A molecular dynamics simulation of the adsorption of water molecules surrounding an Au nanoparticle

This study uses molecular dynamics simulations performed in a parallel computing environment to investigate the adsorption of water molecules surrounding Au nanoparticles of various sizes. An observation of the oxygen and hydrogen atom distributions reveals that the adsorption of the water molecules creates two shell-like formations of water in close vicinity to the Au nanoparticle surface. These shell-like formations are found to be more pronounced around smaller Au nanoparticles. The rearrangement of water molecules in this region reduces the local hydrogen bond strength to below that which is observed in the bulk region. Finally, the simulation results indicate that the absolute value of the interaction energy between the water molecules and the Au nanoparticle is reduced when the water molecules surround a nanoparticle of larger diameter. This observation implies that a stronger adsorption effect exists between smaller Au nanoparticles and water molecules. Hence, the value of the adsorption constant increases for smaller Au nanoparticles. (C) 2005 American Institute of Physics.