Stability Of Gold Nanoclusters Research Articles

Effect of Ligands on the Stability of Gold Nanoclusters.

Gold nanoclusters (AuNCs) are atomic architectures that can be precisely tailored for catalytic applications. In this work, we studied two benchmark AuNCs, Au25(SR)18 and Au144(SR)60, covered by aromatic and aliphatic ligands to envision how the 3D structure of the ligand impacts the stability of the nanomaterial. Surprisingly, we found that increasing the alkanethiol length has a poor or null effect on the stability of the AuNCs, a trend opposite to that on Au(111) surfaces. When considering the aromatic or aliphatic nature, the AuNC stability follows the same trend as on Au(111): the thermodynamical stability is dictated by the ligand density rather than its chemical nature, where the aliphatic ligand imparts more stability than the aromatic one. Our findings provide a tool to predict how an ultrasmall gold core can interact with the environment, substrate, and themselves according to the stability of its protecting ligand shell.

Support effect on the reactivity and stability of Au25(SR)18 and Au144(SR)60 nanoclusters in liquid phase cyclohexane oxidation

Abstract Using oxide supported atomically precise gold nanoclusters is an emerging field in heterogeneous catalysis. Such well-defined nanocatalysts represent a rather new model system enabling fundamental insights in catalytic reactions. In the present work, the stability of Au25 and Au144 clusters, supported either on TiO2 or SiO2, was examined upon thermal air pretreatment and, for the first time, upon liquid phase oxidation reaction. A pronounced influence of the support (TiO2 vs. SiO2) and cluster size (Au25 vs. Au144) was revealed by XAS, DRS and STEM. Upon pretreatment, Au144 was more stable which may be related to its specific cluster core structure and staple configuration. The catalytic properties in liquid phase cyclohexane oxidation were clearly size dependent, with Au144 yielding higher TOF values, particularly in the case of SiO2 supported catalysts. However, with respect to selectivity, TiO2 supported catalysts led to higher KA production than SiO2 supported ones. This can be explained by the different reaction pathways, as observed by in situ ATR. HERFD-XAS measurements of Au144/TiO2 catalysts revealed a pronounced cluster structure modification towards bulk gold during the reaction, in contrast to a high stability of Au144/SiO2. This study demonstrates the important role the support material has on the reactivity and stability of gold nanoclusters, which is key for their catalytic function.

Molecular Dynamics Simulation of Au-TiO<sub>2</sub> Catalysts: Deposition of Gold Nanoclusters on Rutile (110) Surface

In this work, molecular dynamics simulation was used to investigate the deposition process of a gold nanocluster on rutile TiO2(110) surface. The effects of surface defects (i.e., point, step, and groove) were examined in terms of interaction energy, morphology and structure. It was found that the gold nanocluster can be strongly attracted to rutile TiO2(110) surface. Moreover, a higher degree of defect results in a stronger attractive interaction between gold nanocluster and TiO2(110) surface. The simulated results also indicated that the stability of gold nanoclusters can be effectively controlled by adding citrate ions, which could lead to a high catalytic activity of gold/metal oxide catalysts.