Quantum Charge Tunneling through Self-Assembled Monolayers (SAMs)

Harvard University, Cambridge MA

Investigators

Abstract

With support from the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program in the Division of Chemistry, Professor George Whitesides of Harvard University is studying how electrons are transported through molecules. Electrons do not move through molecules like they do when they flow through a metal. Instead, they tunnel through them. Tunneling is a quantum mechanical behavior that pertains only to very small particles, like electrons. The length that an electron can tunnel through a molecule, and how efficiently it can do it, depends on the molecule's structure and the arrangement of the chemical bonds. However, studying electron tunneling through molecules presents a significant challenge, as it requires separating two electrodes by a distance equivalent to the length of a single molecule. Professor Whitesides and his group will develop new methods for studying quantum tunneling in organic and bioorganic matter. Their discoveries could lead to new electronic devices and sensors, as well as a better understanding of molecular catalysis and enzymes that catalyze electron transport. This highly interdisciplinary project will also contribute to the development of the future science and technology workforce by training postdoctoral scholars on how to combine concepts, techniques, and tools in chemistry, biology, and physics. The project will advance the liquid eutectic Gallium-Indium (eGaIn) electrode system for characterizing quantum tunneling in organic self-assembled monolayers (SAMs). Surface plasmon spectroscopy, x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) will be used to relate structural features to observed electrochemical behavior. The project aims to correlate rates of tunneling with molecular electronic structure and understand the effects of applied electric and magnetic fields on tunneling currents. Studies of bio-relevant SAMs in liquid environments will provide insights into the role surrounding liquids (and dissolved ions) play in charge conduction and establish a basis for electron-transfer rates in bioorganic systems. Studies of SAMs with embedded catalysts will examine the effect of oriented electric fields on catalytic transformations. 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.