Size-controlled synthesis of β-Co(OH)_{2 hexagonal nanoplates and their conversion into CoO octahedrons using cobalt naphthenate under solvothermal conditions

β–Co(OH)2 hexagonal nanoplates with a size range from 300 nm to 3 μm have been synthesised successfully by a template and surfactant–free solvothermal route in a very simple system composed only of water, LiOH and cobalt naphthenate in xylene solution. This method is high–yield, simple and environmentally benign. The as–obtained Co(OH)2 hexagonal nanoplates can be easily converted into CoO octahedrons with the size of 15 μm by increasing reaction temperature.