Doping of Cu(i) ions into CdS/ZnS core/shell nanocrystals through a cation exchange strategy

The optical properties of doped semiconductor nanocrystals (NCs) are strongly affected by the dopant position inside the host lattice. However, controlling the dopant position in Cu(i) doped core/shell semiconductor NCs is still unexplored due to the high ionic mobility of Cu(i) ions at the doping temperature. In this paper, we report the doping of Cu(i) ions into CdS/ZnS core/shell NCs via a cation exchange strategy. During the doping, the exciton emission of CdS NCs is reduced and the dopant emission becomes intensified as the doping level is increased from 0 to 1.1%, and the PL profile of the final product is very similar to that of uncoated CdS:Cu(i) NCs. Such an optical change is very different from that observed in the products synthesized by a conventional method, in which no exciton emission of CdS NCs is observed. During the Cu(i) doping process, the variation of the dopant emission may arise from the doping position change from the outside ZnS shell to the inside CdS core in the CdS/ZnS core/shell NCs. The deduction can be further verified by the optical change by direct heating of a small amount of Cu(i) doped CdS/ZnS NCs in a non-coordinating solvent. This work offers a cation exchange strategy for fabricating Cu(i) doped core/shell NCs with tuned dopant positions, which will open up rich opportunities for tuning the optoelectronic properties of Cu(i) doped semiconductor NCs.