Butterfly‐Shaped Nanographenes with Excellent Second‐Order Nonlinear Optical Properties: The Synergy of B/N and Azulene

Abstract

Azulene, a simple polar polycyclic aromatic hydrocarbon with connected electron donor and acceptor (DA), ignites the hope of designing second-order nonlinear optical (NLO) molecular materials from pure nonpolar carbon nanomaterials. In this work, a butterfly-shaped nanographene (πÀ DAÀ π) was designed by incorporating azulene between two coronenes. One more electron in a N atom or one electron fewer in a B atom with respect to a C atom can polarize charge distribution in carbon nanomaterials, and further doping of B and N in the designed butterfly-shaped nanographene changes the system from πÀ DAÀ π to DÀ πÀ A, leading to strong NLO responses. For example, the largest static first hyperpolarizability even reaches 173.89 × 10 À 30 esu per heavy atom. The synergetic role of B, N and azulene in the nanographene is scrutinized, and such a doping strategy is found to provide an effective means for the design of carbon-based functional materials. The strong second-order NLO responses of these butterfly-shaped carbon-based nanographenes under external fields, for example, sum frequency generation and difference frequency generation, could inspire future experimental exploration.

External electric field driven electronic structures: tunable nonlinear optical properties of helical bilayer nanographenes

“…45 Nanographenes present promising prospects for designing high-performance NLO materials. 46–48 In this study, we explore the influence of the external electric fields along the positive directions of the z -axis ( F z ) on the molecular structure and electronic properties of helical bilayer nanographenes with a helicene moiety length of [9] ([9]HBNG), as shown in Fig. 1.…”