Anglin et al , J. Phys. Chem. C 2011 , 115 , 16027.

1. Molecular Structure at Organic Transistor InterfacesAaron Massari, University of Minnesota-Twin Cities, DMR 1006386 Organic field-effect transistors hold great promise for next generation circuits that are light-weight, flexible, and energy efficient. The conduction of charges through these devices relies on the molecular structures at a buried interface in the device, yet there are few ways to characterize this region directly. We have used vibrational sum frequency generation (VSFG) spectroscopy to determine the orientation of the thiophene rings at silica surfaces with varying surface energies. These measurements demonstrate that low surface energies lead to edge-on orientation of the rings, which facilitates high charge mobilities through the stacked rings of neighboring molecules. The orientations of the thiophene rings in a poly(thiophene) organic semiconductor are influenced by the surface energy of the silica. When the silica is coated with hydrophilic molecules (red dots), the rings lay face down yielding stronger VSFG signals in the out-of-plane direction (blue curve, frame a); when coated with hydrophobic molecules, the rings stand on edge, and the in-plane contributions (red curve) dominate the signals. Anglinet al,J. Phys. Chem. C 2011, 115, 16027.

2. Surface Spectroscopy and Rural Outreach Aaron Massari, University of Minnesota-Twin Cities, DMR 1006386 Two 8th graders examine the spectrum of a dye solution using home-built spectrometers during University on the Prairie. Undergraduate Austin Lane (inset) used a cryostat to measure organic transistor hole mobilities in-situ during a thermal annealing treatment. In August, the group brought spectroscopy to rural communities in Minnesota directing the Chemistry portion of the University on the Prairie program. Nearly sixty 7th – 10th graders spent three days working with the PI and four members of his research group performing hands-on experiments that included simple, but effective spectrometers constructed from compact discs and flashlights. Annealing treatments can sometimes improve the performance of organic devices, but the molecular origins of these enhancements are not well-understood. Sum frequency generation spectroscopy was used during the annealing process to monitor molecular rearrangements. (photos provided with participants’ permission)