Atomically Precise Large-Sized Aun(SR)m Nanoclusters and Scaling Relationships between Size, Bandgap and Excited-State Lifetime

Abstract

The synthesis of atomically precise, large-sized Aun(SR)m nanoclusters (SR = thiolate) with n of 100 or more atoms has long been a challenge. In this work, we report the synthesis of Au100(Napt)42 and Au102(IPBT)44 nanoclusters (where, Napt stands for 1-naphthalenethiolate and IPBT for 4-isopropylbenzenethiolate). Their optical absorption, single-electron charging, and femtosecond electron dynamics are investigated. Both Au100(Napt)42 and Au102(IPBT)44 exhibit multiple discrete absorption bands in their optical spectra owing to quantized electronic structure in ultrasmall metal nanoclusters. Electrochemistry analysis determines the precise HOMO–LUMO gaps of Au100(Napt)42 and Au102(IPBT)44 by single-electron charging. The electronic excited-state lifetimes of Au100(Napt)42 and Au102(IPBT)44 are determined by femtosecond transient absorption spectroscopy. The scaling relationship between the Eg and size (n), and the excited state lifetime versus the Eg of large-sized Aun(SR)m are discussed. The findings promotes fundamental understanding of large-sized metal nanoclusters, which will benefit their future applications in optics, electronics, and other fields.