Fig. 3: Chirality dependence of the coalescence reaction.

a Map of (n, m) nanotubes examined in this study with optical images of the dispersions of each (n, m) carbon nanotube. b Optical absorption (−logT, where T is transmittance) spectra of the membranes after vacuum heat treatment at 1000 °C (the one for (6,5) is the same as that in Fig. 2d). E_P, photon energy. The filled circles and asterisks indicate the lowest energy exciton peaks of (n, m) and (2n, 2 m) nanotubes, respectively. The solid arrows indicate the photon energy of the lowest energy exciton peak of (2n, 2 m) nanotubes, but no peak appears. The insets show the schematics of nanotubes with two lines showing the chiral angles. c Efficiency of the coalescence reaction as a function of chiral angle. The error bar for the data at θ = 30° represents the standard error obtained by performing multi-peak fitting to the spectral data of a single representative sample, using Igor Pro® software. These errors for other chiral angles are negligible and not shown. d Schematic depicting the coalescence of the enantiomers of (6,5) and (5,6) nanotubes. Optical absorption spectrum of (6,5) and (5,6) nanotube membranes before (e) and after (f) heat treatment. The open triangles indicate the expected photon energy corresponding to the first sub-band exciton of (11,11) nanotubes. Source data are provided as a Source Data file.