Unraveling a generic growth pattern in structure evolution of thiolate-protected gold nanoclusters

Precise control of the growth of thiolate-protected gold nano-clusters is a prerequisite for their applications in catalysis and bioengineering. Here, we bring to bear a new series of thiolate-protected nanoclusters with a unique growth pattern, i.e., Au-20(SR)(16), Au-28(SR)(20), Au-36(SR)(24), Au-44(SR)(28), and Au-52(SR)(32). These nanoclusters can be viewed as resulting from the stepwise addition of a common structural motif [Au-8(SR)(4)]. The highly negative values of the nucleus-independent chemical shift (NICS) in the center of the tetrahedral Au-4 units suggest that the overall stabilities of these clusters stem from the local stability of each tetrahedral Au-4 unit. Generalization of this growth-pattern rule to large-sized nanoclusters allows us to identify the structures of three new thiolate-protected nanoclusters, namely, Au-60(SR)(36), Au-68(SR)(40), and Au-76(SR)(44). Remarkably, all three large-sized nanoclusters possess relatively large HOMO-LUMO gaps and negative NICS values, suggesting their high chemical stability. Further extension of the growth-pattern rule to the infinitely long nanowire limit results in a one-dimensional (1D) thiolate-protected gold nanowire (RS-AuNW) with a band gap of 0.78 eV. Such a unique growth-pattern rule offers a guide for precise synthesis of a new class of large-sized thiolate-protected gold nanoclusters or even RS-AuNW which, to our knowledge, has not been reported in the literature.