Characteristics of SiOx-cored composite nanowires with Pd shell layers

This paper describes the fabrication of Pd-coated SiOx nanowires via a simple approach and reports the effects of subsequent thermal annealing. While the as-synthesized Pd-coated SiOx nanowires exhibited smooth one-dimensional (1D) nanostructures, the thermal annealing induced a rough surface. X-ray diffraction, selected area electron diffraction, and lattice-resolved transmission electron microscopy coincidentally revealed that the assynthesized Pd-coated SiOx nanowires were comprised of a cubic Pd phase, whereas annealing generated a tetragonal PdO phase. Micro-Raman spectroscopy measurements showed the presence of 630 cm(-1)-peak, which can be assigned to the B-1g mode of single crystal PdO, whether samples had been annealed or not. Although both Pd and PdO phases did not exhibit PL emission, the PL intensity of core SiOx nanowires has been significantly reduced by the Pd-coating, presumably due to the covering effect.