(6ai) Mesoscale Modeling of 2D Materials for Energy and Biomedical Applications

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.

Reference:

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.