Mesoscale Modeling of 2-D Materials for Energy and Biomedical Application
Sanket A. Deshmukh
Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL
We have shown recently that 2-D materials ranging from one atom thick graphene layer to one nanoparticle film of a closely packed ligated metal nanoparticle can have dramatically different functionality than bulk counterpart. The potential applications of these 2-D materials include, but not limited to, lubricants, chemical and pressure sensors, and catalysis. I will specifically highlight two case studies where we employ mesoscale modeling to probe the existing 2-D materials and design a new class of hybrid 2-D materials with specific emphasis on their mechanical properties. In the first case study, we discovered the role played by graphene to achieve superlubricity - almost zero friction - at macroscale. To probe the mechanism of superlubricity we have performed meso-scale all-atom simulations of a system consisting of graphene, nanodiamond, and diamond like carbon (DLC).1 Our simulations suggest that the macroscopic superlubricity originates from an intriguing nanomechanical phenomenon: graphene patches at a sliding interface, wrap around the tiny nanodiamond particles and form nanoscrolls with reduced contact area that slide easily against the amorphous DLC surface, achieving an incommensurate contact (a necessary condition to achieve superlubricity) and near zero coefficient of friction (0.004). In the second case study, we probe the ligand dynamics during the self-assembly process of 2-D nano-thin membrane of ligated metal nanoparticles.2 We have conducted meso-scale simulations of self-assembly of ligand-modified gold nanoparticles at the air-water interface to elucidate the exact role of ligands that contributes to their asymmetric distribution during the membrane formation process. Our simulations suggest that the experimentally observed anisotropic distribution of ligands originates from ligand re-distribution that is greatly facilitated by the mobility of ligands at gold surface. The mobility of the ligands in turn is a strong function of their surface coverage. Fully ligated nanoparticles have much lower ligand mobility and do not display an asymmetric distribution in the self-assembled membranes. On the other hand, for lower ligand coverages, we find the ligands to be highly mobile which reorganize to form Janus-like membranes. This asymmetry is shown to have interesting consequences on the mechanical and bending properties of these 2-D membranes.
1. Macroscale superlubricity enabled by graphene nanoscroll formation
Diana Berman*, Sanket A. Deshmukh*, Subramanian KRS Sankaranarayanan, Ali Erdemir, Anirudha V Sumant (* Shared First Author)
Science, 348, 6239, 1118-1122, 2015
2. Subnanometre ligand-shell asymmetry leads to Janus-like nanoparticle membranes
Zhang Jiang, Jinbo He, Sanket A. Deshmukh, Pongsakorn Kanjanaboos, Ganesh Kamath, Yifan Wang, Subramanian K. R. S. Sankaranarayanan, Jin Wang, Heinrich M. Jaeger and Xiao-Min Lin
Nature Materials, doi:10.1038/nmat4321, 2015.
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