Chirality Cascade and Atomic-Scale Helicity in Hierarchical Chiral CuO Nanostructures

“Bottom-up” transmission of chirality between different length scales in hierarchically structured materials, which display intricate interplay between inorganic compounds and chiral organic ligands, is a complex phenomenon that requires insight into the origin and evolution of chiroptical activity (optical asymmetry), an understanding of chiral bias, and real-time visualization of atomic-level helicity. In this study, we employ a comprehensive study on chiral antipodal hierarchical CuO nanostructures as an archetype of a comprehensive approach to reveal the origin of broadband chiroptical activity in a stepwise manner and real-time demonstration of atomic-scale chirality/helicity and the transfer of chirality from organics to inorganics followed by their primary building block to their hierarchically assembled structures. We report atomic-scale chirality in hierarchically organized d/l-CuO nanoflowers manifested through primary building blocks of putative Boerdijk-Coxeter-Bernal (BCB)-like tetrahelical fragments, with corresponding handedness, prepared through a simple one-pot, template-less method. The atomic-scale chirality in the as-prepared d/l-CuO nanoflowers has been preserved on calcination (at 600 °C) through screw dislocation-driven helicity on transformation into toroid-like nanostructures. We also explore the intriguing presence of the BCB helix in polycrystalline CuO and its connection to the nanocrystallite size of the nanoflowers. Additionally, the phenomenon of cooperative chirality in d/l-CuO nanostructures, emerging from chiral synergism between the crystallographic and geometric morphologies, could be corroborated through microscopic and spectroscopic studies. This comprehensive approach not only unveils the intricate details of chiral inorganic materials but also opens avenues for tailoring chiral transfer pathways, offering promising technological advancements. Our findings have implications for understanding the translation of chirality and asymmetry across structural motifs and length scales, which play a fundamental role in nature, enabling unique functionalities in contexts ranging from biological systems to synthetic materials.