Plum-like and octahedral Co3O4 single crystals on and around carbon nanotubes: large scale synthesis and formation mechanism

Abstract

An in situ growth strategy has been developed for the large scale production of novel nanoarchitectures consisting of single crystalline Co₃O₄ particles strung together by multi-walled carbon nanotubes (MWCNTs). Both Co₃O₄ plum-like and octahedra crystals have been grown on and around MWCNTs to form necklace-like structures. Solvents used in the reaction can dramatically affect the size and morphology of Co₃O₄ single crystals. Plum-like Co₃O₄ crystals are readily converted to octahedra, after changing the volume ratio of ethylene glycol (EG) to water. The size of Co₃O₄ single crystals also decreases on lowering the volume ratio of EG to water due to the enhanced polarity of the solvents. The MWCNTs are routinely oriented through the (400) planes of Co₃O₄ octahedra. This preferred growth orientation can be attributed to a lattice match between the MWCNTs and single crystalline Co₃O₄ particles.