Silver (Ag) nanowires with a pentagonal cross section have been synthesized by polyvinylpyrrolidone (PVP)-assisted polyol reduction in the presence of Pt nanoparticle seeds. The UV–visible absorption spectra and scanning electron microscopy have been used to trace the growth process of the Ag nanowires. X-ray photoelectron spectroscopy investigation further shows that the PVP molecules are adsorbed on the surface of the Ag nanowires through Ag : O coordination. Comparing with the growth process of Ag nanoparticles, a possible growth mechanism of the Ag nanowires has been proposed. It is implied that the PVP molecules are used as both a protecting agent and a structure-directing agent for the growth of Ag nanowires. It is concluded that the five-fold twinning Ag nanoparticles are formed through heterogenous nucleation after the introduction of Pt nanoparticle seeds and then grow anisotropically along the ⟨110⟩ direction, while the growth along ⟨100⟩ is relatively depressed.

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of silica gel using 20 % CH 2 Cl 2 /hexane as eluant. The best fractions were pooled, evaporated, and recrystallized twice from chloroform/ acetonitrile to yield 12.2 g (23 %) of the title compound as off-white crystals, mp 178±181 C [11].

The temperature-dependent frequency shift of resonant Raman spectra of double-wall carbon nanotubes is investigated in the range of 78–650 K. We show here that different radial breathing mode (RBM) peaks, which are relative to different tube diameters, have a different temperature coefficient of frequency shift, and the larger diameter carbon nanotubes have more RBM frequency downshift with increasing temperature. We attribute the RBM frequency variation to the temperature dependence of the stretching force constant of C–C bond.