While electrons flow easily through metals, they have much greater difficulty passing through insulators such as glass and plastics. At least this is the situation when the insulator is thick. Reduce the thickness to a single molecular layer, and electrons can undergo charge tunneling, a Quantum Mechanical process that allows them to pass through insulating barriers. With support from the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry, Professor George Whitesides at Harvard University is exploring how electrons tunnel though molecular layers. Working with his students, Professor Whitesides is developing new experimental tools to probe tunneling and using them to study how charge flows through self-assembled monolayers (SAMs). The discoveries could have broad implications for our understanding of biological processes, such as photosynthesis, where charge is transferred across cellular membranes, as well as advance technologies ranging from modern electronics to the lubrication, friction, and wear in soft materials.
The project is examining the rates of quantum tunneling across organic and organometallic SAMs using EGaIn junctions, which are constructed by sandwiching a SAM between a metal electrode (e.g. Au or Ag) on one side, and an EGaIn (i.e. liquid eutectic between Ga and In) electrode on the other. The project's goal is to correlate the tunneling current density with the atomic structure of the molecules that make up the SAM, as well as monolayers in contact with polar and non-polar liquids. The team is collaborating with theorists from around the world, who are aiding in the interpretation of the observations. This highly interdisciplinary project is contributing to the development of the Nation's science and technology workforce by training students on how to combine concepts, techniques, and tools in chemistry, biology, and physics, and at the same time is producing knowledge that is relevant to high-technology companies.
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.
