Absolute quantification of enantiomeric purity of sorted carbon nanotubes by correlating hyperspectral fluorescence microscopy with ensemble chiroptical spectroscopy

Accurate determination of enantiomeric purity is essential for advancing chiral materials in nanotechnology, optoelectronics, and quantum information science. Chiroptical spectroscopic techniques provide rapid, non-destructive measurements of enantiomeric excess (ee), but their use for complex systems like single-walled carbon nanotubes (SWCNTs) is limited by the lack of enantiopure references for calibration. Here we demonstrate an absolute approach combining hyperspectral imaging (HSI) with single-nanotube counting statistics and ensemble chiroptical spectroscopy such as electronic circular dichroism (ECD) and Raman optical activity (ROA) to quantify ee without requiring such standards. Analysis of thousands of individual nanotubes reveals sensitivity of HSI and chiroptical responses to synthesis, purification, and SWCNT concentration, highlighting pronounced source-dependent inhomogeneity. Nevertheless, universal calibration curves for ECD and ROA intensities are established from the purest, most uniform enantiomer-sorted samples. This methodology is extendable to other SWCNT chiralities and chiroptical techniques, enabling quantitative enantiomer sorting and systematic investigations of chirality-dependent properties and applications. Accurately measuring the chirality of carbon nanotubes is a challenge in the absence of pure reference samples. Here, the authors combine hyperspectral imaging and chiroptical spectroscopy to quantify enantiomeric purity without having to rely on such standards.