title: The growth of Co:ZnO/ZnO core/shell colloidal quantum dots: changes in nanocrystal size, concentration and dopant coordination.
abstract: We report a synthesis route for the growth of Co:ZnO/ZnO core/shell quantum dots. This procedure consists of successive steps, comprising the addition of diluted precursor salt solutions, and heat treatment at 50 degrees C. By deriving a relation between the extinction coefficient at 250 nm and the nanocrystal diameter, we are able to monitor changes in quantum dot concentration during shell growth. We found that a mechanism based on the nucleation of new particles after salt addition and subsequent Ostwald ripening during the heat treatment is responsible for the shell growth. Based on ligand-field absorption spectroscopy, we demonstrate that the Co(2+) ions adsorbed at the surface of Co:ZnO quantum dots are incorporated inside the ZnO shells. Finally, EPR spectroscopy indicates that the surface-adsorbed Co(2+) ions can be incorporated as substitutional as well as interstitial Co(2+) ions.
authors.affiliation: Physics and Chemistry of Nanostructures, Ghent University, Krijgslaan 281-S12, 9000 Ghent, Belgium.
authors.forename: Petra
authors.initials: P
authors.lastname: Lommens
authors.forename: Karel
authors.initials: K
authors.lastname: Lambert
authors.forename: Frank
authors.initials: F
authors.lastname: Loncke
authors.forename: David
authors.initials: D
authors.lastname: De Muynck
authors.forename: Timuçin
authors.initials: T
authors.lastname: Balkan
authors.forename: Frank
authors.initials: F
authors.lastname: Vanhaecke
authors.forename: Henk
authors.initials: H
authors.lastname: Vrielinck
authors.forename: Freddy
authors.initials: F
authors.lastname: Callens
authors.forename: Zeger
authors.initials: Z
authors.lastname: Hens
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D003102:Colloids / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D045663:Quantum Dots; D013499:Surface Properties; D015034:Zinc Oxide / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D003102:Colloids; D003035:Cobalt; D015034:Zinc Oxide