Achiral Plasmon Nanostructures for Identifying Single-Walled Carbon Nanotube Enantiomers via Enhancing Their Raman Optical Activity

Single-walled carbon nanotube (SWCNT) enantiomers are useful for mechanism research and application exploration in optoelectronic components, integrated circuits, biophotonics, and other applications due to their tunable and uniformly responsive photoelectric properties. Herein, surface-enhanced Raman optical activity (ROA) was utilized to identify the structure and behavior of SWCNT enantiomers with a sensitivity of two to four SWCNTs/μm² driven by the achiral plasmon nanostructure. The achiral plasmon nanostructure with C₆ symmetry was adopted to convert far-field chiral light to significantly enhanced near-field light. The resultant Raman scattering intensities of SWCNT enantiomers with chiral indices of (7, 6) and (13, −6) have been increased ∼40 times by the achiral plasmon nanostructure compared with the SWCNT enantiomers dispersed on the silicon wafer by the same method. Thus, the difference of chiral near-field enhanced Raman scattering intensities of SWCNT enantiomers can break the limitation of the background noise to obtain the ROA spectra with vibrational-level information on target analytes. Our strategy provides a convenient and effective platform for identifying SWCNT enantiomers, as well as with extension function for ROA examination of molecular enantiomers.