DFT study of the influence of impurities on the structural, electronic, optoelectronic, and nonlinear optical properties of graphene nanosheet functionalized by the carboxyl group -COOH.

In this work, we propose a modified model of graphene oxide nanosheet (GON), based on the Lerf-Klinowski model, through which we attach a carboxyl group (GON-COOH) to the non-equivalent C atom of coronene-based graphene oxide with formation of sp3-like orbital bond. Beryllium, boron, nitrogen, oxygen, and fluorine atoms are integrated into the GON at identical sites in order to study their impact on the physical and chemical properties of GON. Our aim is to propose new efficient materials for applications in optoelectronics and nonlinear optics (NLO). Chemical reactivity and structural, optical, and nonlinear optical properties of GON and its derivatives GON-X (X: Be, B, N, O, and F atoms) were investigated by using the density functional theory (DFT) at the B3LYP-D3/6-31+G(d,p) level of theory. According to the results obtained, the binding energy per atom of GON compound decreases slightly with addition of atoms of the second period elements of the periodic table. The GON-F compound exhibits the smallest value of gap energy compared to other studied compounds and can then be considered a proficient candidate for photovoltaic applications. In regard to NLO properties, we found that the studied models of GON compound theoretically exhibit a larger value of the first static hyperpolarizability than urea, the reference compound for NLO properties.