Transient Formation Of The Radical Dianion In The SERS Of Benzoate

• Main Authors: Lopez-Ramirez, M R, Ruano, C, Arenas, J F, Castro, J L, Soto, J, Otero, J C
• Format: Conference Proceeding
• Language: English
• Subjects: Adsorbates; Benzoates; Carboxylates; CHARGE EXCHANGE; Charge transfer; Charging; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Electric potential; Electrode potentials; ELECTRODES; Electron states; Electron transfer; Excitation; Ground state; Interphase; ION EXCHANGE; Lasers; Nanostructure; Pyridines; RADICALS; RAMAN EFFECT; SCATTERING; Spectra; SURFACES; TRANSIENTS
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.3482923

When a molecule is adsorbed on some metallic nanostructured surfaces experiments an enormous enhancement of the Raman signal giving rise to the SER scattering through two different mechanisms: Electromagnetic (EM) and Charge Transfer (CT). Although it is now widely recognized that the EM is a general enhancement mechanism operating in SERS [1-4], it is unable to account satisfactorily for the strong dependence of these spectra on the electric potential of the interphase, for instance. The electrode potential tunes up-down the energy of CT electronic states of the metal-adsorbate complex making possible the resonance with the laser excitation line and the occurrence of photoinduced electron transfer between both moieties [5]. An important difference exists between neutral adsorbates as pyridine, and organic carboxylates as benzoate (Bz(-)) because the latter ones are already charged in the ground state. In this case the respective radical dianion (Bz(2-)) will be formed in the transient CT excited state, a much less stable species given that it supports two negative charges: M- Bz(-)+ hv arrow right M(+)- Bz(2-).