Towards Computation-Guided Design of Tunable Organic-Inorganic CdS Quantum Dot Binary Superlattices

Inspired by naturally occurring hierarchical materials, numerous beautiful and functional mesoscale architectures have been constructed in labs via the assembly of solid-state nanoscale building blocks with the assistance of bio- or biomimetic ligands. Their structures and assembly dynamics are responsive to and tightly regulated by the system's convoluted energetics and entropic information. In this study, we observed a 2D square superlattice formation of CdS quantum dots (QD) in the presence of molar equivalent peptoids, which cannot be explained by known superlattice formation mechanisms. Further, the complexity of the organic-inorganic colloidal system often makes it difficult to probe the detailed driving force via experimental means. To resolve the challenge, we constructed a multi-scale theoretical toolkit by joining first-principles DFT and atomistic molecular dynamics simulations to connect the scales and gain physical insights into the assembly mechanisms. Based on theoretical evidence, we show that the assembly is a hybrid binary superlattice where both the CdS QDs and the peptoids serve as building blocks. We further validated our hypothesis and predictions with varying lengths of peptoids. This new design principle inspires new routes that utilize sequence-defined tunability of the organic building blocks to achieve tunable superstructures.