  We present a quantitative exploration, combining experiment and simulation,
of the mechanical and electronic properties, as well as the modifications
induced by an alkylthiolated coating, at the single NP level. We determine the
response of the NPs to external pressure in a controlled manner by using an
atomic force microscope tip. We find a strong reduction of their Young modulus,
as compared to bulk gold, and a significant influence of strain in the
electronic properties of the alkylthiolated NPs. Electron transport
measurements of tiny molecular junctions (NP/alkylthiol/CAFM tip) show that the
effective tunnelling barrier through the adsorbed monolayer strongly decreases
with increasing the applied load, which translates in a remarkable and
unprecedented increase of the tunnel current. These observations are
successfully explained using simulations based on finite element analysis (FEA)
and first-principles calculations that permit to consider the coupling between
the mechanical response of the system and the electric dipole variations at the
interface.
