Kevin Stamplecoskie

Photonic Materials Research

The optical properties of metals depend strongly on their size/shape and the choice of metal. Plasmon absorption is a property that has become commonly associated with colloidal metal particles like gold and silver. It is described by a collective oscillation of electrons in the particle, excited by light. The particular wavelength (energy) of Plasmon modes in metal particles can be tuned throughout the visible spectrum by manipulating the particle shape, giving rise to a rainbow of possible colours of these colloids.
When metal particles become extremely small (less than ~1 nm in diameter), the particles are referred to as 'clusters' and no longer behave like pieces of metal with loosely bound electrons, but more like molecules with discrete electronic states. This gives rise to phenomena like intense emission, that is not observed for any other form of the metal. The unique properties of clusters make them an interesting new material for harvesting solar energy.

Metal Nanomaterials - Nanoparticles and Clusters

Metal materials from single atoms to bulk material

Atomically Precise Clusters - Light Harvesting

thiolated gold clusters absorption overlap with solar flux

Atomically precise metal clusters have molecule like absorption properties associated with HOMO-LUMO type transitions. The optical properties, such as absorption or excited state lifetimes can be tuned by varying the exact atomic number, metal species, or stabilizing ligands. For light-harvesting applications, it is key that the absorption properties of clusters maximize overlap with the solar spectrum in order to harness the suns power. Once a photon is absorbed, the excited-state properties then dictate the overall performance of the material. We investigate the optical properties of clusters, especially gold and silver clusters, and evaluate their potential in photovolatics.