Isotope-labeled growth histories reveal persistent chirality in individual carbon nanotubes despite catalyst evolution.

In catalytic growth of carbon nanotubes (CNTs), the stability of catalyst structures is critical for achieving structural uniformity and scalability. Continuous synthesis configurations often expose catalysts to spatially varying temperatures and gas compositions along the reactor. The structural integrity along CNTs growing under such dynamic environments remains largely unexplored, due to the inaccessibility of transient catalyst evolution. Here, we use isotope labeling to indirectly read out, from the growth history recorded within each CNT, how its catalyst evolves in a substrate-supported system. The growth rates exhibit hysteresis, varying up to twofold at the same temperature, indicating irreversible catalyst coarsening; nevertheless, the same nanotubes retain atomically identical lattice structures over hundreds of micrometers. This structural robustness, corroborated by molecular dynamics simulations under evolving catalyst conditions, calls for caution against the interpretation of catalyst-CNT structural relationships from static ex situ snapshots. The contrast between structural memory and adaptive growth kinetics further provides a mechanistic design principle of multiple-stage strategies, toward overcoming the conventional quality-quantity trade-off.