Dr. Plusquellic's research interests in the Molecular and BioPhotonics Project center on fully-state resolved studies of biomolecules and chromophores in the microwave (MW), terahertz (THz), and ultraviolet (UV) spectral regions. The THz spectral region provides access to the lowest frequency collective motions of biomolecular systems that are responsible for the large scale conformational changes associated with folding and activation of protein, polynucleotide and polysaccharide backbones. We have pioneered the use of high-resolution THz laser sources to investigate the fully state-resolved vibrational spectra of polypeptides and to characterize the spectral response to hydration of hydrophobic and hydrophilic sites in a wide variety of crystalline structures. We are also developing new instrumentation to enhance the spectral and spatial resolution and sensitivity in this region using waveguides, dual beam and adaptive near-field imaging approaches.
In the UV, high resolution laser and cavity ringdown techniques are used to investigate a series of aromatic bichromophores to fully understand the coupling mechanisms and electronic energy transport dynamics arising from excitonic interactions between chromophores in close proximity. This work is done in collaboration with Prof. Timothy S. Zwier's group at Purdue University. Completed studies have revealed that the transition dipole coupling and deactiviation mechanisms (through internal conversion) depend strongly on the 3D structure, symmetry and conformational flexibility of the attached chromophores, properties that define the energy landscapes of the coupled electronic states. Together with detailed theoretical investigations, there results may serve to optimize designs of charge transfer systems for more efficient solar energy conversion.
Dr. Plusquellic is fellow of the American Physical Society (since 2009). Other professional associations include membership in American Chemical Society (since 1992) and American Association for the Advancement of Science (since 2001). He has served as co-organizer of "Sub-millimeter and THz Spectroscopy in the Gas and Condensed Phases" at Ohio State University Molecular Spectroscopy Symposium in June, 2008 and has co-authored over 65 technical peer-reviewed papers, delivered over 28 invited talks and holds three U.S. Patents.