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Covalent Functionalization of Graphene with PAMAM Dendrimer and Its Implications on Graphene’s Dispersion and Cytotoxicity
journal contribution
posted on 2020-08-04, 15:39 authored by Mounika Gosika, Vasumathi Velachi, M. Natália D. S. Cordeiro, Prabal K. MaitiFunctionalizing
graphene with polymers is an important area of
research, owing to the potential applications of graphene in biomedicine
and nanotechnology. In this paper, we investigate the covalent functionalization
of graphene with a G2 poly(amidoamine) (PAMAM) dendrimer using all
atom molecular dynamics simulations. Specifically, we study the dependence
of the grafting approach (grafting-from and grafting-to) and the binding location of the PAMAM dendrimer
to graphene (top, edge, and top-edge), on the functionalization. The
instantaneous snapshots and the thickness profiles of the equilibrated
dendrimer-graphene complexes reveal that the thickness of the adsorbed
dendrimer is more in the grafting-to case. We have
also observed that the edge-binding dendrimers of grafting-from approach can coat the graphene on either of its sides, whereas the
top-binding dendrimers adsorb mostly on the side of their binding.
In addition to the grafting approach and the binding location, we
find that the dimension of the graphene sheet also determines the
extent of surface coverage by the dendrimer. From the radii of gyration
analysis and the thickness profiles of the dendrimers, we illustrate
that an increase in the sheet dimensions gives rise to smoother surface
coverage, whereas increasing the grafting density results in rough
surface coverage. We also find that the percentage of surface coverage
is higher in the grafting-to approach when compared
with the grafting-from method, for a given binding
condition and sheet dimensions. Our results on the dispersion of the
functionalized graphene in water suggest that the dispersion of graphene
depends on its surface coverage and is more probable with the grafting-from approach. Furthermore, our results on the
interaction of functionalized graphene with a dimyristoylphosphatidylcholine
(DMPC) lipid membrane demonstrate no bilayer disruption, hence illustrating
the noncytotoxicity of the graphene–dendrimer complex.