Revealing the Tunability of Electronic Structures and Optical Properties of Novel SWCNT Derivatives, Phenine Nanotubes

Single-walled carbon nanotubes (SWCNTs) have evoked great interest for various luminescent applications, but the large emission heterogeneity resulted from the structural complexity of the samples seriously restricts further developments. Herein we theoretically explore the electronic structures and optical properties of phenine nanotubes (pNTs), which are typical luminescent SWCNT derivatives with determined molecular structures that are synthesized until recently (Science 2019, 363:151-155; Nat Commun. 2020, 11:1807). Interestingly, pNTs are found to feature distinctly different semiconducting properties to SWCNTs, resulted from the periodic structural vacancies. The HOMO-LUMO and optical gaps of pNTs inversely depend on their lengths and diameters, but diameter variation is found to be an ineffective way for property tuning due to the negligible influence. By contrast, chemical modifications via N doping or hydrogenation highly affect the HOMO-LUMO gaps and their distributions and greatly broadens the light absorption/emission range, and importantly, low-dose hydrogenation is predicted to be a feasible strategy to enhance luminescence. This work, by studying the fundamental photophysical properties of pNTs and making comparisons to SWCNTs, shows the great promise of structural vacancy engineering on the tube skeletons and surface functionalization in acquiring versatile tube-like materials.