Synthesis of nontoxic Co:CuInS2@ZnS nanocrystals with both fluorescence and room temperature ferromagnetism

Room temperature ferromagnetism is the precondition of the application of diluted magnetic semiconductors. At present, diluted magnetic nanocrystals (NCs) with room temperature ferromagnetism usually contain toxic elements, such as Cd. In this work, we report nontoxic Co:CuInS2 diluted magnetic NCs, which exhibit room temperature ferromagnetism. After growth of a ZnS shell outside Co:CuInS2 NCs, bright fluorescence can be observed, making as-prepared Co:CuInS2@ZnS NCs with both fluorescence and room temperature ferromagnetism. Besides ZnS shell encapsulation, the preparation of fluorescent–ferromagnetic bi-functional Co:CuInS2@ZnS NCs also relates to the doping amount of Co. Excess Co dopant would quench the fluorescence of the NCs whereas insufficient Co dopant could not offset the diamagnetism of the CuInS2@ZnS NCs. Only under appropriate Co doping do Co:CuInS2@ZnS NCs have both fluorescence and room temperature ferromagnetism.