Sol-gel synthesis of nanostructured cobalt oxide in four different ionic liquids

In this paper we report on the sol-gel synthesis of cobalt oxide in four different ionic liquids with two different cations and anions. The employed ionic liquids are; 1-ethyl-3-methylimidazolium trifluoromethylsulfonate ([EMIm]TfO), 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate ([Py 1,4 ]TfO), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIm]TFSA), and 1-butyl-1-methylpyrrolidiniumbis(trifluoromethylsulfonyl)amide ([Py 1,4 ]TFSA). The influence of the cation and anion of the ionic liquids on the morphology of the synthesized oxides was explored. The results showed that octahydron-shaped Co 3 O 4 nanoparticles with different average sizes depending on the type of the employed ionic liquid. The imidazolium cation was found to play a significant role in reducing the particle size of the synthesized Co 3 O 4 nanoparticles. The samples prepared in the imidazolium-based ionic liquids showed smaller particle sizes than those of the samples prepared in the pyrrolidinium-based ionic liquids. The shape of the particles of the synthesized Co 3 O 4 was not affected by the type of the ionic liquids. Graphical abstract SEM images of sol-gel synthesized cobalt oxide obtained from the ionic liquids [EMIm]TFSA, [EMIm]TfO, [Py 1,4 ]TFSA and [Py 1,4 ]TfO, and calcined at 500 °C. Highlights Co 3 O 4 nanoparticles were obtained in the ionic liquids [EMIm]TfO, [Py 1,4 ]TfO, [EMIm]TFSA and [Py 1,4 ]TFSA via the sol–gel approach. Octahydron-shaped Co 3 O 4 nanoparticles with different average sizes depending on the type of the employed ionic liquid were obtained. The imidazolium cation plays a significant role in reducing the particle size of the synthesized cobalt oxide. The type of the anion or cation of the employed ionic liquids does not show an obvious influence on the shape of the synthesized cobalt oxide particles.