Abstract
Vertically aligned Zn2SiO4-SiO (x) (x < 2) core-shell nanotube arrays consisting of Zn2SiO4-nanoparticle chains encapsulated into SiO (x) nanotubes and SiO (x) -coated Zn2SiO4 coaxial nanotubes were synthesized via one-step thermal annealing process using ZnO nanowire (ZNW) arrays as templates. The appearance of different nanotube morphologies was due to size-dependent thermal instability and specific melting of ZNWs. With an increase in ZNW diameter, the formation mechanism changed from decomposition of "etching" to Rayleigh instability and then to Kirkendall effect, consequently resulting in polycrystalline Zn2SiO4-SiO (x) coaxial nanotubes, single-crystalline Zn2SiO4-nanoparticle-chain-embedded SiO (x) nanotubes, and single-crystalline Zn2SiO4-SiO (x) coaxial nanotubes. The difference in spatially resolved optical properties related to a particular morphology was efficiently documented by means of cathodoluminescence (CL) spectroscopy using a middle-ultraviolet emission at 310 nm from the Zn2SiO4 phase.