Using Organic molecules as Electronic Components in Nanoscale Devices

In an effort to develop alternative energy sources such as fuel cells and solar fuel from "artificial" photosynthesis, scientists at the U.S. Department of Energy's Brookhaven National Laboratory are taking a detailed look at electrons - the particles that set almost all chemical processes in motion.

Electron transfer plays a vital role in numerous biological processes, including nerve cell communication and converting energy from food into useful forms. It's the initial step in photosynthesis as well, where charges are first separated and the energy is stored for later use - one of the concepts behind energy production using solar cells. Understanding and controlling the movement of electrons through individual molecules also could allow for the development of new technologies such as extremely small circuits, or help scientists find catalysts that give fuel cells a much-needed boost in efficiency and affordability. Three Brookhaven chemists will discuss how these applications are related to their most recent findings at the 234th National Meeting of the American Chemical Society.

Using organic molecules as electronic components in nanoscale devices could lead to various technological advances including small-scale circuits for improving solar cells. One of the most important issues in this field is the role of molecule-metal contact and the electron transfer that occurs between the two. With this idea in mind, Brookhaven chemist Marshall Newton and former Brookhaven research associate Vasili Perebeinos studied the electronic activity involved in the self-assembly of sulfur-capped organic molecules supported on a gold surface. Their results were surprising:

"The bottom line is that the electrical action in the formation of this interface has already happened within the organic layer, without direct involvement of the metal," said Newton, who develops models to understand these interactions in molecular systems. "That's somewhat unexpected because people typically say that the big electrical action involves charge moving from or between the organic part and the metal surface. But in this case, the electronic rearrangement occurs internally during the process of bringing all of these organic chains together before they are in contact with the metal."

Newton believes this phenomenon is caused by the need to reduce electrical repulsions between the side-by-side organic chains.