Schematic illustration of the effects of metal salt precursor on the morphology of Co3O4 on CuO NWs. A CuO NW is dip-coated with a cobalt precursor solution containing the solvent and cobalt salt and then annealed in the flame. (Left column) In the case of a volatile precursor (e.g., Co(CH3COO)2·4H2O), the precursor evaporates into vapor and nucleation of the Co3O4 occurs in the gas phase, resulting in the formation of the NP-chain morphology. (Right column) In the case of a non-volatile precursor (e.g., Co(NO3)2·6H2O), the precursor does not evaporate but stays in the solvent, where nucleation happens in the liquid phase, resulting in the formation of the shell morphology.
Luo et al. Nanoscale Research Letters 2013 8:347 doi:10.1186/1556-276X-8-347