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Two-Dimensional CdSe-PbSe Heterostructures and PbSe Nanoplatelets: Formation, Atomic Structure, and Optical
Bastiaan B V Salzmann1, Jur de Wit1, Chen Li2
1Condensed Matter & Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508TA Utrecht, The Netherlands.
The Journal of Physical Chemistry. C, Nanomaterials and Interfaces
|February 4, 2022
Summary
Cation exchange transforms cadmium selenide nanoplatelets into lead selenide structures. This process, controlled by temperature, allows detailed study of intermediate stages and reveals unique interfacial and electronic properties in the resulting nanomaterials.
Area of Science:
- Materials Science
- Nanotechnology
- Solid-State Chemistry
Background:
- Cation exchange is a key method for synthesizing nanomaterials not accessible through direct routes.
- Cadmium selenide (CdSe) nanoplatelets (NPLs) serve as a versatile platform for exploring novel material transformations.
- Understanding phase transitions and interfacial phenomena in nanomaterials is crucial for advanced applications.
Purpose of the Study:
- To investigate the Pb2+-for-Cd2+ cation exchange process on CdSe NPLs.
- To characterize the formation of 2D CdSe-PbSe heterostructures and PbSe NPLs.
- To elucidate the structural, optical, and electronic properties of the resulting materials.
Main Methods:
- Applying Pb2+-for-Cd2+ cation exchange to CdSe NPLs at controlled temperatures.
- Utilizing atomically resolved high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) for structural analysis.
- Employing optical spectroscopy, including temperature-dependent and time-resolved photoluminescence (PL), to probe electronic properties.
Main Results:
- The cation exchange initiates at the vertices of CdSe NPLs, progressing into the lattice as a rock salt PbSe (rs-PbSe) phase while preserving the anion sublattice.
- Interfaces between zinc blende CdSe (zb-CdSe) and rs-PbSe exhibit shared {001} and {011} planes.
- PbSe NPLs show high crystallinity with rotated edge protrusions, indicating atomic reconfiguration. Emission peak shifts correlate with PbSe domain growth.
- Temperature-dependent band gap variations and anisotropic shape effects were observed, alongside unique dark-bright exciton-state splitting in time-resolved PL.
Conclusions:
- Controlled cation exchange provides a pathway to novel 2D heterostructures and PbSe NPLs.
- The study reveals the mechanism of phase transformation and interface formation during cation exchange.
- The resulting PbSe NPLs exhibit distinct size- and shape-dependent optical properties, differing from 3D quantum dots.
