(117a) Graduate Student Award: Investigating the Properties of Nanoparticles Containing Fullerene-like Molecules

Investigating the properties
of nanoparticles containing fullerene-like molecules

Kimberly
Bowal¹, Jacob W. Martin^1,2, Laura Pascazio¹,
Markus Kraft^1,2,3

¹University of Cambridge, ²Cambridge Centre
for Advanced Research and Education in Singapore, ³Nanyang
Technological University

The structure and properties
of nanoparticles containing curved polycyclic aromatic hydrocarbons (cPAHs) are
investigated using molecular modelling. Due to the inclusion of one or more
five-membered rings within their hexagonal lattice, these polar fullerene-like
molecules possess unique steric and electronic properties that make them good
candidates for many applications including microporous materials for gas
storage, organic electronic devices such as imaging probes and batteries,
sensors, and micelles for targeted nanomedicine.  Development of these
applications requires an understanding of the self-assembly and dynamic
nanostructure of cPAH nanoparticles, which has not yet been well explored.

This work uses replica exchange
molecular dynamics to determine the energy-dependent nanostructure of cPAH
particles. The interactions between cPAH molecules are described using the new curPAHIP
potential^[1]. A range of cPAH sizes and ratios are investigated,
along with systems containing planar PAHs and ions, to explore the homogeneous
and heterogeneous particle internal arrangements and properties.

Homogeneous cPAH particles
are found to be tightly packed and less stacked than their planar PAH
counterparts. The constituent cPAH size plays a role in the molecular
arrangement, with large 15 ring cPAHs (C₄₂H₁₄) displaying
long-range order absent in nanoparticles containing small 7 ring cPAHs (C₂₀H₁₀).
Heterogeneous particles containing cPAHs of different sizes, such as those
shown in Figure 1, display a core-shell structure in which the larger molecules
make up the core and the smaller molecules comprise the shell, as seen with
planar PAH nanoparticles. This trend is not strongly influenced by the molecule
ratio. In addition, the presence of planar PAHs and ions within cPAH
nanoparticles promotes distinct arrangements dominated by weak dispersive
interactions and strong electrostatic interactions, respectively. These systems
may be indicative of nanoclusters generated in processes such as combustion.

These results provide new
information on structures and properties of nanoparticles containing cPAHs,
including density, molecular structure, surface composition, and melting point
estimation. This provides valuable understanding of the self-assembly and
growth of nanoparticles with great potential in many applications.

^[1]Bowal, K, Martin, J W, Misquitta, A J, Kraft, M: Ion-induced
soot nucleation using a new potential for curved aromatics, 2019, Comb Sci
Tech, doi: 10.1080/00102202.2019.1565496