Tailoring properties and functionalities of metal nanoparticles through crystallinity engineering

Metal nanoparticles (NPs) with size comparable to their electron mean free path possess unusual properties and functionalities(1), serving as model systems to explore quantum and classical coupling interactions as well as building blocks of practical applications(2-8). Although advances in strategies for synthesizing metal NPs have enabled control of size, composition and shape(9-13), the requirement that defects are simultaneously controlled, to ensure essential perfect nanocrystallinity for physics modelling as well as device optimization, is a potentially more significant issue, but has posed substantial technological challenges. Here we report that crystallinity of monodisperse silver NPs can be well controlled by judicious choice of functional groups of molecular precursors, thus facilitating investigation of their scope for versatile applications. We demonstrate how nanoscale chemical transformation, electron-phonon interactions and nanomechanical properties are modified by nanocrystallinity. Lastly, we find that performance of NP-based molecular sensing devices can be optimized with significant improvement of figure of merit if perfect single-crystalline NPs are applied. Our approach represents a versatile synthetic route for other metal nanomaterials with unprecedented control of their structure, creating a rational pathway for understanding and manipulating nanoscale chemical and physical processes as well as technological applications of metal NPs.