title: Evolution of size distribution in pressure drop induced decomposition synthesis of cobalt nanoparticles.
abstract: Cobalt nanoparticles with average diameters of 8.8 nm and a standard deviation of 8% were obtained in a pressure drop induced decomposition synthesis in an autoclave. Samples were taken during the experiment and characterized with TEM. A significant narrowing of the size distribution coincident with particle growth was observed. The standard deviation decreased from 31% to 8% while the average size increased from 5.5 nm to 8.8 nm. In order to explain the experimentally observed narrowing of the size distribution, a model that accounts for the influence of the capping layer on the growth rate was developed. The transfer of the reacting monomer into the capping layer was considered to be similar to an adsorption process. A rate constant of 4x10(-5) cm(4) mol(-1) s(-1) was obtained for the growth reaction, and it was thus concluded that the growth reaction proceeds under kinetic control rather than under diffusion control.
authors.affiliation: Department of Chemistry, Helsinki University of Technology, P.O. Box 6100, FI-02015 TKK, Finland.
authors.forename: Maija
authors.initials: M
authors.lastname: Huuppola
authors.forename: Nguyet
authors.initials: N
authors.lastname: Doan
authors.forename: Kyösti
authors.initials: K
authors.lastname: Kontturi
authors.forename: Christoffer
authors.initials: C
authors.lastname: Johans
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008958:Models, Molecular; D010316:Particle Size; D011312:Pressure; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D013501:Surface-Active Agents; D003035:Cobalt