CAREER: CAS: A Building Block Approach to Study Charge Transport: From Single-Molecule to Bulk

With this CAREER project, supported by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Michael Inkpen of the Department of Chemistry at the University of Southern California (USC) seeks to develop integrated methods that explore how electrical charges move through materials across different length scales (from single-molecule to bulk). The proposed approach draws inspiration from the chemical building blocks and linkages used to build conducting and permanently porous ordered polymers (OPs). The key goals of this project are to provide a deeper fundamental understanding of how the atomic details of these molecular structures influence their electronic function(s), and to evaluate possible correlations between charge transport through chemically comparable single-molecule and bulk materials. This research ultimately aims to expose new design principles for molecular-scale devices, such as wires and switches, that approach the limit of miniaturization for electronic circuits used in computation and data storage. The goal is to identify the most promising molecular building blocks for constructing functional OPs with potential applications in energy storage, energy conversion, or sensing. Concurrently, Dr. Inkpen and his research team will leverage development of a new academic search database to engage underrepresented 1st and 2nd year undergraduate students, by improving the teaching of molecular nanoscience at USC and beyond, and by implementing a virtual, asynchronous summer workshop to reach students who cannot easily attend in person outreach activities. The fields of molecular electronics and conducting ordered polymers (OPs) each are directed at the understanding and manipulation of charge transport through molecularly well-defined systems, yet efforts in these research domains are rarely coordinated. Bridging these research areas, this proposal aims to explore fundamental structure-electronic property relationships across different length scales by studying model single-molecule, extended oligomeric, and bulk materials using a combination of scanning tunneling microscope-based break junction (STM-BJ), conducting-probe atomic force microscopy (CP-AFM), and 4-point probe methods. Quantum interference (QI), d-π conjugation, and redox effects will be probed in new families of molecular devices inspired by the multi-topic and metal-containing structures used in two-dimensional and three-dimensional OPs. Possible trends between single molecule conductance and band transport in structurally analogous bulk materials will be evaluated as a means to select specific building blocks for the construction of extended ordered systems with targeted electronic properties. New synthetic strategies will be developed that target the construction of compositionally distinct OPs with comparable crystallinity and defect concentrations. Studies of such model extended materials, on surfaces and in bulk, have the potential to improve structure-property comparisons and to allow practitioners to build new nanoscale-to-bulk transport property correlations. 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.