Silver Nanowires Can Be Directly Coated with Amorphous Silica to Generate Well-Controlled Coaxial Nanocables of Silver/Silica

This paper describes a simple and convenient approach that allowed for the facial synthesis of silver/silica coaxial nanocables with well-controlled sheath thicknesses in the range of 2-100 nm. The lengths of these nanocables could be up to ∼50 μm. Such nanocables were prepared by directly coating bicrystalline silver nanowires with conformal sheaths of silica through a sol-gel process. The silver nanowires were, in turn, synthesized using a polyol method that involved the reduction of silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone). The thickness of silica coating could be controlled by changing the concentration of the precursor solution and/or the reaction time. Selective removal of the silver cores led to the formation of silica nanotubes having well-controlled dimensions and wall structures.