The synthesis and arrested oxidation of amorphous cobalt nanoparticles using DMSO as a functional solvent

Magnetic nanoparticles exhibit a strong tendency to become overly oxidized and unstable during synthesis, ultimately leading to nanoparticle agglomeration and degradation. Capping agents can be used during nanoparticle synthesis to provide particle surface coverage and to improve nanoparticle dispersibility in solution, while preventing excessive oxidation and agglomeration. This paper presents a technique to synthesize amorphous 3.7 ± 1.5 nm cobalt (Co) nanoparticles using dimethyl sulfoxide (DMSO) to function as both the stabilizing agent and the solvent for Co nanoparticles via a quick, solvent-based reduction of Co²⁺ with NaBH₄ in a DMSO solvent. UV–visible spectroscopy analysis was used to determine the minimum amount of reducing agent needed to produce Co nanoparticles so as to limit the waste of reagents. TEM and SEM imaging were used to study the morphology of the Co nanoparticles from the DMSO dispersion and of the Co nanoparticle powder. FT-IR was used to elucidate the nature of the interaction between the Co nanoparticle surface and DMSO. Furthermore, SEM–EDS elemental mapping was used to determine the composition and surface properties of the Co nanoparticles. This synthesis method demonstrates that Co nanoparticles can be successfully synthesized by simply using DMSO as a functional solvent, thereby avoiding excessive oxidation and agglomeration in solution.