Synthesis of crystalline lead Di-oxide nanowires and their electron-beam-induced phase transformation to oxygen deficient lead mono-oxide

We report a synthesis and a structural characterization of crystalline metal-oxide PbO₂ (lead di-oxide) nanowires. Single crystalline PbO₂ nanowires with an average diameter of about 42 nm were successfully synthesized by a spin-coating process of putting a lead oxide sol-gel solution into a nano-porous anodic alumina membrane (nPAAM). The high-resolution transmission electron microscope (HRTEM) images of the nanowires showed clearly resolved inter-planar fringes that corresponded to the (Oil) lattice distance of α-PbO₂ with an orthorhombic structure (α = 4.938 Å, b = 5.939 Åand c = 5.486 Å). Their selected area electron diffraction (SAED) patterns also showed sharp diffraction spots of crystalline α-PbO₂. SAED patterns, taken from different positions along the PbO₂ nanowire, were also found to be identical, indicating that the entire nanowire was single crystalline. It was found that the crystalline PbO₂ nanowires were very sensitive to electron-beam-irradiation. This irradiation resulted in a phase transformation from the α-PbO₂ to the orthorhombic β-PbO (a = 5.490 Å, b = 5.892 Åand c = 4.752 Å). These experimental results suggest that the electron-beam-irradiation technique can be used to manipulate the phase of metal-oxide nanostructures, even in the surface reconstruction of metal-oxide nanowires or nanotubes.