Transformation Pathway from CdSe Nanoplatelets with Absorption Doublets at 373/393 nm to Nanoplatelets at 434/460 nm.

For those colloidal semiconductor CdSe nanospecies that exhibit sharp optical absorption doublets, different explanations have appeared in the literature regarding their morphological nature and formation, with no consensus reached. Here, we discuss the transformation pathway in two types of CdSe nanoplatelets (NPLs), from NPL-393 to NPL-460, exhibiting absorption doublets at 373/393 and 433/460 nm, respectively. Synchrotron-based small/wide-angle X-ray scattering (SAXS/WAXS) was performed to monitor the transformation associated with the temperature. Combining the results of SAXS/WAXS, optical spectroscopy, and transmission electron microscopy, we propose that the transformation pathway experiences corresponding magic-sized clusters (MSCs), which display similar optical properties but with zero-dimensional structure. From stacked NPL-393 to stacked NPL-460, the transformation goes through sequentially individual NPL-393, MSC-393, MSC-460, and individual NPL-460 at their corresponding characteristic temperature. The present findings provide compelling evidence that both MSCs and their assembled NPLs exhibit similar optical absorption.