Uncovering Tunable Self-Assembly Pathways in Halide Perovskite Nanoplatelets Through Post-Synthetic Chiral Organic Ligand Addition, or Halide Anion Exchange Techniques

Self-assembly mechanisms in colloidal CsPbBr₃ nanoplatelets or quantum wells were studied using either (a) post-synthetic ligand or (b) anion exchange techniques. (a) Although chirality in hybrid organic-inorganic single crystals have been studied in detail, we present a comprehensive investigation in into the intriguing morphological transformations observed when chiral organic ligands interact with CsPbBr₃ nanoplatelets. Our study encompasses a multi-faceted approach, combining optical, chiral, and transmission electron microscopy (TEM) techniques, shedding light on the emergence of chiral intermediates and their dependence on ligand chirality. Our optical and chiral spectroscopic studies of various aliquots of ligands added to the nanoplatelets allowed us to elucidate the spectral fingerprints associated with the emergence of these chiral intermediates. Notably, our findings highlight the intricate interplay between ligand chirality and the evolution of intermediates in the spectra. Our results reveal distinct pathways and morphological transformations driven by both the absolute configuration r-/s- of the ligands through unusual, oriented attachment mechanisms. Furthermore, we investigated the lifetime of these intermediates and found a strong dependence on the chirality of the ligands added. Our study not only advances our fundamental understanding of chiral ligand-nanoplatelet interactions, but also opens exciting possibilities for the rational design and manipulation of chiral nanostructures for various technological applications employing sensitivity to light polarization.<br/>(b) We present a study on anion exchange techniques in colloidal CsPbBr₃ nanoplatelets using various inorganic precursors, examining the resulting structural, emissive, and morphological transformations. Our findings indicate that the selection of precursors and reaction conditions can be strategically utilized to control self-assembly behavior and induce morphological transformations in these materials. This technique offers significant improvements and experimental ease over existing synthetic protocols, which typically involve high temperatures and etching agents to elucidate more rigid ion exchange transformation pathways. Our approach not only simplifies the experimentation process but also provides greater flexibility in tuning the properties of CsPbBr₃nanoplatelets.