Colloidal Cd_xM_{1- x}Te Nanowires from the Visible to the near Infrared Region: N, N-Dimethylformamide-Mediated Precise Cation Exchange

Cation exchange has been a successful methodology for tuning the bandgaps of nanomaterials, while the most popular protocol in the toluene/methanol system lacks precise compositional control due to its inherent poor solvent compatibility. We herein report an alternative cation exchange route in N,N-dimethylformamide (DMF) solvent for converting preformed colloidal CdTe nanowires into Cd_xM_1-xTe (M = Pb²⁺, Zn²⁺, Ag⁺, Hg²⁺) nanowires with good batch-to-batch reproducibility. The resulting Cd_xM_1-xTe nanowires show a tunable bandgap from 2.26 to 0.63 eV, and the energy levels of these nanowires can be finely tuned. Furthermore, a comparative study for the cation exchange of CdTe nanowires with Pb²⁺ ions in toluene/methanol and DMF illustrated that the reduction of Cd²⁺ extraction and the Pb²⁺ introduction barrier accounts for precise compositional control. The cation exchange reaction in the DMF phase provides an efficient way to obtain nanomaterials with precise composition control. Moreover, these available high-quality colloidal semiconductor nanowires also pave the way for near-infrared device exploration.