Ultra-thin double-walled carbon nanotubes: A novel nanocontainer for preparing atomic wires

Double-walled carbon nanotubes (DWCNTs) with high graphitization have been synthesized by hydrogen arc discharge. The obtained DWCNTs have a narrow distribution of diameters of both the inner and outer tubes, and more than half of the DWCNTs have inner diameters in the range 0.6–1.0 nm. Field electron emission from a DWCNT cathode to an anode has been measured, and the emission current density of DWCNTs reached 1 A/cm² at an applied field of about 4.3 V/μm. After high-temperature treatment of DWCNTs, long linear carbon chains (C-chains) can be grown inside the ultra-thin DWCNTs to form a novel C-chain@DWCNT nanostructure, showing that these ultra-thin DWCNTs are an appropriate nanocontainer for preparing truly one-dimensional nanostructures with one-atom-diameter.      

Equilibrium piezoelectric potential distribution in a deformed ZnO nanowire

The equilibrium piezoelectric potential distribution in a deformed ZnO semiconductive nanowire has been systematically investigated in order to reveal its dependence on the donor concentration, applied force, and geometric parameters. In particular, the donor concentration markedly affects the magnitude and distribution of the electric potential. At a donor concentration of N _D>10¹⁸ cm⁻³, the piezopotential is almost entirely screened. Among the other parameters, a variation in the length of the nanowire does not significantly affect the potential distribution.      

Simple and rapid synthesis of α-Fe2O3 nanowires under ambient conditions

We propose a simple method for the efficient and rapid synthesis of one-dimensional hematite (α-Fe₂O₃) nanostructures based on electrical resistive heating of iron wire under ambient conditions. Typically, 1–5 μm long α-Fe₂O₃ nanowires were synthesized on a time scale of seconds at temperatures of around 700 ° ⊂. The morphology, structure, and mechanism of formation of the nanowires were studied by scanning and transmission electron microscopies, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman techniques. A nanowire growth mechanism based on diffusion of iron ions to the surface through grain boundaries and to the growing wire tip through stacking fault defects and due to surface diffusion is proposed. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.     

Synthesis of monodisperse CoPt3 nanocrystals and their catalytic behavior for growth of boron nanowires

Monodisperse CoPt₃ nanocrystals (NCs) have been synthesized in oleylamine solution by an organic solvothermal method. The NCs were ellipsoidal particles with a diameter around 6.6 nm and length around 10 nm with a good single crystal structure. Using CoPt₃ NCs as catalysts, large-area boron nanowires with diameters ranging from 30 to 50 nm were successfully prepared by chemical vapor deposition using a C/B/B₂O₃ mixture as the precursor. Structural analysis indicated that these nanowires were single crystalline with a β-rhombohedral structure. Measurement of the field emission properties of boron nanowire films showed that the boron nanowires have good field emission characteristics.      

Preparation of monodisperse Se colloid spheres and Se nanowires using Na2SeSO3 as precursor

Nearly monodisperse spherical amorphous Se colloids are prepared by the dismutation of Na₂SeSO₃ solution at room temperature; by altering the pH of the solution, amorphous Se colloid spheres with sizes of about 120 nm, 200 nm, 300 nm, and 1 μm can be obtained. Se@Ag₂Se core/shell spheres are successfully synthesized by using the obtained amorphous Se (a-Se) spheres as templates, indicating the potential applications of these Se nanomaterials in serving as soft templates for other selenides. Meanwhile, selenium nanowires are obtained through a “solid-solution-solid” growth process by dispersing the prepared Se spheres in ethanol. This simple and environmentally benign approach may offer more opportunities in the synthesis and applications of nanocrystal materials. This article is published with open access at Springerlink.com     

Inkjet printing of single-walled carbon nanotube/RuO<Subscript>2</Subscript> nanowire supercapacitors on cloth fabrics and flexible substrates

Single-walled carbon nanotube (SWNT) thin film electrodes have been printed on flexible substrates and cloth fabrics by using SWNT inks and an off-the-shelf inkjet printer, with features of controlled pattern geometry (0.4–6 cm²), location, controllable thickness (20–200 nm), and tunable electrical conductivity. The as-printed SWNT films were then sandwiched together with a piece of printable polymer electrolyte to form flexible and wearable supercapacitors, which displayed good capacitive behavior even after 1,000 charge/discharge cycles. Furthermore, a simple and efficient route to produce ruthenium oxide (RuO₂) nanowire/SWNT hybrid films has been developed, and it was found that the knee frequency of the hybrid thin film electrodes can reach 1,500 Hz, which is much higher than the knee frequency of the bare SWNT electrodes (˜158 Hz). In addition, with the integration of RuO₂ nanowires, the performance of the printed SWNT supercapacitor was significantly improved in terms of its specific capacitance of 138 F/g, power density of 96 kW/kg, and energy density of 18.8 Wh/kg. The results indicate the potential of printable energy storage devices and their significant promise for application in wearable energy storage devices.      

Stabilization of the anatase phase of Ti1?xSnxO2 (x < 0.5) nanofibers

We experimentally investigate the stabilization of the anatase phase of Ti_1−x Sn _x O₂ (x < 0.5) nanofibers when synthesized by an electrospinning method. The as-spun nanofibers became nano-grained, polycrystalline nanofibers after calcination and the diameters of the nanofibers depend on Sn content. Stabilization of the anatase phase in Ti-rich compositions and incorporation of Sn ions were confirmed by X-ray diffraction, Raman, X-ray absorption near-edge structure, and photoluminescence (PL) spectroscopies. Results from the PL study also demonstrated the tunable nature of the optical properties, with the emission maximum shifting towards higher wavelength with increasing Sn concentration.      

Symmetric growth of Pt ultrathin nanowires from dumbbell nuclei for use as oxygen reduction catalysts

This work demonstrates the synthesis of Pt ultrathin nanowires assisted by chromium hexacarbonyl [Cr(CO)₆]. The nanowires exhibit a uniform diameter of 2–3 nm. The length can reach up to several microns. It was found that Cr species produced dumbbell-like nuclei which play a pivotal role in the formation of the Pt nanowires. Such Pt nanowires can be tuned to nanocubes by simply decreasing the concentration of [Cr(CO)₆]. Compared to a commercial Pt/C catalyst (45 wt%, Vulcan, Tanaka) and Pt black (fuel cell grade, Sigma), the synthesized Pt nanowires exhibit superior performance in electrocatalytic oxygen reduction with a specific activity of 0.368 mA/cm², which was 2.7 and 1.8 times greater than that of Pt/C (0.138 mA/cm²) and Pt black (0.202 mA/cm²), respectively. The mass activity of Pt nanowires (0.088 mA/μg) is 2.3 times that of Pt black (0.038 mA/μg) and comparable to that of Pt/C (0.085 mA/μg).      

Synthesis of WS2 and MoS2 fullerene-like nanoparticles from solid precursors

Inorganic fullerene-like WS₂ and MoS₂ nanoparticles have been synthesized using exclusively solid precursors, by reaction of the corresponding metal oxide nanopowder, sulfur and a hydrogen-releasing agent (NaBH₄ or LiAlH₄), achieved either by conventional furnace heating up to ∼900 °C or by photothermal ablation at far higher temperatures driven by highly concentrated white light. In contrast to the established syntheses that require toxic and hazardous gases, working solely with solid precursors permits relatively safer reactor conditions conducive to industrial scale-up.      

Tailoring the diameter of single-walled carbon nanotubes for optical applications

Single-walled carbon nanotubes (SWCNTs) with specific diameters are required for various applications particularly in electronics and photonics, since the diameter is an essential characteristic determining their electronic and optical properties. In this work, the selective growth of SWCNTs with a certain mean diameter is achieved by the addition of appropriate amounts of CO₂ mixed with the carbon source (CO) into the aerosol (floating catalyst) chemical vapor deposition reactor. The noticeable shift of the peaks in the absorption spectra reveals that the mean diameters of the as-deposited SWCNTs are efficiently altered from 1.2 to 1.9 nm with increasing CO₂ concentration. It is believed that CO₂ acts as an etching agent and can selectively etch small diameter tubes due to their highly curved carbon surfaces. Polymer-free as-deposited SWCNT films with the desired diameters are used as saturable absorbers after stamping onto a highly reflecting Ag-mirror using a simple dry-transfer technique. Sub-picosecond mode-locked fiber laser operations at ∼1.56 μm and ∼2 μm are demonstrated, showing improvements in the performance after the optimization of the SWCNT properties.      

Magnetic field-induced solvothermal synthesis of one-dimensional assemblies of Ni-Co alloy microstructures

One-dimensional magnetic Ni-Co alloy microwires with different microstructures and differently shaped building blocks including spherical particles, multilayer stacked alloy plates, and alloy flowers, have been synthesized by an external magnetic field-assisted solvothermal reaction of mixtures of cobalt(II) chloride and nickel(II) chloride in 1, 2-propanediol with different NaOH concentrations. By adjusting the experimental parameters, such as precursor concentration and Ni/Co ratio, Ni-Co alloy chains with uniform diameters in the range 500 nm to 1.3 μm and lengths ranging from several micrometers to hundreds of micrometers can be obtained. A mechanism of formation of the one-dimensional assemblies of magnetic Ni-Co microparticles in a weak external magnetic field is proposed. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users. This article is published with open access at Springerlink.com     

Shape-controlled synthesis of octahedral α-NaYF4 and its rare earth doped submicrometer particles in acetic acid

Submicrometer sized pure cubic phase, Eu³⁺ doped, and Yb³⁺/Er³⁺ co-doped α-NaYF₄ particles with octahedral morphology have been prepared in acetic acid. The acetate anion plays a critical role in the formation of such symmetric octahedral structures through its selective adsorption on the (111) faces of the products. The size of the as-prepared octahedra can be tuned by varying the amount of sodium acetate added to the acetic acid. A possible formation mechanism for these octahedra has been proposed. The doped α-NaYF₄ octahedral submicrometer particles show down-conversion and up-conversion photoluminescence typical of these materials. This article is published with open access at Springerlink.com     

Nanotrains and self-assembled two-dimensional arrays built from carboranes linked by hydrogen bonding of dipyridones

The strong hydrogen bonding ability of 2-pyridones were exploited to build nanotrains on surfaces. Carborane wheels on axles difunctionalized with 2-pyridone hydrogen bonding units were synthesized and displayed spontaneous formation of linear nanotrains by self-assembly on SiO₂ or mica surfaces. Imaging using atomic force microscopy confirmed linear formations with lengths up to 5 μm and heights within the range of the molecular height of the carborance-tipped axles. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users. This article is published with open access at Springerlink.com     

On the growth mechanism of nickel and cobalt nanowires and comparison of their magnetic properties

Magnetic nanowires (NWs) are ideal materials for the fabrication of various multifunctional nanostructures which can be manipulated by an external magnetic field. Highly crystalline and textured nanowires of nickel (Ni NWs) and cobalt (Co NWs) with high aspect ratio (∼330) and high coercivity have been synthesized by electrodeposition using nickel sulphate hexahydrate (NiSO₄·6H₂O) and cobalt sulphate heptahydrate (CoSO₄·7H₂O) respectively on nanoporous alumina membranes. They exhibit a preferential growth along 〈110〉. A general mobility assisted growth mechanism for the formation of Ni and Co NWs is proposed. The role of the hydration layer on the resulting one-dimensional geometry in the case of potentiostatic electrodeposition is verified. A very high interwire interaction resulting from magnetostatic dipolar interactions between the nanowires is observed. An unusual low-temperature magnetisation switching for field parallel to the wire axis is evident from the peculiar high field M(T) curve.      

Two distinct fluorescent quantum clusters of gold starting from metallic nanoparticles by pH-dependent ligand etching

Two fluorescent quantum clusters of gold, namely Au₂₅ and Au₈, have been synthesized from mercaptosuccinic acid-protected gold nanoparticles of 4–5 nm core diameter by etching with excess glutathione. While etching at pH ∼3 yielded Au₂₅, that at pH 7–8 yielded Au₈. This is the first report of the synthesis of two quantum clusters starting from a single precursor. This simple method makes it possible to synthesize well-defined clusters in gram quantities. Since these clusters are highly fluorescent and are highly biocompatible due to their low metallic content, they can be used for diagnostic applications. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users. This article is published with open access at Springerlink.com     

Synthesis and optical properties of cubic gold nanoframes

This paper describes a facile method of preparing cubic Au nanoframes with open structures via the galvanic replacement reaction between Ag nanocubes and AuCl₂ ⁻. A mechanistic study of the reaction revealed that the formation of Au nanoframes relies on the diffusion of both Au and Ag atoms. The effect of the edge length and ridge thickness of the nanoframes on the localized surface plasmon resonance peak was explored by a combination of discrete dipole approximation calculations and single nanoparticle spectroscopy. With their hollow and open structures, the Au nanoframes represent a novel class of substrates for applications including surface plasmonics and surface-enhanced Raman scattering.      

Bi<Subscript>2</Subscript>S<Subscript>3</Subscript> nanostructures: A new photocatalyst

Uniform colloidal Bi₂S₃ nanodots and nanorods with different sizes have been prepared in a controllable manner via a hot injection method. X-ray diffraction (XRD) results show that the resulting nanocrystals have an orthorhombic structure. Both the diameter and length of the nanorods increase with increasing concentration of the precursors. All of the prepared Bi₂S₃ nanostructures show high efficiency in the photodegradation of rhodamine B, especially in the case of small sized nanodots—which is possibly due to their high surface area. The dynamics of the photocatalysis is also discussed.      

A lamellar ceria structure with encapsulated platinum nanoparticles

A novel lamellar feather-like CeO₂ structure has been fabricated by using a triblock copolymer as the structure-directing agent. This material was characterized in detail by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and BET surface area measurements. Compared with conventional spherical shaped ceria prepared by ammonia gelation, the ceria feathers have superior ability to support nanosized platinum particles due to their special structure. The “skeletons” of ceria feathers can serve as an ideal host matrix to anchor the platinum particles. Furthermore, the inter-crossing pattern of the “skeletons” also acts as a partition to separate platinum particles, allowing the Pt nanoparticles (average diameter ∼6 nm) to be highly dispersed in the structure. The Pt/feather-like CeO₂ catalyst exhibits high activity in the water gas shift reaction.      

Ni1−x Pt x (x=0–0.08) films as the photocathode of dye-sensitized solar cells with high efficiency

Films of Ni_1−x Pt _x (x=0, 0.02, 0.04, 0.06, and 0.08) have been prepared on fluorine-doped tin oxide-coated (FTO) glass substrates by a chemical plating method and used as the photocathode for dye-sensitized solar cells (DSCs). The Ni_0.94Pt_0.06 film consisted of nanoparticles with a size of 4–6 nm and a Pt loading of 5.13 μg/cm². The Ni_0.94Pt_0.06 photocathode exhibited high catalytic performance toward triiodide reduction, high light reflectance, and low charge-transfer resistance. The DSC assembled with the Ni_0.94Pt_0.06 photocathode gave a short-circuit photocurrent density (J _sc) of 16.79 mA/cm², an open-circuit photovoltage (V _oc) of 736 mV, and a fill factor (FF) of 66.4%, corresponding to an overall conversion efficiency of 8.21% under standard AM 1.5 irradiation (100 mW/cm²), which is higher than that for the DSC with a pure Pt photocathode obtained by conventional thermal decomposition. Furthermore, the DSC based on the Ni_0.94Pt_0.06 photocathode showed good stability. The results indicate that Ni_0.94Pt_0.06 films are promising lowcost and high-performance photocathodes for use in DSCs. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.     

Electrocondensation and evaporation of attoliter water droplets: Direct visualization using atomic force microscopy

Working with a biased atomic force microscope (AFM) tip in the tapping mode under ambient atmosphere, attoliter (10⁻¹⁸ L) water droplet patterns have been generated on a patterned carbonaceous surface. This is essentially electrocondensation of water leading to charged droplets, as evidenced from electrostatic force microscopy measurements. The droplets are unusual in that they exhibit a highly corrugated surface and evaporate rather slowly, taking several tens of minutes.