Excitonic Fano Scattering Behaviors of Carbon Nanotubes from Interference with Dispersant

Rayleigh scattering behavior of single-walled carbon nanotubes (SWNTs) has been instrumental in understanding their exciton behaviors, but their bulk scattering interactions with molecules in dispersion remain unexplored. Here, we found the excitonic Fano scattering behaviors in interfering dispersant-wrapped SWNT dispersions and characterized them both experimentally and theoretically. Using an integrating sphere, we differentiated scattering spectra from extinction and absorption spectra at both single-chirality and ensemble levels. The scattering spectra revealed asymmetric excitonic and exciton-phonon bands contrasting Lorentzian shapes from noninterfering dispersant-wrapped SWNT. A scattering cross-sectional equation, derived from Fano resonance theory and incorporating the dielectric constants of SWNT and its environment, successfully simulates the experimental result. The analysis underscored the impact of the surrounding molecules on the excitonic interactions, with significant implications for the optoelectronic properties of SWNTs. The findings suggest potential applications of SWNTs in sensory and modulator schemes, where the optoelectronic response of nanomaterials is tuned by selection of molecules.