  Water near detonation nanodiamonds (DNDs) forms a Hydrogen Bond (HB) network,
whose strength influences DNDs' fluorescence intensity and colloidal stability
in aqueous suspensions. However, effects of dissolved ions and DND's surface
chemistry on dynamics of water that manifest in rupture and formation of HBs
still remain to be elucidated. Thus, we carried out molecular dynamics
simulations to investigate the aforementioned effects in the aqueous salt (any
of KCl, NaCl, CaCl\_2, or MgCl\_2) solution of DND functionalized with any of
-H, -NH\_2, -COOH, or -OH groups. We observed the specific cation effects on
both translational and reorientational dynamics of water around the negatively
charged DND-COOH. In the whole hydration shell of this DND, we obtained K\{+} <
Na\{+} < Ca\{2+} < Mg\{2+} ordering for the impact of the cation on reducing
the translational diffusion coefficient of water. In the immediate vicinity of
the charged DND-COOH, the slowdown impacts of cations on the reorientational
dynamics of dipole and OH vectors of water were according to Na\{+} < K\{+} <
Ca\{2+} < Mg\{2+} and Na\{+} < Ca\{2+} < K\{+} < Mg\{2+} ordering,
respectively. Furthermore, regardless of the type of dissolved ions, positively
charged DND-NH\_2 and negatively charged DND-COOH induced, respectively, the
slowest dipole and OH reorientational dynamics in the first hydration layer of
DND. Our results led us to conclude that charged groups on the surface of DNDs
on the one hand and the adsorbed counterions on the other hand cooperatively
slow down the reorientational dynamics of water in multiple directions.
