Autocatalytic Nucleation and Self-Assembly of Inorganic Nanoparticles into Complex Biosimilar Networks.

Self-replication of bioorganic molecules and oil microdroplets have been explored as models in prebiotic chemistry. An analogous process for inorganic nanomaterials would involve the autocatalytic nucleation of metal, semiconductor, or ceramic nanoparticles-an area that remains largely uncharted. Demonstrating such systems would be both fundamentally intriguing and practically relevant, especially if the resulting particles self-assemble into complex structures beyond the capabilities of molecules or droplets. Here, we show that autocatalytic nucleation occurs with silver nanoparticles, which subsequently self-assemble into chains through spatially restricted attachment. In dispersions containing "hedgehog" particles, these reactions produce complex colloids with hierarchical spike organization. On solid surfaces, autocatalytic nucleation of nanoparticles yields conformal networks with hierarchical organization, including nanoparticle "colonies." We analyzed the complexity of both types of solid-stabilized particle assemblies via graph theory (GT). The complexity index of idealized spiky colloids is comparable to that of complex algal skeletons. The GT analysis of the percolating nanoparticle networks revealed their similarities to the bacterial, but not fungal, biofilms. We conclude that coupling autocatalytic nucleation with self-assembly enables the generation of complex, biosimilar particles and films. This work establishes mathematical and structural parallels between biotic and abiotic matter, integrating self-organization, autocatalytic nucleation, and theoretical description of complex systems. Utilization of quantitative descriptors of connectivity patterns opens possibility to GT-based biomimetic engineering of conductive coatings and other complex nanostructures.