TY - JOUR
T1 - The Missing Link
T2 - Au191(SPh- tBu)66Janus Nanoparticle with Molecular and Bulk-Metal-like Properties
AU - Sakthivel, Naga Arjun
AU - Shabaninezhad, Masoud
AU - Sementa, Luca
AU - Yoon, Bokwon
AU - Stener, Mauro
AU - Whetten, Robert L.
AU - Ramakrishna, Guda
AU - Fortunelli, Alessandro
AU - Landman, Uzi
AU - Dass, Amala
N1 - Funding Information:
We gratefully acknowledge Dr. Allen G. Oliver, Ms. Charlotte Stern, Dr. Christos Malliakas, Dr. Pierre LeMagueres, and the 2019 American Crystallographic Association summer course for screening the crystals and their help with SC-XRD data analysis. We thank Dr. Fengrui Qu and Dr. Elizabeth Papish for the SC-XRD data collection. G.R. acknowledges the support of Western Michigan University-FRACAA and Dr. Gary Wiederrecht, Argonne National Laboratory, for help with the TA measurements. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357. NSF-CHE-1808138 and NSF-CHE-1255519 supported the work performed by N.A.S. and A.D. The work of B.Y. and U.L. has been supported by the Air Force Office of Scientific Research (AFOSR) under grant no. FA9550-15-1-0519. Calculations of the electronic structure were carried out at the Georgia Institute of Technology Center for Computational Materials Science. We thank NSF-CHE-MRI-1828078 and the University of Alabama for the purchase of SC-XRD instrument. A.F., L.S., and M.S. acknowledge the support from the Cineca Supercomputing Center for TDDFT simulations and analysis.
Publisher Copyright:
Copyright © 2020 American Chemical Society.
PY - 2020/9/16
Y1 - 2020/9/16
N2 - Understanding the evolution of the structure and properties in metals from molecule-like to bulk-like has been a long sought fundamental question in science, since Faraday's 1857 work. We report the discovery of a Janus nanomolecule, Au191(SPh-tBu)66 having both molecular and metallic characteristics, explored crystallographically and optically and modeled theoretically. Au191 has an anisotropic, singly twinned structure with an Au155 core protected by a ligand shell made of 24 monomeric [-S-Au-S-] and 6 dimeric [-S-Au-S-Au-S-] staples. The Au155 core is composed of an 89-atom inner core and 66 surface atoms, arranged as [Au3@Au23@Au63]@Au66 concentric shells of atoms. The inner core has a monotwinned/stacking-faulted face-centered-cubic (fcc) structure. Structural evolution in metal nanoparticles has been known to progress from multiply twinned, icosahedral, structures in smaller molecular sizes to untwinned bulk-like fcc monocrystalline nanostructures in larger nanoparticles. The monotwinned inner core structure of the ligand capped Au191 nanomolecule provides the critical missing link, and bridges the size-evolution gap between the molecular multiple-twinning regime and the bulk-metal-like particles with untwinned fcc structure. The Janus nature of the nanoparticle is demonstrated by its optical and electronic properties, with metal-like electron-phonon relaxation and molecule-like long-lived excited states. First-principles theoretical explorations of the electronic structure uncovered electronic stabilization through the opening of a shell-closing gap at the top of the occupied manifold of the delocalized electronic superatom spectrum of the inner core. The electronic stabilization together with the inner core geometric stability and the optimally stapled ligand-capping anchor and secure the stability of the entire nanomolecule.
AB - Understanding the evolution of the structure and properties in metals from molecule-like to bulk-like has been a long sought fundamental question in science, since Faraday's 1857 work. We report the discovery of a Janus nanomolecule, Au191(SPh-tBu)66 having both molecular and metallic characteristics, explored crystallographically and optically and modeled theoretically. Au191 has an anisotropic, singly twinned structure with an Au155 core protected by a ligand shell made of 24 monomeric [-S-Au-S-] and 6 dimeric [-S-Au-S-Au-S-] staples. The Au155 core is composed of an 89-atom inner core and 66 surface atoms, arranged as [Au3@Au23@Au63]@Au66 concentric shells of atoms. The inner core has a monotwinned/stacking-faulted face-centered-cubic (fcc) structure. Structural evolution in metal nanoparticles has been known to progress from multiply twinned, icosahedral, structures in smaller molecular sizes to untwinned bulk-like fcc monocrystalline nanostructures in larger nanoparticles. The monotwinned inner core structure of the ligand capped Au191 nanomolecule provides the critical missing link, and bridges the size-evolution gap between the molecular multiple-twinning regime and the bulk-metal-like particles with untwinned fcc structure. The Janus nature of the nanoparticle is demonstrated by its optical and electronic properties, with metal-like electron-phonon relaxation and molecule-like long-lived excited states. First-principles theoretical explorations of the electronic structure uncovered electronic stabilization through the opening of a shell-closing gap at the top of the occupied manifold of the delocalized electronic superatom spectrum of the inner core. The electronic stabilization together with the inner core geometric stability and the optimally stapled ligand-capping anchor and secure the stability of the entire nanomolecule.
UR - http://www.scopus.com/inward/record.url?scp=85091127100&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85091127100&partnerID=8YFLogxK
U2 - 10.1021/jacs.0c05685
DO - 10.1021/jacs.0c05685
M3 - Article
C2 - 32881489
AN - SCOPUS:85091127100
SN - 0002-7863
VL - 142
SP - 15799
EP - 15814
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 37
ER -