Transformative Synthesis of a Single-Sized PbSe Nanocluster via Cation Exchange.

Achieving atomic-level control in IV-VI semiconductor nanomaterials remains an important challenge. Here, we report the synthesis of an ultrasmall, single-sized PbSe nanocluster via cation exchange of a CuSe template cluster with an atomically defined lead(II) 4--butylbenzoate compound. The resulting PbSe cluster exhibits a sharp and reproducible excitonic absorption peak at 546 nm (linewidth, 61 nm or 0.25 eV) and red emission at 750 nm with a quantum yield of 5-10%. In contrast to the starting icosahedral Se lattice, the resulting PbSe cluster adopts a rock salt structure with a cubic close packing of anions, indicating a transformation of the anion lattice during cation exchange. A combined analysis using structural modeling, powder X-ray diffraction, and X-ray photoelectron spectroscopy suggests that the single-sized cluster is likely a PbSe species. Our method demonstrates the feasibility of cation exchange transformation for synthesizing single-sized IV-VI nanoclusters, offering a new approach toward atomic-level control of these materials.