An international team has observed a new paradigm in the formation behavior of gold nanocrystals using in-situ TEM to capture fast movies at the atomic scale.
Significance and Impact
Direct observation of nanocrystal nucleation challenges the previous paradigm describing how tiny crystals grow. This fundamental process affects almost all material growth and such fundamental understanding could be used to improve particle and thin film growth.
- The research team synthesized gold nanocrystals by shining an electron beam onto gold cyanide nanoribbons on a graphene membrane, which decomposed the nanoribbons into gold atoms.
- Observations at atomic resolution using advanced detectors showed the abrupt disappearance and reappearance of a crystal lattice prior to the emergence of a stable crystal structure, challenging longstanding nucleation theory that instead predicts a non-reversible transition.
- The team proposed a new thermodynamic theory of crystal nucleation: the energy barrier between crystalline to disordered transformations tends to be very low in the earliest stage of nucleation when the cluster size is small and increases as more atoms are added to the structure.