Novel hexagonal WO3 (h-WO3) nanorods have been successfully prepared on a large scale by a simple hydrothermal method by adding Na2SO4. Uniform nanorods with diameters of 100–200 nm and lengths of up to several micrometres are obtained. The morphology evolvement and the growth mechanism were studied carefully with different quantities of Na2SO4. Different experimental parameters can lead to different structures and morphologies of the final products in our experiment. The current understanding of the growth mechanism of these nanostructures potentially provides important information about the structure design and morphology-controlled synthesis of WO3 and other oxides. The electrochemical performances of the as-prepared h-WO3 nanowires as anode materials of Li-ion batteries have also been investigated. These batteries have a discharge capacity of 215 mA h g−1 at the initial cycles and show an extreme capacity retention. The results imply that these h-WO3 nanorods are promising anode materials for Li-ion batteries.

The ultraviolet (UV) photoconductance properties of a single hexagonal WO 3 nanowire have been studied systematically. The conductance of WO 3 nanowires is very sensitive to ultraviolet B light and a field-effect transistor (FET) nanodevice incorporating a single WO 3 nanowire exhibits excellent sensitivity, reversibility, and wavelength selectivity. A high photoconductivity gain suggests that WO 3 nanowires can be used as the sensing element for UV photodetectors. Measurements under UV light in vacuum show that the adsorption and desorption of oxygen molecules on the surface of the WO 3 nanowire can significantly influence its photoelectrical properties. The WO 3 nanowires have potential applications in biological sensors, optoelectronic devices, optical memory, and other areas. KEYWORDSHexagonal WO 3 nanowire, ultraviolet, photodetector Since discovery of ultraviolet (UV) radiation, the applications of UV light in biotechnology, medical applications, astronomy, and materials science research have been an active research area [1]. In these activities, much attention has been paid to the issue of the safety of UV radiation. UV irradiation of human bodies can damage DNA structure, suppress the immune system, and increase skin photoaging, leading to an increasing number of cancer cases [2]. Therefore, highefficiency and low-energy consumption UV detectors are in high demand. Nano-photodetectors based on one-dimensional wide bandgap semiconductor materials in the form of nanowires, nanotubes, or nanofibers have been demonstrated to have very attractive performances due to the low dimensions and large surface-to-volume ratios of such nanomaterials [3][4][5][6]. To date, photoconductance based on wide bandgap semiconductors, for example, GaN, ZnO, Ga 2 O 3 , and Si 3 N 4 nanostructures, has been employed for UV detection [7][8][9][10].Tungsten oxide (WO 3 ), a very important type of semiconductor material, has been extensively investigated due to its promising physical and chemical properties [11][12][13][14]. By virtue of its outstanding electrochromic, optochromic, and gasochromic properties, in the past few decades WO 3 has been used to manufacture various devices such as flat-panel displays, electrochromic "smart" windows, optical modulation devices, write-read-erase optical devices, gas sensors, and field emission devices [15][16][17]. WO 3 is a potential material for detecting UV radiation because it has an indirect large energy band gap Nano Res (2010) 3: 281-287

We report the development of complete structural AlGaN-based deep-ultraviolet light-emitting diodes with an aluminum thin layer for increasing light extraction efficiency. A 217% enhancement in peak photoluminescence intensity at 294 nm is observed. Cathodoluminescence measurement demonstrates that the internal quantum efficiency of the deep-UV LEDs coated with Al layer is not enhanced. The emission enhancement of deep-UV LEDs is attributed to the higher LEE by the surface plasmon-transverse magnetic wave coupling. When the proportion of the TM wave to the Al layer increases with the Al content in the AlxGa1-xN multiple quantum wells, i.e., the band edge emission energy, the enhancement ratio of the Al-coated deep-UV LEDs increases.

Well-aligned ZnO/ZnSe core/shell nanowire arrays with type-II energy alignment are synthesized via a two-step chemical vapor deposition method. Morphology and structure studies reveal a transition layer of wurtzite ZnSe between the wurtzite ZnO core and the cubic ZnSe shell. Type-II interfacial transitions are observed in the spectral region from visible to near infrared in transmission and photoluminescence. More significantly, for the first time, the interfacial transition is shown to extend the photoresponse of the prototype photovoltaic device based on the coaxial nanowire array to a threshold much below the bandgap of either component (3.3 and 2.7 eV, respectively) at 1.6 eV, with an external quantum efficiency of $4% at 1.9 eV and 9.5% at 3 eV. These results represent a major advance towards the realization of all-inorganic type-II heterojunction photovoltaic devices in an optimal device architecture.

Well-dispersed Fe3O4 nanocrystals were synthesized by a simple hydrothermal method. The as-synthesized products were characterized by field emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, x-ray diffraction, vibrating sample magnetometer and vector network analysis. The complex permittivity and permeability of paraffin wax and Fe3O4 with different Fe3O4 volume fractions were measured to increase linearly with the increase in the volume fraction of Fe3O4. The magnetic loss was caused mainly by natural resonance, which is in good agreement with the Kittel equation results. When the matching thickness is 3 mm, the calculated reflection loss reaches a maximum value of −21.2 dB at 8.16 GHz with 30% volume fraction of Fe3O4.