Conformational mobility in monolayer-protected nanoparticles: from torsional free energy profiles to NMR relaxation

In this work, we develop a self-consistent route to inspect the conformational mobility of single chains in gold nanoparticles passivated with a monolayer of decanethiols. The approach is based on the match between a theoretical modeling under a coarse-grained level (i.e., system definition, buildup of the free energy profiles along relevant coordinates, modeling/parametrization of the friction, production of stochastic trajectories) and experimental spectroscopic investigations. The agreement between calculated and experimental values of 13C NMR longitudinal relaxation times supports the theoretical assumptions and the model parametrization. On physical grounds, it emerges that the mobility of the single chains resembles that of an ideal chain made of connected n-butane-like bonds.