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      On doping CdS/ZnS core/shell nanocrystals with Mn.

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          Abstract

          This paper presents a mechanistic study on the doping of CdS/ZnS core/shell semiconductor nanocrystals with Mn based on a three-step synthesis, which includes host-particle synthesis, Mn-dopant growth, and ZnS-shell growth. We used a combination of electron paramagnetic resonance spectroscopy (EPR) and inductively coupled plasma atomic emission spectroscopy (ICP) to monitor Mn-doping level and growth yield during doping synthesis at both the dopant-growth and ZnS-shell-growth steps. First, our kinetic study shows that Mn adsorption onto the nanocrystal surface includes the formation of weakly and strongly bound Mn. The formation of weakly bound Mn is associated with a chemical equilibrium between adsorbed Mn species on the nanocrystal surface and free Mn species in growth solution, while the formation of strongly bound Mn exhibits first-order kinetics with an activation-energy barrier of 211 +/- 13 kJ/mol. Second, our results demonstrate that both weakly and strongly bound Mn can be removed from the surface of nanocrystals during ZnS-shell growth. The replacement of strongly bound Mn requires a higher temperature than that of weakly bound Mn. The yield of the replacement of strongly bound Mn is strongly dependent on the temperature of ZnS-shell growth. Third, our results show that the Mn-growth yield is not dependent on the size and crystal structure of nanocrystals. All together, these results suggest a mechanism in which nanocrystal doping is determined by the chemical kinetics of three activation-controlled processes: dopant adsorption, replacement, and ZnS-shell growth.

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          Author and article information

          Journal
          J. Am. Chem. Soc.
          Journal of the American Chemical Society
          American Chemical Society (ACS)
          1520-5126
          0002-7863
          Nov 19 2008
          : 130
          : 46
          Affiliations
          [1 ] Department of Chemistry, University of Florida, Gainesville, Florida 32611, USA.
          Article
          10.1021/ja805736k
          18950179
          0131564e-1c97-4f2d-b7dc-5651631e6165
          History

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