The Growth of Co:ZnO/ZnO Core/Shell Colloidal Quantum Dots: Changes in Nanocrystal Size,Concentration and Dopant Coordination |
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| Authors: | Petra Lommens Karel Lambert Frank Loncke David De Muynck Timuçin Balkan Frank Vanhaecke Prof Dr Henk Vrielinck Dr Freddy Callens Prof Dr Zeger Hens Prof Dr |
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| Institution: | 1. Physics and Chemistry of Nanostructures, Ghent University,Krijgslaan 281‐S12, 9000 Ghent, Belgium, Fax: (+32)?9‐2644‐971;2. Department of Solid State Sciences, Ghent University, Krijgslaan 281‐S1, 9000 Ghent, Belgium;3. Department of Analytical Chemistry, Ghent University, Krijgslaan 281‐S12, 9000 Ghent, Belgium |
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| 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 °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 Co2+ ions adsorbed at the surface of Co:ZnO quantum dots are incorporated inside the ZnO shells. Finally, EPR spectroscopy indicates that the surface‐adsorbed Co2+ ions can be incorporated as substitutional as well as interstitial Co2+ ions. |
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| Keywords: | colloidal quantum dots magnetic semiconductors doping EPR spectroscopy UV/Vis spectroscopy |
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