RUI: Photoisomerization Potential of Molecular Switches on Surfaces

Western Washington University, Bellingham WA

Investigators

Abstract

Professor Andreas Riemann of Western Washington University (WWU) is supported by the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program of the Division of Chemistry to investigate the behavior of spiropyran molecular switches. A molecular switch is a molecule that can swing back and forth between two or more stable states. In each state, the molecule has a distinctive shape, structure, and electronic and optical properties. The molecules switch from one state to another in response to external stimuli, such as light. The goal is to control the switching mechanism and create surface structures consisting of functional molecular switches. Molecular switches are important components of molecular electronics used in electronic devices. Undergraduate students at WWU are an integral part of this project and are given relevant experiences for their futures in scientific research or in industry. Additionally, Professor Riemann is involved in outreach through "Compass 2 Campus," a Western Washington University initiative to increase science literacy of students from traditionally underrepresented backgrounds, by stimulating their interest in research and providing them with pathways to higher education. The goal of this research is to study molecule/substrate combinations which are able to undergo a photoisomerization process with a large enough cross-section to make it suitable for further application in molecular electronics. The systems under investigation are spiropyran/merocyanine isomers deposited on noble metal substrates and graphite. Thin molecular films where individual molecules can be excited to switch their configuration are created. Conformational behavior of these molecules and control of the photoisomerization process are investigated using a variety of experimental surface science techniques such as STM, LEED and XPS as well as computational chemistry methods including DFT and Molecular Mechanics calculations. The project is conducted in three stages: 1) the analysis of adsorption behavior of various spiropyran-based molecules at various temperatures and substrate coverages; 2) the use of light and heat to trigger and monitor isomerization switching; and 3) the use of computational chemistry to simulate the adsorption behavior of spiropyran-based isomers. 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.