Spectroscopy/Microscopy Of Heterogeneous Materials

Research in the Vanden Bout group is focused on spectroscopically probing condensed phase systems that are inherently heterogeneous in nature. The difficulty in studying these non-ideal heterogeneous materials is that they contain a wide variety of environments. Bulk spectroscopic methods average together multitudes of these different environments, thereby masking the source of particular features and complicating the interpretation of experimental results. Two recent experimental developments have made direct probing of heterogeneous systems possible: near-field scanning optical microscopy (NSOM) and single molecule spectroscopy (SMS).
Our NSOM studies are devoted to investigating the electronic and optical properties of organic thin film materials. In these materials, it is critical to understand the role of various charge and energy carriers in the system. However, vapor-deposited and spin cast thin films have widely varied morphologies that strongly affect their properties. Our research is eliminating these problems by directly probing thin films with NSOM. A wide array of techniques can be used for imaging including transmission, fluorescence, polarization, and time-resolved spectroscopies. We are currently studying a number of materials including polyfluorene, sexi-thiophene, poly thiophene and others.
The second half of our work deals with dynamics near the glass transition in small molecule liquids and polymers. We are developing a microscopic picture of molecular motion near the glass transition by following individual probe molecules dissolved in a glass forming material. Our first experiments are probing highly dilute dye molecules in ortho-terphenyl. Future work will study dynamics in other heterogeneous systems including micelles, ultra-thin polymer films, and phase separated polymer films.