Controlling the Dynamic Instability of Capped Metal Nanoparticles on Metallic Surfaces.

Small metal nanoparticles (NPs) with core-sizes ranging from 1 to 3 nm constitute a bridge between molecules and colloids with unique electronic, catalytic, and other properties. Many applications entail immobilization onto solid supports, but while NP behavior in solution is well studied, the effect of the interaction between NPs and the substrate surface is understood less. Here, we follow the structural evolution of thiolated monolayer-protected AuNPs on Au(111) substrates at the single-particle level in real-time using high-resolution in situ scanning tunneling microscopy. We show how the reactivity of the substrate affects the stability of the immobilized NPs and how their structural identity can be preserved. Entropically driven redistribution of the NP's protective capping layer is an important element in the disintegration process and at the same time rather generic. Our findings may thus have wider implications on the design and optimization of functional surfaces involving NPs, made of materials other than Au.