Local Reactivity on Carbon Quantum Dots: The Influence of the Geometries and Chemical Doping for Chemical Sensor Applications

Carbon-based compounds have been considered materials of great technological interest, mainly due to their high synthesis flexibility, low cost, and unique properties. In particular, graphene-based compounds, such as modified graphene, graphene nanoribbons, and carbon quantum dots (CQD) show improved performance for a variety of applications. CQDs are particularly interesting; such zero dimensional structures usually show strong fluorescence, good water solubility, chemical stability, ease of functionalization and other properties that depend on the CQDs' geometries, sizes, and terminal edges. To better understand the influence of these factors on the electronic and reactivity properties of the CQDs, here we evaluate five different geometries and 11 chemical modifications of this material in a DFT framework using low computational cost electronic descriptors. The results indicate that geometries, edges, and chemical modifications have different roles in the local reactivities of these compounds. For instance, geometric features govern the orbital-based chemical reactivities, while the substituents' nature governs the molecular electrostatic potentials. The evaluation of frontier energy level alignments point out CQDs as potential materials for Cl2 and SO2 detection, which is reinforced by simulations via fully atomistic reactive molecular dynamics (FARMD).