Development of a microemulsion-based process for synthesis of cobalt (Co) and cobalt oxide (Co 3O 4) nanoparticles from submicrometer rods of cobalt oxalate

Abstract

Rod-shaped nanostructures of cobalt oxalate dihydrate were synthesized at room temperature by the microemulsion (reverse micellar) route. These rods are highly uniform in length and can be modified with temperature (from ∼6.5 μm at 50 °C to ∼2.5 μm at 150 °C) while keeping the diameter nearly constant (200–250 nm). Thermal decomposition of these rods in a controlled atmosphere (air and H 2) leads to nanoparticles of Co 3O 4 and Co, respectively, while in a helium atmosphere a mixture of Co and CoO nanoparticles is obtained. Co 3O 4 nanoparticles (∼35 nm) were slightly agglomerated, while Co nanoparticles were monodispersed and highly uniform (∼25 nm). The oxalate rods and Co 3O 4 nanoparticles show an antiferromagnetic ordering at 54 and 35 K, respectively.