A comprehensive multi-scale modeling of defective CdSe colloidal nanocrystals through advanced X-ray scattering techniques

The dissertation includes a comprehensive multi-scale modeling of defective CdSe colloidal nanocrystals through advanced X-ray scattering techniques. Chapter 1 introduces the reader to the entire work of the Ph. D. thesis and to its main topic of research, which is focused on structural and microstructural characterization of colloidal quantum-dots. The following Chapter is dedicated to the description of conventional and unconventional characterization methods at the nanoscale, discussing their limits and potentiality in characterizing real nano-systems. Chapter 3 serves as a mathematical description of the DSE, and its implementation in the DebUsSy suite for the characterization of real ensembles of nanosized samples. Therein, the data collection and reduction procedures are also reported, together with a brief section in which the DSE to PDF approaches are compared. The need of introducing strains and defects in the complex atomistic model of CdSe nanocrystals makes it necessary to describe these defects, with a brief state of the art of their characterization methods (Chapter 4). Chapter 5 is completely dedicated to describing the computational model used for the characterization of cQDs and its use as a part of the overall data analysis strategy. The final Chapters focus on the application of the model to real systems in which its potentiality and sensitivity are tested on different materials, disclosing new size-dependent fault driven relaxation and faceting features in CdSe cQDs. An additional section presents an alternative method for the characterization of metallic NPs with larger sizes, but (much) lower stacking fault probabilities.