title: Competition between Hydrophilic and Argyrophilic Interactions in Surface Enhanced Raman Spectroscopy.
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.
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, Mississippi, 38677, United States.
authors.forename: John T
authors.initials: JT
authors.lastname: Kelly
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, Mississippi, 38677, United States.
authors.forename: Annie K
authors.initials: AK
authors.lastname: McClellan
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, Mississippi, 38677, United States.
authors.forename: Lynn V
authors.initials: LV
authors.lastname: Joe
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, Mississippi, 38677, United States.
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Wright
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, Mississippi, 38677, United States.
authors.forename: Lawson T
authors.initials: LT
authors.lastname: Lloyd
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, Mississippi, 38677, United States. tschumpr@olemiss.edu.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Tschumper
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, Mississippi, 38677, United States. nhammer@olemiss.edu.
authors.forename: Nathan I
authors.identifier: http://orcid.org/0000-0002-6221-2709
authors.initials: NI
authors.lastname: Hammer
keywords: NBO analysis; Raman spectroscopy; SERS; charge transfer; silver island films