Direct Cd-to-Pb Exchange of CdSe Nanorods into PbSe/CdSe Axial Heterojunction Nanorods
- Direct Cd-to-Pb Exchange of CdSe Nanorods into PbSe/CdSe Axial Heterojunction Nanorods
- Dongkyu Lee; Whi Dong Kim; Seokwon Lee; 배완기; 이상헌; Doh C. Lee
- Surface; Ligand; Synthesis; Quantum Dot; Density functional theory
- Issue Date
- Chemistry of materials
- VOL 27, NO 15, 5295-5304
- We report synthesis of PbSe nanorods (NRs) and PbSe/CdSe axial heterojunction NRs via direct Cd-to-Pb cation exchange in CdSe NRs. Use of suited ligand−cation combinations enables the cation exchange while keeping the nanomaterial morphology intact. For example, solvation of Cd2+ using oleylamine (OLA) allows for the cation exchange process, which would not be possible by using oleic acid instead of OLA. A mild cation exchange process, such as mixing Pb-oleate and OLA with CdSe NRs at 130 or 150 °C, results in anisotropic replacement of CdSe into PbSe along the ⟨0001⟩ direction of wurtzite CdSe, and a partial conversion leads to the formation of heterostructure NRs containing axial CdSe/PbSe heterojunctions. While the cation exchange proceeds at both tips of CdSe NRs, exchange appears to be faster on (0001̅) planes. Binding
energy calculation based on density functional theory reveals that OLA binds strongly to the (0001̅) facet of CdSe NRs, leading to asymmetric cation exchange. This protocol to convert CdSe nanocrystals directly into PbSe broadens the design range of CdSe/PbSe heterojunction nanomaterials potentially with various morphologies because template CdSe nanocrystals can be prepared in different shapes via colloidal synthesis.
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