Resolving Peptide-Based Supramolecular Architecture Emerging at Reactive Copper/Water Interface

Understanding how molecular interactions evolve into ordered architectures at reactive solid/liquid interfaces remains a major challenge because surface reactivity can profoundly influence adsorption mechanisms. In such systems, multiple interfacial processes, including redox reactions, adsorption/desorption, coordination, and supramolecular organization, may occur simultaneously, making both chemical and structural characterization particularly challenging. Here, we investigate the adsorption behavior of small peptides at the copper/water interface and reveal the complex interplay between surface reactivity, self-assembly, and (supra)molecular organization. Specifically, by combining surface-sensitive techniques with density functional theory (DFT) calculations, we provide converging experimental and computational evidence on the formation of CuI-peptide units generated through interfacial copper oxidation and assembled into an interconnected three-dimensional network driven by the formation of Cu-S coordinative bonds and stabilized by weaker electrostatic and hydrogen-bonding interactions. AFM force spectroscopy further reveals reproducible nanomechanical events associated with a characteristic structural length scale of approximately 1 nm, in agreement with DFT predictions, indicating the existence of an elementary structural motif within the CuI-peptide network. The resulting assembly forms a thick, hydrated, and mechanically soft multilayer extending several tens of nanometers beyond the molecular dimensions of the peptide. Time-lapse AFM reveals a growth mechanism driven by the local reorganization of colloidal building blocks, resulting in dynamic film porosity that sustains continued growth of the adlayer. The combined experimental and theoretical results support a coupled redox-coordination-assembly-transport-controlled growth mechanism describing how molecular adsorption evolves into a supramolecular architecture at a reactive copper/water interface.