  The goal of the present study is to explore how the size and
functionalization of graphene quantum dots (GQDs) affect their sensing
capabilities. Specifically, we investigated the adsorption of SO$_2$, SOF$_2$,
SO$_2$F$_2$, and SF$_6$ on GQDs that were functionalized with -CH$_3$, -
COCH$_3$, and -NH$_2$. We used density functional theory to analyze the
electronic properties of these functionalized GQDs and found that the
functionalization significantly altered their electronic properties. For
example, the B3LYP H-L gap of pristine triangulene was 3.9eV, while the H-L gap
of functionalized triangulene ranged from 2.8 eV-3.6 eV (using the B3LYP
functional). Our results indicate that -NH2 functionalized phenalenyl and
triangulene provide strong interaction with SO$_2$, with adsorption energies of
-0.429 eV and -0.427 eV, respectively. These adsorption properties exhibit
physisorption, leading to high gas sensitivity and superior recovery time. The
findings of this study provide new insights into the potential use of GQDs for
detecting the decomposed constituents of sulfur hexafluoride, which can be
beneficial for assessing the operation status of SF$_6$ insulated devices.
Overall, our calculations suggest that functionalized GQDs can be employed in
gas insulated systems for partial discharge detection.
