“…The interior of CNTs has been widely used to confine molecules to form new hybrid nanostructures with interesting mechanical, electronic, and vibrational properties. − In particular, the hollow core of CNTs has been an effective environment to synthesize and stabilize linear carbon chains, the thinnest ultimate limit of a one-dimensional solid material. Carbyne (hereafter referred to as C n ) is theoretically proposed to exist in two possible structures: the polyyne, with an alternate single–triple bond chain (...–CC–CC–...) and the cumulene, a chain with double bonds (...CCCC...). , These systems present electronic, mechanical, and vibrational properties extremely dependent on the chain length. − Theoretical calculations predict that C n has extreme tensile stiffness, high shear and Young’s modulus, and a strain-dependent insulating-to-metallic transition. ,, …”