  We examine the aggregation behavior of AuNPs of different sizes on graphene
as function of temperature using molecular dynamic simulations with Reax Force
Field (ReaxFF). In addition, the consequences of such aggregation on the
morphology of AuNPs and the charge transfer behavior of AuNP-Graphene hybrid
structure are analyzed. The aggregation of AuNPs on graphene is confirmed from
the center of mass distance calculation. The simulation results indicate that
the size of AuNPs and temperature significantly affect the aggregation behavior
of AuNPs on graphene. The strain calculation showed that shape of AuNPs changes
due to the aggregation and the smaller size AuNPs on graphene exhibit more
shape changes than larger AuNPs at all the temperatures studies in this work.
The charge transfer calculation reveals that, the magnitude of charge transfer
is higher for larger AuNPs-graphene composite when compared with smaller
AuNPs-graphene composite. The charge transfer trend and the trends seen in the
number of Au atoms directly in touch with graphene are identical. Hence, our
results conclude that, quantity of Au atoms directly in contact with graphene
during aggregation is primarily facilitates charge transfer between AuNPs and
graphene.
