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

Abstract 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 (Co 3 O 4 ) 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 Co 3 O 4 nanorings is proposed on the basis of time-dependent experimental results.