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Large-scale Y2O3:Eu nanotubes have been successfully fabricated by an improved sol–gel method within the nanochannels of porous anodic alumina templates. In this method, yttrium nitrate, europium nitrate and urea were used as precursors, yttrium nitrate and europium nitrate were acting as sources of europium and yttrium ions, and urea offered a basic medium through its hydrolysis. X-ray diffraction techniques, scanning electron microscopy, transmission electron microscopy and selected-area electron diffraction were used to characterize the Y2O3:Eu nanotubes obtained. It is found that the prepared Y2O3:Eu nanotubes can be indexed as a polycrystalline cubic structure and their outer diameters are about 50–80 nm, with the thickness of the tube wall estimated to be around 5 nm. The emission peaks of the as-prepared Y2O3:Eu nanotubes are broader than those of bulk Y2O3:Eu because of the disordering of the crystal phase possibly induced by the increase of the surface/volume ratio in the nanotubes. [ABSTRACT FROM AUTHOR]

This article describes both electrochemical deposition and electrophoretic deposition of high-density tellurium (Te) nanowire arrays with wire diameters of 60 nm and lengths of 15-20 µm in the nanochannels of anodic aluminum oxide (AAO) templates. The Te nanowires synthesized via electrochemical deposition (ECD) are generally single crystalline in nature with the wire longitudinal axis along the [001] direction, whereas those synthesized via electrophoretic deposition (EPD) show polycrystalline structures with numerous tiny Te crystallites packed randomly in the wires. The single-crystalline Te nanowires produced by the ECD route are believed to form under a near chemical equilibrium condition; however, the imposed transport and the rapid packing of Te nanocrystallites in the nanochannels of AAO template in external fields lead to polycrystalline Te nanowires in the EPD process. This comparative study of the Te nanowire formation in the nanochannels of AAO template will facilitate the tailoring of the growth of other inorganic nanowires of high quality. [ABSTRACT FROM AUTHOR]

Bi nanotubes embedded in anodic alumina membranes were fabricated by pulsed electrodeposition. Scanning electron microscope, x-ray diffraction, and high-resolution transmission electron microscope analyses revealed that the Bi nanotubes are highly oriented and single crystalline. Electronic transport measurements proved that there is a metal–semiconductor transition of Bi nanotube arrays with the decrease of the wall thickness of the nanotubes, and this transition depends only on the wall thickness and is independent of the diameter of the nanotubes. The quantum confinement effect is believed to play an important role in determining transport properties. The Bi nanotubes may find applications in thermoelectric nanodevices. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) of anodic alumina membranes with different pore sizes is investigated in this paper. We observe that a small pore size leads to a decrease of photoluminescence intensity, an increase of the recombination lifetime, and a broadening of the emission band. The origin of the PL characteristics are discussed together with the decay measurement of the emission band. [ABSTRACT FROM AUTHOR]

The lattice parameter of bismuth nanowires has been measured using the in situ high-temperature x-ray diffraction method. Single-crystalline Bi nanowire arrays with the diameters from 10 nm to 250 nm have been fabricated within the porous anodic alumina membranes by a pulsed electrodeposition technique. Different temperature dependencies of lattice parameter and thermal expansion coefficient were found for Bi nanowires with different diameters, and there is a transition from positive thermal expansion coefficient at low temperature to negative one at high temperature, and the transition temperature shifts to high temperature with the increase in the diameter of Bi nanowires. [ABSTRACT FROM AUTHOR]

Alumina nanowire arrays standing on the surface of a porous anodic alumina membrane have been achieved by first forming a porous anodic alumina membrane with parallel Y-branched nanochannels by reducing the applied anodizing voltage by a factor of [inline image] in the anodization process of high-purity Al foil, and then chemically etching the Y-branched nanochannel alumina membrane in an aqueous phosphoric acid solution. The novel nanostructures may be used for two-dimensional photonic bandgap structural materials. [ABSTRACT FROM AUTHOR]