Computational Simulations of Molecular Junctions and Antifouling of Membrane Surfaces

Understanding the structural and dynamic behaviors of complex metal-organic junctions is one of the long-standing efforts crucial to the development of molecular electronics. We use driven dynamics molecular dynamics (MD) simulations to investigate the dynamic evolutions of molecular binding structures and breaking forces of gold/thiolate molecular junctions under mechanical pulling. We identified two distinct force quanta at 1.5 and 2.0 nN, corresponding to the Au−Au and Au−S bond breaking. These findings revealed new structure-force-conductance correlations.

Membrane fouling is a challenging issue in drinking water purification. We carried out MD simulations to study the fouling mechanisms of cross-linked polyamide (PA) membrane, and PA membrane with surface chemistry modifications by either polyethylene glycol (PEG) or polyzwitterion (PZ) coatings. For bare PA membranes, we find that fouling is attributed to the hydrogen bonding and ionic bridge binding interactions between alginate gels on PA surface. When PA membrane surface is grafted by PEG or PZ coatings, repulsive hydration force between the alginate gel and the hydration water layer surrounding the PEG/PZ coatings has a dominant contribution to the antifouling. However, at a comparably lower grafting density, the PZ brush array exhibits a randomly oriented structure. In this case, antifouling of the brush array is through the deformation of the PZ branches.