iChEM researchers, Prof. Nanfeng Zheng’s group made important progress in the area of metallic nanoclusters. The result was published in J. Am. Chem. Soc. as Total Structure and Electronic Structure Analysis of Doped Thiolated Silver [MAg24(SR)18]2- (M = Pd, Pt) Clusters(J. Am. Chem. Soc., DOI: 10.1021/jacs.5b07186).

The metallic cluster protected by thiol groups (-SRs) is paid close attention to because it’s the epitome of stable noble metallic nanoparticles. Till now, there is no report published saying that Au and Ag nanoclusters protected by thiol groups have the same structure, although Au and Ag are family metals. After the confirmation of the structure of star nanocluster, Au25(SR)18, a plenty of experiments have taken place to study the synthesis and properties of Ag25(SR)18 and Ag doping Au25(SR)18. The theoretical computation also gave a prediction that Ag25(SR)18 may have a similar structure with Au25(SR)18. But all of those above are not confirmed. This work successfully obtained [MAg24(SR)18]2-(M=Pd, Pt) which was protected by thiol groups by introducing Pd and Pt and then analyzed its single-crystal structure. The structural analysis indicated that though the cluster [MAg24(SR)18]2- has a similar framework as Au25(SR)18 which was composed of a M@Ag12, a solid dodecahedron, and six [Ag2(SR)3], the superficial “staple” units, there are still some differences that the six [Ag2(SR)3] on the surface of [MAg24(SR)18]2- have different degrees of distortion and there exist adjacent [Ag2(SR)3]s Ag…S non-covalent bonds. The bonds also promote the π-π effect of benzene rings on the superficial ligands so that two [MAg24(SR)18]2- chiral clusters with two different distributions of the superficial ligands occur. Moreover, this work indicated that doping exotic metals in metallic clusters can be a valid way to control the electronic structures and optical properties. Even the doping of one atom can change the properties of clusters.

The work was completed together by Xiamen University and Hannu Häkkinen’s group from University of Jyvaskyla. Synthesis of the cluster and characterization of structure and property were completed by Dr. Juanzhu Yan, post-doctor Haifeng Su and iChEM post-doctor Huayan Yang. Then Häkkinen’s group analyzed the electronic structure and absorption spectrum of M@Ag24 by theoretical calculation. All works above were under iChEM researchers, Professor Nanfeng Zheng and senior engineer Chaoshui Lin’s guidance. The research was funded by the Natural Science Foundation of China (NSFC) and Ministry of Science and Technology (MOST) of China.