title: Surface-enhanced Raman spectroscopy of soft-landed polyatomic ions and molecules.
abstract: Surface-enhanced Raman spectroscopy (SERS) was used to detect and characterize polyatomic cations and molecules that were electrosprayed into the gas phase and soft-landed in vacuum on plasma-treated silver substrates. Organic dyes such as crystal violet and Rhodamine B, the nucleobase cytosine, and nucleosides cytidine and 2'-deoxycytidine were immobilized by soft landing on plasma-treated metal surfaces at kinetic energies ranging from near thermal to 200 eV. While enhancing Raman scattering 10(5)-10(6)-fold, the metal surface effectively quenches the fluorescence that does not interfere with the Raman spectra. SERS spectra from submonolayer amounts of soft-landed compounds were sufficiently intense and reproducible to allow identification of Raman active vibrational modes for structure assignment. Soft-landed species appear to be microsolvated on the surface and bound via ion pairing or pi-complexation to the Ag atoms and ions in the surface oxide layer. Comparison of spectra from soft-landed and solution samples indicates that the molecules survive soft landing without significant chemical damage even when they strike the surface at hyperthermal collision energies.
authors.affiliation: Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Volný
authors.forename: Atanu
authors.initials: A
authors.lastname: Sengupta
authors.forename: C Brant
authors.initials: CB
authors.lastname: Wilson
authors.forename: Brian D
authors.initials: BD
authors.lastname: Swanson
authors.forename: E James
authors.initials: EJ
authors.lastname: Davis
authors.forename: Frantisek
authors.initials: F
authors.lastname: Turecek