We report the fabrication of vertically aligned NiO nanowalls on nickel foils using a plasma assisted oxidation method. Electrochemical properties of as-synthesized NiO nanowalls were evaluated by galvanostatic cycling and cyclic voltammetery. The results show a capacity of ∼638 (mA h)/g (at 1.25C rate), with excellent capacity retention of up to 85 cycles, when cycled in the range, 0.005−3.0 V vs Li. The superior electrochemical performance of NiO nanowalls in comparison to the previously reported results on nanosized NiO particles can be attributed to its large surface area and shorter diffusion length for mass and charge transport. A possible reaction mechanism is discussed. We also report that electron field emission studies show that the verticllay aligned NiO nanowalls are efficient field emitters with a turn-on field of 7.4 V/µm and a maximum current density of ∼160 µA/cm2 can be achieved.

In recent years, the synthesis and applications of magnetic nanoparticles (MNPs) have attracted increasing interest in catalysis research, and MNP‐derived catalysts have been employed in such industrially important reactions as hydrogenation, hydroformylation, Suzuki–Miyaura and Heck couplings, and olefin metathesis. The hybrid nanocomposite species display sustainable catalytic activities and great advantages concerning catalyst recycling processes. A number of examples using these innovative hybrids in catalysis have been reported with promising results. This Minireview primarily addresses recent catalytic applications of magnetic nanocomposites, including a discussion of the synthetic methodologies that are commonly used.

Using a simple method of direct heating of bulk copper plates in air, oriented CuO nanowire films were synthesized on a large scale. The length and density of nanowires could be controlled by growth temperature and growth time. Field emission (FE) measurements of CuO nanowire films show that they have a low turn-on field of 3.5-4.5 V µm −1 and a large current density of 0.45 mA cm −2 under an applied field of about 7 V µm −1. By comparing the FE properties of two types of samples with different average lengths and densities (30 µm, 10 8 cm −2 and 4 µm, 4 × 10 7 cm −2 , respectively), we found that the large length-radius ratio of CuO nanowires effectively improved the local field, which was beneficial to field emission. Verified with finite element calculation, the work function of oriented CuO nanowire films was estimated to be 2.5-2.8 eV.

Nanoscale materials, the basis of nanoscience and nanotechnology, have attracted a great deal of interest from researchers. Due to their large surface areas that can be exposed to gaseous environments, two-dimensional (2D) nanostructures such as nanowalls, [1] nanosheets, [2] and nanojunctions or networks [3] form an important category of nanostructured materials with great potential as important components for nanoscale devices with various interesting functions. Thus, in the past decade, many techniques have been developed for the synthesis of such nanostructured materials. For example, Lieber et al. developed the method of laser-assisted vapor±liq-uid±solid (VLS) growth; [4,5] the oxide-assisted growth technique was systematically studied by Lee et al.; [6] and semiconducting oxide nanobelts were fabricated by evaporating the appropriate commercial metal oxide powder. [7] More recently, metal oxide nanowires of low-melting-point metals were successfully synthesized by directly heating metal powder in a tube furnace.[8]Cobalt oxide-based materials have many applications, such as in solid-state sensors, [9] heterogeneous catalysts, [10] electrochromic devices, [11] and as absorbers of solar energy.[12]Furthermore, Co 3 O 4 nanoparticles show some interesting magnetic, optical, and transport properties.[13±15] A few methods of fabricating Co 3 O 4 nanotubes and nanofibers have been reported. [16,17] However, to the best of our knowledge, there has been no report on the preparation of Co 3 O 4 2D nanostructures. In this paper, we report the growth of freestanding, vertically oriented Co 3 O 4 nanowalls by a surprisingly simple method: directly heating Co foil on a hot plate in ambient conditions. The dimensions, such as thickness and length, of the nanowalls were controlled by the growth temperature and duration. The field-emission properties of Co 3 O 4 nanowalls were also investigated for the first time. Figure 1a shows the scanning electron microscopy (SEM) image of the Co foil heated at 350 C for 12 h. It reveals a surface covered with a large quantity of nanowall-like morphologies, with most of them perpendicular to the substrate. The edges of the nanowalls are irregular and the sides of some of the nanowalls are not smooth. The high magnification image (Fig. 1b) shows that the thickness of the nanowalls fabricated using this method was around 25 nm. In order to study the composition of the as-synthesized product, the sample shown in Figure 1 was subjected to glancing-angle X-ray diffraction (GAXRD) measurements; the XRD pattern is shown in Figure 2a. Two phases of cobalt oxide, CoO and Co 3 O 4 , are present and no Co pattern is observed.[18] Since the top surface contributes most significantly to the GAXRD measurements, we deduce that the top layer is predominantly cobalt oxide. To further characterize the nature of the nanowalls, we scraped the nanowalls from the sample surface onto a piece of glass slide and performed micro-Raman spectroscopy on them.

A hybrid system of ZnO nanoparticles on multiwalled carbon nanotubes (MWNTs) is fabricated by simply heating Zn‐coated MWNTs on a hot plate in air. Ultrafast optical switching and three‐photon adsorption are observed from this hybrid system, and the absorption coefficient can be readily adjusted by changing the Zn‐coating thickness. These results provide opportunities for cost‐effectively integrating carbon nanotubes with functional oxide nanoparticles in future nanodevices.

We report an efficient method to synthesize vertically aligned Co3O4 nanostructures on the surface of cobalt foils. This synthesis is accomplished by simply heating the cobalt foils in the presence of oxygen gas. The resultant morphologies of the nanostructures can be tailored to be either one‐dimensional nanowires or two‐dimensional nanowalls by controlling the reactivity and the diffusion rate of the oxygen species during the growth process. A possible growth mechanism governing the formation of such nanostructures is discussed. The field‐emission properties of the as‐synthesized nanostructures are investigated in detail. The turn‐on field was determined to be 6.4 and 7.7 V μm–1 for nanowires and nanowalls, respectively. The nanowire samples show superior field‐emission characteristics with a lower turn‐on field and higher current density because of their sharp tip geometry and high aspect ratio.

Substituted C(2)B(10) carborane cages have been successfully attached to the side walls of single-wall carbon nanotubes (SWCNTs) via nitrene cycloaddition. The decapitations of these C(2)B(10) carborane cages, with the appended SWCNTs intact, were accomplished by the reaction with sodium hydroxide in refluxing ethanol. During base reflux, the three-membered ring formed by the nitrene and SWCNT was opened to produce water-soluble SWCNTs in which the side walls are functionalized by both substituted nido-C(2)B(9) carborane units and ethoxide moieties. All new compounds are characterized by EA, SEM, TEM, UV, NMR, and IR spectra and chemical analyses. Selected tissue distribution studies on one of these nanotubes, {([Na(+)][1-Me-2-((CH(2))(4)NH-)-1,2-C(2)B(9)H(10)][OEt])(n)(SWCNT)} (Va), show that the boron atoms are concentrated more in tumors cells than in blood and other organs, making it an attractive nanovehicle for the delivery of boron to tumor cells for an effective boron neutron capture therapy in the treatment of cancer.

Nanostructures on a plate! Single‐crystalline metal oxide nanostructures (see SEM images) have been synthesized on a large scale and at low cost on a wide range of substrates by directly heating the metal foils or metal‐coated substrates at low temperatures in air. Such a hotplate method could be potentially useful in the fabrication of nanomaterials for further fundamental research and industrial applications.