nanoparticle center, marking a preferable location for Na+,
while the electrostatic potential of AuNP+ rised almost
monotonically and attracted Cl− (in principle) further inside.
However, other factors (such as reduced water concentration
and larger ionic radius) exhibited Cl− from entering inside
AuNP+. Despite its larger atomic mass, the self-diffusion
coefficient of Cl− was about 20% larger than that of Na+, which
is related to the details in ionic bonding with the terminal
carboxylate/amine groups (reduced lifetime for Cl− contacts).
The short-time diffusion analysis around AuNPs revealed that
the solvent diffusion is slower near AuNP due to H-bonds and
ionic contacts with the terminal groups, and that the effect
extends over 3 nm from the AuNP surface because of several
solvation shells that transmit the effect.