A novel method to encapsulate a Au nanorod array in 15 nm radius multiwalled carbon nanotubes

In this paper we demonstrate a novel complex array structure comprising well-aligned Au nanorods (10 nm in diameter) encapsulated inside 15 nm radius multiwalled carbon nanotubes (MWCNTs). A pre-aligned and open-ended nanoporous MWCNT membrane is used as the starting material. Au nanorods are precisely deposited and aligned inside the hollow channels of CNTs by inter-diffusing the HAuCl4 precursor and the reductant solution. Ultra-long Au nanowires and spherical Au nanoparticles are also observed in the CNT cavity with the same diameter in special cases. Using high-resolution TEM (HRTEM), scanning transmission electron microscopy (STEM), 3-dimensional TEM (3D-TEM) and energy dispersive X-ray spectroscopy (EDX), the precise location and composition of the encapsulated Au components with various structures are confirmed. This aligned Au@CNT endohedral material has important potential applications in nanocatalysis, waveguides, as well as in novel plasmonic devices.