Understanding the Ensemble of Growth Behaviors of Sub-10-nm Silver Nanorods Using <i>in Situ</i> Liquid Cell Transmission Electron Microscopy

Abstract

Desirable properties of nanomaterials in practical applications are directly associated with their specific size and morphology. Nanostructure growth behaviors in the synthesis process should be therefore studied for controlling and adjusting optimal configurations. In this work, the multistep liquid-phase growth mechanism of sub-10 nm silver nanorods in diameter is revealed using in situ liquid cell transmission electron microscopy. We observed that small-sized silver nanoparticles were first formed from precursor solution by monomer attachment. Then, larger nanoparticle building blocks were generated by nanoparticle attachment. Subsequently, shape-directed attachment growth of nanoparticle building blocks resulted in the formation of silver nanorods. During these processes, two approaching nanoparticles jumped to contact and coalesced into a dimer nanoparticle. When another particle approached the dimer nanoparticle, the nanoparticle chain would be formed by the end-to-end attachment. After the chain straightened, accompanied by mass redistribution and lattice rotation, single-crystalline silver nanorods dominated by {111} planes were finally produced. We attributed the jump-to-contact of individual nanoparticles and end-to-end attachment of nanorods in liquid to the formation of transient paired nanoparticle surfaces associated with the hydration layers and the weaker hydration force at the nanorod ends. Understanding these growth trajectories provide important fundamental insight connecting sub-10-nm crystal morphologies to the development of kinetically stabilized surface features.