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The Growth of Co:ZnO/ZnO Core/Shell Colloidal Quantum Dots: Changes in Nanocrystal Size, Concentration and Dopant Coordination
Author(s) -
Lommens Petra,
Lambert Karel,
Loncke Frank,
De Muynck David,
Balkan Timuçin,
Vanhaecke Frank,
Vrielinck Henk,
Callens Freddy,
Hens Zeger
Publication year - 2008
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200700753
Subject(s) - nanocrystal , quantum dot , ostwald ripening , nucleation , dopant , materials science , ion , chemical engineering , colloid , adsorption , absorption spectroscopy , spectroscopy , inorganic chemistry , nanotechnology , chemistry , doping , organic chemistry , physics , optoelectronics , quantum mechanics , engineering
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 °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.