Competition between Hydrophilic and Argyrophilic Interactions in Surface Enhanced Raman Spectroscopy. Issue 18 (7th July 2016) - Kelly, John T.
Abstract: The competition for binding and charge‐transfer (CT) from the nitrogen containing heterocycle pyrimidine to either silver or to water in surface enhanced Raman spectroscopy (SERS) is discussed. The correlation between the shifting observed for vibrational normal modes and CT is analyzed both experimentally using Raman spectroscopy and theoretically using electronic structure theory. Discrete features in the Raman spectrum correspond to the binding of either water or silver to each of pyrimidine's nitrogen atoms with comparable frequency shifts. Natural bond orbital (NBO) calculations in each chemical environment reveal that the magnitude of charge transfer from pyrimidine to adjacent silver atoms is only about twice that for water alone. These results suggest that the choice of solvent plays a role in determining the vibrational frequencies of nitrogen containing molecules in SERS experiments. Abstract : Competiton for binding in SERS : The binding of either water molecules or silver to nitrogen‐containing heterocyclic molecules in SERS experiments results in vibrational energy level shifts that originate from partial electron transfer from the nitrogen atoms. The shifts are similar and the magnitude of charge transfer from pyrimidine to adjacent silver atoms is only about twice that for water alone.