The Department of Chemistry at the University of North Carolina at Chapel Hill, offers a wide range of research opportunities in theoretical and experimental physical chemistry. Our program has broadened from its traditional areas of excellence in molecular chemical physics to include research activities in biophysical and surface chemistry, and materials and environmental sciences. Experimental efforts within these areas utilize state-of-the-art instrumentation, such as high-resolution and ultra-fast laser systems, molecular beam techniques, mass spectrometry, ion-scattering, scanning probe microscopy, and magnetic resonance spectrometry.
Research in theoretical chemistry involves developing computational models of chromatin, the structure of complex fluids, and polymer dynamics. Students at UNC have access to high-performance computer workstations, as well as RENCI/UNC Research Computing, which is home to one of the best computing facilities in the world, including a 4160-processor Dell Linux cluster.
Researchers in the Papanikolas Group, in collaboration with colleagues in the Cahoon Group, both here at Carolina Chemistry, have developed a pump–probe microscope capable of exciting a single semiconductor nanostructure in one location and probing it in another with both high spatial and temporal resolution. Their findings are published in NanoLetters.
Experiments performed on Si nanowires enable a direct visualization of the charge cloud produced by photoexcitation at a localized spot as it spreads along the nanowire axis. The time-resolved images show clear evidence of rapid diffusional spreading and recombination of the free carriers, which is consistent with ambipolar diffusion and a surface recombination velocity of 104 cm/s. The free carrier dynamics are followed by trap carrier migration on slower time scales.
Published in Inorganic Chemistry, a collaboration between the Waters and Papanikolas groups outlines energy transfer studies in a series of Ru(II) and Os(II) linked coiled-coil peptides in which the supramolecular scaffold controls the functional properties of the assembly. The researchers describe a general and convergent method for the site-specific incorporation of bipyridyl Ru(II) and Os(II) complexes using solid-phase peptide synthesis and the copper-catalyzed azide–alkyne cycloaddition. Supramolecular assembly positions the chromophores for energy transfer.
Using time-resolved emission spectroscopy the groups measured position-dependent energy transfer that can be varied through changes in the sequence of the peptide scaffold. High level molecular dynamics simulations were used in conjunction with the spectroscopic techniques to gain molecular-level insight into the observed trends in energy transfer. The most efficient pair of Ru(II) and Os(II) linked peptides as predicted by molecular modeling also exhibited the fastest rate of energy transfer. Additionally, the emission quenching for the Ru(II) and Os(II) peptides can be fit to binding models that agree with the dissociation constants determined for the peptides via chemical denaturation.
Interplay between Vibrational Energy Transfer and Excited State Deactivation in DNA Components. Brantley A. West, Jordan M. Womick, and Andrew M. Moran. J. Phys. Chem. A, 2013, 117 (29), pp 5865–5874.
Uncovering Molecular Relaxation Processes with Nonlinear Spectroscopies in the Deep UV. Brantley A. West, Brian P. Molesky, Paul G. Giokas, Andrew M. Moran. Chemical Physics, Volume 423, 23 September 2013, Pages 92-104.
Gas Phase Acidity Measurement of Local Acidic Groups in Multifunctional Species: Controlling the Binding Sites in Hydroxycinnamic Acids. Andres Guerrero, Tomas Baer, Antonio Chana, Javier González, and Juan Z. Dávalos. J. Am. Chem. Soc., 2013, 135 (26), pp 9681–9690.
Melittin Creates Transient Pores in a Lipid Bilayer: Results from Computer Simulations. Kolattukudy P. Santo , Sheeba J. Irudayam , and Max L. Berkowitz. J. Phys. Chem. B, 2013, 117 (17), pp 5031–5042.
Pump–Probe Microscopy: Spatially Resolved Carrier Dynamics in ZnO Rods and the Influence of Optical Cavity Resonator Modes. Brian P. Mehl, Justin R. Kirschbrown, Michelle M. Gabriel, Ralph L. House, and John M. Papanikolas. J. Phys. Chem. B, 2013, 117 (16), pp 4390–4398.
Interfacial Energy Conversion in RuII Polypyridyl-Derivatized Oligoproline Assemblies on TiO2. Da Ma, Stephanie E. Bettis, Kenneth Hanson, Maria Minakova, Leila Alibabaei, William Fondrie, Derek M. Ryan, Garegin A. Papoian, Thomas J. Meyer, Marcey L. Waters, and John M. Papanikolas. J. Am. Chem. Soc., 2013, 135 (14), pp 5250–5253.
Two-Dimensional Electronic Spectroscopy in the Ultraviolet Wavelength Range. Brantley A. West, and Andrew M. Moran. J. Phys. Chem. Lett., 2012, 3 (18), pp 2575–2581.
Direct Imaging of Free Carrier and Trap Carrier Motion in Silicon Nanowires by Spatially-Separated Femtosecond Pump–Probe Microscopy. Michelle M. Gabriel, Justin R. Kirschbrown, Joseph D. Christesen, Christopher W. Pinion, David F. Zigler, Erik M. Grumstrup, Brian P. Mehl, Emma E. M. Cating, James F. Cahoon, and John M. Papanikolas . Nano Lett., Article ASAP, DOI: 10.1021/nl400265b.
Tunable Energy Transfer Rates via Control of Primary, Secondary, and Tertiary Structure of a Coiled Coil Peptide Scaffold. Dale J. Wilger, Stephanie E. Bettis, Christopher K. Materese, Maria Minakova, Garegin A. Papoian, John M. Papanikolas, and Marcey L. Waters. Inorg. Chem., 2012, 51 (21), pp 11324–11338.
Role of Four-Fold Coordinated Titanium and Quantum Confinement in CO2 Reduction at Titania Surface. Donghwa Lee and Yosuke Kanai. http://pubs.acs.org/doi/abs/10.1021/ja309871m.