Investigation of Boron and Boride Nanoclusters: Laying the Foundation for New Boron Nanostructures and Nanomaterials

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In this project funded by the Chemical Structure, Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Lai-Sheng Wang of Brown University and his students are using sophisticated laser spectroscopy techniques to study clusters of boron and metal borides. The clusters being studied are aggregates of 3-40 atoms. The chemical and physical properties of these clusters depend on their size. The Wang research group is able to continuously vary the number of atoms in a cluster, which means that they can explore in detail how the atoms are bonded to each other. The chemical bonds in boron clusters are very strong, which might mean that these clusters may make possible new materials with new and useful properties. Prof. Wang and his research team are interested in creating and characterizing novel boron cluster structures including clusters containing a few metal atoms such as bismuth (Bi) cobalt (Co), rhodium (Rh), and iridium (Ir). In addition to the lasers used in the experimental work, the Wang research team also do theoretical calculations that help interpret experimental data and predict new, never before seen structures (for example, what to clusters containing more than 50 atoms look like?). The long-term goal of the project is to discover new boron-based molecules and new forms of boron materials.The project focuses on three sub-topics: 1) structural evolution of large size-selected boron clusters, 2) neutral boron clusters and borospherenes (cage-like boron clusters), and 3) metal-doped boron clusters. These clusters are produced by a laser-vaporization supersonic cluster source and studied by a variety of experimental and theoretical techniques. Photoelectron spectroscopy is used to probe the structures and bonding of large negatively-charged boron clusters with more than 40 atoms. High-resolution photoelectron imaging of negatively-charged boron clusters is employed to provide vibrational and structural information for the associated neutral clusters. An infrared and ultraviolet double-resonant approach is used to directly probe neutral boron clusters, as a complementary technique to the high-resolution photoelectron imaging experiment. The structures and bonding of metal-doped boron clusters are studied by both photoelectron spectroscopy and high-resolution photoelectron imaging. These experiments provide vibrational and electronic structure fingerprints, which are combined with computational chemistry to elucidate the structure, stability, and chemical bonding of boron and metal-doped boron clusters. The broader impact of this work is to build the foundation and knowledge base to discover new boron-based nanomaterials, which can have potential technological applications and societal benefits. This project is integrated to the teaching of physical chemistry by the PI, as well as providing research-training opportunities for graduate and undergraduate students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.