Atomically resolved mechanical response of individual metallofullerene molecules confined inside carbon nanotubes

Abstract

The hollow core inside a carbon nanotube¹ can be used to confine single molecules^2,3 and it is now possible to image the movement of such molecules inside nanotubes^4,5. To date, however, it has not been possible to control this motion, nor to detect the forces moving the molecules, despite experimental and theoretical evidence suggesting that almost friction-free motion might be possible inside the nanotubes^{6,7,8,9,10,11,12,13}. Here, we report on precise measurements of the mechanical responses of individual metallofullerene molecules (Dy@C₈₂) confined inside single-walled carbon nanotubes to the atom at the tip of an atomic force microscope operated in dynamic mode^14,15. Using three-dimensional force mapping with atomic resolution¹⁶, we addressed the molecules from the exterior of the nanotube and measured their elastic and inelastic behaviour by simultaneously detecting the attractive forces and energy losses with three-dimensional, atomic-scale resolution.