CCMST Seminar - Dr. Christine Aikens, Northwestern University

Intriguing interactions from Au to Zwitterions

(a) The interactions between amino acids and water are of great interest to chemists and biochemists. Amino acids are zwitterions in solution, yet they are nonionized in the gas phase. Using electronic structure theory methods, glycine(H2O)n clusters with n = 0-8 are examined in order to determine at what point this crossover occurs and which types of structures predominate. The importance of considering multiple amino acid conformers and thoroughly sampling the configuration space will be discussed.

(b) Surface enhanced Raman scattering (SERS) is an important technique for studying molecules adsorbed on nanoparticles and surfaces because it combines high sensitivity with high information content. The enhancement mechanism involves both chemical and electromagnetic enhancements, but is not completely understood in part due to complicated experimental conditions. Thus, valuable information may be obtained from a theoretical examination of the enhancement for a model system. The enhancement factors and mechanisms for pyridine interacting with a 20-atom gold cluster will be presented and compared to the results for a 20-atom silver cluster. Resonant frequency-dependent polarizabilities are calculated using TD-DFT.

For more information contact Dr. David Sherrill (404) 894-4037.