Abstract

The study of carbon clusters led to the discoveries of fullerenes, carbon nanotubes, and graphene. Are there other elements that can form similar nanostructures? To answer this question, the speaker and his research group have focused on boron clusters, which have been investigated using photoelectron spectroscopy in combination with computational chemistry. They have found that bare boron clusters possess planar structures, in contrast to that of bulk boron, which is dominated by three-dimensional polyhedral building blocks. The discovery of planar boron clusters laid the foundation for 2D boron nanomaterials. In particular, the observation of the planar B36 cluster with a central hexagonal vacancy provided the first experimental evidence that single-atom boron-sheets with hexagonal vacancies (borophenes) were viable. Borophenes have since been synthesized and characterized on inert substrates, forming a new class of synthetic 2D materials. The B40 cluster was found to be an all-boron fullerene, whereas the largest boron cluster (B48–) characterized to date possesses a bilayer structure, suggesting the feasibility of bilayer borophenes. Boron forms important bulk boride materials with most metals in the periodic table. Many transition-metal borides are superhard materials, while lanthanide borides are essential magnetic materials. Metal boride clusters are ideal systems to probe the metal-boron bonding in boride materials. They have observed a quadruple bond between Rh and B (Rh≣B), as well as a lanthanide-boron cage cluster. The study of larger transition-metal boride clusters suggested the possibility of metallo-borophenes. The speaker will also discuss recent advances in their investigation of large boron clusters.

About the Speaker

Prof. WANG Lai-Sheng obtained his BS in Chemistry from Wuhan University in 1982 and his PhD in Chemical Physics from the University of California, Berkeley in 1990. He did postdoctoral work at Rice University before he took a joint position in 1993 between the Department of Physics at Washington State University and Pacific Northwest National Laboratory. In 2009, he joined Brown University and is currently the Jesse H. and Louisa D. Sharpe Metcalf Professor of Chemistry. Since July 2019, he has been serving as the Chair of the Department of Chemistry at Brown University.

Prof. Wang’s research involves experimental studies of size-selected nanoclusters using photoelectron spectroscopy and imaging. Research in his lab has led to the discoveries of golden cages and golden pyramids, planar and aromatic boron clusters, borophenes, and borospherenes. His group has also pioneered the application of electrospray ionization for spectroscopic studies of solution anions in the gas phase, in particular, multiply-charged anions and microsolvated anions. His lab has developed cryogenically-cooled 3D quadrupole ion-trap techniques to create cold anions from electrospray ionization for spectroscopic investigations using photoelectron spectroscopy and high-resolution photoelectron imaging. Current research projects in Prof. Wang’s lab include the investigation of the structures and bonding of size-selected boron and boride clusters, probing noncovalent excited states of cold anions using photodetachment and photoelectron spectroscopy, the investigations of astronomically relevant anions and molecules, as well as the syntheses of ligand-protected gold nanoclusters with in situ catalytic active sites. He has served on the editorial board of Journal of Physical Chemistry, Chinese Journal of Chemical Physics and Chemical Physics Letters.

Prof. Wang is the recipient of the 2023 Herbert P. Broida Prize and the 2021 E. Bright Wilson Award in Spectroscopy, both from the American Chemical Society. He also received the 2016 Creativity Award from the US National Science Foundation and the 2014 Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics from the American Physical Society. He was elected as a Fellow of the American Association for the Advancement of Science in 2007, the John Simon Guggenheim Memorial Foundation in 2005, and the American Physical Society in 2003.

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