Characterization and Optical Properties of the Single Crystalline SnS Nanowire Arrays

The SnS nanowire arrays have been successfully synthesized by the template-assisted pulsed electrochemical deposition in the porous anodized aluminum oxide template. The investigation results showed that the as-synthesized nanowires are single crystalline structures and they have a highly preferential orientation. The ordered SnS nanowire arrays are uniform with a diameter of 50 nm and a length up to several tens of micrometers. The synthesized SnS nanowires exhibit strong absorption in visible and near-infrared spectral region and the direct energy gap E _g of SnS nanowires is 1.59 eV.     

Synthesis and Growth Mechanism of Ni Nanotubes and Nanowires

Highly ordered Ni nanotube and nanowire arrays were fabricated via electrodeposition. The Ni microstructures and the process of the formation were investigated using conventional and high-resolution transmission electron microscope. Herein, we demonstrated the systematic fabrication of Ni nanotube and nanowire arrays and proposed an original growth mechanism. With the different deposition time, nanotubes or nanowires can be obtained. Tubular nanostructures can be obtained at short time, while nanowires take longer time to form. This formation mechanism is applicable to design and synthesize other metal nanostructures and even compound nanostuctures via template-based electrodeposition.     

Fe21Ni79合金纳米线阵列的制备与磁性

用交流电化学沉积方法,在多孔铝阳极氧化膜的柱形孔内制备直径约60 nm,长度约为9.7 μm的Fe₂₁Ni₇₉合金纳米线.采用扫描电镜、透射电镜、X射线衍射仪和振动样品磁强计对纳米线的形貌 、结构和磁学性质进行了测试.结果表明,Fe₂₁Ni₇₉纳米线排列有序,长径比可控,合金呈fcc结构.当将其在外磁场下进行垂直磁化时,磁滞回线出现较高的矩形比0.86,矫顽力达1203Oe.且随着退火温度升高,矫顽力迅速增大,500℃时达到最大值1315Oe,之后又随退火温度的升高而下降.矩形比也呈现类似的变化规律.     

Synthesis and Characterization of Tin Disulfide (SnS2) Nanowires

The ordered tin disulfide (SnS₂) nanowire arrays were first fabricated by sulfurizing the Sn nanowires, which are embedded in the nanochannels of anodic aluminum oxide (AAO) template. SnS₂ nanowire arrays are highly ordered and highly dense. X-ray diffraction (XRD) and corresponding selected area electron diffraction (SAED) patterns demonstrate the SnS₂ nanowire is hexagonal polycrystalline. The study of UV/Visible/NIR absorption shows the SnS₂ nanowire is a wide-band semiconductor with three band gap energies (3.3, 4.4, and 5.8 eV).     

Nickel electroless deposition process on chemically pretreated Si(100) wafers in aqueous alkaline solution

Pretreating Si wafer surfaces with hydrochloric acid and hydrogen peroxide mixture (HPM) or ethanol was found to enhance the reactivity of chemical Ni deposition on Si(100) wafers in a simple bath of NiSO₄-(NH₄)₂SO₄ at pH 9.0. This phenomenon was identified as the acceleration of anodic reaction involved in chemical Ni deposition reaction on Si wafer surfaces, namely oxidation process of surface Si. Just after immersing into the alkaline bath, a reactive surface where oxidation reaction of Si was accelerated was formed on Si wafer surface with HPM or ethanol pretreatment. On the reactive surface, uniform and glossy Ni deposition film was obtained. In order to clarify the effects of HPM- or ethanol-pretreatment on anodic reaction, the pretreated Si(100) wafers were immersed into aqueous alkaline solution excluding NiSO₄, resulting acceleration of Si oxidation compared to the unpretreated Si(100) surface. The progress of surface reactivity was also clarified by open circuit potentials (OCP), XPS, and ex-situ ATR FTIR. Moreover, by using this pretreatment, selective deposition onto nano-patterned Si substrate was performed. A two-dimensional array of fine Ni dots (diameter ca. 80 nm) was successfully fabricated.     

Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16?×?2 surfaces

The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process.     

Electrochemical deposition of branched hierarchical ZnO nanowire arrays and its photoelectrochemical properties

Branched hierarchical ZnO nanowire arrays are synthesized on fluorine-doped tin oxide (FTO) substrate via a two-step electrochemical deposition process, which involves the electrodeposition of ZnO nanowire arrays on conductive glass substrate, followed by the electrochemical growth of ZnO nanorod branches on the backbones of the primary ZnO nanowires. The formation mechanism of the branched hierarchical nanostructure is discussed. It is demonstrated that coating the primary nanowire arrays with ZnO nanoparticles seed layer plays a key role in synthesising the branched hierarchical ZnO nanostructure. By adjusting the concentration of Zn(CH₃COO)₂ colloid in coating process and the reaction time of the second-step deposition, the density and the length of the secondary nanorod branches in the hierarchical nanostructures can be both varied. Moreover, the photoelectrochemical properties of the dye-sensitized solar cell (DSSC) based on branched hierarchical ZnO nanowire arrays are investigated. Due to the enlargement of the internal surface area within the branched nanostructure photoelectrode, the DSSC consisting of branched hierarchical ZnO nanowire arrays yields a power conversion efficiency of 0.88%, which is almost twice higher than that of the DSSC fabricated using bare ZnO nanowire arrays.     

Large-scale synthesis of SiC/PyC core-shell structure nanowires via chemical liquid-vapor deposition

In carbon/carbon (C/C) composites, SiC/PyC core-shell structure nanowires were successfully fabricated via chemical liquid-vapor deposition (CLVD). The influences of heat-treatment temperature on the microstructure and composition of SiC nanowires were studied, and meanwhile the growth mechanism of SiC nanowires was discussed. Additionally, the microstructure and morphology of SiC/PyC core-shell structure nanowires were also investigated. The results displayed that the low heat-treatment temperature could not meet the requirements of SiC nanowires growth, but the too high temperature made the nanowires appear agglomerate easily. Only when the heat-treatment temperature was 1800 °C, SiC nanowires possessed a uniform distribution. The diameter of SiC nanowire was about 300 nm, and there was a SiO₂ layer with the thickness of about 1 nm existing on the surface of SiC nanowire. The growth behavior of SiC nanowire was governed by vapor-solid (V–S) mechanism. After the PyC deposition, SiC/PyC core-shell structure nanowires were constructed, and the nanowires were about 450 nm in diameter. These nanowires displayed a core-shell structure with three layers, which were SiC nanowire core, SiO₂ interlayer and PyC shell, respectively. Meanwhile, SiC/PyC core-shell structure nanowires connected the matrices with each other, and the core-shell structure nanowires generated a stable network.     

Vertical nanowire probes for intracellular signaling of living cells

The single living cell action potential was measured in an intracellular mode by using a vertical nanoelectrode. For intracellular interfacing, Si nanowires were vertically grown in a controlled manner, and optimum conditions, such as diameter, length, and nanowire density, were determined by culturing cells on the nanowires. Vertical nanowire probes were then fabricated with a complimentary metal-oxide-semiconductor (CMOS) process including sequential deposition of the passivation and electrode layers on the nanowires, and a subsequent partial etching process. The fabricated nanowire probes had an approximately 60-nm diameter and were intracellular. These probes interfaced with a GH₃ cell and measured the spontaneous action potential. It successfully measured the action potential, which rapidly reached a steady state with average peak amplitude of approximately 10 mV, duration of approximately 140 ms, and period of 0.9 Hz.     

Ordered CoFe2O4 nanowire arrays with preferred crystal orientation and magnetic anisotropy

CoFe₂O₄ nanowire arrays were fabricated by electrodeposition of Fe²⁺ and Co²⁺ into anodic aluminum oxide (AAO) templates and further oxidization. The phase structure of the nanowires is cubic spinel-type, and the XRD result exhibits perfect preferred crystallite orientation along the nanowire axes. Compared with CoFe₂O₄ nanowire arrays synthesized by other methods, the magnetic hysteresis loops demonstrate that the arrays of nanowires exhibit uniaxial magnetic anisotropy with easy magnetization direction along the nanowire axes owing to the large shape anisotropy. This approach provides a facile technology to fabricate oxide nanowires with uniaxial magnetic anisotropy.     

Electrodeposition of Pd–Ag alloy nanowires on highly oriented pyrolytic graphite

This paper reports findings of an investigation of Pd–Ag alloy nanowires on the step edges of highly oriented pyrolytic graphite (HOPG) by electrochemical deposition at room temperature. Scanning electron microscopy (SEM) images reveal that these alloy nanowires (109–430 nm) are uniform in diameter, and have lengths up to 100–500 μm. The electrodeposition process involves the initial formation of nanowires induced at the step edges of the oxidized HOPG substrate at a very negative potential and subsequent growth at a constant low current density to coalesce the discontinuous nanowires. Alloy nanowires with a 20–25% silver content can be obtained when the ratio of Pd and Ag in the solution is carefully controlled. The SEM images demonstrate that the alloy nanowire arrays are continuous, parallel, ordered, well-aligned and have a narrow distribution of diameters. The Pd–Ag alloy nanowire arrays are promising materials for fabricating hydrogen nanosensors.     

Control of composition and size for Pd–Ni alloy nanowires electrodeposited on highly oriented pyrolytic graphite

In order to fabricate effective Pd–Ni alloy nanowire arrays with given compositions and size, the process of nucleation and growth and the dependence of alloy composition on deposition potential were investigated. The results reveal that the compositions and sizes of Pd–Ni alloy nanowires can be controlled within a desired range through adjusting suitable nucleation and growth potentials as well as the time. The Ni content in the alloy nanowires was found to vary from 6 to 28% when the deposition potential was changed from −0.3 to −1.9 V. A growth potential of −0.35 to − 0.50 V was applied to fabricate Pd–Ni alloy nanowires with 8–15% Ni content. Continuous and parallel nanowire arrays can be successfully fabricated when nucleation is performed at a potential of −1.2 V for 50 ms with further growth at −0.45 V for 800 s. Pd–Ni crystal phases exist in the alloy structure forms of 〈111〉, 〈200〉, 〈220〉, 〈311〉. The nanowires have an average diameter of 150 nm and a length of 100–450 μm.     

Synthesis,Magnetic Anisotropy and Optical Properties of Preferred Oriented Zinc Ferrite Nanowire Arrays

Preferred oriented ZnFe₂O₄ nanowire arrays with an average diameter of 16 nm were fabricated by post-annealing of ZnFe₂ nanowires within anodic aluminum oxide templates in atmosphere. Selected area electron diffraction and X-ray diffraction exhibit that the nanowires are in cubic spinel-type structure with a [110] preferred crystallite orientation. Magnetic measurement indicates that the as-prepared ZnFe₂O₄ nanowire arrays reveal uniaxial magnetic anisotropy, and the easy magnetization direction is parallel to the axis of nanowire. The optical properties show the ZnFe₂O₄ nanowire arrays give out 370–520 nm blue-violet light, and their UV absorption edge is around 700 nm. The estimated values of direct and indirect band gaps for the nanowires are 2.23 and 1.73 eV, respectively.     

Electrodeposition of mesoporous manganese dioxide nanowires arrays from a novel conjunct template method

We report here for the first time on the synthesis of mesoporous MnO₂ nanowire array on conductive Ti/Si substrate. The morphology of the material is significantly controlled by the conjunct template of anodic aluminum oxide (AAO) and the hexagonal phase of a lyotropic liquid crystalline. Low-angle X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) studies show that the nanowires have a mesoporous structure consisting of cylindrical pores. Such a promising synthesis procedure may be a versatile approach that can be extended to the fabrication of other mesoporous metal/metal oxide, semiconductor, and polymer nanowire arrays.     

Fabrication of Dense Arrays of Platinum Nanowires on Silica, Alumina, Zirconia and Ceria Surfaces as 2-D Model Catalysts

High-density arrays of platinum nanowires with dimensions 20 nm × 5 nm × 12 μm (width × height × length) have been produced on planar oxide thin films of silica, alumina, zirconia, and ceria. In this multi-step fabrication process, sub-20 nm single crystalline silicon nanowires were fabricated by size reduction lithography. The Si nanowire patterns were then replicated to produce a high density of Pt nanowires by nanoimprint lithography. The width and height of the Pt nanowires are uniform and are controlled with nanometer precision. The Pt surface area is larger than 2 cm² on a 5 × 5 cm² oxide substrate. The catalytic oxidation of CO was carried out on zirconia-supported Pt nanowires. The reaction conditions (100 Torr O₂, 40 Torr CO, 513–593 K) and vacuum annealing (1023 K) did not change the nanowire structures.     

Synthesis and magnetic properties of complex oxides La0.67Sr0.33MnO3 nanowire arrays

As a new approach of melt-injection-decomposition method, it has been successfully adopted for the synthesis of the complex oxides La_0.67Sr_0.33MnO₃ nanowire arrays. X-ray diffraction studies confirmed the formation of perovskite manganite phase of the sample. Transmission electron microscope and scanning electron microscope characterizations showed a large quantity of one-dimensional nanowires is obtained and the nanowires are continuous, concrete, oriented and rather uniform with an average diameter of 170 nm and length of several tens of micrometers. Magnetic measurements exhibited good ferromagnetic properties at the temperature of 10 K and 300 K respectively. The transition temperature of the complex oxides La_0.67Sr_0.33MnO₃ nanowire arrays is about 350 K, which will endow their great potential applications in magnetoresistance, spintronics or sensor fields at room temperature.     

Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

Novel hierarchical Cd₄SiS₆/SiO₂ based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd₄SiS₆/SiO₂ heterostructure nanowire is composed of a single crystalline Cd₄SiS₆ nanowire core sheathed with amorphous SiO₂ sheath. Furthermore, secondary nanostructures of SiO₂ nanowires are highly dense grown on the primary Cd₄SiS₆ core-SiO₂ sheath nanowires and formed hierarchical Cd₄SiS₆/SiO₂ based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd₄SiS₆/SiO₂ heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd₄SiS₆/SiO₂ heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.     

Fabrication of ultrahigh-density nanowires by electrochemical nanolithography

An approach has been developed to produce silver nanoparticles (AgNPs) rapidly on semiconductor wafers using electrochemical deposition. The closely packed AgNPs have a density of up to 1.4 × 10¹¹ cm^-2 with good size uniformity. AgNPs retain their shape and position on the substrate when used as nanomasks for producing ultrahigh-density vertical nanowire arrays with controllable size, making it a one-step nanolithography technique. We demonstrate this method on Si/SiGe multilayer superlattices using electrochemical nanopatterning and plasma etching to obtain high-density Si/SiGe multilayer superlattice nanowires.     

Angle-dependent photodegradation over ZnO nanowire arrays on flexible paper substrates

In this study, we grew zinc oxide (ZnO) nanowire arrays on paper substrates using a two-step growth strategy. In the first step, we formed single-crystalline ZnO nanoparticles of uniform size distribution (ca. 4 nm) as seeds for the hydrothermal growth of the ZnO nanowire arrays. After spin-coating of these seeds onto paper, we grew ZnO nanowire arrays conformally on these substrates. The crystal structure of a ZnO nanowire revealed that the nanowires were single-crystalline and had grown along the c axis. Further visualization through annular bright field scanning transmission electron microscopy revealed that the hydrothermally grown ZnO nanowires possessed Zn polarity. From photocatalytic activity measurements of the ZnO nanowire (NW) arrays on paper substrate, we extracted rate constants of 0.415, 0.244, 0.195, and 0.08 s^-1 for the degradation of methylene blue at incident angles of 0°, 30°, 60°, and 75°, respectively; that is, the photocatalytic activity of these ZnO nanowire arrays was related to the cosine of the incident angle of the UV light. Accordingly, these materials have promising applications in the design of sterilization systems and light-harvesting devices.     

Fabrication of integrated arrays of ultrahigh density magnetic nanowires on glass by anodization and electrodeposition

Integrated nanowire arrays of Fe-Pt, Co-Pt, and Ni-Pt alloys were successfully fabricated on glass substrates by successive anodization and electrodeposition. Porous alumina films, which were formed from an aluminum layers sputter-deposited on glass substrates covered with transparent oxide conductive films, were used as template-electrodes to deposit various magnetic alloys (Fe-Pt, Co-Pt, and Ni-Pt) in the nanopores by a cathodic electrodeposition, thus leading to integrated nanowire arrays with ultrahigh densities of (0.6-2.1) × 10¹⁵ wire m⁻². The as-deposited nanowires of Fe-Pt, Co-Pt, and Ni-Pt alloys are polycrystalline and composed of fine crystals (4-7 nm across) of chemically ordered tetragonal FePt, CoPt, or NiPt phase. The integrated nanowire arrays may be the promising candidate materials for ultrahigh density perpendicular magnetic recording media in terabits per square inch regime, due to the predictable enhanced perpendicular magnetic performance after appropriate annealing.