Bimetallic Superatomic Bi-icosahedral Au_xCo_y Clusters for Data Storage

Atomically-precise gold nanostructures have garnered considerable research interest over recent years because of their applications in imaging, catalysis, sensing, medicine, and more. One of the most investigated gold nanostructures is the thiol-capped Au25 nanocluster due to its exceptional stability, facile synthesis, and the ease with which its physiochemical properties can be manipulated. The stability of this nanocluster derives from its “magic-number”, meaning its closed outer-electron shell. Au₂₅also exhibits superatomic properties due to its ultra-small size and construction from an even smaller superatom: the Au₁₃ nanocluster. The Au₂₅ cluster has been synthesized in two structural varieties: the icosahedron and the bi-icosahedron forms. Recent studies have shown this cluster can be easily doped with other metallic atoms, each offering unique properties and insights, although most of these studies focus on the icosahedron structures. Many of these studies demonstrate some advanced property, such as increased fluorescent quantum yield, increased catalytic effect, or magnetism, which have been taken advantage of for applications in both the biomedical field and advanced chemical research.<br/><br/>Herein, we report a method to synthesize and purify a novel bi-icosahedron cobalt-doped Au_25-xCo_x(PPh)₁₀(SR)₅Cl₂ cluster for the first time. Although the synthesis is straightforward, the purification is cumbersome. Once purified, UV-vis absorption, fluorescence, NMR, and electrochemical analysis were utilized to characterize the novel cluster. Data gathered using these methods showed results consistent with the expected results based off previous reports on its theoretical icosahedral counterpart, as well as the un-doped bi-icosahedral cluster. The UV-vis spectra of the novel clusters is highly similar to that of the un-doped cluster, with the most notable difference being a splitting of the peak in the NIR region. The fluorescent quantum yield shows a slight decrease from that of the un-doped cluster. Most importantly we see the effect of spin-orbit coupling in the doped clusters. These results suggest a number of future potential applications for these clusters in computers.