A study of Mn ²⁺ doping in CdS nanocrystals

We report here the synthesis of water soluble Mn ²⁺-doped CdS nanocrystals in which it has been possible for the first time to obtain a distinct Mn ²⁺ d-related emission well-separated from the defect state emissions. By varying the reaction temperature systematically, we establish 55°C as the optimum temperature to maximize the Mn ²⁺ d emission, the existence of this optimum synthesis temperature being shown as the result of two opposing influences of the temperature. Most interestingly, present results establish that Mn ²⁺ favors preferential doping of larger-sized particles even within the narrow size distribution achieved in the present synthesis, rendering the relatively smaller-sized nanocrystals depleted of Mn ²⁺ for any given synthesis. One important aspect of the present approach is that the synthesized nanocrystals readily dissolve in water without any deleterious effect on the Mn ²⁺ d-related emission intensity.