Nicolas Giovambattista
Brooklyn College of CUNY, New York, USA
We perform molecular dynamics simulations to study the effects of temperature and pressure on the water-mediated interaction (WMI) between two nanoscale (apolar) graphene plates at 240 ≤ T ≤ 400 K and −100 ≤ P ≤ 1200 MPa. These are thermodynamic conditions relevant to, for example, cooling-, heating-, compression-, and decompression-induced protein denaturation. We find that at all (T,P) studied, the potential of mean force between the graphene plates, as a function of the plates separation r, exhibits local minima at specific plate separations r = rn that can accommodate n water layers (n = 0,1,2,3). In particular, our results show that isobaric cooling and isothermal compression have a similar effect on the WMI between the plates; both processes tend to suppress the attraction and ultimate collapse of the graphene plates by kinetically trapping the plates at the metastable states with r = rn (n > 0). In addition, isobaric heating and isothermal decompression also have a similar effect; both processes tend to reduce the range and strength of the interactions between the graphene plates. Interestingly, at low temperatures, the WMI between the plates is affected by crystallization. However, crystallization depends deeply on the water model considered, SPC/E and TIP4P/2005 water models, with the crystallization occurring at different (T, P) conditions, into different forms of ice. In the last part of this talk, we will explore the WMI between hydroxylated graphene surfaces inspired on graphene oxide. Our results show that WMI between hydrophilic-hydrophilic and hydrophilic-hydrophobic surfaces can play a fundamental role in self-assembly processes in aqueous solutions, alike hydrophobic interactions.