Competition between ordered morphologies of functionalized silver nanoparticles elucidated by a joint experimental and multiscale theoretical study

Abstract

A multiscale approach, combining density functional theory models of functionalized silver nanoparticles and extended surfaces, is introduced to predict the competition between ordered nanoparticles at experimentally relevant size. An original theoretical descriptor, named synthesis energy, is defined and validated by high resolution transmission electron microscopy characterizations of silver nanoparticles synthesized in a solvated amine and amidine medium. Microscopy images show that icosahedral clusters cover 90 % of statistics around 7 nm, with very minority face-centered cubic particles (1 %). This trend is counter-intuitive compared to face-centered cubic morphologies reported in the literature. The ab initio models show a larger stability for octylamine over methyl amidine ligands on small silver nanoparticles (1.5 nm). At larger size (2.5 nm), the octylamine-covered silver nanocluster models indicate a clear preference for icosahedra. To reach the experimental size, the computed synthesis energy is decomposed into several contributions and shows the prevalence of the clean nanoparticle cohesion energy normalized by its surface area, over the ligand adsorption strength, the precursor dissociation and the adhesion of the cluster on the support. A mathematical model fitting ab initio data and predicting this cohesion energy at any size, relevantly captures the competition between morphologies, by showing a net preference for icosahedra at 7 nm, in agreement with experiments.