Quadratic nonlinear optical (NLO) properties of borazino (B3N3)-doped nanographenes

Abstract

Borazino-doped nanographenes belong to a special class of flat heteroaromatic networks comprising one or more fully formed borazino (B₃N₃) units in their framework. These systems carry the same number of electrons and feature similar structural forms as pristine nanographenes; however, they are characterized by different optoelectronic properties. As their full carbon analogues, borazino-doped graphene molecules could serve as excellent candidate molecules for flexible organic electronic and optical devices. In this study, we provided the results of a systematic study dealing with the effect of borazino units on the quadratic microscopic nonlinear optical (NLO) properties of finite graphene sections. These symmetry-dependent quantities describe the nonlinear polarization (hyperpolarization) of the electron cloud of molecules in the presence of external electric fields and they are associated with fundamental processes of extreme technological interest in the realm of nonlinear optics. More precisely, we investigated the evolution of the first dipole hyperpolarizability in several, purposely chosen, borazino-doped graphene flakes and ribbons, relying on long-range corrected density functional methods. Our results indicate that the presence of inorganic benzene in the honeycomb structure of graphene finite sections gives rise to some impressive structure–property variations driven by local electron delocalization effects. The take home message of this study suggests that borazino doping can deliver a vast assortment of nanographene molecules bearing amplified octupolar and/or dipolar NLO responses that can be fine-tuned by applying minor modifications in the structure and morphology of their edges.