title: Surface-enhanced Raman scattering at the silver electrode/ionic liquid (BMIPF6) interface.
abstract: This is the first report of in situ SER spectra of chemical species adsorbed on a Ag/room temperature ionic liquid (RTIL) interface. We have investigated the dependence of the SERS intensity of the RTIL derived from 1-n-butyl-3-methylimidazolium hexafluorophosfate (BMIPF6) adsorbed on a silver electrode. It has been shown that the BMI+ adsorbs on the silver electrode for potentials more negative than -0.4 V vs a Pt quasireference electrode (PQRE). In the -0.4 to -1.0 V potential range the SER spectra are similar to the Raman spectrum of the RTIL BMIPF6. At potentials more negative than -1.0 V some imidazolium ring vibrational modes and N-CH3 vibrations are enhanced, suggesting that the imidazolium ring is parallel to the surface and for potentials <-2.8 V the BMI+ is reduced to the BMI carbene. The potential dependence of the SERS intensities of Py adsorbed on a silver electrode in BMIPF6 has also been investigated. The results have shown that at potentials less negative than -0.8 V (vs PQRE) Py adsorbs at an end-on configuration forming an Ag-N bond. In the -0.9 to -1.4 V potential range Py molecules lie flat on the electrode surface and at potentials <-1.4 V Py is replaced by the BMI+. The electrochemical and SERS results have shown that Py has the effect of changing the oxidation of silver in that medium as well as the reduction of BMI+ to the BMI carbene. In the presence of Py the BMI+ reduction is observed at potentials near -2.4 V. The Ag electrode has presented SERS activity from 0.0 to -3.0 V.
authors.affiliation: Laboratório de Materiais e Combustíveis (LMC), Instituto de Química da Universidade de Brasília, CP 04478, 70919-970, DF, Brazil.
authors.forename: Vianney O
authors.initials: VO
authors.lastname: Santos
authors.forename: Melquizedeque B
authors.initials: MB
authors.lastname: Alves
authors.forename: Myller S
authors.initials: MS
authors.lastname: Carvalho
authors.forename: Paulo A Z
authors.initials: PA
authors.lastname: Suarez
authors.forename: Joel C
authors.initials: JC
authors.lastname: Rubim