Mesophase Formation Stabilizes High-purity Magic-sized Clusters

Douglas R. Nevers, Curtis B. Williamson, Benjamin H Savitzky, Ido Hadar, Uri Banin, Lena F. Kourkoutis, Tobias Hanrath, Richard D. Robinson

Research output: Contribution to journalArticlepeer-review

67 Scopus citations

Abstract

Magic-sized clusters (MSCs) are renowned for their identical size and closed-shell stability that inhibit conventional nanoparticle (NP) growth processes. Though MSCs have been of increasing interest, understanding the reaction pathways toward their nucleation and stabilization is an outstanding issue. In this work, we demonstrate that high concentration synthesis (1000 mM) promotes a well-defined reaction pathway to form high-purity MSCs (>99.9%). The MSCs are resistant to typical growth and dissolution processes. Based on insights from in-situ X-ray scattering analysis, we attribute this stability to the accompanying production of a large, hexagonal organic-inorganic mesophase (>100 nm grain size) that arrests growth of the MSCs and prevents NP growth. At intermediate concentrations (500 mM), the MSC mesophase forms, but is unstable, resulting in NP growth at the expense of the assemblies. These results provide an alternate explanation for the high stability of MSCs. Whereas the conventional mantra has been that the stability of MSCs derives from the precise arrangement of the inorganic structures (i.e., closed-shell atomic packing), we demonstrate that anisotropic clusters can also be stabilized by self-forming fibrous mesophase assemblies. At lower concentration (16 acid-to-metal), MSCs are further destabilized and NPs formation dominates that of MSCs. Overall, the high concentration approach intensifies and showcases inherent concentration-dependent surfactant phase behavior that is not accessible in conventional (i.e., dilute) conditions. This work provides not only a robust method to synthesize, stabilize, and study identical MSC products, but also uncovers an underappreciated stabilizing interaction between surfactants and clusters.
Original languageEnglish (US)
Pages (from-to)3652-3662
Number of pages11
JournalJournal of the American Chemical Society
Volume140
Issue number10
DOIs
StatePublished - Jan 27 2018
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1-018-02
Acknowledgements: This work was supported in part by the National Science Foundation (NSF) under Award No. CMMI-1344562. U.B. acknowledges funding for this project from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement n° 741767). U.B. also thanks the Alfred & Erica Larisch memorial chair. B.H.S. and L.F.K. acknowledge support by the Packard Foundation. B.H.S was supported by NSF GRFP grant DGE- 1144153. This work also made use of the Cornell Center for Materials Research Shared Facilities, which are supported through the NSF MRSEC (Materials Research Science and Engineering Centers) program (Grant DMR-1719875). The FEI Titan Themis 300 was acquired through NSF-MRI-1429155, with additional support from Cornell University, the Weill Institute and the Kavli Institute at Cornell. This work includes research conducted at the Cornell High Energy Synchrotron Source (CHESS), which is supported by the National Science Foundation and the National Institutes of Health/National Institute of General Medical Sciences under NSF award DMR- 1332208. Dynamic light scattering measurements were performed in a facility supported by Award No. KUS-C1-018-02, made by King Abdullah University of Science and Technology (KAUST). This work made use of the Cornell Chemistry NMR Facility, which is supported in part by the NSF-MRI grant CHE- 1531632. R.D.R. thanks the U.S. Fulbright Scholar Program for partial funding during this work. The authors would like to thank the following individual for assistance with experiments and material characterization as well as useful discussion. Specifically, Detlef Smilgies provided equipment and helpful discussion regarding the X-ray scattering experiments. Stan Stoupin set-up and calibrated the beamline and detector for SAXS/WAXS, and helped with data analysis. Ivan Keresztes performed the NMR data acquisition, helped with analysis, and provided useful guidance.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

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