* Corresponding author's E-mail address: ayiayi72@gmail.com, a.anyama@unical.edu.ng, Tel.: +2348035961521 Inorganic Materials Research Laboratory, Department of Pure and Applied Chemistry, University of Calabar, Nigeria. Advanced Journal of Chemistry-Section A, 2019, 2(2), 175-183 Research Article http://ajchem-a.com On The Use of Methylimidazolium Acetate Ionic Liquids as Solvent and Stabilizer in the Synthesis of Cobalt Nanoparticles by Chemical Reduction Method Walter Efiok John, Ayi Anyama Ayi ,*, Chinyere Ayi Anyama, Providence Betelwhobel Ashishie, Bassey Enyi Inah A R T I C L E I N F O A B S T R A C T Received: 15 January 2019 Revised: 24 January 2019 Accepted: 31 January 2019 Available online: 16 February 2019 K E Y W O R D S 1-ethyl-3-methylimidazolium acetate (EMIMOAC) and 1-buthyl-3- methylimidazolium acetate (BMIMOAC) ionic liquids have been used as a solvent and stabilizing agent in an attempt to prepare cobalt nanoparticles via chemical reduction method. The SEM and UV-Vis techniques confirm the formation of nanoparticles. XRD reveals the Nano crystalline nature of the products with average crystallite size of 27.5 and 24.1 nm for CoEMIMOAC and CoBMIMOAC, respectively. The SEM and EDAX morphological/atomic weight ratio analyses do not show much difference between the Nano crystals formed in EMIMOAC or BMIMOAC. These results indicate that the cationic part of the ionic liquid did not play significant role during nucleation and growth of the particles. The inhibition zone diameter (IZD) shows moderate susceptibility against Staphylococcus aureus to CoBMIMOAC (15 mm) but high susceptibility to CoEMIMOAC with a larger inhibition zone diameter of 23 mm. Gram-negative microorganism E. coli is moderately susceptible to both CoEMIMOAC (14 mm), and CoBMIMOAC (15 mm). Nano crystals Ionic liquids Chemical reduction Nanoparticles Antimicrobial activities G R A P H I C A L A B S T R A C T