We report a simple and efficient route to synthesize nanoarrows shaped zinc oxide (ZnO) combining electrospinning and high temperature calcination for photocatalytic applications. A comparison of the photo catalytic degradation of methyl orange with ZnO nanoparticles showed that the ZnO nanoarrows were superior to ZnO nanoparticles. These novel ZnO nanoarrows could have wide range of applications such as energy materials, gas sensors, UV–visible blockers and catalyst for organic synthesis.

The morphological and structural characterization of CeO2 nanocrystallites prepared by forward and reverse precipitation techniques were investigated and compared by powder x-ray diffraction (PXRD), nitrogen adsorption (BET) and high resolution transmission electron microscopy (HRTEM) analysis. The two routes gave quite different materials although in both cases the products were essentially highly crystalline, dense particulates. It was found that the reverse precipitation technique gave the smallest crystallites with the narrowest size dispersion. This route also gave as-synthesized materials with higher surface areas. HRTEM confirmed the observations made from PXRD data and showed the two methods resulted in quite different morphologies and surface chemistries. The forward route gives products with significantly greater densities of Ce3+ species compared to the reverse route. Data are explained using known precipitation chemistry and kinetic effects.

The ceria–terbia solid solution system has been studied in order to assess whether ultra-small crystallites have any propensity to form stable anion vacancies at their surface. This has been suggested by many authors and has become generally accepted. The presence of anion vacancies should be manifest in lattice expansion brought about by the presence of associated Ce3+ sites. Using X-ray diffraction (XRD), no such lattice expansion was observed here and instead a lattice contraction with reduced crystallite size was observed. Further, X-ray photoelectron spectroscopy (XPS) indicates there is little evidence for the association of any vacancies with cerium cations.

The stability of reduced cerium oxide in ambient conditions is clearly demonstrated in this paper. Well-defined, crystalline, cerium oxide nanodots (predominantly Ce4+ or Ce3+ material could be selectively prepared) were defined at silicon substrate surfaces by a method of block copolymer templating. Here, selective addition of the cerium ion into one block via solvent inclusion and subsequent UV/ozone processing resulted in the formation of well-separated, size mono-dispersed, oxide nanodots having a hexagonal arrangement mimicking that of the polymer nanopattern. The size of the dots could be varied in a facile manner by controlling the metal ion content. Synthesis and processing conditions could be varied to create nanodots which have a Ce2O3 type composition. The stability of the sesquioxide type structure under processing (synthesis) conditions and calcination was explored. Surprisingly, the sesquioxide type structure appears to be reasonably stable in ambient conditions with little evidence for extensive oxidation until heating to temperatures above ambient. Room temperature fluorescence is supposed to originate from a distribution of surface or defect states and depends on preparation conditions.

The authors report a chemical process to remove the native oxide on Ge and Bi2Se3 crystals, thus facilitating high-resolution electron beam lithography (EBL) on their surfaces using a hydrogen silsesquioxane (HSQ) resist. HSQ offers the highest resolution of all the commercially available EBL resists. However, aqueous HSQ developers such as NaOH and tetramethylammonium hydroxide have thus far prevented the fabrication of high-resolution structures via the direct application of HSQ to Ge and Bi2Se3, due to the solubility of components of their respective native oxides in these strong aqueous bases. Here we provide a route to the generation of ordered, high-resolution, high-density Ge and Bi2Se3 nanostructures with potential applications in microelectronics, thermoelectric, and photonics devices.

Nitrogen-doped bamboo-structured carbon nanotubes have been successfully grown using a series of cobalt/molybdenum catalysts. The morphology and structure of the nanotubes were analysed by transmission electron microscopy and Raman spectroscopy. The level of nitrogen doping, as determined by X-ray photoelectron spectroscopy, was found to range between 0.5 to 2.5 at.%. The growth of bamboo-structured nanotubes in the presence of nitrogen, in preference to single-walled and multi-walled nanotubes, was due to the greater binding energy of nitrogen for cobalt in the catalyst compared to the binding strength of carbon to cobalt, as determined by density functional theory.

Halogen-termination and organic functionalization of germanium (Ge) nanowires is described. X-ray photoelectron spectroscopy (XPS), X-ray photoemission electron spectroscopy (XPEEM), infrared spectroscopy (IR) and transmission electron spectroscopy (TEM) were used to characterize the modified nanowire surfaces. The stability of alkyl and alkanethiol monolayers formed on Cl, Br and I-terminated surfaces are compared. The direct covalent attachment of aryl ligands onto H-Ge nanowires can be achieved by the decomposition of arenediazonium salts in acetonitrile solutions. The influence of the ring substituent on the thickness and uniformity of the functionalization layer was investigated.

In this work, we investigate the directly bonded germanium-silicon interfaces to facilitate the development of high quality germanium silicon hetero integration at the wafer scale. X-ray photoelectron spectroscopy data is presented which provides the chemical composition of the germanium surfaces as a function of the hydrophilic bonding reaction at the interface. The bonding process induced long range deformation is detected by synchrotron x-ray topography. The hetero-interface is characterized by measuring forward and reverse current, and by high resolution transmission electron microscopy.

Nickel germanide Schottky contacts, formed by rapid thermal annealing of thin nickel films, have been characterized on n-type germanium wafers for a range of RTA temperatures. The highest Schottky barrier heights for electrons (= 0.6-0.7 eV) were obtained for RTA temperatures of approximately 300°C. For this RTA schedule, the corresponding barrier height for holes is close to zero, ideal for Schottky contacted p-channel germanium MOSFETs. When the RTA temperature was increased to 400oC, a dramatic reduction in electron barrier height (< 0.1 eV) was observed. This RTA schedule, therefore, appears ideal for ohmic source/drain contacts to n channel germanium MOSFETs. From sheet resistance measurements and XRD characterization, nickel germanide formation was found to occur at 300oC and above. The NiGe phase was dominant for RTA temperatures up to at least 435oC.

Heavy metal ion contamination in drinking water poses a major risk to human health, whilst contamination in wastewater streams can cause damage to the wider environment. In this study carbon nanocages, synthesised using a supercritical fluid deposition method, were examined as adsorbents of Pb2+ ions from aqueous solutions. Through careful selection of the catalyst and the carbon deposition temperature and pressure, high yields of nanocages with surface areas up to 1175m2g−1 were synthesised. These high surface area materials were subsequently tested for their ability to absorb Pb2+ ions, as a function of pH, from simulated wastewater. The nanocages were found to be effective at removing the Pb2+ ions at levels of 11.1mgg−1, compared to 7.6mgg−1 for commercially available activated carbon. The kinetics of metal ion adsorption by the nanocages and activated carbon can be described by a pseudo-second-order kinetics model, with a rate coefficient (k2) of 4.8×102gmg−1min−1.

Detailed X-ray photoelectron spectroscopy (XPS) studies on the oxidation of an extensively cleaned, reduced ceria–lanthana solid solution (12.5mol% La to Ce) was performed. Uptake of oxygen during oxidation followed a logarithmic dependence on exposure. Differential charging during oxidation suggests that the oxidation process is diffusion limited. No evidence for surface 3+ cerium states in the fully oxidised samples, which are anion defect free within the limits of experimental accuracy, was found. The data suggest that there is no evidence for the inherent stability of anion vacancies (associated with Ce3+ sites) at the surface of these nanocrystals.

Mixed oxide solid solutions are becoming ever more commercially important across a range of applications. However, their synthesis can be problematical. Here, we show that ceria–lanthana solid solutions can be readily prepared via simple precipitation using hexamethylenetetramine. However, the solution chemistry can be complex, which results in the precipitated particles having a complex structure and morphology. Great care must be taken in both the synthesis and characterisation to quantify the complexity of the product. Even very high heat treatments were not able to produce highly homogeneous materials and X-ray diffractions reveals the non-equilibrium form of particles prepared in this way. Unexpected crystal structures are revealed including a new metastable cubic La2O3 phase.

Ceria (CeO2) has many important applications, notably in catalysis. Many of its uses rely on generating nanodimensioned particles. Ceria has important redox chemistry where Ce4+ cations can be reversibly reduced to Ce3+ cations and associated anion vacancies. The significantly larger size of Ce3+ (compared with Ce4+) has been shown to result in lattice expansion. Many authors have observed lattice expansion in nanodimensioned crystals (nanocrystals), and these have been attributed to the presence of stabilized Ce3+-anion vacancy combinations in these systems. Experimental results presented here show (i) that significant, but complex, changes in the lattice parameter with size can occur in 2-500 nm crystallites, (ii) that there is a definitive relationship between defect chemistry and the lattice parameter in ceria nanocrystals, and (iii) that the stabilizing mechanism for the Ce3+-anion vacancy defects at the surface of ceria nanocrystals is determined by the size, the surface status, and the analysis conditions. In this work, both lattice expansion and a more unusual lattice contraction in ultrafine nanocrystals are observed. The lattice deformations seen can be defined as a function of both the anion vacancy (hydroxyl) concentration in the nanocrystal and the intensity of the additional pressure imposed by the surface tension on the crystal. The expansion of lattice parameters in ceria nanocrystals is attributed to a number of factors, most notably, the presence of any hydroxyl moieties in the materials. Thus, a very careful understanding of the synthesis combined with characterization is required to understand the surface chemistry of ceria nanocrystals.

A low temperature germanium (Ge) to silicon (Si) wafer bonding method was demonstrated by in situ radical activation bonding in vacuum. In order to gain further insight into the bonding mechanism, the Ge surface chemistry after either oxygen or nitrogen radical activation was analyzed by means of angle-resolved x-ray photoelectron spectroscopy. After low temperature direct bonding of Ge to Si followed by annealing at 200 and 300 °C, advanced imaging techniques were used to characterize the bonded interface.

The reactivity of various lanthana powders in air was studied. The materials rapidly hydroxylate to form a stable hydroxide, La(OH)(3), at room temperature. Smaller amounts of an oxycarbonate species (La2O2CO3) are also observed following air exposure. This oxycarbonate phase is stable to hydroxylation. All oxide materials synthesized here show rapid reactions so that 24 h of exposure to atmosphere is generally sufficient to cause complete hydroxylation at room temperature. The rate of reaction was related to the crystallite size as determined by XRD. The reaction was found to follow a two-stage kinetic process, a relatively slow surface reaction followed by a rapid bulk reaction. The relevance of the reactivity of these powders is discussed.

The ambient stability and surface coverage of halogen (Cl, Br, and I) passivated germanium nanowires were investigated by X-ray photoelectron and X-ray photoelectron emission spectroscopy. After exposure to air for 24 h, the stability of the halogen-terminated Ge nanowire surfaces toward reoxidation was found to improve with the increasing size of the halogen atoms, i.e., I > Br > Cl. Halogen termination was effective in removing the native Ge oxide (GeOx) and could also be utilized for further functionalization. Functionalization of the halogenated Ge nanowires was investigated using alkyl Grignard reagents and alkanethiols. The stability of the alkyl and alkanethiol passivation layers from the different halogen-terminated surfaces was investigated by X-ray photoelectron spectroscopy and attenuated total reflectance infrared spectroscopy. Alkanethiol functionalized nanowires showed greater resistance against reoxidation of the Ge surface compared to alkyl functionalization when exposed to ambient conditions for 1 week.

Well-organized, dynamic stable nanostructured oxide films, especially transition-metal oxide films have applications in areas of wide scope but are difficult to be grown from solution directly due to the high-temperature requirement in most formation processes which usually destroys the dynamic stable nanostructures. A novel synthetic method associated with a spin coating procedure broke the confinement and produced many different dendrite-like nanostructured fractal films directly on flat substrates from solutions at room temperature, for example, ZnO, Al2O3, TiO2, Nb2O5, WO3, and so forth. In two dimensions, theses fractal films show abundant surface structures like cypress leaf, daisy, fish bone, fern leaf, tree root, and so forth, and their growth and dimensions comply with the reaction-limited aggregation (RLA) mechanism. Experimental results show that the morphology and dimensionality of the FFs is strongly dependent on the chemical compositions and the interactions between particles and the substrate surfaces. The stronger the interaction between the particles and the surfaces, the more even the films, while the stronger the interaction among the particles, the thicker the films.