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The roles of CTAB and Ag+ have been discovered and given us a deeper understanding of the seed-mediated method in the gold nanorods synthesis. Former work used binary surfactants CTAB + NaOL (sodium oleate) to greatly improve the dimensional tunability and monodispersity of gold nanorods. However, they only used a few of the concentration combinations of the binary surfactants, and the influence of NaOL under this method has not been systematically studied. In this work, we carried out systematic experiments under the variation of NaOL and used transmission electron microscopy and UV–vis-near-infrared spectroscopy to monitor the growth process of the gold nanorods. The results showed that the NaOL contributed to the symmetry breaking process. We discovered the ideal ranges of NaOL concentration under different concentrations of CTAB (10–40 mM). Lower concentrations of NaOL produced many impurities, such as Au spheres, while higher concentrations of NaOL led to the decrease of monodispersity of the obtained gold nanorods. A growth model based on the balance of diffusion/reduction of the growth solution has been proposed in order to explain the formation of the gold nanorods. [ABSTRACT FROM AUTHOR]

ZnO nanowire arrays were grown on semi-insulating intrinsic GaAs substrates, and controlled arsenic-doping process was carried out to realize the n-ZnO/p-ZnO nanowire array/GaAs structures. The constructed ZnO nanowire homojunctions demonstrated a clear rectifying behavior and the turn-on voltage was above 4.0 V. The corresponding ultraviolet electroluminescence spectra were obtained for the applied forward voltage above 30 V (20 mA). The distinct ultraviolet electroluminescence peak, centered at 382 nm, is nonlinearly enhanced with an increase in the applied forward voltage. The origin of the strong ultraviolet electroluminescence was discussed in terms of the controlled arsenic-doping process. [ABSTRACT FROM AUTHOR]