Chemical transformation of Te into new ternary phase Pb_{: M}Cu_nTe_{m + n} nanorods and their surface atom diffusion and optical properties

A new stable phase of ternary Pb_mCu_nTe_m+n with rough surface, including one-dimensional (1D) bamboo-like shaped and curved nanorods with short branches, was first synthesized using Te as a sacrificial template. The structure does not exist in the bulk Cu₂Te-PbTe phase diagram. It is revealed that the optimal Pb²⁺/Cu²⁺ chemical reactivity synergistic effect can preserve the initial shape of the Te nanorod parent template, which involves small volume changes and secondary nucleation phenomenon along the entire length of the nanorods. Furthermore, the diffusion of surface atoms and a surface pre-melting on the short branches of the nanorods were observed upon in situ electron-beam irradiation. The average Cu atom diffusion distance calculated (3 × 10^-11 m s^-1) is higher than the reported value (1.34 × 10^-12 m s^-1) in Cu₂O at 373 K, which is attributed to the local high temperature created by the incident electron irradiation and large surface to volume ratio of the nanomaterials. In addition, the Pb_mCu_nTe_m+n nanorods exhibit well-defined and size-dependent optical band gaps (E_g) in the near-IR region. We envision that the Te template strategy is general and robust and offers easy access to other new phase ternary PbTe-based nanomaterials via carefully balancing the chemical reactivity of the precursor.