Aggregative Growth of Oligopeptide-Protected Gold Nanoclusters into Plasmonic Particles

The stimuli response of nanomaterials represents a highly appealing characteristic, whereas the practical applications (in catalysis, biosensing etc.) are largely restricted by the limited understanding on the recognition mechanism. Herein, we report a pH-regulated size evolution from atomically precise Au nanoclusters (NCs) to plasmonic nanoparticles (NPs). The spectral monitoring demonstrates a three-stage aggregative growth pathway. First, the non-covalent interactions among the exterior oligopeptide ligands are gradually enhanced with the increased alkalinity, and then the Au-S bonding is partially disrupted, with the exposed Au atoms aggregating to form relatively larger, polydisperse clusters under weak alkaline conditions. Finally, size-redistribution occurs slowly under strong alkaline conditions to form the plasmonic particles. The controllable transition sheds light on the transition characteristics from molecular state to metallic state of Au nanomaterials.