Nanoscale

doi: 10.1039/c2nr90053jpmid: N/A

doi: 10.1039/C2NR90053Jpmid: N/A

doi: 10.1039/c2nr90054hpmid: N/A

doi: 10.1039/C2NR90054Hpmid: N/A

doi: 10.1039/c2nr90055fpmid: N/A

doi: 10.1039/C2NR90055Fpmid: N/A

Jin, Rongchao; Eah, Sang-Kee; Pei, Yong

doi: 10.1039/c2nr90052apmid: 22706954

Maity, Prasenjit; Xie, Songhai; Yamauchi, Miho; Tsukuda, Tatsuya

doi: 10.1039/c2nr30900apmid: 22717451

Bare metal clusters with fewer than ∼100 atoms exhibit intrinsically unique and size-specific properties, making them promising functional units or building blocks for novel materials. To utilize such clusters in functional materials, they need to be stabilized against coalescence by employing organic ligands, polymers, and solid materials. To realize rational development of cluster-based materials, it is essential to clarify how the stability and nature of clusters are modified by interactions with stabilizers by characterizing isolated clusters. The next stage is to design on-demand function by intentionally controlling the structural parameters of cluster-based materials; such parameters include the size, composition, and atomic arrangement of clusters and the interfacial structure between clusters and stabilizers. This review summarizes the current state of the art of isolation of gold clusters stabilized in various environments and surveys ongoing efforts to precisely control the structural parameters with atomic level accuracy.

Wang, Lei-Ming; Wang, Lai-Sheng

doi: 10.1039/c2nr30186epmid: 22517376

Gold nanoparticles have been discovered to exhibit remarkable catalytic properties in contrast to the chemical inertness of bulk gold. A prerequisite to elucidate the molecular mechanisms of the catalytic effect of nanogold is a detailed understanding of the structural and electronic properties of gold clusters as a function of size. In this review, we describe joint experimental studies (mainly photoelectron spectroscopy) and theoretical calculations to probe the structural properties of anionic gold clusters. Electronic properties and structural evolutions of all known Aun− clusters as experimentally confirmed to date are summarized, covering the size ranges of n = 3–35 and 55–64. Recent experimental efforts in resolving the isomeric issues of small gold clusters using Ar-tagging, O2-titration and isoelectronic substitution are also discussed.

Pei, Yong; Zeng, Xiao Cheng

doi: 10.1039/c2nr30685apmid: 22635136

Unlike bulk materials, the physicochemical properties of nano-sized metal clusters can be strongly dependent on their atomic structure and size. Over the past two decades, major progress has been made in both the synthesis and characterization of a special class of ligated metal nanoclusters, namely, the thiolate-protected gold clusters with size less than 2 nm. Nevertheless, the determination of the precise atomic structure of thiolate-protected gold clusters is still a grand challenge to both experimentalists and theorists. The lack of atomic structures for many thiolate-protected gold clusters has hampered our in-depth understanding of their physicochemical properties and size-dependent structural evolution. Recent breakthroughs in the determination of the atomic structure of two clusters, [Au25(SCH2CH2Ph)18]q (q = −1, 0) and Au102(p-MBA)44, from X-ray crystallography have uncovered many new characteristics regarding the gold–sulfur bonding as well as the atomic packing structure in gold thiolate nanoclusters. Knowledge obtained from the atomic structures of both thiolate-protected gold clusters allows researchers to examine a more general “inherent structure rule” underlying this special class of ligated gold nanoclusters. That is, a highly stable thiolate-protected gold cluster can be viewed as a combination of a highly symmetric Au core and several protecting gold–thiolate “staple motifs”, as illustrated by a general structural formula [Au]a+a′[Au(SR)2]b[Au2(SR)3]c[Au3(SR)4]d[Au4(SR)5]e where a, a′, b, c, d and e are integers that satisfy certain constraints. In this review article, we highlight recent progress in the theoretical exploration and prediction of the atomic structures of various thiolate-protected gold clusters based on the “divide-and-protect” concept in general and the “inherent structure rule” in particular. As two demonstration examples, we show that the theoretically predicted lowest-energy structures of Au25(SR)8− and Au38(SR)24 (–R is the alkylthiolate group) have been fully confirmed by later experiments, lending credence to the “inherent structure rule”.