnO. Transmission electron microscope analysis reveals good crystallinity of the produced nanofibers. UV–visible spectroscopic analysis has indicated that the produced nanofibers have two band-gap energies, 2 and 3.7 eV, which enhances utilizing of the nanofibers in different applications.     

Growth and micromagnetic simulation of magnetite nanoparticles

Magnetite nanoparticles with different sizes and different assemblies were synthesized via hydrothermal method.Micromagnetic simulation shows the magnetite nanocubes with different sizes have different energy states,which determines the assembly mode.Magnetite nanocubes with the side length of 30-60 nm tended to be dispersed while both nanochains and dispersed nanoparticles were found to grow for the nanocubes with the side length less than 30 nm,which can be explained in the fact that the above two assembl...     

ZnS nanorod arrays synthesized by an aqua-solution hydrothermal process upon pulse-plating Zn nanocrystallines

Via a simple aqua-solution hydrothermal route, uniform ZnS nanorod arrays were fabricated upon pulse-plating Zn nanocrystallines. Particularly, low temperature (95 °C) and short time (1 h) were employed in the hydrothermal reaction. ZnS nanorods were found to be grown along certain Zn crystalline direction. Control experiments which were performed by replacing Zn nanocrystallines with Zn plate found no one-dimensional ZnS nanostructure on the substrate. Therefore, it was proposed that pulse-plating Zn nanocrystallines acted as both reactant and seed during the hydrothermal process. ZnS nanorod arrays could be theoretically fabricated on almost any raw base plate as long as Zn nanocrystallines could be pulse-plated on the plate. The ZnS nanorod arrays with high length-to-diameter ratio were expected to be a potential candidate for future field-emission devices.     

Fabrication of silver-coated silicon nanowire arrays for surface-enhanced Raman scattering by galvanic displacement processes

Silver-coated silicon nanowire (SiNW) arrays were prepared utilizing galvanic displacement processes consisting of three steps: galvanic displacement deposition of silver particles using a HF-AgNO₃ or NH₄F-AgNO₃ aqueous solution; formation of SiNW arrays by a silver-assisted chemical etching process conducted in the HF-H₂O₂ aqueous solution; deposition of silver particles on the SiNW arrays from the NH₄F-AgNO₃ aqueous solution. The effects of the morphology of pre-deposited silver particles and deposition solution on the formation of silver-coated SiNW arrays were discussed. Surface-enhanced Raman scattering (SERS) performances have been studied using Rhodamine 6G (R6G) probe molecules on the silver-coated SiNW substrates.     

On the bending strength of ZnO nanowires

Compared to bulk samples, the bending strength of ZnO nanowires exhibits nearly two orders of magnitude increase and approaches their theoretical value. Statistical analysis on the scatter strength data of ZnO nanowires by using three versatile distributions has shown that, in contrast to Young's modulus, no obvious size effect was observed, and the bending strengths were insensitive to aspect ratios and flaws at the nanoscale. The reasons for this surprising tolerance behavior can be explained by the collective interaction of “flaws” in a nontraditional sense.     

SnO2 / In2O3 one-dimensional nano-core-shell structures: Synthesis, characterization and photoluminescence properties

SnO₂/In₂O₃ one-dimensional nano-core-shell structures have been synthesized at 1350 ^°C by thermal evaporation of the mixture of metal Sn, Fe(NO₃)₃ powders and In particles. The as-synthesized products have been characterized by energy-dispersive X-ray spectroscopy, selected-area electron diffraction and high-resolution transmission electron microscopy. Microstructure characterization indicates the orientation relationship between core and shell is , . The formation mechanism of this nano-core-shell structure can be attributed to the cover of In₂O₃ on the surface of SnO₂ nanochains. The photoluminescence properties of the nano-core-shell structures have been measured. The PL spectrum shows some difference with the result from pure SnO₂ and In₂O₃ nanostructure that be deemed to relate to interface defects in SnO₂/In₂O₃ nano-core-shell structure.     

Enhancement of electron field emission by carbon coating on vertically aligned Si nanowires

Electron field emission properties of vertically aligned Si nanowires, synthesized by chemically etching p-type Si wafers with different etching times were investigated in detail. Fabrication of Si nanowires was confirmed by field emission scanning electron microscopic investigation. It was observed that a thin layer of amorphous carbon coating over the grown Si nanowires enhanced the field emission properties significantly.     

Elaboration and characterization of TiO2 nanoparticles incorporated in SiO2 host matrix

Nanometer-scale TiO₂ particles have been synthesized by sol-gel method. It was incorporated in a glass-based silica aerogel. The composite was characterized by various techniques such as particle size analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and photoluminescence (PL). The bulk glass presents a strong luminescence at wavelengths ranging from 750 to 950 nm. This PL was attributed to various non-bridging oxygen hole centers (NBOHCs) defects resulting from thermal treatment and crystallization of TiO₂ at the interface between titania nanoparticles and silica host matrix.     

Ellipsometric studies on TiO2 thin films synthesized by spray pyrolysis technique

TiO₂ thin films were synthesized on quartz substrates at substrate temperatures of 350 °C and 450 °C by thermal spray pyrolysis technique using titanium oxy-acetyl acetonate as a precursor. The optical properties of the thin films were characterized by a Spectroscopic Ellipsometer (SE). The surface morphology of the thin films was studied using Atomic Force Microscopy (AFM). The surface roughness values obtained using AFM and SE was compared. The refractive indices of the films were computed using a point by point ellipsometric data extraction procedure. The porosity of the films were modeled from the optical data by effective medium approximation and corroborated from empirical relations. Using Forouhi-Bloomer optical dispersion model, further treatment of SE data was carried out. The experimental investigations and modeling of the data were directed towards optical benchmarking of spray pyrolyzed titania thin films.     

Titanium-induced germanium nanocones synthesized by vacuum electron-beam evaporation: growth mechanism and morphology evolution

High-vacuum electron-beam evaporation method is used for large area, metal-nucleated germanium (Ge) nanodots and nanocones on Si₃N₄/Si preparation. Nanodot and nanocone arrays with uniform size in bulk-quantity are synthesized using titanium (Ti) nanocrystals as nucleating center at 750 °C with different Ge deposition amount, respectively. The morphology evolution from nanodot to nanocone is studied by atomic force microscopy (AFM). The structure of the prepared sample is characterized by X-ray diffraction (XRD) and Raman scattering. Ge nanocones formed by this convenient fabrication process could have potential applications on nanoelectronics and vacuum electron field emission.     

Microscale steps and micro-nano combined structures by anodizing aluminum

In this paper, we firstly present a novel microscale-step structure fabricated by anodizing aluminum in a mixture of 0.05-0.5 wt% NaCl (HCl), 2 wt% H₃PO₄ and 20 wt% ethanol under potentials of 1-40 V at room temperature. Then, we present two micro-nano combined structures by integrating the microsteps with nanopores through multi-step anodizations. The microstep-nanopore hierarchical structure was obtained by re-anodizing the sample in oxalic acid, and the regular nanopores can be realized on the microscale patterned aluminum surface. The two-layer porous structure was one layer of nanoporous anodic alumina and another layer of micropores by two-step anodization on sample's both sides. These two novel structures can be useful for surface engineering and high flux filtration, respectively. The current fabrication approach broadens the applications of aluminum anodization, and brings a new method for assembling micro-nano structures.