Three-orders-of-magnitude variation of carrier lifetimes with crystal phase of gold nanoclusters

Atomic packing controls exciton lifetime Like semiconductors, small metallic clusters can absorb light and create excitons (electron-hole pairs). In ligand-capped gold clusters of 30 to 40 atoms (Au 30 to Au 40 ) that adopt the usual face-centered cubic packing, the lifetime of these excitons is ∼100 nanoseconds. Zhou et al. found that atomic packing and molecular orbital overlap can greatly affect carrier lifetimes. Despite having similar bandgaps to those of face-centered cubic clusters, a hexagonal close-packed Au 30 cluster had a much shorter lifetime (∼1 nanosecond), and a body-centered cubic Au 38 cluster had a lifetime of ∼5 microseconds, which is comparable to bulk silicon. Science , this issue p. 279