The catalyst-assisted synthesis of high quality CdS single-crystal nanowires through an epitaxy mechanism.

High quality wurtzite CdS nanowires have been synthesized by thermal evaporation of CdS powder onto Si substrate in the presence of Au catalyst at 650 degrees C by using pure H2 as a carrier gas. The nanowires were 10 nm in diameter and a few tens of micrometers in length. XRD patterns demonstrated that as prepared CdS is a pure crystalline material. High-resolution transmission electron microscopy of the materials showed that all CdS nanowires grew along (0001). According to analysis of selective area electron diffraction patterns taken from the interface, we proposed that there is a kind of epitaxy relationship in the interface region between Au catalyst and CdS grown, i.e., (0001)CdS // (111)Au, and [1210]CdS // [011]Au.

Incorporation of graphenes in nanostructured TiO(2) films via molecular grafting for dye-sensitized solar cell application.

This paper presents a systematic investigation on the incorporation of chemical exfoliation graphene sheets (GS) in TiO(2) nanoparticle films via a molecular grafting method for dye-sensitized solar cells (DSSCs). By controlling the oxidation time in the chemical exfoliation process, both high conductivity of reduced GS and good attachment of TiO(2) nanoparticles on the GS were achieved. Uniform GS/TiO(2) composite films with large areas on conductive glass were prepared by electrophoretic deposition, and the incorporation of GS significantly improved the conductivity of the TiO(2) nanoparticle film by more than 2 orders of magnitude. Moreover, the power conversion efficiency for DSSC based on GS/TiO(2) composite films is more than 5 times higher than that based on TiO(2) alone, indicating that the incorporation of GS is an efficient means for enhancing the photovoltaic (PV) performance. The better PV performance of GS/TiO(2) DSSC is also attributed to the better dye loading of GS/TiO(2) film than that of TiO(2) film. The effect of GS content on the PV performances was also investigated. It was found that the power conversion efficiency increased first and then decreased with the increasing of GS concentration due to the decrease in the transmittance at high GS content. Further improvements can be expected by fully optimizing fabrication conditions and device configuration, such as increasing dye loading via thicker films. The present synthetic strategy is expected to lead to a family of composites with designed properties.