Si/carbon nanotube (CNT) nanocomposites are ideal anode materials for lithium ion batteries with high specific capacities. However, it has been a significant challenge to fabricate uniform Si/CNT nanocomposite anodes with high areal capacities, say above 0.4 mA h cm⁻². In this paper, we demonstrate a layer-by-layer assembling technique as a facile and scalable method to prepare a multilayer Si/CNT coaxial nanofiber anode which possesses an areal storage capacity above 1 mA h cm⁻². In addition, the prepared Si/CNT coaxial nanofiber anodes show an excellent cyclability. The excellent performance of the Si/CNT coaxial nanofiber multilayer anodes is attributed to the unique nanostructure. The CNT network matrix offers mechanical support to accommodate the stress associated with the large volume change of Si coating and the nanoporous multilayer structure provides continuous paths for Li ion and electron transport.

The ultraviolet (UV) photoconductance properties of a single hexagonal WO₃ nanowire have been studied systematically. The conductance of WO₃ nanowires is very sensitive to ultraviolet B light and a field-effect transistor (FET) nanodevice incorporating a single WO₃ nanowire exhibits excellent sensitivity, reversibility, and wavelength selectivity. A high photoconductivity gain suggests that WO₃ 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 WO₃ nanowire can significantly influence its photoelectrical properties. The WO₃ nanowires have potential applications in biological sensors, optoelectronic devices, optical memory, and other areas.

Single-wall carbon nanotubes (SWNTs) suspended in isopropyl alcohol are placed between two cross-structured electrodes using an ac dielectrophoresis technique. The SWNTs are found to attach to the electrodes along the direction of the ac external electric field. The SWNTs predominately bridge the shortest gap between the two electrodes and the spatial distribution of the tubes becomes wider for a long manipulation time (say, greater than 300 s). The observed phenomenon is analyzed in terms of the dielectrophoresis-induced torque and force on the SWNTs. Our simulation shows that the time for rotating SWNTs to the direction of the electric field is much smaller than that for translating SWNTs. We also found that metallic SWNTs are forced along the gradient direction of spacial distribution of the electric field strength while semiconducting SWNTs are forced in the opposite direction.

We present novel light weight three dimensional soft silicon anodes for flexible and stretchable lithium ion batteries. We employ a coaxial flexible Ni/PVDF nanofiber network as the freestanding current collector and active amorphous silicon coating to form a core–shell structure of Si/Ni/PVDF nanofibers. The soft silicon anodes show high specific capacities and good cycling life. We have demonstrated that a soft battery with the freestanding Si/Ni/PVDF membrane as an anode is capable of powering a LED at different bending states.