Tracking single charges in organic semiconductors by surface enhanced Raman scattering

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Prof. Lupton and his group at the University of Utah, with the support of the Analytical and Surface Chemistry Program in the Chemistry Division of the National Science Foundation, will develop and utilize ultra-sensitive spectroscopic techniques to unravel the structural and electronic properties underlying the function of organic semiconductors. By applying Raman spectroscopy to single semiconducting organic molecules, highly local changes in the intramolecular charge density which affects the interatomic separation can be revealed through the characteristic vibrational fingerprints. The project seeks to identify signatures of molecular charging through a change in vibrational frequency. The surface enhanced Raman scattering (SERS) effect dramatically amplifies the selectivity of Raman spectroscopy. This amplification should make it possible to pick out individual charging events within a working device such as an organic light-emitting diode (OLED), enabling a direct tracking of charge migration.The project's uniqueness stems from a synergy between the two fields of organic semiconductors and SERS. While SERS is new as an analytical tool in the study of organic semiconductors, conjugated polymers in particular have recently proven to be excellent materials for the investigation of the underlying physics of SERS itself. Further improvements to the reproducibility, stability, selectivity and sensitivity of SERS are therefore anticipated to come out of this project. The highly interdisciplinary nature of the research necessitates a range of collaborations on and off campus, providing a versatile training background for the students engaged with the venture.