Modeling graphene oxide decorated with FeO, SO and NO.

In this computational investigation, the effect of decoration of graphene oxide (GrO) with three different species FeO, SO, and NO modulates its electronic structure and reactivity for potential electrode and sensing applications. All model structures (pristine graphene, GrO, GrO/FeO, GrO/SO, and GrO/NO) were optimized at the B3LYP/LANL2MB level of theory. We analyzed total dipole moments (TDM), HOMO/LUMO energy gaps (ΔE), global reactivity descriptors (I, A, µ, η, S, ω), density of states (DOS and PDOS), molecular electrostatic potential (MESP), Quantum Theory of Atoms in Molecules (QTAIM) topologies, and noncovalent interaction (NCI) patterns. Oxidation from Gr to GrO created a modest dipole moment (3.06 Debye) and reduced ΔE from 4.483 eV to 3.226 eV. Decoration with FeO raised the TDM to 14.26 Debye and decreased ΔE to 1.625 eV, while SO decoration yielded the largest TDM (20.38 Debye) and the smallest gap (0.576 eV). In contrast, NO decoration produced intermediate values (TDM = 2.90 Debye, ΔE = 2.412 eV). Global reactivity descriptors confirm that GrO/FeO and GrO/SO acquire strong electrophilic character and high softness, and GrO/NO retains moderate reactivity. DOS/PDOS analysis shows that Fe, S, and N introduce new states near the Fermi level, facilitating charge transfer. MESP maps identify electron-rich and -poor regions at functional sites, while QTAIM indicates a covalent Fe-O bond in GrO/FeO and hydrogen-bonding interactions in GrO/SO and GrO/NO. NCI analysis further supports the presence of van der Waals interactions at the decoration interfaces. Taken together, our results demonstrate that choice of decorating species enables precise tuning of GrO's electronic and reactive properties, highlighting GrO/FeO and especially GrO/SO as promising candidates for enhanced electrode performance and gas sensing.