Template synthesis of highly ordered hydroxyapatite nanowire arrays

Highly ordered hydroxyapatite (HA) nanowire arrays were synthesized using porous anodic aluminum oxide (AAO) template from sol-gel solution containing P₂O₅ and Ca(NO₃)₂. Theresults of transmission electron microscopy (TEM) and scanning electron microscopy(SEM) revealed that the obtained HA nanowires had a uniform length and diameter andformed highly ordered arrays, which were determined by the pore diameter and thethickness of the applied AAO template. The results of X-ray diffraction (XRD) and X-rayphotoelectron spectroscopy (XPS) demonstrated that the major component was HA. Theselected-area electron diffraction (SAED) results indicated that HA was a polycrystallinestructure. This novel method of preparing highly ordered HA nanowires with a large areamight be important for many applications in biomaterials.     

Controlled synthesis of highly ordered LaFeO3 nanowires using a citrate-based sol–gel route

Highly ordered LaFeO₃ nanowires of complex oxide were controlled synthesized with a porous anodic aluminum oxide (AAO) template by a citrate-based sol–gel route. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the LaFeO₃ nanowires formed a uniform length and diameter, which were determined by the thickness and the pore diameter of the AAO template, respectively. The results of X-ray diffraction (XRD) and the selected area electron diffraction (SAED) indicated that the LaFeO₃ nanowires had a perovskite-type crystal structure. Furthermore, X-ray photoelectron spectroscopy (XPS) demonstrated that stoichiometric LaFeO₃ was formed.     

镍纳米管阵列的电沉积合成及其磁学性能表征

以氧化铝膜为模板、金属汞为电阴极,采用简单的直流电沉积方法制备出高度有序的镍纳米管阵列。利用扫描电子显微镜、透射电子显微镜、选区电子衍射、能谱仪、X射线粉末衍射和样品振动磁强计对样品进行形貌表征、成分及磁性能分析。结果表明,阵列中的镍纳米管彼此平行,尺寸均匀,纳米管外径为260～360nm;镍纳米管阵列表现出良好的磁各向异性,其易磁化方向垂直于镍纳米管阵列。以金属汞为电阴极是易形成纳米管的关键条件。     

In-situ fabrication of AAO template without oxide barrier layer and its applications

Porous anodic aluminum oxide (AAO) film is the most widely used template in combination with electrodeposition (ED) method to fabricate one-dimensional nanostructures such as nanowires, nanotubes and nanorods. However, the existing oxide barrier layer after the anodization blocks the application of AAO template in synthesis of nanostructures via direct electrodeposition. In this paper, AAO template without oxide barrier layer was successfully fabricated by stepwise voltage decrement; influence of two types of stepwise voltage decrement on the removal of oxide barrier layer was introduced. Field Emission Scanning Electron Microscopy (FESEM) images indicated that stepwise voltage decrement could make the oxide layer thin effectively. Meanwhile, highly ordered gold nanowire arrays were fabricated by using direct electrodeposition method based on AAO template with the second anodization process with stepwise voltage decrement of 1 V/min, FESEM image showed that as-prepared gold nanowires are uniform in diameter and the diameter is in accordance with the diameter of AAO template pores. XRD pattern revealed that gold nanowires were indexed as face-centered cubic phase.     

Fabrication and magnetic properties of Fe<Subscript>3</Subscript>Co<Subscript>7</Subscript> alloy nanowire arrays

Fe₃Co₇ alloy nanowire arrays have been fabricated by direct current electrodeposition of Fe²⁺ and Co²⁺ into anodic aluminum oxide (AAO) templates. The phase structure and magnetic properties of the nanowires were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). Magnetic measurements show that the coercivity and remanence of the as-deposited Fe₃Co₇ Alloy nanowires increase dramatically after heat-treatment at 773 K for 2 h, and the nanowire arrays exhibit uniaxial magnetic anisotropy with easy magnetization direction along the nanowire axes owing to the large shape anisotropy. The great difference between practical coercivity and ideal coercivity was also discussed in detail.     

Synthesis and gas sensing characteristics of SnO2 “dandelions”

SnO₂ dandelions-like architectures that composed of numerous one-dimensional tetragonal prism nanorods were synthesized by a simple hydrothermal method with the help of the surfactant poly(vinyl pyrrolidone) (PVP). The structure and morphology of resulting samples were characterized by means of X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results show that diameter of as-synthesized nanorods are less than 50 nm. The sensors fabricated from the SnO₂ nanorods exhibited good sensitivity, high selectivity and rapid response and recovery times to ethanol vapors at 280 °C.     

Characterization of ordered Cu2O nanowire arrays prepared by heat treated Cu/PAM composite

Cu nanowire arrays were synthesized via a porous alumina membrane (PAM) template with a high aspect ratio, uniform pore size (120–140 nm), and ordered pore arrangement. The Cu₂O nanowire arrays were prepared from the oxidization of Cu metal nanowire arrays. The electrochemical deposition potential of Cu metal nanowires (?180 mV vs. SCE) was determined from X-ray diffraction (XRD) patterns. The microstructure and chemical composition of Cu nanowire arrays were characterized using field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). Results indicate that the Cu/Cu₂O nanowire arrays assembled into the nanochannel of the porous alumina template with diameters of 120–140 nm. The valence of copper was controlled by the porous alumina template during the annealing process. Copper nanowires transformed to the Cu₂O phase with the space limitation of the PAM template. Single-crystal Cu₂O nanowire arrays were also obtained under the template embedded.     

Electrochemical fabrication and magnetic properties of Fe<Subscript>7</Subscript>Co<Subscript>3</Subscript> alloy nanowire array

A new type of magnetic material, Fe₇Co₃ nanowires, was successfully synthesized for the first time via a simple electrodeposition method. Highly uniform, self-ordered porous anodic aluminum oxide (AAO) membranes were prepared by the way of electrochemical. Fe₇Co₃ alloy nanowire arrays were fabricated in the porous alumina template in an aqueous solution of FeCl₂ and CoCl₂ by direct current electrodepositing. The microstructures of nanowires and AAO template were characterized by XRD, SEM, and TEM. The results show that a single Fe₇Co₃ nanowire is 40 nm in width and 2.5 μm in length with a preferred crystal face (110) during growing. The Fe₇Co₃ nanowire arrays have uniaxial magnetic anisotropy with easy magnetization direction along the nanowire axis due to the large shape anisotropy. It also shows that Fe₇Co₃ nanowire is a well-soft magnetic phase compared with Fe nanowires. It illustrates that Fe₇Co₃ possess higher saturation magnetization.     

Nanowires and nanowire–nanosheet junctions of SnO2 nanostructures

Intriguing one-dimensional (1D) nanostructures of SnO₂, including nanowires, dendritic nanorods and falchion-like nanosheets, have been prepared by chemical vapor deposition (CVD) method. To meet the needs of large-scale, controllable, and designable synthesis of nanostructures, it is crucial to systematically study the experimental conditions under which the desired nanostructures can be synthesized reproducibly, in large quantity and with controllable morphology. The most important factors that influence the morphology of the product are temperature and template. The effects of temperature and anodic aluminum oxide (AAO) template with or without Au catalyst particles on the morphology of the final product were studied in this paper. The structures were characterized using X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and high-resolution field emission scanning electron microscopy (FESEM).     

Silver nanowires prepared by modified AAO template method

Thin film containing highly ordered silver nanowires array was prepared by using anodic aluminum oxide (AAO) template method. The morphology of the silver nanowires was confirmed by scanning electron micrograph (SEM). The result of the SEM showed that the silver nanowires were substantive, parallel, and ordered in the AAO template. Diameter distribution of the silver nanowires indicated that the average diameter was about 35 nm. The composition and structure of the Ag nanowires were investigated by Energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) pattern, respectively.     

Water-assisted growth and characterization of SnO2 nanobelts

SnO₂ nanobelts have been synthesized by water-assisted growth at 850 °C using high pure Sn powders as the source materials. The as-synthesized products were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy(TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersed X-ray spectroscopy (EDX), infrared spectrum (IR) and room-temperature photoluminescence (PL) spectrum. XRD pattern of the sample is quite in accord with the standard pattern of the tetragonal rutile SnO₂; SEM and TEM images show that the uniform single-crystalline SnO₂ nanobelts are about tens of micrometers in length, 70-100 nm in width and 5-8 nm in thickness, and is smooth in surface. The special IR and PL properties were also detected by IR and PL testing. The growth mechanisms and special properties relative to the SnO₂ nanostructures are discussed.     

直流电沉积法制备单晶Ag纳米棒阵列

在较低温条件下,采用直流电沉积法在AAO模板中成功制备出了大面积生长均匀的单晶Ag蚋米棒阵列.利用扫描电子显微镜(SEM),能谱仪(EDS),透射电子显微镜(TEM),选区电子衍射(SAED)和XRD等分析手段对样品进行形貌表征及成分分析.结果表明,阵列中的Ag纳米棒尺寸均匀,保持着良好的平行度,直径接近200nm,与AAO模板的孔径大小相当,且可以通过控制沉积时间来实现对Ag纳米棒长度的控制.     

Optimization of the Sol–Gel Chemical Route for Fabrication of Densely Packed NiFe2O4 Nanowires in the AAO Template

In this paper we investigate the thermal decomposition of the citrate-based precursors in order to make the chemical and physical properties appropriate for the fabrication of nickel ferrite nanowires (NWs) through the sol?Cgel chemical route. IR spectroscopy (FTIR) along with X-ray diffraction (XRD) has been performed to select the suitable chemical and physical conditions for the sol?Cgel process. The anodic aluminum oxide (AAO) method was used for the template to control the diameter and length of the aligned wires. The morphology of the samples was studied by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. The magnetic measurements were also done by a vibrating sample magnetometer (VSM). The results showed that the NiFe₂O₄ NWs were parallel ordered in the AAO template and their mean diameter is 80?C100?nm with high aspect ratio of 600.     

Photochemical properties of SnO<Subscript>2</Subscript> nanorods arrays grown on nanoporous stainless steel

The synthesis and characterization of SnO₂ nanomaterials have been extensively studied as photoelectrodes for the potential applications in optoelectronic devices. In this work, SnO₂ nanorods arrays have been synthesized by hydrothermal method on the nanoporous surface of the anodized stainless steel. The prepared SnO₂ nanorods of 1.3–1.4 µm in length and 250–350 nm in width, were uniformly distributed on the anodized stainless steel. This one-dimensional SnO₂ nanostructure directly fabricated on the substrate provides an electron transfer pathway and a Schottky-type contact, resulting in improved photocatalytic and photoelectrochemical performance. The SnO₂ nanorods arrays exhibit fast response towards H₂O₂ determination, producing a linear range from 100 to 3000 μM with a correlation coefficient of 0.984 and a sensitivity of 0.66 μA cm^?2 mM^?1. The results indicate the potential applications of SnO₂ nanorods arrays as the non-enzymatic H₂O₂ sensor.     

Preparation of polyaniline nanotubes array based on anodic aluminum oxide template

In this article, the highly ordered polyaniline (PANI) nanotubes array was prepared by in situ polymerization using anodic aluminum oxide (AAO) as template. Polymerization of aniline was confined in the one-dimensional nanochannel of AAO template. The aniline was adsorbed and polymerized preferentially on the pore walls of template. The structure of PANI nanotubes array was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), selected area electron diffraction (SAED) and dynamic force microscope (DFM). The results show that PANI nanotubes are synthesized successfully in the nanopores of template, the diameter and length of PANI nanotubes are closed to the pore diameter and thickness of AAO template, respectively, the arrangement of PANI nanotubes is very regular and uniform, the crystal form of PANI nanotubes is hexagonal, different from pseudo-orthorhombic crystal form of PANI bulk sample, and cell parameters a and b are 0.5008 nm. The change of crystal form is due to the confinement of AAO template, which makes the molecular chain of PANI arrange more ordered.     

Synthesis and characterization of anatase and rutile TiO2 nanorods by template-assisted method

Well-aligned anatase and rutile TiO₂ nanorods and nanotubes with a diameter of about 80–130 nm have successfully been fabricated via sol-gel template method. The prepared samples were characterized by using thermogravimetric (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The XRD results indicated that the TiO₂ nanorods were crystallized in the anatase and rutile phases, after annealing at 400–800 °C for different periods of time from 0.2 to 10 h.     

One-step template-free synthesis of ZnWO<Subscript>4</Subscript> hollow clusters

ZnWO₄ hollow clusters made up of nanorods were successfully prepared through a tripotassium citrate assisted hydrothermal process at 180 °C. The hollow clusters’ diameter was about 400 nm, and these clusters were made up of nanorods with a diameter of about 10 nm and a length of about 50 nm. X-ray power diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology of the synthesized products. Based on experiments, the growth of these hollow clusters followed an aggregation-Ostwald ripening process. The photocatalytic activities for aqueous Rhodamine B of samples were investigated, and it was seen that ZnWO₄ hollow clusters exhibited a strong photocatalytic activity.     

Sol–gel template synthesis of LiV<Subscript>3</Subscript>O<Subscript>8</Subscript> nanowires

The LiV₃O₈ nanowires are fabricated by using sol–gel process with porous anodic aluminum oxide (AAO) as the template. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) characterizations show that the synthesized LiV₃O₈ nanowires are monodispersed and paralleled to one another. Selected area electron diffraction (SAED) pattern, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) investigations jointly demonstrate that the synthesized nanowires are most consisted of monoclinic phase LiV₃O₈. Since the LiV₃O₈ nanowires can be mass-produced by using this method, it is expected to find promising application as a new cathode material in lithium ion battery.     

One-step anodization fabrication and morphology characterization of porous AAO with ideal nanopore arrays

A fabrication method for one-step anodization of an anodic aluminum oxide (AAO) template with nanopore arrays using pretreated high purity aluminum foil is reported in this article. Morphology of the AAO was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results showed that porous AAO with ideal nanopore arrays can be fabricated by one-step anodization fabrication technology on high purity aluminum foil which had been anodized at 45?V direct current (DC), in 0°C, 0.5?M H₂C₂O₄ solution for 48 hours. The average pore diameter and the interpore distance were 80?nm and 120?nm, respectively. Nanopores in porous AAO had very narrow size distribution and were arranged into hexagonal array. The formation mechanism of nanopore arrays in porous AAO is discussed. Porous AAO with ideal nanopore arrays provide an ideal template for preparation of many one-dimensional nanomaterials. One-step anodization of AAO is a simpler procedure and more applicable in industrial application than the previous two-step anodization technology.     

High-yield solvothermal synthesis of single-crystalline tin oxide tetragonal prism nanorods

The tetragonal prism SnO₂ nanorods with the rutile structure have been successfully synthesized by a simple solvothermal method from high concentration precursors without any surfactant. Their sizes, morphologies and structure were studied by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), select-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The SnO₂ nanorods obtained by the solvothermal method exhibit higher crystalline quality and better dispersion compared with the samples prepared by the hydrothermal method. Our results suggest that the solvent plays an important role to obtain high-yield SnO₂ nanorods with high quality.