title: The critical role of surfactants in the growth of cobalt nanoparticles.
abstract: We report a combined experimental and computational study on the critical role of surfactants in the nucleation and growth of Co nanoparticles synthesized by chemical routes. By varying the surfactant species, Co nanoparticles of different morphologies under similar reaction conditions (e.g., temperature and Co-precursor concentration) were produced. Depending on the surfactant species, the growth of Co nanoparticles followed three different growth pathways. For example, with surfactants oleic acid (OA) and trioctylphosphine oxide (TOPO) used in combination, Co nanoparticles followed a diffusional growth pathway, leading to single crystalline nanoparticles. Multiple-grained nanoparticles, through an aggregation process, were formed with the combination of surfactants OA and dioctylamine (DOA). Further, an Ostwald ripening process was observed in the case of TOPO alone. Complementary electronic structure calculations were used to predict the optimized Co-surfactant complex structures and to quantify the binding energy between the surfactants (ligands) and the Co atoms. These calculations were further applied to predict the Co nanoparticle nucleation and growth processes based on the stability of Co-surfactant complexes.
authors.affiliation: Chemical & Biological Engineering, The University of Alabama, Tuscaloosa, Alabama 35487, USA. ybao@eng.ua.edu
authors.forename: Yuping
authors.initials: Y
authors.lastname: Bao
authors.forename: Wei
authors.initials: W
authors.lastname: An
authors.forename: C Heath
authors.initials: CH
authors.lastname: Turner
authors.forename: Kannan M
authors.initials: KM
authors.lastname: Krishnan
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D004058:Diffusion; D004583:Electrons; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D013501:Surface-Active Agents; D003035:Cobalt