Cobalt oxide (Co3O4) nanorings prepared from hexagonal β-Co(OH)2 nanosheets

Hexagonal cobalt hydroxide (β-Co(OH)2) nanosheets over a size range from 100 nm to 1 μm were synthesized using a very simple hydrothermal route with cobalt naphthenate as the cobalt source. Additionally, hexagonal cobalt oxide (Co3O4) nanorings over a size range from 100 nm to 1 μm consisting of cubic nanocrystals were obtained via a hydrothermal method using as-prepared β-Co(OH)2 nanosheets as the precursors. A probable mechanism of formation of the hexagonal Co3O4 nanorings is proposed on the basis of time-dependent experimental results.