Quantum Dot Solids: From Fundamental Insights into Assembly and Attachment Mechanism Towards Fabrication of Complex Hierarchical Superstructures and Enabled Energy Applications.

Creating quantum dot solids from into epitaxially connected superlattices is a new and exciting route to novel two-dimensional materials. The ability to control the atomic structure of the quantum dot building block (i.e., size, shape and composition) and the geometry of the superstructure creates fertile opportunity space to synthesize and study new classes of 2D materials. Theoretical calculations on these systems predict interesting phenomena including topological states and Dirac cones. We present recent advances in our group to fabricate atomically connected quantum dot superlattices with structural coherence approaching a single atomic bond length. Despite the high degree of structural coherence, surprisingly charge carriers are strongly localized, as shown by the first charge transport measurement in an atomically coherent quantum dot solid. Before theoretically predicted properties can be probed, outstanding knowledge gaps concerning the formation of epitaxially connected superlattices need to be resolved. The formation of superlattice polymorphs (e.g., square or honeycomb lattices) is related to the preferred orientation of constituent nanocrystal building blocks and the rate of assembly. Understanding and ultimately controlling the transformation of the colloidal quantum dot assembly into an atomically coherent superlattices hinges on establishing deeper insights into the fundamental transformation mechanism and the complex interplay of transport and reaction dynamics of the chemical trigger near the quantum dot surface. Building on lessons-learned from 2D interfacial assembly and attachment of colloidal quantum dots, we recently developed nanofabrication approaches that allow us to create quantum dot solids and hierarchical mesoporous structures in programmable 3D shapes. We discuss recent advances and future prospects of this fabrication approach.

About the Speaker

Tobias received a B.S. from University of Tulsa, OK (2000), M.S. from University of Texas at Austin (2002) and PhD., University of Texas at Austin (2004) in the group of Brian Korgel. He served as Postdoctoral Research Fellow, MIT (2005) Postdoctoral Research Fellow, TU Eindhoven, and The Netherlands (2006-2007) before coming to Cornell. Tobias is an Associate Professor in the School of Chemical and Biomolecular Engineering and a field member in the Department of Materials Science and Engineering and the Sibley School of Mechanical and Aerospace Engineering.