title: Beyond the staple motif: a new order at the thiolate-gold interface.
abstract: Staple motifs in the form of -RS(AuSR)x- (x = 1, 2, 3, etc.) are the most common structural feature at the interface of the thiolate-protected gold nanoclusters, Aun(SR)m. However, the recently solved structure of Au92(SR)44, in which the facets of the Au84core are protected mainly by the bridging thiolates, challenges the staple hypothesis. Herein, we explore the surface sensitivity of the thiolate-gold interface from first principles density functional theory. We find that the interfacial structures of thiolates on gold are surface sensitive: while a staple motif (such as -RS-Au-SR-) is preferred on Au(111), a bridging motif (-RS-) is preferred on Au(100) and Au(110). We show that this surface sensitivity is closely related to the coordination number of the surface Au atom on the different surfaces. We further confirm the preference of the bridging motif for self-assembled monolayers of two different ligands (methylthiolate and 4-tert-butylbenzenethiolate) on Au(100). With this surface sensitivity, we categorize the structure-known Aun(SR)mclusters into three groups: (1) no bridging; (2) ambiguous bridging; (3) distinct bridging. We further employ the surface sensitivity of the thiolate-Au interface to predict the protecting motifs of face-centered cubic (fcc) gold nanoparticles of different shapes. Our study provides a unifying view of the Aun(SR)mstructures with guidelines for structure predictions for larger Aun(SR)mclusters of a fcc core.
authors.affiliation: Department of Chemistry, University of California, Riverside, California 92521, USA. djiang@ucr.edu.
authors.forename: Guoxiang
authors.initials: G
authors.lastname: Hu
authors.affiliation: Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Rongchao
authors.initials: R
authors.lastname: Jin
authors.affiliation: Department of Chemistry, University of California, Riverside, California 92521, USA. djiang@ucr.edu.
authors.forename: De-En
authors.initials: DE
authors.lastname: Jiang