Determination of Activation Barriers for the Adsorption and Desorption of Self-Assembling Organic Molecules onto Gold and Graphite from Organic Solvents.

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Electronic devices are playing an ever-increasing role in human life. Future electronic devices will contain not only inorganic materials, such as silicon, but also organic materials. While the inorganic components provide durability and well understood electrical conduction, the organic components offer the potential to easily and inexpensively tune their properties through synthetic modification. However, creating devices that combine these two different types of materials faces several challenges. The organic layer must be structured at the molecular level to provide the desired electronic and photonic properties, and the junction between the organic and inorganic parts must be formed to make it easy for electrons to pass across the interface. With support from the Macromolecular, Supramolecular and Nanochemistry (MSN) program in the Division of Chemistry, Professor K. W. Hipps at Washington State University is using sophisticated microscopies that can see individual molecules to study the factors that determine the ordering of organic molecules on inorganic surfaces. The discoveries from the project could impact applications ranging from electronics to sensor development, and catalysis. The research also provides training opportunities for future researchers at all levels, and is thus contributing to development of the national workforce in science and technology. Professor Hipps actively reaches out to local high schools and engages students in continued education in STEM fields. Professor Hipps and his students are using a combination of surface plasmon resonance and high-resolution scanning tunneling microscopy to understand and predict the thermodynamic and kinetic factors that determine the structure of self-assembled 2-D organic films. The project's focus is on films formed from commonly used organic monomers, inorganic substrates and solvents, with the goal of determining the activation energies and entropies associated with adsorption and desorption of monomers at the solution-solid interface. Molecular dynamics simulations provide insight into the role of solvent, temperature, and pressure in film formation. Observations from experiment and simulation are used in the development of kinetic models that describe the various stages of the adsorption and desorption of molecules from the self-assembled layer. In addition, the project is educating undergraduates, graduate students and post-doctoral associates in the science of hybrid electronic devices, while outreach to local schools introduces high-school students to single-molecule science and technology.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.