Transformation Pathway from CdSe Nanoplatelets with AbsorptionDoublets at 373/393 nm to Nanoplatelets at 434/460 nm

For those colloidal semiconductor CdSe nanospecies that exhibit sharp opticalabsorption doublets, different explanations have appeared in the literature regarding theirmorphological nature and formation, with no consensus reached. Here, we discuss thetransformation 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 thein situtransformation associated with the temperature. Combining the results of SAXS/WAXS,optical spectroscopy, and transmission electron microscopy, we propose that thetransformation pathway experiences corresponding magic-sized clusters (MSCs), whichdisplay similar optical properties but with zero-dimensional structure. From stacked NPL-393to 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 presentfindings provide compelling evidence that both MSCs and their assembled NPLsexhibit similar optical absorption.